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The Australian Resource Information and Environment Satellite (ARIES-1) will offer improved opportunities to map the mineralogical composition of outcropping rocks, hydrothermal alteration zones and the regolith on the Earth's surface in greater detail than before. This paper presents simulated ARIES-1 mineral mapping results for the Comstock mining district, Nevada, USA, and demonstrates how the spectrally- derived information on hydrothermal alteration has been validated through field work and supporting analytical studies. In the Comstock mining district, three types of white mica with short, medium and long Al-OH absorption wavelengths, respectively, were identified based on the simulated ARIES-1 hyperspectral data. Laboratory analytical work confirmed that the low, medium and long Al-OH absorption wavelengths correspond to low, medium and high octahedral Fe+Mg content, respectively, of the white micas. Each of the three types of white mica tends to occur in a particular alteration zone. The spatial distributions of the three types of white mica may have implications for interpreting the hydrothermal alteration processes. The white mica of short wavelength Al-OH absorption, proximal to Au-Ag mineralization, formed in acidic hydrothermal conditions both at the earliest and the last alteration stages. The white mica of medium wavelength Al-OH absorption, characteristics of the propylitic zone surrounding Au-Ag mineralization, was produced mainly in the second, low- sulfidation hydrothermal event. The white mica of long wavelength Al-OH absorption was probably formed in multiple stages, and generally occurs distal to Au-Ag mineralization.
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