Statistical Distribution of the Uranium Resources in the Variscan Hydrothermal Uranium Deposits of Western Europe

A database of European granite-related uranium deposits containing the average grade and resources for individual ore deposits has been constituted from the resources declared by the countries available in the literature and in the UDEPO website of the IAEA. This database was used to evaluate the statistical distribution of deposit size and grade and of the total uranium resources per region. It is shown that most deposits sizes expressed as their uranium content (in t U) are distributed according to a log-uniform distribution. However, the smallest deposits in France and Spain/Portugal fall off this general pattern, together with the largest uranium deposit known in Europe, the Niederschlema deposit, located in south-eastern Germany. These smallest outliers correspond to near surface or skimmed deposits, while the biggest Niederschlema deposit was mined down to a depth of up to five times deeper than most other uranium deposits known in Europe because their mining was not driven by the same economic constraints. It is observed that the total resources defined as the cumulative resources of deposits ranked in increasing size are also log-uniform distributed. Experimental distributions are fit to theoretical log- uniform laws in order to predict the expected largest deposit and the expected total resources in Europe. This statistical approach shows that additional undiscovered uranium resources estimated to be over 40,000 t U can be expected in Europe, and probably more if deposits are mined to depths greater than 400 m. (author)