• journal_title：Geological Society of America Bulletin
• Contributor：A.I. Okay ; M. Satir ; M. Zattin ; W. Cavazza ; G. Topuz
• Publisher：Geological Society of America
• Date：2008-
• Format：text/html
• Language：en
• Identifier：10.1130/B26229.1
• journal_abbrev：Geological Society of America Bulletin
• issn：0016-7606
• volume：120
• issue：7-8
• firstpage：893
• section：TECTONICS

The Uludağ Massif in northwest Turkey represents an exhumed segment of an Oligocene ductile strike-slip shear zone that is over 225 km long and has ~100 km of right-lateral strike-slip displacement. It forms a fault-bounded mountain of amphibolite-facies gneiss and intrusive Oligocene granites. A shear-zone origin for the Uludağ Massif is indicated by: (1) its location at the tip of the active Eskişehir oblique-slip fault, (2) pervasive subhorizontal mineral lineation in the gneisses with a right-lateral sense of slip, (3) foliation with a consistent strike, (4) the presence of a subvertical synkinematic intrusion, and (5) the alignment of the Eskişehir fault, synkinematic metagranite, and the strike of the foliation and mineral lineation. The shear zone nucleated in amphibolite-facies gneisses at peak pressure-temperature (m>Pm>-m>Tm>) conditions of 7.0 kbar and 670 °C, and it preserves Eocene (49 Ma) and Oligocene (36–30 Ma) Rb/Sr muscovite and biotite cooling ages. The shear zone was active during the latest Eocene and Oligocene (38–27 Ma), as shown by the crystallization and cooling ages from synkinematic granite. A 27 Ma postkinematic granite marks the termination of shear-zone activity. The 20–21 Ma apatite fission-track (AFT) ages indicate rapid exhumation during the early Miocene. A 14 Ma AFT age from an Uludağ gneiss clast deposited in a neighboring Neogene basin shows that the shear zone was on the surface by the late Miocene. Results of this study indicate that during the Oligocene, crustal-scale right-lateral strike-slip faults were transporting crustal fragments from Anatolia into the north-south–extending Aegean; this implies that the westward translation of Turkey, related to the Hellenic slab suction, started earlier than the Miocene Arabia-Eurasia collision.