RG 084(A) FANCAMP - HAUY AREA, ABITIBI-EAST ELECTORAL DISTRICT PROVINCE OF QUEBEC, CANADA

DEPARTMENT OF MINES

Honourable W.M. COTTINGHAM, Minister

GEOLOGICAL SURVEYS BRANCH

GEOLOGICAL REPORT 84

FANCAMP-HAUY ARES[

ABITIBI-EAST ELECTORAL DISTRICT

by

STANLEY W. HOLMES

QUEBEC

REDEMPTI PARADIS PRINTER TO HER MAJESTY THE QUEEN

1959

TABLE OF CONTENTS Pate INTRODUCTION 1 General statement 1 Location 1 Access 1 Field work 2 Acknowledgments 2 DESCRIPTION OF THE AREA 2 Topography ••• 2 Drainage 2 GENERAL GEOLOGY 3 General statement 3 Table of formations 4 Keewatin-type rocks 4 General statement 4 Andesites 5 Basalts 5 Tuffs and agglomerates 6 Basic intrusive rocks 7 Post-Keewatin sedimentary rocks 7 Post-Keewatin intrusive rocks 8 General statement 8 Muscocho stock 9 Verneuil stock 9 Eau-Jaune complex 11 Feldspar Porphyry dykes 12 Keweenawan olivine-diabase (dyke?) 12 STRUCTURAL GEOLOGY 12 General statement 12 Folding of Keewatin rocks 13 Structure of the Post-Keewatin sedimentary rocks 13 Fault and shear zones 14 ECONOMIC GEOLOGY 15 General statement 15 Nickel-copper deposits 16 Mineralogy 17 Distribution of ore 19 Tenor of ore 19 Muscocho deposit 19 Eau-Jaune deposit 21 Gold deposits 23 Mineralogy 24 Control and distribution of ore 27 Tenor of ore 27 Assay results 27

Pale DEVELOPMENT 28 BIBLIOGRAPHY 29 APPENDIX 30 ALPHABETICAL INDEX 31

MAP AND ILLUSTRATIONS

Map No. 1237 Fancamp-Hauy Area (In pocket)

FIGURES Page 1. - Sulphide deposit, Eau-Jaune lake 20 2. - Sulphide deposit, Muscocho lake 22

PLATES

I - Aligned glacial deposits on the shores of Verneuil lake. II - Muskeg growing in concentric lines and almost completely filling a small lake. III-A - Pillowed andesites in the northern part of Eau-Jaune lake. B -- Pillowed andesites showing altered centres, Eau-Jaune lake. IV-A - Well banded tuffs in central Fancamp lake. B - Agglomerate containing stretched fragments of felsic material up to 16 by 5 inches; Chico lake. V-A - Conglomerate predominantly composed of granitic boulders elongated many times their original size; Goudreau lake. B - Low hills of basalt on north side of Muscocho lake. C - Brecciated basalt cemented by brown carbonate in a shear zone in northern Eau-Jaune lake. VI-A - Parallel banding in the Muscocho stock where it is in contact with volcanics along the northern end of Muscocho lake. B - Gossan capping a massive basalt partly replaced by pyrrhotite and chalcopyrite; Central Eau-Jaune lake. C - Sulphides (chalcopyrite, pyrrhotite, pyrite) replacing gabbro intruded by a small offshoot of the Muscocho stock; northeastern Muscocho lake. VII-A - Muscocho sulphide ore. Photomicrograph. B - Eau-Jaune sulphide ore. Polished section. VIII-A - Muscocho sulphide ore. Polished section. B - Muscocho sulphide ore. Polished section. FANCAMP-HAUY AREA

ABITIBI-EAST ELECTORAL DISTRICT

by

Stanley W. Holmes

INTRODUCTION

General Statement

The Fancamp-Hauy area was mapped geologically by the writer during the summer of 1951.

The area is underlain by early Precambrian volcanic and sedimentary rocks cut by granitic rocks in the form of stocks and lesser bodies, and by basic intrusions. Keweenawan-type dykes of diabase are rare. Gold and base metal prospects give the area considerable economic interest, and several mining companies had prospecting crews here in 1950 and later.

Location

The Fancamp-Hauy area is situated about 5 miles southwest of Chibougamau lake. It is bounded by latitudes 49°30' and 49°45', and by longitudes 74°30' and 74°45'. The area is about 195 square miles in extent and includes the greater parts of Fancamp and Hauy townships, the eastern portions of Brongniart and Rasles townships, and the southern parts of Scott and Lévy townships.

Access

The area may be reached by canoe along three routes from St. Félicien- Chibougamau highway, which passes about 4 miles outside the northeast corner of the area. The easiest of the three canoe routes starts at Perron lake, Mileage 121.4 on the highway, and leads through lakes Laurent, La Dauversière, Le Royer and northward into Chevrier lake on the eastern boundary of the area. There are only two short portages on this route.

Another convenient route, somewhat shorter than the one just described, starts at Mileage 129.2 on the highway. This is a part of the old "Mistassini Route". It leads south through Calmor lake to Chevrier lake. Three portages are involved, one of which is approximately 4,000 feet long. - 2 -

A third route, almost impassable in time of low water, starts at Mileage 134.3. where the highway crosses Merrill lake. It follows a small creek for 2 miles from the southwest side of the lake. At the head of the creek, two portages separated by a small lake lead into Muscocho lake. This last portage is lâ miles long.

Transportation by air may be provided by any one of several companies with bases located on the highway at Cache lake.

Field Work

The base map, at a scale of two inches to the mile, was compiled by the Quebec Department of Mines from a map provided by the Department of Mines and Technical Surveys, Ottawa, and from stream and line surveys made by the Quebec Department of Lands and Forests. The shores of lakes and streams were surveyed for outcrops and the interstream areas were traversed at one-half mile intervals by the pace and compass method. The results were plotted on the base map.

A preliminary report on the area, P.R. 271, accompanied by a geolog- ical map at a scale of one inch to the mile, was published by the Quebec Depart- ment of Mines in 1952.

Acknowledgments

The writer is indebted to Dr. Alfred L. Anderson of Cornell University whose advice and constructive criticism were very helpful in the preparation of this report, and to Dr. J.-E. Gilbert of the Quebec Department of Mines, who mapped the adjoining area to the southeast in 1951 and whose advice and cooper- ation were also very helpful.

Efficient and conscientious service was rendered by Erwin C. Hamilton of McGill University as senior assistant, and by Gaston Caron of McGill Univer- sity, and Jean Paul Laurencelle of Ecole Polytechnique, as junior assistants.

DESCRIPTION OF THE AREA

Topography

The area lies approximately 10 miles to the west of the divide between the St. Lawrence river and James Bay basins, and has a form of topography simi- lar to that of the Chibougamau region in the northeast. The country is generally low, rolling and widely drift-covered, with numerous lakes and ponds. The only - 3 -

prominent surface features in this area are hills that rise about 150 feet above the northern and eastern shores of Muscocho lake.

A belt of low, elongate hills, composed of unstratified and unsorted till, extends from southwest of Merrill lake, along the shores of Fancamp and Verneuil lakes to the southeastern part of the area (Plate I). The hills are aligned along a southwesterly direction, parallel to the movement of the ice sheet.

The western part of the area is covered by a thick blanket of drift and is low and featureless, except for some parallel northwest-trending ridges of coarse, unsorted till. These ridges probably are recessional moraines (washboard type).

Parts of the northern and eastern shores of Muscocho lake are bounded by extensive deposits of very fine, well sorted sand, probably derived from glacial outwash. Norman (1940) has described similar but more extensive deposits in the area immediately to the north. Drainage The drainage of the area is to the northwest into James bay through the Obatogamau, Chibougamau, and Nottaway rivers.

Approximately one-quarter of the area is covered by lakes of which the largest are Muscocho, Verneuil, Fancamp and Eau-Jaune. These lakes are bounded by low, featureless shores along which are situated numerous outcrops. Most of the small lakes are shallow, with shores of morainic material. Many are being, or recently have been, filled by muskeg which usually grows toward the centre in a concentric pattern (Plate II).

GENERAL GEOLOGY

General Statement

All the consolidated rocks in the area are of Precambrian age. Much of the area is underlain by altered volcanic rocks of Keewatin type. These are associated with, and presumably overlain unconformably by, a sedimentary series varying in type from slate to boulder conglomerate. Both series are in steep isoclinal folds, are cut by faults, and are intruded by igneous rocks of basic to intermediate composition. All the foregoing rocks are intruded by granitic and dioritic types and these in turn are cut by dykes of olivine diabase.

One of the most striking features in the area is the degree of alter- ation, which has destroyed most of the original minerals and formed a varied group of secondary minerals. - 4 -

A prominent shear zone trends northeast through the centre of the area and carries some gold. Several small sulphide bodies are associated with the earlier basic intrusive rocks.

TABLE OF FORMATIONS

Pleistocene CENOZOIC Gravel, sand clay and Recent

Keweenawan? Olivine in diabase dykes

Main Intrusive Masses: Muscocho stock: granodiorite Verneuil stock: biotite granite Eau-Jaune Lake complex: diorite, quartz diorite, feldspar porphyry, hornblendite PRECAMBRIAN Post-Keewatin? Sedimentary rocks: Arkose, feldspathic tuff, slate, grit, agglomerate, boulder conglomerate

Unconformity?

Volcanic rocks: Keewatin-type Andesite, basalt, tuff, Rocks Agglomerate, gabbroic and dioritic intrusives

Keewatin-type Rocks

General Statement

The Keewatin-type volcanic rocks of this area consist of andesites and basalts with intercalated beds of tuffs and agglomerates that are typical of the Keewatin rocks of the Precambrian Shield. They may be correlated directly with rocks mapped immediately to the north (Norman, 1940) and to the east (Imbault, 1951). In effect, they are extensions of the east-west trend- ing Central (Pusticamica-Opawica-Obatogamau) belt, and the Northern (Mattagami- Waconichi) belts of Keewatin rocks, which merge in this area. The flow rocks of the area are in three main bands, separated for the most part by bands of frag- mental volcanic rocks. They belong to the same series and are therefore of the same age. - 5 -

Andesites

Andesitic flows are best exposed along the northern shores and islands of Eau-Jaune and Keith lakes, along the northwest shore of Fancamp lake and the long bays in the central part of Eau-Jaune lake. The flows are generally char- acterized by a well developed pillow structure (Plate III-A), which in the north- west part of the area is irregular and deformed and thus is of little use in top determinations. Some of the pillows are vesicular and, in a few places, have pipe-vesicles around their borders. Massive, amygdaloidal and porphyritic flows are common. In one flow in the northern part of Fancamp lake at least 30 per cent of the amygdules are filled with calcium-carbonate. The main series of flows contains little intercalated flow breccia.

Although the structure and texture of many of the volcanic rocks are well preserved, the individual mineral constituents have generally undergone ex- treme alteration, and it is doubtful whether any of the original minerals remain. Under the microscope the greater part of the rock is seen to consist of a fine feldspathic groundmass, largely altered to a felty aggregate of clinozbisite, zbisite, sericite, epidote, and chlorite. Remnants of chloritized amphiboles and small quantities of carbonates and opaque oxides,along with minute amounts of quartz, some of which is secondary, are scattered through the groundmass. The porphyritic flows are similarly altered.

The centres of some of the pillows, although consisting of essentially the same alteration products as the main rock, are partly replaced by quartz and calcite. Thus, they have a bleached appearance while the remainder of the flow is dark (Plate III-B). The bleached centres are cut by microscopic veinlets of quartz and calcite.

Basalts

Basalts generally occur less extensively than andesites in this area. They are concentrated mainly in the hills along the north side of Muscocho lake (Plate V-B). They vary from strongly schistose to massive, and weather dark green. Most of the flows have well developed pillows, some are ropy and amyg- daloidal, and some are porphyritic.

The basalts are altered to the same high degree as the andesites and are composed largely of secondary hornblende. In some places the hornblende is in turn replaced by chlorite (penninite). The feldspars have been altered to minerals of the epidote-zoisite group. Minor amounts of secondary quartz, iron oxide, and carbonate are present. Here and there traces of original flow struc- ture could be seen. On the western shore of Keith lake the basalts have been intensely sheared, giving rise to recrystallization of the hornblende and - 6 -

chlorite, and development of small garnets. A similar recrystallization (without garnet) has taken place in the contact aureoles around the different granitic intrusives.

Tuffs and Agglomerates

Fragmental volcanics are interbedded with many of the Keewatin flows but they occur most commonly with lavas of intermediate composition. Three fairly well defined bands can be distinguished. Two of these trend east-west in the northern quarter of the area, and the third trends northeasterly across the area between the Verneuil and Muscocho stocks.

The tuffs are usually light-coloured, fine-grained, and laminated, and are composed of fairly well sorted, generally water-laid material. Such rocks are abundant in the northern part of Fancamp lake (Plate IV-A) where bedding and lamination trend northeasterly along the northern contact of the Verneuil stock. These rocks show a good linear structure which is evident on weathered surfaces.

Some of the tuffs are very massive and may be mistaken for flow rocks but,on close examination, small angular felsic fragments can be seen on weath- ered surfaces. In places the massive tuffs are very coarse-grained, and perhaps should be called agglomerates, but all pyroclastics with fragments less than one-half inch in largest dimension are classed here as tuffs.

In thin section, the tuffs are fairly uniform in composition and con- sist of finely divided fragments of quartz and feldspar, the latter partly al- tered to sericite. The more basic varieties also contain as much as 50 per cent chlorite with minor amounts of biotite. The feldspars in the coarser-grained tuffs are completely altered to saussurite. Grains of chlorite and biotite are generally oriented parallel to the bedding.

Agglomeratic volcanics are widespread throughout the area. They are typically exposed on a small island in the northeastern corner of Muscocho lake. The agglomerate, with fragments up to 3 inches in length, is interbedded with basaltic flows. The fragments are cream-coloured and are conspicuous in the dark green matrix. They are fairly uniform in size and all have slightly stretched parallel to the regional trend.

Coarse agglomerate approximately 2,500 feet thick is well exposed along the southern shore of Chico lake, and the northern end of Fancamp lake. On the shore of Chico lake the fragments, standing out in striking contrast to the much darker groundmass, are well rounded and up to 12 by 5 inches in size. They have been stretched to several times their original length (Plate IV-B). - 7 -

Most of the coarse fragments are of an intermediate composition, with a mineral assemblage very similar to that of the tuffs.

Basic Intrusive Rocks

Basic intrusive rocks are abundant in the Keewatin-type formations. In general, they are roughly of tabular form and are elongated in easterly directions parallel to the regional trend of the intruded rocks.

The various basic rocks have a considerable range in composition, but for ease of discussion they are grouped as gabbroic and dioritic types. Many of them probably are related to the various associated flow rocks, and, in general, it is difficult to distinguish between the two types.

The intrusive rocks are massive except where localized shearing has changed them to a talc-chlorite schist. They are talcose and, in part, mottled white and green, on the fresh surface, light to dark brown weathering and medium-grained.

The less altered dioritic rocks are composed of 40 to 50 per cent hornblende. In the more altered types the hornblende has been chloritized in part or in whole to penninite, the fibrous blue variety of chlorite. The feld- spars are also altered to a mass of secondary minerals, namely: zoisite, clinozoisite, epidote, and sericite. Some opaque oxides and small amounts of secondary quartz are also present. North of Eau-Jaune lake one of the dioritic bodies is replaced in part by brown carbonate, which is probably iron-rich calcite.

The gabbros contain 50 to 60 per cent pyroxene which shows various stages of alteration to chlorite and secondary amphiboles. In some places, although alteration is complete, the original outlines of the pyroxene crystals remain. The feldspars are invariably changed to secondary minerals which also preserve the original crystal outlines. Small aggregates of quartz with vary- ing amounts of opaque oxides are present interstitially.

Post-Keewatin Sedimentary Rocks

Post-Keewatin sedimentary rocks underlie the northeastern part of the area, and appear to be the southern extension of the Opemisca series, mapped by Norman (1940) to the north. Also, similar rocks outcrop immediately north of Fancamp lake.

The rocks consist of feldspar-rich tuffs, arkose, boulder conglomer- ates, agglomerates, grit, dark shales and minor interbedded lava flows. The - 8 -

shales and grit weather white or various shades of grey.

The feldspar-rich rocks are generally medium-grained and occur in massive beds up to 20 feet thick. Those of a finer grain occur locally in thinner beds, in one of which cross-bedding was observed. The high feldspar content gives the rock an arkosic appearance. Small pebbles of basic and felsic materials are common, and stand out in relief.

The arkoses proper are composed of large angular to sub-angular fragments of plagioclase and minor amounts of quartz in a very fine matrix of feldspar and quartz with some biotite, secondary epidote, chlorite and uralitic amphibole. The arkosic rocks in the Fancamp Lake area are more quartzose than those in the northern band and show much sericite where sheared.

The boulder conglomerates (Plate V-A) occur in beds up to 30 feet thick intercalated with beds of other sedimentary rocks. The boulders are com- posed of granitic, basic, and felsic materials and are contained in a fine- grained tuffaceous-like matrix. Some of the granite boulders are 18 inches long, being stretched to many times their original length. Thin sections reveal that the granite boulders contain augens of fractured quartz in a finely crushed groundmass of saussuritized feldspars and secondary amphibole, with a tendency to parallel orientation. The pebbles of basic rock are basaltic in composition and consist of chlorite and biotite with minor amounts of secondary amphibole in a finely granulated matrix of quartz and feldspar. Some carbonate is present. The matrix of the conglomerates is very similar in texture and composition to that of the arkoses.

The agglomerates are thickly bedded and are difficult to distinguish from the conglomerates especially where stretching has taken place. Also, apart from containing more felsic fragments, they are very similar in appearance to the Keewatin-type fragmental rocks.

The black shales and light grey grits crop out in thin, finely banded beds. They were observed only in the area immediately north of Fancamp lake.

A light weathering, massive, fine-grained rock, seen along the portage northeast of Muscocho lake, is highly altered, but is thought to be a rhyolitic flow or acidic tuff. It consists of finely divided quartz and feldspar with abundant clinozoisite, chlorite, carbonates and minor sericite.

Post-Keewatin Intrusive Rocks

General Statement

The Keewatin rocks are cut in various parts of the area by intrusive - 9 - bodies of post-Keewatin age. These include the Muscocho granodiorite stock; Verneuil granitic stock; the Eau-Jaune complex, which is essentially a mass of quartz-diorite with numerous related facies; and granitic, pegmatitic, aplitic and porphyritic dykes of various ages. A small body of diabase, possibly of Keweenawan age, also occurs in the area.

Muscocho Stock

The Muscocho stock,some 10 square miles in extent, is situated near Muscocho lake. Outcrops are abundant along the southwestern shores of the lake and in low hills one mile south of the northern arm of the lake.

The rock is a medium-grained pinkish-grey granodiorite. It is very uniform in composition, and consists of 40 to 50 per cent albite-oligoclase, 10 to 15 per cent hornblende, and 25 to 30 per cent quartz. The albite-oligoclase has been extensively altered to sericite and, to a lesser degree, to zoisite. Perthitic feldspar is present in the central part of the stock, where it makes up 15 to 20 per cent of the total feldspar content. The perthite is fresh and appears to have crystallized much later than the other minerals. Hornblende. some of which is altered to chlorite, is particularly abundant in the marginal facies of the stock, locally increasing to 30 per cent. It is interstitial to, and also present as small blebs in, the other minerals. The interstitial quartz contains dust-like inclusions. The accessory minerals include epidote, sphene, zircon, opaque oxides and minor amounts of a carbonate. The zircon is particu- larly abundant in hornblende.

The granodiorite stock is concordant with the schistosity of the vol- canics, and the contact between the two rocks is relatively sharp. In general, the volcanics bordering the granite are partly recrystallized and are converted to hornblende schist. The contact, however, is transitional where the stock is bordered by a band of acid tuffs on the east shore of Muscocho lake. There the granitic rock passes gradually into the tuff through an intervening tuffa- ceous zone impregnated with phenocrysts of feldspar. The feldspars have well defined crystal outlines and are completely altered to clinozoisite.

On a small cliff just north of Muscocho lake (Plate VI-A), and close to the volcanics, segregation of hornblende crystals has produced crude bands about 4 inches wide in an 8-foot zone of granodiorite. The bands strike to the east for about 75 feet. This structure has not been observed elsewhere.

The granodiorite contains many inclusions of greenstone partly re- crystallized to a fibrous amphibole with epidote, chlorite, sericite and minor amounts of quartz and feldspar.

The Muscocho stock displays two well developed sets of steeply dipping - 10 -

joints, one of which strikes northwest and the other,to the northeast. Primary, gently dipping joints with a northwest strike are prominent in the centre of the stock. Most of the joint surfaces are covered with a thin coating of quartz or feldspar.

Small dykes of aplitic and pegmatitic material are common within the borders of the stock. Also many dykes of granite and feldspar porphyry cut the rocks surrounding the stock. Small epidosite veins, up to one inch wide, are common along the contact with the greenstones.

Verneuil Stock

The Verneuil stock underlies about 25 square miles in the southeastern part of the area, and is exposed in scattered outcrops along the shores of Verneuil lake and on several islands in Fancamp lake.

The stock is composed of quartz-biotite granite. It is light grey and medium-grained to massive, with a composition that is farily uniform, being 50 to 60 per cent albite (Abep-Abss), 20 per cent biotite, 25 to 30 per cent quartz, and containing minor amounts of microcline. The albite is in stubby crystals which have been much altered to sericite and, to a lesser extent, to epidote and clinozoisite. Unaltered microcline, most abundant in the centre of the stock and absent in the marginal facies, is interstitial to the other minerals.

The biotite, most of which is green, but some brown, contains zircon crystals surrounded by pleochroic haloes. The quartz is clouded and is inter- stitial to minerals other than microcline. The microcline which penetrates and embays the quartz is of late crystallization. Grains of sphene are plentiful.

In Teck bay the granite has inclusions of partly digested greenstones which weather out to leave cavities in the rock.

Except for its northern boundary, the Verneuil stock is circular and concordant with the surrounding country rock. On the north, the emplacement of the granite was controlled by a pre-intrusive fault.

The stock is cut by prominent steep joints, some of which strike north and some,northeast. Most of the joint surfaces are covered by thin coatings of an aplite or pegmatite.

Dykes of feldspar-porphyry and granite, derived from the stock, cut the surrounding rocks. A few small bodies of aplite and barren quartz occur in the body itself. Eau-Jaune Complex

The Eau-Jaune complex underlies approximately 10 square miles at the southwestern part of the area and is exposed mainly on islands in Eau-Jaune and Irene lakes. The boundaries of this intrusion are very indefinite, espe- cially on the east where it appears to merge with a broad contact zone of meta- morphosed volcanics.

The term "complex" is used because of the considerable variation in appearance and composition of the rocks involved. For the most part it is es- sentially massive quartz-diorite in which the quartz content ranges from 0 to 25 per cent, the quantity increasing with the grain size. Some varieties are rich in amphibole. Textures are either coarse grained in the quartz-rich varieties or fine grained and sub-ophitic in the dark, quartz-poor varieties. Porphyritic and aphanitic facies are common.

The fine-grained facies and the finely divided groundmass of most of the "porphyritic" facies consist of epidote, sericite, altered feldspar, chlorite and some carbonate. This fine material may represent reconstituted and recrystallized volcanics. The "porphyritic" facies generally are best developed near the outer margins of the complex. The phenocrysts are as much as an inch long and consist of feldspar which has been completely altered to clinozoisite.

The quartz-diorite consists of 40 to 50 per cent oligoclase-andesine (An27-An32), 35 per cent hornblende, and up to 25 per cent quartz, together with minor alteration products. The feldspar occurs in well shaped crystals which are generally completely masked by secondary minerals (epidote-zoisite group). Albite and carlsbad twinning is retained in some of the crystals. The hornblende, originâlly green, is almost completely replaced by chlorite. The hornblende in the amphibole-rich facies of the complex is fresh and unaltered; locally it makes up 80 per cent of the rock. Quartz, and minor epidote, are the only minerals in the interstices of the feldspar and amphibole grains. The quartz is clear and appears to have been introduced between the feldspar crys- tals, without corrosion or embayment effects. Thus the feldspar crystals have very sharp outlines.

The Eau-Jaune complex is thought to be the contact zone of a deeper mass of granitic material. This theory is supported by the manner in which the composition of the complex varies from place to place, and by the presence of numerous large remnants of recrystallized or partly assimilated country rock within the mass. It is possible that the complex is related to the Muscocho stock, not only because of their proximity, but also because of the striking si- milarity in their contact facies. - 12 -

Feldspar Porphyry Dykes

Dykes of feldspar porphyry are numerous, especially in areas marginal to the granitic masses. Most of them were formed by injections of magma, but some appear to have evolved from the replacement of the country rock, directed along the schistosity. These dykes are generally less than 5 feet thick.

On the weathered surface well formed feldspar phenocrysts stand out conspicuously in a dark, fine-grained groundmass. The phenocrysts are composed of plagioclase feldspars which have been completely altered to minerals of the epidote-zoisite group. The groundmass consists of an aggregate of quartz and altered feldspar with patches of chlorite, secondary amphibole and minor amounts of sericite and carbonate.

Keweenawan Olivine-Diabase (Dyke?)

Olivine-diabase is well exposed along the shores of a small bay in the northern part of Eau-Jaune lake and on some islands 12 miles to the east. These exposures are fairly large and may be part of one large dyke, or of a body of irregular outline.

The olivine-diabase is a medium- to fine-grained, dark grey, massive rock, locally sheared and broken by joints. The oph•itic texture, apparent on the weathered surface, serves to distinguish the olivine diabase from the finer grained dioritic facies of the granitic intrusives.

The rock consists of 55 to 65 per cent labradorite (An50 to An55), 25 to 30 per cent augite, 5 to 10 per cent olivine, and minor amounts of biotite and secondary minerals. The feldspar crystals are characteristically lath-shaped and have been partly saussuritized. The augite is violet-brown and in large grains which tend to wrap around or engulf the feldspar crystals. The olivine is remark- ably fresh and forms irregular grains commonly mantled by green biotite. Ilmenite and leucoxene are present in small amounts.

STRUCTURAL GEOLOGY

General Statement

The rocks have been subjected to complex folding and faulting, so,as a result their relationships are difficult to decipher. Folds are the most evident structural features. The regional trend of all rocks is to the east or north- east. Dips are steep to vertical. Zones of shearing extend through the area and some of these may represent major faults. Quartz veins are common along most of these zones; they are described in the section on economic geology. - 13 -

Folding of the Keewatin Rocks

The schistosity and bedding of the volcanic rocks conform closely to the regional trend and diverge only near the borders of the intrusive masses. Such divergence is especially well shown around the Muscocho stock.

The belt of volcanics to the north of Muscocho stock may form an anticline that plunges gently to the east. The fold axis would trend eastward and then bend southeast around the north end of the Muscocho stock. The anti- cline is suggested by numerous top determinations in the pillowed flows, and by the presence in the upper part of the Keewatin assemblage of tuffs and agglom- erates intercalated with andesitic flows.

Also, the Muscocho stock may be on the nose of an easterly plunging syncline, which may be the westward extension of the one mapped by Imbault (1951) immediately to the east. The apparent southern limb consists of a thick assem- blage of pillowed basalts which lie immediately south of the stock with their tops facing to the north. The northern limb would be a part of the anticline described above. Dips on the nose of the syncline indicate that it is plunging steeply to the east. However, the plunge has been exaggerated locally by the forceful intrusion of the stock.

In the southern and west-central parts of the map-area the structure is more complicated and the lack of good exposures makes it impossible to work out details of the folding. The intrusion of the Eau-Jaune complex has disrupted the trend of the volcanics, but it appears to be to the northeast in general.

Structure of the Post-Keewatin Sedimentary Rocks

Although this series of sedimentary rock is nowhere observed in contact with the Keewatin volcanics, it appears to be separated from the volcanics by a pronounced unconformity. This unconformity is marked by numerous lenses of boulder conglomerate up to 30 feet thick lying immediately above the volcanics. The boulders are of rock types very similar to types within the older Keewatin rocks and were probably derived from them.

The structure of the Post-Keewatin sedimentary rocks east of Trentholme lake generally corresponds to that of the volcanics to the south. The strikes are generally east or slightly south of east, and the dips, steep to vertical.

There is evidence that this group of rocks forms the southern limb of a syncline. Along the south shore of a small lake 12 miles northeast of Erwin lake, cross-bedding in finely-banded arkosic rocks shows that the beds face north. Here, as well as at the southern end of Trentholme lake, the stratigraphic succession - 14 - from south to north is as follows: conglomerates with boulders up to 18 inches in diameter; agglomerates with fragments of rock from 3 to 10 inches long; and medium- to fine-grained arkoses. This sequence of strata also suggests that the beds face to the north. Furthermore, the sedimentary rocks appear to be on the northerly dipping limb of the anticline to the south, described as above. Mawdsley and Norman (1935) have shown that the sedimentary rocks occurring in the continuation of this belt to the north commonly lie in narrow synclinal basins upon the older Keewatin erosion surface. The belt in the present area may lie in a similar type of trough.

The small band of sedimentary rocks north of Fancamp lake appears to be interfingered with the underlying volcanic rocks. This relationship suggests that the sedimentary rocks may be in part Keewatin and in part Post-Keewatin, and that the contact between the volcanics and the overlying sedimentary rocks is gradational. This is partly confirmed by the absence of boulder conglomer- ates and by the presence of more Keewatin-type lavas than in the sedimentary rocks just described. This relationship is also apparent along the eastern out- let of Obatogamau river north of Fancamp lake. There the banded, light coloured arkosic rocks and dark shales are in contact with Keewatin-type greenstones. On the other hand, it is possible that the interbedded greenstones are not Keewatin in age and that the assemblage is a distinct group lying unconformably on older Keewatin rocks.

Faults and Shear Zones

A fault of large displacement, the Fancamp Lake fault, strikes south- westerly across the south-central part of the area. This fault is clearly de- fined north of Fancamp lake where signs indicate that the rocks have undergone intense movement. At Baker lake the fault is indicated by the abrupt termina- tion of several basic sills striking northwest against a band of tuffs striking northeast. From Baker lake the extension of the fault southwest is marked by the alignment of several small lakes. The fault may extend southwest of the area to a broad zone of shearing along the Opawica river.

Exposures on the islands in Fancamp lake show that the fault there consists of two nearly parallel lines of fracturing and shearing. These lines join on the western side of the lake and continue southwest as a single break.

The fault lines are marked by intense shearing, zones of brecciation, mylonitization, dragging and topographic lineation. These fault zones have permitted the introduction of much iron-rich carbonate material, which,in places, has weathered to a rusty porous material. The fractured rocks also con- tain quartz veins with pyrite and, locally, gold.

This fault, as mentioned previously, has controlled the location of - 15 -

the northern boundary of the Verneuil stock. Apparently the granite took ad- vantage of this zone of structural weakness with the result that the northern side of the stock appears to have been cut off by the fault. The granite is unfractured along the contact with the highly sheared tuffs.

In general, the less competent tuffs appear to have been more sus- ceptible to deformation than the other rocks in the area; consequently, they have localized the main zones of movement. The tuffs failed mainly by shearing along the strike, accompanied by local fracturing and crumpling. On several of the islands in Fancamp lake they have been pulverized to fine-grained breccias and mylonites.

The Fancamp Lake fault is a possible extension of the Taché Lake fault of the Chibougamau district to the northeast. The country adjacent to and between these two faults should be very favourable for prospecting.

Another zone of movement, parallel to the Fancamp Lake fault, is lo- cated along the Obatogamau river just below Muscocho lake. Here, a wide zone of sheared and brecciated basalt, cemented by brown carbonate, strikes northeast. Although the fracturing was observed at only one locality, it may belong to a fault of major magnitude.

Similar breccia (Plate V-C)also occurs at the outlet of Eau-Jaune lake. This breccia,locally, is more than 50 feet across. It strikes northerly, and has been observed at several places for a distance of several thousand feet. This may be a fault of considerable magnitude also, but the scarcity of outcrop makes it difficult to trace.

Numerous small shear zones occur throughout the area, and conform gen- erally with the regional trend. Openings are usually filled with barren-quartz carrying some pyrite.

ECONOMIC GEOLOGY

General Statement

Crossed by one of the main water routes of the region (Obatogamau river), the Fancamp-Hauy area has been visited by prospectors for almost 40 years. The first extensive work in the district was carried on in 1936 by Noranda Mines and McKay (Quebec) Exploration, Limited. These organizations ex- plored several copper- and nickel-bearing sulphide deposits in the central Eau-Jaune Lake area, but the work did not uncover deposits of sufficient size, and active exploration ceased.

During the period 1949-51 the area received renewed attention, largely - 16 -

as a consequence of the gold rush into Queylus township in 1949 and into La Dauversiére and Rohault townships in 1950. Since then, most of Fancamp and Hauy and parts of Brongniart, Rasles, Scott, and Lévy townships, all of which lie west of Queylus, La Dauversiére and Rohault townships, have been staked. The main results were that some gold discoveries were made just west of Fancamp lake by Teck Exploration Company, and base metals at Muscocho lake by Noranda Mines. However, productive mines have not yet been developed.

Much of the area is timbered or covered with a deep mantle of drift, so that prgapecting is difficult and expensive. Nevertheless, the recent con- struction of the Chibougamau highway has improved the accessibility and has served to stimulate interest in the area and in the general region.

The district has two kinds of mineral deposits of particular economic interest, namely, nickel-copper and gold. These deposits are quite dissimilar and apparently represent two entirely different types of mineralization. The nickel-copper deposits occur as sulphide replacements; the gold,as fissure and fracture fillings along with tourmaline, quartz and ankerite.

The mineralization is much like that found elsewhere in the Canadian Shield. The nickel-copper mineralization has some resemblance to that at Sudbury, Ontario, and the quartz-tourmaline-carbonate-gold veins and lodes bear some resemblance to those of the highly productive Porcupine district.

Nickel-copper Deposits

The sulphide replacement bodies contain no metals of value other than nickel and copper. As at Sudbury, the nickel as pentlandite and the copper as chalcopyrite are associated with abundant pyrrhotite, but the resemblance to Sudbury does not carry into the structural and other geologic associations. The sulphides tend to form pods and lenses of massive and disseminated ore as re- placements of generally somewhat silicified country rock. These zones or bodies of mineralized rock are commonly cut and fringed by veins of barren quartz. The deposits appear to have formed at relatively high temperatures and at some depth below the surface (hypothermal).

The most important sulphide deposits are on a small island in the northeastern corner of Muscocho lake and on the mainland and two adjacent islands in central Eau-Jaune lake. The deposits are referred to below as the Muscocho, and the Eau-Jaune. 3

The sulphide deposits are confined to the basaltic and gabbroic rocks that border the Algoman (2) granitic and dioritic intrusives. Such locations suggest that the mineralizing solutions may have taken advantage of a zone of Aligned glacial deposits on theshoresof Verneuil lake. Scale: 1 inch to 2,800 feet. Muskeg growing in concentric lines and almost completely filling a small lake. Scale: 1 inch to 2,800 feet. PLATE III

A.-Pillowed andesites in the northern part of Eau-Jaune lake.

B.-Pillowed andesites showing altered centres; Eau-Jaune lake. PLATE IV

A.-Well banded tuffs in central Fancamp lake.

B.-Agglomerate containing stretched fragments of felsic material up to 16 by 5 inches; Chico lake . PLATE V

A-Conglomerate predominantly composed of granitic bould- ers that have been elong- ated many times their original size; Goudreau lake.

B- Low hills of basalt on the nor- thern side of Muscocho lake.

-Brecciated basalt cemented by brown carbonate in a shear zone in northern Eau-Jaune lake . PLATE VI

-Parallel banding in the Mus- cocho where it is in contact with volcanics along the nor- thern end of Muscocho lake.

B-Gossan capping a massive basalt partly replaced by pyrrhotite and chalcopy- rite; central Eau-Jaune lake.

C -Sulphides (chalcopyrite, pyrrhotite, pyrite) repla- cing gabbro intruded by a small offshoot of the Muscocho stock; north- eastern Muscocho lake. PLATE VII

A.-Muscocho sulphide ore. Photomicrograph showing remnant rims of pyrite (Py) left as a result of incomplete replacement by pyrrhotite (Po) and pentlandite (Pn). x 120.

B.-Eau-Jaune sulphide ore. Photomicrograph showing large grains of pyrrhotite (Po) replacing altered gabbro (M) . x 120. PLATE VIII • •

~µ P I A .-Muscocho sulphide ore. Polished section showing sphalerite (SI) replaced in part by chalcopyrite (Cp) . x 120.

B.-Muscocho sulphide ore. Polished section showing irregular grains of magnetite (Mg) replaced in part by pyrrhotite (Po) . x 120. - 17 - structural weakness bordering the stock.

The Muscocho deposit is on the northeastern nose of the Muscocho stock, where the forceful intrusion of the magma produced an almost vertically plunging synclinal structure in the Keewatin rocks. Numerous secondary structures (fractures, faults, drag folds, shear zones), resulting from the bending of the rocks around the buttress-like stock, apparently served as channel-ways for the ascending ore solutions, and thus localized the mineralization.

At Eau-Jaune lake a tongue projects almost a mile from the main body of the Eau-Jaune dioritic complex along the strike of the Keewatin-type formations. The ore-bearing solutions apparently took advantage of this structure, for there are sulphides along the northeastern contact of the intrusive mass and the coun- try rock.

Feldspar porphyry dykes occur in the mineralized zones. These, however, are pre-mineral and have had no influence in localizing the ore.

Mineralogy

The nickel-copper deposits contain relatively few minerals. The list comprises pyrrhotite, chalcopyrite, pentlandite, pyrite, sphalerite, magnetite, quartz and calcite. Of these, only the pyrrhotite and chalcopyrite are rela- tively abundant.

Pyrrhotite is the most abundant of the minerals and forms at least 80 per cent of the sulphides in the Eau-Jaune deposit and about 40 to 50 per cent in the Muscocho. It occurs in small disseminated grains, in irregular masses and as small veinlets. In the Eau-Jaune deposit alignment of grains along the schisto- sity gives some of the rocks a decided banded appearance. However, for the most part, the grains are so closely disseminated that the rock appears to be composed entirely of massive sulphides. The microscope reveals, however, the presence of much quartz and other minerals of the wall rock in what appears to be massive sulphides. In the Muscocho deposit, the pyrrhotite tends to form granular ag- gregates, massive pods, and small veinlets or fracture fillings.

Chalcopyrite is not as abundant as the pyrrhotite but comprises about 50 per cent of the sulphides in the Muscocho deposit and 20 per cent in the Eau-Jaune. The chalcopyrite may occur by itself in disseminated grains or in granular aggregates and veinlets, but more commonly it is intimately associated with the pyrrhotite, especially in the more massive ore. Where the two minerals are together, the chalcopyrite may form veinlets and lobate embayments in the pyrrhotite, particularly along small incipient fractures. - 18 -

Pentlandite comprises from 8 to 10 per cent of the sulphides in the Muscocho deposit, but is very scanty in the Eau-Jaune. Its occurrence and distribution is much the same as the pyrrhotite, and it can be distinguished from the pyrrhotite only under the microscope. It is generally associated with the pyrrhotite, commonly as penetrating blebs or embayments but in part as included blebs, especially within the larger pyrrhotite grains.

Pyrite is present in small amounts in both deposits. In the Eau-Jaune it occurs in small quartz veins that transgress the nickel-copper bodies. In these veins it forms euhedral crystals as well as irregular grains. It is gener- ally accompanied by minor amounts of pyrrhotite. In the Muscocho deposit the pyrite forms irregular rims about, and in many cases completely encircling, the interlocking grains of pyrrhotite and pentlandite. These relations suggest that the pyrite rims are remnants of formerly complete crystals, largely replaced by the pyrrhotite and pentlandite.

Magnetite occurs in the Muscocho deposit in very small quantities, com- monly as microscopic inclusions within the pyrrhotite and pentlandite. Apparently these inclusions are only remnants of much larger grains, now almost entirely re- placed by the sulphides. No magnetite was observed in the Eau-Jaune deposit.

Sphalerite is scarce, forming microscopic grains and isolated islands in the chalcopyrite.

Quartz is present in variable amounts and in several forms. The most abundant is a barren, fine- to medium-grained, milky white variety, which locally has permeated the wall rock, but which otherwise occurs separately as veins. One small vein at the Muscocho deposit has been fractured and the fractures filled with sulphides. The veins at Eau-Jaune are larger and more numerous, with one measuring as much as 10 feet wide and 30 feet long. They are outside the zones containing the sulphides.

Whereas the milky-white quartz is common to both the Muscocho and Eau-Jaune deposits, the other varieties are found only at the Eau-Jaune. One of these is an opalescent blue quartz which occurs as grains with the pyrrhotite and other sulphides and also in the nearby intrusive rock, apparently as a product of mineralization. Another is a smoky, glassy variety which forms small veinlets less than an inch thick and 10 feet or less long. The veinlets cut mineralized rock at the southern end of the Eau-Jaune deposit, and contain small amounts of calcite, pyrite, and pyrrhotite.

Calcite occurs sparingly in most of the mineralized rock and can be observed only with the microscope. It forms irregular patches and granular ag- gregates between the grains of sulphides and quartz. - 19 -

Distribution of the Ore

The ore is not uniformly distributed through the deposits, but occurs in the form of small irregular bunches, lenses, and pods. In the Eau-Jaune deposit the sulphides are disseminated in irregular bodies scattered along a zone that parallels the contact of the greenstones and the Eau-Jaune intrusive for nearly 5,000 feet. The largest of the bodies measures about 30 feet wide and 50 feet long. Drilling has shown that the bodies form shallow pods extending only 25 to 30 feet below the surface. In the Muscocho deposit the ore is in massive lenses 10 to 12 feet long and 2 to 4 feet wide, and known from drilling to extend more than 40 feet below the surface with little change in width. These lenses appear to have replaced the gabbro along small fractures. Some dissem- inated sulphides surround the lenses of massive ore.

Apparently the ore occurs in greatest abundance where the country rock was not silicified prior to metallization. Thus, the assays of the unsilicified but mineralized gabbro in Trench 2 are much higher than those of the silicified basalts in Trench 1 (see assays Nos. 1 and 2 on pages 21 and 23, Eau-Jaune deposit).

Tenor of the Ore

The tenor of the ore closely parallels the distribution, concentration, and variability of the different sulphides. Grab samples taken systematically from different parts of the mineralized zones show how the values are distributed.

Samples taken at the Muscocho deposit indicate ore of commercial grade. Those taken at Eau-Jaune indicate lesser values. The assay records are given below:-

Muscocho Deposit

(1) Gabbro with massive pyrrhotite

Ounce/ton Per cent

Gold (Au) 0.000 Silver (Ag) 0.940 Copper (Cu) 0.16 Zinc (Zn) 0.06 Lead (Pb) 0.00 Nickel (Ni) 1.79 - 20 -

LAC A L'EAU - JAUNE

LEGEND-LÉGENDE

Sulptiaes Sulfures Quartz vein Veine an quartz eeiaS±)ar corchyry dine Dyke de feidsoatt.b et porphyre - ;~unetz diorite Diorite aunrtzif ire GaLL en ,anuro

Magnetic anona.y Anonali.e nEeynétiÿue Schis:osi:y SCnistosité

1 ~. , oqY 5.W HOLNIES, 1951 G~.éoloqie

.00 1900 Pietls f ee,

DÉPÔTS DE SULFURES LAC A L'EAU-JAUNE SULPHIDE DEPOSITS - 21 -

Muscocho Deposit (con't)

(2) Gabbro with massive chalcopyrite

Ounce/ton Per cent

Gold (Au) 0.000 Silver (Ag) 0.940 Copper (Cu) 12.84 Zinc (Zn) 0.19 Lead (Pb) 0.00 Nickel (Ni) 0.63

(3) Gabbro with mixed chalcopyrite and pyrrhotite

Ounce/ton Per cent

Gold (Au) 0.000 Silver (Ag) 0.176 Copper (Cu) 2.19 Zinc (Zn) 0.04 Lead (Pb) 0.00 Nickel (Ni) 1.04

A qualitative spectrographic analyses was run on a specimen of gabbro from Muscocho deposit containing approximately 8 per cent sulphides with the following results:

Major Elements: Silicon, Aluminum, Iron, Magnesium

Minor Elements: Calcium, Sodium, Titanium

Traces: Barium, Copper, Manganese, Strontium, Potassium, Nickel, Vanadium, Beryllium, Cobalt, Chromium, Lithium, Lead, Zinc

Eau-Jaune Deposit

(1) Silicified gabbro with pyrrhotite and chalcopyrite

Ounce/ton Per cent

Gold (Au) 0.000 Silver (Ag) 0.015 Copper (Cu) 0.20 Zinc (Zn) 0.14 Lead (Pb) 0.00 Nickel (Ni) 0.02

- 22 - \ 2 ,

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Heavy s ulphides + + Granodiorite + + Granodiorite ~f Sulfures massifs + + ~.\\\ Quartz \\\\\ Gabbro, spotty sulphides Quartz \\\\\ Gabbro, sulfures en taches Aplite Sand and gravel Aplite Sable et gravier Fracture Pattern ,r. ~` Feldspar porphyry Porphyre feldspathique \N Systéme des fractures

O 10 20 Geolog y : S.W. HOL MES, 1951 Géologie: Pieds Feet

D. M O. /959 No. 1283 DÉPÔTS DE SULFURES LAC MUSCOCHO SULPHIDE DEPOSITS - 23 -

Eau-Jaune Deposit (con't)

(2) Unsilicified gabbro with pyrrhotite and chalcopyrite

Ounce/ton Per cent

Gold (Au) 0.000 Silver (Ag) 0.015 Copper (Cu) 1.37 Zinc (Zn) 0.00 Lead (Pb) 0.00 Nickel (Ni) 0.28

(3) Quartz stringer with pyrrhotite and pyrite

Ounce/ton Per cent

Gold (Au) 0.012 Silver (Ag) 0.134 Copper (Cu) 2.20 Zinc (Zn) 0.00 Lead (Pb) 0.00 Nickel (Ni) 0.01

(4) Wall rock close to sulphide mineralization

Ounce/ton Per cent

Gold (Au) 0.00 Silver (Ag) traces Copper (Cu) 0.37 Zinc (Zn) 0.00 Lead (Pb) traces Nickel (Ni) 0.20

Gold Deposits

The gold-bearing veins and lodes contain the metals gold, iron, and a little copper. The most interesting feature of the mineralization is the asso- ciation of gold with quartz, tourmaline, and ankerite. The deposits appear to have formed at considerable depths and at moderate temperatures (mesothermal). These deposits have been actively explored but none has yet been brought into production.

The principal gold-bearing veins and lodes occupy fissures and shear - 24 - zones localized along the northeast-trending Fancamp Lake fault. This fault ex- tends from one side of the district to the other, but only that part immediately west of Fancamp lake has been mineralized. There the fault occurs in the less competent but brittle tuffs of the Keewatin-type assemblage. Apparently the tuffs have been more susceptible to deformation than the other rocks and have tended to localize the faulting and attendant crumpling, shearing, brecciation, and fracturing. Some gold has been found in other parts of the area and in rocks other than tuffs, but such occurrences appear to be small.

Although similar in mineral content, the veins and lodes differ in their structural or physical form. The veins are simple fissure fillings; the lodes are much more complicated and may consist of aggregates of closely spaced veins and stringers in drag-folded, sheared, and extensively fractured rock. They tend to form stockwork-like bodies. Single veins are small, with none more than 10 feet long and 2 feet wide. The lodes may range up to 50 feet long and 25 feet wide.

The structural characteristics of the veins and lodes appear to reflect the nature of the openings formed during the shearing, fracturing, and crumpling of the rocks prior to and during the introduction of vein material. They appar- ently represent gash fractures of tensional origin, related to the general shear- ing. Some of the veins, however, are in part sinuous and contorted. These are associated with drag folds and also with openings formed by differential movement along or across planes of schistosity. Many of the veins pinch and swell along the strike in such a way as to resemble boudinage structure. Such veins commonly have been intersected by traverse fractures filled with later vein material.

More complex patterns characteristic of the lodes are developed through branching and formation of braided and handed structures. The banding is best developed in the highly sheared wall rocks or around the noses of drag folds. These bands represent an alternation of vein material and schistose rock. The introduction of quartz and tourmaline bands in some places results in a very striking pattern. Some of the lodes consist of parallel stringers of vein materi- al separated by strips or blocks of brecciated and mineralized wall rock.

Mineralogy

The veins and lodes have a comparatively simple mineralogy. With few exceptions they contain only quartz, ankerite, calcite, tourmaline, albite, pyrite, chalcopyrite, and gold. Quartz, tourmaline and the carbonates comprise most of the vein material. Gold is the only ore mineral.

Quartz is the most abundant mineral and usually composes the greater part of the veins and lodes. In some veins it is the only mineral. The quartz - 25 - shows considerable variation in texture and mineral association, but may be re- solved into three more or less clearly defined varieties which differ in age and mode of occurrence.

The most abundant variety of quartz is that which commonly forms the veins around the noses of the small drag folds, the gash veins bordering the main ore zones, and the lenticular veins cutting schistose vein material. This quartz is milky white, coarsely crystalline, and is made up of interlocking crystal aggregates of tourmaline and pyrite, with minor amounts of calcite. In some places this quartz is completely barren except for rare and scattered bunches of pyrite.

Almost as abundant as the above is a variety that commonly occurs as fillings of small gash fractures in the sheared country rock and as fracture fillings that cut the earlier quartz. This quartz is similar in all respects to the other, but is accompanied by abundant ankerite and albite and only minor amounts of pyrite and tourmaline. The quartz commonly penetrates along cleavage planes and small fractures in the albite. Some of it is somewhat brecciated, and the fragments are cemented by ankerite.

Still another variety of quartz occurs in the schistose wall rocks and as a cement of brecciated vein material. This quartz fills fractures in the other varieties of quartz and penetrates them along intergranular boundaries. It commonly occurs in and around fractured grains of auriferous pyrite and chalco- pyrite. That which has come in contact with tourmaline has embayed and pene- trated the tourmaline in such a way as to produce a peculiar sieve-like struc- ture. This quartz is present in all of the mineralized zones in the form of small veinlets which cut the other fillings. It is fine- to medium-grained, gran- ular, and is accompanied by small amounts of calcite.

Ankerite is second to quartz in abundance, and occurs in all of the deposits both as fracture fillings and as a replacement of the bordering rocks. It forms medium to coarse, brown grains and granular aggregates. These stand out conspicuously in the lighter-coloured vein matter and impart a yellowish-brown cast to the wall rock into which it has penetrated. This penetration extends outwards 5 to 10 feet from the vein fillings. That in the veins is intimately mixed with quartz, albite, and tourmaline. Some of the ankerite is fractured and cemented by calcite.

Calcite is widely distributed but is not as abundant as the ankerite. It is most conspicuous as fillings of minor fractures that cut the veins and lodes, but is most abundant as disseminated grains in the wall rock where it is commonly accompanied by equally abundant,finely granulated quartz. The calcite is white to grey, fine- to medium-grained, and usually occurs as anhedral grains. - 26 -

Tourmaline is relatively abundant in all of the fillings and in the broken country rock. It is associated with the early coarse-grained, granulated quartz and particularly with that which has penetrated along the foliation of the schistose wall rock. In the latter case, a conspicuous banding results from the contrasting colours of the tourmaline, quartz, and schistose rock.

The tourmaline forms short to long prismatic crystals and columnar and fibrous aggregates which, in part, are radial. Although black in the hand spec- imen, the tourmaline is dark green in thin section, and shows pronounced olive- green to dark green pleochroism. It appears to be the iron-rich variety. The tourmaline is generally closely associated with pyrite, ankerite, albite, and quartz. That occurring with the younger, finely crystalline quartz is generally so extensively penetrated by the quartz that only sieve-like remnants are left.

Albite occurs sparingly in some of the earlier quartz veins, particu- larly in those which contain abundant ankerite. It is recognizable only in thin sections, where it appears as subhedral crystals, generally contained in a matrix of quartz, tourmaline, ankerite, calcite, and pyrite. The albite is com- monly corroded and embayed by tongue-like offshoots of quartz and ankerite, which have entered along cleavage lines and small fractures. Most of it is crushed, with the resulting fractures healed by calcite. This albite is almost identical to the albite in the nearby Verneuil stock.

Pyrite occurs in variable but minor amounts in most of the veins and lodes and in their bordering wall rocks. It is particularly abundant along planes of schistosity and may be present in considerable quantities in some of the early ankerite-free quartz veins. The pyrite in the wall occurs as euhedral crystals, irregular grains and small granular aggregates. That in the veins occurs as crystals up to an inch in diameter and as massive aggregates of con- siderable size. In places, fractures in the pyrite are filled by fine-grained quartz, calcite, chalcopyrite, and gold.

Chalcopyrite, present in tather minute amounts, is visible only under the microscope. It occurs mostly in fractures in the pyrite and less commonly as small irregular grains in the quartz close to the crystals of fractured pyrite. That in the pyrite commonly contains small blebs of gold, whereas that in the quartz is without gold. The chalcopyrite appears to accompany the younger, fine-grained quartz.

Gold, visible only in polished sections, is widely distributed through the veins and lodes. It apparently occurs mainly as small lobate blebs in the chalcopyrite, although some grains are large enough to share the veinlets with the chalcopyrite. - 27 -

Control and Distribution of the Ore

The localization of the gold ore was largely determined by structural controls and adjustments prior to and during ore deposition. The ore was de- posited largely by filling of open spaces. As pointed out earlier, the tuffa- ceous rocks were especially susceptible to deformation and to fracturing; con- sequently the tuffs along the fault zone were complexly fractured, fissured, brecciated, and sheared, and locally drag-folded. The fractures served as chan- nels for ore-bearing fluids, and the small, steeply plunging drag-folds produced by shear parallel to the fault proved especially favourable for the localization of ore.

Whether the vein and lode fillings would be of ore grade or not would depend more directly on the availability of openings at the time the gold was in- troduced. As gold was one of the later minerals, it could not be introduced into the deposit unless the earlier filling or fillings were reopened and were in a position to admit the gold-bearing fluids. Consequently, only the fractures and the wall rock then exposed could receive the gold. Any minerals deposited sub- sequently would be non-auriferous, unless introduced into the gold-bearing rock. Such younger minerals would serve to dilute the ore and to decrease its value.

The gold also shows a variable distribution through the ore shoots, a distribution which accords with that of the pyrite. As the pyrite is usually visible to the eye, its presence and abundance may serve in part to differentiate between lean and good ore.

Tenor of the Ore

As no systematic sampling was done by the writer, the tenor of the ore is not accurately known. Mere inspection of the vein substance does not suffice, for barren material may be indistinguishable from that which contains gold.

Assays of representative grab samples are given below. These samples include vein and lode fillings,as well as the altered wall rock, and were assayed by the Quebec Department of Mines.

Assay Results

(1) Banded quartz-tourmaline lode in a drag fold. (2) Schistose and pyritized wall rock bordering (1). (3) Quartz gash-vein containing massive pyrite. (4) Sheared tuffaceous wall rock bordering (3). (5) Quartz-ankerite vein cutting a schistose vein. (6) Wall rock bordering (5). (7) Brecciated lode cemented by ankerite and quartz. - 28 -

Sample Gold Silver No.

(1) 0.470 oz. per ton 0.054 oz. per ton (2) 0.057 " It " 0.054 " " "

(3) 1.689 " " " 0.284 " " " If (4) 0.960 " " 0.158 " " "

(5) 0.478 " " 0.094 " " IT

(6) 0.000 " " " 0.029 " "

(7) 0.729 " " " 0.140 " " "

DEVELOPMENT

Considerable exploratory work has been done in the Fancamp-Hauy area during the past 30 years. Abandoned trenches and prospect pits are found in many parts of the area, and here and there drill cores are dumped at random.

The Eau-Jaune sulphide deposit has been extensively stripped over the greater part of its length. Numerous trenches have been made across the strike at varied intervals and pits have been blasted into the more favourable zones of visible mineralization. A magnetometer survey, followed by diamond drilling, was done by Noranda Mines. In a11,13 holes, 30 to 50 feet long, were drilled in areas of high magnetic anomalies and in areas of visible mineralization. The re- sults were not encouraging and the work was abandoned.

The Muscocho deposit has been stripped and trenched, but it closeness to the water has limited this type of exploration. Four holes were drilled to depths of 80 to 90 feet. These proved the downward extension of the ore. A magnetometer survey indicated high anomalies in the lake to the southeast. This suggests an extension of the ore in that direction. Noranda Mines still holds both properties and more development work has been planned.

The Fancamp Lake gold deposits have been extensively stripped and trenched by Teck Exploration Company, Limited, and The Mining Corporation of Canada, Limited.

Teck Exploration held options on several groups of claims in the northern, southern, and eastern parts of the Fancamp Lake gold-bearing area, and The Mining Corporation's ground was immediately to the northeast of the Teck options. Also, Calmor Mines, Limited, had several groups• of claims near the Fancamp-Hauy township line east of Eau-Jaune lake. Little work had been done by this last company at the time of the writer's visit.

Teck Exploration encountered considerable quicksand,which necessitated the - 29 - use of costly cribbing. At the time of the present study most of the pits were under water. Because of the heavy overburden and difficulty in trenching the easiest and cheapest way to continue the development work would be by drilling

BIBLIOGRAPHY

BARLOW, Alfred E., GWILLIM, J.C., and FARIBAULT, E.R. (1911), Report on the Geology and Mineral Resources of the Chibougamau Region, Quebec; Que. Dept. of Col., Mines, and Fisheries.

DRESSER, J.A. and DENIS, T.C. (1944), Geology of Quebec, Descriptive Geology; Vol. 2, Que, Dept. of Mines, Geol. Rep. 20.

IMBAULT, P.E. (1951), Queylus Area, Abitibi-East and Roberval Counties; Que. Dept. of Mines, Prelim. Rep. 250.

IMBAULT, P.E. (1958), Queylus Area, Abitibi-East and Roberval Electoral Districts; Que. Dept. of Mines, G.R. 83.

MAWDSLEY, J.B. and NORMAN, G.W.H. (1935), Chibougamau Lake Map-Area, Quebec; Geol. Survey Canada, Memoir 185.

NORMAN, G.W.H., Opemisca, (east-half), Abitibi Territory, Quebec; Geol. Survey Canada, Map 401 A.

HOLMES, S.W. (1952), Fancamp-Hauy Area, Abitibi-East County; Que. Dept. of Mines, Prelim. Rep. 271. - 30-

APPENDIX

Economic Geology, 1951-59

G.R. 84

by

J.-E. Gilbert

Ref.: Quebec Department of Mines, P.R. No. 287 pp. 4, 5; No. 330, pp. 15, 16

Exploratory work on occurrences of precious and base metals was carried out almost continuously at one locality or another within the limits of the Fancamp-Hatly area since the date on which this report was written. Some of that work has been reported in the above-mentioned publications of the Quebec Department of Mines.

In Hatly township, the main work was carried out by No- randa Mines Ltd. on its Miscocho Lake property where geological and geophysical surveys were followed by diamond drilling in 1954 and 1957. Aladdin-Chibougamau Mines Ltd. and Burrex Mines Ltd. likewise put down a few diamond-drill holes to test some previously discovered geo- physical anomalies.

Noranda Mines Ltd., Hazeur Chibougamau Mines Ltd. D.R. No. 287), and Brosnan Chibougamau Mines Ltd. also carried out a large amount of exploratory work in that part of Rasless township included within the limits of the present area. Commonwealth Exploration and Development Company Ltd., Quemaque Explorers Ltd. (Quemaque Gold Mines Ltd., P.R. No. 287), Moneta Porcupine Mines Ltd., and Lamaque Mining Company Ltd. drilled a few holes on their respective properties in Fancamp township. Moreover, Dominion Gulf Company (P.R. No. 330) and Canadian Nickel Company Ltd. did a relatively large amount of drilling in the Eau Jaune Lake area, in Brongniart township.

Numerous other companies completed geological and geo- physical surveys of their properties, but no orebodies of economic size and grade were outlined in the various exploration programmes undertaken in the map-area.

Quebec, March 9, 1959.

- 31 - ALPHABETICAL INDEX Pape Pape Access to area 1 Chromium 21 Acknowledgments 2 Clinozoisite 7 Agglomerates 6 Cobalt 21 Aladdin-Chibougamau Mines Commonwealth Exploration and Ref. to work by 30 Development Co.- Albite 10,11,24,26 Ref. to work by 30 Aluminum 21 Consolidated rocks 3 Amphibole 9 Control of distribution of ore 27 Anderson, Dr. Alfred L.- Copper 16,19,21,23 Acknowledgment to 2 Andes it es 5 Denis, T. C.- Ankerite 24,25 Ref. to work by 29 Appendix to G.R. 84 30 Description of area 2 Arkosic rocks 8 Development 28 Augite 12 Distribution of ore 19,27 Dominion Gulf Co.- Barium 21 Ref. to work by 30 Barlow, Alfred E.- Drainage of area 3 Ref. to work by 29 Dresser, J. A.- Basalts 5 Ref. to work by 29 Basic intrusive rocks 7 Dykes 12 Base map 2 Base metal prospects 1 Eau-Jaune deposit 21,23,28 Beryllium 21 Eau-Jaune complex 11 Bibliography 29 Epidote 7, 9,11 Biotite 6,10 Exposures 14 Brosnan Chibougamau Mines Ref. to work by 30 Fancamp Lake fault 15 Burrex Mines Faribault, E. R.- Ref. to work by 30 Ref. to work by 29 Faults 14 Calcite 18,24,25 Feldspar porphyry dykes 12,17 Calcium 21 Feldspars .. 6,7,8, 9,11 Calmor Mines Ltd.- Field work 2 Ref. to work by ...... 28 Folding of Keewatin rocks 13 Canadian Nickel Co.- Formations, table of 4 Ref. to work by 30 Carbonate 8 Gabbro 21,23 Caron, Gaston Geology Junior assistant 2 Economic 15,30 Chalcopyrite ... 16,17,21,23,24,26 General 3 Chlorite 6, 9 Structural 12 - 32 Pape Gilbert, Dr. J.-E. Mineralogy 17,24 Acknowledgment to 2 Mining Corporation of Canada Gold 19,21,26,28 Ref. to work by 28 Gold deposits 23 Moneta Porcupine Mines Gold prospects 1 Ref. to work by 30 Granite 10,15 Miscocho deposit 17,19,21,28 Granodiorite 9 Mascocho stock 9,13 Gwillim, J.C.- Ref. to work by 29 Nickel 16,19,21,23 Nickel-copper deposits 16,17 Hamilton, Erwin C.- Noranda Mines Ltd.- Senior assistant 2 Ref. to work by 15,28,30 Hazeur Chibougamau Mines - Norman,.G.W.H.- Ref. to work by 30 Ref. to work by 3,4, 7,14,29 Holmes, S. W.- Ref. to previous work by 29 Olivine-diabase 12 Hornblende 7, 9,11 Ore 19 Outcrops 9 Imbault, P.E.- Ref. to work by 4,13,29 Penninite 7 Intrusive rocks 7, 8 Pentlandite 16,17 Iron 21 Perthite 9 Post-Keewatin intrusive rocks 8 Keewatin rocks ... 4, 8,13 Post-Keewatin sedimentary rocks 7,13 Keweehawan olivine-diabase 12 Potassium 21 Keweenawan-type dykes 1 Pyrite 18,23,24,26 Pyrrhotite 17,21,23 Labradorite 12 Lamaque Mining Co.- Quartz 9,10,18,23,24,25 Ref. to work by 30 Quartz-diorite 11 Laurencelle, Jean Paul Quemaque Explorers Ltd.- Junior assistant 2 Ref. to work by 30 Lead 19,21,23 Quemaque Gold Mines Lithium 21 Ref. to work by 30 Location of area 1 Sedimentary rocks 7,13 Manganese 21 Sericite 7, 9 Magnesium 21 Shear zones 14 Magnetite 18 Silicon 21 Mawdsley, J.B.- Silver 19,21,23 Ref. to work by 29 Sodiunf 21 McKay (Quebec) Exploration- Sphalerite 18 Ref. to work by 15 Sphene 9 - 33 - Page Page Strontium 21 Topography of area ...... 2 Structure of Post-Keewatin Tourmaline 24,26 sedimentary rocks 13 Tuffs 6,15 Sulphide deposits ...... 4,16,28 Vanadium 21 Table of formations 4 Verneuil stock 10 Teck Exploration Company- Ref. to work by 16,28 Zinc 19,21,23 Tenor of ore 19,27 Zircon 9 Titanium 21 Zoisite 7, 9