Using hyperspectral imagery for identification of pyrophyllite-muscovite intergrowths and alunite in the shallow epithermal environment of the Yerington porphyry copper district

Hydrothermal mineral deposits are the primary source of many commodities global importance. Since hydrothermal alteration minerals associated with formation these active in visible and infrared range, analysis spectral absorption features can be used to identify mineralogy different events. Some events responsible for occurrence commodities, while other create unrelated introduction base precious metals. Therefore, it is crucial develop a exploration strategy rapidly map indicator linked mineralising event. The separation which spectrally same overlapping range spectrum, challenge addressed this study. High spatial resolution airborne laboratory-based hyperspectral images combined detect visualise textures muscovite replacing pyrophyllite shortwave (SWIR) imaging spectroscopy survey over Buckskin Range, volcanic-hosted lithocap part Yerington porphyry district, Nevada (USA). Spectral wavelength maps SWIR ranges at both laboratory (26 µm) (1 m) scales. data define outward zoning from alunite ± characterized by variable positions its Al-OH feature. 1650–1850 nm differentiate zones predominance within inner domain. improves characterisation mineralogy, includes alunite, pyrophyllite, muscovite, dickite, chlorite, topaz zunyite. textural relationship through development novel index, pyrophyllite-muscovite index (PMI). intergrowths scale based on two aspects: (1) definition pervasive versus veinlet-controlled (2) subtle shift detection position feature 2189 2195 nm. combination patterns association allows identification areas contain replacement pyrophyllite. recognition late suggests that advanced argillic reflecting intense acid leaching followed near-neutral pH magmatic-hydrothermal fluids, adding K+ potentially alkali elements metals epithermal environment. As result study, we document muscovite-pyrophyllite intergrowth relationships study area, thus contributing an improved understanding system better assessment potential Au, Ag Cu mineralisation.