Subduction and continental collision in the Neoproterozoic: Sanukitoid-like magmatism and paired metamorphism in SE Brazil

• Published in: Precambrian research 2022-12, Vol.383, p.106888, Article 106888
• Main Authors: Marimon, Rodrigo S., Hawkesworth, Chris J., Trouw, Rudolph A.J., Trouw, Camilo, Dantas, Elton L., Ribeiro, Andre, Vinagre, Rodrigo, Hackspacher, Peter, Ávila, Ciro, Motta, Rafael, Moraes, Renato
• Format: Article
• Language: English
• Subjects: Arc-related magmatism; Continental collision; Mantle metasomatism; Neoproterozoic Southern Brasília Orogen; Paired metamorphism; West Gondwana
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2022.106888

•Paired metamorphism in the Southern Brasília Orogen.•Coeval high T/P and intermediate T/P domains.•High T/P domain associated with pre- to syn-collisional calc-alkaline magmatic rocks.•Magmatic rocks derived from mantle enriched by crustal material during subduction.•Magmatic rocks were emplaced in accretionary to collisional settings. Collisional orogens are a periodic manifestation of plate tectonics on Earth. They form by the amalgamation of continental blocks, and they take place along both active and passive continental margins. The Neoproterozoic Southern Brasília Orogen is a collisional orogen related to the formation of West Gondwana, broadly composed of two tectonometamorphic domains, the Upper Tectonostratigraphic Domain (UTD), intruded by subduction-related magmas, and the Lower Tectonostratigraphic Domain (LTD) of passive margin affinity. New metamorphic zircon SHRIMP and LA-ICP-MS U-Pb ages are presented for rocks from both domains, a high-grade mylonitic orthogneiss (∼623 Ma) and a granulitic garnet-sillimanite-K-felspar metapelite (∼621 Ma) from the Upper Tectonostratigraphic Domain, and medium T retro-eclogites (∼616–610 Ma) and a garnet-kyanite-K-feldspar granulitic metapelite (∼615 Ma) from the Lower Tectonostratigraphic Domain. New and compiled U-Pb metamorphic ages, together with published P-T data, indicate the existence of Neoproterozoic coeval metamorphic belts in the Southern Brasília Orogen: an intermediate T/P region (LTD) and a high T/P domain (UTD). This is a characteristic of modern and ancient accretionary and subduction-to-collision orogens. The high T/P domain is dominated by Neoproterozoic sanukitoid-like magmatic rocks emplaced at the pre- to late-collsional stages (∼750–610 Ma) and the most primitive members of these suites (49–53 SiO2 wt.%; #Mg 40–60) are enriched in both compatible and incompatible elements (i.e., Th, Ba, Sr, etc), a characteristic inherited from their subduction-metasomatized garnet-bearing mantle source. Relatively high heat-flux from the mantle to the crust, associated with magmatic activity, combined with heating by radioactive decay in response to crustal thickening, are responsible for ultra-high temperature metamorphism (UHT) in the UTD. Barrovian-style intermediate T/P metamorphism was attained in the Lower Tectonostratigraphic Domain at the same time, in response to crustal thickening.