HYDROGEOCHEMISTRY OF THE NORTHERN BARBADOS ACCRETIONARY COMPLEX TRANECT - OCEAN DRILLING PROJECT LEG 110

Detailed studies of the major element geochemistry, oxygen and hydrogen isotope ratios of pore fluids, and the 87Sr/86Sr ratio of dissolved strontium have made it possible to unravel physical and chemical processes that affect the pore fluid chemistry in a transect of drill holes across the northern Barbados accretionary complex. These processes include 1) alteration of volcanic ash buried in the Pleistocene-Pliocene sediment columns; 2) alteration of underlying basalts of layer 2 of the oceanic crust; 3) movement of fluids from deep in the accretionary complex along fault zones (particularly the decollement) and minor permeable layers; these fluids from deeper in the complex are characterized by low chloride concentrations and increased δ18O(H2O) values, presumably as a result of dehydration of smectite interlayers; and 4) mixing processes involving the migrating fluids cause incongruities in the geochemical anomalies of these fluids. -Authors