Geochronology of Igneous Rocks in the Sierra Norte De Córdoba (Argentina): Implications for the Pampean Evolution at the Western Gondwana Margin
RESEARCH Geochronology of igneous rocks in the Sierra Norte de Córdoba (Argentina): Implications for the Pampean evolution at the western Gondwana margin W. von Gosen1,*, W.C. McClelland2,*, W. Loske3,*, J.C. Martínez4,5,*, and C. Prozzi4,* 1GEOZENTRUM NORDBAYERN, KRUSTENDYNAMIK, FRIEDRICH-ALEXANDER-UNIVERSITÄT ERLANGEN-NÜRNBERG, SCHLOSSGARTEN 5, D-91054 ERLANGEN, GERMANY 2DEPARTMENT OF EARTH AND ENVIRONMENTAL SCIENCES, UNIVERSITY OF IOWA, 121 TROWBRIDGE HALL, IOWA CITY, IOWA 52242, USA 3DEPARTMENT FÜR GEO- UND UMWELTWISSENSCHAFTEN, SEKTION GEOLOGIE, LUDWIG-MAXIMILIANS-UNIVERSITÄT MÜNCHEN, LUISENSTRASSE 37, D-80333 MÜNCHEN, GERMANY 4DEPARTAMENTO DE GEOLOGÍA, UNIVERSIDAD NACIONAL DEL SUR, SAN JUAN 670, 8000 BAHÍA BLANCA, ARGENTINA 5INGEOSUR-CONICET ABSTRACT U-Pb zircon data (secondary ion mass spectrometry [SIMS] and thermal ionization mass spectrometry [TIMS] analyses) from igneous rocks with differing structural fabrics in the Sierra Norte de Córdoba, western Argentina, suggest that the sedimentary, tectonic, and magmatic history in this part of the Eastern Sierras Pampeanas spans the late Neoproterozoic–Early Cambrian. A deformed metarhyolite layer in meta- clastic sedimentary rocks gives a crystallization age of 535 ± 5 Ma, providing a limit on the timing of the onset of D1 deformation and meta- morphism. The new data coupled with published Neoproterozoic zircon dates from a rhyolite beneath the metaclastic section and detrital zircon ages from the section indicate a late Neoproterozoic to Early Cambrian depositional age, making this section time equivalent with the Puncoviscana Formation (sensu lato) of northwest Argentina. A synkinematic granite porphyry gives a crystallization age of 534 ± 5 Ma, pro- viding a limit on the age of dextral mylonitization in the Sierra Norte area (D2 event).
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