INTEGRATED STRUCTURAL AND MINERAL ALTERATION STUDY OF THE ZONA URANIUM ANOMALY, NORTHEAST NIGERIA

The Zona U anomaly is a sandstone-hosted anomaly which is structurally controlled. Three main zones of mineral alteration are recognised, na mely a silicified zone; a red-brown ferruginised (hematite) zone and a brownish/yellowish-brown ferruginised (goethite) zone. These zones ar e typified by brecciation and kaolinitisation. The U mineralisation is epigenetic in origin and post-dates the main tectonic deformations. U ranium was leached from the Basement Complex granites and syngenetical ly disseminated in the sandstones. The ore was subsequently concentrat ed by percolating groundwater accompanied by the formation of kaolinit e and goethite at low temperatures. The main U mineral is autunite. (C ) 1998 Elsevier Science Limited.