Organization of volcanic plumbing through magmatic lensing by magma chambers and volcanic loads

Abstract

[1] The development of discrete volcanic centers reflects a focusing of magma ascending from the source region to the surface. We suggest that this organization occurs via mechanical interactions between magma chambers, volcanic edifices, and dikes and that the stresses generated by these features may localize crustal magma transport before the first eruption occurs. We develop a model for the focusing or ''lensing'' of rising dikes by magma chambers beneath a free surface, and we show that chambers strongly modulate dike focusing by volcanic edifices. We find that the combined mechanical effects of chambers, edifice loading, and dike propagation are strongly coupled. Chambers deeper than $20 km below the surface with magmatic overpressure in the range of 20-100 MPa should dominate dike focusing, while more shallow systems are affected by both edifice and chamber focusing.

Time-dependent deformation of Uturuncu volcano, Bolivia, constrained by GPS and InSAR measurements and implications for source models

“…Reservoir inflation via sustained pipe flow through the crust has been shown to reproduce surface uplift at other volcanic zones, such as Laguna del Maule (Le Mevel et al, 2016). Alternatively, quasi-steady intrusion of dikes toward a long-lived reservoir at the level of the APMB could explain observations (e.g., Karlstrom et al, 2009). Assuming fluctuations of surface displacement are due to transient mass addition, we require that transport must be occurring at rates on the order of tens of kilometers per year, either as quasi-steady flow or semi-regular dike intrusions focused into a reservoir zone over multiple decades.…”

The effect of pressurized magma chamber growth on melt migration and pre-caldera vent locations through time at Mount Mazama, Crater Lake, Oregon

“…The free surface is ultimately responsible for generating stress concentrations that produce ring fractures and caldera collapse (Gudmundsson, 1998;Marti et al, 2008). As the chamber grows larger laterally, the free surface begins to project a larger capture zone at depth as the load better approximates a surface load (Karlstrom et al, 2009). Because estimates based on dissolved H 2 O in melt inclusions place the top of the Mazama chamber at ∼5 km with a thickness of perhaps several kilometers Mandeville et al, 2009), we can expect that free surface stress effects are non-negligible.…”

“…The spatial extent and influence of viscoelastic host rocks depends on the enthalpy influx and thermal state of host rocks. Karlstrom et al (2010) show that a stability criterion is the ratio of a chamber pressurization timescale τ E ≈ P V Ch /E Q and relaxation timescale τ VE ≈ μ Ch /E (defining a Deborah number De = τ VE /τ E ). Here V Ch is the chamber volume, Q the magma influx rate, E is Young's modulus of host rocks, and μ Ch the viscosity of the shell.…”

“…Therefore we focus efforts on the "internal" class of models described above, using known locations and timing of eruptive episodes over 55 ky along with petrologically based estimates of melt influx to constrain models for silicic chamber growth and dike capture. Although the idea that mafic magma may be trapped or stalled by a shallow, less dense magma reservoir is not new (e.g., Walker, 1974;Smith and Shaw, 1975;Hildreth, 1981;de Silva, 1989), here we hypothesize that overpressure within the growing climactic chamber generates a deviatoric stress field that reorients more distant rising dikes (Karlstrom et al, 2009(Karlstrom et al, , 2010 to control the rate of chamber growth and surface eruption locations.…”

Assimilation of Deformation Data for Eruption Forecasting: Potentiality Assessment Based on Synthetic Cases

“…The use of more realistic physics-based models that could better interpret field observations such as those that could account for magma rheology and compressibility (e.g., Rivalta and Segall, 2008;Segall, 2011, 2013;Segall, 2016;Got et al, 2017) are then highly encouraged. Data assimilation can also be extended to models representing other plumbing mechanism such as magma reservoirs recharged by dikes at depth (e.g., Karlstrom et al, 2009) or even those eruptions that are related to dike intrusions.…”