On a planetary scale, the carbon cycle describes the movement of carbon between the atmosphere and the deep earth, which affects petrologic processes in a range of geologic settings and the long-term viability of life at the surface. In this context, volcanoes and their associated magmatic systems represent the interface through which carbon is transferred from the deep earth to the atmosphere. Thus, describing the CO2 budget of volcanic systems is necessary for understanding the deep carbon cycle. In this review, Kilauea volcano (Hawaii) is used as a case study, and we present several simple calculations that can be used to account for processes that affect the amount and distribution of CO2 in this relatively well-studied volcanic system. These processes include estimating the concentration of CO2 in a melt derived by partial melting of a source material, enrichment of CO2 in the melt during fractional crystallization, exsolution of CO2 from a fluid-saturated melt, trapping and post-entrapment modification of melt inclusions, and degassing from the volcanic edifice. Our goal in this review is to provide straightforward example calculations that can be used to derive first-order estimates regarding processes that control the CO2 budgets of magmas.
Scientific editing by Maria Luce Frezzotti