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

Toshitaka Gamo, Kei Okamura, Jean Luc Charlou, Tetsuro Urabe, Jean Marie Auzende, Junichiro Ishibashi, Kiminori Shitashima, Hitoshi Chiba, Ray Binns, Kaul Gena, Katell Henry, Osamu Matsubayashi, Takeshi Matsumoto, Roger Moss, Yoshiharu Nagaya, Jiro Naka, Etienne Ruellan

Research output: Contribution to journalArticlepeer-review

179 Citations (Scopus)


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‰ and -5.6‰, 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.

Original languageEnglish
Pages (from-to)139-142
Number of pages4
Issue number2
Publication statusPublished - 1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geology


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