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    Long Wavelength Progressive Plateau Uplift in Eastern Anatolia Since 20 Ma: Implications for the Role of Slab Peel-Back and Break-Off
    (Amer Geophysical Union, 2020) Memis, Caner; Gogus, Oguz H.; Uluocak, Ebru Sengul; Pysklywec, Russell; Keskin, Mehmet; Sengor, A. M. Celal; Topuz, Gultekin
    Stratigraphic evidence is used to interpret that the East Anatolian Plateau with 2 km average elevation today was below sea level similar to 20 Ma and uplift began in the northern part. The presence of voluminous volcanic rocks/melt production across the plateau-younging to the south-corroborates geophysical interpretations (e.g., high heat flow and lower seismic velocities) that suggest progressive removal of the slab subducting under the Pontides. Here, we conduct numerical experiments that investigate the change in the surface uplift as a response to slab peel-back and potential break-off processes under subduction-accretionary complexes as well as continental lithosphere. Model results show similar types of tectonic behavior and magnitudes of uplift-subsidence in both oceanic and continental removal processes, and they satisfactorily explain 1.5 km of plateau rise and a similar to 280 km wide asthenospheric upwelling zone beneath Eastern Anatolia over 18 Myr timescale. Parametric investigation for varying plate strength and convergence velocities show that such model parameters control the amount of surface uplift (1 to 3 km), the width of the asthenospheric upwelling zone, and the potential timing/depth of break-off of the steepening/peeling slab. Experiments show that slab break-off develops during the terminal phase, which may correspond to only a few million years ago. Therefore, the long wavelength plateau uplift and magmatism over the Eastern Anatolian-Lesser Caucasus region since 20 Ma is controlled by progressive slab peel-back and resulting mantle dynamics. The slab break-off process (if it happened) has yet an indiscernible role.
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    Rutile geochemistry and thermometry of eclogites and associated garnet-mica schists in the Biga Peninsula, NW Turkey
    (Elsevier Gmbh, 2017) Sengun, Firat; Zack, Thomas; Topuz, Gultekin
    In northwest Turkey, high-pressure metamorphic rocks occur as exotic blocks within the cetmi m lange located on the south of the Biga Peninsula. Rutile chemistry and rutile thermometry obtained from the eclogite and associated garnet-mica schist in the cetmi m lange indicate significant trace element behaviour of subducted oceanic crust and source-rock lithology of detrital rutiles. Cr and Nb contents in detrital rutile from garnet-mica schist vary from 355 to 1026 pzig and 323 and 3319 g/g, respectively. According to the Cr-Nb discrimination diagram, the results show that 85% of the detrital rutiles derived from metapelitic and 15% from metamafic rocks. Temperatures calculated for detrital rutiles and rutiles in eclogite range from 540 degrees C to 624 degrees C with an average of 586 degrees C and 611 degrees C to 659 degrees C with an average of 630 degrees C at P = 2.3 GPa, respectively. The calculated formation temperatures suggest that detrital rutiles are derived from amphibolite- and eclogite-facies metamorphic rocks. Amphibolite-facies rocks of the Kazdag Massif could be the primary source rocks for the rutiles in the garnet-mica schist from the cetmi m lange. Nb/Ta ratios of metapelitic and metamafic rutiles fall between 7-24 and 11-25, respectively. Nb/Ta characteristics in detrital rutiles may reflect a change in source-rock lithology. However, Nb/Ta ratios of rutiles in eclogite vary from 9 to 22. The rutile grains from eclogites are dominated by subchondritic Nb/Ta ratios. It can be noted that subchondritic Nb/Ta may record rutile growth from local sinks of aqueous fluids from metamorphic dehydration. (C) 2017 Elsevier GmbH. All rights reserved.