Caracterização espectrorradiométrica do minério magnesítico da porção Centro-Sul do Estado do Ceará

• Ano de defesa: 2020
• Autor(a) principal: Souza, Cassiano Dias de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Espectrorradiometria; Magnesita; Sensoriamento Remoto
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/57570

This work has as objective the spectroradiometric characterization of magnesitic ore of the south-central portion of the state of Ceará through reflectance spectroradiometry. The samples collected from the mines of Torto, Riacho Fundo and Cabeça de Negro, located between the municipalities of Orós and Jucás, were cut ad polished, in order to obtain uniform surfaces, and to minimize the effect of the relief and any weather effects of surface. The data were obtained through the FieldSpec Pro FR 3 which collects data in the range between 350nmand 2500nm. The collection procedure was performed in the laboratory, without any interference from external lighting. Three measurements were made in different sample location, each measurement representing the averageof 50 spectra collected. The spectral features found are related to iron ions, to the groups CO32-, H2O, OH-, and Mg –OH bond. Seven of these features stood out for their frequency and intensity, being called Band 1 to Band 7. The spectral behavior at the shortest wavelengths is associated with the electronic transitional processes of iron, as well as the intense and wide absorption band between 1000nmand 1300nm(Band 1), and the band at 1700nm(Band 3). Due to the spectral features at 1390nm(Band 2), 1440nmand 1940nm(Band 5) characteristics, except for the CN –05 sample, it could be said that there is the presence of H2Oinserted as a fluid inclusion or as part of crystalline structure of the samples from the Cabeça de Negro mine,with the features at 950nm, 2070nmand 2390nmbeing attributed to hydroxyl and Mg –OH bond. In the spectra of the samples from Torto, Riacho Fundo, and the CN –05 sample from Cabeça de Negro mine, there are only spectral features related to the hydroxyl and the Mg –OH bond. The spectral features related to the transitional vibrational processes of CO32-are centered at 1850nm(Band 4), 1970nm(Band 5), 2130nm(Band 6) and 2300nm(Band 7) . In the spectra of samples from Cabeça de Negro mine, with the exception of the CN -05 sample, the absorption featureof the Band 5 is masked and shifted to 1940nmdue to H2O absorption. The Band 7 is intense and well-markedin the samples from the three mines, sometimes presenting a double feature.The albedo of the spectra and the intensity of the features are influenced by the presence of organic matter and granulometry. The technique of removing the continuum helped in the better visualization of the spectral features, as well as in the characteristics ofthe features, however it does not, in fact, cancel out the effects of organic matter and/or granulometry