CARACTERIZAÇÃO HIDROGEOFÍSICA DE ESTRUTURAS GEOLÓGICAS CONDUTORAS E ARMAZENADORAS DE ÁGUA SUBTERRÂNEA ATRAVÉS DO MAGNETOTELÚRICO E DA TOMOGRAFIA DE RESISTIVIDADE ELÉTRICA

Abstract

Caxambu, Minas Gerais county, is part of a large Tourist Complex known as Parque das Águas, famous for its hydrothermal richness and character therapeutic of its waters. Geological, geochemical, and hydrogeological studies have already been carried out to understand and characterize hydrothermal sources. The objective of this work is the geophysical study, which will produce information on how the region groundwater behaves, in terms of flow, path traveled in the aquifer, circulation dynamics and deep sources that feed and supply the Caxambu's fissural Aquifer. This research aims at increasing the hidrogeophysical knowledge of Caxambu's Water Circuit. The results obtained were coherent according to the previous geological, hydrogeological and hydrochemical studies developed by UFMG and UERJ. Geophysical-structural and hydrogeophysical studies were carried out applying the Magnetotelluric (MT), Audiomagnetotelluric (AMT) methods and Electrical Resistivity Tomography (ERT) technique that allowed a better understanding of the aquifer of Caxambu. This work included the development and application of two different approaches. The first, inside the park, was carried out a set of measurements with ERT and AMT. These surveys were carried out close to the main sources of water and in order to understand the behavior of shallow subsurface geological structures and the dynamics of circulation in the conduction of mineral waters. The results of the application of these two methods were later integrated and in this work the technique of the Resistivity Cube was developed, whose model presents the AMT and ERT results together. A second set of measures was carried out upstream of the Park, applying the AMT and MT methods. For AMT, similarly as inside the Park, were used an Period range of 10-5 to 10-1 s, and for the MT 10-2 to 104 s. The main objective was to understand the role of deep structures that could be associated with the supplier conductor of the region's hydromineral fissural aquifer and the interaction between these deep conductors and shallow sources. For processing the MT and AMT data, the robust Egbert code was used, and, for inversion, the three-dimensional magnetotelluric inversion algorithm called ModEM was used. For the electrical data, the programs used were AGI EarthImager 2D and AGI EarthImager 3D. The results generated by the three methods were interpreted together, incorporating a priori hydrogeological information. The AMT and ERT results produced a joint model called the Resistivity Cube that integrated and emphasized at different depths the structures found in the region. This study is of public interest that may support the development and organization of hydromineral planning, management and conservation in the short, medium and long terms. Given the current urban occupation, potential contamination factors and other aspects with a potential influence on its characterization as a natural and socio-economic resource, a policy under the demand for water may be developed for the conscious use of these water sources.