Identification of Multi-Style Hydrothermal Alteration Using Integrated Compositional and Topographic Remote Sensing Datasets

Abstract

Abstract:The western part of the island of Milos, Greece has undergone widespread, intense alteration associated with a range of mineralization, including seafloor Mn-Fe-Ba, sub seafloor Pb-Zn-Ag, and epithermal Au-Ag. The surrounding country rocks are a mixture of submarine and subaerial calc-alkaline volcanic rocks ranging from basaltic andesite to rhyolite in composition, but are predominantly andesites and dacites. The current surface spatial distribution of the alteration mineralogy is a function not only of the original hydrothermal, but also subsequent tectonic and erosional processes. The high relief and the excellent rock exposure provide ideal conditions to evaluate the potential of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite remote sensing data to identify and differentiate the different styles of alteration mineralisation. Laboratory spectral reflectance and calculated emittance measurements of field samples, supported by XRD analysis and field mapping, were used to support the analysis. Band ratio and spectral matching techniques were applied to the shortwave-infrared (SWIR) reflectance and thermal-infrared (TIR) emissivity imagery separately and were then integrated with topographic data. The band ratio and spectral matching approaches produced similar results in both the SWIR and TIR imagery. In the SWIR imagery, the advanced argillic, argillic and hydrous silica alteration zones were clearly identifiable, while in the TIR imagery, the silicic and advanced argillic alteration zones, along with the country rock, were differentiable. The integrated mineralogical-topographic datasets provided an enhanced understanding of the spatial and altitude distribution of the alteration zones when combined with conceptual models of their genesis, which provides a methodology for the differentiation of the multiple styles of alteration.

Investigating the capability of Sentinel-2 and Worldview-3 VNIR satellite data to detect mineralized zones at an igneous intrusion in the Koutala islet (Lavreotiki, Greece) using laboratory mineralogical analysis, reflectance spectroscopy and spectral indices

“…A special case of SIs is represented by band ratios, where the ratio of two spectral bands is computed. Several SIs have been proposed using a range of wavelength combinations for mapping various mineral assemblages (Cloutis, 1996;Sabins, 1999;Cudahy and Hewson, 2002;Yamaguchi and Naito, 2003;Henrich et al, 2009;Shim et al, 2021), especially after the arrival of ASTER data with their SWIR spectral bands (Abrams et al, 1983;Abrams & Hook, 1995;Yamaguchi et al, 1998;Yamagushi & Naito, 2003;Kalinowski and Oliver, 2004;Gad and Kusky, 2007;Rajendran et al, 2011;Abrams et al, 2015;Ferrier et al 2016;Askari et al, 2018;Shuai et al, 2022) and/or Landsat 8 data (Anifadi et al, 2016;Ferrier et al 2016;Tompolidi et al, 2020;Anifadi et al, 2022;Sykioti et al 2022), spectral unmixing on (i) S-2, ASTER and Landsat 8 OLI data (Tompolidi et al, 2020) and (ii) EO-1 Hyperion hyperspectral data (Nikolakopoulos et al, 2007), Spectral Angle Mapping and Mixture-Tuned Matched…”

“…During the last three decades, the use of satellite imagery in geological mapping and mineral exploration has grown rapidly in order to detect mineralization-related alterations and associated ore deposits (Van der Meer et al, 2012;Van der Meer and Van der Werff, 2014;Van der Meer, 2015, 2016;Ge et al, 2018(a), 2018(b); Hu et al, 2018;Van der Meer et al, 2018;Pour et al, 2019;Vasuki et al, 2019;Ferrier et al 2019;Tompolidi et al, 2020;Anifadi et al, 2022). Recent multispectral satellites such as the Landsat Operational Land Imager (OLI), and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) have been the most widely used multispectral satellite sensors for the detection and mapping of minerals related to alteration, such as iron oxides, hydroxyl-bearing minerals, and Volume 59 carbonates (Rowan and Mars, 2003;Rowan et al, 2006;Ferrier et al, 2010Ferrier et al, , 2016Mars and Rowan, 2010;Hosseinjani et al, 2011;Pour et al, 2011;Rajendran et al, 2017;Yang et al, 2018;El Kati et al 2018;Abubakar et al, 2019;Pour et al 2019;Ferrier et al 2019;Tompolidi et al 2020;Vural et al, 2021), especially, when the satellites provide spectral information in the shortwave infrared (SWIR) part of the electromagnetic spectrum.…”