Magmatic karst reveals dynamics of crystallization and differentiation in basaltic magma chambers

Role of syn-eruptive plagioclase disequilibrium crystallization in basaltic magma ascent dynamics

Timescales of magma ascent in conduit models are typically assumed to be much longer than crystallization and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallization and exsolution processes are fundamen...

Processes of Magma Evolution and Magmatic Suites

Dynamics of differentiation in magma reservoirs

In large magma chambers, gradients of temperature and composition develop due to cooling and to fractional crystallization. Unstable density differences lead to differential motions between melt and crystals, and a major goal is to explain how this might result in chemical differentiation of magma. Arriving at a full description of the physics of Crystallizing magma chambers is a challenge beca...

The Boycott effect in magma chambers

[1] We investigate the plausibility of the stratified Boycott effect as a source of layering in magma chambers. Crystal settling within the magma chamber will generate buoyant fluid near the sloping sidewalls whose vertical ascent may be limited by the ambient stratification associated with vertical gradients in SiO2. The resulting flow may be marked by a layered structure, each layer taking th...

Crystal sizes in evolving silicic magma chambers

Crystal size distributions (CSDs) of quartz and zircon phenocrysts in individual pumice clasts from several voluminous ash-flow tuffs provide a quenched snapshot view of conditions in preclimactic magma chambers. A common feature of these CSDs is a concavedown, lognormal shape, in contrast to the reported linear CSDs in more mafic systems. This feature is interpreted to be a general result of s...