Development of a rapid and high-precision micro-FTIR geothermometer for thermal history reconstruction of coal and rocks

Abstract

Accurate reconstruction of rock thermal history is prerequisite for understanding fundamental geological processes and assessing resource potential. Geothermometers provide critical constraints on the peak thermal exposure experienced by rocks or minerals during burial, diagenesis, or metamorphism. Conventional methods, such as vitrinite reflectance (VR) and fission-track (FT) thermochronology, yield valuable tem- perature data but are often constrained by time-intensive procedures, high resource consumption, and limitations in sample quantity or analytical spatial resolution. Micro-Fourier Transform Infrared (Micro-FTIR) Spectroscopy presents a viable alter- native for analyzing thermal alteration in geological media. This technique monitors infrared absorption changes in molecular bonds, revealing functional group transfor- mations that are acutely sensitive to thermal maturation and are effective proxies for reconstructing thermal history. This research optimizes an IR Geothermometer proto- col to address the intrinsic limitations of established techniques, thereby enhancing the precision of thermal event reconstruction. The methodology encompasses acid treatment for the isolation of organic components, Micro-FTIR analysis, and continuous heating experiments, resulting in broader sample compatibility and refined tempera- ture constraints. Methodological validation was performed by comparing IR-derived temperature estimates against VR data from coal samples and FT data from sedi- mentary and metamorphic rocks in Taiwan.The findings establish a robust empirical correlation between the observed IR thermal signatures and independent geothermo- metric controls, thereby confirming the technique's efficacy for geological temperature history reconstruction. Utilizing the rapid spectral acquisition, high spatial resolu- tion, and capacity to register multiple thermal events inherent to IR spectroscopy, this technique offers an efficient, high-resolution methodology for thermal assessment in geological samples, with broad utility across resource exploration and petroleum geology.