Features of Reflectance Spectroscopy and Geochemistry Towards REE Mineralization in Weathered Granitic Clays

Abstract

The rising global demand for rare earth elements (REEs) has intensified exploration efforts, particularly in regions like Indonesia with significant REE potential. This study explores the use of reflectance spectroscopy for rapid identification of REE-bearing clay minerals derived from weathered granite in West Kalimantan. Clay samples from distinct weathering horizons were analyzed using X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and reflectance spectroscopy. XRD confirmed the presence of kaolinite, dickite, gibbsite, and quartz, indicating their formation as weathering products of the host granite. While ICP-MS revealed that REE concentrations in the clay samples were lower than in the host rock, this observation suggests that the REE enrichment process within the clay minerals may still be ongoing or influenced by specific local geochemical conditions. Reflectance spectroscopy identified key clay minerals based on their characteristic absorption features in the shortwave infrared (SWIR) region. However, direct detection of REE-related absorption features was challenging due to the likely low concentrations and potential masking by iron oxides. This study highlights the potential of reflectance spectroscopy as a valuable tool for initial screening and identification of clay minerals in REE exploration, particularly when combined with other analytical techniques. Further research focusing on enhancing spectral analysis methods and targeting areas with potentially higher REE concentrations will be crucial in maximizing the effectiveness of this technique for REE resource discovery.