Evaluation of WorldView-3 VNIR and SWIR Data for Hydrothermal Alteration Mapping for Mineral Exploration: Case Study fro
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Original Paper
Evaluation of WorldView-3 VNIR and SWIR Data for Hydrothermal Alteration Mapping for Mineral Exploration: Case Study from Northeastern Isfahan, Iran Touba Salehi1 and Majid H.Tangestani
1,2
Received 2 September 2019; accepted 14 May 2020
This research evaluated the capability of WorldView-3 (WV-3) data in discriminating targets related to porphyry copper mineralization at the Tameh district in the Saveh–Yazd belt, northeastern Isfahan, Iran. The few known porphyry copper deposits in this district were formed in association with Oligo-Miocene intrusive bodies. Hydrothermal alteration zones are characterized by iron oxide/hydroxide, sericite, illite, kaolinite, montmorillonite, chlorite, and epidote minerals. The band rationing method and the mixture-tuned matched filtering (MTMF) algorithm were utilized to map and identify targets. The results of band rationing showed that WV-3 VNIR–SWIR data can map and differentiate corchlorite and epidote as well as kaolinite and montmorillonite because of its superior spatial and spectral resolutions in SWIR region, as compared to ASTER data. Considering the similarity of five SWIR bands of WV-3 to the ASTER bands, both datasets help to enhance sericite–illite in similar patterns; however, areas mapped using WV-3 matched well with field evidence. Implementing the MTMF algorithm on the WV-3 VNIR and SWIR data successfully mapped areas with the highest abundances of desired minerals. Microscopic studies of thin sections, spectral investigations, and X-ray diffraction analysis confirmed the occurrence of alteration minerals, which also corresponded well to surface exposures of alterations in the field. Results showed that WV-3 data, with higher spectral and spatial resolutions, provide capability to map and identify hydrothermal alteration minerals and to produce more detailed mineralogical maps, which are valuable in semi-detailed district-scale exploration stages; in contrast, ASTER data yielded information on hydrothermally alteration zones mainly in regional scale. KEY WORDS: WorldView-3, ASTER, Hydrothermal, Porphyry copper deposit, MTMF, Band rationing.
INTRODUCTION Hydrothermally altered zones around ore deposits, such as porphyries, volcanogenic massive sulfides, and high sulfidation epithermal deposits, 1
Department of Earth Sciences, Faculty of Sciences, Shiraz University, Shiraz, Iran. 2 To whom correspondence should be addressed; e-mail: [email protected]
are recognized by the occurrence of specific mineral assemblages such as iron oxides and hydroxides, OH-bearing minerals, sulfates, and carbonates (Pirajno 2009). They exhibit individual spectral features in the 0.4–1.0, 1.3–2.5, and 8.0–14.0 lm ranges of the electromagnetic spectrum (Clark 1999; Gupta 2003). Therefore, mapping these minerals via satellite earth observing technology and image processing methods is important in mineral exploration, allowing to fo-
2020 International Association for Mathematical Geosciences
Salehi and Tangestani cus exploration activity toward smaller site
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