GEOLOGICAL-GEOCHEMICAL CONDITION OF MINERALI-ZATION OF STRATA-BOUND CARBONATE URANIUM DEPOSITS IN CHINA

A lot of strata-bound carbonate uranium deposits occurred in the Proterozoic Era and Paleozoic Era.Their ore bodies are concentrative, shallow-buried and of the high tenor，so they are the spceial and important economic deposits in China.According to our investigations,the genetic geological-geochemical conditions may be summarized as follows;(1)In the carbonate formations, uranium abundance is higher within the ho-rizons which contain clay, carbonaeous materials and pyrite as absorbents or reduc-tors. They provided the material source and favourable reservoir for the uranium mineralization. (2)Tectonic-magma activities developed intensively from Indo-China to Yan-shan period in the”Diwa"regions where faults mobilized repeatedly and created fa-vourable spatial conditions for uranium activation and mineralization.(3)The mineralization underwent a long.multistage and polygenetic.Generally speaking, the more stages the mineralization underwent，the more distinctly the uranium evolution separated, and the more favourable for mineralization.The reg-ions where underwent the three main evolutional stages, i.e. geosyneline-plate-form一"Diwa" were favourable for mineralization.(4)The areas of fossil hydrothermal development, the terrestrial heat ano-maly and the section containing fossil karst are the places for the medium activa-tion of mineralization.Under certain geological structure and dry paleoclimatic condi-tions, uranium concentration in mineralization solution increased continuously and superimposed on the carbonate section where uranium was initially enriched, and this is often the place where uranium deposits occurred.