QUANTIFICAÇÃO DA DEFORMAÇÃO EM MIGMATITOS METATEXITOS ESTROMÁTICOS E ROCHAS ASSOCIADAS DO COMPLEXO ATUBA, PORÇÃO LESTE DO ESTADO DO PARANÁ

Quantification of deformation in stromatic metathexite migmatites and associated rocks of the Atuba Complex, Eastern Paraná State

Abstract

The Atuba Complex emerges in the eastern portion of the State of Paraná, along an NE-SW elongated swath and comprises the southern part of the Ribeira Belt. This work has as main objective to define the tectonic and deformational regimes of the Atuba Complex. The research was developed through field research, petrography and quantitative structural analysis and complements several tectonic studies already performed. Stromatic metathexite migmatites have medium to high metamorphic grade and are composed of tonalitic residual neosomes interspersed with granitic or tonalitic-granodioritic leukosomes and mafic melanosomes. They can often be classified as belonging to the series of milonites. Amphibolites, schists, granulitic gneisses, schollen diatexites, quartzites and granitoids are also observed. Two foliation planes, both generated by ductile shear, were identified: the first is characterized by Sn-1 foliation associated with thrusting tectonics (Dn-1) and the second by Sn foliation produced by sinistral transpressive tectonics (Dn). The results confirm that the last phase was accommodated by the deformation partition. The quantification of deformation was developed using the Fry, Polar and Rf/φ method, based on analysis of quartz and feldspar crystals on 26 thin section. Samples revealed similar strain ratios for all methods used in the XZ and YZ planes. The ellipsoids are oblate in shape and correspond to the apparent flattening field.

Keywords: Structural analysis. Migmatites. Transpression.