论全球大气氧化事件在元古宙不整合面型铀矿成矿中的作用OA

The article is devoted to the problems of the influence of global processes of Great Oxygenation Event of the Earth's atmosphere on the genesis of Proterozoic unconformity-type uranium deposits in the Canadian sedimentary Athabasca basin,which are the most prominent representatives of large-scale uranium deposits with uniquely rich ores with uranium content up to a few tens of percentages in the world.The influence of the formation of an oxygen atmosphere on the process of ore formation is considered with a comparative analysis of single-stage and multi-stage models of the formation of unconformity uranium deposits.The appearance of free oxygen in the Earth's atmosphere,necessary for the formation of the unconformity deposits,occurred approximately 2.5-2.0 billion years ago during the Great Oxygenation Event(GOE).The Great Oxidation Event caused the atmosphere to form high levels of oxygen,leading to the production of more primary biological matter on the early Earth,thereby forming more organic-rich sediments,which played an important role in U-mineralization of Proterozoic unconformity-related uranium deposits.The formation of the Athabasca basin began approximately 1 740 Ma ago.Uranium mineralization in the deposits occurred 1 590 Ma ago.This was followed by a series of putative post-ore events with rejuvenated ages from 1 525 to 1 000-950 Ma,which in the single-stage deposit formation model were interpreted as re-precipitation of primary ore mineralization with the formation of the deposits'ore resource from both of its main sources:the mobilization of uranium from uranium-bearing minerals of the Athabasca Group sandstones and from the basement rocks of the basin.We adopted an alternative genetic model the way from their source to the basin reservoirs,which formed the resource of primary uranium of the initial stage,and 2)initially barren(after the depletion of the ore reserve of the Athabasca sandstones on basin fluids that leached uranium from uranium-bearing especially organic of multi-stage deposit formation with two spatially and temporally separated uranium sources:1)ore-forming basin brines of the Athabasca sandstones with an initially elevated uranium content during its mobilization from uranium-bearing rocks along the brine migration route on rocks of the basin basement with the formation of an'additional'uranium resource at subsequent stages with a rejuvenated ages.The deposition of primary uranium of the initial stage and'additional'uranium occurred in structural traps localizing the initial stage uranium,with a concomitant increase in the total reserves and ore grades of the deposits.After the depletion of the'additional'uranium in the basement available for mobilization,the formation of the ore resource of the deposits was completed.We adopted this conclusion as a hypothesis for a possible interpretation of the mechanism for the final completion of the geological history of the Athabasca basin deposits in the Mesoproterozoic Era,1 600-1 000 Ma ago.