Felsic melt and gas mobilisation during magma solidification: An experimental study at 1.1 kbar
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Abstract
Melt and gas transfer processes are essential to the formation and growth of the Earth’s crust and for sustaining volcanic activity. These processes also play a major role in magma fractionation at shallow depths (<10 km) where magmas stall rheologically and solidify. In this scenario, the conditions of melt and gas mobilization during progressive cooling of crystal mushes down to their solidus remain poorly understood. We present experimental data (at 1.1 kbar) showing how a combination of temperature and crystal content control the ability of melt and gas to escape from cooling and solidifying hydrous silicic magmas with initial crystal volume fractions (Φ) of 0.6, 0.7, and 0.8, and for temperature snapshots of 850, 800, and 750°. Microstructural observations and chemical data show that the amount of extracted melt increases by 70% from 850 to 750° and by 40% from Φ = 0.6 to 0.8 at 750°, due to the formation of interconnected crystal frameworks, gas expansion in constricted pore space, and filter pressing during cooling. As a result, our experiments suggest that melt and gas extraction from cooling mushes increases in proximity to their solidus and can operate efficiently at 0.6 < Φ <0.93. These observations shed light on maximum estimates of the segregation of gas-rich, crystal-poor magmas (0.02 m/year at 850° to 9 m/year at 750°) to form felsic dykes or eruptible systems feeding volcanoes.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Felsic melt and gas mobilisation during magma solidification: An experimental study at 1.1 kbar |
| Series title | Frontiers in Earth Science |
| DOI | 10.3389/feart.2020.00175 |
| Volume | 8 |
| Year Published | 2020 |
| Language | English |
| Publisher | Frontiers Media |
| Contributing office(s) | Volcano Science Center |
| Description | 175, 18 p. |
| Google Analytic Metrics | Metrics page |