Publication Date:
2015-11-21
Description:
Skiagite-rich garnet was synthesized as single crystals at 9.5 GPa and 1100 °C using a multi-anvil apparatus. The crystal structure [cubic, space group Ia d , a = 11.7511(2) Å, V = 1622.69(5) Å 3 , D calc = 4.4931 g/cm 3 ] was investigated using single-crystal synchrotron X-ray diffraction. Synchrotron Mössbauer source spectroscopy revealed that Fe 2+ and Fe 3+ predominantly occupy dodecahedral (X) and octahedral (Y) sites, respectively, as expected for the garnet structure, and confirmed independently using nuclear forward scattering. Single-crystal X-ray diffraction suggests the structural formula of the skiagite-rich garnet to be Fe 3 2+ (Fe 2+ 0.234(2) Fe 3+ 1.532(1) Si 4+ 0.234(2) )(SiO 4 ) 3 , in agreement with electron microprobe chemical analysis. The formula is consistent with X-ray absorption near-edge structure spectra. The occurrence of Si and Fe 2+ in the octahedral Y-site indicates the synthesized garnet to be a solid solution of end-member skiagite with ~23 mol% of the Fe-majorite end-member Fe 3 2+ (Fe 2+ Si 4+ )(SiO 4 ) 3 .
Print ISSN:
0003-004X
Electronic ISSN:
1945-3027
Topics:
Geosciences
Permalink