The Iron Quadrangle (Portuguese: Quadrilátero Ferrífero) is a mineral-rich region covering about 7,000 square kilometres (2,700 sq mi) in the central-southern part of the Brazilian state Minas Gerais.

The Minas Supergroup was initially deposited approximately 2.5 Ga ago on the edge of the São Francisco craton, the geologic core of southern Brazil.

The larger Iron Quadrangle contains the following five lithostratigraphic units:[3] The area shows evidence for a collisional event (the Transamazonian Orogeny) approximately from 2.2 to 1.8 Ga, based on mapped folds and thrust faults.

In both cases, tailings dams at mines operated in part by Vale S.A. collapsed, leading to flooding and destruction of the downstream areas, as well as severe environmental contamination.

On November 5, 2015, the Fundão dam (part of the Germano mining complex) in the Mariana region collapsed, causing 19 fatalities and the destruction of around 200 homes.

On January 25, 2019, Dam I at the Córrego do Feijão iron mine collapsed, causing the deaths of 165 people,[note 1] and extensive damage to nearby agricultural lands, bridges and the city of Brumadinho.