Hydrothermal alteration of green tuff belt, Japan: Implications for the influence of seawater/volcanic rock interaction on the seawater chemistry at a back-arc basin |
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| Authors: | Naotatsu Shikazono |
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| Institution: | Department of Earth Sciences, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama, Kanagawa 223, Japan |
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| Abstract: | Abstract Chemical data on hydrothermally altered volcanic rocks from a green tuff belt in Japan indicate that the average rate of Mg removal from seawater due to seawater cycling through back-arc basins in the circum-Pacific region during the early to middle Miocene (25–15 Ma) is estimated to be 2.6±1 × 1013 g/year. This is similar to that through present-day mid-ocean ridges (2.4 × 1013 g/year). Hydrothermal fluxes of K, Ca and Si are calculated to be 4.2±1.6 × 1013 g/year, 4.3±1.7×1013 g/year and 1.0±0.4 × 1014 g/year, respectively. These calculated results indicate that the seawater/volcanic rocks interaction at subduction-related tectonic settings have to be taken into account in considering the geochemical mass balance of seawater over geologic time. |
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| Keywords: | back-arc basin green tuff belt hydrothermal alteration Kuroko deposits seawater chemistry seawater circulation |
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