安徽庐枞火山盆地铀成矿作用研究

Study on Uranium Metallogeny in Lu-zong Volcanic Basin in Anhui

庐枞火山盆地位于长江中下游成矿带中段,中生代燕山期强烈的火山-潜火山岩浆作用孕育了盆地内的铀多金属成矿作用。研究表明,盆地内铀成矿是潜火山岩侵位后的地质事件,潜火山岩浆活动对铀成矿起主导作用。潜火山岩浆演化晩期的残余相富铀,在石英正长岩中形成晶质铀矿等高温矿物。结合岩石铀含量分析结果,笔者认为石英正长岩可构成铀源体,潜火山岩浆期后热液与铀源体相互作用,促成了成矿流体演化。早期流体以岩浆水为主,成矿期流体为岩浆水与大气降水混合的产物,成矿流体性质由碱性向酸性演化。温度降低及流体的混合作用,促使矿质在成矿有利空间卸载。

Lu-zong volcanic basin is located at the middle section of uranium metallogenic belt of middle and lower reaches of Yangtze.Volcanism and sub-volcanism in Yanshan stage of Mesozoic generated uranium multimetal metallogenisis in the basin.Uranium metallogenesis in the basin was a consequent geological event after subvolcaism.Magmatism of subvolcanism played leading role in the metallogenesis.Uranium is rich in residual hydrothermal solution in late stage of subvolcanic magmatism,and produces xenothermal minerals of uraninite etc in quartz syentie.Quartz syenite is considered as uranium source based on analytical results of uranium content.Steam hydrotheral solution in post subvolcanic magmatism reacted with uranium sources to promote evolution of metallogenic solution.In the early stage of metallogenesis,magmatic water was the main component of the fluid,and mixed with meteoric water in ore-forming stage.Mineralization fluid changed from alkaline to acid.Temperature descendent and fluids mixture caused the ore mattes to unload in favorable metallogenic spaces.