Abstract

Precambrian rocks extend 3300 km from central Ellesmere Island to the Strait of Belle Isle and form parts of three structural provinces, which are from north to south, the Churchill, Nain, and Grenville. The Churchill Province is composed primarily of gneissic granitic rocks, some of which are of Archean age and were deformed and metamorphosed during the Kenoran Orogeny (~2500 Ma). Aphebian supracrustal rocks unconformably overlie these gneissic rocks and form at least three fold belts, the Committee, Foxe and Dorset, all of which were deposited in the Baffin Geosyncline. These and the older rocks were deformed, metamorphosed, and intruded by granitic rocks during the Hudsonian Orogeny (~1750 Ma). At that time the major structural elements now present were established. Grabens in northern Baffin Island, that probably began to form in Aphebian time, were filled in Neohelikian time with rocks that comprise the Borden Plate. Elements of the Thule Group were deposited in eastern Ellesmere Island as a result of similar tectonism. Block faulting occurred intermittently into the Cenozoic so that present coastal outlines, particularly in Baffin Island, are fault-controlled and were not formed by Precambrian structures.

The Nain Province is composed chiefly of Archean rocks, of which a few were metamorphosed, deformed, and intruded 3600 Ma ago. The major deformation, metamorphism, and intrusion of this province occurred during the Kenoran Orogeny. In Aphebian time supracrustal rocks of the Ramah, Mugford, and Snyder Groups were deposited unconformably in the Archean rocks. These supracrustal rocks, which may also be part of the Baffin Geosyncline, were deformed and metamorphosed during the Hudsonian Orogeny. In the Makkovik Subprovince, in the southern part of the Nain Province, the Aillik Group was also deposited in Aphebian time, and deformed, metamorphosed, and intruded during the Hudsonian Orogeny. Post-tectonic batholiths of anorthosite and adamellite were emplaced in Paleohelikian time during the Elsonian Event (~1400 Ma) in the Nain Province and also in the Grenville Province to the south.

The Grenville Province is composed of gneisses, many of undetermined age and origin, as the Grenvillian Orogeny (~1000 Ma) destroyed evidence of most earlier events. This orogeny also metamorphosed the anorthosite and adamellite intrusive rocks. In Hadrynian time sedimentation occurred in a few fault-controlled areas in southern Labrador.

Archean rocks of Labrador and Aphebian supracrustal rocks of the Foxe Fold Belt correlate well with those in West Greenland. Aphebian rocks of the Committee Fold Belt and associated rocks probably also are present in Greenland.