Pre-eruptive volatile content, degassing paths and depressurisation explaining the transition in style at the subglacial rhyolitic eruption of Dalakv¨ªsl, South Iceland

详细信息    查看全文

• 作者：Jacqueline Owen^a ; ^{j.owen2@lancaster.ac.uk} ; Hugh Tuffen^a ; ^{h.tuffen@lancaster.ac.uk} ; David W. McGarvie^b ; ^{Dave.McGarvie@open.ac.uk}
• 关键词：Volatiles ; Degassing ; Subglacial ; Rhyolite ; Melt inclusions ; Volcano&ndash ; ice interactions ; Solubility&ndash ; pressure relationships
• 刊名：Journal of Volcanology and Geothermal Research
• 出版年：2013
• 出版时间：15 May, 2013
• 年：2013
• 卷：258
• 期：Complete
• 页码：143-162
• 全文大小：3818 K

文摘

Many volcanoes express a variety of contrasting eruptive styles with behavioural transitions between explosive and effusive activities. Understanding eruptive mechanisms is of key importance but we currently have little insight into the behavioural controls for rhyolitic eruptions beneath ice. This paper addresses a subglacial rhyolitic eruption at Dalakv¨ªsl in South Iceland that involved both explosive and effusive activities. We present measurements of pre- and post-eruptive magmatic volatile contents that we use to track magma degassing from the chamber to the surface and reconstruct pressure conditions during the eruption. Explosive and effusive phases involve significant differences in: (1) pre-eruptive volatile contents; (2) the ¡®openness¡¯ of magma degassing; and (3) inferred confining pressure. This final factor is potentially associated with a j?kulhlaup-induced decompression. Due to the combination of these factors Dalakv¨ªsl experienced a change from effusive to explosive behaviour, although we cannot currently resolve cause from effect. Our work points towards complex interactions between the dynamics of magma ascent and the response of overlying ice and meltwater during rhyolitic eruptions beneath ice.