9406624 Carr Objectives are to complete the geochemical stratigraphy of DSDP 495 and to collaborate in the analysis of JOIDES cores planned for the future along the coast of Central America; to determine the variation with time of the elemental fluxes at the volcanic front; to ascertain in the extent of subduction components in the back arc region; to characterize the pre-metasomatized mantle wedge. To accomplish these goals, PIs plan to acquire extensive trace element and isotopic data on sample spanning the last 2-4 my in the Moyuta-Tecuamburro segment of Guatemala; to determine B, Be and 10Be on lavas in the back arc; and to extend the regional Pb isotopic study of volcanic front and back arc lavas begun in the previous proposal.