Yaşar Kibici

Geochemical Constraints on the Genesis of the Günyüzü Pluton, Northwest Anatolia, Turkey

The Tavsanli Zone in northwest Turkey is intruded by many Late Cretaceous to Eocene (91-45 Ma) calc-alkaline granitoids, of which the Günyüzü pluton in the Eskisehir region is the least studied. The Günyüzü rocks are high-K, calc-alkaline (I-type) intrusions, and are comprised of diorite, granodiorite, granite, and granite porphyry. Typical minerals are plagioclase, K-feldspar, quartz, biotite, hornblende and Fe-Ti oxides. Chondrite-normalized REE patterns for the Günyüzü rocks are moderately fractionated and have small negative Eu anomalies. They are enriched in LILE and LREE relative to HFSE, showing characteristics of arc-related granitoids. Low values of molar K2O/Na2O, Al2O3/(FeO+MgO+TiO2), and (Na2O+K2O)/(FeO+MgO+TiO2) ratios demonstrate that the Günyüzü magma(s) were produced from mafic lower crustal rocks.

Collision‐related granite magma genesis, potential sources and tectono‐magmatic evolution: comparison between central, northwestern and western Anatolia (Turkey)

The central, northwestern and western Anatolian magmatic provinces are defined by a large number of late Mesozoic to late Cenozoic collision‐related granitoids. Calc‐alkaline, subalkaline and alkaline intrusive rocks in central Anatolia are mainly metaluminous, shoshonitic, I‐ to A‐types. They cover a petrological range from monzodiorite through quartz monzonite to granite/syenite, and are all enriched in LILE. Their geochemical characteristics are consistent with formation from a subduction‐modified mantle source. Calc‐alkaline plutonic rocks in northwestern Anatolia are mainly metaluminous, medium‐ to high‐K and I‐types. They are monzonite to granite, and all are enriched in LILE and depleted in HFSE, showing features of arc‐related intrusive rocks. Geochemical data reveal that these plutons were derived from partial melting of mafic lower crustal sources. Calc‐alkaline intrusive rocks in western Anatolia are metaluminous, high‐K and I‐types. They have a compositional range from granodiorite to granite, and are enriched in LILE and depleted in HFSE. Geochemical characteristics of these intrusive rocks indicate that they could have originated by the partial melting of mafic lower crustal source rocks.

Natural carbon black (Oltu-stone) from Turkey: a micro-Raman study

This study focuses on the characterization of a carbon black material from the Oltu-Erzurum region (traditionally called in Turkey “Oltu-stone” or “black-amber”), which is of interest in several fi elds, among these archaeometry and jewellery. Raman spectra were recorded between 50 and 3200 cm−1: measurements in a wide spectral range are the basis for effective characterization and identifi cation with respect to analogous materials. Correlations between the spectrum and the structure are discussed: two higher energetic Raman peaks at 1346 and 1585 cm–1 are characteristic of the crystalline carbon regions, whereas the weaker ones at 2654 and 2904 cm–1 are ascribed to amorphous carbon regions on the Oltu-stone surface. In addition, the enhanced background between 250 and 400 cm–1 could be associated with the presence of pyrite.

Photoluminescence Response from the Turkish Dentritic Agates

The three-dimensional photoluminescence emissions between 380 and 800 nm of the dentritic agate with white body color from the Dereyalak-İnönü-Eskişehir (Turkey) region were obtained at the temperatures between 250 and 340 K under 366 nm excitation. The most advantage of three-dimensional photoluminescence graphic in a silica structure is to demonstrate clearly all vibronic structures through temperature increasing on the spectra. Hence, photoluminescence response from the gem-quality material was discussed in relation to chemical impurities of trivalent rare earth elements. In the photoluminescence spectra, two strong and many weaker emission bands became clear at the lower temperature (250 K) conditions. First strong one is the purple band, and the highest emission peak is observed at 394 nm. Second strong one is the red band, and the highest emission peak is observed at 717 nm. The half-width of these main bands is approximately 17–19 nm, and such bands combination is typical for trivalent rare earth elements. Chemical analyses in this study show the abundances of many rare earth elements in the material. In order of abundance, they are yttrium (845 ppm), gadolinium (238 ppm), lutetium (196 ppm), dysprosium (45 ppm), neodymium (41 ppm), promethium (34 ppm), europium (18 ppm), and scandium (3 ppm). However, the two strong emission bands are, of course, due to yttrium and gadolinium ions, respectively. As a result, the intensities of these bands gradually decreased forming a sequence until the temperature of 280 K. Hence, the photoluminescence of the Turkish dentritic agates does not exist at higher temperatures, mainly because of high iron (40.000 ppm) abundance.