INVESTIGADORES
TOMEZZOLI Renata Nela
congresos y reuniones científicas
Título:
Did Patagonia collide against Gondwana in the Late Paleozoic? Some Insights From Magnetic Fabrics of Granitoids in the North Patagonian Massif
Autor/es:
RAPALINI, A.E., M.G.LOPEZ DE LUCHI, TOMEZZOLI, R.
Lugar:
San Francisco?
Reunión:
Congreso; American Geophysical Union, Meeting; 2008
Institución organizadora:
AGU
Resumen:
The Paleozoic tectonic evolution of Patagonia has been a matter of much debate in the
last two decades. There is no consensus on whether the North Patagonian Massif (NPM)
was accreted by a frontal collision to Gondwana or if it shared a similar paleotectonic
evolution with other Gondwana blocks during the Paleozoic. Different geologic,
geochronologic, geophysical and structural data have been interpreted either as
supporting or refuting the collisional model. Paleomagnetic data obtained so far is
consistent with an authochtonous evolution since the Devonian, but it does not rule out
relative displacements of up to 1500 km between Patagonia and Gondwana.Therefore, a
Late Paleozoic frontal collision cannot be definitely ruled out on the basis of
paleomagnetic data alone. As part of a muldisciplinary research project a magnetic
fabric study, by means of the anisotropy of magnetic susceptibility (AMS), was carried
out on Late Paleozoic granitoids exposed in northeastern NPM. Two main composite
units were studied, the highly to variably foliated Yaminue Complex, poorly dated as
Late Carboniferous and ranging in composition from tonalite to leuco-granite, and the
much less deformed granodiorites to monzoganites of the Early Permian (283 Ma)
Navarrete complex. While the former is composed of both ferro and paramagnetic units,
with a dominance of the latter; the Navarrete plutons are basically ferromagnetic.
Directional and scalar AMS results joined with meso and microstructural studies
permitted the characterization of the deformational and magmatic fabric of the different
units. An evolutionary picture of the succesive intrusive events in NPM emerged which
confirms an important NNE-SSW contractional event associated with intrusion of the
different units that compose the Yaminue Complex. This event ended before the
intrusion of the Navarrete Complex, which is governed by a different stress regime. Our
results fit the hypothesis of a collisional event affecting northern Patagonia in the Late
Paleozoic. This event was over by 283 Ma.