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- Title
Towards a revisitation of vesuvianite-group nomenclature: the crystal structure of Ti-rich vesuvianite from Alchuri, Shigar Valley, Pakistan.
- Authors
Aksenov, Sergey M.; Chukanov, Nikita V.; Rusakov, Vyacheslav S.; Panikorovskii, Taras L.; Rastsvetaeva, Ramiza K.; Gainov, Ramil R.; Vagizov, Farit G.; Lyssenko, Konstantin A.; Belakovskiy, Dmitry I.
- Abstract
Vesuvianite containing 5.85 wt% TiO2 from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, Pakistan, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement, 27Al NMR, 57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are: a = 15.5326 (2), c = 11.8040 (2) Å , space group P4/nnc. The structure was refined to final R1 = 0.031, wR2 = 0.057 for 11247 I > 2σ(I). A general crystal-chemical formula of studied sample can be written as follows (Z = 2): [8-9](Ca17.1Na0.9) [8]Ca1.0 [5](Fe2+0.44Fe3+0.34Mg0.22) [6](Al3.59Mg0.41) [6](Al4.03Ti2.20Fe3+1.37Fe2+0.40) (Si18O68) [(OH)5.84O2.83F1.33]. The octahedral site Y2 is Al-dominant and does not contain transition elements. Another octahedral site Y3 is also Al-dominant and contains Fe2+, Fe3+ and Ti. The site Y1 is split into Y1a and Y1b predominantly occupied by Fe2+ and Fe3+, respectively. The role of the Y1 site in the diversity of vesuvianite-group minerals is discussed.
- Subjects
VESUVIANITE; CRYSTAL structure; ELECTRON probe microanalysis
- Publication
Acta Crystallographica Section B: Structural Science, Crystal Engineering & Materials, 2016, Vol 72, Issue 5, p744
- ISSN
2052-5192
- Publication type
Article
- DOI
10.1107/S2052520616010246