Resurgence initiation and subsolidus eruption of cold carapace of warm magma at Toba Caldera, Sumatra

Abstract

Supervolcanoes like Toba Caldera, Sumatra, produce the largest eruptions on Earth. However, the magmatic conditions and processes during the period of recovery after catastrophic supereruptions, known as resurgence, are poorly understood. Here we use Bayesian statistical analysis and inverse thermal history modelling of feldspar argon-argon and zircon uranium-thorium/helium ages to investigate resurgence after the 74-thousand-year-old Youngest Toba Tuff eruption. We identify a discordance of up to around 13.6 thousand years between older feldspar and younger zircon ages. Our modelling suggests cold storage of feldspar antecrysts prior to eruption for a maximum duration of around 5 and 13 thousand years at between 280 °C and 500 °C. We propose that the solidified carapace of remnant magma after the Youngest Toba Tuff eruption erupted in a subsolidus state, without being thermally remobilized or rejuvenated. Our study indicates that resurgent uplift and volcanism initiated approximately 5 thousand years after the climactic caldera forming supereruption.

An appraisal of the observed crystallinities of volcanic materials

“…This observation is consistent with other evidence that in some cases dome emplacement may occur in magmas that are near, or even subsolidus, and Marsh [1981] also suggested that emplacement of some domes might represent a different process to lavas. Evidence includes cataclastic deformation at the margins of dome walls, stick-slip extrusion patterns, and development of spines [Martel 2012;Pallister et al 2013], and geochemical indicators of near-or subsolidus magma storage prior to eruption [Mucek et al 2021]. Collectively, these observations and the high crystallinities recorded are consistent with different magma transport mechanisms for at least some lava dome eruptions [e.g.…”

“…Bachmann and Bergantz 2008;Cooper and Kent 2014;Klemetti and Clynne 2014] or even subsolidus [e.g. Mucek et al 2021;van Zalinge et al 2022]. Thus, the crystallinity at which magmatic mushes can be remobilized and/or erupted is also of importance, but also uncertain.…”

“…Extrusion of highly crystalline or even subsolidus material in lava domes has also been suggested [e.g. Pistone et al 2017;Mucek et al 2021]. There is notable effort currently going into gaining greater understanding of these processes via numerical and experimental studies [e.g.…”

The Qixiangzhan eruption, Changbaishan-Tianchi volcano, China/DPRK: new age constraints and their implications

“…Only two sets of 40 Ar/ 39 Ar SCIH experiments on sanidine have yielded concordant results with our ZDD experiments, that of Heizler et al 17 and our own. Discordance between ZDD and 40 Ar/ 39 Ar ages is being increasingly recognized as several recent works have shown that ZDD consistently provides younger and more robust ages than corresponding 40 Ar/ 39 Ar ages on sanidine from important Quaternary eruptions [22][23][24] . This discordance partly reflects the difference in closure temperatures of the two systems.…”

“…[31][32][33] ), and/or presence of antecrysts or xenocrysts that have not been fully degassed being commonly invoked (ref. 23,[34][35][36] ). In this respect the demonstrably older sanidine crystals in our 40 Ar/ 39 Ar experiments are particularly interesting and should be a target for future investigation, but will require deconvolving the possibility of excess 40 Ar in melt inclusions and xenocrysts or phenocrysts 37 .…”