Static Compression of CO2-bearing Silicate Liquids

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This research focuses on the problem of how carbon dioxide physically interacts with magma when dissolved under very high pressures in the Earth's deep interior. The main physical property that will be measured is the density of compressed magma with varying amounts of carbon dioxide under a wide range of pressure and temperatures. The ultimate goal is to determine the degree to which carbon dioxide alters the magma density, thus revealing how readily CO2-bearing magmas will become buoyant relative to surrounding rock. The experiments will greatly improve our ability to predict the conditions under which magmas rise to the Earth's surface and erupt as lavas or form volcanoes that emit carbon dioxide and other gases into Earth's atmosphere. The experimental data will also provide new insight into the way in which gases such as carbon dioxide were sequestered deep in the rocky part of our planet and how much was degassed from the early Earth during its formation stage. This effort employs experimental techniques that span the entire range of pressure and temperature conditions that exist for melting and magma production in the Earth's upper mantle.The experiments in this project will allow the determination of the partial molar volume of CO2 in silicate melts as a function of pressure and melt composition using the sink/float method in piston-cylinder and multi-anvil devices up to 20 GPa. The experiments will reveal any non-ideality in the pressure effect on silicate melt as a function of alkali metal (K, Na) and alkaline earth metal (Ca) cation concentration. The experiments will also be designed to provide information about effects of different synthesis environments on CO2 partial molar volume in silicate melt and CO2 solubility. It is proposed to refine quantitative analysis techniques to verify and characterize CO2-total in the experimental run products using Fourier Transform Infrared Spectroscopy (FTIR), Secondary Ion Mass Spectrometry (SIMS), and the Electron Microprobe (EMP). In preparation for this project, the team carried out a pilot study on carbonated peridotite partial melt to demonstrate that these experimental techniques will have a high likelihood of success. The results from this project will help establish an experimental foundation and new database for predictive models used for calculating the density of any given carbonated silicate melt composition that could be produced by melting in planetary mantles. The new density data at high pressure will also be used to evaluate the predictive power of equations of state, such as the Birch-Murnaghan and Vinet equations, in calculating densities of volatile bearing silicate liquids at high pressure and temperatures.