Ti/Zr isomorphism in wadeite: The crystal structure of the titanium-dominant K{sub 2}(Ti{sub 0.55}Zr{sub 0.45})Si{sub 3}O{sub 9} member of the series
- Russian Academy of Sciences, Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (Russian Federation)
The crystal structure of the titanium-rich mineral wadeite K{sub 2}(Ti{sub 0.55}Zr{sub 0.45})Si{sub 3}O{sub 9} from rischorrites of the Khibiny Alkaline Massif (Kola Peninsula, Russia) is studied by X-ray diffraction (XCalibur-S diffractometer, R = 0.0459): a = 6.8611(6) Å and c = 10.0611(9) Å; space group P6{sub 3}/m, Z = 6, D{sub x} = 3.03 g/cm{sup 3}. It is shown that the unit-cell parameters and volume of the mineral of mixed (Ti/Zr) composition are naturally intermediate between those of the terminal members of the isomorphous wadeite-based K{sub 2}ZrSi{sub 3}O{sub 9}–K{sub 2}(Ti{sub 0.55}Zr{sub 0.45})Si{sub 3}O{sub 9}–K{sub 2}TiSi{sub 3}O{sub 9} series. The expected correlation is due to the ionic radii of Zr{sup 4+} and Ti{sup 4+} which determine the lengths of Zr/Ti–O bonds in octahedra. The data of field observations and microscopic studies show that the Ti-dominant wadeite is formed on the basis of primary zirconium mineral in the course of a late imposed process under unique geochemical conditions.
- OSTI ID:
- 22758375
- Journal Information:
- Crystallography Reports, Vol. 62, Issue 3; Other Information: Copyright (c) 2017 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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