投稿时间：2021-11-08
修订日期：2022-02-03
网络发布日期：2022-05-06
中文摘要:内蒙古双尖子山超大型银铅锌多金属矿是亚洲最大的银矿床，除了目前已经探明的银、铅锌以外，近年来地质工作者研究发现勘查发现该矿床深部还存在寻找锡矿的潜力。文章对钻孔新揭露的隐伏石英正长斑岩开展了岩石地球化学、锆石U-Pb定年和Hf同位素研究。结果表明：双尖子山石英正长斑岩LA-MS-ICP锆石UPb加权平均年龄为(131.4±0.5) Ma，表明岩体形成于早白垩世。岩体具有富Si、Al、Na、K，贫Mg、Fe、P元素的特征，A/CNK为0.97~1.05，属于准铝质-弱过铝质。岩石富集大离子亲石元素（Rb、Th、U、Pb等），亏损高场强元素（Sr、P、Ti等），Eu负异常明显，具有A型花岗岩的地球特征。花岗岩形成过程中经历了斜长石、锆石、云母、独居石和磷灰石等的分离结晶作用。锆石原位Hf同位素分析结果显示，岩石的εHf(t)值介于2.18~5.84，二阶段模式年龄介于811~1002 Ma，反映了双尖子山石英正长斑岩为新元古代亏损地幔来源的新生地壳部分熔融的产物。结合已有成果表明双尖子山矿区具有多期岩浆-流体成矿作用，成矿主体与早白垩世花岗岩体有关，形成于高温、低压的伸展背景，具有低氧逸度、高演化的特点，双尖子山深部和外围具有形成锡矿的潜力。
Abstract:The Shuangjianzishan giant Ag-Pb-Zn-polymetallic deposit in the southern Great Xing’an Range is the largest Ag deposit in Asia. In recent years, Geologists found through research that deep prospecting and exploration suggest that there is still great potential for tin mineralization in depth. This study carried out whole-rock geochemistry, zircon U-Pb dating, and Hf isotope studies on the concealed quartz syenite porphyry revealed by the latest drilling. LA-ICP-MS zircon U-Pb dating yielded a concordia age of (131.4±0.5)Ma for the quartz syenite porphyry, indicating that the granite was Early Cretaceous in age. The quartz syenite porphyry is characterized by Si, Al, Na, K enrichment, and Mg, Fe, and P depletion. The A/CNK is 0.97~1.05, which belongs to metaluminumweak peraluminous. Lithophile elements (LILE) such as Rb, Th, U, Pb are enriched, while high field strength elements (HFSE) such as Sr, P, Ti are depleted. In addition, the marked Eu negative anomaly likely indicates A-type granite. Fractional crystallization of plagioclase, zircon, mica, monazite, and apatite occurred during the formation of granites. In-situ Hf isotope analysis of zircon shows that εHf(t) values range from 2.18 to 5.84, and the Hf two-stage model age is 811~1002 Ma, suggesting that the rock is the product of partial melting of juvenile crust derived from the Neoproterozoic depleted mantle. Together with the previous studies, we suggest that the Shuangjianzishan mining area experienced multi-stages magmatic-fluids and ore mineralization, while the main ore mineralization is related to the Early Cretaceous granites. The quartz syenite porphyry was formed in low oxygen fugacity and a highly fractionated system under the high-T and low-P extensional setting. Our study has implications for tin exploration at the deep and peripheral parts of the Shuangjianzi deposit.
keywords:geochemistry magma differentiation partial melting oxygen fugacity tin mineralization Shuangjianzishan deposit
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基金项目:国家重点研发计划课题(编号:2019YFC0605202)、国家自然科学基金项目(编号:41772084、41302061、41820104010)和科技部基础资源调查专项(编号:2017FY101300、2017FY101302)联合资助
引用文本：
赵家齐,周振华,欧阳荷根,陈宝全,刘文杰,杨帆.2022.内蒙古双尖子山银铅锌(锡)矿床石英正长斑岩U-Pb年龄、地球化学及其地质意义[J].矿床地质,41(2):324~344ZHAO JiaQi,ZHOU ZhenHua,OUYANG HeGen,CHEN BaoQuan,LIU WenJie,andYANG Fan.2022.Zircon U-Pb age and geochemistry of quartz syenite porphyry in Shuangjianzishan Ag-Pb-Zn (Sn) deposit, Inner Mongolia, and their geological implications[J].Mineral Deposits41(2):324~344
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