Abstract
The crystal structure of a knorringite-type compound, Mg3(Cr1.58Mg0.21Si0.21)Si3O12, synthesized in a multi-anvil press at P = 16 GPa and T = 1,600 °C, was refined from single-crystal X-ray diffraction data up to R = 2.36 % for 314 independent reflections. Garnet was found to be cubic and have space group Ia \(\overline{3}\) d, with the unit cell parameters a = 11.5718 (1) Å, V = 1,549.54 (2) Å3. The knorringite crystal studied contains 21 mol% of majorite end-member. The structural characterization of knorringitic garnet is important because the study of its thermodynamic constants provides new constraints on thermobarometry of peridotitic garnet assemblages of the lowermost upper mantle. The Raman spectra of synthetic knorringite have been obtained for the first time.
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Acknowledgments
The authors thank Sabrina Nazzareni for her review and valuable comments. This study was supported by the Russian Foundation for Basic Research (Project Nos. 12-05-00426, 12-05-33044, and 14-05-31288) and by the Foundation of the President of the Russian Federation for Leading Scientific Schools (NSh-5877.2012.5).
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Bykova, E.A., Bobrov, A.V., Sirotkina, E.A. et al. X-ray single-crystal and Raman study of knorringite, Mg3(Cr1.58Mg0.21Si0.21)Si3O12, synthesized at 16 GPa and 1,600 °C. Phys Chem Minerals 41, 267–272 (2014). https://doi.org/10.1007/s00269-013-0644-y
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DOI: https://doi.org/10.1007/s00269-013-0644-y