蔡宏明, 刘桂萍, 尼加提·阿布都逊, 杨维忠, 邢令. 新疆西天山卡特巴阿苏金矿床锆石U-Pb年龄、地球化学特征及其地质意义[J]. 地质通报, 2019, 38(5): 790-801.
    引用本文: 蔡宏明, 刘桂萍, 尼加提·阿布都逊, 杨维忠, 邢令. 新疆西天山卡特巴阿苏金矿床锆石U-Pb年龄、地球化学特征及其地质意义[J]. 地质通报, 2019, 38(5): 790-801.
    CAI Hongming, LIU Guiping, NIJAT Abdurusul, YANG Weizhong, XING Ling. U-Pb age and geochemistry of zircons from the Katebasu Au deposit, West Tianshan Mountains, Xinjiang, and their geological implications[J]. Geological Bulletin of China, 2019, 38(5): 790-801.
    Citation: CAI Hongming, LIU Guiping, NIJAT Abdurusul, YANG Weizhong, XING Ling. U-Pb age and geochemistry of zircons from the Katebasu Au deposit, West Tianshan Mountains, Xinjiang, and their geological implications[J]. Geological Bulletin of China, 2019, 38(5): 790-801.

    新疆西天山卡特巴阿苏金矿床锆石U-Pb年龄、地球化学特征及其地质意义

    U-Pb age and geochemistry of zircons from the Katebasu Au deposit, West Tianshan Mountains, Xinjiang, and their geological implications

    • 摘要: 卡特巴阿苏大型金矿床位于新疆西天山中部那拉提北缘断裂带南侧,找矿前景较好。为查明矿区容矿岩浆岩的成因及其与矿床形成的联系,对主要矿石类型含金蚀变二长花岗岩和含金石英硫化物脉进行LA-MC-ICP-MS锆石U-Pb测年和地球化学研究。结果表明,锆石稀土元素显示较陡的左倾配分模式,具有明显的正Ce异常和负Eu异常,指示岩浆锆石成因。根据锆石Ce异常值,获得含矿岩石有关岩浆岩氧逸度对数值(Log(fo2))为-29.2~5.1,指示岩浆具有较高的氧逸度,有利于金在岩体中初步富集。同时,氧逸度具有较大的变化范围,指示岩浆演化过程中,存在明显的上地壳混染。应用锆石Ti温度计,获得含金蚀变二长花岗岩锆石结晶温度为765~975℃,反映岩浆来自下地壳缺水条件下的部分熔融。含金石英硫化物脉锆石具有较低的结晶温度(641~823℃),可能与早期角闪石的分异结晶有关。以上2种矿石类型的锆石U-Pb年龄分别为350.4±1.6Ma和348.9±1.4Ma,代表了容矿二长花岗岩的结晶年龄。岩体结晶年龄早于前人报道的矿床成矿年龄,表明岩体侵位与成矿作用无直接关系。

       

      Abstract: The Katebasu Au deposit, located on the southern side of North Nalati fault, is a large-sized deposit with great prospecting potential. In order to study the genetic relationship between intrusions developed in the study area and the Au deposit, the authors separated zircons from two main types of ore, i.e., Au-bearing altered monzogranite and quartz-sulfide vein, for U-Pb isotopic concentrations and trace element content by using LA-MC-ICP-MS. The results show that the chondrite-normalized REE patterns of zircons are characterized by HREE enrichment relative to LREE, with evident positive Ce and negative Eu anomalies, typical of magmatic zircons. The logarithm of oxygen fugacity (Log(fo2)) calculated using δCe of the analyzed zircons is -29.2 to 5.1, suggesting high oxygen fugacity of magma, which is beneficial for preliminary enrichment of Au to provide metallogenic material. The highly variable oxygen fugacity might have suffered from significant contamination of the upper crust. Meanwhile, the application of the Ti-in-zircon thermometer exhibits high temperatures of 765~975℃ for zircons extracted from the Au-bearing altered monzogranite, indicative of dehydration melting of the lower crust. The zircons from Au-bearing quartz-sulfide vein have relatively lower crystallization temperatures of 641~823℃, suggesting crystallization of amphibole before zircon. The obtained zircon U-Pb ages of 350.4 ±1.6Ma for altered monzogranite and 348.9 ±1.4Ma for quartz-sulfide vein are interpreted as the magma crystallization age of the monzogranite, which is the main host rock of the deposit. The crystallization ages are earlier than previously reported metallogenic age, probably suggesting little relationship between the monzogranite formation and metallization of the Katebasu Au deposit.

       

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