Fluid inclusion geochemistry and Ar-40/Ar-39 geochronology constraints on the genesis of the Jianchaling Au deposit, China
Fluid inclusion geochemistry and Ar-40/Ar-39 geochronology constraints on the genesis of the Jianchaling Au deposit, China
复制标题
流体包裹体地球化学和Ar-40/Ar-39年代学对尖茶岭金矿床成因的制约
DOI：
10.1016/j.oregeorev.2016.08.024
复制
发表时间：
2017
影响因子：
3.3
通讯作者：
Zhang Wei
中科院分区：
文献类型：
--
作者：
Yue Su-Wei;Deng Xiao-Hua;Bagas Leon;Lin Zhen-Wen;Fang Jing;Zhu Chao-Hui;Zhang Wei
煎茶岭大型金存款矿床位于中国陕西省。矿化受勉县-略阳-阳平关地区的WNW向断裂控制。根据矿物组合和矿化石英脉的横切关系，可将成矿作用划分为三个阶段。这些阶段从早到晚的矿物组合为：（1）石英-粗粒黄铁矿-磁黄铁矿-镍黄铁矿-白云石，（2）石英-黄铁矿-金-闪锌矿-方铅矿-碳酸盐-毒砂-紫红石，（3）石英-粗粒黄铁矿-磁黄铁矿-镍黄铁矿-白云石，（4）石英-黄铁矿-金-闪锌矿-方铅矿-碳酸盐-毒砂-紫红石。白云石-方解石-石英-细粒黄铁矿-雄黄-根据岩相学和显微测温的结果，本研究识别出三种类型的流体包裹体：纯CO2和/或CH4（PC型），NaCl-H_2O（W型）和NaCl-CO_2-H_2O（C型）流体包裹体。这些流体包裹体类型存在于第一阶段和第二阶段组合的石英中，而第三阶段石英仅包含W型流体包裹体。第2期组合与煎茶岭存款矿化有关。第一阶段石英的流体包裹体主要在250 °~360 ° C之间均一化，盐度高达15.6wt. % NaCl当量，第三阶段白云岩的均一温度为160 °~220 ° C，矿化度为1.1-7.4wt. % NaCl当量这表明成矿流体系统是由富CO2的变质热液向贫CO2的大气降水流体演化的。所有三种类型的流体包裹体都可以在第二阶段的石英中观察到，这表明这种非均质组合是从沸腾流体系统中捕获的。这些包裹体在200 °-250 °C温度和1.2 - 12.4wt. %盐度下均质化NaCl当量第一阶段流体包裹体的捕获压力在117~354 MPa之间，表明流体为岩石静力学-流体静力学交替体系，受12 km深度的断层阀控制。39Ar/36Ar-40Ar/36Ar正常等时线为198 ± 2Ma和199 ± 2Ma。这表明煎茶岭的成矿时代为早侏罗世（约1000年）。1988年，在？煎茶岭金矿是一个造山型金存款矿床，形成于早侏罗世勉略洋板块向北俯冲的大陆碰撞过程中。我们还认为，扬子板块与华北板块的大陆碰撞开始于200Ma左右。
The giant Jianchaling gold deposit is located in the Shaanxi Province, China. The mineralization is hosted by WNW-trending faults in the Mianxian-Lueyang-Yangpingguan (MLY) area. The mineralization can be divided into three stages based on mineralogical assemblages and crosscutting relationships of mineralized quartz veins. These stages, from early to late, are characterized by the mineral assemblage of: (1) quartz – coarse-grained pyrite – pyrrhotite – pentlandite – dolomite; (2) quartz – pyrite – gold – sphalerite – galena – carbonate – arsenopyrite – fuchsite; and (3) dolomite – calcite – quartz – fine-grained pyrite – realgar – orpiment.Three types of fluid inclusions have been recognized in this study based on petrographic and microthermometric measurements, including pure CO2and/or CH4(PC-type), NaCl-H2O (W-type), and NaCl-CO2-H2O (C-type) fluid inclusions. These fluid inclusion types are present in quartz from the Stage 1 and 2 assemblages, whereas the Stage 3 quartz only contains W-type fluid inclusions. The Stage 2 assemblage is associated with the mineralization at the Jianchaling deposit. Fluid inclusions of Stage 1 quartz homogenize mainly between 250° and 360 °C, with salinities up to 15.6 wt.% NaCl equiv., whereas the Stage 3 dolomite with homogenization temperatures of 160° – 220 °C and salinities of 1.1–7.4 wt.% NaCl equiv. This indicates that the ore fluid system evolved from CO2-rich, probably metamorphic hydrothermal to CO2-poor, meteoric fluid. All three types of fluid inclusions can be observed in the Stage 2 quartz, suggesting that this heterogeneous association was trapped from a boiling fluid system. These inclusions homogenized at temperatures of 200°–250 °C and salinities of 1.2–12.4 wt.% NaCl equiv. The estimated trapping pressures of the fluid inclusions are between 117 and 354 MPa in Stage 1, suggesting an alternating lithostatic–hydrostatic fluid system, which was controlled by a fault-valve at the depth of ~ 12 km.Two fuchsite samples collected from the Stage 2 polymetallic-quartz veins yielded well-defined40Ar/39Ar isotopic plateau ages of 197 ± 2 and 194 ± 2 Ma, and39Ar/36Ar-40Ar/36Ar normal isochrones of 198 ± 2 and 199 ± 2 Ma. This indicates that the mineralization at Jianchaling is Early Jurassic (ca. 198 Ma) in age. We propose that Jianchaling is an orogenic gold deposit, and formed during continental collision related to the northward subduction of the Mian-Lue oceanic plate during the Early Jurassic. We also conclude that the beginning of the continental collision between the Yangtze and the North China Cratons took place around 200 Ma.