%0 Conference Proceedings
%4 sid.inpe.br/marte2/2017/10.27.15.32.13
%2 sid.inpe.br/marte2/2017/10.27.15.32.14
%@isbn 978-85-17-00088-1
%F 60170
%T Resultados preliminares de espectroscopia de reflectância e imageamento hiperespectral na região da mina de scheelita de Brejuí (RN), Faixa Seridó, Província Borborema
%D 2017
%A Costa, Manoel Augusto Correa da,
%A Perrotta, Monica Mazzini,
%A Souza Filho, Carlos Roberto,
%@electronicmailaddress manoel.costa@cprm.gov.br
%E Gherardi, Douglas Francisco Marcolino,
%E Aragão, Luiz Eduardo Oliveira e Cruz de,
%B Simpósio Brasileiro de Sensoriamento Remoto, 18 (SBSR)
%C Santos
%8 28-31 maio 2017
%I Instituto Nacional de Pesquisas Espaciais (INPE)
%J São José dos Campos
%P 5737-5744
%S Anais
%1 Instituto Nacional de Pesquisas Espaciais (INPE)
%X The Seridó mobile belt in the Borborema Province, northeastern Brazil, hosts a wealth of metallic occurrences, including the Brejuí W-Mo skarn deposit. Here we present preliminary results on reflectance spectroscopy and hyperspectral remote sensing applied to mineral mapping of host rocks and alteration zones in this classic skarn. Visible and infrared (VNIR-SWIR; 0.4-2,5 µm) lab spectroscopy was conducted using the ASD-FieldSpec-3 Hi-Resolution spectrometer. Contact spectral measurements allowed the identification of hornblende, chlorite (Mg-rich types), epidote, calcite, gypsum, phengitic illite and nontronite in the alteration zones, which correspond to retrograde hydrothermal assemblages associated to the W-Mo ore bodies. Actinolite, calcite, Fe/Mg-biotite, montmorillonite and kaolinite were depicted in the host rocks (schists, marbles, calc-silicate gneisses and pegmatites). Actinolite in calc-silicate gneisses suggests a more pervasive alteration mineral phase. Nontronite and phengitic illite are key minerals that characterize the hydrothermal system. The dominant presence of Mg-chlorite (FeOH = 2,249 µm) in the alteration zones is distinct from the Fe/Mg-biotite (FeOH = 2,253 µm) found in the host rocks (schists). Additionally, the increase in the CO3 feature depth is also typical of these alteration zones (hydrothermal calcites). The Brejui deposit was also remotely sensed by the ProSpecTIR-VS airborne hyperspectral imager, with 357 bands between the VNIR-SWIR range, at 2m spatial resolution. The data was processed by a stepwise approach including Minimum Noise Fraction (MNF), Pixel Purity Index (PPI) and Spectral Angle Mapper (SAM) methods. The classification map yielded from these procedures allowed mapping of marbles and calcsilicate rocks spatially close to the skarn mineralization.
%9 Radiometria e sensores
%@language pt
%3 60170.pdf