TY - JOUR
T1 - High alkalinity due to sulfate reduction in the CLAM hydrothermal field, Okinawa Trough
AU - Gamo, Toshitaka
AU - Sakai, Hitoshi
AU - Kim, Eun Soo
AU - Shitashima, Kiminori
AU - Ishibashi, Jun ichiro
N1 - Funding Information:
We thank H Hotta, T. Tanaka,T . Matsumoto, K. Mltsuzawaa ndT. Naganumoaf Japan Marine Sciencea nd TechnologyC enterfor providingu s many valuablefl uid samplesT. hanksare also due to K. Danno,Y . Imai and the Shmkat 2000 operating group, as well as to officersa nd crew of the tendershlpN atsushtma for their cooperationo n board the ship. T. Oomorl, M. Tsutsumi, F. Yanaglsawa, K. Hasegawa and N. Sueda are greatlya cknowledgefdo r their collaborationI..R . Kaplan and two anonymourse viewerps rovidedu s many critical commentst o improve the initial manuscriptT he senior author wishes to thank J.M. Edmond and A.C. Campbel(l Massachusetts Instituteo f Technologyf)o r allowingh im to learn many usefult echniquefso r submersiblset udieso n board Atlantts H during the Alvin dives on the EscanabaT rough in June 1988. This study was partially supported by grants-in-aid Nos. 60430010,0 1540468,0 1790281,0 2202209,a nd 03248103fr om the Ministry of EducationS, cience and Culturet o the Universityo f Tokyo.
PY - 1991/11
Y1 - 1991/11
N2 - High alkalinity ( > 1.8 mmol kg-1), pH (4.7-5.3), and ammonium ( ∼ 5 mmol kg-1) in hydrothermal fluids from the JADE and CLAM sites in the Mid-Okinawa Trough back-arc basin demonstrate organic matter decomposition during high-temperature fluid-sediment interaction. The endmember fluid from the JADE site ( ∼ 320°C black smoker), which is free of Mg and SO4, has similar chemical characteristics as those at the Escanaba Trough, one of the representative sediment-hosted ridge systems in the eastern Pacific. On the other hand, fluid samples from the CLAM site ( ∼ 100°C) show remarkably high alkalinity (10.3 mmol kg-1) comparable to the highest alkalinity of 10.6 mmol kg-1 (Guaymas Basin) yet observed in hydrothermal fluids, and significantly higher δ34S of SO4 ( > 25‰) than ambient seawater (21‰). It is suggested that sulfate reduction plays a dominant role in decomposing organic matter to increase alkalinity in the CLAM site. Variation of the δ34S values of H2S (from -0.2 to +3.0‰) in the CLAM fluids taken from different vents suggests that the CLAM site should consist of multiple local hydrothermal systems in different evolutionary stages with regard to sulfate reduction.
AB - High alkalinity ( > 1.8 mmol kg-1), pH (4.7-5.3), and ammonium ( ∼ 5 mmol kg-1) in hydrothermal fluids from the JADE and CLAM sites in the Mid-Okinawa Trough back-arc basin demonstrate organic matter decomposition during high-temperature fluid-sediment interaction. The endmember fluid from the JADE site ( ∼ 320°C black smoker), which is free of Mg and SO4, has similar chemical characteristics as those at the Escanaba Trough, one of the representative sediment-hosted ridge systems in the eastern Pacific. On the other hand, fluid samples from the CLAM site ( ∼ 100°C) show remarkably high alkalinity (10.3 mmol kg-1) comparable to the highest alkalinity of 10.6 mmol kg-1 (Guaymas Basin) yet observed in hydrothermal fluids, and significantly higher δ34S of SO4 ( > 25‰) than ambient seawater (21‰). It is suggested that sulfate reduction plays a dominant role in decomposing organic matter to increase alkalinity in the CLAM site. Variation of the δ34S values of H2S (from -0.2 to +3.0‰) in the CLAM fluids taken from different vents suggests that the CLAM site should consist of multiple local hydrothermal systems in different evolutionary stages with regard to sulfate reduction.
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U2 - 10.1016/0012-821X(91)90080-2
DO - 10.1016/0012-821X(91)90080-2
M3 - Article
AN - SCOPUS:0026286611
VL - 107
SP - 328
EP - 338
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
IS - 2
ER -