Yazarlar
- Kaygusuz, Abdullah(3)
- Anvarjonovich, Abdullayev Lochinbek(1)
- Aral, Zehra Deveci(1)
- Arslan, Mehmet(1)
- Aslan, Zafer(1)
- Aydingakir, Emre(1)
- Dovronovich, Mamarozikov Usmonjon(1)
- Dönmez, Cahit(1)
- Gücer, Mehmet Ali(1)
- Günay, Kurtulus(1)
- Ilbeyli, Nurdane(1)
- Maqsud, Isoqov(1)
- Maripova, Saodat(1)
- Movlanov, Jakhongir(1)
- Parlak, Osman(1)
- Saka, Samet(1)
- Satir, Muharrem(1)
- Siebel, Wolfgang(1)
- Sipahi, Ferkan(1)
- Yagcioglu, Kiymet Deniz(1)
- Yildirim, Esra(1)
- Yildirim, Nail(1)
- Şen, Cüneyt(1)
Yayınlar
- MakaleAçık Erişim2025Chromitites of Teskuduk and Nurata Ophiolites (Southern Tien Shan Belt, Uzbekistan): Geochemical characteristics and implications of chromitite genesis
Dönmez, Cahit; Aral, Zehra Deveci; Saka, Samet; Günay, Kurtulus; Yildirim, Nail; Yildirim, Esra; Yagcioglu, Kiymet Deniz; Maqsud, Isoqov; Movlanov, Jakhongir; Dovronovich, Mamarozikov Usmonjon
The Central Asian Orogenic Belt's ophiolites lack a full ophiolitic succession and instead occur as irregular fragments and slices in tectonic melanges and accretionary complexes. The Teskuduk and Northern Nurata ophiolites in Uzbekistan comprise extensively serpentinized mantle rocks that contain minor podiform chromitites, situated in the western area of the southern Tien Shan belt. Chromites in this region are found in a very limited area, and this study aims to determine the geochemical properties and formation environments of chromites by conducting geochemical studies on a limited number of recently discovered chromitites. In this context, mineral chemistry and platinum group element (PGE) geochemistry analyses were carried out on chromites. For Teskuduk chromitites, the Cr2O3, Al2O3, and TiO2 contents range from 53.2 to 55.7wt%, 11.1 to 12.7wt%, and 0.14 to 0.20 wt%, respectively, whereas for Nurata chromitites, the corresponding values range from 36.2 to 37.2 wt%, 23.1 to 30.2 wt%, and 0.10 to 0.30 wt%. The Teskuduk and Nurata chromitites contain a total average of 370 ppb and 117 ppb PGEs, respectively. They are classified as unfractionated chromitites, with low Pd/Ir ratios (0.03-0.20). These chromitite samples have chondrite-normalized PGE patterns that are identical to Cr-rich mantle-derived chromitites found in subduction-related ophiolites. Collectively, these data suggest that the Teskuduk ophiolites formed in a forearc setting, whereas the Nurata ophiolites evolved in a back-arc setting within the same oceanic branch.
- MakaleYalnız künye201440Ar-39Ar age, petrography and geochemistry of the Yoncayolu Metamorphic Rocks (NE Turkey): Subduction-related metamorphism under greenschist fades conditions
Gücer, Mehmet Ali; Aslan, Zafer
The Yoncayolu Metamorphic Rocks (YMR), exposed in the Sakarya zone (Erzincan, NE Turkey), consists mainly of greenschist rocks which are chlorite schists, muscovite-chlorite schists, metabasic rocks and lesser extent of pyhllites and calc-schists. All YMR are fine-grained, weakly foliated and often cut by quartz veins. The common mineral assemblage is chlorite+albite+epidote+quartz+/-clinozoisite+/-actinolite+/-opaques. Geochemically, protoliths of the YMR resemble calc-alkaline volcanic arc rocks. The YMR have high contents of large ion lithophile elements (LILEs) and low contents of high field strength elements (HFSEs) similar to mid-ocean ridge basalt (MORB). (La/Lu)(CN) values are between 0.26 and 6.16. The REE patterns show slight or no Eu anomalies (Eu-CN/Eu* of 0.48 to 1.13), suggesting minor plagioglase fractionation. 40Ar-39Ar dating on plagioclases from the metabasic samples of the YMR gave ages of 100.8+/-3.4 Ma (Albian) and 94.1+/-3.3 Ma (Cenomanian), suggesting that metamorphism was related to the closure of the Neo-Tethyan Ocean. Metamorphism took place during subduction of the Neo-Tethyan Ocean between similar to 90-70 Ma. Chlorite geothermometry yielded a temperature of 320-350 degrees C and a pressure around 4 kbar. All these findings lend support for greenschist facies metamorphic conditions during the formation of the YMR.
- MakaleYalnız künye2011Formation of skarns at Gumushane (Northeastern Turkey)
Sipahi, Ferkan
Skarn deposits are located in the NE Black Sea region of Turkey belonging to the Alpin metallogenic province. The Fe skarn deposit at Arnastal is hosted by Late Cretaceous carbonate rocks comprised of limestone and the skarn occurrence at Camibogazi dolomitic limestone, adjacent to the Eocene Zigana Granitoid. The prograde textures include rhythmic banding, spots, and mossiness, and the retrograde textures are shock-induced and brecciated. These are identified in the Fe skarn deposit at Arnastal, where there are mineral parageneses of andradite, actinolite, tremolite, epidote, quartz, magnetite, and hematite, and less pyrrboune and pyrite. Additionally, well-crystallized vesuvianite, well-crystallized phlogopite, and diopside in the skarn occurrence. at Camibogazi are identified. Some of the skarn minerals are calcic and have high Mg/(Mg + Fe) ratios. Clinopyroxene consists of diopside (Di(96.66-99.04)Hd(0.67-2.80)Jo(0.29-0.55)). Vesuvianite is mostly Mg-rich, and has a very low MnO content (<0.1 %). Other skarn minerals are Fe-rich. Garnet is characterized by oscillatory zoning and has an andradite composition (Ad(72)Gr(28) to Ad(98)Gr(2)). Epidote has an Fe content of 8.96 to 12.42 wt%. Magnetite is generally massive and sporadically banded with some martitization. The formation temperatures of skarn minerals range from 330 to 600 degrees C. In addition, mass change calculations from the granitoid and andesite toward the skarn zone indicate that there is considerable mass transfer of Si, Al, Fe, and Mg to the carbonate rocks during skarn formation. The average mass changes are estimated at a depletion of 41 g/100 g in granitoid and a gain of 8 g/100 g in andesite. Fe skarn deposit and skarn occurrence are characterized by early, high-temperature mineral assemblages dominated by the anhydrous minerals garnet and diopside and late low-temperature assemblages with hydrous minerals, such as vesuvianite, phlogopite, and epidote. The type of garnet and the abundance of magnetite with minor pyrite suggest that the Fe skarn deposit at Arnastal forms under relatively oxidized conditions. The type of clinopyroxene in the skarn occurrence at the Camibogazi shows oxidized skarns.
- MakaleYalnız künye2011Petrogenesis of a Late Cretaceous composite pluton from the eastern Pontides: The Daǧbasi pluton, NE Turkey
Kaygusuz, Abdullah; Aydingakir, Emre
Zircon U-Pb ages, major and trace elements, and Sr-Nd isotope data are reported for the Late Cretaceous Dagbasi pluton from the eastern Pontides, NE Turkey. This pluton has calc-alkaline affinity and displays typical features of volcanic arc granitoids. It is a composite pluton consisting of tonalite, granodiorite, and monzogranite, all containing mafic microgranular enclaves (MMEs). Based on U-Pb zircon SHRIMP dating, magma emplacement ages of the tonalite, granodiorite, and monzogranite are 88.1 ± 1.7 Ma, 86.0 ±2.0 Ma, and 82.9 ± 1.3 Ma, respectively. The tonalites have low SiO2 (60-64 wt%) and display metaluminous to peraluminous characteristics. They have similar Lacn/Lucn (1.5-7.3) and Eu/Eu* (0.65-0.88) values compared to granodiorites and monzogranites. The isotopic signatures of these rocks εNd(i) = -1.4 to -1.7; 87Sr/86Sr(i) = 0.7056-0.7060) are largely similar to granodiorites and monzogranites. Samples from the granodiorites and monzogranites have SiO2 between 69 and 76 wt% and display peraluminous to slightly metaluminous characteristics. Chondrite-normalized REE patterns are characterized by moderate Lacn/Lucn ratios (1.6-7.1), with pronounced negative or positive Eu anomalies (Eu/Eu* = 0.46-1.11). Radiogenic isotope signatures of granodiorites and monzogranites show overlapping 87Sr/86Sr(i), (0.7057-0.7067) and εNd(i) (-3.2 to + 1.5) values. The MMEs have similar geochemical and isotopic features as the host rocks. All plutonic rocks are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE). Fractionation of plagioclase, hornblende, and Fe-Ti oxides played an important role in the evolution of Daǧbasi granitoids. All these geochemical and isotopic characteristics suggest an origin by dehydration melting of an amphibolitic lower crustal source.
- MakaleYalnız künye2010Insight into magma genesis at convergent plate margins a case study from the eastern Pontides (NE Turkey)
Kaygusuz, Abdullah; Siebel, Wolfgang; Ilbeyli, Nurdane; Arslan, Mehmet; Satir, Muharrem; Şen, Cüneyt
Convergent plate margins are the most intense areas of granitoid magmatism on Earth. The Eastern Pontide Magmatic Belt in NE Turkey represents a paleo-arc with numerous quartz diorite to syenite intrusions, ranging in age from 142 to 56 Ma and being composed of K-feldspar, plagioclase, quartz, pyroxene, hornblende, biotite, and Fe-Ti oxides. The granitoids exhibit low- to high-K calc-alkaline, metaluminous to slightly peraluminous I-type features and contain abundant mafic magmatic enclaves (MME). They are characteristically enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE). Chondrite-normalized REE patterns are fractionated (LaN/LuN= 1.49-17.4) with pronounced negative Eu anomalies (Eu/Eu* = 0.46-1.77). Initial 87SrZ86Sr values are between 0.7056 and 0.7079, and εNd(1) values between -5.3 and 1.6. Fractional crystallization, magma mixing/mingling and crustal contamination played an important role during magma evolution. All these characteristics, combined with the low values of K2O/Na2O, Mg-number, ASI and ratios Of Al 2O3/ (FeOT+MgO+TiO2) and (Na 2O+K2O)/(FeOT+MgO+TiO2), suggest an origin by dehydration melting of mafic (amphibolitic) or tonalitic lower crustal source rocks.
- MakaleYalnız künye2009K/Ar ages and geochemistry of the post-collisional volcanic rocks in the Mica (Erzurum) area, eastern Turkey
Kaygusuz, Abdullah
The Neogene Ilica volcanics in eastern Anatolia are of sub-alkaline affinity and present features of post-collisional volcanism. The lava flows in the Ilica area reveal K/Ar ages ranging from 13.9 ± 0.5 to 4.4 ± 0.3 Ma, corresponding to the Miocene- and Pliocene age. The volcanic rocks are composed of calc-alkaline basaltic trachyandesitic-, trachyandesitic-, andesitic- and minor dacitic lavas associated with pyroclastics, with the andesitic lavas being volumetrically the most abundant. Some special textures, such as the dissolution/melting and poikilitic type, and the normal, reverse, and oscillatory zoning in the plagioclase- and pyroxene phenocrysts are attributable to disequilibrium crystallization related to magma mixing. The rocks are characterized by enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), with pronounced depletion of high field strength elements (HFSE). They show depletion in Nb and Ta, indicating the role of crustal contamination. The rocks also have moderately fractionated rare earth elements (REE) patterns with (La/Lu)N ratios of 10-19 for andesitic- and dacitic rocks, and 7-10 for basaltic trachyandesitic- and trachyandesitic rocks. Basaltic trachyandesites show slightly positive Eu anomalies, whereas the deepening of Eu through gradual increase from trachyandesite to dacite, indicating a genetic link between the basaltic trachyandesite and the dacites. The main solidification processes consist of magma mixing and fractional crystallization with minor amounts of crustal contamination which were operative during the solidification of the volcanic rocks. All evidences support the theory that Ilica volcanic rocks were derived from partial melting of lower continental crust, having undergone interaction with subcontinental lithospheric mantle in a post-collisional geodynamic setting.
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