阿尔泰造山带南缘库尔提地区寒武纪变质侵入体的发现及地质意义

在新疆富蕴县库尔提地区下元古界克木齐岩群中发现了一套变质侵入体, 并对其进行了LA-ICP-MS锆石UVPb同位素定年。根据锆石的阴极发光图像和Th、U含量等特征, 锆石可分为岩浆锆石、变质锆石和捕获锆石3类。测得片麻岩的原岩岩浆206Pb/238U加权平均年龄为(496.3±6.4) Ma(MSWD = 0.74), 变质年龄介于444~452Ma之间。结合区域地质资料, 前者可能代表了古亚洲洋向北起始俯冲的时限, 后者代表同造山期变质事件时代。同时, 研究中发现的捕获继承性岩浆锆石年龄为783~901Ma, 暗示阿尔泰造山带存在前寒武纪基底。

Discovery and Geological Significance of Cambrian Metamorphic Intrusions of Kuerti Region in Southern Altay Orogenic Belt

Metamorphic intrusions into lower Proterozoic Kemuqi group were found in Kuerti region of Fuyun County, Xinjiang, and were determined for LA-ICP-MS zircon U-Pb ages. According to zircon cathodoluminescence images and Th, U characteristics, the zircons can be classified into magmatic zircons, metamorphic zircons and captured ones. The result shows that the original rock crystallization age is(496.3±6.4)Ma(MSWD = 0.74), and the age of its metamorphism is between 444 Ma and 452 Ma, indicating the rocks were produced in late Cambrian period. Combined with the data of southern margin of Altay, the authors hold that the Paleo-Asia Ocean may start to subduct from late Cambrian. In addition, from the captured inherited magma zircon, the authors obtained the inherited ages from 783 to 901 Ma, implying the existence of Precambrian basement in Altay orogenic belt.