GRSG 35th Conference 2024 Abstract
Title: Mapping Hydrothermal Alteration Using Wavelength Mapping and Band Ratios: Insights from EMIT Hyperspectral Data over the Haib Porphyry System, Namibia
Author: Giorgia Carano
Organisation: Politecnico di Torino
White micas display distinctive spectral signatures, particularly in the Al-OH absorption feature, offering valuable insights into alteration processes and fluid compositions in hydrothermal systems. Previous studies (e.g., Laukamp & Lau, 2015; Meyer et al., 2022; Portela et al., 2021; van Ruitenbeek et al., 2005) demonstrated the potential of hyperspectral imaging for characterizing white micas and interpreting geological phenomena. This study utilizes the hyperspectral satellite sensor EMIT to examine the Haib region in southern Namibia, known for its porphyry system, an ideal environment for studying hydrothermal alteration and associated geological patterns.
Understanding the properties of hydrothermally altered rocks is crucial for interpreting fluid compositions, alteration patterns, and identifying areas rich in economically significant minerals. Hydrothermal systems frequently host valuable deposits, including copper, gold, and other metals essential to global industries, which is increasingly relevant given the growing demand for minerals critical to technology and clean energy, such as electric vehicles and renewable energy infrastructure.
In this study, we analyzed the spectral signatures of white micas using 60~m EMIT data and we applied wavelength mapping to detect shifts in the Al-OH absorption feature of muscovite at around 2200 nm. Furthermore, we performed band ratio techniques to identify mineralogical variations across the study area. Shifts in the Al-OH absorption feature are significant because they indicate compositional changes in the micas, providing insights related to rock alteration.
The findings of this study offer valuable insights into the composition of white micas and their role in hydrothermal alteration processes in the Haib region. By utilizing the EMIT hyperspectral satellite sensor with a spatial resolution of 60~m, we identified subtle shifts in the Al-OH absorption feature, allowing the detection of distinct mineralogical variations across the area. These results demonstrate the effectiveness of hyperspectral satellite data for detailed geological mapping and establish a solid foundation for future investigations into fluid compositions, mineral distributions, and alteration patterns within porphyry systems and other hydrothermally altered environments.
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Meyer, J. M., Kokaly, R. F., & Holley E. (2022). Hyperspectral remote sensing of white mica: A review of imaging and point-based spectrometer studies for mineral resources, with spectrometer design considerations. Remote Sensing of Environment, 275, 113000. https://doi.org/10.1016/j.rse.2022.113000
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