北秦岭西段黄牛铺岩体锆石U-Pb年代学、岩石地球化学特征及其地质意义

发布时间：2018-12-16 13:50

【摘要】：对北秦岭西段黄牛铺岩体进行了LA-ICP-MS锆石U-Pb年代学与岩石地球化学分析。结果显示,黄牛铺岩体的锆石U-Pb年龄为(449.3±4.9)Ma,表明其形成时代为晚奥陶世。黄牛铺岩体属于准铝质高钾钙碱性系列,在成因类型上具有I型花岗岩的岩石矿物学与地球化学特征,其稀土元素配分曲线呈轻稀土元素富集、重稀土元素亏损(LREE/HREE=9.83~11.55)、铕弱负异常(δEu=0.82~0.95)的右倾型,微量元素Rb、Th、U、Sm等富集,Ta、Nb、Ti、Hf等明显亏损,表现为岛弧岩浆岩的地球化学特征。结合区域地质资料,认为黄牛铺岩体形成于晚奥陶世商丹洋俯冲过程中的岛弧环境,是壳幔岩浆混合作用的产物,这为进一步研究北秦岭的构造演化过程提供了更加充分准确的岩浆活动证据。
[Abstract]:The LA-ICP-MS zircon U-Pb chronology and geochemistry of the Huangniupu rock body in the western part of the North Qinling Mountains have been studied. The results show that the zircon U-Pb age of the Huangniupu rock body is (449.3 卤4.9) Ma, which indicates that the zircon age is late Ordovician. The Huangniupu rock body belongs to the quasi-aluminous high-potassium calc-alkaline series. It has the petro-mineralogical and geochemical characteristics of I-type granite in genetic type, and its REE distribution curve is light REE enrichment. Heavy rare earth element depletion (LREE/HREE=9.83~11.55), europium weak negative anomaly (未 Eu=0.82~0.95) right dip type, trace element Rb,Th,U,Sm enrichment, Ta,Nb,Ti,Hf, etc. It is characterized by the geochemical characteristics of island arc magmatic rocks. Combined with the regional geological data, it is considered that the Huangniupu rock body was formed in the island arc environment during the subduction process of the late Ordovician Shishangdan Ocean and was the product of the mixing of crust and mantle magma. This provides a more complete and accurate evidence of magmatic activity for further study of the tectonic evolution of the North Qinling Mountains.
【作者单位】：陕西省地质调查中心;
【基金】：陕西省财政专项地质调查项目(20150101)
【分类号】：P584;P597.3

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