Cartografia do potencial de Au-Pd-Pt e EGP-Cr-Ni na região de Serra Leste (Carajás) utilizando-se a técnica ACP e classificadores hiperespectrais

Abstract

This work comprises a study about the favorability for occurrence of Platinum Group Elements (PGE) deposits in the Serra Leste region, Carajas Mineral Province (CMP). This region is characterized by adverse atmospheric conditions and difficulties of access due to presently dense equatorial forest cover. Considering these natural characteristics, high density and resolution airborne geophysical data were utilized in case studies associated to two types of PGE mineralizations: (i) the Serra Leste deposit – a particular case of Au-Pd-Pt hosted by metasediments; and (ii) the Luanga deposit - a classical occurrence of PGE-Cr-Ni hosted by mafic-ultramafic rocks. Maps of the amplitude of the analytic signal, individual K, eTh, eU, channels, total count and radioelement ratios (eU/eTh, eK/eTh), were generated. These interpretative products enabled the discrimination of the Serra Leste and Luanga deposits by means of the analysis of its magnetic and radiometric signatures. On the basis of the geophysical signatures and descriptive models of these two deposits, Principal Component Analysis (PCA), Spectral Angle Mapper and Mixture Tuned Matched Filtering techniques were applied to the geophysical database, seeking the mapping of areas with similar characteristics to these two deposits. The results showed the utility of these classification techniques (first developed for processing of multispectral and hyperspectral data) for extended use on airborne geophysical data, permitting the mapping of targets more favorable to host PGE deposits, which are of geological, metalogenetic and economic interests in the study area. Although the present testing proved quite promising and advantageous against other techniques, care must be taken to apply such approcahes to geophysical data, an issue also discussed as a topic of this study.