1:45 PM - 3:15 PM
[SMP27-P05] Effect of CO2 on the structure of sodium silicate melt at high pressure
Keywords:sodium silicate melt, carbon dioxide , structure, high pressure
CO2, along with H2O and other volatile components, is known to cause the melting point of mantle component rocks to decrease, and CO2-rich magmas, such as kimberlites and carbonates, to form in the Earth's interior. Because of the importance of CO2 in silicate melts, many experimental studies have been conducted, including investigations of solubility and morphology, and CO2 is known to alter the physical properties of silicate melts, such as density and viscosity, suggesting that CO2 can alter the structure of silicate melts.
In this study, we aim to understand the function of CO2 by elucidating the structure of CO2 containing silicate melts at pressures up to 5.6 GPa using energy dispersive X-ray diffraction techniques in order to understand essentially the effect of CO2 composition on magma structure. Na2SiO5 and Na2SiO5+0.5 wt.% and Na2SiO5+1.0 wt.% CO2 were used as starting samples.
X-ray diffraction experiments were performed at NE5C of the PF-AR in the High Energy Accelerator Research Organization (KEK), and a two-stage pressurization method was adopted for the high-pressure generator using both the MAX80 and MA6-6 cells installed in the beamline.The first-stage anvil had a 27 mm square tip and a 6 mm square second-stage anvil was used to pressurize the sample. The pressure medium was a 9 mm boron epoxy cube per side, and the heater was cylindrical graphite. Graphite was also used for the sample container, which was sealed with the prepared starting use. Pressure and temperature were calculated from the equation of state of MgO and hBN using a mixture of MgO and hBN powders at a volume ratio of 2:3 as pressure markers. X-ray diffraction data were obtained by an energy dispersive method using a Ge semiconductor detector. After pressurization to the target pressure, the temperature was increased until the sample melted, and then the collection of sample-derived diffraction patterns began.
In order to obtain data in a wide wavenumber Q range, white X-rays (20-140 keV) were used to acquire scattering patterns of the sample in the range of 3-30 degree in diffraction angle 2 theta under a single experimental condition. Those scattering patterns were superimposed and added by the MCEDX method to obtain the structure factor S(Q). Then, the two-body correlation function g(r), which is the Fourier transform of the structure factor, was obtained to obtain the average structure information about the local structure.
In this study, we aim to understand the function of CO2 by elucidating the structure of CO2 containing silicate melts at pressures up to 5.6 GPa using energy dispersive X-ray diffraction techniques in order to understand essentially the effect of CO2 composition on magma structure. Na2SiO5 and Na2SiO5+0.5 wt.% and Na2SiO5+1.0 wt.% CO2 were used as starting samples.
X-ray diffraction experiments were performed at NE5C of the PF-AR in the High Energy Accelerator Research Organization (KEK), and a two-stage pressurization method was adopted for the high-pressure generator using both the MAX80 and MA6-6 cells installed in the beamline.The first-stage anvil had a 27 mm square tip and a 6 mm square second-stage anvil was used to pressurize the sample. The pressure medium was a 9 mm boron epoxy cube per side, and the heater was cylindrical graphite. Graphite was also used for the sample container, which was sealed with the prepared starting use. Pressure and temperature were calculated from the equation of state of MgO and hBN using a mixture of MgO and hBN powders at a volume ratio of 2:3 as pressure markers. X-ray diffraction data were obtained by an energy dispersive method using a Ge semiconductor detector. After pressurization to the target pressure, the temperature was increased until the sample melted, and then the collection of sample-derived diffraction patterns began.
In order to obtain data in a wide wavenumber Q range, white X-rays (20-140 keV) were used to acquire scattering patterns of the sample in the range of 3-30 degree in diffraction angle 2 theta under a single experimental condition. Those scattering patterns were superimposed and added by the MCEDX method to obtain the structure factor S(Q). Then, the two-body correlation function g(r), which is the Fourier transform of the structure factor, was obtained to obtain the average structure information about the local structure.