Magma transport and olivine crystallization depths in Kīlauea’s East Rift Zone inferred from experimentally rehomogenized melt inclusions

Concentrations of H₂O and CO₂ in olivine-hosted melt inclusions can be used to estimate crystallization depths for the olivine host. However, the original dissolved CO₂concentration of melt inclusions at the time of trapping can be difficult to measure directly because in many cases substantial CO₂ is transferred to shrinkage bubbles that form during post-entrapment cooling and crystallization. To investigate this problem, we heated olivine from the 1959 Kīlauea Iki and 1960 Kapoho (Hawai‘i) eruptions in a 1-atm furnace to temperatures above the melt inclusion trapping temperature to redissolve the CO₂ in shrinkage bubbles. The measured CO₂ concentrations of the experimentally rehomogenized inclusions (⩽590 ppm for Kīlauea Iki [n=10]; ⩽880 ppm for Kapoho, with one inclusion at 1863 ppm [n=38]) overlap with values for naturally quenched inclusions from the same samples, but experimentally rehomogenized inclusions have higher within-sample median CO₂ values than naturally quenched inclusions, indicating at least partial dissolution of CO₂ from the vapor bubble during heating. Comparison of our data with predictions from modeling of vapor bubble formation and published Raman data on the density of CO₂ in the vapor bubbles suggests that 55-85% of the dissolved CO₂ in the melt inclusions at the time of trapping was lost to post-entrapment shrinkage bubbles. Our results combined with the Raman data demonstrate that olivine from the early part of the Kīlauea Iki eruption crystallized at