Lithosphere-asthenosphere mixing in a transform-dominated late Paleozoic backarc basin: Implications for northern Cordilleran crustal growth and assembly

Abstract

The Slide Mountain terrane is part of a North American Cordillera–long backarc basinal assemblage that developed between the ensialic arc terranes (Yukon-Tanana and affiliated pericratonic terranes) and the North American craton in the middle to late Paleozoic. The Slide Mountain basin started to open in the Late Devonian, and spreading continued through the late Paleozoic in an oblique (transform-dominated) manner such that the pericratonic terranes were translated into southerly latitudes. The basin closed, also in an oblique manner, by the Early Triassic, resulting in the reaccretion of the Yukon-Tanana terrane to the northwestern Laurentian margin. Both the opening and closing likely involved hundreds to possibly thousands of kilometers of intra-ocean and/or intra-arc strike-slip displacement, sinistral during the ocean's Late Devonian to mid-Permian opening and dextral during its Late Permian closing.