投稿时间：2020-05-08
修订日期：2020-07-22
网络发布日期：2021-01-08
中文摘要:西涝口金矿是胶莱盆地北东缘新近取得找矿突破的蚀变岩型金矿，金矿体主要赋存于古元古界荆山群与牧牛山二长花岗岩之间的构造破碎带中。前期在其深部新发现的角闪辉长岩脉中，通过人工重砂分选，获得了自然金。为探索其与金成矿的关系，文章对其进行了主量、微量元素、锆石U-Pb年代学以及Hf同位素研究。主量、微量元素分析结果表明，角闪辉长岩属钾玄岩岩石系列，全碱、Ba、Sr、轻稀土元素含量高，Rb、P和重稀土元素含量相对较低，无铕异常或有轻微的正铕异常，明显亏损Nb、Zr、Hf等高场强元素，具有富集大离子亲石元素与轻稀土元素、亏损高场强元素与重稀土元素的地球化学特征，类似于富闪深成岩。锆石Hf同位素结果显示，其岩浆锆石的εHf（t）为-14.0~-11.8，暗示其来源于富集地幔源区或存在源区混染的可能性。锆石LA-ICP-MS U-Pb定年结果显示，角闪辉长岩年龄为（108.4±2.2）Ma，属早白垩世晚期，明显晚于郭家岭、伟德山序列岩体。综上，笔者认为西涝口金矿角闪辉长岩形成于俯冲板片脱水而导致上覆地幔楔部分熔融，其成因可能与古太平洋板块向华北板块俯冲所形成的火山弧有关，其与该区金成矿过程密切相关，极有可能在成矿过程中直接提供了金的来源。西涝口金矿的形成时代应当在110 Ma左右，胶东东部应该存在110 Ma的金成矿事件。
Abstract:The Xilaokou gold deposit is an altered rock type gold deposit, and researchers have made a breakthrough in prospecting on the northeast margin of Jiaolai basin. The gold orebodies mainly occur in the structural fracture zone between the Paleoproterozoic Jingshan Group and the Muniushan monzogranite. In preliminary work, several natural gold grains were obtained from a newly discovered hornblende gabbro dike in its deep part by artificial heavy sand sorting. In order to explore its relationship with gold mineralization, the authors studied the major and trace elements, zircon U-Pb geochronology and Hf isotope. The dike has high content of total alkali, Ba, Sr and LREE, relatively low content of Rb, P and HREE, no or slight positive Eu anomaly, and obvious loss of high field strength elements such as Nb, Zr and Hf. Its geochemical characteristics are similar to those of appinite. The εHf(t) of zircons from hornblende gabbro is -14.0~-11.8, suggesting an enriched mantle source or possibility of source contamination. The geochemical characteristics of LILEs, LREEs enrichment and HFSEs, HREEs depletion indicate that it was formed in the partial melting of the overlying mantle wedge resulting from dehydration of subduction plate. Its genesis may be related to volcanic arc environment formed by the subduction of the ancient Pacific plate to the North China Craton. The zircon LA-ICP-MS U-Pb age of hornblende gabbro is (108.4±2.2)Ma, belonging to early Cretaceous, which is obviously younger than the age of Guojialing and Weideshan sequence rocks. There are a lot of primary metallic minerals in hornblende gabbro, and natural gold grains was achieved by previous heavy sand separation, indicating that this dike was closely related to the gold mineralization process in this area, and it was very likely to provide the source of gold directly in the mineralization process. The formation age of the Xilaokou gold deposit should be 110Ma±, and there should be 110Ma±gold mineralization event in the east of Jiaodong area.
keywords:geochemistry deep dike zircon U-Pb dating zircon Hf isotope Xilaokou gold deposit northeast margin of Jiaolai basin Jiaodong
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基金项目:本文得到国家自然科学基金（批准号：41772076，41672084，41372086和41503038），山东省泰山学者项目，山东省重点研发计划项目（批准号：2017CXGC1601、2017CXGC1602&2017CXGC1603）和国家重点研发计划项目（批准号：2016YFC0600105-04&2016YFC0600606）联合资助
引用文本：
耿科,李大鹏,胡秉谦,闫江雁,邹双英,张岩,尉鹏飞,刘强,蔡娜,张超.2020.胶东西涝口金矿深部110 Ma角闪辉长岩脉及其对成矿时代的约束[J].矿床地质,39(6):974~994GENG Ke,LI DaPeng,HU BingQian,YAN JiangYan,ZOU ShuangYing,ZHANG Yan,WEI PengFei,LIU Qiang,CAI Na,ZHANG Chao.2020.110 Ma hornblende gabbro dyke in deep part of Xilaokou gold deposit, Jiaodong and its constraints on metallogenic time[J].Mineral Deposits39(6):974~994
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