Early Precambrian basic rocks of the Canadian Shield

Abstract

Recent work has shown that Archaean greenstones contain several distinct and consistent stratigraphic associations indicative of different environments, namely: 1) shallow marine platform sequences comprising quartz-arenite, BIF and komatiite associations; 2) thick massive basaltic flows and associated deep water pelagic sediments representing an oceanic volcanic or mafic plain environment; 3) cyclic mafic to felsic volcanics with or without an upper sedimentary unit indicative of arc volcanism; and 4) shallow water to fluviatile sediments and alkalic to calc-alkalic volcanics formed in pull-apart basins. These distinct associations form an ordered series in the Superior Province from 1) (oldest) to 4) (youngest). The series is preceded and followed by orogenic events. This work attempts to characterise mafic volcanism in the Superior Province and relate it to the above litho-stratigraphic associations. -from Author