Reassessing the polyphase Neoproterozoic evolution of the Punta del Este Terrane, Dom Feliciano Belt, Uruguay

Some recent models challenge the position and extension of the assumed oceanic basins formed through the break-up of Rodinia, and the tectonic processes involved in the Gondwana assembly, making the investigation of the Early Neoproterozoic record of great relevance. Within the South-American Atlantic margin, the Punta del Este Terrane (PET) of the Dom Feliciano Belt (DFB) comprises a unique Tonian to Ediacaran record, and has a strategic position to reconstruct spatio-temporal relationships with the southern African orogenic belts. Novel zircon U–Pb and Lu–Hf data from the PET basement orthogneisses display Tonian magmatic ages (805–760 Ma) and Hf isotopic signatures indicative of mainly crustal/metasedimentary sources, (Nd TDM ages: 2.2–1.9 Ga, and εHf(t): − 12 to − 4). The basement paragneisses yielded late Paleoproterozoic to Neoproterozoic U–Pb ages, but dominantly positive εHf(t) values. The presented results confirm the correlation of the PET with the Coastal Terrane of the Kaoko Belt, and discard the idea of the Nico Pérez Terrane as a source. Detrital zircon U–Pb and Lu–Hf data from the Rocha Formation yielded a main peak at ca. 660 Ma, with the Neoproterozoic grains showing a εHf(t) between + 1 and + 14. The deposition age of the Rocha Formation is constrained by the youngest detrital zircon age peak (660 Ma), and the beginning of the deposition of the Sierra de Aguirre Formation (580 Ma). The data indicate common sources with the Marmora Terrane, and it is thus proposed that the Rocha Formation belongs to the Gariep Belt, and it was juxtaposed during the Ediacaran to the DFB.Fil: Silva Lara, Hernan. Universität Göttingen; AlemaniaFil: Siegesmund, S.. Universität Göttingen; AlemaniaFil: Oriolo, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Hueck, M.. Universidade de Sao Paulo; Brasil. Universität Göttingen; AlemaniaFil: Wemmer, K.. Universität Göttingen; AlemaniaFil: Basei, M. A. S.. Universidade de Sao Paulo; BrasilFil: Oyhantçabal, P.. Universidad de la República; Urugua

Timing of deformation in the Sarandí del Yí Shear Zone, Uruguay: implications for the amalgamation of western Gondwana during the Neoproterozoic Brasiliano-Pan-African Orogeny

U-Pb and Hf zircon (sensitive high-resolution ion microprobe -SHRIMP- and laser ablation-inductively coupled plasma-mass spectrometry -LA-ICP-MS-), Ar/Ar hornblende and muscovite, and Rb-Sr whole rock-muscovite isochron data from the mylonites of the Sarandí del Yí Shear Zone, Uruguay, were obtained in order to assess the tectonothermal evolution of this crustal-scale structure. Integration of these results with available kinematic, structural, and microstructural data of the shear zone as well as with geochronological data from the adjacent blocks allowed to constrain the onset of deformation along the shear zone at 630-625 Ma during the collision of the Nico Pérez Terrane and the Río de la Plata Craton. The shear zone underwent dextral shearing up to 596 Ma under upper to middle amphibolite facies conditions, which was succeeded by sinistral shearing under lower amphibolite to upper greenschist facies conditions until at least 584 Ma. After emplacement of the Cerro Caperuza granite at 570 Ma, the shear zone underwent only cataclastic deformation between the late Ediacaran and the Cambrian. The Sarandí del Yí Shear Zone is thus related to the syncollisional to postcollisional evolution of the amalgamation of the Río de la Plata Craton and the Nico Pérez Terrane. Furthermore, the obtained data reveal that strain partitioning and localization with time, magmatism emplacement, and fluid circulation are key processes affecting the isotopic systems in mylonitic belts, revealing the complexity in assessing the age of deformation of long-lived shear zone

Reassessing the polyphase neoproterozoic evolution of the Punta del Este terrane, Dom Feliciano Belt, Uruguay

Some recent models challenge the position and extension of the assumed oceanic basins formed through the break-up of Rodinia, and the tectonic processes involved in the Gondwana assembly, making the investigation of the Early Neoproterozoic record of great relevance. Within the South-American Atlantic margin, the Punta del Este Terrane (PET) of the Dom Feliciano Belt (DFB) comprises a unique Tonian to Ediacaran record, and has a strategic position to reconstruct spatio-temporal relationships with the southern African orogenic belts. Novel zircon U–Pb and Lu–Hf data from the PET basement orthogneisses display Tonian magmatic ages (805–760 Ma) and Hf isotopic signatures indicative of mainly crustal/metasedimentary sources, (Nd TDM ages: 2.2–1.9 Ga, and εHf(t): −12 to −4). The basement paragneisses yielded late Paleoproterozoic to Neoproterozoic U–Pb ages, but dominantly positive εHf(t) values. The presented results confrm the correlation of the PET with the Coastal Terrane of the Kaoko Belt, and discard the idea of the Nico Pérez Terrane as a source. Detrital zircon U–Pb and Lu–Hf data from the Rocha Formation yielded a main peak at ca. 660 Ma, with the Neoproterozoic grains showing a εHf(t) between+1 and+14. The deposition age of the Rocha Formation is constrained by the youngest detrital zircon age peak (660 Ma), and the beginning of the deposition of the Sierra de Aguirre Formation (580 Ma). The data indicate common sources with the Marmora Terrane, and it is thus proposed that the Rocha Formation belongs to the Gariep Belt, and it was juxtaposed during the Ediacaran to the DFB