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The effect of nonlinear decompression history on H 2 O/CO 2 vesiculation in rhyolitic magmas
Author(s) -
Su Yanqing,
Huber Christian
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013812
Subject(s) - magma , decompression , rhyolite , volcano , geology , volcanology , geochemistry , petrology , thermodynamics , volcanic rock , physics
Abstract Magma ascent rate is one of the key parameters that control volcanic eruption style, tephra dispersion, and volcanic atmospheric impact. Many methods have been employed to investigate the magma ascent rate in volcanic eruptions, and most rely on equilibrium thermodynamics. Combining the mixed H 2 O‐CO 2 solubility model with the diffusivities of both H 2 O and CO 2 for normal rhyolitic melt, we model the kinetics of H 2 O and CO 2 in rhyolitic eruptions that involve nonlinear decompression rates. Our study focuses on the effects of the total magma ascent time, the nonlinearity of decompression paths, and the influence of different initial CO 2 /H 2 O content on the posteruptive H 2 O and CO 2 concentration profiles around bubbles within the melt. Our results show that, under most circumstances, volatile diffusion profiles do not constrain a unique solution for the decompression rate of magmas during an eruption, but, instead, provide a family of decompression paths with a well‐defined trade‐off between ascent time and nonlinearity. An important consequence of our analysis is that the common assumption of a constant decompression rate (averaged value) tends to underestimate the actual magma ascent time.