Characteristics of Organic Matter in Lower Cretaceous Ore-bearing Sandstone and Its Relationship With Uranium Mineralization in Southwestern Ordos Basin
In recent years,a great breakthrough has been made in the uranium prospecting in the Lower Cretaceous in southwestern Ordos Basin.New uranium deposits have been discovered in some districts of Zhenyuan and Pengyang county.The uranium mineralization in Cretaceous sandstones mainly occurs in the Luohe and Huanhe Formations,a few uranium mineralization occurs in the Jingchuan Formation and Luohandong Formation.The primary sediments of these ore-bearing strata are all formed in arid environment,and lack of visible organic matter.However,the mineralization rocks are rich in disseminated organic matter in the drill cores,but few systematic study was reported on the properties of disseminated organic matter and its relationship with uranium mineralization.In this paper,the types of organic matter in the uranium-bearing sandstone was found determined based on the core observations and laboratory study.The results show that the organic matter from the original sediments in the U-bearing sandstone is very rare,and the organic matter is mainly the macromolecular organic matter filled in the micro-pores of the sandstone with the characteristics of flow and low evolution degree,the source rock of 7th member of Yanchang Formation may be the main source rock.The uranium mineralization is not related to the organic matter as solid carbon debris,but mainly to the"soluble"and"flowing"organic matter.The characteristics of Cretaceous uranium mineralization in the study area are correspond to the exudative uranium metallogeny of sandstone type U-mineralization.
mobile organic matteraeolian sandstoneLower Cretaceoussandstone-type uranium depositOrdos Basin
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