Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland
Postglacial activity on the Askja volcanic system, north Iceland, has been dominated by basaltic volcanism. Over 80% of Askja's postglacial basalts fall within a relatively narrow compositional range containing between 4 and 8 wt.% MgO. The 'main series' is further divided into two gr...
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The University of Edinburgh
2012
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ftunivedinburgh:oai:era.ed.ac.uk:1842/5845 2023-07-30T04:04:23+02:00 Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland Hartley, Margaret Elizabeth Thordarson, Thorvaldur Fitton, Godfrey Natural Environment Research Council (NERC) 2012-06-25 application/pdf application/vnd.ms-excel http://hdl.handle.net/1842/5845 en eng The University of Edinburgh http://hdl.handle.net/1842/5845 Askja volcanic system basaltic volcanism postglacial activity magma reservoirs eruption 1875 postglacial lava succession aphyric Thesis or Dissertation Doctoral PhD Doctor of Philosophy 2012 ftunivedinburgh 2023-07-09T20:34:35Z Postglacial activity on the Askja volcanic system, north Iceland, has been dominated by basaltic volcanism. Over 80% of Askja's postglacial basalts fall within a relatively narrow compositional range containing between 4 and 8 wt.% MgO. The 'main series' is further divided into two groups separated by a distinct compositional gap evident in major and trace element concentrations. The most evolved basalts formed by fractional crystallisation within shallow magma reservoirs, followed by the extraction of residual liquid from a semi-rigid, interconnected crystal network. This process is analogous to the formation of melt segregations within single lava flows, and was responsible for generating several small-volume, aphyric basaltic lavas erupted along caldera ring fractures surrounding the Oskjuvatn (Askja lake) caldera in the early 20th century. Further examples of evolved basalt are found throughout Askja's postglacial volcanic record. However, Askja's early postglacial output is dominated by more primitive compositions. Some of the most primitive basalts erupted within the Askja caldera are found in phreatomagmatic tuff cone sequences which crop out in the walls of Oskjuvatn caldera. one such tuff sequence has been dated at between 2.9 and 3.6 ka. This tuff cone shares geochemical source characteristics, such as Nb/La and Nb/Zr, with basaltic tephras erupted during precursory activity to the Plinian-phreatoplinian eruption of 28th-29th March 1875. It may therefore be considered to be compositionally representative of the primitive basaltic magmas supplied to Askja during the postglacial period. The predominance of relatively primitive basalt (6.8 wt.% MgO) within Askia's postglacial lava succession suggests that it did not have a permanent shallow magma chamber during the postglacial period. It is envisaged that the postglacial Askja magmas evolved by a process of polybaric factionation in transient, sill-like magma storage zones located at various levels in the crust. The most primitive magmas erupted directly ... Doctoral or Postdoctoral Thesis Iceland Edinburgh Research Archive (ERA - University of Edinburgh) Askja ENVELOPE(-16.802,-16.802,65.042,65.042) |
institution |
Open Polar |
collection |
Edinburgh Research Archive (ERA - University of Edinburgh) |
op_collection_id |
ftunivedinburgh |
language |
English |
topic |
Askja volcanic system basaltic volcanism postglacial activity magma reservoirs eruption 1875 postglacial lava succession aphyric |
spellingShingle |
Askja volcanic system basaltic volcanism postglacial activity magma reservoirs eruption 1875 postglacial lava succession aphyric Hartley, Margaret Elizabeth Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland |
topic_facet |
Askja volcanic system basaltic volcanism postglacial activity magma reservoirs eruption 1875 postglacial lava succession aphyric |
description |
Postglacial activity on the Askja volcanic system, north Iceland, has been dominated by basaltic volcanism. Over 80% of Askja's postglacial basalts fall within a relatively narrow compositional range containing between 4 and 8 wt.% MgO. The 'main series' is further divided into two groups separated by a distinct compositional gap evident in major and trace element concentrations. The most evolved basalts formed by fractional crystallisation within shallow magma reservoirs, followed by the extraction of residual liquid from a semi-rigid, interconnected crystal network. This process is analogous to the formation of melt segregations within single lava flows, and was responsible for generating several small-volume, aphyric basaltic lavas erupted along caldera ring fractures surrounding the Oskjuvatn (Askja lake) caldera in the early 20th century. Further examples of evolved basalt are found throughout Askja's postglacial volcanic record. However, Askja's early postglacial output is dominated by more primitive compositions. Some of the most primitive basalts erupted within the Askja caldera are found in phreatomagmatic tuff cone sequences which crop out in the walls of Oskjuvatn caldera. one such tuff sequence has been dated at between 2.9 and 3.6 ka. This tuff cone shares geochemical source characteristics, such as Nb/La and Nb/Zr, with basaltic tephras erupted during precursory activity to the Plinian-phreatoplinian eruption of 28th-29th March 1875. It may therefore be considered to be compositionally representative of the primitive basaltic magmas supplied to Askja during the postglacial period. The predominance of relatively primitive basalt (6.8 wt.% MgO) within Askia's postglacial lava succession suggests that it did not have a permanent shallow magma chamber during the postglacial period. It is envisaged that the postglacial Askja magmas evolved by a process of polybaric factionation in transient, sill-like magma storage zones located at various levels in the crust. The most primitive magmas erupted directly ... |
author2 |
Thordarson, Thorvaldur Fitton, Godfrey Natural Environment Research Council (NERC) |
format |
Doctoral or Postdoctoral Thesis |
author |
Hartley, Margaret Elizabeth |
author_facet |
Hartley, Margaret Elizabeth |
author_sort |
Hartley, Margaret Elizabeth |
title |
Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland |
title_short |
Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland |
title_full |
Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland |
title_fullStr |
Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland |
title_full_unstemmed |
Post glacial volcanism and magmatism on the Askja volcanic system, North Iceland |
title_sort |
post glacial volcanism and magmatism on the askja volcanic system, north iceland |
publisher |
The University of Edinburgh |
publishDate |
2012 |
url |
http://hdl.handle.net/1842/5845 |
long_lat |
ENVELOPE(-16.802,-16.802,65.042,65.042) |
geographic |
Askja |
geographic_facet |
Askja |
genre |
Iceland |
genre_facet |
Iceland |
op_relation |
http://hdl.handle.net/1842/5845 |
_version_ |
1772815790944288768 |