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    Buffering of oxygen fugacity by sulphur redox reactions in calcalkaline magmas

    Matthews, S.J. and Jones, A.P. and Beard, Andrew (1994) Buffering of oxygen fugacity by sulphur redox reactions in calcalkaline magmas. Journal of the Geological Society 151 (5), pp. 815-823. ISSN 0016-7649.

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    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.


    Item Type: Article
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences
    Depositing User: Sarah Hall
    Date Deposited: 11 Jun 2019 15:15
    Last Modified: 02 Aug 2023 17:51


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