Calculation of dike trajectories from volcanic centers

Abstract

[1] Patterns of dike swarms around volcanic centers or above mantle plumes are interpreted by a mechanical analysis of regional and dike-induced stresses, in which dike emplacement is controlled and guided by the stress state. Comparisons of dike patterns with patterns of principal-stress trajectories caused by a source and a regional stress system are commonly used to infer paleostresses. However, dike trajectories are determined by a complex interaction between dike-induced stresses and the source/ regional stress system. We present numerical calculations based on a novel boundary-integral formulation, which examines the simultaneous effects of regional stresses, magma pressure, and dike injection on the local stress state around a continuously curving dike. Dike paths are calculated from the condition that dikes propagate by mode I failure. Our results suggest that the magnitude of the regional stresses would be 2 -5 times higher than previous estimates based on principal-stress trajectory analysis.

Structure of volcano plumbing systems: A review of multi-parametric effects

“…The remote stresses caused the reorientation of the distal parts of dykes that reach a strike parallel to  Hmax . A similar pattern has also been obtained by Meriaux and Lister (2002) by calculation of the trajectories of dyke paths following mode I opening of fractures. When dykes intercept the volcano slopes, they produce radial fissure eruptions and fractures in the central uppermost part of the edifice, and parallel fractures, eruptive…”

“…They found also that, everything else being equal, a decreasing magma supply rate or a decreasing magma viscosity generate eruptive centers at increasing distances from the focal area. Gaffney and Damjanac (2006) found a similar tendency of magma flow to be diverted away from a highland zone ( propagate with less curvature than those with a viscous pressure drop (Meriaux and Lister, 2002).…”

Closure of circular arc cracks under general loading: effects on stress intensity factors

“…These relations have been used to solve various geologic fracture problems with a DDM (e.g., Thomas and Pollard 1993;Tuckwell et al 2003;Olson 2007). Mériaux and Lister (2002) modified the empirical constant from 0.806 to 0.798, resulting in the following SIFs:…”

Using numerical modeling to explore the origin of intrusion patterns on Fernandina volcano, Galapagos Islands, Ecuador

“…At Fernandina, when aspect ratio conditions are right to initiate a radial dike away from the reservoir crest ( Figure 3a and Table 1), the dike can first approach the surface a kilometer or so from the caldera margin, in agreement with observations of radial fissures. The host rock stress state needed for dikes to remain radial does not extend all the way to the surface; however, near-surface differential stress is low, and dikes propagating into the near-surface region are less likely to realign sharply across short distances than when differential stress is high [e.g., Meriaux and Lister, 2002]. Other factors to which lateral propagation of a dike is sensitive, including surface slope and magma supply variations, can also help sustain the existing radial geometry and, by altering stress conditions at the leading and upper edges of a radial dike, help drive dynamic dike height variations to trigger local flank eruptions [Parfitt and Head, 1993;Fialko and Rubin, 1999].…”