Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland
Plagioclase textures were investigated in the products of the voluminous 1783–1784 CE Laki eruption from the Eastern Volcanic Zone (EVZ) of Iceland to establish whether mush disaggregation occurred solely at the onset of the eight-month eruption or throughout its whole duration. Phase proportions an...
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ftdatacite:10.15488/4141 2023-05-15T16:49:11+02:00 Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland Neave, David A. Buisman, Iris Maclennan, John 2017 https://dx.doi.org/10.15488/4141 https://www.repo.uni-hannover.de/handle/123456789/4175 en eng McLean, VA : GeoScienceWorld Creative Commons Attribution 3.0 Unported CC BY 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 CC-BY Mush disaggregation basalt automated mineralogy crystal size distributions textures Dynamics of Magmatic Processes Dewey Decimal Classification500 | Naturwissenschaften550 | Geowissenschaften Other CreativeWork article 2017 ftdatacite https://doi.org/10.15488/4141 2021-11-05T12:55:41Z Plagioclase textures were investigated in the products of the voluminous 1783–1784 CE Laki eruption from the Eastern Volcanic Zone (EVZ) of Iceland to establish whether mush disaggregation occurred solely at the onset of the eight-month eruption or throughout its whole duration. Phase proportions and plagioclase size distributions were determined using standard optical and manual techniques as well as automated approaches based on Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN). Based on optical microscopy and the explicit combination of textural and compositional information in QEMSCAN images, plagioclase crystals were divided into two populations: small (<0.5 mm long), high-aspect ratio (length/width >4) microcrysts with low-anorthite (0.5 mm long), low-aspect ratio (length/width = 2–3) macrocrysts with high-anorthite (An84–An92) cores. Small microcrysts grew from their carrier liquid during the final phase of pre-eruptive crystallization while large macrocrysts, which are out of geochemical equilibrium with their carrier liquids, were entrained from crystal mushes. Changes in phase proportions and plagioclase size distributions between eruptive episodes demonstrate that macrocryst entrainment efficiency varied substantially during the eruption; material erupted in later episodes contain proportionally more mush-derived material. Using stereologically corrected plagioclase size distributions, we estimate that the pre-eruptive residence times of microcrysts in the Laki carrier liquid were probably of the order of 2–20 days. Because microcryst crystallization was concurrent with macrocryst rim growth, these day-to-week residence times also indicate that macrocryst entrainment occurred on much shorter timescales than the eruption's eight-month duration. In line with constraints from independent geochronometers, macrocryst entrainment and mush disaggregation thus appears to have continued throughout the eruption. Magmas were assembled on an episode by episode basis, and the volume of eruptible magma in the plumbing system at any given time was probably closer to 1–2 km3 than the final erupted volume of 15.1 km3. Article in Journal/Newspaper Iceland DataCite Metadata Store (German National Library of Science and Technology) Dewey ENVELOPE(-64.320,-64.320,-65.907,-65.907) Laki ENVELOPE(-18.237,-18.237,64.070,64.070) |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
Mush disaggregation basalt automated mineralogy crystal size distributions textures Dynamics of Magmatic Processes Dewey Decimal Classification500 | Naturwissenschaften550 | Geowissenschaften |
spellingShingle |
Mush disaggregation basalt automated mineralogy crystal size distributions textures Dynamics of Magmatic Processes Dewey Decimal Classification500 | Naturwissenschaften550 | Geowissenschaften Neave, David A. Buisman, Iris Maclennan, John Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland |
topic_facet |
Mush disaggregation basalt automated mineralogy crystal size distributions textures Dynamics of Magmatic Processes Dewey Decimal Classification500 | Naturwissenschaften550 | Geowissenschaften |
description |
Plagioclase textures were investigated in the products of the voluminous 1783–1784 CE Laki eruption from the Eastern Volcanic Zone (EVZ) of Iceland to establish whether mush disaggregation occurred solely at the onset of the eight-month eruption or throughout its whole duration. Phase proportions and plagioclase size distributions were determined using standard optical and manual techniques as well as automated approaches based on Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN). Based on optical microscopy and the explicit combination of textural and compositional information in QEMSCAN images, plagioclase crystals were divided into two populations: small (<0.5 mm long), high-aspect ratio (length/width >4) microcrysts with low-anorthite (0.5 mm long), low-aspect ratio (length/width = 2–3) macrocrysts with high-anorthite (An84–An92) cores. Small microcrysts grew from their carrier liquid during the final phase of pre-eruptive crystallization while large macrocrysts, which are out of geochemical equilibrium with their carrier liquids, were entrained from crystal mushes. Changes in phase proportions and plagioclase size distributions between eruptive episodes demonstrate that macrocryst entrainment efficiency varied substantially during the eruption; material erupted in later episodes contain proportionally more mush-derived material. Using stereologically corrected plagioclase size distributions, we estimate that the pre-eruptive residence times of microcrysts in the Laki carrier liquid were probably of the order of 2–20 days. Because microcryst crystallization was concurrent with macrocryst rim growth, these day-to-week residence times also indicate that macrocryst entrainment occurred on much shorter timescales than the eruption's eight-month duration. In line with constraints from independent geochronometers, macrocryst entrainment and mush disaggregation thus appears to have continued throughout the eruption. Magmas were assembled on an episode by episode basis, and the volume of eruptible magma in the plumbing system at any given time was probably closer to 1–2 km3 than the final erupted volume of 15.1 km3. |
format |
Article in Journal/Newspaper |
author |
Neave, David A. Buisman, Iris Maclennan, John |
author_facet |
Neave, David A. Buisman, Iris Maclennan, John |
author_sort |
Neave, David A. |
title |
Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland |
title_short |
Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland |
title_full |
Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland |
title_fullStr |
Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland |
title_full_unstemmed |
Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland |
title_sort |
continuous mush disaggregation during the long-lasting laki fissure eruption, iceland |
publisher |
McLean, VA : GeoScienceWorld |
publishDate |
2017 |
url |
https://dx.doi.org/10.15488/4141 https://www.repo.uni-hannover.de/handle/123456789/4175 |
long_lat |
ENVELOPE(-64.320,-64.320,-65.907,-65.907) ENVELOPE(-18.237,-18.237,64.070,64.070) |
geographic |
Dewey Laki |
geographic_facet |
Dewey Laki |
genre |
Iceland |
genre_facet |
Iceland |
op_rights |
Creative Commons Attribution 3.0 Unported CC BY 3.0 Unported https://creativecommons.org/licenses/by/3.0/legalcode cc-by-3.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.15488/4141 |
_version_ |
1766039307982733312 |