新疆西准噶尔塔尔根一带花岗岩锆石U-Pb年龄、地球化学特征及其地质意义  

Zircon U-Pb chronology, geochemistry of the Taergen granite in Western Junggar, Xinjiang, and their geological significance

作　　者：支倩[1] 李永军[1,2] 王冉[1,2] 段丰浩 晁文迪 石歌 ZHI Qian;LI Yongjun;WANG Ran;DUAN Fenghao;CHAO Wendi;SHI Ge(School of Earth Science and Resources, Chang＇an University, Xi＇an 710054, Shaanxi, China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi＇an 710054, Shaanxi, China;Northwest Bureau of China Metallurgical Geology, Xi＇an 710119, Shaanxi, China;College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]国土资源部岩浆作用成矿与找矿重点实验室,陕西西安710054 [3]中国冶金地质总局西北局,陕西西安710119 [4]中国科学院大学地球科学学院,北京100049

出　　处：《地质通报》2018年第5期805-818,共14页Geological Bulletin of China

基　　金：国家自然科学基金项目<西准噶尔玉依塔勒盆克提花岗岩中石榴石的形成机制及地质意义>(批准号:41402044);新疆国土厅地质勘查基金项目<新疆西准噶尔地区构造-岩浆带成矿地质作用及矿化特征调查与研究>(编号:Y14-5-LQ06);<新疆东;西准噶尔泥盆系-石炭系典型剖面对比研究>(编号:Y15-1-LQ01)

摘　　要：新疆西准噶尔达尔布特构造-岩浆带分布大量的中酸性侵入体,其成因类型和侵位期次对于认识区域岩浆演化具有重要意义。通过对玛依勒山北段塔尔根一带的岩体进行野外地质调查,并结合LA-ICP-MS锆石U-Pb年代学及岩石地球化学分析,确定其形成时代、岩石成因及形成的构造环境。塔尔根一带岩体主要由正长花岗岩和二长花岗岩组成,正长花岗岩锆石U-Pb年龄为296.6±2.0Ma(n=27,MSWD=0.33),属早二叠世早期。岩石地球化学研究表明,其具有高硅、富碱、低钛和铝、贫钙镁,富集大离子亲石元素Rb、Th、K及高场强元素Zr、Hf,强烈亏损Sr、Eu、P、Ti,中等亏损Ba、Nb、Ta等元素,104Ga/Al值及Zr+Nb+Ce+Y含量较高的特征,属碱性准铝质-弱过铝质A型花岗岩,为低压高温条件下长英质地壳物质部分熔融的产物。综合区域构造演化并结合前人认识可知,西准噶尔地区在晚石炭世—早二叠世仍处于俯冲体系,很可能与晚石炭世洋脊俯冲作用有关。There are large numbers of intermediate-acid intrusions distributed along the Darbut tectono-magmatic belt in Western Junggar, Xinjiang. It is of great significance to understand the regional magmatic evolution through their petrogenesis and emplacement periods. The formation time, petronenesis and tectonic setting of Taergen granites, located in the northern part of Mayile Mountain, are reported in this study through field observation, LA-ICP-MS zircon U-Pb dating and geochemical analysis. The Taergen granites are mainly composed of monzonitic granite and syenogranite, LA-ICP-MS zircon U-Pb dating of monzonitic granite yielded an age of 296.6±2.0 Ma（n=27, MSWD=0.33）, corresponding to early Early Permian. Petrogeochemical analysis indicates that Taer-gen granites are characterized by high silica, alkali, low titanium and aluminum, lean calcium and magnesium. They are also enriched in large ion lithophile elements（e. g. Rb, Th, K） and high strength field elements（e. g. Zr, Hf） and are strongly depleted in Sr, Eu, P,Ti and mediate depleted in Ba, Nb, Ta, with high 104 Ga/Al ratios and Zr＋Nb＋Ce＋Y contents. These features indicate that Taergen granites are metaluminous to weakly peraluminous alkaline series A-type granite, which were originated from the partial melting of felsic crust under high temperature and low pressure conditions. Combined with regional tectonic evolution and previous results, we suggest that the Western Junggar region was still in a subduction-dominated setting in the Late Carboniferous-Early Permian, and probably associated with the ridge subduction during Late Carboniferous period.

关 键 词：A型花岗岩 岩石成因 早二叠世早期 俯冲 西准噶尔 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]