Geology and ore fluid geochemistry of the Jinduicheng porphyry molybdenum deposit, East Qinling, China

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• 作者：Hongying Li ; Huishou Ye ; Xiaoxia Wang ; Lei Yang ; Xiuyuan Wang
• 关键词：Fluid inclusions ; Stable isotopes ; Porphyry molybdenum deposit ; Jinduicheng ; East Qinling ; China
• 刊名：Journal of Asian Earth Sciences
• 出版年：5 January, 2014
• 年：2014
• 卷：79
• 期：Complete
• 页码：641-654
• 全文大小：5266 K

文摘

Jinduicheng deposit is a giant Mesozoic porphyry Mo system deposit in the East Qinling molybdenum belt, Shaanxi Province, China. The mineralization is associated with the I-type Jinduicheng granite porphyry. Both the porphyry stock and country rocks underwent intense hydrothermal alteration. The alteration, with increasing distance from the parent intrusion, changes from silicification, through potassic and phyllic assemblages, carbonation, to propylitic assemblages. Molybdenite, the dominant ore mineral, occurs in veinlets, most of which are hosted by the altered country rocks, with less than 25% of the ore in the porphyry body. The hydrothermal system comprises four stages, including pre-ore quartz and K-feldspar; two ore stages of quartz, K-feldspar, molybdenite, and Pb- And Zn-bearing sulfides; and post-ore quartz and carbonate. Six main types of primary fluid inclusions are present in hydrothermal quartz, including two-phase aqueous, one-phase aqueous, three-phase CO₂-bearing, CO₂-dominated fluid inclusions, gas inclusions, and melt inclusions. The homogenization temperatures of fluid inclusions range from 210 to 290 掳C in the pre-ore stage, 150-310 掳C in ore stage I, 150-360 掳C in the ore stage II, and 195-325 掳C in the post-ore stage quartz. Estimated salinities of the ore-forming fluids range from 6.9 to 13.5, 4.3 to 12.3, 6.2 to 12.4, and 3.4 to 9.9 wt.% NaCl equiv. in stages 1-4, respectively. The 未³⁴S values of pyrite in the two ore stages range from 2.8鈥?to 4.3鈥? whereas the 未³⁴S values of molybdenite range from 2.9鈥?to 6.2鈥? The data suggest both magmatic and crustal sources of sulfur. The 未D and 未¹⁸O values for the hydrothermal fluids are 鈭?7.2鈥?to 鈭?4.4鈥?and 8.0鈥?to 鈭?.2鈥? respectively. The fluid inclusion and stable data indicate that the pre-ore hydrothermal fluids were mostly of magmatic origin, but the fluids responsible for ore deposition were mixed magmatic and meteoric, and eventually meteoric water dominated the system in the post-ore stage.