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Fault reactivation in extensional regime controlling magma pathways: insights from analogue modelling

Elisabetta Panza1, Joël Ruch 1, Nicolas Oestreicher1, 2, 3, Xingjun Luo1, 4

  • Affiliations:  1Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, CH-1205 Genève; 2 WSL Institute for Snow and Avalanche Research SLF, 7260 Davos, Switzerland; 3 Climate Change, Extremes and Natural Hazards in Alpine Regions Research Centre CERC, 7260 Davos, Switzerland; 4 School of Geosciences and Info-Physics, Central South University, 410083 Changsha, China

  • Presentation type: Talk

  • Presentation time: Monday 16:15 - 16:30, Room S160

  • Programme No: 3.16.3

  • Theme 3 > Session 16

Abstract

Dike intrusions during rifting events frequently reactivate pre-existing tectonic structures, as observed in Afar (Ethiopia) and Iceland. While surface observations and geophysical methods provide insights into these processes, direct observations of rupture dynamics in the upper crust remain understudied. We conducted analogue experiments to model magma injection and its interaction with tectonic structures in an extensional regime. We simulated extension-induced fracturing and subsequent magma injection under controlled conditions, varying the extension amount and injection rate, using granular materials to represent the brittle upper crust. Our results show that dike morphologies form only when the host rock is under extensional strain, with magma propagation guided by pre-existing fractures. Surface deformations, including graben deepening and uplift, are consistent with natural examples and predominantly accommodated by reactivated faults rather than new fracture formations. Significant strike-slip components (conjugate fault systems) observed at the model surface, near dike tips, show that magma propagation can locally overprint the tectonic signature. These findings highlight the central role played by magma in upper crustal deformation during rifting events, underscoring the interaction between tectonic extension and magma-driven processes. The results have implications for hazard assessment, highlighting the importance of mapping pre-existing structures and their reactivation potential in magmatically active regions.