Exudative Metallogeny and Model of Saihan Gaobi Sandstone-type Uranium Deposit in Erlian Basin
In order to explore the metallogeny and construct the metallogenetic model to provide guidance for uranium exploration in the periphery and depths of Saihan Gaobi uranium deposit in Erlian Basin,This paper summarized the ore-forming characteristics,extracted the key ore-controlling factor by analyzing the tectonic activity,geological formation,evolution of oil and gas,uranium mineralization,and age of uranium mineralization in Saihan Gaobi uranium deposit.The study made a detailed description of the geochemical characteristics of ore minerals and elements present in the deposit.The Saihan Gaobi deposit was confirmed located at paleochannel between the upper member of Saihai Formation,controlled by the Zhunbaolige deep cut depression and the incised channels in late Saihan period.The uranium ore body are tabular or lenticular.The metallization was found closely related to regional oil and gas escape activity and the compressional tectonic activity.The uranium content in the ore is positive correlated with the content of CaO+Al2O3 and P2O5,while the overall content of Co,Ni,Zn,and Fe2+/Fe3+ is relatively low,usually less than 0.8.Various types of sandstones exhibit a relatively high content of acid-dissolved hydrocarbons,and Th/U ratio is less than 2.These observations indicated that the primary environment of red mottled rock in the upper member of Saihan Formation was formed in oxidized environment and the gray ore-bearing sandstone body was mainly formed by exudative reduction.Uranium occurred in different uranium minerals,mostly co-existed with pyrite,coated with mineral pitch or micro debris uranium mineral.The mineralization in Saihan Gaobi uranium deposit was primarily attributed to exudative reduction,fluids rich in organic matter and tetravalent uranium,stored in the deep region,and transported to the oxidized sand bodies of the upper member of Saihan Formation through fractures or high-angle unconformities and undercutting channels.These fluids decomposed,resulting in the formation of pyrite,compound calcium phosphor uranium ore,and ground asphalt,which was previously crystallized in the ground asphalt.The majority of the uranium minerals are found on the outer side of the larger ground asphalt deposits,while most of the uranium minerals are situated near the smaller bitumen deposits.
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