Fluid

Key-words: carbonates, melting, high pressures apparatus, fluid, mechanism Melting experiments on natural calcite crystal and natural Si-poor dolomite at 1 kbar pressures of fluid of different composition (Ar, Ar + H2O, CO2, CO2 + H2O) and at the temperature up to 1310oC were carried out to understand the effect of fluid composition on the mechanisms of calcite and dolo-mite melting. A unique high gas pressure apparatus has been used for the experiments. The apparatus is composed of an internally heated pressure vessel that is equipped with an internal device [1]. The device involves a special modified piston cylinder-type separator-equalizer [2]. The experimental study of calcite (Cal) and dolomite (Dol) melting under 1 kbar pure and dried CO2 and Ar pressures and at the temperature 1310oC was carried out for the first time. The results obtained indicated that calcite (pure icelandic crystal) incongruently melted at T = 1310oC ± 10оС and carbonatite melt (92.3Cal + 7.7CaO, in wt %, calculated) formed, the weight loss of this sample was 5.27 wt %. This result is consistent with the calculated data for the calcite incongruent melting at 1 kbar CO2 pressures [3]. Table 1. Experimental conditions and results of calcite and dolomite melting at Pfl = 1 kbar The design of Pt capsule