Investigação hidrogeológica e geofísica para caracterização de aquíferos fraturados associados a lineamentos magnéticos

Abstract

The present work consists in a hydrogeological characterization of structures associated with magnetic anomalies of the Sul-rio-grandense Shield (SrgS), previously interpreted as basic dikes feeding the Serra Geral volcanism of Paraná Basin. The study area is located southeast of the Caçapava do Sul city, comprising rocks of the Dom Feliciano Belt, such as the Porongos Metamorphic Complex, Complexo Encantadas and the Camaquã Basin. For the fact that they are crystalline and sedimentary rocks with low water favorability, a study of fractures associated to these rocks plays an important role from the hydrogeological point of view. For the subsurface characterization, the geoconductor EM34-XL will be used, based on the reading of the electrical conductivity, by the interference of the propagation of electromagnetic waves transmitted and received by the apparatus. It is expected from the application of the method and the bibliographical review carried out, to elaborate depth profiles of the hydrogeological situation existing in subsurface, in order to corroborate with the knowledge about the study area, raising discussions about areas favorable to the exploration of water resources, as well as to promote technical knowledge for subsequent exploration campaigns. Four longitudinal profiles were generated, whose results allowed to analyze the shape, dimension and orientation of the investigated igneous bodies. According to the direction of the anomalies, these bodies appear to be plunging into SSW, suggesting we’re dealing not only with dikes but also with thresholds. The structures are mappable to approximately 35 meters deep, and with good lateral continuity of the results, it was possible to generate a figure that suggests in the field where is located one of the bodies. Regarding the hydrogeological conditions of the region, despite being close to the profiles evidence that there is an aquifer, it was not possible to map with the scale used in the profiles. In addition to the fact that the adjacent rocks are little porous and permeable (aquiclude) or crystalline, there was evidence of igneous activity in these rocks, increasing their degree of lithification and cementation of the matrix, making them even more incompatible in hydrogeological investigation.