Earth and Planetary Science

The area in the southern São Francisco Craton, between Itatiaiuçu and Rio Manso (Minas Gerais), constitutes a geological domain that remains poorly constrained regarding the nature, age, and tectono-metamorphic evolution of its metamafic and metasedimentary units. A marked contrast in gamma-spectrometric signatures—expressed by darker tones relative to the surrounding Archean terranes—delineates a distinct lithological association composed of tremolite–actinolite schists, metaconglomerates with strongly stretched clasts, and phyllonitic metapelites containing quartz, graphite (δ¹³C values between −26‰ and −14‰, consistent with an organic source), plagioclase, chlorite, phengite, amphibole, and garnet. The tremolite–actinolite schists yield paleoproterozoic Sm–Nd model ages between 2,354 and 2,110 Ma and positive εNd values (+0.56 to +3.53), indicating derivation from a mantle source. Mineral assemblages in the phyllonitic metapelites are compatible with metamorphism of a flysch–molasse-type mélange developed in a forearc basin associated with subduction-related shear processes within an accretionary orogen. In this framework, the tremolite–actinolite schists are interpreted as metamorphosed oceanic crust, representing remnants of an oceanic domain that separated the Campo Belo–Bonfim and Belo Horizonte blocks around 2.3 Ga. The transition from oceanic to forearc basin conditions was accompanied by deformation within a thrust belt, where flysch and molasse sequences were metamorphosed to produce phyllonitic metapelites and metaconglomerates. Collectively, this domain preserves significant evidence of Paleoproterozoic geodynamic processes comparable to those observed in modern convergent plate settings.