Volume 91, Issue 3 pp. 1025-1040
Original Articles
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Genesis of the Ciemas Gold Deposit and Relationship with Epithermal Deposits in West Java, Indonesia: Constraints from Fluid Inclusions and Stable Isotopes

Chaofei ZHENG

Chaofei ZHENG

State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081 China

University of Chinese Academy of Sciences, Beijing 100049 China

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Zhengwei ZHANG

Corresponding Author

Zhengwei ZHANG

State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081 China

Corresponding author. E-mail: [email protected]Search for more papers by this author
Chengquan WU

Chengquan WU

State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081 China

University of Chinese Academy of Sciences, Beijing 100049 China

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Junhua YAO

Junhua YAO

State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081 China

University of Chinese Academy of Sciences, Beijing 100049 China

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First published: 05 July 2017
Citations: 6

About the first author:

ZHENG Chaofei, male, born in 1988 in Xingtai City, Hebei Province; Doctoral student of Geochemistry, Chinese Academy of Sciences; He is now interested in the study on the geology and geochemistry of gold deposits and zinc-lead deposit. Email: [email protected].

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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