Geochemical signals of volcanic unrest at the Virkisjökull Glacier Iceland

Understanding the relationship between areas of active geothermal or volcanic activity and the glaciers that overlie them remains a significant knowledge gap in the earth sciences. Using Virkisjökull glacier in south east Iceland as a case study, a geochemical approach is taken to this problem by utilising stable isotopes of water and sulphate alongside major chemistry and the noble gases. Analysis of oxygen deuterium data collected over four years revealed a hydrological system dominated by glacial meltwater and aquifer fed groundwater that varied both seasonally and spatially. Sulphate isotopes suggested that water chemistry is the result of a ternary mixing of three endmembers: precipitation, ice melt and bedrock weathering whose relative inputs varied with season. This seasonality demonstrated that prevailing weather conditions have a significant impact on the chemistry of the meltwaters. Oxygen sulphate isotopes were used as an indicator of redox status in the subglacial hydrological regime. This pointed towards a year round fully oxidized channel system operating at the glacier bed, which is in contrast to the seasonality observed at other glaciers in Iceland and around the world. Finally, noble gases were used to identify the relative contribution of basal ice melt at various sites in the sandur. Taken together these chemical indicators hint at a weak to non-existent geothermal regime operating under the Virkisjökull glacier.

Name dc:type.qualificationname

masters

Level dc:type.qualificationlevel

masters

Grantor dc:publisher.institution

Lancaster University

Year dc:date.issued

2015

Authors dc:creator

• Mcdonald, Alistair
• Wynn, Peter
• Tuffen, Hugh
• James, Michael