Eker, Çiğdem Saydam; Yücel, Cem; Kaygusuz, Abdullah; Aydınçakır, Emre; Jeong, Youn-Joong; Yılmazer, Sinan; Sünnetçi, Kadir

Detrital zircons are crucial stand-ins for the history of continental crust growth and disintegration, as well as the dispersal and assembly of supercontinents. Detrital zircons are effectively used to assess crustal history because sediments transport zircons from source rocks that are no longer at the surface. This study presents detailed Lu-Hf isotopic, U-Pb geochronological analyses of zircon, Sr-Nd isotopic analyses and whole-rock geochemical results from sandstone, volcanically derived sandstone and tuff samples of the Campanian-aged Bozbent Member in the Eastern Pontide Orogen belt of the Sakarya Zone. Sedimentological analyses show that the Bozbent Member was transported and deposited by turbidite currents, while petrographic and geochemical analyses show that the sandstones range from greywacke to litharenite. In this study, U-Pb ages of detrital zircon obtained from Campanian sandstones are presented, along with in situ εHf data. A magmatic origin is indicated by the majority of zircons' oscillatory zoning and by Th/U ratios ranging from 0.2 to 1.5. The ages of detrital zircons range from 2819 to 78 Ma, with most of these zircons being Proterozoic (552–994 Ma). Proterozoic zircons are detrital zircons associated with the Gondwana and the African Craton. The whole-rock geochemical data and Sr-Nd isotope compositions of the sandstones are consistent with local Carboniferous felsic plutons, Jurassic mafic and felsic plutons, Jurassic volcanic rocks, Jurassic clastic rocks and clastic material from Precambrian recycled sediments. It was calculated that more than 90% of the detrital zircons had crystallisation ages older than their depositional ages (CA-DA > 150 Ma, indicative of an extensional basin model). These findings indicate that the Campanian-aged Bozbent Member turbiditic sequence in the Eastern Pontides was deposited in an extensional fore-arc basin and therefore exhibits the petrographic and geochemical characteristics of passive margin sandstones.

Kaygusuz, Abdullah; Güloğlu, Zikrullah Samet; Aydınçakır, Emre; Yücel, Cem; Vural, Alaaddin; Saydam Eker, Çiğdem; Cicerali, Derya

The Eastern Pontides Orogenic Belt (EPOB) in northeastern Turkey is a well-preserved continental magmatic arc in the Alpine-Himalayan Orogenic Belt and contains many Eocene I-type high-K plutons. Employing LA-ICP-MS U-Pb zircon geochronology, the crystallization ages of the investigated Yaylalıköy and Taşbaşı plutons were established to be Lutetian (Middle Eocene), ranging from 47 Ma to 46 Ma. These plutons exhibit a compositional spectrum ranging from diorite to granodiorite, characterized by I-type, metaluminous, and high-K geochemical signatures. Notably, they are enriched in large-ion lithophile elements (LILEs) and light rare earth elements (LREEs), displaying pronounced negative Eu anomalies (EuN/Eu* = 0.58–0.96). Isotopic signatures reveal homogeneous and moderately low initial 87 Sr/86 Sr(i) ratios (0.704643–0.705034) and positive εNd(i) values (0.24 to 1.67) for the investigated plutons. These isotopic signatures are consistent with mantle origin, as evidenced by their position within the mantle array on isotope ratio diagrams. Lead isotope compositions exhibit limited variations, with initial ratios of 206 Pb/204 Pb(i) (18.55–18.64), 207 Pb/204 Pb(i) (15.61–15.64), and 208 Pb/204 Pb(i) (38.46–38.75). Zircon εHf(i) values are positive (2.32–6.20), plotting between the depleted mantle and chondritic evolution lines. Additionally, these rocks display low zircon δ18 O values (+4.54 to + 6.53‰), comparable to mantle composition. The petrographic characteristics of the investigated plutons suggest that fractional crystallization with minimal assimilation and/or magma mixing played a dominant role during their solidification. The integration of geochemical and isotopic data, alongside regional geological constraints, advocates for enriched lithospheric mantle as the source for the parental magmas of the studied plutons. These magmas subsequently underwent differentiation within a deep-seated magma chamber, followed by emplacement into the crust.

Yücel, Cem; Aydınçakır, Emre; Kaygusuz, Abdullah; Arslan, Mehmet; Yi, Keewook; Jeong, Youn-Joong; Cicerali, Derya

The Late Cretaceous magmatic history of the Eastern Pontides Orogenic Belt (NE Turkey) was generally characterized by common I-type and lesser A-type plutons in varying size and composition. Of these, A-type plutons from the Şebinkarahisar (Giresun) area yield SHRIMP zircon U-Pb age of 77.36 ± 0.96 Ma. The rocks of these plutons display a wide range of SiO2 contents (53.63 to 70.96 wt.%) and Mg-numbers (6.2–32.19) with A-type affinities characterized by enrichment in K2O and Na2O, Ga, Zr, and strong negative Eu anomalies. They also show arc-type petrochemical features including enrichment of large-ion lithophile elements (e.g. Cs, K, Rb) and light rare earth elements (LaN/LuN = 6.27–15.61), but depletion in high strength field elements (e.g. Nb, Ta, Ti, and P). The (87Sr/86Sr)i ratios and ɛNd(i) values of the studied rocks are in the range of 0.705129 to 0.0705347 and −3.64 to −3.12, respectively, while bulk rock ɛHf(i) values are between 1.86 and 4.36. They are characterized by positive zircon ɛHf(i) (1.74 to 10.88) plotting between the chondrite and depleted mantle evolutionary line values. Our data combined with the previous studies suggest that the magmas, that formed the Late Cretaceous plutons, were generated in an extensional tectonic environment due to slap roll-back and trench ward migration of the subduction zone to the south. The generation of hybrid magmas forming the studied plutons is in response to the melts derived from a metasomatized lithospheric mantle source, a relatively deeper mantle source, and the juvenile crust along with the heat transfer and decompression. Multi-sourced magmas rise through the continental crust and reach the final composition by predominantly fractional crystallization processes.

Kaygusuz, Abdullah; Güloğlu, Zikrullah Samet; Aydınçakır, Emre; Yücel, Cem; Vural, Alaaddin; Siebel, Wolfgang; Jeong, Youn-Joong

The Eastern Pontide Orogenic Belt (EPOB) hosts numerous plutonic bodies with different dimensions, compositions and ages ranging from Paleozoic to Late Eocene in NE Turkey. U-Pb zircon dating suggests that the Arslandede pluton crystallized at 44.50 ± 0.29 Ma, corresponding to the Lutetian (Middle Eocene) period. Rocks of this pluton have monzonitic character, with compositions ranging from monzodiorite to granite (SiO2 = 49˗71 wt%). The studied monzonitic rocks have I-type, metaluminous and shoshonitic character and are enriched in large-ion lithophile elements (LILEs). The rare earth elements (REEs) have concave up shape (LaN/YbN = 6.64–11.57) and show negative to slightly positive Eu anomalies (EuN/Eu* = 0.37–1.24). 87Sr/86Sr(i) values of 0.704801–0.705102 and εNd(i) values of 1.01–1.34 correspond to the mantle series on isotope ratio diagrams. Positive εHf(i) values (5.01–14.91) plot between the depleted mantle and the chondritic evolution lines. The petrological features of the rocks from the Arslandede pluton show that fractional crystallization with low rates of assimilation and/or magma mixing were effective during crystallization. All data show that the magma source of the pluton derived from an enriched lithospheric mantle and emplaced into the crust after differentiation in a deep seated magma chamber contaminated by relatively small proportions of crustal rocks.

Aydınçakır, Emre; Yücel, Cem; Kaygusuz, Abdullah; Bilici, Özgür; Yi, Keewook; Jeong, Youn-Joong; Güloğlu, Z. Samet

The Eastern Pontides in NE Turkey hosts a very limited number of plutonic rocks from the Jurassic period. Here we submit new geochemical, Sr-Nd-Pb and zircon Lu-Hf isotope data, and zircon U-Pb ages for plutonic rocks in this region. Zircon U-Pb dating for the Alemdar and Işıkdere plutons yielded an age of 175–170 Ma (Middle Jurassic). The Alemdar and Işıkdere plutons have I-type, medium to high-K calc-alkaline series, and metaluminous to slightly peraluminous characteristics. On PM-normalized diagrams, the plutons are enriched in large-ion lithophile elements (LILEs) with pronounced depletion of high field strength elements (HFSEs, Ta, Nb, Ti). Chondrite-normalized plots for the plutons show variable enrichment in light rare earth elements (LREEs) with depletion of heavy rare earth elements (HREEs). The rocks of the Alemdar Pluton have homogeneous ISr values (0.70585 to 0.70673), low εNd(i) values (−3.9 to −1.6), pozitif εHf(i) values (+3.3 to +9.1), and Hf single-stage model ages (563–712 Ma), whereas those of Işıkdere have high ISr values (0.70666 to 0.70673), low εNd(i) values (−3.9 to −3.8), εHf(i) values (−3.1 to +1.1), and Hf single-stage model ages (791–969 Ma). These values imply that they have different sources. These results suggest that the magma of the Alemdar was formed by the partial melting of a relatively depleted lithospheric mantle wedge interaction of the OIB-like melts, while those of Işıkdere have derived from the partial melting of an enriched mantle metasomatized by slab-derived sediments and then modified by fractional crystallization and crustal contamination in crustal magma chambers. Considering the available data, we conclude that the studied plutons were related to extensional tectonic events during the Middle Jurassic in response to the roll-back of the Paleotethys oceanic slab in the final stage of oceanic closure. These rocks are an example of the formation of deep subduction products following Early Jurassic subduction.

Aydınçakır, Emre; Yücel, Cem; Ruffet, Gilles; Gücer, Mehmet Ali; Akaryalı, Enver; Kaygusuz, Abdullah

The debate about whether Eocene magmatism is considered to be post-collisional or subduction-related or not still continues. Here we offer new 40Ar-39Ar ad U-Pb zircon geochronology, mineral chemistry, bulk rock and Sr-Nd-Pb isotope geochemistry data obtained from the southern dike (SD) suite, in comparison with the northern dike (ND) suite, from the Eastern Pontides. The geochronological data indicate that the SD suite erupted between 45.89 and 45.10 Ma corresponding to the Lutetian (Middle Eocene). The magmas of the ND suite are characterised by slightly more alkaline affinity compared to the SD suite. The trace and rare earth element (REEs) content of the SD suite is characterised by large ion lithophile element (LILEs; Sr, K2O, Ba, Rb) enrichment and depletion of Nb, Ta, and TiO2 elements to different degree with high Th/Yb ratios, which indicate that the magmas forming the SD and ND suites were derived from lithospheric mantle sources enriched by mostly slab-derived fluids in the spinel stability field. The Sr, Nd and Pb radiogenic isotope ratios of the dikes support the view that the magma for the hydrous group (H-SD) was derived from a relatively more enriched mantle source than the other SD and ND suites. The ND suite and the anhydrous group (A-SD) display similar geochemical features characterised by moderate light earth element (LREE)/heavy rare earth element (HREE) ratios, while the H-SD group has respectively lower LREE/HREE ratios indicating higher melting degree. Detailed considerations of the alkalinity, enrichment and partial melting degree for the source of the studied volcanic rocks indicate that the magmas of the northern dike suite are characterised by slightly more alkaline affinity, whereas the magmas throughout the southern dike suite show increments in the enrichment rate and melting degree. In light of the obtained data and comparative interpretations, the geodynamic evolution and differences in petrogenetic character of the Lutetian magmas from both the northern and southern parts of the Eastern Pontides may be explained by different degrees of melting of a net veined mantle source initially metasomatized by mostly subduction fluids during asthenospheric upwelling due to fragmented asymmetric delamination in a post-collisional extensional tectonic environment.

Kaygusuz, Abdullah; Yücel, Cem; Aydınçakır, Emre; Gücer, Mehmet Ali; Ruffet, Gilles

Discussions continue about whether Middle Eocene magmatism in the Eastern Pontides is associated with collision or subduction. This paper presents new whole-rock geochemistry, Sr-Nd isotopic and 40Ar-39Ar age data for Middle Eocene volcanic rocks from the Bayburt area of the Eastern Pontides (NE Turkey) to investigate their sources and evolutionary history. The new 40Ar–39Ar ages reveal that these volcanic rocks erupted between 44.6 ± 0.1 Ma and 43.5 ± 0.1 Ma, within the Lutetian (Middle Eocene). The studied volcanic rocks are composed of basalt, andesite, basaltic andesite and minor dacite lava and pyroclastic rocks. These rocks consist of plagioclase, amphibole, pyroxene, olivine, biotite, sanidine and minor quartz phenocrysts with Fe-Ti oxides. They have microlithic, hyalo-microlithic, porphyritic and rarely glomeroporphyritic textures. The volcanic rocks have low to high-K calc-alkaline affinities. They display enrichment in large-ion lithophile elements and depletion in high-field strength elements with high Th/Yb ratios, which indicate that the magmas forming the volcanic rocks were derived from lithospheric mantle sources enriched by mostly slab-derived fluids in the spinel stability field. 87Sr/86Sr(i) values vary between 0.70485 and 0.70551 and 143Nd/144Nd(i) values vary between 0.51255 and 0.51267. These data correspond to the mantle array on the isotope ratio diagram. The main solidification processes consist of fractional crystallization with minor assimilation. In light of the data obtained in this study together with data from previous studies, petrogenetic character of the Middle Eocene magmas from the southern parts of the Eastern Pontides may be explained by melting of an enriched lithospheric mantle source initially metasomatized by subduction fluids in a post-collisional extensional-related tectonic setting.

Aydınçakır, Emre; Yazar, Emel Abdioglu; Yücel, Cem; Güngör, Hande; Bilici, Özgür

Bu çalışmada Eosen yaşlı Kışlaköy (Narman/Erzurum) volkanik kayaçlarının minerolojik, petrografik ve mineral kimyası analizleri incelenmiştir. Elde edilen veriler doğrultusunda magmaların kristallenme esnasında etkili olan sıcaklık, basınç gibi fizikokimyasal özellikleri ile fizikokimyasal verileri jeolojik verilerle birleştirerek bu kayaçları oluşturan magmaların kabuktaki gelişimleri irdelenmiştir. Çalışma alanındaki başlıca birimler Eosen yaşlı Kışlaköy Volkaniti, Oligo-Miyosen yaşlı Oltu Formasyonu, Oligo-Miyosen yaşlı Alabalık Formasyonu ve Alüvyonlardan oluşmaktadır. Kışlaköy volkanik kayaçları volkanik fasiyes özelliklerine göre piroklastitler, dayklar ve lavlar olmak üzere üç başlıkta incelenmiş, genellikle bazalt bileşiminde ve başlıca plajiyoklaz (An₄₉₋₈₅), klinopiroksen (Wo₄₀₋₄₆ En₄₁₋₅₀ Fs₅₋₁₈), olivin (Fo₆₈₋₇₅) ve Fe-Ti oksit minerallerden oluşmaktadır. Bu kayaçlar genel olarak hyalo-mikrolitik porfirik, glomeroporfirik, glomerofirik, mikrolitik porfirik, poikilitik, intersertal doku sergilemektedirler. İncelenen volkanitler; plajiyoklaz fenokirstallerinde halkalı zonlanma, elek dokusu ve kemirilme; klinopiroksenlerdeki yenme, kemirilme ve kalıntı merkezler gibi dengesizlik dokuları gözlenmiştir. Termobarometre hesaplamalara göre volkaniklerin kristallenme sıcaklığı 489-1247 0C arasında, basınç 0.5-4.7 kbar arasında değişmekte olup, bütün bu verilere bakılarak incelenen volkanik kayaçların orta-sığ kıtasal kabuk (~4-12 km) içerisinde yerleştiği söylenebilir.

Maden, Nafiz; Akaryalı, Enver; Aydınçakır, Emre

In the original version of this paper the captions of figures 5, 6 and 7 were inadvertently interchanged.

Kaygusuz, Abdullah; Arslan, Mehmet; Temizel, İrfan; CemYücel; Aydınçakır, Emre

The Eastern Pontides Orogenic Belt (EPOB) as a well-preserved ancient magmatic arc situated in the eastern part of the Sakarya Zone and has key importance to allow for proper reconstruction of the geodynamic evolution of the region. The region accepted as important part of Alpine–Himalayan Belt comprises of many granitoids of the Late Cretaceous age. This paper presents new mineral chemistry, bulk-rock petrochemistry, U-Pb geochronology and radiogenic and stable isotope geochemistry data from the Arpaköy and Oyman granitoids in the north part of the EPOB to interpretation of the igneous activity and geodynamic evolution of the region in Late Cretaceous era. Emplacement ages of 86.82 ± 0.58 Ma for the Oyman granitoid and 82.0 ± 2.3 Ma for the Arpaköy granitoid according to laser ablation ICP-MS U–Pb zircon dating. The Arpaköy granitoid are gabbro diorite, diorite and granite, whereas the Oyman granitoid are tonalite and granite in composition. They show metaluminous-peraluminous transitional (ASI = 0.79–1.20) low to medium-K calc-alkaline features. The rock samples from granitoids are characterized by enrichment in large ion lithophile elements (LILE) and high field strength elements (HFSE) depletion with concave-upward shapes (LaN/LuN = 1.88 to 6.04). The crystallization temperatures are 648 °C–913 °C and the pressure values are 0.2–3.0 kbar, which indicates emplacement depth of the studied granitoids varying from ~1 to 9 km correspond to shallow crustal depths. They show considerable variations in εNd(i) (−4.02 to 1.50) and 87Sr/86Sr(i) (0.70478–0.70689). The 206Pb/204Pb ratios are between 17.97 and 18.65, and δ18O are varying from +5.4 to +9.3‰. The parental magma of the Arpaköy and Oyman granitoids originated from a melt of the enriched lithospheric mantle and the fractional crystallization and lesser assimilation processes has important role on the evolution of magmas in the shallow crustal levels.

Maden, Nafiz; Akaryalı, Enver; Aydınçakır, Emre

Herein, we present new 238U, 232Th, and 40K radionuclide concentrations, density and radiogenic heat production (RHP) data on the Tertiary volcanic rocks outcropping in Borçka, Gumushane and Trabzon regions within the Eastern Pontide Orogenic Belt (EPOB). The mean K values for Trabzon, Borçka and Gümüşhane regions were 2.19 ± 0.87%, 0.90 ± 0.70% and 0.59 ± 0.25%, respectively, the mean U values for Trabzon, Borçka and Gümüşhane regions were 2.12 ± 0.76 ppm and 1.29 ± 0.68 ppm and 0.90 ± 0.32 ppm, and the average Th values were calculated as 6.54 ± 2.32 ppm, 2.49 ± 1.93 ppm and 1.33 ± 0.60 ppm for Trabzon, Borçka and Gümüşhane regions, respectively. The average Th/U values are 3.38 ± 1.48 for the Trabzon region, 2.01 ± 1.22 for the Borçka region, and 1.69 ± 1.09 for the Gümüşhane region. Average U/Th values were calculated as 0.35 ± 0.14, 0.71 ± 0.52 and 0.89 ± 0.72 for the Trabzon, Borçka and Gümüşhane regions, respectively. The RHP values were determined as 1.16 ± 0.35 μW m - 3, 0.58 ± 0.33 μW m - 3 and 0.37 ± 0.10 μW m - 3 for Trabzon, Borçka and Gümüşhane regions, respectively. The Tertiary aged rocks in the EPOB that we have examined within this study scope have been derived from an enriched mantle, previously metasomatized by fluids derived from subducted slab. The parental magma of Eocene basaltic rocks was contaminated with crustal material during the ascension of the magma through the crust or in the shallow-level crustal magma chambers.

Aydınçakır, Emre; Şen, Cüneyt; Bak, Tülay; Yağcıoğlu, Ufuk Celal

Sakarya Zonunun güney kesiminde Bayburt, Amasya-Gümüşhacıköy ve Ankara-Kalecik lokasyonlarında ÜstKretase’nin son dönemlerinde benzer stratigrafik seviyelerde yüzeylenen alkalen volkanitler makroskobik olarak irianalsimleşmiş lösit porfirleri ve iri piroksen porfirleri içeren iki farklı litoloji sunarlar. Bu kayaçlar çarpışma öncesiyaşlı okyanus kabuğunun yitim açısının dikleşmesi sonucu, metasomatizmaya uğramış flogopitce zengin mantokayaçlarının düşük dereceli kısmi ergimesi sonucu oluşan kaynak magmalardan itibaren oluşmuşlardır. Oluşumlarınıizleyen süreçte alkalen magma, kabuk içerisindeki orta/sığ derinliklerdeki magma odalarında diferansiyasyonauğrayarak, iki farklı litolojide yeryüzüne ulaşmıştır.

Aydınçakır, Emre; Akaryali, Enver; Maden, Nafiz

Bu çalısmada Dogu Pontid Orojenik kusagında (KD TÜRKIYE) yer alan Artvin-Borçka, Gümüshane ve Trabzon civarında yüzeyleyen Tersiyer yaslı volkanik kayaçların radyojenik ısı üretimi ve bunun jeolojik kaynakları ortaya konulması hedeflenmistir. Böylece yüzeydeki radyojenik ısı üretimi (RHP) ile kabugun derinliklerindeki ısı akısı arasında iliskinin kurulması saglanmıstır. Yüzeyde ölçülen ısı akısı üst kabuk içindeki radyoaktif elementlerin parçalanması sonucunda ortaya çıkan ısı (radyojenik ısı) ile alt kabuk-üst mantodan aktarılan ısı olmak üzere iki farklı kaynaktan olusmaktadır. RHP üst kabukta yer alan kayaçların bünyesinde bulunan Uranyum (U, ppm), Toryum (Th, ppm) ve Potasyum (K, %) gibi radyoaktif elementlerin bozunması sonucu olusmakta ve yüzeydeki ısı akısına katılmaktadır. Bu projede çalısmasında RHP degerlerini belirlemek için kayaçların bünyelerinde yer alan U, Th ve K degerleri Gamma Ray Spektrometre cihazı ile ölçülmüstür. Ortalama K degerleri Trabzon, Borçka ve Gümüshane yöreleri için sırasıyla 2,19±0,87%, 0.90±0.70% ve 0.59±0.53%, ortalama U degerleri Trabzon, Borçka ve Gümüshane yöreleri için sırasıyla 2,11±0,77ppm, 1.29±0.68ppm ve 0.90±0.32ppm, ortalama Th degerleri ise Trabzon, Borçka ve Gümüshane yöreleri için sırasıyla 6,55±2,32ppm, 2.49±1.93ppm ve 1.33±0.60ppm olarak hesaplanmıstır. Ortalama Th/U degerleri Trabzon için 4.21±1.0; Borçka yöresi için 2.81±0.8 ve Gümüshane yöresi için 4.01±1.0 olarak; ortalama U/Th degerleri Trabzon yöresinde 0.25±0.1, Borçka yöresinde 0.39±0.1 ve Gümüshane yöresinde 0.27±0.1 olarak hesap edilmistir. Proje kapsamında toplanan toplam 100 adet kayacın ortalama yogunluk degerleri Trabzon, Borçka ve Gümüshane yöreleri için sırasıyla 2.61±0.23 grcm-3, 2.64±0.18 grcm-3 ve 2.62±0.13 grcm-3 olarak tespit edilmistir. K, U, Th ve yogunluk verileriyle RHP degerleri üç farklı bölge için hesaplandıgında Trabzon için 1,16±0,35 ?Wm^(-3), Borçka için 0.58±0.33 ?Wm^(-3) ve Gümüshane için 0.37±0.11 ?Wm^(-3)olarak belirlenmistir. Bu proje kapsamında inceledigimiz Dogu Pontid orojenik kusagında yer alan Tersiyer yaslı kayaçların tüm bölgelere ait veriler degerlendirilerek üst manto kaynaklı magmadan yitim iliskili olarak türedikleri sonucuna ulasılmıstır. Magmanın yükselmesi asamasında yada magma odacıklarında alt kıtasal kabuk malzemelerince kirletildigi kanaatine varılmıstır.

Kaygusuz, Abdullah; Aslan, Zafer; Aydınçakır, Emre; Yücel, Cem; Gücer, Mehmet Ali; Şen, Cüneyt

This paper presents Sr-Nd-Pb isotopic and whole-rock geochemical data of Miocene to Pliocene volcanic rocks in the Eastern Anatolia (Turkey) aiming to unravel their sources and evolutionary history. The wide compositional range of lavas and pyroclastics includes basaltic andesite, basaltic trachyandesite, trachyandesite, andesite and trachydacite. These calc-alkaline volcanics are enriched in large ion lithophile elements and light rare earth elements and depleted in the high field strength elements. Sr-Nd isotope data indicate low values for 87Sr/86Sr(i) (0.70432–0.70464) and high values for 143Nd/144Nd(i) (0.51272–0.51282). Further, these data are within the mantle array of the isotope ratio diagram. The lead (Pb) isotopic compositions (206Pb/204Pb(i) = 18.33 to 18.62, 207Pb/204Pb(i) = 15.51 to 15.60, 208Pb/204Pb(i) = 38.10 to 38.45) reveals the presence of an enriched source. The main petrological processes involved fractional crystallization and the mixing of at least two fractionated magmas having same source characteristics. All evidence supports the findings that the Kandilli volcanic rocks were derived from a partial melting of the both spinel and garnet bearing subcontinental lithospheric mantle, which had been previously metasomatized by mostly fluids derived from subducted slab during the collisional and post-collisional extension-related geodynamic setting in the Eastern Anatolia region of Turkey.

Yücel, Cem; Aydınçakır, Emre; Akaryali, Enver; Gücer, Mehmet Ali

Doğu Pontid orojenik kuşağında (KD Türkiye) farklı magma türleri altında oluşmuş farklı volkanikkayaçlar yüzeyleme vermektedir. Tersiyer volkanizması, Gümüşhane ve çevresinde asidik, nötr vebazik volkanik ve piroklastik kayaçlardan meydana gelmektedir. Bu volkanizma doğu Pontidler'inevriminde ise önemli bir rol oynamaktadır. Bu çalışma kapsamında Altınpınar (Torul/Gümüşhane)civarında yüzeyleme veren Tersiyer yaşlı hornblendli andezitik kayaçların petrografisi, mineralkimyası ve sıcaklık-basınç koşulları irdelenmiştir. Andezitler başlıca hornblend (amfibol),plajiyoklas (An40-61Ab38-57Or1-5), klinopiroksen (Wo44-45En43-44Fs12) ve opak (genellikle magnetit vepirit) mineralleri, ikincil kil, serizit, kalsit ve klorit mineralleri içerir ve mikrolitik-porfirik vevitrofirik porfirik dokular sergiler. Bazı hornblend mineralleri iri kristalli gelişmiş olup, plajiyoklasve opak mineral kapanımları içermektedir. Tüm hornblendler CaB >= 1.5, (Na+K)A <0.5 ve CaA <0.5parametrelerine sahip kalsik tip olup, magnezyohornblend bileşimi sunmakta, Mg# (Mg/Mg+Fe2+)ise 0.72-0.91 arasında değişmektedir. Andezitlerde kalsik amfibol jeotermobarometri denklemlerinikullanarak hesaplanan tahmini jeotermometre (T), jeobarometre (P) ve oksijen fugasitesi (?O2/ ?NNO) değerleri sırasıyla 765 - 867 °C (ort= 790±20 °C); 2.5 - 4 kbar ve -14.4 ile -11.1 olarakhesaplanmıştır. Elde edilen bu değerler hornblendlerin kıtasal kabukta 9 - 15 km derinliklerdekristallendiğini işaret etmektedir. Minerallerin kimyasal özellikleri inceleme alanındaki andezitlerinkalk-alkali bir ana magmadan itibaren kristallenmiş olduğunu göstermektedir.

Aydınçakır, Emre

Late Cretaceous era is characterized by densely volcanic and granitic activities in the Eastern Pontides that is northeast part of the Sakarya Zone. In this era, thick pile of volcanic-volano-clastic rocks occurred during the activities of acidic and basic volcanic cycles. In this study, preliminary geochemical results of Late Cretaceous aged volcanic rocks that were cut by the plutons of Çaykara Intrusive Complex (Trabzon) are presented. Investigated rocks are cut by both Late Cretaceous and Eocene aged plutonic rocks; therefore, they are altered in some of the locations. They are yellowish- greenish-blackish in hand specimens and show aphanitic textures. They show microlithic porphphyric (including plagioclase porphyries) and intersertal textures under microscope. Euhedral and subhedral plagioclase crystals are anorthite 35 to 55 in composition. From the results of chemical analysis, the volcanic rocks are basalt, basaltic andesite, andesite and dacite in composition and their Mg# is ranging 30 to 65. In the primitive mantle normalized trace element diagram, the samples display negative Nb, P and Ti and positive Pb anomalies. In general, large ion lithophile (LIL) elements enriched compared to the high field strength (HFSE) elements in the same diagram. In chondrite normalized rare earth elements diagram, (La/Lu)N ratios are ranging from 4 to 15. While some samples are shown slightly negative Eu anomaly, some others show slightly positive anomaly. When the samples are plotted in tectonic discrimination diagrams, they fall in island arc volcanic fields. The main solidification processes involved in the evolution of the volcanics consist of fractional crystallization, crustal contamination ± magma mixing. In the light of all evidence supports the conclusion that the parental magma(s) of the Late Cretaceous volcanics probably derived from an enriched lithospheric mantle, previously metasomatized by subduction

Aydınçakır, Emre; Akaryali, Enver; Gücer, Mehmet Ali

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Alçiçek, Mehmet Cihat; Dokuz, Abdurrahman; Aydınçakır, Emre; Kandemir, Raif

Sakarya Zonu?nun doğusunda (Doğu Pontidler) yüzeyleyen Erken Karbonifer yaşlı Cebre Riyoliti Variskan temele ait az sayıdaki yüzey kayaçlarından biridir. Zirkon U-Pb yaşlandırması Cebre Riyoliti?nin 341.8±0.60 my önce Variskan temele yerleştiğini öngörmektedir. S-tipi granitlere benzer şekilde, Al-silikat fazlarından kordiyerit ve muskovit içerir ve güçlü peralümin bir jeokimyasal karaktere sahiptir. Birime ait kayaçların Sr-Nd-Pb izotopik oranları, alt kabuk ile uyumludur. Jeokimyasal ve izotopik veriler Cebre Riyolitinin çarpışma sırasında kilce zengin bir sedimanter kökenden itibaren kısmi ergime yolu ile oluştuğuna işaret etmektedir. Önerilen jeodinamik modelde, Reyik Okyanusu?nun kapanmasını takiben Lavrazya?dan kopan kıtasal yay ile Gondwana?nın Erken Karbonifer?de çarpışması öngörülmektedir. Çarpışma, kısa bir süre sonra, okyanusal litosfer delaminasyonu tarafından izlenmiştir. Okyanusal litosfer tarafından boşaltılan kısmın yükselen astenosfer tarafından hızlı bir şekilde doldurulması metamorfizma ve kısmi ergime için gerekli ısıyı sağlamıştır. Geç Paleozoyik yaşlı sedimanter istif, Variskan sonrası jeolojik olayların kaydedildiği çok az sayıdaki otokton birimlerden biridir. İstif, Variskan temele ait Erken Karbonifer yaşlı düşük dereceli metamorfitleri ve Cebre Riyoliti?ni uyumsuz olarak örter. Geç Paleozoyik istifi tabanda 610 m kalınlığında kuvars arenit ve kireçtaşlarının sekansiyel ardışmından oluşan Çatalçeşme Formasyonu ile başlar. Üzerine, çakıltaşları ile başlayan ve üste doğru sırasıyla arkozik arentlere ve şeyllere geçiş yapan 880 m kalınlığındaki Hardişi Formasyonu uyumlu olarak gelir. U-Pb kırıntı zirkon yaşları her iki formasyon için ~300 ? 2870 my arasında değişmekle birlikte, ana yaş popülasyonları 300 ? 350 my arasındadır. Bununla birlikte Çatalçeşme kumtaşlarına ait 7 adet zirkon Permiyen (298 ? 258 My) yaşı üretmiştir. Çatalçeşme kumtaşları pasif kenar ortamlarına ait kayaçlara benzer jeokimyasal özelliklere sahiptir. Buna karşılık Hardişi kumtaşları yitimle ilişkili ortamların jeokimyasal özelliklerini taşır. Jeokimyasal ve izotopik veriler, Variskan deformasyonlarını takiben Gondwana?nın kuzey kenarı boyunca açılan kısa ömürlü bir kenar havzada çökeldiklerine işaret etmektedir. Mermer, kireçtaşı ve kumtaşı blokları yanı sıra MORB ve IAT karakterli bazik bloklar da içeren Çamdere Ofiyolitik Karışığı?nın, kenar havzanın kapanması sırasında kıtasal kabuk üzerine yerleştiği öngörülmektedir.

Aydınçakır, Emre

Mineral chemistry, major and trace elements, 40Ar/39Ar age and Sr–Nd–Pb isotopic data are presented for the Late Cretaceous Hamsilos volcanic rocks in the Central Pontides, Turkey. The Hamsilos volcanic rocks mainly consist of basalt, andesite and associated pyroclastics (volcanic breccia, vitric tuff and crystal tuff). They display shoshonitic and high-K calc-alkaline affinities. The shoshonitic rocks contain plagioclase, clinopyroxene, alkali feldspar, phlogopite, analcime, sanidine, olivine, apatite and titanomagnetite, whereas the high-K calc-alkaline rocks contain plagioclase, clinopyroxene, orthopyroxene, magnetite / titanomagnetite in microgranular porphyritic, hyalo-microlitic porphyritic and glomeroporphyritic matrix. Mineral chemistry data reveal that the pressure condition of the clinopyroxene crystallisation for the shoshonitic rocks are between 1.4 and 6.3 kbar corresponds to 6–18-km depth and the high-K calc-alkaline rocks are between 5 and 12 km. 40Ar/39Ar age data changing between 72 ± .5 Ma and 79.0 ± .3 Ma (Campanian) were determined for the Late Cretaceous Hamsilos volcanic rocks, contemporaneous with the subduction of the Neo-Tethyan Ocean beneath the Pontides. The studied volcanic rocks were enriched in the large-ion lithophile and light rare earth element contents, with pronounced depletion in the contents of high-field-strength elements. Chondrite-normalised rare earth element patterns (LaN/LuN = 6–17) show low to medium enrichment, indicating similar sources of the rock suite. Initial 87Sr/86Sr values vary between.70615 and.70796, whereas initial 143Nd/144Nd values change between.51228 and.51249. Initial 206Pb/204Pb values vary between 18.001 and 18.349, 207Pb/204Pb values between 15.611 and 15.629 and 208Pb/204Pb values between 37.839 and 38.427. The main solidification processes involved in the evolution of the volcanic rocks consist of fractional crystallisation, with minor amounts of crustal contamination ± magma mixing. According to geochemical evidence, the shoshonitic melts in the Hamsilos volcanic rocks were possibly derived from the low degree of partial melting of a subcontinental lithospheric mantle (SCLM), while the high-K calc-alkaline melts were derived from relatively high degree of partial melting of SCLM that was enriched by fluids and/or sediments from a subduction of oceanic crust.

Akpınar, İbrahim; Akbulut, Kübra; Aydınçakır, Emre; Akaryali, Enver

İnceleme alanı Gümüşhane ilinin güneyinde yer alan Kelkit İlçesi Ünlüpınar (Pekün) Beldesine bağlı Eylence Yayla ve Emirinkomu Köyü yakın çevresini kapsamaktadır. Çalışma alanında Kurtoğlu Metamorfikleri, Şenköy Formasyonu ve Köse Granitoyidi yer almaktadır. Detay inceleme yapılan alan ve yakın çevresindeki birim Erken-Orta Jura yaşlı Şenköy Formasyonu'na ait bazalt, bazaltik andezit ve piroklastları oluşturmaktadır. Eylence Yayla ve Emirinkomu mevkiinde yer alan Zn-Pb-Cu ± Au cevherleşmesi tamamen Şenköy Formasyonuna ait bazaltik andezitler içinde K20D doğrultularındaki kırık hatlarına yerleşmiştir. İnceleme alanında cevherleşmenin parajenezini ortaya çıkarmak içinde çalışma sahasından sistematik örneklerden parlak kesitler yapılarak, cevher mikroskobisi altında incelenmiştir. Cevherleşmenin parajenezi oluşum sırasına göre pirit, kalkopirit, sfalerit, galen, altın, kuvars ve kalsit olarak tespit edilmiştir. Arazide yapılan gözlemler sonucunda alterasyon türleri olarak hematitleşme, limonitleşme ve kükürtleşme tespit edilmiştir. Sıvı kapanım analiz sonuçlarına göre cevherleşmenin oluşum sıcaklığının 80-2800C arasında değiştiği, kükürt izotop termometresine göre ise cevherleşmenin oluşum sıcaklığının ortalama 2640C olduğu belirlenmiştir.