Interpretation of airborne and ground magnetic and gamma-ray spectrometry data in prospecting for base metals in the central-north part of the Itabuna-Salvador-Curaçá Block, Bahia, Brazil

Abstract

Interpretation of airborne and ground magnetic and radiometric geophysical data is fundamental to provide support for geologic mapping and exploration of mineral resources. This is particularly important of the Itabuna-Salvador-Curaçá Block component of the São Francisco Craton in the state of Bahia, Brazil, which bears important base metal mineralization in ultramafic intrusions. The interpreted airborne data covered part of the northern segment, and the ground data comprised an area of [Formula: see text] in the northern segment of that Archean block. The radiometric interpretation was only qualitative, and the magnetic interpretation was qualitative and quantitative. The qualitative interpretation defined distinct configurations of the geophysical signatures. So, it furnished possible regional and local geologic models and also helped to infer the distribution of magnetization and radiometric content in the rocks. The quantitative interpretation started with Werner deconvolution for a preliminary identification of the magnetic sources, and 2D magnetic modeling improved the definition of the anomalous bodies in terms of geometry, depth to the top, and magnetic susceptibility. The combined qualitative and quantitative interpretation allowed mapping of the rocks that contain magnetic and metallic minerals, as well as felsic lithology, such as granites and orthogneisses, and mafic lithology, such as gabbros and amphibolites. It also suggested that most of the northwest–southeast lineaments related to felsic and mafic magnetic intrusions. The analysis may extend to other areas of the block and be integrated with field and laboratory geologic, geophysical, and geochemical studies for an adequate exploration of nickel, copper, and chromium that are potentially present in the region.