江西相山矿田铀成矿的特征、演化及启示

The characteristics,evolution and enlightenment of uranium mineralization in Xiangshan ore-field,Jiangxi Province

寻找富大硬岩型铀矿一直以来面临挑战。据深大断裂-临界水耦合成矿机制等新认识,重新梳理相山矿田火山杂岩铀成矿的主要特征,结合其他富大热液矿床的研究,探索富大热液矿床的共同规律。富大热液矿床多具有以下特征:首先,常有深大断裂与岩浆杂岩隆起组合的“一刀加一饼”的外形,深大断裂这“一刀”具多期次活动特点,因降压、升温、聚水,改变了周边区域的物理化学环境,驱动成岩成矿相关的物质运移、相变等,从而控制着与成矿密切相关的赋矿岩浆杂岩的形成、热液蚀变和铀成矿期次。其次,有3个主要构造层及与其相对应的三阶段式演化。再次,有2个主成矿期,早期高温成矿期(在相山铀矿田是115±0.5 Ma)与岩浆杂岩形成相关,而晚期低温成矿期(在相山铀矿田是98±8 Ma)与控盆断裂活动、盆地脱水相关,2期成矿叠加是富大矿体形成的必要条件。上述富大热液矿床的特征主要体现为具有“一刀加一饼”外形的、由深大断裂与岩浆杂岩隆起组成的构造岩性组合,其形成机制实质上仍是深大断裂多期活动成岩成矿。这些认识可能给中国富大热液铀矿成矿和找矿研究带来一些启示。

Finding the rich and large hard rock type uranium deposits has always been a challenge.Using some new ideas to study the characteristics of some known rich and large uranium deposits and to explore constantly their mineralization process may bring some new understanding.According to the metallogenic mechanism by coupling the deep and large fault with the critical water,this paper has re-analyzed the characteristics and metallogenic process of uranium deposit in Xiangshan magmatic complex uplift,and explores the common law of the rich and large hydrothermal deposit by combining with the research of other rich and large hydrothermal deposits.These rich and large hydrothermal deposits have the following characteristics:First of all,there is often the shape of"one knife overlying one cake"formed by combining the deep and large fault with the magmatic complex uplift.This deep and large fault with the shape of a knife is a multi-stage activity.Due to the pressure reduction,temperature rise and water accumulation,this fault will change the physical-chemical environment of the surrounding area,which drives the material migration and phase transformation related to the mineralization,so as to control the formation of the magmatic complexes uplift,hydrothermal alteration and uranium mineralization stages.Secondly,there are usually three main tectonic layers and their corresponding three-stage evolution.Thirdly,there are alway two main mineralization stages in the rich and large hydrothermal deposits.The early high-temperature mineralization stage(115±0.5 Ma in Xiangshan ore field)is related to the formation of magmatic complex,while the late low-temperature mineralization stage(98±8 Ma in Xiangshan ore field)is related to the basin-controlling fault activity and basin dehydration.The superposition of the two stages of mineralization is a necessary condition for the formation of rich and large ore bodies.These above characteristics are mainly reflected in the structural and lithologic combination composed of deep and large faults and magmatic complex uplift with the shape of"one knife overlying one cake",which their formation mechanism is still the multi-stage diagenesis and mineralization by activity of the deep and large faults in essence.These understandings may bring some enlightenment to the study of mineralization and prospecting of rich and large hydrothermal uranium deposits in China.