Intellectual merit. Knowledge of the distribution and composition of the chemical components associated with convergent margin magmatism is a fundamental requirement for understanding the origin, composition and evolution of the continental crust and the heterogeneity of the mantle. Establishing the budget and distribution of volatiles in the mantle at convergent margins is a necessary step to understand the processes responsible for the generation of arc volcanoes. Volatiles influence mantle melting, magma crystallization and volcanic eruption, and their abundances and spatial distribution provide important constraints on models of mantle flow, slab dehydration and crustal recycling. Over the last 30 years, the Andes Southern Volcanic Zone (SVZ) has been extensively investigated, with geochemical, petrological, geophysical, tectonic and geological studies providing important information on the composition of the magmatic arc, and the structure and evolution of the crust and mantle. However, data on volatile concentration and stable isotopic composition of lavas from the SVZ are virtually nonexistent. This project aims to fill this gap by determining regional variations in volatile contents and isotopic composition in selected SVZ basalts. The new data will help us build a more integrated and realistic portrait of the inner-workings at convergence margins in continental environments. They will be used to discriminate sources of volatiles (e.g., slab dehydration vs. subducted sediments) and to test models of slab-flux versus decompression melting. Combination of the existing seismic information, and two-dimensional temperature and flow models with the geochemical data will provide a more reliable representation of the mantle flow, melt production, migration, and extent of the mantle hydration beneath the SVZ.
Broader Impact. This project will promote collaboration between geophysicists, geochemists and geodynamicists from six domestic (Brown U., DTM, FIU, Cornell U., CWRU, WHOI) and five foreign institutions (U. Cordoba, Argentina; U. Concepcion, Chile; IFM-GEOMAR and GFZ-Postdam, Germany; Okoyama U., Japan). These collaborations will allow cross-fertilization that will benefit all scientists involved, where the sharing of samples, data, models and ideas will flow freely between the parties. Three laboratories: the Eprobe at Brown U., the ion-probe at DTM-CIW, and the ICPMS-labs at WHOI will be financially supported by this research. The project will support one PhD student and several undergraduates from Brown University and undergraduates from University of Cordoba. We anticipate several senior theses from both institutions. Thus, research on recent Andean volcanism will be represented for the first time in the Geology Department at the Universidad de Cordoba.
