Structural features of quench products of melts in the chloride-carbonate-silicate systems revealed by vibrational and X-ray spectroscopy

Abstract

Quench products of melts synthesized at 5 GPa and 1500°C in model system CaMgSi₂O₆–Na₂CO₃(±CaCO₃)–KCl, were studied using vibrational (IR and Raman) and X-ray absorption spectroscopy (XANES). Correlations between structural peculiarities of the quenches with chemical composition are established. Increase of the CaMgSi₂O₆ content of the melts results in gradual substitution of the Са-bearing carbonate groups by Na-bearing, whereas Ca is progressively more bounded with silicate structural units. XANES spectra reveal that chlorine is predominantly present as (K_xNa_1–x)Cl complexes. XANES spectra also indicate distribution of potassium cations between chloride and silicate groups, although its partial bonding with carbonate groups in the melt is not excluded.