Yazarlar
- Sayit, Kaan(5)
- Çimen, Okay(4)
- Aktağ, Alican(3)
- Göncüoğlu, M. Cemal(2)
- Önal, Ayten Öztüfekçi(2)
- Bamyacı, Onur(1)
- Boztug, Durmus(1)
- Cooper, Alan F.(1)
- Erdoğu, Burçin(1)
- Furman, Tanya(1)
- Martin, Candace E.(1)
- Numata, Mihoko(1)
- Palin, J. Michael(1)
- Peters, Bradley J.(1)
- Simonetti, Antonio(1)
- Sivil, Coşkun(1)
- Vuruşkan, Osman(1)
- Çevik, Özlem(1)
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ4Petrography, geochemistry and formation of the Sarıçimen (Van, eastern Türkiye) Fe-Ni-Co laterite deposit
Çimen, Okay
The Sarıçimen Fe-Ni laterite deposit is located in eastern Türkiye (Van province) and represents one of the important Ni and Co-enriched lateritic mineralizations formed in the ophiolitic occurences. This study aims to decipher the petrographic and geochemical signatures of the laterite horizon in order to better figure out the processes controlling Fe-Ni-Co mineralization and the genesis of the deposit. In this study, field and petrographic observations, and whole-rock geochemical data have been used to characterize the mineralogical and geochemical evolution of the lateritic horizon. Petrographic studies indicate that the protolith of the laterite zone is mostly composed of serpentinized ultramafic rocks including relics of Cr-spinel and chromite grains. This lateritic zone is characterized by hematite-and magnetite-rich zones formed above saprolitic levels that may have been derived from the weathering of ultramafic parent rocks. Whole rock geochemical analyses indicate that Fe₂O₃ and SiO₂ are the dominant oxides, and Ni concentrations vary between 0.33 and 1.01 wt.%. Also, Co values are ranging between 330 ppm and 600 ppm in the laterite samples investigated here. More importantly, correlation analyses exhibit a positive relationship between Ni and Fe₂O₃ and this may be attributed to a close association with Fe-oxide minerals during the lateritization. In contrast, a negative correlation between Ni and SiO₂ may indicate the presence of silica depletion during chemical weathering. The geochemical trends investigated here reveal that the laterite zone developed through intense lateritic weathering of ultramafic rocks, which is characterized by the removal of relatively mobile elements such as Si and Ca and the residual enrichment of Fe, Ni, and Co. The presence of Cr-spinel relics once again confirms the ultramafic origin of the parental rocks. Overall, the Sarıçimen deposit represents a Fe-Ni-Co laterite derived from nearby ultramafic sources within the ophiolitic sequence. The occurrence of Fe-Ni-Co laterite deposits at both the southwestern and northeastern segments of the Southern Neotethys Suture Zone suggests that this tectonic belt may represent a promising metallogenic area for lateritic Fe-Ni-Co mineralization in the southern Türkiye.
- MakaleYalnız künye2025Scopus SJRQ1Identification and source provenance of jadeite-bearing jade axes from Ulucak Höyük, Western Anatolia
Sayit, Kaan; Çevik, Özlem; Aktağ, Alican; Erdoğu, Burçin; Bamyacı, Onur; Vuruşkan, Osman; Sivil, Coşkun
The jades from Ulucak Höyük (İzmir, Turkey) are green-colored in hand specimen, and combined petrographic, XRD, and whole-rock analyses indicate that they mainly comprise jadeitic clinopyroxene, characterizing them as jadeite-bearing jades. Primitive mantle (PM)-normalized multi-element patterns reveal two distinct chemical groups. Both groups display depletion in Th and U; however, Group 1 shows a narrower elemental range and marked positive Pb anomaly. The second group, on the other hand, displays a wide elemental range in most elements and strong negative anomalies in Zr and Hf ([Nd/Zr]PM = 1.6–4.2; [Sm/Hf]PM = 1.8–3.5). Regarding REE systematics, both groups are characterized by weak positive slopes ([La/Yb]Ch = 1.7–5.3). However, whereas Group 1 shows coherent LREE-enriched trends, Group 2 displays flat- to LREE-enriched patterns with a wide range in Eu. When the geochemical features of Ulucak jades are compared with the high-pressure (HP) metamorphic rocks from Turkey and Greece, the similar multi-element patterns of Syros eclogites (Greece) to Group 2 Ulucak jades make Syros a possible source area for the Ulucak artefacts. On the other hand, the geochemical resemblance of the Sifnos jadeite-bearing gneisses to Group 1 Ulucak jades may raise the possibility of this island being another source for the Ulucak jades.
- MakaleAçık Erişim2024Scopus SJRQ1Delamination Magmatism in Eastern Anatolia: A Geochemical Perspective
Aktağ, Alican; Sayit, Kaan; Furman, Tanya; Peters, Bradley J.
The Sr-Nd-Hf-Pb isotope geochemistry of the Late Miocene Tunceli Volcanics suggests that they are the products of mixed asthenospheric and lithospheric mantle melts. The combined elemental and mineral chemistry data additionally indicate that a pyroxenite component of lithospheric origin is involved in their genesis. Calculations favor melting depths of ∼2 GPa for the Tunceli lavas, that is, deeper than the current lithosphere-asthenosphere boundary beneath Eastern Anatolia. Geochemical data suggest that during regional Neo-Tethyan subduction, dense (i.e., pyroxenite-bearing) domains formed by progressive melt intrusion into the lower lithosphere resulted in gravitational instabilities. This unstable density configuration eventually led to the foundering of the eastern Anatolian lithosphere in the Late Miocene, resulting in progressive melting of fusible pyroxenite-bearing domains at asthenospheric depths. We demonstrate that these pyroxenitic melts mixed with ambient asthenospheric melts and generated the Tunceli lavas.
AtıfScopus7OpenAlex9
İncele - MakaleAçık Erişim2019Scopus SJRQ2Geochemistry of the post-collisional Miocene mafic Tunceli Volcanics, Eastern Turkey: Implications for the nature of the mantle source and melting systematics
Aktağ, Alican; Önal, Ayten Öztüfekçi; Sayit, Kaan
The East Anatolian Accretionary Complex (EAAC) comprises an ideal example of post-collisional volcanism within the Africa-Eurasia collision zone. The Miocene mafic Tunceli Volcanics, as a part of this post-collisional volcanic system, are located in the western termination of EAAC. The mafic Tunceli Volcanics are characterized by mildly alkaline and tholeiitic basalts, in which olivine, clinopyroxene and plagioclase characterize the main mineralogy. The role of fractional crystallization (FC) and assimilation combined with fractional crystallization (AFC) processes appear to be negligible in the petrogenesis of the primitive mafic Tunceli Volcanics. Relative enrichment in large ion lithophile elements (LILE), Th and La over high field strength elements (HFSE) and heavy rare earth elements (HREE) suggest contribution from a metasomatized mantle source. The wide range of ratios displayed by these elements also calls for some asthenospheric input for the genesis of these volcanics. The metasomatizing agents can be attributed to a past subduction event, probably during the closure of Neotethys. Considering also the geophysical constraints, which limits the lithospheric thickness to about 70–75 km around the region, a melt mixing between lithospheric and asthenospheric melts generated at different depths appear to be an important process in the petrogenesis of these lavas. The combined geochemical and geophysical data, therefore, necessitate a geodynamic model with some remnant lithospheric mantle underlying the Eastern Anatolian region.
AtıfScopus10WoS11OpenAlex13İncele - MakaleYalnız künye2018Scopus SJRQ2Preliminary geochemical data of the mafic rocks from the ovacik and Pülümür ophiolite zone (Eastern Anatolia, Turkey): Implications for the geodynamic evolution of the northern neotethyan ocean
Çimen, Okay; Önal, Ayten Öztüfekçi
The İzmir-Ankara-Erzincan-Sevan-Akera Suture Belt (IAESASB) stretches from the Aegean Sea to the Lesser Caucasus and includes the remnants of the Northern Neotethys. The Ovacık and Pülümür Ophiolite Zone (OPOZ) to the north of Tunceli is less-known members of this belt. In this study, preliminary geochemical data from the basaltic and gabbroic rocks from this zone are presented to provide the first insights into their geochemistry. The studied mafic samples exhibit geochemical characteristics of an intra-oceanic subduction system. Three types of samples were differentiated on the basis of their major, trace and rare earth element (REE) geochemistry. The first one is boninitic and displays highly depleted elemental pattern (relative to N-MORB) and concave REE profile. The second type is akin to back-arc basin basalts (BABB) and generally reflects normal-MORB (NMORB)-like high field strength element (HFSE) patterns coupled with negative Nb anomalies. The last type is relatively similar to the BABB-type, but it lacks the marked negative anomaly in Nb and can be ascribed to the mid-ocean ridge basalt (MORB). The overall geochemical features suggest that these mafic rocks were predominantly generated in a supra-subduction setting from a subduction-modified mantle source. It is further suggested that the Ovacık and Pülümür Ophiolite Zone was formed in an oceanic arc-basin system within the northward subducting Northern Neotethys.
AtıfScopus7İncele - MakaleAçık Erişim2017Scopus SJRQ1Whole rock geochemistry, Zircon U–Pb and Hf isotope systematics of the Çangaldağ Pluton: Evidences for Middle Jurassic Continental Arc Magmatism in the Central Pontides, Turkey
Çimen, Okay; Göncüoğlu, M. Cemal; Simonetti, Antonio; Sayit, Kaan
The Central Pontides (Turkey) includes several igneous complexes, which are predominantly Permo-Carboniferous and Middle Jurassic in age. The Çangaldağ Pluton is one of the largest igneous bodies located in the northern Central Pontides, whose age and tectono-magmatic evaluation is important to constrain the geological evolution of the Northern Neotethys. The pluton tectonically overlies the Çangaldağ Metamorphic Complex, which represents an arc–back-arc complex of Middle Jurassic age. The Çangaldağ Pluton consists mainly of non-metamorphic gabbroic diorite, dacite porphyry, and lesser amount of granitic rocks. Geochemically, the various rock types are akin to volcanic arc magmas displaying Th/Nb and light rare earth element/heavy rare earth element enrichments. In-situ U–Pb age results of zircons from dacite porphyry and granite samples yield ages of 161 ± 5 Ma and 170 ± 2 Ma, respectively. Corresponding in-situ average 176Hf/177Hf initial ratios are 0.28287 ± 0.00004 and 0.28213 ± 0.00002 for the dacite porphyry and granite samples, respectively. These results are consistent with derivation from a subduction-modified mantle source. Based on Hf isotope compositions, TDM model ages vary between 624 and 1512 Ma and suggest that the arc magmatism associated with the Çangaldağ Pluton may have involved partial melting of Neoproterozoic/Mesoproterozoic crustal rocks, a common feature in Gondwana-derived terranes. The geochemical, Hf isotope, and geochronological data reported here confirm the presence of a continental arc system during the Middle Jurassic in the Central Pontides, and suggests that the Çangaldağ Pluton formed during northward subduction of the Intra-Pontide branch of the Northern Neotethys.
AtıfScopus35OpenAlex32İncele - MakaleAçık Erişim2016Scopus SJRQ1Geochemistry of the metavolcanic rocks from the Çangaldağ complex in the central pontides: Implications for the middle jurassic arc-back-arc system in the neotethyan intra-pontide ocean
Çimen, Okay; Göncüoğlu, M. Cemal; Sayit, Kaan
The Cangaldağ Complex in northern central Turkey is one of the main tectonic units of the Central Pontide Structural Complex that represents the remains of the poorly known Intra-Pontide branch of the Neotethys. It comprises low-grade metamorphic rocks of intrusive, extrusive, and volcaniclastic origin displaying a wide range of felsic to mafic compositions. Petrographically the complex consists of basalts-andesites-rhyodacites and tuffs with minor amount of gabbros and diabases. On the basis of geochemistry, the Cangaldağ samples are of subalkaline character and represented by both primitive and evolved members. All rock types are variably depleted in Nb compared to LREEs, similar to the lavas from subduction-related tectonic settings. In N-MORB normalized plots, the primitive members are separated into 3 groups on the basis of levels of enrichment. The first group is highly depleted and displays characteristics of boninitic lavas. The second group is relatively enriched compared to the first group but still more depleted than N-MORB. The third group, however, is the most enriched one among the three, whose level of enrichment is around that of N-MORB. The overall geochemical features suggest that the Cangaldağ Complex has been generated with the involvement of a subductionmodified mantle source. The chemistry of the primitive members further indicates that the melts generated for the formation of the Cangaldağ Complex probably occurred in both arc and back-arc regions above an intraoceanic subduction within the Intra-Pontide branch of the Neotethys.
AtıfScopus39WoS39OpenAlex31İncele - MakaleYalnız künye2011Scopus SJRQ1Petrology and petrogenesis of carbonatitic rocks in syenites from central Anatolia, Turkey
Cooper, Alan F.; Boztug, Durmus; Palin, J. Michael; Martin, Candace E.; Numata, Mihoko
The late Cretaceous A-type Kara double dagger ayA +/- r pluton in Central Anatolia, Turkey, intrudes and entrains xenoliths of Palaeozoic limestone. Carbonatitic magmatic rocks within the syenite have been previously interpreted (Schuiling in Nature, 192:1280, 1961) to result from metasomatic alteration and syntectic melting of marble. Carbonatites and associated calcite-syenites exhibit mineralogical characteristics (Ab-rich plagioclase, Ba-rich K-feldspar, low-Mg# biotite) that are petrogenetically more evolved than the host syenitic suite. Geochemically, carbonate-rich magmatic rocks are greatly enriched in Sr, Ba, Th, and REE and have higher LREE/HREE ratios than either syenites or marbles. In terms of O-C-Sr-Pb isotope ratios, the carbonatite/calcite-syenite suite form a consistent and geochemically coherent group that is distinct from the marble country rock and xenolith population, but similar to some of the syenitic, and particularly the nepheline syenite components of the Kara double dagger ayA +/- r pluton. Other silicate magmatic rocks are geochemically, isotopically, and geochronologically different, suggesting the pluton is composite. Overall, the mineralogical and geochemical characteristics of the carbonatites are incompatible with binary mixing of syenite and marble but are consistent with derivation of carbonatite from petrogenetically evolved foid syenite. Carbonate-silicate rock types have modal variations compatible with an origin by fractional crystallisation, rather than by liquid immiscibility.
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