Integration of multisource data to support the identification of lateritic regolith in Eastern - Bahia, northeastern Brazil

Ano: 2020 | Volume: 3 | Número: 1

Autores: Edgar Romeo Herrera de Figueiredo Iza, Rodrigo Soares Vieira dos Santos, Basílio Elesbão da Cruz Filho

Palavras-chave: LATERITE, LATERITIC CRUST, eTh/K, eU/K, GEOPHYSICS, SRTM

Resumo Inglês:

This work used multi-source data integration techniques (gamma-spectrometry, magnetometry, SRTMaltimetry)
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 Crósta 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.