Caracterização espectrorradiométrica (VNIR-SWIR) do minério magnesítico da porção centro-sul do estado do Ceará

Resumo

Due to the practicality, speed and low cost of operation, the use of spectroradiometry has become an important tool in determining the composition of materials, being used in the characterization of boreholes, support and orientation of mining fronts, and as support to interpretation of remote sensing images. To perform the spectroradiometric characterization of the magnesitic ore of the state of Ceará (Brazil), the FieldSpec Pro FR spectroradiometer (350 to 2500 nm) was used. The samples were collected from the mines Cabeça de Negro, Riacho Fundo and Torto, and subsequently cut and polished in order to obtain uniform surfaces, and thus minimize the effect of the sample relief and of any surface weather. Data acquisition was carried out in the laboratory, without any interference from external lighting, with three spectral measurements made at different points of each sample. The spectral features that characterized the analyzed ore were attributed to iron (350 to 750 nm, 1000 nm and 1700 nm), water/hydroxyl (1390 nm, 1440 nm and 1940 nm), to the Mg-OH bond (2070 nm and 2390 nm) and carbonate (1850 nm, 1970 nm, 2130 nm and 2300 nm), with the albedo and intensity of the features being influenced by the presence of organic matter and particle size. According to the spectral characteristics, the magnesitic ore studied could be classified into four distinct groups, called hydrated magnesite, anhydrous magnesite, ferrous magnesite and carbonaceous magnesite.