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Thermomechanical modelling of stress around dyke tips

John Browning , Jorge Cortez, Carlos Marquardt

  • Affiliations: Departament of Mining Engineering, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile. 

  • Presentation type: Poster

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

  • Poster Board Number: 79

  • Programme No: 1.2.24

  • Theme 1 > Session 2

Abstract

Magma propagates to the surface, eventually feeding volcanic eruptions, through pressure-driven fractures. However, not all dykes reach the surface; many of them become interrupted in their ascent. Whilst there has been focus on the importance of host rock mechanical properties on dyke arrest, temperature effects are often neglected. However, magma may locally disrupt temperature fields leading to thermal expansion or contraction and hence generate thermal stress and in some cases brittle thermal fractures. In this work, we use a thermomechanical approach to investigate potential thermal stress perturbations around dyke tips. The objective of the present study is to understand the role of thermoelastic parameters in signatures generated during dyke emplacement and cooling and consider how this may influence dyke growth dynamics. For this purpose, a two-dimensional nonlinear thermoelastic transient model was implemented using the finite element method. Results show that the most sensitive variables of the model are the modulus of elasticity and coefficient of thermal expansion, in equal magnitude. Furthermore, it was found that the thermal stresses produced in the direction of propagation of the dyke suppressed the tensile stress generated in purely elastic models, potentially changing the dominant fracture mechanics between a purely tensional crack opening to a hybrid displacement near the tip of the dyke as the surrounding rock was heated. This has implications for the amount and style of related seismicity. The fracture propagation mechanism may allow arrested dykes to continue their propagation once the thermal stresses have overcome the strength of the rock.