Abstract
This work used multi-source data integration techniques (gamma-spectrometry, magnetometry, SRTM-Altimetry) to identify areas favorable for the occurrence of well-developed lateritic regolith in the eastern region of the state of Bahia. The variables observed to define target potential were the high eTh/K and eU/K ratios and altitudes (obtained from SRTM). Based on these parameters, Boolean and fuzzy logic were applied to produce favorability maps. The best results were obtained under the fuzzy model (γ= 0.7) with a hit accuracy in the areas for potential laterite occurrence of 97.4% and a kappa value of 0.5, consisting of 118 control points obtained through fieldwork. The cross-referencing of the fuzzy image (γ = 0.7) with the magnetometry, total gradient (ASA-Analytical Signal Amplitude) suggested the predominance of more felsic protoliths in the most favorable areas. The lateritic index [IL = (eTh*eU)/K2)] was also applied, demonstrating good correlation with the areas determined by the Boolean and Fuzzy models. Mineralogical associations (clay minerals and/or iron oxides) of the target areas were estimated by the Crosta Technique in OLI/Landsat-8 images. The processing results were integrated in GIS environment, together with control points and data found in the bibliography (e.g. geological map, vertical electrical profile, drill-holes, occurrence of Fe and Al, lateritic crusts, geochemical anomalies).The observed correlation between the generated models and the direct data validates the effectiveness of the techniques used.
Highlights
IntroductionLateritic regolith occurs mainly in regions within the intertropical belt (latitudes between 30o N and 30o S), where laterization processes are most effective due to high temperatures and rainfall (Freyssinet et al 2005).Studies conducted in Australia (e.g. Wilford 1992, 2012; Anand and Paine 2002) and Central Africa (e.g. Arhin and Nude 2009; Arhin et al 2015) based on the synergy of gamma-spectrometric, altimetric and orbital imaging have reached good results in mapping regolith and predicting relevant information for mineral prospecting (e.g. prospection maps). Smith et al (2000) pointed out that at least thirteen gold deposits were discovered in Australia between 1983 and 1994, through geochemical studies of lateritic profiles integrated with regolith mapping.In Brazil, the study of lateritic regolith has concentrated mainly in the Amazon region due to the extensive regolith presence and economical exploitation of associated mineral deposits (e.g. Al, Mn, Fe, Ni, etc.)
Studies conducted in Australia (e.g. Wilford 1992, 2012; Anand and Paine 2002) and Central Africa (e.g. Arhin and Nude 2009; Arhin et al 2015) based on the synergy of gamma-spectrometric, altimetric and orbital imaging have reached good results in mapping regolith and predicting relevant information for mineral prospecting
Smith et al (2000) pointed out that at least thirteen gold deposits were discovered in Australia between 1983 and 1994, through geochemical studies of lateritic profiles integrated with regolith mapping
Summary
Lateritic regolith occurs mainly in regions within the intertropical belt (latitudes between 30o N and 30o S), where laterization processes are most effective due to high temperatures and rainfall (Freyssinet et al 2005).Studies conducted in Australia (e.g. Wilford 1992, 2012; Anand and Paine 2002) and Central Africa (e.g. Arhin and Nude 2009; Arhin et al 2015) based on the synergy of gamma-spectrometric, altimetric and orbital imaging have reached good results in mapping regolith and predicting relevant information for mineral prospecting (e.g. prospection maps). Smith et al (2000) pointed out that at least thirteen gold deposits were discovered in Australia between 1983 and 1994, through geochemical studies of lateritic profiles integrated with regolith mapping.In Brazil, the study of lateritic regolith has concentrated mainly in the Amazon region due to the extensive regolith presence and economical exploitation of associated mineral deposits (e.g. Al, Mn, Fe, Ni, etc.). Lateritic regolith occurs mainly in regions within the intertropical belt (latitudes between 30o N and 30o S), where laterization processes are most effective due to high temperatures and rainfall (Freyssinet et al 2005). Smith et al (2000) pointed out that at least thirteen gold deposits were discovered in Australia between 1983 and 1994, through geochemical studies of lateritic profiles integrated with regolith mapping. In Brazil, the study of lateritic regolith has concentrated mainly in the Amazon region due to the extensive regolith presence and economical exploitation of associated mineral deposits (e.g. Al, Mn, Fe, Ni, etc.). The main research on regolith using airborne-gamma spectrometry and altimetric data focused on this region Most of the work is concentrated mainly on the geochemical and mineralogical aspects of the regolith profiles, focusing in part on the exploration of mineral resources and secondarily on geophysical and geochronological features
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