Alkaline Rock Complexes in the Wet Mountains Area, Custer and Fremont Counties, Colorado By THEODORE]. ARMBRUSTMACHER GEOLOGICAL SURVEY PROFESSIONAL PAPER 1269 Geology and petrology of rocks of the McClure Mountain Complex, Gem Park Complex, and complex at Democrat Creek and associated alkaline rocks UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984 UNITED STATES DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Armbmstmacher, Theodore J ., 1946- Alkaline Rock complexes in the Wet Mountains area, Custer and Fremont Counties, Colorado. (Geological Survey Professional Paper 1269) Bibliography: 33 p. Supt. of Docs. No.: I 19.161269 1. Alkalic igneous rocks. 2. Petrology—Colorado—Wet Mountains. 1. Title. II. Series. QE462.A4A76 552’.3 82-600104 AACR2 CONTE NTS Page Abstract ............................. 1 Ages of the complexes ..................... Introduction ........................... 1 Geochemistry ........................... Acknowledgments ........................ 1 Major elements ....................... Geologic setting ......................... 2 Mafic-ultramafic rocks ................. McClure Mountain Complex .................. 2 Leucocratic rocks ................... Mafic-ultramafic rocks ................... 2 Mafic nepheline—clinopyroxene rocks ......... Layered series ..................... 2 Additonal observations ................. Discordant intrusions ................. 6 Minor elements ....................... Leucocratic rocks ...................... 6 Mafic-ultramafic rocks ................. Nepheline syenite ................... 7 Leucocratic rocks ................... Hornblende-biotite syenite ............... 8 Mafic nepheline-clinopyroxene rocks ......... Mafic nepheline—clinopyroxene rocks ............ 10 Rubidium-strontium systematics and rare—earth- Gem Park Complex ....................... 11 element distribution patterns ............ Mafic-ultramafic rocks ................... 12 Rare—earth elements .................. Other rocks of the complex ................ 12 Initial 87Sr/WSSr ratios ................. Complex at Democrat Creek .................. 12 Rubidium/strontium ratios ............... Mafic-ultramafic rocks ................... 13 Petrologic conclusions ...................... Quartz syenite ....................... 13 References cited ......................... Carbonatites ........................... 14 ILLUSTRATIONS FIGURE 1. Map of Wet Mountains area showing location of alkaline complexes ........................... 2. Geologic map of the Wet Mountains area alkaline complexes ............................... 3. Ternary diagram of modal variation in plagioclase, clinopyroxene, and olivine from the McClure Mountain and Gem Park Complexes ....................................................... 4. Photomicrograph showing adcumulus growth of clinopyroxene on clinopyroxene .................... 5. Photomicrograph of crystallographically oriented iron oxide exsolving from clinopyroxene ............... 6. Photomicrograph of anorthositic rock with abundant triple-point grain boundaries meeting at 120° .......... 7. Photomicrograph of plagioclase with exsolved iron oxide ................................. 8. Photomicrograph of abundant cracks between nearby olivine grains ........................... 9. Photograph of outcrop of mafic-ultramafic rocks cut by nepheline syenite dikes along McClure Gulch ........ 10. Photograph of outcrop of nepheline syenite showing heterogeneous nature of grain size and heterogeneous distribution of minerals .......................................................... 11. Photograph of xenoliths contained in nepheline syenite .................................. 12. Photomicrograph of aegirine—augite rimmed by sodic amphibole in nepheline syenite .................. 13. Photomicrograph of myrmekitic intergrowth of climopyroxene and nepheline in nepheline syenite .......... ' 14. Quaternary diagram of modal variation in quartz alkali feldspar, plagioclase, and feldspathoid from the McClure Mountain Complex and the complex at Democrat Creek ...................................... 15. Ternary diagram of modal variation in nepheline, mafic minerals, and potassic feldspar from the McClure Mountian Complex ........................................................... 16. Photograph of outcrop of homogeneous hornblende-biotite syenite ............................ 17. Photomicrograph showing the alteration of clinopyroxene to green amphibole in hornblende-biotite syenite 18. Photograph of outcrop of mottled mafic nepheline-clinopyroxene rock .......................... 19. Photomicrograph of poikilitic mafic nepheline-clinopyroxene rock ............................. 20. Photograph of cumulus layering in mafic-ultramafic rocks of the Gem Park Complex ................. 21. Whole-rock isochron of nepheline syenites of McClure Mountain Complex ........................ 22. Whole—rock isochron of quartz syenites of the complex at Democrat Creek ....................... 23. Plots of weight-percent alkalies verus weight-percent Sl02 ................................ 24. Plots of agpaitic index versus weight- percent Si02 .................................... 25. Plots of differentiation index (DI) versus oxide weight percents ............................. In Page 14 15 15 15 16 19 19 22 22 23 25 25 25 27 29 3O 32 Page QC‘JOEQQU‘IU‘ moo-q-q 10 10 11 11 15 15 18 19 22 IV FWGURE 26 TABLE 27. 28. 29. 30. 31. 32. 33. 34. 50.00.49” 10. CONTENTS Diagram of chondrite-normalized rare-earth element data for mafic rocks from McClure Mountain Complex and the complex at Democrat Creek ................................................ Diagram of chondrite-normalized rare-earth element data for liquids from which mafic rocks at the McClure Mountain Complex and the complex at Democrat Creek crystallized ............................... Diagram of rare-earth element patterns for hornblende—biotite syenites from the McClure Mountain Complex Diagram of rare-earth element patterns for nepheline syenites from the McClure Mountain Complex ........ Diagram of rare-earth element patterns for quartz syenites from the complex at Democrat Creek ......... Diagram showing distribution of initial 87Sr/86Sr ratios for rocks of the alkaline complexes .............. Diagram showing rubidium/strontium ratios of rocks from the McClure Mountain Complex .............. Diagram showing rubidium/strontium ratios of rocks from the complex at Democrat Creek .............. Summary of rock distributions in the Wet Mountains area ................................ TABLES Relative and absolute age relationships of rocks of the Wet Mountains area ...................... Chemical and normative data of mafic-ultramafic rocks from the Iron Mountain area of the McClure Mountain Complex . Chemical and normative data of mafic-ultramafic rocks from the Gem Park Complex and the complex at Democrat Creek . Chemical and normative data of hornblende-biotite syenites, nepheline syenites,and mafic nepheline-clinopyroxene rocks, McClure Mountian Complex ................................................ Chemical and normative data of quartz syenites from the complex at Democrat Creek and nepheline syenite pegmatite from the Gem Park Complex ............................................... Summary of minor-element analyses of samples from the McClure Mountain Complex ................. Summary of minor-element analyses of samples from the complex at Democrat Creek and the Gem Park Complex. Abundance of elements in several types of rocks ...................................... Rubidium and strontium content and several ratios for rocks from the McClure Mountain Complex and the complex at Democrat Creek ..................................................... Rare-earth element content of rocks from the McClure Mountain Complex and the complex at Democrat Creek . . Page 28 28 28 29 29 29 30 30 31 Page 16 17 18 20 21 23 25 26 27 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, CUSTER AND FREMONT COUNTIES, COLORADO By THEODORE]. ARMBRUSTMACHER ABSTRACT Three alkaline intrusive complexes of Cambrian age occur in the Wet Mountains area, Colorado. The McClure Mountain Complex con- sists of mafic-ultramafic cumulates, hornblende-biotite syenites, nepheline syenites, and mafic nepheline-clinopyroxene rocks intruded by carbonatite, several kinds of syenite, and lamprophyre, mainly as dikes, and by thorium-bearing Veins. The Gem Park Complex con— sists chiefly of mafic-ultramafic cumulates intruded by carbonatite, lamprophyre, and nepheline syenite pegmatite. The complex at Demo— crat Creek contains subordinate amounts of mafic-ultramafic rocks and abundant quartz syenite bordered partly by a zone of brecciation; the complex is intruded by syenite dikes and a quartz—barite-thorite vem. Contents of major and minor elements, including rare-earth ele— ments, rubidium, strontium, and strontium isotopic ratios, show that these rocks did not form through fractionation of a single magma, but formed as end products of at least three separate magma groups. The mafic-ultramafic rocks in the McClure Mountain and Gem Park Complexes and the hornblende—biotite syenite in the McClure Moun— tain Complex appear to have been derived from an alkali basalt par- ent; the nepheline syenite, mafic nepheline—clinopyroxene rock, and carbonatite from the McClure Mountain Complex and the carbonatite from the Gem Park Complex appear to have had a more alkaline parent rock such as nephelinite; and the quartz syenite and mafic-ul— tramafic rock of the complex at Democrat Creek appear to have evolved from a tholeiitic basalt parent. INTRODUCTION Alkaline rocks in the Wet Mountains area of south- central Colorado, located about 20 km southwest of Canon City, Colo., about 5 km south of the Arkansas River, and northeast of the Sangre de Cristo Range and the Wet Mountain Valley, occur in three distinct complexes: the McClure Mountain Complex, the Gem Park Complex, and the complex at Democrat Creek. Additional spatially and presumably genetically related lamprophyre, carbonatite, and red syenite occur mainly as dikes. Quartz-barite-thorite veins also appear to be related to the episode of alkaline magmatism. The McClure Mountain Complex contains nepheline syenite, hornblende-biotite syenite, mafic nepheline- clinopyroxene rocks, and mafic—ultramafic cumulate rocks (Shawe and Parker, 1967). The Gem Park Com- plex contains mafic-ultramafic rocks nearly identical to those in the McClure Mountain Complex, and a single exposure of nepheline syenite pegmatite (Parker and Sharp, 1970). The complex at Democrat Creek contains quartz syenite and breccia, and mafic-ultramafic rocks that were mapped by Brock and Singewald (1968) as Precambrian gabbroic gneisses and metamorphosed ultramafic rocks, but that were thought by Heinrich and Dahlem (1966) to be similar to the gabbros and pyroxenites 0f the Gem Park and McClure Mountain Complexes. The rocks at Democrat Creek are less nota- ble for their similarities to the rocks of the other two complexes than for their differences. The intrusive complexes and associated dikes are 520 my. old according to Olson and others (1977). How- ever, their dating of leucocratic rocks from the McClure Mountain Complex and the complex at Democrat Creek by fission—track, potassium-argon, and rubidium-stronti- um techniques could not resolve any differences in the ages of the various complexes or in the ages of different syenites at McClure Mountain. Subsequent rubidium and strontium isotopic determinations by C. E. Hedge (Armbrustmacher and Hedge, 1982) yielded ages of 535:5 m.y. for syenites at McClure Mountain and 511 i 8 my for syenites at Democrat Creek. The petrology of the Wet Mountains alkaline rocks, as outlined by major- and minor-element contents, suggests the presence of several different rock series. Data on rubidium, strontium, rare-earth elements, and strontium isotopes show that rocks of the complexes did not form through fractionation of a single magma, but formed instead as end products of several magmas generated from different source materials. ACKNOWLEDGMENTS Studies of the Wet Mountains alkaline rocks benefited from discussions with US. Geological Survey geologists, especially R. L. Parker, W. N. Sharp, M. R. Brock, and J. C. Olson. Determinations of rubidium and strontium isotopes and rare—earth elements by C. E. Hedge of the US. Geological Survey and discussions with Hedge regarding their interpretation resulted in invaluable insight into the petrology of the alkaline com- plexes. I. K. Brownfield assisted in the field and in the laboratory. ‘ 2 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO GEOLOGIC SETTING The alkaline rocks of the Wet Mountains area intrude Proterozoic X metamorphic rocks—chiefly layered granitic gneisses, hornblende gneisses, and amphibo- lites—and Precambrian intrusive granitic rocks of Boul— der Creek or Proterozoic X age (1,720 my) and Silver Plume or Proterozoic Y age (1,450 my.) (Taylor and others, 1975a, b). The western edge of the Gem Park Complex is bordered by Tertiary welded tuffs, boulder gravels, and water-laid tuffs (Parker and Sharp, 1970). According to Scott and Taylor (1975), these rocks are correlative with the Oligocene East Gulch, Thorn Ranch, and Gribbles Park Tuffs of the Thirtynine Mile volcanic field. The host rocks adjacent to the alkaline complexes, carbonatite dikes, and thorium deposits, and parts of the complexes themselves, are typically fenitized (Hein— rich and Alexander, 1976). Quartzo-feldspathic host rocks commonly show loss of quartz; their feldspars are replaced by potassic feldspar containing abundant fer- ric-oxide inclusions, their mafic minerals are destroyed or replaced by blue and green sodic amphiboles and pyroxenes, and their fractures are lined with these min- erals or with epidote. Where mafic- ultramafic host rocks are fenitized, the most conspicuous result is the replacement of mafic minerals by vermiculite; in some places the concentrations are nearly high enough to be commercially valuable. The alkaline complexes, carbonatites, and thorium deposits appear to be bounded by the Ilse fault on the east and the Texas Creek and Westcliffe faults on the west (fig. 1). Relative movement along the Texas Creek fault (Taylor and others, 1975a) and along the Ilse fault (Scott and others, 1976) is east-side upward; this move— ment suggests that the alkaline intrusive rocks may 0c— cupy a different structural level than do the blocks west of the Texas Creek fault and east of the Ilse fault. To date, rocks related to the alkaline complexes have not been observed in the structural blocks east and west of the one containing the complexes. This structural block is in turn broken by a set of predominantly north— west-striking vertical faults that likely served as con- duits for fluids that formed thorium veins, 1am- prophyres, red syenite dikes, and carbonatites, espe- cially southeast of the alkaline complexes. McCLURE MOUNTAIN COMPLEX The largest of the three complexes, the McClure Mountain Complex (fig. 2), consists chiefly of a series of mafic-ultramific rocks at Iron Mountain, leucocratic hornblende-biotite syenite and nepheline syenite, mafic nepheline-clinopyroxene rocks, and various dike rocks including carbonatites, lamprophyres, and syenites. Distance across its widest east-west dimension is about 11 km and across its north-south dimension is 10 km. Exposures of the mafic-ultramafic rocks at Iron Moun- tain are about 5.8 km long in a northwest-southeast direction and 2—3.5 km wide in a northeast-southwest direction. Apparently, Parker and Hildebrand (1963) first men- tioned the McClure Mountain Complex and its alkaline nature. The mafic-ultramafic part of the complex at Iron Mountain has been discussed by Shawe and Parker (1967), who also adopted and defined the McClure Mountain Complex as a formal term. Although the leucocratic part of the complex has been mentioned many times (Shawe and Parker, 1967; Parker and Sharp, 1970; Heinrich and Dahlem, 1966; Heinrich, 1966; Heinrich and Moore, 1970), detailed information on the rocks is sparse. Rock relationships in the com- plex have been interpreted by Heinrich and Alexander (1979) to represent a “mafic-alkalic ring complex.” The rocks of the McClure Mountain Complex do not appear to have much economic potential. Small-scale production of iron from titaniferous magnetite in the mafic—ultramafic rocks at the Iron Mountain mine oc— curred as early as 1873 (Becker and others, 1961); how- ever, the high titanium content of the magnetite, as much as 14 percent TiOZ, and the low tonnage have hindered further development. Several carbonatite dikes intruding rocks of the complex have been pros- pected for thorium and rare-earth elements. MAFIC-ULTRAMAFIC ROCKS Mafic and ultramafic rocks of the Iron Mountain part of the McClure Mountain Complex form a funnel-shaped layered series of rocks intruded by small, discordant bodies of similar mafic and ultramafic rocks as well as by dikes 0f carbonatite and syenite (Shawe and Parker, 1967). Mineral content of rocks in the layered series and in the discordant intrusions is similar. The rocks differ mainly on the basis of texture; rocks in the layered series show stratification, but rocks in the dis— cordant intrusion do not. These two rock types are not distinguished on figure 2, but are shown by Shawe and Parker (1967, pl. 1). LAYERED SERIES The stratified rocks consist of igneous cumulates com- prising essentially five cumulus minerals—plagioclase, a calcium-rich clinopyroxene, olivine, magnetite, and spinel—that occur in varying proportions. All these minerals, except spinel, along with reddish-brown am- phibole and red biotite are present as intercumulus ma- terial; considerable variations in mineral proportions and in grain size can occur within a distance of a few MCCLURE MOUNTAIN COMPLEX 3 105°45' ' 30' U 105°00’ Texas Creek MCCLURE MOUNTAIN U COMPLEX g? *u. Ii“ GEM PARK LEX COMP COMPLEX AT DEMOCRAT CREEK 5 10 15 MlLES 0 if I I | | I | J °°L°R"°° 0 5 10 15 20 KILOMETEHS I EXPLANATION Tertiary, Mesozoic, and Precambrian metamorphic Paleozoic sedimentary and igneous rocks rocks Tertiary volcanogenic rocks 3 Major fault—U, upthrown side; D, downthrown side Cambrian alkaline com lexes p Contact FIGURE 1.—Map of Wet Mountains area showing location of alkaline complexes, Fremont and Custer Counties, Colo. Geology modified from Scott and others (1976). centimeters. These characteristics are typical of igneous (fig. 3) show the diversity of rock types found. These cumulates (Jackson, 1961). Plots of modal plagioclase, rock types include clinopyroxene adcumulates, plagio- clinopyroxene, and olivine for 20 mafic-ultramafic rocks clase adcumulates, and orthocumulates that consist of 4 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO 105°30' 105°25' 38°20’ // Elkhorn / Mtn D#—-D 2 3 4 MlLES l l l l | | 4 5 6 KILOMETERS FIGURE 2.—Alkaline complexes of the Wet Mountains, Fremont and Custer Counties, Colo. Geology modified from Taylor and others (1975a and 1975b) and Olson and others (1977). the cumulus minerals clinopyroxene, plagioclase, oli- vine, magnetite, and rarely spinel in various propor- tions. Most clinopyroxene appears in thin section as a tan- to neutral-colored, unzoned, sometimes pleochroic cumulus mineral—most likely titaniferous augite; rarely does it occur as an intercumulus mineral. In augite—rich rocks, adcumulus growth of the augite is sometimes ap- parent owing to slight differences in optical orientation of the augite primocryst and the later, interstitial au- gite (fig. 4). Augite can also exhibit crystallographically controlled, exsolved, opaque iron oxides (fig. 5). Plagioclase primocrysts commonly exhibit adcumulus growth; triple-point junctions near 120° are abundant in plagioclase-rich rocks (fig. 6). Most optical measure- ments place the plagioclase in the labradorite range. Clouded plagioclase—plagioclase that contains crystal- lographically controlled, exsolved iron oxide—occurs in some rocks, especially in those in which the associated augite also contains exsolved iron-oxide inclusions (fig. 7). This exsolution of crystallographically oriented iron oxide is due to subsolidus cooling at rates slow enough to allow exsolution of structural iron (iron in lattice sites; Armbrustmacher and Banks, 1974). Plagioclase is not obviously zoned. In this study, olivine adcumulates have not been ob- served and intercumulus olivine is not abundant. The maximum modal olivine content observed thus far is about 58 percent by volume. Some olivine is partly al- tered to pale yellowish-green serpentine-type minerals MCCLURE MOUNTAIN COMPLEX CORRELATION OF MAP UNITS QUATERNARY AND TERTIARY CAMBRIAN PRECAMBRIAN LIST OF MAP UNITS Quaternary and Tertiary clastic and volcaniclastic deposits Cambrian (51 1—535 my. -old rocks) Quartz syenite of complex at Democrat Creek Breccia of complex at Democrat Creek Mafic-ultramafic rocks of complex at Democrat Creek Mafic nepheline—clinopyroxene rocks of McClure Mountain Complex Nepheline syenite of McClure Mountain Complex Hornblende-biotite syenite of McClure Mountain Complex . ‘ :3} Mafic-ultramafic rocks of Mountain and Gem Park Complexes PC Precambrian metamorphic and igneous rocks Fault—Dashed where approximately located; dotted where concealed Contact X Localities mentioned in text FIGURE 2.—Continued. and opaque iron oxides. Rocks containing fairly abun- dant olivine that is partly altered show abundant, closely spaced fractures that connect olivine grains (fig. 8). This feature suggests that the alteration process in- troduced a volume change and that the resultant stress is relieved by fracturing. Magnetite occurs both as cumulus and as inter- cumulus minerals. Exploitation of layers of nearly 98 percent cumulus magnetite occurred at the Iron Moun- EXPLANATION v McClure Mountain Complex v Gem Park Complex FIGURE 3.——Modal variation in plagioclase (P), clinopyroxene (C), and olivine (O) of mafic-ultramafic rocks from the McClure Moun- tain and Gem Park Complexes. Values are in percent by Volume. FIGURE 4.—Adcumu1us growth of clinopyroxene on clinopyroxene. Sample 359; partly crossed nicols; bar is 0.5 mm. tain mine. Green spinel is invariably associated with magnetite, and the spinel/magnetite ratio increases as the total magnetite content of a rock increases. Most spinel appears to be associated with cumulus magnetite, and it is rarely associated with intercumulus magnetite. Strongly pleochroic reddish-brown amphibole, which has a large optic angle, is most similar to kaersutite in optical properties. The amphibole, which may poikilitically enclose cumulus augite and magnetite, ap- pears to have formed from intercumulus fluids. Some 6 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO \ . 3;}. FIGURE 5.vCrystallographically oriented iron oxide exsolving from clinopyroxene. Sample 392; plane light; bar is 0.5 mm. FIGURE 7,—Plagioclase with exsolved iron oxide. Sample number 402Z; plane light; bar is 0.5 mm. FIGURE 6.—Anorthositic rock with abundant triple—point grain boundaries meeting at 120°. Sample 457; partly crossed nicols; bar is 0.5 mm. of the amphibole also forms reaction rims around both augite and magnetite. Sparse green amphibole appears to be a product of the alteration of clinopyroxene. Most strongly pleochroic biotite, red to neutral, is associated with magnetite. A few rocks contain euhed- ral apatite, which appears to have coprecipitated with magnetite. The presence of both a single calcium-rich clinopyroxene, as opposed to two pyroxenes, and a sodic amphibole verifies the alkaline nature of these mafic-ultramafic rocks. DISCORDANT INTRUSIONS Field evidence for recognizing the ultramafic discor- dant intrusions include their discordant nature, the FIGURE 8.—Closely spaced fractures in plagioclase (P) connecting olivine grains (0). Sample 396; plane light; bar is 0.5 mm. xenoliths of rocks of the layered complex near contacts, and the lack of layering (Shawe and Parker, 1967). Rocks of the discordant intrusions consist of minerals that commonly are identical to those in rocks of the layered intrusions. In thin section, these rocks tend to be equigranular, and the distribution of various miner— als tends to be more homogeneous than that in the layered rocks. LEUCOCRATIC ROCKS Two distinct, mappable types of leucocratic rocks, hornblende-biotite syenite and younger nepheline syen- ite, occur in the McClure Mountain Complex; neither contains modal or normative quartz. These rocks in- trude the mafic—ultramafic rocks at Iron Mountain and MCCLURE MOUNTAIN COMPLEX 7 are in turn intruded by red syenite dikes, carbonatite dikes, and lamprophyre dikes. The nepheline syenite intrudes the hornblende-biotite syenite. Precambrian host rocks adjacent to syenite contacts are fenitized to varying degrees; one of the best examples is at Red Mountain (fig. 2), just south of the McClure Mountain Complex. Fenitization of mafic—ultramafic rocks at Iron Mountain adjacent to the syenites is generally not ap- parent, probably because of structural complications— much of that contact is a fault contact. However, at McClure Gulch, the mafic—ultramafic rocks are cut by nepheline syenite dikes (fig. 9). The syenites are fenitized along narrow zones adjacent to later dikes of carbonatite and red syenite. The development of ferric- oxide—bearing potassic feldspars has turned the light- gray syenite host rock to pink; the original mafic miner- als tend to be destroyed or replaced by a vermiculite- like mica. Breccia zones have not been observed in the vicinity of rocks of the McClure Mountain Complex, al— though breccia pipes at nearby Pinon Peak, 5.5 km north of the complex (Taylor and others, 1975b), have been related to the episode of development of alkaline rocks at McClure Mountain by Heinrich and Dahlem (1967). NEPHELINE SYENITE Nepheline syenite in the McClure Mountain Complex is centrally located relative to the hornblende-biotite syenite, but is peripheral to the mafic nepheline- clinopyroxene rocks (fig. 2). According to Heinrich and Alexander (1979), the nepheline syenite occurs as a stock that intrudes the central core of an alkaline ring complex. Outcrops of nepheline syenite vary considerably in lithologic details (fig. 10). Outcrop colors range from FIGURE 9.—Outcrop of mafic—ultramafic rocks cut by nepheline syenite dikes (light—colored). This location is along McClure Gulch near contact of mafic—ultramafic rocks and hornblende-biotite syenite. Hammer within circle is 31 cm long. medium bluish gray to light gray, and grain sizes range from medium to coarse. The medium—grained rocks tend to form sharp, angular outcrops, whereas the very coarse grained rocks form rounded outcrops because of exfoliation, and weather more readily to grus. At a few localities, the coarse-grained rocks are foliated; these rocks have some of the characteristics of cumulus rocks, such as abrupt changes in grain size and mineral pro- portions. At some localities, the nepheline syenites con- tain abundant xenoliths, most of which are rounded to subangular fragments of medium- to dark gray nepheline- and sodic pyroxene-rich rocks (fig. 11). Petrographic examination of nepheline syenite shows several textural types, including hypidiomorphic-granu- lar, allotriomorphic-granular, and porphyritic. In hypidiomorphic-granular rocks, the sodic amphiboles are typically euhedral; as the amphiboles become anhed- ral, the texture becomes allotriomorphic-granular. In FIGURE 10.—Outcrop of nepheline syenite showing heterogeneous nature of grain size and heterogeneous distribution of minerals. Scale is 17.5 cm long. FIGURE 11.—Xenoliths contained in nepheline syenite. Scale is 17.5 cm long. 8 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO the porphyritic rocks, phenocrysts are nepheline, micro- perthite, and sodic amphibole in various combinations. In one glomero-porphyritic rock with euhedral nepheline phenocrysts, synneusis structures and groundmass lath-shaped microperthites that swirl around phenocrysts (trachytic texture) give evidence of magmatic turbulence. The major components of nepheline syenites are microperthite, nepheline, and sodic amphibole, although plagioclase and potassic feldspar are abundant in some samples. The major components also vary widely be- tween samples: microperthite ranges between 0 and 84 percent by volume, nepheline ranges between 0.2 and 38 percent, and sodic amphibole ranges between 0 and 26 percent. The inverse relationship of the abundance of potassic feldspar to the abundance of microperthite suggests that the potassic feldspar may be cryptoper— thitic. Sodic pyroxene, which optically best fits aegirine-augite, commonly shows a reaction relationship with sodic amphibole, which optically best fits ecker— mannite-arfvedsonite (fig. 12). However, sodic pyrox- ene also occurs independent of the sodic amphibole, commonly in the more nepheline-rich samples. Brown to yellow-brown biotite occurs in nearly every sample in amounts as much as about 10 percent by volume, but averages about 2.5 percent; biotite occurs alone or clotted together with sodic amphibole and magnetite. Sphene, apatite, and magnetite generally are ubiquit— ous, but rarely exceed about 2.5 percent by volume; they occur separately or clotted together with mafic minerals. Apatite may also form poikilitic inclusions in sodic amphibole. Carbonate minerals, muscovite, and an unidentified isotropic mineral associated with nepheline are all present in small amounts and appear to have a secondary origin. A few samples contain myr- mekitic intergrowths of light-green clinopyroxene and nepheline (fig. 13). At Copper Gulch divide (fig. 2), a sodalite-bearing variety of nepheline syenite occurs. Modal components of the nepheline syenites have been plotted on a QAPF (quartz-alkali feldspar-plagio- clase-feldspathoid) diagram (fig. 14). Most of the sam- ples plot in the alkali syenite and foyaite fields, reflect- ing their typically low plagioclase content. Those sam- ples containing greater amounts of plagioclase plot in the plagifoyaite, essexite, and diorite gabbro fields. Modal nepheline-potassic feldspar-mafic minerals of the same rocks (fig. 15) fall chiefly in the nepheline syenite and adjoining fields. Variation in nepheline/potassic feldspar ratios appears to be considerably greater than variation in mafic-mineral abundance. HORNBLENDE-BIOTITE SYENITE The hornblende-biotite syenite crops out mainly in the northern and eastern parts of the McClure Moun- FIGURE 12,—Aegirine-augite rimmed by sodic amphibole in nepheline syenite. Sample 394K; plane light; bar is 0.5 mm. FIGURE 13.—Myrmekitic intergrowth of clinopyroxene and nepheline in nepheline syenite. Sample WM—62—73; plane light; bar is 0.5 mm. tain Complex. In addition, the occurrence of hornblende-biotite syenite at the west side of the com- plex suggests that the syenite forms a nearly circular outcrop pattern that surrounds nepheline syenite (fig. 2). In the field, the hornblende-biotite syenite is consid- erably more homogeneous at the outcrop scale than nepheline syenite (fig. 16). As discussed later, this homogeneous aspect is characteristic of this rock. Outcrop colors are predominantly light gray and tan, although some pink varieties also occur. Almost all the rocks are coarse grained, and the outcrops weather to rounded boulders that yield abundant grus. The hornblende-biotite syenite tends to cause rolling meadowland if the land is not dissected locally by streams. McCLURE MOUNTAIN COMPLEX O o 3 A G ' =5 9» ranlte at 9/ 6 ’5' o a 0 Q \_)’ @59me PIagifoyaite Essexite Foyaitic foidite EXPLANATION McCLURE MOUNTAIN COMPLEX l El Nepheline syenite O Hornblende-biotite syenite V Mafic nepheline-clinopyroxene rocks COMPLEX AT DEMOCRAT CREEK 0 Quartz syenite FIGURE l4.—Modal variation in quartz (Q), alkali feldspar and plagioclase (Ano_5) (A), plagioclase (An>5) (P), and feldspathoid (F) of syenites and mafic nepheline-clinopyroxene rocks from the McClure Mountain Complex and quartz syenites from the complex at Democrat Creek (modified from Sorensen, 1974a, p. 16). Values are in percent by volume. Petrographic examination shows that the texture of most hornblende—biotite syenite is allotriomorphic- granular. Grain sizes range from medium (1—5 mm) to coarse (>5 mm). A few samples collected in the vicinity of contacts are porphyritic, and the phenocrysts form urtite Juvite Leucocratic nepheHne syenite Melteigite 33$? Feldspar- bearing bearing syenite melteigite « Melanocratic malignite Alkali gabbro Jacupirangite . . / Melanocratlc nepheline- bearing syenite Mesocratic nepheline- bearing syenite EXPLANATION McCLURE MOUNTAIN COMPLEX O Hornblende-biotite syenite CI Nepheline syenite A Mafic nepheline-clinopyroxene rocks FIGURE 15.—Modal variation in nepheline (Ne), mafic minerals (M), and potassic feldspar (A) of rocks from the McClure Mountain Com— plex (from Sorensen, 1974a, p. 17). Values are in percent by vol- ume. FIGURE 16.—Outcrop of homogeneous hornblende-biotite syenite. Lens cover is 6 cm in diameter. 10 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO medium-grained microperthite. The allotriomorphic- granular rocks consist of medium- to coarse-grained, anhedral, lath-shaped, Carlsbad-twinned microperthite with roughly random orientation. Microperthite ranges from 48 to 93 percent by volume. Some samples contain abundant sodic plagioclase, as much as about 34 per- cent, but other samples contain no apparent plagioclase except that in microperthite. The mafic minerals and accessory minerals commonly occur together in clots, and these clots may be 10—15 mm across. Clinopyroxene rarely exceeds 1 percent by volume; it nearly always shows a reaction relationship with sodic amphibole, which ranges from 0.3 to 11 percent, and occurs mainly as remanent cores within the pleochroic, dark-greenish- brown sodic amphibole (fig. 17). Magnetite in some rocks is rimmed by sphene, but euhedral sphene inde— pendent of magnetite also is a common constituent. Magnetite, apatite, and sphene, which typically occur in amounts near 2—3 percent, are ubiquitous; muscovite and carbonate appear to be secondary minerals. Modal components of the hornblende-biotite syenite on a QAPF diagram (fig. 14) plot in alkali syenite, syen- ite, and monzonite fields primarily because of variations in the microperthite/plagioclase ratio. Modal compo- nents of the nepheline—potassic feldspar—mafic minerals (fig. 15) show that the nepheline-bearing samples plot in the melanocratic and mesocratic nepheline-bearing syenite fields. FIGURE 17.—A1teration of Clinopyroxene (Cpx) to green amphibole (Am) in hornblende-biotite syenite. Sample 387BX; plane light; bar is 0.5 mm. MAFIC NEPHELINE-CLINOPYROXENE ROCKS Mafic nepheline-Clinopyroxene rocks, termed “ijolite” by Heinrich (1966), intrude nepheline syenites in the southern part of the McClure Mountain Complex. Out- crops are dark greenish gray in the field and are textur- ally inhomogeneous. One outcrop found on the south- west side of Elkhorn Mountain (fig. 2) has a mottled texture owing to large poikilitic grains of nepheline (fig. 18). These rocks weather rather readily and yield a dark-gray soil mantle. Petrographic studies show at least two textural types, allotriomorphic—granular and poikilitic, and most minerals are medium grained. In the poikilitic type, large grains of nepheline, with or without potassic feld- spar, engulf subhedral sodic clinopyroxenes and am- phiboles (fig. 19). Nepheline and sodic Clinopyroxene, a pale-green aegirine—augite, are the most abundant components. Nepheline ranges from 10 to about 45 per- cent by volume, and sodic Clinopyroxene ranges chiefly between about 30 and 40 percent. One sample contain- ing nearly 30 percent microperthite, the only sample that has identifiable microperthite, contains only 8.4 percent sodic clinopyroxene. Biotite is present in vari- able amounts, 5—50 percent, and is thus a major compo- nent in some samples. Potassic feldspar and sodic am- phibole are present in some samples, whereas sphene, magnetite, and apatite are present in all samples examined. Plots of modal components of mafic nepheline- clinopyroxene rocks on a QAPF diagram (fig. 14) are not too informative because of the lack of plagioclase . g, . a’ _ d. ‘ l, 5' ~ , .fi 4» . ‘ -- , . FIGURE 18.—Outcrop of mottled mafic nepheline-Clinopyroxene rocks. Approximately 12 cm of scale is shown. GEM PARK COMPLEX 11 “l? ‘ '. . ' “'4 y l—l “V ’ ‘1! I ‘ FIGURE 19.—Sodic clinopyroxene (Cpx) and nepheline (Ne) in poikili- tic mafic nepheline-clinopyroxene rock. Sample 415K; partly crossed nicols; bar is 0.5 mm. in these rocks. The plots show only the variation in the sodic feldspar/nepheline ratio, which ranges from 1:1 to 0:1. Plots of modal nepheline—potassic feldspar— mafic minerals (fig. 15) show the paucity of potassic feldspar and the greater abundance of mafic minerals relative to the nepheline syenites. Most of the rocks plot in or near the ijolite and feldspar-bearing ijolite fields. GEM PARK COMPLEX The oval-shaped Gem Park Complex is a maximum of about 2.9 km along a north-south axis and 2.0 km along an east-west axis (fig.2). The first indication that the rocks at Gem Park were part of an alkaline complex was given by Parker and others (1962); the Gem Park Complex was later adopted as a formal term and de- scribed in detail by Parker and Sharp (1970). Various mineral commodities, including nickel, silver, vermicu- lite, niobium, magnetite, and ornamental stone, have been sought at Gem Park in or adjacent to the complex. Recently, diamond drilling has blocked out an area con- taining economically interesting amounts of Nb205 in stockwork carbonatite that intrudes rocks of the com- plex (D. W. Fieldman, oral commun., 1978). At Gem Park, the mafic-ultramafic rocks weather at a rate greater than that of the surrounding Precambri- an granitic gneisses. As a result, rocks tend to be, at best, only moderately well exposed, and are mainly re- stricted to low, rubbly outcrops. The stratiform nature of the complex is well exhibited in a small shaft just west of the center of the complex (fig. 20) by composi- tional layering exposed adjacent to a road along Pine Gulch at the south end of the complex, and by layering in core drilled by several companies. The mineral layer- FIGURE 20.—Cumulus layering in stratiform mafic-ultramafic rocks of the Gem Park Complex. Hammer is 31 cm long. ing in the mafic-ultramic rocks dipping consistently to- ward the center of the complex suggests that the Gem Park Complex may be a funnel-shaped intrusion similar in gross shape to the mafic- ultramafic body at Iron Mountain in the McClure Mountain Complex. The Gem Park Complex is cut by several high—angle normal faults that also cut the volcanic rocks immediately to the west of the complex, the age of the faults is post-Oligocene (Parker and Sharp, 1970). At least two general types of fenitization occur in the Gem Park Complex: fenitization of enclosing Pre- cambrian granitic gneisses because of metasomatic al— teration accompanying intrusion of the rocks of the com- plex, and fenitization of rocks of the complex because of metasomatic alteration accompanying intrusion of later rocks, mainly carbonatites. An example of the first type of alteration occurs on Democratic Mountain just east of the complex, where Precambrian granitic rock has been fenitized to a pink granitic rock with abundant green, fracture-controlled epidote. This rock has been quarried as an ornamental building stone. An example of the second type of alteration occurs in the north-cen- tral part of Gem Park at the Vermiculite mine, where mafic-ultramafic rocks have been metasomatized to an assemblage of aegirine, tremolite-actinolite, augite, phlogopite, vermiculite, dolomite, calcite, barite, apa- tite, magnetite, and fibrous, blue, sodic amphibole (Parker and Sharp, 1970, p. 10). The source of these fenitizing solutions has been postulated by Parker and Sharp (1970, p. 23) to be a buried central carbonatite core. However, Rock (1976) suggested an incompatibil- ity between calcic plagioclase and carbonatite in alkaline 12 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS APEA, COLORADO complexes. This incompatibility would preclude the pos— sibility of a central carbonatite core, but would not ex— plain the occurrence of carbonatite in a calcic plagio- clase-rich alkaline-rock complex. MAFIC-ULTRAMAFIC ROCKS The mafic-ultramafic rocks in the Gem Park Complex, which are predominantly igneous cumulates, comprise the cumulus minerals plagioclase, clinopyroxene, oli- vine, and magnetite. The most abundant rock types are plagioclase-clinopyroxene orthocumulates—the gabbro of Parker and Sharp (1970)—and clinopyroxene ad- cumulates—the pyroxenite of Parker and Sharp (1970). Locally, plagioclase adcumulates and magnetite ortho- cumulates are also found. Plagioclase, clinopyroxene, and magnetite also form intercumulus material along with reddish-brown sodic amphibole and red biotite. Modal variation in plagioclase, clinopyroxene, and oli- vine is shown in the ternary diagram in figure 3. The most obvious characteristic of mafic-ultramafic rocks in the Gem Park Complex, as compared with the McClure Mountain Complex, is the low amounts of olivine. Parker and Sharp (1970, table 2) reported as much as 6 percent olivine by volume in several samples of gab- bro, whereas the current study shows 1 percent or less olivine in any given rock. In thin section, the cumulus minerals clinopyroxene, plagioclase, and olivine appear identical to the minerals in the mafic-ultramafic rocks in the McClure Mountain Complex at Iron Mountain. Pleochroic reddish-brown sodic amphibole, whose opti- cal properties best fit kaersutite, occurs as inter— cumulus material and appears to have a reaction re- lationship with magnetite. Pleochroic green amphibole also appears to be an alteration product of kaersutite and clinopyroxene; it occurs in amounts of less than 2 percent by volume. Biotite, pleochroic neutral to red, does not exceed 1.5 percent by volume and is chiefly associated with magnetite. Apatite containing clusters of small two-phase fluid inclusions is also intercumulus and is typically anhedral. Sphene has been identified in only a few rocks. Drill core from the northern part of the Gem Park Complex has intersections of coarse-grained clinopyroxene adcumulates that contain abundant epigenetic sulfide minerals. These minerals include py- rite, pyrrhotite, and chalcopyrite. Most of the layered mafic-ultramafic rocks in the Gem Park Complex are similar to the layered mafic-ultra— mafic rocksat Iron Mountain in the McClure Mountain Complex. Because of these similarites, the cumulus rocks at Gem Park and at Iron Mountain likely share a common origin. OTHER ROCKS OF THE COMPLEX Lensoid, conformable bodies rich in opaque minerals were mapped by Parker and Sharp (1970) along the contacts of clinopyroxene adcumulates and plagioclase- clinopyroxene orthocumulates mainly in the southern and southeastern parts of the Gem Park Complex. These rocks are best described as magnetite or- thocumulates and they typically contain more than 95 percent euhedral magnetite and minor amounts of green spine], pale-yellow—green biotite, and interstitial fine- grained aggregates of silicate minerals. These syngene- tic rocks are part of the layered sequence and are simi- lar to the magnetite—rich rocks at the Iron Mountain mine. Near the center of the complex a small, shallow pit exposes nepheline syenite pegmatite that most likely intrudes the mafic-ultramafic rocks (Parker and Sharp, 1970, p. 6). These coarse-grained rocks contain un- twinned and microperthitic potassic feldspar, nepheline, aegirine-augite, several amphiboles, including red- brown kaersutite and green hornblende, Sphene, musco- Vite, apatite, opaque minerals, albite, and sodalite(?). Parker and Sharp (1970) also noted the presence of nat- rolite and analcite. The mafic-ultramafic rocks at Gem Park are intruded by several dikes of lamprophyre and syenite porphyry. These types of dikes are found throughout the Wet Mountains area and have been described by Heinrich and Dahlem (1969); dikes at Gem Park were also dis- cussed by Parker and Sharp (1970). Dikes and irregu- larly shaped intrusions of carbonatite also intrude the rocks of the Gem Park Complex as well as the Precam- brian host rocks; these intrusions also were discussed by Parker and Sharp (1970). COMPLEX AT DEMOCRAT CREEK The complex at Democrat Creek is about 14 km east of the Gem Park Complex and 7 km southeast of the McClure Mountain Complex. It is a maximum of 4.5 km along a northwest—southeast axis and 3 km along a northeast-southwest axis (fig. 2). Rocks of the complex at Democrat Creek were partly mapped by Christman and others (1954), who referred to them as “metamorphosed gabbroic and ultramafic rocks,” “breccia,” and “albite syenite.” This reference appears to be the first mention of the complex at Demo- crat Creek, although the associated mafic-ultramafic rocks were considered to be Precambrian in age and therefore not part of the complex. Christman and others (1954) reported an age of 595 my. by the Larsen zircon method. Essentially the same data were pre— COMPLEX AT DEMOCRAT CREEK 13 sented by Singewald and Brock (1956), Christman and others (1959), and Brock and Singewald (1968). Parker and Hildenbrand (1963), who mentioned the albite syen- ite intrusion and the 595-m.y. date, suggested that the syenite at Democrat Creek and the rocks of the McClure Mountain Complex are probably the same age. Heinrich and Dahlem (1966) coined the name “Democrat Creek complex” and related the complex to the McClure Mountain and Gem Park Complexes. They reinter- preted the “metamorphosed gabbroic and ultramafic rocks” of Christman and others (1954) as resembling the gabbros of the other complexes and therefore as being part of the complex at Democrat Creek in the sequence gabbro, breccia, albite syenite, alkalic dikes, and thorium veins and carbonatites. Armbrustmacher (1979) noted that close examination of rocks of the com- plex at Democrat Creek reveals more differences than similarities between these rocks and those of the McClure Mountain and Gem Park Complexes. Most of the rocks in the complex at Democrat Creek are leucocratic, and they show different types of tex— tures and grain sizes. The contact of the leucocratic rocks with the Precambrian host rocks is marked by a breccia zone in some places. The mafic-ultramafic rocks of the complex appear to be restricted to the southern part of the complex. Several satellitic intru- sions of leucocratic rock also surround the main part of the complex. Rocks of the complex are cut by a quartz-barite-thorite vein and by several syenitic dikes, but neither carbonatite dikes nor red syenite dikes have been found within the complex. MAFIC-ULTRAMAFIC ROCKS The most significant petrographic aspect of the mafic- ultramafic rocks, from outcrops south of the large quartz syenite intrusion, is the association of two pyrox- enes—a calcium-rich clinopyroxene and a calcium-poor orthopyroxene. According to Wilkinson (1974), this as- sociation is characteristic of tholeiitic, not alkaline, mafic rocks. On the basis of petrographic data, the clinopyroxene is augite and the faintly pleochroic or- thopyroxene is hypersthene. Plagioclase either is ab- sent, as in the pyroxenites, or constitutes nearly 25 percent of the rock, as in the gabbros. The plagioclase is clear, but is saussuritized to varying degrees. Oriented rodlike inclusions of apatite (?) occur in some plagioclase grains. Interstitial to the pyroxenes, and having the appearance of intercumulus material, is a pale-yellowish-green, faintly pleochroic amphibole that has optical and X-ray—diffraction properties similar to those of minerals in the tremolite—actinolite group. Sparse biotite, pleochroic in shades of green and brown, is also interstitial; apatite and magnetite are accessory minerals. Evidence of stratification is not obvious at the outcrop. Compared with mafic—ultramafic rocks from the McClure Mountain and Gem Park Complexes, which contain minerals typical of alkaline mafic rocks, the mafic-ultramafic rocks from the complex at Democrat Creek contain a mineral assemblage characteristic of tholeiitic mafic rocks. Chemical data discussed later verify the tholeiitic nature of these rocks. QUARTZ SYENITE The leucocratic rocks in the complex at Democrat Creek have been called “albite syenite” by Christman and others (1959) and Heinrich and Dahlem (1966), “medium-grained syenite” by Scott and others (1976), “fine- to medium-grained syenite” by Taylor and others (1975b), and “quartz syenite” by Olson and others (1977). In this report, they are termed “quartz sye- nites.” In the field, several varieties of rocks, mainly light gray, tan, and pink, are present: medium-grained rocks with equigranular textures, coarsely crystalline rocks with pegmatitic textures, and medium-grained porphyritic rocks, all intermixed at about the 1—10 m scale. In hand specimen, the pegmatitic rocks have gra- dational contacts with the equigranular rocks; in some places, the porphyritic rocks cut the pegmatitic rocks. Whether several episodes of intrusion are represented or whether localized variations in crystallization, such as abundances of volatile constituents, are present is not clear. Lithologic variations also result from varia— tions in modal mineralogy. The abundance of mafic min- erals varies from near zero to moderately abundant at the outcrop; in some specimens, the mafic minerals are acicular. At some localities, quartz appears to be abun- dant in the hand specimens, but at other localities quartz is difficult to identify. Xenoliths of both mafic rocks and granitic gneiss have been observed, some- times at localities distant from contacts with the coun— try rock. The mafic rocks are altered, and perhaps rep- resent fenitized equivalents of the mafic—ultramafic rocks, such as those occurring south of the leucocratic part of the complex. Fenitization of the country rock Precambrian granitic gneisses adjacent to rocks of the complex is not obvious. Quartz, which usually occurs as an interstitial min— eral, ranges from 2 to 32 percent by volume. Small fluid inclusions containing daughter minerals are abundant in the quartz, which partly replaces the feldspars. The feldspars, microperthite, microcline, and albite are the most abundant constituents of the quartz sye- nites; they collectively range from 64 to over 93 per- cent. Microperthite is the most abundant mineral, but 14 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO microcline is absent in some samples. Albite may re- place microcline and form discrete grains chiefly inter- stitial to larger microperthite grains. Microperthite ranges from 32 to 83 percent by volume, microcline ranges from 0 to 20 percent, and albite ranges from 6 to nearly 20 percent. Sodic amphibole in the quartz syenites ranges from 0 to 10 percent, has a small extinc- tion angle, is biaxial with a moderate 2V, and is pleoc- hroic olive green to dark blue. This mineral appears to be a member of the eckermannite-arfvedsonite group. Aegirine(?) and riebeckite are sparse. Biotite tends to be altered and replaced, and is pleochroic through shades of reddish brown. Zircon, fluorite, mag- netite, and sparse sphene are accessory minerals that occur in amounts of less than 1 percent. Plots of modal data on a QAPF diagram (fig. 14) show that most of the quartz syenites plot in the syenite and alkali syenite fields; two of the quartz—rich varieties plot in the granite field. CARBON ATITES Carbonatites associated with alkaline rocks of the McClure Mountain and Gem Park Complexes and the complex at Democrat Creek can be classified into two groups, replacement and primary magmatic, on the basis of distinctive petrographic differences (Arm- brustmacher, 1979). These two groups also show dis- tinctive differences in mineralogy and geochemistry. Textures of replacement carbonatites indicate nearly complete pseudomorphous replacement of originally porphyritic or hypidiomorphic-granular igneous dike rocks by carbonate minerals. They contain an element suite characteristic of carbonatites as well as a trace- element signature indicative of a mafic silicate precur— sor. Minerals that contain thorium, niobium, and rare- earth elements as essential constituents generally are rare. Primary magmatic carbonatites, which do not show the distinctive replacement textures, are also en- riched in elements characteristic of carbonatites, but contain greater average amounts of these elements than do replacement carbonatites. Thorite, bastnaesite, syn— chysite, ancylite, and monazite are chiefly responsible for the high thorium and rare-earth-element content of these rocks compared to that in other igneous rocks. Primary magmatic carbonatites are spatially more closely associated with the alkaline intrusions than are replacement carbonatites, which have a somewhat wider distribution. Field data and 8180 and 813C values support an igneous origin for primary magmatic carbon— atites; isotopic values indicate that the carbonatite re- placing the earlier alkaline dikes also was derived from igneous sources. Exchange of isotopes between both types of carbonatite and nonigneous reservoirs appears to be minimal. Abundances of rare-earth elements and niobium in carbonatites of the Wet Mountains area are somewhat lower than those at other carbonatite localities that con— tain economic or near-economic concentrations. Thori- um is more abundant in spatially related vein-type de- posits than in the carbonatites. AGES OF THE COMPLEXES The first known age determinations of Wet Moun- tains alkaline rocks were reported by Jaffe and others (1959). Two samples of nonmetamict zircon from the “albite syenite” at Democrat Creek gave ages of 580 and 601 m.y. by the Larsen zircon method. A K-Ar age reported by Brock and Singewald (1968) for biotite from the syenite at Democrat Creek is 500:25 m.y. Fenton and Faure (1970) calculated a whole-rock Rb—Sr isochron for rocks from the McClure Mountain Complex that indicated an age of 517 i 14 m.y. and an initial 87Sr/ 868r ratio of 0.7059:0.0003. Using a variety of dating techniques, Olson and others (1977) reported ages from a variety of alkaline rocks. Their results for rocks from the McClure Mountain Complex are: 520 m.y. (average hornblende K-Ar age), 521 m.y. (Rb-Sr isochron), 508 m.y. (average biotite K-Ar ages), and 506 m.y. (sphene fission—track age); the quartz syenite in the complex at Democrat Creek has average K-Ar ages of 512 my. (biotite) and 534 m.y. (hornblende). Their data showed that red syenite dikes associated with rocks of the three complexes have an age of 495 m.y. (Rb-Sr isochron), but attempts to date rocks from the Gem Park Complex gave unsuitable results (Olson and others, 1977, p. 683). In more recent studies (Armbrustmacher and Hedge, 1982), whole-rock isochrons were prepared for leucocra- tic rocks from the McClure Mountain Complex and for the complex at Democrat Creek by C. E. Hedge of the U.S. Geological Survey. The hornblende-biotite syenites and nepheline syenites from the McClure Mountain Complex lie along the same whole—rock iso- chron (fig. 21), and, although field relationships indicate that the nepheline syenite is younger than the hornblende-biotite syenite, these differences cannot be resolved with these data. The age of these syenites is 535:5 m.y.; and the initial 87Sr/gGSr ratio is 0.7037i0.0002. The quartz syenites from the complex at Democrat Creek show a greater variation in Rb/Sr ratios; the whole-rock isochron gives an age of 511:8 m. y. and an initial 87Sr/gGSr ratio of 0.7032 : 0.0002 (fig. 22). Thus, an age difference of about 24 m.y. exists between the syenites in the McClure Mountain Com— plex and the quartz syenites in the complex at Democ- rat Creek. The relative and absolute age relationships of the rocks of the Wet Mountains area are given in table 1. GEOCHEMISTRY 15 0-76 I I I I | EXPLANATION 0.75 — McCLURE MOUNTAIN COMPLEX * Nepheline syenite Nepheline syenite (Olson and I I I ' others, 1977) 0'74 _ o Hornblende-biotite syenite 0.7100 — o Hornblende-biotite syenite (Olson ,_. and others, 1977) _ 143 8’ av 21 WM—8-71 °&_ 0.73 g of}: _ 0 WM—12—71 g) «55 h 0'7 75 'WM—21—71 é’ E U) [\ 00 0.72 — — 0.7050 — — _ _ I l J | | 0‘71 0'70250 0.2 ’04 0.6 0.8 0.7037: 87 86 0.0002 Rb/ 5’ I:I Enlargement of boxed area at left 0.70, | I I I I 0 1 2 3 4 5 6 87Rb/86Sr FIGURE 21.—Whole—rock isochron of nepheline syenites of McClure Mountain Complex. 87Sr/858r 0.7032 :0.0002 412 l l l l | i | i | 0 20 40 60 80 100 87Rb/86Sr FIGURE 22,—Whole—rock isochron of quartz syenites of the complex at Democrat Creek. GEOCHEMISTRY Discussion of the geochemistry of the alkaline rock complexes is based on data from several sources. Major- element analyses of mafic-ultramafic rocks from the Gem Park Complex are from Parker and Sharp (1970, table 1), and analyses of rocks from the Iron Mountain part of the McClure Mountain Complex, as well as minor- and trace-element contents of some of the rocks are from Shawe and Parker (1967, table 3). The remain- ing whole-rock analyses are new. Geochemical data based mainly on carbonatites have been presented by Armbrustmacher (1979) and Armbrustmacher and Brownfield (1978). Radiometric ages of rocks in the complexes have been reported by Jaffe and others (1959, p. 127), Fenton and Faure (1970), Olson and Mar- vin (1971), and Armbrustmacher and Hedge (1982). Ad- ditonal minor—element and isotopic data have been re- ported by Roden and Cullers (1976) and Armbrustmacher, Brownfield, and Osmonson (1979). The major- and minor-element distributions in the al— kaline rocks have been summarized by Arm- brustmacher (1980). MAJOR ELEMENTS MAFIC-ULTRAMAFIC ROCKS Chemical and normative data of mafic-ultramafic rocks from the Iron Mountain area of the McClure Mountain Complex are given in table 2; similar data for mafic-ultramafic rocks from the Gem Park Complex and the complex at Democrat Creek are given in table 3. Analyses 1—9 in table 2 are from Shawe and Parker (1967, table 3), except that the norms have been recal- culated from analyses adjusted to 100 percent. Analysis 16 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO TABLE 1.—Relative and absolute age relationships of rocks of the Wet Mountains area, Colorado Geologic Rock types Absolute ages ages E’ (U ‘5 Volcaniclastic rocks a ,_ Quartz-barite-thorite veins; various leucocratic dikes Complex at Democrat Creek: quartz syenite 511 m.y. breccia Inafic-ultramafic rocks Carbonatites, red syenites, lamprophyres (7) C E McClure Mountain Complex: nepheline syenite 535 m.y. .D E hornblende-biotite syenite 535 m.y. L) mafic nepheline-clinc- pyroxene rock Gem Park Complex: nepheline syenite pegrnatite Gem Park and McClure Mountain cumulates Silver Plume or Proterozoic Y age: granitic intrusive E 3 rocks 1,450 m.y. E 5 Boulder Creek or Proterozoic X age: granitic U 0) 5i intrusive rocks 1,720 m.y. Proterozoic X metamorphic rocks 10 (table 2), a plagioclase—clinopyroxene orthocumulate, was obtained by Shawe and Parker but was not in- cluded in their 1967 Iron Mountain report. In table 3, the two analyses of Gem Park rocks are from Parker and Sharp (1970, table 1); the norms also have been recalculated as in table 2. The four analyses of Demo- crat Creek maficlultramafic rocks are new. None of the mafic-ultramafic rocks from the McClure Mountain and Gem Park Complexes and only one from the complex at Democrat Creek contain normative quartz. Seven rocks from McClure Mountain, both rocks from Gem Park, and no rocks from Democrat Creek contain normative nepheline. Only three rocks from McClure Mountain contain normative hyper- sthene, all in amounts of less than 3 percent; neither of the rocks from Gem Park contains normative hyper- sthene, but all rocks from Democrat Creek contain nor- mative hypersthene in amounts exceeding 37 percent. All McClure Mountain rocks contain normative olivine in variable amounts; Gem Park rocks contain some nor- mative olivine, and Democrat Creek rocks contain nor- mative olivine in amounts of less than 2.1 percent. Ac- cording to Wilkinson (1974, p. 67), basaltic rocks con- taining normative nepheline and normative olivine are alkali basaltic types, but rocks containing normative hy- persthene are saturated tholeiitic basaltic types. Rocks from the McClure Mountain and Gem Park Complexes appear to be alkali basaltic, whereas rocks from the complex at Democrat Creek appear to be tholeiitic basaltic. Figure 23, which is modified from Currie (1976, fig. 1), incorporates the boundary line conven- tionally used to partition alkaline basalts from tholeiitic or subalkaline basalts (MacDonald and Katsura, 1964). The plagioclase-bearing rocks from the McClure Moun— tain and Gem Park Complexes plot as members of the alkali basalt family. Plagioclase-poor pyroxenitic rocks plot as subalkaline rocks because of their deficiency in Na20 + K20, and plagioclase-rich anorthositic rocks plot near the boundary. Mafic-ultramafic rocks from the complex at Democrat Creek cluster together, well with- in the subalkaline rock field. Plots of agpaitic index (molecular proportions Na+K/A1) versus weight per- cent Si02 (fig. 24) of Gem Park rocks place them in the alkaline basalt family, whereas McClure Mountain rocks occur within the alkaline basalt family and subal- kaline rocks fields regardless of lithologic type. The Democrat Creek rocks again cluster in the subalkaline rock field. On the basis of whole-rock chemical composition, the mafic-ultramafic rocks of the McClure Mountain and Gem Park Complexes appear to be similar to and to be derived from an alkaline basalt parent. Wager and Brown (1967, p. 540) stated that they “* * *are not aware of any major layered intrusion likely to have stemmed from an alkali-basalt parent magma.” Currie (1976, p. 5) also stated that “* * * plutonic complexes of alkaline basalt composition are rare, although subvol- canic complexes such as the Monteregian Hills are com- mon.” However, Brown (1973) pointed out that layered intrusions of alkaline basalt parentage, such as Lilloise in east Greenland, are not unknown, and Currie (1976) described a few occurrences in Canada in addition to that in the Monteregian Hills. Mafic-ultramafic rocks at Democrat Creek appear to have subalkaline, satu- rated, tholeiitic affinities. LEUCOCRATIC ROCKS Chemical and normative data of hornblende-biotite syenites and nepheline syenites from the McClure Mountain Complex are given in table 4, and those of quartz syenites from the complex at Democrat Creek and of nepheline syenite pegmatite from the Gem Park Complex are given in table 5. The quartz syenites from the McClure Mountain Complex that have the WM sam- ple-number prefix were collected by R. L. Parker and W. N. Sharp of the U.S. Geological Survey; the sye— nites from Democrat Creek were collected for this study. None of the analyses has been published previ— ously. GEOCHEMISTRY TABLE 2,—Chemical and normative data of mafic-ultramfic rocks from the Iron Mountain area of the McClure Mountain Complex, south-central Colorado [Values in weight percent. Leaders (---) indicate no data. Analyses 1—9 are from Shawe and Parker, 1967, table 3; analysis 10 by Shawe and Parker, unpublished data, 1980] Analysis No.* 1 2 3 4 5 6 7 8 9 10 Field No. IM-10-64 HM-64-827 IM-20-64 HM-62-73 NM-64-828 NM-64—829 HM—64-824 IM-28-64 IM-31-64 NM-64-896A Chemical Compositions 5102 40.31 42.81 43.28 46.74 46.88 46.99 44.00 46.07 51.05 46.59 Al203 7.31 17.08 24.82 21.10 11.18 11.47 9.67 8.73 26.94 23.32 Fe203 2.81 5.53 1.54 1.51 3.47 3.09 4.36 4.07 .80 1.92 FeO 15.61 7.49 3.22 4.93 5.12 4.73 4.95 3.83 1.08 3.01 M90 25.22 6.53 9.41 7.48 10.61 10.68 13.66 11.95 1.29 4.89 CaO 5.34 13.59 12.44 13.62 19.47 20.02 20.01 21.42 12.47 15.26 Na20 .88 2.18 1.55 2.41 1.07 .94 .47 .94 3.78 2.69 K20 .14 .22 .19 .21 .09 .07 .12 .18 .62 .26 H20 1.24 .69 2.89 .74 .36 .29 .69 .48 1.00 .70 T102 .54 2.57 .11 .72 1.83 1.71 1.57 1.81 .28 .74 P205 .05 .37 .03 .13 .08 .03 .04 .06 .02 .14 Mn0 .29 .15 .07 .10 .13 .13 .13 .11 .03 .07 (202 .38 .78 .39 .33 .02 .03 .56 .37 .48 .57 Cl .01 .02 .02 .03 -—- --- .01 .02 .01 .03 F .01 .04 .01 .02 .02 .02 .02 .04 .02 .16 Total" 100.14 100.05 99.97 100.07 100.33 100.20 100.26 100.08 99.87 100.35 Normative Composition c m 0.47 -—— m m m Cr 0.83 1.30 1.12 1.24 0.53 0.41 m 3.67 1.53 Ab 7.36 18.24 12.97 18.05 4.14 2.66 m 31.95 17.24 An 15.60 36.23 59.02 46.22 25.35 26.82 23.90 19.13 54.82 50.73 Lc —-_ m -_— --- .56 .83 ——- --- Ne m .03 m 1.14 2.65 2.86 2.11 4.22 m 2.83 H1 .02 .03 .03 .05 —-— --- .02 .03 .02 .05 416 3.38 9.92 —-_ 7.64 29.30 29.98 26.70 33.53 1.60 7.99 En 3.80 6.89 .28 5.17 22.85 23.52 21.56 28.34 3.02 5.86' Fs 1.57 2.21 .06 1.89 3.25 3.14 1.99 .84 .86 1.37 F0 41.29 6.56 16.23 9.42 2.44 2.12 8.67 .98 .14 4.40 Fa 18.83 2.32 3.50 3.79 .38 .31 .88 .03 .04 1.13 Cs m ——— 2.25 1.16 m Mt 4.07 8.01 2.23 2.19 5.02 4.47 6.30 5.90 1.16 2.77 11 1.02 4.88 .21 1.37 3.46 3.24 2.97 3.44 .53 1.40 Ap .12 .88 .07 .31 .19 .07 .09 .14 .05 .33 Fr .01 .01 .02 .02 .03 .04 .03 .07 .04 .30 Cc .86 1.77 .89 .75 .04 .07 1.27 .84 1.09 1.29 01 6.52 19.02 ——- 14.70 55.40 56.63 50.25 62.72 3.05 15.22 Hy 2.23 m .34 ——- --_ —-— —-- m 2.43 -_- 01 60.12 8.88 19.73 13.22 2.82 2.43 9.55 1.01 .18 5.53 *Analysis Nos. are: 1. Clinopyroxene—plagioclase-olivine orthocumulate. 6. Clinopyroxene-plagioclase cumulate. 2. P1agioclase-clinopyroxene orthocumulate. 7. Pyroxenite from discordant intrusion. 3. Plagioclase-olivine orthocumulate. 8. Pyroxenite from discordant intrusion. 4. Plagioclase—clinopyroxene-ulivine cumulate. 9. Anorthosite from discordant intrusion. 5. C1inopyroxene-plagioclase cumulate. 10. Plagioclase-clinopyroxene ortnocumulate. 18 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO TABLE 3.—Chemical and normative data of maflc-ultmmafic rocks from the Gem Park Complex and the complex at Democrat Creek, south-central Colorado [Values in weight percent. Leaders (—--) indicate no data] Gem Park Complex Complex at Democrat Creek Analysis No.* 1 2 3 4 5 6 Field N0. NM—64-859 WM-64-875 754—299 75A—300 754-302 75A-297 Chemical Composition 5102 39.16 45.31 52.8 52.6 53.1 53.4 41203 13.72 7.03 9.3 4.8 7.4 4.8 Fe203 7.50 3.98 1.2 3.0 .5 1.9 Fe0 9.79 6.05 6.5 6.5 7.8 7.8 M90 6.68 12.84 16.8 22.2 18.2 22.5 Cal) 12.12 19.99 10.5 8.2 10.1 7.5 Na20 2.56 .82 1.3 .59 .97 .67 K20 .45 .17 .22 .15 .11 .34 H20 1.16 .84 .82 .57 .68 .66 T102 4.42 2.50 .34 .39 .45 .38 P205 1.06 .14 .08 .05 .08 .09 mo .21 .15 .13 .17 .13 .18 002 .99 .40 .02 .01 -—- .04 C .04 .02 -«- --- -<— --- F .12 .04 _.. -—— --_ —_. Total-- 99.98 100.28 100.0 99.2 99.5 100.3 Normative Composition 0 m --- m 0 5 —-_ m 0 2.66 1.00 1.3 .9 .7 2.0 A 18.84 .12 11.0 5.0 8.2 5.7 A 24.78 15.04 18.9 10.1 15.6 9 1 N 1.37 3.60 —-- «-- --— -—— H1 .07 .03 —-- <-- —-- ——- N0 9.18 33.50 13.6 12.7 14.3 11.4 En 6.49 26.45 40.0 55.7 44.8 53.5 Fs 1.90 3.29 10.1 9.2 13.3 11.9 F0 7.11 3.81 1.3 -—— .5 1.6 Fa 2.30 .52 .4 --- .2 .4 Mt 10.88 5.76 1.7 4.4 .7 2.7 11 8.40 4.74 6 .7 .9 .7 Ap 2.51 .33 2 .1 .2 .2 Fr .05 .06 —-< --- --< —-- Cc 2.25 .91 .04 .02 -—- .09 Di 17.57 63.23 25.9 24.1 27.4 21.6 Hy --- --- 37.8 53.5 45.0 55.2 01 9.41 4.33 1.7 —-— .7 2.1 *Analysis Nos. are: Plagioclase-clinopyroxene orthocumulate (Parker and Sharp, 1970, table 1). Clinopyroxene adcumulate (Parker and Sharp, 1970, Table 1). Gabbro (analyst Floyd Brown). Pyroxenite (analyst Floyd Brown). Gabbro (analyst Floyd Brown). Pyroxenite (analyst Z. A. Hamlin). Gmbwmw All hornblende-biotite syenites and nepheline sye- nites from McClure Mountain contain normative nepheline (less than 1 percent and 9—25 percent respec- tively). However, none of the rocks contains normative quartz. The syenites from Democrat Creek typically contain abundant normative quartz and lack normative nepheline. Three feldspars exist in the norms of hornblende—biotite syenite and nepheline syenite from McClure Mountain: normative Ab>0r>An and norma- | l I l I l Agpaitic 20 — syenite family — Miaskitic syenite family 15 — — O x“ Nephelinite + family 0. 2 10 — — 0 '. Alkaline basalt family 5 __ . __ Subalkalme rocks 0 l l | 30 40 50 60 70 EXPLANATION McCLURE MOUNTAIN COMPLEX D Nepheline syenite GEM PARK COMPLEX Nepheline syenite pegmatite V Mafic-ultramafic rocks 0 Hornblende—biotite syenite COMPLEX AT DEMOCRAT CREEK Quartz syenite <) Mafic nepheline- clinopyroxene rocks 0 v Mafic—ultramafic rocks v Mafic-ultramafic rocks FIGURE 23.—Plots of weight-percent alkalies versus weight—percent silica for samples from the McClure Mountain Complex, Gem Park Complex, and complex at Democrat Creek (modified from Currie, 1976, fig. 1). tive Or>Ab>An, respectively in most norms. Nearly all the quartz syenites from Democrat Creek contain two normative feldspars with Ab>Or. The CaO content of both hornblende-biotite syenites and nepheline sye— nites totals several percent by weight. The CaO content of quartz syenites, which rarely exceeds 1 percent, is so low in several samples that occurs not enough CaO to combine with all the fluorine to make normative Fr (fluorite) in the norm; therefore, excess fluorine must be listed as normative F (fluorine). This relation reflects the abundance of modal fluorite and the paucity of modal plagioclase in the quartz syenites from Democrat Creek. All the hornblende-biotite syenites and nepheline syenites are devoid of normative hyper- sthene, whereas all the quartz syenites contain it. The presence of normative olivine as well as normative nepheline in the hornblende—biotite syenites and nepheline syenites indicates that they are chemically undersaturated; neither normative olivine nor norma- tive nepheline occurs in quartz syenites. GEOCHEMISTRY 19 l I I | I l l | 1.2— Miaskitic Agpaitic syenite family — Carbonatite syenite x A family family 2m— 10% tl< ' z v >< 0.8 — Lu o O_ . E Nephelinite 0-5— family Alkaline _ U f: basalt - family 35 0.4 — 0 Subalkaline rocks < 0.2 _ 1 l 1 l 30 4O 50 60 70 $102 EXPLANATION McCLUFlE MOUNTAIN GEM PARK COMPLEX COMPLEX x Nepheline syenite pegmatite El Nepheline SYenite V Mafic-ultramafic rocks 0 Hornblende-biotite syenite COMPLEX AT DEMOCRAT CREEK Quartz syenite () Mafic nepheline- clinopyroxene rocks 0 V Mafic-ultramafic rocks v Mafic-ultramafic rocks FIGURE 24,—Plots of agpaitic index versus weight-percent silica for samples from the McClure Mountain Complex, Gem Park Complex, and complex at Democrat Creek (modified from Currie, 1976, fig. 2). Plots of the leucocratic rocks on a NaZO + K20 versus SiOz diagram (fig. 23) show that the nepheline syenites from McClure Mountain generally contain somewhat more Na20+K20 and slightly less Si02 than do the hornblende-biotite syenites; the values overlap slightly. The quartz syenites of Democrat Creek, because of their higher SiOz content, tend to plot away from the syenites from the McClure Mountain Complex. One sample of nepheline syenite pegmatite from Gem Park (analyzed by Roden, 1977) contains considerably more Na20+K20 than do the other syenites. All the hornblende-biotite syenites plot within the alkali basalt family field and are homogeneous in distribution; the nepheline syenites plot within various fields and are somewhat heterogeneous in distribution; and the quartz syenites from Democrat Creek plot in the alkaline basalt family and subalkaline rocks fields and also are heterogeneous. These plots do not provide unique solu— tions to problems of leucocratic rock genetic affiliations. Plots of leucocratic rocks on an agpaitic index versus Si02 diagram (fig. 24) provide nearly the same informa- tion. The nepheline syenite pegmatite at Gem Park is the only rock that plots in the agpaitic syenite family field. These chemical data alone show distinct differences between quartz syenites from Democrat Creek and the syenites from the McClure Mountain Complex. Al- though somewhat more subtle, chemical differences also exist between the hornblende-biotite syenites and nepheline syenites at McClure Mountain. The small ex- posure of nepheline syenite pegmatite, represented by one analysis (table 5, No. 8), shows large differences where compared with all other leucocratic rocks. MAFIC NEPHELINE-CLINOPYROXENE ROCKS Chemical and normative data of mafic nepheline- clinopyroxene rocks are given in table 4. These rocks have been found only in the McClure Mountain Com- plex. The Si02 content of the mafic nepheline- clinopyroxene rocks is similar to that of the mafic- ultramafic rocks (table 2), whereas the Na20 content is similar to that of the syenites at McClure Mountain (table 4). The P205 and Ti02 content is higher than that in most of the other rock types. Comparison of the analysis with the average derived from 41 analyses of African ijolites (LeBas, 1977, p. 307) shows a number of similarities, especially in the amounts of Si02 (40.01 percent), Ti02 (2.38 percent), NaZO (7.10 percent), and Na20/K20 ratio (2.3). The P205 content (0.88 percent) is not similar. Plots of the mafic nepheline-clinopyroxene rocks on a diagram of Na20+K20 versus Si02 (fig. 23) show they contain more abundant alkalies but comparable amounts of Si02 in comparison to the mafic-ultramafic rocks of McClure Mountain. These characteristics place these analyses in or near the nephelinite family field. Moreover, plots of these rocks on a diagram of agpaitic index versus Si02 (fig. 24) also place the analyses in the nephelinite family field. ADDITIONAL OBSERVATIONS In the diagram of Na20+K20 versus Si02 (fig. 23), rocks of comagmatic series should plot at least subparal- lel to the boundary separating the alkaline basalt family from the subalkaline rocks. If this is true, one can visu- alize that three separate rock series are illustrated: (1) the mafic-ultramafic rocks and the quartz syenites from Democrat Creek; (2) the mafic-ultramafic rocks of McClure Mountain and Gem Park Complexes and the hornblende-biotite syenites of the McClure Mountain Complex, and (3) the mafic nepheline—clinopyroxene rocks and the nepheline syenite of the McClure Moun— tain Complex, and perhaps the nepheline syenite peg— matite of the Gem Park Complex. Plots of all the analyses on a diagram of differentia- tion index versus oxide weight percent (fig. 25) show 20 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO TABLE 4.—Chemical and normative data of homblende-biotite syem'tes, nepheline syenites, and mafic nepheline-clinopyroxene rocks, McClure Mountain Complex, south-central Colorado [Values in weight percent. Leaders (m) indicate no data. Analyses 1—7 by Ellen Daniels; Nos. 8—10 by K. Coates and H. Smith] Analysis No.* 1 2 3 4 5 6 7 9 10 Fie1d No. “14-62-131 NM-62-14O WM—62-142 NM—62-143 WM-62-114 HM-62-116 NM-64-896C 75—201X 78-496 78A-498A Chemical Composition 5102 59.57 59.50 57.71 59.80 55.95 51.70 57.77 46.9 43.0 37.7 A1203 20.04 18.64 19.18 18.64 21.43 21.41 21.29 16.2 16.5 11.3 Fe203 1.41 1.65 1.86 1.46 1.28 2.31 2.33 4.7 3.1 6.2 FeO 1.80 1.80 2.09 1.93 2.09 2.34 1.73 4.7 7.4 10.6 M90 .96 1.09 1.28 1.11 .69 .67 .37 3.5 5.6 7.3 CaO 2.69 2.55 3.34 2.34 2.49 3.39 1.63 9.9 9.6 12.5 NaZO 5.98 5.37 5.39 5.82 7.36 7.65 7.46 6.7 5.4 2.4 K20 5.25 6.60 5.64 . 5.91 6.32 6.54 5.21 3.6 3.6 3.8 H20 .64 .54 .57 .76 .67 1.11 .81 1.04 1.18 2.04 T102 .86 .92 1.15 .88 .56 .94 .58 2.1 2.7 3.4 P205 .32 .41 .50 .31 .18 .19 .06 1.2 1.2 2.2 MnO .08 .11 .10 .12 .11 .16 .24 .23 .23 .31 C02 .07 .43 .45 .50 .24 1.11 .31 .02 .05 .02 C] .02 .01 .02 .01 .21 .02 .12 --- --— --- F .10 .15 .14 .15 .10 .09 .06 --- -_- ___ Total" 99.79 99.77 99.42 99.74 99.68 99.63 99.97 100.8 99.6 99.8 Normative Composition C 0.78 0.32 0.66 0.66 --— -—-— 1.60 --— --- --- 0r 31.09 39.09 33.52 35.02 37.47 38.79 30.81 21.1 17.2 --- Ab 49.33 44.00 44.79 49.11 28.71 17.51 45.48 9.7 --- --— An 10.31 6.44 9.82 5.54 7.62 4.86 5.34 3.5 10.2 8.9 Ne .66 .80 .51 .10 17.45 25.63 9.11 25.2 24.9 11.0 H1 .03 02 .03 .02 .35 .03 .20 --- --- ——- Lc --- --- --- --- --- --- --- —-- 3.3 17.6 No --- --- --- --- .61 1.33 --- 15.6 12.3 15.1 En ___ _-- --- -_- .27 .76 --- 8.6 7.7 9.4 Fs --- --- --- --- .33 .52 --- 1.7 3.9 4.8 Fo 1.68 1.91 2.25 1.94 1.02 .64 .65 —-- 4.4 6.2 Fa .67 .49 .46 .86 1.34 .48 .57 --- 2.4 3.5 Cs --- --- --- ——- --- --- --- --- ~-- .8 Mt 2.05 2.40 2.71 2.12 1.86 3.36 3.38 6.8 4.5 9.0 11 1.64 1.75 2.20 1.68 1.07 1.79 1.10 4.0 5.2 6.5 Ap .76 .97 1.19 .74 .43 .45 .14 2.8 2.9 5.2 Fr .15 .23 .20 .25 .17 .15 .11 --- --- --— Cc .16 .98 1.03 1.14 .55 2.53 .71 .05 .1 .05 Di --- --- --- --- 1.21 2.61 —-- 21.8 23.8 29.3 Hy --- --- --- --- --- --- -—- 4.1 --- --- 01 2.35 2.39 2.70 2.80 2.36 1.12 1.22 --- 6.9 9.7 *Ana1ys1's Nos. are: 1. Horanende-Diotite syenite. 6. Nepheh‘ne syenite. 2. Hornb1ende-b1'ot1'te syenite. 7. Nepheh’ne syenite. 3. Hor‘nblende-biotite syenite. 8. Mafic nepheh‘ne-ch’nopyroxene rock. 4. Hor‘nb1ende-b1'ot1'te syenite. 9. Mafic nepheline-clinopyr‘oxene rock. 5. Nepneh'ne syenite. 10. Mafic nephehne-ch‘nopyroxene rock. GEOCHEMISTRY TABLE 5.—Chemical and normative data of quartz syem'tes from the complex at Democrat Creek and nepheline syem'te pegmatite from the Gem Park Complex, south-central Colorado [Values in weight percent. Leaders (---) indicate no data. Analysis 1—7 by Z. A. Hamlin and F. Brown] Analysis No.* 1 2 3 4 5 6 7 8 Field No. 75A-363 75A-369 75A—373 75A-381 75A-382 75A-383 75A-385 GP-4 Chemical Composition SiOz 67.7 74.3 66.8 74.9 64.1 68.8 64.3 59.47 A1203 15.4 13.4 15.7 12.7 16.8 16.0 16.6 20.53 Fe203 1.3 .88 1.6 1.0 1.4 .93 1.2 2.86** Fe0 2.2 .72 1.9 .28 3.1 .92 2.5 --- M90 .12 .01 .01 .01 .16 .01 .11 .15 CaO .47 .39 .52 .25 1.1 .39 1.1 .97 NaZO 6.8 5.1 6.8 4.8 6.7 6.6 6.8 8.11 K20 4.9 4.2 4.7 4.1 5.3 4.8 5.3 8.97 H20 .52 .28 .41 .47 .59 .45 .61 —-— T102 .08 .03 .12 .02 .25 .02 .22 3.25 P205 .03 .02 .04 .02 .06 .03 .06 ——- MnO .12 .03 .12 .02 .12 .06 .12 .05 {302 ___ «- .02 .12 --- --— .16 ~- C1 --- --- .01 .02 .03 .02 .01 --- F .25 .36 .37 .1 .08 .15 .14 --- Total-- 99.9 99.7 99.1 98.8 99.8 99.2 99.2 104.36 Normative Composition 0 9.0 28.5 8.6 31.6 1.8 11.6 2.3 --- 0r 29.0 25.0 27.8 24.5 31.4 28.6 31.6 52.99 Ab 52.0 43.0 57.7 40.9 56.6 56.0 56.3 19.93 An --- -—- --— --- .2 --- --- --- Ne --- --- --- --- --- --- --- 19.32 H1 ___ -_- ___ ___ .05 .03 .02 --- Ac 3.8 --- --- --- --- .1 1.4 —-- N5 .3 --— --- --- --- --- --— 3.00 No .1 --- --- --- 1.8 .3 1.3 1.05 En .3 .02 .01 .02 .4 .02 .3 .87 F5 4.1 .5 2.3 .3 4.4 1.0 3.9 --- Mt --— 1.4 2.3 1.4 2.0 1.3 1.0 --- I] .15 .06 .2 .05 .5 .04 .4 5.54 F --— .1 .04 .4 --- --- --- --- Ap .07 .03 .1 .03 .1 .07 .1 --- Fr .51 .7 .7 .2 .2 .3 .3 --- Pf --- -—- --- --- --- --- --- .56 Di .29 --- --- --- 3.8 .6 2.7 .87 Hy 4.28 .6 2.3 .3 2.8 .8 2.7 1.05 01 --- -—- ——- -—— —-— —-- —-— --- *Analysis Nos. are: 1. Quartz syenite. 2. Quartz syenite. 3. Quartz syenite. 4. Quartz syenite. 5. Quartz syenite. 6. Quartz syenite. 7. Quartz syenite. 8. Nepheline syenite pegmatite **Total iron as Fe203. (Roden, 1977, table 1 21 3102 M90 A1203 CaO OXIDE (WEIGHT PERCENT) N320 K20 F80 F8203 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO 75 I I that the compositions of the rocks in the complexes are 65_ typically bimodal, with the exception of the mafic _ nepheline-clinopyroxene rocks. This bimodality is 55; characteristic of rock sequences that form as a result I. ”V of liquid immiscibility, although other evidence of this 45 45% W origin, such as the presence of ocellate structures, has 35 - veal v WW ‘ not been recognized. 30 , , , MINOR ELEMENTS 20— V WV MAFIC-ULTRAMAFIC ROCKS ' W V v A summary of minor-element contents of mafic- 1ojvé7g' ultramafic rocks from the three alkaline complexes is 0 I I i I presented in tables 6 and 7. Nine analyses from the 30 Iron Mountain part of the McClure Mountain Complex - VI I I I (Shawe and Parker, 1967, table 3) are included in the 207 w summary. ' v 105.7%;7 v lz—Tfl I 10— Abundances of elements in Wet Mountains mafic— ultramafic rocks, alkaline ultramafic rocks of the Kola Peninsula (Gerasimovsky, 1974, table 3), and “average” ultramafic rocks (Goles, 1967, table 11.1) are compared with the abundance of elements in igneous rocks of the upper continental crust (Wedepohl, 1971) in table 8. The alkaline rocks of the Kola Peninsula are more alkaline than are Wet Mountains pyroxenitic rocks, and the “av- erage” ultramafic rock is derived chiefly from tholeiitic rocks. Alkaline ultramafic rocks from the Kola Peninsula contain amounts of Ba, Be, Nb, Sc, Sr, V, Zr, Ga, U, Th, and other elements greater than the amounts in average igneous rocks in the Earth’s crust; Cr, Co, Ni, Cu, Pb, and other elements occur in amounts less than, ,or nearly equal to, those in average crustal rocks. The “average” ultramafic rock (Goles, 1967), on the other hand, contains abundant Co, Cr, and Ni, and low con- % 1 onhaum | EXPLANATION McCLURE MOUNTAIN COMPLEX Nepheline syenite Homblende—biotite syenite Mafic nepheline-clinopyroxene rocks OEI Mafic-ultramafic rocks GEM PARK COMPLEX Nepheline syenite pegmatite v Mafic-ultramafic rocks X COMPLEX AT DEMOCRAT CREEK 6 ‘7 o Quartz syenite PW v Mafic-ultramafic rocks 4 - V V . _ W'v FIGURE 25.—Plots of differentiation index (DI) versus oxide welght “ v ,7 WV 00D ‘3‘ . ‘ percent of rocks from the McClure Mountain Complex, Gem Park — ‘I V v 0 Complex, and complex at Democrat Creek. D1 = 2(Q+ Or+ Ab + Ne I l I I l | | l 10 20 30 40 so 60 70 so 90 100 + Lc)‘ DIFFERENTIATION INDEX GEOCHEMISTRY 23 TABLE 6.—Summary of minor-element analyses of samples from the McClure M ountaln Complex, south—central Colorado [Values in parts per million; n, number of samples; Leaders (---) indicate no data] Hornblende-biotite Nepheline syenite, Nepheline-clinopyroxene Mafic-ultramafic syenite, n = 44 n = 11 rocks, n = 8 rocks, n = 20 Mean Range Mean Range Mean Range Mean Range Ba 2527 200-7000 2479 70—5000 1320 300-3000 111 30—200 Be (1.5 (1.5-2 (1.5 (1.5-2 (1.5 (1.5-5.1 (1.5 -—- Co (5 (5—15 8.5 (5-20 27 15-50 42 5-150 Cr (1 (1—50 15 <1-150 167 2—700 285 2-1000 Cu 4.3 (1-30 11 1-50 32 7-50 77 3-200 La 78 (50-150 108 50-200 142 100-200 (30 (30-30 Mo (3 --- (3 (3—5 (3 ——- (3 --- Nb 46 10-150 88 20-300 112 70-220 (10 (10-10 N1 (3 (3-30 8 (3-50 65 7-150 128 (5-500 Pb (10 (10-20 11 <10-30 (10 (10-10 (10 --- Sc (5 (5-10 (5 (5-15 13 7-30 43 5-100 Sr‘ 1559 50—7000 2900 200-7000 1712 700-3000 844 50—3000 V 50 (IO-200 103 (7-300 258 150—500 256 30-700 Y 22 10-70 29 10-70 53 30-100 12 (10-20 Zr 158 10-1000 165 70-300 219 150-390 18 (10-70 Ce (100 (100-200 155 (150—500 1.88 (100-380 (100 --— Ga 20 15-30 24 15-30 24 20-30 14 7-20 Yb 2.2 (1-10 2.8 1.5-7 5 3-9.6 <1 <1-2 Nd (70 (70-150 84 (70-150 114 (70-200 (70 ——- U 2.44 0.53-7.06 4.01 0.9-22.4 1.4 0.9-2.2 0.2 (0.2—0.5 Th 9.04 (2.3—23.4 6.9 4.0—11.7 8.4 6.4-13.4 .7 (.1-1.4 centrations of trace elements characteristic of syenitic and granitic rocks. The mafic-ultramafic rocks from the complex at Democrat Creek (table 7) contain average amounts of Co, Cr, Cu, Ni, and Sc greater than those in average crustal rocks, and amounts of Ba, Sr, Y, Zr, Ga, Ran, and Th less than those in average crustal rocks. Thus, these rocks have minor-element signatures more similar to the “average” ultramafic rocks derived from tholeitic rocks (table 8). Mafic—ultramafic rocks from the Gem Park Complex (table 7) contain amounts of Ba, Co, Cr, Cu, Ni, Sc, Sr, V, and Ga greater than those in average crustal rocks, and amounts of Y, Zr, Ran, and Th less than those in average crustal rocks. This suite of minor ele- ments is partly characteristic of the “average” ul- tramafic rock (table 8) and partly characteristic of Kola Peninsula alkaline ultramafic rocks (table 8). Mafic-ultramafic rocks from the McClure Mountain Complex (table 6) contain amounts of Co, Cr, Cu, Ni, Sc, Sr, and V greater than those in average crustal rocks, and amounts of Ba, Y, Zr, Ran, and Th less than those in average crustal rocks. Except for barium, these minor-element signatures are similar to those of mafic—ultramafic rocks of the Gem Park Complex (table 7). These comparisons suggest that the mafic-ultramafic rocks from the complex at Democrat Creek have minor- element abundances more similar to tholeiitic rocks than to alkaline rocks. The mafic-ultramafic rocks from the McClure Mountain and Gem Park Complexes have minor-element abundances similar to each other, but the minor elements have characteristics of both alkaline and tholeiitic ultramafic rocks. LEUCOCRATIC ROCKS A summary of minor-element analyses of quartz sye- nites from the complex at Democrat Creek is given in 24 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO TABLE 7.—Summary of minor-element analyses of samples from the complex at Democrat Creek and the Gem Park Complex, south-central Colorado [Values in parts per million; n, number of samples; leaders (---) indicate no data] Complex at Democrat Creek Quartz syenite, Mafic-ultramafic Gem Park Complex Mafic-ultramafic n = 21 rocks, n = 4 rocks, n = 7 Mean Range Mean Range Mean Range Ba 320 50—2000 72 50-100 657 100-1500 Be 15 5-50 <1.5 --- <1.5 --- Co <5 —-- 50 30-70 73 50—100 Cr <1 <1-2 1675 700-3000 404 1-1000 Cu 8 <1-70 175 150-200 143 20-500 La 244 <30-500 <30 --- <30 <30-30 Mo <3 <3-5 <3 (3—7 <3 --- ND 340 70-1000 <10 ~-- <10 <10-10 Ni <5 --- 412 150—700 152 5-200 Pb 40 <10-300 <10 —-- <10 ——- Sc <3 <3-7 45 30—70 49 20-70 Sr 30 10-100 135 70-200 757 300-2000 V <5 <5-10 110 70-150 586 <7-1000 Y 95 30-150 10 <10-20 26 20-50 Zr 785 200-2000 16 (10-30 98 50-150 Ce 384 <100-700 <100 -—- <100 ——— Ga 72 50-100 7 <5-10 28 15-50 Yb 12 3-20 1.2 <1-2 <1 -—- Nd 133 <70-200 --- --- <70 <70-70 U 11.8 3-22 0.2 --- 0.4 0.2-0.62 Th 78.3 50-105 0.5 --- 2.4 1.0-3.7 table 7. A similar summary for hornblende-biotite sye- nites and nepheline syenites from the McClure Moun- tain Complex is given in table 6. Abundance of elements in alkali syenite and miaskitic nepheline syenite (Lazarenkov, 1978) and average crustal abundance of certain elements (Wedepohl, 1971) are given in table 8. The quartz syenites of the complex at Democrat Creek contain average amounts of Be, La, Nb, Pb, Y, Zr, Ce, Ga, Yb, Nd, Ran, and Th greater than crustal abundances, and amounts of Ba, Co, Cr, Cu, Ni, Sc, Sr, and V less than crustal abundances. Hornblende- biotite syenites from the McClure Mountain Complex contain average amounts of Ba, La, Nb, and Sr greater than crustal abundances and amounts of Co, Cr, Cu, Ni, Sc, V, Y, Zr, Ran, and Th less than crustal abun- dances. The nepheline syenites from the McClure Mountain Complex contain average amounts of Ba, La, Nb, Sr, Ce, Ga, and Nd greater than crustal abun- dances, and amounts of Cr, Cu, Ni, Sc, Ran, and Th less than crustal abundances; some elements occur in amounts similar to crustal abundances. Considerable differences exist in the average content of minor elements in the syenites from Democrat Creek and McClure Mountain. The quartz syenites from the complex at Democrat Creek contain greater average amounts of Be, La, Nb, Pb, Y, Zr, Ce, Ga, Yb, Nd, Ran, and Th than do the syenites from the McClure Mountain Complex. According to Gerasimovsky (1974, p. 406), all these elements, excluding lead, are charac- GEOCHEMISTRY' 25 TABLE 8.—Abundance of elements in several types of rocks [Values in parts per million. Leaders (—»-) indicate no data] Analysis No.* 1 2 3 4 5 Ba 590 1557 1388 850 0.4 Be 2 --- --— 7.4 . C0 12 14 9.3 15 110 Cr‘ 70 11 16 30 2400 Cu 30 7.8 23 34 30 La 44 146 134 —-- --- MO 1 -—— --- —-— .2 ND 20 70 89 300 --< N1 44 6.9 10 36 1500 PD 15 25 35 13 .05 SC 14 --— —-— 24 16 Sr 290 434 835 1300 20 V 95 26 52 440 40 Y 34 64 62 --- 5 Zr‘ 160 , 510 411 340 30-45 Ce 75 ——- --- ___ -__ Ga 17 27 30 26 5 Yb 3.4 -—— _-- ___ ___ Nd 3O -—-- ___ ___ ___ U 3.5 4.5 4.8 15 .02 Th 11 20 13.2 90 .06 *Analysis Nos. are: 1. Abundance of elements in igneous rocks of the upper continental crust (Wedeponl, 1971, table 7.3). Alkali syenite (Lazarenkov, 1978, table 1). 2. 3. Miaskitic nepheline syenite (Lazarenkov, 1978, table 1). 4 Alkaline ultramafic rocks, Kola Peninsula. (Gerasimovsky, 1974, table 3). 5. "Average" ultramafic rock (Goles, 1967, table 11.1). teristic of agpaitic nepheline syenites, which by defini— tion (Sorensen, 1974b, p. 23) have the ratio (Na20+K20)/A1203 (molecular proportions) greater than one. This agpaitic index (see fig. 24) averages 1.007 for the seven chemical analyses of quartz syenite in table 5, but the quartz syenites possess few addi- tional characteristics of agpaitic nepheline syenites (Sorensen, 1974b, p. 24). The quartz syenites also con- tain less average amounts of Ba, Co, Cr, Ni, Sr, and V than do the nepheline syenites. These elements, ex- cept barium and strontium, chiefly reside in the mafic mineral assemblage; the paucity of mafic minerals in the quartz syenites reflects this characteristic. The paucity of barium and strontium is usually a function of crystallization and removal of feldspar from the mag- matic system. This deficiency, especially of strontium, in the quartz syenites relative to barium and strontium in the associated mafic-ultramafic rocks is perplexing, and may suggest a low concentration of strontium and probably barium in the crystallizing magma. The quartz syenites at Democrat Creek contain high average abundances of uranium and thorium. Eighteen samples contain 12.9 ppm Ran (15 ppm U308) and 80.4 ppm thorium (91 ppm ThOz). For comparison, the Mes- ozoic Conway Granite of New Hampshire contains simi- lar abundances of uranium (15 ppm U308), but some- what less thorium (64 ppm ThOg). MAFIC NEPHELINE-CLINOPYROXENE ROCKS The average composition of eight samples of mafic nepheline-clinopyroxene rocks is given in table 5. These rocks contain average amounts of Ba, Co, Cr, La, Nb. Sr, V, Y, Zr, Ce, Yb, and Nd greater than crustal abundance, and average amounts of lead less than crus- tal abundance (table 8). Be, Cu, Ni, Sc, and Ga occur in amounts similar to crustal abundance. These rocks possess minor-element signatures similar to those of alkaline ultramafic rocks of the Kola Peninsula (table 8). RUBIDIUM-STRONTIUM SYSTEMATICS AND RARE-EARTH-ELEMENT DISTRIBUTION PATTERNS Concentrations of rubidium, strontium, rare-earth elements, and strontium isotopes have been determined in several alkaline rocks by C. E. Hedge and reported in Armbrustmacher, Hedge, and Parker (1979) and in Armbrustmacher and Hedge (1982). These values are given in tables 9 and 10. RARE-EARTH ELEMENTS Chondrite-normalized rare-earth-element (REE) data for mafic rocks from the complex at Democrat Creek and the McClure Mountain Complex are plotted on fig- ure 26, along with data from Kay and Gast (1973) for tholeiitic mid-ocean—ridge basalt, alkali basalt, and nephelinite. The gabbroic rock from Democrat Creek contains less total REE than do the several types of basalts, and it shows some increase in the light— to heavy-REE ratio relative to amounts of REE in the tholeiitic basalt. The mafic cumulate rocks from the McClure Mountain Complex contain total amounts of REE comparable to those in tholeiitic basalt, but the light REE are enriched and the heavy REE depleted relative to the tholeiitic basalt. Total REE content of cumulus rocks from the McClure Mountain Complex is greater than that in the Democrat Creek mafic rock; however, the McClure Mountain cumulates contain less 26 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO TABLE 9,—Rubldium and strontium content (in parts per million) and several ratios for rocks from the McClure Mountain Complex and the complex at Democrat Creek, south-central Colorado [Analyses by C. E. Hedge; leaders (--») indicate no data] Initial Field No. Rock type Rb Sr Rb/Sr 87RD/86Sr‘ 873r/855r 87Sr/86Sr‘ McClure Mountain Complex NM-64-827 Plagioclase—clinopyroxene cumulate 3.17 1010 0.0031 0.0091 0.70484 0.70477 NM-64—829 --do-- 1.69 370 0.0046 0.0132 0.70454 0.70444 417 Nepheline syenite 126 1725 0.0730 0.2113 0.70519 0.70359 NM-62-116 --do-- 134 2939 0.0456 0.1318 0.70497 0.70397 4 —-d0—- 161 2266 0.0711 0.1890 0.70515 0.70372 421 --do—- 194 103 1.883 5.470 0.74548 -~— NM-62-143 Hornblende-biotite syenite 94.6 542 0.1745 0.5048 0.70856 0.70475 8 --do-- 86.9 487 0.1784 0.5166 0.70831 0.70441 12 -—do—- 98.4 530 0.1857 0.5371 0.70819 0.70413 21 --do-- 92.0 531 0.1733 0.5019 0.70821 0.70442 419 Carbonatite 0.3 4997 0.00006 0.00020 0.70378 0.70378 419x -—do-- 0.6 11632 0.00008 0.00016 0.70406 0.70406 496 Mafic nepheline-clinopyroxene rock 97.1 1582 0.0614 0.1775 0.7050 0.7037 498A ——do-— 78.6 1370 0.0574 0.1660 0.7051 0.7038 Complex at Democrat Creek 299 Gabbro 5.25 285 0.0184 0.0535 0.70290 0.70252 302 --do-- 1.32 208 0.0063 0.0183 0.70309 0.70296 359 Pyroxenite 3.42 162 0.0211 0.0609 0.70384 ’0.70340 412 Quartz syenite 96.9 474 0.2044 0.5923 0.70746 0.70315 413 --do-- 251 34.1 7.361 21.61 0.86059 --— 414 --do-- 174 26.1 6.667 19.54 0.84414 --- 363 -—do-- 297 11.0 27.00 82.47 1.3146 --— 369 —-do-- 233 10.4 22.40 67.84 1.1893 -—— 382 --do-- 172 41.9 4.105 12.00 0.79088 --— abundant REE than do the alkali basalt and the nephelinite. Using the modal analyses of the mafic-ultramafic rocks and published crystal-to-liquid distribution coeffi- cients for the component minerals, and assuming that the rocks formed by cumulus processes, one can calcu— late the REE patterns for the liquids from which these mafic rocks crystallized. These patterns are shown with the REE pattern for alkali basalt on figure 27. The close similarity of these REE patterns suggests that the liquids from which the gabbro at Democrat Creek and the cumulus mafic rocks at McClure Mountain Com- plex crystallized are similar in REE composition to a normal alkali basalt magma. Just as the REE content 0f the basalts increases in the order tholeiite-alkali basalt-nephelinite (fig. 26), perhaps the liquid from which the McClure Mountain cumulates crystallized had a slightly higher alkali content than the liquid from which the gabbros at Democrat Creek crystallized; the result is the more tholeiitic composition of the Democrat Creek rocks. Chondrite-normalized REE data for the various sye— nites (table 2) are plotted on the diagrams in figures 28, 29, and 30. The REE patterns of the hornblende— biotite syenites (fig. 28) in the McClure Mountain Com- plex vary only slightly. This small variation correlates with their small variations in modal mineralogy, norma- tive mineralogy, and major-element abundances. Their GEOCHEMISTRY 27 TABLE 10.——Rare-earth-element content (in parts per million) of rocks from the McClure Mountain Complex and the complex at Democrat Creek, south-central Colorado [Analyses by C. E. Hedge; leaders (m) indicate no data] Field No. Rock type Ce Nd Sm Eu Gd Dy Er Yb McClure Mountain Complex NM-64-827 Plagioclase-clinopyroxene cumulate 25.0 15.7 3.71 1.36 5.28 2.71 1.20 0.860 WM-64-829 —~do-- 12.6 13.0 3.97 1.36 5.33 3.57 1.57 1.06 417 Nepheline syenite 108 37.8 5.74 2.34 - 4.34 3.52 1.98 1.90 NM-62-116 --do-- 159 60.5 9.38 2.78 6.39 4.98 2.37 1.95 421 -—do-— 104 32.7 4.58 0.871 4.02 2.30 1.32 1.19 WM-62-143 Hornblende—biotite syenite 119 46.2 7.29 2.64 5.37 3.95 2.25 1.65 8 -—do-- --- 50.0 7.95 2.87 5.93 4.38 2.05 1.64 21 --do-— 104 39.0 6.11 2.54 4.67 3.34 1.69 1.41 419 Carbonatite 3308 1346 177 51 1 --- 116 51.3 38.5 419x --do—— 648 220 34.9 10 3 —-- 22 9 13.2 13.9 Complex at Democrat Creek 299 Gabbro 10.8 6.64 1.71 0.521 2.03 1.43 0.787 0.722 412 Quartz syenite 116 45.6 8.26 2.58 7.05 6.32 3.52 3.40 413 --do-— 470 122 18.8 0.966 17.5 19.4 12.9 14.1 small positive europium anomalies are due to the pres— ence of sodic plagioclase. The REE patterns of nepheline syenites (fig. 29) show small positive and negative europium anomalies, which also correlate re- spectively with more and less modal plagioclase. These patterns also correlate with the variability in modal mineralogy of these rocks. The REE patterns of the quartz syenites of the complex at Democrat Creek (fig. 30) vary considerably. One pattern has a fairly large negative europium anomaly that corresponds to low CaO (<1.0 percent) and low strontium contents (34 parts per million). These data suggest that this rock crystallized from a melt from which plagioclase had been removed. In summary, the REE data show that the Democrat Creek mafic rocks are slightly, but significantly, differ- ent from the McClure Mountain Complex cumulates. The liquids from which the Democrat Creek mafic rocks crystallized appear to have been less alkaline than the liquids from which the McClure Mountain Complex cumulates crystallized. The REE patterns for the sye— nites reflect the homogeneity and apparent lack of evi- dence of fractionation of the hornblende-biotite syenite, the variation in plagioclase content because of some fractionation in the nepheline syenites, and the strong evidence of fractionation because of loss of plagioclase in the quartz syenites at Democrat Creek. INITIAL 87Sr/86Sr RATIOS Initial 87Sr/868r ratios for alkaline rocks of the Wet Mountains area range in value from 0.7025 to 0.7048 (fig. 31). Uncertainty of these ratios is less than $00001. Mafic-ultramafic rocks from the complex at Democrat Creek have initial values that range from 0.7025 to 0.7034, and one sample of quartz syenite has a value of 0.7032. Mafic-ultramafic rocks from the McClure Mountain Complex have values of 0.7044 and 0.7048, nepheline syenites range from 0.7036 to 0.7040, hornblende-biotite syenites range from 0.7041 to 0.7048, mafic nepheline-clinopyroxene rocks have values of 0.7037 and 0.7038, and six carbonatites, including four analyzed by Roden (1977), have values of 0.7036 to 0.7041. The Democrat Creek rocks appear to form a distinct group characterized by rather low initial 87Sr/ 86Sr values. At the McClure Mountain Complex, hornblende-biotite syenite has initial 87Sr/8GSr ratios similar to those of the mafic-ultramafic cumulate rocks but different from the nepheline syenites, the mafic nepheline-clinopyroxene rocks, and the carbonatites, which constitute a separate group having similar val- ues. The carbonatites that intrude the Gem Park Com- plex have ratios (Roden, 1977) similar to carbonatites that intrude the McClure Mountain Complex. A summary of strontium isotopic contents of alkaline 28 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO I I I I I I I EXPLANATION O Tholeiitic midocean ridge basalt (Kay and Gast, 1973, fig. 1, sample 6) O Alkali basalt (Kay and Gast, 1973, 1000 .— table 2F, average of samples 04 and : K12) : X NephelinitelKay and Gast, 1973, table _ ZB,average of samples K17, K23, 023, and 035) W Mafic rock, McClure Mountain Complex I|||||I I l Mafic rock, complex at Democrat Creek 100 IIIIIII REE SAMPLE/REE CHONDRITE | «,3m "3 I _\ O IIIIIII |||I|II I I 1 J I I I I I I I Ce Nd Sm Eu Gd Dy Er Yb RAR E-EARTH ELEM ENTS FIGURE 26.—Chondrite-normalized rare-earth—element data for mafic rocks from McClure Mountain Complex, the complex at Democrat Creek, and other basalt samples (from Kay and Gast, 1973). 100 _— uJ _ I: _ m _ D ._ Z _ O I _ U |.I.l _ LLI a: \ 3 1o _— — LL _ I m — EXPLANATION a w : v Mafic rock, McClure Mountain Complex _ o: - V Mafic rock, complex at Democrat Creek — o Alkali basalt (Kay and Gast, 1973, fig. 7) — I I I I I I I I 1 Ce Nd Sm Eu Gd Dy Er Yb RARE EARTH ELEMENTS FIGURE 27.—Chondrite—normalized rare-earth-element data for liquids from which mafic rocks of McClure Mountain Complex and complex at Democrat Creek crystallized. Data are calculated from published crystal/liquid distribution coefficients. 1°°°: I I I | I I I : Ii‘ _ E 143 100 4 — Z : 21 : o k 8 _ I _ L U a a LIJ L _ Lu 9: _ _ \ LI.| _l _ _ D. 2 < w 10: f Lu ‘ _ LU — _ D: m __ 1 I I I I I I I Ce Nd Sm Eu Gd Dy Er Yb RARE-EARTH ELEM ENTS FIGURE 28.——Chondrite—normalized rare-earth-element data for hornblende-biotite syenite samples from the McClure Mountain Complex. rocks from Australia, Spain, and the Western United States (Powell and Bell, 1970) shows initial 87Sr/868r ratios ranging from 0.7034 to 0.7169; some of the values are similar to those of oceanic basaltic rocks. But ratios for rocks from the Western United States (from 0.703 to 0.709) suggested to Powell and Bell that those rocks may have formed by partial melting of deep crustal rocks that have lower rubidium/strontium ratios than those of average crust. Bell and Powell (1970) showed a range of initial 87Sr/E’GSr ratios between 0.7029 and 0.7061 for carbonatites and alkaline rocks from eastern Uganda; the carbonatites average 0.7034 and the as- sociated alkaline rocks average 0.7045. These differ- ences indicated to them that the rocks are not related solely by magmatic differentiation from a single parent magma. Compared with these data, the Wet Mountains rocks have a considerably narrower range in initial 87Sr/ 86Sr ratios, and the carbonatites have ratios comparable with those of nepheline syenite and mafic nepheline— clinopyroxene rock. In summary, samples from the complex at Democrat Creek have distinctly lower initial 87Sr/868r ratios than do those from the McClure Mountain Complex. Within the McClure Mountain Complex, the mafic-ultramafic cumulates and the hornblende-biotite syenites have in- itial 87Sr/g‘ISr ratios that are similar, and the nepheline syenites, the mafic nepheline-clinopyroxene rocks, and the carbonatites all have similar ratios. These data GEOCHEMISTRY 29 1°°° ; I I I I : Lu — 1 16 — .— E 41 Q _ _a Z 100 : j C — 421 g I — - U — # |.|.l *- _ Lu m — _ \ LL! .1 — _ D. 3 (D 10 _— —: a : a n: : : 1 I I I I I I I I Ce Nd Sm Eu Gd Dy Er Yb RARE-EARTH ELEMENTS FIGURE 29.—Chondrite—normalized rare—earth-element data for nepheline syenite samples from the McClure Mountain Complex. suggest that at least three separate magmatic sources, originating in the upper mantle or lower crust, are re- sponsible for the Wet Mountains alkaline rocks. RUBIDIUM/STRONTIUM RATIOS Rubidium and strontium concentrations and Rb/Sr ratios (table 9) suggest additional petrologic aspects of these rocks. The rubidium content of the mafic- ultramafic rocks from the McClure Mountain Complex and the complex at Democrat Creek is low. Values range from 1.3 to 5.3 ppm. These low values are consis— tent with a cumulus origin for the mafic-ultramafic rocks at Democrat Creek as well as with those from the McClure Mountain Complex, because rubidium tends to be depleted in plagioclase and pyroxene—the major minerals in these rocks—and is concentrated in the residual melt. The highly variable Rb/Sr ratios in quartz syenites in the complex at Democrat Creek range from 4.1 to 27. This wide range reflects the highly fractionated nature of these rocks. The consis- tent Rb/Sr ratios of the hornblende-biotite syenites in the McClure Mountain Complex range from 0.17 to 0.18, and suggest that these rocks are not fractionated. The Rb/Sr ratios of nepheline syenite and mafic nepheline-clinopyroxene rocks also tend to be somewhat variable. Figure 32 shows the distribution of rubidium and strontium values for rocks of the McClure Mountain 100°; | | I I I I 1 — 413 : m _ _ L‘ n: 412 O _ _ z 100 : : O _ _ I _ a U _ _ m — _ Lu CC V - \ Lu _J _ _ D. E < w 10 _— __ ”" ' : “J _ _. I : _ 1 I I I I I I I I Ce Nd Sm Eu Gd Dy Er Yb RARE—EARTH ELEM ENTS FIGURE 30.—Chondrite-normalized rare-earth—element data for quartz syenite samples from the complex at Democrat Creek. I I 9 O o . x O o o I' 'I ' 'IUOC’ODIXo vI V 0.7020 0.7030 0.7040 0.7050 INITIAL ”Sr/8681* RATIO EXPLANATION COMPLEX AT DEMOCRAT McCLURE MOUNTAIN CREEK COMPLEX o Quartz syenite x Carbonatite V Mafic-ultramafic rocks D Nepheline syenite O Mafic nepheline- GEM PARK COMPLEX clinopvroxene rocks . Carbonatites(from 0 Hornblende-biotite syenite Roden, 1977) V Mafic—ultramafic rocks FIGURE 31,—Distribution of initial 87Sr/g‘SSr ratios for alkaline rocks of the Wet Mountains area. Complex. The plotting of the mafic rocks below the Rb— Sr diagonal is a consequence of their cumulus origin— the liquid remaining after the removal of pyroxenes and plagioclase would contain proportionately more rubidi- um than the resulting cumulus rocks. Figure 32 also shows that three of the nepheline syenites and the mafic nepheline-clinopyroxene rocks lie on or near the Rb-Sr diagonal, indicating that the Rb/Sr ratios of these rocks are similar to those of the material from which they were derived. The fourth nepheline syenite and a sam- ple of red syenite lie on a line that is a trend of Rb—Sr 30 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO 100 IIIIIII I O IIIIIIII I EXPLANATION Nepheline syenite Hornblende-biotite syenite IIIIIII O Mafic nepheline-clinc- pyroxene rocks — V Mafic—ultramafic rocks 10 I Red syenite dike ,, IIIIIII RUBIDIUM (IN PARTS PER MILLION) V IIIIIII I II 1000 1 lflml IIIIIII 10 100 STRONTIUM (IN PARTS PER MILLION) FIGURE 32.—Rubidium/strontium ratios of rocks from the McClure Mountain Complex. Patterned area represents approximate Rb/Sr ratios required to yield observed ”Sr/8681' ratios. values best developed by fractionation of nepheline- bearing rocks. The hornblende-biotite syenites homogeneously possess higher Rb/Sr ratios than their calculated parent and do not lie on the Rb—Sr diagonal. Figure 33 shows the Rb/Sr ratios of rocks from the complex at Democrat Creek. The fact that the mafic-ul- tramafic rocks again plot below the Rb-Sr diagonal suggests a cumulus origin for these rocks also. No rocks have Rb/Sr ratios that plot near the Rb/Sr diagonal, and thus a complicated process is required to increase the Rb/Sr ratios of the quartz syenites to more than those of the calculated parent magma—rocks reflecting this process, if present, have not been identified in this study. The distribution of Rb/Sr ratios in the quartz syenites shows a more or less progressive decrease in strontium that suggests fractionation through removal of plagioclase. This fractionation as also suggested by the REE data (fig. 30). PETROLOGIC CONCLUSIONS The mafic-ultramafic cumulus rocks from the McClure Mountain and Gem Park Complexes typically contain normative nepheline and normative olivine but lack nor- mative quartz and normative hypersthene. This as- semblage is characteristic of alkali basalt types. The mafic-ultramafic rocks from the complex at Democrat Creek contain abundant normative hypersthene but lack normative nepheline and normative quartz. This I IIIIIIII I IIIII o _ g $\\\. — o \f\ \ \\ \ g Iooo_— \\ : :l _ _ =1 7 _ E : EXPLANATION : E a . _ n. O Quartz syenIte f2 ‘ v Mafic-ultramafic rocks I: <1; _ n. E E 100* 2 I e _ m _ 3 _ I: 1 I I | I | I | I I I I I | I | | I 10 100 1000 STRONTIUM (IN PARTS PER MILLION) FIGURE 33.—Rubidium/strontium ratios of rocks from the complex at Democrat Creek. Solid line indicates approximate Rb/Sr ratios required to yield observed ”Sr/8681‘ ratios. Dashed line indicates fractionation. assemblage is characteristic of saturated tholeiitic basalt types. Minor-element contents of mafic- ultramafic rocks of the complex at Democrat Creek are similar to those of alpine-type ultramafic rocks and ul- tramafic rocks of layered calc-alkaline intrusions. Minor-element contents of mafic-ultramafic cumulus rocks from the McClure Mountain and Gem Park Com— plexes are similar; they have characteristics of the more silica—saturated alpine-type ultramafic rocks and ul- tramafic rocks of layered calc-alkaline intrusions, as well as of some of the strongly silica-undersaturated alkaline ultramafic rocks. The hornblende—biotite syenites and the nepheline syenites from the McClure Mountain Complex contain normative nepheline and thus lack normative quartz. The quartz syenites from the complex at Democrat Creek contain abundant normative quartz but lack nor- mative nepheline. The hornblende—biotite syenites con- tain normative Ab>Or>An, the nepheline syenites con- tain normative Or>Ab>An, and the quartz syenites contain only normative Ab>Or. The quartz syenites contain normative hypersthene, but the other syenites do not. The hornblende-biotite syenites and nepheline PETROLOGIC CONCLUSIONS 31 COMPLEX AT DEMOCRAT CREEK McCLURE MOUNTAIN AND GEM PARK COMPLEXES Mafia-ultra— Quartz McClure Mountain McClure Mountain: McClure Mountain: McClure Mountain: mafic rocks syenite and Gem Park: mafic- hornblende—biotite nepheline syenite mafic nepheline- (0.7025—0.7034) (0.7032) ultramafic cumulates syenite (0.7041— (0.7036—0.7040) clinopyroxene rocks (01044—07048) 0.7048) (07037—07038) McClure Mountain and Gem Park: carbonatite (0.7036—0.7041) MAGMATIC MAGMATIC MAGMATIC SOURCE A SOURCE B SOURCE C FIGURE 34.—Grouping according to initial 87Sr/gGSr ratios (values in parentheses) of rock types of alkaline complexes in the Wet Mountains area. syenites are chemically undersaturated; this is indicated by the presence of normative olivine as well as norma— tive nepheline. The quartz syenites lack normative oli- vine as well as normative nepheline. Minor-element con- tents are considerably different among the several types of syenites. The quartz syenites contain a suite of elements characteristic of agpaitic nepheline sye- nites, even though they possess none of the other traits of these rocks. The quartz syenites are also deficient in those elements typically concentrated in the mafic- mineral assemblage of a rock. The major- and minor- element contents of the mafic nepheline—clinopyroxene rocks are similar to those of alkaline mafic and ul- tramafic rocks. The significant differences in age, mineralogy, chemistry, and initial 87Sr/E‘GSr ratios between the McClure Mountain Complex and the complex at Demo- crat Creek point out the fundamental genetic differ- ences between the two complexes. How much time might have been involved in the emplacement of the various rock types of the McClure Mountain Complex is not known, but the differences in initial 87Sr/8GSr ratios and minor element geochemis- try require at least two source materials. The nepheline syenites and the carbonatites have similar 87Sr/E‘GSr ratios; therefore, they possibly were derived from the same source, and their profound differences in chemis- try and mineralogy are possibly due to some process such as liquid immiscibility. Initial 87Sr/S‘S'Sr ratios of the hornblende-biotite sye- nites and the mafic—ultramafic rocks are similar, but are distinct from those of the nepheline syenites. A genetic relationship between the hornblende-biotite syenites and the mafic-ultramafic rocks is possible, but such a hypothesis cannot be tested rigorously because the nec— essary intermediate rocks are not available for study. Mafic-ultramafic rocks are cumulates. Their extremely mafic mineralogy and their trace—element geochemistry indicate that they are cumulates of a more mafic magma than are the hornblende-biotite syenites. The hornblende-biotite syenites possibly fractionated from this mafic magma. The rather high Rb/Sr ratios of the hornblende—biotite syenites are consistent with such a process, but the positive europium anomalies are not. The hornblende-biotite syenites have lower strontium contents than do the nepheline syenites but higher in- itial 87Sr/ngSr ratios. Therefore, the hornblende-biotite syenites possibly were derived from the nepheline sye- nites with the addition of radiogenic 87Sr from the Pre- cambrian wall rocks. This hypothesis could explain the data, however, only if significant fractional crystalliza- tion that lowered the strontium content occurred to- gether with the assimilation that raised the 87Sr/S‘BSr ratio. Fractional crystallization that would greatly lower the strontium content would have to involve plagioclase; plagioclase removal would produce negative europium anomalies, whereas the hornblende-biotite syenites actually have positive europium anomalies. The only mechanism that can be envisioned for the genesis of the hornblende-biotite syenites that would be compatible with their high Rb/Sr ratios and positive europium anomalies is that the syenites represent es- sentially primary magmas formed by a partial melting process that left a residue rich in pyroxene. The pyrox— ene would retain significant strontium but would not have a relative preference for europium. Apparently a minimum of three distinct source mate- rials and several geologic processes were necessary to produce the major alkaline rock types observed in the Wet Mountains area. This complicated situation is dia— gramed in figure 34. Only one source material is neces- sary to form the rocks of the complex at Democrat Creek, and the rock types there might be simply de- scribed as products of fractional crystallization. The hornblende-biotite syenites of the McClure Mountain Complex and the mafic-ultramafic rocks of the McClure Mountain and Gem Park Complexes ultimately may have been derived from the same source material, but 32 ALKALINE ROCK COMPLEXES IN THE WET MOUNTAINS AREA, COLORADO mafic-ultramaflc rocks are cumulates from a basaltic magma that was probably not directly related to the hornblende-biotite syenite magma. Similarly, the nepheline syenites and the carbonatites might have been derived from the same source material. The source materials for the alkaline rocks in the Wet Mountains area might have been rocks that differed in basaltic compositions. A gabbro of tholeiitic composition would be a suitable source material for the rocks of the complex at Democrat Creek. A more alkaline gab— bro might be a suitable source for the hornblende-bio- tite syenites of the McClure Mountain Complex, whereas a gabbro of nepheline basalt composition may have been the source of the nepheline syenites. Al- though this narrative is admittedly speculative, a his- tory of formation at least this complicated is necessary to account for rocks so diverse and so closely related spatially. REFERENCES CITED Armbrustmacher, T. J., 1979, Replacement and primary magmatic carbonatites from the Wet Mountains area, Fremont and Custer Counties, Colorado: Economic Geology, v. 74, no. 4, p. 888—901. 1980, Major- and minor-element distribution in alkaline rock complexes of the Wet Mountains area, Custer and Fremont Counties, Colorado: Geological Society of America Abstracts with Programs, v. 12, no. 6, p. 266. Armbrustmacher, T. J ., and Banks, N. G., 1974, Clouded plagioclase in metadolerite dikes, southeastern Bighorn Mountains, Wyom- ing: American Mineralogist, v. 59, p. 656—665. Armbrustmacher, T. J., and Brownfield, I. K., 1978, Carbonatites in the Wet Mountains area, Custer and Fremont Counties, Col- orado—Chemical and mineralogical data: U.S. Geological Survey Open-File Report 78—177, 6 p. Armbrustmacher, T. J., Brownfield, I. K., and Osmonson, L. M., 1979, Multiple carbonatite at McClure Gulch, Wet Mountains a1— kalic province, Fremont County, Colorado: Mountain Geologist, v. 16, no. 2, p. 37—45. Armbrustmacher, T. J ., and Hedge, C. E., 1982, Genetic implications of minor—element and Sr-isotope geochemistry of alkaline rock complexes in the Wet Mountains area, Fremont and Custer Counties, Colorado: Contributions to Mineralogy and Petrology, v. 79, p. 424—435. Armbrustmacher, T. J., Hedge, C. E., and Parker, R. L., 1979, Al- kaline rock complexes in the Wet Mountains area, Fremont and Custer Counties, Colorado: Genetic implications of minor—element and Sr—isotope geochemistry: Geological Society of America Abstracts with Programs, v. 11, no. 7, p. 3804381. Becker, R. M., Shannon, S. 8., Jr., and Rose, C. K., 1961, Iron Mountain titaniferous magnetite deposit, Fremont County, Col- orado: U.S. Bureau of Mines Report of Investigations 5864, 18 p. Bell, Keith, and Powell, J. L., 1970, Strontium isotopic studies of alkalic rocks—the alkalic complexes of eastern Uganda: Geologi- cal Society of America Bulletin, v. 81, p. 3481—3490. Brock, M. R., and Singewald, Q. D., 1968, Geologic map of the Mount Tyndall quadrangle, Custer County, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ-596, scale 1:24,000. Brown, P. E., 1973, A layered plutonic complex of alkali basalt paren- tage—The Lilloise intrusion, east Greenland: Journal of the Geological Society of London, v. 129, p. 405—418. Christman, R. A., Brock, M. R., Pearson, R. C., and Singewald, Q. D., 1954, Wet Mountains, Colorado, thorium investigations, 1952—1954: U.S. Geological Survey Trace Elements Investiga- tions Report 354, 52 p. 1959, Geology and thorium deposits of the Wet Mountains, Colorado—a progress report: U.S. Geological Survey Bulletin 1072—H, p. 491—535. Currie, K. L., 1976, The alkaline rocks of Canada: Geological Survey of Canada Bulletin 239, 228 p. Fenton, M. D., and Faure, G., 1970, Rb-Sr whole-rock age determina— tions of the Iron Hill and McClure Mountain carbonatite-alkalic complexes, Colorado: Mountain Geologist, v. 7, no. 4, p. 269—275. Gerasimovsky, V. I., 1974, Trace elements in selected groups of al- kaline rocks, in Sorensen, H., ed., The alkaline rocks: New York, John Wiley, p. 402—412. Goles, G. G., 1967, Trace elements in ultramafic rocks, in Wyllie, P. J ., ed., Ultramafic and related rocks: New York, John Wiley, p. 352—362. Heinrich, E. W., 1966, The geology of carbonatites: Chicago, Rand McNally, 555 p. Heinrich, E. W., and Alexander, D. H., 1976, Infinite variations on a fenite theme [abs]: 25th International Geology Congress, Au- stralia, v. 1, p. 124—125. 1979, Geology and petrogenesis of the dike retinue of the McClure Mountain mafic—alkalic complex, Colorado, U.S.A. [abs.]: Geological Association of Canada-Mineralogical Association of Canada annual meeting, Program with Abstracts, v. 4, p. 56. Heinrich, E. W., and Dahlem, D. H., 1966, Carbonatites and alkalic rocks of the Arkansas River area, Fremont County, Colorado: Mineralogical Society of India, IMA volume, p. 37—44. 1967, Carbonatites and alkalic rocks of the Arkansas River area, Fremont County, Colorado, pt. 4. The Pinon Peak breccia pipes: American Mineralogist, v. 52, p. 817—831. 1969, Dikes of the McClure Mountain—Iron Mountain alkalic complex, Fremont County, Colorado, U.S.A.: Bulletin Vol- canologique, v. 33, p. 960—976. Heinrich, E. W., and Moore, D. G., Jr., 1970, Metasomatic potash feldspar rocks associated with igneous alkalic complexes: Cana— dian Mineralogist, v. 10, pt. 3, p. 571—584. Jackson, E. D., 1961, Primary textures and mineral associations in the ultramafrc zone of the Stillwater Complex, Montana: U.S. Geological Survey Professional Paper 358, 106 p. Jaffe, H. W., Gottfried, David, Waring, C. L., and Worthing, H. W., 1959, Lead-alpha age determinations of accessory minerals of igneous rocks (1953—1957): U.S. Geological Survey Bulletin 1097—B, p. B65—B148. Kay, R. W., and Gast, P. W., 1973, The rare earth content and origin of alkali-rich basalts: Journal of Geology, v. 81, no. 6, p. 653—682. Lazarenkov, V. G., 1978, Differences in trace-element composition between effusive and intrusive alkalic rocks: Geochemical Inter— national, v. 15, no. 4, p. 80—83. LeBas, M. J., 1977, Carbonatite-nephelinite volcanism—An African case history: London, John Wiley, 347 p. MacDonald, G. A., and Katsura, T., 1964, Chemical composition of Hawaiian lavas: Journal of Petrology, v. 5, p. 82—133. Olson, J. C., and Marvin, R. F., 1971, Rb—Sr whole-rock age determi- nations of the Iron Hill and McClure Mountain carbonatite-alkalic complexes, Colorado—Discussion: Mountain Geologist, v. 8, no. 4, p. 221. REFERENCES CITED 33 Olson, J. C., Marvin, R. F., Parker, R. L., and Mehnert, H. H., 1977, Age and tectonic setting of lower Paleozoic alkalic and mafic rocks, carbonatites, and thorium veins in south-central Colorado: U.S. Geological Survey Journal of Research, v. 5, p. 673—687. Parker, R. L., Adams, J. W., and Hildebrand, F. A., 1962, A rare sodium niobate mineral from Colorado, in Geological Survey re- search 1962: U.S. Geological Survey Professional Paper 450-C, p. 04—06. Parker, R. L., and Hildebrand, F. A., 1963, Preliminary report on alkalic intrusive rocks in the northern Wet Mountains, Colorado, in Geological Survey research 1962: U.S. Geological Survey Pro- fessional Paper 450—E, p. E8—E10. Parker, R. L., and Sharp, W. N., 1970, Mafic-ultramafic igneous rocks and associated carbonatites of the Gem Park Complex, Cus- ter and Fremont Counties, Colorado: U.S. Geological Survey Professional Paper 649, 24 p. Powell, J. L., and Bell, Keith, 1970, Strontium isotopic studies of alkalic rocks—Localities from Australia, Spain, and the western United States: Contributions to Mineralogy and Petrology, v. 27, p. 140. Rock, N. M. S., 1976, The role of 002 in alkali rock genesis: Geologi- cal Magazine, v. 113, p. 97—113. Roden, M. K., 1977, Rare earth elements distributions and strontium isotopic data from the Gem Park igneous complex, Colorado: Kan- sas State University M. S. thesis, 103 p. Roden, M. K., and Cullers, R. L., 1976, Rare earth element distribu- tions and strontium isotope data from the Gem Park igneous com- plex, Colorado: Geological Society of America Abstracts with Programs, v. 8, no. 5, p. 622-623. Scott, G. R., and Taylor, R. B., 1975, Post-Paleocene Tertiary rocks and Quaternary volcanic ash of the Wet Mountain Valley, Col- orado: U.S. Geological Survey Professional Paper 868, 15 p. Q U.S. GOVERNMENT PRINTING OFFICE: 1983—776-041/4022 REGION NO. 8 Scott, G. R., Taylor, R. B., Epis, R. C., and Wobus, R. A., 1976, Geologic map of the Pueblo 1°><2° quadrangle, south-central Col- orado: U.S. Geological Survey Miscellaneous Field Studies Map MF—775, scale 1:187,500. Shawe, D. R., and Parker, R. L., 1967, Mafic-ultramafic layered in- trusion at Iron Mountain, Fremont County, Colorado: U.S. Geological Survey Bulletin 1251—A, p. A1—A28. Singewald, Q. D., and Brock, M. R., 1956, Thorium deposits in the Wet Mountains, Colorado: U.S. Geological Survey Professional Paper 300, p. 581— 585. Sorensen, H., 1974a, Introduction, in Sorensen, H., ed., The alkaline rocks: New York, John Wiley, p. 15—22. Sorensen, H., 1974b, Alkali syenites, feldspathoidal syenites, and re- lated lavas, in Sorensen, H., ed., The alkaline rocks: New York, John Wiley p. 22—52. Taylor, R. B., Scott, G. R., Wobus, R. A., and Epis, R. C., 19753, Reconnaissance geologic map of the Cotopaxi 15-minute quad- rangle, Fremont and Custer Counties, Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map I—900, scale 1:62,500. 1975b, Reconnaissance geologic map of the Royal Gorge quad- rangle, Fremont and Custer Counties, Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map I—869, scale 1:62,500. Wager, L. R., and Brown, G. M., 1967, Layered igneous rocks: Edin- burgh, Oliver and Boyd, 588 p. Wedepohl, K. E., 1971, Geochemistry: New York, Holt, Rinehart, and Winston, 231p. Wilkinson, J. F. G., 1974, The mineralogy and petrography of alkali basaltic rocks, in Sorensen, H. ed., The alkaline rocks: New York, John Wiley, p. 67—95. Element Concentrations in Soils and Other Surficial Materials of the Conterminous United States By HANSFORD T. SHACKLETTE and JOSEPHINE G. BOERNGEN U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1270 An account of the concentrations of 50 chemical elements in samples of soils and other regoliths UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984 UNITED STATES DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Shacklette, Hansford T. Element concentrations in soils and other surflcial materials of the conterminous United States. (Geological Survey professional paper ; 1270) Bibliography: 105 p. Supt. of Docs. No.: I 19.16 1. Soils—United States—Composition. I. Boerngen, Josephine G. II. Title. III. Series S599.AlS§ 631.4’7'73 82-600084 AACRZ For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 CONTENTS Abstract ............................................ Introduction .......................................... Acknowledgments ....................................... Review of literature ........... . ........................... Collection and analysis of geochemical data ........................ Sampling plan ....................................... Sampling media ...................................... Chemical-analysis procedures .............................. Data presentation ....................................... Discussion of results ..................................... References cited ........................................ @QO‘UIO‘WCDNNHD-Ig ILLUSTRATIONS Page FIGURE 1. Map showing location of sampling sites in the conteminous United States where elements not commonly detected in surficial deposits were found, and the amounts of the elements present ................ 12 2-47. Maps showing element content of surficial materials in the conterminous United States: 2 Aluminum ................................ 14 3 Antimony ................................ 16 4 Arsenic ................................. 18 5. Barium ................................. 6. Beryllium ................................ 7 8 9 $8 Boron .................................. Bromine ................................. . Calcium ................................. 10. Carbon (total) ............................. 11. Cerium ................................. 12. Chromium ................................ 13. Cobalt .................................. 14. Copper ................................. 15. Fluorine ................................. 16. Gallium . . ._ .............................. 17. Germanium ............................... l8. Iodine .................................. Molybdenum .............................. Neodymium ............................... Nickel .................................. Niobium ................................. Phosphorus ............................... Potassium ................................ 5 5 5 S388£$88$ESS&SKQS%8§§888§ 0:. so .§$§§ 55-929: 3555 8&33 $83§3§3$$$83f33$3§§3§. 5 8 IV CONTENTS FIGURES 37—47. Maps showing element content of surficial materials in the conterminous Pm United States: 37. Strontium ................................ 84 38. Sulfur .................................. 86 39. Thorium ................................. 88 40. Tin .................................... 90 41. Titanium ................................ 92 42. Uranium ................................. 94 43. Vanadium ................................ 96 44. Ytterbium ................................ 98 45. Yttrium ................................. 100 46. Zinc ................................... 102 47. Zirconium ................................ 104 TABLES TABLE 1. Average or median contents, and range in contents, reported for elements in soils and other surficial materials . . 2. Mean concentrations, deviations, and ranges of elements in samples of soils and other surficial materials in the eonterminous United States ......................................................... ELEMENT CONCENTRATIONS IN SOILS AND OTHER SURFICIAL MATERIALS OF THE CONTERMINOUS UNITED STATES By HANSFORD T. SHACKLETTE and JOSEPHINE G. BOERNGEN ABSTRACT Samples of soils or other regoliths, taken at a depth of approxi- mately 20 cm from locations about 80 km apart throughout the conter- minous United States, were analyzed for their content of elements. In this manner, 1,318 sampling sites were chosen, and the results of the sample analyses for 50 elements were plotted on maps. The arithmetic and geometric mean, the geometric deviation, and a histog- ram showing frequencies of analytical values are given for 47 ele— ments. The lower concentrations of some elements (notably, aluminum, barium, calcium, magnesium, potassium, sodium, and strontium) in most samples of surficial materials from the Eastern United States, and the greater abundance of heavy metals in the same materials of the Western United States, indicates a regional geochemical pat- tern of the largest scale. The low concentrations of many elements in soils characterize the Atlantic Coastal Plain. Soils of the Pacific Northwest generally have high concentrations of aluminum, cobalt, iron, scandium, and vanadium, but are low in boron. Soils of the Rocky Mountain region tend to have high concentrations of copper, lead, and zinc. High mercury concentrations in surficial materials are characteristic of Gulf Coast sampling sites and the Atlantic coast sites of Connecticut, Massachuetts, and Maine. At the State level, Florida has the most striking geochemical pattern by having soils that are low in the concentrations of most elements considered in this study. Some smaller patterns of element abundance can be noted, but the degree of confidence in the validity of these patterns decreases as the patterns become less extensive. INTRODUCTION The abundance of certain elements in soils and other surficial materials is determined not only by the ele- ment content of the bedrock or other deposits from which the materials originated, but also by the effects of climatic and biological factors as well as by influences of agricultural and industrial operations that have acted on the'materials for various periods of time. The diver- sity of ' these factors in a large area is expected to result in a corresponding diversity in the element contents of the surficial materials. At the beginning of this study (1961), few data were available on the abundance of elements in surficial ma- terials of the United States as a whole. Most of the early reports discussed only the elements that were of economic importance to mining or agriculture in a metallogenic area or State; and the data, for the most part, cannot be evaluated with reference to average, or normal, amounts in undisturbed materials because they were based on samples of deposits expected to have anomalous amounts of certain elements, or were based only on samples from cultivated fields. We began a sampling program in 1961 that was de- signed to give estimates of the range of element abun- dance in surficial materials that were unaltered or very little altered from their natural condition, and in plants that grew on these deposits, throughout the contermin- ous United States. We believed that analyses of the surficial materials would provide a measure of the total concentrations of the elements that were present at the sampling sites, and that analysis of the plants would give an estimate of the relative concentrations among sites of the elements that existed in a chemical form that was available to plants. Because of the great amount of travel necessary to complete this sampling, we asked geologists and others of the US. Geological Survey to assist by collecting samples when traveling to and from their project areas and to contribute appro- priate data they may have collected for other purposes. The reponse to this request, together with the samples and data that we had collected, resulted in our obtain- ing samples of surficial materials and plants from 863 sites. The analyses of surficial materials sampled in this phase of the study were published for 35 elements by plotting element concentrations, in two to five fre- quency classes, on maps (Shacklette, Hamilton, and others, 1971). Soon after the publication of the results of this study, interest in environmental matters, particularly in the effects of contamination and industrial pollution, in- creased greatly. At the same time, technological ad— vances in analytical methods and data processing facili- tated measurements of geochemical and other parame- ters of the environment. In response to the need for background data for concentrations of certain elements of particular environmental concern, the samples of sur- ficial materials that were collected for the first study (Shacklette, Hamilton, and others, 1971) (with some ad- 1 2 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES ditional samples) were analyzed for other elements, and the results were published in U.S. Geological Survey Circulars: for mercury, Shacklette, Boerngen, and Turner (1971); for lithium and cadmium, by Shacklette, and others (1973); and for selenium, fluorine, and arse- nic, Shacklette and others (1974). The collection of samples for this study continued, as opportunities arose, until autumn 1975, resulting in the sampling of an additional 355 sites that were selected to give a more uniform geographical coverage of the conterminous United States. This sampling con- tinuation is referred to as phase two. These samples were analyzed, and the data were merged with those of the original samples to produce the results given in the present report. In addition, the availability of analytical methods for elements not included in the ear- lier reports permitted data to be given on these ele- ments in the more recently collected samples. The collection localities and dates, sample descrip— tions, and analytical values for each sample in the pre- sent report were published by Boerngen and Shacklette (1981). The elemental compositions of only the surficial materials are given in this report; the data on analyses of the plant samples are held in files of the U.S. Geolog- ical Survey. ACKNOWLEDGMENTS This study was made possible by the cooperation of many persons in the U.S. Geological Survey. We thank D. F. Davidson, A. T. Miesch, J. J. Connor, R. J. Ebens, and A. T. Myers for their interest in, and con- tinued support of, this study. The sampling plan was suggested by H. L. Cannon, who also contributed analytical data from her project areas and samples from her travel routes. Others of the Geological Survey who collected samples, and to whom we express gratitude, are: J. M. Bowles, F. A. Branson, R. A. Cadigan, F. C. Canney, F. W. Cater, Jr., M. A. Chaffey, Todd Church, J. J. Connor, Dwight Crowder, R. J. Ebens, J. A. Erdman, G. L. Feder, G. B. Gott, W. R. Griffitts, T. P. Hill, E. K. Jenne, M. I. Kaufman, J. R. Keith, Frank Kleinhampl, A. T. Miesch, R. F. Miller, R. C. Pearson, E. V. Post, Douglas Richman, R. C. Sever- son, James Scott, D. A. Seeland, M. H. Staatz, T. A. Steven, M. H. Strobell, V. E. Swanson, R. R. Tidball, H. A. Tourtelot, J. D. Vine, and R. W. White. We thank the following members of the U.S. Department of Agriculture Soil Conservation Service for providing soil samples from areas in Minnesota: D. D. Barron, C. R. Carlson, D. E. DeMartelaire, R. R. Lewis, Charles Sutton, and Paul Nyberg. We acknowledge the analytical support provided by the following U.S. Geological Survey chemists: Lowell Artis, Philip Aruscavage, A. J. Bartel, S. D. Botts, L. A. Bradley, J. W. Budinsky, Alice Caemmerer, J. P. Cahill, E. Y. Campbell, G. W. Chloe, Don Cole, E. F. Cooley, N. M. Conklin, W. B. Crandell, Maurice Devalliere, P. L. D. Elmore, E. J. Finlay, Johnnie Gardner, J. L. Glenn, T. F. Harms, R. G. Havens, R. H. Heidel, M. B. Hinkle, Claude Huffman, Jr., L. B. Jenkins, R. J. Knight, B. W. Lanthorn, L. M. Lee, K. W. Leong, J. B. McHugh, J. D. Mensik, V. M. Mer- ritt, H. T. Millard, Jr., Wayne Mountjoy, H. M. Nakagawa, H. G. Neiman, Uteana Oda, C. S. E. Papp, R. L. Rahill, V. E. Shaw, G. D. Shipley, Hezekiah Smith, A. J. Sutton, Jr., J. A. Thomas, Barbara Tobin, J. E. Troxel, J. H. Turner, and G. H. VanSickle. We were assisted in computer programming for the data by the following persons of the U.S. Geological Survey: W. A. Buehrer, G. I. Evenden, J. B. Fife, Allen Popiel, M. R. Roberts, W. C. Schomburg, G. I. Selner, R. C. Terrazas, George VanTrump, Jr., and R. R. Wahl. REVIEW OF LITERATURE The literature on the chemical analysis of soils and other surficial materials in the United States is exten- sive and deals largely with specific agricultural prob- lems of regional interest. Many of the papers were writ- ten by soil scientists and chemists associated with State agricultural experiment stations and colleges of agricul- ture, and most reports considered only elements that were known to be nutritive or toxic to plants or ani- mals. Chemists with the U.S. Department of Agriculture prepared most early reports of element abundance in soils for large areas of the United States. (See Robin- son, 1914; Robinson and others, 1917). The 1938 year- book of agriculture was devoted to reports on soils of the United States; in this book, McMurtrey and Robin- son (1938) discussed the importance and abundance of trace elements in soils. Amounts of the major elements in soil samples from a few soil profiles distributed throughout the United States were compiled by the soil scientist C. F. Marbut (1935) to illustrate characteris- tics of soil units. The use of soil analysis in geochemical prospecting began in this country in the 1940’s, and many reports were published on the element amounts in soils from areas where mineral deposits were known or suspected to occur. Most of these reports included only a few ele- ments in soils from small areas. This early geochemical work was discussed by Webb (1953) and by Hawkes (1957). In succeeding years, as soil analyses became an accepted method of prospecting and as analytical COLLECTION AND ANALYSIS OF GEOCHEMICAL DATA 3 methods were improved, many elements in soils were analyzed; still, the areas studied were commonly small. An estimate of the amounts of elements in average, or normal, soils is useful in appraising the amounts of elements in a soil sample as related to agricultural, min- eral prospecting, environmental quality, and health and disease investigations. Swaine (1955) gave an extensive bibliography of trace-element reports on soils of the world, and he also summarized reports of the average amounts of elements as given by several investigators. The most comprehensive list of average amounts of rare and dispersed elements in soils is that of Vinogradov (1959), who reported the analytical results of extensive studies of soils in the Union of Soviet Socialist Repub- lics, as well as analyses of soils from other countries. He did not state the basis upon which he established the average values; however, these values are presuma- bly the arithmetic means of element amounts in samples from throughout the world. In their discussions of the principles of geochemistry, Goldschmidt (1954) and Rankama and Sahama (1955) reported the amounts of various elements present in soils and in other surficial materials, Hawks and Webb (1962) and, more recently, Brooks (1972), Siegal (1974), Levinson (1974), and Rose and others (1979) gave average amounts of certain ele- ments in soils as useful guides in mineral exploration. A report on the chemical characteristics of soils was edited by Bear (1964). In this book, the chapter on chemical composition of soils by Jackson (1964) and the chapter on trace elements in soils by Mitchell (1964) gave the ranges in values or the average amounts of some soil elements. Regional geochemical studies conducted by scientists of the U.S. Geological Survey within the past two de- cades have been largely directed to the establishment of baseline abundances of elements in surficial mate- rials, including soils. Most of the earlier work investi- gated these materials that occurred in their natural con- dition, having little or no alterations that related to human activities, with the objective of establishing nor- mal element concentrations in the materials by which anomalous concentrations, both natural or man induced, could be judged. Some of these studies were conducted in cooperation with medical investigators who were searching for possible relationships of epidemiological patterns to characteristics of the environment. In one study, the geochemical characteristics of both natural and cultivated soils were determined in two areas of Georgia that had contrasting rates of cardiovascular dis- eases (Shacklette and others, 1970). In an extensive geochemical study of Missouri, also cond cted coopera- tively with medical researchers, both cultivated and natural soils were sampled. The results were presented for the State as a whole, and for physiographic regions or other subdivisions and smaller areas, as follows: Erdman and others (1976a, 1976b); Tidball (1976, 1983a, 1983b); and Ebens and others (1973). The results of these studies, and of other regional geochemical investi- gations, were summarized and tabulated by Connor and Shacklette (1975). Recent regional studies of soil geochemistry by the U.S. Geological Survey related to the development of energy resources in the western part of the United States, including North Dakota, South Dakota, Mon- tana, Wyoming, Colorado, Utah, and New Mexico. These studies established regional geochemical baselines for soils, both in undisturbed areas and in areas that had been altered by mining and related ac- tivities. Some of these studies considered the elements in soils both as total concentrations and as concentra- tions that were available to plants of the region. The results of these studies were published in annual prog- ress reports (U.S. Geological Survey, 1974, 1975, 1976, 1977, and 1978). The data on soils, as well as on other natural materials, in these reports were summarized and tabulated by Ebens and Shacklette (1981). In a study of the elements in fruits and vegetables from 11 areas of commercial production in the United States, and in the soils on which this produce grew, soils were analyzed for 39 elements, as reported by Boemgen and Shacklette (1980) and Shacklette (1980). The average amounts of elements in soils and other surficial materials of the United States, as determined in the present study, are given in table 1, with the average values or ranges in values that were reported by Vinogradov (1959), Rose and others (1979), Jackson (1964), Mitchell (1964), and Brooks (1972). The averages from the present study given in table 1 are the arithme- tic means. Although the averages were computed by the methods described by Miesch (1967), the values ob— tained are directly comparable with the arithmetic means derived by common computational procedures. COLLECTION AND ANALYSIS OF GEOCHEMICAL DATA SAMPLING PLAN The sampling plan was designed with the emphasis on practicality, in keeping with the expenditures of time and funds available, and its variance from an ideal plan has beenrecognized from the beginning. Because the collection of most samples was, by necessity, incidental to other duties of the samplers, the instructions for sampling were simplified as much as possible, so that sampling methods would be consistent within the wide range of kinds of sites to be sampled. The samples were ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES TABLE 1.—Average or median contents, and range in contents, reportedfirr elements in soils and other surficial materials [Data are in puts per million; each average represents arithmetic mean; leaders (—~) in figure ' ' " ‘ no data " “ A, .3 ,M, ‘“ <, less than; >,gnwwrflnm This report %?;:§)a?:1:;2::: Vinogggdov Jackson (1964) Mitchell (1964) Brooks (1972) useful in (pL I-1y, Element geochemical averages from "Typical",I Range in prospecting) worldwide average, contents in Average Range sampling) or range Scottish sur- Average or in values face soils range A1 ------ 72,000 700 - (10,000 71,300 10,000 - 60,000 As——-——— 7.2 (0.1 — 97 5 5 B ——————— 33 (20 — 300 10 30 ------------------- 10 Ba —————— 580 10 - 5,000 400 — 3,000 500 Be ------ .92 <1 - 15 6 ——————————————————— <5 5 6 Br--—--- .85 (0.5 - 11 5 C, total 25,000 600 - 370,000 20,000 Ca ------ 24,000 100 - 320,000 13,700 7,000 Ce ------ 75 (150 - 300 Co--—--- 9.1 <3 — 70 10 (M) 8 ------------------- <2 - 80 10 Cr ------ 54 l - 2,000 6.3 (M) 200 ------------------- 5 - 3,000 200 25 (1 - 700 15 (M) 20 20 (10 — 100 20 430 (10 — 3,700 300 (M) 200 26,000 100 - >100,000 21,000 (M) 38,000 7,000 — 42,000 10,000 - 50,000 17 (5 — 7O ——————————————————————— 30 ------------------- 15 - 70 20 1.2 (0.1 - 2.5 ----------------------- 1 5 .09 (0.01 - 4.6 0.056 (M) .01 1.2 (0.5 - 9.6 15,000 50 - 63,000 11,000 (M) 13,600 400 - 28,000 37 (30 - 200 <30 - 200 ---------------- L1-----— 24 (5 - 140 6.2 (H) 30 30 Mg———--- 9,000 50 - >100,000 ---------------------- 6,300 <6,000 Mn ------ 550 (2 - 7,000 320 (M) 850 ------------------- 200 - 5,000 850 Ho-—---- .97 (3 - 15 2.5 (A) 2 ------------------- <1 - 5 2.5 Na ------ 12,000 (500 - 100,000 ----------------------- 6,300 Nb— ----- 11 (10 - 100 15 (A) 15 Nd —————— 46 <70 - 300 N1 ------ l9 <5 - 700 17 (M) 40 ——————————————————— 10 - 800 40 P--—-—- 430 <20 — 6,800 300 (H) 800 500 Pb —————— l9 <10 - 700 17 (M) (20 - 80 10 Rb--———— 67 (20 — 210 35 (M) 100 5, total 1,600 (800 - 48,000 100 - 2,000 850 Sb- ----- .66 (l - 8.8 2 (A) .5 Sc--—-- 8.9 (5 - 50 ----------------------- 7 ------------------- <3 - 15 ---------------- Se- ————— .39 (0.1 - 4.3 0.31 (M) .001 .5 Si ------ 310,000 16,000 - 450,000 -------------——-------- 330,000 Sn ------ 1.3 (0.1 - 10 10 (A) 10 Sr ------ 240 (5 - 3,000 67 (M) 300 —————-—-——-—--—-—-— 60 - 700 300 Ti---—-- 2,900 70 - 20,000 ----------------------- 4,600 1,200 - 6,000 9.4 2.2 - 31 13 2.7 0.29 - ll 1 (A) 1 80 (7 — 500 57 (H) 100 20 - 250 100 25 (10 - 200 ----------------------- 50 25 — 100 —--—-——-—--—-——— 3.1 <1 - 50 Zn------ 60 (5 - 2,900 36 (M) 50 50 Zr- ----- 230 (20 - 2,000 270 (H) 300 -—---—------—-—-—— 200 — >1,000 --------------- IAuthor's usage; generally used to indicate the most commonly occurring value. collected by US Geological Survey personnel along their routes of travel to areas of other types of field studies or within their project areas. The locations of the routes that were sampled de- pended on both the network of roads that existed and the destinations of the samplers. Sampling intensity was kept at a minimum by selecting only one sampling site every 80 km (about 50 miles; selected for conveni- ence because vehicle odometers were calibrated in miles) along the routes. The specific sampling sites were selected, insofar as possible, that had surficial ma- terials that were very little altered from their natural condition and that supported native plants suitable for phng. sampling. In practice, this site selection necessitated sampling away from roadcuts and fills. In. some areas, only cultivated fields and plants were available for sam- Contamination of the sampling sites by vehicular emissions was seemingly insignificant, even though many sites were within 100 m or less of the roads. Col- DATA PRESENTATION 5 lecting samples at about 20 cm depth, rather than at the upper soil horizons, may have avoided the effects of surface contamination on the samples. However, we had no adequate way of measuring any contamination that may have occurred. (See Cannon and Bowles, 1962.) Many of the sampled routes had only light veh- icular traffic, and some were new interstate highways. Routes through congested areas generally were not sampled; therefore, no gross contamination of the sam- ples was expected. The study areas that were sampled follow: Wisconsin and parts of contiguous States, southeastern Missouri, Georgia, and Kentucky, sampled by Shacklette; Ken- tucky, sampled by J. J. Connor and R. R. Tidball; Nevada, New Mexico, and Maryland, sampled by H. L. Cannon; various locations in Arizona, Colorado, Mon- tana, New Mexico, Utah, and Wyoming, sampled by F. A. Branson and R. F. Miller; Missouri, sampled by Shacklette, J. A. Erdman, J. R. Keith, and R. R. Tid- ball; and various locations in Colorado, Idaho, Montana, South Dakota, Utah, and Wyoming, sampled by A. T. Miesch and J. J. Connor. Sampling techniques used in these areas varied according to the primary objectives of the studies being conducted, but generally these techniques were closely similar to the methods used in sampling along the roads. In general, the sampling within study areas was more intensive than that along the travel routes. To make the sampling intensity of the two sampling programs more nearly equal, only the samples from selected sites in the study areas were used for this report. The selected sites were approximately 80 km apart. Where two or more samples were collected from one site, they were assigned numbers, and one of these samples was randomly chosen for evaluation in this study. SAMPLING MEDIA The material sampled at most sites could be termed “soil” because it was a mixture of comminuted rock and organic matter, it supported ordinary land plants, and it doubtless contained a rich microbiota. Some of the sampled deposits, however, were not soils as defined above, but were other kinds of regoliths. The regoliths included desert sands, sand dunes, some loess deposits, and beach and alluvial deposits that contained little or no visible organic matter. In some places the distinc- tions between soils and other regoliths are vague be- cause the materials of the deposits are transitional be- tween the two. Samples were collected from a few de- posits consisting mostly of organic materials that would ordinarily be classified as peat, rather than soil. To unify sampling techniques, the samplers were asked to collect the samples at a depth of approximately 20 cm below the surface of the deposits. This depth was chosen as our estimate of a depth below the plow zone that would include parts of the zone of illuviation in most well-developed zonal soils, and as a convenient depth for sampling other surficial materials. Where the thickness of the material was less than 20 cm, as in shallow soils over bedrock or in lithosols over large rock fragments, samples were taken of the material that lay iust above the rock deposits. About 0.25 liter of this material was collected, put in a kraft paper envelope, and shipped to the U.S. Geological Survey laboratories in Denver, Colo. CHEMICAL-ANALYSIS PROCEDURES The soil samples were oven dried in the laboratory and then sifted through a 2-mm sieve. If the soil mate- rial would not pass this sieve, the sample was pul- verized in a ceramic mill before seiving. Finally, the sifted, minus 2-mm fraction of the sample was used for analysis. The methods of analysis used for some elements were changed during the course of this study, as new tech- niques and instruments became available. For most ele- ments, the results published in the first report (Shacklette, Hamilton, and others, 1971) were obtained by use of a semiquantitative six-step emission spec- trographic method (Meyers and others, 1961). The methods used for other elements were: EDTA titration for calcium; colorimetric (Ward and others, 1963) for phosphorus and zinc; and flame photometry for potassi- um. Many of the elements analyzed in the 355 samples collected in phase two of the study were also analyzed by the emission spectrographic method (Neiman, 1976). Other methods were used for the following elements: flame atomic absorption (Huffman and Dinnin, 1976) for mercury, lithium, magnesium, sodium, rubidium, and zinc; flameless atomic absorption (Vaughn, 1967) for mercury; X-ray fluorescence spectrometry (Wahlberg, 1976) for calcium, germanium, iron, potassium, seleni- um, silver, sulfur, and titanium; combustion (Huffman and Dinnin, 1976) for total carbon; and neutron activa- tion (Millard, 1975, 1976) for thorium and uranium. DATA PRESENTATION Summary data for 46 elements are reported in tables 1 and 2. In table 1, the element concentrations found in samples of soil and other surficial materials of this study are compared with those in soils reported in other studies. Arithmetic means are used for the data of this study to make them more readily compared with the ' data generally reported in the literature. These arith- metic means were derived from the estimated geomet- ric means by using a technique described by Miesch (1967), which is based on methods devised by Cohen (1959) and Sichel (1952). The arithmetic means in table 6 1, unlike the geometric means shown in table 2, are estimates of geochemical abundance (Miesch, 1967). Arithmetic means are always larger than corresponding geometric means (Miesch, 1967, p. B1) and are esti- mates of the fractional part of a single specimen that consists of the element of concern rather than of the typical concentration of the element in a suite of sam— ples. ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES Concentrations of 46 elements in samples of this study are presented in table 2, which gives the determi- nation ratios, geometric-mean concentrations and devia- tions, and observed ranges in concentrations. The analytical data for most elements as received from the laboratories were transformed into logarithms because of the tendency for elements in natural materials, par- ticularly the trace elements, to have positively skewed TABLE 2.—Mean concentrations, deviations, and ranges of elements in samples of soils and other smflcial mte'rials in the contermimms United States [Means and ranges are reported in parts per million (pg/g), and means and deviations are geometric except as indicated Ratio, number of samples in which the element was found m .22- minnnto ‘ of _‘ analyzed. <,1essthan; >, greaterthan] Conterminous Western United States Eastern United States United States (west of 96th meridian) (east of 96th meridian) Element Estimated Estimated Estimated Devia- arithmetic Devia- Observed arithmetic Devia— Observed arithmetic Mean tion mean Ratio Mean tion range mean Ratio Mean tion range mean A1, percent 4.7 2.48 7.2 6612770 5.8 2.00 0.5 - )10 7.4 4502477 3.3 2.87 0.7 - >10 5.7 5 2 2.23 7.2 7282730 5.5 1.98 (0.10 - 97 7.0 5212527 4.8 2.56 (0.1 — 73 7.4 6 1.97 33 5062778 23 1.99 (20 — 300 29 4252541 31 1.88 <20 — 150 38 2.14 580 7782778 580 1.72 70 - 5,000 670 5412541 290 2.35 10 — 1,500 420 2.38 .92 310:778 .68 2.30 (1 - 15 .97 1692525 .55 2.53 (1 - 7 .85 2.50 .85 1132220 .52 2.74 <0.5 - 11 .86 782128 .62 2.18 <0.5 - 5.3 .85 C, percent- 1.6 2.57 2.5 2502250 1.7 2.37 0.16 - 10 2.5 1622162 1.5 2.88 0.06 — 37 2.6 Ca, percent .92 4.00 2.4 7772777 1.8 3.05 0.06 — 32 3.3 5142514 .34 3.08 0.01 — 28 .63 C 63 1.78 75 812683 65 1.71 (150 - 300 75 702489 63 1.85 (150 — 300 76 6.7 2.19 9.1 6982778 7.1 1.97 <3 - 50 9.0 4032533 5.9 2.57 <0.3 — 70 9.2 37 2.37 54 7782778 41 2.19 3 - 2,000 56 5412541 33 2.60 1 — 1,000 52 17 2.44 25 7782778 21 2.07 2 — 300 27 5232533 13 2.80 (1 — 700 22 210 3.34 430 5982610 280 2.52 (10 — 1,900 440 3902435 130 4.19 (10 - 3,700 360 Fe, percent 1.8 2.38 2.6 776:777 2.1 1.95 0.1 — >10 2.6 5392540 1.4 2.87 0.01 — >10 2.5 Ca --------- 13 2.03 17 7672776 16 1.68 <5 — 70 19 4312540 9.3 2.38 <5 — 70 14 1.2 1.37 1.2 2242224 1.2 1.32 0.58 - 2.5 1.2 1302131 1.1 1.45 (0.1 - 2.0 1.2 .058 2.52 .089 7292733 .046 2.33 (0.01 — 4.6 .065 5342534 .081 2.52 0.01 - 3.4 .12 .75 2.63 1.2 1692246 .79 2.55 (0.5 — 9.6 1.2 902153 .68 2.81 (0.5 - 7.0 1.2 K, percent1 1.5 .79 None 7772777 1.8 .71 0.19 - 6.3 None 5371537 1.2 .75 0.005 - 3.7 -- La --------- 30 1.92 37 4622777 30 1.89 (30 - 2 0 37 2942516 29 1.98 (30 — 200 37 Li --------- 20 1.85 24 7312731 22 1.58 5 — 130 25 4792527 17 2.16 (5 — 140 22 Mg, percent .44 3.28 .90 7772778 .74 2.21 0.03 - >10 1.0 5282528 .21 3.55 0.005 - 5 .46 Mn ————————— 330 2.77 550 7772777 380 1.98 30 — 5,000 480 5372540 260 3.82 (2 - 7,000 640 Mo --------- .59 2.72 .97 572774 .85 2.17 (3 - 7 1.1 322524 .32 3.93 (3 — 15 .79 Na, percent .59 3.27 1.2 7442744 .97 1.95 0.05 — 10 1.2 3632449 .25 4.55 <0.05 — 5 .78 Nb— -------- 9.3 1.75 11 4182771 8.7 1.82 (10 - 100 10 3222498 10 1.65 (10 — 50 12 40 1.68 46 1202538 36 1.76 (70 — 300 43 1092332 46 1.58 (70 - 300 51 Ni ————————— 13 2.31 19 7472778 15 2.10 (5 — 700 19 4432540 11 2.64 (5 — 700 18 P ---------- 260 2.67 430 5242524 320 2.33 40 - 4,500 460 3802382 200 2.95 (20 - 6,800 360 Pb --------- 16 1.86 19 7122778 17 1.80 (10 — 700 20 4222541 14 1.95 (10 — 300 17 Rb ————————— 58 1.72 67 2212224 69 1.50 (20 - 210 74 1072131 43 1.94 (20 - 160 53 S, percent— .12 2.04 .16 342224 .13 2.37 <0.08 - 4.8 .19 202131 .10 1.34 (0.08 — 0.31 .11 Sb ————————— .48 2.27 .67 352223 .47 2.15 (1 - 2.6 .62 312131 .52 2.38 (1 - 8.8 .76 Sc- 7.5 1.82 8.9 6852778 8.2 1.74 (5 - 50 9.6 3892526 6.5 1.90 (5 — 30 8.0 Se --------- .26 2.46 .39 5902733 .23 2.43 (0.1 - 4.3 .34 4492534 .30 2.44 (0.1 — 3.9 .45 Si, percent1 31 6.48 None 2502250 30 5.70 15 - 44 None 1562156 34 6.64 1.7 - 45 —- Sn ————————— .89 2.36 1.3 2182224 .90 2.11 <0.1 — 7.4 1.2 1232131 .86 2.81 <0.1 - 10 1.5 Sr --------- 120 3.30 240 7782778 200 2.16 10 — 3,000 270 5012540 53 3.61 (5 - 700 120 T1, percent .24 1.89 .29 7775777 .22 1.78 0.05 — 2.0 .26 5402540 .28 2.00 0.007 - 1.5 .35 h 8.6 1.53 9.4 1952195 9.1 1.49 2.4 - 31 9.8 1022102 7.7 1.58 2.2 - 23 8.6 2.3 1.73 2.7 2242224 2.5 1.45 0.68 — 7.9 2.7 1302130 2.1 2.12 0.29 - 11 2.7 58 2.25 80 7782778 70 1.95 7 — 500 88 5162541 43 2.51 <7 — 300 66 21 1.78 25 759:778 22 1.66 (10 — 150 25 4772541 20 1.97 (10 - 200 25 2.6 1.79 3.1 7542764 2.6 1.63 (1 — 20 3.0 4522486 2.6 2.06 (1 - 50 3.3 48 1.95 60 7662766 55 1.79 10 — 2,100 65 4732482 40 2.11 (5 - 2,900 52 180 1.91 230 7772778 160 1.77 (20 - 1,500 190 5392541 220 2.01 (20 — 2,000 290 lMeans are arithmetic, deviations are standard. DISCUSSION OF RESULTS 7 frequency distributions. For this reason, the geometric mean is the more proper measure of central tendency for these elements. The frequency distributions for po- tassium and silicon, on the other hand, are more nearly normal if the data are not transformed to logarithms and the mean is expressed as the arithmetic average. In geochemical background studies, the magnitude of scatter to be expected around the mean is as important as the mean. In lognormal distributions, the geometric deviation measures this scatter, and this deviation may be used to estimate the range of variation expected for an element in the material being studied. About 68 per- cent of the samples in a randomly selected suite should fall within the limits M/D and MD, where M repre- sents the geometric mean and D the geometric devia- tion. About 95 percent should fall between M/DZ and M -Dz, and about 99.7 percent between M/D3 and M ~D3. The analytical data for some elements include values that are below, or above, the limits of numerical deter- mination, and these values are expressed as less than (<) or greater than (>) a stated value. These data are said to be censored, and for these the mean was com- puted by using a technique described by Cohen (1959) and applied to geochemical studies by Miesch (1967). This technique requires an adjustment of the summary statistics computed for the noncensored part of the data. The censoring may be so severe in certain sets of data that a reliable adjustment cannot be made; with the data sets used in the present study, however, no such circumstances were encountered. The use of these procedures in censored data to quantify the central ten- dency may result in estimates of the mean that are lower than the limit of determination. For example, in table 2 the geometric-mean molybdenum concentration in soils from the Eastern United States is estimated to be 0.32 ppm, although the lower limit of determina- tion of the analytical method that was used is 3 ppm. Use of this procedure permits inclusion of the censored values in the calculation of expected mean concentra- tions. The determination ratios in table 2—-—that is, the ratio of the number of samples in which the element was found in measurable concentrations to the total number of samples—permit the number of censored values, if any, to be found that were used in calculating the mean. This number is found by subtracting the left value in the ratio from the right. The distribution of the sampling sites and the concen- trations of elements determined for samples from the sites are presented on maps of the conterminous United States (figs. 1—47). Figure 1 shows the locations of sites where four elements, bismuth, cadmium, praseodymi- um, and silver, were found in the samples. These ele- ments were determined too uncommonly for reliable mean concentrations to be calculated. Each of the re- maining maps (figs. 2—47) gives the locations where an element was found in a sample from a site and the con- centration of the element, shown by a symbol that rep- resents a class of values. By examining the tables of frequency for concentration values of the elements, we were able to divide the ranges of reported values for many elements into five classes so that approximately 20 percent of the values fell into each class. The limited range in values for some elements, however, prohibited the use of more than two or three classes to represent the total distribution. Symbols representing the classes were drawn on the maps by an automatic plotter that was guided by computer classification of the data, in- cluding the latitude and longitude of the sampling sites. A histogram on each map gives the frequency distribu- tion of the analytical values, and the assignment of analytical values to each class as represented by sym- bols. We were able to obtain analyses of 11 more elements for the 355 samples of phase two of this study than for the 963 samples of phase one because of improved analytical methods and services. These elements are an- timony, bromine, carbon, germanium, iodine, rubidium, silicon, sulfur, thorium, tin, and uranium. The con- straints of resources and time prohibited analysis of the 963 samples of the first phase for these additional ele- ments. Results of analysis of the plant samples that were collected at all soil-sampling sites are not pre- sented in this report. Some elements were looked for in all samples but were not found. These elements, analyzed by the semiquantitative spectrographic method, and their ap- proximate lower detection limits, in parts per million, are as follows: gold, 20; hafnium, 100; indium, 10; plati- num, 30; palladium, 1; rhenium, 30; tantalum, 200; tellu- rium, 2,000; and thallium, 50. If lanthanum or cerium were found in a sample, the following elements, with their stated lower detection limits, were looked for in the same sample but were not found: dysprosium, 50; erbium, 50; gadolinium, 50; holmium, 20; lutetium, 30; terbium, 300; and thulium, 20. DISCUSSION OF RESULTS The data presented in this report may reveal evi- dence of regional variations in abundances of elements in soils or other regoliths; single values or small clusters of values on the maps may have little significance if considered alone. Apparent differences in values shown between certain sampling routes, such as some of those across the Great Plains and the North Central States where high values for cerium, cobalt, gallium, and lead predominate, suggest the possibility of systematic er- 8 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES rors in sampling or in laboratory analysis. Some gross patterns and some of lesser scale, nevertheless, are evi- dent in the compositional variation of regoliths, as shown in figures 2—47. The lower abundances of some elements (notably alu- minum, barium, calcium, magnesium, potassium, sodi- um, and strontium) in regoliths of the Eastern United States, and the greater abundances of the heavy metals in the same materials of the Western United States indicate a regional pattern of the largest scale. This visual observation of the maps can be substantiated by examining the mean concentrations for these two re- gions given in table 2. The abundances of these ele- ments differ markedly on either side of a line extending from western Minnesota southward through east-cen- tral Texas. This line is generally from the 96th to 97th meridian, and corresponds to the boundary proposed by Marbut (1935, p. 14), which divides soils of the United States into two major groups—the pedalfers that lie to the east, and the pedocals to the west. Mar- but (1928) attributed the major differences in chemical and physical qualities of these two major groups to the effects of climate on soils. A line approximating the 96th meridian also separates the Orders, Suborders, and Great Groups of moist-to—wet soils in the Eastern United States from the same categories of dry soils that lie to the west, as mapped by the [U.S.] Soil Conserva- tion Service (1969). As shown in table 2, soils of the Western United States have the highest mean values for all elements considered in this report except for an- timony, boron, bromine, mercury, neodymium, seleni— um, titanium, and zirconium. The differences, however, probably are not significant for these latter elements, except for zirconium. Superimposed upon this large-scale compositional variation pattern are several features of intermediate scale. Perhaps the most notable of these are the low concentrations of many elements in soils of the Atlantic Coastal Plain. Soils of the Pacific Northwest are high in concentrations of aluminum, cobalt, iron, scandium, and vanadium, but low in boron, and soils of the Rocky Mountain region tend to be high in copper, lead, and Zinc. Several small-scale patterns of compositional varia- tion can be noted, among them the high mercury con- centrations in surficial materials from the Gulf Coast of eastern Texas, Louisiana, Mississippi, Alabama, and northwest Florida, and a similar pattern on the Atlantic Coast in Connecticut, Massachusetts, and Maine. High phosphorus values occur in soils along a line extending west across Utah and Nevada to the coast of California, then south-east in California and Arizona. At the State level, Florida shows the most striking pattern by hav- ing low soil concentrations of most of the elements con- sidered in this study. The concentrations of certain elements do not show well-defined patterns of distribution, and the regional concentrations of some other elements cannot be evaluated because they were not present in detectable amounts in most of the samples, or because the sam— pling density was insufficient. The degree of confidence in regional patterns of element abundance is expected to be in direct proportion to the number of samples analyzed from the region. As the observed patterns be- come smaller, the probability increases that the charac- teristics that form the patterns are the results of chance. Some features of element-abundance patterns proba- bly reflect geologic characteristics of the areas that the soils overlie. Samples from most of the regoliths overly- ing basic volcanic rocks of Washington and Oregon con— tained higher than average concentrations of iron and other elements, as mentioned earlier. A few soil sam- ples with high phosphorus content are associated with phosphate deposits in Florida, and a single sample in Michigan with high copper content is known to be of soil that occurs over a copper deposit. These data do not provide obvious evidences of north— south trends in elemental compositions that might be expected to relate to differences in temperature re— gimes under which the surficial materials developed. There is, moreover, no consistent evidence of signifi- cant differences in element abundances between glaciated and nonglaciated areas (the general area of continental glaciation includes the northern tier of States from Montana to Maine and south in places to about lat 40°N.; see fig. 1). The world averages of abundance for some elements in soils, as given by Vinogradov (1959) and by others (table 1), do not correspond to the averages of abun- dance for these elements in the soils of the United States, according to the data presented in this report. The world averages are too low for the concentrations of boron, calcium, cerium, lead, magnesium, potassium, and sodium in United States soils and other surficial materials, and too high for beryllium, chromium, galli- um, manganese, nickel, phosphorus, titanium, vanadi- um, and yttrium. The stability of values for concentrations of most ele- ments seems to be satisfactory because the addition of analytical values for 355 samples of phase two of the study to values for 963 samples of the first phase did not significantly change the geometric means and devia- tions of element abundance that were reported earlier (Shacklette, Boerngen, and Turner, 1971; Shacklette, Hamilton, and others, 1971; Shacklette and others, REFERENCES CITED 9 1973, 1974). Although additional sampling of the same type as reported here might give a clearer picture of small-to—intennediate element-abundance patterns, mean values reported herein most likely would not change significantly. REFERENCES CITED Bear, F. E., ed., 1964, Chemistry of the soil [2d ed.]: New York, Reinhold Publishing Corp., 515 p. Boerngen, J. G., and Shacklette, H. T., 1980, Chemical analyses of fruits, vegetables, and their associated soils from areas of com- mercial production in the conterminous United States: U.S. Geological Survey Open—File Report 80-84, 134 p. 1981, Chemical analysis of soils and other surficial materials of the conterminous United States: U.S. Geological Survey Open- File Report 81—197, 143 p. Brooks, R. R., 1972, Geobotany and biogeochemistry in mineral ex- ploration: New York, Harper and Row, 290 p. Cannon, H. L., and Bowles, J. M., 1962, Contamination of vegetation by tetraethyl lead: Science, v. 137, no. 3532, p. 765—766. Cohen, A. G., J r., 1959, Simplified estimators for the normal distribu- tion when samples are singly censored or truncated: Teehnomet- rics, v. 1, no. 3, p. 217—237. Connor, J. J ., and Shacklette, H. T., 1975, Background geochemistry of some rocks, soils, plants, and vegetables in the conterminous United States, with sections on Field studies by R. J. Ebens, J. A. Erdman, A. T. Miesch, R. R. Tidball, and H. A. Tourtelot: U.S. Geological Survey Professional Paper 574—F, 168 p. Ebens, R. J., Erdman, J. A., Feder, G. L., Case, A. A., and Selby, L. A., 1973, Geochemical anomalies of a claypit area, Callaway County, Missouri, and related metabolic imbalance in beef cattle: U.S. Geological Survey Professional Paper 807, 24 p. Ebens, R. J., and Shacklette, H. T., 1981, Geochemistry of some rocks, mine spoils, stream sediments, soils, plants, and waters in the western energy region of the conterminous United States, with sections on Field studies by B. M. Anderson, J. G. Boerngen, J. J. Connor, W. E. Dean, J. A. Erdman, G. L. Feder, L. P. Gough, J. R. Herring, T. K. Hinkley, J. R. Keith, R. W. Klusman, J. M. McNeal, C. D. Ringrose, R. C. Severson, and R. R. Tidball: U.S. Geological Survey Professional Paper 1237, 173 p. Erdman, J. A., Shacklette, H. T., and Keith, J. R., 1976a, Elemental composition of selected native plants and associated soils from major vegetation-type areas in Missouri: U.S. Geological Survey Professional Paper 9540, p. 01-087. —1976b, Elemental composition of corn grains, soybean seeds, pasture grasses, and associated soils from selected areas in Mis- souri: U.S. Geological Survey Professional Paper 954—D, p. D1— D23. Goldschmidt, V. M., 1954, Geochemistry: Oxford, Clarendon Press, 730 p. Hawkes, H. E., 1957, Principles of geochemical prospecting: U.S. Geological Survey Bulletin 1000—F, p. @5355. Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in mineral exploration: New York, N. Y., and Evanston, 11]., Harper and Row, 415 p. Huffman, Claude, Jr., and Dinnin, J. I., 1976, Analysis of rocks and soil by atomic absorption spectrometry and other methods, in Miesch, A. T., Geochemical survey of Missouri—Methods of sam- pling, laboratory analysis, and statistical reduction of data: U.S. Geological Survey Professional Paper 954—A, p. 12—14. Jackson, M. L., 1964, Chemical composition of soils, in Bear, F. E., ed., Chemistry of the soil [2d ed.]: New York, Reinhold Publish- ing Corp., p. 71—141. Levinson, A. A., 1974, Introduction to exploration geochemistry: Cal— gary, Applied Publishing, Ltd., 612 p. Marbut, C. F., 1928, Classification, nomenclature, and mapping of soils in the United States—The American point of view: Soil Sci- ence, v. 25, p. 61—70. 1935, Soils of the United States, pt. 3 of Atlas of American agriculture: Washington, D.C., U.S. Government Printing Office, 98 p. McMurtrey, J. E., Jr., and Robinson, W. 0., 1938, Neglected soil constituents that affect plant and animal development, in Soils and men—Yearbook of Agriculture 1938: Washington, D.C., U.S. Government Printing Office, p. 807-829. Miesch, A. T., 1967, Methods of computation for estimating geochemi- cal abundance: U.S. Geological Survey Professional Paper 574-8, 15 p. Millard, H. T., Jr., 1975, Determination of uranium and thorium in rocks and soils by the delayed neutron technique, in U.S. Geolog— ical Survey, Geochemical survey of the western coal region, sec- ond annual progress report, July 1975: U.S. Geological Survey Open-File Report 75—436, p. 79—81. 1976, Determination of uranium and thorium in U.S.G. S. stan- dard rocks by the delayed neutron technique, in Flanagan, F. J., ed. and compiler, Description and analyses of eight new U.S.G.S. rock standards: U.S. Geological Survey Professional Paper 840, p. 61—65. Mitchell, R. L., 1964, Trace elements in soils, in Bear, F‘. E., ed., Chemistry of the soil [2d ed.]: New York, Reinhold Publishing Corp., p. 320—368. Myers, A. T., Havens, R. G., and Dunton, P. J., 1961, A spec- trochemical method for the semiquantitative analysis of rocks, minerals, and ores: U.S. Geological Survey Bulletin 1084—1, p. 207—229. Neiman, H. G., 1976, Analysis of rocks, soils, and plant ashes by emission spectroscopy, in Miesch, A. T., Geochemical survey of Missouri—Methods of sampling, laboratory analysis, and statisti— cal reduction of data: U.S. Geological Survey Professional Paper 594—A, p. 14—15. Rankama, K. K., and Sahama, T. G., 1955, Geochemistry: Chicago, Chicago University Press, 912 p. Robinson, W. 0., 1914, The inorganic composition of some important American soils: U.S. Department of Agriculture Bulletin 122, 27 p. Robinson, W. 0., Steinkoenig, L. A., and Fry, W. H., 1917, Variation in the chemical composition of soils: U.S. Department of Agricul- ture Bulletin 551, 16 p. Rose, A. W., Hawkes, H. E., and Webb, J. S., 1979, Geochemistry in mineral exploration [2d ed.]: London, Academic Press, 658 p. Shacklette, H. T., 1980, Elements in fruits and vegetables from areas of commercial production in the conterminous United States: U.S. Geological Survey Professional Paper 1178, 149 p. Shacklette, H. T., Boerngen, J. G., Cahill, J. P., and Rahill, R. L., 1973, Lithium in surficial materials of the conterminous United States and partial data on cadmium: U.S. Geological Survey Cir- cular 673, 8 p. Shacklette, H. T., Boerngen, J. G., and Keith, J. R., 1974, Selenium, fluorine, and arsenic in surficial materials of the conterminous United States: U.S. Geological Survey Circular 692, 14 p. Shacklette, H. T., Boerngen, J. G., and Turner, R. L., 1971, Mercury in the environment—Surficial materials of the conterminous 10 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES United States: U.S. Geological Survey Circular 644, 5 p. Shacklette, H. T., Hamilton, J. C., Boerngen, J. G., and Bowles, J. M., 1971, Elemental composition of surficial materials in the contemiinous United States: U.S. Geological Survey Professional Paper 574—D, 71 p. Shacklette, H. T., Sauer, H. 1., and Miesch, A. T., 1970, Geochemical environments and cardiovascular mortality rates in Georgia: U.S. Geological Survey Professional Paper 574—0, 39 p. Sichel, H. S., 1952, New methods in the statistical evaluation of mine sampling data: Institute of Mining and Metallurgy Transactions, v. 61, p. 261-288. Siegel, F. R., 1974, Applied geochemistry: New York, John Wiley and Sons, 353 p. Swain, D. J ., 1955, The trace—element content of soils: England Com- monwealth Agricultural Bureau, Commonwealth Bureau of Soil Science Technical Communication 48, 157 p. 'l‘idball, R. R., 1976, Chemical variation of soils in Missouri associated with selected levels of the Soil Classification System: U.S. Geological Survey Professional Paper 954—3, 16 p. 1983a, Geography of soil geochemistry of Missouri agricultural soils, in Geochemical survey of Missouri: U.S. Geological Survey Professional Paper 954—H, in press. —1983b, Geochemical classification by factor analysis of Missouri agricultural soils, in Geochemical survey of Missouri: U.S. Geological Survey Professional Paper 954—1, in press. U.S. Geological Survey, 1974, Geochemical survey of the western coal regions, first annual progress report, July 1974: U.S. Geolog- ical Survey Open-File Report 74—250, 38 p. —l975, Geochemical survey of the western coal regions, second annual progress report, July 1975: U.S. Geological Survey Open- File Report 75—436, 132 p. —1976, Geochemical survey of the western energy regions, third annual progress report, July 1976: U.S. Geological Survey Open— File Report 76—729, 138 p. + appendix, 44 p. 1977, Geochemical survey of the western energy regions, fourth annual progress report, July 1977: U.S. Geological Survey Open-File Report 77—872, 207 p. 1978, Geochemical survey of the western energy regions, fifth annual progress report, July 1978: U.S. Geological Survey Open- File Report 78—1105, 194 p. [U.S.] Soil Conservation Service, 1969, Distribution of principal kinds of soils—Orders, Suborders, and Great Groups, in National Atlas of the United States of America: U.S. Geological Survey, Sheet 86, 2 p. Vaughn, W. W., 1967, A simple mercury vapor detector for geochemi- cal prospecting: U.S. Geological Survey Circular 540, 8 p. Vinogradov, A. P., 1959, The geochemistry of rare and dispersed chemical elements in soils [2d ed., revised and enlarged]: New York, Consultants Bureau Enterprises, 209 p. Wahlberg, J. S., 1976, Analysis of rocks and soils by X-ray fluores- cence, in Miesch, A. T., Geochemical survey of Missouri— Methods of sampling, laboratory analysis, and statistical reduc— tion of data: U.S. Geological Survey Professional Paper 954—A, p. 1142. Ward, F. N., Lakin, H. W., Canney, F. C., and others, 1963, Analyti- cal methods used in geochemical exploration by the U.S. Geologi- cal Survey: U.S. Geological Survey Bulletin 1152, 100 p. Webb, J. S., 1953, A review of American progress in geochemical prospecting and recommendations for future British work in this field: Institute of Mining and Metallurgy Transactions, v. 62, pt. 7, p. 321—348. ILLUSTRATIONS 12 1 ELEMENT CONCENTRATIONS IN STHLS, CONTERMINOUS UNITED STATES a 128° 128° 124° 122° 120° 118° 118° 114° 112° 110° 108° 108° 104° 102° 100° 88° 48 \/ ./ / 1 1 1 1 1 I 1 1 1 1 1 1 1 45° ' '* , .\ WA V SHINGTON \ 0 49(03) 2 K C«1(2) 1 \“\APPROZ(_\M£[E 44° MONTANAv/ NORTH DAKOTA 03 £06 EGON . 2. \z’; , 2 42°_ r“ \ 10A G Cd“) "0 SOUTH l‘AKOTA A WYOMING 40° 4 9(3). ’9 (/47 o 1 ‘ 0 ‘\/)~ ._ “”1 0+ \ ' C40). I “L Nag/13M 38° _\ . , NEVADA A96) ' OCda) % 0% UTAH . 049(2) > “0 Cd“ _| 36°\ i .Cd(10)% COLORADO . _U “7 Z €412) "' > KANSAS Bras). 0 E 'c 4 .CZ: m o 11(1) , 34 2 E; E AR’ZONA N (n OKLAHOM 328 049(3) EW MEXICO ' Bi(15) I can . .5) 30° \ TEXAS 28° 28a 24° 22° 2 l 1 l I 1 1 1 1 1 1 1 1 18° 115° 114° 112° 110° 108° 108° 104° 102° 100° 98° FIGURE 1,—Location of sampling sites in the contemlinous U deposits were found, and the amounts of the ele ents present, in parts per million, in parentheses. Fwd States where elements not commonly detected in surficial ? ILLUSTRATIONS 94° 92° 90° 83° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 65° 64° 0 | I l l \ \ \ I \ \ \ \ \ \ \ \/ 48 46° ,7 VNESOTA ; 5; .Cdu) , _ Rx WISCONSlN Inf MICHIGAN IOWA y I 7 , .oam / «, OHIO ILLINOIS INDIANA ‘1 , ’/ : 1 i- » was NCONTINENTAL YI‘Q/OV ‘:_ vIRG‘N‘A “RGIMA 36° ‘ MISSOURI V9 0 ed???) .7Cd(1 5) KENTUCKY ”7/ 7 . . HA9“ I ' 7 , ’7 NORTH cAROL‘NA . 34° TENNESSEE .5; “m 'y '2 ”xx SOUTH t) «I 320 ARKANSAS ‘ ‘ xv; CAROLINA ._ . \X‘ :MISSISSIPPIS ALABAMA 650%” Q 5,: . 30° 4 1,5 “1100) (51 PL ATLANTIC ~ LOUISIANA , 1 I ”/2“ 28° 1'71]; I :I \fly ‘90 ‘36 26° 7 9 590 MILES 24° : ' i 22° 1 i 1 l \ \ \ \ S \ \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 13 14 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 0 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 43 \ / 1 1 1 / 1 1 1 I 1 1 1 1 1 1 1 46° \ 44° \ 42° \ 40° \ 38° \ 36° \ 34° \ 32° \ ,1 i D SYMBOLS AND PERCENTAGE \ [:1 a i n D a El ”1' 0 OF TOTAL SAMPLES “ ~~~~~~ x B I if: a . 30 \ 18 191626 21 \“\\ 1:1 1:1 1 M 1.1 CI 13 n I “E" NE.“ 41 M , r—A—fi/M'M ‘ W328 300 l 1: U U 28° \ I \ a i | :1 u 1: I "\- ',.,,.1\_ VVVVVV > 200 l “l a! Q ‘2’ 1 Geometric mean: 4.7 260 \ 1:34 1 Geometric devsatnon 248 8 Number of samples and analyses: 1,247 c: “L 100 24° \ 0 r\ In“ gsaggé‘gfifmmmkoo '— X 220 \ AMOUNT, IN PERCENT l l I l I I 1 1 1 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98" FIGURE 2.—Aluminum content of surficial materials. “‘4 AA “A 4 94° 92° 90° 88° 86° 84° 82° 80° 78° \ ILLUSTRATIONS 15 76° 74° 72° 70° 68° 55° 64° \ \ \ \ \ A 48" \/ / 44° / 40° / 38° / 38° / 34° / 32° / 30° / 28° / 26° 0 590 MILES 9 / 24 a I i : 2 / 22° 1 1 l 1 l \ l \ \ \ 94° 92° 90° 88° 86° 84° 32° \ 800 780 76° 7 4c l6 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 125° 124° 122° 120° 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 43° \/ I / I / I I I I I I I I I 48° 44° \ U 42° \ U LI ~ \ I” II o { U 40 >\ 1‘ LI U U ' U u :\ H 38“ K :> . ‘21 36° \ > I 34° \ ‘ __ U 7:) ’ 1 32° \ ‘t‘ 3 y U U j 1 M I Ll » 1 \N\\ I W I. U ‘ U U ' \\ ,; LJ \_\_ I LI LI 30° N _ I LI : 5 {LI , “A ~ J u SYMBOLS AND PERCENTAGE \ J 1 U . OF TOTAL SAMPLES “ u 1:: 0 U 28° \ 8L] ‘3 U W 1 I 288 \ \U U I 1 \ ,. | 26°\ 2 1 Geometric mean: 0.48 § 100 I Geometric devnauon: 227 E: I Number of samples and analyses: 354 u. I K I I \, 24° \ 0 m N Ix «— “l. '\_I -— N m' «5 <3 AMOUNT. IN PARTS PER MILLION 22° N I I I I I I I I I I I 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 93° FIGURE 3.—Antimony content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 55° 64° 1 1 1 l l \ \ \ \ \ \ \ . \ \ \ \/ 43 ; yr /46° ./ 44° / 42° / 40° / 36° .V, 34° / 32° / 28° / 26° i L‘\_ ‘ o U 5?0 NHLES ‘1, '3', / Z4 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 18 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98" O 43 \I I I I I / I I I I I I I I I 1 iii ~~~~~ \ \~» "\‘w 3 Hwk 5 fix 2,? 8 I7\\ . 0 Av I U Ll lllll “Ba“ 45 \ ’* B” U / a \13~—\2 _ I L1 3 / E I 5 *~ —‘\ .‘ "E\EIU U E E [/- D. U i E E HIT THE ”M... ‘“ “TE a )5 ES 5 III I $3 I a Ilauafifl' agar! ? ’ ‘44}; In I ‘ a x. I: \~\\ 17- E E El a , Ll‘. 440\ I; a \z D j; I a B .fiana?aaa a 14° :1 ”I , LI I a El 9 a 9 1 / 1:: D // u IVA? E! a an EF' 5 uu 1:! u a a a 1“ I . a II U U I' 1.: 5| U El 5 a ‘1 '3‘ D I % Eb \‘ M E a fi“* J—Lg—u. o E El _, a E {max A ‘ ‘ \k‘U i U I I U E < 42 L] B I a ” 1‘ 9 ~11.“ \ ~41 ' '3 I :1 a , n I a u g I! ............. a 1‘ a 9 u u I I I “a I E 1:! ¢ U a E E a B .E D ..... 2\ ".I U E g i I E ‘/"‘-»\._ i 1 E B /U U I \ ‘41:, U I] E E B a S 40° ‘ U c: J a \\\\ E . U a a i L] U 5 Sun I “REL. E a u, “~44M» .2. ' '- I ‘ a E f D u D M \‘wm I10 D a ElIE: CI in; {an B D cu U \ u u D a I El 1 1 n I i n a a I u u u l I n I ' a El 38 U 35° 34° 32° 30° 28° 26° 24° 22° I E I E I u I x . (“x U U ., ,a ‘3 a E ,4 III a i U U B ‘” '\ El a E I ‘3 1:, I 9 B Lb a] E D B L15 95’ a D ’ I Fl 1 E a \.w (E a U a “m,“ _“_ U D n D I E 7f E U I E E E LlI U U a U L! g I u SYMBOLS AND PERCENTA‘GE u E‘ 1:! 1:! U ,1 OF TOTAL SAMPLES E U a {,5 a :1 22 20 2919 9 \\ g a [I U ‘3 E": C! a . a E g u 1:: a a I kn“ Jr~~~~LL ‘7~é—»—~w......_d a a a 368 I 300 l \p I: U u 1 \\\\E E B B i E I E1 \13 E' I»? ,,,,, a 200 ’ M g Geometnc mean: 5.2 \LLxJal '5' Geometric devuation. 2.23 8 Number of samples and analyses: 1,257 K l‘ 100 0 V VVVVVV +838 mmvm $OOOI-v-Nvtoel'ggzg8 AMOUNT, IN PARTS PER MILLION I I I I I I I I I J I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 4.—Arsenic content of surficial materials. 19 ILLUSTRATIONS 80° 78° 75° 74° 72° 70° 68° 66° 64° 82° 46° / 42° / 40° / 38° / 36° / 34° / 32° / 30° / 28° 24° \// 48° o 6 2 / 500 MILES / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° I O 48 \/ / / l / 1 1 I 1 1 1 1 1 1 48° N 44° \ 42° 40° \ 38° \ 36° \ 34° \_ j E U 32° \. a: E , g I El B , I E El 1:! 7 SYMBOLS AND PERCENTAGEB " a i E E E I E D a , 1, , OF TOTAL SAMPLES ‘3 , :1 u a ‘ u 9 " a I E D E 1:: L1 17 18 2526 14 mF I a 1 i a B :1 LI CI B i I r, I [I 30°»s i B (a II Ina E FIE U D EU a E u CI _, LI B LI 0 E H I “a E U E , U L] U U H U E \_E U [:1 El L! I u a :1 D u o a U U 28 \ I E u E E ‘3 U_ U E >— \, V \ ‘2’ Geometnc mean 440 E«_ U B\ E! El 5 El 3 Geomemc deviauon: 2 14 LIE 25° \, 8 Number of samples and analyses: 1.319 U E I E E] D E a . 3 CI 24° \ \E B 51 “x, I 5““53 220 N AMOUNT, IN PARTS PER MILLION / / l I I I I I I 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 5.—Barium content of surficial materials. ILLUSTRATIONS 5 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 0 I 1 1 ‘ \ x \ \ Y \ \ \ \ \ \ \/45 / 46° 44° / 42° /40° ,, 34° / 32° / 30° / 28° / 22° \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 0 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 43 \l / / / / l / I I I I I I I 1 I {\N --~\ ....... 1+“ ~x. ‘4 \I’ “““,"‘~~\\ 0 U U L] i, i ' «a 45 \ u I I U\‘ 3U Ll U I U ‘-,\ B “ ' ‘E'w ~-»- WW.-. “"1“"‘“ V. U U U , 5 I U I I 1 U "' .......................... .’ U E 4 U1 L1 L1 I U I E .U L' B E' ’ 2 I uu I 1 Lu " \ / ‘2 u I a E < E [LI 1:1/«~L¢.,.M, u. 1\ u u E. SE: I ”'13 we EW\1uuWE-a , a ‘ U u U a E L! LI I 42° \ 40° \ 38° \ 35° \ 34° »\ 32° \ SVMBOLS AND Pencéh‘f/IGPH“ . ~§ OF TOTAL SAMPLES ° 63 23 14 x u l a U U U Us u U E I U E L15 I u .5 o WA—fi \ s 30 \ 824 a 1 I ‘~\.\\ U U :13 . E I L1 L? U U E ' 1 I °£“*&»—i_ f” a” 1 “u Uu U | 1 U 1 o 300 | i x u u u 28 \ v i ‘ 5, I U > 1 1 x“. U 2p. B I g j I; Geometric mean: 0.63 ' \__ [J " "14‘ U ”3" 200 | ‘ Geometric deviation: 2.38 i‘L\/l " u U U L] g | Number of samples and analyses: 1.303 U u 26 \ LI. \ U R U 1 \ U _ X 100 ‘“b u 122/ T, U 4:; 24° \ 14E U 53.. L0 .— _ ‘— N m m V\ o LO v .— .— 220 AMOUNT, 1N PARTS PER MILLION F / I I I I I 1 1 1 1 J 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 93° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES FIGURE 6.—Beryllium content of surficial materials. ILLUSTRATIONS 76° \ / 43° / 45° / 44° / 42° / 40° / 38° / 35° / 34° / 32° / 30° / 28° / 25° / 24° / 22° 72° 70° 68° 66° 84° 74° 90° 88° 88° 84° 82° 80° 78° 92° I 94° 74° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 48° 46° 44° 42° 40° 38° 36° 34° 32° 30° ~ 28° 25° 24° 22° 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° ' \ f / / / / 7 / I I l 1 1 1 1 1 l D L1 U a“, __ V _ U U a a- B l I B LD ; d3 Eu ”1.: LIBa ‘ a a El E s u U D a 5'8 \ Uu B-DiDBLJ ULJ U u jEI a u a D E :4 BE % g u a a I I a a BB U % Us UBLI U E L] E B E B E ME1 7 Bi ,5. 3 Li C! u ; B ' " a..-» L1 ‘ U \ a g . u :1 u a UH"; LIE] W.” U E a a.“ nu u g a [j , U E! g I D U a : U u u D ’ U D : B I 1 13 L1 1.1 1 L1 9. l L] E ‘ U I 1 i E ‘ a ; E ‘ \ E j E [j E D 8‘ B 1' ._ k u 'U u U 5 E a a an?“ E U B «a» u 1.: ii I L1, 121 \ SYMBOLS AND PERCENTAGE a U a ; 9 ‘ OF TOTAL SAMPLES U , u U u U? U n u a a “M .V U 1' C] 29152618 H ‘-'.f u U : U E was: I U a J” u u fa u U U U D an a a NWv—Afi * a; 1,. f..m,_*_ :u E; D a 1.: 7E1-“ F U a u u“U” u a B U u U a L‘Ll U E L] - E u U E _ LJ >\ L1 L} U E [1 L1 LJ\Lk (V U D >_ ‘2’ Geometric mean: 26 U Um Ll U U U g Geometric deviation: 197 E1 \ 8 Number of samples and analyses: 1,319 19 a E ~ > a _‘ B Q .\ u E ‘34 u 111‘ 8 8 8 8 2 8 8'8 § V v- F N "‘ AMOUNT. IN PARTS PER MILLION / I I I 1 I 1 I 1 1 1 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 7.—Boron content of surficial materials. ILLUSTRATIONS } 94° 92° 90° 88° 86° 84° 32° 80° 78° 76° 74° 72° 70° 58° 58° 54° 0 \ \ \ \ \ \ \ \/ 43 s / 44° / 40° / 38° / 32° / 30° / 28° / 26° —-— o 590 MILES J l \ \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES a 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 43 \l / I I / I I I I I I I 1 1 1 46°\ 44° \ 42° \ 40° \ 38° \ 36° \ 34° \ 32° \ 30° \ SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES 28° \ Geometric mean: 56 \ Geometric devtation; 2.50 “4 I Number of samples and analyses: 348 \ 26° \ FREQUENCY 24° \ AMOUNT, IN PARTS PER MILLION 22° \ l l l l l I I I l I I 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 8.—Bromine content of surficial materials. ILLUSTRATIONS / 46° / 42° ,40° / 38° / 36° \/480 68° 66° 54° \ X 70" \ 76° 74° \ \ 78° \ 84° \ 92° 90° 88° 1 1 ‘ 94" l o 4 3 x / 32° / 30° / 28° / 28° / 24° 500 MILES A 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 118° 114° 112° 110° 108° 105° 104° 102° 100° 98° 43° \/ / / / I I I I I I I I I I 1 1 45° \ 44° K 42° \ 40° N 38° \ 38° \ 34° \ 32° \. 30° \ \ 1 n a D E B a E‘ D 3 Mg E‘- .V .. “0-“. U 11 I :1 l B E u SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES ' ME . N 3 ‘ E I I I” I E] E 19 20 24 19 18 \g . E! a I I I l I I ii I \ I g l 28° \ E I I \I D »'. :1 a Z; \\l L '. 1; \B I I l I a 26° \ 8 I E u U I 13 LJ _ I -_ :1 L159 0‘: O) a) ‘1 3 I c 5533§<93333~®®~om \ U - 24\ coooo ooooov—vangg \\ [ja- AMOUNT. IN PERCENT M" ‘i Geometnc mean: 0.92 Geomenic deviation: 4.00 220 I Number of samples and ana|yses: 1.291 / 1 I 1 I l I 1 l I 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 9.——Calcium content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 30° 78° 75° 74° 72° 70° 68° 66° 64° 0 \ \ ‘ \ \ \ \ \ \/ 43 I 1 l i \ \ \ V / 44° / 42° / 36° ,2 34° / 32° / 30° / 28° / 26° 590 MILES ’ 24° 1 l V l I ~44 o 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° "-7 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 102° 100° 98" a 128° 125° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 43 \ I I I I I I I I I I I I I I I I o E B V 46 \ E r\-~.-_- n :1 a Mama"““‘v“"’E““~ a V, . ._._.., W. I a D B a ' a :1 a (:1 44° \ n x I: I9 1 a i /x \ I i a ( \> U °\ a» 420 Ill If: LNN’V’JNVVI: “'B~-. “"'“~~~E~ ’ I’ I 2 «fix I I U N I I’ Ii \2\ \K I l D 40° 1‘ U / \ \ a I I ’ u ,1 I ’ ’ U I E U I" j ‘ 38° E , I‘ 2 ”MN?“ \ ix!» 8 B \V E I n 1°: :3 \\ I? I. a. I a é D B D \ =5 .PB'BIE S 36° fl '3 x U a a ’ F \ . .‘ U n a \ U \\ V, U a a 1 B I i 1 ‘ I I I la \ ILWW‘ . I “ U u i D 4 V ‘ a g a \ LI \ (7 I \\\ w ~ . a U D \, “V U U 2° 2 MN" 34° \ \ 5’ I g V \I ‘2 32° \ ‘ I a ,3 1‘““~- ~ C1 ,1 / \\ 1 x 1.: 30° N , Ll \‘ if ~ C1..-I{:“\—»\ SYMBOLS AND PERCENTAGE ' \. OF TOTAL SAMPLES \_ 23° \ 16 1e 25 20 23 \V u D a a I 1- \a 26° {25 Geometric mean: 1.6 \ g Geometric deviation. 2.57 8 Number of samples and analyses: 412 BE 24° \ AMOUNT, IN PERCENT 22° / I l I I 1 1 1 118° 116° 114° 112° 110° 108° 105° 104° FIGURE 10.——Carbon (total) content of surficial materials. 31 ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 75° 74° 72° 70° 68° 68° 64° 94° / 46° , 42° /40° / 38° / 36° / 34° / 32° / 30° / 28° / 26° 24° / 22° \/480 .. i. z? ’ I 50!] MILES 74° 75° 78° 80° 82° 84° 86° 88° 90° 92° 94° 32 48° 45° 44° 42° 40° 38° 38° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° ‘ 98° \ I I / I I / I I I I I 1 1 1 1 l Uu.‘_L1' I Ij‘l I I I. i 2‘ EH u L 0 SYMBOLS AND PERCENTAGE ‘ «U U u u u L OF TOTAL SAMPLES » _. U L1 U L1 0““ L1 L1 L1 \\\ 1“ U, U >. u \ g Geometric mean: 63 ‘ 1—1 8 Geomemc devvation: 1.78 ‘ L1 3:4 Number of samples and analyses: 1,172 _ u 9 AMOUNT, IN PARTS PER MILLION / I I I 1 I 1 1 1 1 1 118° 1 16° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 11,—Cerium content of surficial materials. ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 94° \/48° w / / 42° /40° / 38° / 36° ,, 34° / 32° / 30° / 28° / 26° / 24° 500 MILES I / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 43° 46:: 44° 42° 40° 38° 35° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 128° 124° 122° 120° 118° 116° 114° 112° 110° 108° 108° 104° 102° 100° 98° \/ I I / / I I l / I I I I I I I \ \ y. . A ( INK. ‘ E1 Ex- 1 I I a J \ 9 I) I { I \\ I \ }\ a. , i x 2.; I \ E: i \ ! <1 I x, ”org. -EN 1.2 , El 13 1:1 3 (J: US D E a II E' U; \\ I i U U El uI \ a 'i u a 1 \\ U u I] I I 1 \ 1: ;u E g in a IT‘S \k 1.1 "-2, V ~._.2-\7 ' Ll SYMBOLS AND PERCENTAGE OFTOTALSAMPLES‘HNN-UWJ 9" ‘\ a F"“r~“ 25 22 2119 13 U u D121: I \E a U 300 «Vi/T | \\ u \ | I I U | ‘1 I "L‘J if "R >_ 200 I J o I \ E | Geomemc mean: 37 8 | Geomeiric deviation: 2.37 E : Numbev of samples and analyses. 1,319 100 I I | ‘ I 1 o ’« **~“““928882§§§§§§§§§ .— -— N N AMOUNT, IN PARTS PER MILLION / I I I I I l I 1 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 12.—Chromium content of surficial materials. ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 94° \/480 / 46° / 42° / 40° / 38° / 36° / 34° / 32° / 30° / 28° / 26° / 24° 500 MILES I / 22° 74° 76° 78° 80° 82° 84° 86° 48° 46° 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98 \ / I I / I I I I I I I I 1 I l l 1\ U, V U: n 5' U u‘ SYMBOLS AND PERCENTAGE a B ,5 a ' " \ OF TOTAL SAMPLES .5 a I In ‘31 D U I: a n K E a > , 7 a 1' LJ 1:! U :1 16 21 2220 22 132.28% am“ 1.1 1.1" U a 1:1 1:1 9 a I ‘1: 1.1 U [:1 x :1 U DB in ~. __ LI L] g x u a \ 1: a U u x ' U a ‘9 13 , E, > ~ El"! mu :2: Geomelnc mean: 617 ' B U U U 8 Geomemc deviation: 219 E E Numberof samples and analyses 1,311 1, D .\ 1:1 ‘1‘ \u mmmNRSRRSé AMOUNT, IN PARTS PER MILLION \ 1 1 1 1 1 1 1 1 1 1 1 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 13.—Cobalt content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 86° 64° 0 I l l \ x \ \ \ \ \ \ \ \ \ Y/ 43 46° 44° 42° / 40° 38° ,7 34° ,4 30° / 28° o 500 MILES / 2“ / 22° 94° 82° 90° 88° 86° 84° 82° 80° 78° 75° 74° 48° 46° 44° 42° 400 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° J \I I I I I I I I I I I I I I l E ................ \ UNI ‘ 1:1 , 2 MM U .3 E' I: U I: “W“ ' a 5 I I EIIU I u IBE- n a n E! E , I I \ UIF U I a ' I Us a U I a u I I. a n I: b 9 I I a U E U 1 D / i E .I E I““~~~BF.. ~ _ M vii ~34» E I E If U I \ : Emma “M I a I . i I .71 j 2' u a BIS EI U I El a DE 3 a L D .n I E U I 3 a n E! u '3 E a I U D I I. \ El 3' Wu ..... M-.. I, E u a 5 ”Ia 5' '1 I: U UI‘ LI I n 1 1 . El 5 D E: E E n5 U U U U I In: a u ' " I“ .,,._._ I D I U L‘ U x I U In I If] 55 ~ I a \ I‘ I ‘ I ,4 '——«J~fi.-w‘ -/\\§Ea \IE 9 I ulna qu E; EDD 5’ D U a I El I 5 ,n‘ a )3 D u = U ”Brian ' D a E“: “ L_.,_,_,_.__w_, 2H, L] D X: a E I I a. 53.. CF 9 EII a E I 5""; I ,-’ I U I: I E) x I U Q SYMBOLS AND PERCENTAGE K \ OF TOTAL SAMPLES ~. NEE 300 C 200 \y ‘0 N g E! U E Geometric mean- 17 N \ 8 Geometric dewatIon. 2.44 '2 u E] $ Number 01 samples and analyses, 1,311 U U “L 100 u u\ U LIV: \ u ~‘I \ “LL U E? o m "ENE V’"“°°“998889§§§§§§ AMOUNT, IN PARTS PER MILLION I I I I I I I I I I I 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 14.—Copper content of surficial materials. 39 ILLUSTRATIONS 46° / 44° / 42° , 40° / 38° / 36° / 34° / 32° / 30° / 28° 24° \/48° 64° 65° \ 74° \ 76° \ 82° \ 880 1 94° l o B 2 / 500 MILES OIL / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 480 \ I I I I / I I / I I I I 1 1 I 1 El 1;, D a ' 'I > 46° H E B a 0 .1: I 1E a - -, - fl - ’ ‘1 a E I an a ' a a _ WW I F ‘3 E! 5 I. B I BED ’ 5‘ a B a a ,5 a a. a I B 5 ~ \7 I E I [J “K 111.1" a 9 1 I r" a a B e E I'aaaa H u " \ a a 1: a 1: a a 1:1 f saga-:1 In I I an a ‘ a a. a '3' 1 a 5' ‘Il M. B 1 E E % E ' r u a i 8- F I 420 ;° U E 1 E I an AM" °' ° 'F a. -,. i E \ ; E B a ‘1 a "I 1‘ ,1 E I I 1 B I : E U I E \\\\\\ a0 a E a . Ela a a a g a a 1:1 I l a all B ° 5 i B I 1 E .1 E E , 5 E a 1 D E E1 / LI E - I \2 I I B .’ U B I .1‘ o ' a 40 \ g :1 I B F? a a I IS I U _ a an: ‘ U E Ha I I I - I E E] x- I 'a 1" 1 a a ', Iu ; I an Ilia: 6 Fa ‘_ a a a a a a I :1 :1 1.1 u ‘« n' 1’0 BE 5 ° = “5n: ‘ s 1 1.? B u U 38° \ I E- , a ‘1 w ~ . 3,, gimwma a E] I \IE I I ' .1 . E II a all] fine I I I 1 E i I B E E E E i: ( I -. I x E f I i a I g I i f I ~ INN—IE _ V “;U I - I 1 » I g I I f E I E a 1’ in 36° \ ‘_ a | g B : E E E E I I a 1 u a 1 a In a I :1 ‘1 Fl 1: g E E U 1 ,, ' I $3 0 "a: as I., a __ El , B._ ”U LI 34 \ 5'. IE 9 a; E El a . I ’ a a a a. 13 9 a 5 E u , B a a ,1 a a U E U 1 E USE a 32° 1:, .1 If a D u I , \ 1_ 1 I '1‘ I U _ I I U I E g D \2 B _ “B i I :’ E E D I U _ ~ :1 a I 1.1' I a \1 a a a a a a a u a n I j a a o * _ E' .15 1:1 I I d I 1: g 30 \ SYMBOLSANDPERCENTAGE OFTOTALSAMPLES a a 1 I E' a E a a a BE :1 5 U E_ E , g * 1- NU " *4 “‘52 U E E 12 12 34 24 18 ' I , B a E u ‘ I I u U E 300 g D U E 3 28° I a ”RENE ‘3 200 I 1 a U E Q Geomemc mean: 0.021 * B B E 250 ‘5 Geometnc devnation: 3 34 a \‘ g Number of samples and anaIyses: 1,045 '- 24° \ 0 22° I / I I I I I 1 I 1 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 15,—Fluorine content of surficial materials. 4“ ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64" I I 1 1 \ \ \ \ \ \ \ \ \ \ \ x/48° / 44° 42° 40° ,.- 38° / 36° 30° lJ av ‘ Q 500 MILES \ / 24° . / 22° v 1 x l 1 \ \ \ \ \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 48° 460 4r 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° “ \ I I I I / I I I I I I I I 1 1 l I ,1 (U I ‘3 '1 u 7 ‘ u El 1:! °\ in I .1 I D Cl 5 \\ _ I \ 3 . SYMBOLS AND PERCENTAGE “ \ OF TOTAL SAMPLES \\ I I E 15 23 23 20 20 “ l L] C1 B U I ). “2’ Geometnc mean: 13 “‘3 Geometric devianon: 2.03 \ g Number of samples and analyses: 1316 u. vm~eeaasé AMOUNT, 1N PARTS PER MILLION / l I I I I 118° 116° 114° 112° 110° 108° 108° 104° 102° 100° 98° FIGURE 16.—Gallium content of surficial materials. I ILLUSTRATIONS 92° 90° 88° 88° 84° 82° 80° 78° 76° 74° 72° 70° 58° 65° 54° 94° \/480 o 5 4 / / 44° / 42° , 40° / 38° / 36° / 34° / 32° / 30° / 28° c 0 O 6 4 2 2 2 2 / / / O 4 \ 7 o 6 \ 7 o 8 \ 7 0 0 \ 8 villvyl U H— ,> x 07. 2. fl \ 8 RN— 0 4 \l 8 S E l MD M \ 8 U 0.3 5 o 8 l 8 o 0 ‘ 9 o 2 I. 9 O l 4 Oil g E: 1" FP\\ ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 128° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 88° 0 43 \/ / / / / I / / I I 1 1 1 1 1 1 g - »_ \ 46° \ '1 E' ‘7»:- 1 ’ I ‘~ E ' l a a a _ . U E! I I U '1 _ a u a U u 3 9 E a I E! ’ ,- xfi I : \ ° " I ,/' 1E 44 \__ 5/ u {1 E a i / : LP u p B ‘ B I V U E I : , {p 1 a ‘ a ‘ arr" 42° F1 L ~ '8 ~ 1 ' D i a a u ‘ \\\\\\\\\\\ I ‘ a a , u g ,a , g a a 1 402 ' a ‘ ,1 a ‘ is n a a an ~ ~~ , =1 a a a “ a i I [:1 a I: x ‘3 a a ,1 1 u 1:: 38° \ i A y ------ E . 0‘ ”an i E x B s a I: {3| n \ 3% L1” L] U y u u ' a u ‘ ._ W i U U a 9L] E [F E i 35° ° a u u ’ ”U 59 a \ 1 K , a D a El a El 5 :‘u D . a ,- u U I u a a 3 u I BE a L] 3 U U E ,w U B an E f E B I « a \ '3 .. u E‘ o <_ E i “ ' E ' W13”. ,_ :7 34 \ . a , , g - A ‘ V 9 B 5 n \ a U E i 2‘ 32° “ n D l’ a U I U x, ‘ I 1 E] E U B _ ,y E 13 30° \ g ' U . T . E E i C] 28° 5 U \ SYMBOLS AND PERCENTAGE " OF TOTAL SAMPLES ‘ E E U 17 21 28 24 9 0 D I 1.1 1:! E i I \_ r—WM/A ‘ 250\ >_ 100 1 1 ‘2’ Geometric mean' 12 ; E % 1 Geometric deviation: 1.37 » 8 1 Number of samples and analyses: 355 E] E 0 U «7 N N ‘ a 24°“ §§§::_2222 = a AMOUNT. IN PERCENT U 22° E / 1 1 I 1 1 1 1 1 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 17.—Germanium content of surficial materials. \m 44* A... ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° u l l 1 1 \ \ \ \ \ \ \ \ \ \ \/ 43° 45° / 44° / 42° ,, 34° / 30° U / 28° / 28° 8 580 MILES ” 24 I 94° 92° 90° 88° 85° 84° 82° 80° 78° 76° 74° 7 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° 98° 48° \ / / / / / l I I l I 1 1 1 1 1 1 46° ‘7‘ % El 1 Ta ” _ s’ 1 '1 0 1E \‘ 44 \ 1 U B B 13 5 LI 1 1~W.___ > u_r<_— _ H M 2". '7 42° \ ‘-' a B E U E E U U U o :' ° 7 ( N E E E 40 \ . ,, _ _ WEB ”Mg .W 38° \ 36° N 34° \ j . 32° \ 1 . k "MRI “\uV. “Ix/H I I E S 30° \ a ‘ ~ 4 ’ ~»-.a..__'r*~~~ «7..--.‘22 . ‘1, I SYMBOLS AND PERCENTAGE ‘“""“~ 4w“; “r; E OF TOTAL SAMPLES I I 35 33 32 \ 28° \ 1.1 E I \\ I U I : - :u mm.“ I I 'l / K, > I ,1 «., u M; 1'4 7 o E 1 Geometnc mean: 0.75 1 2° \ 8 | Geomemc devuanon: 2.63 \\ U l E | Number of samples and analyses: 399 LL : \k L] I' 1: 1 1.] 24°\ “2309*? oawmrs 1:] $oo~~~mm- 200 1 L2’ 1 \ g | Geometric mean 1.8 8 I Geometric dewanon. 2838 E : Number 01 samples and analyses‘ 1,317 100 1 l | \ | 0 I L, AMOUNT] IN PERCENT I I / I I I I 1 I I 1 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 19.—Iron content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 0 l 1 1 l x \ \ \ \ \ \ \ \ \ \ \ 48 ’. ‘ 46° 42° 40° / 36° 34° / 32° ,/ 30° / 26° / 24° (‘3 560 MILES 22° 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 128° I uu .1 E B 14. B ,,,,, 1&1 11m: 11.x u a I B m B E m u u a I a 3 a \ m a I \ 1. I \ w I I x w m a 2 w u 9. a s \ 1 m. x x m .. a .aria, , m m , \ 2 t p 7 m m m. 5 II N .w m m m a w I . a m m m m _ A M .W M U .2 T S L \\\11,1 N pl...— W ‘\ :C. P R I R M E n E A P .‘m P s s m L m m A M P m m m 0 F M u N ,. . T. w a 3 2 m m s / 62m38E A \ \ x \ \ \ \ x \ \ \ \ \ \ 0 O 0 C O O 0 O 0 O O 0 0 w M M w mm mm M ad w M E M D 108° 110° 112° 114° 115° 118° FIGURE 20.—Lanthanum content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 78° 74° 72° 70° 68° 86° 64° l l 1 l 1 \ \ \ \ \ \ \ \ \ \ \/43° / 38° / 34° / 24° 5am MILES I 94" 92° 90° 88° 86° 84° 82° 80° 78° 75° 74° P 52 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 48° 46° 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° 128° 128° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102‘7 100° 98° \ I I / I I I I I I I I I I I I I B ‘ E D ‘- a “I a u :1 SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES 5- E E E!- G Ll I D 9 I E E _ 9 I , _ , _ _\ LI C! I a El [3 14163120 20 I , , E x u D a i I I D. U U U a D ‘ D u L' E E E1 LI ‘5' ' ‘3‘ U E E ii I U E D “I E I >- X EL. \_ P I U E [1 El D E) Geomelnc mean. 16 I BE \ a Geometric devoanon 1 86 1 E1 § Number 01 samples and analyses: 1,319 _ “C! I I I I I I I I I I I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 21,—Lead content of surficial materials. ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 94° 24° \/480 45° / 44° / 42° / 40° / 38° / 36° , 34° f“'u 1 4.. / / 32° / 30° / 28° / 26° 500 MILES / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 126° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 0 ‘18 / / / I I I I I I I I I I 1 1 1 46° 44° \ 42° \ 40° \ 38° \ 36° \ 34° \ 32° \ I 1 I 1 V»- SYMBOLS AND PERCENTAGE E a I 5’ a ‘ WHA- OF TOTAL SAMPLES B . 1 a =1 ‘3 a u U u u S :1 -~ El I 21' 172918 15 \\ E, I! a I E, 30°\ L! De: I \\ a 1: Ella EEC] a .I D 5 Hal 3 u ,—-x/\/\/\x—’¥—\ \ i ,- ______ 3. _ -_--.,,_ , L1 9 B 121 J 2&1‘4 N};- \\“1J E] B ‘U U 1:1 1:1 14 U I \ a g E I B x a u a '3‘ a 9 28° \\ 13 E u \ I E ‘E E LL 5 a 5 .\ # H‘ a E 5 Geometric mean: 20 ~12; REE C1 E 26° 8 Geometric dewatlonv 1 85 Q \ g Number 01 samples and analyses: 1,258 3 U LL ‘\ U \n 24° “' \ 1 .fl . 22° ~ AMOUNT‘ IN PARTS PER MILLION l I I I 1 1 1 1 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° FIGURE 22.—Lithium content of surficial materials. ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 94° O O 0 0 0 0 O O O O 0 m m M n mu. m m M n w w m u n / / / / / / / / / / / / / / \ o4 \ 7 \ V, M, U ".0 IN V \ 7 \ «Aug/‘7‘ Pi. \K A" u \o\ a , \ Kim‘s; ,. mo ., UV \ 7 .. n- , ‘‘‘‘‘‘‘‘‘‘ y n- ,Y.\ (\Lu\.n \ w a a / a D W; U I I I I \ m ./ u \ /»,., D B I r, O 2 \ \ oo \ 0 \ M O 6 ul 8 ., Er” BkUU U U \ i. .L x J\., a ,, J 8 . ll 8 ‘ 0 1 M III 0 2 l 9 0 OK I M ‘ II. E ‘7‘! \ ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° 480 \l / / I / l l I I I I 1 1 1 1 I f. _ “a. ._ 46° 44° \ 42°\ 40° .\ E 38° N l E u n ' “ ’3. I B E I. g SID BB: ._ a :3 fi-‘ha_ a I a fag _ a x\| g ; E E El MEME » > ‘ F '51:“ facile.“ Bean”:- 5', E' a a o 1 f a 35\ in U'EEBEB DU '3“: a g a 34°\ 32° \ 30° \. SYMBOLS AND PERCENTAGE ‘ E E E! El 8 E OFTOTALSAMPLES a a a a a, l . 2' u a E. a u an 19 17 32 14 ‘ I- ' DD El ii "I D a El 9 'E I U a B B B 300 | \g B B E B '85 280 ‘ i ‘2‘ a B I 1 a D E ‘B 7.» WE a 5 200 u E? a g E. a E Geometric mean: 044 S 28°\ 8 Geometric deviauon: 3.28 B '5? Numbel of samples and analyses: 1.306 K ‘L 100 24°\ 0 Ln l\ LB 88858888—3o1m5 u} /\ 22° AMOUNT, 1N PERCENT [ l I I i I l 1 I I 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 23.—Magnesium content of surficial materials. 57 ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 58° 68° 64° 94° / 46° / 42° / 34° \/480 WV 4 / / 38° / 36° / 32° / 30° / 28° / 28° / 24° S F. Hk M 0 0 5 A 22° 74° 75° 78° 80° 82° 84° 86° 88° 90° 92° I" 7\} Fl ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 48° \/ I I I I I I I I I I I I I I I 46° \ 44° \ [u] 420 \ 8 2° [é 40° \ “a \ I X a \ 5 38° \ 9 2:; E a 36° \ ‘15 ‘3 34° \ 32° \ King a 8 \~\_ El 30°\ SYMBOLS AND PERCENTAGE \\ D a 1 E! E! Be” a j E OF TOTAL SAMPLES \g > E~«.._w:1..~r__/N“""““‘ 1:1 "11:1 LI 21 29 2113 u ‘51 u LI I: a i I \I LI x E o 300 Ll 28 \ a D \ u \5 D \ 6 200 5K, 1? 25°\ 5 Geometric mean' 330 8 Geometric deVIatIon: 2.77 E Number of samples and analyses: 11317 100 24° \ 0 22° f / I I I I I I I I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° AA FIGURE 24.—Manganese content of surficial materials. —-_ “A A_A 59 ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 75° 74° 72° 70° 68° 66° 84° 94° I A . U I n. M Buuu .I ,w. u I n. 9 kn (”M u I. I i U D a I xix D . . ,u U A? E ._ I u I E \\\\\\ w 2. 7.22va u T! u \ a (I! D B U U I I”. H— U n- ‘ w D a} U a D .m I U w. fl.» “4 I". U I I a a m a u u C u n. I, u u M u \I\ z w W I I D .m 1‘ u Wadzwflfin y n. Ifiufi,Iféibi ., E (J , M . vi a n wk»... 0 I M u I I \G/xxw I a“) u 7‘ a f I U\\ n‘ furl—L D B U m I W. n- ) \ I mx/ 2/ U .~ I W ua I I u L; 523%} uwa a JV 5/, : bx\ u I u u (\I _ 79W k m a a I n a In UM mu m w u U i a 8 LB DI UM E D .\ H fl E a E u “I n u w u \nrrfmfl” U _ a L! .2 \m V . I u Iw I F. 3 B J / i I 500 MILES o o o o o o o o m w M n w w m M a w w w w n / / / / / / / , / / / , / / \ LN... Pay \ xl i Aw \ / \ \v ./ 74° 76° 78° 80° 82° 84° 86" 88° 90° 92° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 48° 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° \/ I I / / I I I I I I I I I I I I 45° \ 'D’ ~ _ 1.1 'E- m. u r , -w __ 1: 1.1 B U B ,, U L! ' E EBB D D - 8L8 E B a Cl 5, , _ 1 '3 1a a ”E. E' 1: 44° \ ‘1 E El a U U B E! ,9 DEF E1 ' U I 1:1 , a u El 9 / LJ L1 5 LID 1—1 a E E a ,/ g a LI 9 1301.1 1:1 (Ewan _ >58 42° U B F E' E E'! U E! E I \ I i E ' g 4 U , =-~ D I D :1 B _______ B .‘ a i i B U E 121: El 5 '- i as A, E i I a 9 U E a ‘ 402 1- ” ‘3 1a a 1, a u u a :1 .\ a B L1 1:! CI“ ._ _ "aka“ 5' B a , ' LJ 1. E E L1 L] o 38 \ t ,5 E :5 1 I E U E a C1 1 VI 8 z 1.1 L“ uE'IJU U u 1:1 U B . I U 1:1 51 1 u u 1 u E' I eF' 9 a: a B a E, :1 ,1 a u 1:1 8 ,~ ‘3 1:1 1‘“ a a :1 g \_ in 36° \, % E \E 8 LJ 9 g ELI U B U Ll EU I] 9 LI ID 1.] L] I U '13 ‘ a El :1 515113 1:1 13 a f E‘ a E 1.1 BEBE \\ U U " U , I i a :1 1.1 D; 51 ‘~ , . ; u D I use a1 U a :1 9 a J: ' E D v , 1.1 :‘1‘ a a a E a D \ U LI 9 IE g, ,1 .,'-I 1 E B L1 340 \y D I U ‘ I E B E E1; CI ,. ,, _ V \ g u a ‘« E 1. g a ,_ B 1.1 u < E E a ‘ B L] U E E ~ .4” WWW“; [_| C] U ".I U a 9 1 a n :3 L15 ; a ; 1.1 1:1 u D B a ‘ 1:1 1:1 9 u: a 1:1 5 I o ‘3 i E a El E1 DI I g 32 \ 31:1 8 § 13 13 LB 1:! C1 E 11:: E a a 1:1? 1:: E! I I U ,1 1.1 1:1 B I :1 a 1:1 13 I L] 1.1 a” a E! U I ‘3 D D: U I: a o 1 \ \ E a fa D i B CI 30 \ ‘ ‘ U U 51.1 D ‘ E U U E1 C1 C] E SYMBOLSAND PERCENTAGE Navi'ufi r , , 41.1 L1 » E I U :1 1.1 a a U OF TOTAL SAMPLES ” ' u E D B E C1 C1 14 16 33 24 13 "~B 1.1 U13 .l Ba 1.1 1:1 D 1: I _, C‘ . '3 a o 417 * U U U 28 \ I- | I E! | K I '3 a :1 200 I g , - a a \‘L-I a; .8 I a , x a E g) I Geometnc mean: 0.058 " ‘ LIE E 25°\ ‘5 1 Geometnc devnauon: 2.52 U 8 100 1 Number of samples and analyses 11267 ‘1 . U 1.1 E I _U L] LII. I 3i a»? \ u U 24°\ 0 I 1:] E -— 2 N F N m N N 638 99g838<~m5mm Nv , a O O O O C O o O O O '— N m LO AMOUNT, lN PARTS PER MILLION 22° K. I I I I I I 118° 116° 114° 112° 110° 108° FIGURE 25.—Mercury content of surficial materials. I I I I I 100° 104° 102° 100° 913° 1 I I I a 94° 92° 86° 82° 80° ILLUSTRATIONS 78° 76° 74° 72° 70° 68° 66° 54° r—“D 94° 92° 90° 88° 590 MILES 86° \ \ W \ \ \ \ \ ‘~ /\~. 1"“ IV 84° 82° 80° 78° 76° \/48° 74° / 46° / 44° / 42° / 38° 34° / 30° 61 62 460 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 48°\I / / I I I / I I I I I I I I I 128° 126° 124° 122° 120° 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES 93 7 | I 1 | 1 | : Geometric mean: 0.59 | Geometric deviafion: 2.72 1 Number of samples and ana|yses. 11298 i I | 1 | FREQUENCY mmmn V 10 15 AMOUNT, IN PARTS PER MILLION l 1 I I l 1 1 1 1 l | 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° FIGURE 26,—Molybdenum content of surficial materials. ILLUSTRATIONS 920 900 880 860 840 820 800 780 760 740 720 700 680 660 640 94" 0 O 0 0 O O 0 O O O O 0 w m n m m w M a w m m m n / / / / / / / / / / / / / \ \\\l\|.U|A1!IVfl// \ u v. AWN. uuu u \2 \ u u uu u u uxum HT/U\ \ 3&9 ..S: m x\ 0 ml ox, 74° 76° 78° 82° 84° 86° 88° 90° 92° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 0 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° 48 \1 1 1 1 1 1 1 1 46° 44° \ 42° \ 40° \ 38° \ 36° \ 34° \ 32° \ 30°\ SYMBOLS AND PERCENTAGE ~ u OF TOTAL SAMPLES ~ 4.1. 1.1 7423 3 '7 -_ U u 1.1 1.11:1 I 28° \ 641 I LJ U L1 1 1 1 1 | 1 | I 1 1 1 | Geometric mean: 40 1‘1» Geometric dev1a1lon: 1.68 ' U Number of samples and analyses: 870 R» 26° \ FREQUENCY 1 50 300 <70 93% p 220 AMOUNT.1N PARTS E MILLION J 1 :U / 1 1 1 1 1 1 1 1 1 _ 118° 116° 114° 112° 110° 108° 106° ' 104° 102° 100° 913° FIGURE 27.—Neodymium content of surficial materials. M “‘4 ILLUSTRATIONS 94° '92° 90° 8° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 0 \ \ \ \ \ \ \ \/ 43 / 45° / 42° / 38° / 26° 0 500 MILES ~ 4' / 24 ‘ \ L ; a ‘ i . / 22° > 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° \ ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES a 126° 126° 124° 122° 120° 113° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° 48 \/ / / I / 1 1 / I 1 1 1 1 1 1 1 415° \ 44° \ 42° \ 40° \ 33° \ 35° \ 34° \ 32° \ 30° \ I ‘ I Diu SYMBOLS AND PERCENTAGE or TOTAL SAMPLES \\B\UE~JI “‘Lw —\_‘ ‘ M 17 23 2318 19 LJ CI Bi I 28"\ 26° \ _ Geomemc devralnon, 2.31 \ Number of samples and analyses: 1.318 \ LI FREQUENCY I I 1 .4 — »»»»» q I \.\\“}Y' E]: D | Geometnc mean: 13 I U I I I 24° ~ I | 22° I\ l I I I I I I I I I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° FIGURE 28.—Nickelcont1ent of surficial materials. 67 ILLUSTRATIONS 4o \/480 o B 4 / /44° / 42° /40° / 38° / 36° / 34° / 32° / 30° / 28° / 26° /2 , 22° 74° 75° 78° 80° 82° 84° 86° 83° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° I 48 \I / I I I I I / I I I I I I 1 46° \ 44° 42° \ 40° \ 38° \ 36° \ 34° \ 32° L I I - I a‘x _ u I ‘ 8 LI 3 a’ ‘ "L SYMBOLS AND PERCENTAGE ~ 5 I u a “e . U I, E ““" ‘ OF TOTAL SAMPLES a U 9 a U U U u ui’ U 6 L1 ‘3 I . I 9 I‘ U 42 27 20 11 \ U I LI 300\ LIED I E II E. In U L1 L1 Ll L] E El U 52s3/\/\A’—/H “In. Uni .7 LI U __ ~ ~ U L1 U B U U U ULI W l I | I 5| u LI U' a U I I | '4. LI a 1 I I \l LI :9 U i 1 I L1 L1 1.1 U US 0 | \ L1 28 I\ i 1 I E U | L LI | 1 a U -'-’ __ u u > \H x, g | Geometnc mean; 9.3 \‘ U. L1 U E B 260 a 200 . 1 Geometric deviation' 1.75 B U 3:4 I Number of samples and analyses: L269 U 1 LL I KI I :9 u 100 I I UM If“ I u 24°\ I u a 1 ‘E. U I ,L o ; . 1 geeagssg D 22 ~~ AMOUNT, IN PARTS PER MILLION I I I I I I I I I I I 1 18° 1 16° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 29.——Niobium content of surficial materials. \ 69 ILLUSTRATIONS ' 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 65° 64° \/480 ./ 45° / 42° / 40° / 38° / 38° 34° / 32° / 30° / 28° / 26° / 24° 590 MILES ,, 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 70 48° 46° 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 125° 124° 122° 120° 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° 98‘" \ / / / / / / / I I I 1 l 1 1 I 1 2 D 5 SYMBOLS AND PERCENTAGE \\2. E J J \ OF TOTAL SAMPLES \\ a g” u a“ u E ‘5 E' U u a a u ~1ng u f M222. .2 1 L] D L] D :1 U 22 16 23 21 18 E‘EN—JN \{J U D Er,,.._..1_| U u a a a I ‘4 u ‘1.- L1 L1 Ll ‘n2\.\= E El \ "2 a E E E D /,«—J\~_2.m g Geomemc mean: 0.026 1‘ 2D ‘9 a E U [ g Geometric devtation: 2.67 in \ 8 Numbel 01 samples and analyses: 906 \\ u: ‘2 LL \\\'\E F \ \2 V 3. §§§§§g§%§:a2a 3000000000000 AMOUNT, IN PERCENT l l l I I I I 1 l 1 I 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 30.—Phosphorus content of surficial materials. 71 ILLUSTRATIONS 92° 90° 88° 36° 84° 82° 80° 78° 76° 74° 72° 70° 58° 66° 64° 94° \/480 , 46° / 42° /40° / 38° / 36° / 34° / 32° / 30° / 28° a 6 2 / / 24° 500 MILES } / 22° 74° 76° 78° 80° 82° 84° 88° 88° 90° 92° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° ° 1 48 \ I I I I I I I I I I I I I I 1 | 1 46° \ 44° \ 42° \ 40° \ 38° \ 38° \ 34° \ 32° \ f a < , a i \ SYMBOLS AND PERCENTAG _ 9 ' I a ', . U I 9 u or TOTAL SAMPLES ». I I :' I B n u; U a g 22 17 24 23 15 I . I l - g 1 13 30° \ U. '3. E'. a. 'A u I. l I g- G g C? U L' D B a 1:1 400 1 ‘- I. ‘ i I . ACE,”- hfi»_k WU L] U C] U U L! LI 1 '4 ...... .I . B D B U 9 E i _\ . L1 U D U U 1 -_ 9 L1 D E El E U 0 28 \ 300 : I D U | E > 1 Q ‘3 r""L‘l“~m a g ‘ Arithmetic mean: 15 \CL VII "U LI D U g 200 Standard deviation: 0‘79 S 25° .\ 8 Number 01 samples and analyses: 1,314 '51 E U B E] 100 I, u 24° \ u - EL. 0 :-: 38:0 mavwowwovn O O '- '— N N N m (V) V v I!) m 0 ‘D 220 " AMOUNT, IN PERCENT I I I I I I I I 1 I 118° 116° 114° 112° 110° 108° 106° 104° 102° 1000 FIGURE 31.—Potassium content of surficial materials. 94° 84° 92° 90° 92° 88° 90° 86° 84° 88° 82° 580 MILES 7 86° ILLUSTRATIONS 72° 70° 80° 78° 78° 84° \ \ 82° 74° \ 800 \ \ 78° 68° 76° 66° 64° 74° /45° /44° / 42° / 40° / 38° / 26° / 24° 73 74 46° 44° 42° 40° 38° 38° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° \ / I I I / I I / I I I I I I I I I a: 2.“ ‘‘‘‘‘‘ B _ M \ I (I E E ' 2 I a B « K a. a W” \ I \‘1 - km—«JMMHHN‘ 5 " El \ -— B hk\/~~ \ \ \ I E 8 I E \ ~\\ I I I _ r I"\ «In; . “MI E .......... u E E \ 2 B \\ I U \ SYMBOLS AND PERCENTAGE I I OF TOTAL SAMPLES x I V , l \u\ v... :_ 33 34 33 U “ \ >. E 3 Geometnc mean: 58 g Geometric deviation: 1.72 \x‘ U E Number of samples and anaIyses: 355 2 \ u. I ,. \ u \ : § § N \\ v E AMOUNT‘ IN PARTS PER MILLION I I l I I I I I I I I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 32.—Rubidium content of surficial materials. 75 ILLUSTRATIONS 48° 46:: / 42° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° l l l l \ \ \ \ \ \ \ \ \ \ \ 94" I 00 4 / / 38° / 35° 912% 5t . xxxxm / 34° / 32° / 30° / 28° / 28° / 24° 500 MILES / 22° 74° 78° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° o 43 / / / r / 1 / / l 1 1 1 1 1 1 1 ’ 1i \1 5, 46° '2'" 8 E D ' ,1 . _ E I i E - E :1 E n D D a a 1 fig I an. :1 13 {FEB u g :1 U I B I LE 5 13“ 0 g 1 44 B [J B a B ‘ U E E [3 E1 i 53 a :1 9 C] a :1 EF 1:1 :1 L1 :1 L1 I D D E g i a. .. D in I 1:1 1 42° 9 “'9' D g l I D 1: g ._ :3 ~ 1. , a ii I a E ‘ E a I ‘1 1:1 :1 :1 I B E I E. E g E E :8 E . B I o E B i a SE] E E? B I 40 E1 8 i D D i a ‘ 1:1 E! u I U . . a D a ,5 E! E E 1:1 I: u U E' E! U a :1 .3 u U L1 U Erél U ‘ Fl :1 . C1 1 I L1 L1 38" \ D I E, 'u» a :1 :1 ID 5 USE] El.El B B 1: a E I U 1.1 E E ‘ u C] B i i I I » '33:): :F E IE1 .. a: 1: y I E :1 g 3 36° 15 i I :1 B E a 1" \ D E39589 1:1“ U 9 1” :1 L1 :1 D E! a: C15 % E L1 : i 3 ‘ :1 ,_ 71—! Q1 EiIE a: E L1 F! E El n i i U U V..- I E E1 in g I .D_ L1 13 U U o E I D , 34 \ 1 a U E I D i E in BE! :1 a E ES """ U E u i 1 g E 9 LJ :1: :1 I 1: a U a a U E E1 E1 L1 ‘3 . , E u 1: a = o ‘ ‘ . E E E :3 a 32 \ n V, :1 EL] U .. g B a a V; :1 U a H in . I I I i :1 a :1 111 1: :"xww \\ I a i E I U a u U =1 1:1 5 u SYMBOLS AND PERCENTAGE * E . E; V a I a 1:1 300 \ OF TOTALSAMPLES a E a i .U D D L] D B I i DU 18 1224 25 21 ‘\ E1 5 g ,, , 9 L 51 L, [1 E1 9 “E» 1 43., W“— H E! D U 1.1 D El a I a , __ 1 :1 U U I U WW—H [:1 L} B KB U E E E ' L] U I i B E L1 : 13 28° \ I a U 13 a _l_l CLl . a u >. 13' L1 I ‘2’ Geometnc mean’ 7.5 B E E S 25°\ é Geometric dewanon: 182 Ill Lu Numberofsamp1es and analyses ‘.304 U E L] E U . :1 U E1 R U 24a ‘3. a ”Na. 9 220 AMOUNT, IN PARTS PER MILLION / 1 L l 1 I 1 1 i 1 1 1 18° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98" FIGURE 33.—Scandium content of surfich materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° I I 1 1 x s \ \ \ \ \ \ \ \ \ \/“° 46° 44° / 42° / 40° / 38° / 36° ,4 34° 0 @mm ‘h ' /“ 94° 92° 90° 88° 85° 84° 82° 80° 78° 76° 74° 78 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 480 \I I I 46° 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° I 1 08° 106° 104° 102° 100° 98° I I I I I I I I I l I \\ U I SYMBOLS AND PERCENTAGE U U S D E L, LI B u D g . B E OF TOTAL SAMPLES \ U D I I Ll ELM, _ D E; g D u u E, n I M‘ ~‘.\_ “"~r\ \* .4 ..... * 21 24 1817 20 “\i- 19D D I U D I I \E, E; E D E] I: E! \ E] El E a E \ 8 LI E1 \2« L] B D \D ‘ I I Q. :1 Q Geometnc mean: 026 ~~~~~~ [1a :1 g E g Geometric devnation, 2.46 \ 8 Number of samples and analyses: 1,267 ‘1, U E] L E 1"\ El \\\ a '\ El 8 a ._ EL x.“ LO ". F, F. N m. 10. '\. m 80 OOOOOI—v—NMLD AMOUNT. IN PARTS PER MILLION I I / I I I I I 1 I I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 88° FIGURE 34.—Selem'um content of surficial materials. 79 ILLUSTRATIONS 64° 65° 88° 70° 72° 74° 78° 92° 90° 88° 86° 84° 82° 80° 94° / 46° / 42° / 40° / 38° / 36° / 34° / 32° / 30° / 28° / 26° 24° \/480 500 MILES ODL / 22° 74° 76° 78° 80:: 82° 84° 86° 88° 90° 92° 94° 48° 46° 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 538° \ / / I / I I I / I I I I T 1 l 1 / [1:1 _\ >. J'QLI a“ ‘~ 8 \7 ., i ._ ‘ ,» a “N” , n LJ I a B 8’ ~- A, 1, A , . U U ; B U > I _ 1.1 U D " u a a a s U x a B E ,1“ fl.» 2," g i \ / U {,4 E a ) U E B ‘I El EP 1.: 1.1 CI D n f U , U D 1 _ {E1 ‘ E El . « 4.1.32. A i? m. . a B a s U 7 i E E y °°°°°°°°°°°°°°°°°°° . E i E U D a B D N ' s' E E D II; B L1 y. ‘ E! (2 EL u i u \ DE! ‘5, E $8 III B. - Hm”- E! L] U 5 n I U 1 E Q \ H ,2 \ u 7 a \ *u- ,. 1;: a u .J a 1 Ex .3 ULL‘ f D D 3‘ E! i j _.__.._..,. 1 D , D i 3'12] \ ‘x U U ,‘ El ' I D 15 E U E u I D I! LIE! a M ., a U V ' Bu 5 B B \ B . D U U \\, ° ’"'~g~~ ‘l ,_, . A u ; El ‘3' \ a x, ‘B-- “W E 1! El 1' E \ V a 1’1 1‘ ~..-g “‘> _\ SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES \ \ 15 18 261B 22 g u D B a I ‘13 ) “LL I 5 Arithmetic mean: 31 8 Standard devia‘ion: 6.48 3 Number of sampies and analyses: 406 u. . I l I I I 1 1 118° 116° 114° 110° 108° 106° 104° 102° FIGURE 35.——Silicon content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 58° 66° 64° 0 i 1 7 l 1 \ \ \ \ \ \ \ \ \ \ \/ 43 ,: fif‘wx ‘ 460 / 44° 42° / 40° / 36° _, 34° H / 32° I L” ,,._ __ . ..«. / 28° , o 580 MILES '1» I, / 24 \ x 7 l l 1 \ \ \ \ \ \ \ 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 48° 460 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 125° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° I \ / I I I I / I I I I I 1 1 1 1 1 I \ V‘ D (E: / \ #4 j; ..... N ‘‘‘‘‘‘‘‘ i N“ {I ‘ I \ V. (J a I I \ \ a \ l‘ a I F- a F \ SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES 17 14 24 21 25 L1 E1 El 9 l 300 | l | \ 1 .* | I ' l I 1 1 1 I | > 200 1 i x 2 I : Geometric mean: 0.59 K \ g 1 1 Geometric de'v-auon: 3.27 \J‘ I g : 1 Number of samples and analyses: 1.193 “x \ “L 100 I I \\ EI ' 1 4. ' 2 1 I \\ El E1 \ I L .... 0 . . I R» gggngmQN n eoooooooorv—Nmmvxg AMOUNT‘ IN PERCENT / I I I I 1 1 1 1 1 118° 115° 114° 112° 110° 108° 105° 104° 102° 100° 98° FIGURE 36.—Sodium content of surficial materials. ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 94° / 46° / 42° / 40° / 38° / 36° / 34° / 32° /30° / 28° \/480 v \ xv.—-—-—‘—~— BK DEE U «41ku uLlUU o 6 2 / / 24° 500 MILES / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 0 128° 126° 124° 122° 120° 113° 116° 114° 112° 110° 108° 106° 104° 102° 100° 90° 43 \/ / I / 1 1 1 1 1 1 1 1 1 1 1 1 46° 44° __ 42° \_ 40° K 38° \ 36° 42 34° \. 32° 4. 30° .2 SYMBOLS AND PERCENTAGE OF TOTAL SAMPLES 20 21 18 29 12 28° \ ‘ Geometnc mean: 120 ° * ' a E L11 ‘ Geometric deviation‘ 3 30 Number of samples and analyses: 1,318 « C] 26° \_ FREQUENCY 24° \ AMOUNT‘ IN PARTS PER MILLION 22° \ I / l I I I I I I I I 1 18° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 37.—Strontium content of surficial materials. 2“ ILLUSTRATIONS 920 900 880 860 B40 820 800 780 760 740 720 700 680 660 640 94" 24° \/48° o 6 4 / o 4 4 / / 42° / 40° / 38° / 38° 34° / 32° / 30° ,., 28° / 26° 500 MILES , 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° 48° 46° 44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° 98° ‘ / \ I I I I I l I I I I I 1 1 1 \\ \\\\\\ I """ "\«x . , I U ‘ ‘ u \ .: I U UN‘N”“"“~~ I \ u I U I I! {x U U I I , \_ I U \ SYMBOLS AND PERCENTAGE \\ L1 OF TOTAL SAMPLES ‘\ L. U \ 85 15 \‘1 I 'L-i r~ 1 I l» ,J k | ./ 5 I “ \ 5 | Geometric mean: 012 k 8 : Geomema deviation: 2 04 \ tag I Number of samp|es and analyses‘ 355 a u. I 1 . I \ \ h I U 8 e t a :._ 8. A. . ~. V O O O O O O t— -— N <9 v AMOUNT, IN PERCENT I l I I I I l 1 I 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 38,—Su1fur content of surficial materials. 87 ILLUSTRATIONS 90° "° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 92° ‘ 94° \/430 / 46° , 42° / 40° / 38° / 36° / 34° / 32° / 30° / 28° / 25° / 24° 500 MILES / 22° 74° 76° 78° 80° 82° 840 86° B80 900 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 0 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° 48 \/ / l / / I I I 1 l I 450 \ 1° U u 3-: U u u we -U Wm, u ija *’ 1‘1 U. a U U 3 E N ,5 \ E 1 / \7,, . a 5 o ' B 1|_l 44 \ I ‘ ' a B /‘ I 7‘ a lJEl ’h E' a 1-1 f x B U . Kim-w” ,7 f -' I \Y a I} u E B _ w m 420 \ ,4 «x E» _ m.» U u\ ¥ .‘ . ________ I I I. 7., 1 L1 w“ / \ 40°\ K ' \ I .~ F a“ E ,_ LJ , I ' -. n \E’ , u 3 , L1 1 , 2. L1 1 L1 : E ,_ r 0 x ‘ ‘ '7 ~ ,. . 38 K N) U a B ’1‘, E! , 1 E1 a B E! LI 5 I ’ . ‘4 ' \ a B U g E 1...“. ~ ‘ W E \\ 5 U u U .5 B - ' 35° 8 a U I a ‘1 ' B u 5 L1 I I I ‘ x I a Li I I . u I : U U BI \ ' LI 41 u I I u. . t; ¥ I 34° 5 ' U I ”‘I‘ , «W .. , E \ \ a JV E ,, 142,151 1 a 5’ U U L! s I /,J .5 32° y\ u 1‘ ‘ muq ,, B U I ; u u a a 1 30° N g B 4 3’ r ' , - U 7 ----- » «2 I I d I U L1 28° \ __ ' SYMBOLS AND PERCENTAGE ‘ ! , I OF TOTAL SAMPLES \LL“ ~\\ ‘ i o 39 31 30 1. 28 \ I C uZJ Geometric mean. 86 l U 8 Geometric dewauon: 1.53 K 240 g Number of samples and analyses: 297 \ ARTS PEfl MILLION 22° \ / 1 I I I 1 1 1 1 | 1 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° FIGURE 39.-—Thorium content of surficial materials. ILLUSTRATIONS 1 94°‘ 92° 90° 88° 85° 84° 82° 80° 78° 76° 74° 72° 70° 58° 65° 64° 0 ‘ I l 1 l \ \ \ x \ \ \ \ \ \ \ \/ 43 / 46° /44° / 42° /40° / 38° / 36° \‘ ° 0 5(IJO MILES ._ / 24 \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° O 43 \/ / / / I / I / I I I 1 1 1 1 1 45° \ 44° \ 42° \ 40° \ 38° \ 35° \ . EH " D /\m E 1, a CI. ~~~~~~~~~~~ ‘4 I a \ I .1 """" " B I a. I .r a 9 ~ m; a M ., \ a 34° \ a \ I NW“ 6' ""‘ 1 I 4 0% K“) 2; a 1 ° 3:21 1,.) I 1 32° \ k 'j I I L] K \ I "\" 1 I L] g u V“ 1;“- i a 1 30° \ g D g -_ ‘j E U I ° I 28° \ E E ‘ SYMBOLS AND PERCENTAGE 1 I OF TOTAL SAMPLES KS VIM». B \E\ 1/ K 23 17 24 21 16 f u u a a I ‘1 26° \ r—‘MM—H \‘ 5 10° 1 I | I | a 1 E l I Geometric mean: 0.89 \\ a I Geometnc deviation: 2.36 N a 3:4 I Number of samples and analyses: 355 X 2 0 LL 0 l ‘ n 4 \ m \ '7 .._ P, N. m_ '4? " LO, soooooo—v—Nmmrxg “ AMOUNT, IN PARTS PER MILLION 22° \ I I I I I I I I I I I 118° 115° 114° 112° 110° 108° 106° 104° 102° 100° 93° FIGURE 40.—'I‘in content of surficial materials. 94° 92° ILLUSTRATIONS '—‘{3 94° 1 92° 90° 88° 5?!) MILES 86° 78° 76° 74° 72° 70° 68° 66° \ \ \ \ \ \ \ F” I ‘\ 84° 82° 80° 78° 76° 74° / 42° /40° / 38° / 36° / 34° / 32° / 30° / 28° / 26° / 24° 91 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 123° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° O 43 \ I / I I I I I I I I I I 1 1 1 1 48° \ 44° 42° \ 40° 38° \ 36° \ 34° \ 32° \ 3 1 n f 9 Am 11 1 n D E 1 1.1 I «r SYMBOLS AND PERCENTAGE u a [a 5 E n 13 U. D E, a 1:1 OF TOTAL SAMPLES , g 2 E, E. 300\ 12 162130 21 \0 1:1 " E'iil EU” a ‘jfU U a u 1: 1: u u 1: B I I 13 “Du --Ei__..,,2_j' . . ,. Emu U 1:1 '3 D 1.1 E u - 5 1:1 1.1 a 1.1 395 CI 1.1 a F I ‘- I U B E E' U 300 | U E El 5 D 13 28° I U a u \ 1 1 I E 1.1 l D [J E C 200 ' I A E! E g E, I Geometric mean: 0.24 I _ ‘ ‘Li El El E a 8 1 Geometric deviation: 1.89 " a E 25° \ g | Number of samples and analyses: 11317 52‘ LL \ 1 ~_ 100 | | 1 24° \ i 0 7\ In 8558888e3~mn~ m OOOOOOOOOOOOOP-‘N 22° AMOUNT, IN PERCENT I I I I I i 1 1 1 1 1 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 41,—Titanium content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 62° 80° 78° 76° 74° 72° 70° 68° 66° 64° | l l 1 \ \ \ V \ \ \ \ \ \ \ \/43° :I ,. 46° 44° / 42° 40° 34° 32° ,- 30° 0 590 MILES , / 24 1 l \ l \ \ \ \ \ \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° I 1 I I 1 1 48° \/ 46° \ -- ”‘F‘E ~ My In M. 1 W‘““ ~ “__ .. B 6 52' U 1L E B 1 1 1 1 .El \ 44° \ a B 1 a U B ‘ 5 LI 3 El 1‘I U E! B B 1 ,,,,,,,,, BU'“M-—‘—~~ “.22., _ E u 42° \ Jixxmj I g a u’ 1 40° \ \ 1 LI I \ El \_ 5 38° \ j, ,,,,, 7 ‘ I 1 L~ a . 1 “‘“W ~ a 1 a El 36 \ I Us L'- I 1' ' u I I 1 El. B 1 E’ 1 s o "“‘h~|~,—‘I._w, 2 _ mm 34 \ g 8 —~- f ******* .14....__E__ L] a ,1 1 '-’ L' I I 1 1 1 o 1 1 32 \ u a 1 1 1 U M 1 L1 L1 L1 VH’JUA ‘_ B 30° 2 \\ U N. U SYMBOLS AND PERCENTAGE __ LI OF TOTAL SAMPLES a U 39 37 24 I 28° \ u a I \ B FAWH 1 200 1 1 1 \ B I 1 | a / m“\ U I | 1 \H\ r ‘\ f3 ' ' | \ 0 z 1 Geometnc mean. 2.3 \ 26 ‘ L3” 100 1 Geomemc devnauon: 1 73 \ LI E 1 Number 01 samples and analyses 354 *\ u. 1| U I i, ' '\ o o . u 24‘ gggqummmm \V U ocooFNNm-nrx: ~\ AMOUNT, 1N PARTS PER MILLION 22° \ l I I I I I 1 1 1 I 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 42.—Uranium content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° M° 78° 76° 74° 72° 70° 58° 56° 64° 0 I 1 1 I \ \ \ \ \ \ \ \ \ \ \ \/ 43 , 44° /40° / 34° E I M!“ E ‘: - ’1 i E g; E / 2 V I film—w..— - h I [II I x / / 32° ‘9 E j? / 30° /28° SK , 26° 7 1 fix. C 0 5530 MILES 94° 92° 90° 88° 86° 84° 82° 90° 78° 76° 74° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 108° 104° 102° 100° 538° O 48 \l I I I I / / I I I I I I I I I 48° 44° \ 42° 2 40° \ 38° \ 36° \. 34° \ 32° ~\ El: LI] g _ U LI" u SYMBOLS AND PERCENTAGE El Bf I B 51' a El 30°‘~ OFTOTALSAMPLES I5 E! a “u a ‘ '3 U El a n a g \ E' D 1 , g '1 FM 1.1 u D a DU 14 28 2616 17 E ELI , 3 ’U a 1:1~ I: U u D LJ III a a I 1:; > U a " I g E] B E D 348 I— | I I u D U a El E E! o 300 I | I B u 28 ~ 1 I | B E, l 1 I u D | l 1 n .,_E | 1 I {I . - - g I D “U E 20° 1 1 D '3 D D D D I: 25° \ g I Geometric mean: 58 B 8 1 Geometric devnauon: 2.25 U E | Number of samples and analyses: 1,319 K L] ‘°° 1 1: E l L 24°\ 1 1? $~9588$E§§§§§ 22° AMOUNTI 1N PARTS PER MILLION I I I I I I I I I I I 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 43.——Vanadium content of surficial materials. ILLUSTRATIONS 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 88° 86° 64° 94° 0 4 2 \/480 O 6 4 / / 42° / 40° / 38° / 36° .1 34° / 32° ., 30° / 28° / 28° f 500 MILES / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 125° 124° 122° 120° 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° O 48 \l I I I I I I I I I I I I I 1 1 45°\ 0 44 \ 13 1:1 /I' 'LI 1’ 422 F {1:1\_N _____ f o a U 40 \ E II :1 1’ El ‘\ 38° 1 E E1 \ 2 E \ a 352 11% ‘1 El ‘1 1 34k 1 “cm, \ LJ.; 322 “j 1 U! G / E 1 I .71]me SYMBOLSANDPERCENTAGE \\\ a E 1 a E :1 U 1: ”1 U E D 13 1: E1" OFTOTALSAMPLES ‘\\ 9 a :11 El 13 1:1 300\ 21 213615 g \‘\7 E .1- E l I E ,‘3 U 13 DE! :1 :1 :1 E1 1.1 [113:1 I 43-311; [PueIiJD—UENQ ”E! El '3 ‘ D E11:1 444 Q 1.1 :1 1 1 El E! 1 1I1 1 \' a B D “ 28°\ 300 7| 1 1 a D | I 1 U E I 1:1 1:2 200 1 1 Us 8 13 E1 E! g | Geometnc mean: 2.6 m 26°\ 8 | Geometnc dev1auon: 1.79 1.1 E : Numberof samples and analyses. 1,250 ‘n\ E] \ 100 1 n 1 F 1 \‘D 24‘: 1 x o m I -— v—‘N m m 7\ o 1.0 o o o FFNMLO 22° AMOUNT, 1N PARTS PER MILLION I I I I I I 1 1 I 1 1 118° 116° 1 14° 112° 110° 108° 106° 104° 102° 100° 93° FIGURE 44.—Ytterbium content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 65° 64° 0 l 1 1 l \ I x \ \ \ x \ \ \ \ \/ 48 /460 / 42° / 38° / 36° / 34° / 32° / 30° / 28° , 26° U a o 5?!) MILES N\ J/ ’ 24 r \ w s r i l l l l \ \ \ \ \ \ 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 100 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES a 128° 125° 124° 122° 120° 118° 118° 114° 112° 110° 108° 106° 104° 102° 100° 98° 43 \/ / / / / I l / I I I I I I I I 45° \ 44° 42° \ 40° \ 38° \ 36° ‘2 34° \ 32° \ E . 30°\ SYMBOLSAND PERCENTAGE D I. B I :0 E, D B ‘-’ El 9 I: CI I OF TOTAL SAMPLES EN 3‘" g u ”Ira U a D L' a E‘ E E E1 17 152432 II ' *4 u U E LI E! B I: I \g U E E: n a E, x-AxA/W—J‘fl . 322 ( 420 | 4' u U a E 28 E 1‘ I I ‘ _ E . I L. 250 I a: E , “.__ a I la ‘1 E a 200 I ' I3 B 5 C I II] D ‘ 28° \ E 1 Geomelnc mean‘ 21 L1 8 : Geometric deviatIon: 1.78 I L] 1,- E 1 Number of samples and analyses: 1,319 \ LJ 3/ 1‘71 ”L 100 I I I? LJ {‘2 24°\ 1 L1 as 0 l 9‘9)?! §_£~8m~§£§ 22,3 AMOUNT, IN PARTS PER MILLION / I I I I I I I l I I 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° FIGURE 45.—-Yttrium content of surficial materials. ILLUSTRATIONS 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° I l \ \ \ \ \ \ \ \ \ \ 6 580 MILES 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 46° / 44° / 42° / 40° 36° 34° ./ 32° / 30° , 28° / 26° / 24° 101 102 ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 126° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 98° 48° \/ I I I I / I I I I I I 1 I I 1 46° \ 44° \ 42° \ 40° 38° \ 36° \ 34° \ 32° \ SYMBOLS AND PERCENTAGE E OF TOTAL SAMPLES \ 30°\ 10 16 3228 13 U CI 5 i I W_._J—_\ r 399 354 I ' W I 28° N ’ I | | I > | (z) I Geometric mean' 48 25° \ g | Geomelnc dewatnon. 1.95 8 : Number of samples and analyses: 1,248 a: ”L 1 I o l 24 \ 1 m | ‘0, vw::2s:§§§§§§§§ v— N l") 220 AMOUNT, IN PARTS PER MILLION I\ l l I I I I I I I 1 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 46.—Zinc content of surficial materials. 103 ILLUSTRATIONS 92° 90° 88° 85° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 94° 0° \/480 o 6 4 / , 42° / 40° / 38° / 36° / 34° / 32° /3 /28° / 26° , 24° S E NIL M U 0 5 / 22° 74° 76° 78° 80° 82° 84° 86° 88° 90° 92° 94° ELEMENT CONCENTRATIONS IN SOILS, CONTERMINOUS UNITED STATES 128° 128° 124° 122° 120° 118° 116° 114° 112° 110° 108° 105° 104° 102° 100° 913° 48° \1 I / I / I l I / I I I 1 I I 1 46° \ 44° \ LJ 1 2- D a 5 U I U 420 \ “W'B‘ '\~—~_‘.u_j a E] \ I 40° 38° N 35° \ 34° \ 32° \ 30° \ SYMBOLS AND PERCENTAGE \ If E OF TOTAL SAMPLES g ‘3 1:1 I N. .g “CL‘L I 23 24 23 18 1 1 \J L_| D B D I 314 m 306 28° \ ‘ ' > 26a “2’ Geometric mean: 180 \ g Geomemc deviation' 1.91 g Number 01 samples and analyses: 1,319 u. 24° \ 22° \ AMOUNT, IN PARTS PER MILLION l I I l I l 1 1 l L 1 118° 116° 114° 112° 110° 108° 106° 104° 102° 100° 98° FIGURE 47,—Zirconium content of surficial materials. ILLUSTRATIONS 105 94° 92° 90° 88° 86° 84° 82° 80° 78° 76° 74° 72° 70° 68° 66° 64° 1 1 1 1 1 \ \ \ \ \ \ \ \ \ \ \/43 o 46° 44° 42° 40° / 36° 34° / 240 Q 590 MILES / 22° 94° 92° 90° 88° 88° 84° 82° 80° 78c 75° 74°