陕西省华阳川铀铌铅矿床成矿流体特征及演化

Huayangchuan U-Nb-Pb deposit is proved to be a super-larger U-Nb-Pb deposit in China in recent years. Ore types of this deposit are unique. The uranium, niobium and lead are the major ore-forming elements. The uranium is positively correlated with niobium, but uncorrelated with lead. Uranium- niobium veins and lead veins are both symbiotic and differentiated in space. The whole deposit experienced multiphase and multistage mineralizations. The pegmatitic stage is early stage of the mineralization, during which pegmatite veins with potassic alteration formed. A small number of blomstrandite and pitchblende are found in these veins. The grades of uranium and niobium reach the industrial grade in part of pegmatite veins. The carbonatite stage is the principle metallogenic epoch. During early carbonatite stage, the aegirine augite-calcite-quartz veins and barite-quartz-calcite veins with biotite and minor aegirine augite formed. This is the main mineralization stage for the uranium and niobium. During late carbonatite stage, the zeolite-quartz-calcite veins formed, which is the main mineralization stage for the lead. We propose an integrated study on the characters of fluid inclusions of various minerals formed during different mineralization stages and located in different veins. Special efforts will be put into understanding the ore-forming physiochemical condition, characters, sources and evolution of the ore-forming fluid, mineralization ages and the mechanism of elemental paragenesis and separation in Huayangchuan U-Nb-Pb deposit.

华阳川铀铌铅矿床是我国近年来探明的一个超大型铀铌铅矿床，该矿床矿石类型独特，主要成矿元素为铀、铌、铅，其中铀与铌呈正相关，而铀与铅不相关，在空间上铀铌矿脉与铅矿脉既共生又有分异。该矿床成矿具有多期多阶段特征：成矿前期为伟晶岩期，对应的脉体主要为钾化的伟晶岩脉，其中含有少量的铌钛铀矿与沥青铀矿，部分脉体铀铌达到工业品位；主成矿期为碳酸岩期，碳酸岩期早阶段对应的脉体主要为含霓辉石方解石石英脉和含黑云母及少量霓辉石的重晶石石英方解石脉，该阶段是铀和铌的主要成矿阶段；而碳酸岩期晚阶段对应的脉体为含沸石石英方解石脉，该阶段是铅的主要成矿阶段。本项目主要研究不同成矿阶段不同矿脉的矿物流体包裹体特征，查明华阳川铀铌铅矿床成矿物理化学条件、成矿流体的性质及来源、确定成矿时代，探讨成矿流体演化及成矿元素共生分异机制。

华阳川铀铌铅矿床是我国近年来探明的一个超大型铀铌铅矿床，该矿床矿石类型独特，成矿作用复杂。本项目主要研究不同成矿期矿石的矿物学特征及矿物流体包裹体特征，取得了以下主要成果。.（1）查明了华阳川铀多金属矿床成矿元素的赋存特征。根据矿物组合、矿化类型及脉体穿插关系，华阳川铀多金属矿床成矿分为两期：早期成矿以含霓辉石碳酸岩为主，铀-铌矿化为主要标志；晚期成矿以含黑云母重晶石碳酸岩为主，铅矿化常叠加在早期铀-铌矿化上。该矿床最主要的矿石矿物为烧绿石、晶质铀矿、铀石、铀钍石和（含铀）长白矿等铀铌矿物及方铅矿，其次为褐帘石和独居石等稀土矿物及钍石。.（2）查明了华阳川铀多金属矿床的成矿流体特征。该矿床石英与方解石中流体包裹体类型有纯液相包裹体（I）、纯气相包裹体（II）、气液两相包裹体（III）、含液体CO2三相包裹体（IV）、含子矿物多相包裹体（V）等5种类型。成矿早期流体包裹体均一温度，220~380℃，盐度2.74~19.41wt%NaCleqv；成矿晚期流体包裹体均一温度160~260℃、盐度2.74~13.07wt%NaCleqv。碳氢氧稳定同位素结果表明，成矿流体中的碳来自深部地幔，成矿流体主要以岩浆水为主，成矿晚期有大气降水的加入。.（3）精确厘定华阳川铀多金属矿床的成矿时代。利用电子探针U-Th-Pb化学定年技术与LA-ICP-MS原位微区技术对华阳川铀-多金属矿床中晶质铀矿开展了定年工作，并获得了2组U-Th-Pb年龄。成矿早期为220Ma左右，成矿晚期为130Ma左右，因此，华阳川铀-多金属矿床经历了岩浆成矿及热液改造作用，早中生代铀-铌矿化发生于220Ma左右，是碳酸岩岩浆作用的产物；晚期铀铌活化-改造发生于130Ma左右，是热液流体活动对早期岩浆铀-铌矿化改造的结果。.本项目研究丰富了我国碳酸岩型铀矿床成矿理论，其研究成果为该矿床的合理开发利用奠定了理论基础。