Abstract

Reflection patterns along Lithoprobe Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) seismic reflection line 1 in the southwestern Slave Province are interpreted as products of tectonic wedging during late Archean lithospheric convergence. The interpretation is aided by application of new seismic imaging techniques, by correlation of upper crustal reflection patterns to known geology, and by a comparison of lithospheric reflection patterns to similar convergent zones elsewhere. In the Yellowknife area, reflection patterns consist of (1) east-dipping reflections at 12–14 s that project into the upper mantle, (2) a wedge-shaped body in the lower crust with an east-dipping reflection fabric that is truncated on the west by (3) a series of west-dipping reflections that outline thrust-and-fold structures in the upper crust. The similarity of these reflection patterns to those of the Proterozoic Fort Simpson – Hottah collision zone ∼300 km to the west provides support for the interpretation that reflection patterns beneath the Slave Province are also products of collisional tectonics. Rocks within the Slave Province preserve evidence of a ∼2.65–2.58 Ga pan-Slave orogenic event, in which the >2.9 Ga Central Slave Basement collided with the ∼2.7 Ga juvenile eastern Slave Province. Their suture is interpreted to be a west-dipping surface at 4–5 s (12–15 km) beneath Yellowknife and to project to the surface east of the profile. In the lower crust and upper mantle, east-dipping reflections are interpreted to delineate a coeval subduction zone and accretionary wedge. The upper crustal thrust-and-fold structures are likely linked to gold-bearing shear zones at Yellowknife. These results provide tantalizing evidence that processes similar to those of modern convergent zones were operational at 2.65–2.58 Ga.

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