Tectonique tangentielle et décrochements d'âge Protérozoïque inférieur (orogenèse transamazonienne, environ 2 000 Ma) au Nord du Quadrilatère ferrifère (Minas Gerais, Brésil)

Structural and geochronological evidence for a Transamazonian age (ca. 2,000 Ma) of a major nappe-forming event occuring in the Quadrilatero ferrifero region are discussed in this paper. The Archaean age of the granite-gneiss basement is confirmed by U-Pb zircon ages and by Sm-Nd TDM model ages in the 2,800-2,600 Ma range. Rb-Sr ages (whole-rock isochrons and biotite model ages) and K-Ar ages (biotite) suggest a basement reworking during the Transamazonian orogeny