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

doi:10.1016/j.epsl.2023.118408

Cited by 6 publications

(2 citation statements)

References 63 publications

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“…According to some authors (e.g., Koulakov et al, 2016), this peculiar geodynamic setting might represent the main cause for the exceptionally vigorous volcanic activity at Toba, where at least four large caldera-forming eruptions have occurred over the last ~1.4 My Chesner, 1998). The latest of these eruptions, the Youngest Toba Tuff (YTT, ~74 ka), represents the largest known Quaternary caldera-forming eruption (Rose and Chesner, 1987;Costa et al, 2014;Mark et al, 2014;Szymanowski et al, 2023). Although Sumatra is mostly known for hosting the Toba caldera, the occurrence of widespread and thick proximal pyroclastic sequences on the island (Westerveld, 1952), together with the presence of abundant tephra layers of Sumatran origin in the distal marine stratigraphic record (Ninkovich et al, 1978;Salisbury et al, 2012;Bouvet de Maisonneuve and Bergal-Kuvikas, 2020;Kutterolf et al, 2023), suggest that Sumatra might have produced a much greater number of large eruptions, many of which have so far received little attention.…”

Section: Geological Settingmentioning

confidence: 99%

Remobilization and eruption of an upper crustal cumulate mush: the Singkut caldera (North Sumatra, Indonesia)

Forni

Oalmann

Fellin

et al. 2022

Preprint

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Understanding the conditions and timescales of storage and remobilization of magma bodies in the upper crust is key to interpret the signals of potential reawakening of the volcanic activity at active volcanic systems.&#160;In this study we provide the first volcanological and petrological characterization of the Singkut volcanic system located in northern Sumatra, ~35 km N of the Toba caldera and ~40 km SW of the major city of Medan.&#160;Singkut is a ~9 km diameter caldera delimited by ~300 m-high rims where pre-caldera lavas are exposed. The inner part of the collapsed structure is occupied by three post-caldera volcanoes and currently hosts an active geothermal field. We utilize field observations and correlation with a distal marine tephra layer to map the extension and thickness of the tuff erupted during the caldera-forming eruption and use these data to estimate the erupted magma volume. We use major and trace element data of bulk-rock, matrix glasses and minerals to characterize the pre-eruptive conditions of pre- and post-caldera lavas and caldera-forming tuff and 14C and U/Th-He zircon dating to determine the eruption ages. In addition, a combination of U/Th and U/Pb in-situ zircon dating and zircon trace element geochemistry provides insights into the mechanisms and timescales that led to the Singkut caldera-forming eruption and those that controlled the post-caldera activity.&#160;Our data show that Singkut caldera formed ~50 ka during a large explosive eruption that deposited ~60 km3 of pyroclastic material. The cataclysmic eruption was preceded by at least 200 ky of mostly effusive pre-caldera activity and followed by effusive and mildly explosive post-caldera activity, with the last eruption reported at 1881 AD. The lavas and pumices have high crystallinity (24-62% crystals) and contain pl+amph+bt+opx+Fe-Ti ox+ap+zr&#177;qtz. Notably, large and strongly resorbed quartz crystals are abundant in the pre-caldera lavas and scarce or absent in the caldera-forming tuff and post-caldera lavas. Bulk-rock composition of pumices and lavas varies from andesitic to dacitic, while the matrix glass in the pumices is rhyolitic. Trace element composition of glass (e.g., positive Eu anomalies) indicate resorption of feldspars. Crystallization ages of the youngest zircons in pre-caldera lavas overlap with eruption ages (~250 ka) while crystallization ages of the youngest zircons in the caldera-forming tuff and post-caldera lavas are significantly older (~100 ka) than the eruption ages (~50 and ~16 ka, respectively). Ti-in-zircon thermometry combined with zircon geochronology show that the Singkut magma body experienced a heating phase which started approximately upon eruption of the pre-caldera lavas and continued at least until the eruption of the post-caldera lavas. Such prolonged heating event determined progressive melting of the least refractory mineral phases (mostly quartz and feldspars) and hampered zircon crystallization for ~50 ky before the caldera-forming eruption and ~80 ky before the effusion of the post-caldera lavas. Heating was likely due to an increase of the recharge flux in the magma reservoir which reduced the crystallinity of the crystal mush and promoted remobilization and eruption of the Singkut magma body.

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Section: Geological Settingmentioning

confidence: 99%

Remobilization and eruption of an upper crustal cumulate mush: the Singkut caldera (North Sumatra, Indonesia)

Forni

Oalmann

Fellin

et al. 2022

Preprint

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“…For very ancient volcanic episodes, erupted volumes may perhaps be best gauged from their exposed plutonic systems. This requires improved understanding of how and on what timescales batholiths develop (e.g., Szymanowski et al., 2023), so that we can better evaluate the tempo of volatile accumulation (and loss) in the upper reaches of magma reservoirs. In addition, computational approaches might consider not only the dynamics of ash plumes, but also the complex chemical and physical interactions of volcanogenic and atmospheric constituents, which remain poorly understood owing in part to the difficulty of in situ observations of the interiors of volcanic plumes.…”

Section: Introductionmentioning

confidence: 99%

On the Budget and Atmospheric Fate of Sulfur Emissions From Large Volcanic Eruptions

Scaillet,

Oppenheimer

2024

Geophysical Research Letters

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Today, volcanic sulfur emissions into the atmosphere are measured spectroscopically from the ground, air and space. For eruptions prior to the satellite era, two main sulfur proxies are used, the rock and ice core records, as illustrated by Peccia et al. (2023, https://doi.org/10.1029/2023gl103334). The first approach is based on calculations of the sulfur content of the magma, while the second uses traces of sulfur deposited in ice. Both approaches have their limitations. For glaciochemistry, the volcano responsible for a sulfur anomaly is often unknown and the atmospheric pathway by which the sulfur reached the ice uncertain. The petrologic method relies, too, on uncertain estimates of eruption size and a number of geochemical assumptions that are hard to verify. A deeper knowledge of processes occurring both within magma bodies prior to eruption, and within volcanic plumes in the atmosphere is needed to further our understanding of the impacts of volcanism on climate.

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Constraining magma storage conditions of the Toba magmatic system: a plagioclase and amphibole perspective

Lubbers,

Kent,

de Silva

2024

Contrib Mineral Petrol

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

Cited by 6 publications

References 63 publications

Remobilization and eruption of an upper crustal cumulate mush: the Singkut caldera (North Sumatra, Indonesia)

Remobilization and eruption of an upper crustal cumulate mush: the Singkut caldera (North Sumatra, Indonesia)

On the Budget and Atmospheric Fate of Sulfur Emissions From Large Volcanic Eruptions

Constraining magma storage conditions of the Toba magmatic system: a plagioclase and amphibole perspective

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