BRITTLE STRUCTURAL ANALYSIS IN THE INFLUENCE ZONE OF THE PONTA GROSSA ARCH: CASE STUDY IN THE AREA OF THE HPP-MAUÁ-PR

Abstract

The research was carried out in the surroundings the Mauá Hydroelectric Power Plant (UHE-Mauá), located on the Tibagi River, northwest of the Telêmaco Borba municipality, central region of the Paraná State. The power plant’s site is underlain by a diabase sill of the Serra Geral Formation, intruded on Paleozoic sedimentary rocks of the Paraná Basin. At the site, structural control occurs due to the intersection of regional structures, such as the Ponta Grossa Arc, located between the São Jerônimo-Curiúva Fault Zones and the Jacutinga Fault Zone. Results from the mesoscale structural analysis allowed the recognition of faults having a dominant N50-60E orientation. In photo interpretation, however, the most striking lineaments have N40-50W azimuth direction.The mapped discontinuities are characterized, mainly by joints, faults and cataclastic fault zones associated with a strike-slip tectonic regime, sometimes transtensive causing negative flower structures and oblique faults, identified in Paleozoic sediments and basic rocks. This work points to the existence of at least two post-Cretaceous deformation pulses, which deformed the diabase sill and the set of sedimentary rocks, altering the rheological behavior of the rock and the final geometric arrangement of the large weakness planes. The first deformation pulse is related to paleostress field ranging between NNE-SSW and NNW-SSE, whilst the second deformation pulse is coherent to a paleostress field varying between WNW-ESSE and ENE-WSW.