Summary
Synthesis of Mn-bearing ilvaites, CaFe 2+2−x MnxFe3+ [Si2O7/O/(OH)], with 0 ≤ x ≤0.19, have been performed under hydrothermal conditions at 2 and 3 kbars, T = 300 -400°C and at oxygen fugacities defined by the Fe2O3/Fe3O4 - and the Ni/NiO -buffer. As shown by X-ray diffraction, the substitution of Fe2+ by Mn2+ decreases the monoclinic angleβ and causes a phase transition from monoclinic to orthorhombic at x = 0.19. The Fe-distribution has been determined by Mössbauer spectroscopy.
Zusammenfassung
Mn-haltiger Ilvait CaFe 2+2−x Mnx Fe3+ [Si2O7/O/(OH)] wurde unter hydrothermalen Bedingungen bei Drucken von 2 und 3 kbar, Temperaturen zwischen 300 und 400°C und bei Sauerstoff Fugazitäten, die durch Festkörperpuffer (Fe2O3/Fe3O4 und Ni/NiO) kontrolliert wurden, hergestellt. Röntgenbeugungsuntersuchungen zeigen, daß mit steigendem Mn-Einbau der monokline Winkelβ kleiner wird, und daß bei x = 0.19 ein Phasenübergang von der monoklinen zur orthorhombischen Struktur erfolgt. Die Fe-Verteilung wurde mit Mössbauer-Spektroskopie bestimmt.
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Ghazi-Bayat, B., Amthauer, G. & Hellner, E. Synthesis and characterization of Mn-bearing ilvaite CaFe 2+2−x MnxFe3+ [Si2O7/O/(OH)]. Mineralogy and Petrology 40, 101–109 (1989). https://doi.org/10.1007/BF01164320
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DOI: https://doi.org/10.1007/BF01164320