A different kind of volcano
The Cana Brava Carbonatite is part of the Goiás Alkaline Province, a region of unusual magmatic activity. Unlike volcanoes that erupt silicate-rich lavas, carbonatites are peculiar igneous rocks composed of more than 50% carbonate minerals. The magma that formed this complex was not thick, red lava of popular imagination. Instead, it would have been a cool, fluid magma, erupting at temperatures as low as 500–600°C.
These formations are almost exclusively associated with continental rift settings—areas where the Earth's crust is being pulled apart. The Cana Brava complex is an intrusive body, meaning the magma cooled and solidified below the surface, forming structures like pipes, dikes, and sills. This specific geological activity is a larger event known as the Mesozoic Activation, linked to the breakup of the supercontinent Gondwana and the opening of the South Atlantic Ocean. The rocks are part of the Late Cretaceous-Eocene magmatic pulse that created several alkaline provinces in south-central Brazil.
The process of emplacement often involves a unique type of hydrothermal alteration called fenitization. Hot, chemically-reactive fluids from the carbonatite magma alter the surrounding country rock, creating a halo of sodium-rich minerals like arfvedsonite and aegirine-augite. This alteration zone can more than double the surface area of the exploration target for geologists.
A concentration of critical elements
Carbonatites are natural concentrators of what geologists call incompatible elements—elements that do not fit well into the crystal structure of common mantle minerals. As magma cools, these elements become concentrated in the remaining liquid. This process makes carbonatites the world's primary source for rare earth elements (REEs) and other valuable minerals.
The nearby Serra Verde mining operation, which targets a similar deposit, extracts four REEs: neodymium (Nd), praseodymium (Pr), terbium (Tb), and dysprosium (Dy). These specific elements are used for manufacturing the high-performance permanent magnets used in electric vehicle motors and wind turbine generators. The Pela Ema deposit at Serra Verde began commercial production in early 2024 and is expected to produce at least 5,000 tonnes of rare earth oxides annually, with plans to reach 6,500 tonnes per year by 2027.
The mineralization in this region is often found within a weathered layer of ionic clay, which is soft and shallow. This allows for open-pit mining techniques that avoid the intensive hard-rock methods, resulting in a lower environmental impact. Brazil holds the world's second-largest reserves of rare earth elements, estimated at 21 million metric tons, making it a location outside of Asia for these critical materials.