山西黄榆沟岩体锆石U-Pb年代学、地球化学特征及其地质意义

为深化对华北克拉通破坏机制的认识,选取山西黄榆沟岩体中较新鲜的石英二长斑岩开展年代学和地球化学研究。研究结果表明,黄榆沟岩体由石英二长斑岩组成,LA-ICP-MS锆石U-Pb谐和年龄为(149.3±0.9)Ma,是晚侏罗世岩浆活动的产物。石英二长斑岩富碱,为钙碱性钾玄岩系列,属于准铝质花岗岩类。相对富集K、Sr、Eu等大离子亲石元素,相对亏损Nb、Ce、Zr、Ti等高场强元素;轻稀土元素相对富集,重稀土元素相对亏损,Eu具弱正异常,为I型花岗岩成因。具高Al₂O₃、Sr、Ba、高Sr/Y比值和低Yb、MgO等特征,具埃达克岩性质。岩石地球化学特征表明,黄榆沟岩体总体为下地壳物质的部分熔融成因,并有幔源物质成分的加入和遭受岩浆混合作用,推测其形成于碰撞造山后的伸展构造环境。

Zircon U-Pb Geochronology,Geochemical Characteristics and Geological Significance of Huangyugou Intrusion,Shanxi Province

To deepen our understanding on the destruction mechanism in the North China Craton, we report new geochronological and geochemical data on the fresh quartz monzonite porphyry from the Huangyugou intrusion in Shanxi. The Huangyugou intrusion is composed of quartz monzonite porphyry, which yielded a Late Jurassic weighted mean ²⁰⁶Pb/²³⁸U age of (149.3±0.9) Ma. The quartz monzonite porphyry samples are metaluminous and shoshonitic, enriched in large ion lithophile elements (LILEs, such as K, Sr and Eu), and depleted in high field strength elements (HFSEs, such as Nb, Ce, Zr and Ti). The rocks exhibit LREE/HREE enrichments and weak Eu anomalies. The quartz monzonite porphyry is classified as I-type and shows adakitic features, including high Al₂O₃, Sr, Ba, and Sr/Y, but low Y and MgO. Geochemical characteristics indicate that the Huangyugou intrusion was formed from partial melting of the lower crust, with mantle-derived inputs and have undergone magma mixing. The rocks may have formed under an extensional tectonic setting.