The Antas orebody is located close to the southern border of the Estrela Granite Complex and is hosted predominantly by mafic metavolcanic rocks of the Parauapebas Formation (Gão Pará Group), which is cut by gabbro dikes.

Host rocks consist of felsic – mafic volcanics, with between a few per cent and 40 per cent deformed quartz, plus sulphide veins. Associated alteration shows a moderate to strong zonation from the surrounding unaltered country rock into the most strongly mineralised portions of the deposit. A broad outer halo consists of chlorite, biotite, weak silicification, and fine-grained magnetite and pyrrhotite. Where veins are particularly dense, the envelopes can coalesce, resulting in pervasive biotite + chlorite alteration.

Antas contains hydrothermal alteration zones similar to those recognised at other IOCG deposits in the Carajas. The orebodies display a generally consistent pattern of early regional sodic alteration (albite-scapolite) followed by potassic (biotite) and calcic alteration (actinolite– cummingtonite), the latter is associated with the formation of ilmenite–(apatite) replacement bodies, which are directly related to copper mineralisation. Carbonate alteration is a later phase. Sodic and sodic– calcic alteration types in most IOCG districts are typically developed below or peripheral to potassic alteration assemblages (Hitzman et al. 1992).

The complex stages of sodic, sodic–calcic, potassic, and hydrolytic alteration observed at Antas North are generally similar to those described by Monterio and Xavier (2008) from the Sossego – Sequeirinho IOCG system in Carajás. The temporal and vertical zonation observed in the Antas North system generally fits the “classical” system of alteration zoning predicted in IOCG systems, with ilmenite as the main oxide phase, rather than magnetite.

The main orebody is oriented northeast and coincides well with the main soil anomaly (>1,000ppm copper) and VTEM anomaly. Zones of massive sulphide near the periphery of the ore zones help to generate the high-grade intercepts, typically seen n results reported historically.

The majority of mineralisation is concentrated within a steeply dipping body that contains fragments of massive sulphide and disseminated sulphide minerals, within a matrix of hydrothermal breccia. The ore body is cut by relatively narrow zones of gabbro dyke that form the focus for later structurally controlled, sub-vertical, breccia-hosted copper–gold mineralisation.

Massive Sulphide High Grade Zone contains variable proportions of chalcopyrite and pyrrhotite as dominant minerals. Chalcopyrite is by far the most abundant sulphide, forming a massive aggregate. Sulphide veins are usually undeformed and planar.

The Medium-High Grade Zone also contains variable proportions of chalcopyrite, pyrrhotite, as dominant minerals, and is by far the most abundant vein type within the mineralised zones. Sulphides frequently form the matrix of hydrothermal breccia’s, form stringers, and occur as fine disseminations in the transparent gangue.

In the Disseminated Zone chalcopyrite occurs as fine-medium grained disseminations in the transparent gangue, usually surrounding transparent minerals. Sulphides also occur as fracture fill and as small blebs. Commonly this ore type occurs between narrow Medium-High grade and Massive Sulphide zones.

Antas is a high-grade open pit copper-gold mine.

The life-of-mine strip ratio is 6.4, and at full scale, the mine will be 650 metres in length, 350 across and 250 meters deep. The surrounding rock is very massive and very competent allowing 80° wall angles degree walls, 10-20 metre benches with 6 meter berms with an overall slope angle of 55° and ramps at 15°.

Mining is contracted to Mining And Civil Australia (MACA), a well-known and respected contractor with activities in Australia Brazil. A conventional mining method is employed with load and haul. The mine operates over three shifts, 24 hours a day, 365 days. All of the operational mining personnel are Brazilian nationals and residents, with no fly-in-fly-out operators. Avanco provides technical support for operations, including engineering, geological and survey control.

The mining is undertaken with a newly purchased fleet tailored the operation and comprising:

- Liebherr R9100 Excavators: 120t class excavator in backhoe configuration, 565kW, 7.6 metre cubed rock bucket

- Volvo A40F articulated off road haul trucks: 6-wheel drive, which is excellent for wet weather conditions, 40 km/hr, with a nominal 40 tonne payload, equal to [14] cubic metres

- Caterpillar 5150 top hammer drill rigs: 32kw Hammer, 97-115mm drill diameter, averaging 22 meters per hour

- Auxiliary equipment: including front-end loaders, dozers, graders, water carts and service trucks.

As announced on 21 January 2020, MACA ceased its Brazilian operations effective January 2020. The contract was due to conclude in 2020. MACA has realised a $2m impairment on closure of its operations. MACA retains ownership of the majority of the plant and equipment utilised at Antas, and will either dispose or redeploy these assets to other operations outside of Brazil.

Processing method: Ore sorting, conventional crushing, grinding, flotation and filtration.