The transfer of the most abundant rock-forming components (Si and Fe) in the reduced H-O-N system (NH3 – 25%; Í2 25-75%; Í2Î 0-50%) was studied using the temperature gradient method at Ò=500-7000Ñ, P=500-1000 bar, and duration 100-500 h. Quartz and leucocratic granite samples were mounted in the autoclave of stainless steel holders. Our experiments showed that addition of NaCl leads to the formation of fayalite after quartz and quartz aggregates in leucocratic granites and Fe-bearing sample holders. The growth of fayalite from the gas phase due to precipitation on quartz and Fe-bearing holders depends on the influx of Si and Fe, respectively, by fluid. The growth of certain faces of the newly formed fayalite is significantly influenced by the composition of the parent substrate. Mainly platy crystals with well-developed pinacoid faces are formed after quartz, while prismatic and short-prismatic crystals are formed on Fe-bearing holders, indicating a significant adsorption influence of components of the medium on the crystal shape. The growth rate of fayalite is high (up to 0.002 mm/h at Ò=5000Ñ).
Our experiments showed that Si and Fe can be transferred to the reduced part of the H-O-N system in the presence of NaCl under both hydrothermal and anhydrous conditions.
Experiment, temperature, pressure, reduced system, fayalite.