Raman Spectroscopy Applications in Fluid Inclusion Analysis

Raman spectroscopy has emerged as a powerful non-destructive tool for the in situ characterisation of fluids trapped within mineral hosts. By measuring vibrational signatures of molecular species, it enables precise determination of fluid composition, density, phase behaviour and isotopic ratios at the microscale. The technique offers rapid, spatially resolved analyses of multi-component systems ranging from simple H₂O–CO₂ mixtures to complex C–O–H–N–S assemblages. Advances in detector sensitivity and laser optics have extended measurements to high-pressure, low-temperature inclusions and to high-temperature, high-pressure hydrothermal environments. Raman data complement traditional microthermometry by providing direct insight into phase transitions, clathrate formation and gas expansion on heating, as well as real-time monitoring of chemical reactions within sealed micro-reactors. Applications span petroleum geology, mineral exploration, geothermal studies and planetary science, where fluid inclusion records yield constraints on trapping conditions, fluid evolution, reservoir overpressure and volatile fluxes in both Earth and extraterrestrial settings.

Research from Nature Portfolio

Recent studies have demonstrated high-resolution mapping of carbon isotopic compositions within individual CO₂-rich fluid inclusions, achieving reproducibility better than 4‰ for 13CO₂/12CO₂ band ratios. This approach has validated δ13C determinations against bulk mass spectrometry and opened pathways for site-specific isotopic labelling at the microscale. Complementary work on natural C–O–H–N–S fluid inclusions has revealed previously undocumented low-temperature phase transitions, including solid–solid polymorphic changes of H₂S and the sequential formation of gas clathrates. These findings provide benchmark Raman spectral features and transition temperatures, underpinning improved models of phase equilibria in complex gas mixtures and guiding interpretations of fluid trapping in both mineral deposits and planetary analogue environments.

Raman Spectroscopy Applications in Fluid Inclusion Analysis publication trend

The graph below shows the total number of articles in raman spectroscopy applications in fluid inclusion analysis across all publications each year (not limited to Nature Index journals).

Technical terms

Fluid inclusion: a microscopic pocket of liquid and/or gas trapped within a mineral during growth, preserving the original fluid composition and conditions.

Raman shift: the change in energy (expressed as wavenumber) between incident and scattered photons, corresponding to molecular vibrational modes.

Isotopologue: a molecule that differs only by the isotopic composition of its constituent atoms, for example 12CO₂ versus 13CO₂.

Homogenization temperature: the temperature at which distinct phases within a fluid inclusion merge into a single phase upon heating, used to infer trapping conditions.

References

1. Spatially resolved CO2 carbon stable isotope analyses at the microscale using Raman spectroscopy. Scientific Reports (2023).
2. Phase transitions in natural C-O-H-N-S fluid inclusions - implications for gas mixtures and the behavior of solid H2S at low temperatures. Nature Communications (2021).
3. Raman vibrational spectral characteristics and quantitative analysis of H2 up to 400°C and 40 MPa. Journal of Raman Spectroscopy (2018).
4. Experimental variable effects on laser heating of inclusions during Raman spectroscopic analysis. Chemical Geology (2021).
5. In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China. Petroleum Science (2019).