Crystal chemistry of K-richterite-richterite-tremolite solid solutions; a SEM, EMP, XRD, HRTEM and IR study

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doi: 10.1127/ejm/12/2/0273
Authors:Melzer, Stefan; Gottschalk, Matthias; Andrut, Michael; Heinrich, Wilhelm
Author Affiliations:Primary:
GeoForschungsZentrum Potsdam, Potsdam, Federal Republic of Germany
Volume Title:European Journal of Mineralogy
Source:European Journal of Mineralogy, 12(2), p.273-291. Publisher: Schweizerbart'sche Verlagsbuchhandlung (Nägele u. Obermiller), Stuttgart, Federal Republic of Germany. ISSN: 0935-1221
Publication Date:2000
Note:In English. 35 refs.; illus., incl. 4 tables
Summary:Solid solutions with composition (KxNay[]1-x-y)(Nax+yCa2-x-y)2 Mg5[Si8O22(OH)2] have been synthesized at 800°C and 200 and 1800 MPa. The synthetic amphiboles are ≤ 1000 × 50 µm in size, chemically homogeneous and structurally well-ordered. Compositions very close to pure richterite and K-richterite end-members, however, could not be synthesized, always showing minor amounts of tremolite; small amounts of cummingtonite are present in most of the amphiboles. The cell parameters of the solid solutions correlate linearly with the cation occupancies on the A and M4 sites and are therefore a linear combination of the parameters oftremolite, cummingtonite, richterite and K-richterite. Two systems of OH-stretching bands are observed, one (3669-3678 cm-1) due to a vacant A site and the other (3721-3737 cm-1) to a filled A site. Using pure tremolite as a standard, the vacancy concentration was determined quantitatively and was found to be consistent with EPMA results. Additional bands at 3659, 3695 and 3710 cm-1 are probably due to triple chains or higher chain multiplicity faults.
Subjects:Amphibole group; Chain silicates; Clinoamphibole; Crystal chemistry; Infrared spectra; P-T conditions; Richterite; SEM data; Silicates; Solid solution; Spectra; TEM data; Tremolite; Unit cell; X-ray diffraction data
Record ID:2000041806
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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