Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The geology and mineralogy of the Yreka copper property, Quatsino Sound, British Columbia Wilson, Philip Roy 1955

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

Item Metadata

Download

Media
831-UBC_1955 A7 W4 G3.pdf [ 11.42MB ]
Metadata
JSON: 831-1.0106708.json
JSON-LD: 831-1.0106708-ld.json
RDF/XML (Pretty): 831-1.0106708-rdf.xml
RDF/JSON: 831-1.0106708-rdf.json
Turtle: 831-1.0106708-turtle.txt
N-Triples: 831-1.0106708-rdf-ntriples.txt
Original Record: 831-1.0106708-source.json
Full Text
831-1.0106708-fulltext.txt
Citation
831-1.0106708.ris

Full Text

THE GEOLOGY AMD MINSRALOGX OF THE TBEKA COPPER PROPERTY, QUAT3IMQ SOUND, BRITISH COLUMBIA fey PHILIP ROY WILSON A THESIS SUBMITTED IM PARTIAL FULFILMENT 0? THE REQUIREMENTS FOE THE MOSES OF MASTER OF APPLIED SCIENCE i a the Department of GEOLOGY AMD GEOGRAPHY We aecept t h i s thesis as conforming to the standard required from candidates for the degree of MASTER OF APPLIED SCIENCE Members of the Department of GEOLOGY AND GEOGRAPHY TIE UNIVERSITY OF BRITISH COLUMBIA ,April, 1955 ABSTRACT The Yreka copper property i s situated on the west sid© of Keroutscs Inlet about nine mile® northwest of Port Alice In the northern part of ?aneouv@r Island, B r i t i s h Columbia. The property i s underlain by rooks of the Vancouver Group, including greenstones, limestones, breccias and t u f f a s t r i k i n g approximately northwest and dipping southwest into the mountainside at about 35 degrees. They, ar© intruded by dykes and s i l l s of quartz-feldspar porphyry, quarts d i o r i t e and basalt* Th© mineral deposits ar® located i n large bodies of skarn which hare been formed i a the tuffaceous rocks of the middle part of the sequence. The skarn zones consist roughly of three subparallel unit® which appear to conform approximately with the bedding. The largest of these akam zones i s about 1500 feet long and more than 100 feet wide, and contain© sulphide bodies of economic int e r e s t . Other sulphide showings have been found on the property but do not appear to be of economic significance. The skarn ^ones are of pyremetaaostatic o r i g i n of the type not related to an ignaoua contact. Development work i n the early part of the century included stripping and trenching, driving a number of adits i n various places i n the skarn zones, and mining of a small tonnage of ore. Recent work, consisting of mapping, sampling and diamond d r i l l i n g , has shown the property to be a prospect of considerable merit. AOKMGWIS&QMSIiTS The writer i s indebted to Mr. B.O. Brynelsen for permission to make use of data obtained by the writer -while i n the employ of Moranda Exploration Company Limited, during th® sumuier of 1954* Mr. Brynelsen has also kindly made available thin-section®, rock samples, diamond d r i l l logs and reports pertaining to the Ireka property. The writer also wishes to thank Dean H.G. Gunning and Professor K.C. McTaggart of the Department of Geology,. The University of B r i t i s h Columbia, under whose supervision the thesis was written, f o r valuable help with the petro-graphie work and fo r numerous help f u l e r i t l c i e a s and suggestions. Mr. J.A*. Donnas made most of the tain-sections. TABLE OF C0HTE1T8 Chapter Page I IMTROPUCTIOS History . . • • * » • • • . • • » • » . 1 Location and A c c e s s i b i l i t y 2 Physical Features 3 Climate and Vegetation k II GENERAL GEOLOGY OF THE ARIA Previous Geological Work . . . . . . . 5 Regional Geology . . . . . . . . . . . 6 III GEOLOGY OF THE YREKA PROPERTY General Statement 9 Table of Formations . . . . . . . . . . 10 Greenstones and Bedded Rocks . . . . . 11 Lower Greenstone . 11 Lower Bedded Member 12 Intermediate Greenstone 13 Upper Bedded Member 14 Upper Greenstones 16 Intrusive Rocks . . . . . . . 22 General Statement . . 22 Quartz-plagioelase aad Plagioclase Porphyry Intrusive® • • 22 GQNTENTS - CONTINUED Ghapter Pa^e III Quartz-diorite Dykes 27 Hypersthene-basalt Intruslves . . . 30 Basalt Dykes 3 2 Structure . . 33 MetaoiorphlSBi 3 7 Greenstones and Bedded Rocks . . . . 3 7 Intruslves , . * . . . . 40 Skarn Zones . 4 1 General . . . . . . . . . . . . . . 42 I? ECONOMIC GEOLOGY. Mineral Deposits 4 4 Main Skarn Deposits 44 Other Showings . 4 7 Mineralogy and Petrology of the Skarn . 4 9 Parage ne s i s 59 Origin of the Skarn and Controls of Ore Deposition . . . . . . 61 Recowaendatloas for Future Work » * . . 6 7 Conclusions 6S Bibliography 71 LIST OF ILLUSTRATIONS Plate Page I A, Li t h i c - c x y a t a l t u f f , Upper Bedded Mannar, showing limestone fragment 75 B. Enlarged view of same limestone frag-ment, showing development of dlopside crystals « 75 0. Medlum~graiaed c r y s t a l t u f f , Upper Bedded Member . • . 75 D. Quartss-feXdspar porphyry dyke showing corroded quarts phenocryst® . . . . . . . . 75 II A. -uarta-feldspar porphyry dyke showing twinned plagioclase c r y s t a l and corroded quarts phenocrysts 77 1* Basaltic dyke showing corroded quarta phenocryst with reaction rim of ehlorit© and Muscovite . . . , 7 7 C. Basaltic dyke showing doubie~eored soned plagioclase c r y s t a l 77 0. Skarn. Quartts replacing garnet 77 III A. Skarn. Calclte replacing garnet 79 . 1 . Skarn. Caleite replacing garnet . . . . . . . 79 C. Skarn. ChXarlte replacing garnet 79 D. Skarn. Sreen b i o t i t e replacing garnet . . . . 79 I? A, Skarn. Sulphides replacing hedenbergite . . . 81 B. Skarn. Cnalcopyrit© replacing garnet . . . . $X X Outline map of Neroutsos Inlet area showing i n pocket location of the Yreka property. UST OF ILLUSTRATIONS (CONT'D) 2 Pressure-temperature diagram and paired composition diagrawa - metaaorphisa* of s i l i c e o u s limestone.. , » 52 3 V e r t i c a l section through l a s , 1, 8 and 9 d r i l l holes. i n pocket G e o l o g i c a l plan of the Xreka property, i n scales 400 feet equals one i n c h . pocket Kates A l l p l a t e s are photomicrographs of t h i n -sections except P l a t e I f 8 which i s a photomicrograph of a p o l i s h e d surface* tm GEOLOGY. Am &IMRALOGX OF THE SOB'SD, BEXTISH COLUMBIA CMPTBE I INTROBUGIIOM H i s t o r y The m i n e r a l c l a i m s c o m p r i s i n g t h e I r e k a c o p p e r p r o p -e r t y a r e s i t u a t e d o n th© west s i d e o f N e r o u t e o s I n l e t , w h i c h i s t h e s o u t h e a s t arm of Quabslno Hound, i n t h e n o r t h e r n p a r t o f Vancouver I s l a n d , B r i t i s h C o l u m b i a . S i x t e e n o f t h e s e claim® a r e Growr^grantsd, and a number of o t h e r s a r e h e l d by l o c a t i o n * The m i n e r a l d e p o s i t s were d i s c o v e r e d a t th© end o f t h e l a s t c e n t u r y , t h e f i r s t c l a i m s b e i n g s t a k e d i n 1$9& and 1 8 9 9 . The d i s c o v e r y was q u i c k l y f o l l o w e d by a c o n s i d e r a b l e amount o f development w o r k , and b y 1903 t h e p r o p e r t y was e q u i p p e d w i t h a n a e r i a l t r a m , a t e n - d r i l l a i r c o m p r e s s o r powered by P e l t o n w h e e l , o r e b u n k e r s , and a w h a r f . I n t h a t year 2500 t o n s o f c o p p e r o r e , o f unknown g r a d e , were s h i p p e d 2 from the property. In May of 1903 the Sorthwestern Smelting and Refining Company assumed control of the proper-ty from the Yreka Copper Company, but a l l work ceased i n 1 9 0 4 . Stimulated, no doubt, by the substantial increase i n the price of copper which took place towards the end of the F i r s t World War, operations were resumed i n 1917 under the direction of M.S. Clarke and associates of Seattle. A new wharf, ore bunkers and a e r i a l traaway were erected i n the spring o f 1917 and a shipment of 900 tons of 3% copper ore was made, but the property was again abandoned l a t e r i n the year. Io further work was done on the property u n t i l 1952, when i t was taken over by loraada Exploration Company Limited. In that year some sampling and general prospecting were carried out. i n 1953 Noraada Exploration Company Limited did a consid-erable amount of detailed mapping and X-Ray diamond-drilling. Further mapping and diamond-drilling were carried out i n the summer of 1 9 5 4 , and more work i s planned for the 1955 season. Location and A c c e s s i b i l i t y The Yreka property extends up the mountainside from tidewater on the west side of Seroutsos Inlet to an elevation of about 2500 feet, and i s about nine miles from Port A l i c e , which i s situated at the head of the Inlet (see F i g . l ) . fhe area ean be reached i n a few hours froa Vancouver* Canadian P a c i f i c A i r l i n e s has a daily f l i g h t from Vancouver to Port Hardy, at the northeast end of Vancouver Island. A 3 good road connects Port Hardy with Coal Harbour on Holberg Inlet, the northwest arm of Quatsino Sound. From Coal Harbour, Frank Hole water t a x i provides daily transportation to Port A l i c e and points on Quatsino Sound and Meroutsos In l e t . A weekly freight service to the area from Vancouver i s provided by the Frank Waterhouse steamer "Chilkoot Physical Features fhe topography of the iieroutsos Inlet area i s generally rugged. On the west side the mountains arise steeply a short distance back from shoreline to elevations exceeding 3000 feet, fhe highest mountains art located to the south of Canyon Creek^ where jagged peaks r i s e to approximately 4000 feet. Slopee of 45 degrees or more are common at elevations around 2000 feet and higher. the west side of the arm i s drained by a number of streams, the largest being the feeta l i v e r which i s about four miles long and flows into the Inlet one and one-half miles northwest of Port A l i c e * Canyon Creek, one of the larger streams, flows into the Inlet just south of the mineral depos-i t s on the Ireka property* fhe area between Meroutsos Inlet and the west coast i s one of the few remaining parts ©f Vancouver Island of which topographic maps have not yet been published. The accompany-ing map of the Ireka property i s based on a contour map pre-pared from a e r i a l photographs for Koranda Exploration Company limited on a scale of 300 feet = 1 inch. 4 fhe Quatsino area has evidently been heavily glaciated. Strongly truncated spurs ean be seen at a number of places be-tween Goal Harbour and Port A l i c e , especially on the west side of Meroutsos Inlet near Quatsino. Canyon Creek has cut down rapidly i n recent geological time i n the lower part of i t s course, resulting i n th® formation of box canyons with walls up to 100 feet high. The rapid downcutting i s obviously a direct result of over-deepening and excavation of Neroutsos Inlet by i c e . Climate and Vegetation As might be expected fro® i t s location, the property has quite a mild eliaate with a heavy r a i n f a l l . Over the past t h i r t y years an average annual pr e c i p i t a t i o n of 110 inches has been recorded at Port A l i c e . According to Gunning '(1929), most of the pre c i p i t a t i o n takes place between October and May, and summers are usually warm and dry. The summer of 1953 was, nevertheless, a very wet one. Snowfall above the 1000 foot l e v e l i s soaewfaat heavy, with snow per s i s t i n g on some of the higher peaks into late summer. The Quatsino area generally i s well wooded, mainly by faemleek with smaller amounts of spruce. At elevations above 2000 feet cedar, both red and yellow, i s increasingly abundant, Douglas f i r i s almost completely absent from Neroutsos Inlet area but i s found i a the Rupert i n l e t area to the north, .A heavy growth of dense underbrush and numerous windfalls at the lower levels combine with the rugged topography and general lack of outcrops to make geological mapping slow and d i f f i c u l t . 5 CMAPTEE I I GENERAL GEOLOGY OF THE AREA Previous Geological Work The f i r s t g e o l o g i c a l work in. the northwestern part o f Vancouver I s l a n d was done by G.M. Dawson (1886). In the summer of 1$B$ he examined the c o a s t a l areas of the' northern part of the I s l a n d from the A l e r t Bay area t o Quatsino Sound. He b r i e f l y described the geology and p h y s i c a l features of the Quatsino a r e a , i n c l u d i n g the southeast arm (Nerouteos I n l e t ) , Eupert I n l e t , and part of fiolberg I n l e t . Nothing f u r t h e r was done u n t i l 191$, when ? . Dolmage {191$) i n v e s t i g a t e d the shores of Quatsino Sound and the adjacent coast and examined a number of mineral prop e r t i e s on the west coast of Vancouver I s l a n d , i n -cl u d i n g the Iretea showings. In 1929 H*0. Gunning (1929) mad© a reconnaiss-ance of the Quatsino-Nimpkish area and v i s i t e d some of the mining p r o p e r t i e s . 6 U n t i l recently no further geological mapping was done in the area, J.A. Jeletzky of the Geological Survey of Canada has been carrying out stratigraphic studies for the past three years on the west coast of Vancouver Island, and i n 1953 was working between Kyuquot Sound and Quatsino Sound. The results of t h i s work have not yet been published. Regional Geology For a concise description o f the geology and phys-i c a l features of the Quatsino Sound area the reader i s referred to the report by Dolmage (1916, pp. 31-33B). B r i e f l y i t may be stated that the Quatsino area i s underlain by rocks of the Vancouver Group, consisting of an extensive assemblage of voleanie, pyroclastic and sediaentary rocks, intruded by dykes, s i l l s , and stocks of various compositions. In a few l o c a l i t i e s the rocks of the Vancouver Group, which are of T r i a s s i c and possibly Jurassic age, are overlain by Cretaceous sediments, notably at Coal Harbour and on the north shore of Rupe r t Ana, The regional s t r i k e i s northwesterly with generally moderate dips to the southwest, with regard to the structure, the s i t u a t i o n i s s t i l l somewhat obscure. L i t t l e or no further detailed information has been forthcoming since Gunning's work in 1929, and Ids remarks may well be quoted here. He says (1929, p.lOU): 7 .... fhere i s not as yet s u f f i c i e n t detailed inf oim ation to reveal the structure across the s t r i k e , but i t i s presumed that the rocks of the Vancouver Group are compressed into a series of p a r a l l e l overturned folds with the prevailing dip to the south-west. If t h i s i s not so we would be forced to conclude that there Is a continuous succession of volcanic and sedimentary beds from the east to the west side of the island, and the result-ant thickness of the group would be so enormous that one i s forced to discredit the p o s s i b i l i t y . Also there i s evidence i n several places of repetition of beds due to tight folding and overturning.... The detailed work recently e&rried out by Jeletzky may c l a r i f y the situation to some extent with res-pect to the age rind structure of the rocks in the northwest part of Vancouver Island. The Quatsino formation (Gunning, 1931, p.23} borders the east side of Weroutsos Inlet from Quatsino to a point about midway between Jeune Landing and Port Ali c e , and extends eastward i n part as far as Alice Lake. It makes up part of Drake (Limestone) Island and probably forms the f l o o r of a considerable part of the Inlet. On the west side of the Inlet the roeks consist of an assemblage of volcanic, pyroclastic and sedimentary types, s t r i k i n g approximately p a r a l l e l to the Inlet in a northwesterly direction. Gunning, i n his report on the Mmpkish Lake Quadrangle (1931, p.23A), proposes the name Bonanza Group f o r the group of roeks over-lying th© Quatsino a formation, and the name Karamtsen v o l c a n i c s f o r the predominantly v o l c a n i c group below the Quatsino formation. It i s questionable whether the rocks on the west side of Seroutsos I n l e t o v e r l i e the Quatsino formation. I f the major s t r u c t u r a l f e a t u r e of the area i s t h a t of a s y n e l i a e overturned to the northeast, as p o s t u l a t e d by Gunning f o r the l i m p k l s h Lake «* Bonanza Lake area, the rocks on the west s i d e o f l e r o u t s o s I n l e t u n d e r l i e the Quatsino form-a t i o n , and belong to the Karmutsen v o l c a n i c s * U n t i l more f i e l d evidence i s forthcoming, therefor®, the w r i t e r proposes t o c a l l the assemblage o f sedimentary, v o l c a n i c and p y r o e l a s t i c rocks as exposed oa th© Ireka property the Treka formation. 9 GHAPTfil III cEOLoer m THE XREKA PEOPIETT General Statement On the Ireka property the rocks consist of a series of greenstone®, limestones, tuffaceous limestones, breccia© and t u f f s , s t r i k i n g approximately northwest and dipping southwesterly into the h i l l s i d e at about 35 degrees. The greenstones and bedded rocks are intruded fey dyke® and s i l l s of quarta-feldapar porphyry aad feldspar porphyry, quarta-diorite and basalt. The geology of the l o c a l i t y i s summarised i n the table on the following page: 10 Table of Formations l a t e Jurassic or T r i a s s i c {? Coast Range Intrusives Dykes and s i l l s of feldspar and quartz-feldspar porphyry, quart^-diorite and basalt Intrusive Contact Lower Jurassic(?) and Tri a s s i c ©rphyritic and amygdaloidal flows with some in t e r -bedded breccias Biseonf©rmity (?) Uppar B^ed Member: XaTThin bedded tuf f s and limy t u f f s with some lenses of limestone. (b) Thin-bedded impure limestones and tuffaeeous limestones Intermediate,, Green-, Massive, probably a flow or flows. Lower Bedded Member Impure limestones and pyroelastics Lower Greenstone Includes fragmental beds White to grey crys t a l l i n e limestone 11 Greenstones and Bedded Rocks Lower Greenstone fhe Lower Greenstone member i s well exposed on the mine road (See accompanying map) between elevations of 200 and 600 feet. It appears to consist mainly of dark green, massive rock, with a w e l l marked fragmental gone i n the middle p a r t , i n places i t i s quite s o f t and calcareous, being traversed by stringers of and containing small i r r e g -ular blebs of white c a l c i t e . The fragraental zone i s well seen on the road i n the v i c i n i t y of the double switch-back about elevation 400 f e e t . Mere the rock i s a greenstone breccia with subangular fragments up to two inches across i n a fine-grained groundiaass. The fragments are almost the same colour as the groundmassi predominantly dark grey t© dark green, and are d i f f i c u l t to distinguish on a freshly-broken surface. However, i n t h i s v i c i n i t y there are a number of ice-smoothed surfaces on which the fragmental nature of the rock i s well seen. A small outcrop on the brink of the lower canyon on Canyon Creek about elevation 300 feet also shows well the fragfiental texture (Spec. 12-1). The member i s probably made up essentially of flows and breccias of o r i g i n a l l y andesitie to basaltic composition, now largely altered and containing, considerable amounts of chbrite, to which the overall term "greenstone" may be 12 appropriately applied. So bedding o r flow structure was noted in the lower greenstone. It has a thickness of about 2000 feet. Lower Bedded Member The lower greenstone grades rather abruptly upward in t o the lower bedded member. This i s a l i g h t to dark grey or greyish-green rock, generally fine-grained. The bedding i s not easily distinguishable, and wag well seen i n only a few outcrops. There i s l i t t l e variation i n colour and texture between the individual beds, b u t i n a, few outcrops the rock has been somewhat protected from weathering by vegetation or overhanging rock masses. Her®, breakdown of the rock has been slow, and d i f f e r e n t i a l weathering has taken place, with the result that the bedding has become easily discernible. Where the rock i s unprotected, disintegration i s rapid, and the bedding i s usually d i f f i c u l t to detect, but sometimes may be recognised by means of the slight colour differences between the individual beds, which average about three inches i n thickness. These rocks are undoubtedly predominantly waterlain, and include beds of fine to coarse tuffaceous material. Many beds are quite calcareous - six out of eight rock specimens effervesce with dilute HC1. Study of a thin-section made from a specimen taken 13 from about the middle of th© member shows the rock here to b© a highly altered c r y s t a l t u f f , consisting largely of c l a s t i c crystals and grains of plagioclase feldspar i n a dusty, fine-grained matrix, i,pi dote and a c t i n o l i t e are secondary. This specimen i s non-calcareous. At one place about 600 feet north of Canyon Creek and at an elevation of 660 feet an excellent outcrop of dark-grey limestone was found. At f i r s t sight th© rock appeared to be a limy breccia, having a very rough surface. Closer examination, however, show© that what were at f i r s t believed to be fragsents are most probably casts of braehiopods and possibly other organic remains. The shells of th© braehiopods appear to have been completely replaced. On exposed surfaces d i f f e r e n t i a l weathering has taken place, so that easts of the braehiopods have weathered out, producing a very rough sur-face having the appearance of a breccia. This bed i s probably near the base o f the Lower Bedded member. The member has a thickness of about 500 feet. Intermediate Greenstone In the course of sapping, a comparatively narrow band of greenstone was found between the Upper and Lower Bedded meab ers. On the south side of Canyon Creek this layer i s about 350 feet thick, but i t appears to thin out north along s t r i k e . I t was not found on a traverse up Edison Creek, 14 and may have pinched out to the south. Wherever seen i t consisted of massive greenstone with no flow structures, and closely resembles the massive parts of the Lower Green-stone. Upper Bedded Member fhe contact between the Intermediate Greenstone and the Upper Bedded Member seems f a i r l y sharp and can be located within 10G/ feet or so i a several places. Nowhere, however, was the actual contact seen. .In the Upper Bedded Member, at least i n i t s lower part, bedding is much more well defined than i n the Lower Bedded Member. In outcrops i n the v i c i n i t y of oanyon Greek the i n d i v i d u a l laminae are on the whole much thinner than i n the Lower Bedded Member. They vary considerably in r e s i s t -ance to erosion, so that i n many places the marked d i f f e r -e n t i a l weathering that has taken place shows well the bedded nature of the rocks. The lower beds are highly calcareous, consisting essentially of thin, beds, averaging about one-half inch in thickness, of dark grey limestone interbedded with very thin laminae of limy a r g i l l i t e or taffaceous material averaging one-eighth to one-quarter inch i n thickness. The microscope shows the limestone to consist essentially of a mass of interlocking grains of c a l c i t e , ranging i n size from 0.01 m.m. 15 and smaller up to about 0.25 ffi.au, with small amounts of feldspar and very fine-grained dark material. Most of the feldspar grains are angular but some are well rounded as though water-worn. They average 0.1 to 0.2 sum. i n width and some show polysynthetie twinging. The dusty, amorphous material tends to be concentrated into thin, sinuous bands and streaks which are p a r a l l e l to the bedding planes. The composition of the thin lamellae appears to be very si m i l a r to, that of the limestone, but with larger amounts of the black amorphous material. Elongated grains and laths of feldspar show a marked preferred orientation p a r a l l e l to the bedding planes. There seems to be l i t t l e doubt that the lower part of the Upper Bedded Member consists of t h i n bedded limestones with varying amounts of tuffaceous material. To the north of Edison Creek the lower part of the member appears to con-s i s t largely of dark grey fine-grained limestone, with well developed beds a l i t t l e thicker than they are to the south. In a stratigraphically upward direction the lime content appears to decrease rather rapidly, and the rocks become harder and finer-grained. The overall colour changes imperceptibly from dark grey to dark grey-green. Some good exposures along Canyon Creek show that the rocks change rapidly i n character from essentially limy varieties to 16 thin-bedded,, cherty-looking types alternating with soft, limy beds, with some laterbedded breccias, probably p y r o c l a s t i c A well developed fragment a 1 stratum a few feet thick i s exposed i n th© creek bed near the old Pelton wheel at an elevation of about 1000 feet* lere the frag-ments, which are dark green and very fine grained, are angular and average one-half to three-quarter© of an inch across, with some as much as six inches i n width. As one follows the creek upward from about the 1000 foot l e v e l the limestone beds are seen to decrease in frequency of occurrence, so that in the v i c i n i t y of the old dam (elevation 1450 feet) the rocks are on the whole very f i n e grained, very hard, l l # t gr^y types, thin bedded and probably tuffaceous. The upper part of th© Upper Bedded Member consists essentially of very thin-bedded, mostly very fine-grained hard t u f f s , with some interbedded lenses of white cry s t a l l i n e limestone. Th® limestone lenses seem to be most numerous in and near the main skarn tone. Usually the bedding i n the t u f f s i s d i f f i c u l t to detect on the surface, but i t i s well shown on a few outcrops In and near th© main skarn zone around elevation 2100 feet. It i s very well seen i n most d r i l l cores. In contrast to the rocks of the lower.members, the tuffaceous rocks of the Upper .Bedded Member are i n many 17 places rusty weathering. This i s probably due to the small amounts of pyrrhotite that these rocks contain. A number of thin-sections of specimens from various places i n the upper part of the Upper Bedded Member were examined. The microscope shows that these thin-bedded rocks are fine to medium-grained basic crystal-lithi© t u f f s . Somewhat broken crystals of plagioclase feldspar and clinopyroxene together with rock fragments occur in a fine grained groundmass of minute c l a s t i c crystals and volcanic dust. The clinopyroxene Is present mostly i n the form of euhedral to subhedral crystals, comprising from 0> to about 40$ of the rock, and averaging 0.2$ a.m. across. In most sections ZAG=40, and where obtainable 2V=40 or s l i g h t l y more, indicating the pyroxene to be most probably augite. Plagioclase feldspar i s present i n most th i n -sections i n the form of subhedral crystals averaging 0.25 a.m. across and usually making up 5-10% of the rock. Many of these crystals are twinned polysynthetically. A few rough determinations indicate the composition to be i n the neighbourhood of An 50 The rock fragments make up about 20-30$ of the rock and are mostly of basic lava. They consist of a mesh of feldspar laths i n a very fine grained groundmass. In some fragments the laths show a distinct preferred orient-18 atiofl, and some fragments contain pyroxene crystals and microphenocrysts of plagioclase* A few fragments of limestone, more or less altered, were found, pa r t i c u l a r l y i n thin-section G4. Here eubedral crystals of clinopyroxene, probably diopsid®, form an interlocking mesh i n ealcite fragments. The pyroxene i s probably secondary (aetaaorphle). It seems significant that almost a l l the t u f f s examined i a thin-section, particularly those from around the / skarn gone, were found to b© calcareous to some degree* Evidence w i l l be presented l a t e r which strongly suggests that the main skarn %®nm have been formed for the most part i n these calcareous t u f f beds. The Upper Bedded member has a thickness of approx-imately 2000 feet. Upper Greenstones Stratigraphies!!? overlying the Upper Bedded Member i s a series of porphyritic and amygdaloidal flows with some interbedded breccias and t u f f s . These have been termed c o l l e c t i v e l y the Upper Greenstones. They are well exposed on the c l i f f s between the south and west forks of Canyon Creek around elevations of I70G-1&0G feet, and between the north and west branches at el & vat ions of about 2700 feet. They consist of a series of dark green to dark grey-green flows, with some interbeddec dark green breccias and tuffs i n 19 the lower part, and coarse dark red breccias and tuffs i n the upper parts. Some of the flows are porphyritic, others are both porphyritic and araygdaloidal, and s t i l l others are fine-grained and massive. It i s possible that different parts of a single flow may exhibit a l l of these textures. In most outcrops th© Upper Green stones do not show bedding or flow structures, so that t h e i r attitudes could not be determined with certainty, fhe only attitude obtained indicated the Upper Greenstones to have the same strike and dip as the Upper Bedded Member. fhe contact between the Upper Greenstones and the Upper Bedded Member does not appear to be conformable with the bedding of the l a t t e r . To the west of the main mineral-ized zone the contact appears to be dipping southwesterly at a low angle, and southeast of the main forks the angle of dip of the contact seems considerably less than 3 5 degrees. More w i l l be said i n this respect under "Structure". At the head of Tuscarora and £dlson Creeks the Upper Greenstones appear to extend to the northwest as a sort of lobe or tongue. The rocks in thi s l o c a l i t y are con-siderably different in appearance and texture to the t y p i c a l porphyritic and amygdalolda! greenstones as exposed farther to the south, i n the f i e l d tney are seen to be hard, dark grey, fine-grained rocks, traversed by innumerable joints 20 and tending t o break into small, angular blocks. They are quite rusty-weathering. Mo beading or flow structures could be found i n these rocks. The contact with tha Upper Bedded member in the v i c i n i t y of Tuscarora and £dison Greeks occurs at about elevation 245G feet, the bard, tough rocks of the Upper Greenstones forming high c l i f f s at this elevation near Tuscarora Greek. In thin-section these fine-grained greenstones are found to consist of an interlocking mesh of plagioclase crystals with the i n t e r s t i c e s f i l l e d with varying amounts of pyroxene, amphibel©, b i o t i t e , magnetite, and c h l o r i t e . The plagioclase crystals average about 0.5 m.ru. long by 0.25 num. wide, and are w e l l twinned, fhey are mostly umgoned, arid ar® of composition An Ab » A few 50 50 crystals show s l i g h t gradations! zoning from a core of about An to a s h e l l of An 53 47 Small amounts of clinopyroxene were found i n t h i n -section 21-2, whereas thin-section 9-4 shows 110 pyrcxane but an approximately equal fee. 10%) amount of amphibole, probably hornblende. The pyroxene probably includes both pigeonite and augite since a few grains were found to have 2f=20 -30 degrees, while i n others 2?>40 degrees. Microscopic examination of th© Upper Greenstone 21 from the v i c i n i t y of the south and west branches of Canyon Creek shows these rocks to be mostly strongly porphyritic basalts. The phenoorysts of plagioclase average about three or four num. across and are unzoned. They vary i n composition from about An to An i n different spec-55 66 imens. These phenoorysts are embedded i n a fine-grained groundmass composed largely of plagioclase laths averaging 0.25 m.m. i n length, with minor amounts of auglte, pigeon-i t e , c h l o r i t e and magnetite. There appears to be at least two varieties of c h l o r i t e . The groundmass feldspar i s strongly twinned and appears to be of approximately the same composition as the phenserysts. Many flows or parts of flows are amygdaloidal, the amygdules averaging two or three num. across and consisting p r i n c i p a l l y of a c t i n o l i t e , chlor-i t e , carbonate and epldote. In specimen 7-1 the amygdules contain small spherulites about 0.4 a.m. i n diameter probably consisting of z o i s i t e . The amygdaloidal nature of these rocks shows up well on many weathered surfaces, whereas i n some fresh hand-specimens such as 7-1 i t canoot be detected. One hand-specimen of the interbedded reddish breccia from the east side of the south fork of Canyon Creek about elevation 2000 feet shows i t to be a hard, tough, dark reddish-brown fine-grained rock containing darker coloured angular fragments up to one-half inch across. A large number of boulders of a very similar breccia, many of a coarser 22 texture, were noted i n the bed of south fork of Canyon Creek at about elevation 2000 feet, indicating that these rocks are i n place a l i t t l e farther up the creek. Intrusive Rocks General Statement No large bodies of intrusive rocks have been found on the property. Dolmage (191#) claimed to have found ?!a small batftolith or stock ©f quarta-diorite", but t h i s may have been one o f the larger quarts-feldspar intruslves out-cropping along the hanging w a l l of the main skara zone. The intrusive bodies so f a r found on the Yreka property may be divided into the following groups: {a) Quartz-plagioclase porphyry and plagioclase porphyry dykes and s i l l s . (b) Quart%-diorlte dykes. io} Hypersthene-basalt dykes. (d) Basalt dykes. Quartz-plagioeias® Porphyry and Plagioclase Porphyry Intrusive® The quartz-plagioclase porphyry and plagioclase porphyry intrusive rocks were seen to cut a i l the bedded roeks except the Lower and Upper Greenstones. They are grey to light grey and tend to weather to a dis t i n c t i v e whitish colour. They seem to he most mweroue in and around, tha main skarn gone, and range i n thickness from about OR© foot up to 70 feet or acre. A large number of these intrusive bodies, usually a few feet i n thickness, have been noted i n the main skara area i n the course of surface mapping and diamond d r i l l i n g . Here they are very irregular in shape and attitude as shown by t h e i r outcrops. Many appear to be s i l l - l i k e , and conform to the existing beading i n the t u f f s , or i f i n skarn, to the pre-existing bedding. Others, however, de f i n i t e l y cut across the st r a t a . The Intrusive bodies contain phenocrysts of plag-ioclase, hornblende, and more rarely quarts i a an aphanitlc groundless. The plagioclase psenoerysts are euaedral to subhe-dral aad average 1 m . i B . across* .They are mostly fresh and unaltered and usually show multiple polyaynthetic twinning* Carlsbad twinning i s not very common* Most crystals are weakly to moderately aeaed. Zoning i s normal and. mostly smoothly gradati or,al, ranging from An (shell }->An (core) to An (shell}-»-An (©ore). Some crystal® have undergone u 51 moderate amounts of aauseuritiaation, with the fores at ion of a l b i t e , ©pidote and c h l o r i t e . A few large phenocrysts show extensive alteration to these minerals. 24 Hornblende i s present i n most o f these i n t r u s i v e bodies i n the form o f subhedral phenoorysts up t o two or three num. l o n g , and making up about 5% of the rock. I t i s weakly p l e o c h r o i c , from c o l o u r l e s s t o pale greenish-yellow, and appears t o have been bleached. The bi r e f r i n g e n c e i s normal, namely c a . 0.023. Most of the c r y s t a l s are bordered by a t h i n rim of a c o l o u r l e s s mineral w i t h a higher r e l i e f than the hornblende. In some c r y s t a l s t h i s h i g h - r e l i e f mineral extends i n t o the hornblende as t h i n bands or s l i v e r s p a r a l l e l to the cleavage planes. One c r y s t a l i s composed of about h a l f hornblende and h a l f the h i g h - r e l i e f m i n e r a l . The l a t t e r has a low b i r e f r i n g e n c e , c a . 0.013, and a large extinct-i o n angle, 2A0=45 degrees, whereas the hornblende has 2AC=24 degress. The marked d i f f e r e n c e i n e x t i n c t i o n angles i© w e l l shown i n the above c r y s t a l . A mineral with a very s i m i l a r appearance to the c o l o u r l e s s , h i g h - r e l i e f mineral above mentioned i s present i a the form o f corroded grains up t o 0.5 m.m. l o n g . This mineral has a l l the properties of clinopyroxene except that the b i r e f r i n g e n c e i s abnormally low, c a . 0.013. I t i s believed to be pyroxene that has been subjected to some l a t e a l t e r a t i o n process that has caused a reduction i n the b i r e -f r i n g e n c e . This mineral and the c o l o u r l e s s , h i g h - r e l i e f mineral rimming and penetrating hornblende are believed t o be one and the same. 25 This b e l i e f i s supported by the following observations. Wherever seen the pyroxene grains are surrounded by reaction rims or zones of very fine-grained, granular material, the identity of which i s doubtful, but may be z o i s i t e . likewise, most of the hornblende crystals show a thin reaction rim of t h i s type of material, and i t i s thought that the alteration product was actually derived from the pyroxene rimming the hornblende. An outline of the processes which gave r i s e to these somewhat unusual textures might be as follows} In a magma consolidating at considerable depth hornblende was i n process of crystaMzation. Part of the magma was then transferred to an environment of reduced pressure, which resulted i n the escape of a large proportion of the volatile©. In t h i s way the formation of hornblende, a mineral containing hydroxyl, was inhibited, and pyroxene, an anhydrous mineral, began to form. Not only did pyroxene crystallize separately, but i t mantled hornblende crystals, and hornblende was partly converted to pyroxene. F i n a l l y the pyroxene became unstable, possibly due to a further change i n th© environment, and i t began to be attacked by the magmatie l i q u i d , thus giving r i s e to the present texture of corroded pyroxene grains and hornblende crystals mantled by corroded rims of pyroxene. The bleaching of the hornblende and the alteration of the pyroxene resulting 26 i n the lowered birefringence may have taken place at t h i s time or s l i g h t l y l a t e r . The quartz content of the intrusives ranges from 0% up to ca. 15$. It i s present both as phenocrysts and as small subhedral to anhedrai grains i n the fine-grained ground-mass* The phenocrysts, which are a l l corroded to a greater or less extent, average about 0.5 a.m. across, and are i r r e g -u l a r l y hexagonal or almost square i n cross-section. Some show only s l i g h t corrosion, whereas others have been almost com-ple t e l y assimilated. A single, almost perfectly e l l i p t i c a l corroded grain of quarts was found i n one thin-section, and the hand specimen shows at least two small, e l l i p t i c a l , smoothly rounded quartz grains that are evidently corroded phenocrysts. Where quarta phenocrysts are abundant, the groundmass i s f i n e l y granular and -contains appreciable amounts of quartz i n the form of very m a l l crystals with square cross-sections and smaller anhedrai grains, whereas the i n -trusive bodies containing no quartz as phenocryst© have a fine-grained, more fibrous grouadmasa which appears to con-s i s t largely of very small lathe of feldspar. The presence of the corroded quartz crystals draws attention to the quartz-porphyry problem i n petrology. Accord-ing to Bowen's theory of the c r y s t a l l i z a t i o n of magma®, quartz should be one of the l a s t minerals to c r y s t a l l i z e . It i s evident that i n the intrusive bodies being discussed quartz c r y s t a l l i z e d early, and then l a t e r became unstable i n i t s environment, resulting i n p a r t i a l reassimilation. 2? The c r y s t a l l i z a t i o n o f the quartz may have follow-ed a similar trend to that of the hornblende. It would seem that a considerable amount of magmatio dif f e r e n t i a t i o n f i r s t took plae®, giving r i s e to a melt with a high s i l i c a and high v o l a t i l e content. Then c r y s t a l l i z a t i o n of quartz and hornblende began, l a t e r followed by environmental changes as previously postulated, resulting i n reaction of quartz and hornblende with the malt, and giving rise to the textures as previously described. A l l thin-sections showed very small amounts of sphene -and apatite as accessory minerals. Sphene occurs as anhedral grains averaging 0,1 ©.at. across, which are mostly considerably altered to a whitish, opaque mineral which i s probably leneo'xene. fery small amounts of apatite are present as euhedral crystals averaging 0.1 - 0.05 m.m. long. The r e l a t i o n o f the quartz-feldspar and feldspar intrusives to the skarn zone and mineral deposits w i l l be discussed under Economic Geology. Quarts-diorite' dykes About 1000 feet west of the main skarn zom and at an elevation of 2100 feet, a light-coloured, medium to f i n e -grained dyk® cuts greyish-green tuffaceous beds. It i s about two and one-half feet thick, i s steeply dipping and was traced along strike for about twenty or t h i r t y feet. A similar rock was found near the head of Tuscarora Creek at an elevation of 2760 feet. The outcrop measured only about ten square feet i n area and i t was impossible to determine whether the intrusive was a s i l l or dyke or to obtain i t s attitude. It i s evidently not a large intrusive body as outcrops of the Upper Greenstones were found p a r t i a l l y surrounding i t at no great distance. Microscopic examination shows the two igneous bodies to be very 'similar i n texture and composition, the chief difference being t h a t the dyke found at the lower elevation contains p r a c t i c a l l y no b i o t l t e whereas the other intrusive has appreciable amounts. Both rocks are made up largely of plagioclase end quartz, with smaller amounts of orthoelase, hornblende, b i o t i t e ( l i t t l e or none i n spec. 21-1), and magnetite. The plagioclase i s present as euhedral to subhedral crystals ranging from ca, 0*25 r u « . to two sum. across and averaging ca. 0.5 sum. I t i s very well twinned and strongly zoned. Zoning is-normal, the cores ranging i n composition from An to An and averaging ca. An » The outer shells 32 63 40 range from An to An and average ca. An . 23 36 27 The orthoelase i s present as untwinned anhedral grains i n t e r s t i t i a l to the plagioclase and quartz. I t also appears to have partly replaced plagioclase. In thin-section 29 21-1 the following examples of what appears to be replace-ment of plagioclase by orthoelase were noted: fa) Core replacement* A small central area ca, 0.25 rn.m. across i n a large plagioclase phenocryst has been con-verted to orthoelase. The replacement i s well shown by the pinkish caste, low r e l i e f and different extinction angle of the orthoelase. (b) Peripheral replacement. A number of plagioclase crystals were seen to be partly replaced i n their outer parts by orthoelase. The orthoelase has a d i s t i n c t l y pale pinkish colour, a r e l i e f considerably lower than balsam, and i n many places shows thin exsolution lamellae, probably of al b i t e , along cleavage planes (microperthit®). An average of five determin-ations of XAQ01 cleavage planes gave 12 degrees. This value Cheeks for s l i g h t l y sodic orthoelase. The orthoelase comprises about 5% of the rock i n spec. 21*1 and s l i g h t l y leas i n spec. 21-4. Quart is i s present i n both igneous bodies to the extent of about 20$ as anhedral grains averaging 0.33 num. across, and appears to have p a r t i a l l y replaced plagioclase. Mafic minerals consist of hornblende and b i o t i t e . The hornblende i s present as greenish, s l i g h t l y pleochroic ragged grains up to two sua* long, and spec. 21-4 contains small amounts of r i c h brown b i o t i t e i n euhedral to subhedral 30 crystals up to four m.m. across. Accessory minerals include sphene, apatite and magnetite. These quartz-diorite dykes appear to be distinct from the quartz-feldspar porphyry intrusive® for at least the following reasons: {a} The average composition of the plagioclase i s more sodic and i s more strongly zoned in the quart z-diorite dykes than i n the quartz-feldspar porphyry Intrusives. (b) In the quartz-diorite dykes, quartz i s present as anhedral grains and shows evidence of being at least p a r t i a l l y secondary, whereas i n the quartz-feldspar porphyry intrusives i t occurs as euhedral crystals, and i s an orig i n a l or primary constituent of the rock. (c) The colour and texture of the two groups of intrusives are considerably di f f e r e n t . Hypersthene-basalt Intrusive® A dark grey, fine-grained porphyritic rock outcrops near the head of the north branch of Canyon Creek (spec. 11-6). In the f i e l d the rock i s massive and has a somewhat different appearance to that of the fine-grained varieties of the Upper Greenstones. It i s evidently more resistant to weathering than the surrounding rocks and forms a small c l i f f about f i f t e e n feet high, but the t o t a l area of outcrop i s small. 31 In thin-section the rock i s seen to be porphyritic, consisting essentially of subhedral crystals of basic plagio-clase together with subhedral crystals of hypersthene and. augite i n a very fine-grained greundmass of what appears to be essentially a mixture of quartz and feldspar. The plagioclase crystals range i n size from about 0.1 m.m. up to 2 m.m, across and are strongly zoned and twinned. The composition ranges from An for the cores to 70 An i n the outer s h e l l s . Most crystals ar© quite fresh and 53 unaltered, but a few of the larger phenoorysts have suffered some core a l t e r a t i o n vfeieh may be a l b i t l s a t i o n . Pyroxene forms about 15$ of the rock , of which about 1Q% i s hypersthene and $f> augite. The remaining mafic minerals include small amounts of b i o t i t e , hornblende and magnetite. The rock contains about 5% of quartz i n the form of small anhedral grains Irregularly distributed. It i s questionable whether this single outcrop i s part of a flow or part o f an intrusive body. Mo other t h i n -section examined contains hypersthene and the rock does not at a l l resemble the porphyritic volcanics or finer-grained varieties of the Upper Greenstones. It i s therefore provisionally classed as an intrusive u n t i l further inform-ation from the f i e l d may be available. 32 • Basalt Dykes i t approximately the 2000 foot l e v e l t h e north branch of Canyon Creek is bounded on th© northeast side by a hard, tough rock that forms almost perpendicular bluffs about 100 feet high, t h i s rock i s very rusty-weathering, and the bluffs are heavily iron-stained. Microscopic examination of a specimen of t h i s rock shows i t te i»/Ve the composition of a porphyritic basalt, aad i n composition and texture i t closely resembles some of the basic flows of the Upper Greenstone horizon. I t Is thought, however, that i t i s more l i k e l y to be an Intrusive for the following reasons! (a) The feldspar phenocryst$ are strongly zoned. In a l l known flows on the property the feldspar pheneeryeta show l i t t l e or a© • atoning, whereas the ones i n the intrusives previously described are strongly zoned. (fe) .The rack-contains a few strongly corroded quarts grains averaging ca. 0.5 a.m. across, and of the same order of size as the feldspar pheaocrysts. These quarts grains are surrounded by well-marked reaction rims or gone® of fine-grained Muscovite or ch l o r i t e . Corroded quarts crystals are characteristic of the quarts-feldspar porphyry dykes and are not found in rocks that are known to be flows. (c} The rock contains small amount© of hornblende* 33 This mineral i s not found in the known flows, but is Qomaon i n known intrusives. (d) Topographic expression; The rock i s consider-ably more resistant to erosion than the t u f f s which bound i t to the east and the greenstones bounding i t on the west. This has resulted i n tha formation of high bluffs as already mentioned, Although^the quartz-basalt i t s e l f i s well exposed on the b l u f f s , ©uterops i n the immediate v i c i n i t y are poor, and the location of tne contacts with the adjoining roeks i s somewhat obscure. A traverse down the creek i n this l o c a l i t y demonstrated that the creek bed i s composed of t u f f s of the Upper Bedded member. Thus the quartz-basalt appears to be confined to the northeast side of the creek. MeKeehnie claims to have found dykes and s i l l s of basalt and diabase on the property i n addition to the quartz-feldspar porphyries* Unfortunately, i t was not u n t i l after leaving the f i e l d that the writer became aware that MeKeehnie had published a report on the Ireka property. The result was that one or two occurrences of diabase and basalt re-ported by MeKeehnie were not seen by the writer. Structure The series of sedimentary, pyroclastic and meta-morphic rocks on the Treka property strike approximately 34 n o r t h - w e s t and d i p s o u t h - w e s t into t h e hillside a t angles o f about 35 d e g r e e s . S t r i k e s and d i p s , where b i d d i n g c a n be s e e n , vary l i t t l e t h r o u g h o u t t h e area mapped. Recording t o M e a z i e a ( 1 9 5 3 ) , however , a t t h e face o f t h e n o r t h d r i f t , So.! t u n n e l , t h e s t r a t a a r e f l a t - l y i n g , while the n o r m a l n o r t h -w e s t e r l y s t r i k e a a d s o u t h w e s t e r l y d i p of 35 degrees a r e f o u n d above on t h e s u r f a c e « He statea a l s o t h a t on the Heady Cash and Superior m i n e r a l c l a i m s t h e r e i s a s t e e p e n i n g of the I n t e r m e d i a t e s k a r n heritor* f r o m t h e normal 35 degrees on the s u r f a c e t o about 50 degrees 100 f e e t down t h e d i p . From a r e v i e w o f a l l t h e d a t a a v a i l a b l e i t appear® to fee writer t h a t t h e s t r u c t u r e i s e s s e n t i a l l y h o m o c l l n a l r a t h e r than t h a t o f a s e r i e s o f t i g h t l y f o l d e d beds f o r m i n g an i s o c l i n a l s t r u c t u r e , fa are does n o t appear t o b e any r e p e t i t i o n o f beds in a s o u t h w e s t e r l y d i r e c t i o n up t h e mountain-side. Any d e v i a t i o n from n o r m a l d i p s of about 35 degrees might be e x p l a i n e d a s b e i n g due t o m i n o r w a r p i n g , d r a g f a i d i n g , or poeeibly drag i n the vicinity o f faults. F i e l d work d i d n o t r e v e a l any p r i m a r y s t r u c t u r e s i n t h e bedded r o c k s t h a t m i g h t i n d i c a t e w h e t h e r o r not t h e y a r e o v e r t u r n e d . I t i s p o s s i b l e , however, t h a t a more t h o r o u g h examination t h a n t h e w r i t e r was a b l e t a make m i g h t be s u c c e s s -f u l i n t h i s r e s p e c t . The l o w e r p a r t o f the Upper Bedded member w o u l d seem t o be t h e most f a v o u r a b l e s t r a t u m f o r t h e development of primary sedimentary structuree. 35 No major displacement of the bedded rocks has been detected. However, faulting of some importance has taken place in the v i c i n i t y of the main skarn zones. A strong fault son© i s exposed i n Ho. 1 adit s t r i k i n g north 45 degrees east and dipping 70 degrees southwest. It i s probable that t h i s f a u l t extends i n a northeasterly direction at least as f a r as Canyon Greek,for at a point just below the f a l l s , a small gulch with almost v e r t i c a l walls joins the main canyon on the north bank at an angle of about 45 degrees. This gulch i s situated approximately at the point where the f a u l t , i f projected, would intersect th© creek. There i s no evidence of the extension of the fault on the south side of the creek. A small shear zone was found in th® bed of the north branch of Canyon Greek at about 2000 feet elevation. It i s about two feet wide and strikes approximately 130 degrees; the angle of dip could not be determined. I t i s ex-posed i n th© creek bed for about ten feet, being obscured by rubble both up and downstream. Chlorite and garnet are developed i n the shear zone, with small amounts of sphalerite, chalcopyrite and p y r l t e . Menzies believes that the upper parts of Edison and Tuscarora Creeks follow f a u l t zones. It i s probable that there are a number of other fault s on the property, particularly i n the v i c i n i t y of the 36 main skara zone. As prev i o u s l y mentioned, while describing the Upper Greenstones, the dip of the contact between t h i s meaner and the Upper Bedded M amber does not appear to be conformable with the dip o f the l a t t e r , fhe p o s i t i o n of the contact as shown on the accompanying map i s believed to be f a i r l y a c curate, fo the west of the main skarn zones i t i s apparent l y dipping t o the southwest at a considerably lower angle than 35 degrees, and between the west and south branches of Canyon Creek i t appears to be dipping east at a low angle, fhe w r i t e r was able to obtain only one a t t i t u d e i n the Upper Greenstones. At a point about e l e v a t i o n 2100 feet and about 400 f e e t from th© south branch of Canyon Creek, an outcrop of bedded fragmental rocks was found s t r i k i n g 155 degrees and dipping 34 degrees southwest - the same a t t i t u d e as the Upper Bedded Member. The dark grey, fine-grained rock, presumably v o l -c a n i c , outcropping on the high ground between the head of the n o rth branch of Canyon Creek and the head of Tusearora and Edison Creeks was not found on the south side of Canyon Creek. Here the strongly p o r p h y r i t i c greenstones appear to be i n d i r e c t contact with the Upper Bedded Member. fhe f i e l d evidence suggests, t h e r e f o r e , that seme erosion of the Upper Bedded Member took place before deposition of the dark grey, fine-grained f l o w . In other 37 words, a disconformity may exist between tbe fine-grained flow and the Upper Bedded Member. A further period of erosion may have partly removed t h i s flow before deposition of the porphyritic flows and pyroclastics. This mlgit account for the absence of the fine-grained flow rock on the south side of Canyon Creek. Met amor phi sta Greenstones and Bedded Rocks Gunning (1929) found that the volcanic and pyroelastic rocks of the Vancouver Group i n the Quatsino-Mimpkish area on the whole have been considerably altered. He says s .... Typically the rocks (flows) are lig h t to dark green or almost black. Flow structures are almost entirely lacking, but many beds of amygdaloid are developed, p a r t i c u l a r l y i n the basalts. The amygdules are f i l l e d with c a l c i t e , quartz, c h l o r i t e , epidote, and occasion-a l l y feldspar, and where quartz and epidote are developed the amygdules generally stand out prominently on weathered sur-faces. Epidote, i n specks and irregular areas up to several feet i n diameter, i s quite t y p i c a l l y but by no means always developed* The common alteration, which i s frequently quite extreme, i s the development of chlorite with lesser amounts of s e r i c i t e , c a l c i t e and epidote... This description applies almost perfectly to the volcanic rocks on the 1'reka property., particularly th© Upper Greenstones. Microscopic examination of specimens of these l a t t e r rocks shows that they are considerably altered, with development of c h l o r i t e , a o t i n o l i t e , carbonate and epidote. C h l o r i t i s a t i o n i s the main alteration. In several specimens the fine-grained groundaaas has been more or less altered to ch l o r i t e , and the plagioclase phenocrysts are veined by and contain many small blebs of c h l o r i t e . In the amygdaloidal rocks the amygdules contain.actinolit®, carbonate, noisite, museovite and b i o t i t e or phlogopite. L i t h i c - c r y s t a l t u f f beds i n the Upper Greenstones have been highly altered, so that what were formerly probably large c l a s t i c crystals of pyroxene are now merely Mghosts w consisting of very fine-grained b i o t i t e or phlogopite with a l i t t l e fine-grained quartz. The groundmass now consists of a fine-grained aggregate of a c t i n o l i t e , b i o t i t e or phlogopite and quartz with some larger ragged grains of a c t i n o l i t e . As previously stated, the Lower Greenstones are highly altered intermediate to basic flows and pyroclastics, now consisting 'essentially of ch l o r i t e , carbonate and epi-dote. The sedimentary and pyroclastic rocks of the Upper and Lower Bedded members do not seem to have undergone a® much alteration as the greenstones, except i n and near the mineralized zones. A number of rock specimens were collected from the 39 lower p a r t of the Upper Bedded member along the t r a i l bet-ween e l e v a t i o n s o f 1000 and 1100 f e e t (II, 18, Y9F yiO, y i l & & B). In hand-specimen these rocks are seen to be l i g h t grey, massive, very f i n e - g r a i n e d types, fhe microscope shows them t o be limestones and tuffaceous limestones, metamorphosed to a greater or l e s s extent. Specimen Y9 c o n s i s t s l a r g e l y of amphibole* probably t r e m o l i t e (oa* , i n the form .of r a d i a t i n g f i n e - g r a i n e d f i b r o u s aggregates' arranged i a clumps aad v e i n l e t s . Scap-o l i t e i s present t o the extent of about as subhedral c r y s t a l s averaging 0*25 at .aw long, fhe mineral was i d e n t -i f i e d by the f o l l o w i n g p r o p e r t i e s : Colour: C o l o u r l e s s Cleavage! One good p a r a l l e l t o length o f c r y s t a l s , b a s a l s e c t i o n s show two cleavages at r i g h t angles. B i r e f r i n g e n c e s 0.022 E x t i n c t i o n : P a r a l l e l t o l e n g t h and cleavage t r a c e . O r i e n t a t i o n : Length f a s t . I n t e r f e r e n c e f i g u r e : U n i a x i a l negative. The r e s t of the rock c o n s i s t s of epldote, dlopeide, a l b i t e ( ? ) , and an unknown, very f i n e - g r a i n e d c o l o u r l e s s m i n e r a l . Specimen TJ i s a h i g h l y a l t e r e d c r y s t a l tuff con-t a i n i n g eoapolite, carbonate, pyroxene (diopside and 4 0 hedenbergite), plagioclase and quartz. Specimens 110 and Y11A are very similar i n part to 19 and in part to IS. They are evidently fine-grained tuffaceous sediments strongly metamorphosed. Specimen I I i s a homogeneous fine-grained limestone containing a few t u f f p a r t i c l e s , and i s l i t t l e altered. Microscopic examination of some of the l i t h i e -c r y s t a l t u f f s f r W the hanging wall of the main mineralized zone showed them to be f a i r l y fresh. Most contained moderate amounts of carbonate. Since some of the t u f f s contain fragstents of re c r y s t a l l i s e d limestone thsr® i s no doubt that at least part of the carbonate i s an or i g i n a l constituent of these rock©. Intrusives The quartz-feldspar and feldspar intrusives are on the whole quite fresh. In a few thin-sections small amounts of carbonatisation and. epidotisatien were noted. Thin-section 123 shows•small amounts of a yellow c h l o r i t e . In the course of diamond d r i l l i n g i n the main skarn zone, however, i t wss found that quartz-feldspar and fsldspar por-phyry intrusives i n skarn were considerably altered within about a foot or so of the walls. The hard, li g h t grey, fresh unaltered rock i s changed to'a strongly mottled green-i s h rock, probably containing considerable amounts of c h l o r i t e and epidote. The change i s gradational. A number of these intrusives cut i n diamond d r i l l holes were found to be mineralized with pyrrhotit© and chal-copyrite mar the walls, p a r t i c u l a r l y where the intrusives were i n mineralized skarn. The a l t e r a t i o n of the quartz-diorite dykes has been previously mentions-ia. It consists chiefly of s i l i c . i f i c a t i on. Skarn Zones In a number of places the sedimentary and pyro-c l a s t i c rocks have been more or l e s s strongly metamorphosed, resulting In the formation of skarn zones consisting e s s e n t i a l l y of garnetite. These skarn zones are mineral-ized with ehalcopyrite, pyrrhotite, magnetite,sphalerite and py r i t e , and constitute the bodies of economic interest on the property. Most are small and do not appear to be of economic significance. The main zone on which most of the work has been concentrated i s located OR tte northwest side of Canyon Creek i n the central part of the Upper Bedded Member. It is roughly 1500 feet long and 100 feet wide. ' It strikes i n a northwesterly direction and appears tc be roughly conformable with the bedding. The original rock has been more or less converted to a medium to coarse-grained garnet skarn. The skarn ranges from a dark reddish-brown to a light green garnetite, with small amounts of 42 c a l c i t e , b i o t i t e , c h l o r i t e , a c t i n o l l t a , epidote and pyro-xene. It i s ir r e g u l a r l y mineralized with pyrrhotite, ehaleopyrite, pyrite and magnetite, in order of abundance. The writer agrees with McKeehnie that the skarn was formed from tuffaceous beds. Evidence for this b e l i e f w i l l be presented i n the chapter on Economic Geology. Smaller skarn zones, mineralogically and texturally p r a c t i c a l l y i d e n t i c a l with the main zone, are located st r a t i g r a p h i c a l l y below i t towards Canyon Creek, and to the northwest of i t near the head of Edison Creek. General To sum up, i t would appear that the rocks of the freka property have been subjected to very low grade region-a l metamorphism, with quite incomplete r©constitution of the rocks, followed by moderate to strong more-localised pyrometasomatism which has resulted i n the formation of the skarn zones and mineral deposits. The question immediately arises as to what has caused the formation of the skarn zones. No large bodies of intrusive rock were found on the property. The quartz-feldspar and feldspar porphyry intrusives ar© very numerous i n and near the main skarn zone. Here they appear to form what almost might be termed an intrusive stoekwork. However, the individual bodies are on the average only a few feet thick, and 43 it would, appear unlikely that they could have transform-ed such large volumes of rock into skarn. The only other alternative would seem to be that the necessary heat for the transformation ha© been supplied from a deep-seated intrusive body, from which the dykes and s i l l s are probably offshoots. 44 CHAPTER IV ECONOMIC GEOLOGY Mineral Deposits Main Skarn Deposits Skarn zones on the Xreka property have been b r i e f l y mentioned i a the chapter on Geologf of th© Treka Property* The important mineral deposits are located i a the main skarn zones, which extend from just northwest of Canyon Creek i a the lower part of the Upper Bedded Wsaber along the h i l l s i d e almost to the upper part of Tuscarora Creek at approximately the 2000 foot l e v e l . Those zones comprise three more or less d i s t i n c t units: The Upper or Main sons, the Intermediate zone, and the Lower zone. The width of the Mala zone ranges from a few tens of feet to 100 feet or more. Within i t , a l l grad-ations from unaltered t u f f to true skarn are found. Mineralization i s somewhat e r r a t i c , but almost a l l the skarn contains some sulphides, particularly pyrrhotite. The ear l i e s t work on the property was con-centrated at the lower or southeast end of the Main skarn zone. Here, at approximately elevation 1300 feet, four 45 adits, Mos, 1-4, were driven, comprising a total length of 1500 feet. About 2500 tons of copper ore were mined and shipped from the Clyde stope, an under-ground opening about 90 feet by 40 feet r©aehed by means of a short adit at approximately the 1250 foot level, Uo, Z adit was driven from the Clyde cut about 150 feet i a a southwesterly direction in barren or poorly mineralized skarn* An internal shaft or winse was sunk froa the floor of the Clyde cut to a shallow depth, but evidently the ore body could not be traced downward, and the workings were abandonedv fhe shaft i s now f i l l e d with water* To the northwest, the Clyde skarn body grades rapidly into little-altered country-rook« This extends to about the 1500 foot level where skarn again begins to appear. From this level a strong skarn zorm extends i n a northwesterly direction to within about 300 feet of the upper part of Tusearora Creek, fhe width as exposed oa the surface ranges from about 70 feet to more than 100 feet. From the attitude of the gone as exposed on the surface, and from data from underground openings and d r i l l holes, i t appears that i t is roughly conformable with the bedding, i.e. strike northwest and dip southwest into the h i l l s i d e . The true thickness i s probably very variable, but more than 100 feet of practically contin-uous skara were cut in vertical diamond d r i l l holes located 46 near the northwest end of the zone, and one hole cut more than 200 feet. The whole zone i s shot through with a ramifying system of quartz-feldspar porphyry and feldspar porphyry dykes and s i l l s , ranging from one foot or less to about ten feet i n thickness. A considerable amount of stripping and trenching was don© by former operators with the result that the greater part of the Main gone i s well exposed, and f a i r l y detailed mapping and sampling can be carried out. Chalcopyrite i n the skarn i s erratic, tending to occur i n bunches and streaks. In many places good grade material grades Into barren skarn over a few feet. Nevertheless, two more or less continuous ort— shoots have been opened on the surface. The f i r s t of these, exposed i n what is termed the Intermediate cut, i s about 350 feet long and averages ten to fifteen feet in width. It is located about 500 feet up the hillside from the Clyde body at approximately the 1800 foot level. The second shoot i s exposed i a the Upper cut and is located near the north-west end of the skarn zone. It ia about 450 feet long and about 14 feet i n width on the surface, but increases rapidly i n width down dip to more than 50 feet, as shown by diamond d r i l l i n g . 47 I he Intermediate skarn a one appears to be a narrow, f a i r l y well-defined sons about 1500 feet long and a few feet thick subparalleling the main son© and located stratlgraphieally and topographically below i t . It i s sparsely and irr e g u l a r l y mineralised with pyrrhotit© and chalcopyrite, although some good grade.material occurs i n places i n narrow bands along the foot-wall., fhe Inter-mediate skarn zone has not been prospected i n a© much d e t a i l as the Main zone, partly because i t outcrops mostly on very steep ground, and seme parts are d i f f i c u l t of access. A t h i r d sulphide-skarn sone l i e s below the Intermediate zone. It extends from just below the portal of Io. 1 adit for 300 or 400 feet in a northwesterly direction subparalleling the larger zones above, fhe t r a i l crosses i t at approximately 1100 feet elevation. An adit i s reported to have been driven In this zone below Mo. 1 adit, aad some good-grade copper ore shipped. The portal, however, was covered by dump-rock from Mo. 1 adit, and is now inaccessible. Where exposed on surface this Lower skarn -zone appears to be largely barren c>f sulphides, but a small pocket of good-grade are outcrops near i t s northwest end on the steep h i l l s i d e above the t r a i l . Other Showing© A number of other smaller showings have been found / IS on th© property, deluding--the Prido of the Isle and Blue Grouse showings. Th© l a t t e r l i e s on a steep bluff on the south side of Canyon Greek about elevation 14GG feet. Menzies (1953) describes the showing as follows: ....Thirty feet of tunnelling and some stripp-ing were don© by the former operators although no records -of t h i s work are now available, l a s t f a l l an area 120 feet i n length by 40 feet i n width was stripped and several shallow trenches blasted across the exposed showing .... The mala Blue Grouse showing l i e s i n a north-westerly pointing wedge of strata which strikes southwesterly and dips 60 degrees southeasterly* The western boundary of the showing i s a north-west fa u l t that dips 60 degrees southwest and the eastern boundary i s a more westerly-striking f a u l t cr shear zone dipping 70 degrees i n th© opposite direction. Sulphide mineralisation i s not uniform but varies from l i g h t to massive pyrrhotite with low copper-zinc valuta. The showing apparently l i e s along the upper contact of a limy horison which i s capped by a very hard, f l i n t y light-grey t u f f .... The Pride of the I s l e showing i s located on the south side of canyon Creek at an elevation of about 660 feet. Here a small open cut i n the h i l l s i d e about 20 feet long shows moderate chalcopyrite-pyrrhotite-sphalerite mineralisation i n fine to medium-grained calcite-garnet skarn. About 600 feet south of the Pride of the I s l e cut and at an elevation of approximately 1000 feet on a steep h i l l s i d e were found large angular pieces up to two feet across of low-grade pyrrhotite-spnalerite f l o a t . 49 Overburden i s heavy and underbrush i s t h i c k i n t h i s area, and the w r i t e r was unable t o locate the source of the f l o a t , but .judging by the s i z e of some of the pieces they have not come f a r . At an elevation of about 2700 feet at tne head of the north branch of Canyon Creek, a number of boulders a foot or so i a diameter and well mineralized with pyrrhotite and ehaleopyrite were found. Overburden i n this l o c a l i t y i s heavy, and trenching f a i l e d to locate the source of the f l o a t . A number of small open cuts near the r i g h t bank of Edison Creek near the 1000 foot l e v e l show low-grade pyrrhotite-sphalerite mineralization i n thin-bedded dark grey-green rocks. . Diamond d r i l l i n g of these showings i n 1953 f a i l e d to i n d i c a t e anything of economic I n t e r e s t . Mineralogy and Petrology of the Skara The skarn rock cons i s t s e s s e n t i a l l y of garnet, u s u a l l y t o the extent of &0-90$, with minor amounts of c a l c l t e , b i o t i t e , c h l o r i t e , a c t i n o l i t e , epidote, quartz, hedenbergite, sulphides and magnetite. The garnet i s massive to coarsely c r y s t a l l i n e ; crystals are euhedral to subhedral and range up to about one-half inch i n diameter. The colour ranges from deep reddish-brown to l i g h t olive-green, with the brown garnet 50 greatly predominating. Most garnet crystals are strongly zoned. This i s well shown i n thin-section, where the outer part of many crystals i s seen to consist of concen-t r i c , alternating dark and l i g h t anisotropic bands. The results of specific gravity and refractive Index determinations carried out on brown and green garnet are as follows; (e) -imM^^mm Green Average 3.79 Average 3.76 discarded <*>) Refractive Inde^c Both the red and the green garnet were found to have refractive indices greater than l.$2, which was the value of the highest index o i l available. Referring to the diagram on p.4&2 (Winehell, 1951), the above experimentally-determined values indicate both th© red and green garnet to be i n the grossularite-andradite region. Winehell (1951, p.463) makes the following point: 51 ....Natural garnets only rarely approach any single formula, but are cry s t a l solutions of two or more end members. Ford found that one-sixth of a l l analysed garnets could be represented by only two formulas (no others greater than 5%); another sixth required four or more formulas (each at least 5$); and the remaining two-thirds required three formulas.... fhe microscope shows that many of the garnets consist of a strongly-zoned, partly anisotropic core surrounded by a thick isotropic outer zone or rind. Under plane.light the core i s p r a c t i c a l l y colourless, while th© outer part has a pale greenish-yellow colour. In many crystals the dividing l i n e between the two parts i s well -marked by an abrupt colour change. Garnet has been p a r t i a l l y replaced fey ealeite, sul-phides, ch l o r i t e and b i o t i t e (see Plates ULA,B,ctD; \V& } Corroded garnet crystals and grains, embedded i n a groundmass of medium to coarsely c r y s t a l l i n e c a l c l t e , are abundant (see Plates EE A , B ) , Bowan (1940) has shown that at certain temperatures and pressures a mixture of quartz and ealeite becomes un-stable, and a reaction between the two takes place result-ing i n the formation of wollastonite and carbon dioxide, v i z : 52 W o l l a s t o n i t e SiOp + CaCOj GaS.103 -+• CO P F i g . 2 Pressure-temperature diagram aad paired composition diagrams of above reaction equation (i) Mixture k —*• Wollastonite + Quartz ( i i ) Mixture I Wollastonite + l i t t l e Quartz ( i i i ) Mixture C Wollastonite+ Calclte Any given condition of temperature (T) and pressure (P) can be expressed by a point on the above graph. I f the point l i e s on the curved l i n e , a state of equilibrium w i l l exist, and the four phases w i l l co-exist. If the point l i e s to th® l e f t of the l i n e , a mixture of quartz and c a l c l t e or a siliceous limestone w i l l be stable, and no reaction w i l l take place. I f , however, the point l i e s to the right of the l i n e , the s i l i c a and c a l c l t e w i l l react to form wollastonite, and carbon dioxide w i l l be 53 given o f f . It is probable that a similar reaction takes place when garnet i s formed from calcareous rocks during metamorphi3m, v i s ; andradite O&CG -r Fe (introduced) +- SiO =^Ga Fe~ ( S 1 0 ~ l + G0 3 2 3 2 4 3 2 As the pyrometasomatic processes begin to wane the temperature w i l l f a l l , and the temperature-pressure point w i l l move to the l e f t . As soon as i t crosses the reaction l i n e , the above chemical reaction w i l l tend, to reverse and go to the l e f t * Usually a i l or most of th© carbon dioxide w i l l have escaped, and no change w i l l take place as the rock cools* I f , however, carbon dioxide i s present i n su f f i c i e n t amounts and under su f f i c i e n t pressure, i t I s conceivable that the reaction would start to reverse, the carbon dioxide attacking the garnet and forming c a l c i t e and s i l i c a . This situation might occur in a particular zone into which large quantities of carbon dioxide were migrat-ing from below, either from a cooling magma or from meta-morphism of calcareous rocks. Conversion of s i l i c a t e s to carbonates by reaction with carbon dioxide has been b r i e f l y discussed by Turner and Terhoogen. They say ( 1 9 5 1 , p. 4 9 4 ) : 54 ....Whereas s i l i c a readily displaces carbon dioxide from carbonates at moderate and high temperatures, many s i l i c a t e s are eon-verted with equal ease to carbonates by hydrothermal reaction with solutions contain-ing carbon dioxide or soluble carbonates, at low temperatures. Autometasomatic replacement of such minerals as feldspars, augite and ol i v i n e by carbonates is a common deuteric process i l l u s t r a t e d by igneous rocks of widely different composition, and in extreme cases may give r i s e to rocks composed largely of oarborate such as the Pea'area of Norway, for which a true magmatic or i g i n has even been suggested..*. The evidence suggests, therefore, that c a l c l t e was formed from garnet by reaction with carbon dioxide or with carbon-bearing f l u i d s during the l a t e r stages of metasomatism, probably when temperatures were f a l l i n g : andi-adite Ga Fe (SiO ) -»- GQ-^ CaCO + Fe + SiO 3 2 4 3 ' t 3 2 Ca A l (SiO )3 + CQ—>CaCQ + AH-SiO 3 2 4 2 3 ' 2 Iron, s i l i c a and alumina, released from grossu-l a r i t e or andradite by reaction with carbon dioxide, were probably carried away by circ u l a t i n g solutions or f l u i d s , since there i s no evidence of the formation of quartz, or of any minerals containing iron or aluminum, as a result of replacement of garnet by calcit®. Most thin-seetions of skarn showed small amounts of hedenbergite (GaFeSi 0 ). The mineral was well seen 2 6 in thin-section M.S.I where i t i s present in th© form of narrow, blade-like crystals and aggregates up to ca. 1 m.m. 55 long. In other thin-sections hedehbergite i s present as small, subhedral crystals' averaging ca. 0.2 a.m. long, closely associated with garnet, the mineral was ident-i f i e d by the following characteristics! Birefringence: 0.01$ ZAC: 4lf Relief! 1.70 - 1.75 Cleavages • Two at~90°, basal ; sections Some excellent examples of replacement of heden-bergite by sulphides were noted i n thin-seetioas 119 and M$ 2 (see Plates SA ). Several thin-sections ehow moderate amounts of a strongly pleoebroic, green mineral closely resembling c h l o r i t e . The birefringence, however, i s much too high for c h l o r i t e . The op t i c a l properties ar© as followsJ Colour: greenish. See pleochroisa Pleoehrolsm: X I and 2 ( K I & z) pal© straw yellow grass green Forms Subhedral subequidimensional crystals averaging 0.05 - 0.1 m.m. across, lamellar or micaceous habit Cleavage; Good i n one' direction. Relief; Fair, n>balsam. Birefringence; 0.035* 56 Extinction: P a r a l l e l to cleavage traces. Orientation: Slow r a j p a r a l l e l to cleavage traces. Interference figure: Uniaxial negative. These properties indicate the mineral to be green b i o t i t e (Winehell, 1951, p.376). It is present to the extent of ca. 10$ i a thin-section I I and ca. % i a thin-section MS 3 * It was seen to have p a r t i a l l y replaced garnet i n a number of thin-sections. Core replacement seems to be p a r t i c u l a r l y common* Plate© JjjD show replace-ment of garnet by green b i o t i t e . Closely associated with the b i o t i t e are snail amounts of a very fine-grained, dark olive-green mineral. It i s f a i r l y strongly pleoehroie and appears to have a birefringence of about 0.015, but i s so fine-grained (grains ca. 0.005 m.m. across) that the optic a l properties could not be determined with any degree of accuracy. The mineral may be a variety of c h l o r i t e . Small amounts of a greenish, fibrous mineral, associated with b i o t i t e and c h l o r i t e , were noted. It appears to be developing in c a l c i t e , and i s present i n the form of aggregates of long, thin, bladelike or needle-l i k e c r y s t a l s , strongly pleoehroie from colourless to sea-green, and with a small extinction angle. Although no basal sections were seen to confirm the determination, 57 this mineral i s i n a l l probability a c t i n o l i t e . Quartz i s present in the skarn i n very small amounts in the form of euhedral to subhedral crystals about 0,5 m.m. long, and appears to be associated with the sulphides. Sulphides were seen to have corroded and eaten into quartz crystals i n a number of places. Epidote appears to be a very minor constituent of the skarn, A /few irregular crystals averaging 0.5 m.m. long were noted i n thin-section MS 4 replacing garnet and ealeite.' Sulphides found on the Yreka property i n order of abundance are pyrrhotite, ehaleepyrite, pyrite, dark brown resinous sphalerite, cubanlte and galena. Magnetite occurs in some abundance at the southern end of the Inter-mediate «ut i n coarse-grained skarn. Mcleehnie (1953) reports small amounts of specularlte and notes that sphaler-i t e and galena occur sparsely on Edison Greek i n skarn beds from four to six inches thick. Sphalerite is present i n only very ©mall amounts i n the main skarn ssones, but i s prominent i n the smaller showings, p a r t i c u l a r l y the Pride of th® Isle cut and the Blue Grouse showing. In material from the main zones, the microscope showed sphalerite to be present as minute, Irregular i n -56 elusions i n chaleopyrite. Sphalerite, chaleopyrite and pyrrhotite were noted i n a polished section of material from the Pride of the I s l e cut. The three minerals, ex-cept as noted below, show mutual boundary textures and appear to be contemporaneous. Much of the sphalerite contains minute inclusions of ehalcopyrite, probably ex-solved from the sphalerite. Gubaaite was found i n a polished section of min-eralieed skarn from the northern end of the Main skarn gone. It i s present as small. Irregular p a r a l l e l laths i n some of the ehalcopyrite grains. Cubanlte has been reported from a number of places i n forth America, as well as i n several foreign deposits, i t i s probably more abundant than i s generally realised, as i t can usually be detected only by microscopic examination of polished surface®. In the Unit ed States, cubaaite has been reported i n the c ontact-m et amorphic deposit© at Fierro, lew Mexico (Schwarts, 1923), the Duektowa copper deposits, Tennessee (Schwartz, 1927), and the Mlzpah copper property, Idaho, a high-temperature replacement deposit of the Ducktown Type (Anderson,1941)• In Ontario, eubanite i s found i n the nickel-copper ores of the Sudbury d i s t r i c t (Lindgren, 1933, p.$07; Burns l$k&\ Witherspoon, 1952; X&tes, 1948, p.604), and In copper deposits at Parry Sound (Schwartz, 1924). Gunning (1932 p.45) found eubanlte i n m a t e r i a l fr o a a copper prospect i n the Zebailos area, fancouver I s l a n d , B r i t i s h Columbia* Schwarts; (1927) proved experimentally that a s o l i d . s o l u t i o n could be formed from the natu r a l intergrowth of ehaleepyrite and eubanlte at 450 degrees C, aad that by slow coo l i n g the two mineral phases could be r e p r e c i p i t a t e d . Edwards (1947, p.#5) states that .... Cubaaite (Ca Fe 3 )commonly occurs as 2 4 © p a r a l l e l l a t h s or bands i a the (111) d i r e c t i o n s of ehaleepyrite (Cuf@$2^» Sue& intergrowths are found only i n high-temperature deposits, and i f heated above' 450 degree® C , the eubanlte enter© i n t o s o l i d s o l u t i o n i a the e h a l c o p y r i t e . •.. I t i s evident that cubaaite i s a not-u&eoaaon mineral of pyx-ometasomatic and high-temperature replacement d e p o s i t s . Mineral deposits i n which i t i s found were formed at temperatures i n excess of 450 degrees C« Paragoneeia The e a r l i e s t minerals t o form from the o r i g i n a l bedded rocks were garnet and hedenbergit©. These minerals probably formed simultaneously i n the early stages of the 6o metasomafcle episode. In thin-section, garnet i s seen to be replaced by sulphides, b i o t i t e , c h l o r i t e , quartz and c a l c i t e . Both hedenbergite and c a l c i t e are replaced by sulphides, b i o t i t e , c h l o r i t e , quart2 and epidote. To summarise, the sequence'of mineralization i n the main skarn zones wa© probably as follows. Metasomatism caused formation of skarn rock, consisting essentially of garnet and bedenbergite, and possibly some c a l c i t e , from calcareous beddei rocks, As temperatures began to f a l l , but while they were s t i l l quite high, of the order of 500 degrees 0*^ hydrothermal f l u i d s , permeating the skarn, deposited b i o t i t e , c a l c i t e and chlorite, shortly followed by magnetite, sulphides, quarts, a c t i n o l i t e and epidote. Pyrite, pyrrhotite, and ehalcopyrite appear to be contempor-aneous, and are found i n intimate association, particularly ehalcopyrite and pyrrhotite. Uubanite exsolved from th© ehalcopyrite v.hen temperatures f e l l below 450 degrees G. The hydrethermal f l u i d s contained large quantities or i ron and sulphur, and smaller amounts of copper and zinc. The presence of traces of scapolite In some of the metamor-phosed rocks as already mentioned suggests that small amounts of chlorine also were added. The whole sequence of mineralization was probably continuous and took place i n a comparatively abort time. 61 Origin oi* the skarn and voutrols of Ore Deposition The structure of the rocks on the Treka property-presented favourable conditions for the formation of pyromefcasomatic deposits. Bedded calcareous rocks dip into the mountainside at moderately steep angles* Emanations from a deep-seated intrusive body to the southwest under-l y i n g the mountain would tend to migrate upward along bedding planes or f a u l t s * It has already been pointed out that the main skarn mm® roughly follow the strike and dip of the enclosing rocks, i l l the evidence indicates, therefore, that the mineralized skarn zones are of the pyrometasomatic type not related to an igneous contact (Lindgren, I f 3 3 , p.735) • Sertain feeds i a the Upper Bedded Member appear to have been p a r t i c u l a r l y favourable for the formation of th© deposits. The skarn has been formed i n calcareous t u f f s containing some thin, interbedded limestone lenses. A number of limestone remnant® can be seen i n various places i n the main skarn zone. One of the largest of these i s about 100 feet long by about ten feet thick. It con-si s t s of a medium-grained white to l i g h t grey r e c r y s t a l l i z -ed limestone. Similar limestone i s also present along the footwall of th© Main skarn zone for several hundred feet i n the form of bed® and lenses several feet thick, assoc-62 iated with very thin band® of garnetite and thin, s i l l -l i k e intrusive®. Mc&echnie (1953) believes the skarn to have formed i n limy t u f f s . He says: .....The epidote - garnet alteration seems to have been confined to a particular type of bed which, for the following reasons, the writer believes to have been a limy t u f f rather than a -limestone; (1) Where r e c r y s t a l i i z e d limestone aad skarn ar® i a contact, the contacts uniformly ar© sharp and regular, showing no sign of gradation from one rock type to the other. (2) Thin bedding i s v i s i b l e i n some of the skarn, and elsewhere i s seen only in th© tuffaceous beds* (3) Some less-altered remnants i n the skarn beds resemble t u f f rather than limestone. (4) Bedding planes where v i s i b l e i n contiguous limestone and skarn., do not pass d i r e c t l y from one type to the other - they are conformable but not continuous.... The writer agrees with MeKeehaie that most of the skarn has formed from calcareous tuffs. A l l of the above four pieces of evidence have been v e r i f i e d by the writer. In many places i n the main skarn ssoae tuffaceous rocks can be seen in various stages of transformation to garnetite or skarn rock. Evidence from diamond d r i l l i n g i s also strongly i n favour of t h i s t h e s i s , A number of holes were d r i l l e d v e r t i c a l l y downward into the Main skarn eone from the h i l l s i d e above, and aimed to intersect i t 63 about 300 feet down the dip. Study of d r i l l GOres shows that as the main skarn gone i s approached from the hanging wall, usually the f i r s t sign of alteration i s the development of very fine-grained garnetite along bedding planes i n the t u f f s . Gradually the amount of gar-net increases and I t becomes coarser grained, and mafic minerals such as ch l o r i t e begin to appear, u n t i l f i n a l l y the rock i s completely converted to skarn. D r i l l i n g also shows that the skarn contains numerous partly altered beds of t u f f and a very few thin bands of c r y s t a l l i n e limestone. The limestone gives evidence of being markedly l e n t i c u l a r , and shows no sign of mineralization with sulphides even though the skarn above and below i t i a so mineralized. Alteration i a limestone lenses i s chiefly epidotisation, with appreciable s e r i c i t i s a t l o n i n some bands * D r i l l i n g indicates that the main skarn zone dips into the h i l l s i d e at roughly the same angle as the bedded rocks, namely.about 35 degrees. ¥ery thin bedding i n the t u f f s i s well seen i n d r i l l cores, especially when they are wetted. The angle of dip of the bedding does not change appreciably through a v e r t i c a l range of several hundred feet and a horizontal distance along strike of more than 500 feet. Most d r i l l holes intersected several porphyritic intrusives a few feet thick. These appear to be dykes, probably steeply dipping. The following evidence suggests that they were intruded before formation of the skarn, and are therefore pre-ore, although i t i s by no means conclusive. (1) Most intrusives show d i s t i n c t alteration at the contact with the skarn f o r one or two feet inward from the walls* t h i s alteration appears to be primarily epidet-i s a t i o n and c h l o r i t i s a t i o n . Contacts are not sharp, and usually skarn appears to grade'into intrusive over a core length of several inches. |2) Most intrusives cutting skarn well mineralised with sulphides are themselves mineralised with sulphides near the walls, fhe following extracts from d r i l l logs w i l l serve as examplest 173-1#6 1*6-203 Good grade copper ore i n skarn. A light-grey mottled rock, with dark grey phenoorysts about 1/16 - X/B inch across. Finely speckled with ehalcopyrite i n places, some thin fractures healed with ehalcopyrite and pyrrhotite. Probably intrusive. Feet 223-227 227-243 Good copper ore i n altered t u f f s . Intrusive. As 243 wall of intrusive i s approached, get increasing ehalcopyrite mineralization, both disseminated and along fractures, Estimate 240-243 grades m cu. Good o r © i n skarn, some massive sulphides. 243-245 65 From surface observations and study of d r i l l cores i t seems that the porphyritic intrusive® have exerted l i t t l e general control on deposition of sulphides, or formation of skarn. iowever, there i s some evidence that suggests that they may have had some l o c a l i z i n g effect i n places on deposition of sulphides. In D.D.H. 54-4 (see Figure 3 ) , two closely adjacent intrusive bodies were inter-sected at about 200 feet depth, separated by four feet of high-grade ore, and with about seven feet of good grade ore on the underside of the lower body. The intrusives, being more resistant to alteration and replacement than the t u f f s , have evidently had a damming effect on the ore - forming f l u i d s , resulting in a concentration of sulphides on their undersides or footwalls. A similar concentration of s u l -phides adjacent to aa intrusive body was noted i n B-.B.H. 54-2. On the other hand, i n D.D.H. 5 4 - 1 , a wide section of good-grade ore not closely associated with intrusive bodies was intersected. At the present stage of investigation of the deposits, few definite controls of ore deposition have been recognised. Mineralization on the Blue Grouse showing appears to be related to fau l t i n g , as may be the mineraliz-ation at the lower or southeast end of the Main skarn zone (Clyde area), fhe Mala and Intermediate skarn zones them-66 selves appear to have formed under stratigraphic control, and do not appear to be related to faulting. However, i t must be admitted tbat at present not much i s known of faulting on the property. The heavy cover of overburden, coupled with the fact tbat no good horigon marker i n the tuffaceous beds of the Upper Bedded member has yet been found, renders d i f f i c u l t detection from surface of fault® ©f small displacement* Th© sulphide mineralisation i n the skarn zones may yet be found to be related to secondary f a u l t i n g after formation of the skarn. A number of fissures and narrow oxidised zones were encountered i n diamond d r i l l -ing especially near the surface, but these may be merely fractures related to the present steep topography. They do sot appear to have any r e l a t i o n to skarn formation or s u l -phide mineralisation. At present, a l l that can be said i s that ore shoots occur i n the main skarn bodies or i n altered t u f f s closely adjacent to skarn. Where the skarn i s poorly developed, mineralisation Is likewise usually poor. Ore-shoots so far discovered are somewhat small, but It i s considered that structural conditions are s u f f i c i e n t l y favourable to warrant the i n i t i a t i o n of underground develop-ment work. 67 fieeoramendatlons f o r Future Work The w r i t e r b e l i e v e s that f u r t h e r development work should be planned along the f o l l o w i n g l i n e s : (1) Extend Io* 6 a d i t along i t ® present d i r e c t i o n through the skarn gone and i n t o the hanging w a l l , © r i f t north and south along the mineralized zone and prepare stopes. (2) A f t e r stoping i s under way, or po s s i b l y before, c o l l a r a new a d i t about 150 f e e t v e r t i c a l l y below Mo. 6 on the h i l l s i d e between Io* 6 and l o . 7 a d i t s . The p o s i t i o n o f the p o r t a l o f the new a d i t would be determined c h i e f l y by topographic c o n s i d e r a t i o n s , as the h i l l s i d e i s very steep i n t h i s l o c a l i t y , {3) Crosscut i n a west-south-west d i r e c t i o n so m to pass d i r e c t l y under the c o l l a r of B.B.M. 54-1» t h i s point should be reached at a distance of about 550 f e e t from the p o r t a l . Continue the crosscut w e l l i n t o the hanging w a l l of the zone. D r i f t northwest - southeast along the ore-shoot and prepare stopes. (4) Explore f o r f u r t h e r ore-bodies at depth by diamond d r i l l i n g from l i n e - d r i v e s put out from th® end of the c r o s s -cut i n the hanging-wall. Search f o r f u r t h e r oreshoots ean probably be best e f f e c t e d by diamond d r i l l i n g from 'underground openings as 68 outlined above. The topography and the attitude of the ore-zone are such that further d r i l l i n g from surface to intersect the skarn zone at depth w i l l e n t a i l deep holes up to 700 or 800 feet. Furthermore, the h i l l s i d e steepens considerably above the 2100 foot l e v e l . This fact alone would make d r i l l i n g slow and d i f f i c u l t . Conclusions Exploration during the past two years has demon-strated that the Yretea property i s a prospect of consider-able merit. The chief problem i s to determine whether or not the skarn zones are strong structural features and e x -tend to considerable depths without appreciable diminution of t h e i r present lengths and thicknesses. Also to be det-ermined i s the pitch or rake of the skarn zones, assuming that they dip approximately p a r a l l e l to the bedding. Diamond d r i l l i n g carried out during the past summer suggests either that the Main skarn sone i s pitching to the north or i t i s diminishing i n length with depth. It seems clear that the property can best be further tested by underground development work i n the cen-t r a l part of the Main skarn sons. Since control of ore deposition i s as yet imperfectly understood, the best method of search for ore would seem to be systematic diamond d r i l l i n g of the Main skarn zone from underground stations. 69 This should quickly y i e l d valuable structural information as well as indicating whether commercial oreboales exist at depth* I f further development along these lines yields disappointing results, then there would seem to be l i t t l e incentive to do further work on the other showings, i n -eluding the Clyde area. The property i s well located with regard to trans-portation and processing of the ©re, A small wharf could be b u i l t at the foot of the h i l l below the main showings at no great cost. This would enable either ore or concentrates to be loaded d i r e c t l y into ocean-going vessels. Th© cost of transportation per ton of material to the smelter at Tacoma should thus be low, i f large enough tonnages are shipped. An a e r i a l tramway would seem to be the solution to the pro-blem of transportation of ore from the mine to tidewater. If reasonably large tonnages of ore can be developed, con-struction of a concentrator would of course be j u s t i f i e d . However, i n the early stages i t might be more advantageous to ship raw ore. This would probably e n t a i l some sorting to obtain a high enough grade f o r shipping. The ore i s r e l a t i v e l y coarse-grained, with simple mineralogy, and concentration should present no d i f f i c u l t i e s . A f i n e grind would probably not be required. The Yreka deposits resemble closely the large, low-70 grade copper deposits at Phoenix, i n tins Boundary D i s t r i c t of B r i t i s h Columbia, mined during the early part of the century by the Granby Company (Brock, 1902; Leiloy, 1912). The two deposits occur l a very similar rocks, namely altered limestones, t u f f s and other calcareous sediments. igneous intrusive bodies of any appreciable size are found near the skarn zones, and the mineralogy of the two deposits i s p r a c t i c a l l y i d e n t i c a l . Approximately 13,000,000 tons of low-grade copper ore were yielded by the Phoenix deposits u n t i l they were exhausted towards the end of the f i r s t World War, It its not suggested t h a t tae Xreka property i s l i k e l y to develop into another Phoenix, but i t i s well to bear i n mind that deposits of this type, upon which many geologists and engineers are apt to look with a somewhat jaundiced eye, have i n the past supported substantial and profitable mining operations* 71 Bibliography References to the Ireka property and the geology of the Quatsino-himpkish area. 1. Dawson, G.M. (1B&6), Report on a Geological Exam-ination of the Northern Part of Vancouver Island and Adjacent Coasts; Geol. Surv. Canada Ann. Sept. (lew Series) Vol.2, Pt. B, pp. gl-129. 2. Bolmage, ?./ (1916), Quatsino Sound and Certain Mineral Deposits of the West Coast of Vancouver Island, B r i t i s h Columbiaj Gaol. Surv. Canada Summ. Kept. Pt. B, pp. 30-3S. 3» Gunning, H.0.(1929), Geology and Mineral Deposits of Quatsino-ilmpkisfa area, Vancouver Island, B r i t i s h Columbia| Geol. Surv. Canada Summ. Rept. Pt. A, pp. 94-143* 4. Gunning, H.0.(1931), Preliminary Report on the Mimpkish lake Quadrangle, Vancouver Island, B r i t i s h Columbia| Geol. Surv. Canada Summ. Sept. Pt. A, pp. 22-35* 5. Hoadley, J .1.(1953), Geology and Mineral Deposits of the Zeballos-Nimpkish area, Vancouver Island, B r i t i s h Columbia| Geol. Surv. Canada Memoir 272. 6. McKeehnie, !,B.(1953), Minister of Mines Annual Rept. B r i t i s h Columbia, pp. A167, 16S. 7. Menfctee, M.M.(1953). Ireka Copper Property (Unpublished Report); Soraada Exploration Company Limited. $, Minister of Mines Annual Reports, B r i t i s h Columbia, 1902-1906 inc.; 1916; 1917; 1953 (see above). The descriptions i n the 1903 and 1916 Reports are detailed. The former i s by H. Carmichael, and th© l a t t e r by W.M. Brewer. 72 References on Metamorphism, Metasomatism, and a l l i e d M i n e r a l Deposits. 9 , B l a c k , J.M. 1 0 . Bowen, N .L. I I . Brock, R.W. 12. Brock, R.W. 13. LeRoy, O.E. (1952), Iron H i l l Deposits, Upper Quinsam Lake, Vancouver I s l a n d , B r i t i s h Columbia; M i n i s t e r of Mines Ann. Rept., B r i t i s h Columbia, pp. 221-22$. (1940), Progressive Ketamorphism of S i l i c e o u s Limestone and Dolomite; Jo u r . Geol. Vol.4^, pp.223 -275. (1901) , Progress o f Mining i n the Boundary Creek D i s t r i c t , B r i t i s h Columbia1 Geol. Surv. Canada Swam. 'Rept. pp.50-65. (1902) , Preliminary Report on the Boundary Creek D i s t r i c t , B r i t i s h Columbia; Geol. Surv* Canada Suma. Rept. pp>. 90-136. (Granby operations at Phoenix). (1912) , Geology and Ore deposits of Phoenix, Boundary D i s t r i c t , B r i t i s h Columbia; Geol. Surv. Canada Memoir 21. 14. Lindgrea, ¥ . (1933), Mineral Deposits; McGraw-Hill, lew fork., pp . 695-745, W. 15. Swanson, 0.0.(1924), The Genesis of the Texada Island Magnetite Deposits: Geol. Surv. Canada Summ. Rept, pp. 106A-144A. Mineralogy and Petrology 16. Anderson, A.1,(1941), A Copper Deposit of the Ducktown type near the Coeur D*Alene D i s t r i c t , Idaho; Economic Geology, Vol.XXXVI, Mo.6, pp. 641-657 73 17. Burns, C.A. (1948), A Report on the Mineralogy of Some Ore from the Frood Mine, Sudbury; Unpublished Thesis, The University of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. 18. Edward®, A.B.(1947), Textures of the Ore Minerals; Aust, Inst. Min. Met., Melbourne, pp.65, 19. Gunning, B.C.(1932), Zebalios River Area, Vancouver Island, B r i t i s h Coluabia; Geol. Surv. Canada Summ. Rept., Ft. A 11, pp.29-50. 20. -Schwartz, G.M. (19.23), Chalmerslte (.Gubanite.) at Fierro, Sew Mexico, with a Mote on i t s Occurrence z at Parry Sound, Ontario; Economic Geology, Vol. XVIII, Mo.3, pp.270-277. 21. Schwartz, G*M.(1$24), Primary Relationships' and Unusual ehaleepyrite i n Copper Deposits at Parry Sound, Ontario; Economic Geology, Vol. I l l , So.2,. pp.209-213-22. Schwartz, O.K.(1927), Intergrowths of Chalcopyrite and Cubanite: Experimental Proof of th© Origin of Intergrowths and t h e i r Bearing on th© Geologic Thermometer; Economic Geology, Vol. .XIII, No.l, pp.45-61. . 23. Turner, F.J. and Verhoogen, J . (1951), Igneous and Metamorphic Petrology; McGraw-Hill, Sew York, p. 494* 24. Winchell, A.N. and Winchell, H. (195D, Elements of Optical Mineralogy; Wiley, Mew fork, pp. 375, 376, 4^ 5. 25. Witherspoon, A.a. (1952), A Mineralogical Study of Some Sudbury Nickel Ores; Unpublished Thesis, The University of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia. 26. fates, A.B. (1948), Properties of the International Nickel Company of Canada; i n Structural Geology of Canadian Ore Deposits, Can, Inst. Min. Met. Montreal, p.604* 74-74 PLATE I A. LIthlo-crystal t u f f , Upper Bedded Lemper, shoving limestone fragment. x!2» Plane l i g h t . B. Enlarged view of same limestone fragment, showing development o f euhedral diopside crystals. x3C Grossed n i c o l s . C. Medium-grained crystal t u f f , Upper Bedded Member. x l 2 . Plane l i g h t . f = plagioclase. D. Quartz-feldspar porphyry dyke showing corroded quartz phenoorysts. x l 2 . Grossed n i c o l s . f = plagioclase, h= hornblende, q = quartz. Tiny white dots are quartz cr y s t a l s . ~76 76 FLA?! U A, Quarts-feldspar porphyry dyke snowing twinned plsgioolase c r y s t a l and corroded quarts pheiiocryste. q= quarts* x l 2 . Grossed n i c o l s . B. Basaltic dyke showing corroded quartz ghenoeryst with reaction riffl of c h l o r i t e and muscovite, x!2, Crossed nicols,* q = quarts,, f = feldspar. G« Basaltic dyke showing double-cored zoned plagioclase c r y s t a l . x l 2 . Crossed ni c o l s . 0. fkern. Quart a replacing garnet. x3Q« Plane l i g h t . q = quartz. PLATE I I PMfS XII Skarn. Calcite replacing garnet. x30. Plane l i g h t , c = c a l c i t e , & = garnet. Skarn. Calcite replacing garnet* xl2. Creesed nicols. e= epidote, g*= garnet, c = calcite. • Skarn. Chlorite replacing garnet* x30. Plane l i g h t , g = garnet, q = quarts, e = chlorite. Skarn. Green biotite replacing garnet. x30. Pleae l i g h t , b = biotite,. § = garnet. L i Skarn. Sulphides replacing hedenbergit x30. Plane l i g h t . h = nedenbergite. Skarn, Chalcopyrit© replacing garnet. xlOO. Plane l i g h t . g = garnet. e ='ehaleepyrite« B LEGEND ^eJded Tuffs . irnes tone V M V V Be'c* ore y&ae *  v ) i t f i g 3 \/ertic&/ Section through No's lt S Jno 9 drill holes. Section strikes 065°. AH dnll noies he in plane oi section. feet so i/ftnfJtO&y ot th<.rr^KJI Copper Propf-ty 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0106708/manifest

Comment

Related Items