CRYSTAL CHEMISTRY OF TREMOLITE-TSCHERMAKITE SOLID SOLUTIONS
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dc.contributor.author | Najorka J. | |
dc.contributor.author | Gottschalk M. | |
dc.date.accessioned | 2022-02-13T04:46:11Z | |
dc.date.available | 2022-02-13T04:46:11Z | |
dc.date.issued | 2003 | |
dc.identifier | https://elibrary.ru/item.asp?id=5082460 | |
dc.identifier.citation | Physics and Chemistry of Minerals, 2003, 30, 2, 108-124 | |
dc.identifier.issn | 0342-1791 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/35290 | |
dc.description.abstract | Tremolite-tschermakite solid solutions have been synthesized between 700 and 850 °C and 200 and 2000 MPa. The starting materials were oxide-hydroxide mixtures and an additional 0.1-1.8 molal CaBr2 solution. The run products were characterized using SEM, HRTEM, EMP, XRD and FTIR. The synthesized Al tremolites formed needles and lath-shaped crystals of up to 300 × 20 μm. HRTEM investigations showed that the majority of the amphiboles were well ordered. The EMP analysis revealed that the Al tremolites were solid solutions in the ternary tremolite-tschermakite-cummingtonite. The highest observed Al content was close to the composition of magnesiohornblende (Xts=0.54). Different cummingtonite concentrations (Xcum=0.00-0.18) were observed, which generally increased with Al content. Rietveld refinements of the lattice constants showed a linear decrease of the cell parameters a and b with increasing Al content, whereas c and β increased. Small deviations from the linear behaviour were caused by variable amounts of the cummingtonite component. For pure tschermakite lattice parameters of a=9.7438(11) A, b=17.936(14) A, c=5.2995(3) A, β=105.68(9)° and V=891.7 ± 1.4 A3 were extrapolated by least-squares regression. Using the a and β lattice parameters for tremolite, tschermakite and cummingtonite, it was possible to derive amphibole compositions using powder XRD. IR spectra of the Al tremolites showed a total of 12 individual bands. The FWHMs of all bands increased with increasing Al content. According to their FWHMs, these bands were grouped into three band systems at 3664-3676 cm-1 (I), 3633-3664 cm-1 (II) and 3526-3633 cm-1 (III). Assuming [6]Al substitution at M2 and/or M3 and [4]Al at T1, three principal different configurational groups could be assigned as local environments for the proton. I: only Si4+ at T1 and one or two Al3+ at M2 and/or M3far, II: one Al3+ at T1 and one to three Al3+ at M2 and/or at M3far, III: either Al3+ on M3near and/or two Al3+ on T1 and additional one to four Al3+ at M2. It is assumed that these three configurational groups correspond to the three groups of observed bands. This was quantitativly supported by Monte-Carlo simulations. A model with random distribution at M2 and M3 including Al avoidance at tetrahedral and octahedral sites yielded the best agreement with the spectroscopical results. | |
dc.subject | AMPHIBOLE | |
dc.subject | TREMOLITE | |
dc.subject | TSCHERMAKITE | |
dc.subject | RIETVELD REFINEMENT | |
dc.subject | IR SPECTROSCOPY | |
dc.title | CRYSTAL CHEMISTRY OF TREMOLITE-TSCHERMAKITE SOLID SOLUTIONS | |
dc.type | Статья |
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