砂岩型铀矿床的有机地球化学分带性及其与铀成矿的关系——以内蒙古皂火壕铀矿床为例

内蒙古皂火壕铀矿床是古层间氧化带砂岩型铀矿床,具有明显的有机地球化学分带性。笔者认为,其过渡带有机质含量高是原地同沉积富集和异地来源有机质"叠加"的结果,二者分别受控于岩相古地理条件和古层间氧化作用中的铀-有机质作用。过渡带中的有机质主要包括腐殖质、有机黏土复合体以及干酪根。铀对有机质具有热演化催化作用,可能导致了过渡带中的有机质成熟度增高。皂火壕铀矿床是成岩作用发展到一定阶段的产物,侏罗系煤系地层在成岩演化中产生了丰富的可溶性有机质和烃类物质,它们参与了铀成矿的全过程。有机地球化学分带性指标可以作为层间氧化带过渡带乃至前锋线定位识别的微观及宏观标志,对铀矿找矿勘探具有重要的指导作用。

Organic Geochemical Zonation Characteristics of Sandstone-type Uranium Deposit and its Relation to Metallization---A Case Study of Zaohuohao Uranium Deposit in Inner Mongolia

Zaohuohao uranium deposit in Inner Mongolia is of sandstone‐type formed by the paleo‐inter‐layer oxidation. Organic indicators shew obvious geochemical zones which can be used as location mark of transitional zone. It was considered that the high content of organic matters was caused by the superposi‐tion of the sedimentation of organic matters within and outside the transitional zones , which were con‐trolled by lithofacies paleogeography and uranium‐organism reaction in the paleo interlayer zone respec‐tively.Organic matters in the transitional zone contains humus , organic clay complex and kero‐gen. Uranium act as the catalyst to thermal evolution of organic matters. This may cause the high matu‐ration of organic matters in the transitional zone.Zaohuohao Uranium Deposit was the product of the dia‐genetic evolution. Organic matters of Jurassic coal measure stratum produced rich soluble organic matter and hydrocarbons which participated in all the process of uranium mineralization. This study broadened the research field of organic geologic process of sandstone type uranium deposit .