Application of Quantitative Analysis and Imaging Techniques of Raman Spectroscopy to Geological Inclusions

Geological inclusions serve as microscopic windows for probing deep Earth processes and their shallow responses. However, their micrometer-scale dimensions and encapsulation within host minerals pose significant challenges for in situ microanalysis. Raman spectroscopy, with its high spatial resolution, non-destructive nature, and visualization capabilities, has emerged as a core technique for the in situ analysis of inclusions. This paper presents a systematic review of recent advances in Raman spectroscopic analysis, categorized according to homogeneous and heterogeneous inclusion types: (1) For homogeneous inclusions, the laser Raman shift of mineral inclusions can be utilized to reconstruct the pressure-temperature (P-T) conditions at the time of entrapment. Quantitative calibration methods based on volatile-bearing glass standards enable precise determination of key volatile species (e.g., H₂O, CO₂, SO₂) in melt inclusions. Moreover, by calculating the Raman scattering cross-sections of each component in complex C-H-O-N-S fluid systems, the physicochemical parameters of fluid inclusions (e.g., molar concentration, density, salinity) can be accurately obtained. (2) For multiphase inclusions, two-dimensional Raman imaging can clearly resolve the spatial distribution of different phases within inclusions. Combined with three-dimensional imaging and quantitative compositional algorithms, this approach enables the full chemical reconstruction of multiphase inclusions. Collectively, the integration of quantitative Raman analysis and three-dimensional imaging constitutes a comprehensive in situ micro-analytical system for tiny geological inclusions. This framework provides critical quantitative constraints on fundamental geological issues, such as deep magmatic processes, crust-mantle interactions, global volatile cycles, and critical metal mineralization, thereby significantly advancing our understanding of the coupled relationship between deep Earth processes and shallow material responses.