Summary
The stability field of scorzalite (FeAl2[OH/PO4]2) was investigated in the P-T range from 487 to 684 °C and 0.1 to 0.3 GPa. in hydrothermal experiments. The oxygen fugacity was fixed by the Ni/NiO buffer. Scorzalite shows a decomposition according to the reaction: FeAl2[OH/PO4]2) → FeAlPO5 + AlPO4 (berlinite) + H2O. The mean standard enthalpy and standard entropy of reaction were determined as ΔH 0R = 94(13) kJ, ASR = 180(16) JK−1. A57Fe-Mößbauer spectroscopic examination showed that about 4 atomic % of the total Fe in scorzalite is trivalent.
Zusammenfassung
Das Stabilitätsfeld von Skorzalith (FeAl2[OH/PO4]2) wurde im P-T-Bereich zwischen 487 und 684 °C und zwischen 0.1 und 0.3 GPa in Hydrothermalexperimenten unter der Sauerstoffugazität des Ni/NiO-Puffers untersucht. Skorzalith zerfällt unter diesen Bedingungen gemäß der Reaktion: FeAl2[OH/PO4]2) → FeAlPO5 + AlPO4 (Berlinit) + H2O. Die Reaktionsenthalpie und -entropie für Standardbedingungen wurden zu ΔH 0R = 94(13) kJ und ASR = 180(16) JK−1 bestimmt.57 Fe-Mößbaueruntersuchungen ergaben, daß ungefähr 4% des Gesamteisens in Skorzalith dreiwertig vorliegen.
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Schmid-Beurmann, P., Morteani, G. & Cemič, L. Experimental determination of the upper stability of scorzalite, FeAl2[OH/PO4]2, and the occurrence of minerals with a composition intermediate between scorzalite and lazulite(ss) up to the conditions of the amphibolite facies. Mineralogy and Petrology 61, 211–222 (1997). https://doi.org/10.1007/BF01172485
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DOI: https://doi.org/10.1007/BF01172485
