东准噶尔卡拉麦里蛇绿岩带南侧侵入体的岩石学、地球化学及年代学特征

    Petrological, geochemical and chronologic characteristics of the intrusive bodies on the south side of Karamaili ophiolite belt in eastern Junngar

    • 摘要: 东准噶尔卡拉麦里蛇绿岩带南侧分布有大量的石炭纪侵入体,主要出露于五彩城、滴水泉一带及野马站地区。通过对卡拉麦里断裂以南侵入体岩石类型、锆石年代学、地球化学的综合分析,划分出早石炭世后碰撞I型花岗岩类及晚石炭世陆内双峰式侵入岩(碱长花岗岩+角闪辉长岩)。结合断裂以北黄羊山、老鸦泉岩体新近发表的数据及区域内火山岩的研究成果,对卡拉麦里地区石炭纪-二叠纪构造-岩浆演化过程给出了新认识,即卡拉麦里地区从后碰撞到陆内伸展的构造转换时间为早石炭世末期-晚石炭世早期,后碰撞阶段岩浆岩以钙碱性I型花岗岩、玄武安山岩、安山岩为特点,陆内伸展阶段以典型的双峰式岩浆岩(辉长岩+花岗岩、玄武岩+流纹岩)及A型花岗岩为特点,卡拉麦里地区具有正εNd值的花岗岩类来源于亏损地幔形成的年轻地壳的部分熔融。

       

      Abstract: There are many Carboniferous intrusive bodies on the south side of Karamaili ophiolite belt in eastern Junngar, which are mainly distributed in Wucaicheng area and Dishuiquan-Yemazhan zone. Based on the study of the characteristics of the intrusive bod-ies such as rock types, zircon geochronology and geochemistry, we can distinguish the early Carboniferous post-collisional I-type gra-nitic rocks from the late Carboniferous intra-continental bimodal rock associations (K-feldspar granite and hornblende-gabbro). Combined with the recently published data for Laoyaquan pluton, Huangyangshan pluton and volcanic rocks in Karamaili area, the au-thors have reached some new conclusions about the tectonic-magmatic evolution in Karamaili from Carboniferous to Permian. Firstly, the tectonic transition from post-collision to intra-continent extension may have occurred between early and late Carboniferous. The post-collisional igneous rocks are characterized by calc-alkaline I-type granite, basalt andesite and andesite, and the intra-continent extensional rock types are mainly composed of bimodal rock associations and A-type granite. Secondly, the granitoids in Karamaili are characterized by positive Nd values, suggesting that they were most probably from the young crust formed by depleted mantle.

       

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