Long-lived basement weak zones and their role in extensional magmatism in the Ogilvie Mountains, Yukon Territory

Abstract

In the Ogilvie Mountains intrusive breccias and volcanic rocks are aligned along faults that were active during evolution of the Cordilleran miogeocline. Character of the magmatic rocks provide clues to changing lower crust or upper mantle conditions beneath the western margin of ancestral North America. The unusually long (Middle Proterozoic to Jurassic) sedimentary record was influenced by episodes of crustal stretching. Although crystalline basement rocks are not exposed in the northern fold and thrust belt, the combination of inferences from the sedimentary record, ancient structures, and igneous chemistry imply recurring zones of weakness and periodic mantle disturbance beneath the ancient continental margin. -from Authors