6 results on '"AYDIN, Faruk"'
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2. Tracking the timing of Neotethyan oceanic slab break-off: Geochronology and geochemistry of the quartz diorite porphyries, NE Turkey.
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Karsli, Orhan, Dokuz, Abdurrahman, Aydin, Faruk, Uysal, İbrahim, Şengün, Fırat, Kandemir, Raif, Santos, José Francisco, and Andersen, Tom
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TONALITE , *RARE earth metals , *GEOLOGICAL time scales , *GEOCHEMISTRY , *ADAKITE , *PORPHYRY , *DIORITE - Abstract
• The Early Eocene porphyries are I-type metaluminous in composition. • These porphyries were derived from an enriched mantle domain. • Infiltration of asthenosphere due to slab break-off event triggered partial melting. • The porphyries represent an early stage of extensional tectonic in the Sakarya Zone. The initiation of the break-off of the northern branch of the Neotethyan oceanic lithosphere is an important but poorly understood event in the geology of the Sakarya Zone (SZ) in northeastern Turkey. Although it is well-known that Latest Cretaceous intrusives (~70 Ma) and early Eocene adakitic magmatic rocks are present in the eastern SZ, the outcrops of the early Eocene non-adakitic rocks are very limited, and their tectono-magmatic evolution has not been studied. We describe a small outcrop of non-adakitic quartz diorite porphyry in the Kov area of the Gümüşhane region in northeastern Turkey. The genesis of these porphyries is significant in evaluating the syn- to post-collision-related magmatism. The LA-ICP-MS zircon U-Pb dating revealed that the Kov quartz diorite porphyries (KQDP) formed at ca. 50 Ma, coeval with adakitic rocks, and ~20 Myr later than the slab roll-back-related intrusive rocks. The KQDPs are calc-alkaline in composition and enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, Ti), with significant negative anomalies of Nb, Ta, and Ti but positive anomalies of Th, U, and Pb. Isotopic compositions of the samples show limited range of variation and slight enrichment of 87Sr/86Sr(t) (0.70489 to 0.70555), ε Nd (t) (−1.4 to −1.2) with T DM of 1.11 to 1.61 Ga. Pb isotopic ratios of the samples point to an enriched mantle source. They were likely crystallized from the melt that originated from an EM2-type spinel-facies subcontinental lithospheric mantle (SCLM), followed by the fractionation with insignificant crustal assimilation. The SCLM was metasomatically enriched, and the metasomatic agent was likely H 2 O-rich fluids rather than sediments released from subducting oceanic crust during the Late Cretaceous closure of the Neotethyan oceanic lithosphere. In conjunction with the geological background and previous data, we propose that the generation of the KQDPs resulted from a slab break-off event that caused ascending or infiltration of hot asthenosphere, triggering mantle melting. Such sporadic occurrences of the KQDPs, with coeval adakitic rocks in the SZ, are likely associated with the onset of extensional tectonics due to the earlier stage of slab break-off along the region during the early Eocene period. [ABSTRACT FROM AUTHOR]
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- 2020
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3. Adakite-like granitoid porphyries in the Eastern Pontides, NE Turkey: Potential parental melts and geodynamic implications
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Karsli, Orhan, Ketenci, Murat, Uysal, İbrahim, Dokuz, Abdurrahman, Aydin, Faruk, Chen, Bin, Kandemir, Raif, and Wijbrans, Jan
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ADAKITE , *PORPHYRY , *GRANITE , *GEODYNAMICS , *STRUCTURAL geology , *SUBDUCTION zones - Abstract
Abstract: The tectonic setting of the Eastern Pontides during the late Mesozoic to early Cenozoic remains a subject of debate. Petrogenesis of adakite-like granitoid porphyries plays a critical role in determining the nature of the lower continental crust and mantle dynamics during orogenic processes in the region. Here we describe, for the first time, the late Paleocene to early Eocene adakite-like granitoid porphyries from the northern part of the Eastern Pontides although their counterparts in the southern part have recently been found. The adakitic porphyries, which emplaced into the subduction-related Turonian–Santonian volcanics from northern part of the region, consist of I-type calc-alkaline quartz monzonite–tonalite (SiO2 =62.89–65.07wt.%) and high-K calc-alkaline granodiorite–granite associations (SiO2 =69.06–70.43wt.%). The former displays peraluminous to metaluminous signatures, whereas the latter shows peraluminous geochemical character. The granite–granodiorite porphyries have high K2O (3.32–3.84wt.%), and low Na2O (3.48–4.61wt.%) and MgO (0.91–1.04wt.%) relative to the quartz monzonite–tonalite association (K2O=1.50–1.92 wt.%; Na2O=4.08–6.45 wt.%; MgO=1.44–2.07 wt.%). Ar–Ar geochronology studies on the amphibole separates reveal that the adakite-like porphyries have a crystallization ages of 51.34±0.27 to 53.55±0.34Ma. Here, we contend that these rocks were formed by partial fusion of a mafic lower continental crust in a collisional phase but not in a subduction setting. All the samples exhibit the typical geochemical characteristics of adakite, that is, high Sr (250–1141ppm), high Sr/Y ratios (16–147), low Y (6.8–14.8ppm) and low HREE concentrations; they are similar to adakites formed by slab melting associated with the subduction zone. However, the rocks exhibit heterogeneity in isotopic composition, with ISr ranging from 0.70554 to 0.70986, εNd (51Ma) from –8.5 to –0.9 and Nd model ages from 0.72 to 1.26 Ga. The samples are characterized by relatively high Th, Th/U and no significant Eu anomalies, implying that garnet was stable in their source during partial melting. The compositional diversity between rock groups is probably related to partial melting of heterogeneous lower crustal source. All of the features are inconsistent with a slab-melting origin and slab-related petrogenetic model, but instead, they favor an origin by melting of heterogeneous lower continental crust due to a thermal anomaly that was induced by the upwelling of the asthenosphere through a slab break-off in a collisional setting. These interpretations argue against the evidence for the presence of an early Cenozoic arc setting in the Eastern Pontides. Instead, the early Cenozoic time in the region may be attributed to a geodynamic response to a post-collisional uplift phase that occurred along the continent-continent collision between the Pontide and the Anatolide-Tauride blocks. [Copyright &y& Elsevier]
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- 2011
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4. Nature of the Early Cretaceous lamprophyre and high-Nb basaltic dykes, NE Turkey: Constraints on their linkage to subduction initiation of Neotethyan oceanic lithosphere.
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Karsli, Orhan, İlhan, Mehdi, Kandemir, Raif, Dokuz, Abdurrahman, Aydin, Faruk, Uysal, İbrahim, and Duygu, Levent
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ADAKITE , *RARE earth metals , *LITHOSPHERE , *LAMPROPHYRES , *SUBDUCTION , *IGNEOUS rocks , *STRONTIUM , *RUBIDIUM - Abstract
Late Mesozoic evolution of the Neotethys Ocean is critical and still remains unclear along the entire Sakarya Zone (SZ), Turkey, because previous interpretations of the Middle to Late Jurassic rifting of the SZ have not been consensually accepted. We identified, for the first time, the Early Cretaceous dykes intruded into the Late Jurassic and Late Carboniferous bodies in the Çamlıkaya (Erzurum) area in the SZ. Here, we present a data set of new field observations, 40Ar/39Ar geochronology, whole-rock geochemical and Sr–Nd isotopes to find out the tectonic setting of previously undated basic to intermediate igneous rocks. 40Ar/39Ar technique on the groundmass separations yielded the plateau ages of 128.78 ± 1.02 to 122.89 ± 0.82 Ma. The investigated dykes are compositionally divided into two sub-groups: calc-alkaline lamprophyres (CAL) and high-Nb alkaline basalts (HNB). They show enrichment in large ion lithophile elements (LILE: e.g., Rb, Ba, K) and depletion in high field strength elements (HFSE: Nb and Ti) as well as moderate fractionation of light rare earth elements relative to heavy rare earth elements. The HNB have high Mg# (47–66), and relatively unradiogenic Sr 87Sr/86Sr(t) = 0.70385 to 0.70510] and Nd [ε Nd (t) = +0.5 to +5.3] isotopic composition, whereas the CAL possess moderate to high Mg# (32–72), and relatively high Sr 87Sr/86Sr(t) = 0.70586 to 0.71379] and Nd [ε Nd (t) = +1.5 to −9.9] isotopic composition. Early Cretaceous high-angle subduction triggered upwelling of the asthenosphere at 126 Ma, which likely generated a heat anomaly. This anomaly has probably induced melting of the oceanic slab and the metasomatized mantle to form the CAL and HNB. The HNB were generated by low degrees of melting of mantle domain that was previously reacted by oceanic slab-related adakitic melts at the depths of the garnet stability field (≥70 km). However, the CAL were probably formed at shallower mantle levels within the garnet-amphibole field by a relatively higher degree of melting of the mantle, also modified by subducted slab sediments. A new field, age, and petrochemical data from the Early Cretaceous dykes, combined with the presence of Aptian deep-water sediments to the north and the Late Jurassic-Early Cretaceous platform carbonates deposited in the passive margin setting along the entire SZ, imply the initiation of active-margin magmatism in the SZ. We suggest that the coexistence of the Early Cretaceous CAL and HNB points to the formation of an Andean-type active margin above a north-dipping Neotethyan oceanic slab. Their emplacement ages are associated with the inception of the magmatic arc structure and refer to a significant geodynamic turnover from passive-margin to active-margin tectonics along the SZ. • Ar–Ar dating suggest presence of an Early Cretaceous volcanism in the Sakarya Zone. • The CALs and HNBs were originated from an enriched mantle wedge. • All geochemical features indicate that they formed in a subduction setting. • All data refer a geodynamic shift from passive- to active-margin tectonics. [ABSTRACT FROM AUTHOR]
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- 2021
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5. Silurian to Early Devonian arc magmatism in the western Sakarya Zone (NW Turkey), with inference to the closure of the Rheic Ocean.
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Karsli, Orhan, Şengün, Fırat, Dokuz, Abdurrahman, Kandemir, Raif, Aydin, Faruk, and Andersen, Tom
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MAGMATISM , *OCEAN , *BACK-arc basins , *LITHOSPHERE , *SUTURE zones (Structural geology) , *ADAKITE ,GONDWANA (Continent) ,PANGAEA (Supercontinent) - Abstract
The Rheic Ocean is the most significant Paleozoic ocean that detached peri-Gondwana terranes from the northern Gondwana margin throughout the closure of the Iapetus Ocean. The suture of the Rheic Ocean spreads from Mexico to the Middle East, and the timing of its final closure is well-documented by the rocks formed in the Variscan-Alleghanian-Ouachita orogeny which led to the formation of the supercontinent Pangaea. However, as robust paleomagnetic and quantitative data are mostly lacking, the onset and evolution of the subduction of the Rheic Ocean are highly speculative, and they require further confirmation. Recently, the well-preserved metagranitoids along the western Sakarya Zone (SZ) in Anatolia have been identified, and they provide new data that improve our knowledge on the evolution of the Early Paleozoic Rheic Ocean along the northern Gondwana. Here, we present new geochronological, in situ zircon Hf isotope, and whole-rock geochemical analyses of these metagranitoids from the western SZ to enhance our understanding of the subduction processes of the Rheic Ocean. LA-ICP-MS zircon U-Pb dating demonstrated that the Bozüyük and Borçak metagranitoids from the western SZ were emplaced during the Silurian to Early Devonian (431 ± 2.7 to 403 ± 3.5 Ma). The both granitoids have medium- to high-K, calc-alkaline magmatic character, and exhibit peraluminous to slightly metaluminous geochemical signature. They show a typical arc pattern in terms of trace elements and have a uniform, moderate negative ε Hf (t) of −3.2 to −9.7, with Mesoproterozoic Hf depleted mantle model ages (T DM1 = 1.2 to 1.4 Ga). The geochemical and isotopic characteristics are not consistent with those of depleted mantle melts and melts derived from the crustal rocks in an intracontinental environment. Instead, the parental magma is likely generated from the partial melting of a homogeneous and enriched mantle wedge source. We propose that the Silurian to Early Devonian arc-related magmatism is associated with a northward subduction episode of the Rheic Oceanic lithosphere beneath the peri-Gondwana terranes. Hence, we consider that the opening of Paleotethys Ocean formed in a back-arc basin of subduction in Andean style to the north rather than a continental rift to the south in response to south-directed and short-lived supra-subduction zone (SSZ)-type subduction during the Silurian to Early Devonian. Unlabelled Image • Silurian to Early Devonian magmatism were recognized in the Sakarya Zone. • The metagranitoids originated from an enriched mantle domain. • Asthenospheric upwelling due to slab roll-back caused partial melting of mantle. • All the geochemical features indicate that they formed in a subduction setting. • The closure of Rheic Ocean triggered opening of Paleotethys in back-arc to north. [ABSTRACT FROM AUTHOR]
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- 2020
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6. Generation Of The Early Cenozoic Adakitic Volcanism By Partial Melting Of Mafic Lower Crust, Eastern Turkey: Implications For Crustal Thickening To Delamination
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Orhan Karsli, Jan R. Wijbrans, Ibrahim Uysal, Faruk Aydin, Raif Kandemir, Abdurrahman Dokuz, Petrology, Wijbrans, Jan -- 0000-0002-8091-1239, [Karsli, Orhan -- Dokuz, Abdurrahman -- Kandemir, Raif] Gumushane Univ, Dept Geol Engn, TR-29000 Gumushane, Turkey -- [Uysal, Ibrahim] Karadeniz Tech Univ, Dept Geol Engn, TR-61100 Trabzon, Turkey -- [Aydin, Faruk] Nigde Univ, Dept Geol Engn, TR-58000 Nigde, Turkey -- [Wijbrans, Jan] Vrije Univ, Lab Isotope Geol, NL-1081 HV Amsterdam, Netherlands, and 0-Belirlenecek
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Peridotite ,Sr-Nd isotopes ,geography ,geography.geographical_feature_category ,Continental crust ,Andesite ,Early Eocene volcanism ,Adakites ,Partial melting ,Geochemistry ,Geology ,Crust ,NE Turkey ,Andesite and dacite ,Volcanic rock ,Geochemistry and Petrology ,Adakite ,SDG 14 - Life Below Water ,Mafic ,Eastern Pontides ,Delaminated mafic lower crust - Abstract
WOS: 000274378300008, Early Cenozoic (48-50 Ma) adakitic volcanic rocks from the Eastern Pontides NE Turkey consist of calc-alkaline and high-K calc-alkaline andesite and dacite, with SiO(2) contents ranging from 56 01 to 65 44 wt.%.. This is the first time that Early Eocene volcanism and adakites have been reported from the region. The rocks are composed of plagioclase, amphibole, quartz, and Mg-rich biotite. They have high and low-Mg# values ranging from 55 to 62 and 13 to 42. respectively. High-Mg# rocks have higher Ni and Co contents than low-Mg# samples. The rocks exhibit enrichments in large ion lithophile elements including the light rare earth elements, depletions in Nb, Ta and Ti and have high La/Yb and Sr/Y ratios. Their relative high I(Sr) (0.70474-0.70640) and low epsilon(Nd) (50 Ma) values (-2.3 to 0.8) are inconsistent with an origin as partial melts of a subducted oceanic slab. Combined major- and trace element and Sr-Nd isotope data suggest that the adakitic magmas are related to the unique tectonic setting of this region, where a transition from a collision to an extension stage has created thickening and delamination of the Pontide mafic lower crust at 50 Ma The. high-Mg adakitic magmas resulted from partial melting of the delaminated eclogitic mafic lower crust that sank into the relatively hot subcrustal mantle, and its subsequent interaction with the mantle peridotite during upward transport, leaving garnet as the residual phase, elevates the MgO content and Mg# of the magmas, whereas low-Mg# magmas formed by the melting of newly exposed lower crustal rocks caused by asthenospheric upwelling, which supplies heat flux to the lower crust. The data also suggest that the mafic lower continental crust beneath the region was thickened between the Late Cretaceous and the Late Paleocene and delaminated during Late Paleocene to Early Eocene time, which coincides with the initial stage of crustal thinning caused by crustal extensional events in the Eastern Pontides and rules out the possibility of an extensional regime before similar to 50 Ma in the region during the Late Mesozoic to Early Cenozoic. (C) 2009 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [107Y177], Financial support of this work was provided by the Scientific and Technological Research Council of Turkey (TUBITAK) with grant# 107Y177. We thank Bin Chen for the Sr-Nd isotopic analyses and Ahmet D. Sen and Murat Ketenci for their assistance with the fieldwork. Special thanks are due to Murat Erduran for his useful comments on an early version of this manuscript. We thank the editor, Professor Nelson Eby, and Pat Castillo and an anonymous reviewer for their constructive reviews.
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- 2010
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