Dendritic crystallization in hydrous basaltic magmas controls magma mobility within the Earth’s crust

• Published in: Nature communications Vol. 13; no. 1; p. 3354
• Main Authors: Arzilli, Fabio, Polacci, Margherita, La Spina, Giuseppe, Le Gall, Nolwenn, Llewellin, Edward W., Brooker, Richard A., Torres-Orozco, Rafael, Di Genova, Danilo, Neave, David A., Hartley, Margaret E., Mader, Heidy M., Giordano, Daniele, Atwood, Robert, Lee, Peter D., Heidelbach, Florian, Burton, Mike R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10-06-2022; Nature Publishing Group; Nature Portfolio
• Subjects: 147/135; 704/2151/431; 704/2151/598; Aspect ratio; Crystal growth; Crystallization; Dendritic structure; Earth crust; Evolution; Growth kinetics; High temperature; High temperature effects; Humanities and Social Sciences; Magma; Mathematical models; Mobility; multidisciplinary; Numerical models; Pyroxenes; Rheological properties; Rheology; Science; Science (multidisciplinary); Supercooling
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-30890-8

The majority of basaltic magmas stall in the Earth’s crust as a result of the rheological evolution caused by crystallization during transport. However, the relationships between crystallinity, rheology and eruptibility remain uncertain because it is difficult to observe dynamic magma crystallization in real time. Here, we present in-situ 4D data for crystal growth kinetics and the textural evolution of pyroxene during crystallization of trachybasaltic magmas in high-temperature experiments under water-saturated conditions at crustal pressures. We observe dendritic growth of pyroxene on initially euhedral cores, and a surprisingly 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. We use a numerical model to quantify the impact of rapid dendritic crystallization on basaltic dike propagation, and demonstrate its dramatic effect on magma mobility and eruptibility. Our results provide insights into the processes that control whether intrusions lead to eruption or not.
In situ 4D experiments at high temperature and moderate pressure reveal that rapid dendritic crystallization in hydrous basaltic magmas promotes a rheological transition within minutes, controlling magma mobility within the Earth’s crust.