The Aegean region experienced a series of continental plate collisions from Late Cretaceous to Eocene time. Post-collisional extension in the region, although controversial in its timing and nature, caused the exhumation of several metamorphic belts. The largest of these, the Menderes Massif, accommodated significant crustal extension, which may have been caused by: (1) tectonic escape and lateral extrusion, in which the Anatolian plate moves westward along the North and East Anatolian Faults, (2) back-arc spreading/slab roll back due to the subduction along the Hellenic Arc, or (3) orogenic collapse of thermally weakened lithosphere that experienced Paleogene contraction. These hypotheses are tested using geochronology, making the Menderes Massif a key locale in identifying the fundamental plate tectonic processes that facilitate extension in the continental lithosphere. The main goal of the research is to characterize the petrologic evolution of rocks in the central Menderes Massif to identify the cause of tectonic transition from compression to extension in the Aegean Region. The project involves fieldwork and geochemical data acquisition, including recently developed techniques of in situ ion microprobe monazite geochronology and argon-argon K-feldspar multi-diffusion domain modeling. The ion microprobe technique preserves the grain and rock fabric, and, when combined with electron microprobe chemical analyses, allow for a clear interpretation of meaning of the age. The argon-argon multi-diffusion domain model shows that a single K-feldspar sample can reveal a broad segment of a cooling history, rather than a single datum. This project is collaborative between a U.S. team including Dr. Elizabeth Catlos, Dr. Ibrahim Cemen (School of Geology; Oklahoma State University) and Dr. Matt Kohn (Dept. Geological Sciences; University of South Carolina), and a Turkish team including Dr. Cemal Goncuoglu (Middle East Technical University, Department of Geological Engineering, Ankara). The two graduate students participating in this proposal are exposed to a different culture, intense fieldwork, and a variety of geochemical methods.