Ore Genesis and Hydrothermal Evolution of the Donggebi Porphyry Mo Deposit, Xinjiang, Northwest China: Evidence from Isotopes (C, H, O, S, Pb), Fluid Inclusions, and Molybdenite Re-Os Dating

Abstract

Research Article| March 01, 2018 Ore Genesis and Hydrothermal Evolution of the Donggebi Porphyry Mo Deposit, Xinjiang, Northwest China: Evidence from Isotopes (C, H, O, S, Pb), Fluid Inclusions, and Molybdenite Re-Os Dating Yin-hong Wang; Yin-hong Wang State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China †Corresponding author: e-mail, wyh@cugb.edu.cn Search for other works by this author on: GSW Google Scholar Fang-fang Zhang; Fang-fang Zhang State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Jia-jun Liu; Jia-jun Liu State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Chun-ji Xue; Chun-ji Xue State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Bo-chao Li; Bo-chao Li State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Xue-chen Xian Xue-chen Xian State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Author and Article Information Yin-hong Wang State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Fang-fang Zhang State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Jia-jun Liu State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Chun-ji Xue State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Bo-chao Li State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Xue-chen Xian State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China †Corresponding author: e-mail, wyh@cugb.edu.cn Publisher: Society of Economic Geologists Accepted: 10 Nov 2017 First Online: 09 Mar 2018 Online Issn: 1554-0774 Print Issn: 0361-0128 © 2018 Economic GeologyEconomic Geology Economic Geology (2018) 113 (2): 463–488. https://doi.org/10.5382/econgeo.2018.4558 Article history Accepted: 10 Nov 2017 First Online: 09 Mar 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Yin-hong Wang, Fang-fang Zhang, Jia-jun Liu, Chun-ji Xue, Bo-chao Li, Xue-chen Xian; Ore Genesis and Hydrothermal Evolution of the Donggebi Porphyry Mo Deposit, Xinjiang, Northwest China: Evidence from Isotopes (C, H, O, S, Pb), Fluid Inclusions, and Molybdenite Re-Os Dating. Economic Geology 2018;; 113 (2): 463–488. doi: https://doi.org/10.5382/econgeo.2018.4558 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract The Donggebi porphyry Mo deposit (441 Mt at 0.115% Mo) is located in the center of the Jueluotage metallogenic belt in Eastern Tianshan, on the southern margin of the Central Asian orogenic belt, Xinjiang, northwest China. Molybdenum mineralization mainly occurs as veins or veinlets in sandstone of the lower Carboniferous Gandun Formation or as dissemination within Triassic granitic porphyry stocks. Four stages (I–IV) of hydrothermal activity have been identified. Molybdenite mainly occurs in veins of stage II (quartz-molybdenite and molybdenite-only veins or veinlets within the altered wall rocks) and III (quartz + molybdenite + fluorite + pyrite ± chalcopyrite ± bornite ± galena ± sphalerite veinlets/veins with phyllic halos). Re-Os dating results for molybdenite samples from stage II yielded an isochron age of 236.6 ± 1.9 Ma (2σ, MSWD = 0.41, n = 10).Fluid evolution during the four stages of mineralization was constrained by a detailed fluid inclusion study: (1) Fluid inclusions during the formation of the early pre-ore stage quartz–K-feldspar veins (stage I) were trapped under two-phase conditions, as evidenced by the presence of liquid-rich fluid inclusions coexisting with vapor-rich ones, and CO2-bearing and solid-bearing inclusions with an opaque daughter crystal; fluid phase separation occurred at 200- to 550-bar pressure (corresponding to a depth of 0.7–2.0 km, assuming lithostatic pressure conditions) and temperatures of 256° to 460°C. (2) Fluid inclusions in quartz veins from the main ore stages (II and III) were also trapped under two-phase conditions (fluid phase separation); these inclusions mostly homogenize to liquid between 220° and 300°C, with salinities of ~2 to 7 wt % NaCl equiv, and record a pressure of entrapment of <50 to 200 bar (corresponding to a depth of 0.5–2.0 km under hydrostatic pressure conditions). (3) Late post-ore stage (IV) fluids are represented by two-phase aqueous inclusions in quartz from quartz-calcite veins, characterized by homogenization temperatures ranging from 106° to 243°C and salinities between 1.6 and 5.7 wt % NaCl equiv. All of these observations combined with the stable and radiogenic isotope results reveal that the formation of the Triassic Donggebi porphyry Mo deposit was dominated by a magmatic-hydrothermal system.Hydrogen, oxygen, and carbon isotope data of quartz and calcite at Donggebi indicate that the hydrothermal fluids had a dominantly magmatic signature and were diluted by meteoric waters. Molybdenite samples from stages II and III record a narrow range of δ34S values between 3.3 and 5.0‰, whereas pyrite samples from stages I to IV show decreasing δ34S values between 2.1 and 5.0‰. Molybdenite also has 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios similar to those of granitic intrusions. In a diagram of 207Pb/204Pb versus 206Pb/204Pb, the Pb isotope data from sulfide samples display a positive trend transecting the growth curves of crustal lead. Sulfur and lead isotope data for sulfide minerals, together with their paragenesis, suggest that the ore-forming components (metal and sulfur) were sourced from a larger magmatic reservoir and some upper crustal materials in a postcollision extensional setting. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

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