40Ar/39Ar age dating of ductile deformation in a shear zone from the Sierra de La Huerta, San Juan, Argentina: evidence of the Famatinian orogeny

CASTRO DE MACHUCA, B.; DELPINO, S.; MOGESSIE, A.; PREVILEY, L.; PONTORIERO, S.; BJERG, E. A.; GALLIEN, F.

Brasilia, Brasil

Simposio; VII South American Symposium on Isotope Geology; 2010

Sociedad Brasilera de Geoquímica

Mylonites associated with ductile shear zones are widespread in the crystalline basement of the Sierra de La Huerta (SLH), Western Sierras Pampeanas, province of San Juan, Argentina. The Arenosa Creek Shear Zone (ACSZ) in east-central SLH (31° 23E 43’’ S - 67° 19E 33’’ W) provides an excellent example for studying the progressive evolution of ductile deformation of a quartzose metagabbro/metadiorite (QM/M) at high-to medium-grade metamorphic conditions, and constraining the age of the mylonitic deformation. Obtained 40Ar/39Ar ages constrain the final stages of the mylonitization event to the interval between 441.9 and 438.7 Ma, at the ending of the Famatinian orogeny.