INVESTIGADORES
GONZALEZ Pablo Diego
artículos
Título:
Early Paleozoic structural and metamorphic evolution of western Sierra de San Luis (Argentina), in relation to Cuyania accretion
Autor/es:
GONZÁLEZ, PABLO D.; SATO ANA MARÍA; LLAMBÍAS EDUARDO; BASEI, MIGUEL; VLACH, SILVIO
Revista:
GONDWANA RESEARCH
Referencias:
Lugar: Bombay; Año: 2004 vol. 7 p. 1157 - 1170
ISSN:
1342-937X
Resumen:
Structural, metamorphic and isotopic data obtained from the Nogolí Metamorphic Complex of western Sierra de
San Luis indicate that the Early Paleozoic Famatinian Orogeny overprinted an already structured and metamorphosed
older basement. The older geological features are relict NW trending fabric associated with high-grade (amphibolite
facies) regional metamorphism preserved within thin strips of schists and paragneisses and in the core of mafic to
ultramafic lenses. Arc magmatism, medium P (Barrovian type)/high T (amphibolite to granulite facies) regional
metamorphism and penetrative NNE to NE trending foliation are related to the building of the Famatinian orogenic
belt. The P-T conditions of the Famatinian prograde metamorphism reached a pressure peak of ca. 8 kb, with a thermal
peak from ~750°C up to ~820°C. U-Pb conventional and chemical dating and Ar-Ar plateau ages constrain the peak of
the main orogenic phase related to the Famatinian belt to 470.457 Ma (Early to Mid-Ordovician). Greenschist facies
retrograde metamorphism closely associated with shear zones and secondary Ar-Ar plateau and Sm-Nd ages suggest
that a late to post-orogenic phase of the Famatinian belt was active at least since ~445 Ma. This phase continued
during the Silurian to Late Devonian times through multiple reactivation of early shear zones. The Famatinian Orogeny
reset a previous thermal history and therefore, the timing of the relict fabric could not be constrained conclusively with
radiometric dates. Despite this difficulty, a range of 520 to 490 Ma suggests some inheritance from Pampean events
registered by the older NW-SE fabric. The Early to Mid-Ordovician regional metamorphism and ductile deformation of
the western Sierra de San Luis is interpreted as the orogenic effects of the collision of the allochthonous Cuyania
terrane with the autochthonous proto-Pacific margin of Gondwana during the Famatinian Orogeny.