Did Patagonia collide with Gondwana in the Late Paleozoic? Some insights from a multidisciplinary study of magmatic units of the North Patagonian Massif

RAPALINI, A.E.; LÓPEZ DE LUCHI, M.G.; MARTÍNEZ DOPICO, C.I.; LINCE KLINGER, F.; GIMÉNEZ, M.; MARTÍNEZ, P.

GEOLOGICA ACTA

UNIV BARCELONA

Lugar: Barcelona; Año: 2010 vol. 8 p. 349 - 371

1695-6133

The origin of Patagonia and its relations with the South American crustal blocks to the north have been a matter of debate for decades. Results from a multidisciplinary study centered on Paleozoic granitoids exposed in the northeastern corner of the North Patagonian Massif are presented and reviewed. Microstructural and magnetofabric studies show two suites of granitoids based upon their deformational pattern. Late Carboniferous (?) deformed granitoids (Yaminué Complex, Tardugno Granodiorite, Cabeza de Vaca leucogranite) record emplacement and subsequent deformation in a major NNE-SSW compressive stress regime that also provoked top-to-the-SW thrust deformation in shallow crustal levels. Gravity and geobarometric studies confirmed that the same major deformational event has been recorded by different crustal levels. Comparison of age and type of deformation for this event across the northern Patagonia boundary strongly supports a Late Carboniferous – Early Permian (?) frontal collision between Patagonia and Gondwana. This major deformational event ceased by 281 Ma when the Navarrete Plutonic Complex was emplaced under a far-field WNW-ESE stress regime. The latter shows basically magmatic fabrics. Sm/Nd and TDM data point to late Paleoproterozoic crustal model ages for the North Patagonian Massif, similar to those from the Sierras Pampeanas and Arequipa-Antofalla terranes, but significantly different from the Rio de la Plata craton. The latter results, plus detrital zircon ages in Early Paleozoic successions, the possible continuation of the Early Ordovician Famatinian arc into the North Patagonian Massif, and paleomagnetic data strongly argue against an allochthonous nature for the North Patagonian Massif. A parautochthonous origin for this crustal block is proposed as the simplest and most likely interpretation.