The Early Cretaceous Weilasituo Zn-Cu-Ag vein deposit in the southern Great Xing'an Range, northeast China: Fluid inclusions, H, O, S, Pb isotope geochemistry and genetic implications

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• 作者：Hegen Ouyang ; Jingwen Mao ; M. Santosh ; Yue Wu ; Lin Hou ; Xifei Wang
• 关键词：Ore mineralization ; Fluid inclusion ; Stable isotope geochemistry ; Weilasituo deposit ; Great Xing'an Range ; China
• 刊名：Ore Geology Reviews
• 出版年：January, 2014
• 年：2014
• 卷：56
• 期：Complete
• 页码：503-515
• 全文大小：3760 K

文摘

The Weilasituo vein-type deposit hosted in Hercynian (Middle to Late Paleozoic) quartz diorite and Palaeozoic gneiss occurs on the western slopes of the southern Great Xing'an Range. In this paper, we present results from fluid inclusion and isotope (H, O, S, Pb) investigations on the Weilasituo deposit. We identify three stages during the ore formation: a barren pre-ore stage (stage 1), a main-ore stage with economic grade Cu-Zn-Ag mineralization (stage 2), and a barren post-ore stage (stage 3). Fluid inclusion and mineral thermometry constrain temperature intervals of approximately 243 to 333 掳C, 192 to 425 掳C, and 141 to 261 掳C, for the three stages, respectively. Fluids in the main-ore stage are characterized by complex NaCl-H₂O-CH₄-CO₂ low-salinity (3.55 to 8.68 wt.% NaCl equiv.) with isotopic signatures consistent with a magmatic source. These fluids evolved by mixing with local meteoric water (未¹⁸O_fluid = 1.15 to 5.15鈥? 未D_fluid = 鈭?#xA0;139.4 to 鈭?#xA0;88.2鈥?. Measured and calculated sulfur isotope compositions of hydrothermal fluids (未³⁴S_fluid = 鈭?#xA0;3.0 to 3.4鈥? indicate that the ore sulfur was derived mainly from a magmatic source. The lead isotope ratios from the ores show mean values of 18.326, 15.553, and 38.242 for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb, respectively, indicating a mantle source. Our study shows that fluid mixing and/or dilution played an important role in copper, zinc, and silver mineralization in the Weilasituo deposit. The Weilasituo and Bairendaba deposits represent a linked ore system genetically related to the late Mesozoic magmatism. The ore-forming fluids associated with the Early Cretaceous mineralization in the southern Great Xing'an Range are of magmatic in origin, and evolved by mixing with local meteoric water. These deposits preserve the signature of a mantle source for lead. However, the deposits formed at ca. 177-160 Ma possess a dominantly magmatic signature with less radiogenic lead.