| Genesis of the Ciemas Gold Deposit and Relationship with Epithermal Deposits in West Java, Indonesia: Constraints from Fluid Inclusions and Stable Isotopes |
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| 作者姓名： | ZHENG Chaofei ZHANG Zhengwei WU Chengquan YAO Junhua |
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| 摘 要： | The Ciemas gold deposit is located in West Java of Indonesia,which is a Cenozoic magmatism belt resulting from the Indo-Australian plate subducting under the Eurasian plate.Two different volcanic rock belts and associated epithermal deposits are distributed in West Java:the younger late Miocene-Pliocene magmatic belt generated the Pliocene-Pleistocene epithermal deposits,while the older late Eocene-early Miocene magmatic belt generated the Miocene epithermal deposits.To constrain the physico-chemical conditions and the origin of the ore fluid in Ciemas,a detailed study of ore petrography,fluid inclusions,laser Raman spectroscopy,oxygen-hydrogen isotopes for quartz was conducted.The results show that hydrothermal pyrite and quartz are widespread,hydrothermal alteration is well developed,and that leaching structures such as vuggy rocks and extension structures such as comb quartz are common.Fluid inclusions in quartz are mainly liquid-rich two phase inclusions,with fluid compositions in the NaCl-H20 fluid system,and contain no or little CO_2.Their homogenization temperatures cluster around 240℃-320℃,the salinities lie in the range of 14-17 wt.%NaCl equiv,and the calculated fluid densities are 0.65-1.00 g/cm~3.The values of δ~(18)O_(H2O-VSMOW)for quartz range from +5.5‰ to +7.7‰,the δD_(VSMOW) of fluid inclusions in quartz ranges from-70‰ to-115‰.All of these data indicate that mixing of magmatic fluid with meteoric water resulted in the formation of the Ciemas deposit.A comparison among gold deposits of West Java suggests that Miocene epithermal ore deposits in the southernmost part of West Java were more affected by magmatic fluids and exhibit a higher degree of sulfldation than those of Pliocene-Pleistocene.
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| 收稿时间： | 2016/3/17 0:00:00 |
Genesis of the Ciemas Gold Deposit and Relationship with Epithermal Deposits in West Java, Indonesia: Constraints from Fluid Inclusions and Stable Isotopes |
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| Authors: | ZHENG Chaofei ZHANG Zhengwei WU Chengquan and YAO Junhua |
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| Institution: | 1 State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of
Sciences, Guiyang 550081, China
2 University of Chinese Academy of Sciences, Beijing 100049, China,1 State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China,1 State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of
Sciences, Guiyang 550081, China
2 University of Chinese Academy of Sciences, Beijing 100049, China and 1 State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of
Sciences, Guiyang 550081, China
2 University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | The Ciemas gold deposit is located in West Java of Indonesia, which is a Cenozoic magmatism belt resulting from the Indo‐Australian plate subducting under the Eurasian plate. Two different volcanic rock belts and associated epithermal deposits are distributed in West Java: the younger late Miocene–Pliocene magmatic belt generated the Pliocene–Pleistocene epithermal deposits, while the older late Eocene–early Miocene magmatic belt generated the Miocene epithermal deposits. To constrain the physico‐chemical conditions and the origin of the ore fluid in Ciemas, a detailed study of ore petrography, fluid inclusions, laser Raman spectroscopy, oxygen‐hydrogen isotopes for quartz was conducted. The results show that hydrothermal pyrite and quartz are widespread, hydrothermal alteration is well developed, and that leaching structures such as vuggy rocks and extension structures such as comb quartz are common. Fluid inclusions in quartz are mainly liquid‐rich two phase inclusions, with fluid compositions in the NaCl–H2O fluid system, and contain no or little CO2. Their homogenization temperatures cluster around 240°C–320°C, the salinities lie in the range of 14–17 wt.% NaCl equiv, and the calculated fluid densities are 0.65–1.00 g/cm3. The values of δ18OH2O‐VSMOW for quartz range from +5.5‰ to +7.7‰, the δ5DVSMOVV of fluid inclusions in quartz ranges from ?70‰ to ?115‰. All of these data indicate that mixing of magmatic fluid with meteoric water resulted in the formation of the Ciemas deposit. A comparison among gold deposits of West Java suggests that Miocene epithermal ore deposits in the southernmost part of West Java were more affected by magmatic fluids and exhibit a higher degree of sulfidation than those of Pliocene–Pleistocene. |
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| Keywords: | fluid inclusions oxygen and hydrogen isotopes epithermal subduction Ciemas gold deposit West Java Indonesia |
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