. Annual report . om the Montreal river to RocheMcLean, is occupied by the massive bedded breccia-conglomerate, which dips in a west-erly direction at an angle of 15 degrees. 138 Bureau of Mines No. 4 In the breccia-conglomerate the matrix is often present in very subordinate quan-tity. The most abundant fragments are the usual biotite-granite type, while others ofa pale granitic rock are seen in thin section under the microscope to consist of pheno-crysts of plagioclase or orthoclase, embedded in a fine-grained quartz-feldspar ground-less. Besides these there are some fragments composed of a
. Annual report . om the Montreal river to RocheMcLean, is occupied by the massive bedded breccia-conglomerate, which dips in a west-erly direction at an angle of 15 degrees. 138 Bureau of Mines No. 4 In the breccia-conglomerate the matrix is often present in very subordinate quan-tity. The most abundant fragments are the usual biotite-granite type, while others ofa pale granitic rock are seen in thin section under the microscope to consist of pheno-crysts of plagioclase or orthoclase, embedded in a fine-grained quartz-feldspar ground-less. Besides these there are some fragments composed of a fine-grained altered dia-base and others of a greenish-grey slaty rock (resembling in a most marked mannerthe compact variety of the greywacke of the Huronian) and some grey quartz. Thematerial filling the interspaces is seen under the microscope to consist of a confusedaggregate of scales and grains of chlorite and epidote, with abundantly disseminatedparticles of iron ore and fine granules of sphene and Fig. 59.—The Notch, near mouth of Montreal river. A specimen obtained from an exposure two miles north of the Montreal river,however, showed the matrix to be relatively more abundant than usual. The diabasepebbles are also more plentiful than those of red granite, while fragments of simpleminerals predominate greatly over those of composite rocks. The quartz and feldsparfragments are sharply angular, while the composite individuals are as a rule some-what rounded.* Greywacke Just west of the No. 3 post of H R 34 is an outcrop of greywacke which overliesthe Keewatin and is overlain to the west by conglomerate. The greywacke, in thin section, is seen to consist principally of orthoclase, finelytwinned plagioclase and calcite, and in subordinate amount, chlorite and quartz. Afragment of greenstone was noticed in the section. This greywacke, which is verydeceptive in appearance, was mistaken by prospectors for fine-grained diabase. •Report on the Geology and Natural
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectminesandmineralresou
