内蒙古沙麦钨矿花岗岩岩石地球化学、锆石U-Pb年代学及其地质意义

沙麦钨矿床位于内蒙古东乌旗地区，是该区目前已探明的中型岩浆热液型钨矿床。矿体主要赋存在黑云母二长花岗岩和黑云母二长花岗斑岩中，对这两种花岗质岩石的岩相学、岩石地球化学和LA-ICP-MS锆石U-Pb年代学进行了研究。结果表明，黑云母二长花岗岩锆石U-Pb年龄为135.6±1.6 Ma和136.3±1.8 Ma,黑云母二长花岗斑岩锆石U-Pb年龄为138.6±1.1 Ma,二者侵位时间均为早白垩世。两种花岗质岩体具有富SiO₂(73.73%～78.23%)、高钾钠(Na₂O+K₂O)(7.56%～8.89%)、贫MgO(0.09%～0.20%)、贫CaO(0.51%～0.89%)、贫TiO₂(0.03%～0.12%)的特征，属于过铝质-高钾钙碱性系列；微量元素富集Rb、K、Th和U,相对亏损Sr、Ba、Nb、P和Ti元素，具有强烈的Eu负异常，具有较高的FeO^T含量，较高的FeO^T/MgO和FeO^T/(FeO^T+M...

Petrogeochemistry, zircon U-Pb chronology and geological implications of granite in Shamai tungsten deposit, Inner Mongolia

Shamai tungsten deposit is a medium sized magmatic hydrothermal deposit located in Dong Ujimqin Banner of Inner Mongolia. The ore bodies mainly occur in biotite monzonite granite and biotite monzonite granite porphyry. In this study, the petrography, LA-ICP-MS zircon U-Pb chronology and petrogeochemistry of biotite monzonite granite and biotite monzonite granite porphyry are studied in order to clarify the genesis and age of the two rocks and provide further data for regional prospecting. The results show that the LA-ICP-MS zircon U-Pb ages of biotite monzogranite are 135.6±1.6 Ma and 136.3±1.8 Ma, and the biotite monzonite granite porphyry is 138.6±1.1 Ma. The main elements show they are peraluminous high potassium calc alkaline granite which are characterized by high SiO₂ (73.73%~78.23%), Na₂O+K₂O (7.56%~8.89%)and low MgO (0.09%~0.20%), CaO (0.51%~0.89%), TiO₂ (0.03%~0.12%). They are enriched in Rb, K, Th, U, and depleted in Sr, Ba, Nb, P, Ti, with strong negative Eu anomaly and high FeO^T content, FeO^T/MgO and FeO^T/(FeO^T+MgO) ratio indicating the characteristics of A-type granite. The zircon U-Pb age of the Shamai granite is consistent with the age range of the large-scale metallogenesis in eastern China. The tectonic environment discrimination diagrams indicate that it was formed in the extensional tectonics environment after the continental collision in the Yanshanian period, which is related to the lithospheric thinning of northern margin of the North China Craton.