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- MakaleYalnız künye2020Eocene tonalite–granodiorite from the Havza (Samsun) area, northern Turkey: adakite-like melts of lithospheric mantle and crust generated in a post-collisional setting
Temizel, Irfan; Arslan, Mehmet; Yücel, Cem; Abdioğlu Yazar, Emel; Kaygusuz, Abdullah; Aslan, Zafer
Eocene intermediate to felsic plutons of different sizes and compositions are widespread in the Eastern Pontides Orogenic Belt in northern Turkey. Of these, the Taşlık Tepe pluton in the Havza (Samsun) area is fine-to-medium-grained, with granular, porphyritic, and micrographic textures, and include mafic microgranular enclaves (MMEs). LA-ICP-MS U-Pb zircon dating yielded emplacement ages of 42.9 (± 1.4) and 40.5 (± 1.3) Ma for the host granodioritic pluton and the dioritic MMEs, respectively. Petrochemically, the host pluton has I-type, high-K calc-alkaline, and metaluminous-to-slightly peraluminous features (A/CNK = 0.95–1.06). The host pluton also shows geochemical features of adakite-like rocks with high SiO2 (67–68 wt%) and Al2O3 (15.5–16.0 wt%) content and Ba/La (17–23), Sr/Y (40.7–61.6), and LaN/YbN (14.4–23.7) ratios and low Y (8.2–9.9 ppm) and YbN (3.1–4.4) contents. Whole-rock major and trace element variations suggest that fractional crystallisation played a significant role in the pluton evolution. The N-MORB normalised trace element patterns of the pluton are similar to those of MMEs with enrichment in large-ion lithophile elements, Th and Ce, and negative Nb and Ti anomalies. Chondrite-normalised rare earth element plots show moderate-to-highly enriched concave patterns (LaN/LuN = 14.2–21.6) with insignificant negative Eu anomalies (EuN/Eu* = 0.86–1.14), all of which imply hornblende fractionation during magmatic evolution. The pluton samples have 87Sr/86Sr ratios of 0.704767 to 0.704927, 143Nd/144Nd ratios of 0.512767–0.512774, εNd values of (+2.52)–(+2.65), and δ18O values of 7.9–9.7‰. The isotopic compositions of the host pluton and MMEs are similar to I-type granitoids derived from mantle sources. The MMEs show incomplete magma mixing/mingling, representing small bodies of mafic parental magma. Combined with regional studies, these new data suggest that the parental magma of the studied adakite-like pluton was generated from the lithospheric mantle and then modified by fractional crystallisation and assimilation in a post-collisional setting.
- MakaleYalnız künye2015Geochronology, geochemistry, and petrogenesis of the Eocene Bayburt intrusions, Eastern Pontides, NE Turkey: Evidence for lithospheric mantle and lower crustal sources in the high-K calc-alkaline magmatism
Kaygusuz, Abdullah; Öztürk, Mürşit
Eocene I-type plutons are widespread in the Eastern Pontides, Northeastern Turkey. Geochemical and isotopic results on two Eocene intrusive bodies located in the southern zone of the Eastern Pontides were utilized to achieve a proper reconstruction of their origin. Based on laser ablation ICP-MS U-Pb zircon dating, Kiliçkaya and Kozluk intrusions present similar 206Pb/238U versus 207Pb/235U concordia ages of 46.75±0.79 and 46.9±0.68 Ma, respectively. Both intrusions exhibit similar petrographical, geochemical, and isotopical features, and contain abundant mafic microgranular enclaves (MMEs). The intrusive rocks are composed of diorite, tonalite, and granodiorite, whereas MMEs are composed of diorite. Both the intrusive rocks and the MMEs are I-type, high-K calc-alkaline in composition and display a metaluminous character. They are enriched in large-ion lithophile and light rare-earth elements and are depleted in high-field strength elements. The intrusive rocks show moderate variation in 87Sr/86Sr(i) (0.70531-0.70576), εNd(i) (+0.3 to -0.5), and δ18O values (+6.6 to +6.9), as well as Nd model ages (0.73-0.82Ga). Their Pb isotopic ratios are 206Pb/204Pb=18.67-18.86, 207Pb/204Pb=15.61-15.62, and 208Pb/204Pb=38.62-39.03. Although the isotope signatures of MMEs (87Sr/86Sr(i)=0.70528-0.70561; εNd(i)=+0.7 to -0.3; δ18O=+6.7 to +6.8) are significantly similar to those of the host rocks, the MMEs are characterized by relatively low contents of SiO2 (57-59wt.%), low aluminum saturation index (0.8-0.9), and high Mg numbers (31-36). All of these data suggest magma generation by mixing of enriched lithospheric mantle- and lower crustal-derived melts. Moreover, Sr-Nd isotopic modeling reveals ~17% to 23% lower crustal magma contribution to the mantle component.
- MakaleYalnız künye2014LA-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.
- MakaleAçık Erişim2013Petrogenesis 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.
- MakaleYalnız künye2012Geochronological evidence and tectonic significance of Carboniferous magmatism in the southwest Trabzon area, eastern Pontides, Turkey
Kaygusuz, Abdullah; Arslan, Mehmet; Siebel, Wolfgang; Sipahi, Ferkan; Ilbeyli, Nurdane
The northern and southern zones of the eastern Pontides (northeast Turkey) contain numerous plutons of varying ages and compositions. Geochemical and isotopic results on two Hercynian granitoid bodies located in the northern zone of the eastern Pontides allow a proper reconstruction of their origin for the first time. The intrusive rocks comprise four distinct bodies, two of which we investigated in detail. Based on LA-ICP-MS U-Pb zircon dating, the Derinoba and Kayadibi granites have similar 206Pb/ 238U versus 207Pb/ 235U Concordia ages of 311.1 2.0 and 317.2 3.5 million years for the former and 303.8 1.5 million years for the latter. Aluminium saturation index values of both granites are between 0.95 and 1.35, indicating dominant peraluminous melt compositions. Both intrusions have high SiO 2 (74-77 wt.%) contents and show high-K calc-alkaline and I-to S-type characteristics. Primitive mantle-normalized element diagrams display enrichment in K, Rb, Th, and U, and depletion in Ba, Nb, Ta, Sr, P, and Ti. Chondrite-normalized rare earth element patterns are characterized by concave-upward shapes and pronounced negative Eu anomalies with L acn/Y bcn=4.6-9.7 and E ucn/Eu*=0.11-0.59 (Derinoba), and L acn/Y bcn=2.7-5.5 and E ucn/Eu*=0.31-0.37 (Kayadibi). These features imply crystal-melt fractionation of plagioclase and K-feldspar without significant involvement of garnet. The Derinoba samples have initial Nd values between-6.1 and-7.1 with Nd model ages and T DM between 1.56 and 2.15 thousand million years. The Kayadibi samples show higher initial Nd (I) values,-4.5 to-6.2, with Nd model ages between 1.50 and 1.72 thousand million years. This study demonstrates that the Sr isotope ratios generally display negative correlation with Nd isotopes; Sr isotope ratios were lowered in some samples by hydrothermal interaction or alteration. Isotopic and petrological data suggest that both granites were produced by the partial melting of early Palaeozoic lower crustal rocks, with minor contribution from the mantle. Collectively, these rocks represent a late stage of Hercynian magmatism in the eastern Pontides.