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Modelling displacement and fracturing dynamics around magma intrusions: laccoliths on the Moon, Mars, and in the Polish Sudetes

Sam Poppe ^1^, Alexandra Morand2, Claire E. Harnett3, Anne Cornillon4, Marek Awdankiewicz5, Michael Heap6,7, Daniel Mège1

  • Affiliations: ^ 1^Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN), Warsaw, Poland; 2School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom; 3UCD School of Earth Sciences, UCD University College Dublin, Dublin 4, Ireland; 4Université Paris-Saclay, CNRS, GEOPS, Orsay, France; 5Institute of Geological Sciences, Wrocław University, Wrocław, Poland; 6Institut Terre et Environnement de Strasbourg, Université de Strasbourg, CNRS, Strasbourg, France; 7Institut Universitaire de France (IUF), Paris, France 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 247

  • Programme No: 1.4.9

  • Theme 1 > Session 4

Abstract

Intrusive domes on the Moon and Mars indicate that laccoliths have deformed and fractured the shallowest 1-2 km of crustal rocks and the surface, similar to those on Earth. However, numerical models only broadly approximate crustal mechanical properties and do not explicitly simulate fracturing. The effect of heterogeneous crustal strength, intrusion depth, and specific gravity forces on laccolith emplacement dynamics remains thus unclear. We have simulated laccolith inflation in a particle-based assemblage with a two-dimensional (2D) Discrete Element Method (DEM). The DEM allows us to investigate magma-induced displacements, high strain concentrations, and dynamic fracturing. We have systematically varied host rock strength and gravitational acceleration. We also applied our model to Permian trachyandesite intrusions in the Polish Intra-Sudetic Synclinorium. There, we sampled intact sedimentary host rocks and measured their mechanical properties in laboratory experiments. We upscaled the intact sample properties to the bulk rock properties in our 2D DEM model by using either the Geological Strength Index or a randomly cracked model. Our results displayed a spectrum of displacement, strain, and fracture patterns between a highly fractured and a poorly fractured end-member. Also, the same amount of laccolith inflation induced more vertical surface displacement at the lower lunar gravity in stiffer rocks. Rock strength controlled the amount of fracturing more than gravitational acceleration. Pre-existing cracks concentrated shear strain and syn-intrusive fracturing in narrower zones. Crustal heterogeneities and gravitational acceleration thus affect the relationship between surface deformation features and laccoliths and are essential factors when modelling laccolith inflation.