![]() Whole-rock trace-element and Nd- and Hf-isotope results are consistent with the low-degree partial melting of an enriched lithospheric mantle source during margin-scale extension. ![]() Chemical abrasion (CA-TIMS) U-Pb dates indicate that Kechika group mafic rocks were generated during the late Cambrian (488–483 Ma) and Early Ordovician (473 Ma). The Kechika group contains vent-proximal facies and sediment-sill complexes within the Cassiar platform, a linear paleogeographic high that developed outboard of continental shelf and trough basins. New zircon U-Pb age and whole-rock geochemical studies were conducted on the lower Paleozoic Kechika group, south-central Yukon, to test these rift models and constrain the timing, mantle source, and tectonic setting of post-breakup magmatism in the Canadian Cordillera. ![]() Along the Cordilleran margin of western North America, several competing rift models have been proposed to explain the origins of post-breakup igneous rocks that crop out from Yukon to Nevada. Post-breakup magmatic rocks are recognized features of modern and ancient passive margin successions around the globe, but their timing and significance to non-plume-related rift evolution is generally uncertain.
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