Abstract
Abstract. WorldView-3 (WV-3), launched in August 2014, is a commercial imaging satellite with high spatial resolution that measures reflected radiation in VNIR-SWIR regions in 16 bands. The main objective of this study was to discriminate the alteration minerals in Chadormalu iron deposit area, central Iran, using band ratio techniques on the selected bands of this satellite. To identify the appropriate band ratios the spectral bands of WV-3 were investigated and assessed. Regarding to Fe3+, Fe2+, Al-OH, Fe-OH, Mg-OH and CO32− spectral absorption features, band ratios B5/B2, B13/B9, B13/B14 and B14/B16 were proposed for enhancement of ferrous and ferric iron bearing minerals, sericite, epidote, chlorite, and dolomite. Combination of field observations, geological map and high resolution spectra of rock samples were used to verify the results. Band ratio B5/B2, B13/B9, B13/B14 gray scale images respectively illustrated that Fe3+-rich minerals are occurring in granite, the Fe2+-rich minerals are enhanced in iron ore, green schist, and diorite units, and sericite is occurring in hydrothermally altered granite and iron ore. Since the Fe/Mg-OH vibrational mode in chlorite-epidote and spectral absorption feature of CO32− in dolomite occur in B16, the B14/B16 ratio highlighted chlorite-epidote-rich green schist, diorite and dolomitic marble. The false color composite image of B13/B14, B13/B9, and B14/B16 as RGB produced a large scale map which successfully discriminated the rock types and accompanying alteration minerals. This study demonstrated that WV-3 data have efficient spectral resolution to discriminate alteration minerals with Fe3+, Fe2+, Al-OH and Fe/Mg-OH or CO32− spectral absorption features.
Highlights
Remote sensing techniques provide information on the characteristics of the exploration target surfaces
WV-3 has PAN and visible near infrared (VNIR) multispectral bands with 0.31 m and 1.24 m spatial resolution, respectively, and supplemented by 8 short wave infrared (SWIR) bands ranging from approximately 1.2 μm to 2.33 μm with 3.7 m spatial resolution (Table 1)
Diagnostic spectral absorption features of these alteration minerals were studied and the appropriate band ratios were identified to recognize the exposure of these minerals in the study area
Summary
Remote sensing techniques provide information on the characteristics of the exploration target surfaces. Alteration minerals play significant role in prospecting of economic deposits and can be mapped by remote sensing when exposed at the surface of the earth. Electronic transitions and molecular vibrations in the mineral lattices lead to form spectral absorption features in visible near infrared (VNIR) and short wave infrared (SWIR) ranges. WV-3 SWIR data was examined on the Cuprite site for mineral mapping including kaolinite, alunite, buddingtonite, muscovite, calcite, and hydrothermal silica (Kruse et al, 2015). WV-3 VNIR-SWIR data have been assessed for lithological mapping at Cuprite, Nevada (Johnson and Koperski, 2017) and Pobei area of the Xinjiang Uygur Autonomous Region, China (Ye et al, 2017), which provided detailed target and classification map at large scale with appropriate ground truth. A comparison between classification accuracy of WV-3, ASTER and OLI/Landsat-8 data in Pobei area of the Xinjiang Uygur
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