Comparison of Sr isotope ratios of ODP Hole 131-808C

Pore fluid and sediment chemical and isotopic data were obtained at ODP Site 808, western Nankai trough, Japan. The isotopic data reported here (Tables 1, 2, 3, 4) were carried out in our shore-based laboratories to complement the shipboard inorganic geochemical data published in Shipboard Scientific Party (1991). The data include: hydrogen, oxygen, and strontium isotopic compositions of the pore fluids, carbon and oxygen isotopic compositions of biogenic and authigenic calcites, and preliminary mineralogical compositions of the authigenic precipitates in veins and in tubular-cylindrical structures, observed in the sediments between 870 and 1080 mbsf. These data do not support active pervasive fluid flow at the décollement zone nor at the frontal thrust. They do, however, support pervasive active lateral fluid flow above and particularly below the décollement.