A complex of basic rocks in the Waswanipi District of northwestern Quebec is described, and the interpretation is advanced that it is a deformed lopolith of the same general character as the Stillwater complex of Montana and the Bushveld complex of the Transvaal. The rocks of the complex are severely altered, and the alterations-serpentinization, hornblendization, and chloritization-are described. The serpentinization is thought to have been caused by deuteric processes within the basic mass, and the other changes are believed to have been brought about by hydrothermal solutions derived from intrusive quartz-diorite.
The granitic masses of the western half of the Waswanipi map-area in northwestern Quebec are of two general types-(1) reddish to gray, coarse-grained, somewhat porphyritic, gneissic quartz-diorites, and (2) red to gray, medium- to fine-grained, quartz-diorites to granodiorites, and rarely soda granites. The rocks surrounding the batholiths are Keewatin-type volcanics, sediments, and anorthosite. Field evidence indicates that the gneiss is older than the massive quartz-diorite, and mineralogic and textural evidence indicates that the gneissic type represents a metamorphosed shell of invaded rocks altered by emanations from a solidifying batholith. The medium-to fine-grained type represents an intermediate zone between metamorphosed country rock-forming Type I and still later solidifying magma.
The igneous petrology of an area near the Long Lake gold mine, Sudbury district. Ontario, is described. The area lies at the contact of a region of folded sediments and one of granite-gneiss. Two rock types, Keweenawan diabase and Long Lake diorite, resulted from the injection of basic magma into the sediments. Later a large granitic batholith invaded the region. Reaction between the magma and the quartz-rich sediments is postulated to account for a border phase of very quartz-rich tonalite. The Long Lake diorite grades into a more acidic phase and this phase is explained as due to emanations from the batholith affecting the diorite and adding silica and soda.
