西藏搭格架热泉型铯矿床同位素特征及形成过程  

Isotope characteristics and formation process of hot spring type cesium deposit in Targejia,Tibet

作　　者：赵元艺[1] 聂凤军[1] 侯增谦[2] 李振清[1] 赵希涛[3] 马志邦[3] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]中国地质科学院地质研究所,北京100037 [3]中国科学院地质与地球物理研究所,北京100029

出　　处：《矿床地质》2006年第5期613-619,共7页Mineral Deposits

基　　金：国家科技部973项目2002CB412606课题资助

摘　　要：文章系统研究了西藏搭格架超大型热泉型铯矿床泉华的Si、O、C、Sr、Nd同位素特征,并探讨了矿床的形成过程。结果表明,泉华的δ30Si=-0.7‰^-1.5‰,平均为-0.9‰;δ18O=0.4‰~19.5‰,平均为8.4‰;δ13CPDB=-5.9‰^-0.1‰,平均为-2.8‰;87Sr/86Sr=0.71062~0.71247,ε(Sr)=85.9~112.1;143Nd/144Nd=0.51214~0.51225,ε(Nd)=-9.7^-7.6。这种同位素特点体现出CO2主要为壳源,其次为生物源,矿床中的铯来源于上地壳内的熔融岩浆。印度—亚洲大陆的碰撞作用,是导致硅华铯矿成矿作用的关键因素。成矿作用的因子分析结果表明,Cs的成矿作用与热水携带物质及氧化作用关系密切,因此这种矿床仅能形成于地表,而形成在地下和海底的可能性很小。Cs与SiO2没有明显相关性,反映出Cs与SiO2的来源不一致。矿床形成的主要因素是热泉水的脱气(CO2)、f(O2)升高和温度压力的骤然降低。The Targejia hot spring geyserite cesium deposit, located in Ang Ren County of Xigaze district in Tibet, remains very active. The extent of its activity is rarely-seen in China. The quantity of cesium in this deposit has reached the reserves of a superlarge deposit. This paper has studied the Si, O, C, Sr and Nd isotopic characteristics of the sinter. The results indicate that δ^30Si values of the sinter are - 0.7‰ - - 1.5‰ with an average of - 0.9‰, δ^18O are 0.4% - 19.5% with an average of 8.4 ‰, δ^13CPDB are - 5.9% - - 0.1% with an average of - 2.8‰, ^87Sr/^86Sr = 0. 71062 - 0. 71247, ε（St） = 85.9 - 112.1, ^143 Nd/^144Nd = 0.51214 - 0. 51225, and ε（Nd） = - 9.7- - 7.6. These isotopic data suggest that the material of the deposit was derived from the melted magma of the upper crust. The key factor controlling the ore-forming process should be the collision of the Indus-Asian continent. Factor analysis of the ore-forming process indicates that Cs was strongly related to the material carried by hot water under an oxidation condition. Cs and SiO2 do not show obvious correlation, which implies that Cs and SiO2 did not have strong genetic relationship. The main factors governing the ore-forming process of this deposit seemed to be CO2 degassing, rising of f（O2）, and sudden temperature-pressure falling of the thermal fluids, with the reaction of Cs and SiO2 possessing the second importance.

关 键 词：地球化学 热泉型铯矿 同位素 硅华 西藏搭格架 

分 类 号：P618.84[天文地球—矿床学]