Determinação das camadas de carvão a partir de tomografia de refração sísmica: uma aplicação na mina de Candiota/RS – Caçapava do Sul, RS

Abstract

Considering the importance of mineral coal in the world economic scenario, it is essential to use geophysical methods in the exploration of this type of mineral resource. This work used the technique of time-domain seismic tomography using shallow seismic refraction data in order to map the coal layers and to relate the seismic wave velocity contrasts with information from drill cores at the coal mine in the municipality of Candiota, state of Rio Grande do Sul. Coal beds are part of the Rio Bonito Formation, located between the Palermo Formation at the top and the Itararé Group at the base, some of the various formations that make up the Paraná Basin. Seismic refraction tomography provided a model of seismic velocities through the inversion of the travel times of the first seismic refraction data breaks, which allowed characterizing the subsurface layers. For the accomplishment of this study three seismic lines with 360 meters extension were acquired that were correlated with the probes present in the place. The application of this technique allowed to stratify the medium in four main layers that can be associated to the main lithology’s that are part of the local geological context. With the information about the survey reports it was possible to interpret the velocity models generated for each of the lines, where it was observed that the carbon carrier layer is limited between 5 and 30 m depth and defined by a velocity range of 1700 - 2800 m / s considering all three models. These data are in agreement with the values established in other works. In summary, the tomography method provided satisfactory results, in order to contribute to future explorations of this mineral resource in the studied area.