A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body

Polycyclic caldera complexes hold clues to understanding why some magmatic systems develop into supersized magma bodies and how they can recover to produce several caldera-forming eruptions. However, the geologic records of the transitions between successive caldera events are very often inaccessibl...

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Main Authors: Szymanowski, Dawid, Forni, Francesca, Phua, Marcus, Jicha, Brian, Lee, Daniel W. J., Hsu, Ying-Jui, Rifai, Hamdi, Schoene, Blair, Bouvet de Maisonneuve, Caroline
Other Authors: Asian School of the Environment
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Language:English
Published: 2024
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Online Access:https://hdl.handle.net/10356/174325
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spelling sg-ntu-dr.10356-1743252024-04-01T15:30:37Z A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body Szymanowski, Dawid Forni, Francesca Phua, Marcus Jicha, Brian Lee, Daniel W. J. Hsu, Ying-Jui Rifai, Hamdi Schoene, Blair Bouvet de Maisonneuve, Caroline Asian School of the Environment Earth Observatory of Singapore Earth and Environmental Sciences Magma reservoir Hafnium isotopes Polycyclic caldera complexes hold clues to understanding why some magmatic systems develop into supersized magma bodies and how they can recover to produce several caldera-forming eruptions. However, the geologic records of the transitions between successive caldera events are very often inaccessible due to limited preservation of eruptive products of inter-caldera activity, prompting the search for alternative archives of magma evolution such as accessory minerals. Here we applied multiple geochemical tools to study one of the most active caldera centres of the Quaternary, the Toba caldera complex in Sumatra (Indonesia), which produced at least four caldera-forming eruptions in the last 1.6 My, including the iconic Youngest Toba Tuff at 74 ka. We combined feldspar 40Ar/39Ar and zircon U–Pb geochronology of proximal pyroclastic deposits with glass and mineral chemistry of both the tuffs and distal marine tephra to revise the eruption chronology of Toba, obtaining new eruption ages of 1417 -31/+14 ka (zircon) or 1339 ± 39/39 ka (plagioclase, internal/full external 2σ uncertainty) for the Haranggaol Dacite Tuff, 783.81 ± 0.85/1.32 ka (sanidine) for Oldest Toba Tuff, and 503.61 ± 1.36/1.50 ka (sanidine) for Middle Toba Tuff. Isotope dilution thermal ionisation mass spectrometry (ID-TIMS) U–Pb crystallisation ages, trace element contents and Hf isotopic ratios of zircons illuminate changes in the shallow magma reservoir which saw near-continuous zircon crystallisation over 1.6 My. Prolonged build-ups to each eruption with highly scattered zircon trace element compositions reflect a complex, heterogeneous character of the shallow reservoir, without a clear temporal trend or indications of the eruption trigger. In contrast, hafnium isotopes in zircon display a pronounced shift towards unradiogenic values immediately after the OTT caldera collapse, followed by a gradual recovery to a baseline value of εHf = -7 at the time of YTT eruption, interpreted as a reflection of the shift in magma reservoir position corresponding to change in the character of assimilated crust. We can show in unprecedented detail how a large caldera collapse affects magma geochemistry; however, identification of patterns in the behaviour of the Toba system and making geochemistry-based predictions about its future development remain a challenge. National Research Foundation (NRF) Published version This work was supported by the National Research Foundation, Singapore [grant NRF-NRFF2016-04] and the U.S. National Science Foundation [award EAR-1735512]. 2024-03-26T05:58:48Z 2024-03-26T05:58:48Z 2023 Journal Article Szymanowski, D., Forni, F., Phua, M., Jicha, B., Lee, D. W. J., Hsu, Y., Rifai, H., Schoene, B. & Bouvet de Maisonneuve, C. (2023). A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body. Earth and Planetary Science Letters, 622, 118408-. https://dx.doi.org/10.1016/j.epsl.2023.118408 0012-821X https://hdl.handle.net/10356/174325 10.1016/j.epsl.2023.118408 2-s2.0-85173581291 622 118408 en NRF-NRFF2016-04 Earth and Planetary Science Letters © 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Earth and Environmental Sciences
Magma reservoir
Hafnium isotopes
spellingShingle Earth and Environmental Sciences
Magma reservoir
Hafnium isotopes
Szymanowski, Dawid
Forni, Francesca
Phua, Marcus
Jicha, Brian
Lee, Daniel W. J.
Hsu, Ying-Jui
Rifai, Hamdi
Schoene, Blair
Bouvet de Maisonneuve, Caroline
A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
description Polycyclic caldera complexes hold clues to understanding why some magmatic systems develop into supersized magma bodies and how they can recover to produce several caldera-forming eruptions. However, the geologic records of the transitions between successive caldera events are very often inaccessible due to limited preservation of eruptive products of inter-caldera activity, prompting the search for alternative archives of magma evolution such as accessory minerals. Here we applied multiple geochemical tools to study one of the most active caldera centres of the Quaternary, the Toba caldera complex in Sumatra (Indonesia), which produced at least four caldera-forming eruptions in the last 1.6 My, including the iconic Youngest Toba Tuff at 74 ka. We combined feldspar 40Ar/39Ar and zircon U–Pb geochronology of proximal pyroclastic deposits with glass and mineral chemistry of both the tuffs and distal marine tephra to revise the eruption chronology of Toba, obtaining new eruption ages of 1417 -31/+14 ka (zircon) or 1339 ± 39/39 ka (plagioclase, internal/full external 2σ uncertainty) for the Haranggaol Dacite Tuff, 783.81 ± 0.85/1.32 ka (sanidine) for Oldest Toba Tuff, and 503.61 ± 1.36/1.50 ka (sanidine) for Middle Toba Tuff. Isotope dilution thermal ionisation mass spectrometry (ID-TIMS) U–Pb crystallisation ages, trace element contents and Hf isotopic ratios of zircons illuminate changes in the shallow magma reservoir which saw near-continuous zircon crystallisation over 1.6 My. Prolonged build-ups to each eruption with highly scattered zircon trace element compositions reflect a complex, heterogeneous character of the shallow reservoir, without a clear temporal trend or indications of the eruption trigger. In contrast, hafnium isotopes in zircon display a pronounced shift towards unradiogenic values immediately after the OTT caldera collapse, followed by a gradual recovery to a baseline value of εHf = -7 at the time of YTT eruption, interpreted as a reflection of the shift in magma reservoir position corresponding to change in the character of assimilated crust. We can show in unprecedented detail how a large caldera collapse affects magma geochemistry; however, identification of patterns in the behaviour of the Toba system and making geochemistry-based predictions about its future development remain a challenge.
author2 Asian School of the Environment
author_facet Asian School of the Environment
Szymanowski, Dawid
Forni, Francesca
Phua, Marcus
Jicha, Brian
Lee, Daniel W. J.
Hsu, Ying-Jui
Rifai, Hamdi
Schoene, Blair
Bouvet de Maisonneuve, Caroline
format Article
author Szymanowski, Dawid
Forni, Francesca
Phua, Marcus
Jicha, Brian
Lee, Daniel W. J.
Hsu, Ying-Jui
Rifai, Hamdi
Schoene, Blair
Bouvet de Maisonneuve, Caroline
author_sort Szymanowski, Dawid
title A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
title_short A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
title_full A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
title_fullStr A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
title_full_unstemmed A shifty Toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
title_sort shifty toba magma reservoir: improved eruption chronology and petrochronological evidence for lateral growth of a giant magma body
publishDate 2024
url https://hdl.handle.net/10356/174325
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