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。
Paleozoic intrusive rocks are extensively developed in the Harlik orogen, and their petrogenesis is important for understanding the geodynamic settings of the magma. This paper studies systematically pe- trology, geochemistry and zircon U-Pb geochronology from quartz diorite of the Qincheng Tianshengquan (QC) pluton in the middle of east Harlik orogen, in order to discuss about its petrogenesis and tectonic significances, and then to provide a basis for solving geological tectonic evolution of Harlik orogen. The li- thology of the QC pluton is quartz diorite, and is dated by LA-ICP-MS to have weighed mean z06pb/238U a- ges of (446.1+_3.3)Ma (Late Ordovician). The U-Pb dating of zircons show that this rock should be the product of the Caledonian tectonic magmatism. Rock geochemical analysis shows that its SiO2 ranges from 57.74% to 62.34%, middle-high K (1.71%--3.01%), rich in CaO(4. 01%--8. 45%), and depleted in A1203(15.03%--16.89%). It has MgO ranging from 1.85% to 3.97%, and Mg~ =37.15--48.29, A/ CNK=0. 78--0. 99, indicating that it belongs to a metaluminous peraluminous middle and high-K calc-al- kaline rock series. The analysis also shows that the QC pluton has low REE(59. 74 X 10.6 --205. 53 X 10 6), and LREE more obvious fractionation than HREE, strong enrichments in large ion lithophile ele- ments(LILEs,e, g. ,Rb,Ba) and incompatible elements(Th,U), depletions in high field-strength elements (HFSEs, e. g. , Nb, Ta, Sr, Ti). These characteristics indicate that the pluton is similar chemically to those island arc magmatic rocks. According to the relevant diagram and the ratio about the trace elements and rare earth elements. This indicates that the magma is affected by subduction, and the primary magmas were most likely derived from partial melting of the thickened lower crust, with the invasion of mantle components. Moreover, the analysis of regional geological data suggests that there is a large island arc e- volution related to the Caledonian tectonic magmatism i