2006 Fiscal Year Final Research Report Summary
Geochemical study of seafloor hydrothermal systems as modern analogue of kuroko-type are deposits
| Project/Area Number |
16340173
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geochemistry/Astrochemistry
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| Research Institution | KYUSHU UNIVERCITY |
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Principal Investigator |
ISHIBASHI Junichiro Kyushu University, Faculty of Science, Associate Professor, 大学院理学研究院, 助教授 (20212920)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMADA Nobutaka Kyushu University, Faculty of Science, Professor, 大学院理学研究院, 教授 (00037235)
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| Project Period (FY) |
2004 – 2006
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| Keywords | fluid chemistry / fluid inclusion / seafloor hydrothermal system / volcanic massive sulfide deposit / southwest Pacific / backarc basin / submarine arc volcano / backarc rifting |
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| Research Abstract |
In order to obtain the key information for ore forming process from fluid inclusions in ore samples of ancient kuroko-type VMSD (volcanic massive sulfide deposits), this research aimed to compare chemical composition of hydrothermal fluid and of fluid inclusion of sulfide/sulfate ores, both are collected from modern seafloor hydrothermal systems and tried to discuss relationship between the fluid chemistry and the tectonic setting. We developed analytical systems, the one is for gas composition determination using a gas chromatograph and the other is for minor anions analysis using a HPLC. Using these apparatuses, we determined gas composition of fluid inclusions in a massive sulfide ore sample. On the other hand, we also conducted field studies participating into some dive program to collect samples from seafloor hydrothermal systems in southwestern and northwestern Pacific. We analyzed both gas species and elemental species of the hydrothermal fluid samples obtained from active venting, and also mineral composition and fluid inclusion properties of the sulfide/sulfate ore samples collected from the same site. Based on these results, we found some geochemical signature reflecting the specific tectonic setting, such as significant enrichment in incompatible elements of the hydrothermal fluid in the tectonic setting where arc and backarc activities occur closely, and as extensive phase separation and fluid migration within sediment layer in the tectonic setting of continental margin. The geochemical data obtained in this study using the newly developed apparatuses also contributed to the collaborative microbiological studies.
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