Catastrophic shear-removal of subcontinental lithospheric mantle beneath the Colorado Plateau by the subducted Farallon slab.

ABSTRACT: The causes of Cenozoic uplift of the Colorado Plateau, southwestern USA, are strongly debated, though most hypotheses acknowledge the importance of northwest-directed subduction of the Farallon oceanic plate beneath North America since c. 100?Ma. Existing thermomechanical models suggest that the Farallon slab underthrust the proto-plateau region at ~200?km depth, removing the basal portions of its subcontinental lithospheric mantle (SCLM) root, although such small-volume subduction erosion cannot fully account for the degree of uplift observed today. Here we show via petrological modeling of lawsonite-bearing eclogite xenoliths exposed in diatremes in the center of the plateau that the Farallon slab surface penetrated through the proto-plateau SCLM at much shallower depths (~120?km) than these previous estimates, allowing shear-removal of ~80?km of SCLM - a volume up to three-times greater than previously suggested. This removal led to asthenospheric upwelling and isostatic rebound of the plateau region during the late Cretaceous to the Eocene. We posit that similar shear-removal of SCLM likely played a major role in inhibiting cratonic growth and stabilization in the Neoarchean and Paleoproterozoic - when low-angle subduction of oceanic lithosphere was more prevalent than today - accounting for the atypically thin roots existing below many ancient cratons worldwide.

SUBMITTER: Hernandez-Uribe D 

PROVIDER: S-EPMC6544764 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature