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Metamorphism at the Andrew Yellowknife property Northwest Territories 1948

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^ ^ 3 3 ? . /y? 3 METAMORPHISM At The AM)REW YELLOWKNIFE PROPERTY NORTHWEST TERRITORIES A Thesis Submitted to the Department of Geology and Geography University of British Columbia In Partial Fulfilment of the Requirements For the Degree of Master of Applied Science in Geology Leon Olivier Gouin Vancouver, B. C. Apri l 15, 1948 / (i) ABSTRACT A study of Precambrian sedimentary rocks belonging to Division three of the Yellowknife group has been made. Samples for this study were obtained from an area 2 miles north of the northeast arm of Russel Lake near the granite contact. The rocks are greywacke, arkose and phyllite that have suffered low grade regional metamorphism. Shear zones that parallel the strike of the sediments have provided channelways for mineral- izing solutions so that these zones now constitute mineral deposits import- ant for their gold content. The shear zones contain, in addition to quartz and sulphides, an intergrowth of grunerite and hornblende n»»h similar to that found in the iron-bearing.district of Lake Superior. This amphibole intergrowth is particularly well developed in an assemblage of thinly banded sediments containing a narrow (about 4") iron formation. Although Almandite garnet is found to a small extent in the shear zones, i t is the characteristic wall rock alteration of these zones. An attempt has been made to show that the elongated "quartz pebbles') which occur in the shear zones, are of hydrothermal origin. S c a l e / < ' « * =4-Miles Frited fr-zrr. C S C . Map 69QA -jjurr Jfit/er ( i i i ) CONTENTS Page ABSTRACT ( 0 PREFACE • l ACKNOWLEDGMENTS . . . . . . . . 2 INTRODUCTION 3 Location •• 3 Accessibility . . 3 Claims .. •• 3 History 3 Topography . 4 Pleistoceneand Recent Geology . 4 BEDROCK GEOLOGY . . . . . . . . . 6 GENERAL STATEMENT . . . 6 THE GRANITE 7 PEGMATITES . . . . 8 THE DIABASE • 10 THE PORPHYRY 11 THE SEDIMENTARY ROCKS - 12 METAMORPHISM OF THE SEDIMENTS 14 GENERAL STATEMENT 14 PRODUCTS OF METAMORPHI SM . . • 15 Quartz • • • • • . . < > . . . . . . . . . . . . . e 15 Feldspar . . . . . . . 16 Biotite, Muscovite, Chlorite . 17 Accessary Minerals 19 SPECIAL FEATURES • 19 Sediments near the Granite Contact . . . . . . . . 19 Spotted Sediments « 21 Tourmalinization . . . 2 3 Retrograde Metamorphism 24- SUMMARY 25 THE IRON FORMATION 2 7 ' OCCURRENCE 2 ? MICROSCOPIC STUDY 27 THE SHEAR ZONES 32 DESCRIPTION No. 1 Zone No. 2 Zone No. 3 Zone No. 4 Zone No. 5 Zone No. 6 Zone No. 7 Zone METASOMATISM OF THE SHEAR ZONES 37 GENERAL STATEMENT 37 MEGASCOPIC DESCRIPTION . . • 37 The Mineralized Zone. . . . . . 37 The Wall Rook • 38 MICROSCOPIC EXAMINATION . . . . . . . 39 The Mineralized Zone . . . . . . . . . . . . . . . 39 The Wall Rock 44 THE MINERALIZING SOLUTIONS 47 Means of Access ...... ..... . 47 Nature of the Solutions . . . . . . . 48 Chemical Processes Involved . . . . . . . . 49 Summary • . . . . . . . 51 Source of the Solutions . . . . . . . . • 51 Classification of the Deposit 52 THE QUARTZ PEBBLES 53 GENERAL STATEMENT . . . . . . 5 3 OCCURRENCE 53 DESCRIPTION r 53 COMPOSITION AND TEXTURE . . . 54 MICROSCOPIC EXAMINATION 54 ORIGIN 56 THE OCCURRENCE OF GOLD 60 STRUCTURE . . 61 CONCLUSIONS 62 APPENDIX 63 Page BIBLIOGRAPHY 65 ILLUSTRATIONS PLATE 1 Showing Loaction of the Andrew property- ( i i ) Map 1 General Geology of the Andrew Property In map-case ti 2 Detail Geology and Assay Results of Open Cut. In map-case Pig. 1 Topography of the area Facing P. 4 it 2 Andrew camp P. 4 » 3 Pegmatitic Quartz Veins P. 6 it 4 Phyllite Beds P. 13 w 5 Z-shape Drag-fold P. 14 n 6 Fluid Pores i n Quartz Pod . P. 16 it 7 Crenulations in sediments P. 18 it 8 Sediments near Granite.Contact P. 20 it 9 Spotted Sediments P. 21 n 10 Quartz Tourmaline Rock. P. 23 it 11 Rutile Chlorite. P. 25 it 12 Rutile Needles i n Chlorite . ' P. 25 ft 13 Haematite Band P. 29 II 14 Haematite Band P. 29 t» 15 Quartz Pebbles, i n Shear Zone P. 35 it 16 Amphibole Clusters with Quartz and Sulphides P. 39 it 17 Quartz-Pyrite Veinlet P. 42 ti 18 Pyrite i n Quartz Pebble P* 43 ft 19 Pyrite i n Quartz pebble P. 43 ft 20 Pyrite Introduced in"Fracture -at"Edge of PebHeit P. 43 it 21 Sulphides Rimming PebbleI P. 43 if 22 Garnets Veined by Chlorite P. 45 « 23 Biotite Replaced by Chlorite P. 46 n 24 Sulphides i n Garnet P. 47 n 25 Small S-shaped'Drag-fold P. 55 it 26 Quartz Pebbles in Shear Zone P. 58 ti 27 Quartz Pebbles in^Shear Zone P. 58 (1) PREFACE During the greater part of the 1947 summer season, the writer was in charge of the Andrew Tellowknife Mines Limited. Although the property- did not prove to be economic, certain features of i t posed an interesting problem and provided good material for the subject of a thesis. For example, the origin of the quartz pebbles and their relation to the gold was a moot point that could be settled only in the laboratory. A suite of over sixty specimens was collected. Thin and polished sections of these together with f i e l d observations provided the information on which the conclusions of this thesis are based. As the work progressed i t became evident 'that the area from which the specimens were obtained provided an interesting and absorbing study of regional metamorphism and hydrothermal alteration of Precambrian sediments. The work, therefore, resolved i t s e l f into these various problems: 1. A description of the Precambrian sediments of the Yellowknife group i n the area i n question with special emphasis on the metamorphism they have undergone. 2. A study of a thin band of iron formation. 3. A study of hydrothermal alteration in the mineralized shear o f zones andAthe paragenesis. 4. A detailed description of the "quartz pebbles" in these shear zones and an attempt to provide a satisfactory explanation for this unusual geological phenomenon. (2) ACKNOWLBDSMBNTS The writer is much indebted to George Radisies, engineer in charge 1 of the Andrew Yellowknife Mines Ltd., who not only placed at the disposal of the writer a l l the available.information on the property but also gave much encouragement in carrying on this study. It is a pleasure to acknowledge the aid received from various members of the Geology Department and in particular fen*) Dr. Gunning under whose supervision and guidance this work was carried out* Thanks are also due to Dr. C. S. Lord of the Geological Survey of Canada for some of his photographs which are included in the thesis. ( 3 ) INTRODUCTION Location; The property is located north of the no^west arm of Russel Lake and just east of Andrew Lake in the Yellowknife Mining Division, Northwest Territories, at latitude 65° 11« and longitude 115° 30». It is approxi- mately 75 airmiles northwest of Yellowknife. (Sea Plate 1) Accessibility; The property can be reached by barges with average draught of from 2-j| to 3 feet by way of the northwest arm of Great Slave Lake, thence through Russel Lake. Andrew Lake is sufficiently large and deep to make the claims readily accessible by ai r , using the usual Norseman types of planes or smaller a i r c r a f t . Claims t The property consists of twenty patented Mining Claims bearing designations L45 to L64 inclusive and disposed as shown on the accompanying map. Total acreage is about 1 , 000 acres. Historyt The claims were staked in the summer of 1945 by Andy Bugow for Frederick Yellowknife Mines Ltd 0 and were later acquired by Bryhern Exploration for cash and a number of shares i n the newly incorporated Andrew Yellowknife Mines Ltd. Exploration work amounting to 7,800 feet of diamond d r i l l i n g and 9 0 0 cubic yards of rock trenching was carried on during the summers of 1946/47. Fy. 1 — 5howuig Relief . View \ookin<j northwest South of Cabin Lake. » (4) Topography; The area i s one of low r e l i e f but in detail the surface i s quite rugged. Rock outcrops form sharp prominent knobs rising 20 to 50 feet above the intervening muskegs. The lower depressions are occupied by lakes. (Pig. 1 and 2) Fig. 2 - Andrew Camp. Note low re l i e f . Pleistocene and Recent Geology* Glaciation and post-glacial action have played an important part in giving the country i t s present appearance. The average strike of seven measured ioe striae was S. 55°W. The strike of the sediments is approximately at right angles to the ice movement and these two factors have determined to a large extent the shape of the outcrops. They tend to be elongated i n the direction of ioe movement or parallel to the strike of the sediments. Boulders are common but found only on rock outcrops. The inter- vening areas between the outcrops consist of clays and s i l t s . These were examined closely where the overburden haa to be stripped to expose part of a mineralized zone at the southern end of claim L55. Here the deposit (5) consisted of poorly sorted, rudely banded sands, s i l t s and clays. The samples obtained from this l o c a l i t y were washed free of s i l t and clay which made up about 65% of the volume. The remaining 35% consisted of a medium to fine sand averaging l/lOO" in size. The largest fragment measured was 1/5'1 in diameter. The fragments consisted of about 50% quartz, 40$ feldspar and 10% of hornblende, mica flakes, olivine, magnetite, ilmenite and 3 or 4 pyrite f grains. The grains were well rounded to angular, smaller grains being better rounded. Coarse feldspar grains displayed cleavage faces. It appears, therefore, that a post-glacial lake occupied this area i n which these sandy s i l t s and clays rapidly accumulated. Rock outcrops were apparently swept bare of d r i f t material by wave action leaving only the large boulders. (6) BEDROCK GEOLOGY General Statement The claims are underlain chiefly by Archean rocks of Division three of the Yellowknife group^ and consist of greywacke , arkosei and some phyllite . They trend in general N 55* W and dip steeply to the southwest. extensive granite area lie s just east of the property and the contact between the granite and sediments passes through the north- east part of the property, the granite forming a nose protruding into the sediments at this point. The granite contact dips about 45° to the southwest under the sediments. Pegmatite dykes and pegmatitic quartz veins (Fig. 3) are f a i r l y Fig. 3 - Pegmatitic Quartz Veins numerous particularly i n the northern section near the granite contact. On claim L47 a diabase dyke cuts a pegmatite dyke. Two acid dykes occur, one on claim L61 and the other on claim Lt)tf. Both cut through mineralized shear zones. Lord, C.S. "Snare River and Ingray Lake Map-Areas Northwest Territories' 1 Geol. Surv. Canada, Mem. 235 PP. 9 and 14. (7) The Granite A nose of granite forms part of the rocks underlying the property in the northeast corner. This granite is medium grained, with small patches of coarse pegmatitic phases. Two prominent sets of joints striking N-S and S 60° W and dipping steeply, give i t a blocky appearance. The latter set is sometimes occupied by pegmatitic quartz veins; small pegmatites and pegmatitic quartz veins were noted to occupy the former set. The plutonic mass dips about 45° under the sediments and platy flow structure was observed close to the contact. Here the tabular f e l d - spar crystals and the muscovite plates tend to be oriented with the largest face parallel to the contact. In thin section the following minerals were noted; quartz 25%, albite 30%, orthoclase 20%, microcline 10%, muscovite 13%, and fluorite 2%, The rock has typical granitic texture. The albite and orthoclase are in part intergrowni Muscovite forms irregular ragged i n t e r s t i t i a l flakes. It i s tinged green and is pleochroic. Twinning on 110 plane is common. In hand specimen the muscovite parts readily along the twinning plane. It has a honey-yellow color suggesting the presence of iron. However, under the microscope i t has a 2v of 40° and the mean index was found to be between 1.588 and 1.578. These optical properties indicate that i t approaches the composition of pure muscovite. The fluorite occurs as rounded grains usually i n the albite. It is tinged purple and has deep purple spots. Under high power these spots seem to be due to inclusions. It is possible that they are due to the presence of minute amounts of radioactive elements. (8) Pegmatites As might be expected from the proximity of a large granite body, pegmatite dykes are numerous i n the area. They vary i n size from a few inches to several feet across and some can be traced for lengths of as much as 500 feet. They strike in a l l directions but the trend of the majority follows three directions, namely N 40° E, N-5 and parallel to the bedding. The f i r s t two directions conform with the strike of the two most prominent sets of joints. They cut, and are cut, by irregular pegmatitic quartz veins. In many instances the dykes are offset by slips parallel to the bedding and by the mineralized shear zones. Offsets vary from 2 to 3 inches by minor slips to 25 feet by shear zones. Almost a l l are oomposed entirely of coarse grained arthoclase, quartz, and minor amounts of albite and muscovite. However, one large dyke on claim L60 that strikes N 75° W contains considerable lepidolite* Its color is violet and i t is quite coarse grained with good twinning on 110 along which parting is easily affected. 27 varies from 20 to 40 degrees. The mineral give6 an excellent flame test for lithium. Along with lepidolite, but sparsely distributed, are coarse crystals of a green mineral with a greasy lustre. It has a l l the optical and physical properties of serpentine. It is clearly a pseudomorph after some other mineral which may possibly have been hornblende. The large pegmatites i n the northern end of the property are worthy of special attention since they exhibit distinct banding throughout the whole width of ths dyke. Alternating bands of feldspar, quartz, and a fine grained granite phase parallel the strike of the dykes. The layers of quartz and feldspar are between 1/4 to l/2 inoh thick and sometimes grade into each other. (9) The granite phase forms bands usually an inch to two inches across* The band next to i t may be either a feldspar layer or a quartz layer but the crystals usually show preferred orientation with long dimension of the crystals perpendicular to the strike of the bands. The muscovite of the granite band has a linear arrangement that parallels the strike of the dykes. Because of the width of the dykes and the regularity of banding i t is inconceivable that this layering is a result of fracture f i l l i n g . A more logical explanation seems to be rhythmic precipitation. Rapid crystallization at the borders of the dyke would give a granite band while the liquid immediately adjacent to this band would be enriched in fluids and feldspar and quartz constituents. These would then crystallize leisurely forming relatively narrow coarse grained.bands of feldspar and quartz. The pegmatitic liquid, however, being i n constant motion would carry away the attenuated f l u i d 3 and a new granite band would crystallize from the new pegmatitic liquid. Repeated surges of the magmatic material would thus result i n the formation of these alternate bands. (10) The Diabase A diabase dyke about 12 feet wide and exposed for a length of 50 feet outs a pegmatite i n the northwest corner of claim L47. Megascopically i t i s fine-grained and appears chloritized and,is slightly mineralized by pyrite. In thin section i t is clearly evident that the rock has undergone considerable alteration. It consisted originally of an open network of labradorite laths i n a pyroxene matrix giving a sub-ophitic texture. Much of the labradorite has been partly altered to serieite which has a smaller optic angle than ordinary muscovite. The pyroxenes consist of augite and pigeonite. Optic angles vary from 20 to 50 degrees. The pyroxenes have been largely altered however to chlorite and uralite. Apparently there was a considerable amount of diffusion since rims of uralite are seen around a pyroxene crystal sandwiched between two altered crystals of labradorite. The sodium released from the alteration of the feldspar probably contributed to the formation of uralite. Irregular patches of chlorite occur both in the pyroxene and feldspar and between grain boundaries, while a considerable amount of carbonate has formed in the labradorite. A few small grains of pyrite and magnetite are sparsely distributed t while semi-opaque brownish cloudy masses of altered ilmenite are present. (11) The Porphyry Two such dykes were observed, one on claim L61 and the other on L54. They are about 2 to 4 feet wide and can be traced only for short distances. Both cross shear zones and so are definitely younger than the shearing. The one on claim L61 contains inclusions of the mineralized zone and i t s injection has resulted i n contortion and drag folding of the beds i n the immediate v i c i n i t y . The dyke rock weathers a light grey but a fresh piece is greenish-grey and appears to be uniformly fine-grained. Microscopically, however, i t consists of about 50$ feldspar phenocrysts set i n a fine-grained matrix of quartz, feldspar and muscovite. The phanocrysts average 3/100" i n diameter and are composed of albite. The grains of the groundmass average l/200" i n diameter. The feldspars have a cloudy appearance and are sericitized. The muscovite forms laths i n the phenocrysts and tends to occur as irregular veinlets i n the fine-grained groundmass. Some of i t has been chloritized. The quartz shows wavy extinction and has sutured boundaries. A few grains of pyrite partly altered to haematite are also present as well as grains of leucoxene. The rock was apparently fractured before i t had completely so l i d i f i e d and the fractures are f i l l e d with deuteric muscovite. (12) The Sedimentary Rooks Before going on to a consideration of the metamorphism of the sediments, i t i s necessary to describe them in some detail. In the f i e l d these rocks form an interbedded succession of grey- wacke, arkose and phyllite, the former two predominating over the phyllite. The arkose weathers a light grey and has a rough sandy texture with angular to rounded grains of quartz and feldspar. They are clastic grains varying i n size from 1/80M diameter in coarse arkoses, which are poorly sorted, to the lower limits of fine sand, i.e. 1/250"1. The greywacke is quite similar but weathers a darker grey or buff and contains more fine grained i n t e r s t i t i a l material. Most of the rocks appear quite normal and seem to have suffered l i t t l e or no metamorphism. They exhibit no schistosity or even tendencies towards any lineation. However, a few beds containing considerable chlorite and micas have a distinct schistosity. These weather a dark grey or dirty green color. Beds range in thickness from a fraction of an inch to about 8 inches. Rarely do individual beds exoeed this thickness except for a schistose bed that forms part of the wall rock along the southwest side of No. 2 Zone. This bed is about 12 feet across. In thin section i t was noted that the proportion of quartz is f a i r l y consistent i n a l l the rocks and varies between 45 and 55 per cent. The amount of feldspar, however, varies a good deal. The coarse grained sediments contain as much as- 40$ feldspar but this percentage decreases proportionately with decrease in grain size such that the fine-grained greywackes contain only about 5$ feldspar. About 95$ of the feldspar is albite, the rest being orthoclase. The i n t e r s t i t i a l clay material (now 1 Tyrrell, G.W. The Principles of Petrology p. 190 (13) • altered largely to chlorite and micas) also increases i n percentage with decrease i n grain size. Hence to summarize, a coarse arkose is composed of about 45$ quartz, 40$ feldspar and 15$ fine flaky material now i n the form of chlorite and mioas, while a greywacke is made up of about -5~.5$ 55~%> quartz, 5$ feldspar and 40$ micas. The composition of the rocks varies between these two extremes. Not included i n the above compositions are minor amounts of accessory minerals. They are rarely i n excess of 1 or 2 percent. They are composed of small hexagonal grains of apatite, a few grains of zircon, and minor amounts of magnetite. But the chief accessory i s a black opaque mineral, white i n reflected light and semi-opaque brownish under high power. It is apparently ilmenite now altered to leucoxene, Phyllite beds occur almost entirely on claim L61, They are dense, black thin-bedded rocks with good cleavage i n places across the bedding. They are interbedded with thin quartzitic bands and arkose and greywacke. They are well sorted and the quartzitic bands grade into the dense black bands. (Fig. 4) Fig, 4 - Phyllite Bade (14) METAMORPHISM OF THE SEDIMENTS General Statement Considering the proximity of a large intrusive mass and the age of these sediments they are remarkably fresh looking. Except for a few schistose bands they present no structures that characterize dynamically metamorphosed rocks. Nevertheless, the shear zones and drag folding i n some beds (Fig. 5) indicate- that the rocks have been subjected to strong Fig. 5 - Z-ehaped Drag Fold shearing stresses. The microscopic study substantiates this fact. The deformation of quartz grains, their sutured boundaries and the consequent (15) development of strain shadows i s testimony of the enormous pressures once applied to these rocks* The textural and mineralogical changes i n the rocks have, therefore, been due chiefly to dynamic metamorphism with l i t t l e rise i n temperature. The overall mineralogical composition indicates low grade metamorphism. In a few instances, however, there has been addition of volatile components resulting i n the development of tourmaline, but these meta- somatic changes are confined to certain argillaceous beds. Metasomatism has played an important role i n the assemblages of thin beds that contain the iron formation, but this case w i l l be treated separately. PRODUCTS OF METAMORPHISM Before dealing with the actual chemical changes undergone by the original constituents of the sediments, l e t us f i r s t examine the minerals, now present i n the rocks^ individually. Quartz t As mentioned before this mineral i s the most abundant constituent. It consists of clastic grains varying in size from 1/80" diameter to 1/250". It is d i f f i c u l t to determine the original shape of the grains since nearly . ' a l l have suffered various degrees of metamorphism. They were presumably well-rounded to sub-angular. They now tend towards dimensional orientation, the long diameter parallel to, or making an acute angle with, bedding. They usually exhibit strain shadows and undulatory extinction and invariably produce a biaxial figure with a 2y of 10 to 20 degrees. Strain shadows show a tendency to be parallel to the bedding but often they are almost at 90° to the bedding even i n crystals that are elongated along the strike. The inference i s that the direction of strain shadows depends on the orientation of the grain and not on the direction of pressure. Considerable recrystallization has occured at grain boundaries where the brunt of the (16) pressure was sustained and they now have sutured boundaries. In rare instances complete recrystallization has occured forming small pods or xenoblasts of quartz. Trains of minute fluid-pores are developed i n parallel planes which are parallel to the strain shadows. An exceptionally broad band of one of these trains was observed in a quartz pod, (Fig, 6) Fig. 6 - Fluid-pores in a Quartz Pod. Crossed Nicols X70 Feldspar; The stress effects exhibited by quartz are l i t t l e apparent i n the feldspar. They show only occasional weak undulating extinction but secondary albite twinning was observed in one thin section. The twinning lamellae are very fine and sometimes end abruptly at a crack which has relieved the stress. Under medium power the grains usually appear quite clear like the quartz, but under high power and condenser removed they have a cloudy (17) appearance and contain small s e r i c i t i c inclusions. A few large grains have long thin oriented laths of serieite and i n the coarser arkose most of the albite has been converted to a fine scaly mass of serieite, Biotite, Muscovite, Chlorite• These three minerals are so closely associated that they are d i f f i c u l t to treat separately. They occur in varying amounts and pro- portions i n a l l the sediments and result from the alteration of the fine sedimentary material between the quartz and feldspar grains. A l l three are stress minerals and they show a marked tendency towards orientation, the largest face being parallel to the strike of the beds. They vary i n size from numerous l i t t l e flakes, that often .serve to indicate the clastic nature of the rock, where metamorphism has not progressed far,^ to fewer larger flakes where metamorphism i s more advanced. In the early stages of metamorphism the fine i n t e r s t i t i a l material has, by the process of local solution and diffusion, collected into irregular patches and recrystallized as chlorite and muscovite. These two minerals have crystallized side by side sometimes with considerable increase i n grain size without mutual reaotion between them. The iron oxides have also collected as small irregular grains or patches dis- seminated throughout the chlorite and biotite. The chlorite-muscovite patches are lenticular shaped with the long axis parallel to bedding and the individual crystals i n these patches are well oriented i n the same direction. Sometimes these patches come to an abrupt stop against a large quartz grain. In other cases, i n fine-grained sediments, the chlorite and muscovite are intimately intergrown and have been thrown into (18) minute folds whose axes are perpendicular to the strike of the bedding, (Fig. 7) Fig. 7 - Intergrown chlorite and muscovite thrown into minute folds X70 These folds stop abruptly against a gritty band. The chlorite i s light green, slightly pleochroic and biaxial negative with a 2V varying between 0 and 20 degrees. Its index is slightly higher than muscovite. It appears to be a relatively iron rich magnesium-free chlorite similar to daphnite. In the more advanced stages of metamcrphism the iron oxide, chlorite and muscovite have reacted to form biotite. This mineral is deep brown, strongly pleochroic and idioblastic towards a l l the other minerals. Although i t tends towards orientation, the flakes are often arranged obliquely to the schistosity. The ore minerals have disappeared but the biotite grains have small round strongly pleochroic black patches (19) that indicate local greater iron content probably due to lack of complete absorption of the iron-oxide grains. The chlorite too is usually absent but clear^well crystallized muscovite i s intergrown with the biotite. This indicates lack of enough magnesia i n the chlorite to convert a l l the muscovite to biotite. Accessory Minerals; Of the accessory minerals, apatite has suffered no change and s t i l l occurs as small hexagonal grains.. The few zircon grains have of course undergone no change either. The ore minerals on the other hand have undergone considerable transformation. It has already been noted how they have reacted with other minerals to form biotite. It seems that these ore minerals were titaniferous or that r u t i l e was originally present. Magnetite has ,reacted with the latter to form ilmenite which is now altered to a semi-opaque brownish mass of leucoxene. Some of these masses contain remnants of a network of rutile laths. This does not, of course, preclude the fact that ilmenite was originally present i n the sediments. Small amounts of tourmaline grains occur scattered throughout the rocks. .They are small and exhibit poeciloblastic structure. In view of a special occurrence of this mineral which w i l l be mentioned later, i t i s believed that the boron has been introduced and was not an original constituent of the sediments. SPECIAL FEATURES IN THE METAMORPHISM OF THE SEDIMENTS Sediments near the Granite Contact; d i / t « M of < i t « ^ f ?<>' from FP>: r^the intrusive mass, the mineral composition has been largely determined by the addition and subtraction of certain components brought about by fluids emanating from the igneous mass. The sedimentary rock has a well developed schistosity and i s coarser grained than most other sediments on the property. It has been (20) entirely recrystallized and quartz grains attain diameters of 3/l00 M, Trains of fl u i d inclusions crossing several crystals are numerous. Large oriented plates of muscovite lend the rock i t s schistose structure and apatite now occurs as large irregular grains. The muscovite is partly altered to chlorite and the irregular leucoxene grains are s t i l l present, (Pig. 8) Except for a few small remnants albite has been almost entirely Fig. 8 - Sediments near granite c ontact.* Whi te-quart z; Light grey-muscovite; Dark grey-chlorita X70 removed. Obviously diffusion and recrystallization have been greatly aided by fluids emanating from the granite. Considerable potash to form muscovite has been added and soda and lime have been removed. In a l l probability, a l i t t l e phosphate has also been added and with some calcium derived from the feldspar has reconstituted the original apatite grains into larger ones. (21) Spotted Sediments; While d r i l l i n g on the property, i t was noticed that many polished surfaces of the d r i l l cores had a spotted appearance as though porphyro- blasts of a dark green mineral were present. The same was noticed on the surface of cut specimens. In thin section these are irregular light green areas with quartz, biotite and sometimes tourmaline inclusions, thus resembling a great deal xenoblasts having poeciloblastic structure. (Fig. 9) Fig. 9 - Spotted Sediment X 70 Under crossed nicols, however, they present a very fine mottled appearance. The interference colors are low, f i r s t order orange being the highest observed but due to the cryptocrystalline nature of the grains the birefringence is much stronger than is indicated. The index is inter- mediate between quartz and biotite. Patches of these small grains within the areas have a common orientation and seem to be i n the process of forming large crystals. They appear to be composed of a very fine-grained (22) scaly mass of serieite, •This occurence is analogous to the spotted slates and bears the same significance, that i s they t e s t i f y to low grade metamorphism. By comparing thin sections 4 and 58, i t can be shown that these spots are at different stages of recrystallization. They vary from an indistinct cryptocrystalline mass'to a minutely crystalline mosaic and fineiy to a fine scaly aggregate of muscovite plates. The spots have a tendency to be arranged along bands that contain a large percentage of micas and ohlorite and are often surrounded by an aureole of intergrown muscovite and biotite. The occurrence of these spots is the result of local solution at isolated points i n the rock where a considerable amount of solvent was present and where there may possibly have been a larger percentage of fine i n t e r s t i t i a l material. Some diffusion of material to the isolated points probably took place increasing the size of the spots. However, the physical conditions obtained were not favorable for the complete recrystallization of the amorphous substance i n the spots. The temperature i n particular was not raised sufficiently to effect the process of re- crystallization. It i s true that., biotite, which results from a higher grade of metamorphism has formed in the spotted sediments, but meta- morphism goes on at a tardy uate and the rock is reconstituted gradually and piecemeal successively at different points in the rock. Solution, chemical reaction and consequent formation of new minerals did not take place as separate stages throughout the whole rock so that biotite was forming while solution was s t i l l going on, f "Ehe a late stage i n the process of metamorphism when the agents of metamorphism were no longer capable of recrystallizing the substance segregated into the isolated areas. (23) Tourmalinizationt Metasomatic effects again manifest themselves i n the tourmalini- zation of the argillaceous rocks. The presence of this mineral i n abundance was noted i n a fine-grained altered greywacke and i n the phyllite. (Fig. 10) Fig. 10 - Quartz-tourmaline rock. Opaque mineral i s leucoxene X 70 It i s medium green i n color with strong pleochroism. No lies between 1.6420 and 1.6521 while Ne is between 1.6218 and 1.6318. It is an§ iron rich tourmaline belonging to the dravite-schorlite series. It is to be expected that such a mineral w i l l be associated with sediments of higher alumina content and hence i t displays a gradual increase from the coarser quartzitic bottom of the beds to the finer argillaceous tops where i t now constitutes about 9 0 $ of the rock. Tourmalin!zation f i r s t began in the fine argillaceous material and (24) then the biotite was attacked converting i t into tourmaline. The l i t t l e prisms of tourmaline have such a perfect orientation that they look like corded wood. They are often crowded along thin particular bands reflecting the original bedding of the rock. The coarser quartzitic bands contain considerable muscovite, some of i t i n the fine s e r i c i t i c form. Leucoxene grains are numerous and a few pyrite grains partly altered to"haematite were" noted* There is l i t t l e doubt that there has been considerable accession of boron. However, a l l the other constituents necessary for the formation of tourmaline were already present and probably nothing else was added. The potash present entered into the formation of muscovite while possibly some soda was removed. Retrograde Metamorphism; A certain amount of retrograde metamorphism has taken place. In several cases the biotite has been partially altered to chlorite. However, one case i s worthy of special attention. Thin section No. 3 is a section of a fine-grained schistose sediment with irregular lenticular-shaped areas of chlorite-. The chlorite is biaxial (->) with 2V from 0 to 20 degrees. These areas are replete with small dark needles arranged in radiating clusters. (Fig. 11 and 12) The needles under high power are brown semis semi-opaque to transparent and have parallel extinction. Their index is high but the strongest birefringence observed was .030. The needles, however, are so thin that their maximum birefringence is probably much higher than that. The properties of this mineral, therefore, conform with those of r u t i l e . Some chlorite grains show f a i r l y high birefringence and perfect basal cleavages, and small muscovite plates are f a i r l y p l e n t i f u l . This seems to be a case of retrograde metamorphism in which biotite was altered back to chlorite with the consequent formation of (25) Pig. 11 - Chlorite lentioles Fig. 12 - No. 11 highly magnified with rutile needles. X 70 to show rutil e needles. X 280 rutile needles and muscovite. Such a transformation involves the addition of water. Whether this water is of meteoric origin or not is unknown. It has already been shown how f l u i d emanations have played an important role in the reconstitution of some sediments and water could easily have been derived from the same source as these f l u i d s , SUMMARY In a general way the metamorphism of these sediments corresponds to the biotite zone and is a result chiefly of dynamic metamorphism, ~The~' — - - r r h i ~ w i n T r - l i pr"in~Tl Tin rtirwsi m1mnrn1st The spotted sediments indicate arrested metamorphism and t e s t i f y to the low grade of meta- morphism. It has been d i f f i c u l t to completely divorce metamorphism from metasomatism. The latter could probably be defined i n terms of the f i r s t as metamorphism plus the addition and subtraction of some constituents. In many cases i t is impossible to t e l l whether water, which plays such an (26) important role i n metamorphism, was already present i n the rock or was derived from a foreign source. The fine detrital i n t e r s t i t i a l material was apparently high i n iron and potash but too deficient i n magnesia to convert a l l the chlorite and muscovite to biotite. (27) THE IRON FORMATION Occurrence An interesting feature of the rocks i n this area is the presence of a thin .band of iron formation. It occurs in an assemblage of thin bedded sediments on the west side of the property just west of the No. 1 Zone.. Where best exposed on an outcrop just north of the t r a i l running east from the camp on claim L53» the sediments consist of thin beds ranging in thickness from l / 8 w to about 3 inches and average l / 2 n . The assemblage is about 35 feet across and the upper part grades into coarser greywacke and arkose. The beds have a very fine sandy texture and weather shades of green and light brown to dark reddish-brown. They are consider- ably drag folded and pegmatitic quartz lenses parallel or cut across the bedding. The lower part of the assemblage contains considerable quartz pebbles and below these occurs a!43 Airon formation. The formation consists of haematite-rich bands with a' l i t t l e magnetite and pyrite. The haematite is usually concentrated into two or three layers about l / 4 w thick and one inch apart. Sometimes, however, i t is uniformly distributed over a width of 2 or 3 inches, but generally with some concentration along very thin bands. The formation can be traced southward along the strike and on one outcrop on claim L57 the haematite oocurs as specularite admixed with quartz and limonite. The quartz is medium grained and colored rose and has well developed crystal faces. It is due to solution and reprecipitation in s i t u . The limonite of course i s a result of hydration of the haematite. Microscopic Study In thin section the thinly-bedded sediments consist of amphiboles and quartz with minor amounts of iron oxide and pyrite. The proportion of (28) quartz and amphibole varies and either one or the other predominates giving the rock a rough banded appearance* Some bands are made up entirely of amphibole. The quartz is clear but under crossed nicols i t shows strain shadows and, commonly, sutured boundaries. The amphibole includes two minerals» One is colorless non** pleochroic, biaxial (-) with a 27 of 80° and extinction angles up to 16° with a birefringence as high as .045. It is probably grunerite. The other i s bluish green, strongly pleochroic, biaxial (-) with a 2v 70° .-aaad" and extinction angles up to 20°. The birefringence i s moderate (,025), The mineral is hornblende with a high ferro-ferric ratio. : The two amphiboles are intimately associated and quite often intergrown but the hornblende is more abundant. They occur as blades or laths oriented i n various directions presenting a decussate structure but with a tendency to parallel the bedding of the rock. Sometimes a blade of amphibole consists in part of grunerite and i n part of hornblende. The cleavage runs from one to the other, showing that both are part of the same crystal but these show a slight difference in extinction. Occasionally they occur in radiating clusters. The grunerite may form the nuoleus of the cluster, ^ surrounded by the hornblende as though i t were an added growth and i n other instances the opposite occurs. Grunerite is commonly twinned and i n rare cases the twinning lamellae consist of alternate grunerite and hornblende lamellae. Haematite occurs as flakes scattered throughout the rock. They usually have a blood-red color in reflected light but sometimes they remain quite dark. They are small with frayed borders and parted along the cleavage. Quite often they are intergrown with the grunerite as though the two had formed together. (29) A crushed sample of the rock reveals that i t contains quite a few magnetic grains. This magnetite is at times d i f f i c u l t to discern in thin section and may be confused with haematite that does not show the red color i n reflected light. It seems to occur scattered along certain bands, and to have been pyritized. A thin section was made of the rock containing two haematite bands. The mineral assemblage between the bands is much the same as already described, except that quartz grains and haematite flakes are more abundant and the minerals are better oriented parallel to the bedding. There is a rather abrupt change as the haematite bands are approached. The proportion of haematite flakes rapidly increases and the quartz almost entirely disappears. (Fig. 13 and 14) The green hornblende too becomes Fig. 13 - Grading into Fig. 14 - Haematite ( haematite band. X 25 band. X 25 rare and grunerite is the chief constituent. Haematite is seen replacing the grunerite along the cleavages. The haematite bands are made up of (30) closely f i t t i n g flakes of haematite usually parted along the cleavage. The grunerite has disappeared and i n i t s place are thin laths of a color- less mineral with low birefringence. It has fine twinning lamellae and fine haematite flakes are often intergrown with i t . The extinction i s undulating and i t is d i f f i c u l t to measure the extinction angle but i t appears to be small. It i s biaxial with 2v very large, but the sign is not known. Much of i t contains a fine aggregation of a greenish-grey mineral moderately pleochroic andAweak birefringence. A small amount of quartz is s t i l l present and fine needles of the colorless mineral project into the quartz grains. A few grains of a carbonate were also noted. Magnetite occurs as small octahedrons i n the haematite or i n the colorless laths. It also occurs as lenticular areas along with pyrite. These two minerals are closely associated but magnetite may occur as isolated grains while pyrite never does* Origin It i s d i f f i c u l t to trace the history of these haematite bands since l i t t l e is known about the composition of the original sediments. There i s nothing to indicate that they were originally ferruginous, but in a l l likelihood they were high i n alumina and contained f a i r amounts of magnesia. Consequently the formation of the amphiboles, particularly grunerite, and of haematite cannot be attributed solely to processes of metamorphism. These two minerals, grunerite and hornblende, constitute a large proportion of the country rock i n the mineralized shear zones where they are clearly the result of hydrothermal alteration. Their presence i n the iron formation i s apparently due to this same cause. Haematite forms under oxidizing conditions and since haematite i s so often intergrown with the amphiboles, i t seems that they too formed under oxidizing conditions. However, we have noted the presence of pyrite (31) with magnetite so that reducing conditions must at one time have prevailed* It seems, therefore, that hydrothermal solutions travelling through these beds were highly ferriferouso They reacted with the sediments to form hornblende and grunerite. The amount of hornblende developed depended on the amount of aluminum originally present i n the rock. S i l i c a was abundant so that as the aluminum became tied up i n the horn- blende molecule the excess iron reacted with the s i l i c a to form grunerite e Aluminum was apparently deficient i n certain bands so that only grunerite formed and this grunerite was later converted to haematite by the continued action of the solutions. Haematite i n the iron bands often ocours as pseudomorphs after grunerite. It is not certain what by-products were formed as a result of this last reaction. Some of the colorless twinned mineral i n the haematite bands has parallel extinction, while some of i t has not. It is possible that both anthophyllite and cummingtonite are present while the small amount of greenish mineral may be actinolite. Grunerite has the following formula: ^ F e y S i g C ^ with variable amounts of magnesium, while cummingtonite is ̂ (FeMg^SigC^e Consequently by the extraction of iron from grunerite and the removal of s i l i c a , several grunerite molecules could be reconstituted as cummingtonite. The proportion of amphibole would of course be greatly reduced and that is actually the case i n the haematite bands. The presence of a carbonate suggests that the iron may have been introduced as the bicarbonate. The nature of the solutions must have changed, however, and become reducing. It is well known that haematite can be easily reduced to magnetite. Sulpheretted solutions were later introduced, reducing some of the haematite to magnetite and at the same time producing pyrite. The pyrite, as was noted, is always associated with the magnetite. (32) THE SHEAR ZONES Description The mineral deposits on the property occur in a series of sub- parallel rusty shear zones. Shearing of the sediments is parallel to the strike and seems to have occured wherever there was an assemblage of„thin- bedded sediments. The intensity of shearing and magnitude of displacement varies a good deal i n different zones, but i t is interesting to note that the more intense shearing and best mineralization occurs i n the zone closest to the granite contact. Although the quartz pebbles w i l l be dealt with separately, some- thing should be mentioned about them now. These, are e l l i p t i c a l shaped structures composed of light bluish, sugary-looking quartz. They resemble a good deal flattened quartzite pebbles with the long axis of the ellipse parallel to the strike. Sometimes they are rod-like down the dip. They tend to occur at definite horizons i n the shear zones but are not confined to any single horizon. Seven of these shear zones were explored either by rock trenching or diamond d r i l l i n g or both. No. 1 Zone> The original discovery on the property was made on the southern end of this zone. It dips almost vertical i n the southern part but flattens progressing northwest to a dip of 65°SW, It varies between 20 and 50 feet in width and is much fractured and mineralized, but the horizontal dis- placement between opposite walls of the zone i s small. It disappears under extensive swamp areas to the north and south. Few quartz pebbles are present i n this zone and the gold values obtained were negligible. (33) No* 2 Zone; This zone, the most promising of a l l , averages about 10 feet wide and can be followed on strike for a distance of 3,500 feet. The southern end disappears under a swamp but i t was intersected i n diamond d r i l l holes d r i l l e d in the swamp between No. 2 and No. 6 Zonese The northern part ends rather abruptly* The succeeding outcrop to the northwest is badly cut up by pegmatite dykes and the zone i s absent. It may l i e under the over- burden between the two succeeding outcrops, but the zone could not be picked up on rock exposures farther to the northwest. The central portion of the zone on claim L51 is badly cut up and consists of disconnected lenses. A number of pegmatite dykes striking in a northeasterly direction cut across the rocks intervening between the lenses. The zone runs along the top of a ridge that is much boulder strewn i n the northwest part. Dips are steep to the northeast i n the southern portion but change to vertical at the northern end. Locally the zone i s bent and twisted, but on the whole i t maintains a f a i r l y consistent strike of N 50°W. The amount of displacement seems to vary from place to place, A dyke in the southern portion was offset 15 feet while the displacement of a similar dyke i n the northern part was only 5 feet. This may be due to the fact that stress effects were absorbed more by the compression of the sediments in some parts of the zone than i n other parts, or i t may be due to sl i g h t l y different ages of the dykes injected during the interval of time in which shearing took place. The boundaries of the zone on the west are generally f a i r l y sharp while the east boundary tends to grade into the country rock. No. 3 Zone; This zone outcrops for only a short distance on claim L54 just west (34) of zona No. 4. Mineralization i s weaker than in the other zones and gold values were insignificant. No. 4 Zone; A very narrow (averages about 2 feet wide) but persistent zone designated as zone No. 4 parallels No. 2 zone west, of i t . I t offsets , csus i na several'pegmatite dykes oe-ve^iag horizontal displacements of 20 to 25 f eet» >< The boundaries of the zone are often limited by coarse pegmatitic quartz. Mineralization is not strong and quartz pebbles are absent. Dips are f a i r l y uniform to the southwest about 85°, No, 5 Zone; This zone outcrops at the base of a prominent knoll i n the northern section of the property on cjaim L46, I t extends into the adjoining claims to the north but i s lost i n the swamp to the south. Diamond d r i l l i n g revealed that another zone parallels i t under the swamp on the east. The zone contains abundant quartz pebbles and is well mineralized. The sulphides (chiefly pyrite) are coarser grained than seen elsewhere on the property, but gold values are not outstanding. The zone averages about 7 feet wide and dips ve r t i c a l . No. 6 Zone; Although this zone is not on strike with No. 2 Zone but is offset to the east, i t is probably i t s extension. It is r - u c h similar i n character to the No. 2 Zone though somewhat weaker. It could be offset by a fault but no sign of faulting was observed on outcrops northeast or southwest of the swamp intervening between Nos. 2 and 6 Zones, The apparent displace- ment is probably due to a bend i n the strike of the sediments under the marsh area. The width of the zone is reduced, mineralization is less pronounced and gold values are low. (35) No. 7 Zone; This zone i s a weak narrow structure occuring on claim L63. Since the strike of the sediments changes to a north-south direction i n the southern section of the property, i t may well be the extension of the No. 1 Zone in this direction. It is only about 3 feet wide and minerali- zation is weak. In addition to the above described principal mineralized zones, several rusty narrow short irregular zones occur i n various localities within the boundaries of the property. Thay are always parallel to the bedding but movement along them has been small. One of these, however, is a wide f a i r l y continuous zone with abundant quartz pebbles. (Fig. 15) Fig. 15 - Shear Zone with quartz pebbles It occurs on the outcrops that l i e on the claim line dividing claims L52 and L53» It outcrops again i n the northwest corner of claim L61 where i t has been intruded by an acid dyke* (37) METASOMATISM OF TUB SHEAR ZONES General Statement In dealing with this problem most of the information has been derived- from the No. 2 Shear Zone. It is the best mineralized and has a l l the cu ; ! : : : ' ' j i features o::\v' the other zones developed to a greater degree. Megascopic Description The Mineralized Zone? As already noted, No. 2 Zone averages ebout 10 feet wide. Locally i t pinches OKO to widths of 3 or 4 feet but i n general i t maintains a f a i r l y uniform width. It can easily be followed on the surface by i t s dark brown rusty appearance resulting from the oxidation of the pyrite in the zone. An open cut 340' long at the southern end of the zone afforded an excellent opportunity to study the unweathered rock. The rock has a dense massive appearance. It is dark green, medium to fine-grained and sometimes studded with coarse, deep-red garnets., The sulphides consist of pyrite with, a l i t t l e arsenopyrite, chalcopyrite, sphalerite and pyrrhotite and make up between 2 and 8 percent of the rock. The pyrite forms fine laminae indicating bedding replacement but i t also occurs as streaks, blebs and sometimes veinlets running i n various directions. The arsenopyrite i s rare but occasional small splashes or irregular blebs of this mineral were noted. Chalcopyrite occurs i n the same manner while sphalerite and pyrrhotite were noted as small, sparsely disseminated grains. Quartz stringers parallel the original bedding but irregular streaks, blebs and •:•-;".:.:•>•; well formed quartz pebbles are quite common. The quartz hasflight bluish or smoky appearance and a granular sugary texture. A good deal of the rook, however, i s closely fractured and broken i p permitting the oxidation of the sulphides to depth. The distribution of the sulphides is the same as described above except that s ome fracture faces w i l l have a thin film of pyrite coating them. The rock breaks in such a manner that the sulphide film i s a l l on one face of the fracture, - t n e The fractures i n \some parts of nopen cufc form a network, one set of fractures being parallel to the strike of the zone, the other running i n a N-S direction. Quartz-pyrite veinlets often f i l l these fractures and usually the pyrite i s limited to one side of the veinlet although at times i t occupies the centre or may entirely f i l l the fracture. A few of these quartz veinlets were observed to coalesce with the quartz pebbles but did not seem to cut them. Parts of the zone eke composed of a dense highly siliceous rock with vzery 4;(**?e; amounts of sulphides. Here the quartz pebbles increase in size and number and are rarely pyrite-rimmed. The Wall Rockt The wall rock of the zone has suffered considerable alteration extending 2 to 6 feet on both sides of the shear zone. The altered country rock is medium to coarse-grained, with a dark green chlo r i t i c appearance and l i b e r a l l y studded with garnets. This last mineral forms the chief constituent. In a few places biotite flakes are conspicuous. The zone of alteration is usually wider and more intense on the hanging wall side of the shear zone. Quartz veins occasionally form a band along the footwall or hanging wall side of the zone and also a stock- work of veins in the zone. These veins always strike parallel to the zone or i n a N-S direction. They are about 6 inches wide and composed of coarse white quartz. Some contain inclusions of the mineralized zone and are, therefore, later than the sulphides. (39) Microscopic Examination Mineralized Zonet The minerals of the shear zone consist essentially of quartz, blue- green hornblende, grunerite and the sulphides. In places garnets, with biotite and chlorite are present in the mineralized zone. The two amphiboles are intergrown i n the same manner as previously described, but here they are generally arranged i n radiating clusters and the grunerite invariably occupies the central part of the cluster. Sometimes a few grains of pyrite form the nucleus. (Fig. 16) Small quartz inclusions Fig. 16 - Amphibole clusters with quartz and sulphides X 25 give the clusters a sieve structure. The length of the amphibole plates vary in such a manner as to give the clusters a rough e l l i p t i c a l shape and these tend to be arranged along certain lines giving the rock a rude kanded appearance. (40) About 50 percent of the rock is made up of quartz. It occurs as polygonal grains but i t has been strained and tends towards dimensional orientation - long diameter parallel to the bedding. It contains abundant dust inclusions many of which under high power have a red color. They are probably magnetite and haematite particles. They form a crude polygonal pattern indicating, the original shape of the quartz grains. Sometimes the present gipain boundaries corresponds with ths linear arrangement of the inclusions. The sulphides are rather uniformly distributed throughout the Abundant rock but are more Ain, and have a distinct relationship to, the quartz. They occur as i f they were "molded'* around the quartz grains, rarely show traces of crystal faces and, therefore, reflect the dimensional orientation of the quartz grains. A very small amount of carbonate is closely associated with the sulphides though at times i t i s found with the amphiboles. A few grains of hornblende are also partly chloritized. The grunerite is not always present and some thin sections contain only the blue-green hornblende. Where grunerite is absent the hornblende shows no tendency towards radial structures and the laths show a strong inclination towards orientation parallel to bedding. The quartz is quite clear and has few dust inclusions but the distribution of the pyrite is the same as that already described. The mineral relationship is somewhat different where the rock i s criss-crossed by quartz veinlets. The amphiboles are absent but their . pre-existence is quite apparent. The radial clusters are present but are now composed of a chlorite. Under crossed nicols the radial arrangement of the original mineral can be clearly seen and the alteration has obviously be.en/mfc£/i/»Hfce for wfee.e. The quartz veinlets are more numerous than i s (41) apparent i n the hand specimen. The quartz of these veinlets is quite clear in contrast with the quartz in the rest of the rock which is f u l l of dust • inclusions. Where the veinlets are closely spaced the intervening quartz is very fine-grained and so f u l l of dust inclusions as to give i t a dark grey appearance. As a matter of fact, the quantity of dust inclusions i s a rough index of the degree of alteration. In most cases, however, the veinlets cannot be distinguished under crossed nicols except by the line of inclusions bordering i t ; Quartz grains form both part of a veinlet and part of the original rock. .The quartz of the veinlets i s also strained. It appears, therefore, that considerable recrystallization followed the introduction of this late quartz. Where the veinlets are wide they contain appreciable sulphides which consist of pyrite and sphalerite. A carbonate and phlogopite are also present. The quartz is i n the form of prismatic and hexagonal grains oriented with the long dimension perpendicular to the wall of the vein so that.the crystals have obviously grown inwards from the vein wall. (Fig© 17) It usually .occupies one side of the veinlet and the sulphides the other side, but sometimes the latter are in the centre of the veinlet and have therefore crystallized last. The pyrite is more abundant than the sphalerite but thtg are intimately associated. The two w i l l run along as short veinlets with the intervening distance occupied by the carbonate. The phlogopite is closely intergrown with the pyrite. It i s colorless to light brown, slightly pleochroic and uniaxial negative. The quartz veinlets sometimes contain a f a i r amount of chlorite and. hardly any sulphides are present in the country rock outside of the quartz veinlets i n the thin sections studied. Where the quartz pebbles occur the surrounding'rock i s composed of the grunerite-hornblende intergrowth, and quartz. I t is not intended to (42) Fig* 17 - Quartz-Pyrite veinlet, Note shape of quartz grains i n veinlet X 25 describe the "pebbles" here i n detail but they cannot be entirely ignored in discussing the shear zones. The quartz in the pebbles is relatively coarse-grained but is strained and grains are elongated parallel to the long axes of the pebble. The quartz is clear but contains streaks of the amphibole and a small amount of pyrite grains molded around the quartz grains (Fig. 18 and 19). Occasionally the pebble has been fractured at the edges and pyrite introduced i n the fracture (Fig. 20) but most of the pyrite forms a rim around the pebble (Fig. 21). A f a i r amount of sphalerite with a carbonate and occasionally phlogopite, are associated with the pyrite. Where garnets occur, the rock close by is very fine-grained, dust inclusions are abundant and may have a streaky arrangement. The amphibole clusters are almost entirely grunerite and the end of the fibres project ( 4 3 ) Pig, 18 - Pyrite in quartz pebble X 25 Fig, 19 - Same as 18.Grossed nicols X 25 Fig, 20 - Pyrite introduced in fracture at edge of pebble X 25 Fig, 21 - Sulphides rimming pebble quartz on the l e f t , amphiboles on the right X 25 (44) i-n the garnet crystals. Some biotite may have formed and is rimmed by magnetite inclusions. Chlorite f i l l s fractures i n the garnet. Mineral grains around some of the garnets have a streaky arrangement and have been deflected a l l i n the same direction indicating that the garnet crystal has been rotated. The relationship between pyrite and sphalerite has already been indicated". Where arsenopyrite occurs i t is intimately associated with the pyrite and is intergrown with i t . The larger arsenopyrite areas are some- times rimmed by pyrite but the reverse also occurs, Chalcopyrite occurs as small grains adjacent to larger pyrite grains while sphalerite occurs as small blebs both i n the pyrite and arsenopyrite. This relationship indicates that a l l the sulphides are contemporaneous, Pyrrhotite was not observed in thin section. Wall Rockt Typical wall rock alteration consists of garnet, biotite, chlorite, quartz and some magnetite. The garnet belongs to the pyralspite group and approaches the composition of almandite, the iron garnet. Its index is greater than 1,74 and i t gave a specific gravity of 4.10, However, i t s true gravity w i l l be a b i t higher since i t contains considerable impurities i n the form of quartz and chlorite. The garnet grains obtain diameters of 1/4" but most of them are between l / l 6 and 1/8 inch across. They are highly fractured and veined by chlorite (Fig. 22) and numerous quartz inclusions give i t a poeciloblastic structure. The centre of a chlorite veinlet cutting a garnet grain i n two is sometimes occupied by clear quartz. The'quartz inclusions show some- times a tendency to be elongated and oriented in the same direction, while at, other times they form a crude hexagonal pattern indicating successive Fig, 22 - Garnets veined by chlorite. Dirty grey is biotite. X 25 stages of growth. The biotite forms large irregular plates between the garnets. Sometimes they are curved around garnet grains and exhibit undulating extinction. It occasionally forms small embayments into the garnet and appears to have formed at the expense of this mineral. The biotite i s i n various stages of alteration to chlorite and contains quartz and magnetite inclusions. The latter are often arranged along the cleavage planes of biotite. Chlorite f i l l s the fractures i n the garnet or forms a ring around i t . A l l of this chlorite has the anomalous blue interference color of penninite. The quartz occurs as small round inclusions in a l l the other minerals and gives the rock a distinct sieve structure. In part i t is (46) the result of incomplete reaction and failure to be absorbed by the garnet and biotite but a large proportion is also the result of the break down of these two minerals by chlorite, Where alteration has progressed to an advanced stage, the rock i s almost entirely penninite. Small residuals of garnet are s t i l l present but the biotite is completely lacking. Under crossed nicols the chlorite appears as a pseudomorph after biotite and often the magnetite has arranged i t s e l f around the original borders of the biotite flakes (Fig. 23) Fig. 23 - Biotite completely replaced by chlorite. X 70 but the quartz has segregated i t s e l f into large irregular patches. This last mineral is much Jess abundant and has largely been removed from the rock. A thin section made from coarse-grained biotite garnet rock taken from the centre of the zone presented an interesting assemblage of minerals. The garnet has been fractured and veined by chlorite, but along (47) some of these fractures thin laths of grunerite have formed and project into the garnet forming rosettes. Some beautifully twinned rhombit'̂ of grunerite have formed. Considerable biotite has developed and i t contains numerous laths and twinned rhombs of grunerite. S t i l l another sample from a similar locality shows the introduction of sulphides along the chlorite veinlets i n the garnet (Fig. 24). The Fig. 24 - Sulphides i n garnet X 70 biotite is absent and instead the blue-green hornblende occupies the space between the garnets. Sulphides associated with a l i t t l e carbonate are f a i r l y abundant in the hornblende and tend to rim the garnet grains. In one instance a l i t t l e bit of apatite has formed with the sulphides. The Mineralizing Solutions Means of Accesst It is quite obvious that the shear zones afforded channelways for the mineralizing solutions. The problem is rather at what stage of the (48) shearing were the solutions introduced. Shearing is a process that takes place by stages and extends over a long period of time; by that i s meant that rupture of the rock occurs when the shearing stresses exceed the shearing strength of the rock. However, as rupture takes place, stresses are relieved and have to be built up again before rupture can again take place. The openings thus produced in the rock are infinitesimal i n size and the fracturing is expressed as innumerable, closely spaced, more or less parallel surfaces of dis- continuous rupture. The movement of solutions under these conditions would be slow hence i t is l i k e l y that the period of mineralization lasted during the whole duration of shearing. It is possible that much of the mineralization occured after the shearing but a l l the quartz i n the shear zones is strained and the quartz pebbles which are of hydrothermal origin have been deformed by shearing stresses. There are no fissure veins i n the zone and sulphides are finely disseminated or replace, the bedding but in some places small fractures providing an easier means of access for the solutions and these fractures now appear as quartz-sulfide veinlets. Nature of the Solutions; The ferriferous nature of the solutions is Unquestionable, Of the sulphides, pyrite makes up 98$, grunerite is an iron rich amphibole . and hornblende i s f a i r l y high i n iron. The chief wall-rock alteration product is the iron garnet aAAranUHe, i t seems, therefore, that consider- able iron must have been introduced for the formation of these various minerals. The solutions were undoubtedly siliceous, but how much of the s i l i c a was derived from the magma source and how much came from the quartz. (49) already present i n the sediments i s d i f f i c u l t to ascertain. The fluids contained also a fai r amount of volatile constituents. Water acted as the chief solvent but i t was aided i n this role by the presence of sulfur and small amounts of carbon-dioxide. The apatite and phlogopite mentioned above, and their close association with sulphides suggests the presence of small amounts of phosphate and fluorine. Finally the solutions were hot, hot enough to heat the rock to temperatures that would permit the formation of the various silicates praticularly garnet. A l l the garnet is isotropic and smoky quartz loses i t s color at 300°C so that crystallization occured between 300°C and 800°c - probably at about 500°C. Chemical Processes Involved; Temperatures were high and pressures great at the time of mineralization. The minerals i n the zone were in a metastable condition as a result of the shearing stresses. These conditions greatly enhanced solution and diffusion of material with the result that the rock could be easily reconstituted into new minerals. The overall composition of the rocks i n the shear zone was probably rrVfh similar to the rest of the country rock. Probably albite was present but i t has now a l l disappeared. Here we then had a l l the elements necessary for the formation of hornblende. This does not preclude the addition of soda and lime, but the fact is that the amount of horn- blende formed was dependent chiefly on the presence of these constituents in the original rock, and particularly on the amount of alumina, other- wise a l l the amphibole would have been grunerite. What was chiefly needed was the addition of iron and a medium by which diffusion could take place. The centre of amphibole clusters are usually grunerite but i t must be remembered that iron was being introduced and reacted with the s i l i c a to (50) form grunerite while the diffusion of soda, lime and alumina to these centres was slow so that hornblende formed the outer rim. The dust inclusions i n the quartz arranged i n irregular patterns testify to the bulk reconstitution of the whole rock. Nevertheless, original bedding was not always wholly destroyed but became reflected by the laminated sulphides. Of course the original rock composition varied from place to place and i n some cases only amphibole formed. As a consequence of these reactions the hydrothermal solutions became more alkaline and excess iron reacted with the sulfur, possibly H2S, to form pyrite and regenerate some water. Arsenic, zinc and copper also reacted at about the same time to form chalcopyrite, sphalerite and arsenopyrite. The wall rock alteration may be looked upon as a case intermediate between thermal and normal regional metamorphism with some metasomatism. The magmatic fluids provided the necessary constituents and raised, the temperature of the rock such as to favor the formation of garnet. An assumption must unfortunately be made and that is that the wall rock was high i n alumina but low in soda and lime. The solutions, besides producing the changes already noted i n the zone permeated the surrounding rock so that with the addition of iron the physical conditions were such as to be favorable for the formation of garnet and biotite. The fact that pressure was being constantly relieved in the mineralized zone, by shearing, but not i n the wall rock may have some bearing on the fact that almandite was formed i n the wall rock since that mineral is generally regarded as a stress-mineral. Nevertheless, one would expect some garnets to form i n the mineralized zone, and that is actually the case. Two such instances have been described. The last stages of metasomatism are manifested by the chlorite alteration, Penninite is low i n alumina and iron but high i n magnesia. (51) It seems, therefore, that i n the dying stages of metasomatism the solutions became enriched i n magnesia and attacked the biotite and garnet converting them to chlorite. This f i n a l transformation rarely went to completion and for the most part the rock is l i t t l e chloritized. Summary; Metasomatic changes resulted from hot aqeous hydrothermal solutions carrying considerable'iron. The rock affected by these solutions was already undergoing regional metamorphism so that the accession of these solutions and consequent rise i n temperature greatly f a c i l i t a t e d the process of solution and diffusion, and the addition of the iron constituent resulted i n the formation of a distinct mineral assemblage characterized by their high iron content. Source of Solutions'; The overall picture of metasomatism is never complete u n t i l a source for the mineralizing solutions is found. The obvious source i n this case is the large granite mass lying to the northeast and which we may safely assume underlies a l l the sediments i n this area. The pegmatite dykes are related to the granite and we have already noted how they are offset by the shear zones. It seems, therefore, that pegmatite injection, shearing of the sediments and introduction of hydrothermal solutions are closely related not only i n space but i n time. This is borne out by the fact that i n the portion of the No. 2 Zone which consists of disconnected lenses, pegmatite dykes cut across the sediments between the disconnected injected parts of the zone. This indicates that pegmatites were -formed over a long period of time and that the mineralizing solutions are contemporaneous with the pegmatites. It i s , therefore, concluded that both the pegmatites and the hydrothermal solutions were derived from the same source, namely (52) the granite. Classification of the Depositst The mineral deposits on the property are shear zones replacement deposits. They were formed at temperatures above 300°C and under high pressures and correspond to the !ov<sr part of the me^othermal range. (53) THE QUARTZ PEBBLES General Statement Attention has already been drawn to certain quartz structures that were referred to as quartz pebbles. A detail description of these w i l l now be given and an attempt w i l l be made to provide a satisfactory explanation for this unusual occurrence. Occurrence The quartz pebbles occur i n nearly a l l the shear zones but are more abundant i n some zones than i n others. They are most prominent i n the No. 2 Zone while No. 1 and No. 4 Zones hardly contain any at a l l . They have not been noticed outside of the shear zones so that the presence of these pebbles seems to be genetically related to those assemblages of sediments that have been shearede Description The f i r s t impression gained by the observer is that they are truly pebbles and thus part of a conglomerate horizon, but on closer examination they present certain features that are d i f f i c u l t to reconcile with this mode of origin. Generally they are e l l i p t i c a l i n shape with the longer dimension parallel to the strike of the beds. The long axis varies i n length from 1/2" to 1 l/2" and the ratio of the long to short axis i s usually about 7t5. However, they vary a good deal i n shape and sometimes are lenticular shaped with pointed ends. Several of these lenticles often coalesce and form a veinlet that appears to have been pinched at regular intervals. At other times they have no distinct shape and are only quartz splashes or streaks in the rock. In some cases a group of four or five perfectly round pebbles were noted. (54) The e l l i p t i c a l ones are often rod-like down the dip and weathering has loosened them so that they can be pulled out of the rock. They then resemble fat cigars. That is not always the case, however, and the outline of the pebble down the dip may be quite irregular. Some pebbles a re ,~3 pointed at one end and blunt at the other end, while others appear to have been rotated so that they are out of line with the strike but the rotational effect may be either to the right or the l e f t . The pebbles invariably occur i n bands three to five feet wide and are strung out more or less along definite lines, but the bands do not maintain the same position throughout the zone. Sometimes i t may be near the foot-wall, at other times near the hanging wall, or i n the centre of the zone. In the No, 2 Zone they also occur irregularly scattered without any apparent preference for certain beds. Two small S-shaped drag-folds with their axis plunging almost verticaltywere also noted i n the No. 2 Zone and i n these two instances the quartz pebbles follow around the drag-fold so that the long axis of the pebbles remain parallel to the bedding, (Fig, 25) Composition and Texture A l l the pebbles consist of bluish-grey quartz having a sugary texture as though the quartz had been crushed and recrystallized. Nearly a l l contain small patches of hornblende that.have a streaky arrangement in the direction of the long axis of the pebble. A few contain sparsely disseminated pyrite. On the weathered surface the hornblende and pyrite have been removed so that the pebbles have a pitted appearance, MicroBCopio Examination In thin section the stress effects on the quartz of the pebbles are quite evident. The quartz grains exhibit undulating extinction and strain shadows and have a 2V as high as 20 degrees. The grain boundaries (55) Fig. 25 - Small S-shaped drag-fold in No. 2 Zone. Note how pebbles follow around drag-fold are highly sutured and trains of minute flu i d inclusions cutting across several grains are quite common. The quartz is much coarser-grained than that of the rest of the zone rock. The grains are much elongated in the direction of the long axis of the pebble but the average width of a grain is about l / 5 0 " . Although strain shadows have a tendency to run parallel to the longest dimension of the grain, they also trend at various angles across i t . There i s no definite boundary between the quartz pebbles and the rest of the rock, the quartz seems to form a matrix i n which the amphiboles and sulphides are almost entirely absent i n certain e l l i p t i c a l areas. However, just at the borders of the pebbles the quartz becomes fine- (56) grained and grades sharply into the amphibole rock of the zone. The sulphides that generally rim the pebbles may be just inside the pebble i n the quartz or just outside i n the amphibole rock. They consist of pyrite and sphalerite; a l i t t l e carbonate, and i n two instances phlogopite, were noted. The sulphides occur as irregular disconnected veinlets or as individual grains molded around the quartz grains (Fig. 21, P. 43) More pyrite and hornblende occurs dispersed throughout the pebbles than is apparent in the hand specimen. They are present as small fine grained clusters or streaks with the pyrite molded around the quartz grains. (Fig. 18 and 19*, P. 43). In places a f a i r amount of dust inclusions (magnetite) accompany the pyrite. One case was noted in which a quartz veinlet containing considerable pyrite connected two pebbles. Origin It i s quite evident that these quartz structures are not pebbles in the sense that they form part of a conglomerate formation. To begin with, i f they were, why are they a l l composed of quartz? One would expect to find some variation i n their composition, possibly granite or f e l s i t e pebbles. Their manner of occurrence i n these beds violates a l l principles of sedimentation. The beds i n general are well sorted so that the pebbles should be concentrated i n the bottom of the beds, but there is no such tendency. You might expect too variations i n grain sizes of the sediments that contain the pebbles from the finest greywacke to the largest pebbles, : but such i s not the case. The fact too that the "conglomerate bands" i n the shear zones do not maintain the same position but occupy different stratigraphic horizons along the strike of the zone is positive evidence against the theory of a (57) sedimentary origin of the pebbles. Finally the indefinite shapes of some of the pebbles, their tendency i n many instances to form veinlets, and the lack of sharp boundaries i n thin section, a l l point to a different mode of origin. Clearly, some other solution must be sought to account for them. The presence of sulphides, molded around the quartz grains, and of hornblende i n the pebbles, and the lack of a definite boundary between the pebbles and the enclosing rock, a l l indicates that metasomatism has played an important part i n their formation. The problem is what physical conditions prevailed at the time of their formation that would have the effect of producing pebble-like structures even though they are the result of replacement. Enough has been said about the shape of these quartz pebbles and of the quartz grains comprising them to indicate that they express some kind of linear structure. During the process of shearing, we have mentioned how innumerable shearlike openings, infinitesimal in size are developed, but the rock, even though i t were quite uniform i n composition, would not yield to the shearing stresses to the same degree throughout the zone. Some of the shear-like openings would be larger than others, resembling small fissures. These small fissures became f i l l e d by mineralizing solutions and the pressure transmitted by these solutions caused some bulging or dilation of the fissures thus enlarging the openings. At the same time replacement of the fissure walls took place. A glance at Figures 26 and 27 w i l l show how the pebbles resemble a great deal small dilated fissure veins. Some of them are strung out like a string of sausages while others are arranged slightly en echelon. The f i n a l shape of the pebbles, however, was determined by the shearing stresses the rocks were subjected to. These stresses caused a Fig. 26 Quartz pebbles. Note how several pebbles tend to coalesce, also distortion of bedding around some of the pebbles Fig. 27 - Quartz pebbles. Note how they tend to occur along definite bands. stretching of the pebbles. Quite often the pebbles are striped and streaked parallel to the maximum elongation. Sometimes the pebbles we slightly rotated and this caused a deformation of the beds around the pebble. One such pebble well illustrates this i n Fig. 26, P. 58. .(60) THE OCCURRENCE OF GOLD • Assay results from diamond d r i l l cores indicate that gold oontent is very erratic. For this reason bulk sampling of an open cut was under- taken. An open cut 340 feet long, averaging 10 feet wide and 2.5 feet deep was excavated at the southern end of No. 2 Zone. A detailed geologi- cal map of the open cut was made and assay results superimposed on this map. (Map 2) In a broad sense the best gold values are with the laminated sulphides and in the rusty fractured sediments high i n sulphides. The highest values too seem to be where the zone is widest. Very l i t t l e visible gold occurs i n these zones. It can be panned from the rusty weathered surface material and i t was noted on two occasions in d r i l l cores. In both cases the gold occurred i n the bluish smoky quartz. Unfortunately, gold was not observed in any of the thin sections studied by the writer. Since the quartz and sulphides are closely associated, i t is probable that gold is closely related to both. (61) STRUCTURE The rocks of the area are apparently part of the east limb of a syncline. The sediments trend i n general N 55°W and dip steeply to the southwest. The strike, however, changes direction i n the southern part of the property and swings to a northeast "direction. The horizontal distance across the strike increases as you proceed southward. Certain argillaceous beds exposed on claim L6l are not found to the north along the strike of the beds. Drag-folds, Z-shaped i n plan, occur i n the assemblages of thinly- bedded sediments. The axes of these folds plunge about 85° to the north- west; obviously they were formed by nearly horizontal movements that .carried the northeast sides southeast. Two small S-shaped drag-folds i n the No. 2 Zone have already been mentioned in connection with the quartz pebbles. The. movement which produced the Z-shaped drag-folds is similar to that along the shear zones, since the displacement along the zones i s , in a l l cases ,right-handed. The dip of the beds varies between 7 0 ° to the southwest and v e r t i c a l , except at the southern end of No. 2 Zone where dips are 70°NE. Two prominent sets of joints are developed. One strikes i n a general N-S direction while the other strikes about N 45°E.. Both dip steeply or verticals (62) CONCLUSIONS The Arohean sedimentary rocks of the Yellowknife group, i n the area considered i n this thesis, suffered regional metamorphism. The grade of metamorphism corresponds to the Biotite-Zone. It is often d i f f i c u l t i n a study of this kind to draw the line between metamorphism and metasomatism. It is certain, however, that the latter process has played an important and essential role i n the production of tourmaline in the phyllite beds, i n the development of muscovite i n sediments near the granite contact, and i n the formation of the haematite bands. A small amount of tourmaline is present i n nearly a l l the sediments studied and i t i s probable that the whole country rock was more or less permeated by magmatic fluids derived from the nearby granite at the time of i t s intrusion. Shear zones i n the sediments afforded channelways for mineralizing solutions and these formed replacement mineral deposits in the zones. The wall rock alteration along the zones consists of garnet and biotite partly altered to penninite. The mineral assemblage produced by the solutions is characterized by a high iron content and attests the ferriferous nature of the hydrothermal solutions. Quartz structures in the shear zones, referred to as quartz pebbles, are believed to be of hydrothermal origin. Their shapes are attributed to the physical conditions, existing i n the rocks, at the time they were formed. Small fissures i n the rock were the loci at which the "pebbles'* started to form. Dilation and replacement of the fissure walls enlarged the pebbles and the shearing stresses imparted to them their f i n a l shape* APPENDIX Thin Sections The following i s a l i s t of the more important thin sections studied by the writer: T.S. No. . 3 Rutile needles i n chlorite ti it 4 Spotted sediments n it 7 Quartz pebble »» it 12 Quartz-sulphide veinlets in zone rock tt it 15 Garnetiferous wall rock n tt 18 Typical quartz-sulphide-amphibole zone rock tt it 20 The granite it it 31 The diabase tt it 32 Sedimentary rock near granite contaot ti it 38 Garnetiferous-biotite-amphibole zone rock tt tt 39 Quartz pod with f l u i d inclusions t * it 44 Wall rock altered to penninite it it 46 Amphibole rock near iron formation II it 47 Haematite bands n it 51 The porphyry tt n 55 Crenulated sediments it it 58 Tourmalinized sediments it it 63 Garnetiferous wall rock t t » 64 Quartz pebble it it 66 Quartz pebble t t n 78 Quartz pebble The following interesting rock samples are included as part of the material handed inj Banded pegmatite The granite Pegmatite with lepidolite Haematite bands in iron formation Quartz pebbles (6 specimens) Garnetiferous wall rock Garnetiferous wall rock with coarse biotite Zone rock (sulphides and garnets) 2 specimens Laminated sulphides with quartz pebble BIBLIOGRAPHY Cloos, E., Gustafson, J. K., Harker, A., Lord, C. S., Tyrrell, G. W., Van Hise, C. R. & Bayley, W. S. Van Hise, C. R., Winchell, A. N., Lineation. Geological Society of America. Memoir 18, 1946 Metamorphism and Hydrothermal Alteration of the Homestake GoId-Bearing Formation. Ec. Geol., Vol. 28, 1933. P. 123-162 Metamorphism. Methuen and Co. Ltd. 36 Essex Street W. C. London Snare River and Ingray Lake Map-Areas, Northwest Territories. Geol. Surv. of Canada. Memoir 235, 1942. The Principles of petrology. Methuen and Co. Ltd. 36 Essex Street W. C. London The Marquette Iron-Bearing District of Michigan. U. S. G. S. Monograph 28 A treatise on Metamorphism. U. S. G. S. Monograph 47 Elements of Optical Mineralogy. Part 2. Descriptions of Minerals. New York, John Wiley and Sons, Inc. M A P 2 L E G E N D R l / S T X , F f t / l C T U f t E P Z O N E p g > C K , R l f r H I N S U t P M I D E 5 Q U A R T Z O R C H I E F L Y Q U A R T Z fr4R/VETIFEROU3 R O C K W I T H Q U A R T Z A N D J O N E S U L P H J P E 5 O A R K J E T S I I V ' Z O N E R O C K . F I N E L Y L A M I N A T E D S U L P H I D E S IN MASSIVE ZONE ROCK F l W f O B A l N » , P E . N S E , O A R N E T t F C R O U J W A L L R O C K R E L A T I V E L Y U I V A L T E R E 0 Z O W R 0 C k QUARTZ PEBBLES IJVCL't/DCS AWflY RffJULTS G-REATfR THAN .llOZ H C m Z m 33 5 > z ~~ R u I s i ^ A A i i i - - - -z===== S U B J E C T S ^ E T A L L ^ _ _ ^ O L O O Y _ O F _ O N T H E N O J 3 J 2-5-^===—===== SCALE.- JT=5: IS -4-46 MAP 1 till d l t t . Ml/ l l i / i u i o . ii/t dl6 o i i dkt uiii fti& L E G E N D . SEDIMENTS- G r e y w a u K e , S l a t e , A r i c c a e . . G R A N I T E PEGMATITE-Banded PEGMATITE DIABASE DYKE FELS1TE DYKE SHEAR ZONES 3 ^ QUARTZ PEBBLES * V E R T I C A L D I P X STRIKE <f D I P H J O I N T I N G ^ & L A C I A L S T R I A E *m ^ O V E R B U R D E N i~xr* T R A I L I R O N F O R M A T I O N 0(0 ilk ML •tilt 0Ja A A N D R E W YELLOWKNIFE MINES LIMITED R o s s E LL L A K E N . W T . G E N E R A L G E O L O G Y OF T H E 2 0 C L A I M S C O M P R I S I N G T H E C R O U P SC ALE - 1" = 400' SHKiT.'Vffl DRAWN BY^~ • I D A T E - 1 5 - 4 " 1948.


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