摘要
国内砂岩型铀矿含矿砂岩中普遍可见蚀变钛铁矿与铀矿物空间关系密切的现象,是国内砂岩型铀矿研究领域全新发现。为探讨砂岩型铀矿含矿砂岩中钛铁矿蚀变特征及其聚铀过程,本文选择鄂尔多斯盆地北缘砂岩型铀矿为例,通过镜下观察、扫描电镜、电子探针等精细微区分析手段对研究区含矿砂岩中蚀变钛铁矿与铀矿物空间赋存关系及对铀富集机理开展研究。研究结果表明,鄂尔多斯盆地北缘砂岩型铀矿含矿砂岩中钛铁矿主要沿其边缘、裂隙或靠近其核部等部位蚀变形成白钛石、含铀白钛石或锐钛矿;铀石呈毛刺状、微细柱状围绕锐钛矿或白钛石生长,或在钛铁矿蚀变空洞中形成大量呈针织状的铀石集合体,反映出钛铁矿-白钛石/锐钛矿-含铀白钛石-含钛铀石-铀石的矿物组合递变顺序;砂岩型铀矿中蚀变钛铁矿可通过吸附-自催化还原的方式造成铀富集沉淀,并可将蚀变钛铁矿的聚铀过程分为钛铁矿蚀变-铀吸附预富集(Ⅰ)与蚀变钛铁矿自催化还原铀成矿(Ⅱ)两阶段,其中蚀变钛铁矿吸附铀衰变过程产生β与γ射线为蚀变钛铁矿自催化还原聚铀提供了条件。
Objectives: Detrital ilmenite and its altered minerals are closely related to uranium minerals which was widely found in sandstone-type uranium deposits in China and regarded as a completely new discovery. In order to study the ilmenite alteration and its process of uranium enrichment,sandstone-type uranium deposits in northern Ordos Basin was selected as an example.Methods: Petrographic observations,SEM-EDS,EMPA have been integrated to characterize the spatial relationship between altered ilmenite and uranium minerals and its mechanism of uranium enrichment.Results: The ilmenite is prevalent in ore-hosting sandstone and completely or partly altered into leucoxene and anatase along its edge and crack. Coffinite grows around anatase or leucoxene in the form of burrs and needles,or occurs in cavity of ilmenite alteration as knitted coffinite aggregate which reflects the mineral assemblages from ilmenite,leucoxene,uraniferous leucoxene,titaniferous coffinite,to coffinite.Conclusions: Uranium enrichment can be achieved by adsorption-autocatalytic reduction of altered ilmenite in sandstone-type uranium deposits. Uranium enrichment process of altered ilmenite in sandstone-type uranium deposits in northern Ordos Basin can be divided into uranium pre-enrichment with adsorption and uranium enrichment with leucoxene and anatase catalytic reduction,which is triggered by β and γ rays produced by the preenriched uranium with adsorption.
作者
丁波
刘红旭
张宾
李平
易超
王贵
DING Bo;LIU Hongxu;ZHANG Bin;LI Ping;YI Chao;WANG Gui(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing,100029;Geological Survey No.208,China National Nuclear Corporation,Baotou,Inner Mongolia,014000)
出处
《地质论评》
CAS
CSCD
北大核心
2020年第2期467-474,共8页
Geological Review
基金
国家科技部973计划项目(编号:2015CB453004)
鄂尔多斯盆地西北部砂岩型铀矿成矿作用与新区突破研究(编号:地D1911)的成果。
关键词
砂岩型铀矿
鄂尔多斯盆地
钛铁矿蚀变
白钛石与锐钛矿
吸附-自催化还原
Sandstone-type uranium deposits
Ordos Basin
Ilmenite alteration
Leucoxene and anatase
Adsorption-autocatalytic reduction
