Project Magma Degassing – Experimental investigation of homogeneous (H2O, CO2) bubble nucleation and growth in silicate…

Basic data

Acronym:
Magma Degassing
Title:
Experimental investigation of homogeneous (H2O, CO2) bubble nucleation and growth in silicate melts during decompression
Duration:
01/05/2017 to 30/04/2020
Abstract / short description:
Volcanic activity is mainly driven by complex dynamic degassing processes during ascent of H2O and CO2 bearing magma that is often related to violent eruptions. The fundamental physicochemical parameters controlling nucleation and growth of fluid bubbles in a homogeneous melt are the initial concentration of dissolved volatiles, the supersaturation pressure (difference between vapor pressure in the melt and far field pressure), the fluid melt interfacial tension (surface tension), diffusivity of volatiles, and melt viscosity. Volatile exsolution results in a complex interaction between nucleation, diffusional growth, expansion, Ostwald ripening, coalescence and segregation of fluid bubbles accompanied by decreasing density and viscosity of the magma. Reliable nucleation and growth data of (H2O, CO2) fluid bubbles are essential to improve fluid bubble nucleation and growth models for silicate melts and to understand dynamic degassing processes prior to volcanic eruptions. The aim of this project is the systematic investigation of nucleation and growth of H2O and mixed (H2O, CO2) bubbles during continuous decompression in the simplified system SiO2-Al2O3-Na2O-H2O-CO2. Experiments start from 200 MPa at 850 °C in a cold seal pressure vessel and at 1050 °C in an internally heated argon pressure vessel, both equipped with piezo actuator controlled decompression valves and with rapid quench devices. The simplified SiO2-Al2O3-Na2O compositional system is perfectly suitable for this project because (H2O, CO2) -solubility, -diffusivity, and -viscosity data are available within a wide pressure and temperature range. Considering the experimental limitations, the expected fundamental results of this project will help to improve future experimental studies of bubble nucleation and melt degassing of natural melt compositions to a point where the decompression experiments are solely controlled by the decompression rate as single variable under otherwise identical conditions. Together with computational modeling the experimental results will contribute substantially to a deeper understanding of magma degassing triggering volcanic eruptions.
Keywords:
silicate melts
decompression
bubble nucleation

Involved staff

Managers

Mineralogy and Geodynamics Research Area
Department of Geoscience, Faculty of Science

Contact persons

Faculty of Science
University of Tübingen
Mineralogy and Geodynamics Research Area
Department of Geoscience, Faculty of Science

Local organizational units

Department of Geoscience
Faculty of Science
University of Tübingen

Funders

Bonn, Nordrhein-Westfalen, Germany
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