| The occurrence of gold in hydrothermal sulfide at Southwest Indian Ridge 49.6°E |
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| 作者姓名： | YE Jun SHI Xuef YANG Yaomin LI Naisheng LIU Jihu SU Wenchao |
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| 作者单位： | Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266007, China;First Insititute of Oceanography, State Oceanic Administration, Qingdao 266061, China;Graduate University of the Chinese Academy of Sciences, Beijing 100049, China;First Insititute of Oceanography, State Oceanic Administration, Qingdao 266061, China;First Insititute of Oceanography, State Oceanic Administration, Qingdao 266061, China;National Oceanographic Center, Qingdao 266071, China;First Insititute of Oceanography, State Oceanic Administration, Qingdao 266061, China;State Key Laboratory of Ore Deposit Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China |
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| 基金项目： | The International Seabed Area 11th Five Year Plan Program of China Ocean Mineral Resources R&D Association under contract No. DYXM-115-01-2-1; the International cooperation program of the Ministry of Science and Technology under contract No. 2006DFB21620 |
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| 摘 要： | Massive sulfide precipitates found in the Southwest Indian Ridge(SWIR) 49.6°E hydrothermal field are enriched in gold.Here,the mineralogy and mineral chemistry of these massive sulfides to constrain the process of gold precipitation were studied.Sulfide samples in this field include lowertemperature Zn-rich sulfides and relative higher-temperature Fe-rich sulfides.Zn-rich sulfides are dominated by sphalerite-pyrite-chalcopyrite assemblages,with concentrations of gold ranging from 9.08 to 17.0 μg/g.Fe-rich sulfides consist mainly of pyrite-marcasite-isocubanite assemblages,with gold concentrations from 2.17 to 3.79 μg/g.The significant enrichment in gold within the lowertemperature Zn-rich sulfides and the effective separation of Zn and Fe in hydrothermal precipitates at the surface of this field are here interpreted to reflect the strong temperature dependence of gold transportation and deposition within the sulfides.In Zn-rich samples,large amounts of isolated native gold grains were identified.They were found mainly as inclusions up to 8 μm in diameter,occupying porous cavities in sphalerite or in the elevated iron content rim of sphalerite.The fineness of the gold ranged from 810 to 830.Unlike previously published results on other hydrothermal fields,these data show a low gold fineness values in SWIR 49.6°E.The FeS content of sphalerite associated with gold grains ranged from 3.2 mole % to 18.9 mole %.This was higher than in other fields,indicating that the sulfur activity is relatively low during the gold precipitation process and that sulfur activity may be one of the main factors affecting gold fineness in the SWIR 49.6°E hydrothermal field.Evidence regarding gold fineness and sulfur activity suggests that gold was quite likely transported as AuHS0 rather than as a Au(HS)-2 complex.
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| 关 键 词： | hydrothermal sulfide Southwest Indian Ridge occurrence of gold mineralogy |
| 收稿时间： | 9/8/2011 12:00:00 AM |
| 修稿时间： | 9/7/2012 12:00:00 AM |
The occurrence of gold in hydrothermal sulfide at Southwest Indian Ridge 49.6°E |
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| YE Jun,SHI Xuef,YANG Yaomin,LI Naisheng,LIU Jihu,SU Wenchao.The occurrence of gold in hydrothermal sulfide at Southwest Indian Ridge 49.6°E[J].Acta Oceanologica Sinica,2012,31(6):72-82. |
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| Authors: | YE Jun SHI Xuef YANG Yaomin LI Naisheng LIU Jihua and SU Wenchao |
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| Institution: | 1.Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266007, China;First Insititute of Oceanography, State Oceanic Administration, Qingdao 266061, China;Graduate University of the Chinese Academy of Sciences, Beijing 100049, China2.First Insititute of Oceanography, State Oceanic Administration, Qingdao 266061, China3.National Oceanographic Center, Qingdao 266071, China4.State Key Laboratory of Ore Deposit Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China |
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| Abstract: | Massive sulfide precipitates found in the Southwest Indian Ridge (SWIR) 49.6°E hydrothermal field are enriched in gold. Here, the mineralogy and mineral chemistry of these massive sulfides to constrain the process of gold precipitation were studied. Sulfide samples in this field include lowertemperature Zn-rich sulfides and relative higher-temperature Fe-rich sulfides. Zn-rich sulfides are dominated by sphalerite-pyrite-chalcopyrite assemblages, with concentrations of gold ranging from 9.08 to 17.0 μg/g. Fe-rich sulfides consist mainly of pyrite-marcasite-isocubanite assemblages, with gold concentrations from 2.17 to 3.79 μg/g. The significant enrichment in gold within the lowertemperature Zn-rich sulfides and the effective separation of Zn and Fe in hydrothermal precipitates at the surface of this field are here interpreted to reflect the strong temperature dependence of gold transportation and deposition within the sulfides. In Zn-rich samples, large amounts of isolated native gold grains were identified. They were found mainly as inclusions up to 8 μm in diameter, occupying porous cavities in sphalerite or in the elevated iron content rim of sphalerite. The fineness of the gold ranged from 810 to 830. Unlike previously published results on other hydrothermal fields, these data show a low gold fineness values in SWIR 49.6°E. The FeS content of sphalerite associated with gold grains ranged from 3.2 mole% to 18.9 mole%. This was higher than in other fields, indicating that the sulfur activity is relatively low during the gold precipitation process and that sulfur activity may be one of the main factors affecting gold fineness in the SWIR 49.6°E hydrothermal field. Evidence regarding gold fineness and sulfur activity suggests that gold was quite likely transported as AuHS0 rather than as a Au(HS)2- complex. |
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| Keywords: | hydrothermal sulfide Southwest Indian Ridge occurrence of gold mineralogy |
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