粤北诸广南部铀矿田流体包裹体的氦氩同位素组成及成矿流体来源示踪  

Helium and argon isotopic compositions of fluid inclusions and tracing to the source of ore-forming fluids for the southern Zhuguang uranium ore field in northern Guangdong Province

作　　者：庞雅庆[1] 范洪海 高飞[1] 吴建勇 谢小占 PANG Ya;FAN HongHai;GAO Fei;WU JianYong;XIE XiaoZhan(CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China;Research Institute No. 290,CNNC,Shaoguan 512026,China;291 Brigade of Guangdong Province Nuclear Industry Geological Bureau,Guangzhou 510800,China)

机构地区：[1]核工业北京地质研究院,中核集团铀资源勘查与评价技术重点实验室,北京100029 [2]核工业290研究所,韶关512026 [3]广东省核工业地质局二九一大队,广州510800

出　　处：《岩石学报》2019年第9期2765-2773,共9页Acta Petrologica Sinica

基　　金：中核集团集中研发项目(LTD1602);中国地质调查局地质调查项目(DD20190159-10)联合资助

摘　　要：粤北诸广南部铀矿田是我国重要的花岗岩型铀矿产地之一,有关诸广南部花岗岩型铀矿田的成因,多年来一直存在较大的争议.本文以诸广南部铀矿田典型铀矿床成矿期萤石、方解石和黄铁矿中流体包裹体为测试对象,研究了成矿流体的He、Ar同位素地球化学.研究表明,萤石流体包裹体的3He/4 He比值为0.021~0.186Ra,40Ar/36 Ar比值为298.4~2515.7;方解石流体包裹体的3 He/4 He比值为0.027~0.209 Ra,40Ar/36Ar比值为295.9 ~ 327.2;黄铁矿流体包裹体的3He/4 He比值为0.021~1.543 Ra,40Ar/36Ar比值为326.9~1735.1;He-Ar同位素系统显示成矿流体的3He/4 He比值略高于地壳氦同位素特征值(0.01~0.05Ra),但低于幔源氦同位素特征值(6~9Ra),40Ar/36 Ar比值接近或高于大气氩的同位素组成(40Ar/36 Ar=295.5),成矿流体为壳-幔混合来源.结合H-O、He-Ar、C和Sr等多元同位素证据表明,成矿流体由两个端元组成:一是含有一定放射性成因Ar的大气降水的地壳流体,二是含幔源He的地幔流体.进一步研究表明,受NNW向断裂控制的棉花坑、书楼丘、长排等铀矿床受地幔流体影响比较大,而受NE向断裂控制的蕉坪、东坑、烟筒岭铀矿床受大气降水影响比较大.Southern Zhuguang uranium ore field is an important producing area of granite type U-deposit in China. The southern Zhuguang uranium deposits have attracted the attention of many geologists and their metallogenesis has long been in dispute. This paper reports He and Ar isotopic data of fluid inclusions trapped by fluorite,calcite and pyrite formed in metallogenic epoch from the southern Zhuguang uranium ore field. 3He/4He ratios of fluid inclusions trapped by fluorite range from 0.021Ra to 0.186Ra,and 40Ar/36Ar ratios of fluid inclusions trapped by fluorite range from 298.4 to 2515.7. 3He/4He ratios of fluid inclusions trapped by calcite range from 0.027Ra to 0.209Ra,and 40Ar/36Ar ratios of fluid inclusions trapped by calcite range from 295.9 to 327.2. 3He/4He ratios of fluid inclusions trapped by pyrite range from 0.021Ra to 1.543Ra,and 40Ar/36Ar ratios of fluid inclusions trapped by pyrite range from 326.9 to 1735.1. 3He/4He ratios of ore-forming fluids are slightly higher than that of the crust,and lower than that of the mantle. 40Ar/36Ar ratios of ore-forming fluids are close to or higher than that of the atmosphere (40Ar/36Ar=295.5). The compositions of He-Ar isotopic system suggest that the ore-forming fluids are characteristics of crust-mantle mixed in source. The compositions of H-O,He-Ar,C and Sr isotopes indicate that the ore-forming fluids are a mixture between crustal fluids containing meteoric water with radioactive Ar and mantle fluids containing mantle-derived He. The synthetical results show that the mantle fluids in source for Mianhuakeng,Shulouqiu and Changpai uranium deposits dominated by NNW faults are more affected than those for Jiaoping,Dongkeng and Yantongling uranium deposits dominated by NE faults.

关 键 词：成矿流体 He-A r同位素 壳-幔混合 诸广南部矿田 

分 类 号：P597[天文地球—地球化学] P619.14[天文地球—地质学]