Deformación dúctil en el basamento ígneo – metamórfico de la cuesta de La Chilca, Sierras Pampeanas Septentrionales del norte argentino

CISTERNA, C. E., MON, R., CAMPOS, F., SLAVUTSKY, E.

S. M. de Tucumán

Jornada; 2 Jornadas Geológicas, Fundación Miguel Lillo; 2008

Fundación Miguel Lillo

The basement rocks that crop out along the Cuesta de La Chilca represent a portion of the metamorphic basement belt in the sierra de Aconquija (Sierras Pampeanas Septentrionales, NW Argentina). The most abundant schists and gneisses are grey, foliated and/or banded rocks. They show an S1 structure, characterized by a crenulation cleavage and associated folds. These rocks commonly enclose concordant quartz-feldspathic folded and boudinated veins. Small folded granitic to granodioritic bodies are concordant or slight discordant to the dominant structure (S1). The F2 structures are dipping oblique to the F1 and folds, varying between one meter or a few centimetres, are accompanied by an axial plane cleavage (S2). Refolding structures are common and generate interferences patterns, examples of them are the partial or complete closures (“eye folds”) indicatives of the effects of the cross-folding. Finally, in the most outcrops are recognized a ductile shear indicators, associated with rotated and rounded layered blocks and megablasts and (S3) foliation. New field, fabric and mineralogical observations allow characterize the deformational phases and offers a new insight into the tectonic evolution of the Central Andes crystalline basement in northwestern of Argentina.