皖南谭山岩体的锆石定年及地质意义

皖南地区广泛分布燕山期岩浆岩，但其年代学方面的工作较为薄弱。为厘定该地区燕山期岩浆岩年代学格架，本文利用LA-ICP-MS锆石U-Pb定年方法对皖南谭山岩体的正长花岗岩进行了锆石U-Pb年代学研究，两个样品的206Pb/238U加权平均年龄分别为128．5±1．7Ma和128．3±1．5Ma，基本一致，为早白垩世岩浆活动的产物。结合本地区高精度年代学数据，皖南地区中生代岩浆岩可划分为三个峰期：第一峰期为142～139Ma；第二峰期为133～130Ma；第三峰期为128～125Ma。

Zircon LA-ICPMS dating of the Tanshan pluton in the area of southern Anhui Province and its geological significances

The Yanshanian magmatic rocks are widely distributed in the area of southern Anhui Pro-vine ,but the chronological works on the magmatic rocks are still weak .For constructing the geochrono-logical framework of these Yanshanian magmatic rocks ,this paper deals with geochronological study on the Tanshan pluton by using zircon LA-ICPMS U-Pb dating for the K-feldspar granites from the pluton . Two coincident weighted mean 206 Pb/235 U ages of 128 .5 ± 1 .7 Ma and 128 .3 ± 1 .5 Ma respectively for two samples from Tanshan pluton are obtained ,which represent magma intrusive age of Early Cretaceous .By combining with the high precision age data of magmatic rocks in the area ,the Mesozoic magmatic rocks in the area of southern Anhui Province can be divided into three stages ,namely 142-139 Ma （the first peak period） ,133-130 Ma （the second peak period） and 128-125 Ma （the third peak period） .