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10 results on '"Basei, M. A. S."'

8. 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

Author

Oriolo, S., Oyhantçabal Cironi, Pedro Bernarndo, Wemmer, K., Basei, M. A. S., Benowitz, J., Pfänder, J., Hannich, F., Siegesmund, S., and Oyhantçabal Cironi, Pedro Bernarndo. Universidad de la República (Uruguay). Facultad de Ciencias. Departamento de Geología

Subjects
Zircon, emplacement, Cataclastic deformation, Shear zone, Geochronology, Shearing machines, Mica, Timing circuits, Fluid circulation, Amphibolite facies, Strontium alloys, Pan African orogeny, Uranium alloys, Argon lasers, Gondwana, Tectonics, deformation, Lead alloys, age determination, Tectonic evolution, Shearing, Binary alloys, Proterozoic, Laser ablation, Rubidium alloys, Inductively coupled plasma mass spectrometry, Metals, Silicate minerals, Strain partitioning, Sensitive high-resolution ion microprobe, Uruguay, Isotopic systems, Crustal-scale structure, Thermal evolution
Abstract

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 zones

Published
2016

9. U-Pb Zircon Dating of Ash Fall Deposits from the Paleozoic Paraná Basin of Brazil and Uruguay: A Reevaluation of the Stratigraphic Correlations.

Author

Rocha-Campos, A. C., Basei, M. A. S., Nutman, A. P., Santos, P. R., Passarelli, C. R., Canile, F. M., Rosa, O. C. R., Fernandes, M. T., Santa Ana, H., and Veroslavsky, G.

Subjects
STRATIGRAPHIC geology, ZIRCON, PERMIAN stratigraphic geology, PALEOZOIC Era, ISOTOPE geology
Abstract

Ash fall layers and vitroclastic-carrying sediments distributed throughout the entire Permian stratigraphic range of the Paraná Basin (Brazil and Uruguay) occur in the Tubarão Supergroup (Rio Bonito Formation) and the Passa Dois Group (Irati, Estrada Nova/Teresina, Corumbataí, and Rio do Rasto Formations), which constitute the Gondwana 1 Supersequence. U-Pb zircon ages, acquired by SHRIMP and isotope-dissolution thermal ionization mass spectrometer (ID-TIMS) from tuffs within the Mangrullo and Yaguari Formations of Uruguay, are compatible with a correlation with the Irati and parts of the Teresina and Rio do Rasto Formations, respectively, of Brazil. U-Pb zircon ages suggest maximum depositional ages for the samples: (1) Rio Bonito Formation: ages ranging from 295.8 ± 3.1 to 304.0 ± 5.6 Ma (Asselian, lowermost Permian), consistent with the age range of the Protohaploxypinus goraiensis subzone; (2) Irati Formation: ages ranging from 279.9 ± 4.8 to 280.0 ± 3.0 Ma (Artinskian, middle Permian), consistent with the occurrence of species of the Lueckisporites virkkiae zone; (3) Rio do Rasto Formation: ages ranging from 266.7 ± 5.4 to 274.6 ± 6.3 Ma (Wordian to Roadian, middle Permian). All the SHRIMP U-Pb zircon ages are consistent with their superimposition order in the stratigraphy, the latest revisions to the Permian timescale (International Commission of Stratigraphy, 2018 version), and the most recent appraisals of biostratigraphic data. The ID-TIMS U-Pb zircon ages from the Corumbataí Formation suggest that U-Pb ages may be >10% younger than interpreted biostratigraphic ages. [ABSTRACT FROM AUTHOR]

Published
2019
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