The Arapiraca Project is underlain by folded, high-grade metamorphic rocks made up of monotonous suites of poorly differentiated gneisses/granites and to a lesser degree, schists. The main lithologies that host the mafic-ultramafic complexes are pink coloured, quartzo-feldspathic gneisses/granites. The mafic-ultramafic bodies occur as lenticular bodies striking north-south or northeast within the gneisses.
Copper-gold mineralization occurs mainly as disseminations and fracture filling within layered norite to gabbro complexes and is strongly concentrated within massive to semi-massive magnetite. The copper is associated, in decreasing order, with hypersthenites, magnetites, norites and gabbros. The sulphide minerals characteristic of the Serrote Deposit and Caboclo deposits are chalcopyrite, bornite, pyrite and pyrrhotite.
Copper was first discovered in the region following the completion of geological and airborne geophysical surveys by the Brazilian Geological Survey in 1977. In the early 1980's Vale followed up geophysical anomalies from these surveys with ground geophysical surveys, stream sediment and soil sampling to identify targets of interest. In 1982, a promising copper-gold-iron ore occurrence was discovered at Serrote da Laje (Rocky Ledge Hill). Vale completed 89 drill holes totalling 16,897 metres in two drilling campaigns in the 1980s and 1990s defining a copper-gold-iron ore deposit extending from surface to 300 metres in depth over a 500 metre by 800 metre area.
During 2007 and 2008, Aura Minerals completed 266 core holes totalling 57,557 metres on the Serrote Deposit. Total core drilling currently amounts to 74,456 metres in 355 drill holes. A total of 66 reverse circulation holes were also completed in 2008, primarily for condemnation of potential plant site, waste dumps, and tailings management facility in the area surrounding the Serrote Deposit. In addition, eight surface trenches were excavated and channel sampled in 2008.
At the Caboclo Deposit, 20 core holes were completed in 2008 totalling 4,303 metres. Total drilling currently amounts to 9,947 metres in 71 core holes. Ten surface trenches were also excavated and sampled in 2008.
Drilling is continuing at the Caboclo Deposit, and Aura Minerals anticipates an updated resource estimate for the Caboclo Deposit in 2010. In addition, the Company has identified several other regional copper and gold targets, and exploration is currently underway.