Holographic characterization of typical silicate minerals by terahertz time-domain spectroscopy

Abstract

The Deep-Time Digital Earth Plan aims to develop a comprehensive digital representation of Earth's global systems, a goal that requires extensive mineralogical data and substantial scientific information. While traditional mineralogical characterization provides critical insights into the mantle's water cycle and geological evolution, existing geological methodologies face challenges due to electromagnetic band gaps and limitations in phase utilization. Leveraging the unique properties of water-sensitive, coherent, and fingerprint spectra, this study introduced Terahertz (THz) spectroscopy as a new method for validating holographic “THz colors” under pyrolytic and optical conditions. This approach enabled the simultaneous analysis of amplitude, phase, and spectral distribution for typical silicate minerals, facilitating the development of a comprehensive library of THz spectra for mineral materials. This library was constructed with support from conventional X-ray and infrared tools. Our research identified several minerals with THz characteristic absorption peaks, including pyrophyllite at 1.10 THz and chamosite at 1.15 THz. These findings challenged existing perceptions in the THz community regarding raw mineral. The experimental results demonstrated the potential of THz technology as a transformative tool for mineral detection and geological analysis, integrating optics and geophysics. Moreover, this advancement provides significant insights and enhances the development of digital Earth models and study of mineral morphology on Earth's surface.