Natural Kaersutite: FTIR, Raman, Thermal, and Thermochemical Studies

Abstract

The paper reports original thermochemical data obtained on natural oxo-amphibole kaersutite Na_0.4K_0.3(Ca_1.6Na_0.4)(Mg_2.9\({\text{Fe}}_{{0.8}}^{{2 + }}\)Al_0.7Ti_0.6\({\text{Fe}}_{{0.5}}^{{3 + }}\))[Si_6.1Al_1.9O₂₂](OH)_0.2O_1.8 from alkaline basalt in Mongolia. The data were obtained using a Tian–Calvet microcalorimeter. The enthalpy of formation from elements Δ_f\(H_{{{\text{el}}}}^{{\text{0}}}\)(298.15 K) = –12102 ± 16 kJ/mol) was obtained by high-temperature melt solution calorimetry. The entropy, enthalpy, and Gibbs energy of formation of the end members of the isomorphic series kaersutite NaCa₂Mg₃TiAl[Si₆Al₂O₂₂]O₂–ferrikaersutite NaCa₂Mg₃TiFe³⁺[Si₆Al₂O₂₂]O₂ were estimated.