矿床地球化学国家重点实验室知识库

Multiple periods of arc magmatism induced by the subduction of the Indian-Australian Plate northward developed on Java Island, and multistage porphyry-epithermal metallogenic systems occurred within the Late Eocene-Early Miocene and the Late Miocene-Early Pleistocene magmatic belts. These porphyry-epithermal metallogenic systems have obvious spatial variations. In West Java, there are large populations of low-sulfidation type epithermal deposits, while East Java and its east are characterized by the occurrences of porphyry deposits. However, the newly discovered Ciemas deposit in West Java, a Middle Miocene (~17 Ma) porphyry-epithermal Au deposit, provides an opportunity for further understanding the porphyry-epithermal mineralization in Java. To elucidate the controlling factors of porphyry-epithermal mineralization in West Java, we analyzed the Hf isotopies of zircons from the igneous rocks and in situ Pb isotopes of sulfides (galena, pyrite, arsenopyrite) in the Ciemas deposit. The results show that the zircons ε_Hf (t) of igneous rocks are uniform with an average value of −11.5 ± 0.39, and the peak value of T_DM2 is 1500–1650 Ma, suggesting the Middle Miocene arc magmatism in Ciemas suffered intense crustal contamination. The Pb isotopic compositions of sulfides are very uniform and have high amounts of radiogenic lead. The mean ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb are 39.343 ± 0.059, 15.73 ± 0.015 and 18.854 ± 0.025, respectively, indicating that the mineralization materials of the Ciemas gold deposit mainly originated from ancient continental crust. The multistage arc magmatism induced by the subduction of the Indian-Australian Plate northward beneath Java Island control the porphyry and epithermal mineralization in Java. The Middle Miocene arc magmatism in Ciemas contaminated intensely by the Sundaland, and the ancient continental crust provides the main metal source for the Ciemas deposit in West Java.