Electromagnetic Studies Of The Região Dos Lagos In Rio De Janeiro State - Brazil: Tectonic Framework And Groundwater Prospects

This work presents results of a geophysical survey<br>employing electromagnetic (magnetotelluric -MT and<br>time domain electromagnetics-TEM) techniques to<br>probe the upper crustal geoelectric structure aiming at<br>contributing to the geophysical knowledge of a poorly<br>understood area in southeastern Brazil. The survey<br>was carried out in Região dos Lagos - “The Lakes<br>Region” of Rio de Janeiro State, Brazil. A total of 34<br>MT-TEM soundings were located along two profiles<br>18 Km and 27 Km long both in the SE-NW direction<br>crossing orthogonally the observed regional faults<br>known from surface geology, aeromagnetic and<br>remote sensing images of the area.<br>The region is characterized by rocks predominantly of<br>pre-Cambrian age, fractured and altered gneisses and<br>sedimentary covers of quaternary age, described as<br>current and sub current sediments deposited in flood<br>plains and close to the coastal region. Twodimensional<br>geoelectrical models of the two profiles<br>evidenced some groundwater prospects at shallow<br>depths associated with quaternary sediments and<br>fracture zones. Anomalously conductive block at<br>depths between 3 and 6 Km may be related to<br>magmatic materials.