MAPPING OF HIGH ELECTRICAL CONDUCTIVITY ON THE TORRES SYNCLINE HINGE, SOUTHEASTERN PARANÁ BASIN

Abstract

A preliminary interpretation of the electrical structures beneath the SE Paraná Basin is presented based on electromagnetic geophysical soundings carried out around the Torres Syncline. GDS induction arrows show a NW-trending conductive anomaly nearly coincident with the hinge of the syncline and strong "ocean effects" observed at longer periods in sites near the coastline. 1-D inversions of MT data at sites located inside this anomaly have distinguished a large electrical conduit, dipping to the NW from a depth of 500 m at the coast to 1000 m at a distance of about 100 km further inland. The conductor, located in the crystalline basement, could be possibly ascribed to residual metassomatic fluids concentrated along a fractured hinge of the downfolded Torres Syncline, as a fossil record of past magmatic activities in the Early Cretaceous that affected the Paraná Basin and underlying lithosphere.