东昆仑祁漫塔格虎头崖铅锌多金属矿成矿时代及其地质意义——黑云二长花岗岩地球化学特征和锆石U-Pb年龄证据

    A study of the ore-forming age of the Hutouya deposit and its geological significance:Geochemistry and U-Pb zircon ages of biotite monzonitic granite in Qimantag, East Kunlun Mountains

    • 摘要: 虎头崖铅锌多金属矿床位于东昆仑祁漫塔格地区,矿区内中酸性侵入岩体广泛发育,且与成矿关系密切。通过高精度LA-ICP-MS锆石微区原位U-Pb同位素测年,获得与矿化、矽卡岩化关系密切的黑云二长花岗岩锆石的206Pb/238U年龄加权平均值为234.2±1.5 Ma。地球化学分析表明,黑云二长花岗岩具有高Al2O3、K2O,低TiO2、Na2O的特征,稀土和微量元素显示其富集轻稀土元素、Rb、Th和部分高场强元素,Nb、Sr、Zr相对亏损,稀土元素表现为LREE/HREE明显分离的配分模式,总体表现为I型花岗岩的特征。在(Y+Nb)-Rb图解中落入后碰撞花岗岩区,在R1-R2因子判别图上落入造山晚期和同碰撞花岗岩重叠区,显示其可能形成于碰撞-后碰撞构造阶段。虎头崖铅锌多金属矿区Ⅵ矿带具有强烈的矽卡岩化,结合矿石组构、脉石矿物、围岩蚀变等特征,认为其具有矽卡岩型矿床的特征,形成于234.2±1.5 Ma(中—晚三叠世)。

       

      Abstract: The Hutouya Pb-Zn polymetallic ore deposit is located in Qimantag, East Kunlun Mountains.Intermediate-acid intru-sive rocks occur widely in this area, and are closely related to iron polymetallic mineralization.The 206Pb/238U weighted average age is 234.2±1.5 Ma, which was obtained by in-situ LA-ICP-MS zircon dating of biotite monzonitic granite that was closely related to mineralization and skarn.The results of geochemical analysis show that the biotite monzonitic granite is characterized by high Al2O3, K2O and low TiO2, Na2O.The I-type granites are characterized by rich LREE, Rb, Th and some of HFSE, but poor Nb, Sr and Zr, and clear separation of LREE from HREE.In diagram of(Y+Nb)-Rb, all samples fall into post-collision granite area, and in R1-R2 diagram, all samples fall into the superimpositon of post-collision granite area and collision granite area, indicating that the gran-ites probably formed in a collision-post-collision structural phase.The Ⅵ belt of the Hutouya Pb-Zn polymetallic ore deposit expe-riended strong skarnization.The authors hold that the deposit has characteristics of skarn deposit, as shown by its ore fabric, gangue minerals, wall rock alteration, and it was formed at 234.2±1.5 Ma (Middle-Late Triassic).

       

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