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How do volatiles escape their shallow magmatic hearth?

Degruyter, Wim, Parmigiani, Andrea, Huber, Christian and Bachmann, Olivier 2019. How do volatiles escape their shallow magmatic hearth? Philosophical Transactions A: Mathematical, Physical and Engineering Sciences 377 (2139) , 20180017. 10.1098/rsta.2018.0017

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Abstract

Only a small fraction (approx. 1–20%) of magmas generated in the mantle erupt at the surface. While volcanic eruptions are typically considered as the main exhaust pipes for volatile elements to escape into the atmosphere, the contribution of magma reservoirs crystallizing in the crust is likely to dominate the volatile transfer from depth to the surface. Here, we use multiscale physical modelling to identify and quantify the main mechanisms of gas escape from crystallizing magma bodies. We show that most of the outgassing occurs at intermediate to high crystal fraction, when the system has reached a mature mush state. It is particularly true for shallow volatile-rich systems that tend to exsolve volatiles through second boiling, leading to efficient construction of gas channels as soon as the crystallinity reaches approximately 40–50 vol.%. We, therefore, argue that estimates of volatile budgets based on volcanic activity may be misleading because they tend to significantly underestimate the magmatic volatile flux and can provide biased volatile compositions. Recognition of the compositional signature and volumetric dominance of intrusive outgassing is, therefore, necessary to build robust models of volatile recycling between the mantle and the surface. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Publisher: The Royal Society
ISSN: 1364-503X
Date of First Compliant Deposit: 10 December 2018
Date of Acceptance: 16 November 2018
Last Modified: 27 Jun 2019 16:42
URI: http://orca.cf.ac.uk/id/eprint/117558

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