Geotectonic study of the southeastern Dom Feliciano Belt in southern Brazil and its connections to the Punta del Este Terrane (Uruguay) and Pan-African mobile belts in southwestern Africa

• Autor(a) principal: Cruz, Rodrigo Fabiano da
• Data de Publicação: 2023
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/44/44143/tde-20062023-122313/
• topic: Cinturão Dom Feliciano; Dom Feliciano Belt; Geocronologia U-Pb; Gondwana Ocidental; Isótopos Lu-Hf; Lu-Hf isotopes; U-Pb geochronology; Western Gondwana

The Neoproterozoic supracrustal units of the Dom Feliciano Belt in southern Brazil and eastern Uruguay provide a record of the tectonic evolution of the Brasiliano/Pan-African cycle in terms of sedimentation, deformation, plutonism and metamorphism during the western Gondwana supercontinent assembly. From the northern Punta del Este Terrane (Jaguarão Domain) and Pelotas Batholith were acquired U-Pb and Lu-Hf zircon data from metasedimentary rocks and granites. The Jaguarão Domain metasedimentary complexes have detrital zircon ages ranging from 3.2 to 0.7 Ga, with prominent age peaks at 2.21.7 Ga, 1.5 1.0 Ga, and 1.00.7 Ga. The Herval Complex (Pelotas Batholith) revealed a similar provenance of detrital zircon ages, with two main intervals of 1.51.1 Ga and 1.00.7 Ga, and minor Paleoproterozoic (2.01.7 Ga) and Archean (2.82.4 Ga) ages. The maximum depositional age of the complexes is constrained to age populations between 700 and 650 Ma. Metamorphic zircon overgrowths range from 680 to 570 Ma. The Lu-Hf data from the mesoto Paleoproterozoic zircons have Hf(t) values between -10 to +10 and model ages from Paleoproterozoic to Archean. The Hf(t) values in Neoproterozoic zircons are dominantly negative (-15 to +5) with meso- to Paleoproterozoic model ages. U-Pb zircon data from calcalkaline to peraluminous granites, including mylonitic intrusive lenses in the metasedimentary sequences, present crystallization ages of 580-570 Ma, which point to a widespread Ediacaran magmatism in the northern Punta del Este Terrane. These results demonstrate that sedimentary deposition ceased and underwent metamorphism during the development of the Cryogenian/Ediacaran arc-related magmatism of the Dom Feliciano belt. Given the scarcity of Mesoproterozoic rocks in the Mantiqueira Province and nearby cratonic areas, the obtained data suggest that these detrital populations originated in southwestern African rocks, most likely the Congo/Kalahari cratons. The Pelotas Batholith (Magmatic-arc domain) have UPb and LuHf zircon data acquired from plutonic rocks with evidence of magma mixing and mingling, as well as assimilation of wall rocks, which suggest multi-stage magmatism related to flare-up episodes of magmatism, potentially triggered by changes in the tectonic setting. U Pb zircon analyses yielded crystallization ages of granodioritic gneiss xenolith at 691.5 ± 7 Ma, microgranodiorite xenolith at 645.9 ± 3.7 Ma, host monzogranite at 634.4 ± 4.4 Ma, and intrusive syenogranite at 620.1 ± 4.7 Ma, all intruded by syenogranitic pegmatite at 606.9 ± 1.7 Ma. Other analyses were performed on calc-alkaline granite (633 ± 4 Ma) and peraluminous granite (609.6 ± 2.2 Ma). The LuHf data highlights a model age interval ranging from 1.7 to 1.3 Ga with Nd values between -4 and 1, except for the pegmatite sample with Paleoproterozoic and Archean model ages (3.3-1.6 Ga) and Nd values between - 33 and -1. Furthermore, the acquired data emphasizes a contribution from slightly juvenile to crustal sources, with model ages ranging primarily from Statherian-Orosirian to Mesoproterozoic. The geological context and isotopic results point to a prior extensional tectonic setting during the Tonian (~800 Ma), with regional deformation and metamorphism linked with accretionary and collisional stages (690570 Ma).