Hekla Revisited: Fractionation of a Magma Body at Historical Timescales
Abstract Hekla is an elongate volcano that lies at the intersection of the South Iceland Seismic Zone and the Eastern Volcanic Zone. We report major and trace element, oxygen isotopic, and H2O analyses on rocks, glass, melt inclusions, and minerals from almost all of the historical lavas and tephra...
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2021
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croxfordunivpr:10.1093/petrology/egab001 2024-06-23T07:53:32+00:00 Hekla Revisited: Fractionation of a Magma Body at Historical Timescales Geist, Dennis Harpp, Karen Oswald, Peter Wallace, Paul Bindeman, Ilya Christensen, Branden National Science Foundation 2021 http://dx.doi.org/10.1093/petrology/egab001 http://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egab001/36105102/egab001.pdf https://academic.oup.com/petrology/article-pdf/62/8/egab001/42439783/egab001.pdf en eng Oxford University Press (OUP) Journal of Petrology volume 62, issue 8 ISSN 0022-3530 1460-2415 journal-article 2021 croxfordunivpr https://doi.org/10.1093/petrology/egab001 2024-06-11T04:16:20Z Abstract Hekla is an elongate volcano that lies at the intersection of the South Iceland Seismic Zone and the Eastern Volcanic Zone. We report major and trace element, oxygen isotopic, and H2O analyses on rocks, glass, melt inclusions, and minerals from almost all of the historical lavas and tephra deposits. This new dataset confirms the remarkable observation that not only are many eruptions compositionally zoned from felsic to mafic, but the extent of zoning relates directly to the length of repose since the previous eruption. Compositional data are consistent with the origin of the basaltic andesites and andesites by fractional crystallization, with no measurable crustal interaction once basaltic andesite has been produced. Although the 1104 CE Plinian rhyolite and 1158 CE dacite are also created by fractional crystallization, uranium–thorium isotopic disequilibria measured by others require that they evolved in a separate body, where magma is stored in a molten state for >104 years. Consistent trace element trends and ratios, as well as oxygenisotopic data, preclude significant crustal input into the evolving magma. The phenocryst assemblages are dominated by crystals that formed from their host melt; an exception is the 1158 CE dacite, which contains abundant crystals that formed from the 1104 CE rhyolite melt. A suite of thermobarometers indicates that most crystals formed in the lower crust at temperatures ranging from ∼1010 to 850 °C. Hekla’s unique and systematic petrological time series and geophysical activity are attributed to the unusual geometry of the magma body, which we propose to be a tabular, vertically elongate macrodike, extending from the lower to the upper crust. The vertical body is recharged with basaltic andesite magma at the end of each eruption, which then undergoes cooling and crystallization until the subsequent eruption. The entire system is supplied by a lower-crustal body of basaltic andesite, which is produced by fractional crystallization of basaltic magma in a reservoir ... Article in Journal/Newspaper Hekla Iceland Oxford University Press Journal of Petrology |
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Oxford University Press |
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English |
description |
Abstract Hekla is an elongate volcano that lies at the intersection of the South Iceland Seismic Zone and the Eastern Volcanic Zone. We report major and trace element, oxygen isotopic, and H2O analyses on rocks, glass, melt inclusions, and minerals from almost all of the historical lavas and tephra deposits. This new dataset confirms the remarkable observation that not only are many eruptions compositionally zoned from felsic to mafic, but the extent of zoning relates directly to the length of repose since the previous eruption. Compositional data are consistent with the origin of the basaltic andesites and andesites by fractional crystallization, with no measurable crustal interaction once basaltic andesite has been produced. Although the 1104 CE Plinian rhyolite and 1158 CE dacite are also created by fractional crystallization, uranium–thorium isotopic disequilibria measured by others require that they evolved in a separate body, where magma is stored in a molten state for >104 years. Consistent trace element trends and ratios, as well as oxygenisotopic data, preclude significant crustal input into the evolving magma. The phenocryst assemblages are dominated by crystals that formed from their host melt; an exception is the 1158 CE dacite, which contains abundant crystals that formed from the 1104 CE rhyolite melt. A suite of thermobarometers indicates that most crystals formed in the lower crust at temperatures ranging from ∼1010 to 850 °C. Hekla’s unique and systematic petrological time series and geophysical activity are attributed to the unusual geometry of the magma body, which we propose to be a tabular, vertically elongate macrodike, extending from the lower to the upper crust. The vertical body is recharged with basaltic andesite magma at the end of each eruption, which then undergoes cooling and crystallization until the subsequent eruption. The entire system is supplied by a lower-crustal body of basaltic andesite, which is produced by fractional crystallization of basaltic magma in a reservoir ... |
author2 |
National Science Foundation |
format |
Article in Journal/Newspaper |
author |
Geist, Dennis Harpp, Karen Oswald, Peter Wallace, Paul Bindeman, Ilya Christensen, Branden |
spellingShingle |
Geist, Dennis Harpp, Karen Oswald, Peter Wallace, Paul Bindeman, Ilya Christensen, Branden Hekla Revisited: Fractionation of a Magma Body at Historical Timescales |
author_facet |
Geist, Dennis Harpp, Karen Oswald, Peter Wallace, Paul Bindeman, Ilya Christensen, Branden |
author_sort |
Geist, Dennis |
title |
Hekla Revisited: Fractionation of a Magma Body at Historical Timescales |
title_short |
Hekla Revisited: Fractionation of a Magma Body at Historical Timescales |
title_full |
Hekla Revisited: Fractionation of a Magma Body at Historical Timescales |
title_fullStr |
Hekla Revisited: Fractionation of a Magma Body at Historical Timescales |
title_full_unstemmed |
Hekla Revisited: Fractionation of a Magma Body at Historical Timescales |
title_sort |
hekla revisited: fractionation of a magma body at historical timescales |
publisher |
Oxford University Press (OUP) |
publishDate |
2021 |
url |
http://dx.doi.org/10.1093/petrology/egab001 http://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egab001/36105102/egab001.pdf https://academic.oup.com/petrology/article-pdf/62/8/egab001/42439783/egab001.pdf |
genre |
Hekla Iceland |
genre_facet |
Hekla Iceland |
op_source |
Journal of Petrology volume 62, issue 8 ISSN 0022-3530 1460-2415 |
op_doi |
https://doi.org/10.1093/petrology/egab001 |
container_title |
Journal of Petrology |
_version_ |
1802645252753850368 |