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Geology and Mineralization

Ninety percent of the Eastern Brazilian Pegmatite Province (EBPP) lies in the State of Minas Gerais. It is one of the most significant lithium-bearing pegmatite populations in the world, hosting large volumes of spodumene, a lithium-rich mineral that is considered today as one of the best sources of the metal. Besides a plethora of other lithium-bearing minerals, the EBPP also hosts deposits of Nb-Sn-Ta oxides, industrial minerals (feldspars, mica, and quartz), beryl, gemstones, and dimension stones.

The Itinga and Salinas projects lie in the Araçuaí Pegmatite District, the most important cluster of lithium-rich pegmatites within the EBPP. These projects focus on spodumene-rich pegmatites (SRP) hosted by the Salinas Formation, which was intruded by leucogranites during the Cambrian. These granitic intrusions were the sources of residual magmas that crystallized as countless pegmatites around 500 Ma. Amongst them, SRP bodies are non-zoned to poorly zoned pegmatites, composed of disseminated spodumene crystals (up to 30 vol%) within a matrix of albite, quartz, perthite, and muscovite (spodumene + matrix reaching up to 95 vol%), with traces of Li-phosphates, Li-mica, petalite, Nb-Sn-Ta oxides, and other accessory minerals.

Some pegmatite fields of the Araçuaí District show the same petrologic and metallogenetic features of many other lithium-rich pegmatite districts in the world. They comprise late orogenic (post-tectonic) lithium-fertile intrusions composed of two-mica and albite-muscovite leucogranites with pegmatoid cupolas (the Cambrian G4 granites, according to local classification), hosted by metasedimentary rocks recrystallized under low-pressure/high-temperature metamorphic conditions (the Salinas Formation). These granitic intrusions released residual magmas that formed classical pegmatite aureoles, including the SRP bodies found in the Itinga and Curralinho (NE Salinas) pegmatite fields.

Lithium mineralization on the Itinga and Salinas projects forms dense swarms of tabular-shaped SRP bodies, like in the Bandeira deposit (and CBL’s Cachoeira mine), or single, but much larger and thicker, SRP bodies, like the Outro Lado pegmatite (and several of Sigma’s pegmatites). Together, spodumene-rich pegmatites from all these projects and mines, found as post-tectonic igneous intrusions hosted by the regional foliation (concordant bodies) or fractures (discordant bodies) of cordierite-mica schists, outline a NE-trending, lithium-mineralized zone: the SRP Araras* polygon, the most important lithium producing region yet found in Brazil.

*Araras is the plural form for the Brazilian Portuguese word for macaw and lends the name to the Araçuaí river and town.

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