GRSG 34th Conference 2023

Title: Comparison of EnMAP and Fenix Airborne Hyperspectral over the Yerington Magmatic District, NV

Author: Siebe Breed, David Coulter & David Cimadevilla Fuente

In 2022 EnMAP was launched, a hyperspectral imaging (HSI) satellite with a spatial resolution of ~30m. Compared to previous HSI satellites, EnMAP has more spectral bands (smaller sampling interval) and a higher signal-to-noise ratio, in the ~2100 – 2440 nm wavelength range. Through analysis of the shapes and wavelengths of characteristic absorption features in this range, spectral geologists are able to remotely recognize the presence of numerous minerals that are abundant in hydrothermal alteration systems.

Airborne HSI sensors have been acquiring hyperspectral datacubes, which cover both VNIR & SWIR wavelength ranges, for several decades. One established operator is SpecTIR, who currently use the Fenix 1K system (Specim) for VNIR & SWIR HSI acquisitions. The spectral sampling interval of Fenix 1K is ~6 nm, and data is typically acquired at a spatial resolution ~2.5m, although by changing the flight altitude during acquisition, other resolutions are possible.

In September/Autumn 2023, both EnMAP and SpecTIR acquired data over (part of) the Yerington Magmatic District. In this area, different parts of a Jurassic porphyry-epithermal system (emplaced sub-vertically at different paleodepths), are exposed sub-horizontally, as a result of Cenozoic extensional tectonics, which included rigid-block rotation along listric normal faults.

In this contribution, the authors will compare the spectral profiles from EnMAP & Fenix 1K, over areas with presence of a number of typical alteration minerals in outcrop. These minerals include illite, chlorite, calcite & dolomite. Where the exposure of specific alteration minerals is consistent over relatively large areas (several 100s of m²), spectra for EnMAP are consistent with Fenix 1K spectra, but in areas where alteration mineralogy changes significantly over relatively small areas (up to several 10s of m²), spectra for EnMAP show an average of the spectra in the Fenix HSI data.

We conclude that EnMAP provides useful HSI data for regional exploration, as it allows for more detailed mapping of alteration mineralogy, chemical changes within specific minerals, and crystallinity changes, than previous hyperspectral satellite sensors. For recognizing more smaller areas of exposure of minerals that are often more directly related with mineralization, it is still necessary to acquire higher spatial resolution hyperspectral imagery, such as the data provided by SpecTIR.