纳米比亚白岗岩型铀成矿作用评述  

A Review of the Mineralization of Leucogranite‑Type Uranium Deposit in Namibia

作　　者：陈金勇[1,2] 范洪海 何德宝 耿瑞瑞[1] 王生云 陈东欢 陈旭[1] CHEN Jinyong;FAN Honghai;HE Debao;GENG Ruirui;WANG Shengyun;CHEN Donghuan;CHEN Xu(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology Beijing Research Institute of Uranium Geology,Beijing 100029,China;State Key Laboratory of Nuclear Resources and Environment East China University of Technology,Nanchang,Jiangxi 330013,China;CNNC Geology&Mineral Technology Group Co.,Ltd,Beijing 100029,China)

机构地区：[1]核工业北京地质研究院中核集团铀资源勘查与评价技术重点实验室,北京100029 [2]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [3]中核地矿科技集团有限公司,北京100013

出　　处：《世界核地质科学》2023年第4期889-907,共19页World Nuclear Geoscience

基　　金：中核集团集中研发项目“罗辛铀矿及外围资源扩大研究”;中国铀业有限公司与东华理工大学联合创新基金项目(编号:NRE2021-04)共同资助。

摘　　要：纳米比亚铀矿资源十分丰富,被誉为“战略金属储备库”,其中白岗岩型铀矿更是铀矿中最主要的类型,成矿潜力巨大,主要受构造、岩性和地层控制,部分矿床还受后期热液活动的叠加改造。在6类白岗岩及Salem型等花岗岩中,赋铀白岗岩仅为D型和E型两种白岗岩,主要是由于非矿化白岗岩或花岗岩形成于D_(3)期间或之前,而矿化白岗岩是由富铀基底深部重熔而形成的,产于D_(3)构造变形及穹隆构造之后,两者的物质来源不同。千岁兰深大断裂是白岗岩型铀矿活化迁移的通道,穹隆、NNE向韧性剪切带及褶皱等构造膨大变异部位为矿化白岗岩的侵入提供了充足的就位空间。另外,赋铀白岗岩常以网脉状、脉状侵入罗辛组大理岩和可汗组片麻岩、卡里毕比组大理岩和卡塞布组黑云母片岩,在侵入过程中,岩浆与罗辛组或卡里毕比组大理岩发生脱碳反应,致使二氧化碳含量增加,岩浆易于沸腾,促进铀沉淀富集。就后期热液而言,在靠近断裂破碎带等部位,矿化白岗岩明显发生强烈的热液蚀变,使得铀矿化品位显著增高,可见局部存在后期热液的叠加富集。因此,白岗岩型铀矿的成矿作用大体划分为原始岩浆的结晶分异作用、后期热液的叠加富集作用和表生氧化淋积作用3个期次。Namibia is very rich in uranium resources,known as the“strategic metal reserve”,among which the leucogranite⁃type uranium deposit is one of the most important uranium deposits,with huge metallogenic potentiality,mainly controlled by structure,lithology and stratum,some deposits also exist late hydrothermal superimposition enrichment.Metalization are of lithological specialization which means only type D,type E leucogranite are mineralized and the other four types of leucogranite and Salem⁃type granite are barren as a result of the differences of formation age.Type D,type E leucogranite are U⁃rich because they formed after D_(3) deformation associated with the partial melting of uranium rich baserock,while the other types formed before the D_(3) formation without the participation of uranium baserock melting.The ore bodies mainly occur in ductile shear zone with predominant direction of NNE,corner of fold,margin of dome and structural variation position(twist or expand),which provide abundant space for uranium mineralization.At the same time,Welwitschia regional faults act as the transportation way of uranium.In terms of strata,mineralized leucogranite presented as veins and network veins intruded into Rössing formation,Khan formation,Chuos formation,Karibib formation(with respect to the loss or reduction of Rössing formation).The decarbonization reaction between marble and magma resulted from the creasing of the contents of CO_(2) in the ore forming fluids,led the magma boiling easily,which was profitable for the precipitation of uranium.The mineralization of the leucogranite⁃type uranium deposit can be divided into three stages:crystallization differentiation of protomagma,superimposed reformation of late hydrothermal fluid and supergene oxidation.

关 键 词：白岗岩型铀矿 铀成矿作用 成矿机理 达马拉造山带 纳米比亚 

分 类 号：P598[天文地球—地球化学] P619.14[天文地球—地质学]