南蒙古地区西南欧玉花岗岩LA-MC-ICP-MS锆石U-Pb定年及其地质意义

LA-MC-ICP-MS zircon U-Pb dating of granite of southwestern Oyu Tolgoi region in South Mongolia and its geological significance

摘要: 对蒙古国南戈壁省东部的西南欧玉岩体黑云母花岗岩锆石进行了阴极发光照相, 结果显示, 其具有明显的振荡环带, 为典型的岩浆锆石特征。对22颗锆石进行了LA-MC-ICP-MS U-Pb年龄测定, 结果显示, 21个测点的²⁰⁶Pb/²³⁸U年龄介于334±2~335±2Ma之间, 年龄加权平均值为335±1Ma, 表明西南欧玉岩体形成于早石炭世。

Abstract: The zircons from biotite granite in southwestern Oyu Tolgoi region show clear oscillatory zoning, indicating that they were formed by normal crystallization of magma. U-Pb dating of 22 zircons was conducted by LA-MC-ICP-MS method. The re-sults show that the data of 21 zircons are clustered around the concordia of 334±2~335±2Ma, yielding a weighted mean ²⁰⁶Pb/²³⁸U age of 335.6±1Ma, which implies that the crystallization of biotite granite in southwestern Oyu Tolgoi region occurred in Early Car-boniferous.