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Metal-silicate Partitioning at High Pressure and Temperature: Experimental Methods and a Protocol to Suppress Highly Siderophile Element Inclusions
Published on: June 13, 2015
Structure and speciation in hydrous silica melts. 2. Pressure effects
Kelly E Anderson1, Lorna C Grauvilardell, Marc M Hirschmann
1Department of Chemistry University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431, USA.
The Journal of Physical Chemistry. B
|September 25, 2008
Summary
High pressure significantly alters liquid silica structure and water speciation. Molecular water content decreases with increasing pressure and temperature in hydrated silica melts.
Area of Science:
- Geochemistry
- Materials Science
- Computational Chemistry
Background:
- Understanding the behavior of water in geological melts is crucial for interpreting Earth's interior processes.
- Previous simulations using the Feuston-Garofalini (FG) potential have provided insights into liquid silica but require further exploration under varying pressures and temperatures.
Purpose of the Study:
- To investigate the impact of pressure on the structure and water speciation in hydrated liquid silica.
- To determine the stability of the melt phase and observe structural transformations under extreme conditions.
Main Methods:
- Isobaric-isothermal Monte Carlo simulations were employed.
- The Feuston-Garofalini (FG) potential was utilized to model hydrated liquid silica.
- Simulations covered a range of pressures (0.25–10 GPa), temperatures (2000–9000 K), and water compositions (0.0–0.4).
Main Results:
- A stable melt phase was observed at pressures >= 1.0 GPa and/or low water content (x_w <= 0.1).
- The characteristic volume minimum persisted up to 2.5 GPa, indicating gradual structural changes, but disappeared at 10 GPa, signifying more significant alterations.
- Molecular water species constituted a small fraction (approx. 2%) even at high water concentrations, decreasing with increased pressure and temperature.
Conclusions:
- Pressure plays a critical role in modifying the structure of hydrated liquid silica.
- The stability and speciation of water in silica melts are highly sensitive to pressure and temperature conditions.
- Computational simulations provide valuable data for understanding deep Earth processes involving hydrous silicate melts.
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