CIGEOBIO   24054
CENTRO DE INVESTIGACIONES DE LA GEOSFERA Y BIOSFERA
Unidad Ejecutora - UE
artículos
Título:
Tectono-metamorphic evolution of a convergent back-arc: The Famatinian orogen, Sierra de Quilmes, Sierras Pampeanas, NW Argentina
Autor/es:
FINCH, MELANIE A.; WEINBERG, ROBERTO F.; HASALOVÁ, PAVLÍNA; BECCHIO, RAUL; FUENTES, M. GABRIELA; KENNEDY, ALLEN
Revista:
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
Editorial:
GEOLOGICAL SOC AMER, INC
Referencias:
Año: 2017
ISSN:
0016-7606
Resumen:
Back-arcs are hot regions of enduringweakness in the hinterland of subductionzones that are commonly sites of strain localization,forming mobile belts that, in somecases, develop into mountain belts. Theirevolution results from their strength, a functionof thickness, heat flux, and stresses.Contractional back-arcs may be too weakto form thick crusts, whereas in other cases,they can thicken considerably and lead tomountain building. The stress and thermalhistories of back-arcs can be retrieved frominvestigation of the relationships betweendeformation and metamorphism. The 490?430 Ma Famatinian orogen of the SierrasPampeanas is associated with a back-arc thathas a complex development. We focus on theSierra de Quilmes within the northern sectionof the back-arc and present new structuraldata tied to anatexis and constrained bygeochronology. We find that low-pressure?high-temperature conditions prevailed overan ~35 m.y. thermal peak between 497 and461 Ma, as indicated by U/Pb ages of monazite.Anatexis coincided with thrusting to thewest and northwest, as evidenced by leucosomesin axial planes of folds and in thrustplanes. As rocks were thrust upward, theycooled, melt solidified, and deformation localizedinto two major thrust zones. Theserecord the same thrust-to-the-west or northwestkinematics as the earlier syn-anatecticdeformation and ultimately placed hot rocksover cold ones. Continuous thrusting duringcooling from peak metamorphism, accompaniedby strain localization, is consistentwith a number of shear zones in the northernSierrasPampeanas. The low-pressure metamorphicassemblages indicate that shorteningwas not accompanied by pronouncedcrustal thickening, suggesting that the lithospherewas too hot, and the partially meltedcrust was too weak for substantial stacking.