Formational nature and physico-chemical analysis of mineral parageneses in the metasomatic Zones of acid leaching in the Western Srednogorie

Abstract

This study of the formational nature ot melaso matites from the zones of acid leaching in the Western Srednogorie is based on an integral zonal metasomatic column and on composition-paragenesis diagrams of each zone constructed to follow out the thermodynamic behaviour of components and the reactions between mineralpar ageneses at the zone boundaries. The propylite type of rocks forming aureoles around proper secondary quartzites is not a separate formational unit but belongs to the outermost zone of the secondary quartzite formation. The physico-chemical analysis of mineral parageneses in the propylite type of rocks shows the equilibria between actinolite, epidote, chlorite, sericite, calcite and magnesite as dependent on temperature and potassium oxide chemical potential. Epidote-chlorite, actinolite-epidote-chlorite and epidote-actinolite parageneses are distinguished as a function of temperature. The physico-chemical analysis of mineral parageneses in the rocks of inner zones gives the equilibria between quartz, kaolinite, alunite, illite and pyrophyllite as dependent on two of the intensive parameters, namely the chemical potentials of K+, SO42- and H2O, and pH of the mineral-forming environment.