An Early Cretaceous carbonate replacement origin for the Xinqiao stratabound massive sulfide deposit,Middle-Lower Yangtze Metallogenic Belt,China |
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| Institution: | 1. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;2. Department of Earth Sciences, Durham University, Durham DH1 3LE, UK;3. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;4. 321 Geological Team, Bureau of Geology and Mineral Exploration of Anhui province, Tongling 244033, China;5. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;1. Earth Science Institute, Slovak Academy of Sciences, 840 05 Bratislava, Slovakia;2. Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, BP 10448, F-63000 Clermont-Ferrand, France;3. CNRS, UMR6524, LMV, F-63038 Clermont-Ferrand, France;4. IRD, R 163, LMV, Clermont-Ferrand, France;5. Department of Mineralogy and Petrology, Comenius University, 842 15 Bratislava, Slovakia;6. Institute of Geological Sciences, Masaryk University, 611 37 Brno, Czech Republic;7. Matúškova 11, 831 01 Bratislava, Slovakia;8. Geoafrica Prospecting Services cc, PO Box 24218, Windhoek, Namibia;9. Earth Science Institute, Slovak Academy of Sciences, 917 04 Banská Bystrica, Slovakia;1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China;2. Centre of Excellence in Ore Deposits (CODES), University of Tasmania, Private Bag 79, Hobart, Australia |
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| Abstract: | Stratabound massive sulfide deposits are widespread along the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and serve as an important copper producer in China. Two contrasting genetic models have been proposed, interpreting the stratabound massive sulfide deposits as a Carboniferous SEDEX protore overprinted by Cretaceous magmatic-hydrothermal system or an Early Cretaceous carbonate replacement deposit. These two contrasting models have been applied to the Xinqiao stratabound Cu-Au sulfide deposit, which is dominated by massive sulfide ores hosted in marine carbonates of the Carboniferous Chuanshan and Huanglong Formations, with minor Cu-Au skarn ores localized in the contact zone between the Cretaceous diorite Jitou stock and the Carboniferous carbonate rocks. New SIMS zircon U-Pb dating suggests that the Jitou stock formed at 138.5 ± 1.1 Ma (2σ, MSWD = 0.6). Pyrite Re-Os dating yields an imprecise date of 142 ± 47 Ma (2σ, MSWD = 7.8). The geochronological data thus constrain the mineralization of the Xinqiao deposit at Early Cretaceous.Fluid inclusions in prograde skarn diopside have homogenization temperatures of 450–600 °C and calculated salinities of 13–58 wt.% NaCl equiv. Quartz from the stratabound ores and pyrite-quartz vein networks beneath the stratabound ores have homogenization temperatures of 290–360 and 200–300 °C, with calculated salinities of 5–12 and 2–10 wt.% NaCl equiv., respectively. Quartz from the skarn ores and veins beneath the stratabound ores have δ18O values of 12.32 ± 0.55 (2 SD, n = 22) and 15.57 ± 1.92‰ (2 SD, n = 60), respectively, corresponding to calculated δ18O values of 6.22 ± 1.59 (2σ) and 6.81 ± 2.76‰ (2σ) for the equilibrated ore-forming fluids. The fluid inclusion and oxygen isotope data thus support a magmatic-hydrothermal origin rather than a SEDEX system for the stratabound ores, with the hydrothermal fluids most likely being derived from the Jitou stock or associated concealed intrusion. Results from this study have broad implications for the genesis and exploration of other stratabound massive sulfide deposits along the MLYMB. |
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