info:eu-repo/semantics/article
Petrological, geochemical, isotopic, and geochronological constraints for the Late Devonian–Early Carboniferous magmatism in SW Gondwana (27–32°LS): An example of geodynamic switching
Fecha
2018-10Registro en:
Dahlquist, Juan Andrés; Alasino, Pablo Horacio; Basei, Miguel A.S.; Morales Camera, Matías Martín; Macchioli Grande, Marcos Simón; et al.; Petrological, geochemical, isotopic, and geochronological constraints for the Late Devonian–Early Carboniferous magmatism in SW Gondwana (27–32°LS): An example of geodynamic switching; Springer; International Journal of Earth Sciences; 107; 7; 10-2018; 2575-2603
1437-3254
CONICET Digital
CONICET
Autor
Dahlquist, Juan Andrés
Alasino, Pablo Horacio
Basei, Miguel A.S.
Morales Camera, Matías Martín
Macchioli Grande, Marcos Simón
Campos Neto, Mario da Costa
Resumen
We report a study integrating 13 new U–Pb LA-MC-ICP-MS zircon ages and Hf-isotope data from dated magmatic zircons together with complete petrological and whole-rock geochemistry data for the dated granitic rocks. Sample selection was strongly based on knowledge reported in previous investigations. Latest Devonian–Early Carboniferous granite samples were collected along a transect of ~ 900 km, from the inner continental region (present-day Eastern Sierras Pampeanas) to the magmatic arc (now Western Sierras Pampeanas and Frontal Cordillera). Based on these data together with ca. 100 published whole-rock geochemical analyses we conclude that Late Devonian–Early Carboniferous magmatism at this latitude represents continuous activity (ranging from 322 to 379 Ma) on the pre-Andean margin of SW Gondwana, although important whole-rock and isotopic compositional variations occurred through time and space. Combined whole-rock chemistry and isotope data reveal that peraluminous A-type magmatism started in the intracontinental region during the Late Devonian, with subsequent development of synchronous Carboniferous peraluminous and metaluminous A-type magmatism in the retro-arc region and calc-alkaline magmatism in the western paleomargin. We envisage that magmatic evolution was mainly controlled by episodic fluctuations in the angle of subduction of the oceanic plate (between flat-slab and normal subduction), supporting a geodynamic switching model. Subduction fluctuations were relatively fast (ca. 7 Ma) during the Late Devonian and Early Carboniferous, and the complete magmatic switch-off and switch-on process lasted for ~ 57 Ma. Hf TDM values of zircon (igneous and inherited) from some Carboniferous peraluminous A-type granites in the retro-arc suggest that Gondwana continental lithosphere formed during previous orogenies was partly the source of the Devonian–Carboniferous granitic magmas, thus precluding the generation of the parental magmas from exotic terranes.