Cl, O, and H stable isotope compositions of variably hydrated North American SCLM xenoliths
The sub-continental lithospheric mantle (SCLM) beneath the Colorado Plateau is enriched in volatile elements likely due to interaction with fluids or melts derived from the subducted Farallon plate. This dataset examines bulk rock chlorine (δ37Cl) and hydrogen (δD) isotope compositions, bulk water content, and oxygen (δ18O) isotope compositions of clinopyroxene mineral separates from variably hydrated SCLM xenoliths from the Navajo Volcanic Field on the central Colorado Plateau and from anhydrous SCLM xenoliths from the southern Rio Grande Rift. These stable isotope ratios suggest that the metasomatic fluid source had elevated chlorine and hydrogen isotope ratios relative to the mantle, but lower oxygen isotope ratios. The most likely source of such stable isotope signatures is subducted gabbroic altered oceanic crust in the subducted Farallon plate. This finding has implication on the retention of volatile elements in subducted oceanic crust and on Cl isotope variation in the deep mantle.
Division of Earth Sciences