TY - SER ID - wei2005gopf T1 - Geochemistry of pore fluids and bulk solids of ODP Site 195-1200, South Chamorro Seamount AU - Wei, Wei AU - Kastner, Miriam AU - Deyhle, Annette AU - Spivack, Arthur J PY - 2005 T2 - Supplement to: Wei, W et al. (2005): Geochemical cycling of fluorine, chlorine, bromine, and boron and implications for fluid-rock reactions in Mariana forearc, South Chamorro Seamount, ODP Leg 195. In: Shinohara, M; Salisbury, MH; Richter, C (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 195, 1-23, https://doi.org/10.2973/odp.proc.sr.195.106.2005 PB - PANGAEA DO - 10.1594/PANGAEA.778487 UR - https://doi.org/10.1594/PANGAEA.778487 N2 - At the South Chamorro Seamount in the Mariana subduction zone, geochemical data of pore fluids recovered from Ocean Drilling Program Leg 195 Site 1200 indicate that these fluids evolved from dehydration of the underthrusting Pacific plate and upwelling of fluids to the surface through serpentinite mud volcanoes as cold springs at their summits. Physical conditions of the fluid source at 27 km were inferred to be at 100°-250°C and 0.8 GPa. The upwelling of fluid is more active near the spring in Holes 1200E and 1200A and becomes less so with increasing distance toward Hole 1200D. These pore fluids are depleted in Cl and Br, enriched in F (except in Hole 1200D) and B (up to 3500 µM), have low 11B (16-21), and have lower than seawater Br/Cl ratios. The mixing ratios between seawater and pore fluids is calculated to be ~2:1 at shallow depth. The F, Cl, and Br concentrations, together with B concentrations and B isotope ratios in the serpentinized igneous rocks and serpentine muds that include ultramafic clasts from Holes 1200A, 1200B, 1200D, 1200E, and 1200F, support the conclusion that the fluids involved in serpentinization originated from great depths; the dehydration of sediments and altered basalt at the top of the subducting Pacific plate released Cl, H2O, and B with enriched 10B. Calculation from B concentrations and upwelling rates indicate that B is efficiently recycled through this nonaccretionary subduction zone, as through others, and may contribute the critical missing B of the oceanic cycle. ER -