Quantifying dendritic crystallization in hydrous basaltic magmas through 4D experiments with in situ view: implications for magma mobility within the Earth’s crust
- 1University of Camerino, School of Science and Technology - Geology Division, Camerino, Italy
- 2Department of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK
- 3Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo, Sezione di Catania, Catania, Italy
- 4Department of Mechanical Engineering, University College London, London, UK
- 5Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
- 6School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
- 7Centre of Geosciences, National Autonomous University of Mexico, Queretaro 76230, Mexico
- 8Institute of Environmental Geology and Geoengineering, National Research Council of Italy, Rome, Italy
- 9Department of Earth Science, University of Torino, 10125 Torino, Italy
- 10Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
The mobility and the rheological behaviour of magma within the Earth’s crust is controlled by magma viscosity. Crystallization and crystal morphology strongly affect viscosity, and thus mobility and eruptibility of magma, by locking it at depth or enabling its ascent towards the surface. However, the relationships between crystallinity, rheology and eruptibility remain uncertain because it is difficult to observe dynamic magma crystallization in real time.
Here we show the results of in situ 3D time-dependent, high temperature, moderate pressure experiments performed under water-saturated conditions to investigate crystallization kinetics in a basaltic magma. 4D crystallization experiments with in situ view were performed using synchrotron X-ray microtomography, which provides unique quantitative information on the growth kinetics and textural evolution of pyroxene crystallization in basaltic magmas. Crystallization kinetics obtained with 4D experiments were combined with a numerical model to investigate the impact of rapid dendritic crystallization on basaltic dike propagation, and demonstrate its dramatic effect on magma mobility and eruptibility.
We observe dendritic growth of pyroxene on initially euhedral cores, and a sur- prisingly rapid increase in crystal fraction and aspect ratio at undercooling ≥30 °C. Rapid dendritic crystallization favours a rheological transition from Newtonian to non-Newtonian behaviour within minutes. Modelling results show that dendritic crystallization at moderate undercooling (30-50 °C) can strongly affect magma rheology during magma ascent within a dike with important implications for the mobility of basaltic magmas within the crust. Our results provide insights into the processes that control whether magma ascent within the crust leads to eruption or not.
How to cite: Arzilli, F., Polacci, M., La Spina, G., Le Gall, N., Llewellin, E. W., Brooker, R. A., Torres-Orozco, R., Di Genova, D., Neave, D. A., Hartley, M. E., Mader, H. M., Giordano, D., Atwood, R., Lee, P. D., and Burton, M. R.: Quantifying dendritic crystallization in hydrous basaltic magmas through 4D experiments with in situ view: implications for magma mobility within the Earth’s crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2569, https://doi.org/10.5194/egusphere-egu24-2569, 2024.
