桂北沙子江花岗岩型铀矿床碳、氧、硫同位素特征及其成因意义  

Isotope Compositions of Carbon,Oxygen and Sulfur in the Shazijiang Granite-hosted Uranium ore Deposit,Northern Guangxi,China and Their Genetic Significance

作　　者：石少华[1,2] 胡瑞忠[1] 温汉捷[1] 孙如良 王加昇[1,2] 陈恒[1,2] 

机构地区：[1]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵阳550002 [2]中国科学院研究生院,北京100049 [3]广西310核地质大队,广西桂林541213

出　　处：《矿物岩石地球化学通报》2011年第1期88-96,共9页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家重点基础研究发展规划项目(2007CB411408);国家自然科学基金重大项目(40634020)

摘　　要：测定了沙子江矿床及邻区矿床中与矿化密切有关的脉石矿物的稳定同位素,测知沙子江矿床方解石的δ13CPDB值为-2.8‰^-11.0‰,集中于-5‰^-9‰;表明矿化剂CO2主要来自地幔,混有少量有机质和沉积碳酸盐物质。δ13CPDB与δ18OSMOW呈显著的负相关关系,暗示流体去气(CO2)是方解石沉淀的主控因素。铀沉淀为多因素耦合作用的结果;去气作用导致成矿流体中碳酸铀酰络离子的解体,有利于铀的沉淀。S2-作为还原剂对铀沉淀也起了很大的作用。沙子江矿床黄铁矿的δ34SCDT值为-18.36‰^-8.92‰,可能主要来源于赋矿的花岗岩,而邻区孟公界和白毛冲矿床的δ34SCDT值为-30.51‰^-27.64‰,更多地继承了赋矿花岗岩源岩中沉积硫的特征。The stable isotope compositions have been respectively analyzed for calcites and pyrites,which are closely related to the uranium mineralization in Shazijiang and in adjacent uranium ore deposits.The δ13CPDB values of the calcites from the Shazijiang ore deposit are in the range of-2.8‰～-11.0‰,mostly in the range of-5‰～-9‰.It indicates that the mineralizer,CO2,mainly originated from mantle and that only a little originated from organic matter and sedimentary carbonate.The negative correlation between δ13CPDB and δ18OSMOW indicates that the degassing of CO2 is a major controlling factor for calcite precipitation,while uranium precipitation may be controlled by multi-factors.The process of CO2 degassing reduces the activity of uranyl-carbonate complexes,therefore causes uranium precipitation.S2-,one of important reduction agents,also contributes to reduction of hexavalent uranium and to uranium precipitation.The measurement of S isotope in pyrites suggests that the most part of sulfur in the Shazijiang ore deposit came from the host granite,the δ34SCDT values are in the range of-18.36‰～-8.92‰.Whereas,Menggongjie and Baimaochong ore deposits inherit more sulfur from the granite originated sedimentary carbonate,so their δ34SCDT values are in the range of-30.51‰～-27.64‰.

关 键 词：稳定同位素 方解石 黄铁矿 沙子江 苗儿山 桂北 

分 类 号：P619.14[天文地球—矿床学]