Abstract

The influence of Mn content on the stability of the high-pressure CaCO3 phases CaCO3-I, CaCO3-II, and CaCO3-III at 300 K has been investigated up to 40 mol% MnCO3 using Raman spectroscopy recorded in situ with a diamond-anvil cell at pressures up to 14 GPa. Beyond about 5 mol% MnCO3, there is a progressive linear upward shift in the pressure of the CaCO3-I → CaCO3-II and CaCO3-II → CaCO3-III transitions, and expansion of the field of the CaCO3-II phase, with increase in MnCO3 content. The shifts in transition pressure are 0.19 GPa/mol% for I → II and 0.26 GPa/mol% for II → III over the 5 to 40 mol% MnCO3 composition interval, results fully consistent with elevation of transition pressure by the introduction of a smaller cation. However, minor and trace amounts of Mn appear to have a relatively insignificant influence on the pressure of these transitions.

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