SO₂ emissions from basaltic eruptions, and the excess sulfur issue

Sharma, K.; Blake, S.; Self, S. and Kreuger, A.J. (2004). SO₂ emissions from basaltic eruptions, and the excess sulfur issue. Geophysical Research Letters, 31(13), article no. L13612.

DOI: https://doi.org/10.1029/2004GL019688

Abstract

Volcanic SO₂ can affect the Earth's environment. Where no direct measurements of SO₂ in the atmosphere are available, a petrologic method of assessing sulfur release from the magma must be used. However, in studies of arc-derived eruptions, satellite-based measurements of SO₂ emissions using Total Ozone Mapping Spectrometer (TOMS) data are orders of magnitude greater than those calculated petrologically, implying that a separate S-rich gas phase in the magma chamber may be responsible for the excess sulfur. We test whether this applies in other settings. For Icelandic and Hawaiian basalts we find that petrologic SO₂ values are comparable to measurements of SO₂ by TOMS. Thus, for non-arc basalts, the petrologic method gives reliable estimates of SO₂ released. The implied absence of excess sulfur in non-arc basaltic magmas is a reflection of source magma conditions, notably lower fO₂ and volatile contents than arc magmas, inhibiting the exsolution of a S-rich gas prior to eruption.

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