Dike Channelization and Solidification: Time Scale Controls on the Geometry and Placement of Magma Migration Pathways

Abstract

We investigate the conditions under which magma prefers to migrate through the crust via a dike or a conduit geometry. We performed a series of analogue experiments, repeatedly injecting warm, liquid gelatin, into a cold, solid gelatin medium and allowing the structure to evolve with time. We varied the liquid flux and the time interval between discrete injections of gelatin. The time interval controls the geometry of the migration, in that long intervals allow the intrusions to solidify, favoring the propagation of new dikes. Short time intervals allow the magma to channelize into a conduit. These times are characterized by the Fourier number (Fo), a ratio of time and thermal diffusion to dike thickness, so that long times scales have Fo > 102 and short time scales have Fo < 100. Between these time scales, a transitional behavior exists, in which new dikes nest inside of previous dikes. The flux controls the distance a dike can propagate before solidifying, in that high fluxes favor continual propagation, whereas low fluxes favor dike arrest due to solidification. For vertically propagating dikes, this indicates whether or not a dike can erupt. A transitional behavior exist, in which dikes may erupt at the surface in an unstable, on‐and‐off fashion. We supplemented the experimental findings with a 2‐D numerical model of thermal conduction to characterize the temperature gradient in the crust as a function of intrusion recurrence frequency. For very infrequent intrusions (Fo > 104 to 105) all thermal energy is lost, while more frequent intrusions allow heat to build up nearby.

The building blocks of igneous sheet intrusions: Insights from 3-D seismic reflection data

“…11C-11D) (Magee et al, 2013c). Identifying this channelized magma flow in sheet intrusions has important implications for: (1) better understanding of the architecture of sill complexes and how they are built (e.g., Thomson and Hutton, 2004;Cartwright and Hansen, 2006;Hansen and Cartwright, 2006a;Guo et al, 2013;Magee et al, 2016a;Schofield et al, 2017); (2) assessing areas of potential fissure eruptions emanating from areas with localized magma flow (e.g., Pansino et al, 2019); and (3) exploration for Ni-Cu-PGE deposits, since sulfide liquids are commonly accumulated in elongate parts of intrusions, which may trap sulfide liquids (e.g., Barnes et al, 2016).…”

New Insight Into a Volcanic System: Analogue Investigation of Bubble‐Driven Deformation in an Elastic Conduit

“…Indeed, gelatin shows a variable behavior depending on its state (elastic to viscoelastic rheology in the solid one and viscous rheology in the nonsolid one), composition, concentration, temperature, ageing, and the applied strain rate (Barrangou et al, ; Bot et al, , ; Kavanagh et al, ; Kavanagh & Ross‐Murphy, ; Norziah et al, ). Gelatin is often used as rock analogue to study shallow crustal processes, especially propagation of dykes (Heimpel & Olson, ; Muller et al, ; Pansino et al, ; Pansino & Taisne, ; Rivalta et al, ; Takada, ) as it can scale to the Earth's crust. It has also been used to simulate the volcanic edifice (Acocella & Tibaldi, ; Walter & Troll, ).…”

Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone

“…Higher in the conduit, the temperature gradient between the inside of the dyke and the dyke walls eventually decreases due to heat loss from the dyke to the country rock, which in turn results in a decrease of the melt temperature via conduction (Pansino et al 2019). Such temperature change results in a slower, moderate cooling rate, potentially creating favourable conditions for phase exsolution observed as Ca-rich lamellas in Ca-poor pyroxenes (Fig.…”