Stable isotope ratios of interstitial fluids from the northern Barbados accretionary prism, ODP Leg 110

Abstract

δ18O values of the pore waters range from -0.3 to -3.6‰ and reflect pervasive reaction of volcanic ash to form smectite within the sedimentary sequence and continued low temperature alteration of basalt in the underlying ocean crust with the overprint of diffusive exchange between water in the sediment pores and the open ocean. δD values of pore waters in sediments sampled seaward of the deformation front drop from +5‰ at the sediment surface to -6‰ at the deepest levels sampled. Sediment deformation caused by impingement of the Caribbean plate on the Atlantic plate has instigated migration of chemically and isotopically distinct fluid. δ18O values of pore waters are also locally affected by thrust stacking. Migrating fluids are distinguished by anomalous δ18O values that are as much as 1‰ higher than those of surrounding fluids. Stable isotope analyses of pore waters help constrain the fluid migration history of the accretionary prism by limiting the source of fluids, the paths along which fluid flows, and the timing of faulting and subsequent fluid flow. -from Authors