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Structure of Lardeau group rockes, Albert Canyon, British Columbia. Karvinen, William Oliver 1970

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STRUCTURE OP LARDSAU GROUP ROCKS ALBERT CANYON, BRITISH COLUMBIA by WILLIAM 0. KARVINEN B.Sc. Queen's U n i v e r s i t y , 1968 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Geology We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA MAY, 1970 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study . I f u r t h e r agree tha permiss ion fo r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed without my w r i t t e n p e r m i s s i o n . Department pf Geology  The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date 29 M a y , 1970 FRONTISPIECE D i s t r i b u t i o n of rock types at Corbin Pass, Albert Canyon, looking NW along the axis of the I l l e c i l l e w a e t Synform ABSTRACT At the north end of the Kootenay Arc, i s o l a t e d patches of g r i t t y q u a r t z i t e of the upper Lardeau Broadview Formation (Ord.?) l i e i n the core of a northwesterly trend-i n s t r u c t u r e , the I l l e c i l l e w e a t Synform. These rocks over-l i e , i n tectonic, contact, black, carbonaceous p h y l l i t e of the lower Lardeau Index Formation (lower to middle Ord.). The contact i s enclosed i n a zone of h i g h l y sheared and r e . c r y s t a l l i z e d rocks designated here as a p h y l l o n i t e zone. The Broadview rocks were thrust i n t o .juxtaposition with the Index during an e a r l y phase of i s o c l i n a l , recum-...ent f o l d i n g which ',: - e l a t e s with the development of nappe s t r u c t u r e s during deformation along the Kootenay. Arc. I n t e r s t r a t a l formations of the middle Lardeau were sheared out. The phase was accompanied by r e g i o n a l meta-morphism of greenschist grade which aided r e c r y s t a l l i z a t i o n and r e o i e n t a t i o n of quartz and mica. S i m i l a r f o l d i n g , nearly c o - a x i a l with Phase 1 and accompanied by waning metamorphism, f o l d e d , tightened, and r e a c t i v a t e d earlier-formed s t r u c t u r e s . This r e s u l t e d i n t r a n s p o s i t i o n of l i t h o l o g y and the asymmetric I l l e c i l l e -waet Synform. The r e l a t i v e age of the Broadview, which i s very s i m i l a r l i t h o l o g i c a l l y to Horsethief Creek e l a s t i c s of Windermere age, has not been e s t a b l i s h e d from t h i s study. i TABLE OF CONTENTS Page INTRODUCTION General Introduction. ................ ^ ........... ^  . .;. 1 Location and Access............................. . . . ••' 3 Geological Setting. .... . 3 Previous Work...... ,• .: j . . . '6 Current Hypotheses i . . . . . , # Acknowledgements.. ^  ........ •. . 9 STRATIGRAPHY AND GENERAL GEOLOGY General Stratigraphy, of the Kootenay Arc...' ..11 Stratigraphy and Rock Types at Albert Canyon. ^...... 15 Index Formation 15 Broadview Formation... . i .• 17 The Phyllonite Zone 2 0 Summa ry . 2 0 Comparison of Broadview at Albert Canyon to the Horsethief Creek C l a s t i c s . 21 Stratigraphy 2 1 Mineralogy. <.... t. ^ ....................... 2 2 C l c i s i i/S •• • • « « * c 9- • A- * • o *•< • £ • • «* * o • • « • • • o • • • 22 The Broadview-Index Contact 2 3 STRUCTURAL GEOLOGY Fold Sets,. . 2 5 Phase 1 ' 2 5 a) F o l i a t i o n , F 1 2 5 b) Lineation, L-^  i 2 6 c) Tension gashes 2 9 d) Fold style and the phyllonite zone 3 1 Phase 2 • 3 2 a) S t r a i n - s l i p cleavage, 3 2 b) Lineation, L p 3 4 i i • - • Page c) Style of Phase 2 f o l d i n g 3 4 d) The I l l e c i l l e w a e t Synform . ............. 3 7 Phase 3 . 3 7 a) Fracture cleavage, F^ 3 3 b) Lineation, ..........•* 3 $ c) Style of fo l d i n g « 3 # d) Summary • • 4 2 Petrofrabrics . • • 4 2 F l a t stage investigation 4 3 U-stage in v e s t i g a t i o n ... 4 3 a) Lower Index Formation 4 4 b) Lower Broadview Formation .-. 4 4 c) Upper Broadview Formation ^. 5 1 d) Discussion • 5 1 Summary of Structural and Metamorphic Events 5 2 DISCUSSION . Time of Lit h o l o g i c Transport 5 4 Correlation of Deformational Phases ..................... 6 0 RESUME AND CONCLUSIONS ' . 6 2 SELECTED REFERENCES '"6.4 APPENDIX A. Plates ' 6 8 • • • 1 1 1 LIST,. OF ILLUSTRATIONS FIGURE PAGE 1 Location map 4 2 General geology i n the v i c i n i t y of Albert Canyon 5 3 Cross-section of the I l l e c i l l e w a e t Synform 14 4 Equal-area plot of poles to F, and Phase 1 l i n e a t i o h s 2 7 5 The development of tension gashes 2 $ 6 Style of Phase 1 folds 30 7 Style o f Phase 2 folds* 30 3 Equal-area plot of L ? and poles to F 2 33 9 Cross-section of marble at. Corbin Pass 35 1 0 Spread of poles to F, on a great c i r c l e 3 6 whose' pole i s L^ 11 Equal-area plot of L^ and poles, to F^ 3 9 1 2 Dispersion of L ? and L^ by Phase 3 f o l d i n g 4 0 . 1 3 Equal-area plot of quartz c-axes from lower Index 4 5 14 Equal-area plot of quartz c-axes from lower Broadview (phyllonite) 4 6 1 5 Eoual-area plot of quartz c-axes from lower Broadview (phyllonite) 4 7 16 Combined, data from figures .14 and 15 projected on -a 'horizontal plane 4$ 17 Equal-area plot of quartz c-axes from upper Broadview ' ;49 1$ Equal-area plot of quartz c-axes from upper Broadview 5 0 i v LIST OP ILLUSTRATIONS FIGURE PAGE 19 Diagramatic sequence of events i n v o l v i n g large-scale t r a n s p o s i t i o n of l i t h o l o g y 55 20 Folding of transposed l i t h o l o g y i n t o the I l l e c i l l e w a e t - Synform 56 21 Diagramatic sequence of events using a nappe model 59 TABLES TABLE PAGE I General Stratigraphy of the Kootenay Arc 12 II Summary of Rock Types and Stratigraphy at Corbin Pass, Albert Canyon 13 V PLATES Number 1 Massive, upper Broadview quartzite 2 Photomicrograph of the muscovite-auartz-phyllonite 3 Rootless Phase 1 folds i n Broadview 4 Refolded rootless Phase 1 folds i n Broadview 5 S u p e r f i c i a l l y undeformed s i l t s t o n e of lower Index 6 Tension gashes i n muscovite-quartz-phyllonite of Broadview 7 Minor Phase 1 structure i n Index 6 A t y p i c a l Phase 2 s i m i l a r f o l d 9 A Phase 2 minor f o l d 10 Muscovite growth along ; a micro-photograph 11 Photomicrograph of a Phase 2 microfold 12 Photomicrograph of g r i t t y quartzite showing a r e l i c t e l l i p s o i d a l c l a s t 13 Minor Phase 1 fold i n marble 14 Sheared-out hinge of a Phase 1 minor f o l d , Index Formation MAPS ( i n pocket) Map 1 Rock types and F, structures at Corbin Pass, Albert Canyon, BtC. Map 2 F 9 and F_ structures at Corbin Pass, Albert Canyon,B.C. 1 CHAPTER I  INTRODUCTION General Introduction In the western Selkirk Mountains of B r i t i s h Columbia, west of'Revelstoke, three iso l a t e d patches of a g r i t t y ouartzite unit are exposed i n the core of a north-northwesterly-trendinH structure which was mapped as the I l l e c i l l e w a e t Syncline during reconnaissance work by Wheeler (1963). The quartzite, which l i t h o l o g i c a l l y and s t r a t i g r a p h i c a l l y correlates with the Broadview Formation of the upper Lardeau Group of Paleozoic age, l i e s d i r e c t l y on top of the lower Lardeau Index Formation. Middle Lardeau formations as defined by Fyles and Eastwood (1962) i n the Ferguson Lake area some 40 miles to the southwest, are missing i n the I l l e c i l l e w a e t Syncline. Recent speculation (Read, 1966, Wheeler, 196tf, 1970) that the Broadview may not be as young as the upper Lardeau but perhaps older and equivalent to the Horsethief Creek g r i t t y quartzite of Windermere- age has raised concern about the contact r e l a t i o n s between the Broadview and i t s underlying rocks. Along the Kootenay Arc, the Broadview quartzite, with minor i n t e r c a l a t i o n s of p h y l l i t e and volcanics, has been-manned as overlying various formations of the Lardeau Group (Wheeler, 1963, 1970). However, the contact has been observed only i n a few places. Where i t 2 has been seen i t i s knife-sharp and d i s t i n c t (Wheeler, pers-» comm.). I f the contact i s a shear surface which cuts up and down section through the Lardeau, then i t may well be a decollement along which the Broadview was thrust over younger rocks (Wheeler, 1963, 19^0) or i t may be a sole thrust of a napne thrust east as suggested by Ross (1970). The o r i g i n of the g r i t t y cmartzite i n the I l l e c i l l e w a e t Syncline and i t s possible equivalence to the Horsethief Creek, i t s contact r e l a t i o n s to the underlying Index Forma-t i o n and the. detailed structure of the Syncline are the basic objectives of t h i s t h e s i s . The writer spent some f i v e weeks mapping i n d e t a i l rock tynes and structures within the central patch of g r i t t y quartzite located at Albert Canyon on the Trans-Canada High-way (Fig. 2). The contact was observed and "walked-out" where nossible and the detailed r e l a t i o n s h i p between the Broadview and Index Formations was determined. Oriented specimens were collected f o r l a t e r petrofabric study. Results of the investi g a t i o n indicate that l ) the Broadview-Index contact i s a phyllonite zone and i s tectonic i n o r i g i n , 2) at least three nhases of fo l d i n g have affected the rocks, 3 ) the I l l e c i l l e w a e t Syncline i s a late phase, si m i l a r , assymetric, f o l d which i s overturned to the west,.and k) the r e l a t i v e age of the Broadview i s uncertain and so the f o l d i s here called a synform. 3 Location and Access The area investigated i s located i n the "high" Selkirk Mountains of east central B r i t i s h Columbia some 430 miles east of Vancouver (Fig. l ) . It i s bordered by the Tangiers River to the northwest and the Trans-Cahada Highway to the southeast. The nearest Canadian P a c i f i c Railway sidings are the Albert Canyon and I l l e c i l l e w a e t stations. Access to the northwestern side of the mountain i s possible along a logging road which follov/s the Tangiers River f o r about 2 miles from Albert Canyon. The southern slopes are accessible from the Trans-Canada Hirrhway v i a old logging roads which reach an elevation of about 3$00 f t . above sea l e v e l . There are no t r a i l s or roads to the top of Corbin Pass which i s at an elevation of about 6500 f t . above sea l e v e l . Geological Setting. The man-area i s situated just east of the easternmost margin of the Shuswap Complex at the northern end of the Kootenay Arc'. The rocks have been regi o n a l l y metamorphosed under low-grade conditions and are separated from the Kootenay Arc".....is a r e l a t i v e l y narrow curving s t r u c t u r a l b e l t i n southeastern B r i t i s h Columbia extending southeast from near Revelstoke, south along Kootenay Lake, and south-west across the International Bo\mdary into Washington It i s a highly deformed b e l t of r e l a t i v e l y steeply-dipping sedimentary and volcanic rocks bowed about and l y i n g mainly east of a major gran i t i c area containing the Nelson and Kuskanax batho l i t h s " (from Fyles, 1962). Fig. 1 Location Map 5 p o s t k i n e m a t i c i n t r u s i o n B a d s hot Fm. Upper L a r d e a u Gp, ( B r o a d v i e w Fm.) H a m i l l Gp, Lower L a r d e a u Gp, ( I n d e x Fm 0) H o r s e t h i e f C r . Group s y n k i n e m a t i c i n t r u s i o n G r a n i t e G n e i s s 6 higher-grade Shuswap rocks to the west by a northwesterly-trending zone of rapid change of metamorphic grade. S t r u c t u r a l l y , the area l i e s i n the western part of the Selkirk Mountains where structures are overturned to the west and separated by steeply-dipping f a u l t s (Wheeler, 1963). The patch of g r i t t y quartzite at Albert Canyon i s the central patch of three such i s o l a t e d erosional remnants of Broadview completely surrounded by and o v e r l i n g the Index Formation (Fig. 2). Previous work A l l previous work i n the immediate v i c i n i t y of Albert Canyon has been on a reconnaissance scale except f o r the detailed mapping by Ross just to the west between Albert Canyon and. Revelstoke (Ross, 196$). The e a r l i e s t investigations were by G.M. Dawson (l#90, 1891, 1*93, 1901) and R.A. Daly (1915) who are credited f o r laying the foundations of structure, stratigraphy, and h i s t o r i c a l geology of the Selkirk Mountains. In h i s general cross-section of the structures across the S e l k i r k s , Daly designated the area at Albert Canyon as a "contorted zone" i n the "Laurie m e t a r g i l l i t e " . In the summer of 194*, V.J. Okulitch spent some six weeks on a reconnaissance mapping t r i p along the Canadian P a c i f i c Railway between Albert Creek and Beaver Creek i n the Glacier Park Map-Area (Okulitch, 1949). It i s i n his report 7 where the f i r s t general cross-section of the I l l e c i l l e w a e t Synforra (then called the Laurie syncline) appears. He inter-prets the structure as a syncline overturned to the west which i s outlined by the Hamill quartzite. He did not map the i s o l a t e d patch of Broadview at Corbin Pass i n the present map area. Okulitch's general interpretation of the structures led him to suggest thrusting towards the west. No further work was done i n the area u n t i l Wheeler's Reconnaissance mapping i n the early 1960fs f o r the Geologi-c a l Survey of Canada (Wheeler, 1963). In his report on the Roger's Pass map-area, Wheeler redefined the structure at Albert Canyon and call e d i t the I l l e c i l l e w a e t Syncline since i t had g r i t t y quartzite resembling the Broadview i n i t s core. He suggested that the syncline was "a t i g h t l y - f o l d e d struc-ture which i s overturned to the southwest and r o l l s over into a t i g h t l y overturned a n t i c l i n e whose limb i s sheared o f f " . He recognized and mapped the three patches of g r i t t y quartzite and suggested that they were probably eauivalent to the Broadview Formation as defined by Fyles and Eastwood (1962). No detailed work has been done i n the Corbin Pass map-area. However, just to the west, i n the highly metamorphosed rocks of the easternmost Shuswap Complex, Ross has mapped structures and stratigraphy i n d e t a i l (Ross, 196#). Work-in' t h i s area and i n various areas along the Kootenay Arc. has 8 led him to postulate a tectonic model f o r the evolution of the Kootenay Arc (Ross, 1970). Current Hypotheses Two hypotheses currently e x i s t regarding the age and o r i g i n of the Broadview Formation. These hypotheses are the result of the evolutionary model of the Kootenay Arc ^ut fo r t h by Ross (1970) and the s t r u c t u r a l and h i s t o r i c a l hypo-theses proposed by Wheeler (l96#, 1970) f o r the evolution of the Kootenay Arc. Wheeler advocates that the Broadview i s a western faci e s of the Horsethief Creek e l a s t i c s and thus i s Windermere i n age. He bases his argument on the' l i t h o l o g i c a l s i m i l a r i t y of the two rock types, the presence of blue quartz i n both ( f i r s t noted by Read, 1966) ,. and the fact that a possible decollement exists below the Broadview throughout the Kootenay Arc. He suggests that the Broadview was thrust from the west to the east over younger rocks during the mid-Paleozoic Caribooan Orogeny. Detailed mapping and work along the Kootenay Are by Ross has led him to propose an evolutionary model f o r the Kootenay Arc involving large-scale nanpes which were thrust to the east. He recognizes two main nanne regimes which are separated by a l i n e that follows the Index Formation throughout the whole length of the Arc. The rocks of the Index are my l l o n i t i c and thus the l i n e i n e f f e c t i s a zone of movement 9 which separates easterly closing nappes i n the west from westerly c l o s i n g nappes i n the east. The easterly closing structures are the allochthonous mass which was thrust east-ward against a parautochthonous mass which had slumped o f f of the P u r c e l l basement. Ross has outlined three main allochthonous nappes at d i f f e r e n t s t r u c t u r a l l e v e l s : l ) the lowermost Clachnacudainn nappe near Revelstoke, 2) the Albert nappe exposed on Albert Peaks just southwest of Albert Canyon, and 3 ) the MiIford nappe which i s s t r u c t u r a l l y the highest and has been thrust over the two lower nappes and across the main thrust zone (Fig. 2 and Ross, 1970, p. 64). The isolated patches i n the I l l e c i l l e w a e t Synform, he sug-gests, cnuld be "either easterly klipnen of the s t r u c t u r a l l y highest and discontinous Milford nappe or remnants of easter-l y Horsethief Creek erosive products" (Ross, 1970, p . 6 3 ) . Thus the Broadview Formation has at least two possible ori g i n s and r e l a t i v e ages: l ) i t could be equivalent to the Horsethief Creek Group and thus Windermere i n age (Wheeler, 196ft, 1970) , or 2) i t could be an erosive product of the Horsethief Creek, deposited during lower Paleozoic times i n front of r i s i n g nappes and. thus Lower and/or Middle Paleo-zoic i n age (Ross, 1970). Both views are possible and as yet, neither has been proven or disproven. Acknowledgements This project was supported f i n a n c i a l l y by a National 10 Research Council grant through the guidance of Dr. J.V. Ross of the Geology Department of U.B.C., who suggested the problem. His excellent supervision, h e l p f u l suggestions and advice, and time devoted f o r discussion are here acknow-ledged; the writer i s sincerely grateful to him. The f i e l d work and w r i t i n g of t h i s thesis has been a most valuable experience to the writer. Helpful advice was also provided by Dr. J.O. Wheeler of the Geological Survey of Canada and able f i e l d assistance by Karl Karvinen. To a l l these people, the writer wishes to express his sincere thanks and appreciation. 11 CHAPTER II STRATIGRAPHY AND GENERAL GEOLOGY General" Stratigraphy of the Kootenay Arc The sequence of sedimentary and volcanic rocks which outcrop along the Kootenay Arc can be divided into two general groups on l i t h o l o g y alone: Late Proterozoic to Lower Cambrian e l a s t i c s , quartzites, and. limestone and a younger group of lower Paleozoic grawackes, shales, a r g i l l i t e s and minor volcanics and limestone (see Table I ) . The Lardeau Group belongs to the l a t t e r group. The age of the Lardeau has not been well defined. It i s known, however, that the lower Lardeau Index Formation conformable overlies the Badshot limestone which contains Lower Middle Cambrian archeocyathids (Wheeler, 1 9 6 6 ) , No f o s s i l s have been found i n any of the Lardeau rocks, how-ever, the Index Formation i s probably Lower and Middle Ordovician i n age since i t appears to correlate l i t h o l o g i -c a l l y with the Active Formation of the Salmo area from'which Middle and Lower Ordovician f o s s i l s have been collected ( L i t t l e , I 9 6 0 ) . The ages of the other formations of the Lardeau, along with the Broadview, as defined by Fyles and Eastwood ( 1 9 6 2 ) i n the Ferguson Lake area,are unknown. The upper l i m i t i s the lower Mississippian unconformity and so the upper Lardeau could be as young as Devonian (Table I ) . Rocks of the Lardeau Group are exposed along the whole length of the Kootenay Arc; the g r i t t y quartzite and 12 JURA. TRIAS. DEV SIL. ORD. CAMB. WIND. NELSON BATHOLI TH 16Ax10Vs K-A SLOCAN GRP ? KASLO FM. MILFORD GRP. BROADVIEW FM. LARDEAU GRP AJAX FM. INDEX FM. BADSHOT FM. HAMILL GRP. HORSETHIEF CREEK GRP. S h a l e ; A r g i l l . 1st; CHzt.; G w k e . . V o l c a n i c s ; Vole. ss t . S e r p e n t i n e .  A r g i l l . 1st.; s s . 1st.; S h a l e ; G w k e . ; Q t z t . C o n g l o m . . G w k e . ; S h a l e . V o l c a n i c s ; Vole. s s t . V o l c a n i c s ; G w k e . ; S h a l e ; Q t z t . ; G w k e . ; S h a l e ; C a l c shale ; Ca lc . ss t . ; Lst .  Qtzt . A r g i l l . 1st.; Sst . - S h a l e ; Conqlom. . PURC. Table I General Stratigraphy of the Kootenay Arc (Ross, 1970). 13 SUMMARY OP ROCK TYPES AND STRATIGRAPHY AT CORBIN PASS Table II SYSTEM GROUP Miss. Dev. Lardeau S i l , — 9. Ord ( Lardeau FORMATION MEMBER micaceous gritty-quart z i t e Broadview (upper Lardeau) missing '/////////// Index (lower Lardeau) Badshot muscovite-quartz-p h y l l o n i t e at Corbin Marble Carbonaceous s i l i c e o u s , p h y l l o n i t e Limestone LITHOLOGY muscovite, blue, c l e a r quartz c l a s t s or e l l i p -soids i n a matrix of cl e a r quartz; massive but well f o l i a t e d . h i g hly sheared, w e l l -laminated and myloniti c ; muscovite, c l e a r matrix quartz and few stretched c l a s t s ; some sheared-out lenses of above mem-ber; s t r i n g e r s and lenses of mobilized quartz. pure c a l c i t e with quartz and muscovite abundant close to upper and lower con-t a c t s . h i ghly sheared and f i s s i l e ; mica, quartz and disseminated carbon; aphanitic« massive but w e l l -laminated; muscovite, c h l o r i t e , quartz, c a l c i t e , p y r i t e , p y r r h o t i t e and carbon. occurs just west of t h i s map-area. 14 15 graywacke with intercalated volcanic rocks of the Broadview outcrop i n a large area along the Arc and appear to rest with some angular relationship on lower Lardeau rocks since i n some places they rest on the Index and i n other places on middle Lardeau formations (Wheeler, pers. comm.). This angular rel a t i o n s h i p has been interpreted as a decollement beneath the Broadview by Wheeler ( 1 9 6 $ , 1 9 7 0 ) and as a thrust surface by Ross ( 1 9 7 0 ) . Stratigraphy, and Rock Types at Albert Canyon The only Lardeau rocks exposed i n the map area at Albert Canyon are the Index and Broadview Formations (Map 1 , F i g . 3 and Table I I ) . The underlying Badshot limestone outcrops just to the west of the map-area and l i e s conform-able below the Index (Ross, 1 9 6 8 ) . Rocks of the Index underlie the whole area and are exposed from road l e v e l up to 4 5 0 0 f t . above sea l e v e l ; the remaining 2 0 0 0 feet or so on top of the mountain consist of the Broadview i n the core of the I l l e c i l l e w a e t Synform (Fig. 3 ) ; wedged i n between the Index and the Broadview i n the northeastern part of the area i s an exotic mass of marble which i s believed to be an upper member of the Index (Table II and Fig. 3 ) . Index Formation: the Index Formation at Albert Canyon which i s a black, p h y l l i t i c , carbonaceous, calcareous, s i l t s t o n e , was divided by the writer into three mappable members: l ) a lower p h y l l i t i c s i l t s t o n e (map-unit l c ) , 16 ?) a phyllonite member (map-unit l b ) , and 3) a marble member (map-unit l a ) . The lower member is a massive, but well f o l i a t e d s i l t -stone which outcrops along the Trans-Canada Highway i n the southwestern part of the area. It i s r e l a t i v e l y well-sorted and displays well-developed composition layering (Plate 14). The main minerals are auartz (15-35/0 , c a l c i t e (20-35%), muscovite (12-20%), graphite (10-15%), c h l o r i t e (5-15%) and pyrite-pyrrhotite (§%). Quartz grains are p a r t i a l l y recrys-t a l l i z e d and micaceous minerals are strongly aligned within the main f o l i a t i o n . Composition layering i s outlined by layers r i c h i n graphite and muscovite and those r i c h i n quartz and c a l c i t e . Hemobilized ^uartz occurs ubiauitously as stringers and lenses p a r a l l e l to composition layering and as rootless f o l d cores (Plates 5, 7, and 3 ) . The middle member, which varies in thickness from 1100 to 1500 f t . , i s a very f i s s i l e , black, aphanitic rock. It outcrops below the Broadview-Index contact in the south-western part of the area and reappears again on top of the mountain just to the east of Corbin Pass (Fig. 3 and map l ) . Mineralogically, t h i s member i s similar to the underlying s i l t s t o n e s , however, It has been much more highly sheared and r e c r y s t a l l i z e d ; i n t h i n section, i t s texture i s myllon i t i c and as a r e s u l t , i t has been called a phyllo n i t e . It makes up the lower part of the phyllonite zone as 17 i l l u s t r a t e d i n Figure 3• The uppermost member of the Index i s as exotic lense of gray marble wedged between the Broadview and the two lower members of the Index. It outcrops i n the northeastern part of the area and varies from zero to 700 feet thick (Fig. 3). Mineralogically the marble i s nearly pure c a l c i t e , however, i t i s quite s i l i c e o u s and micaceous at both con-ta c t s . It contains numerous rootless folds (Plate 13) and remobilized lenses and stringers of white c a l c i t e . The main f o l i a t i o n i n the marble i s outlined by muscovite and i s associated with the minor fo l d s . ( P l a t e 11). Broadview Formation: the Broadview at. Albert Canyon i s a micaceous quartzite unit which reaches a maximum thickness of about 3500 feet at Corbin Pass. In t h i s map area, the writer has divided the Broadview into two mappable members: 1) a lower muscovite-quartz-pteyllonite (map-unit 2b) and 2) an upner muscovite-gritty-quartzite (map-unit 2a). The d i v i s i o n was made purely on the presence or absence of angular to sub-rounded quartz-and feldspar fragments; mineralogically, both members are e s s e n t i a l l y i d e n t i c a l . The upper member is a massive, but well f o l i a t e d , micaceous quartzite which contains angular to rounded frag-ments of quartz and some feldspar. It may be described as a g r i t ' , however, here has been designated a g r i t t y "...poorly sorted, c l a s t i c , sedimentary rock with rounded and angular grains, mainly quartz, up to several millimeters i n diameter" (Fyles and Eastwood, 1962 p. 27). 16* quartzite since the angular fragments or clasts generally make up less than 50% of the whole rock. No bedding was recognized i n any of the outcrops examined, however, p h y l l i t i c horizons or very g r i t t y horizons could be followed along s t r i k e a few tens of feet before pinching out at minor shear zones which p a r a l l e l the main f o l i a t i o n . These lenses then, could represent o r i g i n a l bedding which has been transposed and disrupted through movement along t h i s f o l i a t i o n . The w r i t e r found no evidence of Cross-bedding, graded-bedding, or any other such struc-ture which could have been used to determine whether the section examined was upright. Mineralogically, the quartzite consists predominantly of quartz (70-95%) -, muscovite (0-15%), plagioclase (^-3%), and orthoclase (^-1%). Quartz occurs i n two forms: 1) as rounded lensoids and e l l i p s o i d s averaging 2-U mm. i n si z e , and 2) as an equi-granular, fine-grained, r e e r y s t a l l i z e d matrix. Quartz of form 1 appear to be r e l i c t sedimentary fragments which have been deformed into lensoidal and e l l i p s o i d a l shanes which now l i e within the main f o l i a t i o n plane.. This form of quartz, which makes up 25 to 50 percent of the whole rock consists of two main types: l ) clear to glassy quartz and smokey to blue quartz, and 2) white, opaque quartz. Those of type 1 are more common, making up about #0 to 90 percent of the c l a s t s 19 whereas those of type 2 make up less than 2 0 percent; These r e l i c t quartz clasts have average dimensions as follows: long axis: 2-L mm., intermediate axis: 1 - 2 mm,$ and short axis: 1 to less than 1 mm. The cla s t s are crude e l l i p s o i d s which are flattened i n the plane of the main f o l i a t i o n . Feldspars, even though scarce, occur ubiquitously as angular r e l i c t sedimentary fragments making up a combined average of about 1 percent Of the whole rock* Generally these fragments have not been deformed into lensoids or e l l i p s o i d s but are angular and i n t h i n section are often found, oriented: across the main trend of the f o l i a t i o n . It appears that conditions of deformation.and metamdrphism were not favourable f o r the cohesive deformation of feldspar; instead;, the fragments were bodily rotated and ground up during deformation. Very fi n e fragments of feldspar presum-ably o r i g i n a t i n g from c a t a c l a s i s of t h i s sort are common i n the matrix of nuartz. The upper member of the Broadview grades downwards into the lower member whichhas been designated the muscovite-quartz-nhyllonite. This member i s s l i g h t l y more micaceous than the upper member., but i s otherwise mineralogically;:.'. i d e n t i c a l to i t . It contains very few long, attenuated., quartz lenses (Plate 2 ) which probably at one time were r e l i c t sedimentary c l a s t s such as those described above. However., t h i s member has been highly sheared along perietra-20 ti v e shear surfaces and the quartz has been nearly a l l re-c r y s t a l l i z e d . The rock i s massive, f i n e l y laminated and aphanitic and thus i s mylT-.onitic. The thickness of t h i s member varies from 2 0 0 to 1 2 0 0 feet with the thickest section near the nose of the f o l d . This member i s the upper part of the nhyllonite zone i l l u s -trated i n Figure 3 . The Phyllonite Zone: the highly sheared phyllonite member of the upper Index and the muscovite-quartz-phyllonite of the lower Broadview together constitute the phyllonite zone. This zone encloses the Broadview-Index contact In the southwestern part of the map area; towards the northeast, t h i s zone-appears to became p a r t l y dissipated into the marble unit, however, myl".onitic Broadview rocks d* r ;ccur above the marble i n the northeastern part i:of the area. F i s s i l e , myll.oriitic rocks of the upper Index appear again on top of the mountain just east of the marble at Corbin Pass. Summary: i n summary then, the two main rock tynes, the Broadview and the Index, although they are now i n mutual contact, have two very d i f f e r e n t l i t h o l o g i e s representing two d r a s t i c a l l y d i f f e r e n t environments of deposition. This difference along with the presence of a phyllonite zone en-closi n g t h e i r contact suggests that r e l a t i v e movement has :, occured between these two formations since t h e i r consolidation. 21 Comparison of the Broadview at Albert Canyon to the  Horsethief Creek C l a s t i c s The lower formation of the Horsethief Creek Group which reaches a thickness of about 3000 feet, consists of f e l d -spathic, .coarse, quartzite and pebble conglomerate with interbands of slates and p h y l l i t e s (Evans, 1932), The upper formations are predominantly sl a t e s , phyllites$ arid lime-r stones. This lower formation i s the c l a s t i c unit which may have i t s western equivalent i n the Broadview g r i t t y quartz r i t e . Samples of g r i t t y quartzite collected from t h i s forma-t i o n along the Trans-Canada and along the western flanks of the Rocky Mountain Trench were examined under a r e f l e c t i n g microscope. The compositions and percentages of the c l a s t s were p a r t i c u l a r l y noted and are here compared with the g r i t t y quartzite at Albert Canyon. Stratigraphy: both the lower Horsethief Greek forma-tions, and the Broadview g r i t t y quartzite are. predominantly c l a s t i c i n nature, and reach thicknesses of about 3000 feet. Minor intercalations: of phyll i t e . are. present i n both, however., they apnear to be more, common i n the Horsethief Greek. Bedding i n the Broadview at Albert Canyon i s v i r t u -a l l y absent, whereas the Horsethief Creek elastics, are• weii-r bedded and i n d i v i d u a l beds can be followed along the s t r i k e f o r hundreds of feet. Both units contain r e l i c t c l a s t s 22 mainly of quartz and some feldspar, which now are e l l i p s o i d a l i n shane. Mineralogy: both consist predominantly of quartz with minor amounts of muscovite ( s e r i c i t e ) , feldspar, and iron oxides. Feldspars, however, are much more common i n the Horsethief Creek (1-6%), whereas i n the Broadview, they are very scarce ( 1%). Potassic feldspar i s present as very f i n e grains i n some of the rocks of the Broadview;in the Horse-t h i e f Creek, potassic feldspar makes up to 4 percent of the rock and i s mainly microcline (Evans, 1932). The plagioclase i n both units i s about the same composition ( a l b i t e -o l i g o c l a s e ) , but i s le s s common i n the Broadview. Clasts: i n general, r e l i c t sedimentary c l a s t s are much more common i n the Horsethief Creek than i n the Broadview; i n the former, the average percentage of c l a s t s i s about 60 to 70, whereas, i n the l a t t e r i t i s about 20 to 25 percent. Three types of c l a s t s are common i n both: l ) blue, clear, and smokey quartz, 2) opaque, white,, quartz, and 3) white angular feldspar. The most common i s type 1 which makes up about #0 per-cent of the c l a s t s ; least common are angular feldspar c l a s t s . In general, the sizes of c l a s t s i n the Horsethief Creek are larger (2-7 mm.) than those i n the Broadview (1-4 mm.), but t h e i r r e l a t i v e proportions are about the same i n each. Blue quartz c l a s t s which are related to the smokey and 23 glassy quartz c l a s t s , are scarce i n the Broadview at Albert Canyon, but are quite common i n the Horsethief. This b r i e f comparison i l l u s t r a t e s the s t r i k i n g resem-blance between these two c l a s t i c rock units. The contrasts seem to be the difference in. percentages of c l a s t s and i n t h e i r sizes, the unbedded character of the Broadview i n con-tr a s t to the good bedding i n the Horsethief, and the general lack of feldspar c l a s t s i n the Broadview. None of these differences rule out the p o s s i b i l i t y of these two units being equivalents; however, the Broadview, could also very well be an erosive product of the Horsethief Creek. This l a s t view i s supported by the more mature and less c l a s t i c character o f the Broadview. The Broadview-Index Contact In general the Broadview-Index contact i s poorly ex-posed except on top of the mountain at Corbin Pass and i n a few very steep c l i f f faces on the northwestern slope of the mountain. The contact was examined on several outcrops on the southern slope down from Corbin Pqss (map l ) where the lower Broadview i s i n contact with the marble unit. A l l such outcrops examined revealed a knife-sharp contact which could be defined to within a few inches. There i s no indication-of. an erosional unconformity such as an erosion surface or i n -clusions of the lower rock i n the overlying u n i t . The marble just beneath the contact i s well f o l i a t e d and r i c h i n muscovite and quartz, but i t quickly grades downwards into 24 pure marble away from the contact. The contact observed on the northwestern slope of the . mountain was on a c l i f f face where the Broadview., marble, and Index s i l t s t o n e were a l l exposed. Here- the marble i s about 2 feet thick and separates the overlying Broadview from the underlying Index along very sharp, d i s t i n c t , contacts. Again, there Is no i n d i c a t i o n of an erosional unconformity. At the southwestern end of the mountain, outcrons are well enough exposed to define the Broadview-Index Contact to' within a few feet under overburden. Examination of rocks on both sides of the contact revealed that i t i s enclosed i n the highly sheared rocks of the lower Broadview and upper Index. Here the marble unit i s e n t i r e l y missing. Thusj the Broadview-Index contact i s knife-sharp, has no c h a r a c t e r i s t i c s i n d i c a t i n g an erosional unconformity, i s enclosed by highly sheared rocks of the phyllonite zone, and contains an exotic lens\ of marble. 2 5 CHAPTER III  STRUCTURAL GEOLOGY Mapping of l i t h o l o g i e s and contacts indicates that the main structures at Albert Canyon are the I l l e c i l l e w a e t Syn-form which i s overturned to the west (Fig. 3 and f r o n t i s -piece) and the phyllonite zone which appears to represent a major zone of movement. Detailed mapping of small-scale structures such as fol d s , f o l i a t i o n s , l i n e a t i o n s and the s o r t i n g out of se-quences Of deformation have revealed three d i s t i n c t but overlapping phases of f o l d i n g which have been responsible for the structures as we see them at Albert Canyon. These phases have been designated as Phases 1 , 2 , and 3 which are r e l a t i v e terms, applicable only to thi s area; they are hot, at t h i s time., intended to be correlated with other such deformational phases elsewhere. Foid Sets Phase.1: the e a r l i e s t phase of deformation a f f e c t i n g the rocks of the present map-area, which also was the most intense, was a phase of i s o c l i n a l , recumbent, similar f o l d i about a north-northwesterly trending axis. Common Phase 1 s t r u c t u r a l elements seen i n the f i e l d are a very prominent, penetrative f o l i a t i o n , a penetrative l i n e a t i o n and minor rootless folds with long, attenuated limbs. a) F o l i a t i o n , F-, : the Phase 1 planar element i s a 2 6 g'ently-dipning, penetrative structure which i s best developed i n the Index but "i's present i n a l l the rocks. It i s the most obvious planar element seen i n the f i e l d and the rocks readi-l y break along i t . F^ i s p a r a l l e l to composition layering and on the average dips about 17 degrees to the northeast: i n the southern part of the area and 16 degrees southwest i n the northeastern part (map 1; F i g . 4). In th i n section F^ i s v i s i b l y outlined by a strong alignment of musCovite (Plate 2) and l e n s o i d a l quartz fragments (Plate 12). . ... Movement along F^ i s indicated by the numerous shear surfaces which are p a r a l l e l to It... Such shear surfaces occur on various scales such as the mesoscopic shear surfaces bounding tension gashes (Plate 6) , on a microscopic scale where r e l i c t quartz c l a s t s are often displaced by microshears p a r a l l e l to F^ and on the .".macroscopic scale where shear sur-faces displace and1 dlsrunt l i t h o l o g y . An example of the macroscopic scale of'shearing is. i l l u s t r a t e d i n Plate 14 where a r e l i c t rootless f o l d indicates that o r i g i n a l l i t h o -logy has been transposed through movement along F^. In e f f e c t , then, F^ Is a "transposition cleavage" (Knopf,, .1931) and. movement along i t on various scales has completely transposed the o r i g i n a l l i t h o l o g y into composition layering. Thus any o r i g i n a l bedding which may have been preserved has . been o b l i t e r a t e d . b) Lineation, L, :•• Phase 1 l i n e a r elements recognize i n F i g , 4. A lower hemisphere equal-area plot of poles to F-^  (dots) and L-^  (crosses). The average P 1 attitudes are 132/16SW and 132/17NE. The major L 1 concentrations l i e at 146/2 and 326/5. / 28 (A) I< [ ^ d i l a t i o n 11 in f racture U (B) -> <-(C) • F I F, The development of a tension f r a c t u r e at some angle 0 to the main shear surfaces, •P1. (McKinstry, 1953; Wilson, 1961) With continued movement, the fracture rotates and opens up. Compare with sigmoidal shapes of S-folds i n Plate 6 . With increased movement on F=,, another i n c i p i e n t surface may become active and movement on It may r e s u l t i n the t r a n s p o s i t i o n of l i t h o l o g y as shown by the small a r r o w s . 29 the f i e l d are e l l i p s o i d a l quartz clasts which occur i n the Broadview and quartz rods which are better developed i n the Broadview but are also found i n the Index. C a l c i t e grains i n the marble also indicate, some preferred elongation i n the L-^  d i r e c t i o n . A lower hemisphere eoual-area plot of L-^  measurements made i n the f i e l d reveal two concentrations: one trend plunging gently to the north-northwest and another plunging gently to the south-southeast (Fig. 4 ) . e) Tension gashes: common small-scale Phase 1 struc-tures which are well developed i n the lower Broadview are tension gashes... These gashes are f i l l e d with aphanitic, re-c r y s t a l l i z e d ,. quartz and are bound by microshears which are p a r a l l e l to F^ (Plate 6).•Intersections between the gashes and the F.^  planes are l i n e a r elements outlined by quartz and p a r a l l e l to L^. Since these tension gashes are intimately associated:' with movement on F^ and also impart a l i n e a t i o n p a r a l l e l to L-^  on F^ surfaces, i t appears that these gashes were developed during Phase 1.. These, gashes may have been reactivated'during l a t e r phases, however, conditions for the remobilization of quartz were most favourable during Phase 1 and c e r t a i n l y much of the quartz now f i l l i n g the gashes was remobilized that time. Accenting the premises that tension gashes originate from the development of tension fractures at some angle to 30 F i g . . Style of Phase 1 minor f o l d s . P Q i s comp-o s i t i o n l a y e r i n g whereas P^ i s the penetrative cleavage associated with Phase 1 f o l d i n g . P i g . 7, Style of Phase .2.similar f o l d i n g . Note very attenuated, r o o t l e s s Phase 1 f o l d s . P 2 i s the second phase s t r a i n - s l i p cleavage. 31 adjacent shear surfaces and with continued shearing, rotate into dilatent., sigmoidal, gashes (McKlnstry, 1953, Wilson, I960) thon the r e l a t i v e sense of movement can be deduced from the r e s u l t i n g cross-sectional shapes of the gashes (Fig. U A, B). The writer examined oriented hand specimens and outcrops with tension gashes i n an attempt to determine the r e l a t i v e sense of movement during Phase 1. A l l such observations made have indicated the r e l a t i v e sense of movement was s i n i s t r a l , that i s left-handed. Often tension gashes have been p a r t i a l l y destroyed by movement along an F^ surface which has l a t e r become active between the txvo main shears (Fig. 5C). d) Fold Style and the Phyllonite Zone: only minor, small-scale, Phase 1 folds have been seen i n the f i e l d however, a l l those examined suggesto-<' that the sty l e of fo l d i n g was i s o c l i n a l and si m i l a r i n nature (Plates 3, k, and 13; Fig. 6), As a resu l t most Phase 1 folds are very tight with sharp, angular, hinges and are often rootless due to accompanied movement along F^ (Plate 14). In an e a r l i e r section, i t was established that move-ment along F^ has occured on a l l scales (page 26). Mapping also revealed that the Broadview-Index contact i s a sheared zone of m y l l o n i t i c , well—laminated rocks; t h i s lamination i s a f o l i a t i o n which i n ef f e c t i s F^. The orientation of the planar Broadview-Index contact and the phyllonite zone 3 2 which encloses i t i s p a r a l l e l to the average orientation of F^ obtained from numerous f o l d measurements (Fig. 3 and 4 ) . These facts indicate that the phyllonite zone originated during Phase 1 deformation during which time movement along F^ surfaces occured on various scales and to various degrees. The Broadview-Index contact may be thought of as a large-scale F^ shear surface. Phase 2 : the intense deformation of Phase 1 gave v/ay to a milder phase of si m i l a r f o l d i n g , nearly co-axial to Phase 1 , which refolded and tightened e a r l i e r folds and folded e a r l i e r planar and l i n e a r elements. Phase 2 s t r u c t u r a l elements examined and measured i n the f i e l d are a s t r a i n - s l i p cleavage, l i n e a t i o n s , and small-scale f o l d axes. a) S t r a i n - s l i p cleavage, F^: the most common Phase 2 s t r u c t u r a l element i s a non-penetrative s t r a i n - s l i p cleavage. It i s best developed i n the Index where i t i s commonly ob-served di s p l a c i n g F^ and involved in' Phase 2 similar f o l d i n g (Plate 8). In th i n section, F^ i s evident as a slip-plane which p a r t i a l l y bends and breaks 'earlier micas along F^ and i s i t s e l f p a r t l y outlined by muscovite growth (Plates 2 , 1 0 and 1 1 ) . An eaual-area plot of F^ measurements made i n the f i e l d indicates a general attitude of 123/73NE (Fig. #). The sense of movement on F 5 where i t has been observed dis p l a c i n g F, F i g . 8. A lower hemisphere equal-area plot of poles to F 2 (dots) and L 2 (crosses). This i n d i c a t e s an average attitude f o r F 2 of 123/78NE. The main L 2 concentrations are at 123/5 and 307/5 and l i e i n F Q 33 N T 34 i s i n v a r i a b l y s i n i s t r a l ; t h i s i s consistent with the sense of movement deduced from the tension gashes. b) . Lineation, L^: two common types of l i n e a r struc-tures which developed during Phase 2 f o l d i n g are l i n e s of interse c t i o n between F^ and F^, which are v i s i b l e as minute crenulations. of mica on the F^ surface, and quartz rodding which i s best developed i n the Broadview. Measurement of these elements i n the f i e l d and t h e i r equal-area plot indicate a nearly horizontal northwesterly trend (Fig. S); dispersion of these li n e a t i o n s into two gently-plunging directions i s due to l a t e r Phase 3 f o l d i n g . c) Style of Phase 2 f o l d i n g : Phase 2 folds are predomi-nantly s i m i l a r i n s t y l e , normal to open, and have rounded hinges (Plate Such folds are best developed i n the Index where they are seen f o l d i n g e a r l i e r minor rootless folds (Plate 4 ) . Chevron f o l d i n g , however, characterizes the style of f o l d i n g i n the marble unit where such f o l d i n g has ser-rated the upper and lower contacts and steepened i t s contact to nearly 90 degrees. A good example of t h i s f o l d i n g style i s evident on top of the mountain at Corbin Pass where isola t e d wedge-shaped, masses of Broadview quartzite occur as erosional remnants i n the cores of chevron-shaped synforms. Since these are Phase 2 f o l d s with a x i a l planes dipping steeply to the northeast, then the present ground l e v e l on top of the mountain i s the 35 quartzite marble p h y l l i t e F i g . 9 . A northeast-southwest c r o s s - s e c t i o n of the marble unit on top of the mountain east of Corbin Pass. Note i n f o l d e d Broadview quart z i t e i n the cores of Phase 2 synforms and how r a p i d l y the marble pinches out. F i g . 10. Poles to l i e on a great c i r c l e (CD) whose pole (P) i s almost coincident with L ? . 36 37 contact between the quartzite and the marble; thus the marble unit never extended above the present mountain top; instead i t pinches out as i l l u s t r a t e d i n Figure 9. The marble unit then, was roughly lensoidal i n shape before Phase 2 f o l d i n g . F^ i n the marble i s folded into chevron folds which have nearly horizontal and v e r t i c a l limbs and wavelengths i n the tens of feet; i t i s continuous through the marble and cuts across the contacts of the marble at a small angle (Fig. 9). d) The I l l e c i l l e w a e t Synform: s i m i l a r f o l d i n g and the development of a steeply-dipping s t r a i n - s l i p cleavage folded the phyllonite zone and composition layering into an asym-metrical f o l d which.is the I l l e c i l l e w a e t Synform. This Syn-form has an. a x i a l plane dipping steeply to the northeast and as eastern limb overturned to the west (Fig. 3). The limbs of the f o l d are best outlined by the two average orientations of F^ and the phyllonite zone; poles to these limbs l i e on a great c i r c l e whose pole i s coincident with L 2 (Fig. 10). Phase 3' late phase folds nearly at r i g h t angles to e a r l i e r f o l d trends are found deforming both Phase 1 and Phase 2 structures. Fracture cleavages and lineations developed during t h i s phase cross-cut a l l e a r l i e r struc-tures and are themselves undeformed. a) Fracture cleavage, Fj*. the common Phase 3 planar element i s an even-snaced, non-penetrative, h a i r l i n e f r a c -ture which her i s designated a fracture cleavage. It i s best developed i n the Broadview, but i s common i n the Index as well. In t h i n section, F^ cuts across and s l i g h t l y displaces quartz grains and earlier-formed muscovite-rich layers; there i s no in d i c a t i o n of mineral growth p a r a l l e l to i t . A lower hemisphere equal-area plot of poles to F^ measured i n the f i e l d indicate a consistent orientation of 055/#ONW (Fig. 11). b) Lineation, : Phase 3 l i n e a r structures common i n both the Broadview and the Index are l i n e s of int e r s e c t i o n between F^ and F^; these l i n e s are the colinear trend of minor crenulations of mica on F^ surfaces due to minor move-ment on F^. Lines of in t e r s e c t i o n between F^ and F^ have also been observed on F^ surfacesj but are not re a d i l y measured since F^ surfaces are not commonly exposed. Thus^ a l l the measurements i n Figure 11 have'been made on F^ sur-faces i An equal-area plot indicates a consistent L^ trend of 055/18. The dispersion of L^ i n figure 11 i s due to measurements which have been made on minor Phase 2 folds which have been refolded by Phase 3. c) Style of fold i n g : Phase 3 folds are very open and broad, f l e x u r a l - s l i p folds which have wavelengths i n the hundreds of feet and very small amplitudes. This type of F i g , 11, A lower hemisphere plot of poles to F^ (dots) and (crosses). The average F^ plane has an attitude of 055/80NW; the general plunge of i s 055/18. 39 F i g . 1 2 . i s dispersed along a great c i r c l e whose pole (P) i s nearly coincident with L^, whereas i s dispersed along a great c i r c l e , Fg, whose pole i s not coincident with L 0 . 40 41 f o l d i n g has caused a general wrinkling of the earlier-formed f o l i a t i o n and a dispersion of and (Fig. 1 2 ) . L-^  i s dispersed along a great c i r c l e whose pole i s nearly c o i n c i -dent with ; however, i s dispersed along a great c i r c l e whose pole i s not coincident with . Instead, i s d i s -persed symmetrically along F^ (Fig.. 1 2 ) . This discrepancy i s due to the fact that most of the measurements were of l i n e s of in t e r s e c t i o n between F^ and Fg. When such l i n e s are folded about an axis ( i . e . ) almost perpendicular to F^, they obviously become dispersed along F^. L^, on the other hand, since i t represents not l i n e s of i n t e r s e c t i o n , but quartz rods and e l l i p s o i d s are dispersed on a great c i r c l e roughly perpendicular to . The symmetrical dispersion of and on great c i r c l e s indicates that Phase 3 folds are symmetrical. 4 2 Summary: Character of Structural Elements FOLD GENERATION Deformed surface Fold style Structures produced Lineations Axial surface PHASE 1 PHASE 2 PHASE 3 Bedding, F o si m i l a r , i s o -c l i n a l ; trans-position of l i t h o l o g y ; phyllonite zone F Q and F ^ ; phyllonite zone sim i l a r , open, asymmetric; rounded hinges; chevron i n marble; I l l e c i l l e w a e t Svnform F F F r0>  rl> 2 F l e x u r a l - s l i p ; very broad; rounded hinges; small-scale folds L-^ ; qtz rods, L^; crenulations L^ ; crenulations qtz e l l i p s o i d s ; on F, and minor on F^; plunge to plunging gently ouartz rodding; , N F . NWW and SSE; plunge gently NW ™ f c ' and SE; F-j^ ; transposi-t i o n cleavage; outlined by micas; dips gently NE and SW; F 9; s t r a i n - s l i p F^; fracture cleavage; p a r t l y cleavage; not outlined by mica; outlined by dips steeply to mineral growth; the NE; dins steeply to the NW: Petrofabrics Oriented t h i n sections of both the Broadview and Index Formations were examined using a p o l a r i z i n g microscope equipped with a f l a t stage and a U-stage.. The purpose of the exercise was to determine r e l a t i v e age rel a t i o n s between planar elements of various phases of deformation, to deter-mine what mineral assemblages were stable during each phase 43 and whether there was any l a t t i c e reorientation of quartz during these phases* Fl a t stage investigation: f l a t stage examination was done on about 30 oriented t h i n sections cut from various horizons of the Index and Broadview. This examination i n d i -cates that conditions of metamorphism were most favourable for muscovite and c h l o r i t e growth and quartz r e c r y s t a l l i z a -t i o n during Phase 1, This conclusion i s based on the facts that muscovite i s everywhere aligned p a r a l l e l to F^ (Plate 2),. deformed c l a s t s of quartz have been p a r t i a l l y r e c r y s t a l l i z e d and have grown i n the F^ plane (Plate 12), and that remobi-l i z e d and r e c r y s t a l l i z e d quartz commonly outlines Phase 1 rootless folds and f i l l s tension gashes (Plates 3, 4, and 6), Phase 2 s t r a i n - s l i p cleavage traces are common i n most sections and are found f o l d i n g and d i s p l a c i n g e a r l i e r F^ planes Which are at a high angle to F^ (Plate 11).. F^ i s a. p a r t i a l l y annealed fracture which bends and. displaces muscovite grains, cuts around e a r l i e r - r e c r y s t a l l i z e d quartz grains, and i s i t s e l f n a r t l y outlined by muscovite (Plate 10) , Phase 3 fracture cleavages are not commonly recognized i n t h i n section, but where they have been seen., they are a clear fracture along which minute movement has occured; there i s no i n d i c a t i o n of mineral growth p a r a l l e l to it.. U-stage investigation': examination with the universal 44 stage-was done on three samples; these samples were c o l l e c -ted from the lower Index, the lower Broadview, and the upper Broadview. In each, the orientation of the quartz c-axes were determined i n t h i n sections cut at various angles. This data was then plotted on lower hemisphere equal-area projec-tions and contoured; the f i n a l r e s u l t s were then transferred to a horizontal equal-area projection. a) Lower Index Formation: only one oriented t h i n section from t h i s sample was used; t h i s was a horizontal section which was nearly p a r a l l e l to F^. It was found that there was a poor orientation of quartz c-axes i n thi s sample and no r e a l pattern emerged u n t i l some 500 grains were measured. Contouring of the data indicated three major concentrations: (Fig. 13) two i n the northwest quadrant and a lone concen-t r a t i o n i n the southwest and northeast quadrants. The sym-metry of t h i s pattern indicates a good orthorhombic f a b r i c . b) Lower Broadview Formation: two oriented t h i n sections cut at 007/90 and 098/30S were used to determine preferred orientation of quartz c-axes i n t h i s member. This sample showed a much better preferred orientation than the previous sample; th i s i s to be expected since i t has been nearly completely r e c r y s t a l l i z e d and has suffered intense deforma-t i o n . The results of the data are contoured i n Figures 14 and 15. The centres of major concentrations from these plots have been transferred to a horizontal projection plane i n F i g . 13. A lower hemisphere equal-area plot of about 500 c-axis orientations of quartz i n a p h y i l i t i c s i l s t o n e of the lower Index. The plane of p r o j e c t i o n i s Fn and i s h o r i z o n t a l . F i g . 14. A lower hemisphere plot of about 440 c-axes of quartz i n a sample of the lower Broadview. The plane of p r o j e c t i o n i s 007/90 with the l e f t side of the p r o j e c t i o n being down dip. F i g . 15. A lower hemisphere plot of about 430 c-axes of quartz i n the same sample as F i g . 14. The plane of pro j e c t i o n i s 098/30S with the ri g h t side of the pro j e c t i o n being down dip. 47 0 9 8 _1 no lO Pig. 16. A synoptic diagram showing the centres of major concentrations ( c i r c l e s with crosses) from Figures 15 and 15 projected onto a h o r i z o n t a l plane. Great c i r c l e s Fg and P^ along with L-^ , and are also shown. 48 F i g . 17. A lower hemisphere plot of about 465 c-axes of quartz from the upper Broadview g r i t t y q u a r t z i t e . The plane of pr o j e c t i o n i s 160/90. F i g 18. A lower hemisphere plot of about.450 c-axes of quartz from the same sample as was used f o r F i g . 17. The plane of pr o j e c t i o n i s h o r i z o n t a l and i n t h i s sample i s p a r a l l e l to F,. 50 N J _ 51 Figure 16. From t h i s i t Is evident that three preferred orientations are present: two i n the southeast and one i n the southwest. The symmetry of the f a b r i c i s orthorhombic. . c) Upper Broadview Formation: one section s t r i k i n g nearly p a r a l l e l to and another nearly horizontal were used to determine c-axes orientations i n the gritt}^ quartz-i t e . Here again, as i n the lower Index, there i s a poor orientation and thus about 550 measurements had to be made and contoured before a pattern emerged. The contoured plots are i l l u s t r a t e d i n Figures 17 and 18. Figure 19 i s the pattern of the measured data on a horizontal plane; i t i s evident from t h i s p l o t , that again, three preferred orienta-tions e x i s t : there are two i n the northwest and southeast quadrants and one i n the southwest and northeast quadrants. The symmetry of the pattern again indicates a good orthor-hombic f a b r i c . d) Discussion: these r e s u l t s indicate that during meta-morphism and deformation, conditions were such as to favour the l a t t i c e reorientation of quartz. The preferred o r i e n t a l t i o n of quartz c-axes approximately p a r a l l e l to the l i n e a r trends (L-^ and L Q) developed during Phases 1 and 2 indicates that this reorientation took place during these phases of deformation. Hence the two concentrations which occur side by side i n the c-axes plots just described can be related to L-, and L 9 (Figure 17). The one lone concentration which 52 occurs-.in a l l the plots trends nearly at right angles to the other two trends; i t may be the reorientation of quartz in the d i r e c t i o n of movement. The fact that quartz l a t t i c e reorientations are much more pronounced i n the micaceous-quartz-phyllonite of the lower Broadview (Fig. 15, 16 and 17), reinforces the e a r l i e r suggestion that rocks of the phyllonite zone have been intensely sheared and r e c r y s t a l l i z e d ; i n comparison, the more massive members such as the g r i t t y quartzite and the si l t s t o n e show poorer preferred orientations and thus have been less sheared and less r e c r y s t a l l i z e d . The good orthorhombic symmetry of the f a b r i c i n a l l the rock types indicates that these rocks.have been sheared at least some and are c h a r a c t e r i s t i c a l l y m y l l o n i t i c . The fac t that s i m i l a r quartz l a t t i c e orientations are present i n a l l three rock types and t h e i r f a b r i c symmetries are s i m i l a r , indicates that both the Broadview and the Index along with the rocks of the phyllonite zone have suffered a similar h i s t o r y of deformation and metamorphism. Summary of Structural and Metamorphic Events 1«: Phase 1: similar f o l d i n g about a north-northwesterly trending axis produced i s o c l i n a l , t i g h t , recumbent folds and a strong penetrative f o l i a t i o n , F^. Accompanying t h i s phase was a period of regional metamorphism of green-schist grade which r e c r y s t a l l i z e d muscovite, c h l o r i t e , 53 and quartz. Combined deformation and metamorohism reorien-ted the l a t t i c e s of quartz grains r e s u l t i n g i n an orthorhombic f a b r i c . Phase 2 : s i m i l a r f o l d i n g , nearly coaxial with Phase 1 , r e s u l t e d In the formation of the asymmetric, I l l e c i l l e -waet Synform which i s overturned to the west, and a steeply-dipping s t r a i n - s l i p cleavage. The e f f e c t of t h i s was to tighten-up, r e f o l d , and reactivate e a r l i e r struc-tures. The conditions of metamorphism. which were so ef f e c t i v e during Phase 1 , were waning during Phase 2 times. However, temperatures were high enough to recrys-t a l l i z e some mica and to aid i n the reorientation of quartz l a t t i c e s . Phase ,3: late i n the sequence of deformation was a phase of very broad, open, f l e x u r a l - s l i p f o l d i n g nearly at right angles to e a r l i e r trends. Conditions were b r i t t l e and such as to develop a non-penetrative fracture cleavage with no mineral growth p a r a l l e l to i t and no quartz reorientation. 54 CHAPTER IV DISCUSSION Time of L i t h o l o g i c Transport. In- an e a r l i e r section, F-^  w a s described as a trans-j p o s i t i o n cleavage along which movement had occurred. There i s l i t t l e doubt that movement took place along F^ surfaces, but there i s some speculation as to when the movement and r e s u l t i n g t r a n s p o s i t i o n of l i t h o l o g y occurred. Two p o s s i -b i l i t i e s e x i s t i 1) the shearing and t r a n s p o s i t i o n occurred only during Phase 1 and was complete before Phase 2, or 2) shearing and t r a n s p o s i t i o n i n i t i a t e d during Phase 1 continued into Phase 2 during tightening of e a r l i e r s t r u c -tures. Accepting the f i r s t p o s i b i l i t y , a model can be pro-posed which incorporates the idea of large-scale l i t h o l o g i c transport as being responsible f o r bringing the Broadview and Index into j u x t a p o s i t i o n during Phase 1. The sequence pf events were as follows: i ) a sequence of formations ( i . e . the Lardeau Group) were folded during Phase 1. During t h i s phase, a pene-t r a t i v e t r a n s p o s i t i o n cleavage, F-^ , developed at a small angle to bedding, F Q (Pig. 19A). i i ) d i f f e r e n t i a l movement on a grand scale folded the rocks as outl i n e d by the black unit i n Figure 1SB. Continued d i f f e r e n t i a l movement sheared out limbs and hinges and the r e s u l t was a sequence of transposed 55 F i g . 19 The t r a n s p o s i t i o n o f l i t h o l o g y t h r o u g h move-ment along. F^j. The sequence o f e v e n t s i s i l l u s t r a t e d by t h e f o l d i n g o f a t h i n m a r b l e u n i t ( b l a c k ) . 56 F i g . 2 0 . (A) Transposed Broadview ( s t i p l e d ) over Index (dashed.) along zone containing marble lense ( b l a c k ) . (B) S i m i l a r f o l d i n g of e a r l i e r structures i n t o the I l l e c i l l e w a e t Synform. 57 l i t h o l o g i c units which appear to be s u p e r f i c i a l l y undeformed (Pig. 19D). (The black uni t could be thought of as the marble member of the upper Index and t h i s i s a possible o r i g i n f o r i t s l e n s o i d a l shape). i i i ) movement concentrated along a shear zone brought widely separated formations such as the Index and the Broadview in t o j u x t a p o s i t i o n along the p h y l l o n i t e zone (Pig. 20A) and i n t e r s t r a t a l formations such as the middle Lardeau were sheared out. i v ) Phase 2 f o l d i n g , nearly c o - a x i a l with Phase 1, folded the formations into the I l l e c i l l e w a e t Synform (Pig. 20B). This sequence of events accounts well f o r the ph y l l o n i t e zone and the shaping of the marble, but i t f a i l s to consider the possible r e a c t i v a t i o n of e a r l i e r structures during Phase 2 f o l d i n g . The second p o s s i b i l i t y , which does take into account t h i s possible r e a c t i v a t i o n , I s a more p l a u s i b l e model. The fundamental p r i n c i p l e of t h i s model i s that F^ surfaces, developed during Phase 1, continued as movement surfaces during the tightening-up of structures during Phase 2. Thus the minor r o o t l e s s f o l d s and transposed l i t h o l o g y may have been produced as late as Phase 2. Using t h i s model, the sequence of events may have been as follows -; 58 i ) the Broadview was thrust over the Index along the p h y l l o n i t e zone during Phase 1 during which time i n t e r s t r a t a l formation were sheared out and the marble unit was t e c t o n i c a l l y shaped i n t o a lens;.. This may have been a nappe structure whose sole thrust was the p h y l l o n i t e zone ( i . e . Ross 1 M i l f o r d nappe). I f the Broadview was the underside of the nappe, then the '. sense of movement was as depicted i n Figure 21A. i i ) Phase 2 f o l d i n g , nearly c o - a x i a l with Phase 1, produced the I l l e c i l l e w a e t Synform. The sense of movement on the limbs of t h i s synform were analogous with the sense during Phase 1 (compare Figures 21A and 21B). The r e s u l t of t h i s was to tighten a l l e a r l i e r f o l d s ; with a "room problem" i n the cores of tightened f o l d s , movement became int e n s e l y concentrated along F^ and r e s u l t e d i n l i t h o l o g i c t r a n s p o s i t i o n and shear-ing out of earlier-formed Phase 1 limbs and hinges (Plate 14). Thus, even though structures which i n d i -cate l i t h o l o g i c t r a n s p o s i t i o n are Phase 1, they could well be the r e s u l t of l a t e r movement of F-^  during Phase 2. WithJ t h i s model, small-scale l i t h o l o g i c t r a n s p o s i t i o n structures associated with Phase 1 cannot be extrapolated to large-scale t r a n s p o s i t i o n as a mechanism f o r bringi n g the Broadview and Index i n t o j u x t a p o s i t i o n , Instead, the 59 (B) F i g o 21 (A) A nappe enveloped by the Broadview was thrust over Index (dashed) along a sole thrust (heavy black l i n e ) during Phase 1. Note sense of movement i n both un i t s as denoted by diagramatic 'drag f o l d s ' . (B) This shows the lower limb of the nappe folded about Fg. The sense of movement during F 2 i s the same as during P^ as diag r a m a t i c a l l y i l l u s t r a t e d by 'drag f o l d s . E a r l i e r structures are tightened. 60 Broadview has to be thrust over the Index during Phase 1. A nappe structure as proposed by Ross (1970) seems to be a favourable mechanism; This second model best explains the structures at Albert Canyon. The s i n i s t r a l sense of movement deduced from the tension gashes (which may also have been r e a c t i v a t e d ) , and the Phase 2 s t r a i n - s l i p cleavage i s consistent with the senses of movement depicted i n Figures 21A and 21B. Also, movement along F-^  i s not l i m i t e d to a Certain time, but i s thought bf as occurring continuously during Phases 1 and 2. Moreover, t h i s model proposes a continuous episode of f o l d i n g and does not l i m i t any s t r u c t u r a l development to a p a r t i c u l a r phase. Thus t h i s model i s adopted here as the most plausible, and the one which best explains the observed f a c t s i . 61 Correlation of Doformational Phases. The three phases of f o l d i n g , designated, i n t h i s study as 1, 2, and 3, corre-late i n many respects with those described by Ross to the .west and along the Kootenay Arc (Ross, 196*, 1970). The style and trends of Ross' Phase 1 and the Phase 1 of t h i s area are similar and thus appear to be the same. It was during t h i s phase that large-scale, recumbent nappes were thrust eastward (Ross, 1970) and t h i s f i t s i n w e l l with the transport of the Broadview over the Index during the e a r l i e s t nhase described for th i s map-area. The Phase 2 described by Ross has hot been recognized i n t h i s area and i t may be that these rocks were s t r u c t u r a l l y too high to have been affected; this phase has been mapped, i n the Kootenay Arc by Fyles and. Ross, however, i t appears to die out i n an easterly d i r e c t i o n (Ross, pers. comm.)-. The Phase 2 of Albert Canyon correlates exactly with Ross T Phase 3 and there i s l i t t l e doubt that they are not the same. The Phase 3 described here i s a very weak phase which had l i t t l e a f f e c t and i s probably not evident i n rocks at lower s t r u c t u r a l l e v e l s . 62 RESUME AND CONCLUSIONS This study has established the following facts concer-ning the Lardeau Group at Albert Canyon: 1.. The Broadview-Index contact i s a phyllonite zone or a decollement,. 2. Three .phases of f o l d i n g accompanied by regional meta-morphism of greenschist grade, deformed the rocks during a mid-Paleozoic orogeny (Caribooan) .. 3 . .The phyllonite zone i s a Phase 1 structure. L. The I l l e c i l l e w a e t Synform i s a la t e phase (Phase 2 of this study) similar f o l d , overturned to the west and trending northwest-southeast. 5. Movement along probably during both Phases 1 and 2 ,-has resulted i n the o b l i t e r a t i o n of earlier-formed folds and o r i g i n a l bedding. 6. The exotic marble unit was lensoidal i n shape p r i o r to Phase 2 f o l d i n g . It l i e s i n the pJryllonite zone and was probably reshaped t e c t o n i c a l l y during Phase 1. 7. The Broadview g r i t t y quartzite at Albert Canyon i s l i t h o l o g i c a l l y s i m i l a r to the e l a s t i c s of the Horsethief Creek Group. The r e l a t i v e age of the Broadview and the Index, however,- has not been established from t h i s study. From these f a c t s , the following may be concluded: 1. The Broadview was thrust into juxtaposition over the 63 Index during the e a r l i e s t phase of i s o c l i n a l , s i m i l a r f o l d i n g about a north-northwesterly trending axis. Thus, the phyllonite zone can be regarded as a sole thrust to a structure which was probably a nappe (Ross' Milford nappe). 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E l a s t i c i t y , fracture and flow,. Methuen, London, 152 p. K n i l l , J.L., i 9 6 0 . A c l a s s i f i c a t i o n of cleavage with special reference to the Craignish d i s t r i c t of the Scottish Highlands. 21st Intern.Geol.Congr. , Copenhagen I960-, Pt. 1*, pp. 317-325. Knopf, E.B., and E. Ingerson, 193*. Structural petrology. Geol.Soc .Am. , Mem.6, 270 p., McKinstry, H.E., 1953- Shears of the second order. Amer, Journ.Sci., vol . 2 5 1 , P P . 4 0 1 - 4 0 4 . Okulitch, V.J., 1949. Geology of part of the Selkirk Mountains i n the v i c i n i t y of the main l i n e of the Canadian P a c i f i c Railway, B r i t . C o l . , Geol.Surv.Canada, Bull. 1 4 . Ramsay, J.G., i 9 6 0 . The deformation of early l i n e a r struc-tures i n areas of repeated f o l d i n g . Journ.Geol.,vol . 6 * , P P . 75-93. , 1962. The geometry and mechanism of formation of " s i m i l a r " type f o l d s . Journ.Geol., vol.70, pp.309-327. 66 Ramsay, J.G., 1964. The uses and l i m i t a t i o n s of be t a - d i a g r a m s and p i - d i a g r a m s i n the g e o m e t r i c a l analysis of f o l d s . : ' Q u a r t . J o u r n . G e o l . S o c . L e n d . , v o l . 1 2 0 , pp.435-454. ; — , 1967. F o l d i n g and F r a c t u r i n g o f r o c k s , M c G r a w - H i l l , 562 v. Rast-', N . , 1 9 6 6 . Recent t r e n d s i n g e o t e c t o n i c s . E a r t h - S c i . Rev. , v o l . 2 , pn . 1-/..6 . Read, P., 1966. P e t r o l o g y and s t r u c t u r e o f the P o p l a r Creek map-area, B r i t i s h Columbia. U n p u b l i s h e d P h . D . t h e s i s , U n i v e r s i t y o f C a l i f o r n i a . Ross, J.V., I 9 6 5 . The s t r u c t u r e and metamorphism o f t h e Mesa Lake map-area, N.W.T. *6B/14. Geol.Surv.Canada, B u l l . 1 2 4 . , 196*. S t r u c t u r a l r e l a t i o n s a t t h e e a s t e r n margin o f the Shuswap Complex, near R e v e l s t o k e , B.C. Can.Journ. E a r t h S c i . , v o l . 5 , pp.*31-*49-, 1 9 7 0 . S t r u c t u r a l e v o l u t i o n o f t h e Kootenay A r c , s o u t h e a s t e r n B r i t i s h Columbia. Geol.Ass.Canada, Spec. Paper 6, pp.53-66. Ross, J.V., and P. K e l l e r h a l s , 196*. E v o l u t i o n o f the S l o c a n S y n c l i n e i n s o u t h c e n t r a l B r i t i s h Columbia. Can.Journ. E a r t h S c i . , v o l . 5 , P P . * 5 1 - * 7 2 . T u r n e r , F . J . , and I.E. We i s s , 1963. S t r u c t u r a l a n a l y s i s o f metamorphic t e c t o n i t e s . McGraw-Hill,• N.Y., 545 . P . W a l k e r , J.F., 1926. Geology and m i n e r a l d e p o s i t s o f the Windermere map-area, B.C. Geol.Surv.Canada, Mem.14*. Walk e r , J.F. , and M..F. B a n c r o f t , 1929. Lardeau map-area,B.C. Geol.Surv.Canada, Mem.172. Weiss, L.E., 1959. Geometry o f superposed f o l d i n g . G e o l . Soc.Am.Bull., v o l . 7 0 , pp.91 - 1 0 6 . W h i t e , W.H., 1959, C o r d i l l e r a n t e c t o n i c s . Am.Ass.Petr.Oeol., B u l l . , v o l . 4 3 , PP.60 - 1 0 0 . W h e e l e r , . J . 0 . , 1963. Rogers Pass map-area, B.C. and A l b e r t a . Geol.Surv.Canada, Paper 6 2 - 3 2 . , 1966. E a s t e r n t e c t o n i c - e l t ^ f the Western C o r d i l l e r a ; i n : T e c t o n i c h i s t o r y a n d . m i n e r a l d e p o s i t s of the Western C o r d i l l e r a . Can. I n s t .Min.Met. ,• Spec. V o l . No.*, pp . 2 ° - 4 5 ° •67 Wheeler, J.O., 1 9 6 8 . Lardeau map-area, west half, B r i t i s h Columbia.. Geol.Surv.Canada , paper 68 - 1 , part A , n . 5 6 . , 19n0. Summary and discussion; i n : Structure of the southern Canadian C o r d i l l e r a . Geol.Ass.Canada, Spec. Paper 6 , pp.155-166. Whitten, E„H., 1966. Structural geologv of folded rocks. Rand-McMally h Co., 66.3 n. Plates Plato 1 LlaeoiVG, f l a t - l y i n c , g r i t t y quart G i t G of tho Broadview Poraat ion (nap-unit 2a )• P l a t o 2 LSuscov i te -qtz -phy l lon i to of tho l c T e r Lroadvlow P o r a a t i o n . ITote tho otrotohed c l o o t c and tho Phase 2 e t r a l n-elip cleavage c r o s o - c u t t i n g and f o l d i n g P j « (croaood n i c l s , 100S). Plate 3 Rootless Phase 1 f o l d s i n p h y l l i t i c q u a r t z i t e , Broadview Formation. • Plate 4 Refolded r o o t l e s s Phase 1 f o l d i n p h y l l i t i c q u a r t z i t e , Broadview Formation. Plate 5 S u p e r f i c i a l l y undeformed p h y l l i t i c s i l t s t o n e of the lower Index Formation Plate 6 Q u a r t z - f i l l e d tension gashes i n muscovite-qtz p h y l l o n i t e , lower Broadview Formation. P l a t e 7 : : inor Pnaee 1 struoturoo i n p h y l l i t i c s i 1 s t o n e , loner Index Formation. P l a t e 8 A t y p i c a l Phaoo 2 e i n i l a r f o l d , note re fo lded Phase 1 f o l d o . Plat© 9 A Phase 2 s i m i l a r f o l d w i t h s t r a i n - s l i p cleavage d ipp ing to the l e f t Upper Index Formation, P l a t e 10 : uscov i te growth along a Phase 2 s t r a i n -s l i p c leavage, (crossed n i c o l s , 100X). Plate 11 Phase 2 micro-fold i n marble. Note p a r t i a l bending of muscovite around f o l d hinges, (crossed n i c o l s , 100X), Plate 12 Cross-section of an e l l i p s o i d a l quartz c l a s t i n g r i t t y q u a r t z i t e , Broadview Formation, (crossed n i c o l s , 100Z). P l a t e 13 Minor Phase 1 f o l d i n marble. P l a t e 14 Sheared-out hinge of a Phase 1 minor f o l d , Index Formation. l a i b IC + L E G E N D m e t a - d i o r i t e L a r d e a u G r o u p B r o a d v i e w F o r m a t i o n 2 a : m i c a c e o u s g r i t t y q u a r t z i t e 2 b ' m u s c o v i t e - q u a r t z p h y l l o n i t e I n d e x F o r m a t i o n i a t w h i t e t o g r a y m a r b l e i b i b l a c k , c a r b o n a c e o u s , s i l i c e o u s p h y l l o n i t e i d b l a c k , c a r b o n a c e o u s , s i l i c e o u s p h y l l i t l c , s i l t s t o n e S Y M B O L S F i f o l i a t i o n , I n c l i n e d a n d v e r t i c a l * ^ ^ J F | l i n e a t i o n , p l u n g i n g a n d h o r i z o n t a l O b s e r v e d o u t c r o p G e o l o g i c c o n t a c t , o b s e r v e d a n d a s s u m e d C o n t o u r l i n e ^ p h a s e 2 s y n f o r m a l t r a c e Rock Types and F-j Structures at Corbin Pass, Albert Canyon, B. C, S c a l e ; t o u r i n c h e s t o o n e m i l e M I L E S G e o l o g y a n d D r a f t i n g b y W . O . K a r v i n e n 1 9 6 9 S Y M B O L S F 3 f o l i a t i o n , i n c l i n e d a n d v e r t i c a l P h a s e 3 l i n e a t i o n , p l u n g i n g a n d h o r i z o n t a l F 2 f o l i a t i o n , i n c l i n e d a n d v e r t i c a l ' " P h a s e 2 l i n e a t i o n , p l u n g i n g e n d h o r i z o n t a o b s e r v e d o u t c r o p g e o l o g i c c o n t a c t , o b s e r v e d a n d a s s u m e d c o n t o u r l i n e \ \ '• v s \ \ \ V ] > I \rf f /> J' \ST v ¥ 20° 11 ( % V 11 ELSTOKE jj UPPER HARROW (\LAKE SCALE' 1'= 30 MILES F 2 and F 3 Structures at Corbin Pass, Albert Canyon, B.C. S c a l e : f o u r I n c h e s t o o n e m i l e m i l e s G e o l o g y a n d D r a f t i n g b y W . O . K a r v l n e n 1 9 6 9 

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