诸广中段印支期花岗岩LA-ICP-MS锆石U-Pb年龄及微量元素特征  

LA-ICP-MS U-Pb Ages and Trace Element Compositions of Zircon from Indosinian Granites in Middle Zhuguangshan

作　　者：李杰 黄宏业[1] 刘子杰 张涛 王前林[1] 方适宜 邹明亮 LI Jie;HUANG Hongye;LIU Zijie;ZHANG Tao;WANG Qianlin;FANG Shiyi;ZOU Mingliang(Research Institute No.230,CNNC,Changsha 410007,Hunan,China)

机构地区：[1]核工业二三〇研究所,湖南长沙410007

出　　处：《大地构造与成矿学》2021年第6期1216-1232,I0001-I0007,共24页Geotectonica et Metallogenia

基　　金：国家重点研发计划项目(2017YFC0602600);国防预研项目(3210402);中核集团菁英项目联合资助。

摘　　要：诸广中段是华南重要的花岗岩型铀矿集区之一,区内已发现的铀矿床(点)均集中分布于印支期花岗岩内外接触带附近。为了更好地限定花岗岩源区特征和成因,探讨其与铀成矿的关系,本次研究选择鹿井地区花岗岩(文英、大场坪、官庄岩体)为研究对象,开展LA-ICP-MS锆石U-Pb年代学和微量元素特征研究。结果表明,花岗岩成岩时代集中于227~238 Ma,均为印支早期岩浆活动产物。锆石微量元素特征指示,该区花岗岩属于典型的壳源S型花岗岩,形成于同碰撞挤压构造环境,是华南地块和印支地块碰撞结束后地壳叠置熔融作用过程中,由加厚地壳中的泥质沉积变质岩系发生部分熔融形成。该地区铀成矿作用受燕山晚期‒喜山期区域性岩浆‒构造‒热液活动的统一制约,铀矿床的空间定位则往往受燕山期构造‒岩浆热事件叠加的印支期过铝质富铀花岗岩控制。The middle section of the Zhuguangshan batholith is an important production area of granite type uranium deposits in South China.The uranium deposits(spots)in the area are mainly concentrated near the inner and outer contact zone of the Indosinian granite plutons.These U-bearing granites generally contain zircon grains with high-U-concentrations.LA-ICP-MS U-Pb analyses for high-U zircon grains show much less pronounced matrix effect than SHRIMP analyses and likely yield more reliable U-Pb ages for the high-U zircon grains.In order to further enrich the geochronological data and better define the source characteristics and genesis of the granites in the area,so as to explore its relationship with uranium mineralization,LA-ICP-MS U-Pb dating and trace element analyses of zircon were carried out for the representative granite samples in the Lujing area of the middle Zhuguangshan batholith.The new dating results of the granites,with ages of 227 to 238 Ma,indicate that the granites were formed during the Early Indosinian magmatic activity.Among them,the main body of the granite was formed at 236 to 238 Ma,which is consistent with the ages of the Indosinian granites in the southern Zhuguangshan batholith and the U-bearing granites in the Guidong area.It is further confirmed that the main granites in the Lujing area were formed in the second stage of the early Indosinian period and part of which lasted to the third stage of the early Indosinian period.The magmatic temperatures estimated using the zircon saturation thermometry(T_(Zr))and Ti-in-zircon thermometry(T_(Ti-in-Zircon))are 768 to 807℃.A/CNK values of the granites vary from 1.09 to 1.92.The granites have high SiO_(2) contents(71.2%to 79.2%),belonging to S-type granite.The granites are likely formed by partial melting of the over-thickened muddy sedimentary metamorphic rocks in a syncollisional compressional environment subsequent to the collision between the South China Block and the Indosinian Block.The uranium mineralization in this area is restricted by the

关 键 词：LA-ICP-MS 锆石U-PB定年 锆石微量元素 印支早期 诸广中段 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]