Mineralization within the Curaçá Valley is hosted by a series of irregular-shaped, layered or zoned mafic-ultramafic intrusive bodies of Archean to Proterozoic age. Determination of genetic models for the deposition of copper has been complicated by the multiple episodes of metamorphism and deformation. These deposits are generally believed to be magmatic sulphide deposits and interpreted to be similar to those found in O’okiep, South Africa, Mayer and Barnes (1996).

The MCSA Mining Complex’s active mining and development projects are located within the Curaçá Valley mafic-ultramafic complex, located within the Curaçá high-grade metamorphic gneissic terrain, a part of the Salvador-Curaçá orogen, a northern extension of the Atlantic Coast Granulite Belt in the São Francisco Craton.

The mines are located in a high-grade metamorphic terrain, composed by gneiss and migmatite that were intruded by mafic, ultramafic and granitic rocks. The mafic and ultramafic intrusions are mainly composed by pyroxenite, melanorite, gabbro and serpentinite. Dibasic dykes and quartz veins crosscut the metamorphic and intrusive units.

The mafic and ultramafic units as well as the granitic intrusions are oriented north-south with steeply-dipping. The gneissic country rocks show fold-interference patterns and shear-zone structures suggesting several superimposed deformation events. The mineralized bodies have two preferential directions: N-S in the west part of the deposit and NW-SE in the east portion of the deposit.

Mineralized intrusive bodies are commonly affected by various alteration assemblages including potassic (phlogopite and K-feldspar) and calc-silicate (epidote and lesser garnet). Mineralized intrusive bodies generally trend 350° to 0° and dip from 50° to 90° to the west.

Mineralization is composed of copper sulphides in the form of chalcopyrite, bornite and rarely chalcocite that occur in three different styles: disseminated, remobilized and massive or brecciated. Minor ore minerals include pyrite, pyrrhotite and magnetite. The sulphides are heterogeneously distributed in the pyroxenite, melanorite, variably fresh or altered. The sulphides are present in variable concentrations in the form of lenses that trend N-S, dip steeply to the west and range from less than 1 m up to 20 m in thickness. The mineralized bodies occur in sharp contact with migmatites and generally conform to the main foliation of the host-rock. However, evidence of mineralized bodies that cross-cut the foliation are observed at the local scale. Strongly foliated sub-vertical anastomosing shears appear to break and transpose the flanks of folds.

Four genetic models have been presented, which has the most available information:
- sulphide segregation from mantle material;
- a hydrothermal model;
- metamorphic de-sulfidation from primary magmatic minerals; and
- orthopyroxene fractionation from a dioritic protolith.

If a sulphide segregation model is used for Caraíba, the mineralization is confined to sills derived from a tholeiitic magma that has undergone magmatic differentiation through crystal fractionation after emplacement. The absence of dunite and peridotite supports this interpretation as these crystals would have settled to the bottom of the sill and separated from the norite and pyroxenite layers. Above the peridotite and dunite, dense magma would form pyroxenite and norite with copper-rich zones, while less dense magma would result in barren gabbro, norite and anorthosite. Emplacement is thought to have occurred at mid- crustal levels.

The Pilar UG Mine has previously employed or currently employs the following mining methods: Sublevel Stoping and VRM. Sublevel Stoping, no longer planned for future development, is a method whereby the ore is blasted by fan drilling or in a parallel array. Ore is removed from the stope after it is blasted at a reinforced draw-point leaving an open stope. VRM is a method whereby the mine is divided into vertical zones of approximately 50m consisting of two operational levels – one for drilling and one for extraction. In the Pilar UG Mine, mined stopes are filled with cemented paste, comprised of mill tailings and approximately 4% cement by weight, to improve mine recovery and geotechnical stability.

Stope size within the Pilar UG Mine varies according to the geotechnical conditions at depth due to magnitude of induced stress and rock mass classification, but, on average, stopes have the following dimensions:
- in non-faulted zones: 10m width x 20m length x 35m height; and
- in fault zones, the size of stopes is reduced to: 10m width x 15m length x 35m height.

The Vermelhos UG Mine, currently under development, will utilize the SOS method due to the dips, plunge and thicknesses of the ore- bodies and competence of the host rock. Variations of this method are planned for the high grade central portion of the deposit to maximize mining recoveries through the utilization of CRF.

The Vermelhos UG Mine design entails mining panels of up to 35m in vertical dimension without the need of rib pillars to support the open excavation. The high grade areas will be mined using subhorizontal stopes. In these areas panel size has been reduced to 25m and will be filled in using CRF to maximize mining recovery and limit in-situ stress. Panel size and thickness has been constrained by the geotechnical design parameters as determined by geotechnical core logging and numerical modeling.

In both the Pilar UG Mine and the Vermelhos UG Mine operations, ore from production stopes is hauled via 30 tonne capacity trucks loaded by Load-Haul-Dump vehicles (“LHDs”), while waste rock from underground is hauled by 25 tonne capacity trucks to underground temporary storage (remuck bays) or to surface waste stockpiles.

The Surubim OP Mine is a past producing open- pit mine that is currently being re-opened for new open pit mining activity. Ore will be hauled by 35 tonne capacity production trucks from the bottom of the pit where it will be stored in temporary surface piles.

Ore from the Surubim OP Mine and the Vermelhos UG Mine will be loaded by conventional loaders and hauled by 70 tonne highway trucks to the Caraíba Mill, as performed in past producing open pit mines forming part of the MCSA Mining Complex.

The Caraíba Mill (MCSA) is of a conventional three-stage crush, milling and flotation design. Three-stage crushing is used to prepare a nominal 12.5mm crushed feed for the ball milling circuit prior to being sent to flotation for the recovery of copper-bearing minerals.

There are two primary crushing operations. Ore from open pit mining is delivered to the surface primary cone crusher, featuring a nominal capacity of 1,600t/h. Ore from underground mining is crushed underground by one of two primary jaw crushers with a nominal capacity of 400t/h each. Feed enters the primary crushing operations with maximum size of 48” and is discharged with maximum size of 10”.

The blended product of the primary crushing operations is transported via conveyors to an apron feeder stockpile with a capacity of 12,000 tonnes and fed to one of two secondary cone crushers (seven-foot (“ft.”) standard Symons; 1,400t/h of capacity each) set to 28mm aperture. The secondary discharge feeds two primary double deck screens, configured with 100mm gaps on the top and 40mm gaps on the bottom decks. Screen undersize passes to the collection conveyor while oversize material passes to the secondary crushers in an open circuit configuration.

The flotation circuit at Caraíba consists of a conventional rougher-cleaner-scavenger flotation process. The rougher circuit consists of three rougher banks divided into two stages of flotation (rougher, cleaner) with four cells in each unit operation. The first four cells of each bank produce a rougher concentrate that passes to the four cleaner cells. In practice, the concentrate of second rougher stage is returned to the head of the circuit to increase total rougher mass pull and retention time. Rougher concentrate is fed to the cleaner circuit and tails are fed to the scavenger circuit.

The scavenger concentrate from the cleaner cells is recycled back to the cleaner circuit. Scavenger concentrate recycles to the beginning of the recleaner circuit, while the tails of the recleaner circuit are pumped to the final tails thickener.

The final copper flotation concentrate is sent to one of two thickeners for dewatering prior to the filter press. Both concentrate thickeners are 2.4m in diameter and configured such that one is operating and one is on standby or undergoing routine maintenance. Water from the concentrate thickeners is recycled for plant process water. The thickener underflow is transferred to holding tanks that feed the filter press.

The Caraíba Mill’s primary concentrate shed, located adjacent to the filter press, has storage capacity for approximately 8,000 tonnes of final concentrate. The building has a concrete floor, steel siding and dimensions of 50m in length, 36m in width and an average height of 11m (peak height of 13m). A secondary, uncovered cemented floor storage area adjacent to the primary shed has capacity for an additional 6,000 tonnes of final concentrate (covered with canvas tarps). The dimensions of the uncovered storage area are 60m by 36m.