Resumo

LARROVERE, Mariano A; ALASINO, Pablo H  e  BALDO, Edgardo G. La faja de cizalla dúctil doble-vergente del noroeste de la Sierra de Velasco: deformación de la corteza media durante la orogenia Famatiniana. Rev. Asoc. Geol. Argent. [online]. 2016, vol.73, n.1, pp.117-133. ISSN 0004-4822.

Field, petrographic and structural studies in mylonitic rocks from the northern part of the Señor de La Punta-El Cantadero ductile shear zone, sierra de Velasco, reveal the existence of conjugate ductile shear zones with reverse kinematic generated at medium- to high-grade metamorphic conditions in response to crustal shortening. The Señor de La Punta-El Cantadero ductile shear zone is composed of mylonites and protomylonites derived from granites. At regional scale, it represents a megastructural element of areal extension with a relatively uniform strain distribution. Estimated metamorphic conditions during ductile deformation range from 500 to 700 °C, at pressures consistent with the sillimanite stability field. The Señor de La Punta-El Cantadero ductile shear zone shows a main double-vergent structure defined by C planes that strike with N/NNW and dip toward the W and ENE. The kinematic is reverse, with displacements in opposite senses linked to an E/ENE regional principal shortening direction. This main structure is interpreted as a mid-crustal “root zone” where deformation is nucleated and from which, discrete ductile shear zones with opposite vergency, diverge towards upper crustal levels. These structural features define, at crustal scale, a conjugate system of shear zones. This ductile deformational event occurred during syn- to post-orogenic climax deformational phases of the famatinian orogeny in a contractional tectonic regime.

Palavras-chave : Structure; Kinematics; Metamorphism; Señor de La Punta-El Cantadero shear zone; Sierras Pampeanas.

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