准噶尔盆地北部黄花沟地区铀矿地质特征与成矿时代OA

Three types of uranium mineralization have been identified in sandstones of the Lower Cretaceous Tugulu group in the Huanghuagou area,northern Junggar basin:apatite-type,infiltration-type,and supergene-type.Detailed petrological,mineralogical,geochemical,and geochronological studies on these three types of uranium ore samples yield the following insights:1)In the apatite-type uranium ores,no independent uranium minerals are developed;uranium occurs as an isomorphous substitution in microcrystalline apatite,which exists as cement.A whole-rock U-Pb isochron age of 76.5±6.6 Ma was obtained,indicating that the mineralization occurred during the sedimentary hiatus between the Upper Cretaceous Honglishan formation and the Lower Cretaceous Tugulu group.2)In the"infiltration-type"uranium ores,coffinite is the main uranium mineral,spatially closely associated with plant fragments and pyrite.Uranium mineralization is located at the redox transition zone.U-Th-Pb chemical dating of uranium minerals yields an age of 11.5 Ma,suggesting that the"infiltration"uranium mineralization took place during the sedimentary hiatus between the Neogene Suosuoquan formation and the Paleogene Ulunguhe formation.3)The supergene-type uranium ores are the oxidized surface remnants of the"infiltration-type"uranium ores,in which uranium occurs as secondary uranium minerals(carnotite,tyuyamunite,and metatyuyamunite).Lead contents in these uranium minerals are below the detection limit,indicating that the supergene alteration occurred during the Quaternary.Based on the characteristics of the three uranium mineralization types,it is concluded that future uranium exploration in the Huanghuagou area should focus primarily on the"infiltration-type"uranium deposits.