四川会理芭蕉箐地区铀矿化特征研究

Characteristics of Uranium Mineralization in Bajiaoqing Area,Huili,Sichuan

四川会理芭蕉箐地区位于上扬子成矿省西南缘,康滇地轴中段东部,是我国少有的元古宙铀矿区,其中1841铀矿点是本区最主要的铀矿点,区内地质条件复杂,研究程度较低。文章在前人研究基础上,通过对芭蕉箐地区1841铀矿点矿石的岩石学、矿物学、地球化学特征进行研究,取得了以下认识:铀矿化产出于构造与岩脉接触的构造蚀变带中,与断层和中基性岩浆岩脉关系密切;含矿岩系为中元古代的浅变质沉积岩及中基性岩脉,强烈亏损大离子亲石元素、富集高场强元素;铀矿物以团块状、脉状、网脉状的沥青铀矿、次生铀矿的形式产出于岩石碎裂带中;研究区岩石的U、Th含量明显高于其本底值,为铀矿化的形成提供了充足的铀源;研究区普遍发育的退变质作用与后期的碱交代促进了铀的富集。铀矿化具有明显的构造-热液叠加改造的特征,属于热液成因铀矿。

Bajiaoqing 1841 uranium occurrence is located at the eastern part of midlle Kangdiang geotectonic axis in the southwest margin of the Upper Yangtze metallogenic province.Bajiaoqing is one of the rare Meso-Proterozoic uranium mineralization area in China.Geological conditions is quite complex and seldom the research was conducted in Bajiaoqing area.Based on the previous studies,the petrological,mineralogical and geochemical characteristics of uranium occurrence 1841 were studied and some new results were finished.The Mineralization was found in the alteration zone which is closely related to the fracture structure and magmatic dike.The ore-bearing rocks are Meso-Proterozoic lightly metamorphosed sedimentary rock.The intermediate-basic dikes were formed in the early stage of an intracontinental rift and severely deficient in LILE and enriched with HFSE.Uranium ores are composed of pitchblende and secondary uranium minerals which were produced in the rock fragmentation zone in the crumb,veined,stock work.The U-Th content of rocks in uranium mineralization area is obviously higher than the background value,which provided a sufficient uranium source for the formation of uranium mineralization.The uranium mineralization is characterized by obvious structural-hydrothermal superimposition and reformation.Uranium mineralization is closely related to retrometamorphism and alkali metasomatism,which belongs to hydrothermal genesis.