鄂尔多斯盆地北缘砂岩型铀矿含矿砂岩中钛铁矿蚀变及其吸附-催化还原聚铀新机制  

Ilmenite Alteration and Its Adsorption-Catalytic Reduction for U Enrichment of Sandstone-hosted U Deposits in the Northern Ordos Basin,North China

作　　者：丁波 刘红旭[1,2] 王文全 邱林飞[1,2] DING Bo;LIU Hongxu;WANG Wenquan;QIU Linfei(National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing,Beijing 100029,China;Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]铀资源探采与核遥感全国重点实验室,北京100029 [2]核工业北京地质研究院,北京100029

出　　处：《铀矿地质》2025年第2期215-227,共13页Uranium Geology

基　　金：铀资源探采与核遥感全国重点实验室基金(编号:NKLUR-2024-ZD-001);中核集团基础研究项目(编号:地JCYJ2401);中国核工业地质局项目(编号:D2414)联合资助。

摘　　要：为了深入研究砂岩型铀矿中钛铁矿蚀变过程及其在铀成矿中的作用,文章以鄂尔多斯盆地北缘砂岩型铀矿为研究对象,综合利用微区分析技术对含矿砂岩中钛铁矿蚀变产物及其与铀矿物空间分布关系进行了详细剖析。结果显示,含矿砂岩中钛铁矿多沿边缘、裂隙及接近核部的位置发生了不同程度的蚀变,形成了白钛石或锐钛矿,局部可见草莓状和胶状黄铁矿。与蚀变钛铁矿密切相关的铀矿物主要为呈毛刺状或微细柱状产出的铀石,多围绕锐钛矿、白钛石产出,或以集合体的形式产于钛铁矿蚀变产生的孔隙中。依据铀矿物成分特征可将其分为含铀白钛石、含钛铀石(Ⅰ)与铀石(Ⅱ)两期,指示与蚀变钛铁矿有关的铀矿化形成可分为两个阶段。基于有光照与无光照条件下TiO_(2)聚铀实验综合研究,提出了蚀变钛铁矿的吸附-自催化还原的聚铀机制,结合含矿砂岩中钛铁矿蚀变过程剖析,将砂岩型铀矿中钛铁矿蚀变的聚铀过程分为两个阶段:①钛铁矿蚀变-铀吸附预富集阶段,强调在弱酸性环境下钛铁矿蚀变产物多孔白钛石对铀的吸附作用;②TiO_(2)自催化还原铀成矿阶段,认为吸附铀在衰变过程中产生的β与γ射线能为TiO_(2)催化还原反应提供类似光照条件,进而将成矿流体中的U(Ⅵ)还原为U(Ⅳ),为铀富集沉淀提供了一种催化还原的新途径,丰富了砂岩铀成矿机制。In order to investigate the alteration process of ilmenite in sandstone-hosted uranium(U)deposits and its role in U mineralization,this study focuses on the deposits in the northern Ordos Basin,with advanced micro-area analysis techniques.Detailed analyses were conducted on ilmenite alteration products in ore-bearing sandstones,examining their spatial relationships with U minerals.Research shows that ilmenite in ore-bearing sandstone have underwent different degree of alteration along its edges,in the fractures and its core and forming leucoxene or anatase and locally visible pyrite in shape of strawberry and colloid.U minerals closely related to altered ilmenite are dominated by coffinite,which grows around leucoxene or anatase in the form of burrs and fine columns,or forms a large number of knitted aggregates of uranium minerals in the altered cavities of ilmenite.The U mineral can be divided into uraniferous leucoxene(I),titaniferous coffinite(I),and uraninite(II),indicating that the formation of U mineralization related to ilmenite alteration can be divided into two stages.The adsorption-autocatalytic reduction mechanism of U accumulation of altered ilmenite in sandstone-hosted U deposits was proposed through experimental studies of TiO₂-facilitated U aggregation with and without lightening.Combined with the study of the alteration process of ilmenite in ore-host sandstone,the U enrichment mechanism of ilmenite alteration was divided into ilmenite alteration and pre enrichment of U by adsorption and autocatalytic reduction by TiO_(2)(leucoxene or anatase).The former emphasized the adsorption of porous leucoxene on U(Ⅵ)in a weak acidic environment.The latter believes that theβandγX-rays produced in the decay of adsorbed uranium can provide energy for the catalytic reduction reaction of TiO_(2)and reduce U(Ⅵ)in the ore-forming fluid to U(Ⅳ).This catalytic reduction provides a novel pathway for U precipitation which will enhance the understanding of U enrichment mechanisms in sandstone-hosted deposits.

关 键 词：砂岩型铀矿 钛铁矿蚀变 白钛石与锐钛矿 吸附-自催化还原 鄂尔多斯盆地 

分 类 号：P619.14[天文地球—矿床学]