Next to H2O, carbon dioxide is the second most abundant volatile in magmas and plays a crucial role in the degassing of ascending magmas [1]. Even at low concentrations, dissolved CO2 serves as a driving force for bubble formation. Understanding CO2 diffusion in silicate melts is crucial for modelling degassing and eruption mechanisms in magmatic systems. However, while water diffusion has been extensively studied, CO2 diffusion remains poorly constrained, particularly in hydrous systems [2-5].
This study aims to provide a systematic dataset of CO2 diffusion coefficients in silicate melts as a function of water content, focusing on key magma types. We examined CO2 diffusion in a basalt from Stromboli using diffusion couple experiments conducted at 300 MPa and 1200–1300 °C in a rapid-quench, internally heated pressure vessel. Symmetrical CO2 concentration-distance profiles, measured via FT-IR micro-spectroscopy on doubly polished glass sections, were fitted with error functions to determine individual diffusion coefficients (DCO2).
Preliminary results under anhydrous conditions show clear Arrhenius behavior for the investigated P-T-X conditions and CO2 concentrations, with DCO2 values consistent with previous findings for Fe-free basalt [2]. Ongoing experiments aim to investigate the influence of different water contents on CO2 diffusion and to extend the temperature range, offering new insights into CO2 mobility in melts.
[1] Papale P. and Polacci M. (1999). Bulletin of Volcanology 60, 583–594.
[2] Watson E. B., Sneeringer M. A. and Ross A. (1982). Earth and Planetary Science Letters 61, 346–358.
[3] Blank J. G. (1993). California Institute of Technology.
[4] Watson E. B. (1991). Geochimica et Cosmochimica Acta 55, 1897–1902.
[5] Koch L. and Schmidt B. C. (2023). European Journal of Mineralogy 35, 117–132.
| Subject : | : | Poster |
| Topics | : | Magma, Melts and Volcanoes |
| Keywords | : | Hydrous melts ; CO2 diffusion ; FTIR |
| PDF version | : |  PDF version |
