Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution.
The Torfajökull central volcano lies in Iceland’s southern flank zone (a non-rifting zone) and last erupted in the 15th century. Peralkaline rhyolites from its pre-Holocene formations have been dated by the Ar-Ar method. Ages from 67±9 ka to 384±20 ka indicate Pleistocene eruptions, with the oldest...
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ftulancaster:oai:eprints.lancs.ac.uk:27170 2024-09-15T18:12:21+00:00 Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. McGarvie, D. W. Burgess, R. Tindle, A. G. Tuffen, Hugh Stevenson, John A. 2006 https://eprints.lancs.ac.uk/id/eprint/27170/ unknown McGarvie, D. W. and Burgess, R. and Tindle, A. G. and Tuffen, Hugh and Stevenson, John A. (2006) Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. JÖKULL, 56. pp. 57-75. ISSN 0449-0576 Journal Article PeerReviewed 2006 ftulancaster 2024-07-17T00:35:27Z The Torfajökull central volcano lies in Iceland’s southern flank zone (a non-rifting zone) and last erupted in the 15th century. Peralkaline rhyolites from its pre-Holocene formations have been dated by the Ar-Ar method. Ages from 67±9 ka to 384±20 ka indicate Pleistocene eruptions, with the oldest age (384 ka) also being from the most evolved rhyolite (a pantellerite). The oldest age indicates that a mature and evolved magmatic-volcanic system was well established by the mid-Pleistocene and that the central volcano has been active for at least 400 ka. Good correlation is found between the Ar-Ar ages of sustained rhyolite eruptions into ice sheets (i.e. rhyolite tuya formation) and oxygen isotope stages dominated by cold conditions. This is the first stage of developing a new proxy that uses rhyolitic glaciovolcanic edifices to provide estimates of past Icelandic ice sheet thicknesses. The geochemistry of the dated samples corroborates earlier work showing a simple but enigmatic trend of steadily-decreasing alkalinity towards the present (i.e. older rocks are more evolved). The new ages reveal a hitherto-unrecognised drop in rhyolite alkalinity after 83 ka, which may be linked to the evacuation of c. 16 km3 of rhyolite during a subglacial eruption into the last (Weichselian) ice sheet, for which two new and overlapping Ar-Ar ages of 67±9 ka and 72±7 ka have been obtained. This rhyolite eruption, which is the largest known from Torfajökull, heralded a major change in the magma system as all subsequent eruptions are of small volume (<0.3 km3), dominated by subalkaline compositions, and characterised by interactions with mafic magmas. This change may be linked to lower rhyolite magma replenishment rates and/or to the increasing influence of rift zone volcano-tectonics. Article in Journal/Newspaper Ice Sheet Iceland Lancaster University: Lancaster Eprints |
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Open Polar |
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Lancaster University: Lancaster Eprints |
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ftulancaster |
language |
unknown |
description |
The Torfajökull central volcano lies in Iceland’s southern flank zone (a non-rifting zone) and last erupted in the 15th century. Peralkaline rhyolites from its pre-Holocene formations have been dated by the Ar-Ar method. Ages from 67±9 ka to 384±20 ka indicate Pleistocene eruptions, with the oldest age (384 ka) also being from the most evolved rhyolite (a pantellerite). The oldest age indicates that a mature and evolved magmatic-volcanic system was well established by the mid-Pleistocene and that the central volcano has been active for at least 400 ka. Good correlation is found between the Ar-Ar ages of sustained rhyolite eruptions into ice sheets (i.e. rhyolite tuya formation) and oxygen isotope stages dominated by cold conditions. This is the first stage of developing a new proxy that uses rhyolitic glaciovolcanic edifices to provide estimates of past Icelandic ice sheet thicknesses. The geochemistry of the dated samples corroborates earlier work showing a simple but enigmatic trend of steadily-decreasing alkalinity towards the present (i.e. older rocks are more evolved). The new ages reveal a hitherto-unrecognised drop in rhyolite alkalinity after 83 ka, which may be linked to the evacuation of c. 16 km3 of rhyolite during a subglacial eruption into the last (Weichselian) ice sheet, for which two new and overlapping Ar-Ar ages of 67±9 ka and 72±7 ka have been obtained. This rhyolite eruption, which is the largest known from Torfajökull, heralded a major change in the magma system as all subsequent eruptions are of small volume (<0.3 km3), dominated by subalkaline compositions, and characterised by interactions with mafic magmas. This change may be linked to lower rhyolite magma replenishment rates and/or to the increasing influence of rift zone volcano-tectonics. |
format |
Article in Journal/Newspaper |
author |
McGarvie, D. W. Burgess, R. Tindle, A. G. Tuffen, Hugh Stevenson, John A. |
spellingShingle |
McGarvie, D. W. Burgess, R. Tindle, A. G. Tuffen, Hugh Stevenson, John A. Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
author_facet |
McGarvie, D. W. Burgess, R. Tindle, A. G. Tuffen, Hugh Stevenson, John A. |
author_sort |
McGarvie, D. W. |
title |
Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
title_short |
Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
title_full |
Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
title_fullStr |
Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
title_full_unstemmed |
Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
title_sort |
pleistocene rhyolitic volcanism at torfajökull, iceland : eruption ages, glaciovolcanism, and geochemical evolution. |
publishDate |
2006 |
url |
https://eprints.lancs.ac.uk/id/eprint/27170/ |
genre |
Ice Sheet Iceland |
genre_facet |
Ice Sheet Iceland |
op_relation |
McGarvie, D. W. and Burgess, R. and Tindle, A. G. and Tuffen, Hugh and Stevenson, John A. (2006) Pleistocene rhyolitic volcanism at Torfajökull, Iceland : eruption ages, glaciovolcanism, and geochemical evolution. JÖKULL, 56. pp. 57-75. ISSN 0449-0576 |
_version_ |
1810449940797718528 |