The crust and upper mantle structure of eastern Anatolia, Turkey from gravity modeling constrained by seismic data

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The Eastern Anatolian region is part of a young continental collision zone between the Arabian and Eurasian plates. The lithosphere in Eastern Anatolia is underlain by a low-velocity zone associated with asthenospheric flow in the upper mantle. The asthenospheric flow might have been caused by lithospheric delamination and slab detachment. There are many debates about the thickness of the mantle lithosphere, the effect of the hot asthenospheric material on the crustal structure, and the geodynamic evolution of Eastern Anatolia. To better understand the geodynamic evolution of Eastern Anatolia, a 2.5-D gravity model of the crust and upper mantle structure between 38°E/37°N and 44°E /41°N was developed using terrestrial and satellite gravity data. The model is constrained by all available geological and geophysical data. The results of the gravity modeling reveal low-density structures within the lower crust, indicating a thermally heated crust, and a low-velocity zone in the upper mantle associated with the hot asthenospheric flow in the region. The presence of the asthenospheric flow in the upper mantle might have an effect on the crustal and lithospheric structures in the region. The lithospheric thicknesses in the Anatolian and Arabian plates are significantly different. The lithospheric thickness increases from 60 km in the northern segment of the Anatolian plate to 95 km in the Arabian Plate. Thus, the lithosphere beneath Eastern Anatolia is extremely thin. This is attributed to lithospheric delamination and slab break-off. The extremely thin lithosphere, the presence of a hot asthenosphere, the rapid uplift of topography and widespread volcanism across the region may indicate that lithospheric delamination and slab detachment occurred in Eastern Anatolia. The topography in Eastern Anatolian is not isostatically compensated. There is a residual topography of approximately 1.7 km that cannot be explained by crustal roots. Thus, part of the Eastern Anatolian Plateau may be dynamically supported by asthenospheric flow in the upper mantle.

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