The role of AlIV and AlVI in transformation and synthesis of layer silicates

The regularities of transformations of layer silicates under hydrothermal conditions have been examined. For solid phases reactions (transformation of AlSi layer silicates, reactions in AlSi gels) the main factors that control the formation of alumosilicates besides PT‐pH are the presence of admixtures of alkali and alkaliearth cations, likewise the presence of AlIV in the starting materials. The increasing of T and decreasing of P also promotes the preferred formation of layer alumosilicates than silicates of Al. For the reactions that pass through the dissolution of components the leading factor (under PTX = const) is the pH of the surrounding. In acid surrounding silicates with AlVI are formed and in alkaline conditions such phases, in which Al is an analog of silicon and supplies the tetrahedral positions. The results have significance for comprehend geological processes which take place in zones of hydrothermal alterations, of epigenesis and low‐grade metamorphism likewise for comparison of experimental studies.