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Geology of the Aiken Lake map-area, British Columbia Roots, Ernest Frederick 1947

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LEI*? GEOLOGY OF THE AIKEN LAKE MAP-AREA BRITISH CQLUMBIA A t h e s i s submitted i n p a r t i a l f u l f i l m e n t of the requirements of the oourse l e a d i n g to the degree Master of A p p l i e d Soienoe i n G e o l o g i c a l Engineering at the U n i v e r s i t y of B r i t i s h Columbia Ernest F r e d e r i c k Roots \ The U n i v e r s i t y of B r i t i s h Columbia A p r i l 17, 1947. G 0 I I a I T s . Page FOREWORD i ABSTRACT i i i INTRODUCTION 1 PHYSIOGRAPHY .4 GENERAL GEOLOGY Summary 5 Table of Formations 7 Stratified Hooks 8 Intrusive Rocks 39 STRUCTURAL GEOLOGY Folding 45 Faulting 47 ECONOMIC. GEOLOGY Plaoer Deposits 49 Lode Deposits 50 Deposits in the Pre*Gambrian and Cambrian Rocks 50 Deposits Related to the Omineoa Intrusions 54 BIBLIOGRAPHY 59 Maps In pocket. FOREWORD. During the 1946 f i e l d season the writer was in charge of mapping the areal geology of the Aiken Lake area, Oassiar District, B r i t i s h Golumbia, for the Geological Survey of Canada. The following winter, while attending the University of Br i t i s h Golumbia, he was required by the Department of Mines and Resources, Ottawa, to prepare a map and descriptive report based on the f i e l d work ocf the previous summer. The laboratory investigations and research of the literature entailed in the preparation of the map and report were carried on with the view that a portion of the report could be adapted to f u l f i l the thesis requirement of the course leading to the degree of Master of Applied Science 4h Seelogical Engineering at t h 6 University of Bri t i s h Golumbia. The accompanying thesis is the result of this work. It consists primarily of a map and portions of a report on f i e l d work submitted to the Geological Survey of Canada, together with minor additions which enlarge upon certain features of the subject only briefly treated in the original report. The report i s essentially a description of the geology of a given area, and i t is assumed that publications describing related areas would be available to the reader, therefore definitions of geological map-units, etc., which i i . have already been described, are omitted from the text of this paper, and there has been no attempt to relate the geology of the area here described to the regional geology of northern Bri t i s h Columbia. i i i . ABSTRACT. Aiken Lake map-area l i e s in the Gassiar District of north^oantral British-Colombia between 56°00'anci 57°00£ north and longitudes 1E5°00' and 126°00' west. It i s a relatively rugged, glaciated area lying almost entirely within the Omineca-Cassiar Mountain System. The oldest rocks within the map-area are quartz-mica schists, garnetiferous schists and quartzites of probablp Proterozoic age conformably overlain by Lower Cambrian chlorite schists, slates, quartzites, and limestones. A relatively large area of these Proterozoic and Cambrian rocks has been further metamorphosed to feldspathized quart-zite and gneiss. A total of nearly 30,000 feet of interbedded volcanic pyroclastic and true sedimentary rocks ranging in age from Devonian or Mississippi an. to Upper Triassic outcrops in a broad belt across the central part of the map-area. These rocks are intruded by dykes, s i l l s , stocks^and batholithe of Upper Jurassio or Lower Cretaceous age. The intrusive bodies range from granite to pyroxenite in composition, granodiorite being the dominant rock type. A body of conglomerate at least 5500 feet thick of probably Lower Cretaceous age, containing many pebbles of intrusive rocks, i s faulted into Triassic or Upper Palaeozoic rocks. The Proterozoic and Lower Cambrian rocks have been folded, apparently daring their period of metamorphism, into large anticlinoria. The planes of schistosity of the metamorphosed rocks l i e approximately parallel to the limbs and to the crests of the anticlinoria. The grade of regional metamorphism of these rocks increases uniformly as lower stratigraphic horizons are reached. Known mineral deposits with^he area are almost entirely confined to the Lower Cambrian and Proterozoic schists and limestones, or to the aureoles of the Jurassic-Cretaceous igneous bodies. Those in the Lower Cambrian and Proterozoic rooks are typically of t h 6 lead-zinc-silver type. Many of these mineral occurrences have no known association with igneous rocks. The deposits found within the aureoles of the Jurassic-Cretaceous igneous bodies have characteristic gold-quartz, gold-copper, or copper-lead mineralization. AIKEN LAKE MAP-AREA, BRITISH GOLUMBIA. INTRODUCTION• ? Aiken Lake map-area l i e s in the Cassiar District of north-oentral B r i t i s h Colombia between latitudes 56°00 o i 7 and 57 OO1 north and longitudes 1£5°00 and 126900' west, and occupies an area of approximately 2640 square miles. Aiken Lake i n the centre of the area may be reached by a winter tractor road, 95 miles long, from Genaansen Landing on the Omineca River. A f a i r motor road extends about 185 miles south from German sen Landing via Fort St. James, to Vanderhoof on the Prince Rupert branch of the Canadian National Railway. The eastern part of the area may be reached by water from Summit Lake, 40 miles by road from the city of Prinoe George, by means of the Crooked, MoLeod, Parsnip and Finlay Rivers. Except during extreme low water the Ingenika River, crossing the northern part of the area, is navigable for small river boats as far west as Wrede Creek. A wagon road rapidly f a l l i n g into disrepair connects Delkluz Lake in the map-area with the Finlay River a short distance above Fort Grahams. The area may be conveniently serviced, through several suitable lakes, by charter aircraft based at Port St. James. - 2 -The f i r s t geological wortk i n the area w§s done in 1893 by MoGonnell1 who mapped a strip of country bordering the Omineoa River just south of the map-area, and the northeastern part of the area, adjacent tovthe Finlay River valley. The 2 geography of the region was mapped i n 1912-14 by F.C. Swannell of the Br i t i s h Columbia Department of Lands. In 1927 Dolmage3 examined the geology of the Finlay River valley, the lower part of the Ingenika River valley, including the Ferguson lead-zino property, and traversed the abandoned R.N.W.M.P. t r a i l which crosses the oentral part of the map-area. An examination of several mineral prospects i n the vicinity of Uslika Lake and 4 Aiken Lake was carried out i n 1940 by Douglas Lay of the British Columbia Department of Mines. Systematic mapping of the areal geology was oommenced in 1945 by J.E. Armstrong5 and continued by the writer in 1946. The writer i s indebted to o f f i c i a l s of various concerns interested in the area, particularly to Mr. E.O. Brunlund of the Consolidated Mining and Smelting Company Ltd.; and to Mr. J.W. Burton of Springer Sturgeon Gold Mines, Limited, J for many courtesies extended. In the f i e l d work he was ably assisted by J.O.Wheeler, R.L. Christie, P.E. Olson, W.H. Dow, and L.G. Dickinson. The map was completed and the report written at the University of B r i t i s h Columbia. The writer i s grateful to the members of the staff of the Department of Geology and ueography of that Institution for placing laboratory f a c i l i t i e s and equipment at his disposal. He particularly wishes to thank Dr. H.C. Gunning and Dr. £• DeP. Watson for their helpful advice on many problems of the work, and Dr. V.J. Okulitch for the determination of f o s s i l specimens. 1. MoConnell, H.G.; Geolo Surv.Canada, Arm.Rpt.Vol.Vll,pt.C 18,94. 2. Ann.Rept.Surveys Branch,Dept.of Lands,B.C. 1914, p. 83. 3. Dolmage,V.,Geol.Surv.Canada, Summ.Rept.1927,Pt.A,p. 19. 4. Lay, D.,Aiken Lake Area, Bull.No.1,B.C.Dept.Mines,1940. 5. Geol.Surv.Canada, Pfrelim.Paper 46-11. - 4 PHYSIOGRAPHY. The Rooky Mountain Trench, here occupied by the Finlay River, outs across the extreme northeast corner of the map-area. The rest of the area l i e s within the Omineca-Oassiar Mountain System and i s characterized by irregular deeply dissected mountainous units and broken massifs with l i t t l e tendency toward well-defined ranges. The r e l i e f averages 3000 to 4000 feet, and reaches an overall maximum of 6000 feet between the Finlay River in the northeast corner of the area and the high peaks near the headwaters of the Osilinka River. The mountains immediately west of the Rooky Mountain Trench exhibit bold, rounded summits and smooth ridges only slightly modified by alpine glaoiation. The effects of glacial sculpturing become increasingly conspicuous toward the west, producing in the southwest corner of the map-area an extremely rugged, intensely glaciated topography. The continental ice sheet has ooffered a l l parts of the map-area, depositing erratics at elevations up to 7600 feet. The overall direction of ice movement was to the northeast. The map-area l i e s entirely within the Finlay River watershed, and the main streams flow east or southeast. Owing to the characteristic "land; forms produced by asymmetrical glaciation, however,, the drainage of the tributary streams within the mountain masses is predominatently to the northeast, - 5 -Timberline i s at an altitude of about 550G feet; above i t bedrock is well exposed, but lower slopes and valley floors are deeply mantled with d r i f t and colluvium and took outcrops are chiefly confined to stream canyons. GENERAL GEOLOGY. SUMMARY Consolidated formations within the map-area range in age from possibly Pre-Cambrian to possibly Oretaoeous and include a great variety of sedimentary, volcanic, metamorphio and intrusive types. A thick, folded succession of regionally metamorphosed rocks whose upper members are lower Cambrian and whose lower members may extend into Pre-Oambrian, strikes northwest across the no rth» central part of the area. Near the eastern border of the map-area, these rocks have been further altered by processes of metamorphism and granitization to a highly granitized sedimentary-igneous complex. An assemblage of volcanic and sedimentary rocks, ranging in age from Devonian or Mississippian to possibly Triassic occupies a belt 10 to 15 miles wide to the southwest of the Cambrian formations. In the southeast and extreme southwest corners of the map-area rocks of this general group are lithologioally similar to and can be structurally correlated with rooks which have been classified as belonging to the ©ache Greek group of probable Permian age. Elsewhere in the map-area these rooks appear to be in part Devonian or Mississippian in age. The upper Palaeozoic formations are overlain, for the most part without angular discordance, by a thioh series of volcanic and minor sedimentary rooks of Upper Triassic to possibly Jurassic age. Intrusive bodies tanging in composition from dunite and pyroxenite to granite and syenite out the Triassic and a l l older formations. A body of conglomerate of possibly Upper Jurassic or Lower Cretaceous age i s apparently faulted into position ' ,in the Triassio volcanic and sedimentary rocks. Unconsolidated deposits of Pleistocene and Reoent age cover the lower elopes and valley floors in a l l parts of the region. 0 - 7 -Era Table of Formations Period or Epoch Group Thickness Feet Lithology, Stream deposits;talus; s o i l Ceno-zovic Meso-zoio Palae-ozoic Recent fileisiocene 5500' "Glacial & fluvio-deposits g l a c i a l Lower Cretaceous or Upper Jurassic EROS; G onglome rat a;minor a r g i l l i t e  ON Omineca Intrusions Granodiorite.quartz monzonite, quartz diorite, granite Diorite, monzonite; minor gabbro, syenite. Eornblendite.pyroxenit^ minor serpentine ,dunit@» INTRUSIVE CONTACT Jurassic(?) and Upper Triassic Takla Group L2000' Upper Triassio(?) to Mississ-ippian or Devonian EROSION In part Takla(?) Andesitic flows and breocias;minor basaltic flows;tuff,agglomerate, shale,limestone.  "Vega"granodiorlte. Andesitic flows, tuff, conglomerate.  Asitka(?) Cache Creek Groups 18000' Tuff, andesitfto flows, argillite,limestone, sandstone,conglomerate, chert. EROSION?DEFORMATION.MINOR INTRUSION,GENERAL METAMORPHISM Lower Cambrian Ingenika Group 18000' Qaartz-ohlorite schist crystalline limestone, serioite schist.quartz conglomerate,phyllite. Pre-Gambr Prote zoic( ian ro-?)' Ruby Group 12000' Quartz-mica schist, gametiferous schist, quartzite. "Wolverine Gomplex" i'eldspathized quartzite granitoid gneiss,quartz -mica-feldspar schist, chloritoid schist,minor skarn,pegmatite .Granitic equivalent of Ruby S Ingenika Group Post-lower Cambrian Uranodiorite,diorite, alaskite,aplite,feld-spar porphyry - 8 -STRATIFIED ROOKS. PROTEROZOIO (?) and/or LOWER CAMBRIAN. . Ruby Group. Thai oldest rooks in the Aiken Lake area are exposed in an irregular belt 4 to 8 miles wide extending diagonally across the map-area from the Osilinka River oh the east border to Wrede Greek on the west. Elsewhere a small area of these rooks outcrops southeast of Ingenika Gone. This assemblage, containing at least 13,000 feet of quartz-mica schists, micaceous quartzites and quartzites, i s typically developed around the nRaby " group of mineral claims north of the Osilinka River, and has accordingly been designated the "Ruby group*. The most abundant rock i s a golden brown to grey relatively coarse-grained quartz-mica schist, consisting chiefly of quartz and muscovite, with more or less plentiful biotite. Minor members of the series represent a l l gradations from quartz-mica schist through mioaoeous quartzite to relatively pure quartzite. The rock has a distinctly layered appearance. In many places adjacent layers exhibit marked differences of mineralogical content, and texture, but individual layers oan be traced many thousands of feet with no appreciable variation in composition or texture. To some extent the differences between individual layers appear to represent differences in mineral or ohemioal composition of the original rocks, and i s seems likely that most of these rooks probably represent metamorphosed sed«* imentary strata, and that the layering of schist and quartzite corresponds in a certain degree to the bedding of the original sediments. The sohistosity was observed to be developed approximately parallel to the limbs and to the orests of the major bedding structures. In many of the smaller folds the sohistosity cuts across the bedding. The individual members of any one part of this group are very similar to members found at other stratigraphio horizons of the same group, and no distinctive horizon markers have yet been recognized. Consequently i t i s very d i f f i c u l t to trace smaller structures or to oorrelafe beds across drift-covered areas. In a broad sense, however, a rough stratigraphio sequence oan be recognized which i s relatively consistent for a l l parts of the map-area where the Ruby group rooks are well exposed. The oldest formations include up to 1000 feet of golden brown, buff or white quartzite, typically in beds up to 20 feet thick separated by beds of quartz-mica schist rarely over five feet thick. Ragged, interlocking, fresh-appearing quartz grains up to 2 millimeters in length make up about 98 per cent of the average quartzite. Minor constituents include muscovite and biotite in approx-? - i o -ximately equal proportions, small anhedral gcwnets, and minute amounts of chlorite and magnetite. The biotite, and to a lesser extent the masovite, shows i n many oases a rough parallel orientation, which may be responsible for the smooth platy joint surfaoes characteristic of the outcrops of this rook. The quartz i s clear, Instrained, and in places surrounds th© grains of mica, indicating perhaps, that at the time of the f i n a l reorystallization of the quartz the rock was not subjected to differential pressure such as may have influenced the formation of oriented biotite flakes, and that there has been no appreciable deformation of the rook after r e c r y s t a l l i ization of the quartz. The quartz-mica schists constitute less than IG per cent of the rock volume of the lowest members of this group. At higher horizons, however, the proportion of schist increases, until the "quartzite series" K i s overlain by an assemblage 4000 feet thioh* consisting of approximately 80 per oent quartz-mica schist and 20 per oent quartzite. Most of the beds of quartzite i n this assemblage are less than 10 feet thiok. Hear the bottom of this assemblage there is preserved at one locality on Ghase Mountain a bed of what appears to have been originally a conglomerate. Rounded fragments of light grey to pinkish-buff medium-grained quartz-biotite gneiss up to 10 inches diameter are enclosed in a dark grey to silvery fine-grained schistose micaceous quartzite. The "oontacts" between the "pebbles" and the groundmass have been recrystallized and diffused to a certain extent, but - 11 are distinctly marked by a coarsening of texture and an j. a, , #J. a t the margin of the pebbles abrupt diminuition of biotite/ She orientation of the gneissosity of these pebbles varies with eaoh pebble, and bears no relation to that of the general schistosity of the matrix or of the overlying formations. It would seem that the "pebbles" represent fragments of an originally stratified rock or of a rock whioh had been dynamically metamorphosed to a sohiet or gneiss previous to i t s erosion and deposition in it s present position i n the quartz-mica schists of the Ruby Group. The typical schist i s golden brown to silvery in color, coarse-grained, f i s s i l e , in many places minutely crennulated. Some horizons contain over 60 percent muscovite, occurring as well-oriented anhedral plates up to 2 oehtimeters in diameter in a groundmass of semi-rounded quartz grains and small shreds of biotite. Other horizons, commonly finer-grained, are correspondingly rich in biotite. The schist shows considerable variation in i t s individual laminae and almost a l l possible proportions and combinations of quartz, muscovite, and biotite are represented. The quartz-rich rooks contain, in ganeral, more biotite than musoovite. It was noted ahat the minutely crenhulated or crumpled schist shows many oases of a concentration of biotite at eaoh swelling or ore/fculation. Some horizons of this assemblage are rioh in reddish-brown euhedral crystals of alm0ndine garnet up to 1 oentimeter diameter. - 12 -Overlying the "golden" quartz-mica s c h i s t assemblage are about 1000 f e e t of s t r a t a in'which q u a r t z i t e s make up more than h a l f of the rook t h i c k n e s s ; these are i n t u r n succeeded by 4000 to 6000 f e e t of interbedded, i n t i m a t e l y mixed quartz-mioa s c h i s t s and q u a r t z i t e s . These s t r a t a are, l i k e the lower members of the Ruby Group, composed p r i n c i p a l l y of quartz, muscovite, and b i o t i t e ; but w i t h s u c c e s s i v e l y higher horizons the proportion of muscovite decreases, that of b i o t i t e i n c r e a s e s ; the garnets become p r o g r e s s i v e l y s m a l l e r and l e s s coherent, and there i s an i n c r e a s i n g , but s t i l l very minor, amount of c h l o r i t e ; the rock becomes dark grey or s l i g h t l y g reenish, medium-grained, i n contrast to. the golden or buf f - c o l o r e d c o a r s e g r a i n e d s c h i s t s found at lower s t r a t i g r a p h i o h o r i z o n s , iit one l o c a l i t y west o f $he Swannell R i v e r , t h i s s e r i e s i n c l u d e s a 6 f o o t bed of o oar se ( c r y s t a l l i n e ) marble. The youngest horizons of the Ruby Group include up to 2000 f e e t of banded ooarse-and f i n e - g r a i n e d quartz-mica s c h i s t and micaceous, s c h i s t o s e q u a r t z i t e , t y p i c a l l y s i l v e r -grey to brownish-grey, con t a i n i n g r e l a t i v e l y l i t t l e muscovite and only a few rudimentary garnets. I n some places these rooks oontain considerable c h l o r i t e , g r a i n s o f whioh oan be observed i n various stages of a l t e r a t i o n to b i o t i t e . A few specimens were found to be r e l a t i v e l y r i c h i n magnetite. Some of the highest horizons of the Ruby Group have a smooth, greenish, l u s t r o u s surface and appear to grade i n t o c h l o r i t i o - p h y l l i t e s . - 13 -The age of these rooks is unknown beyond the faot that they underlie, with local unoonformity, less intensely metamorphosed rooks of Lower Cambrian age. L i t ho log io ally similar rooks in comparable stratigraphio relations have, in the Cariboo region to the south, been oonsidered Proterozoio i n age. - 14 -LOWER OAMBRIAU. Ingenika Group. Rooks of Lower Cambrian age outcrop on both sides of the band of quartz-mica schist with but local structural unconformity. They consist of not less than 18,000 feet of interbedded quartz-chlorite schist and phyllite, orystalline limestone, sericite schist, quartz i t i o conglomerate, and slate. From their characteristic development in the mountains south of the Ingenika River, these schists have been called the "Ingenika group". Fine-grained quartz-ohlorite schistose or phyl l i t i o strata, typically i n thin beds of variable composition, compose over 60 per oent of this assemblage. X'he limestone is confined largely but not entirely to the lower members of this series, and occurs in large lens-like bodies whioh attain a maximum thickness, of 4800 feet. The typical limestone i s blue-grey to creamy, highly orystalline, poorly bedded, in many places containing persistent horizons of sugary or sheared buff-oolored rock consisting of recrystallized calcite with a high proportion of sericite. Beds of conglomerate up to 200 feet thiok containing rounded quartz pebbles about one-third of an inch diameter in a silioeous matrix are found in the lower and middle horizons of this series. Ohlorite is a characteristic mineral of a l l rooks of this assemblage except the limestone and conglomerate. - 15 -T y p i c a l s e c t i o n s o f the Ingenika group from widely-s c a t t e r e d l o c a l i t i e s i n the map-area are as f o l l o w s : Seotion North of the O s i l i n k a R i v e r -Thickness, i n f e e t . 1000 700 Q u a r t z - o h l o r i t e s c h i s t and p h g l l i t e . T o p of Group unknown* Blue-grey c r y s t a l l i n e limestone. 4300 Grey-green c h l o r i t e s c h i s t and p h y l l i t e , c o n t a i n i n g a few lenses of "Miisoo v i t e - l i m e s t e n e " . 100 Buff-oolored sugary "musoovite-limestone". 600 C h l o r i t e s c h i s t , g r a n u l a r q u a r t z - o h l o r i t e rock. . 400 Interbedded q u a r t z - o h l o r i t e s c h i s t and p h y l l i t e and b u f f - c o l o r e d sugary "musoovitei limestone*. 200 Interbedded q u a r t z - o h l o r i t e p h y l l i t e and blue-grey limestone containing Lower Cambrian pleospongia. 600 Green or grey c h l o r i t e s c h i s t and p h y l l i t e . 4800 Massive to c r y s t a l l i n e poorly-bedded blue-grey, grey, and oream-oolored limestone. 2600 Green or brownish-grey o h l o r l t i o s l a t e and s c h i s t , i n truded by s i l l s of quartz porphyry. 1400 Q u a r t z - o h l o r i t e s c h i s t c o n t a i n i n g a sm a l l amount of b i o t i t e . 300 L i g h t blue-grey massive to p a r t l y o r y s t a l l i n e non-bedded limestone. 17000 (approximately) Seotion South of the M e s l l l n k a R i v e r * Thickness 1^ f e e t . 3300 Blue-grey to creamy c r y s t a l l i n e limestone, i n p a r t s l a t y , sheared. 300 Grey " q u a r t z i t i o conglomerate" interbedded w i t h minor grey-brown epeokled q u a r t z i t e . 800 Grey-brown speckled q u a r t z i t e , s l a t y s c h i s t . 1100 Grey-brown speckled arkoaio q u a r t z i t e , m i n o r conglomerate, 1000 Interbedded grey " q u a r t z i t i o conglomerate" and black to s i l v e r - g r e y l u s t r o u s s l a t e . 800 Dark grey o r gree n i s h grey s l a t e or p h y l l i t e . 800 Interbedded rusty brown q u a r t z i t e and dark grey s l a t e , i n p l a c e s h e a v i l y coated w i t h n i t r e . 40 " Q u a r t z i t i o conglomerate", rounded pebbles o f white quartz i n a rusty q u a r t * i t i o m a t r i x . 100 B l a c k to grey l u s t r o u s s l a t e . 1000 Grey to brown s c h i s t o s e q u a r t z i t e c o n t a i n i n g a few p a r t i n g s of black s l a t e . 1200 Coarse a r k o s i o s c h i s t o s e q u a r t z i t e and sheared quartz-f e l d s p a r conglomerate w i t h minor beds o f g r a p h i t i c p h y l l i t e and q u a r t z - s e r i c i t e - g r a p h i t e s c h i s t . 2000 Dark grey to g r e e n i s h q u a r t z - s e r i c i t e - g r a p h i t e s c h i s t , s l a t e , and p h y l l i t e . Some beds are o h l o r i t & e . " M y l o n i t i o " q u a r t z i t e o r conglomerate; elongated, l e n t i c u l a r , broken fragments of s t r a i n e d quartz i n n 400 a sheared, r e - c r y s t a l l i z e d m a t r i x of q u a r t z , c h l o r i t e and s e r i c i t e . 1600 Interbedded q u a r t z - o h l o r i t e s c h i s t and o h l o r i t i o s c h i s t o s e q u a r t z i t e . Some of the lower horizons c o n t a i n co n s i d e r a b l e b i o t i t e . 14000 (approximately) Seotion l n the Upper Swannell R i v e r V a l l e y -ThioknesB l n f e e t . 150 Very f i n e - g r a i n e d green s l a t e , composed of quartz and c h l o r i t e w i t h minor b i o t i t e . 200 Interbedded b u f f - e o l o r e d sugary c r y s t a l l i n e limestone and grey-green to s i l v e r y telo-ohlorite s c h i s t . 400 I v o r y - b u f f to rose-yellow o r y s t a l l i n e mioaoeous limestone, i n p a r t s l a t y , w i t h t a l o o s e o r c h l o r i t e p a r t i n g 8. 1500 Blue-grey or oreamy c r y s t a l l i n e limestone,poorly bedded. Fine-gr a i n e d orange-brown oaloareoas " q u a r t z i t i o conglomerate", composed of rounded quartz augen i n 80 a f i n e - g r a i n e d r e o r y s t a l l i z e d quartz-carbonate groundmass. 800 Interbedded grey-brown "speokled" impure sohistose q u a r t z i t e and greenish q u a r t z - o h l o r i t e s c h i s t . 100 Blue-grey poorly bedded c r y s t a l l i n e limestone. 100 Q u a r t z - o h l o r i t e s c h i s t and pale brown " q u a r t z i t i o conglomerate". 3300 (approximately) Seotion South of Cutbank Creek -Thiokness i n f e e t . 7000* 200 60 1800 2500 1200 2100 200 900 1000 700 Grey-green to brownish-green q u a r t z - o h l o r i t e s c h i s t , q u a r t z - s e r i o i t e - o h l o r i t e s c h i s t , and s c h i s t o s e q u a r t z i t e , The q u a r t z i t e i s composed of sub-angular, w e l l - s o r t e d p a r t i c l e s of c l e a r quartz w i t h uniformly o r i e n t e d l a t h s of o h l o r i t e and a few g r a i n s of fl.agioolase f e l d s p a r . Interbedded grey-green nodular o h l o r i t i o q u a r t z i t e and s o f t , medium-grained o h l o r i t e s o h i s t . F i n e - g r a i n e d , somewhat s l a t y o h l o r i t e s c h i s t . Blue-grey o r y s t a l l i n e limestone, w i t h t h i n p a r t i n g s of o h l o r i t e s c h i s t . Grey to grey-green f i n e - g r a i n e d sohistose q u a r t z i t e . c Interbedded q u a r t z - c h l o r i t e s e r i o i s e s o h i s t and o h l o r i t i o s ohistose q u a r t z i t e containing a few gr a i n s of p l a g i o o l a s e f e l d s p a r . Grey-green to s i l v e r - g r e y q u a r t z - o h l o r i t e - s e r i c i t e s o h i s t w i t h minor q u a r t z i t e . A s m a l l amount of b i o t i t e i s present i n some of the o h l o r i t e s o h i s t . L i g h t grey " q u a r t z i t i o conglomerate" containing round quartz pebbles i n a f i n e - g r a i n e d q u a r t z i t e m a t r i x . Grey o h l o r i t i o q u a r t z i t e , interbedded w i t h minor q u a r t z - o h l o r i t e s o h i s t and beds of " q u a r t z i t i o conglomerate" up to ten f e e t t h i c k . Q u a r t z - s e r i o i t e - o h l o r i t e s o h i s t , q u a r t z - o h l o r i t e s o h i s t , minor q u a r t z i t e . O h l o r i t i o q u a r t z i t e c o n s i s t i n g of poorly sorted aagajLar to subangular quartz, and about t e n percent o h l o r i t e i n w e l l - o r i e n t e d g r a i n s whioh i n some specimens have almost completely converted to b i o t i t e . Minor q u a r t z - b i o t i t e - o h l o r i t e s o h i s t . 17700 (App ro ximat e l y ) - 16 -The blue-grey s e r i c i t i c phyllites and sohists of this group produce, upon weathering, a characteristic encrustation of soluble salts. For the most part these efflorescences are sulphates of magnesium, calcium and iron, but at one locality south of the liesilinka River consist of potassium nitrate with appreciable amounts of sodium sulphate. Fossils oollected from limestone in this group were submitted to Dr. V.J. Okulitoh of the University of Br i t i s h Columbia for examination. He kindly reported that Collection F 1R, from a small lens of limestone i n ohloritic phyllite north of the Osilinka River, includes Ajaoioyathus Puroellensis Okulitoh A. olarus (Vologdin) A. Osilinka n.sp. Cosoinooyathus n.sp. DendrooyathoiB inexpectans \. n.sp. Protopharetra roots! n.sp. Arohaoioyathus sp. Age: Lower Oambrian, equivalent to the Donald formation of the Purcell Range. Collection F 6R, from the large bed of limestone east of the Swannell River on Chase Mountain, contain algal remains, similar in appearance to algae common in fossils of the Donald formation. Age: Lower Palaeozoic, probably Lower Cambrian. Collection F 7R, from an open pit on No.4 vein, Ferguson Prpperty, Iwgenika Mines Limited, contain poorly preserved tubes resembling Salterella, or Hyolithes. Age: possibly Lower Cambrian. - 17 -"Wolverine Complex" Approximately 200 square miles of Lower Cambrian and Pre-Cambrian formations outcropping on the north side of the Mesilinka River valley between Jackpine Lake and Ingenika Cone have been converted to an igneous-met amorphic complex of feldspathized quartzite. granitoid gneiss, quartz-mioa-feldspar schist, with minor skarn, chloritoid schist, and pegmatite. At the southwest corner of this area, just east of Jaskpine Lake, a small granodiorite stock intrudes this assemblage. The area has gradational boundaries, and structural features of the adjacent schists and quartzites are retained across i t . These rocks appear to owe their dis-tinctive composition and texture to extreme plutonic metamorphism superimposed on the general "regional 1! metamorphism which has affeoted a l l of the Cambrian and Pre-Cambrian rooks. The small stock near Jackpine Lake may represent part of the igneous body responsible for the additional alteration. Rocks of this type are well developed in the Wolverine Mountains in the Eanson Creek map-area to the southeast. In 6 7 this locality Lang , and Armstrong and Thurber , found < granite, granite-gneiss, and pegmatite intimately mixed with quartzite, sohist, and limestone. They gave the name "Wolverine Complex" to the whole assemblage, i n the Aiken Lake map-area, 6. Geol.Surv.Canada, paper 4 2 - 2 7. Geol.Surv.Canada, paper 46 - 11. - 18 -a l l the lower Palaeozoic or earlier rocks have been regionally metamorphosed. The name "Wolverine Complex" has been reserved in this area for those rooks whioh have a distinctive appearance as a result of additional granitization or extreme dynamo-thermal metamorphic processes. Within the "granitized area", the quartzites have been reorystallized; there has been a slight but general coarsening of texture and a tendency toward gneissosity, accompanied by the development of considerable i n t e r s t i t i a l orthoolase and sodio plagioolase. The quartz-mica schists, in addition to the development of feldspar, are characterized by an almost complete loss of musoovite and a marked increase in the proportion of biotite. Garnets, common in the se-gionally metamorphosed rocks, are almost entirely absent from the more highly granitized types. The ohloritic schists and slates have developed distinct rock types characterized by a deorease of chlorite and sericite, an inorease of biotite, and a marked increase of quartz. In some horizons, ohloritoid schists are well developed. Beds of limestone in the granitized area have been converted into a distinctive skarn composed principally of quartz, grossular garnet, tremolite, diopside, and clinozoisite. A few small irregular bodies of orthoolase-musoovite pegmatite were observed. A l l have sharp, apparently intrusive contacts and are located close to the granodiorite stock near Jackpine Lake. 19 -Note on the Metamorphism of the Cambrian and Pre-Oambrian Rooks. The most striking features of the metamorphosed Ingenika and Ruby rocks, taken as a whole, are the uniformity of the grade of metamorphism with respect to the original bedding planes and the characteristic correspondence of attitude between the planes of bedding and sohistosity. It would appear that, except for the distinct bodies of limestone, the bulk of the Ingenika Group rocks were originally argillaceous and arenaceous seaiments, which differed chemically from one another chiefly in the percentage of s i l i c a . These rocks have been subjected to regional metamorphism of remarkably uniform character. Beerystallization of their constituent minerals has taken place under conditions i n which temperature, hydro-static pressure, and stress have reached a given equilibrium at, as far as can be determined, very nearly the same strat-igraphio horizon over the whole area studied. At every locality where a considerable section of these rocks has been exposed there can be observed a gradual, uniform inorease of grade of metamorphism in successively lower stratigraphio horizons. These mainziones of metamorphism oan be distinguished. The boundaries of these zones show a truly remarkable co-incidence with given stratigraphio horizons. - ao -In a l l rooks of the Ingenika Group of appropriate bulk-composition chlorite i s a characteristic mineral. The rooks of this group were f i r s t recognized as a distinct map-the basis of unit on/their structural and stratigraphio relations, but in subsequent mapping i t was found that the lowest horizons in whioh chlorite i s abundant corresponded so exactly with the oldest members of the Ingenika group that in plaoes the drawing of the upper contact of the underlying Ruby group may have been influenced to some extent by the purely mineralpgical ohange evidenced by the sudden appearance of chlorite. The entire Ingenika group, therefore, oomes within the "ohlorite-zone" commonly reoognized as a typical zone of low-grade regional metamorphism. The Ingenika group rooks show many features typical of this zone. The least altered rooks, found, with one exception, almost exclusively in the higher members of the group, appear to be black argillaceous slates, composed chiefly of serioitio mica, chlorite, and quartz, with varying amounts of fine flaky graphite, minute needles of rut i l e , pyrite, and iron oxide which may be in part hematite. This rock i s the only one of the metamorphic series here under consideration whioh oould be regarded as a product of pure dynamic metamprphism. In a l l lower horizons, the effects of progressively increased temperature are apparent. With successively lower horizons, quartz-chlorite-sericite schists predominate. The schists differ from the slates in that the quartz has been recrystallized from i t s originally angular - fel» -particles into smooth or interlocking lentioles more or less, oriented parallel to the sohistosity, and in that the chlorite grains show a tendenoy to coalesce. Some of the rocks, especially those rich in sericite, develop a finely wrinkled arrangement, of thin films of mica and ohlorite whioh give the rock a very perfect s o h i s t o s i t y a n d grade into true chlorite-sericite-phyllites. In the lower horizons of the Ingenika group the quartz has been almost completely reorystallized, and even the quartzites show a certain degree of sohistosity. The most significant change, however, i s the appearance of biotite. Ohlorite-rich rocks from the lower 1000 feet of the Ingenika group show, upon microscopic examination, strings and patches of biotite developing from the grains of chlorite, and the very lowest horizons, containing typical elongated flakes of biotite lying more or less olosely parallel to the plane of sohistosity, are typioal quartz-biotite-chlorite schists. At about the same horizons that biotite makes i t s appearance several strata of finer-grained quartz-ohlorite schists and phyllites show a pronounced "knotty" structure, with prominent "knots" or "eyes" of subhedral garnet. In some specimens the garnets reach a diameter of • •§• inch, but most of the larger crystals are badly corroded, so that determination of the type of garnet is d i f f i c u l t . The best preserved crystals are amber-yellow, greenish or brownish grey, and are probably close to grosaularite or andradite in - 22 -composition. These garnets do not persist in the more intensely metamorphosed lowest hofrizons of the Ingenika group, and, even where most abundant, are seen i n thin section to be badly corroded by quartz. Their presence seems to indicate, not a stage of higher metamorphism than that represented by the "ohlorite-zone" in general, but rather a distinctive response of strata of somewhat different (probably more highly calcareous) chemical composition than most of the Ingenika group sediments. The appearance of biotite in the lower members of the Ingenika group marks the limit of the " ohlorite-zone" of relatively low-grade dynamothermal metamorphism. The rocks of th6 upper half of the underlying Ruby group show the effects of a marked, but uniform, increase of temperature, hydrostatic pressure and stress, whioh produce the grade of metamorphism typical of the''biotite-zone". Biotite i s a characteristic and conspicuous mineral in a l l rooks of the upper 7000 feet (approximately) of the Ruby group. Ohlorite i s in insignificant amount in these rooks, and except for the uppermost horizons is chiefly oonfined to the purer quartzites, where i t persists in increasingly diminishing proportions right to the highest grades of metamorphism. There may have been a temporary retrogression of metamorphism, for some specimens of these rocks of higher metamorphic grade show two distinct ages of biotite, one older, one younger, than the chlorite. The relations of the biotite - E 3 and chlorite are suoh that the ohlorite could have formed by alteration of original biotite, after which the ohlorite i t s e l f oould have been partially re-converted into biotite by a succeeding "wave" of metamorphism. The same relationship would, of course, be achieved i f the earliest biotite represented an original, constituent of the sediments, and the chlorite was formed and later altered to biotite under a single period of increasingly intense metamorphic conditions without completely destroying the original biotite. Sericite, whioh was farirly abundant in the less-metamorphosed upper horizons of the Ingenika group, seems to b6 absent or relatively inconspicuous in the higher horizons of the Ruby group. As successively higher grades of metam-orphism are reached within the "biotite-zone", however, white mica is reconstituted as coherent flakes of muscovite, which increase in size and abundance as lower horizons (and therefore presumably higher temperatures and pressures) are reached. At higher metamorphic grades, rudimentary garnets appear, and the "biotite-zone" gives way to the "garnet-zone". Garnets are present i n almost a l l the rocks comprising the lower 5000 feet of the Ruby group, and in some horizons K makes up over half of the rock volume. The garnet seems toobe almost entirely of the iron-aluminum or almandite variety, and i s apparently stable down to the lowest horizons of the Ruby Group. This garnet bears no apparent relation to the - 24 -"grossularite " garnet found in a few horizons of the ingenika Group, and seems to be formedmainly from a decomposition of the remaining ohlorite in the rock, though i t probably also draws material from the magnetite and biotite present. The proportion of muscovite in relation to biotffite increases as deeper horizons within the garnet-zone are reached. This change is accompanied by a general coarsening of texture. The sohistose rocks of the lower horizons of the garnet-zone are best described as coarse-grained garnetiferous quartz-muscovite schists, and are a typical golden or buff color in contrast to the grey rocks of the biotite-zone. The garnet-zone extends to the lowest exposed horizons of the Ruby group without the addition of any distinct-ive new mineral. In some of the quartzites from the lowest strata grains of a l k a l i feldspar are quite numerous, but exposures are too limited to indicate whether this phenomenon is due to the distinctive composition of a single bed or to a general change of metamotphic effect. The striking correspondence of limits of metamorphic zones to stratigraphio horizons of the Ingenika and Ruby groups has been noted in the foregoing description. Another unique feature of these metamorphosed rocks, related perhaps to the aforementioned correspondence, i s a marked parallelism between the sohistosity of the rocks and the major bedding structures. The Ingenika group and the Ruby group strata are essentially structurally conformable, and have been folded - 25 -into a series of antiolinoria approximately 15 miles across. The overall dips of the limbs of these antiolinoria are steep or even overturned. Lesser folds are characteristically open. The schistosity of the metamorphosed sediments i s in almost a l l lo c a l i t i e s parallel to the limbs and to the crests of the antiolinoria. i t cuts right across the bedding of many of the smaller folds. The explanation of the parallelism between the' schistosity and the major bedding structures i s somewhat obscure in the light of .present knowledge of the area. Regional metamorphism of the type shown by these rocks i s generally conceived as being the result of differential pressure or stress as well as hydrostatic pressure and increased temperature. The schistosity of the rock should normally develop in the plane of least resultant stress. The metamorphosed rocks of the Ingenika and Ruby groups show, by their marked f i s s i l i t y , even among the '*purer,T quartzites, by the abundance of "stress" minerals such as garnet and by the complete absence, despite an appropriate bulk-composition, of minerals such as andulusite and cordierite which do not develop in the presence of a shearing stress, every indication of having formed under the influence of differential pressure. Furthermore, almost without exception the quartz of the me tame.-orphosed rooks is clear and unstrained; even the garnets of the lower horizons of the Ruby group are in some specimens relatively unfraotured; the quartzites show no evidence of - 26 -having been distorted after crystallization, and the schists, though highly f i s s i l e , are physically coherent rocks which appear to have suffered l i t t l e mechanical shearing. The evidence seems fai r l y definite that the rooks were metamorphosed,or at least that the final crystallization or recrystallization took place, after they had reached their present folded attitudes. If such is the case, the differential pressure active during metamorphism must have acted in a direction per-pendicular to the general plane of the bedding. This direotion would be vertical over the central portion of the area under-lain by these rocks and inclined toward the centre over the marginal portions. The mechanics of supplying differential pressure at such diverse angles — t h e resultant direction changes as much as 90 degrees across a distance of three milee — is d i f f i c u l t to explain. Deep burial w i l l , of course, simply give a high hydrostatic pressure; and even i f i t i i s assumed that there is a considerable freedom of lateral expansion at depth ( a rather "forced" assumption; resulting in what might be termed a "squashing" of the sediments under the direct action of an overlying load, the uniform anticlinal development of the schistosity would not be accounted for. Many anticlines and antiolinoria are looked upon as being the result of essentially horizontal compressive stresses; suoh a stress, to produce the bedding structure found in the Ingenika and ituby groups, would.have to be relatively wide-- 27 -spread and of uniform intensity, and. would almost certainly produce a sohistosity in an essentially vertical plane of more or less uniform orientation over the whole area. The most reasonable explanation which the author has been able to devise for the parallel relations between sohistosity and overall bedding i s the hypothesis that the anticlinoria were produced by essentially vertical forces of (for the time being] unknown origin under a relatively heavy incompetent uniform load. Metamorphism i s assumed to have taken place.progressively during the formation of the anti-clinoria. The resistance to the uplifting of the strata would be supplied by the weight of the overlying sediments, which would also of neoessity be arched in the process. At the crest of the anticlinoria, the incompetent overlying sediments, being unable to withstand a tensional pull by portions of the same beds on limbs of the arch, would exert a simple gravitational pressure on the rising rocks. There must be some slipping, and hence re l i e f of pressure, between the beds of the rising anticlinoria, so that the gravitational load would be transmitted to underlying rock as a single vertioally-acting differential pressure. On the limbs of the anticlinoria, resistance to deformation would be offered by the same vertically-acting load of superincumbent rocks. In addition, the rocks on each side of the rising anticlinoria would oppose the forcible crowding aside caused by the deformation, by a horizontal stress directed towards, and 28 -oriented roughly at right angles to, the axes of the antiolinoria. The resultant of these vertical and horizontal pressures would be a stress inolined downward toward the axial plane of eaoh anticlinoriam, roughly perdendicular to the general plane of bedding on eaoh limb of the aroh. In any oase, i f there was any slipping or r e l i e f by recrystallization along planes of weakness bewvteen strata of different degress of oompetenoe, the only force whioh could be applied continuously to the underlying beds would be a resultant force essentially perpendicular p t t o the bedding. Such an araangement oould conceivably develop the parallel relationship between schistosity and bedding observed in the Ingenika group rocks, and would also explain to some extent how stress, hydrostatic pressure, and temperature oould reach a given equilibrium and thus produce a given grade of metamorphism at a relatively uniform stratigraphio horizon over large areas. It has already been noted that i n some horizons grains of reorystallized quartz completely enclose well-oriented flakes of muscovite and biotite without themselves shewing any evidence of oriented structure, and the Inference was drawn that the fi n a l recrystallization of the quartz must have taken place free from the influenoe of differential pressure, after the strata had reached the folded arrangement in which they are now found. It is therefore concluded that the-metamorphism of the Ingenika and Euby group sed-iments, whioh was assumed to have taken place more or less - 2 9 -continuously during the period of formation of the anti-clinoria, continued until or slightly after the strata had reached their present position. Information regarding the geologic period in which the metamorphism of the Ingenika and Ruby group sediments took place i s very scanty. The youngest strata known to be regionally metamorphosed are Lower Cambrian in age; adjacent strata of Devonian or Mississippian age are unaffected, so that the prooess must have gone on in lower or middle Palaeo-zoic time. The Devonian or Mississippian rooks are underlain by at least 35G0 to 8000 feet of anoesit&o tuffs, breccias, and minor flows, indicating very extensive vulianism in middle Palaeozoic time. Such vuloanism could be connected with a general period of diastrophism such as was probably associated with the metamorphism of the Ingenika and Ruby group rocks. The relatively great thiokness of tuffs and breooias could represent part of the covering load under whioh the metamorphism took plaoe. The lowest known horizons of these younger rocks, however, are relatively fresh and i t does not seem likely that they were resting directly upon the Ingenika group sediments. With the possible exception of the stock near Jack-pine Lake, described elsewhere i n this report, there are no known exposed igneous intrusions of any size which might,ibe regarded as being associated with the metamorphism of the Ingenika and Ruby group rocks. The rate of increase of metamorphio grade with depth in these rocks would point toward the existence of a rel&tively large intrusive body at a s t i l l quite considerable depth below the lowest horizons uncovered by erosion. - 31 -DEVONIAN (?) TO TRIAS SI 0 (?) May include parts of Oaohe Creek, Asitka, Takla Groups. A thick assemblage of interbedded volcanic and sedimentary rooks i s exposed in the south-central part of the map-area, unoonformably overlying the Lower Gambrian formations. This assemblage appears to inolu.de parts of the Gaohe Greek, Asitka, and Takla groups, whioh have been described in the Manson Greek, Takla, and McGonnell Greek areas to the south Q and west. In the Aiken Lake area i t has been mapped partly on the basis of lithology. The total succession includes a maximum of at least 18,000 feet of bedded tuffs, andesitio flows, a r g i l l i t e , chert, limestone, sandstone, and conglomerate. Conspicuously banded light to dark green, medium-to-fine grained tuffs underlain by black a r g i l l i t e s predominate in the vicinity of the Osilinka River; the proportion of tuffs diminishes toward the northwest, until the Ingenika Range, north of Lay Greek, is composed of intercalated basaltic and andesitic flows, tuffs, limestone, chert, sandstone, g r i t , and conglomerate. One bed of conglomerate in the Ingenika Range contains rounded boulders of weathered syenite, granite, and diorite. The upper part of the general assemblage contains approximately 2000 feet of dark grey to black massive to 8. Geol. Surv. Canada, papers 45-6, 45-9, 46-6. slaty oaloareoas to carbonaceous argillaceous rooks, inter-beaded with andesite tuffs. The highest horizons have been more or less sheared, and local alterations has developed much serpentine in the andesitic rocks and graphitic or ankeritic material in the argillaceous and calaareous sediments. I'ossils have been found at several l o c a l i t i e s in the tuffs and limestones of this assemblage. The most diagnostic oolleotion to date, from a limestone bed in the Ingenika Range near the middle of the exposed section includes forms resembling Qyathaphyllum of Devonian or Eississippian age.-The southward extension of these rocks has, in the map-area to the south, been considered, in part, to be of Triassic age. Although t h i B group forms a distinct structural map-unit, i t s relatively great thiokness, i t s diversity of rock types indicating repeated vuloanism and varying conditions off deposition, and the presence of at least one loaal erosional unconformity within the group, lead to the inference that i t s formation occupied a somewhat extended period of late Palaeozoic and possibly early Mesogoio time. - 33 -Typical sections of this assemblage are as follows : Section at Osilinka River -Thickness in feet 800 3500 6000 400 I 600 • 11300 A r g i l l i t e , g r i t , banaea tuffs, uniform, very flne-grainea banded tuffs uniform banaed taffs with minor anaesite uniform banaea tuffs with minor slaty a r g i l l i t e uniform banded tuffs. Seotion at Tatlalka River -Thickness in feet 100 Sheared, serpentinized, oarbonatized andesite 1200 Banded tuffs, breccias, partly serpentinized 400 A r g i l l i t e 500 Interbeaaea a r g i l l i t e and alterea tuff or anaesite 100 nrhyolite"(?), minor tuff, a r g i l l i t e 1200 (+) Slate ana a r g i l l i t e , in part calcareous 1000 (t) Andesite, a r g i l l i t e . 4500 ! ! Seotion at Polaris Greek -Thickness in feet 500 Tuff ana a r g i l l i t e 2000 Tuff ana aaaesitio flows 600 Tuff, minor a r g i l l i t e 4500 Tuff, minor anaesite 1200 Limestone, tuff, conglomerate,sandstone, g r i t . 1600 Tuff 2500 Tuff and breccia 4000 Tuff ana andesite 16900 Seotion North of Lay Greek -Thickness in feet 5000 Interbedded andesite ana tuff 1500 Tuff, g r i t , limestone, conglomerate 1E00 Basalt, anaesite, tuff, breooia 40 Conglomerate 50 Serpentine (probably originally a pyroxenite s i l l ) 600 Sandstone, g r i t , tuff, andesite, limestone 1200 800 Tuff and limestone with corals of Devonian or Miss-J-ssiplan age. Limestone 2000 Interbedded andesite ana tuff 1000 Very fine-grainea bandea tuff, minor anaesite 400 fine tuff ana anaesite 13200 - 34 -Cache Creek Group. Forming a more or less distinct lithological unit in the general assemblage desoribed above, an apparently conformable succession of interbedded sedimentary and altered volcanic rooks, not less than 8000 feet thick, is exposed in the southeast portion of the map-area. Similar rooks are exposed in the valley of the Omineca Biver in the extreme southwest corner of the map-area. The dominant sedimentary rook is a thin-bedded, grey to black, rusty weathering, carbonaceous a r g i l l i t e . Lens-like bodies up to 3000 feet thick of blue-grey massive limestone are intercalated with the a r g i l l i t e . Einor sed-imentary rocks include thin-bedded, crumpled, ribbon cherts, consisting of contorted beds of blue-grey to creamy chert separated by fine partings of a r g i l l i t e . Bands of greenstone up to 1500 feet thick are interbedded with the sedimentary rocks. The greenstones represent chloritized and amphibolitized flows, tuffs, brecoias, and agglomerates of original andesitic or basaltic composition. In the Aiken Lake area, this lithological unit has yielded no diagnostic f o s s i l s , but i t appears to represent the northward extension of roeks which contain foraminifera of Middle Permian age and have been correlated with the Cache Cifreek group of Gentral British Golumbia. - 35 -UPPER TRIAS SIC. Part of the Takla Group. The Devono-Mississippian or later rocks are overlain, with erosional unconformity but for the most part without apparent angular discordance, by a thick succession of flows and minor intercalated sedimentary rocks. This succession, which corresponds to part of the Takla group, as defined in the Takla area to the south, is exposed in a belt 5 to 10 miles wide to the southwest of the Palaeozoic rooks and attains a maximum thickness of at least 12,000 feet near Aiken Lake. Grey, green and black porphyritic and non-porphyritio andesites and basalts predominate. Intercalated with the lavas are coarse angular breccias and black,, grey, and green tuffs. West of uslika Lake, the lower horizon of this assemblage is marked by a bed of conglomerate at least 100 feet thick. The conglomerate is composed of well-rounded pebbles up to six inches in diameter of grey granodiorite, diorite, fresh and serpentinized andesite and basalt, minor chert and sedimentary rocks, and many coaly or woody fragments in a grey-gr6en gritty matrix. On the -south fork of Thane Greek, approximately 4000 feet st rat ig rap hie ally above the base of the Takla group section, andesite flows and tuffs are unconformably underlain by small stocks of pink granodiorite. The stocks presumably - 36 -out, hut were not observed in contact with, lower members of the group. At the Vega property, the lava exposed underground contains rounded pebbles of similar granodiorite. Small lenses and narrow, discontinuous beds of dark-grey to black carbonaceous limestone are found at several horizons. The upper part of the section west of Lay Greek contains at least 3000 feet of interbedded a r g i l l i t e , s i l t -stone, greywaoke, and limestone. The only diagnostic fossils yet collected from these rocks within the map-area were obtained from a small N limestone lens in andesite west of Lay Greek. This lens contained Halobia or paonella, sp., Juvavites 2 sp., of Triassic, probably Upper Triassio age. - 37 -UPPER JURASSIC (?) OR LOWER ORETAQSOUS. i A body of conglomerate not less than 5500 feet thick i s exposed east and north of Uslika Lake. Well-rounded boulders and pebbles up to 10 inches diameter of a great variety of volcanic rocks, tuffs, fine clastic sediments, cherts and schists make up some horizons; other horizons, amounting to about one third of the total observed thickness, are principally composed of granitic pebbles superficially, similar to the various rook types found in the Omineca Intrusions; the pebbles of s t i l l other horizons are chiefly white vein quartz and oh art. The matrix is a grey to brown, fine sandy to gritty greywacke. In a.few horizons the pebbles are coated with shiny hematite. The conglomerate is remark-ably uniform, the largest sandy or shaly lenses being no more than a few inches thick. On Vega Greek, just west of the conglomerate but not observed in contact with i t , about 300 feet of black to dark grey oarbonaoeous a r g i l l i t e containing thin beds of fine chert-pebble conglomerate are exposed in what appears to be conformable relations with the main conglomerate body. Rocks of pre-Upper Triassic, probably Upper Palaeozoic age outcrop on both sides of the conglomerate body. The st r a t i f i c a t i o n of the conglomerate is roughly parallel to that of the surrounding rocks, and it may be passible that the conglomerate is part of the same general assemblage, - 38 -whioh is known to include beds of conglomerate containing intrusive pebbles. However, wherever observed, the contact • of the conglomerate J.ies along a fault. This fact, together with the abundance of granitic pebbles similar to the rocks of the Omineca Intrusions, as well as pebbles similar to the various rock types present in the TakLa Group, has led to the conclusion that the conglomerate i s probably younger than the main period of intrusions and has been downfaulted into older trooks. The a r g i l l i t e on Vega Greek, possibly the same age as the conglomerate, contains species of Gladophlebls and Ooniopteris of Upper Jurassic or Lower Cretaceous age. - 39 -INTRUSIVE ROCES POST-LOWER CAMBRIAN. An irregular body of granodiorite and granite i s exposed east of Jackpine Lake. Intrusive oontaots, looal development of skam and other typical contact-metamorphic rocks indicate that this body i s at least locally intrusive. However, i t occurs in highly metamorphosed gneisses and schists, and the possibility of i t s originating through the processes fiif extreme metamorphism and granitization cannot be completely disregarded. This body cuts Lower Oambrian strata but shows no evidence of having been subjected to the deformation which has so profoundly affected the Lower Oambrian rocks; no other evidence chf i t s age has been obtained. 'The only other definitely intrusive rocks found in the Oambrian or Pre-Oambrian assemblage are small dykes of aplite, daoite, and feldspar porphyry in the vicinity of Jlmraay Greek and south of Chase Mountain. These are most abundant in the rocks assigned to the Ruby Group and are lithologioally quite distinct from any other intrusive rocks found in the map-area. 40 -PO ST-DEVONIAN-MIS SISSIP PIAN. PRE-UPPER TRIASSIO. A bed of conglomerate immediately overlying a known Devonian or Mississippian horizon in the Ingenika t Range contains rounded, weathered boulders of syenite, granite and diorite, indicating the existence of an exposed intrusive body in Palaeozoic time. The boulders are lithologioally distinct from any intrusive bodies observed cutting the pre-Devonian or Mississippian rocks. The basal member of the Takla group exposed' west of Uslika Lake is a bed of conglomerate at least 100 feet thick containing rounded boulders of relatively fresh granodiorite and diorite. The source of these boulders has not been found. 41 -UPPER TRIASSIO OR EARLIER. "Vega" Intrusions. Stooks of pink granodiorite, too small to be shown on the map, are exposed along the south fork of Thane Greek, unconf ormably overlain by andesites of the Takla group. The exposures are in the lower part but not at the base of the exposed Takla group seotion, and the stooks presumably out the lower members of the group. Boulders of this granodiorite are found embedded in the lavas exposed by the underground workings at the "Vega" prpperty, and the intrusions have been locally named "Fega" intrusions. The Vega intrusions represent a^ period of minor • intrusion and erosion within the general period of formation of the Takla group. Tuffs interbedded: with the andesites containing fragments of the intrusive have supplied fossils whioh, while not in themselves diagnostic, are similar to fossils found in association with Upper Triassio fossils in the Takla group elsewhere in the map-area. The Vega intrusions are therefore presumed to be Upper Triassio or earlier age. 42 -JURASSIC OR LOWER CRETACEOUS (?) Omlneoa Intrusions. The name Omlneoa Intrusions has been applied to the numerous bodies of intrusive rooks of Jurassic or Lower Cretaceous age thay. are exposed in the Omineca mountain system, These bodies range in size from s i l l s and dykes to batholiths, and in composition from pyroxenite to granite. Granodiorite and quartz diorite are the predominant rock types. The largest known body of these rocks i s the batholith that extends from the Nation Lakes northwest across the Manson Creek, Takla, Aiken Lake and MqGonnell Creek map-area*. The batholith, generally known as the Omineoa-Cassiar batholith, is exposed over an area of approximately 450 square miles in the southwest portion of the Aiken Lake map-area. A wide range of rock types is present in this body, which probably represents a prolonged and complex period of intrusion. The predominant rooks are uniform, medium to ooarse-grained, grey, buff, and pink quartz monzonite, granodiorite, and quartz diorite. Isolated bodies of pink or white granite, up to 20 square miles in area, usually with sharp intrusive contacts, are quite common, and a few small bodies of syenite and alaskite were observed. - 43 -Approximately one-quarter of the exposed batholith l s composed of distinct bodies of diorite and gabbro. the boundaries of most of these bodies show a uniform gradational change within a few feet from dark green or grey diorite to light grey or buff granodiorite and quartz diorite. The mountains south of the Mesilinka River near the heaa of Abraham Greek show a rude horizontal stratification from granodiorite at the bottom upward through diorite and gabbro to hornblendite within a vertical range of 3500 feet. The explanation of this phenomenon i s not apparent on the basis of present data, but i t may be that erosion has not penetrated very deeply below the original roof of the batholith, and that the hornblendite of the higher peaks represents a basio marginal phase of the batholith. At several l o c a l i t i e s within the batholith, irregular bodies of quartz diorite and diorite, usually less than 15 square miles in area, show a pronounced gneissic structure. The gneissosity does not show a general overall orientation and bears no obvious relation to the predominant shear zones or fraoture patterns cutting the batholith. The bodies of gneiss have sharp contacts, and in some places are definitely Intruded by fresh, uniform-structured rooks. They may represent assimilated inclusions of country rock or older, sheared phases of the Omineca Intrusions. - 44 -The stock in the vicinity of M i l l s r ana Croydon Creek is a ooarse-grained hornblende diorite consisting chiefly of dark green hornblende and pink feldspar. Pegmatitio patches, with hornblende crystals up to 8 inches in-length, are common in this body, and intrusive breeoias, frequently accompanied by abundant epidote, are well developed. Bodies of altrabasio rock are found in several parts of the map-area. A small band of serpentinized peri-dotite outs the Permian strata south of f a s i Lake. An irregular stock about 25 miles in area in the Ingenika Bangs east of Polaris Creek i s composed of coarse-grained horn-blendite and pyroxenite with minor peridotite, dunite, serpen-tine and gabbro. Bodies of medium-to. coarse-grained horn-blendite with minor pyrosenite are found along the eastern margin of the batholith north of Tutizzi Lake and south of the Mesilinka Biver. These rooks are intruded by the diorite ana granodiorite of the main part of the batholith. Small stocks of hornblendite and biotite-pyroxenite outcrop along the extreme west border ox the map-area north and south of Miller Creek. The Omineca Intrusions out the Upper Triassic or Jurassic formations of the Takla Group9. The conglomerate near Uslika Lake, possibly Upper Jurassic or Lower Cretaceous in age contains boulders lithologioally similar to the rocks 9 In the Takla area to the south,Takla group rocks contain formations of probable Jurassio age. See.GeolSurv. Canada, paper 4 4 - 5 . - 45 -of the Omineoa Intrusions. In the McConnell Greek map-area to the west, the granitic rocks are overlain by Upper Cretaceous rocks of the Sustut Group. Therefore, the Omineoa Intrusions are probably Jurassic or early Gretaceous in age. - 45 -STRUCTURAL GEOLOGY. Folding A l l stratified formations in the map-area have a northwesterly regional trend. The lower Palaeozoic and older rocks have been folded into two f a i r l y open, northwesterly trending anti-olinoria, each about 15 miles wide, which may be portions of the earns structure, displaced by a fault along the Mesilinka River Valley. The axial plane of each anticlinoriam i s inclined to the north, so that dips south of the crest are in general considerably Siteeper than those to the north. Subsiduary folds, 1000 to 5000 feet from crest to crest, with their axes approximately parallel to that of the major anti-cline, are characteristically! open. The schists of the Ruby group are commonly minutely crumpled and drag-folded. In general the Ingenika group strata are not as highly contorted as the underlying Ruby Group. The rocks of the Butler Range southeast of Ingenika Cone dip eastward. Here the limestone and ohloritio schists of the Ingenika Group outcrop to the west of, and so apparently underlie, the older quartzites and mica schists of the Ruby Group. The apparent inferior stratigraphic position of the younger rqeks seems to be due to an overturned fold. The synclinal axis of this fold appears to pass through the - 46 -Tomias Lake valley and to cross the Swannell River near the Swannell mineral showing, where intense distortion has resulted in isoclinal folding and pronounced shearing of slaty a r g i l l i t e s and impure limestones. The upper Palaeozoic rocks show a genez^al steep dip to the west. The a r g i l l i t e s exposed near Wasi lake and tentatively correlated with the Oache Greek group are c h a r a c t e r i z e d by tight isoclinal drag folding accompanied by much shearing. No attitudes were observed in the Oache Greek group rocks southwest of the Omineca River, but similar rocks to the south strike northwesterly and dip steeply northeast, Elsewhere in the: map-area, with the exception of the faulted relations present in the upper Lay Greek valley, the Upper Palaeozoic formations are structurally conformable with the strata of the Takla group. The whole assemblage is t i l t e d 30 to 70 degrees to the west, and appears to form the eastern limb of a large syncline whose axis, partly obliterated by the Omineoa-Oassiar batholith, l i e s west of the map-ar6a. Locally, Takla group rocks are contorted into small folds whose attitudes differ widely from the regional trend. The conglomerate exposed near the Uslika Lake has a general northwest tBend with moderately steep southwest dip, but faulted sections on the west side of the Osilinka River exhibit a wide range of attitudes. - 47 -gag1ting. A l l of the rocks in the map-area have been dis-located by faulting to a greater or lesser extent, and in some places faults and shear zones are so prevalent that they cannot be adequately mapped on the present scale. The western part of the antiolinorium of Cambrian and Pre-Cambrian rocks has been displaced a total of nearly ten miles to the south relative to the eastern part by a series of northerly trending faults near the middle portion of the Swannell River. It i s possible that the major arch of thesB rocks between the Osilinka and Mesilinka Rivers represents part of the same structure, displaced by a large fault along the Mesilinka River valley. If such faulting took place, i t must have occurred before Devonian or Mississ-ippian time, for rocks to the west have not been displaced. The upper Palaeozoic formations contain several steeply-dipping, northwesterly trending faults and shear zones, some of which may be connected with the "Manson Fault Zone" as defined in the Manson Area. 1 0* The Pinchi Fault Zone 1 1 a taajor structural break extending over 150 miles northwest from Pinchi Lake near Fort St. James, underlies the Omineoa River valley in the extreme southwest corner of the map-area and forms the contact between the Omineca-Cassiar. batholith and the Cache 10. Geol.Surv.Canada, paper 45, - 9 11. Geol.Surv.Canada, paper 4E -11, 44 - 5. - 48 -Creek formations. • The uppermost members of the rocks underlying the Takla Group have been sheared, but in most cases there is l i t t l e evidence of appreciable net movement along the contact. Along the upper portion of Lay Creek valley, however-, the two map-units are structurally discordant and probably separated by a distinct fault. There has been l i t t l e , i f any, faulting along the east contact of the Omineoa-Cassiar batholith, but most of the outlying stocks l i e along faults. Wherever observed, the oontact between the con-glomerate near Uslika Lake and the surrounding rooks i s along a fault, and i t seems likely that the conglomerate was down-faulted into i t s present position. Both the conglomerate and the upper Palaeozoic rooks have been offset by a fault along the Osilinka Biver valley through Uslika Lake. Many of the faults, particularly those in the Takla Group rooks, have acted as channelways for oarbonatizing solutions, and their wall*rocks have b6en altered to buff-weathering silioeous and ankeritic carbonate material. - 49 -ECONOMIC GEOLOGY. Plaoer Deposits. Plaoer gold has been found in workable quantities at only two loc a l i t i e s within the map-area. Jimmay Greek, a tributary of the Osilinka River, has been intermittently worked since 1899, but recovery has never been large. The deposit for the most part appears to represent re-sorted glaoial debris, though some gold has been recovered from a buried pre-glaoial channel. Several bars on the Ingenika River near Wrede Greek have been worked, but returns have not warranted continuous operations. It is noteworthy that although the only sign-ificant amount of gold recovered to date in the map-area has come fam streams eroding the highly metamorphosed Cambrian and Pre^Cambrian rocks, no lode gold deposits of importanoe have been found in these rocks. The younger rooks exposed to the west, in whioh gold mineralization has been noted, have produced no known looal plaoer deposits within the map-area, but have supplied much of the glacial material mantling the stream valleys now containing plaoer gold. - 50 -Lode Deposits. The lode deposits in the map-area may be broadly classified on the basis of geological occurence as follows; (1) deposits in the highly metamorphosed Pre-Cambrian and Cambrian sohists and limestones; and (2) deposits in or grouped around and apparently related to the various bodies of the "Omineoa Intrusions". Deposits in the Pre-Gambrian and Cambrian Rooks ; Mineralization in the Pre-Cambrian and Lower Cambrian rocks i s , with the exception of relatively unimportant pyrometasomatio pyrrhotite deposits on the contact of a small stock, typically of the silver, silver-lead, and silver-lead-zino type. As noted previously, although the rooks have been subjected to intense metamorphism and local intense granit-izarion, the only definitely intrusive body of any size is a granodiorite stook east of Jaokpine Lake. Along the borders of this body, associated with Jiypioal dippside-garnet-tremolite skarn and feldspathized gneissio quartzite, are deposits of pyrrhotite, containing minor amounts of pyrite, arsenopyrite, and ohaleo/pyrite. The deposits (e.g. Hope group) do not appear to have any oommeroial significance. The. Ruby prospect i s on Jimmay Creek in the quartz-mica schists of the Ruby group near small granitic stocks and s i l l s . Here a northeasterly trending, s i l i c i f i e d fault 51 * zone carries erratic mineralization of ruby silver, arsemo-pyrite, and pyrite along dip planes. Good silver values are reported to have been obtained from some parts of the fault zone. Similar mineralization has been reported in the Ruby group rocks east of the head of Jimmay Greek. The metallic mineral deposits of the Ingenika group are, with one exception, confined to the limestones or calcareous argillaceous rocks, The largest known deposits are those of the Ferguson group, near Lookout H i l l in the Ingenika River valley. Here, thick bedded, relatively pure limestone, locally highly silioified,, has been intensely sideritized and replaced along bedding planes by crystalline galena and sphalerite with minor pyrite, pyrargyrite, tetrahedrite, ohaloopyrite and maroasite. The best mineral-ization is confined to four bed-like bands, EOto 8 feet thick, which have been traced for about 450 feet down the dip. The mineralized bands average approximately 18 per oent lead, 7 per cent zinc, and 7.5 ounces silver per ton. At the Onward property, l i miles south and con-siderably lower stratigraphically than the Ferguson deposits, small fla t - l y i n g , sheet-like bodies of relatively coarse-grained galena and sphalerite are found lying parallel to • thinly-bedded s i l i c i f i e d iron-stained limestone. - 52 -Mineralization of both the fraoture-filling type and the replacement type i s found in highly folded and sheared a r g i l l i t e s and impure limestones on the Swannell group of olaims. Quartz veins and s i l i c i f i e d beds are sporadically mineralized with sphalerite, galena, pyrite, and chaloopyrite over an exposed width of about 450 feet across the strike. The best mineralization is in quartz veins • lying parallel to the bedding. Selected samples assay as high as 9 ounces silver per ton, 25 per cent lead, and 27 per cent zinc across one foot. The large bed of limestone forming the ofsst of the ridge east of the mouth of May Greek somtains a vein approximately one foot wide composed almost entirely of fine-grained galena. A representative sample assayed 83.24 per cent lead and 47.69 punces silver per ton. The Beverly group, located a few miles east of the above showing, includes three exposures of lead-zinc mineralization close to a prominent shear or fault zonal The exposures cover a relatively large area and are reported to average 7 to 10 per cent lead, 1 per cent zinc, and, H ounces silver per ton. The Weber group of claims i s located in massive unaltered limestone south of the Osilinka River near Wasi Greek and contain galena, pyrite and barite in a strong northwesterly trending fracture zone. Assays on selected - 53 -samples yielded 10 per oent lead, 4 per oent barite, 2 ounces silver per ton, and a traoe of gold. The only appreciable known mineralization in the Ruby or Ingenika group rocks, distant from igneous contacts, which i s not of the distinctive lead-silver variety is that shown by the Burden group of claims on the Swannell River east of the.Ferguson Deposit. This showing consists essentially of a large quartz vein sparsely mineralized with chaloopyrite in talcose sericite schists. - 54 -Deposits Related to the Omineoa Intrusions, Mineraliearion is widespread in the upper horizons of the upper Palaeozoic formations, in the Takla group rocks, and in the bodies of the Omineoa Intrusions. A l l of i t appears to.have some genetic connection with the Omineoa Intrusions. Several metallic mineral deposits are found along the eastern margin of the Omineca-Oassiar batholith or around the contacts of its associated stocks, and the deposits in the country roeks are a l l located on structural ; breaks which presumably could form deep connections with the intrusives. A few deposits are found along shear zones in the intrusive bodies themselves. Types of deposits range from disseminated mineralization in country rock to normal f i s s u r e - f i l l i n g quartz veins. The Omineca-Oassiar batholith contains many shear zones which are mineralized with pyrite and. copper sulphides, but<vmost suchlmineralization carries no appreciable precious metal values. One of the largest of these mineralized shear zones occurs at the head of the east fork of Itatetlo Greek. Here closely spaced fractures form a permeable, mineralized zone at least 120 feet wide in medium-grained granodiorite. The fractured rook is sparsely but uniformly mineraliz/ied with pyrite, chalcopyrite, and bornite. A representative sample of the mineralized rook assayed 2.02 per cent copper and a trace of gold. The zone also contains five veins, 2 to 10 inches wide, composed almost entirely of pyrite and chalcopyrite. - 55 A grab sample of one of the larger veins assayed 18.93 per oent copper, 0.01 ounces gold per ton, and 1.31 ounces silver per ton. The complex of sedimentary and volcanic rocks cut by small intrusive bodies along the west border of the map-area between the Mesilinka Biver and Lay Greek contains several heavily pyritized "bands up to 1000 feet wide and several miles long. These bands traverse several rock types but are frequently centred around a diorite dyke or s i l l . One ojs. the pyritized bands of this type exposed at the Granite Basin workings contains minute amounts of ohaloopyrite, tetrahedrite (?) and magnetite and is reported to carry up to one-third ounne gold per ton across a width of 30 feet. Quartz veins are very numerous in many parts of the area. Those cutting the Omineca-Cassiar batholith are for the most part barren, and appear to be high-temperature veins whioh grade into quartz-feldspar pegmatite dykes. A large carbonate zone on the Elizabeth group north of the Osilinka River in the interior of the batholith contains many quartz veins, some of whiohearry gold and silv e r values. The nearby "Chief Thomas " vein is 6 to 10 feet wide, at least 300 feet long, and carries ohaloopyrite, pyrite, and bornite, with low values in gold and si l v e r . Quartz veins are particularly numerous in an area extending northwest from Tutizzi Lake along the west border of the map-area to Lay Greek and continuing into the McOonnell Greek map-area to the west as far as Goldway Peak and the headwaters. of Wrede Greek. The larger ones are, in general, massive white quartz veins barren of metallic sulphides or precious metals. Smaller veins, stringer lodes, and s i l i c i f i e d shear zones exhibit wide variations of mineral content! The boss-like quartz body exposed on Porphyry Greek contains pyrite, magnetite, and molybdenite; the nearby Oroydon Group veins and stockworks contain massive pyrite, ohaloopyrite and molybdenite, with f a i r gold values; the somewhat smaller veins of the Shell group, whose main showings l i e just off the west border of the map-area, contain pyrite and ohaloopyrite with considerable gold values and, in places minor magnetite and erythrite. A small amount of cobalt bloom was observed coating fractures in small quartz veins in hornblende diorite east of Croydon Creek. North of Tutizzi Lake, several of the quartz veins contain orystalline galena, often accompanied by ohaloopyrite or specular hematite. The mineral showings on the Vega property oocur in intensely faulted and sheared andesites at the base of the Takla group. The andesite contains small pebbles of granodiorite similar to that exposed in small stocks on Thane Greek. Ohaloopyrite, pyrite, andbomite are dis-seminated through the andesite and concentrated along oaloite veinlets. The be«t mineralized body i s reported to be about 10 feet wide and 25 feet long, and to average 0.25 ounces gold per ton and 1.5 per oent copper. 57 -Elsewhere in the Vega group, ,oarbonatized zones along faults carry small amounts of oinnabar. The workings on Thane Greek expose a s i l i o i f i e d shear zone about 4 feet wide in amphibolitized andesite near the eastern contact of the Omineca-Oassiar batholith. The shear carries pyrite, chalcopyrite, speoularite and magnetite, with low values in gold. lenses of pjirite and arsenopyrite up to 50 feet long and 9 feet wide i n sheared greenstone near the contact of a s i l l of granodiorite porphyry are exposed by the Pluto workings. They are reported to oarry some values i n gold. As has been noted, the upper members of the map-unit underlying the Takla group consist of relatively incompetent sheared calcareous and carbonaceous a r g i l l i t e , banded tuff, and altered andesite. These rocks contain relatively abundant, dissemenated finely crystalline pyrite which appears for the most' part to be the product of general metamorphism rather than mineralization. Stringers and veins of quartz and calcite are numerous, but most are small and discontinuous. In these strata, several distinct types of mineralization are found. A l l deposits are located close to small igneous bodies which appear to be related to the ©mineoa Intrusions. The most widespread type of mineraliz-ation is found on the Jupiter, Eoaaris, and Stranger showings and consists of highly breociated quartz-calcite veins or fracture zones associated with much black, lustrous graphite - 58 -and mineralized with grs'nular pyrite. Some of these veins have been found to carry f a i r gold values; most of them, however, are very narrow and lensy. A different type of mineralization occurs on th6 Jupiter property in f ault fissures which are earlier than the pyrite-bearing fracture zones. These fissures have been healed by quartz-calcite veins mineralized with sphalerite, galena, tetrahedrite, chalcopyrite, and minor pyrite, and contain, in places, up to two hundred ounces of silver per ton. The known veins ape for the most part less than one foot wide. Lens-like replacement bodies of pyrrhotite and pyrite with some chalcopyrite occur in the a r g i l l i t e on Polaris Greek, close to small stooks and dykes of granite • and andesite porphyry. These bodies attain a width of up to 25 feet and a length of several hundred feet, but none have been found to contain appreciable preoious metal values. B I B L I O G R A P l i H Y. Armstrong,J.E. The Pinchi Lake Mercury Belt, British Colombia; Geol.Surv.Canada, Paper 42-11 (1942). Northern Part of the Pinchi Lake Mercury Belt. British Colombia; Geol.Sorv.Canada,paper 44-5 11944). Takla, British Colombia; Geol Sorv.Canada, Paper 45-6 (1945) Geology and Mineral Deposits of Northern British  Colombia West of the Rooky Moontains; Geol.Surv.Canada,Bulletin No.5,(1946) Aiken Lake (South Half), British Colombia; Geol.Sorv.Canada, Paper 46-11 (1946) Armstrong.J.E. Manson Creek Map-Area, British Colombia; and Geol.Sorv.Canada, Paper 45-9, (1945) Thurber, J.B. Prospeoting Po s s i b i l i t i e s in Part of the Omlneoa Mining Division. British Columbia; Can.Min.Jour.,Vol.66,No4,pp.217-222 (1945) ginlay River District, British Columbia; Geol.Surv.Canad a;Summ.Rept.1927,pt.A, pp. 19-41; and map N0.207A (2156), (1928). Manson Creak Map-Area, British Columbia; ~~ Geol.Surv.Canada,Paper 42-2, (1942). Northern Mineral Survey District No.2; Ann,Repts.,Minister of Mines, British Columbia; 1926, pp.A116-A117; 1927,pp.0116-C182; 1928,pp.C138-C203; 1929 to 1938, part C. Aiken Lake Area, North-Central British Columbia; Dept.of Mines, British Columbia, Bulletin No.l, (1940). McOonnell Creek, British Columbia; Geol.Surv.Canada, Paper 46-6, (1946). Dolmage, V., Lang, A.H. Lay, Douglas Lord, C S . McOonnell, R.G..Report on an Exploration of the ffinlay and  Omlneoa Rivers; Geol.Surv.Canada; Ann.Sept. (new series) 1894, Vol.Vll, pt.C, and map No. 567; (1896). The accompanying maps of the Ferguson property of the Ingenika Mines Limited are included to illustrate the replacement type of deposit found im the lower Cambrian limestones. A detailed report on this property i s being prepared:. The mineralogy of the deposit is described in a report by E.R. Lea, submitted in connection with the course Mineralography (geology 409) at the University of British Golumbia, April, 1947.. L I B R A R Y U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r , C a n a d a A/O. S ADIT ELEV. 232.5 \ \ \ \ \ \ \ ^ \ \ NOTE. • Plan of No,5 Adit +<*ke.H from D. Lay, \ Annua/ Report of Minister of Mines, Br-ifish Co/umbioc, /SJO PAI50. \ \ A/O / ADIT EJ-FV- 29&0 NO 4- ADIT ELEV. 2.SOS L EG END CRYSTALLING LHYiejrone S/.L/QtMEG LIMESTONE SHEARED SKRlC/TfC I / A * G s T O H E CALCITE. - sioeRfTe RO<ZK 9UAGTK~ SIOJSRITS ffocn SiOCA?lTei Q/f^ElVA AiYO S P H A L E R I T E : GALEA/A A No Sf>HAL£.ftJ-r£ INGENIKA MINES LIMITED FERGUSON PROPERTY COMPOSITE PLAN or UNDERGROUND WORKINGS SCALE - F£~£T So !_ So J L lo o _J E • F R. • O 5 c 194 6 Vancouver, Canada A/O-S ADIT ELEV. ( ~ -2 8 4 ° NQ. * ADIT £t.£.l/. SSOS / 7 / / 29 / / L 4 < / / * Ufa -/ / / No- I MOlT ELEV. 29$Q J / I / -4 I s 7 / - A 7 V Approximate limits of heavy ip hide rn rre ra J•'2 <z ?~tort o N \ \ \ \ \ \ \ \ INGENIKA MINES LIMITED FERGUSON PROPERTY STRUCTURE CONTOURS ON TOP OF NO.3 MINERALIZED ZONE SCALE - F'EET E. F. R. - O. S. C. / 9 4-6 LEGEND C R Y S T A L L I N E LfM£sro/V£ S/L/C/rsGO LIMEsTo<V£ SHEARED •se/yrc/rvc L/OOGSTO^ Slog/it re, GALG/V/* st/va s0H<9LE#irG QAilENA A/VO SA<VAL£/R< re. INGENIKA MINES LIMITED FERGUSON PROPERTY NORTH-SOUTH SECTION THROUGH PORTALS OF NO A AND NO. 5 AP/TS SCALE - FEET j 5 C. . • NO. 4 ADIT E L E V . ZBOS so l i, So /oo -1 ELEVATIONS IN EEET ABOVE. SEA LEVEL A/O. S AOfT ELEV. 2B2S NORTH S.Q00 SOUTH F. F. R. - G.5. C. f34.6. C o m p r e s s o r 6Acrf NO- S AOlT ELEV. 282.5 FERGUSON PROPERTY PLAN OF OUTCROPS AND SURFACE WORKINGS So SCALE FEET So CONTOUR INTERVAL So FEET ELEVAT/ONS IN E£CT AGQVE SEA LE^EL LIBRARY University of British C o l u m b i a V a n c o u v e r , C a n a d a LEGEND —^-^2) OUTCROP STRIPPING, POCK EXPOS£0 STRIPPING, SI OUQHEO CRYSTALLINE LIMESTONE •S/L fClF/EO LIMES TONE SHEARED SERICIT/C L/ASESToNE CALCITE - SIOERITE. fi?OC/< <p(/ARTX-SIDERITE ffoCM SIOERITE , GALE/VA A}AZO SPHFtLER ITE GALENA ANO SPHALERITE. C A N A D A D E P A R T M E N T O F M I N E S A N D R E S O U R C E S M I N E S A N D G E O L O G Y B R A N C H B U R E A U O F G E O L O G Y A N D T O P O G R A P H Y I26°00' T O P O G R A P H I C A L S U R V E Y 45' 57°oo S H E E T 9 4 C (West Half) 125°00' 57°00' Bedding, i n c l i n e d */ Bedding, v e r t i c a l / Bedding, overtarned $ Gn e i s s o s i t y , S c h i s t o s i t y , or Shearing A n t i c l i n a l a x i s S y n c l i n a l a x i s F a u l t F o s s i l L o c a l i t y M i n e r a l Occurrence X V a n c o u v e r , u n a « d JURASSIC OH CRETACEOUS. mem JURASSIC (?) OR LOWER CRETACEOUS. v9 Conglomerate. Minor a r g i l l i t e . UPPER JURASSIC OH LOWER ORETACEOtJ"S. 0MIKKOA INIHUS1OK3. G r a n o d i o r i t e , i n patft g n e i s s i o , quartz d i o r i t e , 8<* quartz monzonite,granite; minor s y e n i t e , " d i o r i t e , gabbro. 8.M 7 D i o r i t e , i n part gneissio,monzonite,gabbro; minor g r a n i t e , g r a n o d i o r i t e , h o r n b l e n d i t e , Hornblendite, pyroxenite; minor serpentine.dunite, be i n part older than Takla group. TRIASSIO 6 UPPER TRIASSIO (Mainly or e n t i r e l y ) TAKLA GROUP. Ande s i t i o flows and b r e c c i a s , b a s a l t , t u f f , agglomerate, shale, limestone, conglomerate. DEVONIAN TO SiRlASSlC I ? ) DEVONIAN OR MISSISSIPPI AH TO UP PER TRIASSIO (?) Inoludes part of CACHE CREEK, A SITKA, TAKLA GROUPS. Tu f f , a n d e s i t i o flows, a r g i l l i t e , s a n d s t o n e , limestone, conglomerate. S PENNSYLVANIAN (?) ||| immm CACHE CHEEK GROUP A r g i l l i t e , s l a t e , greenstone; minor t u f f , c h e r t , limestone. Probably corresponds to part of (S ). j Limestone. May be p a r t l y or e n t i r e l y o l d e r . CAMBRIAN LOWER CAMBRIAN IMGENIKA GROUP Limestone, i n part micaceous. Interbedded with ( 2 ) Z Q u a r t z - o h l o r i t e s o h i s t , s e r i c i t e s c h i s t , q u a r t z i t e , s l a t e , p h y l l i t e , q u a r t z i t i o conglomerate, minor limestone. rrtOTEROZOlC (V) RUBY GROUP quartz-mica s c h i s t , g a r n e t i f e r o u s s o h i s t , q u a r t z i t e . WOLVERINE COMPLEX Peldspathized q u a r t z i t e , g r a n i t o i d gneiss,quartz-mica-feldspar s c h i s t , minor c h l o r i t o i d s o h i s t , skarn, pegmatite. G r a n i t i z e d equivalents of ( 1 , 2 ) G r a n o d i o r i t e , d i o r i t e , a l a s k i t e , a p l i t e , f e l d s p a r porphyry. © ® ® PROSPECTS AMD MINERAL Ferguson Group Burden Groap Onward Group Swannell Group Porphyry Creek Workings Croydon Group Granite Basin Workings J u p i t e r Group P o l a r i s Creek Workings Tutuzzu Lead Showings ^ Hope Group MINERAL OCCURENCES. SHOWINGS. Stranger Group E l i z a b e t h Group (C h i e f Thomas showings) Matetlo Copper showing Ruby Group P l u t o Group Thane Group Vega Group &ay Creek Lead Showing Beverley Group Weber Group X A l l x Ju - - - -x Pb X CO - - - -x K x p - - - -- - - - - - - Gold - - - - - - - Copper - - m mm Lead - Cobalt - - - - - - potassium n i t s a t e and r e l a t e d s a l t s - - - - - - pla o e r Gold Geology by J.E.Armstrong, 1945; E.F.Roots, 194^, 1946. Trail and cabin Adit Mineral prospect X Lake and stream (position approcc.)..C7?r">—' Falls Glacier..,. •:'.'.<£/•' Marsh i*J&"r.vsjfc; Sand or gravel ==nJS2>> Contours (interval 500 Feet) 0<25g>==: Contours (position approximate) ; 3 e 2 c 5 = Height in feet above Mean sea-level 5530' Compiled by the Topographical Survey, 1942, From original surveys, and From inFormation supplied by the British Columbia Department oF Lands. Cartography by the DraFting and Reproducing Division, 1943. l 3 O 0 125 S C A L E , t I N C H T O 2 0 0 M I L E S 

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