Comment on 'Geodynamics of synconvergent extension and tectonic mode switching: Constraints from the Sevier-Laramide orogen' by Michael L. Wells et al

摘要

Wells et al. [2012] utilize geothermobarometry and geochronology of garnets in metamorphic rocks from the northern Grouse Creek Mountains in the Albion-Raft River-Grouse Creek metamorphic core complex to infer a P-T-t path that involves burial by crustal shortening at 85 Ma followed by ～3 kbar of exhumation during extensional thinning of the crust beginning at 75 Ma. This was followed by 1 kbar burial by crustal shortening between 68 and 50 Ma. Their proposed geodynamic driving mechanisms for these events involve the sub-crustal mantle lithosphere and upper asthenospheric mantle, with potentially far-reaching implications for Cordilleran orogenesis during its transition from crustal shortening to extension (Figure 1 is their Figure 9; subsequently referenced to as Figure 1).