Zircon U–Pb ages and Hf isotope compositions of Açucena Granite (Borrachudos Suite): Implications for Statherian-Cambrian tectono-magmatic evolution of the southern border of the São Francisco Craton, Brazil

Isotopic Lu–Hf and geochronological studies on the zircon grains of the Paleoproterozoic Borrachudos Suite provide constrains of the evolution of the tectonomagmatic events that affected the southern border of the São Francisco Craton and leaded to the formation of the associated iron and emerald deposits. The granite records magmatic crystallization in the 1740-1688 Ma time range, and A2-type geochemical signature. Zircon grains present hydrothermal and anatectic areas with Cambrian age that are related to the gravitational collapse of the final stages of the Brasiliano orogen. During this event the granite was deformed and metamorphosed in the amphibolite facies, leading to anatexis and the formation of large amount of pegmatite bodies. The Hf isotope data on the hydrothermal/anatectic areas indicate partial melting were accompanied by hydrothermal fluids enriched in radiogenic Hf. These fluids contributed to the formation of large volume of hydrous melts (pegmatites), the formation of the emerald deposits and the high-grade iron orebodies.