As of December 31, 2024, the Barro Alto mine is 100% owned by Anglo American.
On February 18, 2025, Anglo American announced an agreement to sell its nickel business, including Barro Alto, to MMG Singapore Resources Pte. Ltd., a wholly owned subsidiary of MMG Limited. The transaction is expected to be completed in 2025.
Summary:
The Barro Alto mineral resource is primarily saprolite overlain by laterites and extends for 35 km in an arc from southwest to northeast. The deposit is in the Barro Alto mafic-ultramafic complex, which is part of the Pre-Cambrian shield in the state of Goiás. The complex is composed of a sequence of serpentinised dunites and pyroxenites, enveloped by gabbros.
The Barro Alto deposit occurs in a curved strip within the ultramafic zone of the Barro Alto Complex. Valleys and fault zones allow for the division of the deposit into seven separate areas. The relative concentration of iron and nickel occurring at the top of the profile (limonite zone typical of oxidised deposits), is the result of leaching and intense tropical weathering of the ultramafic lithologies. In more developed areas, the nickel is leached downwards, where it concentrates in the lower saprolite zone, forming areas rich in garnierite (silicified deposits).
The nickel deposits of the Barro Alto have the shape of a bow with concavity to NW. Presents approximately 156 km in length, with a width of 8 km (North) up to 25 km (central region).
The mineralisation corresponds to the surficial weathered portions of the serpentinites. There are three types of saprolitic ore. The West type ore tends to have higher nickel grades and silica/magnesia ratios than the East type and Plain type ores.
The Barro Alto complex is bounded by metamorphic volcanic-sedimentary sequences (Ferreirafilho et al., 1992) and is a major mafic-ultramafic layered intrusion that was subjected to granulite facies metamorphism. It is composed mainly of gabbronorite, with minor dunite, peridotite, norite, gabbro, anorthosite and banded clinopyroxene-garnet amphibolite (Moraes and Fuck, 2000). In the complexes of Niquelandia and Barro Alto, lateritic weathering has formed important reserves of extractable Ni ore, representing around 2 million tons of metallic Ni (Raous et al., 2010). Ultramafic areas are characterized by a natural enrichment in heavy metals. In the case of the Barro Alto complex, this enrichment is mainly in Ni, however the Cr content has been reported as high as 6030 mg kg-1 (Ratié et al., 2015) and 46800 mg kg-1 (Raous et al., 2010), which is not high enough to be extracted, but potentially harmful for the environment. Mineral phases containing Cr include Cr-rich magnetite (Fe2+(Fe3+,Cr)2O4), chromite (FeCr2O4), talc (Mg3Si4O10(OH)2) chlorite ((Mg, Fe)5 Al[(OH)8 AlSi3O10]) and spinels (Oze et al., 2004).