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Hydrogen, Oxygen and Sulfur Isotope Studies of Seafloor Hydrothermal System at the Desmos Caldera, Manus Back‐arc Basin, Papua New Guinea: An Analogue of Terrestrial Acid Hot Crater‐lake
Author(s) -
Gena Kaul R.,
Chiba Hitoshi,
Mizuta Toshio,
Matsubaya Osamu
Publication year - 2006
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2006.tb00278.x
Subject(s) - hydrothermal circulation , geology , caldera , geochemistry , hydrothermal vent , sulfur , volcano , mineralogy , paleontology , chemistry , organic chemistry
. The Onsen site is an active submarine hydrothermal system hosted by the Desmos caldera in the Eastern Manus Basin, Papua New Guinea. The hydrothermal fluid is very acidic (pH=1.5) and abundant native sulfur is deposited around the vent. The δ 34 S values of native sulfur range from ‐6.5 to ‐9.3 %o. δ 34 S values of H 2 S and SO 4 in the hydrothermal fluid are ‐4.3 to ‐9.9 %o and +18.6 to +20.0 %o, respectively. These δ 34 S values are significantly lower than those of the other hydrothermal systems so far reported. These low δ 34 S values and the acidic nature of the vent fluids suggest that volcanic SO 2 gas plays an important role on the sulfur isotope systematic of the Onsen hydrothermal system. Relationship among the δ 34 S values of S‐bearing species can be successively explained by the model based on the disproportionation reaction starting from the volcanic SO 2 gas. The predicted δ 34 S values of SO 2 agree with the measured whole rock δ 34 S values. δD and δ 18 O values of clay minerals separated from the altered rock samples also suggest the contribution of the magmatic fluid to the hydrothermal system. Present stable isotopic study strongly suggests that the Onsen hydrothermal site in the Desmos caldera is a magmatic submarine hydrothermal system.