Lithium in the Eastern Brazilian Pegmatite Province: A Synthesis Highlighting Spodumene-Rich Deposits

Covering 150,000 km2, the Eastern Brazilian pegmatite province stands out as one of the largest populations of rare element pegmatites in the world. The province is a result of metamorphic-magmatic processes that produced enormous volumes of distinct granite types and countless pegmatites in the Ediacaran-Cambrian Araçuaí orogen. Among the 12 pegmatite districts of the Eastern Brazilian pegmatite province, only three contain spodumene-bearing pegmatites, and only one contains spodumene-rich deposits that may reach tens of million tons of lithium ore. This is the Araçuaí district, which accounts for most of the lithium ore produced in Brazil and all recent discoveries of spodumene-rich deposits, reaching over half a billion tons of lithium ore resources. This world-class lithium district comprises distinct spodumene-bearing deposits named, for prospecting purposes, spodumene-rich pegmatites (SRP), spodumene-petalite pegmatites (SPP), spodumene-perthite pegmatites (PSP), perthite-tourmaline pegmatites (PTP), and albite-tourmaline pegmatites (ATP). All these pegmatites postdate the regional tectono-metamorphic events and are found close (1–5 km) to intrusions comprising two-mica, muscovite-albite, and pegmatoid leucogranites. Low-pressure/high-temperature metasedimentary successions with cordierite-biotite (± andalusite) schists host the SRP, SPP, and PSP deposits. They contain spodumene disseminated in unzoned to poorly zoned pegmatites that form dike swarms or large single bodies or in spodumene-rich units of simple zoned pegmatites. The PTP and ATP deposits are relatively poor in spodumene, which is found in internal zones, quartz cores, and/or albite-rich units of complex zoned pegmatites. Field mapping, soil geochemistry, trenching, and intensive drilling revealed the large Bandeira spodumene deposit in just 2 years, which is described here as an example of highly successful, knowledgedriven exploration work.