LAGOA REAL ALBITITE URANIUM DEPOSITS, BAHIA, BRAZIL

Discovered in 1977 during DNPM-airborne geophysical surveys, the Lagoa Real Uranium Province revealed the most important uranium concentrations in Brazil. Airborne magnetometric, gammaspectrometric and SLAR images allowed the interpretation of the several geological ambient at the Lagoa Real region helping significantly in the uranium distribution, elucidating the structure of the province. Almost twenty uranium anomalies have been discovered in an area of about 300 sq. km which culminated in the opening of the Cachoeira Mine open pit resulting in the production of yellow cake or 400t U₃O₈/year, since 1999.

The Cachoeira deposit as well as the whole province consists of an unique albitite type of mineralization representing an estimate resource of 90,000 tons U₃O₈ (measured) and 30,000 tons U₃O₈(indicated). Strongly folded, U-albitite lies within high- to medium-grade gneisses which also constitute a different type of uranium mineralization.

The anomalous, discordant shear belt in the middle of the Province was previously detected and confirmed by recent geophysical surveys. Relief is flat and does not reflect ground structure, in opposition of the creeks which follow a definite underground structure. The U/Th contour curves show persistent low values at the central, north-south trending U-deposits. However, observing carefully the U/Th data, it can be perceived that there is a zone with high U-values in respect to Th in contrast and surrounding low values eastward. There are numerous alignments of anomaly contrasts between the central zone of lower and higher U/Th ratios and the shapes of the U/Th contour curves which may indicate relative displacements caused by shear zones.

Total counting (K+Th+U) curves reveal interesting aspects, such as to discriminate the São Timoteo K-rich granite. It is clear that tectonic affected significantly the distribution of rock units. Each formation exhibited different patterns, as granitoid and regional gneiss. Lenticular bodies of iron formation form positive magnetic anomalies and albitites show higher U-pattern and low magnetic values contrasting with the surrounding gneisses.