Two types of sediment-hosted Pb-Zn deposits in the northern margin of Lanping basin, SW China: Evidence from sphalerite trace elements, carbonate C-O isotopes and molybdenite Re-Os age
Two types of sediment-hosted Pb-Zn deposits in the northern margin of Lanping basin, SW China: Evidence from sphalerite trace elements, carbonate C-O isotopes and molybdenite Re-Os age
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DOI：
10.1016/j.oregeorev.2021.104016
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发表时间：
2021-01
影响因子：
3.3
通讯作者：
Yue-Fu Liu;Huawen Qi;X. Bi;R. Hu;Lin-Kun Qi;R. Yin;Yongyong Tang
中科院分区：
文献类型：
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作者：
Yue-Fu Liu;Huawen Qi;X. Bi;R. Hu;Lin-Kun Qi;R. Yin;Yongyong Tang
兰坪盆地是中国西南地区大型铅锌铜银多金属矿大省，矿床类型主要有脉状型铜矿床、盆相卤水型铅锌矿床（如李子坪、伏龙场）和少量石英脉状铅锌矿床（如上鹿罗、白集）。在本研究中，我们进行了EPMA和LA-ICP-MS闪锌矿微量元素分析，以及脉石碳酸盐C-O稳定同位素分析和辉钼矿Re-Os定年。利用这些资料，讨论了这两类铅锌矿床的矿物组合、闪锌矿微量元素组成、矿液来源和成矿年龄。除闪锌矿和方铅矿外，黎子坪和伏龙场的主要矿石矿物为富砷矿物（如：gratonite、jordanite、bournonite、富砷黄铁矿），而上芦罗和白集的主要矿石矿物为富锑矿物（如：boulangerite、jamesonite、辉锑矿、锌辉锑矿）。闪锌矿的微量元素组成特征（低Mn、Fe、Co、in和Sn，高Cd）与中低温热液矿床（MVT和金顶矿床）相似。黎子坪分带闪锌矿中，深褐色带Co、Cu、Ga、As、Sb含量较高；基于闪锌矿地温计- GGIMFis （Frenzel et al., 2016）计算的闪锌矿形成温度与包裹体均一温度基本一致，表明闪锌矿中Ga、Ge、Fe、Mn、in等元素的含量主要受温度控制。此外，黎子坪（- 14.7）和伏龙场（- 13.6）的硫逸度（logfS2）明显低于上努洛（- 7.1）和白集（- 8.5）。碳酸盐C-O同位素组成表明，这些铅锌矿床成矿流体中溶解的碳和氧主要来源于沉积碳酸盐溶蚀。白集矿床早期辉钼矿Re-Os加权平均模式年龄分别为21.4 Ma和12.93 Ma， 4个较年轻辉钼矿样品Re-Os平均模式年龄为11.88±0.77 Ma。这些年龄明显小于已报道的盆地卤水相关铅锌矿成矿年龄（约30 Ma）。这些结果表明，蓝平盆地北缘存在两种不同类型的铅锌成矿事件。
Lanping basin is a large Pb-Zn-Cu-Ag polymetallic mineral province in SW China, with major deposit types including vein-type Cu deposits, basinal brine-related Pb-Zn deposits (e.g., Liziping, Fulongchang) and minor quartz-vein-type Pb-Zn deposits (e.g., Shangnuluo, Baiji). In this study, we have conducted EPMA and LA-ICP-MS sphalerite trace element analyses, together with gangue carbonate C-O stable isotope analysis and molybdenite Re-Os dating. Using these data, we discuss the mineral assemblage, sphalerite minor/trace element composition, ore-fluid source, and mineralization age of these two types of Pb-Zn deposits. Except sphalerite and galena, major ore minerals from Liziping and Fulongchang are As-rich (e.g., gratonite, jordanite, bournonite, As-rich pyrite), whereas those from Shangnuluo and Baiji are Sb-rich (e.g., boulangerite, jamesonite, stibnite, zinkenite). The trace element compositional characteristics in sphalerite of these deposits (low Mn, Fe, Co, In and Sn, and high Cd) mimic those of medium-low-temperature hydrothermal deposits (MVT and Jinding deposits). For the Liziping zoned sphalerite, the dark-brown zones have relatively high Co, Cu, Ga, As, and Sb; whilst the light-colored zones have relatively high Fe, Mn and Cd. The calculated sphalerite formation temperature based on sphalerite geothermometer – GGIMFis (Frenzel et al., 2016) are basically in agreement with those homogenization temperature of inclusions, indicating that the contents of these elements (Ga, Ge, Fe, Mn and In) in sphalerite are mainly controlled by temperature. Moreover, the estimated sulfur fugacity (logfS2) for Liziping (−14.7) and Fulongchang (−13.6) are distinctly lower than those for Shangnuluo (−7.1) and Baiji (−8.5). Carbonate C–O isotope compositions indicate that the dissolved carbon and oxygen of ore forming-fluids of these Pb-Zn deposits were mainly derived from sedimentary carbonate dissolution. Early-ore-stage molybdenite from Baiji deposit yielded two Re-Os weighted average model ages of 21.4 Ma and 12.93 Ma, and a Re-Os concordia age of 11.88 ± 0.77 Ma was obtained from four younger molybdenite samples. These ages are distinctly younger than those reported mineralization age (ca. 30 Ma) for basinal brine-related Pb-Zn deposits. All these results indicate that there are two different types of Pb-Zn metallogenic events in the northern margin of Lanping Basin.