Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures
Detailed field observations of structures within the flow front of a Holocene trachyandesite lava from Snæfellsnes, Iceland, are presented. The lava provides exceptional three-dimensional exposure of complex brittle and ductile deformation textures that record processes of lava fracture and quenchin...
Published in: | Journal of Volcanology and Geothermal Research |
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2012
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Online Access: | https://eprints.lancs.ac.uk/id/eprint/54746/ https://doi.org/10.1016/j.jvolgeores.2012.07.007 |
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ftulancaster:oai:eprints.lancs.ac.uk:54746 2023-08-27T04:10:13+02:00 Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures Forbes, Anne Blake, Steven McGarvie, David W. Tuffen, Hugh 2012-11-01 https://eprints.lancs.ac.uk/id/eprint/54746/ https://doi.org/10.1016/j.jvolgeores.2012.07.007 unknown Forbes, Anne and Blake, Steven and McGarvie, David W. and Tuffen, Hugh (2012) Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures. Journal of Volcanology and Geothermal Research, 245-24. pp. 68-80. ISSN 0377-0273 Journal Article PeerReviewed 2012 ftulancaster https://doi.org/10.1016/j.jvolgeores.2012.07.007 2023-08-03T22:22:19Z Detailed field observations of structures within the flow front of a Holocene trachyandesite lava from Snæfellsnes, Iceland, are presented. The lava provides exceptional three-dimensional exposure of complex brittle and ductile deformation textures that record processes of lava fracture and quenching driven by external water. The flow front interior is characterised by structures consisting of a large (metre-scale) curviplanar master fracture with many smaller (centimetre-scale) subsidiary fractures perpendicular to the master fracture. Such structures have previously been recognised in a range of lava compositions from basalt to dacite and called pseudopillows or pseudopillow fractures. We propose the term pseudopillow fracture systems to emphasise the consistent package of different fracture types occurring together. All documented occurrences of pseudopillow fracture systems are in lavas that have been inferred to interact with an aqueous coolant (i.e. liquid water, ice or snow). We use fracture surface textures and their orientation in relation to flow banding to identify three distinct types of master fracture and two types of subsidiary fractures. Master fracture surface textures used to identify fracture mechanisms include chisel marks (striae), cavitation dimples, river lines and rough/smooth fracture surface textures. These indicate both brittle and ductile fracture happening on different types of master fracture. Chisel marks on subsidiary fractures indicate comparative cooling rates, cooling directions and isotherm orientations at the time of fracture. We propose a model for pseudopillow fracture system formation taking into account all the various fracture types, textures and fracture propagation mechanisms and discuss their implications for interaction mechanisms between lava flows and external coolants. Article in Journal/Newspaper Iceland Lancaster University: Lancaster Eprints Journal of Volcanology and Geothermal Research 245-246 68 80 |
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Lancaster University: Lancaster Eprints |
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ftulancaster |
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unknown |
description |
Detailed field observations of structures within the flow front of a Holocene trachyandesite lava from Snæfellsnes, Iceland, are presented. The lava provides exceptional three-dimensional exposure of complex brittle and ductile deformation textures that record processes of lava fracture and quenching driven by external water. The flow front interior is characterised by structures consisting of a large (metre-scale) curviplanar master fracture with many smaller (centimetre-scale) subsidiary fractures perpendicular to the master fracture. Such structures have previously been recognised in a range of lava compositions from basalt to dacite and called pseudopillows or pseudopillow fractures. We propose the term pseudopillow fracture systems to emphasise the consistent package of different fracture types occurring together. All documented occurrences of pseudopillow fracture systems are in lavas that have been inferred to interact with an aqueous coolant (i.e. liquid water, ice or snow). We use fracture surface textures and their orientation in relation to flow banding to identify three distinct types of master fracture and two types of subsidiary fractures. Master fracture surface textures used to identify fracture mechanisms include chisel marks (striae), cavitation dimples, river lines and rough/smooth fracture surface textures. These indicate both brittle and ductile fracture happening on different types of master fracture. Chisel marks on subsidiary fractures indicate comparative cooling rates, cooling directions and isotherm orientations at the time of fracture. We propose a model for pseudopillow fracture system formation taking into account all the various fracture types, textures and fracture propagation mechanisms and discuss their implications for interaction mechanisms between lava flows and external coolants. |
format |
Article in Journal/Newspaper |
author |
Forbes, Anne Blake, Steven McGarvie, David W. Tuffen, Hugh |
spellingShingle |
Forbes, Anne Blake, Steven McGarvie, David W. Tuffen, Hugh Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures |
author_facet |
Forbes, Anne Blake, Steven McGarvie, David W. Tuffen, Hugh |
author_sort |
Forbes, Anne |
title |
Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures |
title_short |
Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures |
title_full |
Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures |
title_fullStr |
Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures |
title_full_unstemmed |
Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures |
title_sort |
pseudopillow fracture systems in lavas: insights into cooling mechanisms and environments from lava flow fractures |
publishDate |
2012 |
url |
https://eprints.lancs.ac.uk/id/eprint/54746/ https://doi.org/10.1016/j.jvolgeores.2012.07.007 |
genre |
Iceland |
genre_facet |
Iceland |
op_relation |
Forbes, Anne and Blake, Steven and McGarvie, David W. and Tuffen, Hugh (2012) Pseudopillow fracture systems in lavas: Insights into cooling mechanisms and environments from lava flow fractures. Journal of Volcanology and Geothermal Research, 245-24. pp. 68-80. ISSN 0377-0273 |
op_doi |
https://doi.org/10.1016/j.jvolgeores.2012.07.007 |
container_title |
Journal of Volcanology and Geothermal Research |
container_volume |
245-246 |
container_start_page |
68 |
op_container_end_page |
80 |
_version_ |
1775352079240396800 |