RESULTADOS PALEOMAGNÉTICOS DE UNIDADES ÍGNEAS PERMO-TRIÁSICAS DEL MACIZO NORPATAGÓNICO, RÍO NEGRO, ARGENTINA. IMPLICANCIAS PARA EL ORIGEN DE PATAGONIA.

MARTÍNEZ DOPICO, C.; MIGUEZ, M.; RAPALINI, A.E.; FANNING, C.; LUPPO, T.; LÓPEZ DE LUCHI, M. G.,

San Miguel de Tucuman

Congreso; XX Congreso Geologico Argentino; 2017

Universidad de Tucumán-Asociacion Geológica Argentina

A paleomagnetic study was carried out on late Permianto early Triassic magmatic units exposed in the North Patagonian Massif(Argentina) in order to provide better paleogeographic and tectonic constraintson the evolution of Patagonia and its relations with Gondwana in the latePaleozoic. A paleomagnetic pole (C) was obtained for the Collinao Units (48.3°S,349.9°E, N=7, A95=15.1), with an age of 253± 2 Ma. Asecond paleomagnetic pole (A) was computed from12 acidic dykes (87°S, 51.5°E,N=12, A95=8.1°), which strongly disagrees with the C position. The C pole fallson the Gondwana/South America different reference paths, but in a much olderposition (late Carboniferous) which indicates that it is clearly anomalous. TheA pole, in turn, is consistent with the Triassicreference poles. Other twopreliminary paleomagnetic poles corresponding to volcanic units of Los MenucosComplex (between 257± 2 and248± 2 Ma) and younger acidic dykes and altered units produce analogousresults. Since the discrepancy cannotby explained in terms of local tectonics,a working-model is presented thatinvolves aCCW rotation of the whole NPM of 30° during the latest Permian andearliest Triassic, closing a V-shaped basin, as the final stages of collisionof an allochthonous or para-autochthonous Patagonia terrane.