Buffering of melt oxygen fugacity by sulphur redox reactions in calc-alkaline magmas
Buffering of melt oxygen fugacity by sulphur redox reactions in calc-alkaline magmas
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DOI：
10.1144/gsjgs.151.5.0815
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发表时间：
1994-09
影响因子：
2.7
通讯作者：
S. Matthews;A. Jones;A. Beard
中科院分区：
文献类型：
--
作者：
S. Matthews;A. Jones;A. Beard
计算的氧逸度的岩浆从拉斯卡火山，北方智利，和1991年喷发的皮纳图博山，菲律宾，被认为是随着温度的降低而增加，相对于铁橄榄石磁铁矿石英缓冲。中等压力（2-4 kbar）下的恒定H2S/SO2等值线与数据平行。我们的结论是，岩浆混合喷发前释放大量的SO2气体的氧化溶解硫化物的镁铁质端员。氧逸度的岩浆，然后缓冲这种气体还原为硫化氢，导致越来越氧化的岩浆。这样的过程可能被用来解释其他富硫的演化钙碱性岩浆，特别是El Chichon粗安岩的高度氧化的性质。
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.