SPECIFIC FEATURES OF THE FORMATION OF FAYALITE IN REDUCED SYSTEMS

Abstract

Processes of mineral formation in reduced fluid systems are among the most interesting aspects of experimental mineralogy. In these systems, ore and petrogenic components can be transferred in both hydrothermal and dry conditions, as was shown previously. The transfer of the most abundant rock-forming components (Si and Fe) in the H–O–N system (NH3 25%, H2 25–75%, H2O 0–50%) was studied using the temperature gradient method at T = 500–700°C (gradient 50–100 °C), P = 500–1000 bar, and duration 100–500 h. A model granite glass was placed into the lower part of the autoclave, while quartz and leucocratic granite samples in the form of polished bars (≈ 25 × 10 × 8 mm in size) were mounted in the upper part of stainless steel (1X18H9T) holders. The exoclave was filled with fluid of the required composition, which was produced either through the interaction of metallic Al with aqueous NH 4OH in the reactor module of the autoclave or in a special reactor and then was supplied along a hot pipe line in the exoclave.