SYNTHESIS, CRYSTAL STRUCTURE AND CRYSTAL CHEMISTRY OF FERRI-CLINOHOLMQUISTITE, □LI2MG3 FE3+2SI8O22(OH)2
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dc.contributor.author | Iezzi G. | |
dc.contributor.author | Cámara F. | |
dc.contributor.author | Oberti R. | |
dc.contributor.author | Della Ventura G. | |
dc.contributor.author | Pedrazzi G. | |
dc.contributor.author | Robert J.-L. | |
dc.date.accessioned | 2022-11-08T06:07:41Z | |
dc.date.available | 2022-11-08T06:07:41Z | |
dc.date.issued | 2004 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=14506472 | |
dc.identifier.citation | Physics and Chemistry of Minerals, 2004, 31, 6, 375-385 | |
dc.identifier.issn | 0342-1791 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/39593 | |
dc.description.abstract | This work reports the synthesis of ferri-clinoholmquistite, nominally □Li2(Mg3Fe3+2)Si8O22(OH)2, at varying f O 2 conditions. Amphibole compositions were characterized by X-ray (powder and single-crystal) diffraction, microchemical (EMPA) and spectroscopic (FTIR, Mössbauer and Raman) techniques. Under reducing conditions (≤ NNO+1, where NNO = Nickel–Nickel oxide buffer), the amphibole yield is very high (>90%), but its composition, and in particular the FeO/Fe2O3 ratio, departs significantly from the nominal one. Under oxidizing conditions (≤ NNO+1.5), the amphibole yield is much lower (<60%, with Li-pyroxene abundant), but its composition is close to the ideal stoichiometry. The exchange vector of relevance for the studied system is M2(Mg,Fe2+) M4(Mg,Fe2+) M2Fe3+–1M4Li−1, which is still rather unexplored in natural systems. Amphibole crystals of suitable size for structure refinement were obtained only at 800 °C, 0.4 GPa and NNO conditions (sample 152), and have C2/m symmetry. The X-ray powder patterns for all other samples were indexed in the same symmetry; the amphibole closest to ideal composition has a = 9.428(1) Å, b = 17.878(3) Å, c = 5.282(1) Å, β = 102.06(2)°, V = 870.8(3) Å3. Mössbauer spectra show that Fe3+ is strongly ordered at M2 in all samples, whereas Fe2+ is disordered over the B and C sites. FTIR analysis shows that the amount of CFe2+ increases for increasingly reducing conditions. FTIR data also provide strong evidence for slight but significant amounts of Li at the A sites. | |
dc.subject | Synthetic ferri-clinoholmquistite | |
dc.subject | Microprobe analysis | |
dc.subject | Infrared spectroscopy | |
dc.subject | Mossbauer spectroscopy | |
dc.subject | Structure refinement | |
dc.subject | Short-range order | |
dc.title | SYNTHESIS, CRYSTAL STRUCTURE AND CRYSTAL CHEMISTRY OF FERRI-CLINOHOLMQUISTITE, □LI2MG3 FE3+2SI8O22(OH)2 | |
dc.type | Статья |
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