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Rapid assembly of a super-sized magma body over a millennial timescale

Xuanyu Chen , Yigang Xu, Xiaolong Huang

  • Affiliations: State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 261

  • Programme No: 1.3.10

  • Theme 1 > Session 3

Abstract

The accumulation and pre-eruptive storage of large silicic magma bodies in the upper crust are pivotal not only for understanding igneous petrology and volcanology but also for volcanic hazard mitigation. Yet, the elusive nature of timescales associated with these magmatic processes continues to challenge researchers. Currently, zircon dating and diffusion geochronometry offer conflicting estimates: zircon dating implies prolonged upper crustal magma residence times (104-106 years), while diffusion geochronometry consistently points to much shorter timescales (101-103 years). Both methods rely on mineral grains from silicic plutonic and volcanic rocks, which may record intricate thermal histories that complicate the direct dating of magma accumulation. Here, we introduce a novel approach that synergizes volcanic glass geochemistry, eruption magnitude, and tephrochronology to elucidate the processes of magma accumulation leading to a catastrophic caldera-forming eruption. By meticulously integrating proximal and distal tephra records, we show that a super-sized magma body (100s of km3) can form within a millennial timescale. Moreover, employing the cryptotephra extraction technique, we uncover previously overlooked ash records that signify rapid remobilization events of the shallow magma reservoir following caldera collapse. These findings support the concept that large melt-dominant bodies within the upper crust are short-lived structures, which are rapidly assembled from deep source reservoirs and erupt on short timescales.