High-energy X-ray diffraction of a hydrous silicate liquid under conditions of high pressure and temperature in a modified hydrothermal diamond anvil cell

Abstract

In situ high-energy X-ray diffraction measurements were made for the first time on a water-saturated silicate melt at high pressure and temperature. A modified hydrothermal diamond anvil cell (HDAC), designed to minimize the path length of the X-ray beam within a diamond anvil and to increase the solid angle of the diffracted beam, was used to reduce high background contributions and extend X-ray diffraction data collection in Q space. Quantitative differential pair distribution function (PDF) analysis of X-ray diffraction data show that the first measurable (Si–O) peak is 0.095 Å greater in length in the hydrous melt than in the starting glass. Contributions from the H₂O O–O correlations, as well as from the second nearest neighbor O–O correlations within the silicate melt, are evident within the second peak of the differential PDF. The procedure described opens new opportunities to directly investigate volatile-rich melts at high pressure and temperature.

• high-energy X-ray diffraction
• hydrothermal diamond anvil cell
• hydrous silicate liquid
• high pressure
• high temperature

Acknowledgements

We thank Dr Jon Almer and Dr S. Shastri for their assistance with our experiments at sector 1-ID of the APS. We are grateful to Dr Richard Wirth of the GFZ, Potsdam for his TEM examination of the glass samples used in this study. A.J.A. acknowledges support from the GEN-IV program. Prof. Peter Ulmer (ETH Zurich) is acknowledged for assisting G.S. in the preparation of the glass used in this study. Funding to the Canada Gen-IV National Program was provided by Natural Resources Canada through the Office of Energy Research and Development, Atomic Energy of Canada Limited, and Natural Sciences and Engineering Research Council of Canada. R.A.M. and H.Y. were supported as part of the EFree, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SG0001057. Use of the APS, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the US DOE under Contract No. DE-AC02-06CH11357.