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西天山阿吾拉勒东南部艾肯达坂花岗岩和2752高地闪长玢岩浅成小岩体侵入于石炭系火山-沉积岩中,岩石无变形,呈均一块状,具斑状/似斑状结构,属准铝质到弱过铝质高钾钙碱性花岗岩类,富集Rb、Th、U、K和Pb等大离子亲石元素,贫Zr、Hf等高场强元素,显示中等到弱的负Eu异常,亏损Nb、Ta、P、Ti和Sr等元素,具壳源岛弧区岩浆作用的地球化学特征。这两个岩体锆石均为正εHf(t)值和新元古代Hf陆壳模式年龄,指示其主要源自新元古代陆壳物质的部分熔融,个别锆石εHf(t)值明显高表明岩体形成过程还有幔源岩浆物质的加入。LA-ICP-MS锆石U-Pb定年分别获得2752高地闪长玢岩307 Ma和艾肯达坂花岗岩282 Ma的形成年龄,与区域上同期小岩体一同对应于西天山大规模壳-幔花岗岩浆活动末期,证明在晚石炭世—中二叠世期间,伴随着西天山大规模花岗岩浆活动的减弱,出现一期重要的小规模中酸性岩浆活动。综合分析西天山晩石炭世—中二叠世各类岩浆作用,该时期中酸性小岩体为后碰撞向陆内伸展拉张过渡阶段岩浆活动的产物,指示西天山晚石炭世晚期深部动力学背景和构造环境发生了重要转折。
The Aiken Daban granite in the southeastern Ulaanlar of the West Tianshan Mountains and the shallow dacite porphyry of the diorite porphyry in the 2752 highland intrusive into the Carboniferous volcanic-sedimentary rocks. The rocks show no deformation and are of a block-like, patchy / speckle-like structure Al to weak Al-Alkali, high-K calc-alkaline granites, enriched in large ion lithophile elements such as Rb, Th, U, K and Pb, depleted in high field strength elements such as Zr and Hf, showing moderate to weak negative Eu Abnormal, depleted elements such as Nb, Ta, P, Ti and Sr have the geochemical characteristics of magmatism in the arc zone of the source rocks. The zircons of these two rocks are both positive εHf (t) values and Neoproterozoic Hf continental crustal age, indicating that they are mainly derived from the partial melting of Neoproterozoic continental crustal materials. The εHf (t) values of some zircons are significantly higher It shows that there are some mantle-derived magmatic materials in the formation of rock mass. The LA-ICP-MS zircon U-Pb dating of the age of 27 Ma and the Aikanda Daban granite, respectively, resulted in the formation age of the 307 Ma and the Aikandabashan granite of 282 Ma, corresponding to the large-scale crust-mantle of the western Tianshan During the Late Granitic magmatic activity, it was proved that during the Late Carboniferous-Middle Permian period, accompanied with the weakening of the large-scale granitic magmatism in the western Tianshan Mountains, an important small-scale magmatic activity occurred in a small scale. Comprehensive analysis of all types of magmatism from Carboniferous to Middle Permian in western Tianshan shows that the small-medium-acidic rocks in this period are the products of magmatic activities after the post-collision to extensional extension and extension, indicating that the Late Late Carboniferous Late Kinetics An important turning point came in the background and the tectonic environment.