新疆东部哈尔里克造山带沁城天生圈岩体岩石成因及其构造意义

发布时间：2018-04-28 02:04

本文选题：LA-ICP-MS锆石U-Pb定年 + 地球化学　；参考：《地质科技情报》2017年02期

【摘要】：新疆哈尔里克造山带广泛分布着古生代的侵入岩体,其成因对正确认识该区岩浆的动力学背景具有重要意义。对位于哈尔里克造山带中段东部的沁城天生圈岩体进行了岩石学、地球化学及锆石U-Pb年代学研究,探讨其岩石成因及构造属性,以期为解决哈尔里克造山带的地质构造演化提供依据。沁城天生圈岩体岩性为石英闪长岩,LA-ICP-MS锆石U-Pb定年结果表明,石英闪长岩形成时代为(446.1±3.3)Ma(晚奥陶世),属加里东期构造岩浆活动的产物。岩石地球化学分析结果显示,其w(SiO2)介于57.74%~62.34%之间,中钾-高钾(1.71%~3.01%),富CaO(4.01%~8.45%)、贫Al2O3(15.03%~16.89%),w(MgO)介于1.85%~3.97%之间,Mg#值为37.15~48.29,铝饱和指数值A/CNK为0.78~0.99,属准铝质中钾—高钾钙碱性岩石系列;且岩石稀土元素质量分数较低(59.74×10-6~205.53×10-6),轻稀土元素分馏较重稀土元素明显,富集Rb、Ba等大离子亲石元素(LILE)和活泼的不相容元素(Th、U),相对亏损Nb、Ta、Ti、P等高场强元素(HFSE),显示出与典型岛弧型岩浆岩相似的特征。有关微量元素、稀土元素的相关图解以及宏观地质特征指示,沁城天生圈岩体石英闪长岩的形成受俯冲作用影响,其岩浆源区应为增厚大陆下地壳物质部分熔融的产物,并可能含有幔源基性岩浆的加入。此外,综合区域地质资料分析,认为早古生代期间(中奥陶世-早志留世),哈尔里克造山带存在大面积的与真正岛弧演化有关的加里东期岩浆活动,哈尔里克早古生代岛弧的形成可能与东准噶尔南部克拉麦里洋向南俯冲作用有关。
[Abstract]:Paleozoic intrusive rock bodies are widely distributed in the Hallik orogenic belt of Xinjiang. The genesis of the intrusive rock bodies is of great significance for correctly understanding the dynamic background of magma in this area. Petrology, geochemistry and zircon U-Pb chronology of the Qincheng natural circle rock body located in the eastern part of the Hallik orogenic belt are studied, and its petrogenesis and tectonic properties are discussed. It is expected to provide the basis for solving the geological tectonic evolution of the Hallik orogenic belt. The lithology of Qincheng natural circle rock body is the result of U-Pb dating of LA-ICP-MS zircon from quartz diorite. The age of quartz diorite formation is 446.1 卤3.3 Ma (late Ordovician), which is the product of Caledonian tectonic magmatism. The results of petrogeochemical analysis show that the value of wnisio _ 2 is between 57.74% and 62.34%, and the medium and high potassium content is 1.71and 3.01K, which is rich in Cao 4.01 and 8.4545, and the poor Al _ 2O _ 3 _ 3 _ (15.03) is 16.89mg ~ (2 +) between 1.85 and 3.97%, and the value of aluminum saturation index (A/CNK) is 0.780.99, which belongs to the series of quasi-aluminous medium and high potassium calc-alkaline rocks. The mass fraction of REE in rock is 59.74 脳 10-6, 205.53 脳 10-6, and the fractionation of light REE is more obvious than that of heavy REE. The enrichment of large ion lithophile elements such as RbLi Ba (LILE) and the activity of incompatible elements, such as the high field strength elements, such as NbTa-TaTiP, are relatively depleted, showing similar characteristics to typical island arc magmatic rocks. The related diagrams of trace elements, rare earth elements and macroscopic geological characteristics indicate that the formation of quartz diorite in Qincheng natural circle is affected by subduction, and its magma source region should be the product of partial melting of the material in the lower crust of thickening continent. And it may contain the addition of mantle-derived basic magma. In addition, based on the analysis of regional geological data, it is concluded that during the early Paleozoic period (Middle Ordovician early Silurian, Harrick orogenic belt) there was a large area of Caledonian magmatism related to the real island arc evolution. The formation of the early Paleozoic island arc in Harrik may be related to the southward subduction of the Clamery Ocean in the southern part of East Junggar.
【作者单位】：四川省地质矿产勘查开发局川西北地质队;西南科技大学环境与资源学院;贵州省地质调查院;中国科学院地球化学研究所;
【基金】：国家自然科学基金项目(41472310) 中国地质调查局项目“新疆天山哈密地区五幅1∶5万区域地质矿产调查”(12120113042400)
【分类号】：P581

【参考文献】