华南花岗岩型铀矿床的成矿特征

本文综述我国华南近20个花岗岩型铀矿床的成矿特征,其中包括矿体形态、围岩蚀变、矿石成分、矿石结构构造、矿化类型和矿物共生组合等特征。研究结果表明,华南花岗岩型铀矿床可形成于花岗岩体内(内带型)或花岗岩体外(外带型),矿体形态可各异,主要受构造破碎带、地层层间破碎带、基性岩脉等形态的控制。矿石的矿物组成较简单,主要矿石矿物为沥青铀矿、铀石;外带型铀矿床的矿石成分较内带型铀矿床的复杂。该类型铀矿床中大多数矿物的粒度较细小,胶状、偏胶状结构发育。矿石结构构造以细脉浸染状、角砾状为主,这些均反映华南花岗岩型铀矿床成矿作用的低温、快速、浅矿源特征。矿床围岩的热液蚀变种类较多,但是蚀变程度大多较弱,铀矿化仅出现于面型热液蚀变区的某些部位,围岩的线型热液蚀变较强烈的地段常是富矿体的赋存部位。分布范围较大的面型围岩蚀变是在华南寻找花岗岩型铀矿床的重要标志。

MINERALIZATION FEATURES OF THE GRANITE-TYPE URANIUM DEPOSITS IN SOUTHERN CHINA

The present paper deals with the mineralization features of nearly 20 granite-type uranium deposits in Southern China. These features includ one in shape of ore bodies, host-rock alteration, mineralogical composition of ore, texture and structure of ore, mineralization type and paragenetic association of min- eral. It is shown that the granite-type uranium deposits in Southern China may be situated not only in granite bodies (i. e. interbelt-type), but also in an exocotact belts of granite bodies (i. e. exobelt-type). Shspe of ore bodies may be various and is essentially controlled by shape of fracture belts of host-rock and basic veins. Mineralogical compositions of ore are relatively simple. Pitchblende and coffinite are the most important original uranium minetals in this type of uranium deposits. The assemblage of gangue ore-minerals in exobelt-type uranium deposits is more complex than in interbelt-type uranium deposits. Most of minerals in ore are fine and Show gel texture. The ores of this type of uranium de- posits in form of veinlet-disseminative and brecciative. These features suggest tha mineralization of the granite-type uranium deposits in Southern China is characterized by low temoreture, rapid diposition and shallow ore-source. Kinds of host-rock alteration in this type of uranium deposits are many and varied. The degree of alteration, however, is rathr weack. Uranium mineralization in this type of deposits on- ly occurs in certain positions within area of hydrothermal face-type alteration of host rocks. Ore-rich bodies are generally located in the peition of strong line-type alteration of host rocks. Various face-type alterations of host rocks which are dispersed in a large limit are an important sign for search after the granite-type uranium deposits in Southern China.