Reliability of Raman analyses of CO2-rich fluid inclusions as a rapid barometer at Kīlauea

Interpreting signals of volcanic unrest requires knowledge of the architecture of the magmatic system, particularly the depths at which magmas are stored. Such information can also be vital to help predict changes in eruptive style and vigour. However, popular petrological tools to assess magma storage depths (e.g., melt inclusions - MI) are costly, uncertainty-ridden, and too slow for real-time monitoring. Here, we evaluate the reliability and efficiency of Raman Spectroscopy measurements of CO2-dominated fluid inclusions (FI) as a rapid geobarometer relative to more established methods such as microthermometry and MI barometry. We calculate storage pressures for 130 olivine-hosted FI from the 2018 Lower East Rift Zone eruption of Kīlauea, which are statistically indistinguishable to those determined from MI. We show that calibrated Raman spectroscopy yields densities within 5-10% of microthermometry measurements for CO2 dominated FI but is a far more suitable method for systems like Kīlauea dominated by shallow magma storage. Overall, pressures determined from FI by Raman spectroscopy are robust, and require only a fraction of the work, time, and resources, with potential for near real-time monitoring.