Tracking the timing of Neotethyan oceanic slab break-off: Geochronology and geochemistry of the quartz diorite porphyries, NE Turkey

The initiation of the break-off of the northern branch of the Neotethyan oceanic lithosphere is an important but poorly understood event in the geology of the Sakarya Zone (SZ) in northeastern Turkey. Although it is well-known that Latest Cretaceous intrusives (~70 Ma) and early Eocene adakitic magmatic rocks are present in the eastern SZ, the outcrops of the early Eocene non-adakitic rocks are very limited, and their tectono-magmatic evolution has not been studied. We describe a small outcrop of non-adakitic quartz diorite porphyry in the Kov area of the Gümüşhane region in northeastern Turkey. The genesis of these porphyries is significant in evaluating the syn- to post-collision-related magmatism. The LA-ICP-MS zircon U-Pb dating revealed that the Kov quartz diorite porphyries (KQDP) formed at ca. 50 Ma, coeval with adakitic rocks, and ~20 Myr later than the slab roll-back-related intrusive rocks. The KQDPs are calc-alkaline in composition and enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, Ti), with significant negative anomalies of Nb, Ta, and Ti but positive anomalies of Th, U, and Pb. Isotopic compositions of the samples show limited range of variation and slight enrichment of 87Sr/86Sr(t) (0.70489 to 0.70555), εNd(t) (−1.4 to −1.2) with TDM of 1.11 to 1.61 Ga. Pb isotopic ratios of the samples point to an enriched mantle source. They were likely crystallized from the melt that originated from an EM2-type spinel-facies subcontinental lithospheric mantle (SCLM), followed by the fractionation with insignificant crustal assimilation. The SCLM was metasomatically enriched, and the metasomatic agent was likely H2O-rich fluids rather than sediments released from subducting oceanic crust during the Late Cretaceous closure of the Neotethyan oceanic lithosphere. In conjunction with the geological background and previous data, we propose that the generation of the KQDPs resulted from a slab break-off event that caused ascending or infiltration of hot asthenosphere, triggering mantle melting. Such sporadic occurrences of the KQDPs, with coeval adakitic rocks in the SZ, are likely associated with the onset of extensional tectonics due to the earlier stage of slab break-off along the region during the early Eocene period.publishe

Comparison of the effects of different types of tube inserts on two-phase flow instabilities

Turbulence promoting inner elements such as rings, wings or winglets, twisted tapes, etc., is widely used in single- and two-phase flows. In this experimental work, the two-phase flow instabilities of forced convection boiling in a horizontal tube with ring- and twisted-tape-type inner elements inside are investigated. In order to analyze the two-phase flow of water, the experiments were conducted under a constant system pressure of 7.5 bar, and a constant heat input of 24 kW was applied to the outer surface of the circular test pipe with constant exit restriction. Three different inlet temperatures (Ti = 15, 25, and 35°C) were used to see the effect of inlet sub-cooling, and the mass flow rate was decreased from 110 to 20 g/s to obtain the characteristic curve. Two different pitch ratios for both the ring and twisted tape were evaluated in terms of stability. The results were evaluated in terms of appropriate variables for both the tube with insertions and the smooth tube. The analysis shows that the pressure drop increases with decreasing mass flow rate for all cases. The presence of the inner elements in the test pipe causes the boundaries of the oscillations to narrow in comparison with smooth tube. On the other hand, with the increase in the effective diameter of the test pipe the boundaries of the oscillations broaden. For each type of insertion, the increase of the pitch ratio makes the system less stable. © 2013 by Begell House, Inc

Magma interaction processes inferred from Fe-Ti oxide compositions in the Dölek and Sariçiçek plutons, Eastern Turkey

Magnetite-ulvöspinel and ilmenite-hematite solid solution intergrowths from the high-K calc-alkaline Dölek and Sar?çiçek plutons, Eastern Turkey, were investigated using microprobe analyses. Compositions of twenty-eight samples from the host rocks and their enclaves' in the plutons were used to estimate the oxygen fugacity and temperature. The ilmenite and ulvöspinel component exsolves out along certain preferred crystallographic planes in the titanomagnetite of the host rocks, while they are always absent in those of the mafic-microgranular enclaves. The titanomagnetite and ilmenite show variations as Mt98-70Usp02-30 and Ilm99-65Hm01-35 in composition, respectively. Estimations of oxygen fugacity and temperature using the titanomagnetite-ilmenite thermometry/oxygen barometry range from log/O2 of -15.30 to -20.48 in host rocks, log/O2 of -15.39 to -20.80 in the mafic microgranular enclaves and 617±6 to 758±23 °C in host rocks, 622±6 to 735±24 °C in the mafic microgranular enclaves, possibly indicating crystallisation temperature. Applying magnetite-ilmenite thermometry/ oxygen barometry to the granitoid rocks also involves microprobe analyses of ilmenite lamellae in titanomagnetite and this method yielded mean temperatures of 679±18 °C. The specific forms and chemical properties of Fe-Ti oxides, and similarities in crystallization temperature and oxygen fugacity of the host rocks and the mafic microgranular enclaves (MME) obtained from the Fe-Ti oxide pairs imply that thermal equilibrium probably occurred between two contrasted magmas, which mixed invarious proportion so that possibly a felsic and a more mafic magma interaction occurred in a convectively dynamic magma chamber during crystallization of the plutons. Probably, underplating may be responsible for genesis of the hybrid plutons. Thus, for mixing of coeval magmas derived from a lithospheric upper mantle (mafic end-member) and lower crust (felsic end-member), a thermal anomaly should be supplied. Upwelling of hot asthenospheric material result in thermal perturbation and melting of lithospheric mantle. Intrusion of hot lithospheric mantle-derived mafic magma then induced lower crustal melting, producing felsic melt. Mixing of the lower crust-derived melt and lithospheric mantle-derived magma formed the hybrid pluton. This process requires a post-collisional extensional tectonic setting during the Eocene in the Eastern Pontides. Copyright © TÜBİTAK

FINAL STRUCTURE & DESIGN PARAMETERS OF TARLA RF SYSTEM*

Abstract Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is an oscillator mode IR-FEL facility which is under construction since 2011. ELBE licensed superconducting modules housing TESLA RF cavities have been manufacturing for one year and the first module will be delivered in 2015. He Cryogenic System has also started to be manufacturing at similar time with the accelerator structures. It will be delivered in 2014. High Power RF amplifiers are started to tender procedures and delivery time is planning as 2015. The installation of high power transmission lines have to be completed at the same time with the delivery date of HPRF amplifiers to test the cavities and amplifiers. In this study, the final structural design of high power RF transmission lines and design parameters of RF amplifiers for TARLA is discussed

Gingival melanin pigmentation and its treatment with the CO 2 laser

PubMedID: 15529122Objective There are only a few reports in the literature evaluating the effects of the carbon dioxide (CO 2) laser on gingival melanin pigmentation (GMP). This study was performed to evaluate the effects of the CO 2 laser at superpulse mode, applied for gingival depigmentation. Study design GMP at the anterior maxillary and mandibular gingiva of 10 patients was treated using the superpulsed CO 2 laser (10 watts, 0.8 mm spot size, 20 Hz, 10 milliseconds). Pigmented areas were measured on pre- and postoperative standard digital images by the aid of an image- analyzing software. Statistical analysis of the data was performed by Mann Whitney U test. Results Ablation of the hyperpigmented gingiva was accomplished with minimal carbonization and almost no bleeding. Postoperative healing was uneventful with no significant postoperative pain. Two cases of partial repigmentation were observed during 24-month follow-up. Statistical analysis of the data revealed a significant difference between pre- and postoperative measurements of pigmented area. Conclusion Application of the superpulse mode of CO 2 laser appears to be an effective and safe method for the elimination of GMP

Re: The effect of prophylactic treatment with shohl's solution in children with cystinuria

[No abstract available