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Geology of the south half of the Tiburon Peninsula 1924 BIBLIOGRAPHIC RECORD TARGET University of California at Berkeley Library Master negative storage number: 03-67.27 (national version of the master negative storage number: CU SN03067.27) GLADIS NUMBER: 184788047H FORMAT : BK AD:991012/FZB LEVEL:b BLT:am DCF:a CSC:d MOD: EL:7 UD:030604 /MAP CP: cau L:eng INT: GPC: BIO: FIC: CON: ARCV: PC:S PD:1924/ REP: CPI: FSI: ILC: 1:0 040 CUScCU 090 SbDISS.HARDY.GEOL 1924 100 1 Hardy, Norman H. 245 10 Geology of the south half of the Tiburon peninsula. 260 $cl1924. 300 [1], 19 p. :$bcol. ill., col. maps ;$c29 cm. 502 Thesis (B.A. in Geology) -- University of California, Berkeley, May 1924. 504 Includes bibliographical references. 610 20 University of California, Berkeley.S$bDept. of Geology and Geophysics$xDissertations. 690 0 Dissertations, Academic$xUCB$xGeology$y1921-1930 Microfilmed by University of California Library Photographic Service, Berkeley, CA FILMED AND PROCESSED BY LIBRARY PHOTOGRAPHIC SERVICE, UNIVERSITY OF CALIFORNIA, BERKELEY, 94720 DATE: 7/03 | REDUCTION: 10 X 235 22 20 18 Lo I I 36 I 2 28 32 un << nn ba hi ha ia 32) a wm = ofl - MEE E OQ) wn) oe oO Qf - E ,25 6 NBS 1010a ANSI/ISO #2 EQUIVALENT = w Oo < = >= o. Oo Q o © o = Q x o < oc Oo Oo f— Oo XI a T x x ™ v = a. sl iL [1 3lt 11 0 Norman H. Hardy Geology of the south half of the Tiburon Peninsula DISS.HARDY.GEOL 1924 EART Thesis for the Degree of Bachelor of Arts. Geology of the South Half of Tiburon Peninsula. NORMAN HARDY May, 1924. PURPOSE ACKNOWLEDGEMENTS LOCATION PETROLOGY and PXTROGRAPHY OF FORMATIONS sandstone Conglomerate Greenstone Chert Serpentine STRATIGRAPHY OF FORMATIONS. Relation of sandstone and conglomerate. Relation of greenstone and chert. Nature of the serpentine. Summary of historical sequence. STRUCTURE METAMORPHISM Acidschist series. Metamorphic chert summary of derivea schists. lietamorphic sandstone and conglomerate summary of derived schists. Basic schist series Metamorphic greenstone Summary of derived schists. Type of Metamorphism. VIII - SUMMARY. LIBRARY COPY PURPOSE The purpose of this paper is to satisfy the thesis requirement for the degree of A B in the Department of Geology of the University of California. ACKNOWLEDGEMENTS The author is greatly indebted to Professor R. R. Morse u der whose direction the work was carried on, for the interest he has shown in our work and for his many helpful suggestions and criticisms. Appreciation must also be expressed to Mr. To. Ww. Koch with whom all field and laboratory work was conducted, for his able assistance, advice and cooperation in compiling data for this papers LOCATION Tiburon Peninsula is in San Francisco Bay, north of the city of San Francisco. The peninsula is five miles long and 8 mile and a half wide anu has a northwest - southeast trend. It is bounded on the east by San Francisco Bay, separated from Angel Island on the southeast by Kaccoon Strait, and separated from Marin Peninsula to the east by the smaller Richardsons Bay. PETROLOGY AND PETROGRAPHY OF FORMATIONS. Sandstone - This formation is in general well laminated, possessing a massive facies in relatively few cases. It grades to a pebbly sandstone in places and varies rapidly in color from le gray to yellow brown, Another gradation is to a finer . sand- stone that grades to a sandy brown shale, All facies of sand- stone are cut by irregular stringers of quartz. The sandstone is a typical arkose and contains: 1. Abundant plagioclase 2. Black shale fragments 3. Quartz grains 4. Mica 5. Chert fragments Conglomerate - The continuity of the sandstone is inter- rupted by two conglomerate horizons, the relations of which will be considered below. This is an epiclastic psephitic, moderately indurated sediment. The matrix, comprising sixty per cent is a typical arkose resembling the sandstone formation of the area, and is composed of: l. Plagioclase feldspars (abundant) 2. Quartg grains 3. Black shale fragments. The boulders consist of the following: l. Hard pale greenish white quartzite. 2. Dense black asphanitic lava, probably basalt. Jd. Greenstone 4, Radiolarian chert 5. Hornblende diorite 0. Black shale 7. Dark gray sandstone, Greenstone = llegascopically the greenstone affords little or no evidence of mineralogical or textural relationships. It is a hard dense asphanitic to cryptocrystalline rock with a uniform green color, from which it has derived its name. A weathered specimen shows granulation that might possibly resemble a common diabase. There are certain features of this formation that become distinctive and characteristic. The first and most Ze (7) striking feature is the pillow structure. This in all pro- bability is not strictly a weathering phenomena but weather- ing serves to bring out such a structure more clearly. (See Plate No. 1). Rounded and elliptical nodules of greenstone ranging from a few inches to a foot or more in diameter stand boldly from an apparent matrix of the same greenstone, Upon careful examination however, there appears to be no difference between this se-called matrix ana the pillows. A second and truly weathering feature gives a hackly appearance. The mass weathers out into cubes and angular fragments varying from 1/8" to 2" square. Upon cracking they are seen clearly to be greenstone. Where weathering has advanced farther the mass appears with a deep readish brown color and the fragments resemble a sandstone varying from pelitic to psammitic. The ultimate product is one that resembles a badly disintegrated or friable sandstone, A microscopic examination of this greenstone showed phenocrysts of basic labradorite and augite in a ground mass of second generation acid, labradorite and glass. (See Plate 7, Fig. 1) The labradorite feldspars occur as euhedral prismatic crystals showing carlsbad and albite twiming. They are somewhat altered and show an incipient or 2989 of sericite mica. The augite is a colorless non-pleechroic variety and is represented in many instances by its alteration pro=- ducts,calcite and chlorite. The ground mass eomprises about sixty per cent of the rock and shows lathe shaped feldspar, microlites, altered somewhat in a residual of isotropic glass. d The texture of the ground mass is intersertal. F. L. Ransome has described this same formation from Angel Island, as being a caida It is possible that such a variation might occur. Slides were examined from Tiburon Peninsula that might well be termed fourchite, composed of euhedral augite phenocrysts in a matrix of isotropic glass. In general however, there is an association of labradorite feldspar, and the rock is a basalte Radiolarian Chert (Ii) This formation is predominately a deep red variety eross cut in many directions by small quartz veins. Upon weathering the veins stand in high relief giving the sur- face a web appearance. In some instances the red variety is distinctly color banded, the colors being sharply defined and are red, brown, pink, white and buff, In many localities the chert is entirely white, in other places buff and in regions close to the contact of the intrusive it assumes a greenish white to a decidedly blue cast. This latter type will be discussed more fully in considering the metamorphic equivalent of this formation. The chert is rich in manganese (MNOs) which occurs in small cracks aud partings throughout, but which is too small an amount to be commercially valuables The cherts are characteristically thin bedded with alternate lamelli of shale. (Plate 2, Fig. 1). The chert bands range from one to five inches thick and the entire series has been folded and contorted giving a great variation in dip accom=- 4, panied by minor sharp folds, crenulations and numerous small slips. A careful megascopic examinat ion may reveal minute sphereoidal or circular silicious rings in a mass of dense cryptocrystalline to aphantiic silica. These minute spheres are silicious tests or skeletons of radiolaria. A microscopic examination revealed these radiolarian forms very clearly (See Plate 8, Fig. 1) im a microscrystalline mass of quartz. Some slides showed no radiolaria tests and the holocrystalline quartz showed more Or less sutured boundaries, with marked undulatory extinction. This is believed to be a recrystallization due to dynamic agencies that shall be considered later. Aside from the microcrystalline quartz, the boundaries of which were sharply marked and which showed no partic- ular pattern. Serpentine ~ A characteristic outcrop of this formation may be seen in Plate 3. There are a number of hard more homoganeous irregular masses of serpentine in a soft more altered, féliated, slickensided mass of serpentine. These residual masses have been fractured at various angles and these fractures now contain the soft slickensided variety of serpentine. The hard boulders showed a pseudo porphrytic texture with large erystals of bastite imbedded in a serpentine matrix. Under the microscope the large pseudo porphyriticcrystalls proved to be chrysotile and antigorite instead of bastite 5 as would normally be supposed. Both chrysotile and antigorite proved to be pseudomorph after an orthor- hombic pyroxene. Small irregular granules of olivine are present separated by fiberous serpentine giving the typieal mesh structure. Plate 7, Fig. 2.) Mag- netite is also very abundant. Palache has described this serpentine as a therzolite, but with the slides examined no evidence was seen of monoclinic pyroxene and it is believed that the serpentine of this particular area is derived from a saxonite. STRATIGRAPHY OF FORMATIONS. Relation of Sandstone and Conglomerate. The sandstone is the oldest formation of the series exposed. Its continuity is notably interrupted at two horizons by a rapid gradation to a conglomerate. The matrix of the conglomerate is identisal with the sandstone, The sandstone is estimated to be 1500 ft. thick with the conglomerate horizons varying in thickness from 0 to 500 feet. Relation of Greenstone and Chert. Overlying the sandstone there is in general a chert, but in some localities a greenstone was observed in contact with the sandstone. (See Cross Sec. B.B.) Oe The exact nature of the chert-greenstone relationship is obscure. Both formations have been brecciated to no little degree,upon which have been superimposed an abundance of metamorphic products. However, there are certain relation- ships that are clear, from which an effort will be made to draw the most logical conclusion. Large chert inclusions are found in the greenstone (Plate No. 4) These inclusions vary in shape and size from a foot or so up to ten feet, In one instance, a mass of black carbonaceous to graphite shale was observed surrounding the chert inclusion. In following the strike of the chert, greenstone may be Seen on either or both sides of the chert. This feature nowever, is hidden to a considerable extent by the presence of soil and the contacts are traced by a series of isolated out- crops of one or the other of the rock types. There were no inclusions of sandstone observed in the greenstone. The close association of gresmstone with chert following closely the structural deformation of the latter seems to indicate two possible modes of occurrence for the greenstone. Either it is a thin sill injected into the chert formation or it is a series of intercqlated flows. In summing up the evidence in support of either of the above hypotheses one must bear in mind the fact that the greenstone is a lava and a rock type that may be either a flow or a shallow hypabyssal intrusive; and that in general the greenstone follows the bedding of the cHrt, which facts limit the 7. possible modes of occurrence to that of an injected sill or an intercalated flow. In the field it is very diffi- cult to secure evidence that conclusively points to one of the above hypotheses, while there is abundant evidence ~ that may support either hypothesis. 1. Inclusions of chert in greenstone are charascter=- istic, but it could not be determined whether these inclusions were at the upper or lower contact with the chert. 2. Greenstone follows the chert bedding. de. Alternate occurrence of chert and greenstone may characterize either hyro7hess 4. The most intense metamorphic products are found associated with the cherts and greenstones but the greenstone iteself is metamorphosed which overrules this as evidence for either gyporhes’ 5. The hypoerystalline, microcrystalline texture supports either sides In support of the sill hypothesis there is evidence of brecciation in the chert but this, like the metamorphism, is due to a later serpentini% mass that is unmistakably intrusive, | Greenstone and chert have been observed in contact with no intrusive relations apparent, not even the baking of the shale partings. Though conclusive evidence is lack- ing it seems to point stronger for the hypothesis of inter- 8. calated flow. The pillow structure observed has been described from the Hunter Point region as bei ng due te sudden cooling and contraction due to submarine lava flow. The pillow structure of Hunter Point and that on the extreme southeastern end of Tiburon Peinsula are identical and it is very possible that the same principle is applicables The Nature of the Serpentine. The serpentine has been derived from an intrusive Peroditite (Saxonite) . The intrusive parallels the direction of the peninsula having a general northwest- southeast trend. It cuts through vie center of the regional syncline locally tilting adjacent strata and show- ing the transgressive nature of the intrusive (Plate 2 Fig. 2) It intersects the axis of the syncline one and one-half miles from the southeast end of the peninsula, Half a mile north- west of this point it fails to outerop through the series but reappears some distance to the northwest, beyond the area studied. The mass is almost continuous for four miles and has a width of one quarter mile that is very persistent with two exceptions, one of these is where it fails to outcrop through the series as above mentioned, the other may readily be observed on the map, where the outcrop narrows down to about two hundred feet. The mass truncates the strata with & decid- edly trangressive character; the adjacent strata are every- where vertical or nearly so. Thus, the ground plan, the steep contacts and relation to bedding suggest strongly that 9. the serpentine has been derived from a body having the mode of occurrence of a steep dike. From the textural features it represents a rather deep-seated type. Summary of the Sequence: Serpentine dike intrusive Chert ) Greenstone) intercalated. Conglomerate Sandstone STRUCTURE The formations exposed on Tiburon Peninsula com- prise a series of Franciscan rocks. Sandstone, conglomer- ate, chert and greenstone form a stratified series that has been folded into a syncline. The axis of the synecline trends northwest-southeast following the general direction of the peninsula. The dips on either side of the axis . nO are symmetrical varying locally from 30° te 60°. METAMORPHISM The metamorphic rocks in general will be classified under two heads: l, The acid series serived from the more silicious formations namely, sandstone, conglomerate and chert containing principally quartz, albite, muscovite (margarite) lawsonite, glaucophane, garnet and some epidote. This series is also 10. marked by a decided relic and inherited bedded structure, 2. The basic series derived principally from the greenstone showing no inherited bedded structure and consisting principally of actinolite and other amphiboles, chlorite and biotite. It is to be noted here that variation and gradation among the schists could not be traced from one to the other across the strike of such a series. The schists outerop very irregularly with a thick mantle of soil separ=- ating isolated outcrops. Any two outcrops may show only varying proportions of the same constituent minerals or they may show a change in proportion of the minerals with or without other minerals. From this possible variety of schists it is apparent that the problem of assigning each particular schist to that formation from which it was derive ed may be a difficult one. Here again it is impossible to trace an unaltered formation uninterruptedly through its varying metamorphic stages to the ultimate product. The chert offers the nearest approach to this ideal conditions Acid Schist Series. The Metamorphic Chert. The most common and the normal chert is of a deep red color as has been stated. Near the serpentine contact in some places the chert becomes a very hard silicious mass with a decided blue cast. A microscopic examination was 11 made of many of the gradational facies of this metamor- phic type. [Plate 8, Fig. 1). The above mentioned blue metamorphic chert consists of a mass of microcrystalline quartz with several small veins of reerystallized quartz showing sharp vein boundaries. The quartz of the main mass is colorless, showing undulatory extinction and sutured dovetailing terminals or boarders. Impregnated throughout the entire mass are innumerable euhedeal elongated tufts of blue amphibole (Plate 8, Fig. 2) They appear to have a central square or rectangle with fiberous clumps project- ing from the terminal plates. Some of these showed high relief and marked pl@ochroism, parallel elongation, blue; normal to elongation, greenish yellow. The central por- tion with tufts from the terminal plates showed a similar relief, pleochroism and parallel extinction, while the tufts projecting from the ends showed pleochroisim corres=- pending to glaucophane or crossites Another section wherein the mineml development was on a larger scale showed a similar mass of quartz, contain- ing actinolite and erossite (Plate 9, Fig. 1). The actin- olite is a light green faintly pleogchroic variety Q=>¢ ghowing a cA = ré6° The crossite is readily distinzuished by the position of the axial plane which is normal to the principal cleavage with ¢-A4=9" amd showing characteristic pleochroism {v= yellowish green 4) - deep blue {- violet. 1& In the field large white veins could be seen cutting this echist normal to the schistosity plane. Under the microscope this appeared to be albite, which occurs as a color- less variety characteristically untwinned., The metamorphism of the chert may be traced farther. The field relations show that there is a metamorphic product that is principally a blue amphibole with irregular chert fragments throughout and the whole mass impregnated with garnet. The amphibole of this occurrence proved to be glaucophane. It occurs as prismatic crystalls parallel to ¢ with index of refraction 1.63 and a characteristic pleechroism of = yellow 4 violet; { blue. ~¢ 4 ranging from 2° to 11° 1a atfferent mineral sections. The variation im the optie axial angle is also noticeable ranging from 15° to 40° and in one instance almost approaching a uniaxial mineral, From this type there is an apparent gradation to an antinolite, crossite, glaucophane schist with lesser amounts of rutdle and pyrite. (Plate 9, Fig. 2) Here, however, there is good reason to believe this schist to be the end product of t he basic schist series; which it is remains unknown, The actinolite is pale green faintly pléechroiec showing a maxi- mum of cA 77° The crossite distinguished from glaucophane by the orientation of the axial plane showed cenNg:=2" 2v=2o0° and characteristie pleéeechroisin {$d - yellow; {J -blue; ( - purples Glaucophane occurs similar to previous descriptions. Epidote occurs in prismatic crystalls elongated parallel te 4 with 6-4 13 and @ /i¢ 19° and showing no pleoehroishm. The axial plane is normal to the prineipal cleavage. Rutite is a common accessory in many of the schists observed and is recognized by its very high relief and birefringence. It occurs in irregular grains showing fracturing. Pyrite and limonite pswiomorph after pyrite are common and are readily seen megascopicallye The shale partings between the chert bands have been altered to sericite schists. With‘'further metamorphism they have become true quartz mica schists so that the chert then appears as a microcrystalline mass of quartz impregnated with blue amphibole and separated by mica schist lamelli. Summary of schists derived from chert. 1. Metamorphosed quartzite. a 2. Quartz glaweophane schists, S. Quartz albite glaucophane schists, 4. Albite glaucophane crossite epidote schists. 5. Glaucophane quartz garnet schists, 6 Glaucophane schists, 7. Actinolite glaucophane crossite epidote pyrite rutile schists, 5 The metamorphic sandstone and conglomerate. Both the sandstone and the conglomerate of the region become metamorphosed in the proximity of the serpentine contact. The sandstone grades rapidly from the highly schistose quartz muscovite, quartz biotite muscovite schists to the less schistose 14. schistose structure on a large scale, not evident in a hard gray sandstone. The metamorphosed conglomerate was only : hand specimen. Further metamorphism showing increasing observed in one loeality of the region and here the metamor- granularity. Then there was developed anu actinolite phism was not intense. The pebbles of quartzite, lava, green- chlorite biotite schist, grading through a tremolite stone, chert, hornblende diorite were unaffected. The pebbles Wigwi chlorite schist to the end product, an aetinolite, glaucophane of sandstone and shale which are in general intermediate : ; crossite epidote pyrite réetile schist (plate 9 Fig 2) that between the above pebbles and the matrix have suffered some p may be confused with the end product of the metamorphie change along with the matrix. The matrix formally an arkose chert, sandsto has become a schist without any striking change 2ulslens ha Sco a J 8 & Summary of schists derived from greenstone. in the arkose appearance except a rough parallelism of the con- 1. Hard mieroerystalline basis igneous reck showing u « The conglomerate has thus become a schistose : A : Britusnts song] slickensided schistose structure on a large scales conglomerates | 2. Same as above showing inereasing granularity. Summary of schists derived from sandstone and conglomerate. | 3. Actinolite chlorite schists | + % l. Quartz muscovite schists. 4, Actinolite biotite chlorite schists, 2. Quartz muscovite biotite schists. 5. Tremolite chlerite schists J. Sehistose sandstone. | + 6. Actinolite glaucophane crossite epidote pyrite reétile 4. Schistose conglomerate. | schists. A notable feature in the me tamor phic greenstone is 5. Muscovite (margarite) lawsonite chlorite schists. the development of glaucophane om fractured surfaces and in 6. Muscovite biotite quartz pyrite schists, cracks that is seldom observed until that surface has been exposed to Basic Schist Series. P weatheringe Metamorphic greenstone. Iype of Metamorphism. The series of schists traced from the greenstone There are certain features about the metamorphism was not traced directly across the strike of the formation. by the intrusive perodite (serpentine) that should be The first gradation from a normal greenstone was that of a hard | enumeratede microcrystalline basic igneous rock showing slickinsided le There has been a decided mechanical action in connection 15. with the intrusion (see Cross Sec.) 16. 2. The metamorphism decreases rapidly in leaving the contact, J There has been a notable concentration of the blue soda HE amphibole in the chert and to a lesser extent in the greenstone, 4. The concentration of blue amphibole varies from a minute amount to schists which are almost wholly of that minerale. O¢ The cherts and greenstones are not penetrated by glaucophane everywhere along the contact with the serpen- tine, but on the other hand its distribution is sporadic and very irregular. 6s The blue amphibole in associat ion with chert and green= stone shoots off in straight fissure-like occurrences some- times across the contact (Plate 5) other times in any random direction (Plate 6). 7. Veins of albite are common cutting the amphibole schists. 8s Amphibole schists as well as other types of schists are always near to serpentine. The sporadie and fissure-like occurrence of the blue amphibole schists together with the fact that they are confined almost wholly to the chert and greenstone which are the most brittle beds and have suffered the most fracturing tends to point to a pneumatolytic origin with soda rich vapors emanating from the basic intrusive permeating the 17. fissures resulting in the introduction of new mineralse J. R. Smith has declared (2) that there is sufficient sods in all sediments to account for all the glaucophane formed. This is possibly true of sandstone and greenstone but is certainly not true of the chert. All chemical analyses made of this chert have shown it to be composed of 95% to 98% silica. With the large amount of blue amphibole associated with the metamorphic equivalent of this format ion a8 described above it is hardly possible to conceive of any other than pneumatolytic processes that have done the work. This feature together with the association of all schists of the area with the intrusive, and the sporadic aceurrence of such schists is conclusive of contact pnemmato- lytic metamorphism. SUMMARY There is a series of Franciscan rocks exposed on Tiburon Peninsula. They comprise sandstone, conglomerate, chert, and greenstone and have been folded into sa syncline whose axis has a northwest-southeast trend paralleling the peninsula. A perodite (serpentine) &ike has intruded this folded series locally tilting the strata. This dike likewise parallels the trend of the peninsula and intersects the axis of the syncline at a small angle, The metamorphic rocks due to the intrusive contain an abundance of ssod bearing amphiboles the origin of which has been the subject of much controversy, 18, It is here shown to be contact pneumatolytic metamorphism : REFERENCES with the sodium introduced from the &ntrusive. Ransome F. L. The Geology of Angel Island. U. C. Dept. Geol. Bull. Vel. 1. omith, J. P. ‘The Paragenesis of the Minerals in the Glaucophane Bearing Rocks of California. Lawson, A. C. San ¥#rancisce Folie U.S.G.S. Folie 193. Davis, E. F. The Franciscan Sandstone U. C. Dept. Geol, Bull, Vol. VII. lurgoci ~ Contribution to the Classification of Amphiboles Ue Co Dept. Geole Bull. Vel, IV, Palache Chas, Lherzolite Serpentine, U. C. Dept. Geol. Ball, Voll. Capps 5. Fo. Some Ellipsoidal Lavas on Prince William Sound, Alaska. Jour. Geol. Vol. 23 p. 45 1915. Palache, Chas. On a reck in the Vicinity of Berkeley Containing a New Soda Amphibole. De. Co Dept. Geol. Bull. Yol. 1. 9. Palache, Chas. The Lherzolite Serpentine and Associated Rocks of Potrero, S.J. U. C. Bull. Vol. 1. 10. Knopt, Adolph An Alteration of Ceast Range Serpentine U. C. Dept. Geol. Bull. Vol. 4 1906. 11. Davis, E. F. Radiolarian Cherts of the Franciscan U. C. Dept. Geol. Bull. Vel VII, 7 pr A Sandstone Conglomerate Shale Cher? Greenstone Se tperifine Me am orpbics od k LEGEND PLATE | SANDSTONE EL [eee [ coneiomerme © boo. Fu rr Lh Mr Xa ARE cai 3 pan hd Rey L ab joi Ts PRICE AN ATs ie AR BAG === 27 \- 4 Pillow Structure in Greernsrone. PLATE 2 PLATE 3 ’ Charac’er/Stic Cher’? OUIcrop . Serpentine showing Sof? foliated variety Lprvrned chert? near Serpentine Contract Serpersine snowing nodular masses. PLAT £ b5 Dike like occurrerice of mero- /m0rplIcs cutting greenstone 0 hi Ty FLAT EL 4 N g X Q \\ JY w ANN S RQ Q > N QQ S ~~ Q NY < QQ PLATE 6 Fg. /. Greenstone (Basal?) Dihe [the occUrrernce of merlamo rphics. Frg 2. Serpentine PLATE 8 F 9. / Normal Radrofarion Cher? Fig 2 Incipient growth 37 blue amphibole in chert PLATE 9 Fig. 1. Crossi/fe in center and boarderin actinolite i/n metamorphic chert rg 2 Glaticophane crossite actinolite epidote rvtrile schist END OF TITLE