9633415 Fryer A major focus of marine geoscience research is elucidating global chemical mass balance for dissolved species in the oceans. A major uncertainty in these calculations is an estimate for fluxes associated with fluid flow through convergent margins. For some chemical species this omission is significant. Before better estimates of global mass balances can be determined, the chemical composition of venting fluids from subduction zones must be determined and the diagentic reactions that form these fluids must be understood. Recent work on this problem has focussed on subduction zones characterized by large accumulations of underthrust sediment. In such regions, however, the diagentic reactions in the thick sediment sequences may obscure the primary signal of fluids from the underthrusting ocean crust. The present recommended project will focus on fluid flow and chemistry of fluids from the Mariana forearc region. Sediment accretion is minimal in this area, and study of fluid flow and chemistry should provide an excellent guide to understanding primary chemical signature of fluids derived from the ocean crust. A combination of remote vehicle sampling, coring from surface ship, and measurements of sediment heat fluid and pore fluids will provide data from three areas in the Marianas where fluid flow appears to be channelized along fault zones. In addition to addressing significant scientific questions, the project will provide important background information for proposed ocean drilling in this region. ***
