Chalcopyrite deposits in northern Manitoba

Everend Lester Bruce
1920 Economic Geology and The Bulletin of the Society of Economic Geologists  
The deposits of chalcopyrite recently discovered and developed in Northern Manitoba lie near the western boundary of the province, a short distance northwest of Lake Athapap.uskow, which is shown on Maps of Canada, fifty miles north of the Saskatchewan river. A large part of the journey from the railway at the town of The Pas, must be made by canoe in summer, or by sleigh in winterl and all the ore has been brought out during the winter months to the lakes that can be reached by steamers, and
more » ... ence by scows down the Saskatchewan river. TOPOGRAPHY. The topography is rather monotonous for most of the distance from the railway to the producing area. Saskatchewan river flows in a number of changing channels through swampy country, and in many places is separated from broad, shallow lakes only by willow-covered levees. These lakes and the muskeg areas that border them act as reservoirs which are flooded ,during periods of high water. Northward from the Saskatchewan the same monotonously flat muskeg country continues to the boundary between the Pre-Cambrian and the Palaeozoic formations. The rocks of the latter in many places stand up in an escarpment 7o to 8o feet above the lower lying but more rugged surface of the older rocks. In contrast to the unbroken level of the southern district with shallow, islandless lakes with low shores, the northern district abounds in ridges and hills, has only s•nall muskeg areas and is dotted with almost countless, clear, island-studded, rock-bounded lakes of all sizes. 386 CH.4LCOPYRITE DEPOSITS IN NORTHERN MANITOBA. 387 Since the rocks associated with the ores are all of Pre-Cambrian age it will be necessary only to mention that Palaeozoic dolomites cover the older rocks 'south of lake Athapapuskow, and that Glacial and post-Glacial deposits form a discontinuous cover of varying thickness over all of the consolidated rocks. Volcanic rocks and derived schists Volcanic Rocks.--The oldest rocks are comparable to the oldest rocks of Pre-Cambrian age found in other areas; but, as they are separated from similar formations by great stretches of granites and gneisses. to the east and by the Palaeozoic cover to the south, it is not and may never be certain that they are of the same age as the Keewatin rocks of Lake Superior. They consist almost entirely of volcanic rocks of various types. The most common variety is massive, green to grayish-green in color and weathers to brownish color. The ellipsoidal structure figured in so many descriptions of Pre-Cambrian lavas is very strikingly developed and there are, in addition, certain other typical volcanic forms. Autoclastic bands have been formed by the rolling of the semi-solidified lava and by shearing. Pyroclastic beds are common. They have been formed. by the incorporation of bombs of all sizes, from those a foot in diameter down to the finest ash, in the still molten rock. The pyroclastics have, superficially, much t. he appearance of some of the altered conglom-
doi:10.2113/gsecongeo.15.5.386 fatcat:3pjta42cxrha3jnzcgd7y45yke