Quantifying microstructural evolution in moving magma

Dobson, Katherine J. and Allabar, Anja and Bretagne, Eloise and Coumans, Jason and Cassidy, Mike and Cimarelli, Corrado and Coats, Rebecca and Connolley, Thomas and Courtois, Loic and Dingwell, Donald B. and Di Genova, Danilo and Fernando, Benjamin and Fife, Julie L. and Fyfe, Frey and Gehne, Stephan and Jones, Thomas and Kendrick, Jackie E. and Kinvig, Helen and Kolzenburg, Stephan and Lavallée, Yan and Liu, Emma and Llewellin, Edward W. and Madden-Nadeau, Amber and Madi, Kamel and Marone, Federica and Morgan, Ceryth and Oppenheimer, Julie and Ploszajski, Anna and Reid, Gavin and Schauroth, Jenny and Schlepütz, Christian M. and Sellick, Catriona and Vasseur, Jérémie and von Aulock, Felix W. and Wadsworth, Fabian B. and Wiesmaier, Sebastian and Wanelik, Kaz (2020) Quantifying microstructural evolution in moving magma. Frontiers in Earth Science, 8. 287. ISSN 2296-6463 (https://doi.org/10.3389/feart.2020.00287)

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Abstract

Many of the grand challenges in volcanic and magmatic research are focused on understanding the dynamics of highly heterogeneous systems and the critical conditions that enable magmas to move or eruptions to initiate. From the formation and development of magma reservoirs, through propagation and arrest of magma, to the conditions in the conduit, gas escape, eruption dynamics, and beyond into the environmental impacts of that eruption, we are trying to define how processes occur, their rates and timings, and their causes and consequences. However, we are usually unable to observe the processes directly. Here we give a short synopsis of the new capabilities and highlight the potential insights that in situ observation can provide. We present the XRheo and Pele furnace experimental apparatus and analytical toolkit for the in situ X-ray tomography-based quantification of magmatic microstructural evolution during rheological testing. We present the first 3D data showing the evolving textural heterogeneity within a shearing magma, highlighting the dynamic changes to microstructure that occur from the initiation of shear, and the variability of the microstructural response to that shear as deformation progresses. The particular shear experiments highlighted here focus on the effect of shear on bubble coalescence with a view to shedding light on both magma transport and fragmentation processes. The XRheo system is intended to help us understand the microstructural controls on the complex and non-Newtonian evolution of magma rheology, and is therefore used to elucidate the many mobilization, transport, and eruption phenomena controlled by the rheological evolution of a multi-phase magmatic flows. The detailed, in situ characterization of sample textures presented here therefore represents the opening of a new field for the accurate parameterization of dynamic microstructural control on rheological behavior.

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