Types of Pyrophyllite Deposits in Foldbelts

Abstract. Pyrophyllite deposits can be divided into five types on the basis of geology and genesis. The first two types are associated with hydrothermally altered rocks in felsic and intermediate volcanogenic suites. They are characterized by their metasomatites and their subsequent mineralogic transformations under varying volcanic conditions. The third type includes deposits and occurrences of metamorphic-metasomatic genesis, which is caused by transformations of terrigenous-sedimentary interbeds in felsic volcanics under greenschist facies conditions. The fourth type is associated with low and mid-temperature stages of hydrothermal vein formation at the limits of volcanogenic and metamorphic strata. The fifth type comprises pyrophyllite occurrences in weathering crusts on metamorphic strata and metasomatite.
The formation conditions and distribution of raw pyrophyllite deposits were influenced by the geodynamic situations and geochemical conditions, such as character of tectonic dislocations, volcanism and chemical composition of hydrothermal solutions.