Browsing by Author "Uner, Tijen"

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The Ankara Melange: an Indicator of Tethyan Evolution of Anatolia
(Slovak Acad Sciences Geological inst, 2016) Cakir, Uner; Uner, Tijen
The Ankara Melange is a complex formed by imbricated slices of limestone block melanges (Karakaya and Hisarlikaya Formations), Neotethyan ophiolites (Eldivan, Ahlat and Edige ophiolites), post-ophiolitic cover units (Mart and Kavak formations) and Tectonic Melange Unit (Hisarkoy Formation or Derekoy Melange). The Karakaya and Hisarlikaya formations are roughly similar and consist mainly of limestone block melange. Nevertheless, they represent some important geological differences indicating different geological evolution. Consequently, the Karakaya and Hisarlikaya formations are interpreted as Eurasian and Gondwanian marginal units formed by fragmentation of the Gondwanian carbonate platform during the continental rifting of the Neotethys in the Middle Triassic time. During the latest Triassic, Neotethyan lithosphere began to subduct beneath the Eurasian continent and caused intense deformation of the marginal units. The Eldivan, Ahlat and Edige ophiolites represent different fragments of the Neotethyan oceanic lithosphere emplaced onto the Gondwanian margin during the Albian-Aptian, middle Turonian and middle Campanian, respectively. The Eldivan Ophiolite is a NE-SW trending and a nearly complete assemblage composed, from bottom to top, of a volcanic-sedimentary unit, a metamorphic unit, peridotite tectonites, cumulates and sheeted dykes. The Eldivan Ophiolite is unconformably covered by Cenomanian-Lower Turonian sedimentary unit. The Eldivan Ophiolite is overthrust by the Ahlat Ophiolite in the north and Edige Ophiolite in the west. The Ahlat ophiolite is an east-west oriented assemblage comprised of volcanic-sedimentary unit, metamorphic unit, peridotite tectonites and cumulates. The Edige Ophiolite consists of a volcanic-sedimentary unit, peridotite tectonites, dunite, wherlite, pyroxenite and gabbro cumulates. The Tectonic Melange Unit is a chaotic formation of various blocks derived from ophiolites, from the Karakaya and Hisarlikaya formations and from post-ophiolitic sedimentary units. It was formed during the collision between Anatolian Promontory and Eurasian Continent in the middle Campanian time.
Chemical Characterization of Patnos Scoria (Agri, Turkey) and Its Usability for Production of Blended Cement
(oficyna Wydawnicza Politechniki Wroclawskiej, 2012) Depci, Tolga; Efe, Tugba; Tapan, Mucip; Ozvan, Ali; Aclan, Mustafa; Uner, Tijen
This paper reports results of investigations on suitability of scoria (PTS), collected from Patnos (Agri) in Turkey, for blended cement production. Scoria (basic pumice) was chosen as cement replacement materials due to its availability and cost in Agri in Turkey. The portland cement was replaced by scoria within the range of 0, 5, 10, 20, 30, 40 and 50%. Characterization of scoria was subjected by the X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), BET surface area and porosity, zeta potential (zeta) and thin sections. The standard tests were conducted for the obtained fresh and hardened states of scoria blended cement paste. Furthermore, the obtained cements were characterized by the XRF. According to experimental results, scoria up to 20% ratio could be added into clinker and it has a good potential of manufacturing blended scoria cement.
Geochemistry and Origin of Plagiogranites From the Eldivan Ophiolite, Cankiri (Central Anatolia, Turkey)
(Slovak Acad Sciences Geological inst, 2014) Uner, Tijen; Cakir, Uner; Ozdemir, Yavuz; Arat, Irem
The Eldivan Ophiolite, exposed around Ankara and Cankiri cities, is located at the central part of the Izmir-Ankara-Erzincan Suture Zone (IAESZ). It represents fragments of the Neotethyan Oceanic Lithosphere emplaced towards the south over the Gondwanian continent during the Albian time. It forms nearly complete series by including tectonites (harzburgites and rare dunites), cumulates (dunites, wherlites, pyroxenites, gabbro and plagiogranites) and sheeted dykes from bottom to top. Imbricated slices of volcanic-sedimentary series and discontinuous tectonic slices of ophiolitic metamorphic rocks are located at the base of tectonites. Plagiogranitic rocks of the Eldivan Ophiolite are mainly exposed at upper levels of cumulates. They are in the form of conformable layers within layered diorites and also dikes with variable thicknesses. Plagiogranites have granular texture and are mainly composed of quartz and plagioclases. The occurrences of chlorite and epidote revealed that these rocks underwent a low grade metamorphism. Eldivan plagiogranites have high SiO2 content (70-75 %) and low K2O content (0.5-1 %) and display flat patterns of REE with variable negative Eu anomalies. LREE/HREE ratio of these rocks varies between 0.2-0.99. All members of the Eldivan rocks have high LILE/HFSE ratios with depletion of Nb, Ti and P similar to subduction related tectonic settings. Geochemical modelling indicates that the Eldivan plagiogranites could have been generated by 50-90 % fractional crystallization and/or 5-25 % partial melting of a hydrous basaltic magma.
Identification of Chrysotile in Local Soil at Beypinari Village (sivas-Turkey) Regarding Mine and Health Issue
(Springer india, 2016) Onal, Yunus; Depci, Tolga; Onal, Ayten; Onal, Ali; Uner, Tijen
Asbestos is dangerous for health and is forbidden to use in Turkey, but villagers who live in rural eastern part still use it especially for their home for insulation purposes and even as a substitute for baby powder. Therefore, geological and chemical properties of this type of soil, which is near the settlement, should be characterized and identified from the point of view of health. Beypinari asbestos deposits are located at Beypinari village, about 90 km southeast of Sivas, Turkey within Central Anatolian Ophiolites. Therefore, in the present study, the existence of chrysotile in Beypinari asbestos deposit were characterized and identified by mineralogical analysis and by major, trace, REE analysis. The results show that the samples contain different amount of calcite mineral, the main mineral being chrysotile.
Listwaenitization and Enrichment of Precious Metals in the Hydrothermal Mineralization Zones of Serpentinites in Sugecer-Van (Eastern Anatolia, Turkey)
(Geological Soc Publ House, 2020) Uner, Tijen
An ophiolitic complex containing hydrothermally altered serpentinized ultramafic rocks was studied in an area on the eastern side of Lake Van near the village of Sugecer, Eastern Anatolia. Field observations and petrographic and geochemical analyses clearly showed that the serpentinites were altered to listwaenites via silicification and carbonatization. The listwaenites were classified as type-I and type-II listwaenites based on their mineral composition. The type-I listwaenites contained carbonate minerals, rare serpentine minerals, chromite and mariposite, whereas the type-II listwaenites contained mainly silicate minerals. The listwaenites were enriched in Au, As, Cu, Ni and Co relative to the serpentinites. The listwaenites also showed chondrite-normalized enrichment in light rare earth elements and depletion in heavy rare earth elements. The effects of tectonism were widely observed in the study area. Mineral enrichment in the Sugecer region was shown to be associated with the transport of minerals by hydrothermal fluids under the influence of tectonism.
Multi-Stage Evolution of Forearc Mantle Peridotites of Kagizman Ophiolite (agri-Eastern Anatolia)
(Pergamon-elsevier Science Ltd, 2020) Uner, Tijen
The Kagizman Ophiolite, constituting the easternmost part of Tethys ophiolites in Anatolia, is located on the Izmir-Ankara-Erzincan ophiolitic belt. Ophiolitic rocks include a range of mantle peridotites, gabbros, pillow basalts and isolated sheeted dykes. The studied mantle peridotites are investigated with regard to geochemical and petrographical characteristics. MgO content of peridotites varies from 41.24 to 45.63 wt % while that of Al2O3 is in the range of 0.20-0.32 wt % indicating a high partial melting degree. Highly depleted mantle peridotites represent residues of primitive mantle formed by 17-23% melting. Whole rock trace element patterns point to variable partial melting conditions. Petrographical and geochemical results reveal that mantle peridotites of Kagaman Ophiolite are the residues of two-stage partial melting process. The first melting (consuming) stage occurred in a mid-ocean ridge setting which was later metasomatized in a subduction zone by interaction between peridotites and fluids derived from the subducted crust. According to all data, these rocks are hypothesized as forearc peridotites affected by high degree partial melting.
Supra-Subduction Zone Mantle Peridotites in the Tethyan Ocean (East Anatolian Accretionary Complex-Eastern Turkey): Petrological Evidence for Melting and Melt-Rock Interaction
(Springer Wien, 2021) Uner, Tijen
The East Anatolian Accretionary Complex formed as a result of the natural process of collision between the Arabian and Eurasian plates and the subduction of the Neotethys oceanic lithosphere located between them, covers a broad area, largely east of Lake Van. This study presents new information about the formation environment of mantle peridotites located within the East Anatolian Accretionary Complex and its rock-melt interactions. According to petrographic and geochemical investigations, peridotites comprise olivine, orthopyroxene, and chromite with low modal content in clinopyroxene (<1 vol%) while whole rock geochemical data indicates that they contain a high MgO (40.56-43.31 wt%) and low Al2O3 (0.16-0.48 wt%) and CaO (0.02-0.38 wt%) content. These values show that these rocks have a high degree of depletion, revealing typical arc peridotite features. Studies on olivine and pyroxene minerals, which are commonly observed in peridotites, show that these rocks are related to the arc. When peridotites are normalized to chondrite, partial enrichment takes place in light and heavy rare earth elements, while partial depletion occurs in medium rare earth elements. The enrichment of the rare earth elements is considered sufficient proof that the mantle peridotites underwent a boninitic mantle-induced enrichment during subduction. Analysis of chromites in the main melt, and its contents (Al2O3, TiO2 and FeO/MgO) suggest boninitic effects in peridotites. All data obtained from peridotites reveal formation of a subduction zone within the Neotethys oceanic lithosphere with an advanced degree of melting leading to re-enrichment of forearc peridotites in advancing periods. These features compare with southern Neotethys and Iran ophiolites.