鄂尔多斯盆地砂岩型铀矿流体包裹体特征

Characteristics of fluid inclusions in sandstone-type uranium deposit of Ordos Basin

对鄂尔多斯盆地北部东胜地区的砂岩型铀矿赋矿多口钻井的岩心样品的流体包裹体的均一温度、盐水包裹体的盐度以及主成分和氢氧同位素组成系统的测定结果表明,该砂岩型铀矿赋矿砂岩至少经历过2期热流体活动,成矿流体温度有2个峰值,即高温段140~180℃和低温段100~120℃。成矿流体盐度NaCl主要分布约为4%~10%,但不同钻孔的样品有多个不同的峰值。流体中以水为主要成分,其次为CO2和CH4等,其他气体含量很少。流体包裹体的氢-氧同位素分析表明,成矿流体的δ18O值为9.8‰~12.3‰,δD值分布为-5‰^-48.6‰。氢-氧同位素图解投点全部落在建造水的范围内,部分为变质水,据此推测,成矿流体可能是原生的岩浆水和大气降水形成的混合变质水和建造水。

The temperature, salinity, chemical compositions and hydrogen oxygen isotopic compositions of fluid inclusions residenting in quartz from uranium-bearing sandstones in drilling holes of Dongsheng uranium deposit in Ordos Basin were investigated. Two major mineralization temperature ranging from 140 ℃to 180℃ and from 100℃ to 120℃ were obtained. The salinity （NaCI） of the fluid inclusions was mainly ranging from 4 percent to 10 percent, and there were multiple climaxes in different drilling holes. The fluid inclusions were mainly composed of H2O, and the minor compositions contained CO2 and CH4. The hydrogen and oxygen isotopic compositions of fluid inclusions showed that the ore fluids had higher values of δ^18O ranging from 9.8 ‰ to 12.3 ‰ , and the value of δD ranged from negative 5 ‰ to negative 48.6 ‰ . All the data of hydrogen and oxygen isotopes fall into the region of formation water on the diagram, parts of them fall into the region of metamorphic water. Thus it is inferred that the fluids for the uranium formation are the mixtures of original formation water and meteorite water.