Open AccessThermal impact of dykes on ignimbrite and implications for fluid flow channelisation in a caldera
Author(s) -
Ben Kennedy,
Michael Heap,
Steffi Burchardt,
Marlène Villeneuve,
Hugh Tuffen,
H. Albert Gilg,
Jonathan Davidson,
Neryda Duncan,
Élodie Saubin,
Einar Bessi Gestsson,
Marzieh Anjomrouz,
P. H. Butler
Publication year - 2022
Publication title -
volcanica
Language(s) - English
Resource type - Journals
ISSN - 2610-3540
DOI - 10.30909/vol.05.01.7593
Subject(s) - geology , caldera , geochemistry , rhyolite , basalt , quartz , petrology , plagioclase , hydrothermal circulation , porosity , permeability (electromagnetism) , dike , volcanic rock , volcano , seismology , geotechnical engineering , paleontology , membrane , biology , genetics
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.