Early Carboniferous sub- to mid-alkaline magmatism in the Eastern Sierras Pampeanas,NW Argentina: A record of crustal growth by the incorporation of mantle-derived material in an extensional setting |
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| Institution: | 1. CRILAR-CONICET, Entre Ríos y Mendoza, 5301, Anillaco, La Rioja, Argentina;2. INGeReN-CENIIT-UNLaR, Av. Gob. Vernet y Apostol Felipe, 5300, La Rioja, Argentina;3. CICTERRA-CONICET-UNC, Av. Vélez Sarsfield 1611, Pab. Geol., X5016CGA-Córdoba, Argentina;4. British Geological Survey, Keyworth, Nottingham NG12 5GG, United Kingdom;5. Depto. de Petrología y Geoquímica – IGEO (Universidad Complutense, CSIC), 28040 Madrid, Spain;6. CIG-CONICET-UNLP, Calle 1 No. 644, 1900, La Plata, Argentina;7. Research School of Earth Sciences, The Australian National University, Canberra 0200, Australia;1. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (Provincia de La Rioja-UNLaR-SEGEMAR-UNCa-CONICET), Anillaco, Argentina;2. Instituto de Geología y Recursos Naturales, Centro de Investigación e Innovación Tecnológica, Universidad Nacional de La Rioja (INGeReN-CENIIT-UNLaR), La Rioja, Argentina;3. Dirección General de Minería, La Rioja, Argentina;1. CICTERRA, CONICET – Universidad Nacional de Córdoba, Av. Haya de la Torre s/n, X5015GCA, Córdoba, Argentina;2. Instituto de Geociências, Universidade de São Paulo, São Paulo, Brazil;1. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR-CONICET), Entre Ríos y Mendoza s/n, Anillaco, 5301, La Rioja, Argentina;2. INGeReN-CENIIT-UNLaR, Av. Gob. Vernet y Apostol Felipe, 5300, La Rioja, Argentina;3. CICTERRA-CONICET-UNC, Av. Vélez Sarsfield 1611, Pab. Geol., X5016CGA, Córdoba, Argentina;1. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología, Av. Roca 1242, 8332, General Roca, Río Negro, Argentina;2. Universidad Nacional del Comahue, Facultad de Ingeniería, Depto. de Geología y Petróleo. Buenos Aires 1400, 8300, Neuquén, Argentina;3. Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET). Instituto de Investigación en Paleobiología y Geología. Av. Roca 1242, 8332, General Roca, Río Negro, Argentina;4. Instituto Geológico y Minero de España, Oviedo Unit, C/Matematico Pedrayes 25, 33005, Oviedo, Spain;1. Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, Av. Julio A, Roca 1242, R 8332 EXZ General Roca (Río Negro), Argentina;2. Centro de Investigaciones Geológicas (UNLP-CONICET), Calle 1 N° 644, B 1900 TAC La Plata (Buenos Aires), Argentina;3. Centro de Pesquisas Geocronológicas (Instituto de Geociências, USP), Rua do Lago 562, CEP 05508-080 São Paulo, SP, Brazil |
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| Abstract: | A recently discovered granitic intrusion at Cerro La Gloria in western Sierra de Famatina (NW Argentina) is representative of sub- to mid-alkaline Carboniferous magmatism in the region. The main rock type consists of microcline, quartz and plagioclase, with amphibole, magnetite, ilmenite, biotite, epidote, zircon, allanite and sphene as accessory minerals. We report a U–Pb zircon SHRIMP age for the pluton of 349 ± 3 Ma (MSWD = 1.1), i.e., Tournaisian. Whole-rock chemical composition and Nd isotope analyses are compatible with an origin by melting of older mafic material in the lower crust (εNdt between ? 0.58 and + 0.46 and TDM values of about 1.1 Ga). The pluton is intruded by penecontemporaneous to late alkaline mafic dykes that are classified as back-arc basalts. Coeval, Early Carboniferous A-type granites occur farther east in the Sierras Pampeanas, probably generated during lithospheric stretching. Overall, the Early Carboniferous granitic rocks show a west-to-east mineralogical and isotopic zonation indicating that magma genesis involved a greater contribution of juvenile material of mantle character to the west. Based on the observed patterns of geochronology, geochemistry and field relationships we suggest that A-type magma genesis in the Eastern Sierras Pampeanas was linked to an Andean-type margin where the lithospheric mantle played a role in its generation. |
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