In collaboration with a Mexican colleague the PIs are conducting an integrated geological, petrological, and geochemical study of Miocene to Recent volcanic rocks from a transect across the southernmost Basin and Range Province (BRP) of central Mexico. The plan is to extend this work in the transect area by conducting a comprehensive petrological and geochemical study of mantle-derived spinel-lherzolite xenoliths. Major-element analyses of whole-rock samples and constituent minerals will enable the PIs to evaluate petrogenetic models for the xenoliths as residues of partial melting of fertile peridotitic mantle and to evaluate regional differences in upper-mantle composition, temperature, oxygen fugacity, and degree of melt extraction. They also plan to conduct detailed studies of Sr-Nd-Pb isotopic ratios and trace-element abundances in clinopyroxenes, which will allow them to investigate complex metasomatic modifications of the upper-mantle geochemistry by fluid/melts, such as those related to the Tertiary subduction event and those related to on- going lithospheric extension.
