钱家店铀矿床含矿建造后生改造作用探讨:来自蚀变特征及地球化学的证据

Discussion on the alteration of the ore-bearing structure and subsequent transformation of the Qianjiadian uranium deposit:Evidence from alteration characteristics and geochemistry

基于开鲁盆地钱家店铀矿床含矿砂岩的偏光显微镜、扫描电子镜显微镜下观察以及元素地球化学分析,探讨了该砂岩型铀矿的形成过程。镜下观察结果显示,该矿床矿石中存在5种矿物蚀变作用类型:高岭石化、褐铁矿化、碳酸盐化、重晶石化和水云母化;钻孔伴生元素特征表明,钱家店部分铀矿体在初次形成后,可能又遭受后期流体叠加改造作用;元素迁移特征表明,矿区总体可能经历了两期不同性质的成矿流体,前期流体导致矿化砂岩的形成,后期流体在此基础上叠加改造,使铀再次富集成高品位铀矿石。综合前人研究资料,认为钱家店铀矿床经历三阶段成矿流体作用:第一阶段为同生沉积铀成矿;第二阶段为油气/热液改造叠加成矿;第三阶段为层间氧化铀成矿。

A sandstone-type uranium deposit has been found in the Upper Gretaceous Yaojia Formation in the Qianjiadian area of the Kailu Basin.To assess the origin of the uranium,the host sandstone was analyzed for element geochemistry through observation under a micropolariscope and scanning electronic microscope.This deposit contains five types of alteration:kaolinization,ferritization,carbonatation,baritization,and hydromicazation.The associated elements(U,etc.)in borehole samples indicate that the Qianjiadian uranium deposit was subjected to fluid epigenetic superimposed alteration after its initial formation.The element migration characteristics indicate that the ore deposit may have been subjected two phases of ore-forming fluid with different properties;in the early stage,the fluid led to the formation of mineralized sandstone,and in the later stage,the fluid was superimposed on the base ore,thereby enriching uranium to form a high-grade uranium ore.According to previous research data,the author suggests that the metallogenesis of the deposit occurred in three stages:synsedimentary metallogenesis,metallogenesis with oil field flow/hydrothermal fluid epigenetic superimposed alteration,and metallogenesis with superimposed alteration of oxo and uranous flow.