湖南锡田花岗岩体锆石U-Pb年代学研究

摘要

In this paper,the U-Pb geochronology of zircon of the 8 samples in Xitian pluton of Hunan Province has been measured,using SHRIMP and LA-ICP-MS technique.All zircons from Xitian granite pluton have the oscillatory zoning and high Th/U ratio revealed by the cathodoluminescence (CL)images,which suggest that zircons are magmatic zircons.Based on the new data and the latest reported high-precise dating of the related granites,the magmatic activities in the study area can be ascribed to four stages as follows:The first stage of Indosinian(230-224 Ma),the peak was about 228 Ma;The second stage of Indosinian was about 215 Ma;The first stage of Yanshanian(160 -147 Ma),the peak was about 151 Ma;The second stage of Yanshanian was after 141 Ma.%采用SHRIMP 和LA-ICP-MS 测年方法，对湖南锡田花岗岩体8个样品中的锆石进行了U-Pb同位素年代学测定。对样品中的锆石进行成因研究，在阴极发光图像上锆石具有典型的振荡环带，呈现较高的Th/U比值特征，显示锆石为岩浆锆石。根据新获得的花岗岩SHRIMP和LA-ICP-MS锆石U-Pb数据，结合已经报道的高精度成岩年代学资料，将锡田岩体的岩浆活动归纳为2期4个阶段：印支期第一阶段，侵位于230～224 Ma间，峰值在228 Ma左右；印支期第二阶段，侵位于215 Ma 左右；燕山期第一阶段，侵位于160～147 Ma间，峰值在151 Ma左右；燕山期第二阶段侵位于141 Ma之后。