Synthesis and crystal chemistry of mukhinite, V-analogue of clinozoisite on the join Ca 2 Al 3 Si 3 O 12 (OH)–Ca 2 Al 2 VSi 3 O 12 (OH)

Mariko Nagashima, Daisuke Nishio-Hamane, Nobuhiko Nakano, Toshisuke Kawasaki

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

This is the first report of the crystal structure of mukhinite, V-analogue clinozoisite, on the join Ca 2 Al 3 Si 3 O 12 (OH)–Ca 2 Al 2 V 3+ Si 3 O 12 (OH) synthesized at 1.5 GPa and 800 °C. The study was performed to clarify the distribution of V 3+ among structurally independent octahedral M1, M2, and M3 sites, and the effect of V 3+ on the crystal structure. Mukhinite and V 3+ -bearing clinozoisite in all run products are associated with zoisite, and also coexist with V-bearing phases such as vanadomalayaite, goldmanite, V-oxides, and unidentified Ca–Al-bearing vanadates. Mukhinite and V 3+ -bearing clinozoisite crystallized in the Run 20 product show a compositional gap between 0.33 and 0.74 V atoms per formula unit (apfu), and the V content attains 1.14 apfu. The coexistence of low V 3+ - and high V 3+ -clinozoisites indicates the presence of a miscibility gap at 1.5 GPa and 800 °C. Two mukhinite crystals with 0.75 and 0.83 V 3+  apfu were used for X-ray single-crystal structure analysis. The unit-cell parameters are a = 8.8995(2), b = 5.6299(1), c = 10.1532(2) Å, β = 115.327(1)°, and V = 459.81(2) Å 3 for the former, and a = 8.8999(1), b = 5.6357(1), c = 10.1499(1) Å, β = 115.306(1)°, and V = 460.24(2) Å 3 for the latter. The resulting V 3+ occupancies among the octahedral sites are M1 (Al 0.894(6) V 0.106 ) M2 (Al 0.976(6) V 0.024 ) M3 (V 0.621(6) Al 0.379 ) for the former and M1 (Al 0.868(4) V 0.132 ) M2 (Al 0.957(4) V 0.043 ) M3 (V 0.652(2) Al 0.348 ) for the latter. Site preference of V 3+ at the octahedral sites is M3 > M1 > M2 as that of Fe 3+ and Mn 3+ . The intracrystalline partition coefficient of V 3+ and Al 3+ between the M1 and M3 sites, K D = (V 3+ /Al) M1 /(V 3+ /Al) M3 , is 0.07–0.08, which is greater than those of Fe 3+ and Al 3+ (0.03–0.05) and of Mn 3+ and Al 3+ (0.04–0.06). Variations of the unit-cell parameters are strongly related to the variations of the M3−Oi and M1−Oi distances.

Original languageEnglish
Pages (from-to)63-76
Number of pages14
JournalPhysics and Chemistry of Minerals
Volume46
Issue number1
DOIs
Publication statusPublished - Jan 21 2019

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Geochemistry and Petrology

Fingerprint Dive into the research topics of 'Synthesis and crystal chemistry of mukhinite, V-analogue of clinozoisite on the join Ca <sub>2</sub> Al <sub>3</sub> Si <sub>3</sub> O <sub>12</sub> (OH)–Ca <sub>2</sub> Al <sub>2</sub> VSi <sub>3</sub> O <sub>12</sub> (OH)'. Together they form a unique fingerprint.

Cite this