The neoproterozoic Mantiqueira Province and its African connections: a zircon-based U–Pb geochronologic subdivision for the Brasiliano/Pan-African systems of orogens

Abstract

The Mantiqueira Province (MPV) is a large, complex structural province deformed by the Neoproterozoic/Early Paleozoic Brasiliano Orogenic event in South America. Its evolution is herein detailed on the basis of the geological and geometric characterisation, structural and thermal overlapping of the distinct phases of the orogenic collage. In addition to the tectono-structural analysis, some 50 new zircon U–Pb SHRIMP data from a large number of selected units provided a powerful tool for understanding the granitic chronostratigraphy and the orogenic evolution. We also integrated existing U–Pb analyses, totalling some 240 determinations, which also furnished important constraints to delineate the precise tectono-magmatic succession (orogenic episodes). The study delineated a highly complex evolution, comprising three successive systems of orogens: Brasiliano I, II and III. New crustal growth including juvenile intraoceanic volcano-plutonic arcs characterises the earlier Brasiliano I orogenic system, which presents collisional climaxes at ca. 790 Ma (Embu Domain) and 730–700 Ma (São Gabriel Orogen). On the other hand, recycling of pre-existing crustal sources are the dominant processes operating within the systems Brasiliano II and III. The collisional climaxes within the Brasiliano II are recorded at 640–620 Ma (Dom Feliciano Orogen) and 600 Ma (Paranapiacaba and Rio Piên orogens), whereas the Brasiliano III climaxes are bracketed between 590–560 Ma (Araçuaí Orogen) and 520–500 Ma (Búzios Orogen). The available geochronological data from the Pan-African literature suggests temporally similar orogenic succession. The protracted, dominantly accretionary, Pan-African I system lasts from 850 to 700 Ma, whereas the Pan-African II (collisional peak at 650–600 Ma) and the Pan-African III (collisional peak at 590–540 Ma) are characterised dominantly by crustal recycling processes. The study reinforced previous attempts to correlate the northernmost Araçuaí Orogen and the West Congo Orogen (AWCO), both belonging to the system Brasiliano/Pan-African III. Additionally, our study does not confirm models for a direct linkage between the south-eastern orogens from Ribeira and Dom Feliciano belts (Brasiliano II) and the south-western African orogens, i.e. Kaoko, Damara, Gariep, and Saldania (Pan-African III). Finally, taking advantage of the large U–Pb SHRIMP database, we also reassessed the extent of the Brasiliano reworking on the Archean/Paleoproterozoic basement, namely on the controversial and poorly constrained eastern margin of the São Francisco Craton.