Thermochronology of the Miocene Arabia-Eurasia collision zone of southeastern Turkey

The Bitlis-Pütürge collision zone of SE Turkey is the area of maximum indentation along the >2400-km-long Assyrian-Zagros suture between Arabia and Eurasia. The integration of ( i ) fission-track analyses on apatites, ( ii ) (U-Th)/He analyses on zircons, ( iii ) field observations on stratigraphic and structural relationships, and ( iv ) preexisting U-Pb and Ar-Ar age determinations on zircons, amphiboles, and micas provides for the first time an overall picture of the thermo chronometric evolution of this collisional orogen. The data set points to ubiquitous latest Cretaceous metamorphism of a passive margin sedimentary sequence and its igneous basement not only along the suture zone but across the entire width of the Anatolia-Tauride block north of the suture. During the early Paleogene the basement complex of the Bitlis and Pütürge massifs along the suture was rapidly exhumed due to extensional tectonics in a back-arc setting and eventually overlain by Eocene shallow-marine sediments. The entire Oligocene is characterized by a rather flat thermochronometric evolution in the Bitlis orogenic wedge, contrary to the widely held belief that this epoch marked the inception of the Arabia-Eurasia collision and was characterized by widespread deformation. Deposition of a thick Oligocene sedimentary succession in the Mu ş -Hınıs basin occurred in a retroarc foreland setting unrelated to continental collision. During the Middle Miocene, the Bitlis-Pütürge orogenic wedge underwent a significant and discrete phase of rapid growth by both frontal accretion, as shown by cooling/exhumation of the foreland deposits on both sides of the orogenic prism, and underplating, as shown by cooling/ exhumation of the central metamorphic core of the orogenic wedge. We conclude that continental collision started in the mid-Miocene, as also shown by coeval thick syntectonic clastic wedges deposited in flexural basins along the Arabian plate northern margin and contractional reactivation of a number of preexisting structures in the European foreland. of more general syn- and post-collisional processes like ( i ) the development of large-scale strike-slip systems accommodating plate convergence and ( ii ) the development of continental plateaux. In the Bitlis-Pütürge massifs of southeastern Turkey, i.e., the area of maximum continental indentation, high-temperature radiometric systems indicate a discrete episode of high-pressure–low-temperature ( HP - LT ) metamorphism in the latest Cretaceous the the microplate. only low-temperature thermochronometric (based on fission-track analyses on apatite in samples both the the to a discrete phase of rapid mid-Miocene cooling/exhumation interpreted as the onset of the Arabia-Eurasia hard collision. The results do not rule out the possibility that the documented episode of Miocene cooling was only the last stage of a longer thermochronometric evolution and that the collision could started somewhat earlier. This paper advances the state of the knowledge on this crucial area by integrating new apatite fission-track (AFT) and ZrHe data (this study) with other radiometric data from the literature (U-Pb on zircon and Ar-Ar on amphiboles and micas). The data ultimately provides a more complete picture of the thermo-tectonic evolution of selected segments of the Arabia-Eurasia collision zone. The results of this study indicate that the basement complex of the Bitlis and Pütürge massifs along the Assyrian suture branch Evidence for this in the of Late rocks extending from the Izmir-Ankara-Erzin-can suture to the north to the Bitlis-Pütürge metamorphic complex to the south. The basement complex of the Bitlis and Pütürge massifs along the suture was then rapidly exhumed between ca. 65 and 55 Ma and eventually overlain by Eocene shallow marine sediments. Integrated statistical modeling shows that the Oligocene thermochronometric of the was rather featureless, to the this marked the beginning and was thus characterized by widespread deformation. during the Middle the Bitlis- Pütürge orogenic significantly by ( ) frontal accretion, as shown by cooling/exhumation of the foreland deposits on both sides of the orogenic prism, ( ) underplating, as shown by cooling/exhuma tion of the central metamorphic core of the orogenic wedge. Orogenic growth is also substanti-ated by the stratigraphy of the lower (Arabian) plate, which shows the presence of a coarse-grained clastic wedge in the Middle Miocene as well as evidence of growth structures.