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Heat capacities and thermodynamic properties of braunite (Mn7 SiO12) and rhodonite (MnSiO3)

R. A. Robie·J.S. Huebner·B. S. Hemingway
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Abstract

The heat capacities, C0P, of synthetic rhodonite and braunite have been measured by adiabatic calorimetry from 6 to ~350 K. The heat capacity of braunite was also measured to ~900 K by differential scanning calorimetry. Brunite exhibits a ??-peak in C0P in the temperature region 93.4-94.2 K. Rhodonite did not show the expected peak in C0P characteristic of the co-operative ordering of the Mn2+ spins at temperatures above 6 K. A revised petrogenetic grid for the system Mn-Si-O-C at 2000 bars is presented and is consistent with both thermochemical values and occurrence of natural assemblages. -from Authors

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R. A. Robie, J.S. Huebner, B. S. Hemingway. 1995. Heat capacities and thermodynamic properties of braunite (Mn7 SiO12) and rhodonite (MnSiO3). https://pubs.usgs.gov/publication/70019145

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