Acidic and sulfate-rich hydrothermal fluids from the Manus back-arc basin, Papua New Guinea

• Published in: Geology (Boulder) 1997-02, Vol.25 (2), p.139-142
• Main Authors: Gamo, Toshitaka, Okamura, Kei, Charlou, Jean-Luc, Urabe, Tetsuro, Auzende, Jean-Marie, Ishibashi, Junichiro, Shitashima, Kiminori, Chiba, Hitoshi, Binns, Ray A, Gena, Kaul, Henry, Katell, Matsubayashi, Osamu, Moss, Roger, Nagaya, Yoshiharu, Naka, Jiro, Ruellan, Etienne
• Format: Article
• Language: English
• Subjects: acidic composition; Australasia; back-arc basins; basins; Bismarck Sea; deep-sea environment; DESMOS hydrothermal field; geochemistry; Geology; hydrothermal vents; Manus Basin; marine environment; Oceanography; Oceans; Pacific Ocean; Papua New Guinea; sea water; South Pacific; Southwest Pacific; submarine volcanoes; sulfate ion; Sulfur; volcanoes; water; West Pacific
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/0091-7613(1997)025<0139:AASRHF>2.3.CO;2

Hot (±88-120°C) and acidic (pH≤2.1) hydrothermal fluids rich in sulfate were discovered venting in the DESMOS caldera (depth = 1926 m), eastern Manus back-arc basin, Bismarck Sea, surrounded by Papua New Guinea. The abundant sulfate (≥32.8 mM, higher than the seawater value of 28 mM) with elemental sulfur deposition around the vents, and remarkably low δD(H2O) and δ34S(H2S) values (-8.1 per mil and -5.6 per mil, respectively), are suggestive of the incorporation of a magmatic fluid and the disproportionation of the exsolved SO2 from a magma body. The DESMOS fluid may be similar in origin to the acidic sulfate-chloride hot springs associated with subaerial volcanic activity. In contrast to the typical hydrothermal end member Mg concentration of 0, the DESMOS fluids are rich in Mg (46-52 mM), probably because of Mg dissolution by acid attack upon magnesium silicate minerals.