REGIONAL MAPPING OF PRECAMBRIAN BASEMENT BENEATH PHANEROZOIC COVER INSOUTHEASTERN TRANS-HUDSON OROGEN, MANITOBA AND SASKATCHEWAN

The northern edge of Phanerozoic platformal rocks of the Western Canad a Sedimentary Basin overlies the Flin Pion Belt (Trans-Hudson Orogen) in Manitoba and Saskatchewan. A program of regional mapping of the Pha nerozoic-covered basement has been undertaken, involving the integrati on of high-resolution aeromagnetic and gravity data with extensive dri ll core information. Several major domains are recognized in the burie d basement, each with a distinct lithotectonic character and potential field anomaly pattern. Three lithotectonic domains in the buried base ment (Clearwater, Athapapuskow, and Amisk Lake domains) are characteri zed by northerly-trending positive gravity and aeromagnetic anomalies and correlate with the 1.92-1.83 Ga volcanic and plutonic rocks of the exposed Flin Pion Belt (Amisk collage and Snow Lake assemblage). An u pper amphibolite grade orthogneiss complex (Namew Gneiss Complex), con taining calc-alkaline intrusive rocks ranging in age from 1.88 to 1.83 Ga and screens derived from the older volcano-sedimentary rocks, is i nterpreted as the middle crust of a 1.88-1.84 Ga are exposed in the Fl in Flon Belt. Discordant intrusive complexes, such as the 1.830 Ga Cor morant Batholith, are centred on magnetic-gravity lows and truncate th e structural trend of adjacent lithotectonic domains. Correlation of F lin Pion Belt geology with that beneath the Phanerozoic cover shows th at its constituent lithotectonic elements have north-south strikes of up to 150 km, and form a predominantly east-dipping crustal section, c onsistent with Lithoprobe seismic reflection profiles.