Early Cambrian U-Pb zircon age and Hf-Isotope data from the Guasayán pluton, Sierras Pampeanas, Argentina: implications for the northwestern boundary of the Pampean arc

An Early Cambrian pluton, known as the Guasayán pluton, has been identified in the central area of Sierra de Guasayán, northwestern Argentina. A U-Pb zircon Concordia age of 533±4 Ma was obtained by LA-MC-ICP-MS and represents the first report of robustly dated Early Cambrian magmatism for the north...

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Detalles Bibliográficos
Autores principales: Dahlquist, Juan A., Verdecchia, Sebastián O., Baldo, Edgardo G., Basei, Miguel A. S., Alasino, Pablo H., Urán, Gimena A., Rapela, Carlos Washington, Costa Campos Neto, Mario da, Zandomeni, Priscila S.
Formato: Articulo
Lenguaje:Inglés
Publicado: 2016
Materias:
Ciencias Naturales
Hf isotopes
Pampean granites
Sierra de Guasayán
U-Pb Geochronology
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/86520
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
Descripción
Sumario:An Early Cambrian pluton, known as the Guasayán pluton, has been identified in the central area of Sierra de Guasayán, northwestern Argentina. A U-Pb zircon Concordia age of 533±4 Ma was obtained by LA-MC-ICP-MS and represents the first report of robustly dated Early Cambrian magmatism for the northwestern Sierras Pampeanas. The pluton was emplaced in low-grade metasedimentary rocks and its magmatic assemblage consists of K-feldspar (phenocrysts)+plagioclase+quartz+biotite, with zircon, apatite, ilmenite, magnetite and monazite as accessory minerals. Geochemically, the granitic rock is a metaluminous subalkaline felsic granodiorite with SiO<SUB>2</SUB>=69.24%, Na<SUB>2</SUB>O+K<SUB>2</SUB>O=7.08%, CaO=2.45%, Na<SUB>2</SUB>O/ K<SUB>2</SUB>O=0.71 and FeO/MgO=3.58%. Rare earth element patterns show moderate slope (La<SUB>N</SUB>/Yb<SUB>N</SUB>=8.05) with a slightly negative Eu anomalies (Eu/Eu*=0.76). We report the first <i>in situ</i> Hf isotopes data (ε<SUB>Hft</SUB>=-0.12 to-4.76) from crystallized zircons in the Early Cambrian granites of the Sierras Pampeanas, helping to constrain the magma source and enabling comparison with other Pampean granites. The Guasayán pluton might provide a link between Early Cambrian magmatism of the central Sierras Pampeanas and that of the Eastern Cordillera, contributing to define the western boundary of the Pampean paleo-arc.

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