Structural geometry of uraniferous rocks in the Umra area, Aravalli Supergroup, India

Uranium mineralization occurs in Palaeoproterozoic metasediments of the Aravalli Supergroup in the Umra area, Udaipur district, Rajasthan, India. The host rocks for mineralization were deposited in a shallow marine shelf type environment over an Archaean basement gneiss, the Banded Gneissic Complex. A reducing environment at the depositional site, associated with large-scale biogenic activity, was responsible for precipitation of uranium bearing minerals. Our structural analysis shows that the rocks of the mineralized area have been involved in four phases of deformation. The carbonaceous phyllite unit near Umra shows a 'mirror-image' pattern, resulting from the superposition of upright F2 folds with NE-SW striking axial planes over early (F1) isoclinal folds. The exploration block is located on one limb of the regional F2 fold.