Thermal impact of dykes on ignimbrite and implications for fluid flow compartmentalisation in calderas

Kennedy, Ben M. and Heap, Michael J. and Burchardt, Steffi and Villeneuve, Marlène and Tuffen, Hugh and Gilg, H. Albert and Davidson, Jonathan and Duncan, Neryda and Saubin, Elodie and Gestsson, Einar Bessi and Anjomrouz, Marzieh and Butler, Philip (2022) Thermal impact of dykes on ignimbrite and implications for fluid flow compartmentalisation in calderas. Volcanica, 5 (1). pp. 75-93. ISSN 2610-3540

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Abstract

Ignimbrites within calderas host intrusions with hazardous and/or economically significant hydrothermal systems. The Hvítserkur ignimbrite at Breiðuvík caldera, north-eastern Iceland, is intruded by basaltic dykes. Our data show that the ignimbrite immediately adjacent to the dyke is hard, dark-coloured, recrystallised quartz, plagioclase, and alkali feldspar with a low permeability and porosity and frequent macrofractures. At 1-2 m from the dyke, the ignimbrite is hard, dominantly glassy with pervasive perlitic microfractures, has high permeability, but low porosity and frequent macrofractures. A narrow zone of pervasive unlithified clay exists 2 m from the dyke. Beyond this, the ignimbrite is soft and zeolite-rich, has low permeability, high porosity and fewer macrofractures. The dyke intrusion promoted a narrow zone of welding, fracturing and perlitisation in the ignimbrite resulting in high permeability and focussed alteration. Our study shows how intrusions and their thermal aureoles create vertical pathways for, and horizontal barriers to, geothermal fluid flow.

Item Type:
Journal Article
Journal or Publication Title:
Volcanica
Subjects:
ID Code:
166972
Deposited By:
Deposited On:
07 Mar 2022 17:50
Refereed?:
Yes
Published?:
Published
Last Modified:
09 May 2022 12:55