Chronologies of Magma Chamber Assembly and Eruption for Supervolcanoes: Long Valley and the Taupo Volcanic Zone

Wednesday, 10 January 2018: 11:15
Salon Quinamavida (Hotel Quinamavida)
Katy Chamberlain1,2, Dan J Morgan3, Colin J N Wilson2, George Frederick Cooper2,4, Simon J Barker2,5 and Aidan Allan2, (1)NERC Natural Environment Research Council, Swindon, United Kingdom, (2)Victoria University of Wellington, Wellington, New Zealand, (3)University of Leeds, Leeds, United Kingdom, (4)University of Durham, Department of Earth Sciences, Durham, United Kingdom, (5)University of Auckland, Auckland, New Zealand
Abstract:
Understanding the timescales associated with magmatic processes, and the cascade of events that eventually leads to eruption, are important questions for all volcanoes. However for supervolcanoes, where hundreds to thousands of km3 of melt-dominant magma are accumulated in the crust prior to eruption, understanding the longevity of these bodies (including the thermal conditions required for this storage) and the potential triggering mechanisms are of particular importance.

Diffusion modelling of elemental gradients across compositional zones within crystals is now a well-established technique used to investigate timescales of magmatic processes prior to eruption. In the past, however, generally only a single crystal phase has been used for interpretation. By utilising well-constrained diffusion models in multiple crystal phases, in conjunction with detailed field observations and petrological understanding, the application of diffusion chronometry can yield important insights into the timescales of magmatic processes. In contrast to diffusion modelling, where timescales are all relative to eruptive quenching, the absolute timescales from U-Th disequilibrium or U-Pb dating of zircons yield insights into longer-term processes of magma accumulation and storage. By comparing timescales from multiple methods of chronometry and integrating these with textural context, the sequence and timing of events leading to eruption can be identified and ordered, with implications for magmatic accumulation, storage and eventual eruption.

Here, I summarise results of diffusion modelling in multiple phases and zircon age data from the: ~0.76 Ma Bishop Tuff (Long Valley), the paired 1.0 Ma Kidnappers and Rocky Hill eruption deposits (Taupo Volcanic Zone), and the 25.4 ka Oruanui and 8 subsequent and smaller post-Oruanui deposits (Taupo Volcanic Zone). These results from multiple (super)eruptions highlights the temporal resolution achievable when using diffusion geospeedometry in multiple crystal phases, coupled to detailed petrography and field constraints. Overall, in all cases our results highlight the rapid timescales associated with magma accumulation in the final melt-dominant magma chamber.

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