Infiltration Metasomatism under High-Pressure Granulite-Facies Conditions Based on Orthopyroxene-Sillimanite Rocks in Shear Zones of the Lapland Granulite Belt

摘要

The influx of mantle fluids is an important process affecting the evolution of the granulite complex. Some researchers suggest that these fluids in the granulite areas consisted mainly of CO_2 with insignificant content and low activity of H_2O. However, H_2O-depleted fluids can hardly promote infiltration metasomatism with significant transfer of major components in granulites. Recent theoretical and experimental studies showed that, at high PT parameters of the granulite-facies level, fluids can be significantly hydrous with a low activity of water owing to the high salinity of fluids at moderate and fairly high pressures.