The Rio Grande Rift is a major tectonic and volcanic feature of the southwestern United States. The study proposed here will characterize the petrology and geochemistry of late Cenozoic lavas in the southern New Mexico portion of the Rift. Emphasis will be place on the dynamics of melt generation in continental rift zones and the chemical and isotopic nature of the subcontinental mantle. There have been a number of geochemical studies in the northern portion; the southern part has had few studies of comparable detail. This is the first stage of a study which will attempt to remedy the deficiency with detailed stratigraphic study of three different fields in southern New Mexico. Major-and trace-element compositions of the lavas, phenocrysts, xenocrysts, and mantle-derived xenoliths will be used to model source lithology, depth of magma generation, and melt evolution.
