Ibrahim Uysal

Geochemical modelling of early Eocene adakitic magmatism in the Eastern Pontides, NE Anatolia: continental crust or subducted oceanic slab origin?

Early Eocene adakitic volcanic and granitoid rocks are widespread in the Eastern Pontides of NE Turkey, providing significant constraints for the early Cenozoic tectonomagmatic evolution of the region. These adakitic rock units exhibit relatively high Sr/Y and La/Yb ratios, but low Y and Yb values, similar to modern adakites generated by partial fusion of a subducted oceanic slab. They also have high K2O and low MgO contents, and show moderately enriched ISr and low ϵNd(t) isotopic signatures. Our trace element modelling suggests that these adakitic magmas were generated from partial melting at low pressures of a garnet-bearing amphibolitic source in the continental lower crust. This lower crustal melting resulted from slab break off-induced asthenospheric upwelling and related magmatic underplating beneath the Eastern Pontides. We interpret this melting event and the adakitic magmatic activity as a syn- to post-collisional process involving early Cenozoic collision of the Pontide and Anatolide–Tauride continental blocks. The geochemical and tectonic constraints presented here indicate that early Eocene adakitic magmatism in the Eastern Pontides did not result from partial fusion of a subducted oceanic slab, but instead represent continental-type adakite formation.

Melt Penetration in Oceanic Lithosphere: Li Isotope Records from the Pozantı-Karsantı Ophiolite in Southern Turkey

Understanding melt penetration in ophiolites is important in revealing the formation and evolution of the oceanic lithosphere, as well as the formation of chromite deposits. We conducted in situ Li isotope analysis of olivine grains from the harzburgite, podiform chromitite and dunite envelope of the mantle sequence, and dunite and wehrlite cumulates from the crustal sequence of the Pozantı-Karsantı ophiolite. Olivine in the different rocks has variable and distinctive Li concentrations (0.95 to 2.01 ppm) and δLi The Author 2018. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com Downloaded from https://academic.oup.com/petrology/advance-article-abstract/doi/10.1093/petrology/egy023/4911783 by University of Manchester user on 27 February 2018

Subduction Initiation for the Formation of High-Cr Chromitites in the Kop Ophiolite, NE Turkey

fragment of Neo-Tethys ocean, mainly consists of a paleoMoho transition zone (MTZ) and a harzburgitic upper mantle unit. The Kop MTZ locally contains cumulate dunite and high-Cr chromitites (Cr up to ca. 79), which are cut by pyroxenites. Dunites and chromitites in the MTZ have lower REE concentrations than the primitive mantle by 1-2 orders of magnitudes; their REE patterns vary from depleted to concave shapes. These features probably reflect that the cumulate rocks were produced by magmas derived from depleted mantle, and their concave REE patterns were the modification products of LREEenriched fluids. Clinopyroxenes from pyroxenites are diopsidic and featured by high Mgs (ca. 92-96) and CaO contents (ca. 24%-25%); their Al2O3 contents (1.0-3.0 wt.%) fall between those of clinopyroxenes in N-MORB and komatiite/boninite, suggesting the parental melts originated from more refractory mantle than abyssal lherzolite. However, these clinopyroxenes display depleted REE patterns highly consistent with those of clinopyroxenes in abyssal lherzolites, indicating their genetic connection with decompression melting of asthenosphere. The cross-cutting relationship between pyroxenite veins and chromitiferous rocks suggests depleted mantle still remained beneath the proto-forearc after chromitite formation; they had not been remarkably modified by slab-derived components and continued interacting with asthenosphere before pyroxenites were generated. This study offers a temporal constraint on the formation of high-Cr chromitites in the Kop ophiolite; they were possibly formed around the transition period between early and late proto-forearc spreading, during which subduction dehydration had not well developed. ZHANG Pengfei, Ibrahim UYSAL, ZHOU Meifu, SU Benxun and Erdi AVCI, 2016. Subduction Initiation for the Formation of High-Cr Chromitites in the Kop Ophiolite, NE Turkey. Acta Geologica Sinica (English Edition), 90(supp. 1): 253.

Öğretmen Adaylarının Ölçme ve Değerlendirme Konusundaki Öz-Yeterlik Algılarının İncelenmesi

Bu calismanin amaci, ogretmen adaylarinin olcme ve degerlendirme konusundaki oz-yeterlik algilarini cinsiyet, sinif, bolum ve ogretim durumu degiskenleri acisindan incelemektir. Tarama modelinin kullanildigi bu calismada, arastirma grubunu 2012-2013 egitim-ogretim yili bahar doneminde Abant Izzet Baysal Universitesi Egitim Fakultesinde ogrenim gormekte olan 181 ogretmen adayi olusturmaktadir. Calismada veri toplama araci olarak Kilinc (2011)’in gelistirdigi “Ogretmen Adaylarinin Egitimde Olcme ve Degerlendirmeye Yonelik Oz Yeterlik Algi Olcegi” kullanilmistir. Verilerin analizinde cinsiyet, ogretim durumu (I. ve II.ogretim) ve sinif duzeyi faktorlerinin olcme ve degerlendirme konusundaki oz-yeterlige etkisi bagimsiz orneklemler icin t testi; sinif degiskeninin olcme ve degerlendirme konusundaki oz-yeterlige etkisi ise tek yonlu Anova ile incelenmistir.. Arastirma sonucunda ogretmen adaylarinin olcme ve degerlendirmeye yonelik oz-yeterlik algilarinin cinsiyet, ogretim durumu, sinif degiskeni ve bolum degiskenlerine gore istatistiksel olarak onemli bir farklilik gostermedigi sonucuna ulasilmistir.