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    Metamorphic evolution of blueschists of the Altinekin Complex, Konya area, south central Turkey
    (WILEY-BLACKWELL, 2005) Droop, GTR; Karakaya, MQ; Eren, Y; Karakaya, N
    The Altinekin Complex in south central Turkey forms part of the south-easterly extension of the Tavsanh Zone, a Cretaceous subduction complex formed during the closure of the Neo-Tethys ocean. The protoliths of metamorphic rocks within the Altmekin Complex include peridotites, chromitites, basalts, ferruginous cherts and flysch-facies impure carbonate sediments. Structurally, the complex consists of a stack of thrust slices, with massive ophiolite tectonically overlying a Cretaceous sediment-hosted ophiolitic melange, in turn overlying a sequence of Mesozoic sediments. Rocks within the two lower structural units have undergone blueschist-facies metamorphism. Petrographic, mineral-chemical and thermobarometric studies were undertaken on selected samples of metasedimentary and metabasic rock in order to establish the time relations of deformation and metamorphism and to constrain metamorphic conditions. Microstructures record two phases of plastic deformation, one predating the metamorphic peak, and one postdating it. Estimated peak metamorphic pressures mostly fall in the range 9-11 kbar, corresponding to burial depths of 31-38 km, equivalent to the base of a continental crust of normal thickness. Best-fit peak metamorphic temperatures range from 375 to 450 degrees C. Metamorphic fluids had high H2O:CO2 ratios. Peak metamorphic temperature/depth ratios (T/d values) were low (c. 10-14 degrees C/km), consistent with metamorphism in a subduction zone. Lawsonite-bearing rocks in the southern part of the ophiolitic melange record lower peak temperatures and T/d values than epidote blueschists elsewhere in the unit, hinting that the latter may consist of two or more thrust slices with different metamorphic histories. Differences in peak metamorphic conditions also exist between the ophiolitic melange and the underlying metasediments. Rocks of the Altinekin Complex were subducted to much shallower depths, and experienced higher geothermal gradients, than those of the NW Tavsanli Zone, possibly indicating dramatic lateral variation in subduction style. Retrograde P-T paths in the Altmekin Complex were strongly decompressive, resulting in localized overprinting of epidote blueschists by greenschist-facies assemblages, and of lawsonite blueschists by pumpellyite-facies assemblages. The observation that the second deformation was associated with decompression is consistent with, but not proof of, exhumation by a process that involved deformation of the hanging-wall wedge, such as gravitational spreading, corner flow or buoyancy-driven shallowing of the subduction zone. Copyright (c) 2005 John Wiley & Sons, Ltd.
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    Palaeozoic deformation and magmatism in the northern area of the Anatolide block (Konya), witness of the Palaeotethys active margin
    (BIRKHAUSER VERLAG AG, 2004) Eren, Y; Kurt, H; Rosselet, F; Stampfli, GM
    The study area. located north of Konva (Central Turkey), is composed of Silurian to Cretaceous metamorphosed rocks. The lower unit of the oldest formation (Silurian-Early Permian) is mostly made up of Silurian-Early Carboniferous metacarbonates. These rocks pass laterally and vertically to Devonian-Early Permian series having continental margin, shallow water and pelagic characteristics. They are intruded or juxtaposed to different kinds of metamagmatic rocks. which show MORB. continental arc and within plate characteristics. The Palaeozoic units are covered unconformably by Triassic-Cretaceous metasedimentary units. All these rocks are overthrusted by Mesozoic ophiolites. The Palaeozoic sequence can be seen as a northern Palaeotethys passive, then active margin. The northward subduction of the Palaeotethys ocean during the Carboniferous-Triassic times, induced the development of a magmatic arc and fore-arc sequence (Carboniferous-Permian). Before the Early Triassic (?Late Permian) time. the fore-arc sequence was uplifted above sea level and eroded. The Triassic sequences are regarded as marking the onset of back-arc opening and detachment of the Anatolian Konya block from the active Eurasian margin. Finally. a suture zone formed during the Carman between the Konya region and the Menderes-Tauride Cimmerian block due to the closing of Palaeotethvs. This geodynamic evolution can be correlated with the evolution of the Karaburun sequence in western Turkey.