Genesis of the Gaosong Sn–Cu deposit, Gejiu district, SW China: Constraints from in situ LA-ICP-MS cassiterite U–Pb dating and trace element fingerprinting
Genesis of the Gaosong Sn–Cu deposit, Gejiu district, SW China: Constraints from in situ LA-ICP-MS cassiterite U–Pb dating and trace element fingerprinting
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DOI：
10.1016/j.oregeorev.2017.11.033
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发表时间：
2018
影响因子：
3.3
通讯作者：
Jia Guo;Rongqing Zhang;Cong-ying Li;Wei-dong Sun;Yong-bin Hu;Deming Kang;Junde Wu
中科院分区：
文献类型：
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作者：
Jia Guo;Rongqing Zhang;Cong-ying Li;Wei-dong Sun;Yong-bin Hu;Deming Kang;Junde Wu
个旧矿区高松锡铜存款矿床是一个大型的辉长岩-硫化物存款矿床，总矿石储量为67.4 Mt@1.3%Sn和19.0 Mt@1.1%Cu。存款中发育两种类型的矿化，即与高峰山黑云母花岗岩接触的近端矽卡岩中的硫铁矿-硫化矿和远端碳酸盐围岩中受断层控制的层状硫铁矿-氧化铁±硫化矿。两种矿石中均嵌布有锡石颗粒，其中1个锡石-硫化物矿石和2个锡石-氧化铁-硫化物矿石中的锡石样品的原位U-Pb测年结果分别为84.3 ± 1.4Ma、85.1 ± 1.0Ma和83.5 ± 2.1Ma。3个成矿年龄与高峰山花岗岩侵位年龄（85.8 ± 0.6Ma）在误差范围内一致，表明锡石成矿与花岗岩岩浆活动有密切的时间联系，锡石颗粒可根据阴极发光（CL）图解分为自形Cst Ⅰ和细脉状Cst Ⅱ两种类型。在硫铁矿-硫化矿中，Cst Ⅰ具有明显的振荡分带，发光暗淡。在硫铁矿-氧化铁±硫化物矿石中，Cst I核心是暗淡的发光（在OM−CL中为蓝色），周围是明亮的发光Cst I边缘（在OM−CL中为黄色）。Cst I被Cst II细脉所取代，具有明亮的发光（在OM−CL中为黄色）。钛钙石的SEM-CL发光强度主要受钛含量的控制。高松存款中的锡矿岩富W、Fe而低Nb、Ta、Zr、Hf，与VMS/SEDEX锡矿中的锡矿岩明显不同，而与花岗岩型锡矿相似。晚白垩世结晶年龄和微量元素特征表明，两个矿石中的镁铝石均形成于与高峰山花岗岩共生的岩浆-热液体系中，排除了层状镁铝石-氧化铁±硫化物矿石的SEDEX成因。
The Gaosong Sn–Cu deposit in the Gejiu ore district, SW China, is a large cassiterite–sulfide deposit, hosting total ore reserves of 67.4 Mt @1.3% Sn and 19.0 Mt @1.1% Cu. Two types of mineralization developed in the deposit, i.e. cassiterite-sulfide ore within the proximal skarn in contact with the Gaofengshan biotite granite, and fault-controlled stratiform-like cassiterite–iron oxide ± sulfide ore in the distal carbonate country rock. Cassiterite grains are disseminated in both ores.In situU–Pb dating of one cassiterite sample from the cassiterite-sulfide ore and two from the cassiterite–iron oxide ± sulfide ore yielded weighted mean206Pb/238U ages of 84.3 ± 1.4 Ma, 85.1 ± 1.0 Ma and 83.5 ± 2.1 Ma, respectively. The three mineralization ages are consistent with the emplacement age of the Gaofengshan granite (85.8 ± 0.6 Ma) within error, suggesting a close temporal link between tin mineralization and granitic magmatism.Cassiterite grains can be divided into two types based on cathodoluminescence (CL) illustrations, namely euhedral Cst I and veinlet-like Cst II. In the cassiterite–sulfide ore, Cst I has clear oscillatory zonation and is dull luminescing. In the cassiterite–iron oxide ± sulfide ore, Cst I core is dull luminescing (blue in OM−CL) and surrounded by a bright luminescing Cst I rim (yellow in OM−CL). Cst I is replaced by Cst II veinlets with bright luminescing (yellow in OM−CL). The SEM−CL luminescing intensity of cassiterite is mainly controlled by Ti content. Elevated W and Fe but low Nb, Ta, Zr and Hf concentrations of cassiterites from the Gaosong deposit, are distinctly different from those of cassiterites in VMS/SEDEX tin deposits, but similar to those from granite-related tin deposits. The Late Cretaceous crystallization ages and trace element characteristics demonstrate that cassiterites from both ores were formed in a magmatic-hydrothermal system associated with the Gaofengshan granite, and preclude the SEDEX origin of the stratiform-like cassiterite–iron oxide ± sulfide ore.