Experimental investigations in the system MnCO3-CaCO3-MnCl2-CaCl2-H2O.

Reactions between aragonite and hydrothermal CaCl2-MnCl2-solutions have been investigated experimentally in closed and open systems as a function of temperature, ionic strengths, and Ca / (Ca + Mn)-ratios of the solutions. The solid products have been analyzed by X-ray-diffraction, infrared spectroscopy and microprobe methods.

In the temperature range between 100º and 170 ºC the formation of a complete series of Ca-Mn-carbonate solid solutions has been observed, depending on the Ca / (Ca + Mn)-ratios of the solutions. Pronounced shifts were observed in several of the carbonate infrared bands, which are reflecting the differing ionic radius and mass of substituting cations and possible compression of the carbonate ion. These results have been applied to natural carbonate samples.