Vein, uranium resources

Vein deposits constitute about 9% of world uranium resources. Major deposits include Jachymov (Czech Republic) and Shinkolobwe (Zaire). 

Much of the world s currently minable uranium is found in vein-like deposits of uncertain origin. They consist of three general types of unequal importance. Most important are unconformity-related deposits and vein-like deposits in meta-morphic rocks. Least important and probably of different origin are vein-like deposits in sedimentary rocks. The origin of all three types is a matter of much conjecture. Major unsolved genetic questions are the source of the uranium and its mode of transport, the source of the mineralizing solutions, the nature and role o f reductants and the control exerted on uranium deposition by structural and lithologic features of the host rocks. Unconformity-related deposits and vein-like deposits in metamorphics commonly occur in brecciated and foliated metamorphic rocks in stable Precambrian Shield areas. They contain about 24.4% of the Western world s reasonably assured 30 uranium resources. 

Vein-like deposits in sedimentary rocks are generally quite small and relatively low-grade, ranging from a few to several hundred tons of UsOs at grades of 0.05-0.25% UaOg. They represent less than ICKX) ton of the Western world s reasonably assured 30 uranium resources. 

Minerals of the different phases may occur in separate veins or as a single orebody. There is no formal information available on the uranium resources of that district, but it is likely that they are important by European standards. 

The Precambrian European province proper contains limited resources in vein-type deposits in northern Sweden and, again, a huge low-grade uranium natural stock in Cambrian black shales. Grades, under present market conditions, are not economic. 

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