华南铀成矿期及其特征的初步探讨

A TENTATIVE DISCUSSION ON URANIUM METALLOGENIC EPOCHS OF SOUTH CHINA AND THEIR CHARACTERISTICS

本文从地洼构造与成矿学的角度,论述了华南铀成矿期及其特征。根据162个铀矿石同位素年龄资料统计,把区内划分为四个成矿期。同时指出:晚侏罗世—早白垩世是华南比较重要的聚铀期,所形成的火山岩型铀矿,是地洼型构造-岩浆活化作用强烈阶段的产物;晚白垩世-老第三纪是华南铀矿的高峰期,矿床类型多,分布广,铀矿与该处地洼型构造-岩浆活化作用进入激烈与余动交替阶段密切相关;其他成矿期铀矿化相对较弱。最后,探讨了该区四个成矿期的相互关系。

In the light of geotectonics and metallogeny, this paper deals tentatively with the uranium metallogenic epochs and their characteristics. According to isotopic age data of 162 uranium ore samples, four metallogenic epoch can be recognized: (1) Late Devonian-Late Carboniferous (378-293Ma). It possesses 2.47% of the total reserves; the uranium deposits only occur in limited areas and are of small-size; it is therefore a metallogenic epoch of secondary importance and the deposit in Xuefengian granite(760Ma) can be taken as an example; (2) Late Jurassic-Early Cretaceous(149-100Ma): It possesses 27.6% and is a relatively important uranium metallogenic epoch. In Zhejiang-Jiangxi-Fujian region a series of volcanic type uranium deposits were formed which are products of strong diwa activities and belong mostly to hydrothermal type; (3) Late Cretaceous-Paleogene(98-23Ma). It possesses 66.68%, and is the most important period for uranium metallogenesis. In this epoch, lots of granite type, carbonate type, carboneous-siliceous mudstone type and part of volcanic type uranium deposits were formed. They are widely distributed, include a variety of types and possess over 80% of the total uranium ore deposits. The uranuim deposits were mainly associated with tile period when the evolution of the diwa entered the alternate active and tranquil stage and are mostly of complex geneses; (4)Neogene(21-1.5Ma): It possesses 3.18% and is also a less important metallogenic epoch. Represented by sandstone type uranium ores, the uranium deposits were related mainly to the groundwater or underground hotwater leaching (transformation) action when the diwa developed into the residual-mobility period.