UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Hanging wall quartzites, Sullivan mine Williams, Edwin Philp 1942

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1942_A7 W5 H2.pdf [ 18.53MB ]
Metadata
JSON: 831-1.0053055.json
JSON-LD: 831-1.0053055-ld.json
RDF/XML (Pretty): 831-1.0053055-rdf.xml
RDF/JSON: 831-1.0053055-rdf.json
Turtle: 831-1.0053055-turtle.txt
N-Triples: 831-1.0053055-rdf-ntriples.txt
Original Record: 831-1.0053055-source.json
Full Text
831-1.0053055-fulltext.txt
Citation
831-1.0053055.ris

Full Text

HANGING WALL QUARTZITES, SULLIVAN MINE by Edwin P l i i l p Williams A Thesis submitted i n P a r t i a l F u l f i l m e n t of The Req.uirem.ents f o r the Degree of MASTER OF APPLIED SCIENCE i n the DEPARTMENT OF GEOLOGY The U n i v e r s i t y of B r i t i s h Columbia A p r i l 1942 Preface The problem with which t h i s t h e s i s i s concerned was suggested by Dr. C. 0. Swanson i n August 1941. Arrangements were made by Dr. Swanson whereby the w r i t e r could remain a f t e r the close of the f i e l d season i n September to c o l l e c t the necessary specimens and data. The main part of the work was a petrographic study of t h i r t y - n i n e t h i n s e c t i o n s , on the basis of which the minerals and specimens were described. This microscopic work was preceded by a megascopic study of over two thousand feet of d r i l l core. The w r i t e r wishes to acknowledge h i s indebtedness to Dr. Swanson and the Consolidated Mining and Smelting Company for the arrangements whereby the thes i s m a t e r i a l could be c o l l e c t e d , and to Mr. F. M. l a l d i e and Dr. A. Pent-land f o r the use of the draughting o f f i c e , access to d r i l l core f i l e s and p r o v i s i o n of necessary equipment. In t h i s regard, i t should be stated that the w i l l i n g help and afiiricee of the engineering s t a f f was g r e a t l y appreciated. C O N T E N T S. Page Preface , i Introduction A. The Precambrian Section as exposed i n the Cranbrook Map Area ' ? 1 .By The Aldridge Formation 2 C. The Section Examined 3. The Sedimentary Sections 4 The R e l a t i v e P o s i t i o n s of the D r i l l Holes, and the Structure Indicated. 5 The Microscopic Examination of the Specimens 6 Descriptions of the Minerals 6 C l a s s i f i c a t i o n of the Minerals 24 C l a s s i f i c a t i o n of the Specimens 25 Descriptions of the Specimens 30 Conclusions A. P o s s i b l e Source l o c k s 35 B. Stage of Erosion and Type of Old Land 36 0. S i t e of Deposition 37 D. Metamorphism 37 Bibliography 40 i i T A B L E S Page Table I Proterozoic .(Belt!an:) Formations of the Oranbroofc Map Area 2 Table I I C l a s s i f i c a t i o n of the Minerals 25 Table I I I C l a s s i f i c a t i o n of the Specimen^ Part 1 27 Part 2 28 Part 3 29 E I G U R E S F i g . I . Logs of D r i l l Holes 3A" F i g . I I . Progress P l a n , S u l l i v a n Mine,:, with added: Area shorn i n F i g . I I I . 4A F i g . I I I . Location of D r i l l Holes and .Indicated Structure of the Hanging Wall ' 5A F i g . IVi Growth of Quartz Grains 7 F i g . V. , Quartz .Stringer — •• 8 F i g . VI. Pl e o c h r o i c Halos i n C h l o r i t e around Zircon 1& F i g . V I I . M i c r o c l i n e and C a l c i t e 18 Fig.VIII.Fibrous Tremolite 21 F i g . IX. Garnet 22 F i g . X* Pebbles in. Quartzite ,23 i i i HANGING WALL QJJARTZTTES, SULLIVAN MINE Introduction A. The Precambrian Section as exposed i n the Cranbrook Map Area, B r i t i s h Columbia ^ In the C o r d i l l e r a n Geosyncline from Idaho to Central B r i t i s h Columbia, a uniform group of sediments was l a i d down during the l a t e Precambrian. This group i s known i n the United States as the B e l t Terrane and i n Canada as the B e l t i a n . In Canada i t , has been subdivided i n t o the P u r c e l l Series and the Windermere S e r i e s , and the former has been further subdivided i n t o the Lower and Upper P u r c e l l s e r i e s . The P u r c e l l d i o r i t e s , Precambrian i n age, occur p r i n c i p a l l y as s i l l s and dykes. They cut the Lower P u r c e l l but not the Upper P u r c e l l s e r i e s . The younger B e l t i a n , i . e . , the Windermere s e r i e s , i s not represented i n the Cranbrook map area. 1. Rice, Mem.207, pp. 3-4. 1 Table I . Proterozoic ( B e l t i a n ) formations of the Granbfook Map Area Unconformity Upper P u r c e l l Gateway Lower Puree11 P u r c e l l Igneous Rocks In t r u s i v e Contact Siyeh Kitchener Creston A l d r i d g e Fort Steele Base Unexposed 1 B. The Aldridge Formation The Aldridge formation i s a g e o l o g i c a l u n i t of great thickness, persistence, and u n i f o r m i t y . I t i s by f a r the t h i c k e s t formation i n the lower P u r c e l l s e r i e s , being not l e s s than 16,000 f e e t t h i c k . The sediments are fin e - g r a i n e d f o r the most part and c o n s i s t of grey r u s t y weathering a r g i l l i t e and a r g i l l a c -eous q u a r t z i t e . The formation i s , i n general, not limey, but some beds are calcareous and, i n a few p l a c e s , limestone lenses occur. 1. Rice, Mem. 207, pp.6-8. "The a r g i l l a c e o u s q u a r t z i t e s c o n s i s t of f i n e ragged-edged quartz grains and small f l a k e s and aggregates of brown b i o t i t e . P l a g i o c l a s e , about the composition of andesine, occurs s p a r i n g l y . C a l c i t e i s u s u a l l y absent, but may, l o c a l l y , be abundant. A r g i l l a c e o u s m a t e r i a l , garnet, tourma-l i n e , z i r c o n , sphene, magnetite, p y r i t e , c o l o r l e s s mica', c h l o r i t e , and a p a t i t e occur i n small amounts. The a r g i l l i t e s are generally smooth, dense looking rocks d i f f e r i n g i n composition from the q u a r t z i t e s only i n a lower proportion of quartz g r a i n s . " The Aldridge formation has rather i n d e f i n i t e upper1 and lower l i m i t s . I t grades downward in t o the Fort Steele formation with the appearance of grey-green dolomitic a r g i l l i t e a l t e r n a t i n g v/ith black a r g i l l i t e , and upward i n t o the Greston formation where, above a few hundred feet of a l t e r n a t i n g grey and greenish a r g i l l i t e s , the c h a r a c t e r i s t i c greenish a r g i l l i t e s and a r g i l l a c e o u s q u a r t z i t e s of the Greston become dominant. C. The Section Examined The s e c t i o n examined i s i n the hanging w a l l of the S u l l i v a n ore body, and extends upward from the hanging w a l l f o r a distance of 700 fe e t s t r a t i g r a p h i c a l l y . Information obtained during the summer of 1941 places the ore horizon at 14,200 fe e t below the lowest beds of the Greston formation. The se c t i o n was measured from the contact on Mather (Cherry) Creek, near the highway bridge seven miles east of Kimberley, to a diamond d r i l l hole one ha l f mile north of Lois Lake and hence down the d r i l l hole to 1. Personal communication from Dr.N.F.G.Davis. 5A fr/G. 7. y c J i J / / / / / ) / i i C ^ <u? <> c L ~ 1 f / / / ( / ( —• 1 > j _ L _ L i J | c \ c r \ s Or-A f ^ ° _> M f\ i s s \\ ( \ s 0 1 11 s i VI ft i % J C7 'rr i | u t 1 0-1 ij j . 1 • -• -ei . 1 -• ,-r. • / • <t\' /• 7 ?• / e — • /7" 1 r • Q a • t-\ - - j -(7' - c IJ / =£<b_ J n t J I I)/ i ! ' j -—^— • i 7~~ ! •v <\ i i £> ' £^ > »^ * - \ \ < • W • N *~ ~IJ 7- 1 V • l • m - gf_ * It te ? t-a/ n 1 l - V J /< • j • u a t-i I. t' -N I N o - ^ •I • N SO .1 > - — | s ft Z / • * | < \ 0 £7 j i: ^ • A ; _ f • »|c k s if, / • • ; \ J i • • - Ti T ' 1 • I y J f - • A* Lf CI *• *'. i «; # * J • • • m • t > M - r7 • •9 • * >-[ I \ a. • u 1 - <5 fT* 1 c V -h, -L c 1 -7 — a "e J a i # * 0 s j .* 1" J. 1 1 •> \ i n i"-! - 1 • j • , | Y a ft • • • • ! ill ! s. c N i. ! °-<>. i r Y I -K -f-d- - | x: : I j • - | • • 1 j - j j j _s_ ) I i ! V f /lh' * • I • f< s — | . i -'l •' : 1 ! • -_ i ! | 1 ! "1" i ! : 1 I i \ 1 1 .4( ^ • - | j •a ! 1 •• | ! 1 4 1 i 1 '] 1 | 1 i •at-~J— i | 1 i « V f ! i I f— ! i i — j — | 1 1 ) I ! l j J { - i - j j 4 the hanging w a l l of the ore horizon. Thus the S u l l i v a n ore body i s somewhere near the base §£ fche/JLldridge formation. The Sedimentary Sections The sections were obtained by the d e t a i l e d examina-t i o n of d r i l l core from three holes, namely D.D.104, D.D.235, and D.D.468. The core was examined over a length of 700 to 800 f e e t i n each hole. Detailed logs were made, based on hardness, r e a c t i o n to 1:1 HCl, grain s i z e , c o l o r , and content of m e t a l l i c s . The angle between the core and the bedding was measured at regular i n t e r v a l s , where p o s s i b l e , so that the core lengths could be converted i n t o s t r a t i g r a p h i c t h i c k -nesses . The d e t a i l e d logs were condensed and s i m p l i f i e d , and graphic logs p l o t t e d against s t r a t i g r a p h i c thickness. F i n a l l y , these logs were r e p l o t t e d using terminology to f i t the microscopic d e s c r i p t i o n s . Figure I shows the three sections as l a s t p(Lotted. The graphic l o g s , a l l p l o t t e d against s t r a t i -graphic thickness from the hanging w a l l up, do not correspond as c l o s e l y as might be expected, considering that the greatest distance between holes i s only 1200 f e e t . 1. c f . "Site of Deposition", p. 37. f^/G. I T -/I '' f o r /rt'j.~3%£") 5 The R e l a t i v e P o s i t i o n s of the D r i l l Holes and the Structure Indicated The information regarding the r e l a t i v e p o s i t i o n s , e l e v a t i o n s of c o l l a r s , and dips and d i r e c t i o n s of the three diamond d r i l l holes, the core from which was examined, was obtained from, the company's d r i l l core f i l e s i n the Engineer-ing O f f i c e . The p o s i t i o n s of the d r i l l holes r e l a t i v e to the mine workings are shown on the accompanying Progress P l a n ( F i g . I I ) . They are shown again on a l a r g e r scale i n F i g . I I I . Assuming the hanging w a l l to be a plane w i t h i n the area marked o f f by the d r i l l hole i n t e r s e c t i o n s , contours 1. were drawn and the average s t r i k e and dip thus obtained. These worked out to N39°W and 27°NE. At the nearest outcrop above the area (at around 119Q0N, 6500E) the s t r i k e and dip were M16°to 23°W, and 27°to 30°N1. However, the hanging w a l l i s apparently f a r from being a plane, f o r i t i s hardly l i k e l y t h a t the 3356 X.G. would be d r i v e n i n t o the hanging w a l l to a p o s i t i o n 150 f e e t v e r t i c a l l y above ore. • 1. see F i g . I I I . . 2. Compare contoured plane i n F i g . I l l with p o s i t i o n of 3356 X.C. i n F i g . I I . F i g . I l l 5A LOCATIONS OF D R I L L HOLES AMD INDICATED STRUCTURE OF THE HANGING YiALL 1 J i L U JL l« -4 a d H x 1 i U j J j 1 4 J. L kt J i ? )H i? / T \ | d 8 u j] 1 1 H If- 1 1 6 V )( i ! \ 1 1" i | 1 \\ | 6 0 0 i i - I \ \ 1 | J \ \ K / J. i \ / e F r f y hi l i :e K i (J 1 r> 1 \ \ K 0 w " ? c M R ! \ -i 1 c >y 0 0 i k i / \ -i \ \ i i /> \ l 'd N. / 5 \ / \ | \ 1 i i x .c 0 (E 1 1 , 0 U i ; f i AC F 1 =• T 0 6 i f i ft \ 1 j \ / s s / \ T 1 A Li 1 J ft 1 / ' I ) \ 0 i i l , L - t 3 -i. k ! / 1 < ! pi )C c E 1 1 i \y 1 (h o i I ! y I u s ! , i > \ 1, - A /" tr LP •a n J 1 c 1 i C J. L .t r 1/ y i i 1^ r 1 (-• r t U 4 T. u >-» / y 1 1 / r • u )L 1u V\ i i i / j 1 l !r 1 i i i 1 II ! 1 i ! !M /—i y i | \ I i i i i i i i a 7 / I 1 5 r E i \| 1 i ' i i i / \ 1 | l 1 r i ll 1 i J ' i I ! y \ V 1 1 i ! i ! i i I !• i i y 1 i 1 I i I ! 1/ I ). I • i / i . L: T 1 •7 / ±1 n i ' 0 "il lie t i 0 m A 1 ' \ yr\ \ i i \ 1 i i_>' -y i i i T. ,( f i f ' 1 "i V in 1 1 1 I . i S r )C ! ! 1 1 r e 0 •'• K j n b ei H Vt-r 1 .! ! i ! 1 1 1 l i ' i I c i r n s, m 1 1 Vf | i i G r' fl V •ITT s u s e:d > 1 j i i i ! i 1 l \ i ~f~ 1 1 J 1 i ji I 1 1 ! 1 I l i 1 i 1 5 31 ul i &. 2< c n d I ii IC e -1 2: I The Microsooplo Examination of the Specimens Thirty-rnine t h i n sections were, examined, with a petrographic microscope. Twenty-six d i f f e r e n t minerals were encountered and determined. In t h i s regard the w r i t e r i s indebted to Dr. C. 0. Swanson f o r the f i n a l determination of seven or eight species. The r e l a t i o n s h i p s of the various minerals were noted, so that they could be c l a s s i f i e d accord ing to o r i g i n . The size-and r e l a t i v e abundance of each mineral were observed with the a i d of a micrometer eyepiece and ordinary mechanical stage. The grain s i z e i s therefore accurately determined but the percentage compositions are subject to e r r o r . These estimated percentages are, however, accurate enough f o r the purpose of c l a s s i f y i n g the specimens Descriptions of the Minerals The f o l l o w i n g minerals are described below:-Quartz, B i o t i t e , C h l o r i t e , S e r i c i t e , Muscovite, C a l c i t e , Magnetite, Carbonaceous Matter, Z i r c o n , A p a t i t e , A l b i t e , T i t a n i t e , Leucoxenej Z o i s i t e or C l i n o z o i s i t e , M i c r o c l i n e , Tourmaline, Aegerine-Augite, Green Amphibole, K a o l i n , P y r r h o t i t e , P y r i t e , S p h a l e r i t e , Galena, Phlogopite, Tremolite, Garnet, (and Pebbles). 7 A. Quartz Quartz grains e x h i b i t a l l shapes from very ragged to w e l l rounded. In general the medium and coarse quartz grains are better rounded than the smaller gr a i n s . However many f i n e and s i l t y grains show good rounding. The i r r e g u l a r -i t y i n shape, shown e s p e c i a l l y w e l l i n some specimens with g r a i n size from 0.2 to 0.5 mm., i s due to c r y s t a l growth. No "textbook"' examples"of quartz g r a i n growth were observed, but the f o l l o w i n g photomicrograph shows compaction of quartz against quartz which could hardly be explained other-wise. In contrast, see the w e l l rounded grains i n F i g . X. F i g . IV. Growth of Quartz Grains Calcareous Medium-grained Quartzite. - Crossed N i c o l s (X63) (from s l i d e #13) Quartz s t r i n g e r s are not common i n the s l i d e s examined. The one i l l u s t r a t e d below i s 0.36 am. wide and the i n d i v i d u a l components making up the s t r i n g e r are mostly between 0.5 and 1.1 mm. long. As the photomicrograph shows, the i n d i v i d u a l c r y s t a l s are i n a l l o r i e n t a t i o n s . The one under the cross h a i r s shows s t r a i n shadows, as do about one quarter of the c r y s t a l s i n t h i s v e i n l e t . In the rock, the quartz grains are poorly sorted and very ragged, i n d i c a t i n g , probably, grain growth. F i g . V. Quartz S t r i n g e r Fine-grained Quartzite - Crossed N i c o l s (X25) (from s l i d e #67) What appears to be f i n e c l a s t i c quartz i n the a r g i l l i t e s and f i n e r - g r a i n e d s i l t s t o n e s i s probably recryst' a l l i z e d from much f i n e r quartz i n the o r i g i n a l sediment, or produced by the breaking down of clay minerals. Quartz occurs as an a l l o g e n i c , an epigen e t i c , and a metamorphic mineral. The a l l o g e n i c quartz i s i n the form of d e t r i t a l g r a i n s ; the epigenetic quartz i s i n v e i n l e t s ; and the metamorphic quartz i s the r e c r y s t a l l i z e d quartz. B. B i o t i t e B i o t i t e occurs as small brown pleochroic f l a k e s , generally 0.05 to 0.3 mm. i n s i z e , and aggregates of these f l a k e s . . As the t h i n sections were cut perpendicular to the bedding, and as most of the b i o t i t e appeared as f l a t f l a k e s , ? a metamorphic o r i g i n i s i n d i c a t e d . B i o t i t e i s common i n the section examined. Only three s l i d e s have none, and only s i x others have l e s s than 4 percent. Most s l i d e s have from 4 to 19 percent, and three have over 20 percent. The rocks having over 15 percent b i o t i t e would be described as brown i n the hand specimen. 1 • . B i o t i t e i s the index mineral f o r the metamorphic stage of the Hanging Wall Quartzites considered as a u n i t . 0. C h l o r i t e C h l o r i t e i s present i n a l l but f i v e s l i d e s , making up, g e n e r a l l y , 2 to 6 percent of the s l i d e . Occasion-a l l y i t i s more abundant, amounting to 15 percent of one medium-grained q u a r t z i t e . A d e f i n i t e greenish cast i s given to the hand specimen by 10 percent or more c h l o r i t e . The c h l o r i t e f l a k e s are g e n e r a l l y s m a l l , 0.08 to 0. 3 mm., and appear i n a l l o r i e n t a t i o n s . In two specimens c h l o r i t e occurs as a very narrow bedded band, having the appearance of a v e i n l e t . C h i o r i t e shows the i n t e r e s t i n g feature of pleochroic halos around z i r c o n i n two specimens. The best occurrence 1. B i o t i t e zone; see Harker, Me tamorphism, Chap. XIV. i s i n the c h l o r i t i c s i l t s t o n e part of s l i d e #19. Here p o e c i l o b l a s t i c c h l o r i t e /makes up over h a l f the bed, and quartz about 40 percent. Zircon grains make up 3 percent of the bed, and the remainder c o n s i s t s of p y r r h o t i t e , s p h a l e r i t e , garnet, and c l i n o z o i s i t e . On one side of t h i s bed i s a g a r n e t - c a l c i t e - f i n e - g r a i n e d q u a r t z i t e and on the other a normal fine-grained q u a r t z i t e . A l l three beds appear i n the one s l i d e . F i g . VI. shows the p l e o c h r o i c halos. C h l o r i t e represents a low grade of metamorphism, but the more abundant b i o t i t e i n d i c a t e s that the c h l o r i t e -forming stage has been passed. M / ^ M " ^ - ^ D. S e r i c i t e White mica occurred as both s e r i c i t e and muscovite. S e r i c i t e i s not d e f i n i t e l y separated from muscovite, but the overlap i s small. In general., f o r the purpose of s u b d i v i s i o n , white mica was c a l l e d s e r i c i t e when i t occurred as narrow f l a k e s under 0.15 mm., long, and showed interference c o l o r s up to f i r s t order yellow. Muscovite., on the other hand, includes a l l large f l a k e s of white mica, which show a v a r i e t y of i n t e r f e r e n c e c o l o r s up to high second order, and those small f l a k e s , the size of the l a r g e s t s e r i c i t e f l a k e s , which showed'-either two long dimensions, or second order i n t e r f e r -ence c o l o r s , or both. S e r i c i t e i s c h a r a c t e r i s t i c of s i l t s t o n e s , c a l c a r -eous s i l t s t o n e s , and a r g i l l i t e s , occurs i n some fine-and I* Barker, Me tamorphism. Chap. XIV. medium-grained q u a r t z i t e s -(with c a l c i t e under 6 percent), and i s rare i n a l l ether types. Metamorphism of a r g i l l a c e o u s sediments (kaolin,etc 1 produces white mica i n Harker's "0" zone of Regional Metam-orphism.' This zone i s outside the f i r s t r e g i o n a l l y metamor-phosed zone (the C h l o r i t e Zone) and represents Dynamic Metamorphism before the temperature increased g r e a t l y . However, c h l o r i t e or b i o t i t e or both are always present showing that s e r i c i t e i s not the index mineral. I , Muscovite The museovite f l a k e s , as defined above, are probably the r e s u l t of f u r t h e r r e c r y s t a l l i z a t i o n , although an a l l o g e n i c o r i g i n i s suggested f o r the coarser mica occurs i n the coarser sediments. However a great many of the large f l a k e s (G*30 mm. and larger) are oriented p a r a l l e l to or nearly p a r a l l e l to the s l i d e s , which are, as noted before, cut perpendicular to the bedding* ^^>-^ Twinned f l a k e s were observed i n one s l i d e , but t h i s was an exceptional occurrence. F. C a l c i t e No crcagineOi; c a l c i t e remained i n the s l i d e s examined for,, under the metamorphic conditions which e x i s t e d , i t was e n t i r e l y r e c r y s t a l l i z e d . The average c a l c i t e content of the t h i r t y - n i n e s l i d e s examined was over 9 percent, and, 1. Harker, Metamorphism,Chap.XIV. as only a small part of t h i s was obviously epigenetic, i t i s concluded that there was o r i g i n a l l y perhaps 6 percent c\..i,lo c a l c i t e i n t h i s part of the Aldridge formation. The r e o r y s t a l l i z e d c a l c i t e occurs as i r r e g u l a r f i l l i n g matter. Some twinning i s generally evident. I t i s cementing matter and, as such, i s authigenie. However i t s present form i s due to metamorphism. C a l c i t e s t r i n g e r s are common i n t h i s s e c t i o n of hanging w a l l sediments. Many of the s t r i n g e r s are only about 0.2 mm. wide, but c a l c i t e i n the rock next to the st r i n g e r i s more abundant them normal and the r e a c t i o n to aci d gives the appearance of a much wider s t r i n g e r . A f u r t h e r occurrence of ve i n c a l c i t e i s i n a bedded v e i n , 6 mm. wide, with m i c r o c l i n e , quartz, c h l o r i t i e matter, p y r i t e , p y r r h o t i t e , s p h a l e r i t e , and galena* This occurrence i s described l a t e r under " M i c r o c l i n e " . The twinned c a l c i t e alongside microcline i s shown i n J i g . VII.. G. Magnetite : Magnetite amounts to as much as 2 percent of some s l i d e s , but does not commonly occur. The g r a i n s , 0.05 to 0.12 mm. i n s i z e , were d u l l brownish black i n r e f l e c t e d l i g h t and were d i f f i c u l t to determine with c e r t a i n t y . Magnetite i s probably d e t r i t a l i n o r i g i n , but may be formed by meta-morphic processes. 13 Hi Carbonaceous Matter Small black specks are present i n s u f f i c i e n t numbers i n wavey bands i n some specimens to give a very d e f i n i t e banding to those specimens. The bands are p a r a l l e l to the bedding and show up e s p e c i a l l y w e l l under the low power. Examination at high magnifications showed these specks to have no a n g u l a r i t y , to be about 0.004 mm. i n diameter, and to be not so numerous .'as low power examination would i n d i c a t e . These specks are almost c e r t a i n l y carbonaceous matter, and therefore represent organic remains, f o r no other o r i g i n f o r carbonaceous matter i n such an occurrence i s accepted. Carbonaceous:matter would be classed with'the authigenic minerals, being part of the matrix surrounding the d e t r i t a l g r a i n s , . Wftue<« , I . Zircon Round, o v a l , or pear-shaped grains of z i r c o n occur i n nearly h a l f the s l i d e s . This common accessory mineral ranged i n s i z e from 0.03 to 0.12 mm., and1 often amounted to ^  or | percent of the s l i d e . A f i n e large z i r c o n i s shown i n F i g . I;"]y» The i n t e r e s t i n g occurrence of z i r c o n i n p e o c i l o b l a -s t i c c h l o r i t e i s shown below. The pleo c h r o i c halos are produced by the r a d i o e t i v i t y of the z i r c o n . Zircon i s hi g h l y r e s i s t a n t to weathering and 14 hence occurs commonly as a d e t r i t a l mineral. F i g . VI. Pleochroic Halo3 i n C h l o r i t e around Zircon C h l o r i t i e S i l t s t o n e ; P o e c i l o b l a s t i c C h l o r i t e enclosing Z i r c o n , Quartz, and P y r r h o t i t e . (X63) (from s l i d e #19) J . A p a t i t e Very small prisms (long sections) of a p a t i t e were determined i n two s l i d e s . I t i s possible that the occurrence i s more wide-spread, because the small prisms are nearly c o l o r l e s s , are the same s i z e as the small s e r i c i t e f l a k e s , and are dark (grey) between crossed n i c o l s . Hence only a close examination reveals t h e i r presence. The grains are d e t r i t a l i n o r i g i n . K. A l b i t e D e t r i t a l p l a g i o c l a s e was observed i n only one s l i d e , and made up only ifo of the rock. The smooth g r a i n s , maximum si z e 0.12 X 0.27 mm., had a r e f r a c t i v e index l e s s than quartz and a birefringence of .009, gave a b i a x i a l p o s i t i v e interference f i g u r e with large 2V, and showed 16 - 20° e x t i n c t i o n angles f o r almost symmetrically cut a l b i t e twioas. These determinations i n d i c a t e a l b i t e or a l b i te-oligoclase. L. T i t a n i t e T i t a n i t e occurred as semi-opaque grains about 0.1 mm. diameter. Other s i m i l a r grains i n the same s l i d e s were opaque and white. An interference f i g u r e from one of the cl e a r e r grains i n d i c a t e d t i t a n i t e , and, according to Dr. Swanson, the a s s o c i a t i o n i s t i t a n i t e a l t e r i n g to amorphous leucoxene (see below). The t i t a n i t e i s a l l o g e n i c i n o r i g i n . M.. Leucoxene Leucoxene, opaque and white, occurs i n round patches about 0.1 to 0.2 mm. i n s i z e . I t i s sometimes associated with t i t a n i t e and may simply be formed from the a l t e r a t i o n of d e t r i t a l t i t a n i t e . According to Milner''" leucoxene i s "a decomposition product of i l m e n i t e , as yet i l l - d e f i n e d . I t i s 0 p r o b a b l y f o r the most part a form of t i t a n i t e , with p o s s i b l y some carbonate. I t has been described by Iddings as a form of anatose^ or p e r o v s k i t e i ' 4 ____ ; i 1. M i l n e r : Sed. Petrog.,£.205. 2. T i t a n i t e = GaTiSi05 3. Anat&se (= Octahedrite) = TiOg (as for R u t i l e ) . 4. Perovskite - GaTiO* 16 The l a t e s t e d i t i o n of Dana 1 l i s t s leucoxene as an a l t e r a t i o n product of ilme n i t e and f u r t h e r states that " t h i s (leucoxene) f o r the most part i s to be i d e n t i f i e d with t i i a n i t e . " 2 ' According to Rogers and K e r r , leucoxene, the white opaque a l t e r a t i o n product of i l m e n i t e , i s "according to a recent investigation...amorphous hydrous t i t a n i u m d i o x i d . " The f o l l o w i n g notes are from copies of M i n e r a l o g i c a l 5 Abstracts. (1) Leucoxene obtained from sandstone i n Oklahoma "ranges from white to reddish brov/n- i n color and shows a great v a r i e t y of forms. I t may be derived from ilmenite or r u t i l e or from intergrowths of these with magnetite and haematite«M -(2) The a n a l y s i s of the earthy opaque m a t e r i a l i s in t e r p r e t e d as 72,2 percent leucoxene (TiOg*nHgO) with 24 percent quartz and minor i l m i n i t e and hematite. The combined water i s small i n amount and n i s probably l e s s than one. (3) "X-ray photographs of leucoxene give i n nine cases 6 the pattern of r u t i l e , and i n one that of anatase." The various authors do not agree, but the most recent evidence a i l . i n d i c a t e s that leucoxene i s a form of titanium dioxide. In order to give an X-ray photograph i t must be c r y s t a l l i n e , hence "amorphous leucoxene" may be nothing more nor l e s s than very f i n e r u t i l e or anatase. 1. Textbook of Mineralogy, 4th Ed*, p. 486, 2. Thin Section Mineralogy, p. 171, 3* See Bibliography. 4. Min.Abstr., vol.4,1929-31,p.506. 5, M i n . A b s t r v o l . 5 , 1932-34,p*285. 6. M i n . A b s t r . v o L 7 , 1938-40, p.234. 17 The water shown by a n a l y s i s would not be part of the c r y s t a l s t r u c t u r e , f o r the X-ray patterns of the an-hydrous minerals, r u t i l e and anatase, were obtained. A variable amount of water might be adsorbed on to the surface of the minute c r y s t a l s , and, i f t h i s were the case, n, i n the formula TiOg'nHaO, would be anything but constant. Thus the formula f o r leucoxene i s reduced to TiOg. The occurrence of t i t a n i t e , as observed i n some s l i d e s , i s not mentioned i n the l i t e r a t u r e . There i s nothing, however, to i n d i c a t e that t h i s leucoxene should be any d i f f e r e n t from other white leucoxene. I t i s therefore an a l t e r a t i o n product and should be classed as authigenic. N. Z o i s l t e or C l i n o z o i s i t e These minerals are almost impossible to separate by petrographic means. The f o l l o w i n g occurrences are suggestive of c l i n o z o i s i t e : - i n a v e i n l e t with c a l c i t e (one occurrence), and as i r r e g u l a r patches, e i t h e r alone or surrounding p y r r h o t i t e (seven occurrences). ' These would i n d i c a t e ah epigenetic o r i g i n . On the other hand, z o i s i t e , of metamorphic o r i g i n , i s suggested by the three occurrences as wavy banding, p a r a l l e l to the bedding and associated with carbonaceous matter. This banding could, however, be epigenetic. Thus the sum t o t a l of occurrences i n d i c a t e s c l i n o z o i s i t e , i f there i s present only one of. the two 18 minerals, but very l i k e l y both occur. 0. M i c r o c l i n e The only occurrence of microcline i s along one edge of the bedded c a l c i t e vein p r e v i o u s l y mentioned. The photomicrograph below shows most of a c r y s t a l 3 mm. long by 0.36 mm. wide. I t i s p a r a l l e l e d , on the edge away from the v e i n w a l l , by a well-twinned c a l c i t e c r y s t a l of about the same s i z e . The microcline and c a l c i t e twinning i n d i c a t e a movement p a r a l l e l to the w a l l of the v e i n . Away from the v e i n w a l l having the m i c r o c l i n e , the r e s t of the vein consists mainly of twinned c a l c i t e , with some st r a i n e d quartz "grains", scattered p y r i t e , p y r r h o t i t e , s p h a l e r i t e , and galena, and c h l o r i t i c matter c h i e f l y around c a l c i t e g r a i n s . F i g . V I I . M i c r o c l i n e and C a l c i t e A part of a bedded v e i n l e t i n si_tstone-crossed n i c o l s (X57). (from s l i d e #27) 19 P i Tourmaline Tourmaline .-occurred as prisms, eith e r long sections (0.14 by 0.0.5 mm.) or cross sections (0.05 mm.) i n eight' s l i d e s . The cross sections are greenish or g r e y i s h and the long sections are h i g h l y pleochroic greenish brown to c o l o r l e s s . Some show what appears to be a l t e r a t i o n to b i o t i t e , but, on the other hand, the tourmaline may be produced from the b i o t i t e by hydrothermal a c t i o n . Thus the tourmaline may be d e t r i t a l or may be produced as an epigenetic a l t e r a t i o n . Q,. Aeger ine-Augite C r y s t a l fragments, up tp 0.5 mm., which were s l i g h t l y p l e o c h r o i c , the darkest c o l o r s being blue-grey or yellow-green, were determined by Dr. Swanson as sodie pyroxene, i . e . , aegerine-augite* They are most l i k e l y d e t r i t a l grains showing c r y s t a l or cleavage edges. R. Green Amphibole A prism 0.17 mm. long with a b r i g h t -green color,, a r e f r a c t i v e index of 1.7 and an e x t i n c t i o n angle of 35° could not be a c c u r a t e l y determined. The amphibole fa m i l y i s suggested. I t i s assumed to be a d e t r i t a l g r a i n . S. K a o l i n Foggy white agglomerations o f k a o l i n occur i n two s l i d e s . These agglomerations measure 9.2 to 0.3 mm. and are 20 translucent i n strong l i g h t . They show a f i r s t order grey interference color which i s e i t h e r due to quartz or to , c r y s t a l l i n e k a o l i n i t e . This i s i n marked contrast to the somewhat s i m i l a r leucoxehe, vrtiich may show a high b i r e f r i n g -ence (that of t i t a n i t e ) . T. The S u l f i d e s Of the four sulphides, p y r r h o t i t e i s the most common. I t occurs as bands p a r a l l e l to the bedding, i n i r r e g u l a r patches, i n patches surrounded by c l i n o z o i s i t e and sometimes al s o c h l o r i t e , ' a n d as a minor constituent of a c a l c i t e v e i n l e t . P y r i t e may accompany the p y r r h o t i t e or may occur alone i n bands or as i s o l a t e d cubes. Sphalerite occurs as angular "grains^, generally under 0.25 mm. i n s i z e , widely dissemin-ated In the rock.: Galena i s rare In the s l i d e s examined, occurring as very small scattered specks i n one s l i d e and as a few small specks associated with c l i n o z o i s i t e i n another. As might be expected t h e ? s u l f i d e s are most common i n the specimens taken from w i t h i n 100 f e e t of the hanging w a l l . The epigenetic o r i g i n of the s u l f i d e s i s very evident. U. Phlogoplte and Tremolite The occurrence of phlogopite and tr e m o l i t e together i s l i m i t e d to one s l i d e . They are apparently of metamorphic o r i g i n . u r l L t * * P L -•. The phlogopite i s d i s t i n g u i s h e d from muscovite by i t s pale brown c o l o r , and small ( 2 V ( 1 0 o i ). Flakes up to 21 0.36 ram. i n s i z e make up 2 percent of the s l i d e . Radiating f i b r o u s t r e m o l i t e , l i g h t green i n the hand specimen and c o l o r l e s s i n t h i n s e c t i o n , makes up 16% of the s l i d e . The photomicrograph below shows very c l e a r l y the occurrence of t h i s mineral. (Tremolite occurs i n only one other s l i d e , amounting to l e s s than 1 percent of the s l i d e . ) F i g . V I I I . Fibrous Tremolite Tremolite C r y s t a l s i n a Calcareous Coarse-grained Quartzite,-crossed n i c o l s (X63) (from s l i d e #38) The r e s t of the s l i d e i s made up of:- coarse well-rounded quartz g r a i n s , 35%; pebbles, 10%; c a l c i t e , 25%; muscovite, 7%; p y r r h o t i t e , 5f0; and c l i n o z o i s i t e , 1%. Fig.X shows a part of t h i s s l i d e , showing quartz g r a i n s , pebbles, etc. 22 V. Garnet The hanging w a l i immedlately at the ore zone con-t a i n s garnet. I t occurs as rough hexagons or as parts of c r y s t a l s without any p a r t i c u l a r shape, and represents a higher grade of metamorphism than the b i o t i t e zone. A development of small amounts of garnet at 200 feet or more above the hanging w a l l was observed i n s l i d e s #78 and #29. The outstanding occurrence of garnet i s i n s l i d e #19 where i t makes up 30% of a g a r n e t - c a l c i t e - f i n e - g r a i n e d q u a r t z i t e . This bed i s le s s than 1 cm. t h i c k , and includes numerous garnets, showing well-developed dodecahedral shape, up to 5 mm. i n diameter. These garnets, one of which i s shown below, are frac t u r e d and contain i n c l u s i o n s of z o i s i t e ( c l i n o z o i s i t e ? ) , quartz, and p y r r h o t i t e . The r e s t of the F i g . IX. Garnet A large garnet, showing frac t u r e pattern and in c l u s i o n s of quartz, z o i s i t e , and p y r r h o t i t e . (X25) (from s l i d e #19) 23 bed i s composed of f i n e quartz-grains, c a l c i t e f i l l i n g matter, b i o t i t e , c h l o r i t e , and muscovite f l a k e s , a l i t t l e p y r r h o t i t e , and some z o i s i t e or c l i n o z o i s i t e i n i r r e g u l a r patches. The ad j o i n i n g c h l o r i t e bed has been described above. W. Pebbles Two specimens contained 9 or 10% pebbles. A c a l -careous medium-grained q u a r t z i t e and a calcareous coarse-grained q u a r t z i t e both contained rounded pebbles of sizes equal to the quartz grains present. The pebbles i n the coarse q u a r t z i t e were of a fine*grained q u a r t z i t e which was p r a c t i c a l l y pure quartz, with g r a i n s , measuring 0.11 mm., close packed by r e c r y s t a l l i z a t i o n . The photomicrograph below shows t h i s occurrence. The pebbles i n the medium-grained q u a r t z i t e were of s i l t s t o n e , composed of quartz Fig:. X. Pebbles i n Quartzite Calcareous Coarse-grained Quartzite with Fine-grained Quartzite Pebbles,-crossed n i c o l s (X57) (from s l i d e #38) 24 grains (0.05}mm.) with s e r i c i t e f l a k e s l y i n g along the boundaries between these g r a i n s . I t i s i n t e r e s t i n g to note that the only white mica i n the s l i d e occurred i n these s i l t s t o n e pebbles. C l a s s i f i c a t i o n of the Minerals The accompanying- table gives the c l a s s i f i c a t i o n of the minerals according to t h e i r o r i g i n and mode of occurrence, •The four classes are: a l l o g e n i c , authigenic, epigenetic, and metamorphic. ' The four-way c l a s s i f i c a t i o n i s necessary because the s e c t i o n shows the e f f e c t s of metamorphic and i n t r u s i v e processes added to those of the sedimentary processes. The al l o g e n i c minerals are the d e t r i t a l minerals, and the iaartJaig^niO' minerals are' the cementing minerals formed i n t h the c o n s o l i d a t i o n ,of sediment's. The metamorphic minerals are produced by metamorphic processes and may be e i t h e r new minerals or d e t r i t a l minerals r e e r y s t a l l i z e d . The epigenetic minerals are ve i n minerals, or replacements and a l t e r a t i o n s by hydrothermal or other metasomatic processes* The a l l o g e n i c suite gives a h i n t as to the source rocks. The metamorphic s u i t e t e l l s of the type and grade of met amor phi sin to which the formation has been subjected. The epigenetic s u i t e r e f l e c t s to some extent the ore-forming processes which went on j u s t beneath the se c t i o n examined. Ihe authigenic s u i t e i n d i c a t e s very l i t t l e because the l a t e r metamorphic and epigenetic processes have changed the rooks considerably, and. e s p e c i a l l y affected the authigenic minerals* Table I i ' . C l a s s i f i c a t i o n of the Minerals Mineral * ;- • • Quartz B i o t i t e C h l o r i t e S e r i c i t e Muscovite C a l c i t e Magnetite Carbonaceous Matter Zircon A p a t i t e A l b i t e • T i t a n i t e Leucoxene Z o i s i t e or C l i n o z o i s i t e M i c r o c l i n e Tourmaline Aegerine-Augite Green Amphibole K a o l i n The Sulphides:-P y r r h o t i t e pPy-ri<|e Sp h a l e r i t e Galena Phlogopite Tremolite '.. Garnet n i . . . ' Meta-A l l o g e m c Authigenic Epigenetic morphio x x X X X X X X X X X X ? X X X X X X X X X X X X X X ? X X X Pebbles C l a s s i f i c a t i o n of the Specimens Two v a r i a b l e s only were considered f o r the c l a s s i -f i c a t i o n of the, rook types as observed i n t h i n s e c t i o n . 1 . •1. She p r e v i o u s l y described garnet and c h l o r i t e beds were . not considered i n t h i s c l a s s i f i c a t i o n . The f i r s t v a r i a b l e i s grain s i z e . The diameter of the l a r g e s t quartz grains (excluding e r r a t i c s } was used f o r naming the specimens as shown i n the f o l l o w i n g plan:-diameter i n m i l l i m e t e r s 0.01 i 0.1 L _ 0.25 0.5 i _ 1.0 2.0 L _ A r g i l l i t e S i l t s t o n e Fine-grained Quartzite 7 Coarse-grained Quartzite Medium-grained Quartzite Con-glomer-ate Very Coarse Quartzite The second v a r i a b l e i s the c a l c i t e content. The specimens were a r b i t r a r i l y divided on t h i s basis i n t o , (1) those with 10% or more c a l c i t e , and (2) those with l e s s than .10% c a l c i t e . The f i r s t group were c a l l e d calcareous, and the second group merited no modifier. Table I I I (parts 1, 2, &,.3) l i s t s the specimens as so c l a s s i f i e d . Where the quartz:white mica r a t i o appears to have some.significance ( s t a t i s t i c a l l y ) , the.specimens of each group are l i s t e d i n order of t h i s r a t i o . Otherwise they are l i s t e d i n order of percentage of quartz. From the. examination of t h i s t a b l e , the following are observed: l a . Almost constant q u a r t z : s e r i c i t e r a t i o i n s i l t s t o n e s . 27 -P (4 erf ft H H H 0) H /a erf EH m d <D •H O CD ft! CO <D P o d o •H P Ctf o •ri <<H •H CO CO Crf H O §J J8q.q.^sno80t}tIoclJBo 9q.TAoosnw:zg-reri^ vO • H CO H OJ K\,CK OrlHHHHWWW OJ <M OJ i—I ~a— H SUTIOTUnOJ, eaisfoz JO QgTSTOZOTtTXO 1 HTH" OWHH H noojfz eg T oiB o eaxoTjeg egtAOoetiH enezoonei eajaen-h 8aTaoqjj___ a_ GO O H VO CM O 0 0"N OJ OJ H H H H OO QC0 KNO Q KM_"\oj<X> «d-K\KWK\,c\JC\IOJOJ S0 © O OJ OJ OJ OJ H H HI o OJ OJ vO ^OW^H H d H OOOH f\ H H SO OJ OJ H H'H HI-OJ o Os os -*t c~ OJ H HHCVIr! u-\©s© c— O C~-C~-00 us\ K\*5fr K\"sf -s}- Lf\v_5 LT\ O OJ l£\0 O LT\I OJ KN-sf ur\LnJ COHNN OJ HI • —R-OJ H O H tf\H tAOJ O HI Hf H CK UT\SO t—9 CO OJ K\ OS P- K\CQ if «\ OJ tf\s© c~-OJ -«^-vO KNO LT\H, _r\s0 OJ OJ rH urv ft !*> EH M a o W © -P •H H H •H -JO CD d o -p ra •p H CO 02 o rt CD O %4 P Crf CO o p H H Crf -H O CO H •fl cd p CO CO © H CO CD 43 erf o •H d . d H 28 sq.TAoosn]?f ••9 « •• • • ff c •r cc 1 ; ©q.TAoosni;:zq.JBnb > NMA | ON OJ ©vO H H CD Pi •H ff c •r cc eq.xox.ies:zq..n3nfe ir\ H K\ —— [ .. • • H -<t IA 1 H CD Pi •H nxxoB2 .O CVJ P Pi O ©q.x§ny -©ttxjsSlsy ;HI' o 9q.TSTO<7 &o ©tfTsxozorcjxo •A CM -^^j. . : ... H OJ 1 eufxiBTnjnoj, < H ' CQ Pi CD HrlrlHrlH HHrlrlrl Spec in fA P! i-4 •. OH O C-lACM H H H H H H CD •p ons •A ; xo >sj- 0 H H H <i-i o mpositi ©q-X-Aoosnn IACVJCO 00 "AC-O OOO , H H H H , ion ©q-TjoxTio OJ •^•VO (AV0 fAtAlACM VO CM OJ xfr K\vD -p o 0 0 8q.Tq.oxa H H OJ LAOO O CM CM • H ; H H •H 4+ •H m 0) cd C—H IA K\ OJ ON K\CO fA CO OO C~>.C—C—vOvO if\ LT\ . N\0 lAH O O CQ cd >-s PI CO ' 0 ©rr83:oon©i H' o PH CO Pi Bn©XBQ ©q.xj:©xBqdg .:Pl ^ . M «A\ sq.xq.etrgBp'i Ps c-t ©q-xj^d ; H • H H ©q.xq.oqjjjfj OJ CM UT\|—| OJ OJ IA <sf OO CM fA CM jGqnmM Tioxq.o9g ONVJ3 C~ IA HI ON tr\ -4- ON H / AO C— IA KV-0 OJ HCO CM HOD CM C—tACM K\C--IA id 0 0 « © -CD «t* P 1 CD -H fl) N. P| 'HP t-i vH U <3> ; CO 0 E) tip O I CD -H CD CO p| N P-l Pi -H pi cd «H cd O |i( fH <d H ti 2 cd a? 29 l b . More v a r i a b l e r a t i o i n calcareous s i l t s t o n e s . l c . Nearly constant b i o t i t e content (around 20%) i n calcareous s i l t s t o n e s (one exception). 2a. Calcareous fine-grained q u a r t z i t e s have muscovite and no s e r i c i t e . 2b. Two-thirds of the calcareous f i n e - g r a i n e d q u a r t z i t e s have quartz:muscovite r a t i o approximately 6. 2c. With one notable exception, the b i o t i t e content of f i n e - g r a i n e d q u a r t z i t e s i s much greater f o r the specimens w i t h l e s s than 70% quartz. 2d. The b i o t i t e , muscovite, and c a l c i t e i n c a l c a r -eous fine-grained q u a r t z i t e s vary together. (N.B.: the specimen without any b i o t i t e i s " exceptional. ) 3. In medium and coarse grained q u a r t z i t e s , whether calcareous or not, s e r i c i t e i s not. generally present. f • • Descriptions of the Specimens A* A r g i l l i t e Only one specimen was examined i n t h i n s e c t i o n . I t consisted, of 88% a r g i l l a c e o u s matter and 12% secondary minerals. The a r g i l l a c e o u s matter consisted of quartz grains 0.008 mm., and narrow s e r i c i t e f l a k e s , 0.015 mm. long, i n 31 •the r a t i o 50:38 (approximately 1.3:1). The remainder was made up of: aggregates of garnet and quartz occurring together, .12 to .2 mm i n s i z e ; a few b i o t i t e and c h l o r i t e f l a k e s up to 10X the s i z e of the quartz grains i n the a r g i l l a c e o u s matter; small bronze pyrr-h o t i t e "grains*'; and a very few patches of c a l c i t e f i l l i n g . A narrow v e i n l e t of c a l c i t e , quartz, p y r r h o t i t e , and c h l o r i t e cuts the s e c t i o n examined. The 12% of secondary minerals i s divided as f o l l o w s : 1% Garnet, 4% Quartz, 1% B i o t i t e , 1% C h l o r i t e , 4% Pyrrhotite,.and 1% C a l c i t e . B. S i l t s t o n e The most nearly t y p i c a l s i l t s t o n e i s #52. The groundmass (70% of the s l i d e ) c o n s i s t s of i r r e g u l a r quartz grains (0.03 mm., diameter) and s e r i c i t e f l a k e s (0.025 mm. long ) - . ' • • In a narrow v e i n l e t and i n i r r e g u l a r agglomerations occur the f o l l o w i n g : p y r r h o t i t e , surrounded i n part by c l i n o z o i s i t e and c h l o r i t e , the whole being rimmed by b i o t i t e . A few small angular grains of s p h a l e r i t e accompany some of the p y r r h o t i t e . C a l c i t e f i l l i n g matter, b i o t i t e f l a k e s , and muscovite f l a k e s oocur rather s p a r i n g l y . A few tourmaline c r y s t a l s surrounded by b i o t i t e suggests a l t e r a t i o n by epigenetic processes. I t i s i n t e r e s t i n g to note the near constancy of the q u a r t z - s e r i c i t e r a t i o . In seven out of ten specimens i t l i e s between 1 and 2. In general, with both increasing and decreasing q u a r t z - s e r i e i t e r a t i o , the c h l o r i t e content drops o f f . C. Galcareous S i l t s t o n e Apart from the f a c t that specimen #23 (calcareous s i l t s t o n e ) corresponds quite c l o s e l y with specimen #79(B) ( s i l t s t o n e ) , . the composition of the calcareous v a r i e t i e s d i f f e r considerably from the non-calcareous or l o w - c a l c i t e v a r i e t i e s . Specimen #20 i s taken as t y p i c a l . I t s high s u l f i d e content i s explained by noting that the specimen i s taken from j u s t w i t h i n the ore zone. Otherwise the,rock i s near-average f o r calcareous s i l t s t o n e . Quartz geralns, mostly about 0.04 mm. (and a few as large as 0.07 mm.), small s e r i c i t e f l a k e s , irregular-appearing b i o t i t e f l a k e s , and c a l c i t e matrix make up 80$> of the s l i d e . The e a l e i t e tended to be concentrated i n bands p a r a l l e l to the bedding, i n l e s s e r amounts were c h l o r i t e f l a k e s and d e t r i t a l magnetite and t i t a n i t e . I n d i c a t i v e of the ore zone i s the occurrence of p y r i t e , p y r r h o t i t e , s p h a l e r i t e , and garnet. P y r i t e i s the most common i n t h i s specimen, making up 10% of the s l i d e and two-thirds o f the s u l f i d e s . I t occurs i n bands p a r a l l e l to the bedding. P y r r h o t i t e has a s i m i l a r occurrence, and also occurs as minute specks and rods scattered i n the rock. S p h a l e r i t e occurs as aggplar "grains". The garnet c r y s t a l s are poorly developed and small i n number. 33 B. Fine-grained Quartzite This very common rock-type shows great v a r i a b i l i t y , and no t r u l y t y p i c a l specimen e x i s t s . #41 i s i n many ways an average f i n e - g r a i n e d q u a r t z i t e . Ragged grains of quartz up to 0.25 mm., i n diameter make up 72% of the s l i d e . Flakes, of muscovite (up to 0.35 mm.)', c h l o r i t e (up to 0.18 am.), and b i o t i t e (0.08 mm.) together with i n t e r s t i t i a l c a l c i t e makes up the matrix. Accessories are: 2% p y r r h o t i t e and minor galena and z i r c o n , E. Calcareous Fine-grained Quartzite The " t y p i c a l " calcareous fine-grained q u a r t z i t e c o n s i s t s of 65% w e l l - s o r t e d , poorly-rounded quartz grains up to 0.15 mm. i n diameter. The matrix c o n s i s t s of approximately equal amounts of muscovite, b i o t i t e , and c a l c i t e and a small amount of c h l o r i t e . The muscovite and c M o r i t e f l a k e s are 0.2 to 0.4 mm. long and the b i o t i t e f l a k e s are 0.1 mm. i n s i z e . I n t e r s t i t i a l c a l c i t e occurs i n patches up to 0.36 mm. across. Accessory minerals are p y r r h o t i t e , p y r i t e , aegerine-augite, and z i r c o n . Medium-grained Quartzite None of the three specimens corresponds to an ' average or t y p i c a l medium-grained q u a r t z i t e . #79(A) has no c h l o r i t e , #47 has an ex c e p t i o n a l l y large amount of c h l o r i t e , and #10 has s e r i c i t e instead of muscovite. Specimen #47 consists of the f o l l o w i n g : - quartz, poorly rounded and poorly sorted grains up to 0.5 mm., 58%; chl o r i t e , f l a k e s up to 0.9 mm. long, 15$; muscovite f l a k e s , i n a l l o r i e n t a t i o n s , up to 0.2 mm., 12%; b i o t i t e f l a k e s up to 0.2 mm., 10%; i r r e g u l a r patches of c a l c i t e 0.2 to 0.35 mm. i n s i z e , 5%; and accessory z i r c o n and t i t a n i t e . The other specimens d i f f e r fundamentally only as noted above. G. Calcareous Medium-grained Quartzite The most nearly average calcareous medium-grained q u a r t z i t e i s #60. Ragged quartz g r a i n s , make up 63% Of the s l i d e . They are poorly sorted, being mostly under 0.3 mm. but ranging a l l the way up to 0*56, mm. ( e r r a t i c s ) . Muscovite, b i o t i t e , c h l o r i t e and c a l c i t e make up the matrix. The-chlorite and muscovite f l a k e s are mostly-about 0.25 mm., the b i o t i t e f l a k e s about 0.17 mm. Irregular, patches of p y r r h o t i t e make up 1% of the slidfe. H. Calcareous Coarse-grained Quartzite Of the two specimens examined. #38 i s an unusual occurrence and has already been described under "Phlogopite and Tremolits'** -The other spxeclmen, #11, co n s i s t s of 55% smooth, round or o v a l , quartz gcseins, the largest measuring 0.65 :X 0.4 mm,. The matrix i s mostly c a l c i t e which i s more or l e s s continuous infcer s t i t a a l i L y . M a t r i x and ve i n c a l c i t e make up 34% of the s l i d e . The r e s t of the s l i d e c o n s i s t s of 3% c h l o r i t e f l a k e s , 2% s e r i c i t e f l a k e s , 1% muscovite f l a k e s , a very few b i o t i t e f l a k e s , 2% magnetite grains., a few specks of p y r i t e , 1% z i r c o n , 1% t i t a n i t e with 1% leucoxene, and a few tourmaline c r y s t a l s . Gonclusions A. Possible Source Bocks The a l l o g e n i c s u i t e , shown i n Table I I , i s made up of quartz, magnetite, z i r c o n , a p a t i t e , a l b i t e , t i t a n i t e , tourmaline, aegerine-augite, green amphibole, k a o l i n , s e d i -mentary pebbles, and p o s s i b l y muscovite. The quartz content of the rocks averages around 60%. Zircon occurs commonly i n amounts up to 1%. The other minerals occur only r a r e l y or never appear i n large amounts. ' A l l the minerals which make up t h i s a l l o g e n i c suite could have been derived from an area of sedimentaryQiimeta-morphic and Igneous rocks of the more common types. A l b i t e and aegerine-augite suggest a sodic g r a n i t e ; t i t a n i t e , an intermediate igneous rock; tourmaline, aametamorphic rock; and z i r c o n , a g r a n i t i c rock or pegmatite. Furthermore, magnetite and z i r c o n p e r s i s t through many sedimentary cycles 'and might have t h e i r o r i g i n i n older sediments- Quartz, could come from a l l of these sources. K a o l i n i s indicat^ST© iQsfiLy df chemical weathering of alumino-siliceous rocks. -Pebbles are the best c r i t e r i a of source rocks, and 36 here they i n d i c a t e - t h a t p a r t , at l e a s t , of the d e t r i t a l m a t e r i a l came from older sediments. The f a c t that the pebbles were w e l l rounded and about the same s i z e as the quartz grains present indi c a t e s that the source .sediments were w e l l consolidated and perhaps even metamorphosed before erosion took place. Much of the evidence as to the nature of the source rocks i s l a c k i n g . The common metamorphic minerals - s e r i c i t e , muscovite, b i o t i t e and c h l o r i t e - contain only the 4substance of minerals i n the source rock. Thus micas, felspars,* amphiboles, pyroxenes, e t c . have probably a l l been decomposed, leavi n g very l i t t l e to i n d i c a t e the exact nature of the source rocks. 'B. Stage of Erosion and Type of Old Land The .old land from which the sediments o f the Aldridge formation'came was probably a land of complex geo-l o g i c a l h i s t o r y with the erosion cycle i n a mature stage. Deep erosion i s indicated i f one aecepts the con-c l u s i o n that the pebbles observed were e i t h e r . w e l l c o n s o l i -dated or metamorphosed p r i o r , t o erosion*, The o r i g i n a l '7 rocks must have been almost completely decomposed before rk*~t/,n removal from t h e i r source, because quartz i s the only abun-dant d e t r i t a l mineral. The sediments deposited are almost e n t i r e l y f i n e - g r a i n e d q u a r t z i t e s and s i l t s t o n e s , i n d i c a t i n g that the mate r i a l was brought i n by streams of moderate ca r r y i n g power. A l l t h i s i n d i c a t e s a mature stage of erosion. The old land need not have been high, but must have r i s e n continuously f o r a long period of time. This p a r t i c u l -ar s e c t i o n was o v e r l a i n by nearly 12,000 f e e t of s i m i l a r sediments before the a r g i l l i t e s at the top of the Aldridge formation'were l a i d down. Thus a long period of erosion must have ensued,, during which time the land mass remained at about the same elevation, r e l a t i v e to the l e v e l of the geosynclinal sea, and the erosion cycle remained i n the mature stage. G. S i t e of Deposition The graphic logs, F i g . I , show that the amount of d e f i n i t e c o r r e l a t i o n between the sections i n each hole i s very s m a l l . The sequence i s probably disturbed e i t h e r by a h o r i z o n t a l change i n the character of the beds or by lensing,. In e i t h e r ease a near shore or d e l t a i c deposit i s suggested. . D. Metamorphism The metamorphic s u i t e of minerals consists of . c a l c i t e , quartz, s e r i c i t e , muscovite, c h l o r i t e , b i o t i t e , garnet, phlogopite., t r e m o l i t e , and p o s s i b l y magnetite and z o i s i t e . Apparently there are two periods of metamorphism, one being wide-spread r e g i o n a l metamorphism a f f e c t i n g the whole of the s e c t i o n examined, and the other being a s l i g h t l y higher grade of metamorphism contemporaneous with the forma-t i o n of the S u l l i v a n ore body and l o c a l i z e d to the proximity of the ore zone. S e r i c i t e , muscovite, c h l o r i t e , and r e c r y s t a l l i z e d c a l c i t e and quartz represent low grade r e g i o n a l metamorphism of s l i g h t l y calcareous a r g i l l a c e o u s sediments. B i o t i t e i s the index mineral f o r the next highest grade of r e g i o n a l metamorphism.of the same type of rock. As the normal assem-blage of metamorphic minerals includes only these s i x , the whole of the. s e c t i o n examined may be said to be i n the 1 b i o t i t e zone. Phlogopite and tremolite represent magnesian lime-stone or dolomite i m p u r i t i e s i n the o r i g i n a l sediment. They belong to a zone of f a i r l y low grade metamorphism, probably the b i o t i t e zone. < Z o i s i t e is.produced i n calcareous sediments by the r e a c t i o n of muscovite, c h l o r i t e , and c a l c i t e = to give b i o t i t e 2 and z o i s i t e . . Therefore z o i s i t e too belongs i n the b i o t i t e zo ne. * Magnetite, i f metamorphic, represents o r i g i n a l i r o n minerals. I t does not ; f i t d e f i n i t e l y i n t o •themtoeta-morphic zone c l a s s i f i c a t i o n . ; Garnet i s the index mineral f o r the next higher grade of r e g i o n a l metamorphism. This i s the Almandine 1 zone. Garnet occurs i n the ore zone, and only r a r e l y at any great distance above the hanging w a l l . I t i s therefore considered to represent a more advanced grade of metamorphism 1. Earker: Me tamorphism, Ghap. XIV. 2. I b i d . , Ghap. XVI. produced at the time when the S u l l i v a n ore body was being formed. 40 B I B L I O G R A P H Y Dana, E.S. , A Textbook of Mineralogy; Fourth E d i t i o n , Revised and Enlarged by Wm.E.Ford; New York; John Wiley & Sons, Inc.; London: Chapman & H a l l , L t d . ; 19 32. Harker,. A.., Metamorphism; Methuen&Go;; Ltd . , London; 1932, Krumbein, W.C* and P e t t i John, F.J., Manual of Sedimentary Petrography; D. Appleton-Century Co., New York and London; 1938. .Milner, H.D., Sedimentary Petrography; Second (Revised and Complete) E d i t i o n ; London: Thomas Murby & Co.; New York: D.Van Nostrand Co.; 1929. Rice, H*M.A., Cranbrook Map-Area, B r i t i s h Columbia; Canada, Geological Survey, Memoir 207; Ottawa, 1937. Rogers, A.F. and Kerr, P.F., Thin-Section Mineralogy; McGraw-H i l l Book Co., Inc.; New York andLondon; 1933. M i n e r a l o g i c a l Abstracts; London: Humphrey M i l f o r d , Oxford U n i v e r s i t y Press. A . J j 4 . J \ , - .-, „ C; ' " j 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0053055/manifest

Comment

Related Items