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    Ar-40/Ar-39 geochronology, elemental and Sr-Nd-Pb isotope geochemistry of the Neogene bimodal volcanism in the Yilkselen area, NW Konya (Central Anatolia, Turkey)
    (PERGAMON-ELSEVIER SCIENCE LTD, 2017) Korkmaz, Gulin Gencoglu; Asan, Kursad; Kurt, Huseyin; Morgan, Ganerod
    Bimodal volcanic suites occur in both orogenic and anorogenic geotectonic settings. Although their formation can be attributed to either fractional crystallization from basaltic parents to felsic derivatives or partial melting of different sources, the origin of bimodal suites is still unclear. By reporting mineral chemistry, Ar-40/Ar-39 geochronology, elemental and Sr-Nd-Pb isotope geochemistry data, this study aims to investigate the genesis of bimodal basalt-dacite association from the Ytikselen area located on the northern end of the Sulutas Volcanic Complex (Konya, Central Anatolia). The Ytikselen area volcanic rocks are represented by basaltic lava flows, and dacitic dome with enclaves and pyroclastics. Basaltic flows and pyroclastic rocks are interlayered with the Neogene fluviolacustrine sedimentary units, while dacitic rocks cut the pre-Neogene basement in the area. A biotite separation from dacites yielded Ar-40/Ar-39 plateau age of 16.11 +/- 0.18 Ma. On the other hand, a whole rock sample from basalts gave two plateau ages of 16.45 +/- 0.76 Ma and 22.37 +/- 0.65 Ma for the first steps and next steps, respectively. The investigated basalts are sodic alkaline, and characterized by ocean island basalt (OIB)-like anorogenic geochemical signatures. However, dacites are calc-alkaline and metaluminous, and carry geochemical signatures of orogenic adakites. Sr-Nd-Pb isotopic systematics suggest that the basalts were derived from an asthenospheric mantle source enriched by recycled crustal rocks. The dacites show more enriched Sr and Pb ratios and more depleted Nd ones relative to the basalts, which at the first glance might be attributed to crustal contamination of the associated basalts. However, trace element features of the dacites rule out cogenetic relationship between the two rock types, and point to an origin by melting of lower crust. On the other hand, enclaves share several elemental and isotopic characteristics with the dacites, and appear to be fragments of sub-volcanic intrusions closely related to the dacitic host magma. Based on the obtained geochemical data combined with the published geological and geophysical data, the investigated bimodal volcanic activity can be explained by slab break-off process in the convergence system between the African and Anatolian plates. (C) 2017 Elsevier Ltd. All rights reserved.
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    CHARACTERISTICS OF THE ALANYA UNIT METAMORPHITES, ALANYA-ANTALYA, TURKEY
    (INT SCIENTIFIC CONFERENCE SGEM, 2009) Kansun, Gursel; Bas, Halil; Asan, Kursad
    [Abstract not Available]
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    EARLY MIOCENE MILDLY-ALKALINE VOLCANISM IN THE KARACADAG AREA (CENTRAL ANATOLIA, TURKIYE)
    (INT SCIENTIFIC CONFERENCE SGEM, 2009) Asan, Kursad; Kurt, Huseyin
    In the Karacadag area (Central Anatolia, Turkiye), small volumes of mildly-alkaline lavas associated with large volumes of calcalkaline lavas crop out. 40Ar/39Ar age data indicate that the mildly-alkaline lavas were erupted during Early Miocene (ca. 18 Ma). The lavas are composed of alkali basalt, hawaiite, mugearite, benmoreite and trachydacite, and include olivine, ortho/clinopyroxene, amphibole, plagioclase, opaque and rare anorthoclase. The mildly-alkaline lavas have a sodic tendency (Na2O/K2O = 1.5-3.2) and resemble those of within-plate lavas. Alkali basalts of the suite were derived from a heterogeneous mantle source which is lithospheric mantle previously enriched by small degree melts from the astenosphere, plus possibly a depleted asthenospheric mantle. Melting modeling based on REE indicates that alkali basalts formed by 1-5 % partial melting of a spinet lherzolithic mantle source. Also, petrologic modeling based on trace element and isotopic data shows that fractional crystallisation played an important role in the evolution of the mildly-alkaline suite than AFC (assimilation and fractional crystallisation).
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    First Evidence of Lamprophyric Magmatism from the Konya Region, Turkey: a Genetic Link to High-K Volcanism
    (WILEY, 2013) Asan, Kursad; Erturk, M. Ali
    In the vicinity of Konya (Turkey), mafic, micro-porphyritic sub-volcanic rocks intrude into the Mesozoic units, which represents the only example of such a rock type in the region. Ar-40/Ar-39 dating of two whole rock samples from the sub-volcanics gave ages of 13.72 +/- 0.13 and 12.40 +/- 0.11 Ma, suggesting temporal association to the Late Miocene-Pliocene high-K calc-alkaline volcanism in the region. The mineral chemistry and geochemical data permit us to classify the rocks as minette lamprophyres. They include diopside and phlogopite phenocrysts in a microcrystalline groundmass composed of sanidine, phlogopite, diopside and titano-magnetite. Segregation and ocelli-like globular structures occur commonly in the samples. In terms of major elements, the lamprophyres are calcalkaline, and potassic to ultrapotassic rocks. All the lamprophyres display strong enrichments in LILE (Rb, Ba, K, Sr), radiogenic elements (Th, U) and LREE (La, Ce) and prominent negative Nb, Ta, and Ti anomalies on primordial mantle-normalized trace element diagrams. Geochemical data suggest that the lamprophyres and high-K calc-alkaline rocks in the region derived from a subduction-modified lithospheric mantle source affected by different metasomatic events. Lamprophyric magmatism sourced phlogopite-bearing veins generated by sediment-related metasomatism via subduction, but high-K calc-alkaline magmas are possibly derived from a mantle source affected by fluid-rich metasomatism.
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    Petrogenesis of the late Cretaceous K-rich volcanic rocks from the Central Pontide orogenic belt, North Turkey
    (WILEY, 2014) Asan, Kursad; Kurt, Huseyin; Francis, Don; Morgan, Ganerod
    Subduction-related volcanic rocks are widespread in the Central Pontides of Turkey, and represented by the Hamsaros volcanic succession in the Sinop area to the north. The volcanic rocks display high-K calc-alkaline, shoshonitic and ultra-K affinities. 40Ar/39Ar age data indicate that the rocks occurred during the Late Cretaceous (ca 82Ma), and the volcanic suites were coeval. Primitive mantle-normalized trace element patterns of all the lavas are characterized by strong enrichments in large ion lithophile elements (LILE) (Rb, Ba, K, and Sr), Th, U, Pb, and light rare earth elements (LREE; La, Ce) and prominent negative Nb, Ta, and Ti anomalies, all typical of subduction-related lavas. There is a systematic increase in the enrichment of incompatible trace elements from the high-K calc-alkaline lavas through the shoshonitic to the ultra-K lavas. In addition, the shoshonitic and ultra-K lavas have significantly higher 87Sr/86Sr (0.70666-0.70834) and lower 143Nd/144Nd (0.51227-0.51236) initial ratios than coexisting high-K calc-alkaline lavas (87Sr/86Sr 0.70576-0.70613, 143Nd/144Nd 0.51245-0.51253). Geochemical and isotopic data show that the shoshonitic and ultra-K rocks cannot be derived from the high-K calc-alkaline suite by any shallow level differentiation process, and point to a derivation from distinct mantle sources. The shoshonitic and ultra-K rocks were derived from metasomatic veins related to melting of recycled subducted sediments, but the high-K calc-alkaline rocks from a lithospheric source metasomatized by fluids from subduction zone.
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    Petrogenesis of the uckapl Granitoid and its Mafic Enclaves in Elmal Area (Nide, Central Anatolia, Turkey)
    (WILEY, 2013) Kurt, Huseyin; Kocak, Kerim; Asan, Kursad; Karakas, Mustafa
    The Late Cretaceous uckapl Granitoid including mafic microgranular enclaves intruded into metapelitic and metabasic rocks, and overlain unconformably by Neogene ignimbrites in the Nigde area of Turkey. It is mostly granite and minor granodiorite in composition, whereas its enclaves are dominantly gabbro with a few diorites in composition. The uckapl Granitoid is composed mainly of quartz, K-feldspar, plagioclase, biotite, muscovite and minor amphibole while its enclaves contain mostly plagioclase, amphibole, minor pyroxene and biotite. The uckapl Granitoid has calcalkaline and peraluminous (A/CNK= 1.0-1.3) geochemical characteristics. It is characterized by high LILE/HFSE and LREE/HREE ratios ((La/Lu)(N)= 3-33), and has negative Ba, Ta, Nb and Eu anomalies, resembling those of collision granitoids. The uckapl Granitoid has relatively high (SrSr(i))-Sr-87-Sr-86 ratios (0.711189-0.716061) and low epsilon Nd-(t) values (-5.13 to -7.13), confirming crustal melting. In contrast, the enclaves are tholeiitic and metaluminous, and slightly enriched in LILEs (K, Rb) and Th, and have negative Ta, Nb and Ti anomalies; propose that they were derived from a subduction-modified mantle source. Based on mineral and whole rock chemistry data, the uckapl granitoid is H-(hybrid) type, post-collision granitoid developed by mixing/mingling processes between crustal melts and mantle-derived mafic magmas.
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    Petrology and Geochemistry of Post-Collisional Early Miocene Volcanism in the Karacadag Area (Central Anatolia, Turkey)
    (WILEY-BLACKWELL, 2011) Asan, Kursad; Kurt, Huseyin
    Early Miocene (ca. 21-18 Ma) volcanism in the Karacadag area comprises three groups of volcanic rocks: (1) calcalkaline suite (andesitic to rhyolitic lavas and their pyroclastics), (2) mildly-alkaline suite (alkali basalt, hawaiite, mugearite, benmoreite and trachydacite), and (3) a single trachyandesitic flow unit. Field observations, (40)Ar/(39)Ar ages and geochemical data show that there was a progressive temporal transition from group 1 to 3 in a post-collisional tectonic setting. The cakalkaline suite rocks with medium-K in composition resemble those of subduction-related lavas, whereas the mildly-alkaline suite rocks having a sodic tendency (Na(2)O/K(2)O=1.5-3.2) resemble those of within-plate lavas. Incompatible element and Sr-Nd isotopic characteristics of the suites suggest that the lithospheric mantle beneath the Karacadag area was heterogeneously enriched by two processes before collision: (1) enrichment by subduction-related processes, which is important in the genesis of the calcalkaline volcanism, (2) enrichment by small degree melts from the astenosphere, which dominates the mildly alkaline volcanism. Perturbation of the enriched lithosphere by either delamination following collision and uplift or removal of the subducted slab following subduction and collision (i.e., slab breakoff) is the likely mechanism for the initiation of the post-collision volcanism.
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    The relationship between weathering and welding degree of pyroclastic rocks in the Kilistra ancient city, Konya (Central Anatolia, Turkey)
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) Bozdag, Ali; Bayram, A. Ferat; Ince, Ismail; Asan, Kursad
    Pyroclastic rocks used in both historical and modern structures are inevitably exposed to various weathering processes, leading to damage and destruction of them. To reduce the effects of weathering caused by various atmospheric effects, geologists need to know what processes are more effective and how they affect rock bodies. In this study, our aim is to show the relationship between the weathering and welding degree of pyroclastic rocks, sampled around the Ancient City of Kilistra in Konya (Central Anatolia, Turkey). For this purpose, we conducted field trips, and used petrographic and laboratory techniques such as, physico-mechanical tests and accelerated weathering tests (i.e., Freeze-Thaw, F-T; Wetting-Drying, W-D and Salt Crystallization, SC). Pyroclastic rocks around Kilistra ancient city comprise two different sub-units: the unwelded, lower pyroclastic unit (LPU) and the welded, upper pyroclastic unit (UPU). Following cycles of F-T and SC tests, we observed an increase in porosity values, but a decrease in uniaxial compressive strength values, which was more evident in unwelded-LPU samples. Also, the significant macroscopic textural changes occurred in LPU samples, linked to their unwelded nature. However, physico-mechanical features of both LPU and UPU samples were not significantly changed after W-D tests. Altogether, our findings show that welding degree is one of the main factors controlling weathering and physico-mechanical properties of pyroclastic rocks, and also F-T and SC are more effective processes than W-D on weathering. Accordingly, our approach here could be used to protect the endangered historical structures carved into pyroclastic rocks around the world. (C) 2016 Elsevier Ltd. All rights reserved.