青海南山当家寺花岗岩体锆石U-Pb年代学、地球化学及其地质意义

发布时间：2018-05-27 08:44

本文选题：青海南山 + 西秦岭北缘　；参考：《地质学报》2017年03期

【摘要】：青海南山构造带发育北西—南东向展布的印支期花岗岩带,其研究对厘清古特提斯演化阶段西秦岭造山带与南祁连构造带的衔接转换关系具有重要意义。当家寺花岗岩体是由花岗闪长岩和二长花岗岩组成的复合花岗岩基。本文对当家寺花岗岩体进行了详细的岩石学、岩石地球化学和LA-ICP-MS锆石U-Pb同位素年代学研究。结果表明,花岗闪长岩和二长花岗岩的结晶年龄分别为240.1±2.1 Ma和241.0±2.6 Ma,属于中三叠世。地球化学研究显示岩体相对高硅(SiO_2=66.37%~73.99%)和富钾(K_2O=3.37%~4.73%),属于准铝质—弱过铝质高钾钙碱性I型花岗岩。岩石稀土配分曲线表现为轻稀土富集的右倾型,具中等程度的铕负异常(δEu=0.32~0.64)。微量元素显示富集大离子亲石元素Cs、Rb、K,相对亏损高场强元素Nb、Ta、P、Ti。岩石成因研究表明其形成于下地壳基性岩为主的源岩的部分熔融,同时存在一定程度幔源岩浆贡献。结合区域地质背景资料,认为当家寺花岗岩体形成于洋壳俯冲阶段,可能为宗务隆洋向南俯冲的地球动力学背景下的产物。
[Abstract]:In the Nanshan tectonic belt of Qinghai Province, the Indosinian granite belt is developed in the NW-SE direction. Its study is of great significance to clarify the connection and transformation relationship between the West Qinling orogenic belt and the South Qilian tectonic belt in the PaleoTethys evolution stage. The Dangjiasi granite body is a composite granite base composed of granodiorite and monzomorphic granite. In this paper, detailed petrology, geochemistry and U-Pb isotopic chronology of LA-ICP-MS zircon have been carried out on the dangjiasi granite body. The results show that the crystallization ages of granodiorite and monzomorphic granodiorite are 240.1 卤2.1Ma and 241.0 卤2.6Marespectively, which belong to the Middle Triassic. Geochemical studies show that the rock body is relatively high in silicon content, SiOShi (66.37) and K _ 2O _ (3.37), which belongs to the quasi-aluminum-weak peraluminous high-potassium calc-alkaline I-type granite. The REE partitioning curve of the rocks shows a right-dip type of LREE enrichment with moderate negative europium anomaly (未 EU ~ (2 +) 0.32 ~ (0.64). Trace elements show enrichment of large ion lipophilic element Csfus Rbtl K, and relative depletion of high field strength element NbBX TaPU Pu Ti. The petrogenetic study indicates that it was formed in the partial melting of the source rocks dominated by the basic rocks in the lower crust, and there is a certain degree of mantle magma contribution at the same time. Based on the regional geological background data, it is considered that the Yu Yang crust subduction stage of the Dangjiasi granite body may be the product of the geodynamic background of Zongwulong ocean subduction southward.
【作者单位】：西部矿产资源与地质工程教育部重点实验室国土资源部岩浆作用与找矿重点实验室长安大学地球科学与资源学院;山东理工大学资源与环境工程学院;中国地质大学(北京)地球科学与资源学院;南阳理工学院土木工程学院;
【基金】：国家自然科学基金项目(编号41472191、40572121、41172186、40972136) 国家自然科学青年基金项目(编号41502191) 中央高校基本科研业务费专项资金项目(编号CHD2011TD020、2013G1271091、2013G1271092、310827161002、30827161006) 中国地质调查局地质调查项目(青海共和曲什那地区,编号12120114041201)资助的成果
【分类号】：P597.3;P588.121

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