资源环境科技发展态势分析平台

Geophysical and geological data indicate that the lithosphere in the northern Canadian Cordillera (NCC) is thin and hot. However, lack of direct constraints on mantle structure is fueling debates on the origin and nature of this lithosphere. Here we image the crust and uppermost mantle beneath the NCC and resolve the Moho at similar to 35-km depth, the lithosphere-asthenosphere boundary similar to 15 km deeper, and a westward dipping structure in the mantle below the eastern NCC. We examine end-member tectonic models where the thin lithosphere is either long-lived or has been rejuvenated by gravitational removal. In the long-lived model, steady state thermal calculations indicate a Moho at similar to 1,000 degrees C; alternatively, time-dependent calculations suggest that a removal event 5-25 Myr ago reproduces the seismic constraints. Combined with geologic evidence, these results suggest that the mantle lithosphere beneath the NCC is either exotic or the result of progressive thickening and cooling since the Miocene.