Abstract
This study produces alteration mineral maps based on WorldView-3 (WV-3) data and field shortwave-infrared (SWIR) spectroscopy. It is supported by conventional analytical methods such as X-ray diffraction, X-ray fluorescence, and electron probe X-ray micro analyzer as an initial step for mineral exploration in eastern Tsogttsetsii, Mongolia, where access is limited. Distributions of advanced argillic minerals (alunite, dickite, and kaolinite), illite/smectite (illite, smectite, and mixed-layered illite-smectite), and ammonium minerals (buddingtonite and NH4-illite) were mapped using the decorrelation stretch, band math, and mixture-tuned-matched filter (MTMF) techniques. The accuracy assessment of the WV-3 MTMF map using field SWIR data showed good WV-3 SWIR data accuracy for spectrally predominant alteration minerals such as alunite, kaolinite, buddingtonite, and NH4-illite. The combination of WV-3 SWIR mineral mapping and a drone photogrammetric-derived digital elevation model contributed to an understanding of the structural development of the hydrothermal system through visualization of the topographic and spatial distribution of surface alteration minerals. Field SWIR spectroscopy provided further detailed information regarding alteration minerals such as chemical variations of alunite, crystallinity of kaolinite, and aluminum abundance of illite that was unavailable in WV-3 SWIR data. Combining WV-3 SWIR data and field SWIR spectroscopy with conventional exploration methods can narrow the selection between deposit models and facilitate mineral exploration.
Highlights
The purpose of this study is to show how information from WV-3 SWIR data can be used with other conventional analytical methods such as X-ray diffraction (XRD), Xray fluorescence (XRF), and electron probe X-ray micro analyzer (EPMA) for mineral exploration in an unknown area
The field SWIR reflectance spectra collected at the prospects of the eastern Tsogttsetsii were characterized by absorption features indicating the presence of advanced argillic alteration minerals, buddingtonite, NH4 -illite, illite, smectite, and mixed-layered illite-smectite (Figure 4; Table A1)
The field spectroscopy and WV-3 mixture-tuned-matched filter (MTMF) mineral mapping results indicate the complex distribution of various alteration mineral assemblages in the eastern Tsogttsetsii district
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Porphyry Cu deposits are mostly found in magmatic arcs associated with subduction zones, and are generated by hydrothermal fluid processes which accompany porphyry emplacement and alter the mineralogy and geochemistry of the host rocks. The movement of these hydrothermal fluids generates broad-scale alteration zones. These alteration zones are composed of sodic-calcic, potassic, propylitic, chlorite-sericite, sericitic (phyllic), and advanced argillic, which are characterized by the occurrence of specific mineral assemblages [1,2,3]
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