Abstract
L III edge extended X-ray absorption fine structure (EXAFS) spectra of Gd, Er and Lu environments in synthetic epidotes of composition CaLa0.9 X 0.1Al2MgSi3O13H (X=Gd or Er or Lu) were recorded using synchrotron radiation. The Fourier transforms of the Gd-, Er- and Lu-EXAFS are clearly different from one another indicating wholly or partially different site occupancy. Model fitting of the Fourier-filtered partial EXAFS and comparison of pair distribution functions with those calculated for natural epidote leads to the conclusion that three different sites are probably involved in the accommodation of these elements in the epidote structure, and that site preference is a function of the rare earth ionic size. Gd is located in A2-type sites, whereas the local atomic environment of Er is consistent with A1 site occupancy and the Lu environment has been modelled on an M3-type octahedral site.
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Affholter KA, Hewitt DA, Wones DR (1983) Synthesis of rare earth element allanites. Geol Soc Am Abstr Prog 15:511
Binsted N, Greaves GN, Henderson CMB (1985) An EXAFS study of glassy and crystalline phases of compositions CaAl2Si2O8 (anorthite) and CaMgSi2O6 (diopside). Contrib Mineral Petrol 89:103–109
Blank SL, Nielsen JW, Biolsi WA (1976) Preparation and properties of magnetic garnet films containing divalent and tetravalent ions. J Electrochem Soc 123:856–863
Brooks CK, Henderson P, Ronsbo JG (1981) Rare-earth partition between allanite and glass in the obsidian of Sandy Braes, Northern Ireland. Mineral Mag 44:157–160
Calas G, Bassett WA, Petiau J, Steinberg M, Tchoubar D, Zarka A (1984) Some mineralogical applications of synchrotron radiation. Phys Chem Minerals 11:17–36
Dollase WA (1971) Refinement of the crystal structures of epidote, allanite and hancockite. Am Mineral 56:447–464
Exley RA (1980) Microprobe studies of REE-rich accessory minerals: implications for Skye granite petrogenesis and REE mobility in hydrothermal systems. Earth Planet Sci Lett 48:97–110
Gabe EJ, Portheine JC, Whitlow SH (1973) A reinvestigation of the epidote structure: confirmation of the iron location. Am Mineral 58:218–223
Gashurov G, Sovers OJ (1970) Theoretical calculation of structural parameters of C-type sesquioxides. Acta Crystallogr B26:938–945
Greaves GN (1985) EXAFS and the structure of glass. J Non-Cryst Solids 71:203–217
Gurman SJ, Binsted N, Ross I (1984) A rapid, exact curved-wave theory for EXAFS calculations. J Phys C17:143–151
Harbron SK, Higgins SJ, Levason W, Feiters MC, Steel AT (1986) Coordination chemistry of higher oxidation states. 19. Synthesis and properties of diphosphine and diarsine complexes of iron (IV) and iron K-edge EXAFS data on [Fe(o-C6H4(PMe2)2)2Cl2]n+[BF4]n (n=0–2). Inorg Chem 25:1789–1794
Harries JE, Hukins DWL, Hasnain SS (1986) Analysis of the EXAFS spectrum of hydroxyapatite. J Phys C19:6859–6872
Krishnan KM, Rez P, Thomas G (1985) Crystallographic site occupancy refinements in thin film oxides by channelling-enhanced microanalysis. Acta Crystallogr B41:396–405
Shannon RD (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr A32:751–767
Teo BK (1981) Extended X-ray absorption fine structure (EXAFS) spectroscopy: techniques and applications. In: Teo BK, Joy DC (eds) EXAFS Spectroscopy. Plenum, New York, pp 13–58
Waychunas GA, Brown GE, Apted MJ (1986) X-ray K-edge absorption spectra of Fe minerals and model compounds: II EXAFS. Phys Chem Minerals 13:31–47
Wyckoff RWG (1964) Crystal structures Vol 2. Wiley, New York
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Cressey, G., Steel, A.T. An EXAFS study of Gd, Er and Lu site location in the epidote structure. Phys Chem Minerals 15, 304–312 (1988). https://doi.org/10.1007/BF00307521
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DOI: https://doi.org/10.1007/BF00307521