Gümüşhane ÜniversitesiGümüşhane ÜniversitesiAçık Erişim Arşivi · RDL Open

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  • MakaleYalnız künye2026
    Late Cretaceous hybrid melt sources and flare-up magmatism in the eastern Sakarya Zone, NE Türkiye: Zircon Hf-O constraints and implications for VMS fertility

    Aydin, Faruk; Oguz-Saka, Simge; Karsli, Orhan; Dokuz, Abdurrahman; Moghadam, Hadi Shafaii; Zhao, Junxing; Schmitt, Axel K.

    Understanding melt source evolution during arc-back-arc magmatism is essential for resolving crustal growth processes and the development of felsic-hosted volcanogenic massive sulfide (VMS) systems. Here we integrate new zircon HfO isotope data with published geochronological and whole-rock geochemical datasets to reassess the petrogenesis of Late Cretaceous arc and back-arc magmatic flare-ups in the eastern Sakarya Zone (ESZ), NE T & uuml;rkiye. Two high-flux magmatic episodes are recognized: a Turonian-Santonian pulse (similar to 92-86 Ma) forming the lower volcanic sequence (LVS), and a younger Campanian pulse (similar to 84-75 Ma) forming the upper volcanic sequence (UVS), accompanied by contemporaneous arc-related granitoids. Zircons from both LVS and UVS display predominantly positive epsilon Hf(t) values (+2 to +12) coupled with mantle-like delta O-18 (5.0-5.6 parts per thousand), but contain abundant inherited Mesoproterozoic-Paleozoic cores and show variable two-stage model ages (T-DM (c) = 0.4-1.4 Ga). Together with the peraluminous affinity of many felsic units, these features indicate that the dacite-rhyolite suites hosting VMS deposits were generated by melting of compositionally heterogeneous lower crust variably hybridized by juvenile basaltic inputs. Arc granitoids likewise record a transition from dominantly juvenile, I-type magmatism during the Coniacian-Santonian to more evolved, crust-influenced signatures during the Campanian. We propose that both flare-ups reflect repeated episodes of basaltic underplating and deep-crustal heating, producing voluminous felsic magmas capable of sustaining long-lived hydrothermal systems. The spatial and temporal coincidence between felsic-dominated flare-ups and VMS mineralization suggests that hybridized felsic magmas, rather than purely juvenile mantle melts, played a central role in generating the physiochemical conditions required for metal-bearing hydrothermal fluids in the ESZ.

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  • MakaleYalnız künye2024
    Petrogenesis of Late Cretaceous A-type plutonic rocks from the Eastern Pontides Orogenic Belt (NE Turkey): constraints from zircon U-Pb geochronology, zircon Lu-Hf and whole-rock Sr-Nd-Pb-Hf isotopes

    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.

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  • MakaleYalnız künye2023
    Two-stage bimodal volcanism in a Late Cretaceous arc/back-arc setting, NE Turkey: Constraints from volcano-stratigraphy, zircon U-Pb and 40Ar/39Ar geochronology and whole-rock elemental and Sr-Nd-Pb isotope geochemistry

    Oguz-Saka, Simge; Aydin, Faruk; Karsli, Orhan; Dokuz, Abdurrahman; Aiglsperger, Thomas; Miggins, Daniel P.; Sen, Cuneyt; Kandemir, Raif; Sari, Bilal; Koppers, Anthony A. P.

    The eastern Blacksea magmatic arc (EBMA) in the eastern Sakarya Zone (ESZ) provides an excellent opportunity to investigate birth of an extensional intra-arc and back-arc settings in the Late Cretaceous over the Early Cretaceous northern passive margin of the Neotethys Ocean. Volcano-stratigraphy clearly shows that the Late Cretaceous volcanic activity of the EBMA occurred in two major phases. Bimodality, characterized by mafic/ basaltic rocks at the base and felsic/silicic types on top of it, is a typical feature of the lower (LVS) and upper (UVS) volcanic successions in the Giresun region of the ESZ. U-Pb and Ar-Ar ages support the volcanic suc-cession as two-stage (LVS: ca. 92-85 and UVS: ca. 83-67 Ma) bimodal volcanism. Both the volcanic successions are represented by similar rock types consisting of tholeiitic to calc-alkaline basalt-basaltic andesites and calc-alkaline to shoshonitic dacite-rhyolites. Basaltic (M1-and M2-series) and felsic/silicic (F1-and F2-series) sam-ples of the LVS and UVS have an arc-like signature with enriched large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted high field strength elements (HFSEs). Also, the felsic/silicic samples of the F1-and F2-series show prominent negative Sr and Eu anomalies (Eu/Eu* = 0.4 to 0.9), suggesting that plagioclase fractionation played a key role on the evolution of both felsic series. Bimodal rock series in two phases have a wide range of 87Sr/86Sr(i) (0.7048-0.7075) and 143Nd/144Nd(i) (0.5123-0.5127) ratios with var-iable epsilon Nd(i) values of-3.8 to +3.0. 206Pb/204Pb(i), 207Pb/204Pb(i) and 208Pb/204Pb(i) isotope ratios of the Giresun volcanic rocks vary in the range of 17.97-18.52, 15.55-15.65 and 37.53-38.56, respectively. Geochemical and isotopic data suggest that the parental magma of the M1-basaltic rocks were probably derived from a shallow (spinel-bearing) mantle metasomatized by slab/sediment-derived fluids. In contrast, the M2-basalts seem to have been originated from a deeper mantle source (spinel-garnet transition zone) enriched by slab/sediment-derived fluids and hydrous melts (bulk sediment) metasomatism with some contributions of lower/upper crustal materials. The least evolved basaltic samples in two phases are consistent with moderate (-10-15%) to high degree (-20-30%) partial melting of the metasomatized mantle. The silicic melts of the F1 -and F2-rocks series, on the other hand, were likely derived from melting of lower crustal materials consisting of meta-basalts/andesites and lesser amount of meta-sediments. Subsequently, these melts experienced FC +/- AFC and mixing processes during their ascent and emplacement to generate high-silica (rhyolitic) melts. Our data, combined with previous studies, suggest that two-stage bimodal volcanic rocks of the Late Cretaceous in the ESZ were formed in the transition from an extensional continental intra-arc to a back-arc setting during the north-ward subduction of the northern branch of Neotethys Ocean.

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  • MakaleAçık Erişim2021
    Geochemistry and Pb isotopic proof for sources of heavy metal(loid)s in Late Cretaceous sandstones from Eastern Pontides (NE Turkey)

    Saydam Eker, Çiğdem

    Upper Cretaceous sedimentary rocks are widely exposed around Trabzon, Giresun and Gümüşhane in the eastern Pontides. The sedimentary rocks are mainly composed of sandstones and marls, and the thicknesses of these rocks range from 170 to 400 m. This paper focused on Late Cretaceous sandstones of Trabzon, Giresun and Gümüşhane regions to identify the concentrations, sources, deposition environment and conditions of certain heavy metal(loid)s (Zn, Pb, Cu, Ni, As, Co, Mo and V). Enrichment factor (EF), geo-accumulation index (Igeo), Pollution index (Pi), Pollution load index (Pln), Pb isotope and multivariate statistical analysis were performed to elucidate the pollution levels and sources. In general, the evaluation indices exhibited that the sandstones were moderately polluted by As in the Trabzon area, and strongly polluted by Ni and As, moderately polluted by Co and V in the Giresun and Gümüşhane areas. The results of multivariate statistical analyses indicated that As and partly Pb might be originated from anthropogenic sources, whereas other metals were derived from geogenic origin. Lead isotopic analysis demonstrated two characterized signatures of the pollution sources in the sandstones, one related to geogenic origin and the other to coal, gasoline and pesticides. The sandstones were deposited in transition—marine environment under oxic—weak oxic conditions and paleoclimatic conditions ranged from arid to moist during Late Cretaceous period.

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  • MakaleYalnız künye2020
    Temporal, geochemical and geodynamic evolution of the Late Cretaceous subduction zone volcanism in the eastern Sakarya Zone, NE Turkey: Implications for mantle-crust interaction in an arc setting

    Aydin, Faruk; Oğuz Saka, Simge; Şen, Cüneyt; Dokuz, Abdurrahman; Aiglsperger, Thomas; Uysal, İbrahim; Kandemir, Raif; Karslı, Orhan; Sarı, Bilal; Başer, Rasim

    The Late Cretaceous Artvin volcanic rocks (LCAVs) from the eastern Sakarya zone (ESZ) of NE Turkey are composed of mafic/basaltic (S1-Çatak and S2-Çağlayan) and felsic/acidic (S1-Kızılkaya and S2-Tirebolu) rock types that occurred in two successive stages: (i) first stage (S1: Turonian–Early Santonian) and (ii) second stage (S2: Late Santonian–Campanian). Clinopyroxene thermobarometric results point that the S2-Çağlayan basaltic rocks have crystallised at higher temperatures and under deeper crustal conditions than those of the S1-Çatak basaltic rocks. The LCAVs show a wide compositional spectrum, ranging from tholeiite to calc-alkaline/shoshonite and are typically represented by a geochemical composition resembling subduction-related arc rocks although the 87Sr/86Sr(i) (0.7044–0.7071) and ɛNd(i) values (−0.63 to + 3.47) as well as 206Pb/204Pb(i) (18.07–18.56), 207Pb/204Pb(i) (15.57–15.62) and 208Pb/204Pb(i) (37.12–38.55) ratios show very limited variation. The parent magmas of the S1-Çatak and S2-Çağlayan mafic volcanic rocks were derived from underplated basaltic melts that originated by partial melting of metasomatised spinel lherzolite and spinel-garnet lherzolite, respectively. It is proposed that the compositions of the S1-Kızılkaya (mainly dacitic) and S2-Tirebolu (rhyolitic to trachytic) felsic rocks were particularly controlled by metasomatised mantle–crust interaction and MASH zone + shallow crustal fractionation processes. Our data, together with data from previous studies, suggest that the S1- and S2-mafic and felsic rocks of the LCAVs (~95–75 Ma) are the products of two-stage volcanic event that took place during the northward subduction of the northern Neotethys Ocean (NNO).

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  • Derleme MakaleAçık Erişim2018
    Late Cretaceous arc igneous activity: the Eğrikar Monzogranite example

    Sipahi, F.; Kaygusuz, A.; Saydam Eker, Ç.; Vural, A.; Akpınar, İ.

    The geochemical and Sr–Nd–Pb isotope properties, as well as the Laser Ablation Inductively Coupled Plasma and Mass Spectrometry (LA-ICP-MS) U–Pb zircon age, of Eğrikar Monzogranite in the eastern Pontides, are primarily investigated in this study with the aim of determining its magma source and geodynamic evolution. The U–Pb zircon age obtained from Eğrikar Monzogranite is 78 ± 1.5 Ma, thereby reflecting the age of monzogranite. The I-type Eğrikar Monzogranite comprises quartz, plagioclase (An35–45), orthoclase, muscovite, and biotite. The geochemical analyses of the Eğrikar Monzogranite indicate being medium K calc-alkaline, peraluminous, and resembling magmatic arc granite. The Eğrikar Monzogranite is enriched in large ion lithophile elements and light rare earth elements relative to high field strength elements. Chondrite-normalized rare earth element patterns have concave upward shapes (LaN/YbN 2.47–8.58) with pronounced negative Eu anomalies (EuN/Eu* = 0.29–0.65). Initial εNd(i) values vary between 1.85 and 2.18 and initial 87Sr/86Sr values between 0.7048 and 0.7067. Fractionation of plagioclase, hornblende, and apatite played an important role in the evolution of Eğrikar Monzogranite. The crystallization temperatures of the melts ranged from 770°C to 919°C based on zircon and apatite saturation temperatures. The geochemical and isotopic data suggest being generated by the partial melting of mafic lower crustal sources.

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  • MakaleYalnız künye2014
    LA-ICP MS zircon dating, whole-rock and Sr-Nd-Pb-O isotope geochemistry of the Camiboǧazi pluton, Eastern Pontides, NE Turkey: Implications for lithospheric mantle and lower crustal sources in arc-related I-type magmatism

    Kaygusuz, Abdullah; Arslan, Mehmet; Siebel, Wolfgang; Sipahi, Ferkan; Ilbeyli, Nurdane; Temizel, Irfan

    Late Cretaceous I-type plutons are widespread in the Eastern Pontides, NE Turkey. The studied Camiboǧazi pluton is a composite pluton consisting of diorite, tonalite, monzodiorite, monzonite, quartz monzonite, granite, and mafic microgranular enclaves (MMEs). Laser ablation ICP-MS U-Pb dating of zircon yielded crystallization ages of 76.21±0.79Ma, 75.65±0.50Ma, 75.04±0.83Ma, and 74.73±0.86Ma for diorite, monzodiorite, monzonite, and granite, respectively. The rocks of the pluton have I-type, high-K to shoshonitic and metaluminous character, displaying whole-rock geochemical features of arc-related granites. They are enriched in large-ion lithophile and light rare-earth elements, and depleted in high-field-strength elements. Major element variations can be attributed to fractionation of plagioclase, clinopyroxene, hornblende, and Fe-Ti oxides. The rocks show considerable variation in 87Sr/86Sr(i) (0.70498 to 0.70622), εNd(i) (-2.79 to -0.36), δ18O values (+6.3 to +11.4) and Nd model ages (TDM) (0.81Ga to 1.26Ga). Besides, they have (206Pb/204Pb)=18.44-19.09, (207Pb/204Pb)=15.64-15.69, and (208Pb/204Pb)=38.37-38.89. Although isotope signatures of the mafic microgranular enclaves (MMEs) (87Sr/86Sr(i)=0.70551 to 0.70622; εNd(i)=-2.9 to -1.23; δ18O=+8.3 to +9.7) are largely similar to the host rocks, MMEs are characterized by relatively high Mg-numbers (32-36), low contents of SiO2 (52-56wt.%) and low ASI (0.7-0.9). Estimated crystallization temperatures for the rocks of the pluton range from 735±58°C to 844±24°C and a shallow intrusion depth (<10km) is estimated from Al-in-hornblende thermobarometry. Whole-rock geochemical and isotopic data suggest magma generation by dehydration melting of an amphibolite-type lower crustal component with additional input of a subcontinental lithospheric mantle component. Furthermore, Sr-Nd isotope mixing model reveals ~30% to 40% lower crustal magma contribution to the mantle component.

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  • MakaleAçık Erişim2013
    Petrogenesis of the late Cretaceous Turnagöl intrusion in the eastern Pontides: Implications for magma genesis in the arc setting

    Kaygusuz, Abdullah; Sipahi, Ferkan; Ilbeyli, Nurdane; Arslan, Mehmet; Chen, Bin; Aydinçakir, Emre

    A series of Cretaceous plutons is present in the eastern Pontides of northeastern Turkey. The Turnagöl intrusion is the least studied and, thus, the least understood plutons in the orogen. This intrusion consists of hornblende-biotite granodiorites emplaced at 78 Ma based on LA-ICP-MS U-Pb zircon dating. It is of sub-alkaline affinity, belongs to the medium- to high-K calc-alkaline series, and displays features typical of I-type granites. The rocks of the intrusion are enriched in large-ion lithophile elements and light rare earth-elements with negative Eu anomalies (Eu/Eu* = 0.69-0.82), but are deficient in high-field-strength elements. They have a small range of ( 87Sr/86Sr)i (0.7060-0.7063), ÉNdi(-2.6 to -3.1), and δ18O (+8.1 to +9.1) values. Their Pb isotopic ratios are 206Pb/204Pb = 18.63-18.65, 207Pb/ 204Pb = 15.62-15.63, and 208Pb/204Pb = 38.53-38.55. The fractionation of plagioclase, hornblende, and Fe-Ti oxides had key functions in the evolution of the Turnagöl intrusion. The crystallization temperatures of the melts ranged from 758 to 885 C as determined by zircon and apatite saturation thermometry. All these characteristics, combined with the low values of K2O/Na2O and (Na 2O + K2O)/(FeOt + MgO + TiO2), as well as the high values of (CaO + FeOt + MgO + TiO2), suggest an origin by dehydration melting from a metabasaltic lower crustal source.

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  • MakaleYalnız künye2011
    Mineralogy and whole rock geochemistry of lzate Cretaceous sandstones from the eastern Pontides (NE Turkey)

    Eker, Cigdem Saydam; Korkmaz, Sadettin

    This study focuses on Upper Cretaceous sandstones of the Eastern Pontides to identify the source area, subaerial weathering level, and tectonic environment. Thirty four sandstone samples from six stratigraphic sections were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MC) and by petrographic investigation. The late Cretaceous sandstones are defined as lithic arenites and feldspathic wackes, and lithic wackes depending on mineralogical and matrix content. The sandstones have low to moderate SiO2 contents (25-59%; on average -56%). There are high positive correlations between SiO2 Al2O3, and TiO2 and negative correlations between SiO2 and K2O. Geochemically, the sandstones are classified mainly as grey wackes and lithic arenites. Chemical index of alteration (CIA) and chemical index of weathering (CIW) values for Upper Cretaceous sandstones vary from 19 to 48 % and 20 to 49 % respectively. The combination of CIW/CIA values suggests little transportation until final deposition. The ratios of Th/Sc (on average -0.42), La/Sc (-1.81), Co/Th (-5.05) and Zr/Hf (-39.1) of sandstone samples in the study area indicate a mafic source. Furthermore, high light rare earth elements (LREE)/heavy rare earth elements (HREE) ratios (on average -19.72) and negative Eu anomalies (except in the Dagbasi section) suggest a contribution from a felsic source. The lower trace element contents of the Upper Cretaceous sandstones in relation to the Post-Archean Australian Shale (PAAS), which are considered to be representative of the upper continental crust, show that the recycling processes in their source areas were probably less intense than those of the PAAS. SiGyAlA (3.2-7.9) and K2O/Na20 (0.3-1) ratios, together with the Th (on average -3.3 ppm), Zr (on average -91.9 ppm), Co (on average -15 ppm), and Sc (on average -12.6 ppm) contents of the late Cretaceous sandstones of the eastern Pontides indicate a magmatic arc origin. Sandstones of the Trabzon region were probably deposited in fore-arc basins, and those from the Gumushane and Giresun regions in back-arc basins.

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  • MakaleYalnız künye2008
    Source rock characteristics and hydrocarbon potential of the late cretaceous deposits in the eastern black sea region, NE Turkey

    Saydam, C.; Korkmaz, S.

    In this article, source rock characteristics and hydrocarbon potential of the late Cretaceous turbidite sequences in the eastern Black Sea region were investigated. The total average organic carbon (TOC) contents of sequences in Trabzon, Gümüshane, Giresun, and Erzurum are 0.06, 0.18, 0.12, and 0.30 wt%, respectively. In addition, low potential yield (PY), low hydrogen index (HI), and very high oxygen index (OI) values were calculated for these sequences. On the basis of Tmax values, most of sequences are thermally immature, and only some parts are mature and over-mature. Sequences generally contain residual organic matter and lesser amounts of type III kerogen. CPI values higher than 1, n-alkane distributions with high carbon numbers, and type III kerogen content indicate that organic matter has a terrestrial origin. The Pr/Ph ratios calculated as 1.10 and 2.15 for the Mescitli section of the Gümüshane region and the Tortum section of the Erzurum region reveal that the Mescitli section was deposited in a suboxic environment, while the Tortum section was in an oxic environment. According to these data, late Cretaceous sequences show weak source rock characteristics.

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