1 research outputs found
Age of the El Hornito pluton and thermobarometry of its thermal aureole: Insights into achalian (Devonian) magmatism in the Sierras Pampeanas of Argentina
A comprehensive study of the El Hornito Pluton, located in the Sierra Grande de San Luis (Argentina) is presented in this work. The intrusive body is a composite pluton constituted by four main units: 1) Granitic Porphyritic Unit, 2) Granitic Red Unit, 3) Granitic External Unit and 4) Mafic-Hybrid Unit. The main intrusive (granitic) units are crosscut by syn-magmatic felsic dikes. A Devonian age of 385 ± 2 Ma was obtained by U–Pb SHRIMP analyses on zircons belonging to the Granitic Porphyritic Unit. This age is considered representative of the El Hornito Pluton crystallization since the Granitic Porphyritic Unit is the most voluminous one. The Granitic Red Unit crops out in the central zone of the El Hornito Pluton and hosts the largest proportion of the rocks that comprise the Mafic-Hybrid Unit, where mingling/mixing processes are evident. The host rocks located in the western sector of the El Hornito Pluton present an intense contact metamorphism. Electron microprobe analyses of plagioclase, garnet, biotite, and muscovite in a garnet-sillimanite hornfels were performed to calculate thermobarometry from multireaction procedures in these hornfels, yielding P-T values of 3.7 ± 1.1 kbar and 626 ± 32 °C. These conditions are considered representative of the emplacement level of the El Hornito Pluton. The results of this study show that the El Hornito Pluton was emplaced at a depth of 14.1 ± 4.2 km, evidencing deeper crustal levels of emplacement than the Achalian granites of the Sierra de CĂłrdoba. The age obtained in this work, along with others reported for the Sierras de San Luis and CĂłrdoba, indicate that the intrusions occurred first in the west and later in the east. Moreover, according to the emplacement levels at which intrusions took place, different exhumation rates are proposed to have occurred across the orogen (in an NE-SW direction) after the Devonian magmatism, being greater in the Sierra de San Luis (southwest) than in the Sierras de CĂłrdoba (northeast).Fil: Muñoz, Brian Lucas. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; ArgentinaFil: Enriquez, Eliel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; ArgentinaFil: Morosini, Augusto Francisco. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; ArgentinaFil: Demartis, Manuel. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente.; ArgentinaFil: Ortiz Suárez, Ariel Emilio. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; ArgentinaFil: Pinotti, Lucio Pedro. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente.; ArgentinaFil: D'eramo, Fernando Javier. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente.; ArgentinaFil: Christiansen, Rodolfo Omar. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, FĂsicas y Naturales. Instituto GeofĂsico SismolĂłgico Volponi; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Basei, Miguel Angelo. Universidade de Sao Paulo; BrasilFil: Grosso Cepparo, Pablo M.. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; ArgentinaFil: Pagano GĂ©nero, Diego Sebastián. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; ArgentinaFil: Ramos, Gabriel Alejandro. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico Matemáticas y Naturales. Departamento de GeologĂa; Argentin