阿尔泰乌希里克地区满克依顶萨依岩体地球化学特征、形成时代及其构造环境

    Geochemical characteristics, formation age and tectonic environment of the Mankeyidingsayi rocks in the Wuxilike area of Altay

    • 摘要: 阿尔泰乌希里克地区位于西伯利亚板块阿尔泰陆缘活动带的阿尔泰古生代深成岩浆弧内,花岗岩广泛分布。通过对满克依顶萨依岩体进行LA-ICP-MS锆石U-Pb测年和岩石地球化学分析,探讨该岩体形成的时代及构造环境。乌希里克南部满克依顶萨依岩体中细粒白云母二长花岗岩的LA-ICP-MS锆石U-Pb年龄为217.9±2.3Ma,表明岩体侵位于早中生代晚三叠世早期。岩石具有高的SiO2(70.86%~74.32%)和Al2O3(14.51%~14.96%)含量,低P2O5(0.24%~0.33%)和MgO+FeO(0.39%~1.25%)含量,富碱(K2O+Na2O=8.07%~8.29%),具有低的CaO/Na2O值(0.13~0.30,≤0.3)。以上特征表明,该岩体属高钾钙碱性过铝质岩类,具有S型花岗岩的典型特征。结合前人研究成果综合分析,推测岩体形成于板内(陆内)环境,与地幔柱有关。岩体主要由源自地壳的泥质沉积物部分熔融形成,在部分熔融过程中有富钙的斜长石、钛铁矿等矿物的残留。

       

      Abstract: The Wuxilike area of Altay is located in Siberian Altay terrigenous mobile belt and the Altay Paleozoic plutonic magmatic arc, where granite is widely distributed. By LA-ICP-MS zircon U-Pb dating and geochemical analysis, the authors studied the age and tectonic environment of the Makeyidingshayi granite body. The LA-ICP-MS zircon U-Pb age of the medium-fine grained muscovite adamellite of Mankeyidingsayi granite body in southern Wuxilike area is 217.9±2.3Ma, showing that the granite body was emplaced in the early Late Triassic of the early-Mesozoic. The rocks have high SiO2 (70.86%~74.32%) and Al2O3 (14.51%~14.96%), low P2O5 (0.24%~0.33%) and MgO+FeO (0.39%~1.25%) content, high alkali (K2O+Na2O=8.07%~8.29%), and low CaO/Na2O (0.13~0.30, ≤0.3) ratio. These characteristics indicate that the granite body belongs to high-K calc-alkaline peraluminous rocks, with the typical features of S-type granites. In combination with the work and the results from previous comprehensive analysis, the authors infer that the granite body was formed in an intercontinental (inland) environment, related to the mantle plume. The granite body was mainly derived from partial melting of argillaceous sediments in the crust, and during the partial melting process, residuals of calcium-rich plagioclase, ilmenite and other minerals were preserved.

       

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