青海东昆仑东段加当辉长岩LA-ICP-MS锆石U-Pb测年及其地质意义

发布时间：2018-05-29 14:39

本文选题：地球化学 + 锆石U-Pb定年　；参考：《地质与勘探》2017年05期

【摘要】：本文对青海东昆仑东段加当辉长岩进行了岩石学、年代学和地球化学分析,有助于丰富东昆仑古特提斯构造岩浆演化的整体认识。利用LA-ICP-MS锆石U-Pb定年技术,获得加当辉长岩加权平均年龄为262.5±2.5Ma(n=38,MSWD=0.18),表明岩体形成时代为中二叠世晚期。岩石地球化学研究表明,加当辉长岩具有低TiO_2(0.79%~1.09%)、贫P_2O_5(0.06%~0.09%)、低碱(K_2O+Na_2O=1.99%~2.39%)及Na_2OK_2O的特征,属拉斑玄武岩系列。岩石微量元素总体上富集大离子亲石元素(LILE:Rb、Ba、K)和Pb,相对亏损高场强元素(HFSE:Nb、Ta、P),稀土元素总量(ΣREE)为32.08×10~(-6)~46.41×10~(-6),(La/Yb)N为1.59~2.00,平均1.82,δEu=0.95~1.32,具有弱的Eu正异常。地球化学特征表明辉长岩源区为岩石圈幔源岩浆,岩浆在演化过程中遭受了地壳物质的同化混染;构造环境分析表明加当辉长岩是形成于俯冲环境的岛弧岩浆岩。结合东昆仑区域构造演化,认为加当辉长岩是阿尼玛卿古特提斯洋向北俯冲的产物,这为东昆仑晚古生代-早中生代构造演化提供了新的年代学证据。
[Abstract]:In this paper, Petrology, geochronology and geochemistry analysis of the Kadang gabbro in the eastern part of eastern Kunlun, Qinghai Province are carried out, which is helpful to enrich the overall understanding of the evolution of paleotectonite magma in the East Kunlun Mountains. By using LA-ICP-MS zircon U-Pb dating technique, the weighted mean age of gabbro is 262.5 卤2.5 Mai ~ (38) Mwd ~ (0.18), which indicates that the age of formation is late Middle Permian. The petrogeochemical study shows that the Kadang gabbro has the characteristics of low TiO20.79 + 1.09%, poor P2O50.06 + 0.09 and low alkaline-K _ 2O Na _ 2O Na _ 2O 1.99g ~ (2.39) and Na_2OK_2O, which belong to the tholeiite series. The trace elements in the rocks are generally enriched in large ion lithophile elements (LILE: RbPK) and Pb, the relative depletion of the high field strength element is HFSE: NbPU, and the total REE of rare earth elements (危 REE) is 32.08 脳 10 ~ (10) ~ (-6) ~ (6) ~ (66.41 脳 10 ~ (10) ~ (-6) (1.592.00), with an average of 1.82, 未 EU _ (0.951.32) and weak EU positive anomalies. The geochemical characteristics indicate that the gabbro source area is a lithospheric mantle source magma, and the magma suffered from assimilation of crustal materials during its evolution, and the tectonic environment analysis shows that the gabbro is an island arc magmatic rock formed in a subduction environment. Combined with the tectonic evolution of the East Kunlun region, it is considered that the Kadang gabbro is the product of the northward subduction of the Animachin PaleoTethys ocean, which provides new chronological evidence for the late Paleozoic to early Mesozoic tectonic evolution in East Kunlun.
【作者单位】：国土资源部岩浆作用成矿与找矿重点实验室中国地质调查局西安地质调查中心;
【基金】：国土资源大调查项目(编号DD20160013、12120115022101、12120113029000)联合资助
【分类号】：P588.124;P597.3

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