An Early Cretaceous carbonate replacement origin for the Xinqiao stratabound massive sulfide deposit, Middle-Lower Yangtze Metallogenic Belt, China
An Early Cretaceous carbonate replacement origin for the Xinqiao stratabound massive sulfide deposit, Middle-Lower Yangtze Metallogenic Belt, China
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DOI：
10.1016/j.oregeorev.2016.08.017
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发表时间：
2017
影响因子：
3.3
通讯作者：
Yang Li;Jian-wei Li;Xian‐Hua Li;D. Selby;Guang-huan Huang;Linjie Chen;Kai Zheng
中科院分区：
文献类型：
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作者：
Yang Li;Jian-wei Li;Xian‐Hua Li;D. Selby;Guang-huan Huang;Linjie Chen;Kai Zheng
长江中下游成矿带（MLYMB）广泛分布有层控块状硫化物矿床，是中国重要的铜矿产地。人们提出了两种截然不同的成因模型，将层状块状硫化物矿床解释为白垩纪岩浆-热液系统叠印的石炭纪 SEDEX 原型或早白垩世碳酸盐替代矿床。这两种对比模型已应用于新桥层控铜金硫化物矿床，该矿床以石炭系穿山组和黄龙组海相碳酸盐岩中的块状硫化物矿为主，少量铜金矽卡岩矿集中在白垩系闪长岩基头岩群与石炭系碳酸盐岩的接触带中。新的 SIMS 锆石 U-Pb 定年表明 Jitou 岩浆形成于 138.5 ± 1.1 Ma (2σ, MSWD = 0.6)。黄铁矿铼锇测年得出的日期不精确，为 142 ± 47 Ma (2σ, MSWD = 7.8)。因此，地质年代学数据限制了新桥矿床在早白垩世的成矿作用。原矿夕卡岩透辉石中的流体包裹体的均一温度为 450–600 °C，计算盐度为 13–58 wt.% NaCl 当量。来自地层结合矿石和地层结合矿石下方的黄铁矿-石英脉网络的石英的均一温度为 290–360 和 200–300 °C，计算盐度分别为 5–12 和 2–10 wt.% NaCl 当量。来自地层矿石下方的矽卡岩矿石和矿脉的石英的 δ18O 值分别为 12.32 ± 0.55 (2 SD,n= 22) 和 15.57 ± 1.92‰ (2 SD,n= 60)，对应计算的 δ18O 值为 6.22 ± 1.59 (2σ) 和6.81 ± 2.76‰ (2σ) 对于平衡 成矿流体。因此，流体包裹体和氧同位素数据支持岩浆-热液起源，而不是层状矿石的 SEDEX 系统，热液流体很可能来自 Jitou 矿藏或相关的隐蔽侵入体。这项研究的结果对于 MLYMB 沿线其他层控块状硫化物矿床的成因和勘探具有广泛的意义。
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.