Roddy Campbell (M.Sc., 2018), Luke Beranek, and colleagues from Memorial University and University of British Columbia have published a new article in Geosphere.
The precise age and tectonic significance of post-breakup igneous rocks along the Cordilleran margin of western North America are uncertain. In this article, Campbell et al. (2019) use the volcanic and intrusive rock record from the Kechika group, south-central Yukon, to test published models for Cordilleran rift evolution that have populated the literature since the 1980s. New 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), which post-dated the presumed timing of lithospheric breakup by 10s of Myr. 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. We concluded that ancient post-breakup igneous successions along western North America were generated in a plate tectonic setting analogous that that of the magma-poor Newfoundland-Iberia rift system. |