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Geology of Mount Kobau Okulitch, Andrew Vladimir 1969

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5»io GEOLOGY OF MOUNT KOBAU by ANDREW VLADIMIR OKULITCH B.Sc, U n i v e r s i t y of B r i t i s h . Columbia, 1964 A THESIS SUBMITTED IN THE REQUIREMENTS DOCTOR OF PARTIAL FULFILMENT OF FOR THE DEGREE OF PHILOSOPHY i n the Department of GEOLOGY We a;ccept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH September, 1969 COLUMBIA In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree tha permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Depa rtment The University of British Columbia Vancouver 8, Canada i i ABSTRACT Rocks of the Kobau Group occur between the Okanagan and Similkameen V a l l e y s i n southern B r i t i s h Columbia and northern Washington. The Group co n s i s t s of q u a r t z i t e , p h y l l i t e , greenstone and minor limestone deposited w i t h i n a synorogenic, eugeosynclinal environment i n pre-Cretaceous, p o s s i b l y post-Devonian, time. I n t r u s i o n and extrusion of basic igneous rocks accompanied de p o s i t i o n . The observed succession has been divided i n t o nine u n i t s with t o t a l o r i g i n a l thickness under 5,000 f e e t . E a r l i e s t recognized deformation of the Group formed t i g h t recumbent f o l d s with e a s t e r l y trending axes. Transposition of compositional l a y e r i n g to f o l i a t i o n and extensive shearing occurred at t h i s time and was accompanied by r e g i o n a l dyna-mothermal metamorphism which atta i n e d the middle subfacies of the greenschist f a c i e s . Later (second phase) deformation produced overturned and normal f o l d s with steep a x i a l planes and south-easterly trending axes, and refolded e a r l y recumbent s t r u c t u r e s . Several quartz l a t i t e dykes cut the Group during or s h o r t l y a f t e r l a t e f o l d i n g . Emplacement of g r a n i t i c and d i o r i t i c stocks with r a d i o -metric ages of 144 x 10^ years or l e s s followed second phase i i i f o l d i n g . Contact raetamorphic zones of varying extent are present around l a r g e r i n t r u s i v e bodies and a t t a i n the hornblende-hornf e l s f a c i e s . A l a t e s t ( t h i r d ) phase of deformation about poorly defined n o r t h e r l y trending axes may be r e l a t e d to t h i s i n t r u s i v e episode. A number of dacite and b a s a l t dykes intruded both stock and country rocks. Extensive f r a c t u r i n g during T e r t i a r y time broke pre-e x i s t i n g structures i n t o numerous blocks and wedges. Fractures p a r a l l e l a x i a l planes of e a r l y and l a t e f o l d s as w e l l as f a u l t s i n the Okanagan V a l l e y . Relationships between the Kobau Group and rocks i n adja-cent areas are unknown. The Group possesses l i t h o l o g i c and s t r u c t u r a l s i m i l a r i t i e s to parts of the Shuswap Complex and may share some of the complex's h i s t o r y . Part of the southerly adjacent Anarchist Group may be c o r r e l a t i v e with the Kobau Group. • i v TABLE OF CONTENTS Page CHAPTER I: INTRODUCTION 1 GENERAL INTRODUCTION 1 PREVIOUS WORK 5 GENERAL GEOLOGY 11 CHAPTER I I : STRATIGRAPHY 13 INTRODUCTION 13 STRUCTURAL SUCCESSION 16 OVERLYING SUCCESSIONS 23 SUMMARY 24 CHAPTER I I I : STRUCTURE 26 INTRODUCTION 26 MESOSCOPIC STRUCTURES AND AGE RELATIONSHIPS 27 FOLD SETS 44 Latest ( T h i r d Phase) Folds 44 Late (Second Phase) Folds 45 E a r l y ( F i r s t Phase) Folds 50 FRACTURES 57 F a u l t s . . . . 57 J o i n t s 66 STRUCTURAL HISTORY 69 V Page CHAPTER IV: METAMORPHISM 72 INTRODUCTION 72 MINERAL ASSEMBLAGES 72 METAMORPHIC FACIES 76 RELATIONS BETWEEN STRUCTURE AND METAMORPHISM 78 CHAPTER V: IGNEOUS INTRUSIONS 84 INTRUSION PRECEDING EARLY DEFORMATION 84 INTRUSION FOLLOWING EARLY DEFORMATION 85 INTRUSION FOLLOWING LATE DEFORMATION 86 Age 86 Composition 89 Mode of Emplacement 91 YOUNGEST INTRUSION 99 CHAPTER VI: INTERPRETATION AND CONCLUSIONS 103 AGE AND CORRELATION 103 In t r o d u c t i o n 103 The A n a r c h i s t Group 105 The Shuswap Complex 107 The Cache Creek Complex 112 DEPOSITIONAL ENVIRONMENT 113 STRUCTURAL HISTORY 115 The Problem of E a r l y Deformation 115 v i Page STRUCTURAL HISTORY (Cont'd.) Early Folding 115 Late Folding 118 Latest Structures 120 CONTRIBUTION 121 FUTURE WORK 122 REFERENCES CITED 124 APPENDICES 131 A. D e f i n i t i o n of Greenstones 131 B. De s c r i p t i o n of C o r r e l a t i v e S t r u c t u r a l Successions w i t h i n the Kobau Group 132 C. Determination of Temperature of C r y s t a l l i z a t i o n of C r y s t a l l i n e C a l c i t e 138 v i i LIST OP TABLES TABLE Page 3- 1 27 4- 1 73 6-1 109 C-l 139 C-2 140 v i i i LIST OF FIGURES Figure Page 1-1 2 1-2 4 1- 3 10 2- 1 14 3- 1 Pocket 3-2 Pocket 3-3 56 3-4 59 3-5 67 3- 6 68 4- 1 79 5- 1 92 B - l 133 C - l 141 LIST OP PLATES i x Plate Page 3-1 28 3-2 29 3-3 31 3-4 32 3-5 32 3-6 33 3-7 35 3-8 36 3-9 37 3-10 38 3-11 39 3-12 41 3-13 42 3-14 43 3-15 49 3-16 60 3-17 62 3-18 64 3- 19 65 4- 1 35 4-2 35 X LIST OP PLATES Pl a t e Page 4-3 82 4-4 82 4-5 83 4- 6 83 5- 1 87 5-2 : 93 5-3 94 5-4 100 5- 5 102 6- 1 106 x i ACKNOWLEDGEMENTS I thank Dr. J.V. Ross f o r h e l p f u l suggestions and c r i t i c i s m s i n a l l phases of my work, the Department of Geology, U n i v e r s i t y of B r i t i s h Columbia f o r making a v a i l a b l e equipment and f a c i l i t i e s , p a r t i c u l a r l y those of the f i e l d school, and the Na t i o n a l Research Council of Canada f o r supplying funds f o r f i e l d work and winter study. The Department of Energy, Mines and Resources and p a r t i -c u l a r l y Mr. J . Crawford are thanked f o r a l l o w i n g me the use of roads and s e r v i c e s of the Queen E l i z a b e t h II astronomical observatory. I thank George Stonehouse who a s s i s t e d during the 1965 f i e l d season. A p p r e c i a t i o n i s a l s o due my wife f o r encouragement and help at a l l times and e s p e c i a l l y during the summer of 1966. FRONTISPIECE MOUNT KOBAU SEEN FROM A N A R C H I S T MOUNTAIN , LOOKING TO THE NORTHWEST ACROSS OSOYOOS LAKE. CHAPTER I INTRODUCTION GENERAL INTRODUCTION Mount Kobau i s l o c a t e d i n s o u t h - c e n t r a l B r i t i s h Columbia between the Okanagan and Similkameen V a l l e y s , s i x miles north of the f o r t y - n i n t h p a r a l l e l . I n v e s t i g a t i o n of s t r a t i g r a p h y and s t r u c t u r e on Mount Kobau was done to e s t a b l i s h the geolog-i c a l h i s t o r y and age of the Kobau Group (Bostock, 1940) that crops out on Mount Kobau and to the south-east on Kruger Mountain. Mapping during three f i e l d seasons (1965 to 1967) was c a r r i e d out on a scale of four inches to the mile on an enlarged v e r s i o n of an advance p r i n t of the Keremeos sheet (82 E / 4 ) , supplemented by a e r i a l photographs ( B r i t i s h Columbia Department of Lands and F o r e s t s , BC5123-O01 to 044, November 5, 1964). An area of approximately s e v e n t y - f i v e square miles between l a t i t u d e s 49°04' and 49°13' north and lon g i t u d e s 119°32-g"' and 119°44' west was examined. S p e c i f i c g e o l o g i c a l and geographical l i m i t s to the map-area are the Okanagan and Similkameen V a l l e y s to the east and vest, r e s p e c t i v e l y , B l i n d Creek and the O l i v e r Granite to the north, and Ric h t e r Pass to the south (Figure l - l ) . 3 Access to Mount Kobau i s provided by highways i n the Okanagan and Similkameen V a l l e y s and from R i c h t e r Pass (Figure 1-2). A good d i r t road passes from O l i v e r along B l i n d Creek to Cawston and a poor B r i t i s h Columbia Forest Service road extends along the crest of the Mount Kobau ri d g e . Numerous lumber roads are open west of O l i v e r , and i n 1966 the Federal 0 Department of P u b l i c Works constructed an e x c e l l e n t road to the summit of Mount Kobau to provide access f o r the proposed Queen E l i z a b e t h I I Observatory. Sparse vegetation makes movement by foot easy over most of the area. Exceptions are burnt-off areas and canyons: choked with second growth and heavy vegetation, and steep western slopes f a c i n g the S i m i l -kameen V a l l e y . Mount Kobau l i e s i n the southwest corner of the Thompson Plateau j u s t west of the Okanagan Highlands (Holland, 1964; p.71 and map). The plateau and highlands represent a l a t e T e r t i a r y erosion surface (Holland, 1964; p . 7 l ) , a gently r o l l i n g area of low r e l i e f deeply disected by the Okanagan and Similkameen Rivers and t h e i r t r i b u t a r i e s . S t r u c t u r a l con-t r o l of these channels by f r a c t u r e s i s postulated (see Chapter I I I ) . The most prominent v a l l e y s p a r a l l e l north-trending f a u l t s . Presence of ice-sheets during the Pleistocene i s eviden-ced by prominent g l a c i a l s t r i a e at a l l e l e v a t i o n s and d r i f t - •• MAIN TRAILS. FIGURE 1-2 ACCESS ROUTES WITHIN THE MAp-AREA. 5 covered v a l l e y f l o o r s and lower slopes. Marginal meltwater channels and g l a c i o - l a c u s t r i n e s i l t beds are f u r t h e r i n d i c a -t i o n s of extensive g l a c i a t i o n . These s i l t s , a l l u v i a l fans and other s u r f i c i a l deposits, together with the g l a c i a l h i s t o r y of the area, have been discussed by Nasmith (1962). PREVIOUS WORK Between 1859 and 1861, G. Gibbs and H. Bauerman, attached to a j o i n t I n t e r n a t i o n a l Boundary Commission, surveyed lands near the f o r t y - n i n t h p a r a l l e l . In the area of the Ashnola, Similkameen and Okanagan Rivers Gibbs (1874) noted the pres-ence of mica s c h i s t , lammellar quartz and syenite i n t e r s t r a t i f i e d with s l a t e . Bauerman (l884, p.l9B) observed "...black s i l i -ceous s l a t e s . . . beds of g n e i s s i c mica-slate...". He considered these to be representative of the lower part of the Chilukweyuk ( C h i l l i w a c k ) s l a t e s . G.M. Dawson (1879) while mapping p h y s i c a l and g e o l o g i c a l features of the southern i n t e r i o r of B r i t i s h Columbia, des-cribed some of the rocks observed on h i s traverse down the Similkameen V a l l e y as f o l l o w s : "The wide v a l l e y . . . marks the appear-ance of schistose and often s i l v e r y rocks, i n colour varying from b l a c k i s h and greyish to greenish. These are fre q u e n t l y quart-z i t e s with d i v i s i o n planes rendered l u s t r o u s by t a l c on im p e r f e c t l y c r y s t a l l i z e d mica... "Further on, these are replaced by greener rocks, often f e l d s p a t h i c and o c c a s i o n a l l y 6 s c h i s t o s e , which become i n places actually-coarse green decomposed d i o r i t e , with veins of epidote, and so massive that i t i s im-p o s s i b l e to a s c e r t a i n t h e i r ' a t t i t u d e . These rocks are again followed by pale banded cherty q u a r t z i t e interbedded with greenish s c h i s t o s e rocks, hornblendic or c h l o r i t i c . . . " — Dawson, 1879, p.87B. He included the f o l d e d and metamorphosed sediments i n the Okan-agan and Similkameen V a l l e y s w i t h i n the Cache Creek Group of Carboniferous age (Dawson, 1878). He s t a t e s : "The general impression conveyed by an examination of the rocks from V e r m i l l i o n Porks ( P r i n c e t o n ) , by the Similkameen River to Osoyoos, i s , t h a t . . . t h e r e i s represented but a s i n g l e great formation; or, that i f two or more of the g r e a t e r g e o l o g i c d i v i s i o n s are i n c l u d e d , they have been f o l d e d together at one p e r i o d . " — Dawson, 1879, p.87B. Smith and Calkins (1904), from i n f o r m a t i o n gathered during g e o l o g i c reconnaissance i n northern Washington, c o r r e l a t e d low grade metamorphic rocks near O r o v i l l e with Dawson's Cache Creek Group. Umpleby ( l 9 1 l ) observed deformed and metamorphosed shales, limestones, and v o l c a n i c s i n the United States near O r o v i l l e and Nighthawk. He subdivided these rocks i n t o three parts (lower: c l a y s l a t e and a r g i l l a c e o u s s c h i s t s ; middle: s l a t e and limestone; upper: s i l i c e o u s a r g i l l i t e s and v o l c a n i c s ) and c o r r e l a t e d them on l i t h o l o g i c grounds with the Cache Creek 7 Group. He also observed west-dipping reverse and normal f a u l t s . In 1912, Daly traversed the North American C o r d i l l e r a at the f o r t y - n i n t h p a r a l l e l . He proposed the name Anarchist Series f o r a succession of meta-sediraents of presumed Palaeo-zo i c age found on Anarchist Mountain and near B r i d e s v i l l e . This s e r i e s iis made up of deformed q u a r t z i t e s , p h y l l i t i c s l a t e s , greenstones and limestone pods, and t h e i r more metamorphosed equivalents ( s c h i s t , marble and amphibolite). Daly (l912, p. 389) believed that west of Osoyoos Lake the s e r i e s : "...was probably represented by a yet more ex t e n s i v e l y metamorphosed group of rocks..." He c o r r e l a t e d roof pendants of s c h i s t found on Chopaka, Snowy, and Horseshoe Mountains (west of the Similkameen Valley) with the Anarchist S e r i e s , and a l s o d i s -cussed aspects of the Osoyoos B a t h o l i t h , a g n e i s s i c g r a n o d i o r i t e body l y i n g west and east of Osoyoos Lake (Daly, 1912, pp. 439-443) . Campbell (1939) studied a l k a l i n e syenite rocks on Kruger Mountain and t h e i r r e l a t i o n s h i p to surrounding i n t r u s i o n s and meta-sediments of the Anarchist S e r i e s . He found evidence that deformation of the Osoyoos B a t h o l i t h postdated i t s i n t r u s i o n . Bostock (1940) f i r s t defined rocks on Mount Kobau as a d i s t i n c t group and assigned a questionable Carboniferous age to them. Mapping on a scale of one inch to the m i l e , he was able to o u t l i n e a s e r i e s of northwesterly trending f o l d s with 8 s t e e p l y d i p p i n g a x i a l planes. These are shown d i a g r a m a t i c a l l y on c r o s s - s e c t i o n s accompanying h i s map (341 A). He described the group as f o l l o w s : "...a great thickness of metamorphosed, s t r a t i -f i e d rocks mainly of sedimentary o r i g i n . The q u a r t z i t e members are thinly-bedded and commonly micaceous or g r a p h i t i c . There are a l s o f i n e -grained, s i l i c e o u s , mica s c h i s t s and others c o n t a i n i n g c h l o r i t e , hornblende, graphite and t a l c . The a s s o c i a t e d greenstones are v a r i o u s l y sheared." — Bostock, 1940. He b e l i e v e d the Kobau Group o v e r l i e s a g n e i s s i c complex of unknown age east of the Okanagan V a l l e y and dips under the Similkameen V a l l e y and Mesozoic formations to the west. Cairnes' (1940) map of the K e t t l e River (west h a l f ) area showed the Kobau Group as part of the A n a r c h i s t S e r i e s , both of which he considered to be Carboniferous (?) i n age. He b e l i e v e d the Osoyoos B a t h o l i t h and other g r a n i t i c i n t r u s i o n s on Mount Kobau to have been h i g h l y metamorphosed and hence part of a s e r i e s of h i g h l y metamorphosed rocks known as the Shuswap Complex (Dawson, 1898). He i n t e r p r e t e d t h e i r state and that of the complex to be a r e s u l t of extreme metamorphism by Meso-z o i c i n t r u s i o n s . In 1941, Krauskopf i n v e s t i g a t e d i n t r u s i v e rocks of the Okanagan V a l l e y near the f o r t y - n i n t h p a r a l l e l . He found that "...deformation (of the Osoyoos B a t h o l i t h ) preceeded f i n a l 9 c r y s t a l l i z a t i o n , . . . that g n e i s s i c and c a t a c l a s t i c s t r u c t u r e s developed by the same deforming s t r e s s . " (Krauskopf, 1941, p.15). He a l s o commented on a l t e r e d quartz d i o r i t e north and east of Kruger Mountain, c o n s i d e r i n g i t to be a part of the Osoyoos B a t h o l i t h because of s i m i l a r contact metamorphic e f f e c t s . Waters and Krauskopf ( l 9 4 l ) examined the C o l v i l l e B a t h o l i t h and surrounding i n t r u s i o n s and sediments east of the Okanagan V a l l e y i n Washington. They d i v i d e d the A n a r c h i s t S e r i e s i n t o three parts much as Umpleby ( l 9 1 l ) d i d . On the b a s i s of poorly preserved f o s s i l s they assigned a: "...probably Carboniferous and most l i k e l y Permian..." age. (Waters and Krauskopf, 1941, p. 1364). L i t t l e ( l 9 6 l ) r e v i s e d Cairnes' map of 1940 and placed the Kobau Group below the Permian (Dunbar, 1932) Cache Creek Group, g i v i n g the former a p o s s i b l e Carboniferous age. He considered i t impossible to d i s t i n g u i s h the A n a r c h i s t Group* from s i m i l a r groups ranging i n age from Carboniferous to Upper T r i a s s i c . He b e l i e v e d g r a n i t i c i n t r u s i o n s on Mount Kobau are r e l a t e d to Nelson i n t r u s i o n s of Mesozoic age. Subsequent mapping by L i t t l e and Thorpe (1965) enabled them to subdivide the A n a r c h i s t Group i n t o s i x u n i t s Permian and/or younger i n age. (Figure 1-3). *The change i n status from s e r i e s to group i s not explained. LEGEND Sedimentary and Volcanic Early Tertiary. 5~| Upper Triassic. [T] Triassic. Anarchist Gp. | 3 | Pennsylvanian and Permian. Cache Cr. Gp., Blind Cr. Fm. OA). [TI Kobau Gp. Lower Palaeozoic and/or Pre-Cambrian. Shuswap Complex, Monashee Gp. Intrusive Jurassic and/or Cretaceous. Okanagan Batholith Complex including Osoyoos(a), Similkmeen(b), Colville(c), Oliver(d), Krugerfe), Fairview(f) intrusive bodies. - Faults MILES 20 i 49° 00' N •" *.*v \ • • • • • •" v 120° FIGURE GENERAL GEOLOGY OF THE 1-3 SOUTHERN OKANAGAN. 11 White, e t . a l . (1967) have dated r a d i o m e t r i c a l l y Mesozoic i n t r u s i o n s near O l i v e r and obtained ages of 140 and 110 m i l l i o n years f o r the O l i v e r Granite and F a i r v i e w G r a n o d i o r i t e , r e s -p e c t i v e l y . GENERAL GEOLOGY The Kobau Group i n s o u t h - c e n t r a l B r i t i s h Columbia i s a part of a body of pre-middle Mesozoic ( C a l l o v i a n ) metamorphic rocks bounded f o r the most part by the "Okanagan Composite B a t h o l i t h " (Daly, 1912), and i n f a u l t contact with T r i a s s i c v o l c a n i c rocks and sediments (Figure 1-3). The type area of the Kobau Group i s on Mount Kobau (Bostock, 1940). The predominant rock type i s q u a r t z i t e but s c h i s t o s e and massive greenstone and p e l i t i c u n i t s i n c l u d i n g micaceous and a m p h i b o l i t i c s c h i s t and p h y l l i t e are a l s o present. Marble forms a pure, h i g h l y r e c r y s t a l l i z e d u n i t found i n l a r g e and small l e n t i c u l a r bodies. Three phases of f o l d i n g have e x t e n s i v e l y deformed the group. The f i r s t phase produced l a r g e , recumbent, t i g h t l y compressed nappes. Regional meta-morphism a s s o c i a t e d with t h i s f o l d i n g a t t a i n e d the g r e e n s c h i s t f a c i e s . The second phase deformed f i r s t phase s t r u c t u r e s and produced overturned and normal f o l d s . Numerous small g r a n i t i c and d i o r i t i c i n t r u s i o n s cut and deformed these e a r l i e r s t r u c -tures i n Mesozoic time, and thermally metamorphosed country 12 rocks to the '• hor.nfrlende-hornfels f a c i e s within contact aureoles. The t h i r d phase of f o l d i n g formed gentle f o l d s and may be r e l a t e d to t h i s episode of i n t r u s i o n . F a u l t i n g i n T e r t i a r y time broke up p r e - e x i s t i n g s t r u c t u r e s i n t o numerous blocks and wedges. R e l a t i o n s h i p s between the Kobau Group and rocks i n adjacent areas are unknown. The group possesses l i t h o l o g i c and s t r u c t u r a l s i m i l a r i t i e s to p a r t s of the e a s t e r l y adjacent Shuswap Complex and may share some of the complex's h i s t o r y . The A n a r c h i s t Group i s a l s o l i t h o l o g i c a l l y s i m i l a r to the Kobau and at the I n t e r n a t i o n a l Boundary the two groups have been mapped as one (Bostock, 1940; Campbell, 1939, Waters and Krauskopf,<1941). A member of the Cache Creek Group ( B l i n d Creek limestone) of probab/le upper Carboniferous-lower Permian age (R.Y. Best, W.R. Danner, personal communications, 1969) according to Bostock (1940) i s i n presumed f a u l t contact with the Kobau Group. T r i a s s i c or o l d e r formations.found west and northwest of Mount Kobau (Bostock, 1940) are a l s o i n presumed f a u l t contact with both B l i n d Creek limestone and the Kobau Group. CHAPTER I I STRATIGRAPHY INTRODUCTION The metamorphosed succession of sedimentary and basic igneous rocks which makes up the Kobau Group has been estab-l i s h e d by d e t a i l e d mapping and i n t e g r a t i o n of l i t h o l o g i c and s t r u c t u r a l data. Extreme shearing and transformation of bedding during e a r l y phases of f o l d i n g have obscured the o r i g -i n a l s t r a t i g r a p h i c succession and deformed compositional l a y e r i n g i n t o l e n t i c u l a r bodies of l i m i t e d l a t e r a l extent. Composites of l i t h o l o g i c a l l y d i s t i n c t lenses comprise presently e x i s t i n g mappable u n i t s . L o c a l l y s p a t i a l r e l a t i o n s h i p s be-tween such u n i t s have been determined and c o r r e l a t i o n between r e s u l t i n g s t r u c t u r a l sections has been es t a b l i s h e d (Figure 2 - l ) . The observed sequence, of which neither top nor bottom has been observed, i s i l l u s t r a t e d i n Figure 2-1. In no i n -stance has i t been possible to a s c e r t a i n the o r i g i n a l o r i e n t a -t i o n of any part of the succession because sedimentary s t r u c t u r e s , i f any e x i s t e d , have been destroyed by severe deformation. Facies changes and unconformites, i f any were present, are impossible to detect f o r the same reason. STRUCTURAL LITHOLOGIC SUCCESSION WITHIN THE KOBAU GROUP. Measured Sections 5 6000 - i 5000 H 4000 H 3000 2000 H 1000 H 0 -I N a p p e core/ 9 Feet . ( V W • Faults. L i t h o l o g y Massive quartzite Fol iated phy 11 it ic quartzite Phyllite and schist Greenstone Marble and calcareous phyll ite F I G U R E 2-1 15 Estimates of present thickness of the sequence have been made from l o c a l sections (Figure 2-1 and Appendix B, Figure l ) but do not r e f l e c t o r i g i n a l thickness because of extreme deforma-t i o n of the rock u n i t s . The Kobau Group i s composed of a mixed assemblage of metamorphosed sedimentary and basic igneous rocks. Psammitic and p e l i t i c sediments make up most of the group but rocks of probable v o l c a n i c o r i g i n are common. Calcareous sediments are scarce, the primary occurence being lenses of pure c r y s t a l l i n e limestone w i t h i n p h y l l i t e and greenstone.* The most evident feature of most u n i t s of the group i s f o l i a t i o n which p a r a l l e l s compositional l a y e r i n g . This pene-t r a t i v e structure was developed during the f i r s t phase of f o l d i n g (see Chapter I I I ) as a r e s u l t pf t i g h t compression and shearing which forced o r i g i n a l bedding and a x i a l plane f o l i a t i o n i n t o near p a r a l l e l i s m . P l a t y and prismatic minerals developed along f o l i a t i o n planes i n response to re g i o n a l dynamo-thermal metamorphism which accompanied f o l d i n g . P e l i t i c s e d i -ments, basic rocks, and a r g i l l a c e o u s quartz sandstone that a l t e r e d to p h y l l i t e , c h l o r i t e s c h i s t and micaceous q u a r t z i t e , r e s p e c t i v e l y , possessthis f o l i a t i o n , the postulated formation of which i s i l l u s t r a t e d i n Pl a t e s 3-1 to 3-6. *See Appendix A f o r discussion and d e f i n i t i o n of t h i s term. 16 Sections have been measured i n a number of l o c a l i t i e s (Map l ) . They are l i m i t e d by megascopic stru c t u r e s which repeat and overturn parts of the succession and by l a t e f a u l t s (see Chapters I and I I I ) , and must therefore be considered i n r e l a -t i o n to large scale f o l d s which are described i n l a t e r parts of t h i s t h e s i s . STRUCTURAL SUCCESSION As the o r i g i n a l o r i e n t a t i o n of the s t r a t i g r a p h i c succession i s unknown, i t i s necessary to e s t a b l i s h a s t r u c t u r a l succes-sion wherein the " o l d e s t " u n i t l i e s w i t h i n a n t i f o r m a l nappe cores. Northerly verging nappes have been defined as a n t i -formal on the basis of present o r i e n t a t i o n . As o r i g i n a l o r i e n -t a t i o n i s unknown, such a d e f i n i t i o n i s a r b i t r a r y . What i s believed to be the core of such a nappe i s exposed about one mile northeast of the Testalinden Granodiorite (Map 2). F o l i a -t i o n and compositional l a y e r i n g i n t h i s area generally s t r i k e east and dip south at about 45 degrees. Section A, measured south (from nappe core upwards through i t s upper limb) i s l i m i t e d by f a u l t i n g i n Testalinden Creek, but contains Units one and part of two. Section B, measured north from the nappe core through an overturned sequence i n i t s lower limb, con-ta i n s these u n i t s as w e l l as Units three, four , and f i v e . 17 Unit one i s a r e p e t i t i v e sequence of i n t e r f o l i a t e d q u a r t z i t e and p h y l l i t e with minor amounts of greenstone and s c h i s t . Q u a r t z i t e i s f o l i a t e d with b i o t i t e , c h l o r i t e , tremo-l i t e , and white mica i n f i n e l a y e r s between s i l i c e o u s bands. P h y l l i t e i s f i n e grained, d i s t i n c t l y f o l i a t e d and composed of b i o t i t e and white mica with quartz and s e r i c i t e . Sphene, p l a g i o c l a s e (An 6) and c h l o r i t e are present i n small amounts. Greenstone i s g e n e r a l l y massive, yet s c h i s t o s e i n some areas and i s composed of a c t i n o l i t e , opaque fe r r u g i n o u s minerals, p l a g i o c l a s e (An 5), b i o t i t e and minor amounts of quartz. Estimates of t h i c k n e s s are u n r e l i a b l e because of complex f o l d i n g w i t h i n the nappe core, but the present t h i c k n e s s of Unit one i s l i k e l y more than 1,000 f e e t . Unit two contains l i g h t green c h l o r i t i c p h y l l i t e and s c h i s t , p h y l l i t e with small lenses of dark green amphibolite and c h l o r i t i c greenstone c o n t a i n i n g sheared lens-shaped bodies of p o s s i b l e p y r o c l a s t i c o r i g i n . C h l o r i t e , t r e m o l i t e , b i o t i t e and p l a g i o c l a s e (An 5-7) are common c o n s t i t u e n t s . Quartz, sphene, and epidote are present i n small amounts. C a l c i t e i s present as t h i n s t r i n g e r s and f o l i a e w i t h i n c h l o r i -t i c p h y l l i t e . This calcareous p h y l l i t e forms a d i s t i n c t . sub-unit (2a). F o l i a t i o n a s s o c i a t e d with e a r l y f o l d i n g i s w e l l developed, c o n s i s t i n g of c l o s e l y spaced s l a t y (more pro-p e r l y p h y l l i t i c ) cleavage and f i n e c h l o r i t i c and micaceous 18 s c h i s t o s i t y . Present thickness of Unit two, measured i n section B, i s about 400 f e e t . Unit three c o n s i s t s of f i n e to coarse grained massive and i n d i s t i n c t l y f o l i a t e d q u a r t z i t e , and massive, extremely f i n e grained, pure s i l i c e o u s rock. The l a t t e r may be e i t h e r metamorphosed chert or m i c r o c r y s t a l l i n e q u a r t z i t e . O r i g i n a l texture has been obscured by extensive r e c r y s t a l l i z a t i o n . Where present, nearly coplanar f o l i a t i o n and compositional .'. l a y e r i n g are o u t l i n e d by b i o t i t e and r a r e l y c h l o r i t e . Colors of q u a r t z i t e range from white through grey to dark blue. A band of c h l o r i t i c p h y l l i t e s i m i l a r to that of Unit two l i e s w i t h i n Unit three and i s designated sub-unit 3a. The t o t a l present thickness of Unit three i s not known because an east-trending f a u l t w i t h i n Hester Creek cuts out or repeats parts of t h i s s e c t i o n (Map l ) . The greatest continuous ex-posure of Unit three i s approximately 2,000 feet t h i c k . A sequence of f o l i a t e d p h y l l i t i c q u a r t z i t e and s i l i c e o u s p h y l l i t e comprise Unit four.. Colours are commonly grey, white and blue, although minor parts containing ferruginous i m p u r i t i e s are yellow and reddish-brown. Quartz i s f i n e to medium grained and h i g h l y r e c r y s t a l l i z e d . Fine p h y l l i t i c f o l i a e of b i o t i t e , c h l o r i t e , t r e m o l i t e and ferruginous minerals o u t l i n e l e n t i c u l a r s i l i c e o u s l a y e r s . Parts of t h i s u n i t are hi g h l y quartzose with p h y l l i t i c f o l i a e under .01 inches 19 t h i c k ; other parts contain over 25 percent p h y l l i t e and a few bands are best termed s i l i c e o u s p h y l l i t e . The l a s t u s u a l l y contains up to 20 to 30 percent p y r i t e , graphite, and other o p t i c a l l y opaque minerals ( u n i d e n t i f i e d ) as w e l l as minor amounts of c h l o r i t e and s e r i c i t i z e d p l a g i o c l a s e (composition uncertain but p o s s i b l y a l b i t e ) . Present thickness measured i n s e c t i o n B i s 700 f e e t . Unit f i v e contains mainly massive and i r r e g u l a r l y f o l i a t e d q u a r t z i t e s i m i l a r to that of Unit three. F o l i a t e d p h y l l i t i c q u a r t z i t e comprises a number of minor subunits (not formally subdivided), one of which i s the uppermost part of Unit f i v e . Quartz i s white and l i g h t grey i n colour and medium to f i n e grained. Fine, often discontinous, micaceous and p h y l l i t i c f o l i a e o u t l i n e i r r e g u l a r l e n t i c u l e s of quartz. B i o t i t e f l a k e s , up to .04 inches across are developed w i t h i n these f o l i a e near i n t r u s i v e bodies (see Chapter IV). F o l i a t e d q u a r t z i t e contains a high proportion of p h y l l i t i c m a t e r i a l that defines bands of f i n e grained quartz under .125 inches t h i c k . The maximum present thickness of Unit f i v e i s about 600 f e e t . D i f f e r e n t i a t i o n among s i l i c e o u s u n i t s i n sections A and. B i s not possible where no d i s t i n c t i v e u n i t s such as Unit two are a v a i l a b l e f o r reference. Beyond Unit f i v e to the north more' s i l i c e o u s u n i t s are encountered (Map l ) which are 20 i n d i s t i n g u i s h a b l e from Units three, four, and f i v e . Section C i s located j u s t west of s e c t i o n B. Measured northwest, C includes the upper part of Unit four, Units f i v e , s i x and part of Unit eight. Unit seven, present i n other areas, i s not found here. Farther to the northwest, Unit s i x i s encountered again, followed by f i v e , four and three. Such r e p e t i t i o n i m p l i e s the presence of a second macroscopic f o l d core which i s delineated by Unit s i x and described i n Chapter I I I (Maps 1 and 3). Outcrops of s i l i c e o u s u n i t s north of Unit f i v e i n s e c t i o n B are now explained as r e p e t i t i o n of Units three, f o u r , and f i v e by f o l d i n g . Section C, l i k e B, i s overturned with respect to s e c t i o n A. Unit s i x i s composed mainly of l i g h t to dark green amphi-b o l i t i c and c h l o r i t i c p h y l l i t e and s c h i s t and some green metamorphosed basic igneous rocks. A d i s t i n c t subunit (6a) of marble i s seen i n t h i s s e c t i o n . C h l o r i t e , t r e m o l i t e / a c t i n o -l i t e , l e s s e r amounts of white mica and p l a g i o c l a s e (An 6), and minor q u a n t i t i e s of b i o t i t e comprise most of Unit s i x . Some parts are s i l i c e o u s , others contain ferruginous minerals. This u n i t i s i n d i s t i n g u i s h a b l e from Unit two except for the presence of subunit 6a, a white, l i g h t grey to blue, pure c r y s t a l l i n e c a l c i t e marble found i n two bands of sheared lenses 10 to 30 feet t h i c k , l e s s than 50 feet apart, with exposed l a t e r a l extents of under 100 f e e t . Extensions of these 21 lenses are t h i n c a l c i t e bands three to eighteen inches t h i c k and t h i n calcareous s t r i n g e r s i n t e r f o l i a t e d with p h y l l i t e . C r y s t a l l i n e c a l c i t e i s the predominant mineral; only minor amounts of dolomite, t r e m o l i t e , and graphite are pise sent. Complete r e c r y s t a l l i z a t i o n has o b l i t e r a t e d any o r i g i n a l f e a -tures such as c l a s t i c p a r t i c l e s or f o s s i l s . C r y s t a l s are coarse to medium grained i n s i z e , g e nerally of the order of .05 inches across. The present thickness of Unit s i x i n t h i s s e c t i o n i s about 350 f e e t . In sec t i o n C, Unit eight i s composed of grey and white massive and i r r e g u l a r l y f o l i a t e d q u a r t z i t e and m i c r o c r y s t a l l i q u a r t z i t e or meta-chert s i m i l a r to that of Unit three. Thickness of t h i s u n i t as seen i n sect i o n C i s d i f f i c u l t to determine because of r e p e t i t i o n by t i g h t f o l d i n g w i t h i n the second nappe core. Section D was measured within.a part of the Kobau Group that i s separated from other outcrops by extensive areas of Recent alluvium. Exposed thickness of a l l u n i t s i n t h i s area i s 700 to 800 f e e t . The s t r u c t u r a l l y uppermost u n i t , whose top i s not seen, i s composed of l i g h t to dark green p h y l l i t e and s c h i s t containing t r e m o l i t e / a c t i n o l i t e , c h l o r i t e , and micas, and i s s i m i l a r to Units two and s i x . In three l o c a l -i t i e s , pure c a l c i t e marble was observed i n a band up to 20 feet t h i c k and i n t h i n s t r i n g e r s under one foot t h i c k . The 22 mineralogy of t h i s marble i s very much l i k e that of subunit 6a. On the b a s i s of m i n e r a l o g i c a l and l i t h o l o g i c a l s i m i l a r i -t i e s the uppermost u n i t of s e c t i o n D i s c o r r e l a t e d with Unit s i x of s e c t i o n C. The succession below Unit s i x contains a number of r e l a -t i v e l y t h i n (under 200 fe e t ) u n i t s of v a r y i n g l i t h o l o g y . The f i r s t u n i t i s composed of f o l i a t e d q u a r t z i t e c o n t a i n i n g v a r i a b l e amounts of p h y l l i t i c m a t e r i a l . T h i s u n i t i s under-l a i n by green c h l o r i t i c and a m p h i b o l i t i c p h y l l i t e followed by massive q u a r t z i t e , f u r t h e r green p h y l l i t e and l a s t l y f o l i a -ted p h y l l i t i c q u a r t z i t e . This succession i s quite d i s t i n c t from that u n d e r l y i n g Unit s i x i n s e c t i o n s B and C (about 3,400 f e e t of massive and f o l i a t e d q u a r t z i t e ) and i s t h e r e f o r e placed s t r u c t u r a l l y above Unit s i x . S e c t i o n D i s overturned with respect to the succession i n s e c t i o n A. Unit seven, immediately above s i x , i s composed of two types of f o l i a t e d q u a r t z i t e . The f i r s t i s a r e l a t i v e l y pure, l i g h t grey q u a r t z i t e with l e n t i c u l a r s i l i c e o u s bands o u t l i n e d by t h i n f o l i a e c o n t a i n i n g white mica, b i o t i t e and r a r e l y c h l o r i t e ; the second i s h i g h l y p h y l l i t i c (up to 50 percent) with t h i n bands of c h l o r i t e , t r e m o l i t e / a c t i n o l i t e , and b i o t i t e . The present t h i c k n e s s of Unit seven i s quite v a r i a b l e , ranging from zero f e e t i n s e c t i o n C to 250 f e e t i n the v i c -i n i t y of s e c t i o n D. 23 Unit eight i s made up of p h y l l i t e and massive q u a r t z i t e . Most of t h i s unit i s l i g h t grey-green to dark green p h y l l i t e and sch i s t containing f i n e to medium grained t r e m o l i t e - a c t i n o l i t e and c h l o r i t e , and l e s s e r amounts of h i o t i t e and quartz. Black f e r -ruginous minerals, sphene and c a l c i t e are present i n minor quan-t i t i e s . Some parts of t h i s u n i t contain up to 30 percent bands and f o l i a e of whit,e. q u a r t z i t e . Massive and i r r e g u l a r l y f o l i a t e d q u a r t z i t e comprising the remainder of Unit eight has been des-cribed e a r l i e r i n section C. The present thickness of Unit eight i s about 500 fee t . Unit nine contains grey and white f o l i a t e d micaceous and p h y l l i t i c q u a r t z i t e s i m i l a r to that of Unit seven. Although Unit nine apparently o v e r l i e s Unit eight, outcrops of i t have been ob-served i n only four l o c a l i t i e s and i t s true r e l a t i o n s h i p to the previously described succession i s uncertain. Present thickness i s unknown but l i k e l y exceeds 200 f e e t . OVERLYING SUCCESSIONS Two small outcrops of brecciated s i l i c e o u s sediment have been observed i n the southeastern-most part of the map-area (Map l ) . At the northern outcrop, the sediment l i e s unconformably over the Kobau Group but no contact was observed at the other. The age of both deposits i s unknown. Northwest of B l i n d Creek, limestone of the B l i n d Creek Forma-t i o n i s i n apparent f a u l t contact with the Kobau Group and may o v e r l i e the Group on a thrust f a u l t e d contact (R.V.Best, personal communication, 1969). Further d i s c u s s i o n of t h i s formation and i t s r e l a t i o n s h i p to the Kobau Group i s made i n Chapter VI. 24 SUMMARY A s t r u c t u r a l succession containing nine u n i t s has been established by outcrop mapping of f i v e rock types: massive q u a r t z i t e , f o l i a t e d p h y l l i t i c q u a r t z i t e , c h l o r i t i c p h y l l i t e and s c h i s t , greenstone and marble. The t o t a l present t h i c k -ness measured i n several sections i s between 5»700 and 6,200 fe e t . Assumptions have been made that are only p a r t i a l l y sup-ported by e x i s t i n g data. The most obvious of these i s that the p h y l l i t e / m a r b l e assemblage of Unit s i x i s unique w i t h i n the map-area. Mineralogic p r o p e r t i e s of the marble (see Chapter IV and Appendix C) suggest but do not prove that t h i s i s so. The p h y l l i t e i s al s o s i m i l a r i n d i f f e r e n t l o c a l i t i e s but often cannot by i t s e l f be d i f f e r e n t i a t e d from p h y l l i t e s of supposed other u n i t s . Alternate hypotheses can be put forward, f o r example, that the marble u n i t i s i n f a c t two u n i t s , and a new model of the succession would be constructed on the basis of t h i s assumption. The model presented i s but the simplest of many possible models, one however which i s consistent with a v a i l a b l e l i t h o l o g i c data. I t has also been assumed that no major f a c i e s changes and/or unconformities are present. Such changes i n the normal sequence could i n v a l i d a t e i n t e r p r e t a t i o n s of i s o l a t e d parts of the est a b l i s h e d succession such as that described i n 25 section D but because no evidence has been observed that con-firms or disproves existence of these changes, t h e i r e f f e c t upon a synthesis of g e o l o g i c a l h i s t o r y of the map-area must be l e f t as an (presently) i n s o l u b l e problem. CHAPTER I I I STRUCTURE INTRODUCTION Geometry and h i s t o r y of deformation of the Kobau Group i s based on f i e l d mapping and a n a l y s i s of s t r u c t u r a l data supplemented by knowledge of the s t r u c t u r a l succession estab-l i s h e d i n Chapter I I and by measured sections described i n Appendix B. Evidence of at l e a s t three phases of deformation has been observed on the mesoscopic s c a l e . Tight, h i g h l y sheared n e a r - i s o c l i n a l f o l d s have been deformed into t i g h t and normal f o l d s which i n turn have been cut by f r a c t u r e s and gently deformed by open folds-. A l l of these s t r u c t u r e s have undergone l a t e r f a u l t i n g . P a r a l l e l geometry of macroscopic stru c t u r e s has been confirmed by mapping and c o r r e l a t i o n of l i t h o l o g i c u n i t s . Measurement of l i n e a r and planar s t r u c t u r e s and determination of t h e i r age r e l a t i o n s h i p s was made i n the f i e l d . A n a l y s i s of such data was aided by examination of microscopic structures and stereographic p r o j e c t i o n . S t r u c t u r a l features observed i n the Kobau Group are outl i n e d i n Table 3-1. 27 TABLE 3-1 Symbol S t r u c t u r a l Feature F 0 Compositional l a y e r i n g . F l P h y l l i t i c and schistose a x i a l plane cleavage of n e a r - i s o c l i n a l f o l d s . L l Fold axes, mineral l i n e a t i o n s and f o l i a t i o n i n t e r s e c t i o n s ( F with F^) associated with n e a r - i s o c l i n a l f o l d s . F2 A x i a l plane, s t r a i n - s l i p and other cleavage associated with f o l d i n g a f f e c t i n g F q and F^ surfaces. L2 Fold axes, crenulations and f o l i a t i o n i n t e r -sections (F„ with F and F, ) . 2 o 1 F3 A x i a l planes of f o l d s a f f e c t i n g F q , F^, and F^ planes. L 3 • Fold axes and f o l i a t i o n i n t e r s e c t i o n s (F^ with F q , F 1, and F 2 ) . MESOSCOPIC STRUCTURES AND AGE RELATIONSHIPS Two general c l a s s i f i c a t i o n s of f o l d s and r e l a t e d s t r u c -tures have been observed i n the map-area. The f i r s t has s u b - p a r a l l e l limbs and a x i a l planes. Such t i g h t f o l d i n g has brought about transformation of compositional l a y e r i n g i n t o f o l i a t i o n . This i s accomplished by formation of a x i a l plane cleavage (F^) during i n i t i a l stages of deformation (Plates 3-1 and 2) which i s then brought i n t o near p a r a l l -elism with f o l d : limbs (F ) by continued deformation • PLATE 3-1 TIGHT EARLY FOLD IN FOLIATED PHYLLITIC QUARTZITE OF UNIT SEVEN IN THE OLIVER SEPTUM. L ,= 0 8 3 o / 4 8 ° . F. = I 5 4 ° / 4 9 ° N E . 0 3 I i i I INCHES TIGHT EARLY FOLD IN MASSIVE AND FOLIATED QUARTZITE OF UNIT SEVEN ONE MILE SOUTHEAST OF THE TESTALINDEN GRANODIORITE. L| = 133738°, F, = 072740° SE, F 0 OF UPPER LIMB = 090°/45° S. HAMMER IS ONE FOOT LONG. INTER-LIMB ANGLE = 28° PLATE 3-2 30 and t i g h t e n i n g of structures ( P l a t e s 3-3 and 4). Movement of m a t e r i a l out of f o l d cores i s accomplished by shearing and disharmonic f o l d i n g . Limbs of t i g h t f o l d s are d i s l o c a t e d from c r e s t s ( P l a t e 3 - 5 ) . C l a s t i c p a r t i c l e s and c r y s t a l s are sheared i n t o lenses and r e c r y s t a l l i z e d . In the extreme f o l d c r e s t s are sheared out and s i l i c e o u s beds form extended l e n t i c u l e s of q u a r t z i t e bounded by F Q and F^ surfaces and separated by t h i n f o l i a e of p h y l l i t i c m a t e r i a l , while p e l i -t i c sediments and p y r o c l a s t i c v o l c a n i c rocks are g e n e r a l l y sheared and r e c r y s t a l l i z e d to f i n e l y f o l i a t e d p h y l l i t i c and schistose u n i t s ( P l a t e 3 - 6 ) . Massive u n i t s having widely spaced or no bedding are t i g h t l y folded and r e c r y s t a l l i z e d along surfaces. F o l i a t i o n i s w e l l developed w i t h i n basic igneous rocks whereas massive s i l i c e o u s l a y e r s ( o r i g i n a l l y p o s s i b l y t h i c k chert or sandstone beds) are merely r e c r y s -t a l l i z e d and have few v i s i b l e mesoscopic st r u c t u r e s w i t h i n them. Transformation of bedding appears to take place p r i m a r i l y on the mesoscopic sc a l e . Macroscopic assemblages possess i n t e r f o l i a t e d contacts, the assemblages themselves can be traced i n the f i e l d over considerable areas. As shown i n p l a t e s 3-1 to 3 - 6 , the e f f e c t s of t h i s type of deformation were v a r i a b l e . Compositional l a y e r i n g was not everywhere transformed to f o l i a t i o n and r e l i c t f o l d PLATE 3-3 E A R L Y F O L D W I T H S H E A R E D L O W E R L I M B IN F O L I A T E D Q U A R T Z I T E OF UNIT F I V E SOUTH OF L ITHOLOGIC S E C T I O N D. P H O T O G R A P H F A C E S 100°. PLATE 3-4 ISOCLINAL, SIMILAR EARLY FOLD IN SILICEOUS PHYLLITE OF UNIT SIX O N E - H A L F MILE NORTH OF THE MOUNT KOBAU SUMMIT. F e /F, = 005°/25°W. HALF INCH GRID ON PROTRACTOR. PLATE 3 -5 "FLOWED" SIMILAR E A R L Y FOLDS IN FOLIATED QUARTZITE OF UNIT 5 WITHIN THE EARLY NAPPE WEST OF THE FAIRVIEW GRANODIORITE. PLATE 3-6 LENTICULAR FOLIAE AND REMNANTS OF EARLY FOLDS IN FOLIATED QUARTZITE OF UNIT FIVE NORTH OF THE SMALL LAKE NEAR THE MOUNT KOBAU SUMMIT. F c = l25°/53° SW (I ), l39°/4la SW (2 ). 34 closures and even complete f o l d s remain. These l a t t e r s t r u c t u r e s appear to be formed w i t h i n competent f o l i a t e d q u a r t z i t e , l e s s competent f i n e grained rocks are e i t h e r crumpled disharmonically or sheared so as to destroy such struc t u r e s ( P l a t e 3-7). Lineations ( l * - ^ associated with t i g h t f o l d i n g are seen as aligned minerals, f o l i a t i o n (P^) - bedding (P Q) i n t e r -s e ctions, f i n e crenulations and axes of small f o l d s . These are best seen i n p h y l l i t i c and f i n e l y f o l i a t e d greenstone u n i t s . In h i g h l y s i l i c e o u s u n i t s t h i c k f o l i a t i o n and absence of p r i s m a t i c minerals does not favour development of obvious l i n e a t i o n . The second type of mesoscopic f o l d i s d i s t i n c t from the f i r s t . Cleavage, s c h i s t o s i t y and compositional l a y e r i n g are together deformed about a x i a l surfaces g e n e r a l l y at large angles to f o l i a t i o n . R e s u l t i n g f o l d s are of several r e l a t e d kinds; kink bands, chevron and box f o l d s ( P l a t e 3-8) assymetric s i m i l a r f o l d s ( P l a t e 3-9), and, p a r t i c u l a r l y i n t h i c k l y f o l i a t e d or massive sequences, overturned and normal f l e x u r a l s l i p f o l d s ( P l a t e 3-10). Symmetry of these f o l d s i s monoclinic. Associated f o l i a t i o n ( F 2 ) i s s t r a i n - s l i p cleavage (Plate 3 - l l ) and p o s s i b l y f r a c t u r e or other cleavage which i s u s u a l l y p a r a l l e l to a x i a l planes of observed f o l d s . Lineations (l>0) are commonly f i n e crenulations and axes of P L A T E 3-7 EARLY SIMILAR FOLD OF QUARTZITE BANDS WITHIN SHEARED AND FOLIATED CHLORITIC PHYLLITE OF UNIT SIX NORTHWEST OF LITHOLOGIC SECTION D. PHOTOGRAPH FACES 0 7 0 ° . FEET P L A T E 3-8 CONJUGATE SETS OF LATE KINK BANDS AND MONOCLINIC BOX FOLDS IN FOLIATED GREENSTONE OF UNIT SIX NEAR THE SMALL DIORITE STOCK NORTHWEST OF THE MOUNT KOBAU SUMMIT, NOTE STEEPLY DIPPING FRACTURES PARALLEL TO F 2 „ PHOTOGRAPH FACES EAST. INCHES 0 2 l 1 1 PLATE 3 - 9 ASSYMETRIC SIMILAR L A T E FOLDS IN PHYLLITE WITH SILICEOUS FOLIAE OF UNIT SIX NEAR LITHOLOGIC SECTION E. PHOTOGRAPH FACES EAST. SCALE : F U L L SIZE. PLATE 3-10 O V E R T U R N E D L A T E FOLD IN MASSIVE AND F O L I A T E D QUARTZITE AND PHYLLITIC A R G I L L I TE OF UNIT S E V E N ON THE QUEEN E L I Z A B E T H JL OBSERVATORY ROAD SOU T H OF T H E TESTALINDEN GRANODIORITE. L I M B S ( F 0 / F | ) = 105720° SW, 095778° SW. F 2 = 0 9 0 7 4 2 ° N, L g =27575°. NOTE VERTICAL F R A C T U R E S IN LOWER LIMB. 0 10 i . i • . i _» F E E T PLATE 3-11 LATE FOLDS IN HAND SPECIMEN OF CHLORITIC PHYLLITE OF UNIT SIX ONE-HALF MILE WEST OF THE TESTALINDEN GRANODIORITE. TOP VIEW: AXES OF LATE CRENULATIONS TREND LEFT TO RIGHT ( L 2 = 310725°), CUTTING EARLY Ll NE ATI 0 N (L, = 3 4 3 7 7 ° ) SEETN AS FAINT LINES EXTENDING FROM UPPER RIGHT TO LOWER LEFT. SCALED HALF SIZE. EDGE VIEW: LATE CRENULATIONS WITH STRAIN-SLIP CLEAVAGE (Fg) = 131737° SW. SCALE: 11/2 TIMES FULL SIZE. 40 small f o l d s ( P l a t e 3 - l l ) an.d i n t e r s e c t i o n s of cleavage (P 2) and P /?- surfaces. o' 1 Age r e l a t i o n s h i p s between the two types of f o l d s are not always observed, however, where seen ( P l a t e s 3-11 to 3-14) i n d i c a t e deformation of n e a r - i s o c l i n a l f o l d s and r e l a t e d structures by f o l d s with a x i a l planes at large angles to f o l i a t i o n and compositional l a y e r i n g . Tight f o l d s are r e -folded and cut by a cleavage ( P l a t e s 3-12 and 13), FQ/F^ surfaces are cut by c l o s e l y spaced s t r a i n - s l i p cleavage (P l a t e 3-14) and two generations of l i n e a t i o n have been seen i n a number of l o c a l i t i e s ( P l a t e 3 - l l ) . H i s t o r y of deformation of the Kobau Group can therefore be subdivided into e a r l i e r ( f i r s t ) and l a t e r (second) phases. Whether these phases are i n f a c t two d i s t i n c t periods of deformation or merely d i f f e r i n g aspects of one period i s d i s -cussed i n a f o l l o w i n g s e c t i o n . J o i n t s and other f r a c t u r e s , as w e l l as open minor f o l d s which cut and deform the above mentioned st r u c t u r e s have been observed. Fractures are the most common and occur i n several sets. Both e a r l y (Plate 3-2) and l a t e ( P l a t e 3-10) f o l d s are a f f e c t e d . Likewise, both e a r l y and l a t e s t r u c t u r e s are deformed s l i g h t l y by gentle f l e x u r e s . These f r a c t u r e s and f o l d s c l e a r l y post-date e a r l y and l a t e s t r u c t u r e s and are therefore designated as a t h i r d or l a t e s t phase of deformatio n. PLATE 3-12 EARLY FOLD DEFORMED BY LATE STRUCTURES IN SILICEOUS PHYLLITE OF UNIT FIVE ONE-HALF MILE NORTH OF THE MOUNT KOBAU SUMMIT. STEEPLY DIPPING F 2 CLEAVAGE = 156754° SW, L 2 = 158712°. R E F O L D E D E A R L Y FOLD IN F O L I A T E D Q U A R T Z I T E O F S U B - U N I T 6c ONE AND ONE-H A L F M I L E S N O R T H W E S T OF T H E M O U N T K O B A U SUMMIT. H A M M E R IS O N E FOOT LONG PLATE 3-13 PLATE 3-14 L A T E S T R A I N - S L I P C L E A V A G E C U T T I N G F Q / F , S U R F A C E S IN F O L I A T E D S I L I C E O U S P H Y L L I T E O F UNIT SIX W E S T OF T H E T E S T A L I N D E N GRANO-DIORITE. P H O T O G R A P H F A C E S S O U T H W E S T F 2 = 1 3 7 7 3 2 ° SW, L?_ - 2 8 4 7 2 4 ° . 44 FOLD SETS Fold sets w i l l be described from l a t e s t to e a r l i e s t because the l a t e s t f o l d s are the most obvious macroscopic s t r u c t u r e s i n the map-area and because knowledge of the geo-metry of l a t e s t f o l d s i s needed to understand the present o r i e n t a t i o n and geometry of e a r l i e r f o l d s . L atest ( T h i r d Phase) Folds The major s t r u c t u r e of the Mount Kobau area i s a some-what i r r e g u l a r double plunging antiform or dome centered immediately southwest of the Fairview G r a n o d i o r i t e (Map 4). This s t r u c t u r e (the Fairview dome) i s i l l u s t r a t e d diagrama-t i c a l l y on cross s e c t i o n E-F-G-IL of Bostock's map (1940) and i s shown on c r o s s s e c t i o n A'-A" of Figure 3-1 ( i n pocket). F o l i a t i o n ( F Q / F ^ ) of the northeast quadrant of the dome, i n the septum of meta-sediments northwest of O l i v e r (the O l i v e r Septum), dips s t e e p l y to the northeast and east at angles between 40 and 60 degrees, steepening to the northeast and becoming almost v e r t i c a l w i t h i n the contact zone of the O l i v e r Granite. In the southeast quadrant (southwest of O l i v e r ) dips of f o l i a t i o n are g e n e r a l l y south and southeast at 40 to 50 degrees and w i t h i n the southwest quadrant, to west and southwest at about 50 degrees. The general trend of f o l i a -t i o n i n the northwest quadrant i s near h o r i z o n t a l with 45 gentle e a s t e r l y and westerly dips. The dome i s closed on s l i g h t l y over three-quarters of i t s circumference, only the northwest quadrant i s open. Smaller macroscopic f o l d s believed to be formed during the t h i r d phase of deformation have been mapped i n the south-east and northwest quadrants of the dome (Map 4). A l l are open f o l d s with n o r t h e r l y - t r e n d i n g a x i a l planes of unce r t a i n dip. Fold axes, defined by i n t e r s e c t i o n of l a t e s t a x i a l planes with limbs of early and l a t e f o l d s , have a v a r i a b l e plunge depending upon the a t t i t u d e s of these surfaces. In the south-east quadrant, plunges are to the south at 25° to 45°. A broad synform which forms part of the f l a t - l y i n g segment of the northwest quadrant of the dome, plunges n o r t h e r l y at 20° to 25°. Few mesoscopic s t r u c t u r e s formed i n conjunction with l a t e s t f o l d i n g have been observed. Small open f o l d s with n o r t h e r l y - t r e n d i n g axes and a x i a l planes and c e r t a i n f r a c t u r e sets (described i n the secti o n on f a u l t s and other f r a c t u r e s ) are l i k e l y r e l a t e d to t h i s phase of deformation; Late (Second Phase) Folds Late mesoscopic stru c t u r e s have been described b r i e f l y i n a previous s e c t i o n . Their o r i e n t a t i o n , and that of l a t e macroscopic structures i s i l l u s t r a t e d by stereographic pro-j e c t i o n of f i e l d data. In a l l f i g u r e s presented below, lower 46 hemisphere equal area p r o j e c t i o n has been used. Contouring of data points ( l i n e a t i o n s and poles to f o l i a t i o n s ) was done by the Schmidt or g r i d method (Schmidt, j ln Turner and Weiss, pp. 58-62, 1963). Because l a t e s t r u c t u r e s are p r e s e n t l y disposed at v a r y i n g a t t i t u d e s on limbs of l a t e s t f o l d s , the map-area i s d i v i d e d i n t o domains of approximate homogeniety with respect • to the l a r g e s t n o r t h e r l y - t r e n d i n g l a t e s t f o l d s d escribed i n the previous s e c t i o n . Two domains are defined, one i n c l u d i n g the west, the other the east f l a n k of the F a i r v i e w dome (Figure 3-2, i n pocket). Stereographic p r o j e c t i o n of l a t e s t r u c t u r e s and f o l i a t i o n f o l d e d by them w i t h i n each of these domains i n d i c a t e s some spread of data which i s most l i k e l y caused by l a t e s t deforma-t i o n w i t h i n each domain, (Figure 3-2). Consistency i n trend of l a t e s t r u c t u r e s can s t i l l be seen, however. Most l a t e l i n e a t i o n s and f o l d axes ( L 2 ) plunge at angles l e s s than 40° s o u t h e a s t e r l y i n the east domain and at angles l e s s than 30° northwesterly i n the west domain. A t t i t u d e s of F 2 surfaces o o are v a r i a b l e , but most planes d i p i n the order of 30 to 40 southwesterly i n both eastern and western domains. A number of F 2 planes dipping 20° to 30° n o r t h e a s t e r l y have been observed, mostly i n the western domain. These are b e l i e v e d to be a l e s s w ell developed set of conjugate cleavage surfaces which i n some cases, together with the southwesterly d i p p i n g 47 set, make up box f o l d s and conjugate sets of kink bands ( P l a t e 3-8). D i s t r i b u t i o n of poles to e a r l y f o l i a t i o n and compositional l a y e r i n g (P /P^) i l l u s t r a t e s f o l d i n g about axes plunging s o u t h e a s t e r l y at 25° to 30° and northwesterly at 10° to 15° i n the eastern and western domains r e s p e c t i v e l y . Two f o l d limbs can be seen i n the eastern domain. North-e a s t e r l y dips were obtained p r i m a r i l y i n the O l i v e r septum; the p r o j e c t i o n i l l u s t r a t e s the major l a t e a n t i f o r m which c o n s t i t u t e s a part of the Pairview dome. Preponderance of sou t h e r l y dips i n both domains i s a r e s u l t of gr e a t e r expanse of the southwest limb of t h i s a n t i f o r m . Macroscopic Me f o l d s are d e l i n e a t e d by changes i n o r i e n -tstion of P Q / P ^ planes and by c o r r e l a t i o n of measured s e c t i o n s (Chapter II and Appendix B). The l a r g e s t example of such f o l d s i s the a n t i f o r m mentioned above. I t s a x i a l plane s t r i k e s s o u t h e a s t e r l y and dips 60° to 70°. n o r t h e a s t e r l y . The f o l d s a x i s plunges northwest at 10° to 20° and east at about 40° o f f the sides of the Pairview dome. This a n t i f o r m i s flanked to the northeast i n the O l i v e r septum by a t i g h t overturned synform with Pg s t r i k i n g about 125° and dip p i n g 60° to the northeast, ( C r o s s - s e c t i o n C-C, Figure 3-l) . Lg i s somewhat v a r i a b l e and plunges at low angles to the northwest and south-east . Tight l a t e f o l d s are a l s o found i n the area of outcrop described i n the s t r u c t u r a l succession measured i n V ( C h a p t e r II) S e c t i o n D 48 west o f t h e F a i r v i e w G r a n o d i o r i t e . These f o l d s f o r m a com-p o s i t e b o x - l i k e s t r u c t u r e o v e r a m i l e a c r o s s p l u n g i n g g e n t l y -n o r t h w e s t n e a r l y p a r a l l e l t o t o p o g r a p h y i n t h e a r e a ( C r o s s -s e c t i o n B-B', F i g u r e 3 - l ) • M e s o s c o p i c l a t e l i n e a t i o n s p l u n g e a t a n g l e s l e s s t h a n 20° t o w a r d 290° t o 315°. A x i a l p l a n e s and m e s o s c o p i c c l e a v a g e ( F 2 ) d i p s o u t h w e s t and west a t 15° t o 30° and n o r t h e a s t a t v a r y i n g a n g l e s . The f o r m o f t h i s s t r u c t u r e and i t s mode o f f o r m a t i o n a r e n o t c o m p l e t e l y u n d e r s t o o d . L a t e f o l d s o b s e r v e d i n s o u t h and s o u t h w e s t p a r t s o f t h e map-area a r e g e n e r a l l y o f more l i m i t e d e x t e n t t h a n t h o s e d i s c u s sed a b o v e , r a r e l y g r e a t e r t h a n o n e - h a l f m i l e f r o m one e x p o s e d l i m b t o t h e n e x t (Maps 2 and 3). A l l show a c o n s i s t e n t s o u t h e a s t e r l y t r e n d . L 2 p l u n g e s n o r t h w e s t a n d s o u t h e a s t a t a n g l e s u n d e r 20°, w h i l e s o u t h o f t h e T e s t a l i n d e n G r a n o d i o r i t e p l u n g e i s s l i g h t l y g r e a t e r t o 295° t o 300°. F 2 i s q u i t e v a r i a b l e . Most p l a n e s s t r i k e s o u t h e a s t e r l y and d i p s o u t h w e s t a t a n g l e s b e tween 20° and 50°; some d i p n o r t h e a s t a t s i m i l a r a n g l e s ( P l a t e 3-10). I n a l l i n s t a n c e s L^ i s c o n t a i n e d w i t h i n F L a t e f o l d s have been f o r m e d by b o t h s i m i l a r and c o n c e n -t r i c f o l d i n g . The f o r m e r i s most commonly o b s e r v e d on t h e m e s o s c o p i c s c a l e a l t h o u g h t h e t y p e f o r m e d o f t e n a p p e a r s t o be d e t e r m i n e d by d e g r e e o f c l o s u r e o f t h e f o l d ; i n i t i a l f l e x u r e f o r m i n g a c o n c e n t r i c f o l d w h i c h d e v e l o p s i n t o a s i m i l a r f o l d w i t h c o n t i n u e d a p p l i c a t i o n of s t r e s s ( P l a t e 3-15)- S m a l l PLATE 3-15 C O N C E N T R I C A N D S I M I L A R L A T E F O L D S IN P H Y L L I T I C Q U A R T Z I T E O F U N I T F I V E N E A R T H E M O U N T K O B A U S U M M I T . H A M M E R H E A D IS F I V E I N C H E S LONG. 50 macroscopic f o l d s may also be of both types, the type being determined by competence of the rocks i n v o l v e d . Concentric f o l d i n g took place w i t h i n massive and i r r e g u l a r l y f o l i a t e d q u a r t z i t e , s i m i l a r f o l d i n g within massive and f o l i a t e d c a l -careous and s i l i c e o u s p h y l l i t e . Large macroscopic l a t e f o l d s l i k e l y are c o n c e n t r i c . E a r l y ( F i r s t Phase) Folds E a r l y s t r u c t u r e s are u b i q u i t o u s i n the Kobau Group. In most l o c a l i t i e s , only transposed compositional l a y e r i n g and f o l i a t i o n are seen ( P l a t e s 3-6 and 3-14), however, a few near-i s o c l i n a l f o l d s have been observed ( P l a t e s 3-1 to 3-7). They have been r e f o l d e d by two succeeding phases of deformation and are p r e s e n t l y disposed at various a t t i t u d e s on limbs of l a t e and l a t e s t f o l d s . As i n the treatment of l a t e f o l d s , the map-area i s d i v i d e d i n t o domains of approximate homogeniety with respect to l a t e and l a t e s t s t r u c t u r e s . Six sub-domains are d e f i n e d , three within each of the two p r e v i o u s l y e s t a b l i s h e d domains, each i n c l u d i n g the limb of a major macroscopic l a t e f o l d , (Map 4, Figure 3-2, i n pocket). Northern and c e n t r a l sub-domains contain northeast and southwest limbs of the l a t e anitform l y i n g over the Fairview G r a n o d i o r i t e . Southern sub-domains include areas g e n e r a l l y southwest and west of the T e s t a l i n d e n G r a n o d i o r i t e , separated from the northern part of 51 the map-area by regions of Recent al l u v i u m and i n t r u s i v e bodies. A macroscopic e a r l y f o l d has been mapped l y i n g on'the northeast limb of the overturned l a t e synform w i t h i n the O l i v e r septum (east northern sub-domain, Figure 3-2). Sub-units 6a and 6b (see s e c t i o n H, Appendix B) o u t l i n e t h i s f o l d which cl o s e s to the northwest and contains Unit f i v e i n i t s core (Maps 2 and 3, C r o s s - s e c t i o n C-C, Figure 3 - l ) . Limbs and e a r l y a x i a l plane f o l i a t i o n are s u b - p a r a l l e l , d i p p i n g north-east at angles between 40° and 70°. E a r l y l i n e a t i o n s and f o l d axes (L^) plunge at v a r y i n g angles to east and northeast at angles between 35° and 55° except i n shallow d i p p i n g p a r t s of the trough of the l a t e synform where plunge a t t i t u d e i s 0° to 15° toward 080° and 260°. In the west northern sub-domain, a n o r t h e r l y - c l o s i n g t i g h t f o l d has been observed l y i n g on the northeast limb of the large l a t e a n t i f o r m described e a r l i e r ' (Map 3, C r o s s - s e c t i o n B-B 1, Figure 3-1'). plunges e a s t e r l y at 10° to 30°. C o r r e l a t i o n of l i t h o l o g i c s e c t i o n s F and G with H (Map 1, Appendix B) supports i n t e r p r e t a t i o n of t h i s c l o s u r e as being the same as that i n the O l i v e r septum, brought i n t o i t s present p o s i t i o n by l a t e r e f o l d i n g . Such r e f o l d i n g could leave both f o l d c l o s u r e s a l i g n e d along the o r i g i n a l d i r e c t i o n of as shown by Holmes and Reynolds (1954). E a s t e r l y alignment i s evident on Map 3. F l a t - l y i n g parts of l a t e f o l d s have not been a p p r e c i a b l y a l t e r e d i n o r i e n t a t i o n by 5'2 l a t e f o l d i n g and hence should contain at or near i t s o r i e n t a t i o n p r i o r to such deformation (Ramsey, pp. 470-471, 1967). within n e a r - h o r i z o n t a l surfaces i n both east and west northern sub-domains trends e a s t e r l y (Figure 3-2), par-a l l e l to alignment of macroscopic s t r u c t u r e s . This e a r l y macroscopic f o l d o r i g i n a l l y closed to the north, the north-westerly c l o s u r e observed i n the O l i v e r septum being produced by l a t e r e f o l d i n g and ov e r t u r n i n g ( C r o s s - s e c t i o n C-C 1, Figure 3-1-)'. Extention of limbs of t h i s s t r u c t u r e to the south i s e s t a b l i s h e d by c o r r e l a t i o n of measured s e c t i o n s (Chapter II, Appendix B) and mapping of d i s t i n c t i v e l i t h o l o g y . Part of the lower limb i s exposed i n the v i c i n i t y of s e c t i o n D (Map l ) on the major l a t e antiform whose southwest limb d e f i n e s the H e r e west c e n t r a l sub-domain (Figure 3-2). Seat**J , the e a r l y lower limb i s r e f o l d e d by a b o x - l i k e l a t e s t r u c t u r e ( C r o s s - s e c t i o n B-B,1', Figure 3-l) . F Q / F ^ planes d ip n o r t h e r l y and westerly at angles under 30° to 40°. l y i n g on these planes plunges at angles under 40° to the west and southwest. The upper limb of the n o r t h e r l y - c l o s i n g e a r l y f o l d , l y i n g on the southwest f l a n k of the Fairview dome, i s al s o exposed along western slopes of Mount Kobau. The limb can be traced south over the summit and eastward (as i t curves about the outer f l a n k s of the dome) south of the T e s t a l i n d e n Granodio-r i t e to the Okanagan V a l l e y (Map 2, Appendix B, s e c t i o n s J & K). 53 The core and lower limb of t h i s e a r l y f o l d are exposed north-east of the Testalinden Granodiorite, o u t l i n e d by Units one to four (sections A, B and i ) . The lower limb here i s an extension of that part exposed i n the west c e n t r a l sub-domain described above. This f o l d can be seen to~.be a r e f o l d e d , r e -cumbent nappe-like structure c l o s i n g n o r t h e r l y with a x i a l surfaces s u b - p a r a l l e l to the limbs, dipping o f f the fla n k s of the Fairview dome (Figure 3 - l ) . The f o l d a x i s o r i g i n a l l y had an e a s t e r l y trend with unknown plunge, the a x i a l plane may have been recumbent or have dipped to the north or south. The f o l d i s defined as anti f o r m a l to assign a s t r u c t u r a l order to the l i t h o l o g i c succession (Chapter II). Such i s the assummed gross structure of t h i s f o l d . A l l parts are i n f a c t made up of smaller macroscopic f o l d s which have been deformed by l a t e r s t r u c t u r e s . E f f e c t s of these structures are marked w i t h i n east and west southern sub-domains (Figure 3-2), in:which F^/F^' surfaces are deformed about southeasterly and northwesterly trending axes = TT F Q / F ^ r e s p e c t i v e l y , and i s spread about L^. The lower limb of the an t i f o r m a l nappe can be traced east (sections B and C) into the east c e n t r a l sub-domain where r e p e t i t i o n of the l i t h o l o g i c succession and exposure of a shear ed ear l y f o l d closure i n d i c a t e the presence of a complementary synformal nappe l y i n g s t r u c t u r a l l y below the ant i f o r m a l nappe (Maps 2 and 3). F, dips south-southeast at about 20° to 40^ 54; and plunges southwesterly at about 1 0 ° to 2 0 ° ( e a s t - c e n t r a l sub-domain, Figure 3 - 2 ) . The lower limb of t h i s synformal nappe can be followed i n turn west and northwest to a s t i l l lower small a n t i f o r m a l nappe whose closure i s not seen but whose presence i s i n d i c a t e d by f u r t h e r r e p e t i t i o n of the l i t h o l o g i c succession ( s e c t i o n E, Appendix B). F^ planes of t h i s lowest nappe have been deformed by l a t e s t f o l d i n g (Maps 3 and 4 ) and presently dip to southeast, south and southwest at 3 0 ° to 4 5 ° . plunges southwest and west at angles under 3 0 ° ( e a s t - c e n t r a l sub-domain, Figure 3 - 2 ) . Mesoscopic stru c t u r e s of the east c e n t r a l sub-domain d i f f e r somewhat from those i n areas discussed p r e v i o u s l y . As elsewhere, two generations of s t r u c t u r e s are observed, e a r l y n e a r - i s o c l i n a l f o l d s and sheared f o l i a t i o n are deformed by kink bands, chevron f o l d s and asymmetric s i m i l a r f o l d s . However, i n t h i s sub-domain, f o l d axes and l i n e a t i o n s formed by e a r l y f o l d i n g are scattered w i t h i n the southwest quadrant plunging at angles of less-than 2 0 ° . Many l i n e a r s t r u c t u r e s formed by l a t e r f o l d i n g possess s i m i l a r a t t i t u d e s while others plunge southeasterly at various angles. Age r e l a t i o n -ships between l a t e f o l d s trending southwesterly and those trending southeasterly are r a r e l y seen. Some l i m i t e d data suggest that the l a t t e r are younger and deform both e a r l y and l a t e southwesterly-trending s t r u c t u r e s (Figure 3 - 3 ) • I t FIGURE 3-3 S K E T C H O F O R I E N T E D H A N D S P E C I M E N O F F O L I A T E D P H Y L L I T I C Q U A R T Z I T E O F U N I T F O U R N E A R T H E M O U T H O F H E S T E R C R E E K . F A I N T E A R L Y L I N E A T I O N ( L , = 2 2 2 ° / 3 7 ° ) IS C U T B Y A D I S T I N C T M I N E R A L A N D F O L I A T I O N -I N T E R S E C T I O N L I N E A T I O N ( " L A T E R " L , = 2 4 2 7 1 5 ° ) , B O T H O F W H I C H A R E D E F O R M E D B Y S M A L L K I N K B A N D S ( L 2 = 0 9 8 7 3 3 ° ) . " L A T E R " F, C L E A V A G E A T T I T U D E = 0 3 8 ° / 4 5 ° NW. F 0 / F , ( T O P O F S P E C I M E N ) = 0 7 4 ° / 5 7 ° S E . S C A L E : F U L L S I Z E . 56 i s possible that l a t e southwest stru c t u r e s were formed by a f i n a l stage of deformation r e l a t e d to e a r l y f o l d i n g . * * As closure of e a r l y f o l d s was completed, f u r t h e r s t r e s s could be accommodated only by f o l d i n g of n e a r - i s o c l i n a l e a r l y f o l d s and F T / P surfaces about L., . In the east c e n t r a l sub-domain 1' o 1 (Figure 3-2) , and " l a t e r " plunge southwesterly at 10° to 20°. In most instances, however, age r e l a t i o n s h i p s between southeasterly and southwesterly trending l a t e r s t r u c t u r e s are not observed, hence the above hypothesis must be considered t e n t a t i v e at best. As these structures are seen p r i m a r i l y w i t h i n the core and lower limb of the major'antiformal nappe and w i t h i n underlying nappes described p r e v i o u s l y , i t would appear that t h i s southwesterly trending phase of deformation a f f e c t e d lower s t r u c t u r a l l e v e l s to a greater degree than higher ones. For the most part, the o r i g i n of these s t r u c t u r e s i s not understood. ** These struc t u r e s are designated as " l a t e r " and F^ f o r convenience only. No genetic r e l a t i o n s h i p to e i t h e r e a r l y or l a t e phase stru c t u r e s i s implied. FRACTURES F a u l t s R o c k s o f the K o b a u G r o u p have b e e n e x t e n s i v e l y f r a c t u r e d a f t e r c o m p l e t i o n o f t h e t h r e e p h a s e s o f d e f o r m a t i o n d e s c r i b e d i n p r e c e e d i n g s e c t i o n s . Many f a u l t s f r o m s m a l l d i s l o c a t i o n s w i t h movements o f a few i n c h e s to m a j o r b r e a k s w i t h a p p a r e n t s t r i k e - s l i p movements l i k e l y e x c e e d i n g s e v e r a l h u n d r e d f e e t , have been o b s e r v e d . I n many i n s t a n c e s , l a r g e f a u l t s a r e s e e n o n l y a s l i n e a m e n t s a c r o s s w h i c h l i t h o l o g i c c o n t a c t s a r e d i s -p l a c e d , h e n c e , s l i c k e n s i d e s a n d o t h e r e v i d e n c e o f a c t u a l movement h a s n o t b e e n o b t a i n e d . B e c a u s e o f l o c a l v a r i a t i o n s i n a t t i t u d e o f l i t h o l o g i c c o n t a c t s i t i s o f t e n d i f f i c u l t e v e n to e s t i m a t e m a g n i t u d e o f a p p a r e n t s t r i k e - s l i p d i s p l a c e m e n t . . M e s o s c o p i c f a u l t s have b e e n o b s e r v e d i n many l o c a l i t i e s i n the m a p - a r e a , p a r t i c u l a r l y i n f r e s h r o a d c u t s o f t h e Queen E l i z a b e t h I I O b s e r v a t o r y a c c e s s r o a d ( F i g u r e 2 - 2 ) . E x t e n s i v e f a u l t i n g i n t h e s e l o c a l i t i e s s u g g e s t s t h e p o s s i b i l i t y o f s i m i l a r b r e a k a g e h a v i n g o c c u r r e d i n ; a l l p a r t s o f t h e m a p - a r e a , however c o n s i d e r a b l y l e s s e v i d e n c e has b e e n o b s e r v e d i n w e a t h e r e d o u t - c r o p s . S t e r e o g r a p h i c p r o j e c t i o n o f m e a s u r e d m i n o r f a u l t s r e v e a l s a number o f d a t a p o i n t maxima s u g g e s t i n g t h a t some of t h e s e m e s o s c o p i c b r e a k s p a r a l l e l . n o r t h e r l y 5 8 trending f a u l t s i n the Okanagan V a l l e y ( L i t t l e , 1961a) while others may represent splays from t h i s major fe a t u r e (Figure 3-4). A number of lineaments detected i n the f i e l d and on a e r i a l photographs and topographic maps have been i n t e r p r e t e d as macroscopic f a u l t s . Brown ( l 9 6 l ) i n d i c a t e s that f a u l t s are a c c u r a t e l y depicted as l i n e a r s on a e r i a l photographs. Such i n t e r p r e t a t i o n i s aided by the presence of p a r a l l e l minor f a u l t s and b r e c c i a zones, d i s p l a c e d l i t h o l o g i c u n i t s and s t r u c t u r e s , and topographic f e a t u r e s which suggest f a u l t scarps. Such evidence i n d i c a t e s that two well-developed sets of f a u l t s t r e n d i n g 150°-170° and 120°-130° have broken up fo l d e d s t r u c t u r e s of the Kobau Group. South-southeast trending f a u l t s are p a r a l l e l to f a u l t s i n the Okanagan V a l l e y ( L i t t l e , 1961; Church, 1967). The Similkameen V a l l e y may represent a smaller but s i m i l a r f a u l t -c o n t r o l l e d v a l l e y . The best developed f a u l t i n the map-area p a r a l l e l to the Okanagan system i s one designated the Cawston-R i c h t e r f a u l t passing through creeks of the same name. Evidence of f a u l t i n g has been seen i n Cawston., Creek ( P l a t e 3-16), steep canyon walls which may be f a u l t c o n t r o l l e d f e a t u r e s are present i n the upper part of Cawston Creek and the presence of a zone of f r a c t u r i n g and b r e c c i a t i o n has been confirmed by diamond d r i l l cores near the summit of Mount Kobau ( j . Crawford, personal communication, 1967) . FIGURE 3 - 4 SYNOPTIC LOWER HEMISPHERE , EQUAL AREA STEREOGRAPHIC PROJECTION OF POLES TO MINOR FAULT P L A N E S . PLATE 3-16 S H E A R E D AND B R E C C I A T E D FAULT ZONE S E P A R A T I N G P H Y L L I T E (UPPER RIGHT) FROM PH Y L L I T I C Q U A R T Z I T E (LOWER L E F T ) , BOTH OF UNIT SIX, NEAR T H E MOUTH O F CAWSTON CREEK. PHOTOGRAPH FAC E S 150°. HAMMER IS ONE FOOT LONG. 61 Some displacement of l i t h o l o g i c u n i t s i s evident but s t r a t i g r a p h i c c o n t r o l i s poor and the amount of movement can-not be estimated. V a r i a t i o n s i n the trend of the f a u l t l i n e a -ment suggest a dip of the f a u l t plane i n excess of 45° to the west-southwe s t . Other s u b - p a r a l l e l lineaments are present i n the v i c i n t i y of the Cawston-Richter f a u l t . Some show c l e a r evidence of up to 500 f e e t apparent l e f t - l a t e r a l s t r i k e - s l i p displacement (Map 4 ) . Several minor f a u l t s s t r i k i n g approximately n o r t h e r l y and d i p p i n g west at about 40° have been mapped and the steep slope of the west side of Mount Kobau may be a r e s u l t of f a u l t -i n g along such a trend. Six c l o s e l y spaced f a u l t s observed i n the Similkameen V a l l e y southwest of the map-area (P l a t e 3-17) a l s o s t r i k e n o r t h e r l y and dip s t e e p l y to the west. In t h i s l o c a l -i t y , eastern blocks have moved upwards r e l a t i v e to western ones. In eastern and c e n t r a l p a r t s . o f the map-area, some south-southeast trending lineaments are also i n t e r p r e t e d as f a u l t s p r i m a r i l y on the b a s i s of l i t h o l o g i c changes near lineaments. O f f s e t s d e r ived from areas of patchy outcrop (common to much of the map-area) are u n c e r t a i n . These and other lineaments of unknown a f f i n i t y are i l l u s t r a t e d on Map 4. Observed d i s p l a c e -ments of contacts are nowhere great, the l a r g e s t has l i k e l y occurred along the Spotted Lake f a u l t which extends from south of Spotted Lake to j u s t east of the T e s t a l i n d e n G r a n o d i o r i t e . A lineament^ which represents a p o s s i b l e extension of t h i s f a u l t extends to a point j u s t PLATE 3-17 POLISHED FAULT SURFACE CUTTING MASSIVE AND FOLIATED QUARTZITE IN THE SIMILKAMEEN VALLEY WEST OF RICHTER MT. FAULT ATTITUDE = 0 0 9 7 7 6 ° W. NOTE STEEPLY PLUNGING SLICKENSIDES. FEET 0 5 i i i i i i 6 3 west of the F a i r v i e w G r a n o d i o r i t e . The lineament d e f i n i n g the Spotted Lake f a u l t i s very d i s t i n c t ( P l a t e 3-18) and marked l i t h o l o g i c and s t r u c t u r a l d i s c o n t i n u i t i e s are present across i t . I t i s p o s s i b l e that steep s o u t h e a s t e r l y plunges of l a t e f o l d s observed east of the f a u l t r e s u l t from r o t a t i o n a l movement (clockwise when viewed eastward) on the f a u l t plane. Mapping of s t r u c t u r e s w i t h i n the Shuswap Complex found on both sides of the Okanagan V a l l e y i n d i c a t e s that movement along the Okanagan f a u l t system has not been great (Ross and C h r i s t i e , 1969). In the White Lake basin area north of Mount Kobau, movement along south-southwest trending f a u l t s has been de s c r i b e d as: "...a t r a p d o o r - l i k e downward r o t a t i o n along west-dipping f a u l t s of the Okanagan system..." (Church, 1967, pp. 96-99). F a u l t s i n the Mount Kobau area presumably have s i m i l a r d i splacements. A number of other lineaments p a r a l l e l to the Okanagan system have been i n t e r p r e t e d as f a u l t s , but only i f d e f i n i t e s t r u c t u r a l and/or l i t h o l o g i c d i s c o n t i n u i t i e s are present across them. A l l lineaments are shown on Map 4 and Figure 3-6. Age d i f f e r e n c e s among f a u l t s have not been observed. Cairnes (1940) r e p o r t s f a u l t s older and younger than Mesozoic i n t r u s i o n s i n the southern Okanagan region, however, these PLATE 3-18 T H E S P O T T E D L A K E L I N E A M E N T , E X T E N D I N G F R O M L E F T M I D D L E D I S T A N C E T O R I G H T B A C K G R O U N D N E A R HIGHWAY. T R E N D O F L I N E A M E N T = 140 °. P H O T O G R A P H F A C E S S O U T H E A S T . S P O T T E D L A K E O U T O F P I C T U R E T O R I G H T N E A R R I C H T E R P A S S H I G H W A Y . O S O Y O O S L A K E A N D A N A R C H I S T MT. IN B A C K G R O U N D . PLATE 3-19 C R A G AND TAIL F E A T U R E S ON BENCH LAND AT 2000 F E E T ELEVATION NORTHWEST OF OSOYOOS LAKE. MOVEMENT OF ICE FROM L E F T TO RIGHT (NORTH TO S O U T H ) . S T R I K E S OF F O L I A T I O N IN AREA VARIABLE FROM N O R T H E A S T TO S O U T H E A S T , DIPPING SOUTHERLY. 66 have not been seen. F a u l t i n g i n the map-area and surrounding areas (Church, 1967, pp. 96-99) i s presumed to have taken place during one episode i n e a r l y T e r t i a r y time. J o i n t s Planar j o i n t s have been observed over a l l the map-area. Stereographic p r o j e c t i o n of measured j o i n t planes (Figure 3-5) i n d i c a t e s the presence of at l e a s t two main se t s , one s t r i k i n g n o r t h e r l y , d i p p i n g s t e e p l y to east and west, the other near v e r t i c a l , s t r i k i n g west to northwest. Although i n an area a f f e c t e d by polyphase deformation, numerous j o i n t sets at various a t t i t u d e s may be expected to form, observed j o i n t s appear to be of one age and are not a f f e c t e d by any f o l d i n g . They are therefore , e i t h e r r e l a t e d to l a t e s t f o l d i n g or formed afterwards. I f the former, ob-served j o i n t s represent sets p a r a l l e l to a x i a l planes and perpendicular to f o l d axes of n o r t h e r l y - t r e n d i n g f o l d s . How-ever, as no c l e a r l y d efined age r e l a t i o n s h i p s have been observed among j o i n t s , i t i s not p o s s i b l e to r e l a t e any sets to other s t r u c t u r e s . A comparison of s t r i k e f r e q u e n c i e s of lineaments and j o i n t s i s shown i n Figure 3-6 and shows that lineaments s t r i k i n g 160° to 170° are approximately p a r a l l e l to 20$ of a l l measured j o i n t s i n the map-area. Lineaments i n the s t r i k e range I III JOINTS IN THE SOUTHERN THIRD SYNOPTIC DIAGRAM OF 315 OF THE MAP-AREA. CONTOURS AT JOINTS. CONTOURS AT . 5 , I, 1,2 AND 4% PER 1% AREA. 2 AND 4 % PER 1% AREA. FIGURE 3-5 E Q U A L AREA PROJECTION OF POLES TO J O I N T . P L A N E S . 69 120°-150° do not appear to correspond to any major concen-t r a t i o n of j o i n t s , however, lineaments s t r i k i n g 120°-130° are approximately p a r a l l e l to the s t r i k e of the l a t e a x i a l plane cleavage (Fg). R e l a t i o n s h i p s between j o i n t s and minor f a u l t s are i l l u s t r a t e d i n Figures 3-4 and 3-6. J o i n t sets s t r i k i n g 000° and 100°-120° may be r e l a t e d to f a u l t s i n the same s t r i k e range s. A number of no r t h e r l y - t r e n d i n g lineaments within the map-area are l i k e l y produced by g l a c i a l a c t i o n . G l a c i a l s t r i a e ( Plate 3-19) measured by the author and by Bostock (1940) trend 160°-180° and are therefore p a r a l l e l to many lineaments. STRUCTURAL HISTORY E a r l i e s t recognizable f o l d i n g produced l a r g e , near-iso-c l i n a l recumbent nappes, with n o r t h e r l y vergence and e a s t e r l y trending axes ( L ^ ) . The a t t i t u d e of F^ at the end of e a r l y f o l d i n g i s unknown except that i t was s u b - p a r a l l e l to limbs of the f o l d and had an e a s t e r l y s t r i k e , and i s presumed to have been r e l a t i v e l y f l a t . As neither top nor bottom to the Kobau Group has been observed w i t h i n the map-area, i t i s not possible to designate the major nappe as e i t h e r a n t i c l i n a l or s y n c l i n a l . At lowest observed s t r u c t u r a l l e v e l s , a post-early phase of deformation gave r i s e to r e f o l d i n g of F^ and F q surfaces about axes s u b - p a r a l l e l to I . . 70 A second" phase of f o l d i n g deformed e a r l y nappes i n t o normal upright and t i g h t overturned f o l d s with moderate to steeply dipping a x i a l planes (Fg) a n <* northwesterly-trending axes (Lg). Separation of ea r l y and la t e phases of f o l d i n g i n t o d i s t i n c t periods of deformation i s suggested by d i f f e r e n c e s i n respective f o l d types and degree of metamorphism accom-panying the two phases (Chapter IV) which imply d i f f e r e n c e s i n environment of deformation. Some time i n t e r v a l i s presumably required to bri n g about such changes i n environment as waning of metamorphism and/or erosion of o v e r l y i n g successions ( i e . r e s u l t i n g i n lower temperature and pressure c o n d i t i o n s ) . However, transference of st r e s s from n o r t h e r l y to no r t h e a s t e r l y d i r e c t i o n s may have taken place during such changes i n e n v i r -onment, thus, i t i s not possible to define these phases as d i s t i n c t periods of deformation. Differences i n environment may also be a r e s u l t of p o s i t i o n w i t h i n the c r u s t . Any di f f e r e n c e s i n metamorphic grade at various s t r u c t u r a l l e v e l s as evidenced, perhaps, by mi n e r a l o g i c a l d i f f e r e n c e s between Al.1 and B l . l (Winkler, 1967) sub-facies, are l i k e l y obscured by l a t e r contact metamorphism. A v a i l a b l e information does not permit a choice between these two hypotheses. A t h i r d ( l a t e s t ) phase of deformation r e s u l t e d i n gentle warping of ea r l y and l a t e s t r u c t u r e s and the formation of the Fairview dome. Steep n o r t h e r l y - t r e n d i n g f r a c t u r e s p a r a l l e l 71 a x i a l planes of these f o l d s whose axes l i e at various a t t i -tudes on limbs of l a t e s t r u c t u r e s . I t i s not possible to separate e f f e c t s of t h i s f o l d i n g from possible e f f e c t s of emplacement of Mesozoic igneous i n t r u s i o n s (Chapter V). The marked change i n s t r u c t u r a l trend from e a r l y and l a t e phases suggests that l a t e s t f o l d i n g i s a d i s t i n c t period, of deforma-t i o n . Further evidence f o r t h i s hypothesis depends upon dating of events and i s presented i n Chapter VI. F a u l t i n g p a r a l l e l to the Okanagan f a u l t system a f f e c t e d a l l e a r l i e r s t r u c t u r e s . Stresses responsible f o r p a r a l l e l f a u l t i n g i n the White Lake area were believed to be d i r e c t e d north and south (Church, 1967, p. 96) and wer.e a c t i v e i n e a r l y T e r t i a r y time. This f r a c t u r i n g i s believed to be a d i s t i n c t f i n a l period of deformation i n the Kobau map-area. CHAPTER IV METAMORPHISM INTRODUCTION Study of metamorphism and microscopic s t r u c t u r e s of rocks of the Kohau Group was c a r r i e d out by examination of hand specimens, t h i n s e c t i o n s , and determination of mineral con-tent by X-ray d i f f r a c t o m e t r y . Approximately f i f t y t h i n sections and f i f t y X-ray determinations were analyzed, some samples being tested by both methods. Temperatures of crys-t a l l i z a t i o n were obtained f o r f i v e samples of c r y s t a l l i n e limestone by measuring Mg/Ca r a t i o s by X-ray d i f f r a c t o m e t r y . MINERAL ASSEMBLAGES Mineral assemblages' seen i n various u n i t s of the Kobau Group are l i s t e d i n Table 4-1 together with rock types i n which they are found and possible parent l i t h o l o g i e s . With-out extensive chemical and min e r a l o g i c a l a n a l y s i s , determina-t i o n of parent l i t h o l o g i e s of most metamorphic rocks can only be of a general nature. P a r t i c u l a r l y , d i f f e r e n t i a t i o n among a m p h i b o l i t i c and c h l o r i t i c greenstones derived from e i t h e r basic i n t r u s i v e or .extrusive rocks, or from calcareous TABLE ^-1. Rock Type M i n e r a l Content P o s s i b l e Parent L i t h o l o g y Massive and f o l i a t e d ( p h y l l i t i c ) q u a r t z i t e P h y l l i t e , s c h i s t , . greenstone Marble and c a l c - s i l i c a t e K e t a - u l t r a b a s i c - quartz, white mica (muscovite, s e r i c i t e ? ) , b i o t i t e - quartz, b i o t i t e , p l a g i o c l a s e (An 6), epidote - quartz, b i o t i t e , garnet ( s p e s s a r t i n e ? ) , z o l s i t e , sphene - quartz, b i o t i t e , c h l o r i t e , ferruginous minerals - quartz, a c t i n o l i t e , f e rruginous minerals, s e r i c i t e , epidote - b i o t i t e , p l a g i o c l a s e .{An 6), s e r i c i t e , c h l o r i t e , epidote - c h l o r i t e , a l b i t e , quartz, b i o t i t e , c a l c i t e - b i o t i t e , white mica, quartz, sphene, a l b i t e , c h l o r i t e - b i o t i t e , c l i n o z o i s i t e , sphene, quartz, a l b i t e , s e r c i t e - t r e m o l i t e / a c t i n o l i t e , p l a g i o c l a s e (An 5), b i o t i t e , c h l o r i t e - c h l o r i t e , a c t i n o l i t e , c a l c i t e , quartz, a l b i t e , b i o t i t e - hornblende, a c t i n o l i t e , c h l o r i t e , sphene - a l b i t e , c h l o r i t e , t r e m o l i t e / a c t i n o l i t e , c a l c i t e b i o t i t e - t r e m o l i t e / a c t i n o l i t e , epidote, a l b i t e , sphene - b i o t i t e , c a l c i t e , c h l o r i t e , t r e m o l i t e , a l b i t e , s e r c i t e - c a l c i t e , quartz, c h l o r i t e - c a l c i t e , dolomite, t r e m o l i t e - c a l c i t e - dolomite, c a l c i t e , quartz - t a l c , magnesite, c h l o r i t e Quartz sandstone, c h e r t , a r g i l l a c e o u s sandstone. l i k e l y p e l e t i c ( s h a l e , s i l t s t o n e , greywacke). l i k e l y i n t r u s i v e and e x t r u s i v e igneous. Limestone, l i m e -stone w i t h b a s i c igneous i m p u r i -t i e s , limestone-chert mixtures. U l t r a b a s i c i n t r u -s i v e . 74 p e l i t i c sediments r e q u i r e s d e t a i l e d knowledge of t h e i r chemistry. Q u a r t z i t e s are most of t e n derived from quartz sandstone, chert and sometimes v e i n and "sweated" quartz. Where h i g h l y s i l i c e o u s , obvious f o l i a t i o n does not always develop during deformation, however, the presence of p e l i t i c or f e r r u g i n o u s m a t e r i a l and the a c t i o n of metamorphic d i f f e r e n t i a t i o n ( c f . Turner and Verhoogen, I960) produces a d i s t i n c t l a y e r i n g . Such l a y e r i n g may a l s o be produced by f o l d i n g of t h i n interbeds of o r i g i n a l s i l i c e o u s and a r g i l l a -ceous l a y e r s . Mineralogy of p e l i t i c f o l i a e i s i d e n t i c a l to that of m e t a - p e l i t e s . Under c o n d i t i o n s of low-grade r e g i o n a l dynamothermal metamorphism p e l i t i c sediments give r i s e to p h y l l i t e and s c h i s t c o n t a i n i n g p r i m a r i l y quartz, a l b i t e , muscovite, c h l o r i t e , b i o t i t e , and epidote. Basic igneous rocks r e c r y s t a l l i z e to massive or s c h i s t o s e greenstones composed o f - c h l o r i t e , a c t i n o -l i t e , epidote, a l b i t e , b i o t i t e , and sphene under s i m i l a r c o n d i t i o n s . S i l i c e o u s carbonates are metamorphosed to marbles and c a l c - s i l i c a t e s c o n t a i n i n g c a l c i t e , dolomite, t r e m o l i t e , c h l o r i t e and quartz, depending upon what rock types may be present with limestone. Pure c a l c i t e limestone i s not a l -tered m i n e r a l o g i c a l l y by low grade metamorphism. ( P l a t e 4 - l ) . Only one outcrop of what i s b e l i e v e d to be a metamorphosed u l t r a b a s i c i n t r u s i v e rock was observed. The mineralogy of PLATE 4-1 PHOTOMICROGRAPH OF PURE CRYSTALLINE CALCITE MARBLE (SAMPLE 11-4-107) OF UNIT 6a ONE MILE NORTH OF LITHOLOGIC SECTION D. MAGNIFICATION • 76 X. CROSSED NICOLS. PLATE 4-2 PHOTOMICROGRAPH OF LATE KINK BANDS AFFECTING BIOTITE IN FOLIATED PHYLLITIC QUARTZITE OF UNIT FOUR NEAR THE OKANAGAN VALLEY SOUTH OF THE FAIRVIEW GRANO-DIORITE. QUARTZ, CHLORITE, BIOTITE, WHITE MICA. MAGNIFICATION • 18 X. CROSSED NICOLS. 76 such rock (Table 4-1 •) i s explained by Winkler (P. 101. 1967): "B 1.2 Q u a r t z - A l b i t e - E p i d o t e - B i o t i t e Subfacies... "In metamorphised u l t r a b a s i c rocks: t a l c + a c t i n o l i t e + c h l o r i t e + b i o t i t e ± quartz. "In rocks undersaturated with s i l i c a , t a l c i s replaced by serpentine i n the green-s c h i s t f a c i e s . In the presence of a COg-bearing gas phase with an X C Q2 0.05, serpentine reacts with CO2 through-out the greenschist f a c i e s to give r i s e to t a l c + magnesite (see s e c t i o n 4 . l ) . " METAMORPHIC FACIES Observed mineral assemblages i n d i c a t e that r e g i o n a l meta-morphism did not exceed the greenschist f a c i e s grade. Absence of andalusite or kyanite and, except i n a few cases, (mentioned below) of garnet and hornblende, l i m i t the grade to e i t h e r the lower two Barrovian sub-facies (B 1.1 or B 1.2) or the lower Abukuma sub-facies (A l . l ) (Winkler, 1967). The pre-sence of a l b i t e (An 7) provides another l i m i t to the grade (Winkler, p. 101-102, 1967). Hornblende and one sample of garnet ( l i k e l y spessartine) are r e s t r i c t e d to areas near Meso-zoic i n t r u s i v e bodies and are believed to o r i g i n a t e from con-tact metamorphism which atta i n e d the hornblende-hornfels f a c i e s w i t h i n some inner p a r t s , and the a l b i t e - e p i d o t e -ho r n f e l s f a c i e s i n most outer p a r t s , of contact aureoles. Mineralogy of the l a t t e r f a c i e s i s g e n e r a l l y s i m i l a r to B 1.1, B 1.2, and A 1.1 sub-facies (Winkler, 1967) and i t i s 77 impossible e i t h e r to define the extent of low-grade thermal metamorphism or to d i s t i n g u i s h among these three subfacies of r e g i o n a l metamorphism. Temperature and pressure conditions during metamorphism are defined by various r e a c t i o n s which gave r i s e to the observed mineral assemblages. The absence of andalusite or kyanite r e s t r i c t s temperatures to below 500° C at f l u i d ( t o t a l ) pressures between 1 and 4 k i l o b a r s . Further i n d i c a -t i o n of temperature l i m i t s i s provided by Mg/Ca r a t i o s i n c a l c i t e marble. Measured r a t i o s i n d i c a t e that temperatures during c r y s t a l l i s a t i o n of the marble did not exceed 450° C (See Appendix C). Contact metamorphism of the hornblende-hornfels f a c i e s grade takes place at temperatures as high as 580° C to 690° (4 Kb.). In the Kobau Group, the l i m i t e d extent of zones of t h i s f a c i e s as w e l l as the presence of c h l o r i t e c o e x i s t i n g with r e l a t i v e l y small amounts of hornblende suggests that the r e a c t i o n s : C h l o r i t e + t r e m o l i t e + quartz ^ hornblende + a n t h o p h y l l i t e + H 20 C h l o r i t e + t r e m o l i t e + epidote + quartz ^ hornblende + H 20 did not go to completion and that temperatures did not remain above the lower l i m i t s of the hornblende-hornfels f a c i e s ( i e . 520° to 540° C) f o r long. 78 i Metamorphic isograds w i t h i n the map-area presumably e x i s t between B 1.1 and B 1.2 subfacies (Winkler, 1967) and between a l b i t e - e p i d o t e - h o r n f e l s and hornblende-hornfels f a c i e s . Unfortunately, the B 1.1 and 1.2 sub-facies isograd i s masked by a l b i t e - e p i d o t e - h o r n f e l s contact metamorphism which introduces mimetic b i o t i t e . .The hor.nblende-hornfels f a c i e s isograd l i e s west of the Fairview Granodiorite, i n the O l i v e r Septum, and south of the Testalinden Granodiorite (Figure 4 - l ) . Elsewhere i t must be presumed to l i e very near the i n t r u s i v e contacts. RELATIONS BETWEEN STRUCTURE AND METAMORPHISM With the exception noted below, a v a i l a b l e evidence i n -dicates that r e g i o n a l metamorphism of the greenschist f a c i e s was coeval with e a r l y f o l d i n g and shearing. Development of platey and prismatic minerals (micas, c h l o r i t e , t r e m o l i t e / a c t i n o l i t e , etc.) i s p a r a l l e l to F Q / F ^ planes and L^ d i r e c -t i o n s . This development i s not believed to be mimetic because minerals are aligned p a r a l l e l to f o l d axes, rather than at random w i t h i n f o l i a t i o n planes and because many minerals have been deformed by post-metamorphic but p r e - i n t r u s i o n 1 . stresses. Growth of some of these minerals at low angles to F Q / F ^ planes has taken place. This i s a t t r i b u t e d to c r y s t -a l l i z a t i o n along conjugate shear planes produced during closure of ea r l y s t r u c t u r e s , since other evidence (see Pg. 80) METAMORPHIC — " ISOGRADS ***•-.... / fvTJ] IGNEOUS ?'<- INTRUSION MAJOR AXIAL TRACES 0 FIGURE 4-1 HORNBLENDE-HORNFELS FACIES METAMORPHIC ISOGRAD, MOUNT KOBAU. 80 i n d i c a t e s cessation of metamorphism p r i o r to l a t e f o l d i n g . Elongate minerals deformed by l a t e stresses have been ob-served (Plate 4-2), but no r e c r y s t a l l i z e d minerals have been observed p a r a l l e l to such new stru c t u r e s (Fg, kg)' l a t e micro-structures have been formed by mechanical, not chemical processes. In a number of samples, p a r t i c u l a r l y those from contact metamorphic aureoles of the l a r g e r g r a n i t i c i n t r u s t i o n s (see Chapter V) growth of b i o t i t e and hornblende has occurred (Pla t e 4-3). B i o t i t e plates are seen to be aligned p a r a l l e l to Pg as w e l l as F Q / F ^ planes. Such c r y s t a l l i z a t i o n i s believed to be l a r g e l y mimetic as such mineral development i s observed Only near i n t r u s i v e bodies and hornblende c r y s t a l s are oriented w i t h i n f o l i a t i o n planes but are not p a r a l l e l to f o l d axes (L^or Lg). Microscopic s t r u c t u r e s p a r a l l e l and s i m i l a r to l a r g e r features are commonly observed i n t h i n s e c t i o n . Sheared N l e n t i c u l a r f o l i a e and n e a r - i s o c l i n a l f o l d s formed by e a r l y deformation, k i n k i n g of f o l i a t i o n by continued deformation about L^, as w e l l as l a t e f o l d s and kink bands are i l l u s t r a t e d i n P lates 4-4, 5, and 6. PLATE 4-3 PHOTOMICROGRAPH OF MIMETIC HORNBLENDE DEVELOPED ALONG F, /F 0 SURFACES IN CHLORITIC PHYLLITE OF UNIT SIX IN THE CONTACT ZONE OF THE OLIVER GRANITE. CHLORITE, HORN-BLENDE, MINOR QUARTZ, FERRUGINOUS MINERALS. MAGNIFICA-TION 18 X. PLANE POLARIZED LIGHT. PLATE 4 - 4 PHOTOMICROGRAPH OF EARLY FOLD IN FOLIATED GREENSTONE OF UNIT SIX NEAR THE NORTHWESTERN-MOST PART OF THE FAIRVIEW GRANODIORITE. ACTINOLITE, HORNBLENDE, LENTICULAR FOLIAE OF CHLORITE AND QUARTZ, MINOR EPIDOTE AND BIOTITE. MAGNIFICATION: 18 X. PLANE POLARIZED LIGHT. PLATE 4 - 5 PHOTOMICROGRAPH OF KINK BANDS AND BOX FOLDS FORMED BY FINAL STAGES OF EARLY FOLDING IN CHLORITIC PHYLLITE OF UNIT SIX, NEAR THE CLOSURE OF THE SYNFORMAL NAPPE ONE AND ONE-HALF MILES SOUTH OF THE FAIRVIEW GRANO-DIORITE. CHLORITE, FERRUGINOUS MINERALS, SPHENE, MINOR BIO-TITE. MAGNIFICATION: 18 X. PLANE POLARIZED LIGHT. PLATE 4 - 6 PHOTOMICROGRAPH OF LATE SIMILAR FOLDS IN CALCAREOUS CHLORITIC PHYLLITE OF UNIT SIX ON THE QUEEN ELIZABETH I OBSERVATORY ROAD NEAR THE MOUNT KOBAU SUMMIT. BIOTITE, CHLORITE, CALCITE, QUARTZ AND FERRUGINOUS MINERALS. MAGNIFICATION: 1 8 X . PLANE POLARIZED LIGHT. CHAPTER V  IGNEOUS INTRUSIONS INTRUSION PRECEDING EARLY DEFORMATION Rocks of the Kobau Group have been invaded by igneous rocks during at l e a s t four episodes of i n t r u s i o n (Map 2 ) . The e a r l i e s t of these were of two types, basic and u l t r a b a s i c . What are believed to have been basic i n t r u s i v e rocks .possibly of a n d e s i t i c composition (Daly, 1 9 1 2 ) were metamorphosed to a c t i n o l i t i c and c h l o r i t i c , massive and schistose greenstones. Most are f i n e l y c r y s t a l l i n e with platey and prismatic minerals aligned p a r a l l e l to e a r l y f o l i a t i o n and l i n e a t i o n . Sphene commonly develops along such F^ planes together with p y r i t e , magnetite and other ferruginous minerals. Contact r e l a t i o n s h i p s between i n t r u s i o n s and metamorphosed country rocks have been a l t e r e d by e a r l y f o l d i n g and shearing. Possible e f f e c t s of such deformation are i l l u s t r a t e d i n P l a t e s 3 - 1 to 3 - 6 . Dykes and s i l l s are folded and sheared i n t o large lense-shaped bodies which are i n t e r f o l i a t e d with surrounding meta-sediments. One outcrop of metamorphosed u l t r a b a s i c i n t r u s i v e rock has been observed i n apparently conformable contact with c h l o r i t i c greenstone of Unit s i x . In hand specimen brown 8 5 r o u n d e d c r y s t a l s o f m a g n e s i t e up t o one q u a r t e r i n c h a c r o s s a r e s e e n imbedded i n a f i n e m a t r i x o f w h i t e and l i g h t g r e e n t a l c . F o l i a t i o n i s v i s i b l e b u t n o t w e l l d e v e l o p e d . T h i n s e c t i o n e x a m i n a t i o n r e v e a l s t h e p r e s e n c e o f c h l o r i t e i n a d d i t i o n t o t a l c i n t h e m a t r i x t o g e t h e r w i t h m i n o r amounts o f p y r i t e . M a g n e s i t e c r y s t a l s a r e o x i d i z e d s l i g h t l y t o l i m o n -i t e and a r e p r e s u m a b l y s i d e r i t i c t o some e x t e n t . D e v e l o p m e n t o f p r e s e n t m i n e r a l o g y h a s been d i s c u s s e d i n C h a p t e r I V and o r i g i n a l c o m p o s i t i o n may have been t h a t o f a s e r p e n t i n i t e . I t i s p o s s i b l e t h a t c h l o r i t i c g r e e n s t o n e i n c o n t a c t w i t h t h e u l t r a b a s i c i n t r u s i o n has u n d e r g o n e r e a c t i o n s o f r e t r o g r a d e metamorphism f r o m h o r n f e l s t o g r e e n s c h i s t f a c i e s , b u t i f t h i s was t h e c a s e , s u c h r e a c t i o n s must have gone t o c o m p l e t i o n and l e f t no r e l i c m i n e r a l s a s e v i d e n c e . INTRUSION FOLLOWING EARLY DEFORMATION A f t e r t h e e a r l y phase o f d e f o r m a t i o n b u t b e f o r e a t l e a s t p a r t o f t h e l a t e p h a s e , a number o f d y k e s and s i l l s were i n t r u d e d i n t o metamorphosed r o c k s o f t h e Kobau Group. These i n t r u s i o n s have d i s c o r d a n t c o n t a c t s w i t h f o l i a t e d c o u n t r y r o c k s , c o n t a i n x e n o l i t h s o f f o l i a t e d q u a r t z i t e and have n o t u n d e r g o n e g r e e n s c h i s t metamorphism. They were, t h e r e f o r e , e m p l a c e d a f t e r e a r l y d e f o r m a t i o n . On t h e o t h e r hand, t h e y p o s s e s s a f a i n t f o l i a t i o n a n d, i n a t l e a s t one l o c a l i t y i n t h e O l i v e r septum, have been m y l o n i t i z e d , i n d i c a t i n g c r y s t a l l i z a t i o n 86 p r i o r to the onset of l a t e f o l d i n g ( P l a t e 5 - l ) • These rocks contain f e l d s p a r and amphibole phenocrysts set i n a f i n e l y c r y s t a l l i n e matrix of f e l d s p a r , hornblende, b i o t i t e , quartz and ferruginous minerals. Determination of r e l a t i v e proportions of a l k a l i c and c a l c i c f e l d s pars i s ham-pered by extensive a l t e r a t i o n to white mica and epidote, however, the presence of a l k a l i f e l d s p a r phenocrysts and quartz suggests a probable c l a s s i f i c a t i o n of quartz l a t i t e . INTRUSION FOLLOWING LATE DEFORMATION Age Rocks of the two s a t e l l i t e stocks of the Osoyoos Grano-d i o r i t e B a t h o l i t h seen i n the southeastern-most part of the map-area were emplaced a f t e r e a r l y f o l d i n g yet apparently before the completion of subsequent deformation. Contacts with country rocks are concordant generally and l o c a l l y sharply discordant. In the Osoyoos B a t h o l i t h i t s e l f , which l i e s east of the Okanagan V a l l e y , extensive shearing and dynamic metamorphism have been reported by Daly (1912), Camp-b e l l ( l 9 3 l ) and Krauskopf ( l 9 4 l ) . A t t i t u d e s of r e s u l t i n g g n e i s s i c f o l i a t i o n observed by Krauskopf are s i m i l a r to those of Pg planes measured i n the Mount Kobau area and may, there-f o r e , be r e l a t e d to 1'ate stresses. However, Krauskopf (1941, p.16) believed that: PLATE 5-1 PHOTOMICROGRAPHS OF QUARTZ LATITE DYKE LOCALLY MYLONITIZED BY LATE DEFORMATION IN THE OLIVER SEPTUM. MAGNIFICATION^ 18 X. PLANE POLARIZED LIGHT (TOP) AND CROSSED NICOLS (BOTTOM). 88 "The general absence of l i n e a r s t r u c t u r e s , the frequent f a i l u r e of platey s t r u c t u r e s to f o l l o w contacts, the gradational nature of the exposed contacts, a l l suggest that f o l i a t i o n i n the Osoyoos b a t h o l i t h i s not d i r e c t l y r e l a t e d to l a r g e - s c a l e t r a n s i t i o n a l movement but i s due to p a r t i a l granulation and r e c r y s t a l l i z a t i o n i n place." A l t e r e d , granulated and weakly f o l i a t e d quartz d i o r i t e and gra n o d i o r i t e have been observed i n the Osoyoos Granodiorite s a t e l l i t e stocks, but i n s u f f i c i e n t data i s a v a i l a b l e to decide upon the o r i g i n of any s t r u c t u r a l features. Both the Osoyoos and Fairview Granodiorites were considered by Bostock (1940) to be among the older major i n t r u s i o n s i n the Keremeos map-area because they are more sheared and a l t e r e d than e i t h e r the Testalinden of Similkameen Granodiorites (Map 2), xvhich present a f r e s h s t r u c t u r e l e s s appearance. Radiometric age determinations (White, et. a l , 1967, and White, et. a l , 1968) give ages of 110 + 5 m i l l i o n years to the Fairview Granodiorite and 136-144 + 6 m i l l i o n years to the O l i v e r Granite. The l a t t e r i s also s l i g h t l y f o l i a t e d near contacts with Kobau rocks and a l t e r e d , arid furthermore intrudes a body of gr a n o d i o r i t e s i m i l a r to the Testalinden pluton north of the map-area. I t seems probable that presence of a l t e r a t i o n and f o l i a t i o n may be due • more to conditions present during and a f t e r emplacement rather than age. Numerous small stocks of d i o r i t i c composition crop out i n western parts of the map-area (Map 2). They are s i m i l a r to 89 d i o r i t i c phases of the Osoyoos and Fairview plutons and may be contemporaneous with them (Bostock, 1940). Generally, a l l major a c i d i c i n t r u s i o n s i n the Kobau map-area are believed to be r e l a t e d to T r i a s s i c (?) - J u r a s s i c Nelson i n t r u s i o n s ( L i t t l e , 196l) . Composition As l i t t l e d e t a i l e d study has been made of i n t r u s i v e rocks i n the map-area much information has been drawn from work by Daly, Campbell, Bostock, Krauskopf and Richards. The Osoyoos s a t e l l i t e plutons are comprised of quartz d i o r i t e and gran o d i o r i t e with some d i o r i t i c phases. Outcrops i n the map-area are p r i m a r i l y a l t e r e d quartz d i o r i t e containing f e l d s p a r , pseudomorphs of amphibole and quartz. Extensive hydrothermal a l t e r a t i o n has produced c h l o r i t e and epidote from mafic minerals and a l b i t e with f i n e s e r i c i t e , c a l c i t e and e p i -dote from other f e l d s p a r s . Sphene, magnetite and a p a t i t e are common accessory minerals. Krauskopf (1941, p. 20) stated that t h i s quartz d i o r i t e : "...resembles the hydrothermally a l t e r e d rocks o c c a s i o n a l l y found along the margin of the Osoyoos b a t h o l i t h , but (that) i t d i f f e r s markedly from normal Osoyoos types.", however he nonetheless believed (p. 52) l i k e Daly (1912) and Bostock (1940) that these i n t r u s i o n s were g e n e t i c a l l y r e l a t e d . The Fairview Granodiorite i s s i m i l a r t e x t u r a l l y and m i n e r a l o g i c a l l y to the Osoyoos stocks and although g e n e r a l l y 90 le s s a l t e r e d and f o l i a t e d , i s also considered to be r e l a t e d to the Osoyoos B a t h o l i t h . The Testalinden Granodiorite i s composed of unaltered, homophanous, f i n e to medium grained g r a n o d i o r i t e containing zoned p l a g i o c l a s e ( o l i g o c l a s e - a n d e s i n e ) , m i c r o c l i n e and quartz with large c r y s t a l s of b i o t i t e and hornblende. Accessory minerals are sphene, epidote, a p a t i t e and i r o n ore. Both a s c h i s t i c and d i a s c h i s t i c dykes, i n c l u d i n g pegmatite, lampro-phyre and d i o r i t e and gra n o d i o r i t e porphyry have been noted i n the f i e l d but not mapped i n d e t a i l . The Testalinden stock i s compositionally and t e x t u r a l l y very s i m i l a r to the Similkameen Granodiorite which crops out south of Richter Mountain and west of the Similkameen V a l l e y . Contact metamorphism of country rocks by these two i n t r u s i o n s i s also s i m i l a r , r e s u l t i n g i n hard, black hornfelses of the hornblende-hornfels f a c i e s grade, and they are believed to be g e n e t i c a l l y r e l a t e d (Bostock, 1940). The O l i v e r Granite i s a three phase i n t r u s i o n of granite and/or quartz monzonite and associated dykes. In a recent study, Richards (l968) s t a t e s : "... the O l i v e r quartz monzonite was formed by i n t r u s i o n s of g r a n i t i c magma i n the mesozone. The i n t r u s i o n a s s i m i l a t e d much of the metamorphosed Kobau sediments ( s i c ) and produced the contact biotite-hornblende quartz monzonite and the more c e n t r a l p o r p h y r i t i c quartz monzonite. A resurgence of the magma which formed the above two rock types produced the c e n t r a l muscovite-garnet quartz monzonite." 91 Dykes of younger phases cut older phases. In a d d i t i o n , large and small quartz veins and lamprophyre dykes cut e a r l i e r i n t r u s i o n s . Mode of Emplacement A l l of the observed major igneous bodies w i t h i n the map-area were formed by emplacement and c r y s t a l l i z a t i o n of magma. Evidence of stoping, c r o s s - c u t t i n g and i n t e r f i n g e r i n g of country rocks by i n t r u s i o n s has been observed along most exposed' contacts (Figure 5-1, Plates 5-2,3). In a few l o c a l i t i e s , p a r t i c u l a r l y near some small d i o r i t e stocks, molten mat e r i a l has i n t i m a t e l y mixed with and metasomatised p h y l l i t i c country rocks. R e c r y s t a l l i z a t i o n of p h y l l i t e and s c h i s t has taken place and i n such cases the contact i s a zone progressing from d i o r i t e to contaminated i n t r u s i v e , p a r t i a l l y r e c r y s t a l l i z e d p h y l l i t e and f i n a l l y hornfelsed meta-sediment. A s s i m i l a t i o n of country rock by magma has taken place i n the O l i v e r Granite (Richards, 1968). Igneous i n t r u s i o n r e s u l t e d i n t e c t o n i c i n t e r a c t i o n between deformed and metamorphosed Kobau Group rocks and i n t r u d i n g magma. Movement of magma may have been c o n t r o l l e d i n part by northwesterly-trending l a t e s t r u c t u r e s . Such c o n t r o l could have produced stocks elongated ( i n plan view) i n t h i s d i r e c t i o n . Such elongation i s most evident i n the Testalinden and Osoyoos FIGURE 5-1. SKETCH FROM PHOTOGRAPH OF C O N T A C T OF T H E T E S T A L I N D E N GRANODIORITE WITH B L A C K AND LIGHT GREEN PHYLLITE OF UNIT SIX. N O T E THE S T O P E D B L O C K AND INTER FOLIAT ION OF INTRUSION AND M E T A S O M A T I S E D COUNTRY ROCK (STIPPLED) . HAMMER IS ONE FOOT LONG. PLATE 5-2 I N C L U S I O N O F M E T A S O M A T I S E D P H Y L L I T E IN A SMALL D I O R I T E S T O C K IN T H E S I M I L K A M E E N VALLEY N O R T H W E S T O F T H E S U M M I T O F M O U N T K O B A U . N O T E T H E G R A N U L A R T E X T U R E OF T H E P H Y L L I T E I N D I C A T I N G R E C R Y S T A L L I Z A T I O N A N D T H E L I G H T , F I N E L Y C R Y S T A L L I N E C H I L L E D Z O N E A R O U N D T H E R I G H T C O R N E R O F T H E I N C L U S I O N . PLATE 5-3. CONTACT OF A LARGE GRANODIORITE DYKE NORTHWEST OF THE TESTALINDEN GRANODIORITE WITH SILICEOUS FOLIATED GREEN-STONE (A MINOR MEMBER OF UNIT FIVE). NOTE SMALL D 2 FOLDS TO RIGHT OF HAMMER, INJECTED APLITE VEINLETS (LOWER RIGHT CORNER), AND LATE JOINTS (DIPPING TO LEFT) WHICH CUT COUNTRY ROCK AND INTRUSIVE. 9 5 s a t e l l i t e bodies and i s also seen i n the s t r a i g h t west-northwest trending border of the O l i v e r Granite and the sub-p a r a l l e l northeastern and southwestern contacts of the Fairview Granodiorite. The e f f e c t of e a r l y s t r u c t u r e s i s d i f f i c u l t to assess since these were reoriented by l a t e f o l d i n g p r i o r to i n t r u s i o n . In some areas, however, i n t e r f i n g e r i n g of i n t r u s i o n and country rock has taken place along F Q/F planes. This i s p a r t i c u l a r l y evident i n the O l i v e r Granite contact zone (Map 2 ) . Igneous i n t r u s i o n also produced new structures i n country rocks. In many areas e a r l y f o l i a t i o n (F 0/F^) i s concordant with i n t r u s i v e contacts suggesting warping of these planes to con-form to the igneous mass. Concordant contacts are present around the Osoyoos Granodiorite stocks, the south and southwest parts of the Testalinden Granodiorite, the southeast and north-east contacts of the Fairview stock and along the whole of the south-southeastern contact of the O l i v e r Granite. Only a part of the contact zone of the northern Osoyoos Granodiorite stock i s exposed. Where seen, however, no accom-odation s t r u c t u r e s such as fans of t e n s i o n a l cross j o i n t s or steeply plunging f o l d s have been observed. F 0/F^ planes north-northeast and south-southwest of t h i s stock s t r i k e east to east-southeast, dipping southerly and the exposed form of the pluton 96 suggests emplacement as a p a r t i a l l y concordant i n t r u s i o n . No obvious accommodation s t r u c t u r e s appear to be a s s o c i -ated with the T e s t a l i n d e n G r a n o d i o r i t e . Discordant contacts suggest movement by melting, stoping or a s s i m i l a t i o n c o n t r o l l e d only i n part by s t r u c t u r e s w i t h i n country rocks. A d i s t i n c t lineament, which may represent a p o s t - i n t r u s i o n f a u l t , marks the western l i m i t of the T e s t a l i n d e n p l u t o n . Contacts have not been observed i n t h i s area and s t r u c t u r a l r e l a t i o n s h i p s are unknown. Gen e r a l l y concordant r e l a t i o n s h i p s between the Fair v i e w G r a n o d i o r i t e and Kobau rocks imply emplacement at exposed l e v e l s by deformation of surrounding rocks and gross movement of magma p a r a l l e l to e x i s t i n g s t r u c t u r e s . L o c a l l y , f o l i a t i o n vfithin the g r a n o d i o r i t e i s p a r a l l e l to contacts i n d i c a t i n g flow of par-t i a l l y c r y s t a l l i z e d m a t e r i a l p a r a l l e l to them. Such movement may be caused by convective flow i n boundary l a y e r s of the pluton (Lacy, I960). Formation of the Fair v i e w dome (Chapter I I I ) may be r e l a t e d i n part to emplacement of t h i s stock, however apart from p o s s i b l y f o r t u i t o u s coincidence of i n t r u s i o n and dome, no evidence has been observed that supports such a r e l a t i o n s h i p . The O l i v e r Granite was emplaced by a s s i m i l a t i o n of country rock, upward movement of magma along Fo/F^ planes and def o r -mation of bordering metamorphic rocks. Richards (1968) i n d i -cated that a s s i m i l a t i o n produced a border phase of b i o t i t e - h o r n -91 blende quartz monzonite from a parent muscovite quartz mon-zonite. Considerable i n t e r f o l i a t i o n of i n t r u s i o n and country rock w i t h i n one-quarter mile of the southern margin of the stock has been observed. S t r i n g e r s of metasediment are found w i t h i n the pluton and s i l l s of quartz monzonite intrude Kobau rocks. Accom-panying such emplacement was considerable f o r c e f u l i n t r u s i o n r e s u l t i n g i n southerly d i r e c t e d s t r e s s . A number of examples of steeply plunging accommodation f o l d s have been observed and the overturned l a t e synform (Chapter I I I ) i n the O l i v e r septum i s believed to have been tightened by a combination of v i s e -l i k e forces stemming from emplacement of both O l i v e r and Fairview plutons. S t r u c t u r a l e f f e c t s of many small d i o r i t e stocks seen i n western parts of the map-area are d i f f i c u l t to assess. Near the summit of Mount Kobau e a r l y and l a t e mesoscopic str u c t u r e s are reoriented i n a manner which cannot be analysed with a v a i l a b l e data. Such deformation may be a r e s u l t of doming i n response to i n t r u s i o n of the d i o r i t e body which crops out ju s t northwest of the summit. Presence of numerous small stocks of s i m i l a r composition suggests that they belong to one or more l a r g e r parent plutons underlying the Kobau Group. I f t h i s i s the case, r e l a -t i v e l y l i t t l e s t r u c t u r a l evidence of such bodies e x i s t s . 98-General spread of s t r u c t u r a l data (Chapter I I I ) which could be caused by subsurface a r c h i n g and accommodation, i s more l i k e l y explained by p o s t - t e c t o n i c f a u l t i n g and o r i g i n a l v a r i a -t i o n s i n e a r l y and l a t e s t r u c t u r e s . I n t r u s i o n and c r y s t a l l i z a t i o n of a l l major g r a n i t i c stocks i n the map-area reached i t s culmination at l e v e l s i n the crust where surrounding temperature and pressure c o n d i t i o n s correspond to depths of 5 to 9 miles, i e . the mesozone. With the exception of the T e s t a l i n d e n G r a n o d i o r i t e , which may have been intruded at somewhat higher l e v e l s (upper mesozone - lower epizone), i n t r u s i o n s discussed p r e v i o u s l y possess c h a r a c t e r -i s t i c s t y p i c a l of mesozonal plutons as defined by Buddington (1959): "The degree of metamorphism of the r e g i o n a l country rock i s not more intense that the g r e e n - s c h i s t and epidote-amphibolite f a c i e s The i n f e r r e d temper-ature of the country rock at the timg of i n t r u s i o n i s g e n e r a l l y no higher than 400 -500 C. ...The c h a r a c t e r i s t i c plutons have complex emplacement r e l a t i o n s h i p s to the country rock - in. part d i s c o r -dant . i n part concordant. L o c a l l y there may be some replacement. ... Planar f o l i a t i o n i s often w e l l developed, e s p e c i a l l y i n outer p o r t i o n s of the pluton .... U p l i f t of the roof may be i n f e r r e d . " Basalt dykes c u t t i n g Kobau rocks have been observed i n one outcrop immediately southwest of the map-area i n the Similkameen V a l l e y ( P l a t e 5-4). These are dark grey, un-a l t e r e d s u b - p o r p h y r i t i c o l i v i n e b a s a l t with small p l a g i o c l a s e 99 phenocrysts and may be feeders f o r T r i a s s i c or older b a s a l t flows and s i l l s of the Old Tom Formation or f o r b a s a l t i c lavas of the Marron Formation of Eocene age (Bostock, 1940). The l a t t e r i s more l i k e l y as these dykes have not undergone any deformation. However, no o l i v i n e basalt i s reported i n sub-divisions of the Marron Formation (Church, 1967) and t h e i r age and c o r r e l a t i o n must await f u r t h e r study. YOUNGEST INTRUSION Youngest i n t r u s i o n s i n the map-area are dacite and lamprophyre dykes. The f i r s t of these, and the most common, cut Kobau metamorphic rocks and Mesozoic i n t r u s i o n s and often appear to p a r a l l e l l a t e f a u l t s of probably T e r t i a r y age. Dykes are d i s t i n c t i v e i n outcrop (Plate 5-5) ; massive, white to l i g h t grey i n colour and contain small hornblende, p l a g i o c l a s e and oc c a s i o n a l l y quartz phenocrysts i n a matrix of p l a g i o c l a s e and c h l o r i t e m i c r o l i t e s set i n muscovite, leucoxene and quartz. P l a g i o c l a s e ( a l b i t e ?) i s zoned and together with other minerals i s h i g h l y a l t e r e d . Feldspars are a l t e r e d to white mica, mafic minerals to c h l o r i t e , epidote and i r o n ore. The matrix i s cut by carbonate v e i n l e t s . The o r i g i n of these dykes i s unknown, however, i t i s possible that they are r e l a t e d to l a t e phases of PLATE 5-4 T E R T I A R Y (?) B A S A L T D Y K E C U T T I N G F O L I A T E D A R G I L L A C E O U S Q U A R T Z I T E OF T H E K O B A U G R O U P W E S T OF R I C H T E R M O U N T A I N . F O L I A T I O N A T T I T U D E 0 9 8 ° / 7 9 ° S . D Y K E A T T I T U D E 0 3 2 ° / 5 5 ° NW. F E E T 101 Mesozoic i n t r u s i o n s described e a r l i e r . Only one example of a young lamprophyre dyke i s known. This b i o t i t e - a u g i t e lamprophyre cuts the O l i v e r Granite and has been dated r a d i o m e t r i c a l l y at 53 + 2 m i l l i o n years (White, et. a l . , 1968). Other lamprophyre dykes, believed to be r e l a t e d to Mesozoic' i n t r u s i o n s may i n f a c t be of s i m i l a r age but have not as yet been r a d i o m e t r i c a l l y dated. P L A T E 5-5 OUTCROP OF DACITE DYKE ON THE NORTHWEST SLOPE OF MOUNT KOBAU. BLIND CREEK IN THE BACKGROUND, NOTE THE MASSIVE APPEARANCE AND BLOCKY JOINT-ING. EXPOSED THICKNESS ABOUT TEN FEET, ATTITUDE 175°/35° W. CHAPTER VI INTERPRETATION AND CONCLUSIONS AGE AND CORRELATION Introduction The h i s t o r y of the Kobau Group begins with d e p o s i t i o n of a t h i c k succession of quartz sandstone, greywacke, s i l t -stone and shale. Deposition was accompanied 'by i n t r u s i o n and extrusion of basic igneous rock. Chert may have formed together with submarine extrusion and minor amounts of limestone were deposited e i t h e r as d e t r i t a l m a t e r i a l or as small scale reef growth. The t o t a l thicknes.s of the observed succession, from shales and impure quartz sandstone of Unit one to s i m i l a r sand-stone of Unit nine, i s d i f f i c u l t to estimate. The present thickness obtained from various measured sections (Chapter I I and Appendix) i s between 5500 and 6500 f e e t . Any r e l a t i o n to pre-tectonic thickness i s hi g h l y c o n j e c t u r a l but the combined actions of thickening because of t i g h t f o l d i n g and th i n n i n g as a r e s u l t of shearing and flow f o l d i n g are not l i k e l y to change the order of magnitude. O r i g i n a l thickness quite prob-ably did not exceed 5000 f e e t . 104 P r i o r to or concurrent with deformation and metamor-phism, i n t r u s i o n of a small u l t r a h a s i c body took place. Emplacement may have been by cold i n t r u s i o n as no contact metamorphic e f f e c t s have been observed. Such e f f e c t s p o s s i b l y were o b l i t e r a t e d by l a t e r metamorphism. Time of deposition can only be determined on the b a s i s of s t r u c t u r a l and l i t h o l o g i c evidence. Taken by i t s e l f , the Kobau Group i s known to be older than 140 m i l l i o n years (pre-Cretaceous) because of radiometric ages of i n t r u s i o n s that cut the group. Northwest of B l i n d Creek (Figure 1-3) the group i s i n f a u l t contact with f o s s i l i f e r o u s limestone (Angold, 1957) of the B l i n d Creek Formation. L i t t l e d e t a i l e d work has been done here; f o s s i l ages are given as e i t h e r Permian (Bostock, 1940) and/or Pennsylvanian (McGugan, et. a l . , 1963). Brachiopods and f u s i l i n i d s have been t e n t a t i v e l y dated as lower Pennsylvanian (K. Sada, R.Y. Best, personal communi-; ca t i o n , 1969), whereas Danner (McGugan, et. a l . , 1963) suggests a probable Upper Carboniferous to lower Permian age. Presence of f o s s i l s , f a u l t i n g and b r e c c i a t i o n as w e l l as v i r t u a l absence of f o l d s (R.V. Best, personal communication, 1969) suggests that these limestones did not undergo extreme deformation and metamorphism that a f f e c t e d the Kobau Group. Thus, the l a t t e r i s presumably at l e a s t pre-Pennsylvanian i n age. Support f o r t h i s age l i m i t comes from p o s s i b l y 105 c o r r e l a t i v e successions found south and north of Mount Kobau. The Anarchist Group Previous mapping suggests that the Kobau and Anarchist Groups, at l e a s t i n the Okanagan V a l l e y , are one and the same. L i t h o l o g i e s are very s i m i l a r and both groups have been deformed and metamorphosed. South and southeast of Kruger Mountain the two names have been applied to the same rocks. Reconnaissance traverses by the author i n t h i s area confirm t h i s i n t e r p r e t a t i o n . F o s s i l s obtained from the Anarchist Group are l i k e l y Permian and po s s i b l y Carboniferous i n age (Waters and Krauskopf, 194l) and other f o s s i l s found near Greenwood and Grand Forks give Permian and/or e a r l i e r ages f o r lower Anarchist formations. Three-fold sub-divisions of the Anarchist Group have been made (Umpleby, 1911; Waters and Krauskopf, 194l) but no s t r u c -t u r a l mapping or a n a l y s i s accompanies these and c o r r e l a t i o n of each s u b - d i v i s i o n i s therefore u n r e l i a b l e . Calcareous shale, bedded limestone and greenstone of Middle Anarchist rocks have been observed by the author near Blue Lake west of O r o v i l l e (Figure 1-3). These have been folded at l e a s t once and bedding, not f o l i a t i o n i s observed (P l a t e 6 - l ) . Part of the Anarchist Group has undergone at l e a s t two periods of deformation (the PLATE 6-1 RECUMBENT CLOSE FOLDS IN THIN AND THICK BEDDED ARGILLACEOUS LIMESTONE AND CALCAREOUS SHALE OF THE ANARCHIST GROUP NEAR BLUE LAKE ABOUT SEVEN MILES WEST-SOUTHWEST OF OROVILLE, WASHINGTON. PHOTOGRAPHS FACE NORTHWESTERLY, APPROXIMATELY DOWN-AXIS. 0 40 t i 1 i i FEET 107 f i r s t very severe, i . e . e a r l y Kobau) while the rest has undergone but one (presumably l a t e Kobau). More d e t a i l e d mapping should reveal an unconformity w i t h i n successions presently known as Anarchist Group. Erosion i s suggested by the presence of conglomerate w i t h i n middle and lower Anarchist rocks (Waters and Krauskopf, 194l). I t i s l i k e l y , although not c e r t a i n , that a v a i l a b l e f o s s i l s have been found i n l e s s h i g h l y deformed parts and that these were deposited over already deformed Kobau rocks. The age of the Kobau Group i s therefore again implied to be pre-Permian, p o s s i b l y pre-Carboniferous. The Shuswap Complex Parts of the h i g h l y deformed and metamorphosed Shuswap complex (Vaseaux Formation) crop out w i t h i n two to three miles of the exposed northern l i m i t of the Kobau Group. This formation, c o r r e l a t e d with the Monashee Group found near Vernon ( L i t t l e , 1961; Jones, 1959) has been deformed at l e a s t f i v e times and undergone major i n t r u s i o n three times (Ross and C h r i s t i e , 1969). Comparison of deformation, associated metamorphism and igneous i n t r u s i o n i n the Kobau Group and Vaseaux Formation (Table 6-l) suggests that the Kobau Group was deposited over deformed and at l e a s t p a r t i a l l y metamorphosed Vaseaux rocks p r i o r to second 108 deformation of that formation. No separation of metamorphism has been observed between f i r s t and second phases of defor-mation i n Vaseaux rocks (Ross and C h r i s t i e , 1969) however such separation could w e l l be obscured by high grade meta-morphism accompanying the second phase. What may be the s t r a t i g r a p h i c a l l y uppermost group of the Shuswap Complex crops out i n a n o r t h e r l y - t r e n d i n g zone zpprox-imately 25 miles west of Vernon (Figure 3-l)• Jones (pp. 27, 28, 1959) describes the l i t h o l o g y of t h i s , the Chapperon Group thus l y : " A r g i l l a c e o u s sedimentary rocks or t h e i r meta-morphosed equivalents comprise the greatest part of the assemblage but rocks probably of vo l c a n i c o r i g i n are also common. "... a r g i l l a c e o u s rocks are ... black coarsely bedded ... other(s) ... are grey ... t h i n bedded or platey ... commonly calcareous ... a l l ... contain f i n e f l a k e s of s e r i c i t e . "... q u a r t z i t e s are a r g i l l a c e o u s ... t h i n bedded ... very f i n e grained ... l i g h t to dark grey ... others are t h i c k bedded, f i n e grained and colour banded ... grey and blue-grey. "... limestone i s white, massive, t h i c k bedded, and blue-grey weathering ... i n beds as much as f i v e feet t h i c k ... d i s t r i b u t e d among a r g i l l a c e o u s rocks and green s c h i s t s . "... green s c h i s t s ... are f i n e l y bedded ... others contain no sign of bedding ... h i g h l y calcareous ... contain t h i n carbonate l a y e r s between f o l i a t i o n planes." 109 Table 6-1 Kobau Group Vaseaux Formation Deposition of the Kobau Group Near i s o c l i n a l f o l d i n g and associated metamorphism. Trend of L^: n o r t h e r l y Near i s o c l i n a l f o l d i n g and m y l o n i t i z a t i o n . Metamorphism to uppermost almandine amphibolite f a c i e s . Trend of L 0: lltt°-135°. 2 I n t e r - or syntectonic i n t r u s i o n of granite gneiss Near i s o c l i n a l f o l d i n g and shearing. Metamorph-ism to greenschist f a c i e s . Trend of L^: e a s t e r l y . Overturned and normal f o l d s . Trend of L 0: 120°-140°. 2 Overturned and normal f o l d s . Trend of L^: 090°-130°. Doming and gentle f o l d -i n g . Trend of L_: no r t h e r l y . P o s s i b l y contemporaneous with Gentle warping. Several trends of L. i n c l u d i n g : n o r t h e r l y . J u r a s s i c - Cretaceous i n t r u s i o n . J u r a s s i c - Cretaceous i n t r u s i o n . 110 Jones a l s o s t a t e s (op. c i t . , p. 28): "The Chapperon group has not been sub-d i v i d e d i n t o formations because of the complexity of i n t e r n a l s t r u c t u r e s . . . " and: "... the Chapperon group ( i s ) ... cut by s e r p e n t i n i z e d u l t r a m a f i c dykes of the Old Dave i n t r u s i o n s . " L i t h o l o g i c s i m i l a r i t i e s between Kobau and Chapperon Groups are marked, and support p o s s i b l e c o r r e l a t i o n . No s t r u c t u r a l a n a l y s i s of Chapperon Group s t r u c t u r e s has been done and i t s r e l a t i o n s h i p s to the Mount Ida and Monashee Groups i s u n c e r t a i n , although Jones (l959) p o s t u l a t e d a p o s s i b l e equivalence with the uppermost formation of the Mount Ida Group. A t e n t a t i v e Carboniferous or Permian age has been assigned t h i s group on the b a s i s of observed c r i n o i d stems (Campb e l l , 1966). The Chapperon Group i s o v e r l a i n unconformably by a r g i l l i t e of what may be the lowermost d i v i s i o n of the Permian and Pennsyl-vanian (?) Cache Creek Group (Jones, 1959; Preto, 1964; Schau, 1968). I f c o r r e l a t i o n can be extended between Kobau and Chapperon Groups, such' a r e l a t i o n s h i p provides a d d i t i o n a l i n d i -c a t i o n of a pre-rPermian, Carboniferous (?) age f o r the former. O r i g i n and ages of s t r a t a , metamorphism and deformation of the Shuswap Complex are not as yet agreed upon. Ages of I l l s t r a t a are b e l i e v e d by some to be pre-Cambrian (Dawson, 1879; Daly, 1915; Jones, 1959), by others to range from l a t e pre-Cambrian to p o s s i b l y Mesozoic (Brock, 1934; Cairnes, 1939; Wheeler, 1965, 1966: Hyndman, 1964, 1968) or Palaeozoic (McConnell and Brock, 1904; Gunning, 1928; Reesor, 1957; Ross, 1968). Estimates of time of deformation and metamorphism are a l s o i n d i s p u t e . Culmination of s y n t e c t o n i c metamorphism may have taken place during the f i r s t p e r i o d of f o l d i n g (Jones, 1959 5- Wheeler, 1966) and/or with the second period (Ross, 1968) Some metamorphism may have post-dated deformation ( G a b r i e l s e and Reesor, 1964)• Folds apparently s i m i l a r to Shuswap e a r l i e s t s t r u c t u r e s have been observed w i t h i n Mesozoic succes-sions (Hyndman, 1964, 1968; Cairnes, 1939) and r a d i o m e t r i c ages of mantled gneiss domes w i t h i n the complex ( G a b r i e l s e and Reesor, 1964; Reesor, 1965), i n d i c a t e Mesozoic or younger meta-morphism p o s s i b l y accompanied by extensive deformation. Wheele (p. 37, 1966) s t a t e s : "The e a r l i e s t recognized s t r u c t u r e s i n the complex are warps and i s o c l i n a l , recumbent s t r u c t u r e s developed along east-west axes. S i m i l a r l y o r i e n t e d s t r u c t u r e s a l s o occur i n low-grade metamorphic rocks of T r i a s s i c and Lower J u r a s s i c age j u s t east of the complex ... t h e r e f o r e ... e a r l y s t r u c t u r e s i n the Shuswap developed i n post E a r l y J u r a s s i c time." 112 Preto (1967) supported such ah i n t e r p r e t a t i o n of s t r u c t u r a l h i s t o r y f o r rocks of the Shuswap Complex i n the Grand Porks area hut hinted at the p o s s i b i l i t y of a s t i l l e a r l i e r (mid-Palaeozoic) period of deformation. In the Vaseaux Formation, immediately across the Okanagan Valley from outcrops of the Kobau Group, e a s t e r l y -trending s t r u c t u r e s are not the e a r l i e s t , therefore e a r l i e s t f o l d i n g i n the Shuswap Complex may have taken place i n pre-Permian ( M i s s i s s i p p i a n (?)) time, r e s u l t i n g s t r u c t u r e s (recumbent nappes) being refolded sometime during the Permian and again i n the e a r l y J u r a s s i c (Ross and K e l l e r h a l s , 1968) . Such d i f f e r e n c e s i n i n t e r p r e t a t i o n of r e g i o n a l t e c t o n i c s suggests that c o r r e l a t i o n of periods of deformation over large areas by comparison of s t r u c t u r a l trend may be u n r e l i a b l e , e s p e c i a l l y when two periods of n e a r - i s o c l i n a l f o l d i n g are pre-sent and when trends of e a r l y structures p o s s i b l y vary over large areas. S o l u t i o n of such r e g i o n a l i n c o n s i s t e n c i e s i s beyond the scope of t h i s t h e s i s and must be l e f t u n t i l f u r t h e r d e t a i l e d s t r u c t u r a l a n a l y s i s has been made of the areas i n question. The Cache Creek Complex Parts of the Cache Creek Group found i n western and c e n t r a l parts of the C o r d i l l e r a may be of Pennsylvanian age (McGugan, 113 et. a l . , 1963) and are t h e r e f o r e p o s s i b l e c o r r e l a t i v e s of the Kobau Group. L i t t l e s t r u c t u r a l a n a l y s i s of the Cache Creek Group has been done and r e l a t i o n s h i p s with rocks of s i m i l a r age are g e n e r a l l y unknown. In the Kamloops area, Cache Creek rocks of Pennsylvanian (.Morrowan) age (Danner and N e s t e l l , 1966) are b e l i e v e d to contain e a r l i e s t i s o c l i n a l Shuswap s t r u c -tures (Ross and K e l l e r h a l s , 1968) i n d i c a t i n g a p o s t - E a r l y Pennsylvanian age f o r the Kobau Group, but l i t t l e i s known of these and they may i n f a c t be e a r l y Kobau i s o c l i n a l f o l d s . DEPOSITIONAL ENVIRONMENT Depo s i t i o n of a mixed succession of pure and impure c l a s t i c sediments and v o l c a n i c rock can take place i n a number of p o s s i b l e environments. In a d d i t i o n , t e c t o n i c " b l u r r i n g " of sedimentary environments (Krumbein and S l o s s , pp. 428, 429, 1963) makes i n t e r p r e t a t i o n somewhat u n r e l i a b l e . Nonetheless, comparisons with successions t y p i c a l of v a r i o u s basins of s e d i -mentation suggests the Kobau Group has some a f f i n i t y with syn-orogenic g e o s y n c l i n a l sediments (greywacke s u i t e ) . These are c h a r a c t e r i z e d by greywacke, shale and t u r b i d i t e sandstone de-p o s i t e d i n g e n e r a l l y shallow to moderately deep marine b a s i n s . S p i l i t i c and pillowed greenstones and b a s i c t u f f s , formed during sedimentation, are a s s o c i a t e d with greywackes. Lime-114 stones are r a r e . Upper parts of t y p i c a l successions contain a higher p r o p o r t i o n of sandstone, and grade i n t o deposits of c o n t i n e n t a l o r i g i n ( P e t t i j o h n , pp. 615-622, 1957). Such a general c l a s s i f i c a t i o n i s of l i m i t e d use i n s p e c i f i c areas but i n d i c a t e s p o s s i b l e c o n d i t i o n s present during d e p o s i t i o n . The Kobau Group resembles upper parts of the greywacke s u i t e and was presumably deposited i n water of shallow to moderate depth i n a synorogenic environment. Broad r e g i o n a l s t u d i e s of g e o t e c t o n i c s of the Western C o r d i l l e r a suggest eugeosynclinal d e p o s i t i o n east of the Okanagan V a l l e y during l a t e P a l a . e o z o i c - e a r l i e s t Mesozoic time (Yates, e t . a l . , 1966). Late Palaeozoic subsidence i n c e n t r a l B r i t i s h Columbia was b e l i e v e d to have i n i t i a l l y produced " . . . l o c a l and probably i s o l a t e d b a s i n s . . . " (White, p. 70, 1959) which coalesced to form the d e p o s i t i o n a l s i t e of the Cache Creek Complex. I n t e r -p r e t a t i o n of the course of deformation of the Kobau Group (Chapter I I I ) and of the adjacent Shuswap Complex (Ross and C h r i s t i e , 1969) suggests sporadic development of basins of de-p o s i t i o n coeval with f o l d i n g , w i t h i n a l a r g e s c a l e eugeosyn-c l i n a l s e t t i n g . Kobau sediments may have been derived from r i s i n g nappe s t r u c t u r e s developed during e a r l i e s t Shuswap f o l d i n g east of the Okanagan V a l l e y and p o s s i b l y from western sources now buried by Permian and Mesozoic successions. STRUCTURAL HISTORY The P r o h l e m o f E a r l y D e f o r m a t i o n P r e s e n c e o f e x t r e m e s h e a r i n g and t i g h t f o l d i n g i n t h e Kobau Group and i t s p r o x i m i t y t o t h e V a s e a u x F o r m a t i o n s u g g e s t t h e p o s s i b i l i t y o f a phase o f d e f o r m a t i o n p r i o r t o e a r l y Kobau ( i . e . e a r l i e s t Shuswap) h a v i n g a f f e c t e d t h e f o r m e r . E v i d e n c e f o r s u c h a phase w o u l d n e c e s s a r i l y be s c a n t y b e c a u s e o f de-s t r u c t i v e e f f e c t s o f e a r l y Shuswap f o l d i n g a t h i g h s t r u c t u r a l l e v e l s . No a t t e n u a t e d f o l d s w i t h n o r t h e r l y t r e n d i n g a x e s have been o b s e r v e d , e x c e p t where t h e y a r e t h e r e s u l t o f r e o r i e n t a t i o n o f e a s t e r l y s t r u c t u r e s by r e f o l d i n g . ( e . g . E a s t - n o r t h e r n and c e n t r a l s u b - d o m a i n s , F i g u r e 3 - 2 ) . No i s o c l i n a l l y r e f o l d e d t i g h t f o l d s have been s e e n . N o r t h - n o r t h w e s t e r l y t r e n d i n g l i n e a -t i o n s r e l a t e d t o t i g h t f o l d i n g a r e l i k e l y c a u s e d by r e o r i e n -t a t i o n as a r e s u l t o f l a t e r f o l d i n g . S uch n e g a t i v e e v i d e n c e i s n a t u r a l l y n ot c o n c l u s i v e , however on t h e b a s i s o f d a t a g a t h e r e d i n t h i s s t u d y , t h e Kobau Group i s n o t b e l i e v e d t o have p a r t i c i -p a t e d i n e a r l i e s t Shuswap d e f o r m a t i o n . E a r l y F o l d i n g D e f o r m a t i o n of t h e Kobau Group l i k e l y began d u r i n g depo-s i t i o n o f t h e o b s e r v e d s u c c e s s i o n . The a p p a r e n t p a t t e r n o f c o n t i n u e d and s i m u l t a n e o u s d e f o r m a t i o n and d e p o s i t i o n e v i d e n t 116 i n t h i s area during l a t e Palaeozoic time suggests a r e l a t i v e l y short chronological break between e a r l i e s t Shuswap f o l d i n g and deposition of the Kobau Group over deformed (and l i k e l y de-forming) rocks of the Vaseaux Formation. V a r i a t i o n i n s t r u c t u r a l trend from one period of defor-mation to another i s d i f f i c u l t to ex p l a i n . Northerly-trending e a r l i e s t Shuswap st r u c t u r e s are folded by e a s t e r l y - t r e n d i n g e a r l y structures which are i n turn refolded about l a t e southeasterly axes. The f i r s t trend may be r e l a t e d to struc t u r e s of the pre-Cambrian basement (Ross, 1968) and l a t e s t r u c t u r e s p a r a l l e l a pe r s i s t e n t trend i n most Mesozoic and younger rocks of the Western C o r d i l l e r a . What then of the inte r v e n i n g e a s t e r l y trend? I t may be r e l a t e d to extremely large scale events which brought about changes i n stress f i e l d s of p r o v i n c i a l or even co n t i n e n t a l dimension. Such a hypothesis i s too all-embracing to be of much use, besides, the time i n t e r v a l between e a r l i e s t and e a r l y f o l d i n g appears to be too short to allow great changes i n geotectonic pattern. I t i s possible that i n t e r a c t i o n of several phases of deformation may produce v a r i a t i o n s i n trend of ea r l y s t r u c t u r e s over large areas, however d e t a i l e d s t r u c t u r a l data i s presently i n s u f f i c i e n t to support such a hypothesis. Whatever the cause, a f t e r d e p o s i t i o n of the Kobau Group, presumably over a basement of the Vaseaux Formation (Table 6-l) 117 the t e c t o n i c framework of the region was a l t e r e d so as to produce t i g h t l y appressed nappes with r e l a t i v e l y f l a t - l y i n g a x i a l surfaces and e a s t e r l y - t r e n d i n g axes w i t h i n both succes-sions. Metamorphism accompanied deformation, reaching upper-most almandine-amphibolite and g r a n u l i t e f a c i e s i n more deeply buried Vaseaux rocks and middle g r e e n s c h i s t f a c i e s i n the Kobau Group. Syntectonic r e c r y s t a l l i z a t i o n and extensive shearing are c h a r a c t e r i s t i c of e a r l y Kobau f o l d i n g which may have i n i t i a t e d as f l e x u r a l s l i p but l i k e l y a l t e r e d to f l e x u r a l flow f o l d i n g as r i s e of temperature reduced d u c t i l i t y of deforming rocks ( c f . Donath and Parker, 1964)• Transformation of bedding ( F ) -to f o l i a t i o n ( F ^ ) , described i n Chapter III, accompanied deformation. Deformation a f t e r e a r l y nappes were f u l l y closed and f o l i a t i o n f u l l y developed r e s u l t e d i n r e f o l d i n g of F Q / F ^ surfaces about forming assymetric s i m i l a r f o l d s not u n l i k e those produced by l a t e r tectonism. U p l i f t and e r o s i o n of o v e r l y i n g rocks and p o s s i b l y upper parts of the Kobau Group may have accompanied growth of nappe s t r u c t u r e s . No evidence of unconformities have been found, although one may e x i s t between Anarchist/Kobau equivalent suc-cessions and younger members of the A n a r c h i s t Group. Er o s i o n 118 may not have taken place u n t i l a f t e r l a t e r deformation. Late Folding Major r e f o l d i n g of e a r l y Kobau nappe structures followed t h e i r development and i s believed to have a f f e c t e d rocks of the Cache Creek Group, portions of the Anarchist Group south of the f o r t y - n i n t h p a r a l l e l and the Barslow, Independence, Shoemaker and Old Tom Formations found west and northwest of Mount Kobau. Normal to t i g h t , upright and overturned f o l d s have been reported from most of these successions (Waters and Krauskopf, 1941; Bostock, 1940). Late Kobau deformation i s presumably e a r l y Mesozoic i n age, i n any case older than the O l i v e r Granite which has been dated at 144 x 10^ years (Chapter V). Refolding of F Q / F ^ planes occurred about Lg plunging at low angles to northwest and southeast. Folding took place i n a number of s t y l e s depending upon the character of the rocks i n question. Q u a r t z i t e , which i n some areas r e t a i n s o r i g i n a l bedding, deformed by f l e x u r a l s l i p producing c y l i n d r i c a l appearing f o l d s , which by v i r t u e of presence of e a r l i e r f o l d s must i n f a c t have been s l i g h t l y conic. Most commonly, however, i n c h l o r i t i c p h y l l i t e s and s c h i s t s and f o l i a t e d q u a r t z i t e s , f l e x u r a l flow f o l d i n g and passive s l i p and flow took place. Assymetric 119 s i m i l a r f o l d s , chevron and box f o l d s , and kink bands are c h a r a c t e r i s t i c of l a t e Kobau f o l d i n g . Macroscopic s t r u c t u r e s are of s i m i l a r type. Overturned synforms and antiforms are i l l u s t r a t e d on Map 4 and accompanying c r o s s - s e c t i o n s (Figure 3-1, i n pocket). A l l l a t e f o l d i n g i s a part of the n o r t h - w e s t e r l y - t r e n d i n g r e g i o n a l s t r u c t u r a l p a t t e r n e s t a b l i s h e d i n the western C o r d i l l e r a during the Mesozoic. Pre- or syntectonic i n t r u s i o n of s u b p o r p h y r i t i c f i n e grained dykes of quartz l a t i t e took place at t h i s time. Widespread u p l i f t and erosion followed e a r l y Mesozoic deformation i n the c e n t r a l f o l d b e l t of the C o r d i l l e r a . Approxi-mately 65 miles north of the map-area rocks of the N i c o l a Group were deposited unconformably on upper formations of the Cache Creek Group (Schau, 1968). In the Okanagan V a l l e y south of O r o v i l l e , Washington, f o s s i l i f e r o u s upper T r i a s s i c limestone was l a i d down on the A n a r c h i s t Group (Waters and Krauskopf, 194l) and i n the Grand Forks area middle T r i a s s i c conglomerate i s found o v e r l y i n g the Permian Knob H i l l Formation ( L i t t l e and Thorpe, 1965). Minor outcrops of b r e c c i a t e d s i l i c e o u s sediment i n apparent unconformable contact with the Kobau Group have been observed i n southeastern-most parts of the map-area (Map 2) but t h e i r age i s unknown. 120 Latest Structures Open f o l d i n g about poorly defined n o r t h e r l y axes ( l a t e s t Kobau) took place i n J u r a s s i c or l a t e r time. Few mesoscopic f o l d s r e l a t e d to t h i s period of deformation have been observed with the exception of rare open f l e x u r e s with n o r t h e r l y axes and p o s s i b l y r e l a t e d j o i n t sets s t r i k i n g approximately north. E f f e c t s of t h i s deformation are d i f f i c u l t to separate from those a r i s i n g from emplacement of the Okanagan B a t h o l i t h and r e l a t e d stocks which occurred during the l a t e J u r a s s i c and Cretaceous. Accommodation to igneous i n t r u s i o n also produced t i g h t e n i n g of some l a t e s t r u c t u r e s . Associated contact metamorphism was r e l a t i v e l y mild, reaching lower-most hornblende-hornfels f a c i e s i n narrow contact aureoles. D i a s c h i s t i c and a s c h i s t i c dykes cut Kobau rocks at t h i s time. Development of a conjugate set of gentle f o l d s about no r t h e r l y and e a s t e r l y - t r e n d i n g axes has been observed i n the Vaseaux Formation and also i n the N i c o l a Group northwest of Mount Kobau. In the l a t t e r area, r e l a t e d u p l i f t may have re-sulted i n deposition of the Clapperton Conglomerate i n post-early J u r a s s i c time (Schau, 1968, pp. 13-15). F i n a l deformation of the Kobau Group took place during Cretaceous and T e r t i a r y time i n the form of f a u l t i n g along 121 n o r t h e r l y and e a s t e r l y d i r e c t i o n s . A s s o c i a t e d m i n o r f a u l t s have e x t e n s i v e l y b r e c c i a t e d many p a r t s o f t h e m a p - a r e a . F a u l t i n g i s b e l i e v e d to have o c c u r r e d a l o n g r e a c t i v a t e d p l a n e s o f weakness a s s o c i a t e d w i t h e a r l y and l a t e s t r u c t u r e s and a l o n g d i r e c t i o n s p a r a l l e l to f a u l t s i n t h e Okanagan V a l l e y ( L i t t l e , 1961a). S i m i l a r f a u l t i n g i s l i k e l y p r e s e n t i n t h e S i m i l k a m e e n V a l l e y . N o r t h e r l y f a u l t i n g i n t h i s a r e a may be a s o u t h e r n e x t e n s i o n of t h e V e r n o n - S i c a m o u s f a u l t ( J o n e s , 1959). CONTRIBUTION T h i s s t u d y has p r o v i d e d a d d i t i o n a l k n o w l e d g e o f t h e g e o l o g i c h i s t o r y o f t h e K o b a u G r o u p and shown i t to be a s u c c e s s i o n r e l a t e d s t r u c t u r a l l y to b o t h Shuswap and Cache C r e e k C o m p l e x e s . R o c k s o f t h e g r o u p have b e e n s u b d i v i d e d i n t o n i n e mappab le u n i t s and have b e e n shown t o p o s s e s s a t h r e e phase h i s t o r y o f d e f o r m a t i o n w h i c h has f o r m e d a u b i q u i t o u s f o l i a t i o n f r o m o r i g i n a l c o m p o s i t i o n a l l a y e r i n g . I n t r u s i o n s o f v a r i o u s t y p e s have b e e n shown to cu t t h e g r o u p on a t l e a s t s i x o c c a s i o n s . I n d i r e c t l y , t h i s s t u d y has s u g g e s t e d t h e p o s s i b i l i t y o f a m a j o r m i d - P a l a e o z o i c d e f o r m a t i o n o f t h e Shuswap Complex and s u g g e s t e d a somewhat more complex h i s t o r y f o r t h e A n a r c h i s t Group t h a n was p r e v i o u s l y s u s p e c t e d . D e t a i l e d i n f o r m a t i o n has b e e n p r o v i d e d f o r a n o t h e r p a r t o f t h e E a s t C o r d i l l e r a n F o l d B e l t , a p a r t whose h i s t o r y a l s o b e a r s d i r e c t l y on e v e n t s i n the C o r d i l l e r a as a w h o l e . 122 FUTURE WORK Much a d d i t i o n a l s t u d y c o u l d be made o f i n t r u s i v e r o c k s i n t h e map-area, t h e p r e s e n t work h a v i n g d e a l t o n l y i t f i t h p r o p e r t i e s o f c o n t a c t z o n e s . D e t a i l e d m a pping o f t h e O l i v e r G r a n i t e has r e v e a l e d c omplex i n t e r n a l r e l a t i o n s h i p s . S i m i l a r f e a t u r e s may be f o u n d i n t h e F a i r v i e w , T e s t a l i n d e n and Osoyoos s t o c k s . A d d i t i o n a l r a d i o m e t r i c a g es f o r t h e s e i n t r u s i o n s s h o u l d be o b t a i n e d . C o m p o s i t i o n a l c o m p a r i s o n s c o u l d be made between s m a l l d i o r i t e s t o c k s and l a r g e r g r a n o d i o r i t e i n t r u s i o n s t o d e t e r m i n e any p o s s i b l e g e n e t i c r e l a t i o n s h i p s . S t u d i e s o f r e l a t e d d y k e s c o u l d a l s o be made. A d d i t i o n a l d e t a i l e d mapping o f t h e Kobau Group i t s e l f c o u l d be done t o c l a r i f y s t r u c t u r e s i n complex a r e a s s u c h a s i n t h e c o r e o f t h e m a j o r e a r l y nappe n o r t h e a s t o f t h e T e s t a l i n d e n G r a n o d i o r i t e . E x t e n s i o n o f q u a r t e r - m i l e m a pping c o u l d be made t o s o u t h e r n p a r t s o f t h e map-area and s o u t h o f R i c h t e r P a s s on K r u g e r M o u n t a i n . A n a l y s i s o f many f r a c t u r e s e t s e x p o s e d on t h e Queen E l i z a b e t h II O b s e r v a t o r y r o a d s h o u l d p r o v i d e g r e a t e r k n o w l e d g e o f g e o m e t r y o f l a t e and l a t e s t s t r u c t u r e s . O u t s i d e t h e map-area, i n v e s t i g a t i o n o f r e l a t i o n s h i p s : . . b e ^ -tween Shuswap and A n a r c h i s t r o c k s e a s t o f t h e Okanagan V a l l e y s h o u l d be made, a s w e l l a s s t r u c t u r a l a n a l y s i s o f t h e A n a r c h i s t Group s o u t h o f t h e f o r t y - n i n t h p a r a l l e l . 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Sedimentary Rocks; Harper and Bros., N.Y., Second Ed., 718 pp. S t r u c t u r a l R e l a t i o n s h i p s betx^een the Shuswap Terrane and the Cache Creek Group i n Southern B r i t i s h Columbia; unpublished M.Sc. Thesis, Dept. Geol. Univ. of B.C. Structure and Petrology of the Grand Forks Group, Grand Forks, B r i t i s h Columbia; unpublished Ph.D. Thesis, M c G i l l Univ. Folding and F r a c t u r i n g of Rocks; McGraw H i l l , N.Y., 568 pp. The Proterozoic of the C o r d i l l e r a i n Southeastern B r i t i s h Columbia and South-western A l b e r t a ; _in The Prote r o z o i c i n Canada, Roy. Soc. Canada, Spec. Publ. 2, pp. 150-177. S t r u c t u r a l E v o l u t i o n and Plutonism i n V a l h a l l a Gneiss Complex, B r i t i s h Columbia; B u l l . Geol. Surv. Canada, v o l . 129, 128 pp. 1966 The Thor-Odin Gneiss Dome, Monashee Mountains, Southern B r i t i s h Columbia; Geol. Surv. Canada, Paper 66-1, pp. 78-80. 1 2 9 Rice, H.M.A. 1941 Nelson Map-Area, East Half, B r i t i s h Columbia; Geol. Surv. Canada, Mem. 228. Richards, G.G. 1968 The O l i v e r Quartz Monzonite, O l i v e r B r i t i s h Columbia; unpublished B.Sc. Thesis, Dept. Geol., Univ. of B.C. Ross, J.V. 1968 S t r u c t u r a l R e l a t i o n s at the Eastern Margin of the Shuswap Complex near Revelstoke, Southeastern B r i t i s h Columbia; Can. J . Earth S c i . , v o l . 5, pp. 831-849. Ross,• J . V. and C h r i s t i e , J.C. 1969 Polyphase Deformation w i t h i n the Shuswap Terrane of the Southern Okanagan V a l l e y , B r i t i s h Columbia; Abstr. Geol. Soc. Am. 1969 Annual Meetings, Eugene, Oregon, pt, pp. 57-58. 3 , Ross, J.V. and' K e l l e r h a l s , P. 1968 E v o l u t i o n of the Slocan Syncline i n South-C e n t r a l B r i t i s h Columbia; Can. J . Earth S c i . , v o l . 5, pp. 851-872. Schau, M.P. 1968 Geology of the Upper T r i a s s i c N i c o l a Group i n South C e n t r a l B r i t i s h Columbia; unpub-l i s h e d Ph.D. Thes i s , Univ. of B.C. Selwyn, A.P.C, 1872 Journal and Report of P r e l i m i n a r y Explora-t i o n i n B r i t i s h Columbia; Geol. Surv. Canada, Rept. Prog. 1871-1872, pp. 16-72. Smith, G.O. and C a l k i n s , P.C. 1904 Snook, J.R. 1965 Turner, P.J. and Verhoogen, J. I960 Turner, P.J. and ¥eiss, L.E. 1963 A G e o l o g i c a l Reconnaissance Across the Cascade Range near the F o r t y - n i n t h P a r a l l e l ; B u l l . U.S. Geol. Surv., No. 2 3 5 . Metamorphic and S t r u c t u r a l H i s t o r y of the C o l v i l l e B a t h o l i t h Gneiss, N o r t h - c e n t r a l Washington; B u l l , pp. 759-776. Geol. Soc. Am., vol;. 7 6 , Igneous and Metamorphic Petrology; McGraw H i l l , N.Y., Second Ed., 6 9 4 pp. S t r u c t u r a l A n a l y s i s of Metamorphic Tecto-n i t e s ; M-cGraw H i l l , Toronto, 5 4 5 pp. 130 Umpleby, J.B. 1911 Waters, A.C. and Krauskopf, K. 1941 Wheeler, J.O. 1965 1966 White, W.H. 1959 White, W.H. Harakal, J.E. and Carter, N.C. 1968 White, W.H., S i n c l a i r , A.J. and Harakal, J.E. 1967 Winkler, H.G.F. 1967 Yates, R.G. B e c r a f t , G.E., Campbell, A.B. and Pearson, R.C. 1966 Geology and Ore Deposits of the O r o v i l l e -Nighthawk Mining D i s t r i c t ; B u l l . Washington Geol. Surv., v o l . 5, pt. 2, pp. 53-103. P r o t o c l a s t i c Border of the C o l v i l l e B a t h o l i t h ; B u l l . Geol. Soc. Am., v o l . 52, pp. 1355-1418. Big Bend Map-Area, B r i t i s h Columbia; Geol. Surv. Canada, Paper 64-32. Eastern Tectonic B e l t of the Western C o r d i l l e r a i n B r i t i s h Columbia; i n Tectonic H i s t o r y and Mineral Deposits of the Western C o r d i l l e r a , Can. I n s t . Mining Met., Spec. V ol. 8, pp. 27-45. C o r d i l l e r a n T e c t o n i c s i n B r i t i s h Columbia; B u l l . Am. Assoc. P e t r o l . Geol., V o l . 43, No. 1, pp. 60-100. Potassiumr-Argon Ages of some Ore Deposits i n B r i t i s h Columbia; B u l l . Can. Mining Met., November. Absolute Age of Mineral Deposits i n B r i t i s h Columbia; Abstr. Geol. Soc. Am., 1967 Annual Meeting, Rocky Mtn. Sect., Golden, Colorado, p. 72. Petrogenesis of Metamorphic Rocks; Springer Ver l a g . , Second Ed., 237 pp. Tectonic Framework of North-eastern Washington, Northern Idaho, and North-western. Montana; .in T e c t o n i c H i s t o r y and Mineral Deposits of the Western C o r d i l l e r a , Can. In s t . Mining Met., Spec. V ol. 8, pp. 47-60. 131 APPENDIX A D e f i n i t i o n of Greenstones The term greenstone, as applied to green a l t e r e d basic igneous rocks i s often considered too general a c l a s s i f i c a t i o n to be u s e f u l (glossary of Geology, 1957)• As defined by Moorhouse (1959), however, i t serves as a convenient l a b e l f o r basic igneous rocks whose e x t r u s i v e , i n t r u s i v e or p y r o c l a s t i c o r i g i n i s obscurred by low to medium grade metamorphism and attendant shearing. Such rocks are sometimes termed greenschists, but as both schistose and massive metamorphosed basic igneous rocks are observed i n the Kobau area such c l a s s i f i c a t i o n i s not accurate, besides the term i s also applied to a metamorphic f a c i e s and hence open to m i s i n t e r p r e t a t i o n . In t h i s t h e s i s , greenstones are basic igneous rocks p o s s i b l y of i n t r u s i v e , extrusive and/or p y r o c l a s t i c o r i g i n , metamorphosed to lower and middle greenschist f a c i e s and e i t h e r massive and banded or schisto s e . Of greenstones observed i n the map-area, p r i n c i p a l minerals are t r e m o l i t e / a c t i n o l i t e , and a l b i t e . Horn-blende, b i o t i t e , q u a r t z , c h l o r i t e , white micas, sphene and f e r r u -ginous minerals are u s u a l l y present. Primary textures have not been observed. 132 APPENDIX B D e s c r i p t i o n of C o r r e l a t i v e S t r u c t u r a l S u c c e s s i o n s w i t h i n t h e Kobau Group To e s t a b l i s h c o n t i n u i t y of t h e s t r u c t u r a l s u c c e s s i o n d e s c r i b e d i n C h a p t e r I I and to supplement i l l u s t r a t i o n of mega-s c o p i c s t r u c t u r e s ( C h a p t e r I I I ) , seven a d d i t i o n a l s e c t i o n s (E to K) have been measured. These s e c t i o n s a r e d e s c r i b e d below and c o r r e l a t e d w i t h the e s t a b l i s h e d s t r u c t u r a l s u c c e s s i o n ( F i g u r e B r - l ) . As d e s c r i b e d p r e v i o u s l y ( C h a p t e r I I , p. 2 l ) , a r e p e a t e d s e c t i o n , i m p l y i n g the p r e s e n c e of a second f o l d c o r e , c r o p s out a l o n g the n o r t h w e s t c o n t i n u a t i o n of t h e l i n e of s e c t i o n C. Here, U n i t s i x i s " u n d e r l a i n " by U n i t s f i v e , f o u r and t h r e e . S t i l l , f a r t h e r to the n o r t h w e s t (Maps 1,2), a g r e e n p h y l l i t i c u n i t con-t a i n i n g a m p h i b o l i t e and c h l o r i t e and i n c l u d i n g a band•.• o f f m a r b l e , i s o b s e r v e d . T h i s u n i t i s c o r r e l a t e d w i t h U n i t S i x and the s e c t i o n ( E ) i s a f u r t h e r r e p e t i t i o n of t h e s u c c e s s i o n d e s c r i b e d i n s e c t i o n C. Such a d d i t i o n a l r e p e t i t i o n s u g g e s t s t h a t a t h i r d m a c r o s c o p i c f o l d c o r e l i e s between t h e base of s e c t i o n C and the to p of s e c t i o n E. B o t h s e c t i o n s C and E a r e o v e r t u r n e d x ^ i t h r e -s p e c t to S e c t i o n A. S e c t i o n F l i e s west of the F a i r v i e w G r a n o d i o r i t e and c o n t a i n s a s u c c e s s i o n of u n i t s s i m i l a r to t h a t of s e c t i o n D. The s t r u c t u r a l l y lowermost u n i t of f o l i a t e d p h y l l i t i c q u a r t z i t e i s FIGURE B-l CORRELATIVE STRUCTURAL LITHOLOGIC SECTIONS WITHIN THE KOBAU GROUP. • Lithology. Massive quartzite •Foliated phyllitic quartzite Phyl l i te and schist Greenstone Marble and calcareous phyllite. Igneous intrusion fwv» Faults rvS rvS",-„ 6a 9 ~ 8 * 6a — CPU U K Late .. fold core 6 ...Nappe core*'---Nappe core Measured Sections^ E 5 0 0 0 i 134. c o r r e l a t e d with Unit nine. Units eight to f i v e crop out to the east. The gross s i m i l a r i t i e s between the two sections as w e l l as the presence of d i s t i n c t i v e pure c r y s t a l l i n e limestone w i t h i n green c h l o r i t i c and a m p h i b o l i t i c p h y l l i t e (Unit s i x ) support t h i s c o r r e l a t i o n . In t h i s area, Unit s i x contains a second sub-u n i t (6b) which i s a green and black a c t i n o l i t e s c h i s t . On the mesoscopic scale t h i s sub-unit c o n s i s t s of black, and l i g h t green compositional l a y e r s deformed i n t o sheared lenses and r o o t l e s s f o l d s . Black l a y e r s contain t r e m o l i t e / a c t i n o l i t e and c h l o r i t e , b i o t i t e , and minor amounts of epidote and a l b i t e . Green l a y e r s are s i m i l a r i n composition but contain, i n a d d i t i o n , white mica and c a l c i t e . A l l minerals are f i n e grained. Eastward, beyond outcrops of Unit f i v e i n section P, marble and s c h i s t crop out again over a broad area bounded to the north and northeast by the O l i v e r Granite (Hap 2 ) . As i n previous instances (Sections B, C, and E), such r e p e t i t i o n i s believed to r e s u l t from t i g h t f o l d i n g on the megascopic sc a l e , and t h i s hypothesis i s confirmed by the presence of a t i g h t f o l d core delineated by Unit f i v e . Section G i l l u s t r a t e s the repeated sequence which i s upright with respect to s e c t i o n A. Marble of sub-unit 6a i s f u r t h e r repeated three times i n t h i s s e c t i o n but no evidence has been found that supports the existence of more megascopic t i g h t f o l d i n g i n t h i s area. Presence of f a u l t s and p a r a l l e l lineaments (Map 4) 135 s u g g e s t s t h a t r e p e t i t i o n m a y h a v e r e s u l t e d f r o m m o v e m e n t o n n o r t h w e s t e r l y - t r e n d i n g f a u l t s ( C h a p t e r I I I ) . S e c t i o n H i s m e a s u r e d n o r t h e a s t f r o m a g r e e n p h y l l i t i c u n i t t h r o u g h f o l i a t e d p h y l l i t i c q u a r t z i t e i n t o g r e e n p h y l l i t e c o n t a i n i n g m a r b l e a n d s c h i s t . On l i t h o l o g i c g r o u n d t h i s l a t t e r p h y l l i t e i s c o r r e l a t e d w i t h U n i t s i x , t h e m a r b l e w i t h s u b - u n i t 6a a n d t h e s c h i s t w i t h s u b - u n i t 6b. T h e u n d e r l y i n g s u c c e s s i o n i s m o s t l i k e t h a t s e e n i n U n i t s s e v e n a n d e i g h t . S e c t i o n H i s t h e r e f o r e o v e r t u r n e d w i t h r e s p e c t t o s e c t i o n A . N o r t h e a s t o f s e c t i o n H a r e o u t c r o p s o f f o l i a t e d q u a r t z i t e c o m p r i s i n g t h e u p p e r -m o s t p a r t o f U n i t f i v e , f o l l o w e d b y m o r e o u t c r o p s o f p h y l l i t e , m a r b l e a n d s c h i s t o f U n i t s i x . I n t h i s a r e a a l a r g e t i g h t f o l d i s d e l i n e a t e d b y m a p p i n g o f t h e d i s t i n c t i v e l i t h o l o g y o f U n i t s i x . C o n t i n u a t i o n o f t h e s u c c e s s i o n t o t h e n o r t h e a s t i s t e r m i n a t e d b y t h e O l i v e r G r a n i t e . S e c t i o n s I , J , a n d K a r e s o u t h e r n c o n t i n u a t i o n s o f s e c t i o n A a n d c o n t a i n U n i t s o n e t o e i g h t . I d e n t i f i c a t i o n o f u n i t s i n t h i s a r e a i s u n c e r t a i n b e c a u s e o f t h e r m a l m e t a m o r p h i s m n e a r t h e T e s t a l i n d e n G r a n o d i o r i t e , r e p e t i t i o n b y l o c a l f o l d i n g a n d i n t e r -r u p t i o n o f t h e s e c t i o n s b y f a u l t s . M u c h o f U n i t f o u r i s e i t h e r b u r i e d b y a l l u v i u m o r h i d d e n b y f a u l t i n g . U n i t f i v e i s t h i c k e r i n t h i s s e c t i o n t h a n i n s e c t i o n B a n d m a y b e r e p e a t e d e i t h e r b y f a u l t i n g o r f o l d i n g , o r b o t h . L a t e r a l c h a n g e s i n t h i c k n e s s m a y b e c a u s e d b y d i f f e r e n c e s i n o r i g i n a l t h i c k n e s s o r v a r y i n g e f f e c t s 136 of shearing and i n t e r n a l f o l d i n g . In t h i s s e c t i o n , Unit s i x contains t h i n s t r i n g e r s of marble l e s s than one foot t h i c k which l i k e l y represent sub-unit 6a. A t h i r d sub-unit (6c) i s observed. I t i s composed of several bands of massive and f o l i a t e d q u a r t z i t e under 20 feet t h i c k w i t h i n a zone about 400 feet t h i c k . Unit s i x and i t s contained sub-units has a present thickness of about 550 feet i n s e c t i o n I.. Dark grey, f a i n t l y f o l i a t e d a m p h i b o l i t i c and micaceous s c h i s t seen i n a number of bands i s associated with Units s i x and eight. I t i s not observed i n sections A to H and may be present because of a f a c i e s change. Thickness of any one band i s under 250 feet and generally v a r i a b l e . Outcrops i n the southwest quarter of the map-area are separated from rocks of sections A to K by areas covered wholly or i n part by alluvium, or intruded by l a t e r g r a n i t i c stocks (Maps 1 and 2). A number of outcrops of green c h l o r i t i c and a m p h i b o l i t i c p h y l l i t e and s c h i s t containing s t r i n g e r s and bands of c a l c i t e marble as w e l l as several r e l a t i v e l y t h i n (20 feet t h i c k ) bands of massive and f o l i a t e d q u a r t z i t e have been observed. These have been c o r r e l a t e d with Unit s i x on the basis of general l i t h o -l o g i c s i m i l a r i t y . This un i t can be traced from j u s t south of 137 Cawston Creek i n the Similkameen V a l l e y to the summit of Mount Kobau (Maps 1 and 2 ) . South and west of the summit Unit s i x i s l o s t beneath alluvium and can only be t e n t a t i v e l y traced to outcrops seen i n sections J and K. Over much of t h i s area exposures are on a f o l i a t i o n dip-slope, and i n the r e s t , successions are repeated and displaced by f o l d i n g and extensive f a u l t i n g , thus i t i s i m p r a c t i c a l to set up extensive l o c a l sections for comparison with the es t a b l i s h e d succession. 138 APPENDIX C Determination of Temperature of C r y s t a l l i z a t i o n of C r y s t a l l i n e C a l c i t e F o l l o w i n g the procedure of Morgan (1967), f i v e samples taken from c r y s t a l l i n e limestones i n the northern h a l f of the map-area were analysed f o r mineral content and then f o r Mg/Ca r a t i o s by a P h i l l i p s - N o r e l c o X-ray d i f f r a c t o m e t e r u s i n g CuKOc r a d i a t i o n and a Ni f i l t e r . Each sample was scanned four times at a rate of -^-o/minute. Ah i n t e r n a l standard of s i l i c o n was used to determine angles of 20 between the S i standard and the strong (104) peak of c a l c i t e . The curve of Goldsmith and Graf (1958), which i s based on displacement of the 104 c a l c i t e peak, was used to d e r i v e Mg/Ca r a t i o s and hence, from the curve of Graf and Goldsmith (l958) (see Figure C - l ) , temperatures of c r y s t a l l i z a t i o n . Since i r o n a f f e c t s the 104 c a l c i t e peak more than magnesium, only i r o n - f r e e limestones were used (Table C - l ) . These were determined by s t a i n i n g with a s o l u t i o n of potassium f e r r i c y a n i d e i n d i l u t e HCl; i r o n - b e a r i n g limestones stained blue, i r o n - f r e e limestones are u n a f f e c t e d . T h i s t e s t i s very s e n s i t i v e f o r small amounts of i r o n . 139 Errors i n measurement of 20 are + .025 , producing er r o r s of + .0025 K i n d spacing and + .8 mol $ i n MgCO^ content. This produces errors i n temperature of + 30° C , however, data provided by Graf and Goldsmith (1958) do not cover the temperatures below 500° C. and extr a p o l a t i o n s to 400° C. ( f o r MgCO^ mol percentages below 4.0) give a broad range of possible temperatures of c r y s t a l l i z a t i o n which exceed any experimental e r r o r s (Figure C - l ) . Table C-l Sample Wo. Iron Test Mineral Content 11- 4-107 12- 1-x 13- 2-101 13_4_29a 13- 4-44a 14- 3-10 14-5-16 22-1-208 22-3-8 + + + trace (?) c a l c i t e , dolomite (?) dolomite, c a l c i t e , t r e m o l i t e c a l c i t e c a l c i t e c a l c i t e , quartz c a l c i t e t r e m o l i t e , c a l c i t e c a l c i t e , dolomite, quart z dolomite, c a l c i t e , quartz * See Map 1 for sample l o c a t i o n . 140-Only those samples (22-3-8, 22-1-208 and p o s s i b l y . 11-4-107) which contain dolomite (i'.e. an excess of Mg) can be expected to give r e l i a b l e minimum temperatures of c r y s -t a l l i z a t i o n . Morgan (l967) observed a maximum of 3.5 mol % MgCO^ i n c a l c i t e s of the gre e n s c h i s t f a c i e s i n d i c a t i n g minimum temperatures of 415° to 480° G. Kobau Group c a l c i t e s c ontain up to 2.6 mol fa MgCO^ corresponding to minimum temperatures of c r y s t a l l i z a t i o n of l e s s than 450° C. The number of samples i s admittedly small but r e s u l t s are not c o n t r a d i c t e d by other m i n e r a l o g i c a l data which i n d i c a t e c r y s t a l l i z a t i o n under c o n d i t i o n s of lower g r e e n s c h i s t s u b f a c i e s . Table C-2 Sample No. Avg. 20 between 104 calci t e . . and standard 20 104 c a l c i t e peak 0 dA mol % MR C O , T°C. 11-4-107 1.007 29.473 3 .0306 j 1.6 < 420 14-3-10 .986 29-452 3 .0327 .8 < 400 22-3-8 2 . 1.043 29.509 3 .0269 2.6 <450 .949 29-415 3 .0364 0.1 22-1-208 1.038 29.504 3 .0274 2.2 <440 14-5-16 1 S i l i c o n CuK<<29 = 28. 466 2 Two magnesium c a l c i t e s present i n t h i s sample. MINIMUM TEMPERATURES OF CRYSTALLIZATION OF CALCITE INDICATED BY MOL % OF INCLUDED M g C 0 3 > I I9M0' W •e o0-GEOLOGY OF MOUNT KOBAU BRITISH COLUMBIA -49*I0'N ; 33 \ Mi V . 4 4 45 GEOLOGY BY AV. OKULITCH 1965-1967 V \ oo' ><9 As \ 47 if 84 J J Y \ > * ^ \ - v - J •VC -^7 ^ / \ FAIR VIEW ; v - : ; v v : ^ ! ..AN,, MAP iDIORITE ' " - P * ^ ,5K \N 34- V J 4 8 45- 1 re OLIVER GEOLOGIC LEGEND 1 0 I Limestone Foliated quartzite Chloritic, octirvomic phyllite Foliated phyllitic quartzite Chloritic, actinofitic phyllite 8 schist 6a« marble Massive quartzite Foliated quartzite Massive quartzite Chloritic phyllite Foliated quartzite, phyllite and mica schist *OOo' GEOGRAPHIC LEGEND 1000*— CONTOURS (1000' INTERVAL). - CREEKS (WET, INTERMITTENT ft ORYj — — MAJOR ROAOS ft HIGHWAYS. LAKES(WET 8 INTERMITTENT). S C A L E MILES TRUE NORTH .3 FEET 0 1000 20O0 3000 4000 5000 K ty TO S T R U C T U R A L D A T A Compositional layering and early f o l i a t i o n . to —*— incl ined — v e r t i c a l - j - hor izontal Ear ly ax ia l planes and axial plane f o l i a t i o n . 34 * % i n c l i n e d •« \ v e r t i c a l horizontal E a r l y l i n e a t i o n s and f o l d axes . plunging » horizontal ' F i n a l stage* early s tructures . 62 axial planes and axial plane cieavoge ^ l i n e a t i o n s and : = ^ f o l d axes. A x i a l t r a c e s of major ear ly folds a n t i f o r m a l ""H syn f o r m a l Arrows indicate direction of dip of a x i a l p lane. L a t e r S t r u c t u r e s . «A/VI«/V F a u l t s - - - - Lineaments TOPOGRAPHIC INFORMATION FROM DEPARTMENT OF MINES AND TECHNICAL SURVEYS MAP 82 E/4 (E) KEREMEOS- ADVANCE PRINT 1964. II9# 4 0 ' W 49# 05' N ~« ^ T ^ ' O S O Y O O S •^fg&Fiyi GRANODIORITE % 49°IO ,N :H FAIR VIEW GEOLOGY OF MOUNT KOBAU BRITISH COLUMBIA GEOLOGY BY AV. OKULITCH 1965-1967 wv .1..»!-.'•. mm MAP I •» I V N , - ; i ^ N 0DIORITE ?%T£tf 'V-'}--'-It-'-' \ ./•.'"•'>. -,-<. »#„** " OLIVER GEOGRAPHIC LEGEND sooo"— CONTOURS (1000' INTERVAL). CREEKS (WET, INTERMITTENT 8 ORY.) — MAJOR ROAOS 6 HIGHWAYS. 3 LAKES(WET a INTERMITTENT). SCALE MILES TRUE NORTH .5 1.0 FEET MAGNETIC 235* 1000 200O 3000 4000 5000 • * U • t \ ,:-v::;.'l. 3..... v ? k \ l w GEOLOGIC LEGEND LITHOLOGY KEY Igneous Intrusions 10 I Limestone Foliated quartzite V E R T I C A L C R O S S - S E C T I O N S MEASURED 8 Chloritic,actinolitic LITH0L06IC S E C T I O N S phyllite Foliated phyllitic quartzite • 11-4-107 MARBLE SAMPLE LOCATIONS Chloritic, actinolitic phyllite 8 schist 6a> marble O 4 - 5 P L A T E LOCATIONS O 3-7 Massive quartzite F IGURE LOCATIONS Foliated quartzite 3 Massive quartzite Chloritic phyllite Foliated quartzite, phyllite and mica schist OSOYOOS TOPOGRAPHIC INFORMATION FROM DEPARTMENT OF MINES AND TECHNICAL SURVEYS MAP 82 E/4 (E) KEREMEOS- ADVANCE PRINT 1964. n POST-KOBAU GROUP BRECCIA V-' . 119* 40'W 49* 05' N - J . OSOYOOS ^ 7? * r r^^ :r.:' GRANODI OR IT E I9°40' W h49*IO'N \ < « 1 » \ \ G E O L O G Y O F M O U N T K O B A U <3 BRITISH COLUMBIA GEOLOGY BY AV. OKULITCH 1965-1967 MAP 2 FAIRVIEW V '• 9 ^ 1 V... 8? NO D E T A I L E D "" i \]\ V v l f ' V / .•' 1J ft \ / ' \^  ° \ / GRVNODIORITE^  / OLIVER ft 1 3 : 8a "4T l0o< MAPPING Hv. \V» •<» GEOLOGIC LEGEND LITHOLOGY Dacite Diorite Granodiorite 1/ -'•.•'"•I Qtz. monzonite Qtz. latite Ultra-basic intrusive Mesozoic 8 younger intrusive rocks Permian and/or Pennsylvanian(7) Limestone Foliated quartzite | K O B A U GROUP pre - Mesozo ic 8 a ' 1 Chloritic, actinolitic phyllite 8a> quartzite Foiioted phyllitic quortzite Chloritic, actinolitic phyllite 8 schist 6a» marble 6b'- schist 6 c : quartzite Massive quartzite Foliated quortzite Massive quartzite 3a= chlor i t ic phyllite Chloritic phyilite 2a- c a l c a r e o u s phyllite Foliated quartzite, phyilite and mica schist A GEOGRAPHIC LEGEND 3000'— CONTOURS 0000' INTERVAL). CREEKS (WET,INTERMITTENT a DRY.) — MAJOR ROADS B HIGHWAYS. c 9 LAKES(WET a INTERMITTENT). S C A L E MILES 5 FEET 1 0 0 1000 20O0 3 OOO 4 0 0 0 5 0 0 0 TOMOGRAPHIC INFORMATION FROM DEPARTMENT OF MINES AND TECHNICAL SURVEYS MAP 82 E/4 (E) KEREMEOS- ADVANCE PRINT I9S4. L I T H O L O G I C C O N T A C T S 1 cts?-«ed approximate - —• assumed F O L I A T I O N «>•-" incl ined - \ ~ horizontal F A U L T S v A / v w \ o b s e r v e d *AA \At\ assumed L I N E A M E N T S Unco loured areas are overlain by Recent al luvium. ^ \^ se 4 9 # 05' N A MAPPING ^ < < ; r . : G R A N O D I O R I T E '}•': II9# 40'W 5 0 0 0 h FIGURE 3-1 VERTICAL CROSS-SECTIONS, MOUNT KOBAU AREA. SECTION B - B SECTION C - C SECTION - D-D 5 0 0 0 h B1 028° LITHOLOGIC CONTACTS observed approximate assumed F A U L T S C W V A A / \ observed v i assumed UPPER ANT IFORMAL N A P P E X I 5 0 0 0 ' K o b a u Grou p HORIZONTAL AND VERTICAL SCALE . 5 1 .0 0 L ml I L SECTION A - A ' SEA L E V E L 0 L. M I L E S J L 5 0 0 0 F E E T C 206° Mount Kobau Hester Creek 5 0 0 0 C 026° Similkameen Valley Oliver Septum GRANODIORITE ^ " ' ~ 1 v - V ' T^\Kv'_N 1 UPPER A N T I F O R M A L N A P P E UPPER ANTIFORMAL N A P P E SYNFORMAL NAPPE SEA LEVEL FAIRVIEW OLIVER GRANITE 5 0 0 0 SECTION A ' -A" SEA L E V E L L I T H O L O G Y Dacite Diorite '< ,>•->/. Granodiorite Quartz monzonite Quartz latite TO 1 Limestone Blind Creek Fm. D Foliated quartzite • Chloritic, octinolitic phyllite E Foliated phyllitic quartzite Chloritic, actinolitic phyllite 8 schist 6 a s marble 5 Massive quartzite Q Foliated quartzite 3 Massive quartzite Chloritic phyllite 3 Foliated quartzite, phyllite and mica schist 5 0 0 0 V SEA L E V E L LITHOLOGIC C O N T A C T S , F A U L T S AND MACROSCOPIC S T R U C T U R E S P R O J E C T E D ONTO PLANES OF S E C T I O N S TO AID ILLUSTRATION OF GEOLOGY. SECTION A'-A" I I 9M0 ' W GEOLOGY OF MOUNT KOBAU BRITISH COLUMBIA 1-49*10' GEOLOGY BY AV. OKULITCH 1965-1967 8 X \ * r.' 57" [24 JOKj its . w v — — F A I R V I E W s 4' 17 42 * 0 G R A N O D I O R I T E ?%l 3 , f—-"... ikV'A'^.-'v.'ro^;.-^:. , - v i if * \ % ~ , MAP 4 • » » " - » * ^ O L I V E R 3 V 22 v \\\ B \ \ « S 7\ ,30 50 ft 5 ^ 7 / \ ^ + w -TESTAL1N0E .1 9 !9 GEOLOGIC LITHOLOGY m Igneous intrusions io | Limestone Foliated quartzite 9 e Chloritic, octinolitic phyllite Foliated phyllitic quartzite Chloritic, octinolitic phyllite 8 schist 6a< marble Massive quartzite Foliated quartzite 3 Massive quartzite Chloritic phyllite Foliated quartzite, phyllite and mica schist LEGEND KEY TO STRUCTURAL DATA Compositional layering and early foliation. 20 + inclined vertical horizontal Late axial planes and axial plane cleavage. 5 6 .• ^ —I—*, inclined • ^ H B vertical horizontal Lote lineations and fold axes. •7 plunging i horizontal Latest structures. 78 axial planes and 1 1 " ax. pi. cleavage .v. lineations and GEOGRAPHIC LEGEND looo'— CONTOURS (1000' INTERVAL). CREEKS (WET,INTERMITTENT S DRY.) — — MAJOR ROADS 8 HIGHWAYS. LAKES(WET 8 INTERMITTENT) S C A L E MILES TRUE NORTH .5 FEET 1.0 1000 ZOOO 3000 40O0 SOOO TOPOGRAPHIC INFORMATION FROM DEPARTMENT OF MINES AND TECHNICAL SURVEYS MAP 82 E/4 (E) KEREMEOS- ADVANCE PRINT 1964. fold axes ^Axial traces c* major folds Late • > ^ " antiformal • ^ 111 synformal A Latest y - antiformal ^ synformal Arrows indicate dip of axial plane. Open arrows indicate unknown dip. vwv wv Faults - Lineaments 70 * o.fr 119* 4 0 ' W 49* 05' N -POTTEDv*y^ ^rrrr ^ o s o Y O c i s \:;7 ^ .^-hjir'GRANODIORITfE l{j :.-nus E A S T D 0 M A I N East-northern sub-domain 163 P O L E S TO F 0 / F , SURFACES AND EARLY AXIAL PLANES PRIMARILY IN THE SOUTHWEST QUADRANT. CONTOURS AT 1,2,4 AND 8% PER 1% AREA. 61 EARLY LINEATIONS AND FOLD AXES(L,= ). East-central sub-domain 238 P O L E S TO F 0 / F , S U R F A C E S AND EARLY AXIAL P L A N E S CONTOURED AT 1,2,4 AND 8 % PER 1% AREA. 96 EARLY (-) AND "FINAL STAGE" EARLY (+) LINEATIONS AND FOLD AXES. AGE RELATIONSHIPS BETWEEN LINEATIONS OBSERVED INFREQUENTLY. East-southern sub-domain 408 P O L E S TO F 0 / F , SURFACES AND EARLY AXIAL P L A N E S CONTOURED AT 1,2,4 AND 8% PER 1% AREA. 22 EARLY LINEATIONS AND FOLD AXES (•). E A S T DOMAIN, UPPER NET: 809 POLES TO F 0 / F , SURFACES AND EARLY AXIAL PLANES CONTOURED AT . 5 , 1 , 2 , 4 AND 6 % PER 1% AREA. EAST DOMAIN, LOWER NET: 51 POLES TO F g SURFACES CONTOURED AT 1,2 AND 4 % PER 1% AREA. 171 LATE LINEATIONS AND FOLD AXES(L 2=-) w E S T D 0 M A I N West-northern sub-domain 80 POLES TO F 0 / F , SURFACES AND EARLY AXIAL PLANES CONTOURED AT 2 , 4 AND 8 % PER 1% A R E A . 8 EARLY LINEATIONS AND FOLD AXES (•• ). West-central sub-domain 221 POLES TO F 0 / F , SURFACES AND EARLY AXIAL PLANES CONTOURED AT 1,2,4 AND 6 % PER 1% AREA. 36 EARLY LINEATIONS AND FOLD AXES (L,= -). West-southern sub-domain 4 4 5 POLES TO F 0 / F , SURFACES AND EARLY AXIAL PLANES CONTOURED AT 1 ,2 ,4 AND 6 % PER 1% AREA. 26 EARLY LINEATIONS AND FOLD AXES (•)• FIGURE 3 -2 STEREOGRAPHIC PROJECTION OF STRUCTURAL DATA, MOUNT KOBAU GROUP. West S T R U C T U R A L DOMAINS AND SUB-DOMAINS IN T H E M A P - A R E A . DOMAIN BOUNDARIES LITHOLOGIC C O N T A C T S MAJOR INTRUSIONS MAJOR F A U L T S LOWER HEMISPHERE, E Q U A L A R E A S T E R E O -GRAPHIC P R O J E C T I O N U S E D IN A L L N E T S . CONTOURING OF DATA POINTS BY SCHMIDT OR GRID M E T H O D . DATA CONCENTRATION | f | l GREATER THAN 6 % PER 1% A R E A . 51 GREATER THAN 4 % PER 1% AREA. • LESS THAN 4 % PER 1% AREA. WEST DOMAIN, UPPER N E T : 746 POLES TO F 0 / F , SURFACES AND EARLY AXIAL PLANES CONTOURED AT . 5 , 1 , 2 , 4 AND 6 % PER 1% AREA. WEST DOMAIN, LOWER NET: |84 POLES TO F g SURFACES CONTOURED AT 1,2,4 AND 6 % PER 1% AREA. 235 LATE LINEATIONS AND FOLD AXES 0- 2 =) 

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