Abidin Temel

Neogene ignimbrites of the Nevsehir plateau (Central Turkey): stratigraphy, distribution and source constraints

Abstract In Anatolia (Turkey), extensive calc-alkaline volcanism has developed along discontinuous provinces from Neogene to Quaternary times as a consequence of plate convergence and continental collision. In the Nevsehir plateau, which is located in the Central Anatolian Volcanic Province, volcanism consists of numerous monogenetic centres, several large stratovolcanoes and an extensive, mainly Neogene, rhyolitic ignimbrite field. Vent and caldera locations for the Neogene ignimbrites were not well known based on previous studies. In the Neogene ignimbrite sequence of the Nevsehir plateau, we have identified an old group of ignimbrites (Kavak ignimbrites) followed by five major ignimbrite units (Zelve, Sarimaden Tepe, Cemilkoy, Gordeles, Kizilkaya) and two smaller, less extensive ones (Tahar, Sofular). Other ignimbrite units at the margin of the plateau occur as outliers of larger ignimbrites whose main distributions are beyond the plateau. Excellent exposure and physical continuity of the units over large areas have allowed establishment of the stratigraphic succession of the ignimbrites as, from bottom to top: Kavak, Zelve, Sarimaden Tepe, Cemilkoy, Tahar, Gordeles, Sofular, Kizilkaya. Our stratigraphic scheme refines previous ones by the identification of the Zelve ignimbrite and the correlation of the previously defined ‘Akkoy’ ignimbrite with the Sarimaden Tepe ignimbrite. Correlations of distant ignimbrite remnants have been achieved by using a combination a field criteria: (1) sedimentological characterisitics; (2) phenocryst assemblage; (3) pumice vesiculation texture; (4) presence and characteristics of associated plinian fallout deposits; and (5) lithic types. The correlations significantly enlarge the estimates of the original extent and volume of most ignimbrites: volumes range between 80 km 3 and 300 km 3 for the major ignimbrites, corresponding to 2500–10,000 km 3 in areal extent. The major ignimbrites of the Nevsehir plateau have an inferred source area in the Derinkuyu tectonic basin which extends mainly between Nevsehir and the Melendiz Dag volcanic complex. The Kavak ignimbrites and the Zelve ignimbrite have inferred sources located between Nevsehir and Derinkuyu, coincident with a negative gravity anomaly. The younger ignimbrites (Sarimaden Tepe, Cemilkoy, Gordeles, Kizilkaya) have inferred sources clustered to the south between the Erdas Dag and the Melendiz Dag volcanic complex. We found evidence of collapse structures on the northern and southern flanks of the Erdas Dag volcanic massif, and of a large updoming structure in the Sahinkalesi Tepe massif. The present-day Derinkuyu tectonic basin is mostly covered with Quaternary sediments and volcanics. The fault system which bounds the basin to the east provides evidence that the ignimbrite volcanism and inferred caldera formation took place in a locally extensional environment while the basin was already subsiding. Drilling and geophysical prospecting are necessary to decipher in detail the presently unknown internal structure of the basin and the inferred, probably coalesced or nested, calderas within it.

Pb-Nd-Sr isotope and trace element geochemistry of Quaternary extension-related alkaline volcanism: a case study of Kula region (western Anatolia, Turkey)

Abstract The Quaternary alkaline volcanism of Kula is located in a western Anatolian graben system that resulted from an Aegean extensional regime. The typically silica-undersaturated, alkaline lavas of Kula are distinguished in three different sequences, namely Burgaz, Elekcitepe and Divlittepe, with a range of basanite, tephrite and phonotephrite compositions. To evaluate the source characteristics of the Kula lavas, rare earth elements as well as Sr, Nd and Pb isotopic compositions were determined. The volcanic rocks show significant enrichment in high field strength elements (such as Nb and Ta) and large ion lithophile elements. Furthermore, they exhibit high Nb/Y (>3) ratios, which are typical characteristics of within-plate alkaline volcanic rocks. However, the Rb, Ba, Sr, Nb and Ta contents and Rb/Nb and K/Nb ratios of the Kula lavas are considerably higher than in typical ocean island basalts (OIB), implying a contribution of lithospheric mantle in their genesis. Isotopic compositions of 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb for the Kula lavas range from 0.703029 to 0.703490, from 0.512773 to 0.512941, from 18.689 to 19.064, from 15.606 to 15.683 and from 38.560 to 39.113, respectively. Assimilation and fractional crystallisation modelling indicates that crustal contamination does not play a significant role in the evolution of the Kula lavas but that they evolved via fractional crystallisation processes. Elemental variations are also related to fractional crystallisation. The geochemical characteristics of the Kula lavas suggest a contribution from two mantle sources: (1) mainly an OIB-like asthenospheric component and (2) a limited contribution from a lithospheric mantle component. The volcanism of Kula is linked to an extensional setting in western Anatolia that developed during Late Miocene–Pliocene. It is correlated to the thinning of the crust in a post-collision period and concomitant with the upwelling of the underlying upper mantle.

Ignimbrites of Cappadocia (Central Anatolia, Turkey): petrology and geochemistry

Abstract In Cappadocia (Central Anatolia, Turkey), high-K calc-alkaline volcanic rocks have a volume of at least 1000 km3 and cover an area of about 40,000 km2. Rhyolitic to dacitic ignimbrites and two andesitic lava flows were erupted from Upper Miocene (11.2 Ma) to Quaternary times, in relation to the collision of the Arabian and Eurasian plates. K-rich rhyolitic and locally Na-rich dacitic ignimbrites are commonly intercalated with lacustrine sediments and, more rarely, with andesitic lava flows. Each ignimbrite exhibits its own mineralogical association and trace-element chemistry that enable stratigraphic correlations (i.e., Rb and Sr or Fe, Mg, Mn and Ti contents of biotite). Geochemical data (major, trace elements and Sr–Nd isotopes) show that the origin of the studied volcanic units can be related to fractional crystallisation of a mantle-derived magma. However, crustal contamination is also thought to be a major process that evolved through time. From Miocene (11.2 Ma) to Quaternary times, the ignimbritic rocks exhibit a drastic decrease of 87 Sr / 86 Sr ratio which may be linked with the transition from collisional to extensional tectonics.

Petrogenetic modelling of Quaternary post-collisional volcanism: a case study of central and eastern Anatolia

Extensive continental collision-related volcanism occurred in Turkey during Neogene–Quaternary times. In central Anatolia, calc-alkaline to alkaline volcanism began in the Middle–Late Miocene. Here we report trace elemental and isotopic data from Quaternary age samples from central and eastern Anatolia. Most mafic lavas from central Anatolia are basalt and basaltic andesite, with lesser amounts of basaltic trachyandesite and andesite. All magma types exhibit enrichment in LILE (Sr, Rb, Ba and Pb) relative to HFSE (Nb, Ta). Trace element patterns are characteristic of continental margin volcanism with high Ba/Nb and Th/Nb ratios. 87Sr/86Sr and 143Nd/144Nd isotopic ratios of central Anatolian lavas range between 0.704105–0.705619 and 0.512604–0.512849, respectively. The Quaternary alkaline volcanism of eastern Anatolia has been closely linked to the collision between the Arabian and Eurasian plates. Karacadag and Tendurek volcanic rocks are represented by alkali basalts and basaltic trachyandesites, respectively. As expected from their alkaline nature, they contain high abundances of LIL elements, but Tendurek lavas also show depletion in Nb and Ta, indicating the role of crustal contamination in the evolution of these magmas. 87Sr/86Sr and 143Nd/144Nd ratios of the Karacadag and Tendurek lavas range from 0.703512 to 0.704466; 0.512742 to 0.512883 and 0.705743 to 0.705889 and 0.512676, respectively. Petrogenetic modelling has been used to constrain source characteristics for the central and eastern Anatolian volcanic rocks. Trace element ratio plots and REE modelling indicate that the central Anatolian volcanism was generated from a lithospheric mantle source that recorded the previous subduction events between Afro-Arabian and Eurasian plates during Eocene to Miocene times. In contrast, The Karacadag alkaline basaltic volcanism on the Arabian foreland is derived from an OIB-like mantle source with limited crustal contamination. Tendurek volcanism, located on thickened crust, north of the Bitlis thrust zone, derived from the lithospheric mantle via small degrees (1.5 %) of partial melting.

Bioinorganic Magnetic Core−Shell Nanocomposites Carrying Antiarthritic Agents: Intercalation of Ibuprofen and Glucuronic Acid into Mg−Al−Layered Double Hydroxides Supported on Magnesium Ferrite

This paper describes the synthesis and characterization of a composite constituted by an antiarthritic agent (AA) intercalated into a layered double hydroxide (LDH) supported on magnesium ferrite. Core-shell nanocomposites were prepared by depositing Mg-Al-NO(3)-LDH on a MgFe(2)O(4) core prepared by calcination of a nonstoichiometric Mg-Fe-CO(3)-LDH. Intercalation of ibuprofen and glucuronate anions was performed by ion-exchange with nitrate ions. The structural characteristics of the obtained products were investigated by powder X-ray diffraction, element chemical analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Morphologies of the nanocomposite particles were examined by scanning electron microscopy and transmission electron microscopy. The products were shown to intercalate substantial amounts of AA with enhanced thermal stabilities. Room-temperature magnetic measurements by vibrating sample magnetometry revealed that the products show soft ferromagnetic properties suitable for potential utilization in magnetic arthritis therapy.

Petrological and geochemical characteristics of Cenozoic high-K calc-alkaline volcanism in Konya, Central Anatolia, Turkey

Abstract Late Miocene to Pliocene volcanic rocks outcrop west, northwest and southwest of the Konya area in Central Anatolia, Turkey. Volcanic products are lava domes, nuee ardentes and ignimbrite deposits, predominantly andesitic to dasitic in composition, together with rare basalt, basaltic andesite, basaltic trachyandesite and trachyandesite (50.35–69.39% SiO2). The serie exhibits high-K calc-alkaline affinities. Fractional crystallization of pyroxene, plagioclase and Fe–Ti oxides is the main process in the magmatic evolution of Konya volcanic rocks. Volcanic units exhibit typical high-K calc-alkaline character. Their geochemical characteristics (e.g., enrichments in LIL elements such as K, Rb, Ba, Sr, depletion in HFSE such as Ti, Nb, and high Ba/Nb and Low Nb/Y ratios) are consistent with those of active continental margin regions. High 87 Sr/ 86 Sr (0.704841–0.707340) and low 143 Nd/ 144 Nd (0.512390–0.512618) ratios suggest crustal involvement in their petrogenesis. Correlations between 86 Sr/ 87 Sr isotope with Rb, Rb/Nb, Rb/Ba, and Rb/Sr also emphasize the effect of crustal contamination on the andesitic and dacitic magmas. As a consequence, Konya volcanic rocks are products of assimilation and fractional crystallization (AFC) processes of a magma which seems to be linked to the subduction of the African plate underneath the Anatolian plate during Miocene.

Petrology and geochemistry of potassic rocks in the Gölcük area (Isparta, SW Turkey): genesis of enriched alkaline magmas

Abstract The Lower Pliocene volcanic rocks occurring in the Golcuk area of SW Turkey exhibit alkaline major element trends with a general potassic character. The development of volcanism can be divided into 2 major stages such as trachytic ancient lavas/domes and tephriphonolitic, trachyandesitic to trachytic Golcuk eruptions (ignimbrites, lava/dome extrusions, phreatomagmatic deposits, and finally, young domes). Volcanic rocks consist primarily of plagioclase, clinopyroxene (which ranges in composition from diopside to augite and are commonly zoned), biotite, and phlogopite. Amphibole phenocrysts are restricted to the pyroclastic deposits. Pseudoleucites are also seen only in the lava/dome extrusions. Oxides and apatites are common accessory phenocryst phases. As would be expected from their potassic–alkaline nature, the volcanic rocks of the Golcuk area contain high amounts of LILE (Ba, Sr, Rb and K), LREE, and Zr. Concentrations of compatible elements such as Cr, Ni and V are very low, possibly indicating fractionation of olivine and clinopyroxene. Correlation of SiO2, Rb/Sr and MgO with 87 Sr / 86 Sr (0.703506–0.704142) exhibit an increasing trend in the direction of crustal contamination. However, the isotopic compositions of Sr are not as high to indicate a high level of crustal contamination. Geochemical data are consistent with the derivation of Golcuk volcanic rocks from a metasomatized and/or enriched lithospheric mantle source during crustal extension in the area. This metasomatism was probably occurred by fluids released from the northward subduction between African and Eurasian plates during Tertiary, as the Golcuk volcanic rocks display features of island-arc magmas with having high Ba/Nb (>28) ratios, and Nb and Ti depletions. Lower Pliocene volcanism in the Golcuk was response to extensional tectonics.

Major-element, trace-element, and Sr-Nd isotopic geochemistry and genesis of Varto (Muş) volcanic rocks, Eastern Turkey

Abstract Major-element, trace-element and Sr–Nd isotopic data are presented for the Upper Miocene–Quaternary Varto volcanic rocks (Eastern Turkey) and their relationship to the regional tectonic regime were investigated in this study. The Varto volcanic rocks are located in the eastern part of the North Anatolian Fault Zone (NAFZ), in the East Anatolian Convergence Region (EACR). Volcanic rocks are subdivided into two groups: Lower Volcanic Units (LVU) and Upper Volcanic Units (UVU). These volcanic rocks are composed of volcaniclastics and lavas of both alkaline and calc-alkaline characters. LVU lavas are dacite, andesite, trachyte, basaltic andesite, benmoreite, and mugearite, whereas UVU lavas are basalt, basaltic andesite, mugearite, hawaite, benmoreite, and basanite in composition. Variation diagrams of SiO2 with major- and trace-elements are consistent with fractional crystallization process involving olivine, plagioclase, pyroxenes, and Fe–Ti oxides. Both units appear to be on the same fractionation trend, implying similar origins, but different degrees of evolution. Correlation between Sr–Nd isotopes with SiO2, MgO, Rb/Sr, 100/Sr, and Nd/Sm emphasize the effect of crustal contamination on these volcanic rocks. Sr–Nd isotopic data plot along the mantle array. However, rocks of Lower and Upper Volcanic Units are isotopically distinct. UVU have relatively low 87 Sr / 86 Sr (0.70334–0.70466) and high 143 Nd / 144 Nd ratios (0.51279–0.51288), which plot in the field of Oceanic Island basalts, Ararat lavas and the Eastern Anatolian alkaline province; in contrast, LVU exhibit higher 87 Sr / 86 Sr (0.70438–0.70507) and lower 143 Nd / 144 Nd (0.51265–0.51276) ratios. All the Varto volcanic rocks are products of mantle-derived magma and have experienced assimilation and fractional crystallization (AFC) during uprise through the continental crust, and formed in a within-plate environment along the Eastern part of the NAFZ that is closely related to deep lithospheric fractures.

Chemical and Ultramorphologic Effects of Ethylenediaminetetraacetic Acid and Sodium Hypochlorite in Young and Old Root Canal Dentin

OBJECTIVES The objectives of this study were to evaluate and compare the time-dependent chemical and ultramorphologic effects of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) in young and old dentin. METHODS Sixty-four teeth scheduled for extraction were collected from young (<30 years) and old (>60 years) patients. In 48 teeth, the dentin was reduced to a powder state and treated with EDTA or EDTA + NaOCl for 1 and 10 minutes, respectively. X-ray diffraction analysis was used to determine the changes in the composition of dentin through dissolution of hydroxyapatite (HAp). In the remaining teeth (n = 16), the root canals were prepared, bisected, and subjected to the same time-dependent treatment regimens. The changes in the number and area of dentinal tubules were calculated by image analysis. The data were analyzed statistically by paired t test and one-way analysis of variance, followed by Tukey honestly significant difference test at P = .05. RESULTS In both young and old dentin, EDTA significantly decreased the HAp intensity at 1 and 10 minutes, whereas EDTA + NaOCl only decreased that of old dentin at 10 minutes. Pair-wise comparisons revealed that in old dentin, the reduction in HAp intensity after treatment with EDTA and EDTA + NaOCl was significantly greater at 10 minutes than at 1 minute, whereas in young dentin, a significant decrease was only observed in the EDTA/10-minute subgroup. Compared with their 1-minute counterparts, 10-minute treatment with EDTA + NaOCl significantly increased the tubular diameter and tubular area of old dentin. In young dentin, the tubular area and diameter values were not affected by treatment time (P > .05). CONCLUSIONS In young root dentin, 10-minute treatment with EDTA + NaOCl does not significantly alter the chemical and ultramorphologic structure and thus appears to be unnecessary. In old dentin, extended treatment time with EDTA + NaOCl should be avoided owing to excessive demineralization and erosion. In both types of dentin, EDTA was not effective in complete removal of the smear layer.

Quaternary Tholeiitic to Alkaline Volcanism in the Karasu Valley, Dead Sea Rift Zone, Southeast Turkey: Sr-Nd-Pb-O Isotopic and Trace-Element Approaches to Crust-Mantle Interaction

Rare-earth-element, radiogenic and oxygen isotope, and mineral chemical data are presented for tholeiitic and alkaline Quaternary volcanism from Karasu Valley (Hatay, southeastern Turkey). Karasu Valley is the northern segment of the Dead Sea transform fault and is filled with flood-basalt type volcanics of Quaternary age. This valley is an active fault zone that is known as “Karasu fault,” extending in a NE-SW direction. The Karasu Valley basaltic volcanics (KVBV) are subaphyric to porphyritic, with variable amounts of olivine, clinopyroxene, and plagioclase phenocrysts. Alkali basalts are generally characterized by high contents of olivine, clinopyroxene, and plagioclase phenocrysts. Their groundmass contains olivine, clinopyroxene, plagioclase, and Fe-Ti oxides. Tholeiitic basalts are subaphyric to porphyritic (high contents of olivine, clinopyroxene, and plagioclase). Their groundmass is similar to that of alkali basalts. The range of olivine phenocryst and microlite compositions for all analyzed samples is Fo81 to Fo43. Plagioclase compositions in both tholeiitic and alkali basalts range from andesine, An38 to bytownite, An72. Clinopyroxene compositions range from diopside to calcic augite. Most of the olivine, plagioclase, and clinopyroxene phenocrysts are normally zoned and/or unzoned. Fe-Ti oxides in both series are titanomagnetite and ilmenite. Based on normative and geochemical data, the Karasu Valley basaltic volcanics are mostly olivine and quartz-tholeiites, and relatively lesser amount of alkali olivine-basalts. KVBV have low K2O/Na2O ratios, typically between 0.25 and 0.45. Olivine- and quartz-tholeiites are older than alkali olivine-basalts. Olivine tholeiites have Zr/Nb and Y/Nb ratios similar to alkaline rocks, but their Ba/Nb, Ba/La, and La/Nb ratios are slightly higher than alkali olivine-basalts. In contrast, quartz-tholeiites have the highest Ba/Nb, Ba/La, Zr/Nb, and Y/Nb and the lowest Nb/La ratios among the KVBV. Alkali basalts have 87Sr/86Sr and 143Nd/144Nd ratios ranging from 0.703353 to 0.704410 and 0.512860 to 0.512910, respectively. In contrast, quartz-tholeiites have higher 87Sr/86Sr and lower 143Nd/144Nd ratios, which vary from 0.704410 to 0.705490 and 0.512628 to 0.512640, respectively. Olivine tholeiites have intermediate isotopic compositions ranging from 0.703490 to 0.704780 and 0.512699 to 0.512780, respectively. 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb isotopic ratios of KVBV range from 18.817 to 19.325, 15.640 to 15.718, and 39.054 to 39.223, respectively. The range of O isotope values is between +5.84 and +7.97‰. The higher O and Sr isotopes in olivine- and quartz-tholeiites relative to alkali olivine-basalts can be explained by contamination of magmas by crustal materials. The KVBV have intraplate chemistry similar to that of other tholeiitic and alkaline basalts in other within-plate environments, and isotopes range from isotopically depleted mantle to enriched isotope compositions similar to some enriched ocean islands. Trace-element and isotope data indicate that the KVBV are derived from a common OIB-like asthenospheric mantle source, but they have experienced different degrees of crustal contamination during their ascent to the surface, contemporaneous with little fractional crystallization. Although quartz-tholeiites display significant effects of crustal contamination, alkali olivine-basalts appear to have negligible or no crustal contamination in their geesis.