中文摘要：

本文对出露于南天山南缘断裂带的欧西达坂岩体进行了系统的岩石学、地球化学和锆石U-Pb年代学研究,重点讨论了其岩石成因、源区性质及其大地构造意义。岩体主要由石英闪长岩、二长花岗岩和花岗斑岩组成,并且显示了强烈的后期变形特征。LA-ICP-MS微区定年获得了两组年龄：421±3Ma,273±2Ma,前者为二长花岗岩结晶年龄,而后者则代表了南天山后碰撞伸展走滑作用的时代。地球化学特征显示,二长花岗岩的SiO2含量介于65.16%～75.50%之间,Mg^#值低（0.23～0.41）,A/CNK=0.86～1.15,为过铝-强过铝质,钙碱-高钾钙碱系列花岗岩;（La/Yb）N为4.40～6.32,δEu=0.58～0.77。与二长花岗岩相比,石英闪长岩的SiO2含量较低（55.46%～58.29%）,相对富钛、钙、铁、铝和MgO等;铝饱和指数A/CNK=0.88～1.04,Mg^#值高（0.45～0.50）,为钙碱性系列。二长花岗岩的（La/Yb）N为7.84～9.48,δEu=0.52～0.78。在原始地幔标准化蛛网图上,样品均明显富集Rb、Ba、Th、K等大离子亲石元素和LREE,亏损Nb、Ta、P、Ti等高场强元素。而二长花岗岩表现为更加亏损Nb、Ta、P、Ti等元素,并具有明显的Sr负异常。该岩体高的Al2O3、La/Nb、Th/Ta值和原始地幔标准化图解中Nb-Ti的负异常说明该套岩石形成于板块边缘环境或来自岛弧环境下的陆壳源区。石英闪长岩可能来源于镁铁质岩浆底侵导致的下地壳部分熔融,二长花岗岩可能是来自于中下地壳的无水熔融。欧西达坂岩体体现了南天山洋早古生代向南短暂而局部的平坦的低角度板片俯冲。综合区域地质资料分析推测在早古生代南天山洋可能存在双向俯冲,从而形成同一洋盆中的蛇绿岩在南天山南北两侧的就位;而在晚古生代南天山洋一直向北俯冲,具有长期、多阶段的特征。

英文摘要：

South Tianshan is one of the regions with most complicated tectonic evolution history in the Tianshan Orogenic Belt. The Oxidaban pluton, located in the southwestern section of South Tianshan, is studied in this paper in detail. This paper put much emphasis on the petrogenesis, magmatic source, and tectonic significance based on geochemical and geochronologcial data. Lithologically, the pluton comprises mainly quartz diorite, granite porphyry and monzonitic granite, which are characterized by strong deformation at the late stage. U-Pb LA-ICP-MS dating yields two ages. 421±3Ma and 273±2Ma. The former represents the emplacement age of monzonitic granite and the latter implys the time of extension and slip of South Tianshan during the post-collision. Geochemically, the monzonitic granite has SiO2 concentration （65.16 % -75.50%）, low Mg^# （0.23-0.41） ,and A/CNK （0.86-1.15） ,which fall into the range of metaluminous to slightly peraluminous rocks, suggesting the granite belongs to calc-alkaline to shoshonitic series. Compared to the monzonitic granite, the quartz diorite has by low SiO2 content （55.46%-58.29%）, and high Ti, Ca, Fe, Al and MgO contents, the A/CNK values between 0.88 and 1.04, δEu （0.52-0.78） and high Mg number （ranging from 0.45-0. 50）, which all indicate a calc-alkaline series. In the PM- normalized trace element diagram, all samples are distinctly enriched in Rb, Ba, Th, K and LREE and depleted in Nb, Ta, P and Ti. However, the monzonitic granite is more depleted in Nb, Ta, P, Ti and of obviously negative Sr anomaly. The quartz diorite and monzonitic granite of the Oxidaban pluton contain high Na2O and CaO. The quartz diorite is likely generated by partial melting of the lower crust which mafic magmas intrudes into, while the monzonitic granite probably from anhydrous melting of the middle-lower crust. The Oxidaban pluton expresses a short-lived but locally low-angular sourthward subduction of South Tianshan Ocean during early Paleozoic. Based on the regional geological dat