Metasomatism of the Wyoming craton lower crust during the Laramide orogeny: Extending the record of lithosphere hydration across western North America

New zircon and titanite U-Pb and trace-element data from minette- and kimberlite-hosted lower crustal xenoliths from near the northern margin of the Wyoming craton document multiple periods of metasomatism from 62 to 50 Ma. Metasomatism was either coincident or preceded eruption of the host magmas by up to 14 Myr (eruption dated at 52 Ma and 48 Ma based on new zircon U-Th/He data). Thus, fluid/melt interactions were not solely related to magmatic entrainment and eruption. Accessory mineral trace element data reveal metasomatism by fluids from multiple sources, including water and carbonatite potentially sourced from the subducted Farallon slab. These metasomatic episodes are interpreted to reflect pan-lithospheric hydration events that weakened the deep cratonic lithosphere and facilitated partial removal following rollback and foundering of the Farallon plate. The new data corroborate previous suggestions that subduction-related metasomatism may be a key requisite for the destruction of otherwise stable cratons.