Type of uranium deposits in the Austrian Alps

The Permian uranium ore deposits in the Eastern Alps are of the sandstone type, but they show some special features as a result of the orogenic environment of their deposition and of posterior transformation. the deposition was conditioned by a post-Hercynian relief of the Alps: the deposits are localized in lagoonal basins, transverse to the Alpine east-west direction; the type of the deposits was originally tabular; the uranium is connected with organic matter. The Alpine orogeny displaced the original sites of sedimentation, so that now they are situated in different tectonic units, and produced folding, schistosity and an elongated shape of the ore layers in the east-west direction. A mineralogical-petrological comparison of the deposits discloses some differences in composition (uraninite, pitchblende, brannerite, thucholite, uranothorianite and sulphides of Fe and of Cu), which are characteristic for variations of sedimentation and metamorphism. The effect of metamorphism is remarkably low; however, it has a certain influence on the fabrics of the ore-bearing schists and therefore on their porosity; the latter controls the formation of secondary uranium minerals and probably also the possibility of extraction processes. The Permian deposits in Austria are comparatively small (several thousand tons U) and of low grade (about 800 ppm U on average), but some do represent economic prospects. (author)