Raman spectroscopic study of natural cordierites and indialites in the metamorphic aureole of Mishow, located in the southwest of Marand, East Azerbaijan Province, Iran

Abstract The contact aureole of Misho is about 1 km wide around Cadomian igneous intrusions and is located in the northwest of Iran near the city of Tabriz. The granite intrusion has injected into the Kahar formation, causing thermal contact in county rock ranging from the albite-epidote hornfels facies to the pyroxene hornfels facies. The Misho's aureole country rock, located south of Eyshabad, exhibits the following metamorphic stages in ascending order of metamorphic grade: 1) Cordierite Hornfels, Musscovite, and spotted slate chlorite 2) Biotite-Cordierite-Hornfels differentiates the two minerals from their initial occurrence in county rocks. 3) Garnet, Andalusite, Cordierite, Biotite, Hornfels, which are composed of porphyroblasts cordierite and andalusite with anatectic Migmatite, have partially melted during high-grade metamorphism. Due to contact metamorphism, the mineral cordierite, which composes the majority of pelites, has developed in large quantities throughout the aureole. The mineral cordierite is polymorphic and has a high temperature Cordierite is called Indialite , crystallizes as a hexagon. The Raman spectra of cordierite at specific distance from the intrusive granites have been analyzed in this paper. The substitution of Fe and Mg in the structure of orthorhombic cordierite is responsible for the shift in the Raman spectra of these cordierite toward lower wavelength bands at distances between 500 and 350 M from the igneous contact. This shift is characteristic of pure Mg-cordierite and is proportional to the concentration of Fe. These cordierites' Raman spectra exhibit a distinct band that is identifiable as indialite at a distance of 100 to 300 meters adjacent to the intrusive contact. Petrography investigations indicate that hexagonal cordierite crystallizes most likely as a result of melting cordierite around 700 C֯. As a result of this melting, the cordierite structure becomes distorted. Key words: contact metamorphism,cordierite, indialite, Raman spectra, Misho, Iran