Stepwise accumulation and ascent of magmas

Abstract

One of the currently popular theories on magma ascent is that it mainly occurs by propagating hydrofractures (dykes) and that magma viscosity is the primary rate‐controlling factor. This theory is based on mathematical models for single hydrofractures under idealised conditions. We simulated magma ascent with air ascending through gelatine and observed that the air ascended in batches, following paths made by their predecessors. Multiple batches accumulate at obstacles along the path. Although magma viscosity may control ascent rate during movement, obstacles ultimately control the size and average ascent velocity of ascending batches. We propose that step‐wise movement of magma batches is the mechanism of primary accumulation and ascent from the partially molten source rock of a magma to its first emplacement site and therefore the main ascent mechanism for granitic magmas. ‘Classical’ dyking is the mechanism for secondary ascent from a magma chamber.

Laboratory Modelling of Volcano Plumbing Systems: A Review

“…f Surface view photograph of model using conceptual magma chamber (Troll et al 2002). The inflation/deflation of a balloon represents the replenishment and draining of a magma chamber, and the deformation induced in the overburden is observed at the surface of the models b Laboratory Modelling of Volcano Plumbing Systems … Takada (1990), Bons et al (2001), Menand and Tait (2001), Muller et al (2001), Ito and Martel (2002), Rivalta et al (2005), Rivalta and Dahm (2006), Le Corvec et al (2013) Hexane Interactions between two ascending dykes Ito and Martel (2002) Water Propagation or ascent of intermediate viscosity dykes and sills (internal pressure driven) Fiske and Jackson (1972), McGuire and Pullen (1989), Takada (1990), McLeod and Tait (1999), Menand andTait (2001, 2002), Walter and Troll (2003), Kavanagh et al (2006), Menand (2008); Kervyn et al (2009), Tibaldi et al (2014, Daniels and Menand (2015) Water-gelatin solution Water-Glycerin Dyke propagation and nucleation, and composite dyke emplacement Koyaguchi and Takada (1994), McLeod and Tait (1999), Takada (1999) Molten wax Cooling effects on dyke propagation Vegetable oil Cooling effects on dyke and sill emplacement Chanceaux and Menand (2014) Silicone oils Dyke propagation and nucleation Takada (1990Takada ( , 1994b, McLeod and Tait 1999), Watanabe et al…”

Particle simulation of spontaneous crack generation associated with the laccolithic type of magma intrusion processes

“…This can be justified by the fact that according to the heat conduction theory, the thickness of a thermal boundary layer around the intruded magma is much smaller than the diameter of the solid particle [1,[21][22][23][24][25][26]. For example, for a given thermal diffusion coefficient, = /c p s , where is the thermal conductivity of the solid particle, c p and s are the specific heat and density of the solid particle, the thickness of the thermal boundary layer can be estimated by using = √ t, where t is the contact time between the fluid and solid particles.…”

Numerical modelling of chemical effects of magma solidification problems in porous rocks

“…The key problem associated with the numerical modelling of chemical effects of intruded magma solidification processes is that the characteristic dimension of the whole geological system under consideration is on the scale of tens and hundreds of kilometres, but the characteristic dimension of the intruded magma, such as sills and dikes [16][17][18][19][20][21] is on the scale of metres and tens of metres. Due to the particular feature of ore body formation and mineralization in geological systems, the detailed solidification process of the intruded magma might not be important, but the chemical effect caused by the release of volatile fluids during the solidification of the intruded magma is important, at least, from the ore body formation and mineralization point of view.…”