赣杭铀成矿带燕山期岩浆岩年代学研究存在的主要问题分析  

Main problems in geochronology of Yanshanian magmatic rocks in Gan-Hang uranium metallogenic belt

作　　者：夏寅初 Xia Yinchu(College of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China)

机构地区：[1]东华理工大学地球科学学院,江西南昌330013

出　　处：《地质学刊》2021年第4期391-399,共9页Journal of Geology

基　　金：江西省研究生创新专项基金项目“相山南、北花岗斑岩成因与南部花岗斑岩成矿性评价:矿物学特征约束”(YC2020-B159)。

摘　　要：赣杭铀成矿带是我国最重要的火山岩型铀成矿带。前人对与铀成矿有关的燕山期火山岩及基性岩脉进行了大量年代学研究,获取了一批高精度的年龄数据。精确厘定与铀成矿有关的火山岩及基性岩脉的成岩时代,是深入研究两者与铀成矿关系的前提,对铀矿床成矿模型的建立至关重要,而部分火山岩及基性岩脉成岩年龄的精确度有待商榷。为此,总结了带内岩浆岩年代学研究存在的主要问题,认为部分火山-侵入杂岩样品因MSWD偏离置信区间、未剔除高U锆石等因素导致年龄精确度较低;锆石U-Pb定年精度用于厘定短时序、多期次、大规模火山-侵入活动有困难,主要表现在各种岩石年龄差异总体不大,在误差范围内高度一致;基性岩脉采用锆石U-Pb定年(基性岩中多为捕获锆石)或全岩K-Ar/^(40)Ar-^(39)Ar定年(易受热液活动或热事件影响),成岩年龄精确度较低。The Gan-Hang uranium metallogenic belt is the most important volcanic type uranium metallogenic belt in China.A lot of geochronological studies have been carried out on the Yanshanian volcanic rocks and basic rocks related to uranium mineralization,and a number of high-precision age data have been obtained.Accurate determination of the diagenetic age of volcanic rocks and basic rocks related to uranium mineralization is the premise of in-depth discuss of their relationship with uranium mineralization,and plays an important role in building the uranium deposit metallogenic model.However,the accuracy of diagenetic age of some volcanic rocks and basic rocks remains to be discussed.Therefore,this paper summarizes the three main problems in the study of magmatic geochronology in the belt.First,the age accuracy of some volcanic intrusive complex samples is low due to MSWD deviation from confidence interval and failure to exclude high U zircon.Second,the accuracy of zircon U-Pb dating is difficult to determine the short-term sequence,multiple period and large-scale volcanic-intrusive activities,which is mainly reflected in the fact that the age differences of various rocks are generally small and highly consistent within the error range.Third,Zircon U-Pb dating of mafic dikes(mostly captured zircons in mafic rocks)or K-Ar/^(40)Ar-^(39)Ar dating of whole rocks(susceptible to hydrothermal activity or thermal events)shows low diagenetic age accuracy.

关 键 词：年代学 火山岩 基性岩脉 赣杭铀成矿带 

分 类 号：P597.3[天文地球—地球化学]