Dollier - Charron Area, Abitbi-East and Roberval Electoral Districts Province of Quebec, Canada

RG 082(A) DOLLIER - CHARRON AREA, ABITBI-EAST AND ROBERVAL ELECTORAL DISTRICTS PROVINCE OF QUEBEC, CANADA

DEPARTMENT OF MINES

Honourable W.M. COTTINGHAM, Minister

GEOLOGICAL SURVEYS BRANCH

GEOLOGICAL REPORT 82

DOLLIER - CHARRON AREA

ABITIBI-EAST AND ROBERVAL

ELECTORAL DISTRICTS

E.R.W. NEALE

QUEBEC REDEMPTI PARADIS PRINTER TO HER MAJESTY THE QUEEN

1959

TABLE OF CONTENTS

Page

INTRODUCTION 1 General statement 1 Location and access 1 Previous work 2 Field work and acknowledgments 3 DESCRIPTION OF THE AREA 3 Timber, game, and fish 3 Drainage 4 Topography 4 GENERAL GEOLOGY 5 Table of formations 6 "Keewatin-type" volcanic rocks 7 Andesites and basalts 8 Metadiorites 9 Diorite porphyry 9 Andesite breccia 9 Tuff 9 "Temiskaming-type" sedimentary rocks 10 Feldspathic sandstones 11 Greywacke 11 Hornblende schists and garnetiferous hornblende schists 12 Hornblende schists 13 Garnetiferous hornblende schists 14 Contacts with the southeastern gneisses 15 Metamorphic grade 16 Garnetiferous muscovite schists and gneisses 16 Muscovite schist 17 Garnetiferous biotite-muscovite schist r. 17 Garnetiferous biotite-muscovite gneiss 18 Hornblende-muscovite schist 18 Garnetiferous hornblende gneiss 19 Staurolite-kyanite.schist 19 Metamorphic grade 20 Chibougamau intrusive complex 20 Anorthosite 21 Gabbro 22 Granite rocks 22 Metamorphic grade 23 Garnetiferous conglomerate 23 Page

Conglomerate on the Dollier-Lemoine line 25 Conglomerate on Conglomerate lake 26 Metamorphic grade 27 Southeastern gneisses 28 Biotite orthogneisses and composite gneisses 29 Pink muscovite granite gneiss 31 Aplite and pegmatite 32 Gabbro dykes 32 Pleistocene and Recent 33 STRUCTURAL GEOLOGY 34 Bedding, schistosity 34 Folds 35 Lineation 36 Shear zones and faults 37 Structural interpretation 38

ECONOMIC GEOLOGY 39 Recommendations 40

BIBLIOGRAPHY 41 APPENDIX 43 ALPHABETICAL INDEX 44

MAPS AND ILLUSTRATIONS

Map No. 1235 Dollier-Charron Area (In pocket)

PLATES

I - Barrière Boisvert, at Mile 112.4, St. Félicien-Chibougamau highway.

II - Pillowed andesite; south end of Pillow lake.

III - Cross-bedded, feldspathic sandstone; island in Stella lake.

IV - Garnetiferous conglomerate, Dollier-Lemoine township line.

V - Garnetiferous conglomerate, Dollier-Lemoine township line.

VI - Augen pegmatite; St. Félicien-Chibougamau highway.

VII - Swirly gneissosity in composite gneiss.

VIII - Stella lake. DOLLIER-CHARRON AREA

ABITIBi-EAST AND ROBERVAL

ELECTORAL DISTRICTS

E.R.W. Neale

INTRODUCTION

General Statement

Geological mapping of the Dollier-Charron area was carried out during the 1953 field season. This was part of a systematic mapping program in the Chibougamau region initiated by the Quebec Department of Mines after completion of the St..Félicien-Chibougamau highway.

The location of the map-area adjacent to the Lake Chibouga- mau gold-copper belt, and the fact that it is underlain in part by similar rock-types, point to potential economic possibilities. Of more theoretical interest is the fact that a segment of the postulated boundary between the Grenville and Superior provinces is included in the area.

Location and Access

The Dollier-Charron map-area is part of the Chibougamau Sheet, East Half (Map 397A),of the Geological Survey of Canada. It is bounded by latitudes 49030' and 49045', and by longitudes 71+°00' and 74°15', comprising about 200 square miles. It includes Dollier township, almost all of Charron township, and small parts of Queylus, La Dauversière, Lemoine, Vimont, Mance, Obalski and Rinfret townships.

The St . Félicien-Chibougamau highway crosses the southwest corner of the map-area and makes it easily accessible by automobile or autobus from all points in the Lake St— Jean region. The southern boundary of the map-area is 112 miles from St.... Félicien.

Travel in the eastern and central parts of the area is facilitated by Boisvert river which offers a canoe-route from the highway bridge at Charron lake to the northeast corner of the area. Good portages connect this river with the large lakes of the region. - 2-

The chain of lakes extending north-northeast of Lake Du- fresne, used in conjunction with the old winter road, affords an ardu- ous, but convenient, canoe-and-portage route from the highway to the northwestern part of the area. This part is also accessible from the southeasternmost bay of Chibougamau lake, at the terminus of the old winter road, in the extreme northwest corner of the area.

Wynne creek, which flows north through Lake Cinq Milles to Lake Chibougamau, provides easy access to the north-central part of the area during periods of high water.

Overland travel is pleasant in the southern part of the area, for the terrane is dry and there is little undergrowth. In the northern part of the area, particularly the eastern half of Dollier township, wet, treeless swamps are numerous and local patches of alders are obstacles to easy travel.

Short flights to any of the larger lakes of the area can be scheduled from aircraft bases on Caché and Chibougamau lakes.

Previous Work

Branch lake, Malo lake (1) and Hauteur lake, in the southwest corner of the area, formed part of a historic canoe route from Lake St-Jean to lakes Chibougamau and Mistassini. James Richardson (1872) surveyed this route in 1870 when travelling north to Lake Mistassini. He noted the presence of grey biotite and hornblende gneisses of the "Laurentian System" in the present map-area. Many geologists and prospectors followed this route in later years, chiefly to explore the mineral deposits discovered around Chibougamau lake in 1903. They contributed little to the geology of the Dollier-Charron area. An excellent summary of this early history of exploration is contained in the Report of the Chibougamau Mining Commission (Barlow, Gwillim, and Faribault, 1911, pp 27-63).

(1) The name Poisson Blanc lake (Whitefish) originally referred to the small lake here called Three-Mile lake. The lake now named Malo lake was originally called Narrow Ridge lake - the name referring to an esker on the southern shore of the lake (Richardson, 1872, p. 284; also Faribault, Gwillim, and Barlow, 1911, p. 86). - 3

Work in the Chibougamau region by J.B. Mawdsley in 1927 and 1930 and G.W.H. Norman in 1935 culminated with the publication of the Chibougamau Sheet, East Half (Geol. Surv. of Canada, 1938). The distribution of the major rock-types in the Dollier-Charron area is accurately shown on this reconnaissance map.

Mapping on the scale of one inch to a mile has been carried out in the adjacent area to the north by Mawdsley and Norman (1935), in that to the west by Imbault (1959), and in those to the southwest and northeast by Gilbert (1959) and Longley (1958).

Field Work and Acknowledgements

The base map was compiled from various surveys of the Department of Lands and Forests, Quebec. Minor additions and correc- tions were made with the aid of vertical aerial photographs.

Rock outcrops along navigable lakes and streams were examined and the intervening ground was covered by pace-and-compass traverses spaced 1,500 to 2,000 feet apart. Segments of adjacent map- areas were examined to compare rock-types and strengthen correlations.

André Laurin of McGill University, Pierre Crépeau of Ecole Polytechnique, and Hugh Wynne-Edwards of the University of Aberdeen were excellent geological assistants and cheerful field companions. Marcel and Clément Siméon were capable canoemen. J. Armand Lapointe served as cook. Mr. and Mrs. Phydime Simard, employees of the Depart- ment of Game and Fisheries at Barrière Boisvert, on the Chibougamau highway, showed many courtesies to the party during the field season.

DESCRIPTION OF THE AREA

Timber, Game, and Fish

Except in its swampy northern part, the area is heavily wooded. Black spruce, rarely measuring more than 12 inches through the butt, is the dominant growth. White spruce, jackpine, and balsam are common. Birch, tamarack, and poplar are relatively rare, although stands of large birch are abundant on the drumlinoid ridges northwest of Stella lake, in the northwest corner of the area. Cedar was seen only in the northwest corner of Charron township. Wild life is abundant throughout the area and moose, bear, otter, muskrat, wolf, fox, rabbit, and ruffed grouse were seen during the field season. Pike and pickerel are the common game fish;trout are rare. Two ouananiche were taken from Charron lake in July, 1953.

The northern gate, Barrière Boisvert (Plate 1), of the Chibougamau Park and Game Preserve is located at Mile 112.4 of the highway, on the outlet of Charron lake. The Department of Game and Fisheries maintains guides, boats, and excellent tourist accommodations on this lake.

Drainage

The northeast-trending boundary line between Abitibi-East and Roberval counties is located along the height-of-land separating the St. Lawrence and James Bay drainage basins. Three-quarters of the map-area lies east of the county line and drains southwestward through Boisvert river. This river enters the northeast corner of the area at an elevation of approximately 1,300 feet and flows to Charron lake, elevation 1,190 feet near the southern border of the area. Charron lake drains via Branch lake into Nicobau lake and from here southeast to Lake St..Jean and the St. Lawrence.

The land west of the county line drains northward to Chi- bougamau lake, elevation 1,152 feet, and westward to La Dauversière lake and thence, by devious routes, to James Bay.

Topography

The map-area has an average elevation of about 1,250 feet. The highest point is Patrick mountain (1), a bedrock ridge immediately west of Lake Malo. It has an elevation of 1,700 feet, 500 feet above that of the lake. Bald mountain, near the southern boundarÿ of Dollier township, and several rock ridges east of Boisvert and Coquille lakes have comparable elevations but less pronounced local relief.

(1) Named after Patrick Cleary, a fur-trader in the region during the early part of this century (see Faribault, Gwillim, and Barlow, 1911, p. 87). - 5 -

With the exception of Patrick and Bald mountains, the area west of Boisvert river is characterized by low relief and gentle slopes. Most of this area is covered by glacial deposits, and the north and north-northeast trends of ridges, swamps, lakes and stream valleys are largely the result of Pleistocene glaciation. In the northwest corner of Charron township, some of the north-northeast-trending stream valleys and lake shores are controlled by bedrock structures which, in this region, parallel the direction of ice movement. In the northeast corner of Dollier township, the elongation of Conglomerate and Couteau lakes is controlled by bedrock and trends across the direction of ice movement.

East of Boisvert river, the country is, on the whole, more rugged. Steep cliffs flank the many bedrock ridges of this region. The topography has been largely controlled by bedrock structures and only slightly modified by glacial processes. A good example of this is found in the southeast corner of Dollier township and the northeast corner of Charron township. Here, the topography is arranged in an arcuate pattern which is convex toward the north and reflects the structural trend of the underlying gneisses. Similar examples occur east and northeast of Coquille lake where the easterly trend of the topographic grain is parallel to the gneissic structure and at right angles to the direction of ice movement.

GENERAL GEOLOGY

All bedrock exposed in the map-area is Precambrian in age. On the basis of origin, it is divided into two major groups:

(1)Metamorphosed volcanic and sedimentary rocks. (2)Intrusive rocks, including some composite (or mixed) gneisses.

Volcanic and sedimentary rocks,of low (greenschist) metamorphic grade, crop out as a broad, northeast-trending band in the northwestern part of the area. These rocks are similar to those known as "Keewatin-type" and "Timiskaming-type" throughout the Superior (Timiskaming) province of the Canadian shield. Eastward, these sedimentary and volcanic rocks grade into garnetiferous schists and gneisses which represent a higher grade of metamorphism. The metamorphic grade increases with proximity to the gneisses underlying the southeastern half of the area.

The southeastern gneisses resemble those referred to as "Grenville-type" by workers in adjacent areas. They include orthogneisses and composite gneisses, the latter being a mixture of the -6- orthogneisses with the garnetiferous schists and gneisses mentioned above.

Anorthositic and granitic rocks exposed in the extreme northwest corner of the area are part of the southeastern border zone of a large, intrusive complex which underlies the Chibougamau Lake region.

Gabbro dykes, which cut the southeastern gneisses, are the youngest intrusive rocks of the area.

All the sedimentary and volcanic rocks of this area are older than the southeastern orthogneisses. Some of these rocks are definitely older than the Chibougamau Lake intrusive complex. However, at least one sedimentary unit is younger than the intrusive complex. This is the garnetiferous conglomerate that crops out near Couteau lake in the northeastern part of the area. It contains pebbles and boulders of anorthositic and granitic rocks from the intrusive complex. Possibly some of the other sedimentary and volcanic rocks are also younger than the Chibougamau Lake intrusive complex.

Table of Formations

Cenozoic (Pleistocene Peat, sand, clay, silt, sandy and Recent) and boulder-rich till Coronitic gabbro Pink, muscovite granite gneiss Southeastern Grey, biotite orthogneiss and Gneiss composite gneiss; hornblende facies of composite gneiss Garnetiferous conglomerate Altered granitic rocks Chibougamau Precambrian Altered anorthositic and gabbroic Complex rocks Garnetiferous muscovite schists and gneisses Hornblende schists and garnetiferous hornblende schists "Temiskaming-type" sedimentary rock. "Keewatin-type" volcanic rock. - 7

"Keewatin-type" Volcanic Rocks

A broad belt of "Keewatin-type" volcanic rocks, with some associated sedimentary rocks, extends northeastward across the northwest corner of the map-area. This is the eastward extension of similar rocks mapped by Imbault (1959) in the adjacent area to the west. The northeastern limit of this belt has been mapped by Longley (1958) in the adjacent area to the northeast.

Owing to scarcity of outcrops, the boundaries of this volcanic belt cannot be accurately drawn. The northwestern boundary, with granitic rocks of the Chibougamau complex, appears to trend east-northeasterly from the west boundary of the area to the north end of Stella lake, where it swings abruptly to north-northeast. Numerous inclusions of greenstone within the granitic and anorthositic rocks and intense alteration of pillowed basalt near•the north end of Stella lake suggest that the Chibougamau complex is intrusive into at least some of the volcanic rocks.

The southeastern boundary of the "Keewatin-type" volcanic rocks is, in part, a transition zone from low to higher grade metamorphic rocks. Thus, in the northwest corner of Charron township, the fine-grained, chloritized "Keewatin-type" rocks grade into coarse- grained, garnetiferous hornblende schists, which are mapped as a separate unit. All transitional stages exist, and the first appearance of garnet is used to delineate the boundary. Northward, the "Keewatin- type" rocks are flanked on the southeast by garnetiferous mica schists and gneisses of sedimentary origin.

Most of the "Keewatin-type" rocks exposed in this belt are andesitic and basaltic flow rocks. Metadiorite occurs at three localities in the southwest quarter of Dollier township. These occurrences may represent either the cores of thick flows or concordant bodies of intrusive rock genetically related to the flow rocks. A dyke of diorite porphyry cuts pillowed lava near Mile Post 9 of the Charron-La Dauver- sière line. Andesite breccia occurs at one locality, northwest of Mile Post 5 on the Dollier-Queylus line. Thin tuffaceous beds are inter- calated with the lava flows but are common only in the northwest corner of Charron township, particularly near Mile Post 8 of the Charron-La Dauversière line.

Only one outcrop of "Keewatin-type" rock is known beyond the boundaries of the main outcrop belt. This crops out near the -8 - northeast corner post of Dollier township, deep within the zone of higher-grade metamorphic rocks, and is pillowed basalt.

The andesites and basalts are typically aphanitic to fine- grained, greenish grey (1) on weathered surfaces, dusky green to greenish black on fresh surfaces, and schistose. The colour of these rocks reflects the variety rather than the amount of mafic mineral present, a fact that precludes distinction between andesites and basalts in the field.

Pillows are abundant and average about one foot in length. In general, they are well-formed and useful for determining tops of flows. Locally, however, and especially along the southeastern boundary of the outcrop belt, they are too deformed for top determinations. In most exposures, the interspaces between pillows have weathered out, leaving the pillows in positive relief. Near Pillow lake, however, the opposite is true and the siliceous material of interspaces is resistant to weathering and forms rims around the pillows (Plate II).

Light-coloured amygdules, consisting chiefly of epidotized plagioclase and averaging 2 mm. in diameter, are common in the andesites and basalts. Larger, elongated amygdules, ranging up to 2 cm. in length, occur in flow rocks located west of the north end of Dufresne lake.

Microscopic examination shows that these andesites ands basalts have undergone complete recrystallization and consist of a crystalloblastic schistose aggregate of hornblende, chlorite (clinochlore), epidote (pistacite), clinozoisite, quartz, and altered albite- oligoclase. In basalts, hornblende and/or chlorite are in excess of the other constituents; in andesites, the reverse is true. Magnetite is abundant in some specimens and lacking in others. Rutile and pyrite are present as minor constituents. Secondary carbonate forms up to 30 per cent of some specimens from the southeastern fringe of the outcrop belt.

Where both mafic minerals are present, chlorite apparently has formed at the expense of hornblende. However, in andesites from the region south and east of Pillow lake, randomly oriented, euhedral, hornblende porphyroblasts cut across the schistosity of the rock and

(1) Colour terms used in this report follow the Rock Colour Chart of the National Research Council. 9 obviously have formed at the expense of chlorite in the groundmass. Small amounts of biotite also have formed at the expense of chlorite in these rocks.

It is worthy of note that the isolated occurrence of pillowed basalt, near the northeastern corner post of Dollier township, consists of 60 per cent chlorite (optically negative penninite), 20 per cent magnetite, 15 per cent carbonate, and 2 per cent biotite.

Metadiorites which crop out at several localities in the southwest corner of Dollier township are greyish green to dusky green, medium-grained rocks. Megascopically, they appear to consist of about 4 0 per cent blocky hornblende prisms ranging from 1 to 5 mm. in length, and 60 per cent pale green or grey plagioclase. Although the texture appears massive in hand specimen, examination of thin sections and s•aw- cut surfaces shows that a strong schistosity is imparted by finely- divided, light-coloured minerals which wrap around the hornblende grains.

Microscopically, the blue-green hornblende porphyroblasts are seen to be surrounded by a crystalloblastic aggregate of epidote (pistacite), clinozoisite, quartz, and untwinned albite-oligoclase. This aggregate has been replaced in part by secondary sphene, carbonate, and pyrite. The pyrite is flattened in the plane of the schistosity. Some chlorite (clinochlore) has formed at the expense of hornblende. The texture gives no evidence on the origin of these rocks, whether intrusive or extrusive.

Diorite porphyry which forms a dyke near Mile Post 9 of the Charron-La Dauversière township line contains large (15 mm.), euhedral to subhedral moderate greenish yellow phenocrysts of epidotized andesine in a dark greenish grey, medium-grained, hornblendic groundmass. The poikilitic hornblende is surrounded by a fine-grained aggregate of clinozoisite, chlorite, quartz, untwinned andesine, and minor sphene. Veinlets of clinozoisite and carbonate are common throughout the rock. Pyrite is rare.

Andesite breccia from Mile Post 5 of the Dollier-Queylus line consists of angular fragments of yellowish grey, altered feldspar in a groundmass of greenish grey andesite. The fragments are up to 3 cm. in greatest dimension.

Tuff from Mile Post 8 of the Charron-La Dauversière line is a thinly laminated, aphanitic rock which is greenish grey on weathered - 10-

surfaces and dark greenish grey on fresh surfaces. It consists of 40 per cent hornblende, 10 per cent chlorite (clinochlore), 30 per cent clinozoisite, 20 per cent quartz, and minor sphene. The lamination is due to alternation of thin bands rich in hornblende with those rich in clinozoisite, and is accentuated by stringers of secondary quartz.

Most of the Keewatin-type rocks described above belong to the greenschist metamorphic facies as described by Turner and Verhoogen (1951, pp 466-472). The abundance of hornblende in some of these rocks is a common feature in low-grade metamorphic rocks derived from intermediate and basic igneous rocks (Tilley, 1938). In most cases it represents either a metastable relic or a transitory stage between original pyroxene and metamorphic chlorite. In a few transition-zone specimens, as from andesites of Pillow lake, hornblende metacrysts have formed at the expense of chlorite. This suggests a transition to the albite-epidote-amphibolite facies, which represents a higher grade of regional metamorphism.

"Timiskaming-type" Sedimentary Rocks

"Timiskaming-type" sedimentary rocks crop out between Stella lake and Pillow lake, within the northern part of the "Keewatin- type" volcanic belt. Exposures of these sedimentary rocks occur on the shores and islands of the central part of Stella lake, on the banks of Wynne creek between Stella and Pillow lakes, and on the west shore of Pillow lake where it drains into Wynne creek.

These rocks are flanked on the east by volcanic rocks that crop out on Pillow lake. Otherwise, due to the heavy cover of drift, the area underlain by the sedimentary rocks is not accurately known.

A thin bed of "Timiskaming-type" rock is interstratified with volcanic rocks south of Pillow lake. However, the bulk of these sedimentary rocks occupies the axial zone of an overturned syncline and sc seems to overlie, and be younger than, the surrounding, concordant, volcanic rocks..

Granitic members of the Chibougamau intrusive complex have caused metamorphism of the volcanic rocks at the north end of Stella lake. It is, therefore, possible that these granites are also younger than some of the "sedimentary" rocks. However, there is no reason to believe that all the "sedimentary" rocks are older than the intrusive complex. Indeed, it is probable that the garnetiferous conglomerate near Conglomerate lake, known to be younger than the intrusive complex, represents a coarser-grained and more highly metamorphosed facies of some of these "Timiskaming-type" sedimentaries.

The "sedimentary" rocks in this area are chiefly medium to coarse feldspathic sandstones. Similar feldspathic rocks have been mapped in various places in the Chibougamau region (Dresser and Denis, 1944, pp 128-129). Greywacke was noted at only two localities: at the junction of Wynne creek and Pillow lake, and one mile to the northwest on the west bank of Wynne creek. Feldspathic conglomerate is interbedded with feldspathic sandstone on the east bank of Wynne creek, 1/2 mile from its outlet into Stella lake. Unfortunately, this outcrop is a foot or more below water level and no specimen was obtained for examination.

The feldspathic sandstones are greyish green, schistose rocks. Clastic grains, recognizable in hand specimens, include: dull grey, altered feldspar; clear, twinned plagioclase; clear and smoky quartz. They range from 0.5 to 1.5 mm. in diameter and are set in a green, micaceous matrix. The sandstone is stratified and individual beds are from a few inches to 2 feet thick. The bedding is recognized by slight differences in colour and grain size and by cherty seams along the bedding planes. Small and large scale cross-bedding is well- preserved in exposures on the islands of Stella lake (Plate III), and was used to determine tops of beds. Cross-bedding is also preserved in exposures on Wynne creek but is too deformed to be used for top determinations.

Microscopic examination shows that subangular to subrounded clastic fragments of quartz and plagioclase, present in approximately equal amounts, constitute 50 to 60 per cent of these rocks. The matrix consists of finely divided quartz together with muscovite, hiotite, chlorite, epidote, and clinozoisite which have formed at the expense of the original argillaceous cementing materials. The micaceous minerals, particularly muscovite which is most abundant, are aligned so as to form bedding-schistosity. Sphene, pleochroic in reddish brown, occurs as scattered, subhedral porphyroblasts. Secondary carbonate, pyrite, and tourmaline (schorlite) are present in small amounts.

The greywacke is dusky blue-green and schistose, and contains angular fragments of dark rocks and minerals, together with traces of clear quartz, in a chloritic groundmass. Inspection of saw-cut surfaces shows that these clastic fragments constitute 30 to 40 per cent of the. - 12- rock. No stratification was noted in the greywacke; however the distribution of outcrops suggests that the greywacke is concordantly interbedded with near-by feldspathic sandstones.

Microscopically, the dark fragments are shown to be angular to subrounded grains of actinolite partly altered to biotite and chlorite. The fragments are set in a "paste" or matrix of finely divided quartz, sericite, chlorite and minor biotite.

This rock-type probably represents a rapidly-deposited sediment derived from mechanical weathering of a basic rock. It could be a basic crystal tuff.

The "Timiskaming-type" sedimentary rocks of this area belong to the greenschist metamorphic facies (Turner and Verhoogen, 1951, pp 465-473).

Hornblende Schists and Garnetiferous Hornblende Schists

Hornblende schists and garnetiferous hornblende schists underlie the southwest corner of the map-area west of Malo lake, and also a narrow belt that extends from the vicinity of Dufresne lake northeastward to Boisvert river. Smaller bodies of the schists occur in the extreme northeast corner of the area and north of Con- glomerate lake.

These schists are higher grade metamorphic equivalents of "Keewatin-type" volcanic rocks. Those around Malo lake were traced southwestward through hornblende schists mapped by Imbault (1959) into "Keewatin-type" basalts mapped by Gilbert (1959). Those northwest of Dufresne and Tippecanoe lakes, and those east of Pillow lake were also traced westward into "Keewatin-type" volcanic rocks. Gradational rock-types, mainly hornblende-chlorite schists with distorted pillows and amygdules, occur in all three localities. They contain small amounts of garnet and are coarser grained than the typical "Keewatin- type" volcanic rocks.

Northeastward from Tippecanoe lake, mica schists and gneisses of sedimentary origin intervene between the hornblende and garnetiferous hornblende schists and their "Keewatin-type" equivalents. Small bodies of hornblende schist within these mica schists and gneisses apparently were derived from volcanic flows. - 13-

The hornblende and garnetiferous hornblende schists are intruded by orthogneisses. The body of schists in the southwest corner of the area is bounded on three sides by grey orthogneisses. Sills and dykes of orthogneiss and related pegmatite and aplite cut these schists at several localities.

The belt of hornblende schist that extends northeastward from Dufresne lake is flanked on the southeast partly by pink muscovite granite gneiss and partly by grey orthogneisses. A sill of the muscovite granite gneiss cuts the hornblende schist exposed on the east wall of a north-northeast-trending stream valley, half a mile west of the central part of Tippecanoe lake. Exposures of muscovite granite gneiss along the Chibougamau highway contain numerous inclusions of hornblende schist, although not in the immediate vicinity of the contact zone. North of Pierre lake, the hornblende and garnetiferous hornblende schists have been intruded lit-par-lit by the grey orthogneisses that flank them on the southeast. Streaky inclusions and broad bands of garnetiferous amphibolite are common within the grey gneisses as far as half a mile from the contact zone. The hornblendic composite gneisses which are common throughout the southeastern part of the area are probably also the result of intrusion of hornblende schists by the grey orthogneisses.

Hornblende Schists: The hornblende schists near the Keewatin-type rocks are medium-grained and greenish black. In hand specimen they seem to consist chiefly of aligned prisms of dark hornblende averaging about 5 mm. in length, with small amounts of light grey quartz and plagioclase. Some of the quartz and plagioclase is segregated into thin streaks and bands which, in a few specimens, outline very small-scale folding about axes that parallel the schistosity. A few small metacrysts of red garnet are visible in some specimens. A thin-section of a typical specimen consists of an esti- mated 50 per cent bluish green hornblende, 35 per cent plagioclase (Ab75An~5), 15 per cent quartz, and small amounts of biotite, epidote, pyrite, rutile, and carbonate. Highly-deformed pillows and amygdules in some of the hornblende schists prove that these rocks formed from "Keewatin-type" lavas. These schists grade eastward into coarser- grained, garnetiferous varieties.

Non-garnetiferous hornblende schists are interbanded with medium- and coarse-grained garnetiferous schists in several localities - particularly in the region west of Lake Malo. The former are dark grey, medium-grained, laminated rocks with an overall salt-and-pepper appearance caused by approximately equal amounts of dark hornblende and light grey plagioclase. The lamination is caused by slightly varying proportions of light and dark minerals. Laminae vary from half an inch to one inch in width. The contact planes of adjacent laminae have been etched out on weathered surfaces. Microscopic study of one of the lighter-coloured laminae shows a crystalloblastic, schistose aggregate of 50 per cent bluish green hornblende with 47 per cent anhedral, slightly sericitized plagioclase (Ab75An~5). About 3 per cent of the rock is biotite and chlorite (clinochlore), which have formed at the expense of hornblende. Allanite is rare. These laminated hornblende schists were probably derived either from intermediate to basic tuffs or from greywackes.

Some fine-grained hornblende schists are found west and northwest of Dufresne lake and near Mile 119 of the Chibougamau highway. At the latter locality they were mapped as "recrystallized sedimentary rocks" by Imbault (1959). These rocks are greyish to greenish black and, in hand specimens, appear to consist almost wholly of dark hornblende prisms generally less than 1 mm. long. Pyrite, in elongated blebs, is the only other mineral distinguishable with the naked eye. A thin section showed that the rock consisted of 60 per cent hornblende, 30 per cent quartz, 10 per cent epidote (pistacite), and traces of magnetite. The prismatic hornblende and the platy quartz and epidote all contribute to the pronounced schistosity of the rock. Minute stringers of secondary quartz, carbonate and pyrite lie both parallel to and athwart the schistosity. These rocks may be metamorphosed sedimentary rocks,as Imbault has suggested, or they may be recrystallized equivalents of laminated tuffs that crop out half a mile to the west. In either case, recrystallization would have been sufficiently intense to have obliterated evidence of original lamination or bedding.

Garnetiferous Hornblende Schists: Hornblende schists that contain 10 to 35 per cent garnet are the chief rock-types in the extreme southwest corner of the area. They are also the dominant rocks in the northern part of the belt of hornblende schists that extends northeastward from Dufresne lake to Boisvert river. In the southern part of this belt, west of Tippecanoe and Dufresne lakes, they dominate in the east, but grade westward into non-garnetiferous varieties such as described in the preceding section.

The garnetiferous hornblende schists vary in garnet content and grain size, and hence vary considerably in appearance. As a general rule, garnet is most abundant in the coarser-grained varieties. - 15 -

Typically, the medium-grained varieties are dark grey, schistose rocks consisting chiefly of hornblende prisms. 1 mm.. in average length, and grey feldspar. Red garnet forms 15 to 20 per cent of these rocks. It occurs as well-formed crystals, 1.5 mm. in diameter, that stand out in relief on the weathered surfaces. Thin sections show a porphyroblastic-schistose fabric — with euhedral garnet porphyroblasts truncating the schistosity of an assemblage of hornblende, epidote, plagioclase (Ab70An30), and quartz. Secondary carbonate has formed at the expense of garnet, hornblende and plagioclase.

The coarse-grained garnetiferous hornblende schists are dark grey on fresh surfaces and dark greenish grey weathering. Pale reddish brown garnets up to the size of walnuts stand out in relief on the weathered surfaces. The rocks consist of 20 to 35 per cent garnet, 30 to 40 per cent hornblende, 25 to 30 per cent quartz and plagioclase (Ab.70An30) in approximately equal amounts, 10 to 20 per cent epidote, and small amounts of magnetite. The large garnet (almandine) crystals contain numerous inclusions of hornblende, plagioclase, quartz and epidote. Hornblende, pleochroic in brownish green, is in prisms up to 2 cm. long. Locally, bands and streaks of epidote and secondary quartz impart a gneissic structure to the rocks. Traces of allanite occur within clinozoisite and hornblende, and has produced pleochroic haloes within the hornblende.

Contacts with the Southeastern Gneisses: Carbonate-rich zones are common within the belt of hornblende schists extending northeastward from Dufresne lake, and also within the adjacent muscovite schists and gneisses. Locally, the hornblende and garnetiferous hornblende schists have been replaced by more than 50 per cent of rusty- weathering iron carbonate. This carbonation, with some accompanying pyritization, is probably related to hydrothermal activity associated with emplacement of the southeastern orthogneisses.

Study of an intrusive contact between hornblende schist and muscovite granite gneiss shows that the plagioclase of the schist is sericitized and that chlorite and abundant biotite have formed at the expense of hornblende within a few centimeters of the contact. Contacts between hornblende schist inclusions and grey (granodioritic) orthogneisses show less evidence of biotite replacing hornblende.

A specimen of zoisite-rich garnetiferous hornblende schist from the contact zone between the schist and the grey orthogneiss in central Dollier township contains a pale green-blue, actinolitic amphibole instead of the deep-coloured hornblende typical of these schists. - 16-

The garnet porphyroblasts in this rock are partly altered to chlorite. This suggests that, locally at least, processes that accompanied emplacement of the grey orthogneiss produced retrograde metamorphism.

Metamorphic Grade: Practically all the hornblende schists and garnetiferous hornblende schists contain hornblende and oligoclase or sodic andesine, the critical minerals of the amphibolite metamorphic facies. The mineralogy of the garnetiferous schists suggests that they belong to assemblage No.4 of the staurolite-kyanite subfacies of the amphibolite facies (Turner and Verhoogen, 1951, p. 454). This assemblage is typical of basic igneous rocks formed by medium- or high-grade regional metamorphism involving strong deformation under high pressure and stress.

Garnetiferous Muscovite Schists and Gneisses

Garnetiferous muscovite schists and gneisses of sedimentary origin crop out as a lens-shaped belt that extends from the northwest corner of Charron township northeastward to the northeast corner of Dollier township. The belt increases in width northeastward to a maximum of about 3 miles near Couteau lake, in the northeastern part of Dollier township. Garnetiferous hornblende schists within the central part of this belt, in the northeast corner of the area, may represent an infolded body of volcanic rock. The muscovite schists and gneisses apparently wedge out on either side of this body of hornblende schists, for they could not be traced beyond the boundaries of the present map- area, and Longley (1958) has not mentioned their presence in the adjacent area to the northeast.

Throughout most of its length, the outcrop belt of these muscovite schists and gneisses is flanked on the northwest by "Keewatin- type" volcanic rocks and, locally, by their more highly metamorphosed equivalents. On the southeast, the belt is flanked by the garnetiferous hornblende schists described in the previous section. Hornblende and garnetiferous hornblende schists of ultimate volcanic origin are inter- calated with the muscovite schists and gneisses near both boundaries of the outcrop belt.

In the north-central part of the area, around Couteau lake, the belt of muscovite schists and gneisses is bounded on the northwest by garnetiferous conglomerate. The relationship between these rock- types is not definitely known due to lack of outcrops at that locality. Petrographic similarities suggest that some of the schists and gneisses are derived from fine-grained members of the sedimentary sequence to - 17 - which the conglomerate belonged.

The garnetiferous muscovite schists and gneisses were not seen in contact with the southeastern orthogneisses. It is likely, however, that extensive carbonation and minor pyritization of these schists and gneisses were caused by hydrothermal activity of the grey orthogneiss. Also, it is possible that biotitic bands and inclusions within the southeastern gneisses are genetically related to these muscovite schists and gneisses.

Although garnet and muscovite are the distinctive minerals of this map-unit, locally one or both may be absent or subordinate to other minerals — particularly hornblende and biotite. For this reason, several rock-types are distinguished and described in the succeeding section. One of these, a staurolite-kyanite schist which crops out one- quarter mile north-northeast of Mile Post 6 of the Dollier-Vimont line, has not been reported previously from the Chibougamau region.

Muscovite Schist: This rock-type is known only around Mile Post 9 of the Dollier-Charron line, and may be related to shearing in this locality. It is interbedded with light-coloured garnetiferous hornblende-muscovite gneiss. The schist is a rusty-weathered, greyish orange, medium-grained rock with an overall micaceous sheen due to the high content of muscovite. It consists of 35 per cent muscovite, 5 per cent biotite, 45 per cent anhedral quartz in grains averaging 0.3 mm. in diameter, traces of untwinned plagioclase, 2 or 3 per cent ilmenite and about 12 per cent hematite and limonite. The schistosity shows intense micro-folding. This rock is probably a metamorphosed feldspathic sandstone, but there is no intrinsic evidence of its origin.

Garnetiferous Biotite-Muscovite Schist: This is the most common rock-type in the northern part of the outcrop belt, and is particularly well-exposed on the shores of Couteau lake. The average specimen is greyish orange with a silvery sheen caused by the high content of muscovite. Large, euhedral crystals of deep red garnet stand out in marked contrast to the light-coloured, medium-grained, quartz-mica groundmass. The garnet crystals commonly form 10 to 15 per cent of the rock and average between 5 and 10 mm. in diameter. Exceptionally, they form l+O per cent of the rock, and attain diameters of 5 cm. (2 inches) or more.

Microscopic examination shows that the groundmass consists of 50 to 60 per cent quartz, 25 to 30 per cent muscovite, 10 to 15 per - 18- cent biotite, 3 per cent chlorite, 2 per cent magnetite, and traces of plagioclase, zircon, and pyrite. The quartz grains are subangular to subrounded. They average 0.15 mm. in diameter but range up to 0.5 mm. Many appear to be original detrital grains, and are surrounded by biotite which apparently has formed at the expense of an original argillaceous cement. The schistosity of the rock is largely due to alignment of muscovite and biotite flakes. In part, the garnet porphyroblasts transgress the schistosity of the groundmass and the garnet is riddled with lines of quartz inclusions which parallel the schistosity. In part, the porphyroblasts have dilated the schistosity so that it bends around them. Chlorite, in some of these rocks, occurs as euhedral laths which are arranged in subparallel groups athwart the schistosity. It has formed late, and apparently represents retrograde metamorphism.

These schists are believed to have been argillaceous quartz sandstones originally.

Garnetiferous Biotite-Muscovite Gneiss: Where adjacent layers of the garnetiferous biotite-muscovite schist differ in biotite content, the rock assumes the character of a banded gneiss. Some of the. medium grey biotitic bands contain up to 20 per cent biotite and small amounts of associated hornblende. The banding undoubtedly represents original sedimentary bedding in argillaceous quartz sandstones.

Hornblende-Muscovite Schist: Hornblende-muscovite schist is the most common rock in the central part of the outcrop belt. It also occurs as bands within garnetiferous biotite-muscovite schist around Couteau lake. The colour of the hornblende-muscovite schist varies from light to dark greenish grey. Sheared varieties in the southern part of the outcrop belt, near the Dollier-Charron line, are rusty-weathering.

The schist consists of 25 to 35 per cent finely divided (0.15mm.) quartz and plagioclase (Ab73An27), 25 to 60 per cent hornblende, 15 to 20 per cent muscovite, 0 to 10 per cent garnet, 2 or 3 per cent magnetite, and variable small amounts of biotite, chlorite, epidote, zircon, and pyrite. Secondary carbonate is common in many specimens and, in some, forms as much as 20 per cent of the rock.

Muscovite and hornblende are the most prominent minerals in hand specimens. Parallelism of muscovite flakes causes the pronounced schistosity, and the abundance of muscovite accounts for the usual micaceous sheen. Hornblende occurs both as individual prisms up - 19 - to 3 cm. long and as radial aggregates or clusters of prisms. The individual prisms are either aligned or randomly oriented in the planes of schistosity. The radial aggregates are elongated in the dip direction of the schistosity, but the apices of the aggregates may point either up or down dip. The hornblende prisms contain numerous minute zircon crystals surrounded by pleochroic haloes. Most hornblende grains appear to have formed at the expense of the plagioclase, muscovite, and chlorite of the groundmass. They are riddled with inclusions of "un- digested" quartz.

The mineralogical composition of the hornblende-muscovite schist suggests a derivation from greywacke-type sedimentary rocks similar to those which crop out on Wynne creek, in the northwestern part of the area.

Garnetiferous Hornblende Gneiss: Garnetiferous hornblende gneiss occurs at several localities within the outcrop belt but is particularly common along its southern flank, near Boisvert river. It is a medium- to coarse-grained rock consisting of alternate greyish black and greyish orange bands and streaks. The lighter bands consist chiefly of quartz and plagioclase (Ab73An27) with minor interstitial biotite, all extensively replaced by carbonate and clinozoisite. The darker bands consist chiefly of porphyroblastic hornblende which appears to have formed at the expense of biotite, plagioclase, and quartz. Red garnet porphyroblasts occur in both light and dark bands.

This gneiss probably derived from a greywacke-type sedimentary rock.

Staurolite-kyanite Schist: The staurolite-kyanite schist that crops out near Mile Post 6 of the Dollier-Vimont line is brownish grey and medium-grained. Megascopic examination shows the presence of biotite, muscovite, quartz, garnet; finely-divided brown staurolite, and prisms up to 3 mm. long of pale blue kyanite. Parallelism of the muscovite and biotite flakes causes the schistosity of the rock. Biotite may be segregated into streaks which impart a poorly-defined gneissic structure parallel to the schistosity.

Microscopic examination shows 15 per cent plagioclase (Ab76An24), 20 per cent quartz, 20 per cent staurolite, 15 per cent kyanite, 10 per cent biotite, 5 per cent garnet, 5 per cent muscovite, 5 per cent chlorite, and small amounts of magnetite, apatite, tourmaline and carbonate. - 20-

This schist developed from an argillaceous sedimentary rock — possibly a feldspathic sandstone with an argillaceous matrix, similar to the sandstone that crops out on the west shore of Stella lake.

The rock was identified as a garnetiferous muscovite- biotite schist in the field, and its correct mineralogy was determined only after laboratory study. It is possible, therefore, that similar staurolite-kyanite schist crops out elsewhere within the belt of garnetiferous muscovite schists and gneisses.

Metamorphic Grade: Most, if not all, of these garnetiferous schists and gneisses belong to the amphibolite metamorphic facies. Min- eralogically, they are similar to the assemblages that Turner and Verhoogen (1951, pp 452-454) have listed as typical of those rocks of the staurolite-kyanite subfacies that are deficient in potash. All could have been derived from feldspathic sandstones and greywackes similar to the sedimentary assemblage around Stella lake.

Chibougamau Intrusive Complex

Altered anorthositic, gabbroic, and granitic rocks underlie about 10 square miles in the northwest corner of the area. These rocks form part of the south and southeast border zones of a group of altered intrusive rocks that underlies a large part of the Chibougamau Lake region. This group of rocks has been mapped in the adjacent area to the north by Mawdsley and Norman (1935), the adjacent area to the west, by Imbault (1959), and that to the northeast,by Longley (1958). Dresser and Denis (1944, p. 134) have proposed the term "Chibougamau complex" for the group.

Evidence that the Chibougamau complex is younger than some of the surrounding "Keewatin-type" volcanic rocks and "Timiskaming-type" sedimentary rocks is given below. Dark, chloritic inclusions occur within all members of the complex; these probably represent inclusions of the sedimentary and volcanic rocks. Intense alteration of pillowed lava at the north end of Stella lake may be related to intrusion of adjacent rocks of the complex. In one locality, about three quarters of a mile north-northeast of Mile Post 1 of the Dollier-Lemoine line, a polymictic dyke cuts gneissic gabbroic anorthosite. This dyke consists of 80 per cent angular greenstone fragments in an anorthositic cement. The greenstone fragments probably derived from volcanic rocks which were intruded at depth. - 21 -

There is no evidence that the Chibougamau complex is younger than all the greenschist grade sedimentary and volcanic rocks of the area. The garnetiferous conglomerate described above is younger than the intrusive complex, and may once have been a greenschist grade sedimentary rock.

The rocks of the Chibougamau complex have been subjected to the same low-grade, greenschist type of regional metamorphism as the immediately surrounding rocks and the rocks which underlie a vast region to the west. Southeastward, the grade of metamorphism increases. This higher grade of metamorphism is apparently younger than, and superposed on, the greenschist metamorphism. Either the higher grade of metamorphism was caused by intrusion of the southeastern orthogneisses, or both grades were due to a common cause. In either case, the southeastern orthogneisses are younger than the final period of greenschist grade metamorphism and, consequently, younger than the Chibougamau complex.

In the Dollier-Charron area, the anorthositic and gabbroic members of this complex are distributed so erratically that it was not practical to map them separately. In general, gabbroic rocks are pre- dominant in the eastern part of the outcrop area, east of Wynne creek. Although the rock-types are intergradational in most exposures, dykes of anorthosite cut the gabbro at several localities. A few dykes and irregular bodies of fine-grained greenstone cut both anorthositic and gabbroic rocks.

The granitic members of the complex occur as dykes that cut the anorthositic and gabbroic rocks and, hence, are younger than these rock-types. However, they are chiefly restricted to the southern and eastern margins of the outcrop area, where they are mapped as a separate unit.

The outcrop pattern of the entire Chibougamau complex, together with detailed observations on distribution of rock-types in certain areas (Allard, 195*), has suggested that it constitutes a differentiated, sheet-like body which has been folded about northeast axes. No evidence for or against this hypothesis was found within the small part of the complex exposed in the present area.

Anorthosite: The typical anorthosite of this area is massive and medium-grained. It has a very pale green colour and waxy lustre on fresh surfaces but weathers greyish-orange pink. Its apparent mineral composition is 90 per cent light greenish grey plagioclase and 10 per cent dark greenish grey chlorite. The chlorite is interstitial - 22 - to the plagioclase and, locally, is aligned so that it imparts a faint gneissic structure to the rock. Rocks intermediate between anorthosite and gabbro include greenish grey gabbroic anorthosite (10 to 20 per cent dark minerals), and dark greenish grey anorthositic gabbro (20 to 35 per cent dark minerals). Chlorite and green amphibole are the megascopically recognizable dark minerals in these rocks. In some specimens of the anorthositic gabbro, the plagioclase occurs as laths in rough alignment.

Thin sections show that these rocks have undergone a complete alteration of their original constituents. They consist of 50 per cent or more epidote (pistacite) and clinozoisite, and varying amounts of muscovite, scapolite, quartz, actinolite, and chlorite. Small amounts of albite-oligoclase occur in some specimens. Most of these minerals have formed at the expense of original calcic plagioclase, such as Mawdsley and Norman (1935, p.28) have described from unaltered rocks that crop out around the northeast part of Chibougamau lake. The chlorite and actinolite probably formed from the breakdown of original pyroxene.

Gabbro: The gabbro is a dusky green medium-grained, massive to slightly schistose, heavy rock. In hand specimen, it appears to consist of 60 per cent chloritized hornblende and 40 per cent greyish green plagioclase. Microscopic work shows that the plagioclase has broken down completely to a fine-grained aggregate of quartz, albite, epidote, and carbonate. Hornblende, chlorite, and epidote have formed at the expense of original pyroxene. Traces of a relic ophitic texture are shown by euhedral laths of the completely altered plagioclase partly or completely enclosed by alteration products of pyroxene. Apatite and titaniferous magnetite occur as anhedral grains; these were probably interstitial to the original plagioclase and pyroxene.

Granitic Rocks: Granitic rocks are mapped as a separate unit on the southern and eastern sides of the Chibougamau complex. Those that form the southern margin of the complex are medium-grained, massive to schistose rocks. They strongly resemble nearby anorthositic rocks on weathered surfaces. On fresh fractured surfaces pale blue quartz, pale brown to pale green feldspar, and dark green chlorite can be distinguished with the naked eye. Microscopic examination shows that these granitic rocks contain no potash feldspar -- a distinctive feature of the granitic rocks of the Chibougamau complex (Mawdsley and Norman, 1935, pp 37-39). In the massive varieties, 50 to 60 per cent euhedral to subhedral plagioclase (Ab85An15) occurs in hypidiomorphic Plate I Plate 11 Plate III Plate IV Plate V Plate VI Plate VII Plate VIII

h . t nor king o lo

ke, la

lla Ste f o View -23 - granular intergrowth with 30 to 40 per cent anhedral quartz. The plagioclase is sericitized, and the quartz shows pronounced strain shadows. Interstitial aggregates of chlorite and magnetite make up 10 to 15 per cent of the rock and, probably, formed at the expense of original biotite or hornblende. Where sheared, these granitic rocks have been converted to quartz-rich sericite schists in which relic plagioclase grains survive as small augen.

The granitic rocks at the eastern margin of the complex are distinguished by their high quartz content, hydrothermal alteration, and evidences of mechanical deformation. They consist of 40 to 60 per cent pale blue quartz and 30 to 40 per cent highly sericitized plagioclase. Chlorite, green biotite, and magnetite together form about 10 per cent of the average specimen although chlorite is up to 25 per cent in a few mafic types. Zircon and sphene are present as traces. Late hydrothermal minerals form 5 per cent or more of these rocks and include iron carbonate, pyrite, and brown tourmaline (schorlite). Remnants of an original hypidiomorphic texture are discernible. These, however, are largely obliterated by the effects of granulation which, locally, has produced a mortar texture.

These rocks are referred to as "granitic" for simplicity and in order to follow the nomenclature used in adjacent areas. However, due to the complete absence of potash feldspar, they cannot properly be classified as granite or granodiorite. The large quartz content pre- vents their being classed as quartz diorite. In composition, they are most similar to the intrusive quartz-oligoclase-biotite rocks known as trondhjemites.

Metamorphic Grade: The rocks of this intrusive complex have been subjected to the same low grade of regional metamorphism as the surrounding "Keewatin-type" and "Timiskaming-type" rocks. Min- eralogically, they represent an almost complete adjustment to the greenschist metamorphic facies (Turner and Verhoogen, 1951, pp 465-472).

Garnetiferous Conglomerate

Garnetiferous boulder and pebble conglomerate crops out at several localities along the southeastern shore of Conglomerate lake, a small lake toward the northeastern corner of the area. Similar conglomerate crops out on the Dollier-Lemoine township line, 1,400 and 3,600 feet west of Mile Post 7. Enormous erratics of conglomerate, obviously not far removed from their source, are common between these - 24 -

two localities. Two doubtful outcrops occur a half mile and one mile north-northwest of Mile Post 7. The latter is just beyond the northern boundary of the map-area. Due to scarcity of outcrops, the limits of the conglomerate cannot be closely defined.

The conglomerate contains pebbles, cobbles, and boulders of anorthositic and granitic rocks from the Chibougamau intrusive complex and, hence, is known to be younger than this complex. This is the only definite information available in regard to its age relative to that of other rock units of the area. However, some logical infer- ences can be made.

Numerous quartz veins cut the conglomerate and, in the exposure 1,400 feet west of Mile Post 7, it is cut by a thin pegmatite stringer. Locally, pyritization and carbonate replacement are prominent. All these features are probably related to intrusion of the southeastern (Grenville?) orthogneisses. Although these orthogneisses are not exposed within 3 miles of the conglomerate they are, nevertheless, the nearest intrusive rocks and, excepting the gabbro dykes, they are the only intrusive rocks of the region that do not occur as fragments within the conglomerate.

The matrix of the conglomerate exposed on Conglomerate lake is practically identical to some of the garnetiferous biotite-muscovite schists and gneisses that crop out on Couteau lake. This suggests that the schists and gneisses may belong to the same sedimentary sequence as the conglomerate, and, unless overturned, the southeast-dipping conglomerate beds underlie the schists and gneisses.

The matrix and the sandy lenses within the conglomerate on the Dollier-Lemoine line are petrographically similar to the "Timis- kaming-type" sedimentary rocks that crop out around Stella lake and Wynne creek. This fact, together with the proximity of these rock units, suggests that they may be approximately equivalent in time. The objection to this correlation is that, in adjacent areas, the "Timis- kaming-type" sedimentary rocks are interpreted as older than the Chi- bougamau intrusive complex (e.g. Mawdsley and Norman, 1935). However, the term "Timiskaming-type" refers to a great variety of clastic sedimentary rocks whose only common feature is their low, greenschist grade of metamorphism.

There is petrographic evidence that the garnetiferous conglomerate passed through such a greenschist stage. Therefore, it -25 -

was once a "Timiskaming-type" rock. This indicates a period of erosion and deposition after intrusion of the Chibougamau complex and before the (final) period of regional, greenschist-grade metamorphism. The author's favoured hypothesis is that this conglomerate, together with all the sedimentary and volcanic rocks of the map-area, was part of a thick, not necessarily conformable, sequence that included rocks both older and younger than the Chibougamau complex. This sedimentary-volcanic sequence was subjected to the greenschist-grade metamorphism common throughout the Superior (Timiskaming) province. Later, certain parts of the sequence, including the conglomerate, were subjected to a second period of more intense metamorphism.

An alternative theory is that the garnetiferous conglomerate is a metamorphosed correlative of the Late Precambrian Chibougamau series which crops out ground the northern part of Chibougamau lake (Retty, 1929; Mawdsley and Norman, 1935) and, north of there, around Waconichi lake (Gilbert, 1958). Conglomerates of the Chibougamau series do not contain fragments of anorthosite or associated rocks of the Chi- bougamau complex and, for this reason, their source area is assumed to have been north of Chibougamau lake. This, however, does not preclude the possibility that the present conglomerate originated in a different basin of sedimentation but at the same time as the Chibougamau series. The fact that the Chibougamau series has been rendered schistose locally by late, northeast faulting favours the correlation. However, Smith (1954) reports that the Chibougamau series contains cobbles of high- grade schists and gneisses and is, therefore, much younger than the metamorphism which affected the garnetiferous conglomerate and surrounding rocks.

The conglomerate on the Dollier-Lemoine line is a coarse- grained, schistose, clastic rock made up of about 30 per cent vari- coloured pebbles, cobbles, and boulders in a medium-grained, medium light to medium dark grey matrix. The rock is best studied on surfaces from which moss has been freshly stripped (Plates IV and V). Here the clastic fragments are greenish grey anorthosite, dark greenish grey diorite, light greenish grey granite, white• to greyish orange quartzite and sericitic sandstone, and greenish black, slightly garnetiferous hornblende-biotite and hornblende-chlorite schists. The anorthosite, diorite, granite, quartzite, and sandstone that form the larger fragments have apparently resisted deformation, for they are massive, unsheared rocks. These large fragments, with diameters up to 2 feet are roughly circular or slightly elliptical with a tendency to be elongated down the dip of the schistosity. In contrast, the fragments of schist and small pebbles of the other rock-types are "smeared out" - 26- in the planes of schistosity and, locally, cause a streaky, gneissic structure in the conglomerate. Small crystals of red garnet are scattered through the clastic fragments and the matrix of the conglomerate. Although abundant in small patches, they probably constitute only 2 or 3 per cent of the whole rock.

Due to their importance in correlation, the anorthositic and granitic rocks merit description. In hand specimen, the anorthosite is massive, and appears to consist chiefly of blocky plagioclase crystals averaging 4 mm. in length, and about 15 per cent mafic mineral in interstitial clots. Small red garnets occur in some specimens. Micro- scopic examination shows that the subhedral plagioclase is epidotized sodic oligoclase which probably formed from an original calcic plagioclase. Biotite, 10 per cent, and chlorite, 5 per cent, are the mafic minerals. The biotite has formed, in part at least, from the chlorite. Secondary quartz and carbonate are interstitial and form 10 to 15 per cent of the rock. Magnetite and zircon are minor accessories.

The granitic rocks resemble the anorthosite in appearance but are lighter coloured due to the presence of 20 to 35 per cent, clear to light grey quartz. A typical thin section consits of 65 per cent epidotized oligoclase, 20 per cent quartz, 10 per cent biotite, 5 per cent magnetite, and small amounts of hornblende and chlorite. Some of the quartz may be secondary but most occurs in an apparently primary intergrowth with the blocky, subhedral oligoclase. Interstitial clots of biotite have formed at the expense of chlorite. Compositionally, these rocks are very similar to the granitic rocks of the Chibougamau complex.

Under the microscope, the schistose grey matrix of the conglomerate proves to be metamorphosed, greywacke-type, sedimentary material. It consists of subangular to subrounded fragments of quartz, epidotized oligoclase, quartz-oligoclase rocks, and stretched fragments of biotite schist. These rock and mineral fragments average 0.3 mm. and range up to 1.5 mm. in diameter. They are set in a paste of finely- divided quartz and 20 per cent biotite. The biotite has formed at the expense of original muscovite and chlorite. Transgressive porphyroblasts of green-brown hornblende and red garnet have formed at the expense of the micaceous minerals and, together, form 5 to 10 per cent of the rock. Traces of carbonate, pyrite, and tourmaline (schorlite) occur as late, hydrothermal replacements.

The conglomerate on the shores of Conglomerate lake have uniform greyish brown weathered surfaces; there is no moss cover which -27 - can be peeled back to reveal the contrasting colours and lithologies of the rock. However, the character of the conglomerate is readily apparent due to differential resistance to weathering and wave action. Re- sistant, cylinder-shaped cobbles and boulders stand out in relief against a background of less-resistant matrix. The cylinder-shaped boulders are up to 8 inches in cross-sectional diameter and 2 feet long down the dip of the schistosity. Pebbles and small cobbles have been flattened in the planes of schistosity and now have the shape of triax- •ial ellipsoids with maximum elongation down dip.

The lithology of the clastic fragments is only determinable on fresh fractured surfaces and in thin sections. All specimens examined appear to consist of older sedimentary rocks., chiefly quartzite, feldspathic sandstone and granule conglomerate, and thus testify to an older period of sedimentation, lithification and erosion. The quartzite is yellowish grey, massive, and breaks with a conchoidal fracture. It consists of about 90 per cent quartz and varying amounts of oligoclase, sericite, small pink garnets, and secondary carbonate. The sandstone and granule conglomerate are light brown, massive rocks in which subangular sand grains and granules of milky quartz and light grey plagioclase (epidotized oligoclase) are megascopically recognizable in an aphanitic groundmass. The groundmass consists chiefly of recrystallized quartz and small amounts of muscovite and chlorite. Small red garnets are scattered through most specimens. Light brown iron carbonate has replaced large parts of some specimens.

The matrix of this conglomerate, and the fine-grained beds and lenses within it, consist of light grey rock which can be appropriately described in hand specimens as garnetiferous muscovite-biotite schist. Microscopic study shows that it consists of 50 to 60 per cent finely-divided (0.1 mm.) quartz, 15 per cent large-flake (2 to 4 mm.) biotite, 10 per cent finely-divided chlorite and muscovite, 10 per cent garnet and varying small amounts of pyrite and secondary carbonate.

A thin bed of garnetiferous quartz sandstone interbedded with pebble conglomerate at the south end of Conglomerate lake is notable for the presence of 15 per cent poikilitic hornblende porphyroblasts which have formed at the expense of chlorite and other matrix minerals. Some of these porphyroblasts are oriented across the schistosity.

Metamorphic Grade: Most of the garnetiferous conglomerates represent a stage of metamorphism transitional between the greenschist - 28-

facies and the amphibolite facies and thus belong to the albite-epidote- amphibolite facies (Turner and Verhoogen, 1951, pp 460-462). The assemblage of muscovite-biotite-almandine-garnet-quartz, so common in the matrix of this conglomerate, is typical for pelitic rocks of normal composition which belong to this metamorphic facies. The metamorphic grade of the conglomerate increases southeastward, as proved by the increase in garnet and hornblende, and those specimens that crop out near the south end of Conglomerate lake belong to the amphibolite metamorphic facies.

Southeastern Gneisses

Orthogneisses and composite gneisses underlie about 60 per cent of the map-area, including most of Charron township and the southeast quarter of Dollier. These gneisses are similar to some reported from other parts of the boundary zone between the Grenville and Superior (Timiskaming) provinces. Although commonly referred to as "Grenville gneisses", the non-committal term "Southeastern gneisses" (Imbault, 1959) is more appropriate for the present because less de- finitive.

The gneisses in this area are flanked on the northwest by hornblende schists and garnetiferous hornblende schists. South of Du- fresne lake, near the central part of the Charron west boundary, a lobe of the gneisses extends southwestward to penetrate the surrounding hornblendic schists and "Keewatin-type" rocks (Imbault, 1959). Southeast of the map-area (Gilbert, 1958), the nature of the contact suggests that the Southeastern gneisses are complexly interfolded with schists and gneisses of sedimentary and volcanic origin.

The Southeastern gneisses are intrusive into the schists which flank them on the northwest. These schists can be traced westward into "Keewatin-type" volcanic rocks, therefore the gneisses must be younger than the "Keewatin-type" rocks. As mentioned above, these gneisses apparently post-date the low grade of regional metamorphism which affected the rocks of the Superior (Timiskaming) province. The Chibougamau intrusive complex has undergone such low grade metamorphism and is, therefore, older than the gneisses. The present study suggests that the Southeastern gneisses are younger than all other rocks of the Dollier-Charron map-area, except the thin gabbroic dykes which cut them at several localities.

The Southeastern gneisses are mapped as two units: (1) grey, rarely pinkish, undifferentiated biotite orthogneisses and - 29- composite gneisses that underlie the bulk of the outcrop area; hornblendic varieties of the composite gneisses were distinguished as a separate sub-unit; (2) pink, muscovite granite gneiss that occurs as a small, northeast-trending body in contact with hornblendic schists in the northwest corner of Charron township; this gneiss is interpreted as a cataclastically deformed, late phase of the biotite orthogneisses.

Satellitic quartz veins, pegmatites and aplites are common within the Southeastern gneisses. Some of these satellitic bodies cut the adjacent hornblende schists and garnetiferous hornblende schists, particularly in the region around Malo lake.

Biotite Orthogneisses and Composite Gneisses: Grey, locally pink, biotitic gneisses constitute 75 per cent or more of the South- eastern gneisses. In part they are orthogneisses, formed by the deformation of intrusive igneous rock; in part composite gneisses, resulting from intimate admixture of the orthogneisses with rocks of ultimate sedimentary and volcanic origin. In many outcrops it is impossible to differentiate orthogneisses from composite gneisses. Even where the two phases can be distinguished, they grade into each other and cannot be mapped separately.

Typically, the orthogneisses are very light to medium light grey, medium-grained, and faintly to distinctly banded. The minerals recognizable in hand specimen are clear to smoky quartz and white to light grey plagioclase in approximately equal amounts, and 5 to 10 per cent black biotite. Microscopically, they are composed of 35 to 50 per cent unaltered to slightly sericitized plagioclase (Ab7SAn~5), 35 to 50 per cent quartz, 2 to 20 per cent microcline, 2 to 10 per cent biotite, and small amounts of muscovite, myrmekite, epidote, apatite, zircon, sphene, and magnetite. The interlocking crystals of anhedral quartz and subhedral plagioclase range from 0.5 to 3.0 mm. in diameter. Microcline is interstitial to both quartz and plagioclase and penetrates the plagioclase along fractures. Myrmekite has grown at the expense of microcline. Alignment of the biotite flakes and their segregation into thin streaks and bands causes the gneissosity. The quartz shows strain shadows but, otherwise, there is little evidence of granulation expect in the orthogneiss of the northwest corner of Charron township. In general, the fabric is suggestive of crystallization under directed pressure. In a few specimens no gneissosity is visible; such are more appropriately classified as granodiorites and quartz diorites than as orthogneisses. -30-

The pink orthogneiss unit includes pale red to moderate reddish orange, weakly to strongly gneissic varieties that are associated with the grey orthogneisses at ^cattered localities throughout Charron township. These rocks contain quartz, plagioclase (Ab75An25), and potash feldspar in approximately equal amounts. Biotite, 5 per cent, is the chief varietal mineral. Microcline and microcline-micro- perthite are interstitial to quartz and plagioclase and have exsolved albitic rims along their contacts with the plagioclase. Muscovite and myrmekite post-date formation of the microcline. The gneissic structure is due chiefly to aligned biotite flakes supplemented, in some specimens, by flattened quartz crystals. At some localities the pink orthogneisses are gradational to the grey orthogneisses; at others, they intrude both grey orthogneisses and composite gneisses. The intrusive relationship is well-displayed 1,000 feet north of Mile 114 on the Chibougamau highway. Compositionally, the pink gneisses can be classified as quartz monzonites. Apparently they are late differentiates of the same magma from which the grey orthogneisses derived.

The grey, biotitic, composite gneisses are uniformly medium- grained but variable in appearance. Bands of the light grey orthogneiss described above alternate with medium grey to medium dark grey biotitic bands which derived from the intruded country rock. Individual bands range from 2 or 3 mm. to 10 cm. in width. Locally, lenses, streaks, and elongated angular fragments of dark grey biotite schist are present. A typical medium dark grey band consists of a granoblastic, gneissic aggregate of 40 per cent anhedral quartz, 35 per cent subhedral plagioclase (Ab75An~5), 20 per cent aligned flakes of biotite, and varying small amounts of epidote, muscovite, zircon, and almandine garnet. This band differs from the orthogneiss in its greater content of biotite, lack of potash feldspar, and traces of garnet. Considered in terms of composition, such a biotitic band could have derived from feldspathic sedimentary rocks of "Timiskaming-type".

Hornblendic varieties of the composite gneisses are common within a mile or so of the contact between the Southeastern gneisses and the hornblende and garnetiferous hornblende schists that flank them on the west and northwest. Such composite gneisses resulted chiefly from lit-par-lit injection of sills and bands of grey biotite orthogneiss into the hornblende schists. Specimens of the injected schists are characterized by their high (30 per cent or more) content of zoisite and clinozoisite, and by small amounts of biotite (formed at the expense of hornblende). One specimen shows a retrogressive breakdown of garnet to chlorite which maybe due to deuteric activity. - 31 -

Hornblendic composite gneisses also crop out around the shores of Coquille lake, in the southeastern corner of the area.. The medium dark grey hornblendic layers in this rock consist of about 55 per cent plagioclase (Ab68An32), 40 per cent hornblende, and small amounts of quartz, biotite, and epidote.

Large inclusions of hornblende schist found at scattered localities within the grey orthogneisses are also mapped as hornblendic composite gneisses. Such inclusions are well exposed near Mile 115 and Mile 118 of the Chibougamau highway. Injections along planes of schistosity by thin bands of white aplite have converted the schist to "layer cake gneisses" in black and white bands.

Pink Muscovite Granite Gneiss: A lenticular body of pink muscovite granite extends from Pierre lake southwestward to Dufresne lake and beyond. It wedges out in the adjacent map-area to the west (Imbault, 1959).

The typical muscovite granite gneiss is a moderate pink to orange pink rock made up of colourless to pale blue quartz, pink to white feldspar, silvery muscovite, and small amounts of black biotite. Its close-spaced gneissic structure is the result of the alignment and segregation of muscovite flakes, quartz leaves, and feldspar tablets, caused by mechanical deformation. In some specimens, muscovite and quartz bend around pod-shaped relics of plagioclase crystals and impart an augen structure to the gneiss. Microscopic examination shows that quartz, plagioclase (Ab9oAn1o) and potash feldspar are in approximately equal amounts. The potash feldspar includes both microcline and ortho- clase microperthites. Sutured boundaries between quartz and feldspar grains suggest that recrystallization followed granulation. Ten per cent muscovite, 2 or 3 per cent biotite and epidote, and traces of garnet are also present. In composition, this gneiss is a biotite- muscovite quartz monzonite.

Near contacts with hornblendic schists, the red hues change to greyish orange. Greyish orange specimens contain little or no potash feldspar. Biotitization of hornblende in the schists apparently depleted the potash content of the intrusive granite gneiss and precluded the formation of potash feldspar.

The pink muscovite granite gneiss grades eastward into grey biotite orthogneisses and composite gneisses. It is interpreted as a cataclastically deformed late differentiate of the magma from which the grey orthogneisses derived and, hence, the deformed equivalent - 32 - of the pink orthogneisses.

Aplite and Pegmatite: Tabular to irregular dykes of aplite and pegmatite are common within the Southeastern gneisses and a few cut the adjacent hornblende schists. Most of these satellitic dykes show little or no evidence of deformation; aplite, for example, has a charac- teristic allotriomorphic-granular fabric as seen in thin section. Except- ions are the striking augen pegmatites that occur within grey orthogneisses and paragneisses in the western part of Charron township. These rocks are well exposed between Mile 116 and Mile 118 on the Chibougamau highway'(Plate VI). The augen pegmatites resulted from the mechanical deformation of giant-grained granite pegmatites. They consist of lens- shaped augen up to 8 inches long of reddish orange microcline-micro- perthite set in a strongly gneissic, light grey ground-mass of quartz, plagioclase, and biotite.

Gabbro Dykes

Five dykes of massive, coronitic gabbro were mapped in the southeastern quarter of Charron township. Probably all of these are intrusive into the surrounding orthogneisses and composite gneisses. However, at only one locality, half a mile north of the west arm of Coquille lake was a dyke seen cutting the gneisses. There the intrusive contact strikes N.550E. and dips steeply southeast, truncating the gneissic structures. This dyke has a minimum thickness of 225 feet.

Gabbroic dykes have been mapped in the adjacent area to the west by Imbault (1959) and in the adjacent area to the southeast by Gilbert (1958). Both authors note the resemblance of these dykes to those which are commonly assigned to the Keweenawan. Some of the dykes described by Gilbert are intrusive into similar gneisses and are petrographically similar to the coronitic gabbro dykes of the present study. Undoubtedly they belong to the same period of intrusion. Coronitic gabbro dykes have been reported from other regions that lie immediately southeast of the boundary between the Grenville and Superior (Timiskaming) provinces (Neale, 1952).

The gabbro is dark bluish grey on fresh surfaces, and greyish brown to rusty on weathered surfaces. It consists of approximately equal amounts of plagioclase and pyroxene, with small amounts of iron ore and red garnet. The plagioclase laths are up to 1 cm. long, and are intergrown with the pyroxene so as to produce ophitic and sub-ophitic textures. Examination of two thin sections showed plagioclase (Ab65An35), pale green clinopyroxene, iron ore, hornblende, -33- biotite, garnet, apatite, and hematite. Small amounts of orange (xylotile?) and red (bowlingite?) alteration products may have formed at the expense of original olivine. The plagioclase is clouded with minute, dust-like inclusions and is light brownish grey in plane polarized light. Clinopyroxene, iron ore, and altered olivine(?) are surrounded by two- and three-tiered coronas that separate them from the plagioclase. Biotite, garnet, and hornblende are the corona minerals. The order through a typical, three-tiered corona is: iron ore — biotite — garnet — hornblende — plagioclase. Garnet is the most important of the corona minerals in terms of volume and constitutes more than 10 per cent of one specimen. Small amounts of quartz, possibly primary, fill triangular areas between divergent laths of plagioclase.

The origin of coronas is problematical. Recent writers favour regional (dynamothermal) metamorphism (Buddington, 1939, pp 294-298) or contact (thermal) metamorphism (Shand, 1945: Osborne, 1949) as the cause. Gilbert (1958) adopts the hypothesis of regional metamorphism to explain the coronitic gabbros in the adjacent area to the southeast.

The coronas of the present study cannot be due to contact metamorphism as the gabbro dykes are the youngest intrusions of the area. The fact that original textures are preserved and that the dykes truncate the surrounding gneissic structures proves that intrusion of the dykes postdates deformation of the Southeastern gneisses and, probably, the latest period of metamorphism. The possibility that the coronas may be due to late magmatic or autometamorphic processes (Neale, 1952MS.) deserves further investigation.

PLEISTOCENE AND RECENT

Striations, chatter marks, and friction cracks show that the line of flow of Pleistocene ice varied from S. 15°W. in the northern part of the area to within a few degrees of south-in the southern part of the area. Rock outcrops on the shores of lakes commonly have smooth, streamlined, stoss sides and abrupt, quarried lee sides — proving that the ice moved from north to south. Boulders of distinctive, cryptozoon-bearing limestones of the Mistassini series are common in some of the till deposits and most probably were derived from the Lake Mistassini region to the north-northeast.

Deposits formed by advancing ice include drumlins and ground moraine. Long, low, drumlinoid ridges are common throughout - 34-

the area, particularly in the region west of Boisvert river. The best developed forms occur in the extreme northwest corner of the area, near the southeasternmost bay of Chibougamau lake. Here, they attain maximum heights of 80 feet and lengths of over half a mile or more. Hummocky ground moraine is widely distributed, particularly in the south-central part of Dollier township and the northwestern quarter of Charron township. Many of the rock ridges east of Boisvert river have been modified by glacial deposition. Rocky cliffs form the abrupt north ends of these ridges, and "tails" of glacial till form their tapering south ends.

Landforms related to wastage of the ice sheet include eskers, kames, and kettles. In the southeastern part of the area, a sinuous esker extends, with several erosional breaks, from the region west of Boisvert lake southward to the west shore of Coquille lake — an overall length of 6 miles. Near Pillow lake, in the north-central part of the map-area, a small esker terminates southward in a delta deposit. Remnants of an esker were noted on the shores and islands of a small lake west of Thérèse lake, in the northwestern part of Charron township. In the southwest corner of Charron township, an esker flanks the west shore of Malo lake and extends from the south end of this lake to Branch lake. A historic portage follows the crest of this narrow, winding ridge. Kettle holes and conical kame mounds are associated with the eskers near Coquille and Malo lakes.

Approximately 15 feet of lake deposits are exposed along the banks of Boisvert river, near the Dollier-Charron township line. At the base of the section are some 3 feet of varved clays, followed above by laminated grey silts and fine sands. Near the top of the section thin layers of cross-bedded, fluvial silts and sands are inter- calated with the lake deposits. These deposits probably formed in a small glacial lake, for no similar deposits were noted elsewhere in the area. It is conceivable, however, that a bay of the great pro- glacial lake, Barlow-Ojibway (Norman, 1938, 1939), extended across the "height-of-land" and covered parts of the present area.

STRUCTURAL GEOLOGY

Bedding, Schistosity

Near the western boundary of the map-area, bedding and schistosity in the low-grade metasedimentary and metavolcanic rocks strike northeast to north-northeast and dip steeply southeast. These northeasterly strikes, together with the northeasterly trend of the - 35 - mappable units, represent a change from the dominant easterly strikes recorded by Imbault (1959) in the adjacent area to the west.

In the northeastern part of the area, the structural trend in the higher grade metasedimentary and metavolcanic rocks swings around to the east, parallel to the contact with the Southeastern gneisses. In the extreme northeastern corner of the area, the northeast strikes re- sume and continue into the adjacent map-area to the northeast (Langley, 1958).

Gneissic structure in the peripheral portions of the South- eastern orthogneisses and composite gneisses strikes parallel to contacts with metasedimentary and metavolcanic rocks. Elsewhere within the outcrop area of these gneisses, the strike varies considerably within short distances and dips from vertical to horizontal. Locally, the banding is swirly (unsystematically contorted; Plate VII), and no consistent pattern of strikes and dips is obtainable. However, broad general trends can be distinguished which are suggestive of large-scale, complex folding within the gneisses.

Folds

Top determinations on the metasedimentary and metavolcanic rocks in the northwestern quarter of Dollier township show that a north- northeast-striking synclinal axis (Stella Lake syncline) is located between Stella and Pillow lakes. The southeast-dipping sedimentary beds and volcanic flows around Stella lake face southeast, whereas the southeast-dipping beds and flows at Pillow lake face northwest. This indicates that the syncline is overturned toward the northwest and that its axial plane dips southeast. As "Timiskaming-type" sedimentary rocks occupy the axial zone of this syncline, they overlie and are younger than most of the surrounding "Keewatin-type" volcanic rocks. This synclinal could be the northeastward extension of a sinuous, east- striking synclinal mapped by Imbault (1959) in the Queylus area to the west. However, the fact that southeast-dipping volcanic flows in the northwestern corner of Charron township face southeast suggests the possibility that the synclinal axis extends south-southwestward toward Dufresne lake and that the overturned, southeastern limb of the fold has been cut out by igneous intrusion or faulting, or both, in this locality.

The garnetiferous conglomerates, schists, and gneisses that crop out southeast of the sedimentary and volcanic rocks are, in -36- part at least, their more highly metamorphosed equivalents. Thus it is possible that some of these schists and gneisses occupy the overturned southeastern limb of the Stella Lake syncline. Alternative possibilities are that the schists and gneisses occupy either an anticlinal structure or several northeast-trending synclinal and anticlinal structures. Due to lack of top-determination criteria, lack of key horizons, and scarcity of exposures in critical localities, definite structural interpretation of these schists and gneisses was not possible.

The divergent attitudes of gneissic structures in the South- eastern gneisses show that these gneisses are complexly folded. An excellent example of this folding near the Dollier-Charron township line, east of Boisvert river, is apparent on aerial photographs. Here,stream valleys, elongated lakes, and arcuate rock ridges form a topographic pattern which is convex toward the north. Thus, the topographic pattern reflects the strike pattern of the underlying biotitic orthogneisses and composite gneisses. The inward dips of gneissosity suggest that the structure is a south- or south-southeast-plunging syncline.

The Southeastern gneisses are, to some extent, interfolded with the metasedimentary and metavolcanic rocks which flank them on the west. This relationship is well-illustrated in the southwestern corner of Charron township. There, a northeast-trending body of garnetiferous hornblende schist is bounded on three sides by orthogneisses. This hornblende schist can be traced southwestward (Gilbert, 1959) into east- striking "Keewatin-type" volcanic rocks. Apparently it represents a lobe of the volcanic rocks which has been intruded by the orthogneisses and, together with them, folded about northeast-striking axes. Similar hornblende schists and orthogneisses are interfolded in the adjacent area to the southwest where Gilbert (1959) has noted that the folds plunge northeast and southwest in contrast to the easterly structures in the "Keewatin-type" volcanic rocks.

Lineation

The trends and plunges of several varieties of linear elements are recorded on the accompanying geological map. Aligned, elongated, quartz crystals and fluting on quartz veins constitute lineations within the Southeastern gneisses. In the metasedimentary and metavolcanic rocks, hornblende prisms are aligned in the planes of schistosity and constitute lineations at diverse low angles to the directions of dip. Stretched pebbles and boulders are linear elements in the garnetiferous conglomerate. The bearings and plunges of crinkles and minor fold axes are distinguished from those of quartz and hornblende -37 - lineations by a separate map symbol.

The region around Stella and Pillow lakes is the only place within the map-area where the attitude of these lineations can be related to known structures. There, minor fold axes plunge toward the north- northeast, parallel to the Stella Lake synclinal axis. In contrast, aligned hornblende prisms plunge toward the east and southeast and thus constitute a lineation in "a" (Cloos, 1946, pp 25-26), at right angles to the fold axis.

Observations of lineation were too few to be of value in interpretation of the larger structures. They are recorded here chiefly as a guide to future, more detailed investigation.

Shear Zones and Faults

Shear zones and minor faults are common within the rocks that underlie the northwestern part of the area. Most of these trend northeastward, roughly parallel to the strike of bedding and schistosity in the sedimentary and volcanic rocks. Two trend eastward, across the strike of bedding and schistosity. One of these is an east-trending cross-shear in gabbroic rocks that crop out on Wynne creek, near the north boundary of the map-area. The other is a north-dipping reverse fault in dioritic and andesitic rocks, 2 miles east of the north end of André lake. Quartz veins, carbonate zones, and sulphide mineralization have been localized by both north-northeasterly and easterly shear zones and faults.

Southeastward, where the sedimentary and volcanic rocks are more highly metamorphosed, few distinct shear zones are recognizable. There is textural evidence of cataclasis however, and, as suggested by Norman (1936, p 124+), it is probable that the numerous quartz veins and carbonate zones in these rocks were localized by the effects of mechanical deformation.

In the northwestern corner of Charron township, the contact between the metavolcanic rocks and the Southeastern gneisses is•characterized by intense mechanical deformation. Three small, north-northeast-striking faults are mapped here on the basis of pronounced linear features recognized on aerial photographs. One of these, half a mile west of Tippecanoe lake, coincides with a straight, relatively high- walled stream valley. Highly contorted hornblende schist, injected by cataclastic muscovite granite, crops out on the east wall of this valley. There are many small, sinuous shears and faults in the grey -38- orthogneisses and composite gneisses of this part of the area, particularly where they grade westward into pink muscovite granite gneiss. The muscovite granite gneiss is itself conspicuously the product of shearing, as previously recognized by Norman (1936, p 124) and Imbault (1959). Granulation, and even the emplacement, of this rock may be related to faulting along northeast-southwest lines.

The remarkably straight course of Boisvert river in the north-central part of Charron township may have been determined by a north-south fault. The straight part of the course terminates southward at Boisvert island, where mylonite is exposed along the river bank. A pronounced, west-facing scarp that extends southward from this locality could be an extension of this postulated fault.

Structural Interpretation

The Dollier-Charron map-area lies across a segment of the boundary between the Superior (Timiskaming) and Grenville provinces of the Canadian shield. These rock provinces differ in lithology, metamorphic grade, and structural trend. It is probable that each represents the root of a former great mountain system. Structural data and radioactive age determinations, compiled and interpreted by Gill (1948, 1949) and J.T.Wilson (1949), suggest that the Grenville province is a much younger mountain-built belt than the Superior province.

The true nature of the boundary between the provinces is problematical. It has long been known (M.E.Wilson, 1913) that the relationships are obscured in part by an intervening belt of orthogneisses. Norman (1936, 1940) has suggested that the boundary, which extends from Lake Huron northeastward to Lake Mistassini and beyond, is the locus of northeast-trending reverse fault zones along which the southeast (Gren- ville) side moved up relative to the northwest (Superior) side. Later workers have recognized this fault zone in some areas (e.g. Neilson, 1950; Neale, 1952) but not in others (e.g. Gilbert, 1958)

The volcanic and sedimentary rocks which underlie the northwestern part of the Dollier-Charron area are identified as "Keewa- tin- and Timiskaming-type" rocks that occur throughout the Superior province. They are characterized by their low, greenschist grade of metamorphism. Anorthositic and granitic rocks of the Chibougamau complex, intrusive into part of this sedimentary-volcanic sequence, also have been subjected to the greenschist grade of metamorphism typical of rocks of the Superior province. Southeastward, the "Keewa- tin- and Timiskaming-type" rocks grade into garnetiferous hornblende -39- schists and garnetiferous muscovite schists and gneisses. Although these coarse-grained, garnetiferous schists and gneisses do not resemble the most distinctive units of the Grenville province (crystalline lime- stone, quartzite), they are identical in lithology and metamorphic grade to rocks which underlie some of the best-known areas of the Grenville province. Hence, if drawn on the basis of lithology, the boundary between the provinces should coincide with the transition zone between the "Keewatin-Timiskaming" greenschists and the garnetiferous schists and gneisses.

The garnetiferous schists and gneisses are intruded along their southeastern margin by "Grenville-type" orthogneisses. The composite gneisses which resulted from this intrusion have been folded about north- and south-plunging axes. Unsystematic contortion of these gneisses suggests that they may have been deformed in a semi-mobile state, synchronous with intrusion.

The effects of faulting and shearing are prominent locally, particularly in the northwestern part of Charron township. However, faulting has played, at most, a very minor part in establishing the structural relationships in the present area. The chief characteristics of the Grenville-Superior boundary in this area apparently are due to igneous intrusion and synchronous directed forces from the east or southeast. These two factors caused the increase in metamorphic grade and the abrupt change in structural trend that mark the boundary zone. If, as seems likely, the intrusion and directed pressure were related to mountain-building within the Grenville province, then the suggestion that the Grenville is tectonically much younger than the Superior province (Norman, 1936; Gill, 1948; J.T.Wilson, 1949) is justified.

ECONOMIC GEOLOGY

Most of the western part of this area has been under claim in the past, but all claims, except a few in the vicinity of Lake Malo, had expired by the summer of 1953 when the mapping leading to this report was done.

One mineral showing is located at the northeast corner of Stella lake. Here, a northeast shear zone, apparently localized by a contact between pillowed andesite and granitic rock of the Chibougamau complex, has been cut across by 6 trenches. Albitization and silici- fication of the andesite was followed by the introduction of rusty- weathering iron carbonate, pyrite, and chalcopyrite. Assays of samples showed no gold and only traces of copper. - 40 -

A northeast-trending, carbonitized, shear zone near the southeast shore of Pillow lake contains small amounts of pyrite and molybdenite. An east-striking shear that cuts medium-grained andesite, 2 miles east of Andre lake, is shot through with pyrite-bearing quartz veins. Quartz stringers and pyrite mineralization are associated with zones of sericite-carbonate schist that are common within the rocks mapped as feldspathic schists and gneisses.

On the west shore of Wynne creek, 200 feet from the north boundary of the area, an east-striking shear in gabbro-anorthosite carries pyrite. The gabbroic rocks east of Wynne creek contain up to 10 per cent disseminated magnetite. Half a mile north of the area, where Wynne creek empties into Cinq Milles lake, an outcrop of gabbro- anorthosite contains numerous thin lenses and stringers of magnetite.

Traces of disseminated pyrite and chalcopyrite were noted within the Southeastern gneisses.

Recommendations

The "Timiskaming-and Keewatin-type" greenschists and the intrusive rocks of the Chibougamau complex offer most promise to prospectors. These rock-types contain favourable structures and mineralogy in the present area and have proved economically interest- ing in adjoining map-areas. The Stella Lake showing suggests the pos= sibility that the Chibougamau complex is flanked on the southeast by a mineralized carbonate zone comparable to that on its northwestern margin, near Lac aux Dorés in the map-area to the north (Mawdsley and Norman, 1935). This possibility bears investigation both within and north of the present area.

The higher grade metamorphic equivalents of the greenschists should not be neglected. Quartz veins and pyritized carbonate zones show that hydrothermal solutions were also active in these rocks. - 41 -

BIBLIOGRAPHY

Allard, Gilles (1954), Personal communication.

Barlow, A.E., Gwillim, J.C., and Faribault, E.R., (1911), Report on the Geology and Mineral Resources of the Chibougamau Region, Quebec: Quebec Dept. Col., Mines, Fish, Mines Branch.

Buddington, A.F. (1939), Adirondack Igneous Rocks and Their Metamorphism: Geol. Soc. America,Mem. 7.

Cloos, Ernst (1946), Lineation, a Critical Review and Annotated Biblio- graphy: Geol. Soc. America,Mem. 18.

Dresser, J.A., and Denis, T.C. (1944), Geology of Quebec: Vol.II, Des- criptive Geology: Quebec Dept. of Mines, G.R. 20.

Gilbert, J.--E.(1958), Bignell Map-Area: Quebec Dept. of Mines, G.R. 79

Gilbert, J.-E. (1959), Rohault Map-Area: Quebec Dept. of Mines, G.R. 86 (In press)

Gill, J.E. (1948), The Canadian Precambrian Shield, Structural Geology of Canadian Ore Deposits, Can, Inst. Min and Metall., pp. 20-48.

(1949), Natural Divisions of the Canadian Shield, Trans. Royal Soc. Canada,Section IV, Vol.XLIII, pp. 61-69.

Imbault, P.-E. (1959), Queylus Map-Area: Quebec Dept. of Mines, G.R. 83

Longley, W.W. (1958), Rinfret Map-Area: Quebec Dept. of Mines, G.R. 81.

Mawdsley, J.B. and Norman, G.W.H. (1935), Chibougamau Lake Map-Area; Quebec: Geol. Survey Canada,Mem. 185.

Mawdsley, J.B. and Norman, G.W.H. (1938), Chibougamau Sheet, East Half, Map No. 397A: Geological Survey Canada.

Neale, E.R.W. (1952), Béthoulat Lake Area, Mistassini Territory: Quebec Dept. of Mines, P.R. No. 264.

(1952), Yale University Ph. D. Thesis (unpublished). - 42 -

Neilson, J.M. (1950), Temiscamie Mountains Map-Area, Mistassini Territory: Quebec Dept. of Mines, P.R. No. 238.

Norman, G.W.H. (1936), The Northeast Trend of Late Precambrian Tectonic Features in the Chibougamau District, Quebec: Trans. Roy. Soc. Canada, Sec. IV, Vol.XXX, pp. 119-128.

(1938), The Last Pleistocene Ice-Front in Chibougamau District, Quebec: Trans. Roy. Soc. Canada, Sec. IV, Vol. XXXII, pp. 69-86.

(1939), The Southeastern Limit of Glacial Lake Barlow- Ojibway in the Mistassini Lake Region, Quebec: Trans. Roy. Soc. Canada, Sec. IV, Vol.XXXIII, pp. 59-65.

(1940), Thrust Faulting of Grenville Gneisses North- westward Against the Mistassini Series of Mistassini Lake, Quebec: Jour. Geol., Vol 48, pp. 512-525.

Osborne, F.F. (1949), Coronite, Labradorite, Anorthosite, and Dykes of Andesine Anorthosite, New Glasgow, P.Q.: Trans. Roy, Soc. Canada, Sec. IV, Vol.XLIII, pp. 85-112.

Retty, J.A. (1929), Township of McKenzie, Chibougamau Region, Quebec: Quebec Bur. Mines Ann. Rept. 1929, Pt. D., pp. 41-72.

Richardson, James (1872) - Report on the Country North of Lake St.John, Quebec: Geol. Surv. Canada, Rept. of Progress 1870-1871, PP. 283-308.

Shand, S.J. (1945), Coronas and Coronites: Geol. Soc. America Bull., Vol. 56, pp. 247-266.

Smith, Robert (1954), Personal communication.

Tilley, C.E. (1938), The Status of Hornblende in Low Grade Metamorphic Zones of Green Schists: Geol. Mag., Vol. 75, pp. 497-511.

Turner, F.J. and Verhoogen, Jean (1951), Igneous and Metamorphic Petrology: McGraw-Hill.

Wilson, M.E. (1913), The Banded Gneisses of the Laurentian Highlands of Canada: American Jodr. Sci., Ser. 4, Vo1.36, pp. 109-122.

Wilson, J.T. (1949), Some Major Structures of the Canadian Shield: Canadian Min. Met. Bull., No. 450, pp. 543-554. - 43-

APPENDIX TO GEOLOGICAL REPORT 82

ECONOMIC GEOLOGY

Developments, 1953-1958

J.-E. Gilbert

A certain amount of exploration work was carried out by individuals and mining companies in Dollier township subsequently to the field work on which this report is based. Most of it was concen- trated in the western part of the township and south of Lac au Couteau, in the northeast quarter.

In the western part, the work consisted of a little drilling in 1953 and of a series of geochemical, magnetometric, elec- tromagnetometric, and geological surveys by the Bishoff-Bengry Pros- pecting Syndicate and by Cyprus Exploration Corporation Limited in 1954. Some anomalies were detected in the geophysical work and Père Marquette Mining Syndicate also put down in 1956 four diamond-drill holes totalling 1,349 feet along the east shore of Stella lake, in the northwest quarter of the township. Some sphalerite and chalcopyrite were found to be present in the core.

Dominion Gulf Co. carried out in 1955 a self-potential and magnetometric survey on the Burrex Mines Ltd. property, south of Lac au Couteau, in the northeast quarter of Dollier. A group of anomalies was discovered during the survey and those were investigated in 1956 through 6 holes totalling 2,000 feet which were put down by Orefield Mining Corporation Limited. Disseminated to 40 per cent, pyrite and pyrrhotite were found in the core but no copper or zinc values were reported.

Quebec, January 31, 1959 -44-

ALPHABETICAL INDEX

Page Page

Access to area 1 Copper 39 Acknowledgements 3 Crépeau, Pierre Actinolite 22 Geological assistant 3 Allard, Gilles Cyprus Exploration Corp.

Ref. to work by 21,41 Ref. to work by 43 Allanite 14 Andesite 7,8 Denis, T.-C.- Anorthosite 21,25 Ref. to work by 11,20,41 Anorthositic rocks 6,38 Description of area 3 Apatite 19,29,32 Diorite porphyry 9 Dominion Gulf Co. Barlow, A. E.- Ref. to work by 43 Ref. to work by 2,4,41 Drainage of area 4 Basalts 8 Dresser, J. A.- Bedding 34 Ref. to work by 11,20,41 Bibliography 41 Dykes 6,7,32 Biotite 19,26,33 Biotite orthogneiss 29 Economic geology 39,43 Bishoff-Bengry Prospecting Epidote 14,22,29 Syndicate Ref. to work by 43 Faribault, E.-R.- Buddington, A. F.- Ref. to work by 2,4,41 Ref. to work by 33,41 Faults 37 Feldspathic conglomerate 11 Carbonate 9,11,15,19,23 Feldspathic sandstones 11 Chalcopyrite 39,43 Field work 3,43 Chibougamati Mining Commission Fish in area 3 Ref. to work by 2 Folds in area .. 35 Chibougamau intrusive complex .. 20 Chlorite .... 8,9,18,19,21,22,23,26 Gabbro 22,32 Cleary, Patrick Gabbro dykes 6,32 Ref. to work by 4 Game in area 3 Clinochlore 9 Garnet 19,27,33 Clinopyroxene 33 Garnetiferous biotite-muscovite Clinozoisite 9,22 gneiss 18 Cloos, Ernst Garnetiferous biotite-muscovite Ref. to work by 37,41 schist 17 Conglomerate 11,23,25 Garnetiferous conglomerate 23,27,35 Page Page

Garnetiferous hornblende gneiss 19 Mawdsley, J. B.- Garnetiferous hornblende Ref. to work by 3,20,22,24,25,40 schist 12,13,14 41 Garnetiferous muscovite schists 16 Metadiorite 7,9 Geology - Economic 39,43 Microcline 29,30 Geology - General 5 Muscovite 11,19,22,29 Geology - Structural 34 Muscovite granite gneiss 31 Gilbert, J.-E.- Muscovite schist 16,17 Ref. to work by 3,12,25,28,32,33 Myrmekite • 29 36,38,41,43 Gill, J. E.- Neale, E. R. •W.- Ref. to work by 38,39,41 Ref. to previous work by .. 32,33 Gneiss 16,18,19,28,29,30,31 38,41 Granitic rocks 6,22,38 Neilson, J. M.- Greywacke 11 Ref. to work by 38,42 Gwillim, J. C.- Norman, G. W. H.- Ref. to work by 2,4,41 Ref. to work by 3,20,22,24,25,34 37,38,39,40,42 Hornblende 8,14,18,33 Hornblende schist 12,13,14,31 Oligoclase 27 Olivine 33 Imbault, P.-E.- Orefield Mining Corp.- Ref. to work by 7,12,14,20,28,31 Ref. to work by 43 32,35,41 Osborne, F. F.- Iron carbonate 39 Ref. to work by 33,42 Iron ore 33 Plagioclase .. 13,14,19,21,29,30,33 Keewatin-type volcanic rocks 7,10 Pegmatite 32 Kyanite 19 Pire Marquette Mining Syndicate- Ref. to work by 43 Lapointe, J.-Armand- Pistacite 14,22 Cook for party 3 Pleistocene epoch • 33 Laurin, André - Pyrrhotite 43 Geological assistant 3 Pyrite 8,9,11,14,23,40,43 Lineation 36

Location of area 1 Quartz 13,22,26,27,29,40. Longley, W. W.- Quartzite 27 Ref. to work by 3,7,16,20,35,41 Recent epoch 33 Magnetite 19,23,26 Recommendations 40 - 46-

Page Pape

Retty, J. A.- Structural interpretation 38 Ref. to work by 25,42 Sulphide mineralization 37 Richardson, James- Ref. to work by 1,42 Table of formations 6 Rutile 8 Temiskaming-type sedimentary rocks 10 Sandstones 11,27 Tilley, C. E.- Scapolite 22 Ref. to work by 10,42 Schist 12,13,16,17,18 Timber in area 3 Schistosity 34 Topography of area •4 Schorlite 11,23,26 Tourmaline 11,19,23,26 Sedimentary rocks 5 10,11 Tuff 9 Sericite 27 Turner, F. J.- Shand, S. J.- Ref. to work by 10,12,16,20,23,42 Ref. to work by 33,1+2 Shear zones 37 Verhoogen, Jean - Simard, Mr. and Mrs. Phydime- Ref. to work by 10,12,16,20 Acknowledgement to 3 23,42 Siméon, Clément Volcanic rocks 5,7 Canoeman for party 3 Siméon, Marcel - Canoeman for party3 Wilson, J. T.- Smith, Robert- Ref. to work by 38,39,42 Ref. to work by 25,42 Wilson, M. E. - Sphalerite 43 Ref. to work by 38,42 Sphene 11,23,29 Wynne-Edwards, Hugh - Staurolite 19 Geological assistant 3 Staurolite-kyanite schist 19 Zircon 23,26,29