龙首山成矿带钠交代型铀矿床关键控矿因素研究——以芨岭铀矿床为例

Key Control Factors of Na-metasomatism Uranium Deposits in Longshoushan Metallogenic Belt:A Case Study of Jiling Uranium Deposit

钠交代型热液铀矿床是龙首山成矿带重要的工业铀矿类型,以芨岭和新水井两个矿床为代表。芨岭铀矿床位于龙首山成矿带中段,是我国北方钠交代型铀矿床的典型代表。文章基于野外工作实践及芨岭钠交代型矿床最新勘查和研究成果,重点对芨岭关键控矿因素进行系统梳理和分析。芨岭矿床矿体的产出与定位受断裂、岩性界面和钠交代岩“三位一体”联合控制。北西西向的马路沟断裂带整体控制了矿床、矿(化)点产出与分布;近东西向断裂与北西西向断裂形成较多的构造夹持区,单个矿体呈东西向产出,且严格受东西向压扭性构造控制,东西向构造与成矿最为密切,为含矿构造。岩性接触面是构造薄弱面,有利于后期构造的叠加发育及成矿热液的运移。此外,岩性接触面两侧岩性差异较大,形成地球化学障,利于成矿热液中铀的沉淀、富集与保存。芨岭铀矿床铀矿化均产出于钠交代岩之中;龙首山成矿带中段钠交代型铀矿的形成和分布均受钠交代岩所控制;钠交代岩即是主要控矿因素,又是重要的找矿标志。

Jiling uranium deposit is an important one in the Qilian-Longshuoshan uranium metallogenic belt in Northwest China, and it is also one of the most typical sodium metasomatic uranium deposits in northern China. Based on the field geological work and the latest exploration and research results of the Jiling sodium metasomatic deposit, the key controlling factors of the Jiling sodium metasomatic deposit were systematically sorted out and analyzed in this paper. The Jiling Na-metasomatic deposit is mainly controlled by faults,lithologic interfaces and Na-metasomatic alterations. The WNW trending Malougou fault zone controls the occurrence and distribution of Na-metasomatic deposits and mineral occurrences, which is the ore-controlling structure. Nearly EW trending faults and WNW trending faults form more structural gripping areas, and a single orebody occurs in the EW direction, it is strictly controlled by the EW-trending compressive-torsional structures, and the EW-trending structure is most closely related to mineralization. It is the ore-hosting structure. Lithological interface is a weak structural surface and easy to form structural fissures due to the late tectonic activities. What’s more, the lithologic differences on both sides of the lithologic interface usually form high difference geochemical barriers, therefore, the physicochemical environment formed by lithological interface is conducive to the migration, unloading, enrichment and precipitation of Na-metasomatic type uranium ore-forming materials. Sodium metasomatic uranium mineralization in Longshoushan metallogenic belt occurs in sodic metasomatite without exception;the formation and distribution of sodium metasomatic uranium deposits are controlled by sodic metasomatite;sodium metasomatic rocks are the main controlling factors and it’s also an important prospecting indicator.