Charlotte Laila DeVitre, Penny Wieser

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) are costly, present large uncertainties, and are too slow for real-time monitoring. Here, we evaluate the reliability and efficiency of Raman Spectroscopy measurements of CO2-dominated fluid inclusions as a geobarometer relative to more established methods such as microthermometry and melt inclusion barometry. We calculate storage pressures for 102 olivine-hosted fluid inclusions from the 2018 Lower East Rift Zone eruption of Kīlauea, which are statistically indistinguishable to those determined from melt inclusions. We show that calibrated Raman spectroscopy yields densities within 5-10% of microthermometry measurements for CO2-dominated fluid inclusions (< 10% mol H2O in the fluid phase) but is a far more suitable method for systems like Kīlauea dominated by shallow magma storage. Overall, pressures determined from fluid inclusions by Raman spectroscopy are robust, and require only a fraction of the work, time, and resources of melt inclusion studies.