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Time constraints on the tectonic evolution of the Eastern Sierras Pampeanas (Central Argentina) |
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| Authors: | Siegfried Siegesmund Andre Steenken Roberto D Martino Klaus Wemmer Mónica G López de Luchi Robert Frei Sergej Presnyakov Alina Guereschi |
| Institution: | 1. Geoscience Centre of the Georg-August University G?ttingen, Goldschmidtstrasse 3, 37077, G?ttingen, Germany 2. Institut für Geographie und Geologie, Universit?t Greifswald, Friedrich-Ludwig-Jahn-Strasse 17A, 17487, Greifswald, Germany 3. Cátedra de Geología Tectónica, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, X 5016 GCA, Córdoba, Argentina 4. Instituto de Geocronología y Geología Isotópica, Pebellón INGEIS, Ciudad Universitaria, C 1428 EHA, Buenos Aires, Argentina 5. Institute of Geography and Geology, and Nordic Center for Earth Evolution (NordCEE), University of Copenhagen, ?ster Voldgade 10, 1350, Copenhagen, Denmark 6. Centre of Isotopic Research, All-Russian Geological Research Institute (VSEGEI), 74 Sredny prospect, 199106, Saint Petersburg, Russia |
| Abstract: | The application of the SHRIMP U/Pb dating technique to zircon and monazite of different rock types of the Sierras de Córdoba provides an important insight into the metamorphic history of the basement domains. Additional constraints on the Pampean metamorphic episode were gained by Pb/Pb stepwise leaching (PbSL) experiments on two titanite and garnet separates. Results indicate that the metamorphic history recorded by Crd-free gneisses (M2) started in the latest Neoproterozoic/earliest Cambrian (553 and 543 Ma) followed by the M4 metamorphism at ~530 Ma that is documented in the diatexites. Zircon ages of 492 Ma in the San Carlos Massif correlate partly with rather low Th/U ratios (<0.1) suggesting their growth by metamorphic fluids. This age is even younger than the PbSL titanite ages of 506 Ma. It is suggested that the fluid alteration relates to the beginning of the Famatinien metamorphic cycle in the neighbouring Sierra de San Luis and has not affected the titanite ages. The PTt evolution can be correlated with the plate tectonic processes responsible for the formation of the Pampean orogene, i.e., the accretion of the Pampean basement to the Río de La Plata craton (M2) and the later collision of the Western Pampean basement with the Pampean basement. |
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