Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
DSpace
UBCV
Hoadley, John William
Master of Applied Science - MASc
University of British Columbia
The area near the Sullivan Mine, Kimberley B.C., is underlain by rocks of the Purcell series which consist of two sedimentary formations of late Pre-Cambrian age, the Aldridge and the Creston. Both are composed of argillite, siltstone, and quartzite. The Sullivan ore body is a replacement deposit in certain favourable horizons in the Aldridge formation. The only known igneous rocks near the mine are the Purcell intrusives of late Pre-Cambrian age. These intrusives occur as large sheets, or sills, at a small angle to the bedding of the Purcell series.They are chemically about the same as gabbro. The object of this research was to determine the changes induced in the sedimentary rocks of the Aldridge formation near the Sullivan Mine by the intrusion of the Purcell sills; to compare the alterations found with the alterations known to be present in the wall rocks of the Sullivan ore body; and from this comparison, determine whether there is any justification for relating the mineralization of the Sullivan ore body to the intrusion of the Purcell sills. In order to obtain the information required the writer made a petrographic examination of thirty-six thin sections of specimens of the core of the Sullivan Diamond Drill Hole 249 located just east of the mine. The hole was drilled vertically through a sixty foot sill, and on into the underlying sediments of the Aldridge formation. The results obtained from this examination indicate that the sediments adjacent to the sill have been subjected to low grade thermal metamorphism, which has resulted in the development of a pronounced biotite spotted contact zone. Late magmatic emanations, either from the partially consolidated sill, or from the parent magma chamber caused metasomatism in the sedimentary rocks of the contact zone, and the effects of the metasomatic action are super imposed upon the effects of the thermal metamorphism. Tourmaline, albite, pyrrhotite, sphalerite, sphene and rutile are the main minerals produced by the hydrothermal action. A comparison of the alterations found in these sedimentary rocks examined, with the alteration present in the Sullivan ore body and its wall rocks, reveals a distinct similarity. This similarity, plus the fact that the drill hole is within one half mile of the mine suggests a common origin for the magmatic solutions. Therefore, the solutions which produced the Sullivan Mine ore body may have been genetically related to the Purcell intrusives.
L C3 & J THE METAMORPHISM OF THE ROCKS OF THE f ALDRIDGE FORMATION KIMBERLEY, B.C. BY JOHN W. HOADLEY A THESIS SUBMITTED IK PARTIAL FULFILMENT OF THE.REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE IN THEf DEPARTMENT ,OF GEOLOGY AND GEOGRAPHY THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1947 ACKNOWLEDGMENTS The w r i t e r acknowledges the as s i s t a n c e rendered by Drs. Gunning, Watson and Swans, on. The t e c h n i c a l .advice and as s i s t a n c e given by Mr. J.A. Donnan was i n v a l u a b l e . CONTENTS PAGE Abs t r a c t . : 1 I n t r o d u c t i o n 3 Object of the research 3 Part 1. L o c a t i o n and General Geology ; 5 Wall rock a l t e r a t i o n of the S u l l i v a n Ore Body .* 6 .Petrography of u n a l t e r e d sedimentary rocks 7 Part 2. -Minerals o c c u r r i n g i n the rocks of the A l d r i d g e Formation cut by d r i l l hole 249' ; 9 Part 3. A l t e r a t i o n of the' rocks of the A l d r i d g e Formation 15 General Statement . . . .• 15 D e s c r i p t i o n of the s p o t t i n g 15 V a r i a t i o n i n texture of the spots 16 B i o t i t e content and d i s t r i b u t i o n .'.. . 16 P y r r h o t i t e content 16 Tourmaline content 16 R u t i l e content 17 C l i n o z o i s i t e content 17 C h l o r i t i z a t i o n 17 Part 4. O r i g i n of New M i n e r a l s . • Formation of the b i o t i t e 18 O r i g i n of tourmaline and sulphides 20 O r i g i n of a l b i t e 22 O r i g i n of r u t i l e 24 Part 5. Conclusions 25 B i b l i o g r a p h y 27 Appendix ; 28 ILLUSTRATIONS PAGE Pl a t e 1. V e i n l e t of p y r r h o t i t e i n t h i n s e c t i o n 289A 53 2 . Lens of p y r r h o t i t e shown i n P l a t e 1 53" 3. Pronounced s p o t t i n g i n t h i n s e c t i o n 264A 54 4. Large spots i n t h i n section 340A. ." 54 5.. S i m i l a r to P l a t e 4 -• crossed N i c o l s 55 6. Tourmaline aggregates i n t h i n s e c t i o n 160B-' low power-. 55 7. Tourmaline aggregates i n t h i n s e c t i o n 160B- ' high power; 56 Figure 1. Geologic map of S u l l i v a n Mine, and v i c i n i t y . . . . 57 I l l u s t r a t e d s t r a t i g r a p h i c : s e c t i o n of d r i l l h h o l e 249.... i n envelope on.back cover. THE METAMORPHISM OF THE ROCKS OF THE •ALDRIDGE FORMATION KIMBERLEY B.C. BY J.W. HOADLEY ABSTRACT The area near the S u l l i v a n Mine, Kimberley B.C., i s s u n d e r l a i n Toy rocks of the P u r c e l l s e r i e s which c o n s i s t of two sedimentary formations of l a t e Pre-Cambrian age, the A l d r i d g e and the Creston. Both are composed of a r g i l l i t e , s i l t s tone, and q u a r t z i t e . -The S u l l i v a n ore body i s a replacement deposit i n c e r t a i n favourable horizons i n the A l d r i d g e formation. The only known igneous rocks near the"mine are the P u r c e l l i n t r u s i v e s of l a t e Pre-Cambrian age. These i n t r u s i v e s occur as la r g e sheets, or s i l l s , a t a small angle to the bedding of the P u r c e l l s e r i e s . — i They are che m i c a l l y about the same as gabbro. The object of t h i s research was to determine the changes induced i n the sedimentary rocks of the A l d r i d g e formation near the S u l l i v a n Mine by the i n t r u s i o n of the P u r c e l l s i l l s ; to compare the a l t e r a t i o n s found w i t h the a l t e r a t i o n s known to be present i n the w a l l rocks of the S u l l i v a n ore body; and from '-this comparison, determine whether there Is any j u s t i f i c a t i o n f o r r e l a t i n g the m i n e r a l i z a t i o n of the S u l l i v a n ore body to the i n t r u s i o n of the P u r c e l l s i l l s . In order to obta i n the in f o r m a t i o n r e q u i r e d the w r i t e r made a petrographic examination of t h i r t y - s i x t h i n s e ctions of specimens of the core of the S u l l i v a n Diamond D r i l l Hole 249 lo c a t e d j u s t east of the mine. The hole was d r i l l e d v e r t i c a l l y through a s i x t y f o o t s i l l , and on i n t o the u n d e r l y i n g sediments of the A l d r i d g e formation. The r e s u l t s obtained from t h i s examination indicate^, that the sediments adjacent to the s i l l have been subjected to low grade thermal metamorphism, which has r e s u l t e d i n the develop-ment of a pronounced b i o t i t e spotted contact zone. Late magmatic emanations, e i t h e r from the p a r t i a l l y c o n s o l i d a t e d s i l l , or from the parent magma chamber caused metasomatism i n the sedimentary rocks of the contact zone, and the e f f e c t s of the metasomatic a c t i o n are super imposed upon the e f f e c t s of the thermal metamorphism. Tourmaline, a l b i t e , p y r r h o t i t e , s p h a l e r i t e , sphene and r u t i l e are the main minerals produced by the hydrothermal a c t i o n . of A comparison botwaon the a l t e r a t i o n s found i n these W/T/i sedimentary rocks examined, e«4 the a l t e r a t i o n present i n the S u l l i v a n ore body and i t s w a l l r o c k s , reveals a d i s t i n c t s i m i l a r i t y . This s i m i l a r i t y , plus the f a c t that the d r i l l hole i s w i t h i n one h a l f mile of the mine suggests a common • o r i g i n f o r the" magmatic s o l u t i o n s . Therefore, the s o l u t i o n s which produced the S u l l i v a n Mine ore body may have been g e n e t i c a l l y r e l a t e d to the P u r c e l l i n t r u s i v e s . INTRODUCTION Object of the Research The geology of the S u l l i v a n mine has been stud i e d i n d e t a i l by o f f i c e r s of the G e o l o g i c a l Survey of Canada, and by g e o l o g i s t s employed by the owners, the Consolidated Mining and Smelting Company. The various workers are not i n complete agreement regarding, the age of the m i n e r a l i z a t i o n . H.M.A. Rice (1) b e l i e v e s that the m i n e r a l i z a t i o n occurred during cCretaceous or e a r l y T e r t i a r y time, and i s g e n e t i c a l l y r e l a t e d to the gr a n i t e i n t r u s i v e s of that age. CO.- Swans on and H.C. Gunning ( 2 ) , f e e l that the as s i g n a t i o n of the age of m i n e r a l i z a t i o n to the Cretaceous or T e r t i a r y p e r i o d i s open to' q u e s t i o n . They suggest, as an be a l t e r n a t i v e , that i t may Arelated to the P u r c e l l I n t r u s i v e s that are of Pre-Cambrian age. I t was suggested that a study of the a l t e r a t i o n o c c u r r i n g i n the sedimentary rocks near one of the P u r c e l l s i l l s , and a comparison of t h i s a l t e r a t i o n w i t h that found i n the w a l l rock of the S u l l i v a n ore body,might r e v e a l f u r t h e r i n f o r m a t i o n regarding the age of the ore forming s o l u t i o n s . The w r i t e r , t h e r e f o r e , undertook a p e t r o l o g i c a l examin-a t i o n of specimens of the core of a diamond d r i l l h o l e , l o c a t e d j u s t east of the S u l l i v a n mine. The hole was d r i l l e d v e r t i c a l l y through a s i x t y f o o t s i l l and continued on i n t o the und e r l y i n g sediments f o r approximately f i v e hundred f e e t . • 1. Ri c e , H.M.A. 1937, G.S.C. Mem. 207 2. Swanson, CO. and Gunning, H.C. 1945, Geology of the S u l l i v a n Mine, C.I.M.M. V o l . 48, pp 645 - 667 4 The work c o n s i s t e d of a d e t a i l e d petrographic examination of t h i r t y - s i x t h i n s e c t i o n s and the i n t e r p r e t a t i o n of the r e s u l t s obtained from t h i s examination. The extremely f i n e - g r a i n e d nature of the rock made i t d i f f i c u l t to determine and estimate the r e l a t i v e amounts of the minerals i n the t h i n s e c t i o n s . An important p a r t of the i n t e r p r e t a t i o n was to decide how much of the a l t e r a t i o n was caused by r e c o n s t i t u t i o n of o r i g i n a l m a t e r i a l and how much was due to the i n t r o d u c t i o n of m a t e r i a l from some outside source. GENERAL G E O L O G Y The S u l l i v a n mine i s l o c a t e d i n the south-east corner of B r i t i s h Columbia, about one and one h a l f miles north-east of the town of KImberley, B.C. The area i n the v i c i n i t y of Kimberley i s u n d e r l a i n by g e n t l y f o l d e d sediments of the P u r c e l l s e r i e s , of Pre-Cambrian age. These sediments were intruded by a l a r g e number of s i l l s , known as /the P u r c e l l s i l l s , i n l a t e Pre-Cambrian time. The S u l l i v a n ore body i s a replacement deposit, i n the lower member of the P u r c e l l s e r i e s , c a l l e d the A l d r i d g e formation. This formation i s an .assemblage of t h i n bedded q u a r t z i t e s , s i l t s tones, and a r g i l l i t e s approximately 16000 f e e t t h i c k . The ore body conforms roughly w i t h the s t r i k e and dip of the sediments, and grades i n t o them. The horizons r e p l a c e d represent a s t r a t i g r a p h i c thickness of about 200 f e e t . The ore i s an i n t i m a t e , f i n e - g r a i n e d mixture of galena, and s p h a l e r i t e , w i t h minor amounts of p y r r h o t i t e , - p y r i t e , magnetite, and jamesonite; the scant gangue contains manganese garnet, garnet, tourmaline, d l o p s i d e , a c t i n o l i t e , and b i o t i t e , w ith subordinate c a l c i t e . Some c a s s i t e r i t e i s present. In the v i c i n i t y of the mine, the r e g i o n a l d i p i s east, the r e g i o n as a whole being on the east side of a broad a n t i c l i n e which has an a x i s l y i n g a few miles west of the -area shown i n f i g . 1. However, the r e g i o n a l dip i s modified by s e v e r a l gentle warpings and by minor f o l d s which are f r e q u e n t l y quite sharp. Figure 1 portrays the nature of the gentle warpings by means of subsurface contours of the f o o t w a l l of the ore zone. The Kimberley f a u l t i s one of the major features of the area. As shown i n Figure 1, i t s t r i k e s about E.W. and dips 45 to 55° N. The S u l l i v a n f a u l t , together w i t h a number of s i m i l a r ones which form a w e l l defined, s e t , c o n s t i t u t e the only other important f a u l t s t r u c t u r e s . Of these, the S u l l i v a n , East and L o i s f a u l t s are shown on the map.. The P u r c e l l i n t r u s i v e s , l o c a l l y c a l l e d d i o r i t e s are the only large i n t r u s i v e s known i n the immediate v i c i n i t y of the mine. T y p i c a l l y they occur as l a r g e s i l l s or sheets at a " small angle to the bedding of the P u r c e l l s e r i e s . Many of them are approximately uniform i n composition, and are c h e m i c a l l y about the same as Gabbro. In the upper part of -some of the s i l l s there i s a graduation to a type, that i s d e f i n i t e l y more a c i d . A l l the large s i l l s (see f i g u r e 1) near the S u l l i v a n 1 mine are accompanied by a contact zone 100 f e e t or so thicks i n which the sediments have developed a spotted c h a r a c t e r . WALLROCK ALTERATION OF THE SULLIVAN ORE BODY The formation of the S u l l i v a n ore body was accompanied by considerable a l t e r a t i o n of the w a l l r o c k . B r i e f l y , t h i s w a l l r o c k a l t e r a t i o n may be described as t o u r m a l i n i z a t i o n of the f o o t w a l l sediments and a l b i t i z a t i o n and c h l o r i t i z a t i o n of the hanging w a l l members. PETROGRAPHY OF THE UNALTERED SEDIMENTS In order'that the a l t e r a t i o n i n the sediments i n the v i c i n i t y of the S i l l s "may he p r o p e r l y appreciated i t w i l l be necessary to give a b r i e f d e s c r i p t i o n of the u n a l t e r e d sediments. , " S t r i c t l y speaking, the beds are not u n a l t e r e d sediments, as they have a l l s u f f e r e d more or l e s s r e c r y s t a l l i z a t i o n . However, the changes so produced have been s l i g h t i n compar-i s o n w i t h those caused by replacement and contact metamorphism i n the sediments adjacent to the ore body, and are i n general l e s s than the changes encountered i n the contact zones of the P u r c e l l S i l l s . The beds are l a r g e l y composed of s e r i c i t e f l a k e s JD1 mm. to .03 mm. i n diameter, and quartz grains of s i l t y to sandy s i z e s . The s e r i c i t e f l a k e s have random ori e n t a t i o n s - and e v i d e n t l y represent clayey m a t e r i a l that r e c r y s t a l l i z e d under s t a t i c c o n d i t i o n s . The quartz grains are u s u a l l y i r r e g u l a r i n o u t l i n e but new growth has not m a t e r i a l l y changed the s i z e of the coarser g r a i n s . However, the s m a l l e r ones, l e s s than 0.03 mm. i n diameter, which are intergrdwn w i t h s e r i c i t e , . owe t h e i r shapes and s i z e s e n t i r e l y to r e c r y s t a l l i z a t i o n . L i t h o l o g i c types which range from a r g i l l i t e to s i l t s tone form a l a r g e part of the sediments,'and can be arranged i n t o a l i n e a r s e r i e s . I t has been found convenient to c l a s s i f y as a r g i l l l t e s those which are more than 75% s e r i c i t e , and as s i l t s tones those which are more than 75%' quartz o c c u r r i n g as 8 grains up to .01 mm." (3) This c l a s s i f i c a t i o n w i l l he adhered to throughout t h i s r e p o r t . (3) Swanson, CO. and Gunning, H.C 1944 - Op. C i t : 9 MINERALS OCCURRING IN THE SECTION OF THE . ALDRIDGE FORMATION CUT BY DRILL HOLE 249. In the f o l l o w i n g paragraphs, the minerals are l i s t e d according to Dana's c l a s s i f i c a t i o n . SULPHIDES PYRRHOTITE: F e ^ ^ P y r r h o t i t e i s very wide spread throughout a l l the sediments of the A l d r i d g e formation. I t occurs i n varying amounts i n p r a c t i c a l l y a l l the t h i n s e c t i o n s examined. I t i s found as f r a c t u r e f i l l i n g and, r o r , replacement of c e r t a i n favourable horizons (see Appendix t h i n s e c t i o n 289A), as concentrations of i r r e g u l a r shaped grains i n the spots of the spotted bands, and as sm a l l , more or l e s s evenly d i s t r i b -uted grains i n c e r t a i n h o r i z o n s . i/irhere a p y r r h o t i t e - r i c h l a y e r or v e i n l e t occurs i n or near a spotted h o r i z o n , the con c e n t r a t i o n of the p y r r h o t i t e i n the spots v a r i e s d i r e c t l y w i t h the distance from the p y r r h o t i t e - r i c h zones. The most common ass o c i a t e s are b i o t i t e and c l i n o z o i s i t e . SPHALERITE Zn S. A b r i g h t orange yellow v a r i e t y of s p h a l e r i t e was i d e n t i f i e d i n most of the t h i n sections of specimens taken w i t h i n ten f e e t of the contact w i t h the S i l l . In most cases i t occurred as very minute grains which were only p o s i t i v e l y i d e n t i f i e d w i t h the a i d of a microchemical t e s t f o r z i n c . However, t h i n s e c t i o n 154B contains a coarse b i o t i t e and 10 s p h a l e r i t e - r i c h zone i n -which the s p h a l e r i t e was found i n large grains r e p l a c i n g c a l c i t e . I t was a s s o c i a t e d w i t h some p y r r h o t i t e , c l i n o z o i s i t e , and c h l o r i t e . OXIDES QUARTZ; SlOg This i s the most abundant mineral i n the sediments of the P u r c e l l s e r i e s . I t occurs as very s m a l l i r r e g u l a r shaped' i n t e r l o c k i n g grains g e n e r a l l y l e s s than .01 mm. i n diameter. Spots or concentrations of l a r g e r grains up to .05 mm. i n diameter are common i n some of the beds. The i n t e r l o c k i n g grains and the presence of many i n c l u s i o n s i n d i c a t e t h a t the quartz has been l a r g e l y r e c r y s t a l l i z e d . RUTILE: T i 0 2 There i s abundant development of r u t i l e throughout the m a j o r i t y of the t h i n s e ctions examined. I t most commonly occurs as c l u s t e r s or aggregates of short stubby euhedral c r y s t a l s , which of t e n show good g e n i c u l a t e d twinning. ' I t i s a l s o found as minute needles r e p l a c i n g b i o t i t e . There i s a marked increase i n t h e . c o n c e n t r a t i o n of r u t i l e i n the spots and along the contacts between a r g i l l a c e o u s and s i l t y l a y e r s . I t appears to be c l o s e l y a s s o c i a t e d w i t h the b i o t i t e i n the spots and i s not found i n the bleached zones. CARBONATES CALCITE: CaCo, o i C a l c i t e occurs i n appreciable amounts i n a number of the sections examined. I t i s always a s s o c i a t e d w i t h c h l o r i t e 11 e i t h e r as v e i n f i l l i n g or as i r r e g u l a r patches i n the more h i g h l y c h l o r i t i z e d areas. SILICATES ALBITE: . There appears to be a f a i r l y abundant development of A l b i t e i n the t h i n sections s t u d i e d . I t occurs as small grains' s c a t t e r e d throughout'the general matrix, or as v e i n f i l l i n g m a t e r i a l . A l b i t e twinning was observed i n a few cases. The maximum e x t i n c t i o n angle measured was 12-l/2 to 13°. A b i a x i a l p o s i t i v e i n t e r f e r e n c e f i g u r e w i t h a l a r g e 2V was obtained on a few g r a i n s . An attempt was made to determine the amount of f e l d s p a r present i n the sections by s e l e c t i v e s t a i n i n g of the f e l d s p a r g r a i n s . D e t a i l e d e x p l a n a t i o n of the process used i s i n c l u d e d i n the appendix. The r e s u l t s i n d i c a t e that there was a greater degree of f e ^ s p a t h i z a t i o n than was apparent i n the unstained s e c t i o n s . The s t a i n e d s e c t i o n s showed that there was a tendency f o r the c o n c e n t r a t i o n of f e l d s p a r to be g r e a t e r i n the spots than i n the general ground mass. One s e c t i o n revealed the presence of a s t r o n g l y f e f s p a t h i c l a y e r p a r a l l e l to the bedding. CORDIERITE: H c (MgFe), A L S i . 6 n ' The presence of c o r d i e r i t e was suspected i n some of the t h i n s e c t i o n s , but no d e f i n i t e proof was obtained. See appendix t h i n s e c t i o n 146A. WOLLASTONITB Ca S i 0 3 One f i b r o u s g r a i n of w o l l a s t o n i t e was i d e n t i f i e d i n t h i n 12 s e c t i o n 340B. The o p t i c a l p r o p e r t i e s were found to be as f o l l o w s : Index 1.60 -, B i r e f r i n g e n c e 0.010, o r i e n t a t i o n length slow, b i a x i a l negative w i t h 2V moderate to l a r g e . The c r y s t a l i d e n t i f i e d contained numerous small i n c l u s i o n s of tourmaline. CLINOZOISITE; C a ^ . l g (OH) (S10 4) This mineral i s common i n the t h i n s e c t i o n s examined.. I t i s g e n e r a l l y found i n t i m a t e l y a s s o c i a t e d with p y r r h o t i t e and h i o t i t e and quite o f t e n forms a rim around gr a i n s of the former mineral. I t was noted that i t occurred i n g r e a t e r c o n c e n t r a t i o n i n the spots than i n the matrix, and that'those spots h i g h i n p y r r h o t i t e contained more than those which showed a d e f i c i e n c y of p y r r h o t i t e . EPIDOTE: Ca g ( A l P e ) 3 ( O H ) ( S i Q 4 ) 3 This mineral i s found r e p l a c i n g muscovite and. h i o t i t e i n some of the spots. I t i s commonly a s s o c i a t e d w i t h c l i n o z o i s i t e . Epidote i s much l e s s widespread i n occurrence than c l i n o z o i s i t e . TOURMALINE; A complex b o r o s i l i c a t e of aluminum and other metals. Tourmaline i s of widespread occurrence i n the sediments cut by d r i l l hole 249. I t i s commonly found as minute euhedral c r y s t a l s which appear s l i g h t l y g reenish i n t h i n s e c t i o n . A number of l a r g e r c r y s t a l s of pale yellow tourmaline were encountered which showed marked pleochroism, w i t h maximum absorption p a r a l l e l to the a n a l i z e r . Cross. f r a c t u r e s were w e l l developed. . Large Csievey, anhedra of t h i s yellow p l e o c h r o i c -13 tourmaline were found i n some of the more spotted hands. In t h i n s e ctions 160 A & B , these anhedra range up to.3 mm. i n s i z e and occur w i t h i n the spots, i n some cases, occupying as much as 25% of the t o t a l area of the spot. On the.whole, the c o n c e n t r a t i o n of tourmaline was found to be gre a t e r i n the spots than i n the f i n e - g r a i n e d ground mass. MUSCOVITE: HpKAl (SiO.) , — — — — — — & 4 O Well c r y s t a l l i z e d muscovite i s rare i n the sec t i o n s examined. Where present, i t occurs as l a r g e sievey f l a k e s up to .4 mm. i n s i z e , a s s o c i a t e d w i t h epidote and c h l o r i t e . The. f i n e - g r a i n e d v a r i e t y s e r i c i t e i s second to quartz i n order of abundance. I t occurs as minute, evenly d i s t r i b u t e d , lath-shaped g r a i n s , g e n e r a l l y l e s s than .01 mm. i n l e n g t h . I t was noted that there i s a co n s i d e r a b l y lower con-c e n t r a t i o n of s e r i c i t e i n the spots than i n the surrounding matrix. BIOTITE: H gK ( M g F e ) 3 A l ( S i 0 4 ) B i o t i t e i s . the most common accessory mineral. I t occurs i n three d i s t i n c t ways; (a) As equidimentional g r a i n s , ' averaging .04 - .06 mm. i n diameter, more or l e s s evenly d i s t r i b u t e d throughout some of the beds. I n some cases, i t comprises 25% of the minerals present; (b) as concentrations of l a r g e r g r a i n s , up to .2 mm. i n diameter, i n more or l e s s c i r c u l a r spots, a s s o c i a t e d w i t h l a r g e grains of quartz and f e l d s p a r . In some cases, the bi o , t i t e c l u s t e r s form a c e n t r a l core i n the spots, and are surrounded by a r i n g of b i o t i t e -14 f r e e quartz g r a i n s . In others, the whole spot c o n s i s t s of c l o s e l y packed bio t i - t e f l a k e s , while i n s t i l l other spots, the h i o t i t e grains form a r i n g around the periphery of the spot l e a v i n g a more .or l e s s bleached core of quartz g r a i n s ; (c) In small v e i n l e t s c o n t a i n i n g b i o t i t e g r a i n s more or l e s s o r i e n t e d w i t h t h e i r long a x i s p a r a l l e l to the l e n g t h of the v e i n l e t . The v e i n l e t s cut a l l s t r u c t u r e s i n c l u d i n g the spots. In a l l cases the b i o t i t e i s more or l e s s c h l o r i t i z e d . CHLORITE;. Hg.(Fe,Mg) A l 2 S i 0 7 The sediments examined, have been c o n s i d e r a b l y c h l o r i t i z e d . Pale greenish c h l o r i t e occurs i n s m a l l v e i n l e t s and i n r e l a t i v e l y l a r g e i r r e g u l a r patches. I t i s commonly as s o c i a t e d w i t h c a l c i t e and p y r r h o t i t e . ' TITANOSILICATES SPHENE; CaTiSiO^ _ 5 This mineral was i d e n t i f i e d i n only one t h i n s e c t i o n . I t occurred w i t h a l b i t e i n a small v e i n l e t which cuts a b i o t i t e - r i c h zone i n t h i n secti'on 241B. The g r a i n s average .04 mm. i n s i z e and e x h i b i t t y p i c a l diamond-shaped o u t l i n e s . The index was 1.80 + and the birefringengence very high. The grains were o p t i c a l l y p o s i t i v e w i t h 2V= 20° 1. , I t i s thought that some small i s o l a t e d grains w i t h h i g h index seen i n t h i n s e c t i o n 340A are probably sphene but no p o s i t i v e determination could be made. 15 ALTERATION OF THE ALDRIDGE FORMATION The development of the pronounced s p o t t i n g i s the most no t i c e a b l e change induced i n the rocks of the A l d r i d g e formation by the i n t r u s i o n of the P u r c e l l s i l l s . Other changes have occurred which are e q u a l l y important but which do not m a t e r i a l l y a l t e r the megascopic character of the rocks. They are, t o u r m a l i n i z a t i o n , c h l o r i t i z a t i o n , c a r b o n a t i z a t i o n , and i n t r o d u c t i o n of the s u l p h i d e s , p y r r h o t i t e , and s p h a l e r i t e . The f o l l o w i n g few pages w i l l be devoted to a d e t a i l e d d e s c r i p t i o n of these and other changes. DESCRIPTION OF SPOTTING; The s p o t t i n g i s c h a r a c t e r i z e d by the pronounced develop-ment of areas l a r g e l y composed of coarse quartz and b i o t i t e . The amount of b i o t i t e v a r i e s from almost 100$.to almost zero. The g r a i n s i z e of the main minerals o c c u r r i n g i n these spots i s c o n s i s t e n t l y coarser than that of the same minerals o c c u r r i n g i n the ground mass. The spots are u s u a l l y roughly c i r c u l a r i n o u t l i n e 'and g r a d u a l l y increase i n s i z e from approximately .2 mm,.in diameter i n the beds near the contact w i t h the s i l l - to a maximum of 6 mm. i n diameter i n the beds 500 f e e t below the s i l l . However, as the s i z e of the spots increase^ the number of spots per u n i t area decreases p r o p o r t i o n a l l y , so -that the t o t a l area occupied by spots i s approximately the same throughout the s e c t i o n . (See s t r a t i g r a p h i c s e c t i o n ; i n appendix) 16 VARIATION IN TEXTURE AND COMPOSITION OF. THE SPOTS WITH REGARD TO THE FOLLOWING MINERALS. B i o t i t e : 0 The d i s t r i b u t i o n of the b i o t i t e w i t h i n the spots v a r i e s c o n s i d e r a b l y . I n some cases the grains are concentrated i n the centre of the spots and are surrounded by a d i s t i n c t rim of quartz. In other cases the b i o t i t e i s concentrated around the periphery of the spot l e a v i n g a barren c e n t r a l core. The l a t t e r type i s very w e l l developed i n specimens,340, (see plate s 45 and 5). The gra i n s forming the outer p o r t i o n of the rim are n o t i c e a b l y f i n e r - g r a i n e d than .those o c c u r r i n g . c l o s e r to the centre. The b i o t i t e rim grades i n t o the barren core : 'and shows d e f i n i t e r a d i a l arrangement. • P y r r h o t i t e ; There i s a d i s t i n c t tendency f o r the p y r r h o t i t e i n the spotted l a y e r s to be concentrated w i t h i n the spots. The amount of p y r r h o t i t e i n the spots appears to vary Inverse;!y w i t h the distance between the spots and a p y r r h o t i t e - r i c h l a y e r or v e i n . Tourmaline: There i s , i n general, a wide d i s t r i b u t i o n of tourmaline throughout the rocks examined. In most of the spots there appears to be a s l i g h t increase i n c o n c e n t r a t i o n . In some, the increase i s very pronounced, i n which case, the tourmaline assumes the r o l e of the major c o n s t i t u e n t of the spots. This i s best i l l u s t r a t e d i n se c t i o n s 160 A & B where large s i evey grains of tourmaline occupy approximately 2b% 1 7 of the spots. See P l a t e s 26) and' .1. R u t i l e ; R u t i l e i s probably the most common accessory m i n e r a l . It« - d i s t r i b u t i o n I s not confined to the spots but i s found i n greater amounts i n the spots than elsewhere. R u t i l e appears to be more c l o s e l y a s s o c i a t e d w i t h b i o t i t e than w i t h any other mineral. Minute needles are found r e p l a c i n g b i o t i t e along cleavage planes; c l u s t e r s of l a r g e r stubby c r y s t a l s are common i n the w e l l developed spots, such as appear i n t h i n s e c t i o n 340, and are found i n the b i o t i t e rims and not i n the barren core. See p l a t e s '& and ,5. C l i n o z o i s i t e : >,The ooourrenoe of C l i n o z o i s i t e i s very c l o s e l y a s s o c i a t e d w i t h p y r r h o t i t e , thus i t , i s more commonly found i n the spots and i n the p y r r h o t i t e - r i c h zones. V.c ..... . 7. C h l o r i t i z a t i o n : C h l o r i t i z a t i o n i s not confined to d e f i n i t e areas but i t was noted to be more pronounced where the con c e n t r a t i o n of p y r r h o t i t e i s hi g h . ^ 18 FORMATION OF THE BIOTITE Sediments of the type found i n the P u r c e l l s e r i e s are formed by pronounced chemical and p h y s i c a l decomposition of p r e - e x i s t i n g land masses. I t i s therefore u n l i k e l y that the amount of b i o t i t e now found i n the contact zone could be of d e t r i t a l o r i g i n . A r g i l l a c e o u s sediments are notably low i n lime and ; a. soda, hi g h i n potassiws magnesia and alumina, and u s u a l l y contain some i r o n , g e n e r a l l y present as l i m o n i t e . These c o n s t i t u e n t s w i t h the p o s s i b l e exception of i r o n , are l a r g e l y r e c o n s t i t u t e d to form s e r i c i t e and minerals of the serpentine and c h l o r i t e groups. Under c o n d i t i o n s of r i s i n g temperature, temporary s o l u t i o n would be i n i t i a t e d at i s o l a t e d points i n the rock. With continued e l e v a t i o n of temperature t h i s process would g r a d u a l l y spread and would be f o l l o w e d by r e c r y s t a l l -i z a t i o n and the production of new minerals. According to Harker ( l ) , b i o t i t e i s very o f t e n the f i r s t important new product. I t i s formed from c h l o r i t e , s e r i c i t e , i r o n ore and r u t i l e of the o r i g i n a l sediment. As i t s f i r s t appearance t h i s mineral i s i n numerous very small elements, shapeless, or some-times rounded, but i t soon develops, c h a r a c t e r i s t i c f l a k e s which may have c r i s s - c r o s s or p a r a l l e l arrangement. T h i s , t h e r e f o r e , gives a probable - explanation as to the source of the b i o t i t e , but i t does not e x p l a i n why i t s development i n some layer s i s very pronounced while i n others i t i s e n t i r e l y l a c k i n g . (1) Harker, A l f r e d Metamorphism 2nd E d i t i o n P 49 19 Barker states that the mineral formed at any given p o i n t depends upon the composition of the rock w i t h i n a very small radius about that p o i n t . The l i m i t of e f f e c t i v e d i f f u s i o n thus i n d i c a t e d i s commonly a small f r a c t i o n of an in c h . I t may, t h e r e f o r e , be assumed that m a t e r i a l d i s s o l v e d i n one t h i n bed would not be trans p o r t e d by d i f f u s i o n from that bed i n t o another; and so, while b i o t i t e ' might have been produced i n one l a y e r which contained the r e q u i s i t e m i n e r a l s , i t would not have formed i n an adjacent bed which la c k e d one of the e s s e n t i a l original.components. The increase i n temperature need not have been great, indeed, i t could not have been great, otherwise there would have been a development of the medium and higher temperatures! s i l i c a t e s such as hypersthene, garnet, e t c . However> although the r i s e i n temperature was not gre a t , the d u r a t i o n of the temperature e l e v a t i o n must have been quite prolonged. This i s evident from the f a c t that the s p o t t i n g occurs hundreds of f e e t from the s i l l c ontact. I t i s thought that the a c t u a l s p o t t i n g may have resulted, during t h i s prolonged e l e v a t i o n i n temperature, due to i s o l a t e d l o c a l increases i n the,amount of s o l v e n t , g i v i n g r i s e to s o l u t i o n of the b i o t i t e over small areas,'and d i f f u s i o n of the d i s s o l v e d . m a t e r i a l towards a common centre where r e c r y s t a l l i z a t i o n took place., Continued a c t i o n would tend to form a core of large grains surrounded by an area comparatively f r e e of b i o t i t e . S l i g h t v a r i a t i o n s i n any of the c o n t r o l l i n g f a c t o r s would have a decided e f f e c t on t h i s tendency to form spots, and upon the shape of the spots. In-those spots which e x h i b i t an outer r i n g of b i o t i t e surrounding a barren core, there must have been s o l u t i o n at what i s now the centre of the spot and d i f f u s i o n outward from' t h i s centre. This might -account f o r the r a d i a l arrangement of the b i o t i t e n o t i c e d i n some spots. I t has been noted that there i s a g r a d a t i o n a l change i n the s i z e of the spots throughout the l e n g t h of the d r i l l h o l e . Near the s i l l are numerous small spots, whereas at the f a r t h e s t point from the s i l l , the spots are fewer i n number end c o n s i d e r a b l y l a r g e r i n diameter. However, i t seems that the o v e r a l l a r e a l extent ^of the s p o t t i n g i s approximately the same throughout the l e n g t h of the . d r i l l h o l e . The change i n the number of spots per u n i t area may be due to the f a c t that near the contact, s o l u t i o n and r e c r y s t a l l i z a t i o n was i n i t i a t e d at a l a r g e number of p o i n t s , and that the number of centres of s o l u t i o n decreased as the distance from the contact increased. Why there should be' an increase i n the size' of the spots as the distance from the s i l l increases i s not under-stood. ORIGIN OF TOURMALINE AND SULPHIDES The development of b i o t i t e and s p o t t i n g can be a t t r i b u t e d to r e c o n s t i t u t i o n under the i n f l u e n c e of low grade thermal metarnorphism. However, t h i s process does not e x p l a i n the presence of appreciable amounts of tourmaline, p y r r h o t i t e , and i n some cases, s p h a l e r i t e , found throughout the sediments examined. Moreover, the q u a n t i t y of tourmaline present appears to be too 21 great f o r I t to be merely r e c r y s t a l l i z e d d e t r i t a l m a t e r i a l and the p o s s i b i l i t y of the p y r r h o t i t e and e s p e c i a l l y the s p h a l e r i t e being formed from o r i g i n a l m a t e r i a l i n the rock seems remote. I t t h e r e f o r e , must be assumed that m a t e r i a l has been introduced from outside to form these minerals. I t i s thought that l a t e magnetic emanations from the s i l l s , p o s s i b l y p a r t l y p'neumatolytic i n character were r e s p o n s i b l e f o r t h i s i n t r o d u c t i o n . Whether the tourmaline and the sulphides were formed contemporaneously i s not knowa. I t i s •known, however, that the p y r r h o t i t e i s d e f i n i t e l y l a t e r than the s p o t t i n g . In order to form these minerals, the ascending s o l u t i o n s must have contained appreciable q u a n t i t i e s of boron, sulphur and water, plus some z i n c and t i t a n i u m . The s o l u t i o n s appear to have entered along f r a c t u r e s and along more permeable l a y e r s i n the sediments, and to have penetrated e x t e n s i v e l y i n t o the surrounding rock, g i v i n g r i s e to s o l u t i o n and subsequent formation of the new minerals i n the more porous areas. Evidence to support t h i s theory i s found i n the f a c t that i n the spotted zones both p y r r h o t i t e and tourmaline are found i n greater c o n c e n t r a t i o n i n the spots than i n the ground mass. I t was a l s o noted that where a v e i n l e t of p y r r h o t i t e cuts through a spotted l a y e r , or where a p y r r h o t i t e - r i c h l a y e r occurs i n contact w i t h a spotted l a y e r , the. percentage of p y r r h o t i t e i n the spots i s i n v e r s e l y p r o p o r t i o n a l to the distance the spots are from the p y r r h o t i t e v e i n l e t or band. The tourmaline content i n the spots does not 2 2 show any r e l a t i o n s h i p to p y r r h o t i t e v e i n l e t s . In f a c t i t i s greatest I n the spots i n sections 160 A & B which c o n t a i n l i t t l e or no p y r r h o t i t e . There does not. appear to he any apparent connection between the concentrations of p y r r h o t i t e and tourmaline i n any one l a y e r , and the distance of the l a y e r from the d i o r i t e contact. ORIGIN OF ALBITE During the examination of the sections a o e r t a i n amount of a l b i t e was i d e n t i f i e d . In o e r t a i n instances grains were found to occupy v e i n l e t s which were younger than the s p o t t i n g . In one case i t was found i n a small v e i n l e t a s s o c i a t e d w i t h sphene. S e l e c t i v e s t a i n i n g i n d i c a t e d that some sections were quite h i g h l y f e l s p a t h i z e d . seers'r A- o o r t a i n -amount of t h i s a l b i t e i s . q u i te probably the r e s u l t of r e c r y s t a l l i z a t i o n of d e t r i t a l f e l d s p a r but there seems to be a d i o t i n o t p o s s i b i l i t y that some of i t may have been introduced. Harker ( l ) b e l i e v e s that a r g i l l a c e o u s sediments bordering c e r t a i n b a s i c i n t r u s i o n s may have been a l b i t i z e d and converted to adinoles by the a c t i o n of j u v e n i l e l i q u i d s c a r r y i n g sodic compounds. He postulated t h a t since the igneous rocks responsible f o r the transformation are themselves r i c h i n ' soda tha-% they have been a l b i t i z e d by the j u v e n i l e l i q u i d a f t e r t h e i r f i r s t c o n s o l i d a t i o n , and that the same l i q u i d s o l u t i o n s have invaded the adjacent rock, and have brought about r a d i c a l metasomatic changes. (1) Harker, A l f r e d , Metsmorphism 2nd E d i t i o n P.128 23 The a l b i t i z e d a r g i l l a c e o u s rocks c o n t a i n other minerals i n v a r y i n g p r o p o r t i o n s , such as c h l o r i t e , epidote, a c t i n o l i t e , " i r o n ore", sphene and r u t i l e . At Diwas ; Head, Cornwall, the . adinoles grade i n t o rocks composed e s s e n t i a l l y of d r a v i t e . A comparison of the sedimentary rocks adjacent to the P u r c e l l i n t r u s i v e w i t h the adinoles described by Harker reveals oortain'-points of s i m i l a r i t y . In both cases, the o r i g i n a l sediments were notably a r g i l l a c e o u s . Both contain a l b i t e and have s i m i l a r accessory minerals. Both are as s o c i a t e d w i t h basic igneous i n t r u s i v e s . The i n t r u s i v e s a s s o c i a t e d w i t h the adi n o l e s are r i c h i n soda and i t has been p o s t u l a t e d that the l i q u i d magmatic s o l u t i o n s r e s p o n s i b l e f o r t h i s increase i n soda content were a l s o r e s p o n s i b l e f o r the a l b i t i z a t i o n of the adjacent sedimentary rock. I t i s known that granophyric rocks are a s s o c i a t e d w i t h many of the P u r c e l l i n t r u s i v e s and that these granophyric rocks are r i c h e r i n a c i d p l a g i o c l a s e than the normal type. • I t i s , t h e r e f o r e , suggested that the a l b i t e i n the sedimentary rocks of the A l d r i d g e formation adjacent to the p u r c e l l i n t r u s i v e s may a l s o be of magmatic o r i g i n , and that the same magmatic s o l u t i o n s which caused the a l b i t i z a t i o n , were resp o n s i b l e f o r the increase i n soda content of c e r t a i n ' p o r t i o n s of the adjacent i n t r u s i v e s . 2 4 , . • . ORIGIN OF RUTILE The widespread d i s t r i b u t i o n of r u t i l e throughout these sediments coupled w i t h the f a c t that i t i s a very common d e t r i t a l mineral i n a r g i l l a c e o u s sediments would' a a ova to i n d i c a t e s that i t i s due to r e c r y s t a l l i z a t i o n of r u t i l e i n the o r i g i n a l rock. However, the f a c t that sphene i s a s s o c i a t e d w i t h a l b i t e i n v e i n l e t s , would soon to suggests that the ascending s o l u t i o n s c a r r i e d a c e r t a i n amount of t i t a n i u m . Thus,' there i s a p o s s i b i l i t y that a part of the r u t i l e present i s not authogenic, but has r e s u l t e d from the i n t r o d u c t i o n of t i t a n i u m bearing s o l u t i o n s a f t e r the rocks were subjected to low grade thermal metamorphism. The f a c t that i t i s quite ofton a s s o c i a t e d with p y r r h o t i t e and c l i n o z o i s i t e substant-i a t e s t h i s theory. 25 CONCLUSIONS The i n t r u s i o n of the P u r c e l l S i l l s has r e s u l t e d i n low grade thermal metamorphism of the a d j o i n i n g beds of the A l d r i d g e formation. This thermal metamorphism has r e s u l t e d i n the formation of b i o t i t e i n a l a r g e number of the t h i n beds by r e c o n s t i t u t i o n of o r i g i n a l minerals i n the rock. The metamorphism caused the s p o t t i n g which occurs i n the contact zone, but the reason f o r the increase i n the s i z e of the spots as the distance from the contact i n c r e a s e s , i s not known. The thermally metamorphosed rocks were f u r t h e r a l t e r e d by the a c t i o n of magmatic emanations from the adjacent i n t r u s i v e . I t i s thought that these emanations were e s s e n t i a l l y hydro-thermal, but they may have been p a r t l y pneumato'lyti.c. . The metasomatism r e s u l t e d i n the production- of tourmaline ( d r a v i t e ) a l b i t e , p y r r h o t i t e , s p h a l e r i t e , sphene, and p o s s i b l y some of the r u t l l e . The formation of the new minerals was accompanied by c h l o r i t i z a t i o n , c a r b o n a t i z a t i o n , and the widespread production of c l i n o z o i s i t e plus minor epidote. A comparison between the a l t e r a t i o n i n the w a l l rocks of the S u l l i v a n ore body and the a l t e r a t i o n found i n the sediment-ary rocks of the A l d r i d g e formation adjacent to the P u r c e l l s i l l , r e v e a l s that while the a l t e r a t i o n i n the w a l l rocks i s much more pronounced than that found i n the rocks near the s i l l , the mineralogy of the a l t e r a t i o n , i n both'cases i s e s s e n t i a l l y s i m i l a r . This s i m i l a r i t y combined w i t h the f a c t that the d r i l l hole i s l e s s than h a l f a mile from the ore body may I n d i c a t e 26 that the magmatic s o l u t i o n s which caused the changes may have had. a common source. I f t h i s i s t r u e , and i f i t i s conceded that the a l t e r a t i o n s found i n the rocks near the s i l l r e s u l t e d from the a c t i o n of magmatic s o l u t i o n s that o r i g i n a t e d e i t h e r i n the s i l l , or i n the parent magma chamber of the s i l l , then i t may be p o s t u l a t e d that the S u l l i v a n ore body i s g e n e t i c a l l y r e l a t e d to the P u r c e l l s i l l s . / 27 BIBLIOGRAPHY Harker, A l f r e d . Me tamorphism second e d i t i o n 1939 Rice, H.M.A. 1937, G.S.C. Mem. 207 Swans on, CO. and 1945. The Geology of the S u l l i v a n Gunning, H.G. Mine Trans. C.I.M.M. V o l . 48 pp. 645-667 I \ APPENDIX 28 DESCRIPTION OF THIN SECTIONS THIN SECTION 158 A This s e c t i o n appears to 'be normal s i l i c e o u s a r g i l l i t e grading to a r g i l l a c e o u s s i l t s t o n e . The main c o n s t i t u e n t s are quartz, s e r i c i t e , and b i o t i t e . The quartz grains show very i r r e g u l a r o u t l i n e s and range from .01 - .02 mm. i n diameter. The s e r i c i t e occurs as i n t e r s t i t i a l f l a k e s .02 - .04 mm. i n s i z e , between gr a i n s of quartz. The b i o t i t e appears as r e l a t i v e l y large equidimentional grains .04 - .10 mm. i n diameter and occupies approximately 25$ of the s l i d e . The grains are g e n e r a l l y more or l e s s c h l o r i t i z e d R u t i l e occurs as very small s c a t t e r e d grains and f i n e aggregates of c r y s t a l s . In places i t appears as f i n e needles i n the b i o t i t e . The s e c t i o n has been f r a c t u r e d , and the f r a c t u r e s subsequently f i l l e d w i t h an i n t i m a t e mixture of c a l c i t e and c h l o r i t e . P y r r h o t i t e occurs as i s o l a t e d i r r e g u l a r grains up to .05 mm i n s i z e . THIN SECTION 158 B - ~ . This s e c t i o n i s very s i m i l a r to 138 A but contains a greater amount of b i o t i t e , approximately 20$ *. There- i s one vague b i o t i t e enriched l a y e r . Vague s p o t t i n g i n the form of s l i g h t l y enlarged b i o t i t e and quartz grains plus a c o n c e n t r a t i o n of p y r r h o t i t e i s d i s c e r n a b l e . In g e n e r a l , the p y r r h o t i t e i s more abundant and i n l a r g e r masses (greater than .2 mm.) than i n 138 A.., There i s a vague suggestion of a c o n c e n t r a t i o n of p y r r h o t i t e i n 29 streaks p a r a l l e l to the bedding. R u t i l e i s the most abundant accessory mineral. Tourmaline and p o s s i b l y z i r c o n are present i n very small amounts. THIN SECTION 158 C S i m i l a r to 138 A and B but showing g r a d a t i o n a l t h i n bed-ding, some lamellae contain quartz up to '.05 mm i n diameter. The s e c t i o n contains f e l d s p a r ' o f . a p p r o x i m a t e l y a l b i t e -o l i g o c l a s e composition. I t could only be detected where the g r a i n s i z e was large enough to o b t a i n a f i g u r e . 2V was found to be l a r g e - approaching 90°. In some, cases i t i s p o s s i b l e to see the cleavage by using o i l immersion. R u t i l e i s the most abundant accessory mineral, o c c u r r i n g e i t h e r as short p r i s m a t i c euhedral c r y s t a l s , which sometimes show e x c e l l e n t g e n i c u l a t e d twinning, or as long slender needles, .02 - .03 mm. i n l e n g t h , i n the grains of b i o t i t e . They l i e i n random o r i e n t a t i o n on the cleavage planes and can only be seen d i s t i n c t l y i n b a s a l s e c t i o n s . S p h a l e r i t e occurs as very small euhedral grains l e s s than .01 mm. i n size.. I t s presence was confirmed by a micro-chemical t e s t f o r z i n c . THIN SECTION 146 A • This i s a s e c t i o n of spotted s i l t s t o n e . The matrix i s composed of i r r e g u l a r quartz and f e l d s p a r grains .02 - .04 mm i n diameter w i t h very minor amounts of i n t e r s t i t i a l s e r i c i t e . The spots are roughly c i r c u l a r i n o u t l i n e and range i n s i z e from 0.3 - 0.8 mm. They are composed of quartz grains averaging .05 - .1 mm., b i o t i t e f l a k e s up to 0.1 mm. and 50. sievey grains of muscovite showing p o i k i l o b l a s t i c s t r u c t u r e . The chadocrysts a re, quartz f e l d s p a r , and tourmaline. An attempt, was made to determine the type of f e l d s p a r present, and the approximate percentage. I f was noted that'a few grains showed a l b i t e twinning. The maximum e x t i n c t i o n angle was found to be 12-1/2 - 13°. These grains were ' o p t i c a l l y p o s i t i v e , w i t h a large 2V. Under o i l immersion 90° cleavage was evident. These grains were concluded to be a l b i t e . The s e c t i o n a l s o contains a number of f a i r l y l a r g e grains of what appeared to be quartz. These grains were most commonly clouded by minute i n c l u s i o n s . The index was found to be j u s t s l i g h t l y above that of balsam and greater than the a l b i t e . The b i r e f r i n g e n c e appeared to be s l i g h t l y higher than that of the a l b i t e . The l a t t e r showed a dark grey i n t e r f e r e n c e c o l o r whereas the former showed a l i g h t grey to cream c o l o r , g i v i n g a b i r e f r i n g e n c e of approximately .010. A c a r e f u l check of s e v e r a l g r a i n s proved that the mineral was b i a x i a l negative w i t h 2V from 60° - 70°. One or two g r a i n s e x h i b i t e d what was thought to be a type of r a d i a l twinning. I t I s thought that t h i s mineral may be c o r d i e r i t e . The s e c t i o n contains considerable tourmaline. I t occurs as pale blue-green short s t u b b y - c r y s t a l s which show good euhedral o u t l i n e s . The l a r g e r grains show pleochroism w i t h absorption greatest when p a r a l l e l to the a n a l i z e r . Cross f r a c t u r e s are common. Large sievey anhedra of c h l o r i t e occur commonly through t h i s s e c t i o n . They are f r e q u e n t l y a s s o c i a t e d w i t h c l i n o z o i s i t e . The c l i n o z o i s i t e i s a l s o a s s o c i a t e d w i t h 31 muscovite, where i t i s found r e p l a c i n g the muscovite along cleavage planes. C a l c i t e i s f a i r l y abundant i n the c h l o r i t i z e d areas. R u t i l e i s present i n small amounts as an accessory m i n e r a l . THIN SECTION 146 B This s e c t i o n c o n s i s t s of banded, b i o t i t e specked and spotted a r g i l l a c e o u s s i l t s t o n e . The main ground mass of the s l i d e i s composed of approximately 50% quartz grains averaging .01 - .02 mm. i n diameter and 50% b i o t i t e grains averaging .02 - .04 mm. i n diameter. The spots occur w i t h random arrangement throughout the general matrix. They are roughly c i r c u l a r to e l l i p s o i d a l i n o u t l i n e and range from approximately . 6 - 2 mm. i n diameter. They are f r e q u e n t l y i s o l a t e d from one another but i n many cases i t ' i s ' p o s s i b l e to t race a d i r e c t connection between two or more spots, g i v i n g a c h a i n l i k e e f f e c t . The spots quite commonly e x h i b i t ' a c e n t r a l core or c l u s t e r of lar g e b i o t i t e grains up to .2 mm. i n diameter. Surrounding t h i s core and separating i t from the general b i o t i t e r i c h ground mass i s a bleached rim of quartz g r a i n s . In p r a c t i c a l l y a l l cases the b i o t i t e grains i n the spots have been more or l e s s a l t e r e d and replaced by c l i n o z o i s i t e . The spots have notably higher percentage of' p y r r h o t i t e than the r e s t of the s e c t i o n . Tourmaline i s a common accessory mineral throughout the s l i d e but i t appears i n greater amounts and i n l a r g e r c r y s t a l s i n the spot's than i n the general ground mass. 32 The s e c t i o n i s traversed by an i r r e g u l a r p y r r h o t i t e r i c h band c o n t a i n i n g c l u s t e r s of b i o t i t e i n .a coarse s i l t y ground mass. This l a y e r i s s i m i l a r to the spots p r e v i o u s l y described, except that i t i s .continuous across the whole width of the s e c t i o n , i s p a r a l l e l to the bedding plane, and contains a much higher concentration of p y r r h o t i t e than i s found i n any of the spots. A v e i n l e t of co.ar.se b i o t i t e c r y s t a l s cuts across a l l the s t r u c t u r e s i n c l u d i n g the spots and the p y r r h o t i t e r i c h l a y e r . THIN SECTION 155 A This s e c t i o n i s considered to be a r e l a t i v e l y pure s i l t s t o n e since i t contains p r a c t i c a l l y no s e r i c i t e . The matrix c o n s i s t s of quartz and f e l d s p a r grains w i t h a small percentage of b i o t i t e evenly d i s t r i b u t e d throughout. The s l i d e i s vaguely spotted w i t h i r r e g u l a r shaped c l u s t e r s of b i o t i t e g r a i n s , but no c l e a r l y marked bleached rimming can be seen. • Large slevey f l a k e s of muscovite are common and a large percentage show replacement by c h l o r i t e and epidote. The b i o t i t e i n the spots i s more or less, replaced by c h l o r i t e and epidote and p o s s i b l y some c l i n o z o i s i t e . The most ".notable feature of t h i s s e c t i o n i s the presence of a l a y e r which contains a r e l a t i v e l y high c o n c e n t r a t i o n of p y r r h o t i t e . The p y r r h o t i t e appears to have entered the s e c t i o n along small transverse f r a c t u r e s . Prom these f r a c t u r e s i t has spread out and permeated a considerable amount of the surrounding s i l t -stone. I t i s commonly found r e p l a c i n g b i o t i t e . The i n t r o -d uction of the p y r r h o t i t e appears to have been accompanied by. 33 the formation of c h l o r i t e and carbonate. The carbonate, probably c a l c i t e , i s veined and replaced by s p h a l e r i t e . A dark o l i v e green mineral occurs i n the parts of the s e c t i o n where p y r r h o t i t e i s present. I t i s thought to be c h l o r i t o i d . I t occurs as vague, rims on c a l c i t e g rains and i n a few cases as i s o l a t e d aggregates of very small g r a i n s . Tourmaline occurs as a minor accessory mineral. THIN SECTION 154 A In g e n e r a l , t h i s s e c t i o n i s c l a s s e d as a spotted s i l t y a r g i l l i t e . The matrix i s approximately 80% s e r i c i t e . There i s l i t t l e d i s t i n c t quartz. The spots average 1 mm. i n diameter and occupy roughly 20% of the t o t a l area. .They,are c i r c u l a r i n o u t l i n e and e x h i b i t a bleached rim and b i o t i t e r i c h c e n t r a l cores. Some of the spots contain'up to 25% 0 p y r r h o t i t e and most have coarser quartz grains than i s found i n the surrounding matrix. The p y r r h o t i t e i n the spots i s '. very commonly i n t i m a t e l y a s s o c i a t e d w i t h b i o t i t e , and i n general i t appears that the p y r r h o t i t e has s e l e c t i v e l y replaced the b i o t i t e . Quite f r e q u e n t l y the spots contain f a i r " s i z e d c l u s t e r s of c l i n o z o i s i t e grains and short stubby c r y s t a l s of r u t i l e . Tourmaline i s present as an accessory mineral. THIN SECTION 154 B . ^ The greater part of t h i s s e c t i o n i s very s i m i l a r to 154 A. The rock i s a spotted s i l t y a r g i l l i t e . The m a j o r i t y of the spots show'the b i o t i t e cores, but a few are l a r g e l y composed of coarse quartz grains averaging 10 mm. In diameter. The above s i l t y a r g i l l i t e i s i n sharp contact w i t h a l a y e r of 34 b i o t i t e r i c h (35$) a r g i l l a c e o u s s i l t s t o n e w i t h quartz grains .03 mm. i n s i z e ; having a l a r g e r c o a r s e ' b i o t i t e and s p h a l e r i t e r i c h patch. The s p h a l e r i t e occurs i n l a r g e i r r e g u l a r masses and as smaller euhedral c r y s t a l s (dodecahedrons). It., penetrates along cleavage planes i n the b i o t i t e grains and i n some places appears to almost e n t i r e l y replace some of the b i o t i t e g r a i n s . I t a l s o occurs i n t e r s t i t i a l l y b e t w e e n grains of quartz. The s p h a l e r i t e enriched area contains a consider-able, amount of carbonate, probably c a l c i t e . I t i s commonly found rimming the grains of s p h a l e r i t e . THIN SECTIONS 160 A and B Both, t h i n sections show a f i n e grained massive l a y e r and a specked or spotted -layer. The l a t t e r has round b i o t i t e r i c h spots 1 ram. i n diameter w i t h t h i n pale rims .04 mm. wide plus i n t e r s t i t i a l c r y p t o c r y s t a l l i n e m a t e r i a l s i m i l a r to that found i n the massive l a y e r . The s p o t t i n g i s more pronounced i n 160 B than 160 A. The massive c r y p t o c r y s t a l l i n e l a y e r i s almost e n t i r e l y composed of quartz and s e r i c i t e g rains .01 - .03 mm. i n , diameter. The r a t i o of the quartz to s e r i c i t e v a r i e s from 1.2 to 1.1. B i o t i t e occurs as s c a t t e r e d g r a i n s , averaging .02 mm. i n s i z e . R u t i l e and tourmaline are common accessory minerals occuring as s c a t t e r e d euhedral c r y s t a l s , the former o f t e n showing 'good twinning. What i s thought to be z i r c o n appears as a very minor accessory mineral. The spots contain b i o t i t e g r a i n s ranging from .03 - .12 mm 35 i n s i z e , which, are more or l e s s c h l o r i t i z e d -- the c h l o r i t e p e n e t r a t i n g along cleavage planes. Tourmaline i s found as an accessory mineral throughout both s e c t i o n s . I t occurs i n two d i s t i n c t ways. In the massive c r y p t o c r y s t a l l i n e l a y e r i t appears as small i s o l a t e d -euhedral grains g e n e r a l l y c o l o u r l e s s -to l i g h t greenish. I t occurs i n the b i o t i t e cores of the spots as lar g e s i e v e y anhedra up to .2 - .3 mm. i n s i z e , and forming i n some cases as much as 25% of the area of the spots. C l i n o z o i s i t e and r u t i l e occur quite abundantly as accessory minerals i n some of the spots." THIN SECTION 182 A 'J • ' ' This s e c t i o n c o n s i s t s of two predominately s i l t y l a y e r s separated by a t h i n f i n e r - g r a i n e d h i g h l y a r g i l l a c e o u s l a y e r . The s i l t y l a y e r s are b i o t i t e r i c h . In one l a y e r the b i o t i t e i s l a r g e l y confined to i r r e g u l a r spots, while i n the' other 1, I t i s more or l e s s evenly d i s t r i b u t e d throughout. The spots i n v a r i a b l y contain coarser quartz grains than the surrounding matrix. A number of the spots have, a con c e n t r a t i o n of r u t i l e cry. s t a l s .02 - .04 mm. i n s i z e . These r u t i l e g rains show no common o r i e n t a t i o n , but r a t h e r e x h i b i t complete random arrangement.• One part of the s e c t i o n has been h i g h l y c h l o r i t i z e d by s o l u t i o n s p e n e t r a t i n g along minute f r a c t u r e s . Within the v i c i n i t y of these v e i n l e t s the b i o t i t e has been s e v e r e l y c h l o r i t i z e d . The a l t e r a t i o n appears to have been accompanied 36 by the formation of r u t i l e needles, which are found along cleavage planes i n a l t e r e d b i o t i t e . The r u t i l e found i n the c h l o r i t e does not resemble that p r e v i o u s l y described. I t occurs i n long a c l c u l a r needles. The a r g i l l a c e o u s l a y e r i s r e l a t i v e l y devoid of s p o t t i n g , but i t i s c h a r a c t e r i z e d by the presence of considerable amounts of small stubby r u t i l e c r y s t a l s which occur i n small aggregates i n s t r e a k s , more or l e s s p a r a l l e l to the bedding. The c o n c e n t r a t i o n of the r u t i l e i s g r e a t e s t along the contacts w i t h the s i l t y l a y e r s . THIN SECTION 182 B This s e c t i o n shows banded s i l t y a r g i l l i t e grading to almost pure a r g i l l i t e . Small c l u s t e r s or spots of b i o t i t e occur s c a t t e r e d throughout the h i g h l y a r g i l l a c e o u s .matrix. The s l i d e contains i r r e g u l a r areas of what appears to be coarse r e c r y s t a l l i z e d quartz g r a i n s . They are more numerous, and the grains of quartz are. l a r g e r , i n the more a r g i l l a c e o u s l a y e r s , where they occupy 50 - 75% of the t o t a l area. These areas or spots are devoid of b i o t i t e and co n t a i n only very small amounts of . s e r i c i t e . The quartz grains contain a large number of small i n c l u s i o n s . Two i r r e g u l a r streaks of r u t i l e c r y s t a l s traverse the s e c t i o n more or l e s s p a r a l l e l to the bedding. There i s a s l i g h t amount of c h l o r i t i z a t i o n of the b i o t i t e close to these s t r e a k s . THIN SECTION 182 C This i s a s e c t i o n of s i l t y a r g i l l i t e s i m i l a r to "An and ' "B", but l a c k i n g pronounced t h i n bedding and areas of 37 r e c r y s t a l l i z e d quartz. The s e c t i o n shows a s l i g h t amount of normal s p o t t i n g , i . e . h i o t i t e r i c h core, w i t h bleached rim. P y r r h o t i t e grains occur i n some of the spots. THIN SECTION 190 This i s , a s e c t i o n of mottled s i l t s t o n e mainly composed of quartz grains l e s s than .02,mm. i n diameter. The matrix contains approximately 15 to 20 per cent b i o t i t e , more or l e s s evenly d i s t r i b u t e d throughout as equidimentional grains averaging .02 mm., w i t h a fe?; grains up to .1 mm. Several v e i n l e t s of c h l o r i t e approximately .2 mm. wide cut the s e c t i o n . The areas adjacent to the v e i n l e t s are i n t e n s e l y c h l o r i t i z e d , r e s u l t i n g i n s e v e r a l h i g h l y c h l o r i t i z e d bands separated b y : l a y e r s i n which the b i o t i t e i s only s l i g h t l y a l t e r e d . THIN SECTION 195"A This s l i d e c o n s i s t s of two bands of a r g i l l a c e o u s s i l t -stone. One i s b i o t i t e ' e n r i c h e d and contains l a r g e spots of b i o t i t e , coarse quartz and p y r r h o t i t e . In sharp contact w i t h t h i s l a y e r i s a more a r g i l l a c e o u s band, n o t i c e a b l y d e f i c i e n t i n b i o t i t e . The most prominent mineral i s tourmaline. I t occurs i n three ways: as very small grains g e n e r a l l y l e s s than .01 mm. i n diameter, f a i r l y evenly d i s t r i b u t e d throughout the s e c t i o n : as l a r g e i s o l a t e d p l e o c h r o i c g r a i n s : and as aggregates of very small g r a i n s . 38 THIN SECTION 195 B This i s f i n e grained spotted s i l t s t o n e . The quartz i n the matrix v a r i e s from .01 - .04 mm. i n diameter. The spots are composed of coarser quartz grains averaging .05 - .1 mm. i n diameter, and grains of b i o t i t e more or l e s s c h l o r i t i z e d , up to .4 mm i n s i z e . A few l a r g e , (up to 1.5 mm.) s i e v e y anhedra of mus'covite occur s c a t t e r e d throughout the s e c t i o n . The b i o t i t e i n the spots has been p a r t i a l l y r e p l a c e d by c l i n o z o i s i t e . Subsequent to the formation of t h i s mineral a large percentage' of the remaining b i o t i t e - has been h i g h l y c h l o r i t i z e d . The r e s u l t i s that approximately 50 per cent of the spots are now composed of an intimate mixture of c h l o r i t e , c l i n o z o i s i t e , and coarse grained quartz. Tourmaline i s the most common accessory m i n e r a l . I t occurs as very small s c a t t e r e d grains and as lar g e i s o l a t e d sievey anhedra. THIN SECTION 195 C This a r g i l l a c e o u s spotted s i l t s t o n e has a matrix composed of s e r i c i t e ' , quartz, and b i o t i t e averaging .01 - .02 mm. i n s i z e . The spots range from .2 - .6 mm. i n diameter and show c e n t r a l cores of b i o t i t e surrounded by a rim of coarse quartz g r a i n s . In some cases the spots are j o i n e d together forming i r r e g u l a r bands. One v e i n l e t c o n t a i n i n g large grains of b i o t i t e and quartz cuts across the s e c t i o n at an angle to the bedding. The b i o t i t e grains are more or l e s s o r i e n t e d p a r a l l e l to the v e i n l e t . They are c o n s i d e r a b l y c h l o r i t i z e d and i n some cases replaced by c l i n o z o i s i t e . 39 P y r r h o t i t e i s found concentrated i n the spots and i s always i n close a s s o c i a t i o n w i t h the b i o t i t e and o f t e n replaces i t . R u t i l e i s a l s o a common c o n s t i t u e n t of the spots and appears to be more abundant i n the spots where c h l o r i t -i z a t i o n and development of c l i n o z o i s i t e i s more pronounced. THIN SECTION 210 A (1) This s e c t i o n shows -three d i s t i n c t l y d i f f e r e n t bands: c r y p t o c r y s t a l l i n e l a y e r composed of quartz and . s e r i c i t e i n equal amounts. Grain s i z e .01 - .02 mm.- R u t i l e grains .02 - .04 and coarse (.04 - .10 mm.) f l a k e s of b i o t i t e are s c a t t e r e d throughout. There i s a d e f i n i t e alignment of the s e r i c i t e and r u t i l e g rains p a r a l l e l to the banding. (2) In sharp contact w i t h the crypto l a y e r i s a dark band .3 mm. wide which contains a high percentage) of p y r r h o t i t e (10 - ) o c c u r r i n g as s c a t t e r e d grains .03 - .10 mm. i n s i z e . This band i s approximately 85% quartz i n .02 - .04 mm. s i z e grains and 15% s e r i c i t e . The l a t t e r occurs i n l a r g e r g r a i n s than i n ( 1 ) . (3) The p y r r h o t i t e - r i c h l a y e r grades i n t o a c o a r s e l y spotted band. The matrix i s s i m i l a r to number 2. The spots vary i n s i z e up to approximately 3 mm. i n diameter. They c o n t a i n p y r r h o t i t e i n .considerable q u a n t i t y . The percentage decreases as the distance from number 2 l a y e r i n c r e a s e s . The b i o t i t e i n the spots i s more or l e s s c h l o r i t i z e d . C l i n o z o i s i t e and r u t i l e are present i n considerable q u a n t i t y . In general the l a y e r i s q u i t e s t r o n g l y t o u r m a l i n i z e d , but there i s a d i s t i n c t increase i n c o n c e n t r a t i o n of t h i s mineral i n the spots as 40 compared to the surrounding matrix. In some spots the amount i s over 50$ of the t o t a l . A v e i n l e t of quartz and f e l d s p a r cuts a l l layers.. The f e l d s p a r i s thought to be a l b i t e , b i a x i a l p o s i t i v e - 2V = l a r g e index 1.54. Where the v e i n l e t crosses the p y r r h o t i t e - r i c h l a y e r , i t contains large grains of p y r r h o t i t e . ( A number of grains of a l b i t e were' i d e n t i f i e d throughout the s e c t i o n , and i t i s thought a considerable p r o p o r t i o n of the ground mass i s f e l d s p a t h i c , r a t h e r than p u r e l y quartzose. THIN SECTION 210 B The same s e r i e s of t h r e e . l a y e r s are observed here as i n 210 A. (1) The c r y p t o c r y s t a l l i n e s e r i c i t e band i n t h i s case i s vaguely spotted. There are o c c a s i o n a l muscovite sieves up to 2 mm. i n s i z e with i n c l u d e d r u t i l e needles, and s c a t t e r e d f e l d s p a r sieves .1 mm. i n diameter which are most probably a l b i t e (+) 2V l a r g e . (2) Dark'band 1.5 mm wide s i m i l a r to one i n A c o n t a i n i n g approximately 10 - 12$ p y r r h o t i t e . The remainder i s l a r g e l y quartz .02 - .05 mm. w i t h 10$ - s e r i c i t e . (3) The b i o t i t e spotted band has a f i n e s i l t y matrix of quartz (.01 - .03) plus minor s e r i c i t e . The b i o t i t e spots contain a considerable amount of tourmaline. I t occurs as small grains (.01 mm.) more or l e s s evenly d i s t r i b u t e d throughout the spots and produces n o t i c e a b l e rims. Some of the smaller spots show a g r e a t e r c o n c e n t r a t i o n of tourmaline and a much lower c o n c e n t r a t i o n of b i o t i t e than i s observed i n 41 the l a r g e spots. P y r r h o t i t e i s a s s o c i a t e d w i t h the b i o t i t e i n the spots. One a l b i t e g r a i n was . i d e n t i f i e d near a spot, but most of the c o l o u r l e s s mineral w i t h the b i o t i t e i s quartz. THIN SECTION 241 A This s e c t i o n i s composed of three w e l l defined l a y e r s . A s i l t y a r g i l l a c e o u s band, made up of c r y p t o c r y s t a l l i n e s e r i c i t e plus 5 - 10% s c a t t e r e d quartz grains .02 - .04 mm. i n diameter. This h i g h l y s e r i c i t e l a y e r grades Into a b i o t i t e and p y r r h o t i t e - r i c h band which i n t u r n grades i n t o a c o a r s e l y spotted l a y e r . The zone between the c r y p t o c r y s t a l l i n e s e r i c i t e l a y e r and the b i o t i t e - r i c h l a y e r i s c h a r a c t e r i z e d by abundant r u t i l e grains which occur i n i s o l a t e d streaks p a r a l l e l to the general banding. The ground mass/ i n the spotted l a y e r i s l a r g e l y quartz and s e r i c i t e , of approximately .5 - .6 mm. i n s i z e . Their m o s t ^ s t r i k i n g feature i s the high c o n c e n t r a t i o n of p y r r h o t i t e , which amounts to over 75% i n some cases. The p y r r h o t i t e i s almost always i n t i m a t e l y a s s o c i a t e d w i t h b i o t i t e . The spots show some coarse (.1 - .4 mm) sievey grains of a l b i t e . In some cases, these grains are e n t i r e l y surrounded and engulfed by p y r r h o t i t e . The s e c t i o n i s cut by a v e i n l e t of p y r r h o t i t e and c h l o r i t e . One side of t h e . v e i n l e t i s occupied by p y r r h o t i t e , the other by c h l o r i t e plus a small amount of carbonate. Where the v e i n l e t crosses the l a r g e r spots the p y r r h o t i t e has spread out to form la r g e i r r e g u l a r masses w i t h i n the spots. 42 . THIN SECTION 241 B This s e c t i o n i s very s i m i l a r to A. There are two co a r s e l y spotted bands separated- by a non-spotted b i o t i t e - r i c h l a y e r . The matrix i s quartz and s e r i c i t e i n approximately 1:1 proportions.. The spots are lar g e — up to 2-4 mm. They c o n s i s t of coarse grains of quartz .05 - .1 .mm. i n diameter, l a r g e f l a k e s of b i o t i t e .05 -. .2 mm. and a considerable amount of coarse p y r r h o t i t e . There i s a marked decrease i n the amount of s e r i c i t e as compared to the matrix. C l i n o z o i s i t e i s found as an accessory mineral i n the spots and i s o f t e n very c l o s e l y a s s o c i a t e d w i t h p y r r h o t i t e . Sphene occurs i n a v e i n l e t of a l b i t e which cuts the b i o t i t e - r i c h l a y e r p a r a l l e l to the banding. I t was recognized by i t s h i g h index, high b i r e -f r i n g e n c e , and diamond-shaped c r y s t a l o u t l i n e . 2V=20 - b i a x i a l p o s i t i v e , g r a i n s i z e approximately .04 or l e s s . R u t i l e and tourmaline (some sievey c r y s t a l s ) are a l s o present as accessory minerals. THIN SECTION 246 A Three d i s t i n c t l a y e r s are recognizable i n t h i s s e c t i o n . A mottled l a y e r composed of numerous small spots of quartz grains i n a c r y p t o c r y s t a l l i n e s e r i c i t e matrix occurs i n sharp contact w i t h a p y r r h o t i t e - r i c h band c o n t a i n i n g about 10$ sc a t t e r e d p y r r h o t i t e i n a matrix composed of 50$ s e r i c i t e and 50$ quartz g r a i n s . The p y r r h o t i t e l a y e r grades i n t o one that i s quit© s t r o n g l y s p o t t e d . The spots are l a r g e l y coarse quartz and 43 b i o t i t e g r a i n s . Quite commonly the b i o t i t e f l a k e s i n the centre, of the spots are co n s i d e r a b l y l a r g e r than those on the periphery. This produces a n o t i c e a b l e rimming e f f e c t . The most common accessory mineral i s r u t i l e . I t i s found s c a t t e r e d throughout the whole s l i d e , but is,most abundant along the contact' between l a y e r s 1 and 2-, and i n the spots. C l i n o z o i s i t e and p y r r h o t i t e are present i n most of the spots. Tourmaline occurs as a minor accessory mineral. THIN SECTION 246 B This s e c t i o n Is very w e l l spotted. In ge n e r a l , i t co n s i s t s of l a r g e , well-rounded, b i o t i t e - r i c h spots up to 3 ram. i n s i z e i n . a s l i g h t l y a r g i l l a c e o u s s i l t s t o n e matrix. > The most c h a r a c t e r i s t i c t h i n g about the s p o t t i n g i s the high c o n c e n t r a t i o n of both r u t i l e and c l i n o z o i s i t e i n the spots. The l a t t e r shows a tendency to occur i n the centre of the spots r e p l a c i n g some of the b i o t i t e whereas the former i s quite o f t e n found as a r i n g of small c r y s t a l s around the periphery of the spot. However, t h i s i s not always the case. The s e c t i o n i s s t r o n g l y t o u r m a l i n i z e d throughout. THIN SECTION 264 A This s e c t i o n i s a f a i r l y uniform a r g i l l a c e o u s b i o t i t e enriched s i l t s t o n e w i t h an " A p l i t i c " t e x t u r e . Both the quartz and the b i o t i t e grains average .01 - .02 mm. i n diameter. R u t i l e , c l i n o z o i s i t e and'tourmaline are common accessory min-e r a l s and are found more or l e s s evenly d i s t r i b u t e d throughout 44 the s e c t i o n . THIN SECTION 264. B This s e c t i o n i s w e l l handed w i t h l a r g e c l e a r l y defined spots i n two of the l a y e r s . Other l a y e r s show an " a p l i t i c " .texture s i m i l a r to 264 A. The " a p l i t i c " bands are notable f o r the abundant development of very minute g r a i n s of r u t i l e and tourmaline. These minute c r y s t a l s give the band a dusty appearance. Another c h a r a c t e r i s t i c of these l a y e r s i s that they are cut by one or more very narrow i r r e g u l a r b l a c k bands more or l e s s p a r a l l e l to the bedding. Examination under h i g h magnif-i c a t i o n r e v e a l s that these.bands c o n s i s t of a co n c e n t r a t i o n of small r u t i l e c r y s t a l s l e s s than .01 mm i n s i z e , extremely f i n e g rains of tourmaline approximately .002 mm. i n diameter, and grannular c l i n o z o i s i t e i n close a s s o c i a t i o n with the r u t i l e c r y s t a l s . ' • One of the " a p l i t i c " bands contains a p y r r h o t i t e - r i c h zone. The p y r r h o t i t e ' i s ' i n t i m a t e l y a s s o c i a t e d w i t h c l i n o z o i s i t e . Small r u t i l e c r y s t a l s are s c a t t e r e d throughout the l a y e r . In g e n e r a l , the spotted laminae c o n s i s t of lar g e w e l l -rounded aggregates of coarse quartz and b i o t i t e , approximately 2 mm. i n diameter, plus v a r y i n g amounts of r u t i l e , p y r r h o t i t e , and c l i n o z o i s i t e . In some cases, the spots are almost e n t i r e l y made up of b i o t i t e . However, i t i s more common to f i n d the b i o t i t e form-ing a t h i n p e r i p h e r a l r i n g , l e a v i n g . a more or l e s s barren core 45 of quartz g r a i n s . R u t i l e i s commonly found as c l u s t e r s , of small euhedral grains a s s o c i a t e d w i t h the b i o t i t e . One spot may have up to a dozen such c l u s t e r s . They are not found i n the barren cores. One 'spotted band l o c a t e d near the p r e v i o u s l y described p y r r h o t i t e - r i c h zone has spots which c o n t a i n a very high percentage of p y r r h o t i t e . C l i n o z o i s i t e and r u t i l e are common asso c i a t e s of the p y r r h o t i t e . "See p l a t e 3. THIN SECTION 264 C This s e c t i o n i s very s i m i l a r i n a l l i t s f r a c t u r e s to the one j u s t described. I t i s w e l l banded w i t h a l t e r n a t i n g A " a p l i t i c " *and spotted l a y e r s . I t lac k s the p y r r h o t i t e - r i c h zone and the spots do not contain any appreciable amount of p y r r h o t i t e . They do, however, show a tendency towards bleached rims. THIN SECTION 289 A This s e c t i o n i s moderately w e l l banded. I t grades from a h i g h l y s e r i c i t i c "mottled" l a y e r i n t o a b i o t i t e - r i c h a r g i l l a c e o u s s i l t s t o n e band, which i s cut by two i r r e g u l a r v e i n l e t s o f . p y r r h o t i t e . I t a l s o contains numerous s c a t t e r e d grains of p y r r h o t i t e . The most notable fe a t u r e s o f the s l i d e are. the p y r r h o t i t e v e i n l e t s . They are p a r a l l e l to' the bedding and appear to f o l l o w a set of p a r a l l e l f r a c t u r e s , or porous zones. Some of the quartz grains c l o s e l y a s s o c i a t e d w i t h the v e i n l e t s are cons i d e r a b l y coarser than found elsewhere. The v e i n l e t s are very i r r e g u l a r and tend to pinch and 46 s w e l l . One of the beds near the v e i n l e t s show a .3 mm. r i g h t hand o f f s e t caused by pre-mineral movement. Upon encountering t h i s f e a t u r e , the p y r r h o t i t e f o l l o w s the j o i n t plane f o r a distance equal to the o f f s e t and then continues along the same l a y e r as before. See p l a t e s 1 and 2. THIN SECTION 289 B ' This s e c t i o n i s c o a r s e l y spotted and banded s i l t s t o n e w i t h spots ranging up to 4 mm. i n diameter. In gener a l , they e x h i b i t markedly rounded o u t l i n e s , and are mainly composed of b i o t i t e and quartz. In some cases, the b i o t i t e i s almost, e n t i r e l y a l t e r e d to c h l o r i t e , while others show very l i t t l e c h l o r i t i z a t i o n . Some spots show a marked re d u c t i o n i n g r a i n s i z e around the borders, g i v i n g a pronounced rimming e f f e c t . The percentage of p y r r h o t i t e i n the spots v a r i e s g r e a t l y . I t i s almost always a s s o c i a t e d w i t h c l i n o z o i s i t e and r u t i l e . The degree of c h l o r i t i z a t i o n of the b i o t i t e i n the spots seems to be d i r e c t l y r e l a t e d to the amount of contained p y r r h o t i t e . THIN SECTION 315 A This s l i d e shows w e l l spotted s l i g h t l y a r g i l l a c e o u s s i l t -stone i n which the spots range up to 6 mm. i n diameter. The ground mass i s composed of quartz and b i o t i t e g r a i n s g e n e r a l l y l e s s than .04 mm. i n diameter. The p r o p o r t i o n of quartz to b i o t i t e i s approximately 60 - 40. The ground mass contains s p a r s e l y s c a t t e r e d grains of p y r r h o t i t e w i t h a s s o c i a t e d c l i n o z o i s i t e . There i s a- notable l a c k of b i o t i t e i n the spots. What there i s , i s concentrated i n the cen t r e s . The 'remainder i s 47 almost a l l quartz grains over .2 mm. i n diameter plus access-ory minerals. There i s a decided c o n c e n t r a t i o n of p y r r h o t i t e , epidote, and tourmaline, i n p r a c t i c a l l y a l l the spots. The epidote occurs as c l u s t e r s of small stubby c r y s t a l s . The tourmaline occurs as (a) small i s o l a t e d euhedral c r y s t a l s , and (b) as anhedral cloudy masses or aggregates of small c r y s t a l s .which appear to be replacing; b i o t i t e . The spotted band i s i n sharp contact w i t h a h i g h l y a r g i l l a c e o u s l a y e r . This l a y e r shows a considerable amount of s c a t t e r e d r u t i l e c r y s t a l s . They do not stop at the'contact w i t h the spotted l a y e r , but continue 3 - 4 mm. i n t o the spotted l a y e r before f a d i n g out. THIN SECTION 315 B ' This s e c t i o n i s made up of two d i s t i n c t bands. The contact between them i s marked by a t h i n seam of c h l o r i t e . On one side i s a l a y e r of coarser a r g i l l a c e o u s s i l t s t o n e which was o r i g i n a l l y b i o t i t e enriched. The b i o t i t e i s now l a r g e l y , a l t e r e d and replaced by c h l o r i t e . The a r g i l l i t e l a y e r g r a d u a l l y assumes a mottled appear-ance due to the presence of small c l u s t e r s of quartz grains embedded i n a c r y p t o c r y s t a l l i n e s e r i c i t i c ground mass. The s i z e and number of quartz c l u s t e r s increases as the distance from the contact w i t h the s i l t y band i n c r e a s e s . The a r g i l l a c e o u s matrix contains s c a t t e r e d r u t i l e c r ystals and i r r e g u l a r areas of carbonate. The percentage of r u t i l e appears to be greatest near the contact w i t h the s i l t y band. 48 THIN SECTION 540 A This specimen i s c l a s s i f i e d as a vaguely spotted s i l t s t o n e . The m a j o r i t y of the s l i d e c o n s i s t s of a f i n e -grained matrix of quartz g r a i n s w i t h a few i r r e g u l a r c l u s t e r s of b i o t i t e f l a k e s . There i s a' pronounced development of r u t i l e c r y s t a l s a s s o c i a t e d w i t h the b i o t i t e and r u t i l e . One part of the s l i d e has'been carbonatized to a. s l i g h t extent. S e v e r a l small blue-grey grains occur i n the s e c t i o n . They have a very h i g h index (1.80 t ) and are e i t h e r p o s i t i v e u n i a x i a l or b i a x i a l p o s i t i v e with-a low 2,V. The b i r e -fringence appeared to be approximately .030 - .040, but since the grains are l e s s than .03 mm. i n s i z e t h i s cannot be taken as accurate. They show diamond shapes to pyramidal o u t l i n e s and may p o s s i b l y be sphene -- the colour does not seem to be that of .sphene p o s i t i v e l y i d e n t i f i e d i n s e c t i o n 241 B. The carbonated area p r e v i o u s l y mentioned contains two c a l c i t e grains which appear to be pseudomorphs. The shape of the o r i g i n a l c r y s t a l s i s o u t l i n e d by an u n i d e n t i f i e d greenish mineral. I t i s thought that these grains may be pseudomorphs a f t e r sphene.. THIN SECTION 340 B This s e c t i o n appears to be a r e l a t i v e l y pure s i l t s t o n e c o n t a i n i n g large well-rounded spots up to 5 mm. i n diameter. The s i l t y ground mass contains some a l b i t e which shows good twinning. The spots show a d i s t i n c t tendency towards more or l e s s barren cores surrounded by t h i n r ings of b i o t i t e . In some 49 cases the b i o t i t e has been bleached and,.'partially replaced by what i s thought to be epidote. The spots are c h a r a c t e r i z e d by c l u s t e r s ' o f small r u t i l e c r y s t a l s a s sociated w i t h t h e - b i o t i t e and by a•marked increase i n the c o n c e n t r a t i o n of tourmaline. The l a t t e r g e n e r a l l y occurs i n i s o l a t e d euhedral c r y s t a l s up to .04!mm. long, but i t was a l s o found as minute i n c l u s i o n s i n a c o l o u r l e s s f i b r o u s m i n e r a l . This mineral was found to have the f o l l o w i n g p r o p e r t i e s . Index 1.60 I , p r i s m a t i c cleavage, b i r e f r i n g e n c e 0.010, l e n g t h slow, b i a x i a l negative, 2 V moderate to l a r g e . The mineral i s thought to.be w o l l a s t o n i t e . One one g r a i n was i d e n t i f i e d . THIN SECTION 340 C This specimen i s c l a s s i f i e d as an a r g i l l a c e o u s s i l t s t o n e . I t resembles the more h i g h l y a l t e r e d parts of the ,one j u s t described. The s p o t t i n g i s not as pronounced, but the a l t e r a t i o n of the b i o t i t e and the formation of r u t i l e i s e x a c t l y s i m i l a r . The-most i n t e r e s t i n g f e a t u r e i s the s e l e c t i v e a l t e r a t i o n of the b i o t i t e . I t has been s t r o n g l y bleached, so that i t i s now c o l o u r l e s s , and has been s e l e c t i v e l y r e p l a c e d along cleavage planes by very t h i n n e e d l e - l i k e yellow-brown c r y s t a l s . They are thought to be needles of r u t i l e . THIN SECTION 415 This s e c t i o n shows a vaguely spotted p y r r h o t i t e - r i c h a r g i l l a c e o u s s i l t s t o n e showing a general enrichment of b i o t i t e i n small evenly d i s t r i b u t e d g r a i n s . 50 The s p o t t i n g e f f e c t i s l a r g e l y due to more or l e s s c i r c u l a r ' areas whiph have a marked increase .in the concen-t r a t i o n of p y r r h o t i t e . The p y r r h o t i t e i s very n e a r l y always a s s o c i a t e d w i t h c l i n o z o i s i t e which tends to form as an outer aureole around groups of p y r r h o t i t e g i v i n g the whole "spot" a c i r c u l a r o u t l i n e . The c l i n o z o i s i t e occurs as granular aggregates which' show a d i s t i n c t tendency to be elongated p a r a l l e l to the o v e r a l l banding. The p e r i p h e r i e s of some of these vague spots are marked by a d i s t i n c t ' r i m of r u t i l e g r a i n s . The spots c o n t a i n close grains of quartz and f e l d s p a r ( a l b i t e ) . The l a t t e r i s general i n l a r g e r and more i r r e g u l a r g r a i n s . THIN SECTION 606 A This s e c t i o n contains large well-rounded spots i n a b i o t i t e - r i c h , s l i g h t l y a r g i l l a c e o u s , s i l t s t o n e . The spots.are l a r g e l y composed of coarse i r r e g u l a r grains of quartz up to 2 mm. i n diameter and l a r g e i r r e g u l a r grains of p y r r h o t i t e .3 - .6 mm. i n s i z e . The percentage of b i o t i t e i n the spots i s low and i s g e n e r a l l y only found c l o s e i y a s s o c i a t e d w i t h grains of p y r r h o t i t e which i n some cases appears to replace the b i o t i t e . P r a c t i c a l l y a l l grains of p y r r h o t i t e have a s s o c i a t e d c l i n o z o i s i t e . At times, ,±t i s a l s o found a s s o c i a t e d w i t h r u t i l e . There i s a general increase i n the c o n c e n t r a t i o n and 51 s i z e of the tourmaline grains i n the spots as compared to the surrounding ground mass. THIN SECTION 606 B This s l i d e i s very s i m i l a r to 606 A showing w e l l defined spots w i t h c o n c e n t r a t i o n of p y r r h o t i t e , r u t i l e , and tourmaline centre and a barren rim of coarse quartz. The spots are connected by i r r e g u l a r s t r i n g e r s composed of p y r r h o t i t e grains and associated c l i n o z o i s i t e , and o c c a s i o n a l . r u t i l e . These connecting s t r i n g e r s are p a r a l l e l to the general f a i n t banding seen i n the arrangement of the b i o t i t e grains on the matrix. 52 SELECTIVE STAINING The f o l l o w i n g method of s e l e c t i v e s t a i n i n g of f e l d s p a r was employed. The specimen to be s t a i n e d was f i r s t ground to approx-imately 1 mm. i n t h i c k n e s s . I t was then etched w i t h hydro-i f l u o r i c a c i d f o r one minute, washed, and placed i n a hot s o l u t i o n of a s o d i u m - s i l i c a t e f o r f i v e minutes. The excess sodium s i l i c a t e was removed by washing g e n t l y , and the specimen was then placed i n a bath of Fuchian dye. A.fter ten or f i f t e e n minutes the chip was. removed, allowed to dry, •and made i n t o a t h i n s e c t i o n i n the usual manner. A number of standards were run on specimens of rocks which were known to c o n t a i n f e l d s p a r . The t e s t s were successful, i n that they proved that the dye s t a i n e d f e l d s p a r , but had no e f f e c t on o,uartz, and that i t could be concluded that any s t a i n e d m a t e r i a l was most probably f e l d s p a r . The t e s t s i n d i c a t e d , however, that In one rock a c e r t a i n f e l d s p a r would react p o s i t i v e l y to the s t a i n i n g while i n another rock, the same f e l d s p a r under e x a c t l y the same t r e a t -ment, would remain unaffected. Therefore i t must be concluded that while the method used, may, i n some cases help i n determining the presence of f e l d s p a r the f a c t that the specimen does not r e a c t p o s i t i v e l y i s no guarantee that i t does not c o n t a i n f e l d s p a r . 53 P l a t e 1. Photomicrograph of p y r r h o t i t e - r i c h l a y e r s i n t h i n s e c t i o n 289A. Kag.l6X. Note how p y r r h o t i t e f o l l o w s l e f t -hand o f f s e t . P l a t e 2. Photomicrograph of l e n s of p y r r h o t i t e connected w i t h v e i n l e t shown i n P l a t e 1. IJag.l6X. P l a t e 3. Photomicrograph of pronounced s p o t t i n g i n t h i n section 264A» Note concentration of b i o t i t e i n the centre and rim of b i o t i t e - f - r e e quafctz and f e l d s p a r . Dark mineral in ground mass i s b i o t i t e . I,Iag.l6X. P l a t e 4. Photomicrograph of large spots i n t h i n s e c t i o n 340A. Note pronounced concentration of b i o t i t e around the rim of the large spot. The small b l a c k grains are c r y s t a l s of r u t i l e . I.:ag.l6X. 55 P l a t e 5. Photomicrograph showing same spots seen i n P l a t e 4, hut taken with crossed N i c o l a . Note increase i n g r a i n s i z e of quartz w i t h i n the spots. I»Iag.l6X. Pl a t e 6. Photomicrograph showing large g r a i n s of tourmaline concentrated in the spors i n t h i n s e c t i o n 160B. Tourmaline shows l i g h t to dark grey and e x h i b i t s a grannular t e x t u r e . Mag.l6X. P l a t e 7. Photomicrograph of tourmaline g r a i n i n l a r g e r of two spots seen i n P l a t e 6. Predominant grannular mineral i s tourmaline. Black g r a i n s are r u t i l e . LIag.50X. 57 FIG.1. GEOLOGIC MAP - SULLIVAN MINE. A f t e r CO. Swan son' and H.C.Gunning Trans. C.I.M.M. 1945 STRATIGRAPHIC SECTION OF THE ALDRIDGE FORMATION CUT BY SULLIVAN L I B R A R Y DRILL HOLS 249. University of British Columbia I l l u s t r a t e d - b y photographs of a v a i l a b l e specimens. Vancouver, Ca^oj p h o t 0 g r a p h s i l l u s t r a t e the t h i n bedding that i s c h a r a c t e r i s t i c of these sedimentary rocks. They als o show the general character of the s p o t t i n g and the gradual increase i n the s i z e of the spots w i t h increase i n depth. FOOTAGE 134 Contact w i t h s i l l . No specimen a v a i l a b l e . 138 146 153 154 160 132 195 210 241 246 264 289 315 340 S i l l i c i o u s a r g i l l i t e . No v i s i b l e spotting, Prominent f r a c t u r e s . Thin bedded s i l t s t o n e w i t h numerous small soots. Spotted a r g i l l a c e o u s s i l t s t o n e . Vaguely spotted s i l t s t o n e . Spotted s i l t s t o n e grading i n t o a p y r r h o t i t e -r i c h l a y e r . Vaguely spotted s i l t s t o n e . Vaguely spotted s i l t y a r g i l l i t e . B i o t i t e - r i c h a r g i l l a c e o u s s i l t s t o n e c o n t a i n i n g a patch of coarse b i o t i t e and s p h a l e r i t e . Strongly spotted a r g i l l a c e o u s s i l t s t o n e ; spots up to 1 m.m. i n diameter. A r g i l l a c e o u s s i l t s t o n e . Note absence of s p o t t i n g . Spotted a r g i l l a c e o u s s i l t s t o n e . Interbedded s i l t y and a r g i l l a c e o u s l a y e r s . The s i l t y l a y e r s are r i c h i n b i o t i t e and contain numerous small soots. Uniformly spotted a r g i l l a c e o u s s i l t s t o n e . The spots are l a r g e l y composed of b i o t i t e f l a k e s , which i n some areas, have a bleached appearance caused by c h l o r i t i z a t i o n . F i n e - g r a i n e d a r g i l l a c e o u s s i l t s t o n e . Strongly spotted s i l t s t o n e . The spots are l a r g e l y composed of b i o t i t e and p y r r h o t i t e Fine-grained a r g i l l a c e o u s s i l t s t o n e . S i l t y a r g i l l i t e . Spotted a r g i l l a c e o u s s i l t s t o n e . The spots contain a high percentage of p y r r h o t i t e . S i l t y a r g i l l i t e . S i l t y a r g i l l i t e . W e l l-spotted a r g i l l a c e o u s s i l t s t o n e . A r g i l l a c e o u s s i l t s t o n e . Spotted p y r r h o t i t e - r i c h l a y e r Interbedded spotted and non-spotted beds. The spots are l a r g e l y composed of coarse b i o t i t e f l a k e s . Highly a r g i l l a c e o u s band. A r g i l l a c e o u s s i l t s t o n e l a y e r c o n t a i n i n g two p a r a l l e l v e i n l e t s of p y r r h o t i t e . A r g i l l a c e o u s s i l t s t o n e . Coatsely spotted s i l t s t o n e . Spots are l a r g e l y composed of coarse quartz and b i o t i t e . S l i g h t l y a r g i l l a c e o u s s i l t s t o n e c o n t a i n i n g coarse i r r e g u l a r spots which show bleached rim e f f e c t . Highly a r g i l l a c e o u s l a y e r . Very coarsely spotted s i l t s t o n e . The spots have a core of quartz surrounded by a rim of b i o t i t e f l a k e s . 415 606 A r g i l l a c e o u s s i l t s t o n e l a y e r w i t h l a r g e i r r e g u l a r spots. The spots contain l a r g e amounts of p y r r h o t i t e . Very coarsely spotted a r g i l l a c e o u s s i l t s t o n e . The spots are l a r g e l y composed of coarse quartz gr a i n s and l a r g e i r r e g u l a r grains of p y r r h o t i t e .
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Geological Sciences
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The metamorphism of the rocks of the Aldridge formation, Kimberley B.C
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