A study demonstrates that magmas from continental intraplate volcanoes contain concentrations of dissolved carbon dioxide (CO₂) reaching several weight percent, much higher than previously estimated.
The analysis of magma droplets trapped in crystals reveals that the eruption of these volcanoes is accompanied by massive emissions of CO₂, significantly contributing to CO₂ fluxes to the atmosphere in Earth's carbon cycle.
Directly measuring magma CO₂
Most estimates of magma CO₂ content rely on indirect approaches, as magmas degas massively during their ascent to the surface. In this study, researchers used samples from the Bas-Vivarais volcanic province (Ardèche, Massif Central), one of the most recently active volcanic regions in mainland France. More precisely, they analyzed droplets of magma trapped in olivine crystals, called melt inclusions.
The use of an innovative high-pressure and high-temperature experimental technique, simulating the conditions of a deep magma chamber, allowed them to directly measure the amount of CO₂ contained in the magma before degassing. The results reveal concentrations reaching 4.8 wt% CO₂, the highest reported to date in this type of volcanic setting.
Maximum CO2 contents measured in silica-poor magmas in a continental intraplate context (blue triangle) and for ocean islands (red circle). A long underestimated carbon richness
This study also shows that this exceptional CO₂ richness in magmas actually reflects a carbon enrichment of the source mantle and could concern a wide range of intraplate volcanic provinces globally. The results thus suggest that CO₂-rich magmas are the rule rather than the exception in intraplate settings, and particularly in continental environments.
Rethinking the role of continental intraplate volcanoes in the global carbon cycle
This work indicates that continental intraplate volcanoes can release into the atmosphere amounts of CO
2 far greater than their modest size would suggest. If these values are extrapolated to all intraplate volcanic provinces, these emissions could be higher than anticipated, with major implications for the carbon cycle and the interactions between volcanism and climate over geological timescales.
In the future, the contribution of continental intraplate volcanoes to the global CO
2 flux, although minor compared to anthropogenic emissions, and their potential to trigger warming periods will need to be reassessed in light of these new estimates.
CO2 emissions and volume of magma produced during recent eruptions. Quantity of CO2 emitted per unit volume of magma produced (Mt.km-3; circles, with the right-hand y-axis) and volume of magma produced (km3; rectangles, with the left-hand y-axis) for a series of recent, historical, and prehistoric eruptions, including the Jaujac eruption in the Bas-Vivarais province (this study).