GEOPHYSICAL INTERPRETATION OF THE TORNGAT OROGEN ALONG THE NORTH RIVER - NUTAK TRANSECT, LABRADOR

A 19.3 mGal (1 Gal = 1 cm/s) positive Bouguer gravity anomaly and a br oad aeromagnetic low coincide with the Tasiuyak domain of the early pa leo-Proterozoic Torngat orogen. The domain evolved during the collisio n of the western margin of the Archean Nain Province with an inferred, eastward-facing, platform-to-rise, sedimentary wedge sited on a proto continent of Churchill (Rae) Province. A density contrast of +0.065 g. CM-3 was measured between rocks of the Tasiuyak domain and those of th e flanking Lac Lomier complex of the orogen and Nain Province. Using t his contrast, a two and one-half dimensional model shows that rocks of Tasiuyak domain constitute a triangular prismatic body with maximum t hickness of 13 km adjacent to Nain Province, which thins westward to a feather edge. The model is compatible, qualitatively, with die aeroma gnetic anomaly and consonant with geological interpretation of an east ward-facing and thickening continental slope deposit. Deep exhumation of the Torngat orogen may account for the absence of paired gravity an omalies characteristic of many sutures elsewhere in the Canadian Shiel d.