CONTRASTING GEOTHERMAL REGIMES OF THE BARBADOS RIDGE ACCRETIONARY COMPLEX

Three E-W transects of closely spaced heat flow measurements across the Barbados Accretionary Complex are reported. One transect, about 100 km in length at 14°20′N and a shorter 15-km line at 14°35′N show that heat flow decreases arcward roughly in proportion to the thickening of the wedge over the actively accreting zone. This decrease is due to the combined thermal effects of the underthrusting oceanic lithosphere and thickening of sediments that have been ingested into the wedge. Except for anomalously high heat flow over a mud volcano on the eastern end of the 100-km transect, fluid expulsion appears to have only a secondary effect on the seafloor heat flow in this region. An increase of heat flow is observed at the western end of the 100-km transect where high-angle arcward vergent thrusting is occurring. In strong contrast a short line of stations at 15°30′N found anomalously high heat flow with large variability over the most recently accreted material and also in the adjacent basin. The thermal regime here is dominated by a strong flow of pore fluids along the decollement and upward flow along fault planes in the toe of the wedge and adjacent basin sediments. Heat transport by pore fluids also appears to dominate the subseafloor thermal regime in a zone near 13°50′N. -from Authors