Türkiye Jeoloji Bülteni

Some Petrogenetic Problems of The Kurdoğlu Contact Metamorphic Zone

Abstract: Kurdoğlu contact metamorphic zone consists of metapelitic rocks which surround the Gümüşhane granitepluton. These rocks were influenced by a complex metamorphic process before granite emplacement. The emplacement ofgranite increased the degree of metamorphism of metapelitic rocks from grencshist facies to hornblende-hornfelds facies.Then retrograde metamorphism took place in contact zone with the influence of deuteric and metasomatic processeswhich coincide with the late phases of the granite emplacement.Kurdoğlu contact metamorphic zone is characterised by absence of aluminum silicate (AL2O5) minerals (fibrolite andsillimanite). Another feature is the formation of an Fe-Mg mineral (almandine) whose P-T stability range is very narrow, againstcordierite. The formation of almandine must be related to high M/FM ratio in rock.Sillimanite occurs over biotites and in replacements of them. This relation was formed as a result of metasomaticoperations.Occurrence of temperature effect of granite in a very narrow belt is the result of intrusive pressure being at leastequal to lithostatic pressure. For this reason, quickly coolingmagma in the cold neighbouring rocks could not develop aheated zone of expected dimensions.