Interpretation of the Reflectance Spectra of Lithium (Li) Minerals and Pegmatites: A Case Study for Mineralogical and Lithological Identification in the Fregeneda-Almendra Area

Remote Sensing

Encarnación Roda-Robles¹  Maria Anjos Ribeiro²  Filipa Dias²  Ana C. Teodoro²  João Silva²  Joana Cardoso-Fernandes²  Alexandre Lima²  Jean Cauzid³  Odile Barrès³  Mônica M. Perrotta⁴ 

[1] Departamento de Geología, Universidad del País Vasco (UPV/EHU), Barrio Sarriena s/n, 48940 Leioa, Spain;Department of Geosciences, Environment and Spatial Plannings, Faculty of Sciences, University of Porto, Rua Campo Alegre, 4169-007 Porto, Portugal;GeoRessources Laboratory, Université de Lorraine, CNRS, F-54000 Nancy, France;Remote Sensing and Mineral Spectroscopy Laboratory, Geological Survey of Brazil (CPRM), Rua Costa, 55, São Paulo 01304-010, Brazil;

关键词: remote sensing;    reflectance spectroscopy;    hyperspectral;    geological exploration;    spectral library;    absorption features;   

DOI  :  10.3390/rs13183688

来源: DOAJ

【 摘 要 】

Reflectance spectroscopy has been used to identify several deposit types. However, applications concerning lithium (Li)-pegmatites are still scarce. Reflectance spectroscopic studies complemented by microscopic and geochemical studies were employed in the Fregeneda–Almendra (Spain–Portugal) pegmatite field to analyze the spectral behavior of Li-minerals and field lithologies. The spectral similarity of the target class (Li-pegmatites) with other elements was also evaluated. Lepidolite was discriminated from other white micas and the remaining Li-minerals. No diagnostic feature of petalite and spodumene was identified, since their spectral curves are dominated by clays. Their presence was corroborated (by complementary techniques) in petalite relics and completely replaced crystals, although the clay-related absorption depths decrease with Li content. This implies that clays can be used as pathfinders only in areas where argillic alteration is not prevalent. All sampled lithologies present similar water and/or hydroxide features. The overall mineral assemblage is very distinct, with lepidolite, cookeite, and orthoclase exclusively identified in Li-pegmatite (being these minerals crucial targets for Li-pegmatite discrimination in real-life applications), while chlorite and biotite can occur in the remaining lithologies. Satellite data can be used to discriminate Li-pegmatites due to distinct reflectance magnitude and mineral assemblages, higher absorptions depths, and distinct Al–OH wavelength position. The potential use of multi- and hyperspectral data was evaluated; the main limitations and advantages were discussed. These new insights on the spectral behavior of Li-minerals and pegmatites may aid in new Li-pegmatite discoveries around the world.

【 授权许可】

Unknown