Permian nappe tectonics and high-grade metamorphism related to Gondwanide Orogeny in northern Patagonia terrane.

• Autores: González, Pablo Diego; Oriolo, Sebastián; Schulz, Bernhard; Naipauer, Maximiliano; Marcos, Paulo; Sato, Ana María; Varela, Ricardo; Krause, Joachim; Cábana, María Cecilia
• Año de publicación: 2021
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Ciencias de la Tierra (General); Patagonia; Paleozoic; Igneous-metamorphic Basement; U–Pb zircon; Th–U–Pb monazite; Ciencias de la Tierra (General)
• Institución: Universidad Nacional de Río Negro

Fil: González, Pablo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. Servicio Geológico Minero Argentino, Centro General Roca, Río Negro, SEGEMAR Regional Sur, Independencia 1495, Parque Industrial 1, Gral. Roca, (Río Negro), C. P. 8332, Casilla, Correo, Argentina.
Fil: Oriolo, Sebastián. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires (UBA-CONICET), Güiraldes 2160, Ciudad Universitaria, Pabellón II, C 1428 EHA, Buenos Aires, Argentina.
Fil: Schulz, Bernhard. TU Bergakademie Freiberg, Institute of Mineralogy, Saxony, Alemania.
Fil: Naipauer, Maximiliano. INGEIS (UBA-CONICET), CABA, Argentina.
Fil: Marcos, Paulo. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina.
Fil: Sato, Ana María. Centro de Investigaciones Geológicas (UNLP-CONICET), Diagonal 113 N° 275, B 1904 DPK, La Plata, Argentina.
Fil: Varela, Ricardo. Centro de Investigaciones Geológicas (UNLP-CONICET), Diagonal 113 N° 275, B 1904 DPK, La Plata, Argentina.
Fil: Krause, Joachim. Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Freiberg, Germany.
Fil: Cábana, María Cecilia. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina.
González, P.D., Oriolo, S., Schulz, B., Naipauer, M., Marcos, P., Sato, A., Varela, R., Krause, J., Cábana, M.C. 2021. Permian nappe tectonics and high-grade metamorphism related to Gondwanide Orogeny in northern Patagonia terrane. Metamorphic Studies Group Research in Progress Meeting. The Mineralogical Society. Abstract Volume, p. 54. Virtual meeting 29-31 March 2021.
The focus of this contribution is to characterize a sequential order of deformational structures and associated metamorphic conditions of the igneous-metamorphic basement rocks from northern Patagonia terrane (41°28’30”S-65°40’30”W). Based on field mapping, mesoscopic structures are analysed to evaluate progressive and polyphasic deformation, developed under regional high-grade metamorphism. Three continuous deformational phases are recognized. During D1 phase, the formation of overturned tight F1 folds is associated with penetrative axial plane foliation S1. It exhibits P-T conditions close to the baric peak, and likely represents the progressive metamorphic stage associated with syn-kinematic growth of garnet-kyanite porphyroblasts in meta-pelites. D2 phase is recorded as either shear bands S2 transposition or mylonitic foliation, coeval with polymorphic transformation of kyanite to sillimanite owing to thermal peak. A nappe system related to kilometer scale El Jagüelito ductile shear zone characterizes the large-scale D2 structure of the investigated area. D3 phase is distinguished by refolding of the former fabric and formation of either kink-bands or crenulation cleavage S3 of the S1-S2 foliation planes, under retrogressive metamorphic conditions. The nappe system exhibit a top-to-the S/SW tectonic transport, and the El Jagüelito shear zone served as a right lateral ramp in the exhumation process among D2-D3 events. Petrographic analyses of metamorphic mineral assemblages and reaction textures combined with conventional geothermobarometric estimates and a pseudosection records the pressure-temperature conditions of metamorphism among D1-D3 events. In situ electron probe Th‐U‐Pb monazite dating of 272, 260, and 251 Ma constraints the main tectono-metamorphic event to Late Permian Gondwanide Orogeny. New results combined with existing geological and geochronological constraints allow inferring a clockwise P-T-D-time evolutionary path within the kyanite-sillimanite stability fields. Comprehensive regional comparison of the large-scale structural framework is indicative of an ongoing oblique subduction beneath the proto-Andean margin of Gondwana in the NE direction. This continental subduction and exhumation lasted at least 20 million years, nearly the entire Guadalupian-Lopingian series, producing transpression and metamorphic conditions of amphibolite-to-granulite facies, in medium- to high-pressure regimes, although the studied area occur in a back-arc to intracontinental settings. Geotectonic implications also includes a long-lived tectono-metamorphic history of the El Jagüelito shear zone, which was formed during Early Paleozoic and successively reactivated during Permian and Jurassic times.