NEW GENETIC TYPE OF CORDIERITE ROCK

Abstract

Our petrologic and geochemical study of the Archean Goran group in the southwestern Pamirs has revealed the wide extent of cordierite rocks formed after magnesite. Geologic and petrographic criteria clearly indicate that in the Goran group there are three groups of rocks, formed, respectively, in the metamorphic, ultrameta-morphic and post-ultrametamorphic stages of its Precambrian history. Early-stage rocks were metamorphosed under granulite-facies conditions and served as the substrate for superposed mineral parageneses, formed in a single process of ultrametamorphic and postultrametamorphic alteration. Dolomite and magnesite marbles in the area studied are interbedded with amphibole-plagioclase and biotite-plagioclase schist and gneiss and, together with them, underwent ultrametamorphism, which converted the marbles to skarn, and the schist and gneiss to plagioclase and K-spar migmatite and granite.