The origin of Earth's volatile elements is a key question in planetary sciences due to the diverse sources in the solar system and the complex processes that alter chemical and isotopic signatures. One major influence is magma degassing, which can lead to kinetic isotopic fractionation during vesiculation. Investigating how noble gases like neon interact with magmatic systems is crucial for understanding Earth's volatile evolution.

Neon isotopes in the Earth's mantle provide insights into the incorporation of light noble gases during planetary formation. However, measuring neon abundance and isotopic composition in primary mantle melts is difficult due to its low concentration and potential fractionation during transport and degassing. Natural samples with solar-like neon isotopic signatures, ranging between the Sun's values (20Ne/22Ne = 13.36 ± 0.09; Heber et al., 2012) and those from solar wind implantation (20Ne/22Ne = 12.73; Moreira and Charnoz, 2016) suggest a primordial nebular component in Earth's mantle. However, these high values may also reflect kinetic fractionation during degassing, so we conduct experiments to explore this possibility.

This study examines the effects of magma degassing on noble gas isotopes, focusing on vesicle formation and growth under isobaric conditions. CO2 exsolution from magma reservoirs causes the partitioning of noble gases into the gas phase. We analysed three synthetic vesiculated glasses produced at ~1.7 kbar and 1200 ºC with an air-like neon isotopic composition (20Ne/22Ne = 9.81 ± 0.01) fluxed with CO2. The results reveal significant neon isotopic fractionation in trapped vesicles, with values reaching 20Ne/22Ne = 10.50 ± 0.14. Isotopic variations among individual vesicles align with expectations for kinetic fractionation, demonstrating that magma degassing can alter the neon isotope composition of basaltic melts (Núñez-Guerrero et al., 2025). These findings highlight the role of vesiculation in modifying noble gas signatures and advance our understanding of volatile behaviour in planetary interiors.