Dom Feliciano Belt orogenic cycle tracked by its pre-collisional magmatism: The Tonian (ca. 800 Ma) Porto Belo Complex and its correlations in southern Brazil and Uruguay

•Dom Feliciano Belt arc magmatism migration due to cyclic changes in subduction angle.•Tonian back-arc rifting as Dom Feliciano Belt pre-collisional scenario.•Modern-style tectonic operative in southern Brazil at early-Neoproterozoic times. The Porto Belo Complex orthogneisses are dominantly intermediate, high-K calc-alkaline rocks of Tonian age (ca. 800 Ma) that represent the hinterland basement of northern Dom Feliciano Belt. Their significance and correlation to other pre-collisional, Tonian orthometamorphic rocks of the same belt are discussed and integrated in an Occam’s Razor model for the evolution of the Kaoko-Dom Feliciano-Gariep Orogenic System. The model proposes a single, eastward subduction with temporal variations of subduction angle leading to migration of arc-magmatism before the main collision, in the following stages: a) 925–880 Ma early subduction and forearc magmatism; b) 820–770 Ma flat-slab subduction and arc-magmatism migration towards the back-arc region, with generation of arc-related, Tonian magmatic protoliths; c) 765–700 Ma steepening subduction and arc-magmatism migration towards forearc, as the back-arc area is under extension, and rifting is triggered; d) 700–660 Ma accretionary phase, after final consumption of the oceanic plate; e) 660–640 Ma oblique collision leading to basin inversion and double-verging transpression, with hinterland high-T/low-P metamorphism and exhumation; f) 640–580 Ma post-collisional magmatism and shear belt development.