Abstract

Recent mapping in central Labrador has resulted in the recognition and correlation of two Neohelikian peralkaline silicic igneous centres. The Flowers River igneous suite is circular in shape, covers an area of approximately 1720 km2, and consists of undeformed comenditic granite in contact with extrusive equivalent porphyry, felsite, tuff, and breccia. The Letitia Lake volcanic complex has been deformed by the Grenvillian Orogeny into an elliptical structure that covers approximately 450 km2. The complex consists of comenditic granite and syenite of the Arc Lake intrusive suite and related porphyry, rhyolite, tuff, and volcanogenically derived sediments of the Letitia Lake Group. Undersaturated aenigmatite–nepheline gneisses and syenites of the Red Wine alkaline complex are associated in space and time with the peralkaline silicic rocks of the Letitia Lake complex. The two centres are separated by 175 km and are an integral part of a Neohelikian period of uplift and continental rifting that involved formation of plateau basalts, terrestrial sediments, diabase dikes, and peralkaline magmatic centres in a belt extending from south Greenland to Lake Superior.

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