九龙嶂火山盆地铀矿成矿条件及找矿方向

Uranium metallogenic conditions and prospecting direction in Jiulongzhang volcanic basin

九龙嶂火山盆地位于南岭成矿带安远热隆的西部 ,面积 1 2 0余km2 ,盆地基底为加里东期至燕山期花岗岩和元古界至古生界沉积岩、变质岩 ,盖层为上侏罗统鸡笼嶂组火山岩系地层。盆地基底岩石碱交代蚀变明显 ,火山期后浅成 超浅成侵入岩浆活动频繁 ,火山构造与区域构造多处交接复合并形成派生构造 ,使盆地具有良好的、利于铀矿形成的“源 运 聚”条件。盆地西部半天塘至银坑山一带 ,火山构造发育 ,岩性复杂多变 ,热液蚀变较强烈 ,矿化信息丰富 ,是找矿方向和勘查重点所在。盆地西部银坑山铀矿点 ,受发育于流纹质熔结凝灰岩中的近SN向碎裂带控制 ,地表浅部矿化良好 ,具有岩浆热液体系的顶部矿化蚀变组合特征 ,深部有明显延伸的矿化显示 。

The Jiulongzhang volcanic basin with an area of about 120 km 2 is situated in the western part of Anyuan upwelling structure,Nanling uranium metallogenic belt.The basement of the basin consists of Caledonian-Yanshanian granites and Proterozoic-Paleozoic sedimentary and metamorphic rocks.The cover of the basin is composed of volcanic series of Jiulongzhang Formation,Upper Jurassic.Basement rocks experienced obvious alkaline metasomatism.Post-volcanic hypabyssal-superhypabyssal intrusive activities took place frequently.The multiple intersection and mergence of volcanic and regional structures led to the fomation of subsidiary structures making the basin having favourable source-migration-concentration conditions for uranium ore-formation.The western part(Bantiantang-Yinkengshan area)is characterized by intense development of volcanic structures,complicated and heterogeneous lithology,strong hydrothermal alteration and a great amount of mineralization information being the main prospecting direction and exploration target.The Yinkengshan uranium occurrence in the west of the basin is controlled by SN-trending fractured zone in rhyolitic ignimbrite.Surface uranium mineralization shows features of top mineralization-alteration assemblage of magmatic-hydrothermal system and there exists message indicating the extension of uranium mineralization towards the deep.So,the occurrence may be regarded as the first-round exploration target of the Jiulongzhang volcanic basin.