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Short-term magma-carbonate interaction: A modelling perspective

Earth and Planetary Science Letters, Colucci et al. 2024 - Figura1
Figura 1. Conceptual drawing of short-term magma-carbonate interaction. a) The magma can pick up fragments of carbonate rocks as it rises to the surface; b) the melt shell around the clast is contaminated in CaO and CO2 and CO2-rich gas bubbles nucleate and grow at the melt-clast interface; c) the bubble rising stretches the contaminated melt promoting mingling between contaminated and host melt; d) once migrated outside of the contaminated region, the CO2-rich gas bubbles interact with the host magma; additional gas bubbles are observed at the interface between the two melts; e) When the mixing is complete new gas and melts phases are expected.

Colucci S., F. Brogi, G. Sottili, C.P. Montagna, P. Papale.
Earth and Planetary Science Letters, 628. https://doi.org/10.1016/j.epsl.2024.118592


Short-term interaction of magma with crustal carbonates can affect a volcano’s eruptive style and drive even low-viscosity magmas toward large explosive eruptions. Only a few studies have focused on short-term magma-carbonate interaction under controlled laboratory conditions and the physical processes behind the experimental observations are still poorly understood. In this work, we present the first numerical modelling study of short-term magma-carbonate interaction and provide an interpretative framework for experimental and field observations. We developed thermodynamic and dynamic models for carbonate dissolution and mixing and mingling between contaminated magma pockets and host magma. We find that mixing and mingling can play a central role in modulating the efficiency of volatile exsolution. The increasing viscosity of the host melt slows down melt mingling and hence the mixing process, limiting volatile exsolution. Less efficient mixing and mingling could allow the fingerprints of short-term magma-carbonate interaction to be preserved in volcanic and intrusive rocks. Finally, we highlight that the mechanism and timescale of magma-carbonate interaction open a key question about the anomalous high mobility of CaO during carbonate dissolution.