Chen Niannan, Li Mangen, Mao Guangzhen, Tang Xiangfei, Wu Shengming, Duan Jianbing, Guan Baowen, Fan Pengfei, Jin Rui, Wang Jin
School of Earth Sciences, East China University of Technology, Nanchang, Jiangxi Province 330013, China.
State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang, Jiangxi Province 330013, China.
ACS Omega. 2024 Nov 28;9(49):48681-48696. doi: 10.1021/acsomega.4c07825. eCollection 2024 Dec 10.
The Chepaizi Uplift, situated on the western edge of the Junggar Basin in northwestern China, has recently become a significant target area for in situ leach sandstone-type uranium exploration. The Neogene Shawan Formation, a newly identified uranium-bearing layer, has gained considerable attention for its potential. This study utilizes scanning electron microscopy (SEM), X-ray powder diffraction (XRD), whole-rock geochemistry, and electron probe microanalysis (EPMA) of uranium minerals. Combined with sedimentological and tectonic background analysis, these methods were applied to investigate geochemical characteristics and uranium mineralization processes. The sandstones in the Shawan Formation are primarily lithic sandstone and subarkose, with the provenance dominated by felsic rocks from the upper crust. Coffinite is the predominant uranium mineral, accompanied by titanium-uranium oxides and minor amounts of pitchblende. Coffinite appears as colloidal coatings around framboidal pyrite, in short-prismatic aggregates corroding albite, and as banded structures within calcite cement. Elemental ratios indicate that the Shawan Formation's paleo-hydrological environment was arid, continental, and brackish, with paleo-redox conditions reflecting a hot, dry climate. Uranium mineralization occurred in two stages: initially, uranium-containing oxygenated waters migrated laterally across slope zones, forming a redox transition zone and resulting in the pre-enrichment of uranium. Subsequently, hydrocarbons migrated along faults and unconformities, leading to secondary reduction of the interlayer oxidation zone and resulting in uranium enrichment and mineralization at the interface of grayish-green and gray sandstone layers.
车排子凸起位于中国西北部准噶尔盆地西缘，最近已成为原地浸出砂岩型铀矿勘查的重要目标区。新近系沙湾组是新发现的含铀层，因其潜力而备受关注。本研究利用扫描电子显微镜（SEM）、X射线粉末衍射（XRD）、全岩地球化学以及铀矿物的电子探针微分析（EPMA）。结合沉积学和构造背景分析，应用这些方法来研究地球化学特征和铀矿化过程。沙湾组砂岩主要为岩屑砂岩和亚长石砂岩，物源以来自上地壳的长英质岩石为主。沥青铀矿是主要的铀矿物，伴有钛铀氧化物和少量沥青铀矿。沥青铀矿呈胶状包裹体围绕莓球状黄铁矿，呈短柱状集合体腐蚀钠长石，以及呈方解石胶结物中的条带状构造。元素比值表明，沙湾组的古水文环境为干旱、大陆性和微咸水，古氧化还原条件反映出炎热干燥的气候。铀矿化发生在两个阶段：最初，含氧含铀水横向穿过斜坡带迁移，形成氧化还原过渡带，导致铀的预富集。随后，烃类沿断层和不整合面运移，导致层间氧化带的二次还原，从而在灰绿色和灰色砂岩层界面处形成铀的富集和成矿。
