纳米比亚湖山铀矿地质特征、控矿因素及其成因探讨

湖山铀矿位于泛非期达马拉造山带的南部中央区带内,构造以NNE-SSW向穹窿和断裂为主。矿区内地层自老至新为艾杜西斯组、可汗组、罗辛组、楚斯组、阿兰蒂斯组、卡里比布组和卡塞布组,侵入岩为寒武纪至晚新元古代花岗岩类。晶质铀矿为主要原生矿石矿物。后期热液叠加导致了铀石、硅钙铀矿和黄硅钾铀矿等热液矿物的形成以及高岭土化、蛇纹石化、绢云母化和绿泥石化等蚀变作用。矿床的形成受矿区地层、岩浆岩和构造联合控制,矿化仅发生于D和E型花岗岩内。矿化岩体呈席状侵入于NNE-SSW向湖山背斜转折端和翼部高应力区域,赋存于罗辛组与可汗组不整合接触带及其上部的罗辛组,少量赋存于楚斯组内。矿区内构造-岩浆事件可划分为四个阶段,铀成矿作用与第四阶段构造-岩浆事件密切相关,含矿D和E型花岗岩为后造山伸展环境下富铀阿巴比斯基底重熔形成。

Geological characteristics,ore-controlling factors and genesis analysis of Husab uranium deposit in Namibia

Husab uranium deposit is located in south central zone of Damara orogenic belt, which was formed during Pan-African period and is characterized by the development of NNE-SSW trending domes and faults. The stratigraphic sequence in Husab uranium deposit from old to new consists of Etusis, Khan, RÖssing, Chuos, Arandis, Karibib and Kuiseb formations and the intrusive rocks are composed of Cambrian to Late Neoproterozoic granites. Uraninite is the main primary ore mineral. Later hydrothermal superimposition resulted in the formation of hydrothermal ore minerals such as coffinite, uranophane and boltwoodite, and also led to hydrothermal alteration, e.g. kaolinization, serpentinization, sericitization and chloritization. Uranium mineralization is jointly controlled by stratigraphy, intrusive rocks and structures within mine area. Mineralization only occurred in D-and E-type granites which mainly intruded into hinge and high stress zone of the Husab anticline and occurred mainly in unconformity interface between Khan and RÖssing formations and in RÖssing Formation, with only small amount in Chuos Formation. Tectono-magmatic events within mine area can be divided into four stages, among which uranium mineralization took place in the forth stage. The D-and E-type granites closely related to uranium mineralization are formed from partial melting of uranium-rich Abbabis basement in a post orogenic extensional environment.