Abstract
The compositions of coexisting pyroxmangites, rhodonites, rhodochrosites and manganese calcites in regional metamorphosed manganese cale-silicate marbles from Val Scerscen and Alagna were analysed by microprobe and permit definition of critical tie lines at metamorphic grades appropriate to temperatures between 400 and 450 °C.
Variations in composition of coexisting mineral pairs in one and the same locality are attributed to variations in \(f_{{\text{CO}}_{\text{2}} }\) and not to metamorphic temperatures. From the analysed assemblages isothermal \(f_{{\text{CO}}_{\text{2}} } - X_{{\text{Ca/Ca + Mn}}}\) plots (with SiO2 as excess component) were constructed for the system CaO-MnO-SiO2-CO2.
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Peters, T., Trommsdorff, V. & Sommerauer, J. Manganese pyroxenoids and carbonates: Critical phase relations in metamorphic assemblages from the Alps. Contr. Mineral. and Petrol. 66, 383–388 (1978). https://doi.org/10.1007/BF00403423
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DOI: https://doi.org/10.1007/BF00403423