东胜铀矿砂岩中方解石富集及铀矿成因  

The Enrichment of Calcite and the Genesis of Uranium Deposits in Dongsheng Uranium Sandstone

作　　者：冯乔[1,4] 秦宇[3] 付锁堂 柳益群[3] 周鼎武[1] 

机构地区：[1]山东科技大学地球科学与工程学院,青岛266510 [2]中国石油青海油田分公司,敦煌736202 [3]大陆动力学国家重点实验室,西北大学地质系,西安710069 [4]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266071

出　　处：《高校地质学报》2016年第1期53-59,共7页Geological Journal of China Universities

基　　金：海外及港澳学者合作研究基金(41428201);国家重点基础研究发展计划“973”项目(2003CB214603)资助

摘　　要：东胜铀矿区方解石富集特征、无机碳氧同位素以及邻近气藏包裹体捕获压力、有机碳同位素和~3He/~4He的相关研究表明,东胜铀成矿与深层天然气存在密切关系。方解石的δ^(13)C值-19.6‰^-1.11‰,δ^(18)O值-17.13‰^-9.00‰,δ^(13)C值的变化范围较宽,可能是地表水和深层天然气影响程度不同所致。鄂尔多斯盆地北部气藏储层包裹体捕获压力从深部向浅部和从盆地西南向东北方向逐渐降低的变化趋势表明,天然气为铀的转化提供了充足的还原剂,为大型东胜铀矿形成提供了必要条件。天然气中~3He/~4He比值证明东胜直罗组铀矿砂岩中没有有意义的幔源流体贡献。这些证据表明东胜铀矿砂岩中的方解石是地表水和深部天然气共同作用的结果,这暗示了东胜大型铀矿床是由低温混合成矿作用形成的。Research on calcite in Dongsheng uranium area is carried out including the enrichment characteristics, inorganic carbon and oxygen isotopes, neighboring gas reservoirs inclusions trapping pressure, organic carbon isotopes and 3He/4He ratios. The results show that there is a close relationship between Dongsheng uranium mineralization and deep natural gas. The δ13C values range from-19.6‰to-1.11‰and theδ18O values range from-17.13‰to-9.00‰in calcite. The values ofδ13C vary widely, maybe due to the influence of surface water and deep natural gas. The gas reservoirs inclusion trapping pressures decreased from the deep to the superficial part and from southwest to northeast in northern Ordos Basin, indicating that natural gas has supplied sufficient reducer for the conversion of uranium necessary for the formation of large-scale uranium. The 3He/4He ratio in natural gas indicates that Dongsheng Zhiluo uranium sandstone has no meaningful contribution from mantle fluids. The evidence shows that the calcite is a result of joint actions of surface water and deep gas in Dongsheng uranium sandstone, suggesting that Dongsheng large-scale uranium deposit was formed by the effect of cryogenically mixed mineralization.

关 键 词：方解石 碳氧同位素 3He/4He比值 东胜铀矿 

分 类 号：P619.14[天文地球—矿床学]