Significado geológico de uma anomalia geofísica aeromagnética no escudo sul-rio-grandense

Abstract

The integration of remote sensing and geological data has been very important and effective over the years in the identification and interpretation of structures and their preferred directions. In this context, the present work presents a contribution to the studies that involve details of magnetic lines that cut the Sul-rio-grandense Shield (SrgS), specifically those arranged in NW-SE direction. The main objective of this work is to understand the field meaning of one of these anomalous linear features located in the Tijucas Terrain, in the central portion of SrgS, through geological and petrographic characterization. Therefore, it is intend to find indications that associate said magnetic anomaly with the processes of formation of the Rio Grande Arc, represented by a structural high of basement rocks cut by a series of intrusions related to the basaltic volcanism of the Serra Geral Formation of the Paraná Basin. The analysis and interpretation of the data was carried out through the investigation of remote sensing products, such as map of aeromagnetic anomaly and satellite images, to choose a lineament to be investigated in the field. After that, field work was done to collect data and samples for petrographic characterization in thin sections. By means of the field observations it was possible to recognize that the rocks that are on the magnetic lineament are a gabbroic plutonic igneous rock, structured in the form of a dike. The petrographic analysis was carried out in seven slides made from the samples collected in the area in field works and the project in which this work is linked, titled Investigation of Magnetic Lineaments in Rio Grande do Sul. This analysis made it possible to conclude, through the identification of the mineralogical assembly, the anortite contents and the percentage of minerals estimated by visual field estimation, that the verified rocks are olivinegabbros. According to the studies carried out, in conjunction with the bibliographic review of the area comprising the lineament, it is believed that it is related to the formation processes of the Rio Grande Arc since it has the same NW-SE direction and contains rocks with similar composition to the volcanic equivalents of the Serra Geral Formation basalts.