The P.I.s plan further development of the Be-B systematics and correlation of these tracers with selected trace element ratios and radiogenic isotope compositions for lavas from the Central America, ANdes, Bismarck, Kurile-Kamchatka, Aleutian, Aeolian, Trans-Mexico, Lesser Antilles and Mariana volcanic arcs. These studies are intended to elucidate 1) the nature of crust, mantle and subducted reservoirs, 2) the process by which these reservoirs interact, and 3) the effects of subduction recycling on geochemical budgets in the crust and mantle. 10Be measurements will be made at the University of Pennsylvania, with chemical separations made at DTM. K, Rb, Cs, Ba, Sr, U, Th and Pb measurements by isotope dilution and radiogenic isotope determinations will be made at DTM, along with Be, Li and some B concentration measurements. Determinations of high field strength elements, rare earth elements and the majority of B concentration measurements will be handled through Rice University. ICP major and trace element characterizations will be carried out at DTM and Rice.