MAICASAGI AREA, ABITIBI-EAST COUNTY PROVINCE of QUEBEC, CANADA Department of Mines Honourable C

RG 060(A) MAICASAGI AREA, ABITIBI-EAST COUNTY PROVINCE OF QUEBEC, CANADA Department of Mines Honourable C. D. FRENCH, Minister A.-O. DUFRESNE, Deputy Minister GEOLOGICAL SURVEYS BRANCH L W. JONES, Chief GEOLOGICAL REPORT 60 MAICASAGI AREA ABITIBI-EAST COUNTY by P.-E. IMBAULT QUEBEC RÉDEMPTI PARADIS PRINTER TO HER MAJESTY THE QUEEN 1954 TABLE OF CONTENTS Page INTRODUCTION 1 Location and means of access 1 Field work 1 Previous work 2 Acknowledgments 2 DESCRIPTION OF THE AREA 3 Topography 3 Drainage 3 Preglacial valleys 4 Flora and fauna 6 GENERAL GEOIOGY 6 General statement 6 Table of formations 7 Volcanic and sedimentary rocks 8 General statement 8 Volcanic rocks 9 Sedimentary rocks 11 Concordant intrusives within the complex 12 Basic sills 13 Acid sills 13 Post-folding intrusive rocks 14 Diorite group 14 Northern granite 18 Nomans stock 20 Southern granite 22 Satellitic intrusives 25 Granitic dykes 25 Lamprophyre dykes 27 Diorite breccia 27 STRUCTURAL GEOLOGY 28 Folding 28 Faulting and shearing 29 ECONOMIC GEOLOGY 30 REEEBENCES 31 ALPHABETICAL INDEX 33 Map No. 971 - Maicasagi Area (in pocket) LAICASAGI AREA Abitibi-East County by P.E. Imbault INTRODUCTION Location and Means of Access The Maicasagi area is bounded by latitudes 49°45' and 50°00'N. and by longitudes 76°15' and 76°40'W. It is about 110 miles north- northeast of Senneterre, a town on the Quebec-Cochrane line of the Canadian National railway. It comprises 320 square miles, and includes parts of the following townships: Urfé, Montviel, Monseignat, La Rouvillière, Meulande, and Johnstone. Maicasagi lake, the eastern part of which projects into the northwest quadrant of the map-area, may be reached by canoe from Senneterrc or from Rochebaucourt, 25 miles northwest of Senneterre. From Senneterre, the route is north by Bell river to Mattagami lake; from Rochebaucourt, it is by way of Laflamme and Bell rivers to Mattagami lake. From Mattagami lake, the route'continues eastward across Olga and Goéland lakes, and along the short segments of Waswanipi river joining these three lakes. Goéland lake lies southwest of Maicasagi lake, and is connected to it by a wide, shallow arm, Max narrows: The total distance covered in such a trip is approximately 200 miles. Any paint of the area can be reached in slightly over one hour by hydroplane from bases at Senneterre, Amos, or 'Rouyn. landing facilities are restricted, however, to Maicasagi lake, the longer straighter stretches of Maicasagi river, and, at high water, the lower reaches of Inconnu river. Field Work With the exception of a strip along the eastern side, the area was mapped by the writer in the summer of 1949. That eastern strip, comprising about 60 square miles and lying south of Maicasagi river, wag examined the same summer by J.E. Gilbert, also of the Quebec Department of Mines; his findings are incorporated in this report and its accompanying geological map. The field work was planned so as to cover the area systemat- ically by pace-and-compass traverses at half-mile intervals. Careful -2 - stereoscopic examination of aerial photographs, however, made it possible to modify this plan in many sections of the area. These studies, by revealing the topography of the region to be traversed, permitted avoiding many low,-swampy sections, with the result that more time was available for inspection of the higher ground, where exposures are more plentiful. As much as possible, the traverses were oriented to inter- sect the regional structure in order to obtain complete cross-sections of the rock units. The exposures along the shores of Maicasagi lake and the banks of the main rivers were examined in more detail than required for mapping on a regional scale. Previous Work The main rock groups of the area and their regional trends have been known for more than half a century. The area was visited in 1895 and 1896 by Robert Bell (3)k of the Geological Survey of Canada. In more recent years, much additional information concerning the geology of the general area has been gained as a result of the work of several. observers, including Bancroft, 1912 (1); Cooke, 1927 (6); Lang, 1932 (13); Norman, 1937 (15); and Freeman, 1938 (7). The map-area lies between the Olga-Goéland Lake area, on the west (10); the Capisisit Lake area, on the east (8); the Waswanipi Lake areas — East Half (4) and West Half (5) — on the south; and part of the Mishagomish area, on the north (16). Acknowledgments The party consisted of: W.G. Gillespie, graduate student at the University of Toronto, senior assistant; I.C. Grant and r'. Paquette, third-year students at NcGill University, junior assistants; G. Truchon and U. Therrien, canoemen; and J. Roberge, cook. All discharged their duties in a very satisfactory manner. The maps used for the field work were prepared by the Surveys Branch of the Department of Lands and Forests of Quebec from vertical air-photographs taken in 1946 by Canadian Pacific Airlines.. The photographs themselves (scale: one inch to one-quarter mile) were used constantly In the field and, as mentioned earlier, were very useful. xNumbers in parentheses refer to corresponding numbers in the bibliography at.the end Of the report. -3 - Sincere thanks are due to Fecteau Air Services, Senneterre, who supplied the party and rendered many courtesies. DESCRIPTION OF THE AREA Topography The Maicasagi area belongs to the same topographic unit as the region west.of it, to and beyond Mattagami lake. Its relief is low, and its plain-like aspect is broken only by isolated mounds or groups of hills, the elevation of which seldom exceeds a few tens of feet. Through a gradual eastward rise of the level of the whole region, the map-area stands at a higher altitude than the country surrounding Mattagami lake. The highest hills are found near the northeast corner of the area, north of Maicasagi river, and in Monseignat township, south of Nomans river. Some of these hills reach a height, as estimated visu- ally, of about 150 feet above the surrounding country, which itself stands only a few feet above the nearby rivers. The local watersheds in the north section of Montviel township and in the northwest part of La Rouvillière are more than 1,000 feet above sea-level. Both areas, however, lack conspicuous hills and their elevations are reached only through a gradual, almost unnotice- able, rise of the level of the plain. Drainage All the run-off of the map-area is directed toward Maicasagi lake, excepting a small section, approximately twelve square miles in the south-central part, that drains southward into Waswanipi river and thence to Goéland lake. The area is drained through a well-developed system of. tributaries, arranged in a dendritic pattern that beârs no apparent relationship to the underlying rock structure. The principal elements of the river system are a main river, Maicasagi, which may be termed a stream of the first order, a tributary of the second order, Inconnu, and a tributary of the third order, Nomans. Maicasagi river has its source in Monsan lake, 24 miles northeast of the northeast corner of the map-area. From that lake, it flows in a southeast and then southwest direction to a point near the intersection of longitude 76° with latitude 500. Thence the river flows in a general westerly direction toward Maicasagi lake. Within the map-area, the river is about two miles south of the northern boundary. Its width is from four hundred to eleven hundred feet and - 4 - its waters are generally quiet. There are two small rapids in the central part of Monseignat township, and a stretch of rapids and .fast water extends for more than a mile and a half near the western border of the same township. All these rapids can be run by canoe, although at low water great care must be exercised to avoid the numerous boulders strewn in the channel. Inconnu river is the outlet of Capisisit lake, which lies in the north-central part of Montalembert township, east of La Rouvil- lière. In its westerly course from the lake, it enters the eastern boundary of the map-area one mile north of the southern east-west survey line. About two miles west of the eastern boundary, it turns abruptly northward to follow a comparatively straight course until it. empties into Maicasagi river. Inconnu river is two hundred to three hundred feet wide, and, within the area, is interrupted by three rapids which can be avoided by well-beaten portages, the longest of which is about 1,000 feet. About three miles before its junction with Maicasagi river, Inconnu river receives the waters from its main tributary, Nomans river. This stream has its source in the granitic terrain near the southwest corner of the map-area. Its main fork is.about half a mile south of post 27 on the southern survey line. Below there, it crosses the region in a general northeasterly direction, maintaining a surpris- ingly consistent width. In early June of 1949, the river was at least eight feet above mid-summer level. It could then be ascended easily with fully loaded canoes up to its main fork. The only portage neces- sary'under those conditions was due to a series of rapids, stretching for a mile and a half, near the mouth of the river. When the spring flood has subsided, however, the general shallowness of the river and the numerous boulders that in many places clutter its bed, make it unadvisable to venture in it with heavy loads.

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