Summary
A meta-ironstone, composed essentially of eulite, almandine and quartz, and locally containing ferrifayalite (Fe4−x (SiO4)2), magnetite, clinopyroxene, biotite, graphite and plagioclase, was discovered at Louzi Mountain, Qianan, Eastern Hebei province, China. Its parent in terms of bulk rock chemistry is probably a Fe-rich sediment. The mineral chemistry and the distribution coefficient of Fe2+ and Mg between coexisting ferromagnesian minerals are defined, and also the inferared and Mössbauer spectra. According to the two-pyroxene geothermometers ofWood andBanno (1973),Saxena (1976), andWells (1977), the equilibrium crystallization temperature of the rock was about 750°C, and the pressure according toWood's method (1974) is about 13 kb at that temperature. It is implied that the rock has undergone granulite facies metamorphism.
Zusammenfassung
Eisenreiche Metasedimente wurden im Gebiet des Mt. Louzi, Qianan, im östlichen Teil der Provinz Hebei, China, entdeckt. Diese bestehen aus Eulite, Almandin und Quarz und führen lokal Ferrifayalit (Fe4−x (SiO4)2), Magnetit, Klinopyroxen, Biotit, Graphit und Plagioklas. Der Gesamtgesteinschemismus weist darauf hin, daß das Ausgangsmaterial ein Fe-reiches Sediment war. Die Zusammensetzung der Minerale und die Verteilungs-Koeffizienten von Fe2+ und Mg zwischen koexistierenden ferromagnetischen Mineralen wurden bestimmt. Zu diesen Daten kommen die Ergebnisse von Infrarot- und Mössbauer-Spektroskopie. Anwendung des Zwei-Pyroxen-Geothermometers nachWood undBanno (1973),Saxena (1976) undWells (1977) ergab Gleichgewichts-Kristallisations-Temperaturen von ca. 750°C. Der Druck (nachWood, 1974) wurde mit 13 kb bestimmt. Dies weist darauf hin, daß die Metasedimente unter Bedingungen der Granulit-Fazies metamorphosiert wurden.
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Zhang, Ry., Cong, Bl., Ying, Yp. et al. Ferrifayalite-bearing eulysite from Archaean granulites in Qianan county, Hebei, North China. TMPM Tschermaks Petr. Mitt. 28, 167–187 (1981). https://doi.org/10.1007/BF01084626
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DOI: https://doi.org/10.1007/BF01084626