Garnet (Almandine-Spessartin) zoning and its implication for metamorphic evolution at Deh Salm Metamorphic Complex East of Iran
Deh Salm Metamorphic Complex (DSMC) consists of acidic intrusive masses in association with variety of metamorphic rocks, located in NE Iran. DSMC had been affected by multi-phase metamorphism.
In this research, it has been attempted to recognize P-T-t evolution of multi-phase metamorphism at DSMC based on zoning in almandine-spessartine tie.
EMPA analysis of garnet crystals from core to rim indicated that Fe content increased and Al and Ca content decreased from core to rim. Mg shows small increases while an Mn change is insignificant. All the evidences indicate that garnet zoning is due to crystal growth. Fe content increases mean almandine end-member increase toward crystal rims or increase on metamorphism temperature. Based on staurolite presence in some of metamorphic rocks, 640-670 OC temperatures estimated for metamorphism peak. Perfect zoning in garnet crystals revels that fluids formed during retrograde metamorphism were insignificant and had no effects on garnet zoning. On the other hand there is no sign of diffusion in garnet crystals. Therefore it could be inferred that the second and third phases of metamorphism at DSMC were not widespread and caused no changes on the first phase metamorphic rocks.