U-Pb LA-ICP-MS Geocronology of detrital zircons from lower Paleozoic rocks of the Eastern Cordillera, NW Argentina: Tectonic significance for the evolution of western Gondwana.

DI CUNZOLO S. C., Y PIMENTEL M. M

Göttingen, Alemania

Simposio; International Colloquium on Latin American Earth Sciences; 2009

Universitättsverlag Göttingen

The provenance of Lower Paleozoic sandstones exposed in the central sector of the Humahuaca´s Creek valley, northwestern Argentina, was investigate in the present study. Detrital zircons grains, were analysed by the U-Pb LA-ICPMS method. The studied samples are sandstones from the lower portion of the Cambrian-Ordovician Casa Colorada Formation (Lopez and Nullo 1969) in the neighbourhoods of Casa Colorada and Huacalera. The Cambrian-Ordovician sequence has been interpreted as in a N-S intracratonic basin, developed along the western margin of Gondwana between the Eastern Puna-Famatina Terrane in the west and the Pampean Arc to the east. The main objective of this study, was to contribute to the paleogeographic reconstructions of the western margin of Gondwana Detrital zircon age patterns  display mainly Neoproterozoic ages (0.54-0.63-0.79 Ga), with a subordinate Mesoproterozoic (1.04-1.26-1.44 Ga) population. A small Paleoproterozoic population (1.89-2.12 Ga) is also observed. Neoarchean zircons, were identified in both sections, with peaks at approximately 2.53 and 2.68 Ga. These results are similar to those presented by Di Cunzolo and Pimentel (2008), differing from them only in the absence of Paleoarchean ages. We suggest a Gondwana origin for the original sediments, which  deriver from the erosion of the southwest margin of the Brasilian Platform. Neoproterozoic zircon grains were most probably derived from the Brasiloiano Belts and the Goiás Magmatic Arc, in central Brazil, whereas the Mesoproterozoic and Neoarchean ages derived from the Amazon craton.