Lyell Collection
Journal of the Geological Society
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by MATTHEWS, S. J.
Right arrow Articles by BEARD, A. D.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Journal of the Geological Society; 1994; v. 151; issue.5; p. 815-823;
DOI: 10.1144/gsjgs.151.5.0815
© 1994 Geological Society of London

Article

Buffering of melt oxygen fugacity by sulphur redox reactions in calc-alkaline magmas

S. J. MATTHEWS1, A. P. JONES1 & A. D. BEARD2

1 Department of Geological Sciences, University College London, Gower Street, London WClE 6BT, UK
2 Department of Geology, Birkbeck College, Malet Street, London WClE 7HX, UK

Calculated oxygen fugacities of magmas from Lascar Volcano, Northern Chile, and the 1991 eruption of Mount Pinatubo, Phillipines, are seen to increase with decreasing temperature, relative to the fayalite-magnetite-quartz buffer. Isopleths of constant H2S/SO2 at moderate pressures (2–4 kbar) lie parallel to the data. We conclude that magma mixing prior to eruption liberated large quantities of SO2 gas by oxidation of dissolved sulphide in the mafic end-member. Oxygen fugacity of the magmas was then buffered by reduction of this gas to H2S, leading to increasingly oxidized magmas. Such a process might be used to explain the highly oxidized nature of other sulphur-rich evolved calc-alkaline magmas, notably the El Chichon trachyandesite.




This article has been cited by other articles:


Home page
 J PetrologyHome page
M. C. S. HUMPHREYS, J. D. BLUNDY, and R. S. J. SPARKS
Magma Evolution and Open-System Processes at Shiveluch Volcano: Insights from Phenocryst Zoning
J. Petrology, 2006; 47: 2303 - 2334.
[Abstract] [Full Text] [PDF]