【摘要】 华南是我国重要的花岗岩型铀成矿区,印支期-燕山期花岗岩是最主要的产铀花岗岩。广西北部形成于新元古代的摩天岭岩体是我国目前已知的最古老的产铀花岗岩体之一。前人对华南印支-燕山期花岗岩的铀成矿作用研究较深入,但对以摩天岭岩体为代表的新元古代古老花岗岩的铀成矿作用研究程度较低。本文以摩天岭花岗岩体为对象,进行了岩石学、地球化学、年代学及其铀矿成矿特征和规律的深入研究,取得以下认识:1)摩天岭岩体规模巨大,相带分布明显,内部相带和过渡相带发育,岩性主要为黑云母花岗岩、二云母花岗岩和含电气石二云母花岗岩,花岗岩体具有富硅富碱、铝过饱和、钾大于钠的特点,属S型花岗岩; 2)摩天岭岩体形成于850～760Ma之间的新元古代; 3)摩天岭岩体铀成矿潜力巨大,铀矿化以铀-绿泥石型和铀-硅化带型为主,铀-绿泥石型的代表矿床——达亮矿床形成于360～401Ma,是加里东期区域变质及构造活动共同作用的结果;铀-硅化带型铀矿的代表——新村铀矿形成于47Ma,是喜马拉雅期伸展构造作用下构造-热液活动共同作用的结果; 4)摩天岭岩体中铀矿床的铀源来自于元古界四堡群、丹州群和摩天岭岩体本身;成矿流体主要来源于大气降水,同时有深部流体的参与;热源主要与加里东期区域变质作用和喜马拉雅期伸展背景下的构造作用关系密切; 5)摩天岭岩体铀成矿经过了新元古代铀预富集、加里东晚期到海西早期的区域变质-构造热液成矿作用、喜马拉雅期的构造热液成矿作用等几个阶段,形成了类型丰富、规模较大的铀矿床,铀找矿潜力巨大。更多还原

【Abstract】 South China is an important granite-type uranium metallogenic area in China. Indosinian-Yanshanian granites are the most principal uranium-producing ones and the Neoproterozoic Motianling pluton in northern Guangxi is one of the oldest known uranium-producing granites in China. Uranium mineralization of Indosinian-Yanshanian granites in South China has been studied thoroughly,but that of Neoproterozoic ancient granites represented by the Motianling intrusion is rarely done. In this paper,what has been studied in detail include the petrological,geochemical,chronological and uranium metallogenic characteristics of the Motianling granite and its uranium mineralization regularity. The results are as follows: 1) The Motianling rock mass is large in scale,with obvious distribution of facies belts,developed internal and transitional facies belts. Its lithology is mainly biotite granite,two-mica granite and tourmaline-bearing two-mica granite. These granites have rich silicon,rich alkali,supersaturated aluminum and potassium larger than sodium,and thus can be ascribed to S-type granites. 2) The Motianling granites were formed in the Neoproterozoic between850 Ma and 770 Ma. 3) The Motianling granites have great uranium metallogenic potential and abundant uranium mineralization types,mainly uranium-chlorite type and uranium-silicified belt type. The representative of the uranium-chlorite deposit,Daliang deposit,was formed in 360 ～ 401 Ma by the combined action of Caledonian regional metamorphism and tectonic activities. The Xincun uranium deposit,the representative of the uranium-silicified belt type uranium deposit,was formed at 47 Ma,being the result of the combined action of tectonic-hydrothermal activities under the extensional structure of Himalayan. 4) The source of uranium deposit in the Motianling granite comes from the Proterozoic Sibao Group,Danzhou Group and the Motianling granites themselves; the ore-forming fluids mainly come from meteoric precipitation,but also involve deep-seated fluid; The heat source is mainly closely related with Caledonian regional metamorphism and the tectonization in the regional spreading process of Himalayan. 5) Uranium mineralization in the Motianling granites underwent Neoproterozoic uranium preconcentration, regional metamorphism-tectonic hydrothermal mineralization from Late Caledonian to Early Hercynian,and Himalayan tectonic hydrothermal mineralization. After these multiple metallogenic stages,a large scale of uranium deposits with abundant types have been formed with prospecting potential.更多还原