Wei, Wei; Kastner, Miriam; Deyhle, Annette; Spivack, Arthur J. (2006): Geochemical cycling of fluorine, chlorine, bromine, and boron and implications for fluid-rock reactions in Mariana Forearc, South Chamorro Seamount, ODP Leg 195. Texas A&M University, Ocean Drilling Program, College Station, TX, United States, In: Shinohara, Masanao (editor), Salisbury, Matthew H. (editor), Richter, Carl (editor), Araki, Eiichiro, Barr, Samantha R., D'Antonio, Massimo, Dean, Simon M., Diekmann, Bernhard, Edwards, K. Michelle, Fryer, Patricia B., Gaillot, Philippe J., Hammon, William S., III, Hart, David, Januszczak, Nicole, Komor, Stephen C., Kristensen, Mette B., Lockwood, John P., Mottl, Michael J., Moyer, Craig L., Nakahigashi, Kazuo, Savov, Ivan P., Su Xin, Wei, Kuo-Yen, Yamada, Tomoaki, Proceedings of the Ocean Drilling Program; scientific results; seafloor observatories and the Kuroshio Current; covering Leg 195 of the cruises of the drilling vessel JOIDES Resolution; Apra Harbor, Guam, to Keelung, Taiwan; Sites 1200-1202; 2 March-2 May 2001, 195, georefid:2006-066606

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 degrees -250 degrees 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 mu M), have low delta 11B (16%-21%), and have lower than seawater Br/Cl ratios. The mixing ratios between seawater and pore fluids is calculated to be approximately 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, H (sub 2) O, and B with enriched (super 10) B. 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.
West: 146.0000 East: 146.0100 North: 13.4800 South: 13.4700
Expedition: 195
Site: 195-1200
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Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.195.106.2005 (c.f. for more detailed metadata)
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