The Alta Floresta Mineral Province (AFMP), southern Amazonian Craton, experienced extensive magmatic activity from ca. 2.03 to 1.75 Ga in an uncertain geodynamic setting. New and pre-existing geological, petrographic, geochemical, and zircon geochronological data show that magmatic rocks in the eastern AFMP comprise three magmatic sequences: 2.03–1.93, 1.90–1.85, and 1.83–1.75 Ga. Earlier magmas had garnet-bearing sources, whereas younger ones were derived from shallow, garnet-free sources. We propose a new, four-stage geological framework, comprising five domains, and featuring an accretionary orogen with tectonic switching that alternates between flat subduction and slab-rollback. During flat subduction and crustal thickening in stages A (2.03–1.97 Ga) and C (1.90–1.81 Ga), calc-alkalic to alkali-calcic I-type magmatism was produced, whereas alkali-calcic to alkalic A-type magmatism, and localized I-type granites, were generated during slab-rollback and crustal extension in stages B (1.96–1.94 Ga) and D (1.83–1.75 Ga). The last stage is associated with precious- and base metal porphyry- and epithermal-style systems. We interpret the eastern AFMP as a remaining cratonic block of the eastward Tapajós Domain within the ca. 1.95–1.80 Ga Ventuari-Tapajós Province, and recording 1.85–1.74 Ga magmatism of the Western Amazonia Igneous Belt within the ca. 1.80–1.55 Ga Rio Negro-Juruena Province. Similarities between the AFMP and the Svecofennian orogen (Fennoscandian Shield) suggest that parts of the Columbia supercontinent margins might have operated in similar fashion to Andean-type accretionary orogens.