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    若尔盖铀矿田成矿地质条件及资源潜力分析

    An analysis of metallogenic conditions and resource of the Zoige uranium deposit

    • 摘要: 提要:若尔盖铀矿田是中国重要的碳硅泥岩型铀矿产地,位于南秦岭铀成矿带西段。矿床群产于下志留统羊肠沟组、塔尔组和拉垅组一套浅变质硅-灰岩系中,并严格受岩性、构造和地球化学环境控制。本文在前人勘查和研究工作的基础上分析了矿田铀矿地质特征、成矿地质条件、成矿机理和铀资源前景,并重点对铀矿石的常量元素、微量元素、稀土元素、铀-钍配分和矿物硫、氢、氧同位素特征进行了研究。初步认为:与铀矿化密切相关的硅质岩生成于热水沉积环境,成矿早期的沉积、变质作用形成了相对广泛的初始铀富集,成矿中、晚期在特定的物理-化学环境下,以大气降水为主源的中低温成矿流体对围岩和初始铀富集体进行了强烈改造,最终形成了以热液改造型为主的工业铀矿化。成矿物质主要来自围岩和初始铀富集体,而部分壳幔含矿物质的介入和岩浆岩的热贡献对铀的后期富集成矿及加大成矿深度起到一定作用。矿田U-Pb同位素年龄测定结果具有多达近10组的铀成矿期,从而增加了矿田的铀成矿几率和铀矿的富集程度。资料分析显示,虽然该区资源/储量规模已达大型铀矿勘查基地条件,但其资源前景和发展潜力远未查明,建议应适时开展系统勘查,以最大限度地开发其资源潜力。

       

      Abstract: Abstract:The Zoige uranium deposit is located in the west sector of southern Qinling ore belt. The ore deposit occurs in a set of epimetamorphic siliceous limestones in Lower Silurian Yangchanggou Formation (S1y), Ta’er Formation (S1t) and Laqlong Formation (S1l), and the ore deposit is strictly controlled by lithologic character, structure, deep hot water and geochemical environment. On the basis of previous research results, the authors studied characteristics of major elements, trace elements, rare-earth elements, sulfur isotope and hydrogen, oxygen, carbon isotopes of siliceous limestone in the ore field, and reached the conclusion that siliceous rock closely related to uranium mineralization was formed in a hot water sedimentation environment, extensive ore-forming source was formed during early sedimentation and metamorphism, and the low temperature mineralization fluid was a very important factor for uranium concentration and mineralization extension towards the depth. U-Pb isotopic ages demonstrate that this area has over ten uranium metallogenic periods, thus increasing the field uranium mineralization probability in the ore district. It is held that the uranium resources are so rich that there exists a good developmental prospect in this area.

       

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