Menderes Masifi’nin Pan-Afrikan yafll› temel kayalar› ve Paleozoyik örtü serileri Ödemifl-Kiraz asmasifi’nin do¤usunda yer alan Derbent (Alaflehir) çevresinde yüzlek vermektedir. Pan-Afrikan temele ait granat-mika flistler, ortognayslar ve Triyas yafll› lökokratik ortognayslar›n ilksel kayalar› taraf›ndan intrüze olmufllard›r. Bu çal›flma, Proterozoyik sonunda Menderes Masifi’nin Pan-Afrikan evrimiyle iliflkili olan ortognayslar›n jeokimyas› ve jeokronolojisi üzerinedir. Jeokimyasal veriler ortognayslar›n S-tipli, peralumino ve kalkalkalen karakterli, sin-/posttektonik granitoyidlerden türedi¤ini göstermektedir. Ortognayslardan ayr›lan tipik magmatik ve öz flekilli zirkonlardan Pb-Pb evaporasyon yöntemiyle yafl tayinleri yap›lm›flt›r. ‹ki örne¤in tek zirkon 207Pb/206Pb yafllar› ortalama 561.5±1.8 my ve 570.5±2.2 my olarak elde edilmifltir. Bu yafllar ortognayslar›n ilksel kayalar›n›n sokulum yafl› olarak yorumlanm›flt›r. Menderes Masifi’ndeki bu ana magmatik olay okyanus havzalar›n›n kapanmas› ve Do¤u ve Bat› Gondvana’n›n çarp›flmas›na ba¤lant›l› Pan-Afrikan orojeneziyle iliflkilendirilebilir. 

Pan-African basement rocks and the Palaeozoic cover series of the Menderes Massif are exposed around Derbent (Alaşehir) in the eastern part of the Ödemiş-Kiraz submassif. Garnet-mica schists of the Pan-African basement are intruded by the protoliths of orthogneisses and Triassic leucocratic orthogneisses. This study focuses on the geochronology and geochemistry of orthogneisses related to the Pan-African evolution of the Menderes Massif in latest Proterozoic time. Geochemical data suggest that the orthogneisses were derived from S-type, peraluminous, syn- to post-collisional granitoids of calc-alkaline affinity. Zircon grains from the orthogneisses, which are euhedral with typical igneous morphologies, were dated by the Pb-Pb evaporation method. Single zircon ages of two samples yielded 207Pb/206Pb ages of 561.5±1.8 Ma and 570.5±2.2 Ma. These ages are interpreted as the time of protolith emplacement of the orthogneisses. This major magmatic episode of the Menderes Massif can be attributed the Pan-African Orogeny which was related to the closure of the ocean basins and amalgamation of East and West Gondwana.