ABSTRACTThe east-west trending Taurides form a curved area in central eastern Anatolia known as the Gürün Curl. In order to understand the origin of the Gürün Curl and Tauride evolution in general, the results of a new field study of this region have been synthesized together with previously published data. We suggest that the geodynamic evolution of the area began with the likely presence of a Tethys Ocean transform fault. This fault separated the Taurides into the Akdere Sector in the west and the Munzur Sector in the east in the Late Cretaceous. During the late Santonian–early Campanian, ophiolites obducted onto the Munzur Sector, while platform sediments continued to accumulate in the Akdere Sector. This was followed by the development of an Andean-type arc-type magmatism (the Baskil Arc) during the early–middle Campanian in the Munzur Sector. Continued closure of the Tethys led to the collision of the Bitlis Massif in the south of the Munzur Sector in the Campanian. This, in turn, resulted in continental subduction and slab roll-back that was controlled by a Subduction Transform Edge Propagator (STEP) Fault that lay on the original transform fault between the Akdere and Munzur sectors. Because the subducted slab was free at its western corner, the western edge rolled back faster than in the east, leading to an asymmetrical extensional regime on the upper plate that created the late Campanian Hekimhan Basin. While these geodynamic events were taking place in the Munzur Sector, the Akdere Sector was in a platform setting. During the Palaeocene, the Late Mesozoic units of the Akdere Sector began to overthrust on the Hekimhan Basin and the ophiolites. Following the Palaeocene, all these tectonostratigraphic units were covered by Eocene sediments around the Gürün Curl of which the modern appearance was completed by the Miocene to Recent movements along the strike-slip faults.KEYWORDS: AnatoliaTauridesHekimhan BasinLate CretaceousGürün Curl AcknowledgmentsThis study was supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK), the Department of Scientific Research Projects of Dokuz Eylül University, and the Turkish Academy of Sciences (TÜBA-GEBİP). We would like to extend our gratitude to Dr. Fatih Karaoğlan for his valuable assistance in interpreting the zircon age data.Disclosure statementNo potential conflict of interest was reported by the author(s).Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2258393Additional informationFundingThe Scientific and Technological Research Council of Türkiye - TÜBİTAK (grant number: ÇAYDAG-119Y187); Department of Scientific Research Projects of Dokuz Eylül University (grant number: 2019.KB.FEN.006); Turkish Academy of Sciences - TÜBA-GEBİP (TÜBA-GEBİP/2018).
We report the results of a study on early Miocene to Pleistocene volcanic rocks cropping out west of the Karlıova Triple Junction in Eastern Anatolia (Elazığ, Tunceli, and Bingöl provinces). Here the Eurasia–Arabia convergence resulted in collision, marked by the Bitlis–Zagros suture (∼13 Ma), followed by activation of the dextral transform North Anatolian Fault (NAF). At ∼6 Ma the formation of the sinistral transform East Anatolian Fault (EAF) marked the separation of the Anatolian block, which became a kinematically independent plate. On the basis of petrographic, geochemical and Sr–Nd–Pb isotopic characteristics, as well as new 40Ar–39Ar age determinations, we distinguish three phases of activity: (1) early–middle Miocene (16·3–15·5 Ma) production of calc-alkaline basaltic trachyandesite to dacites in the Pertek and Mazgirt districts; (2) emplacement of late Miocene (11·4–11·0 Ma) transitional basalts in the Tunceli area; (3) emplacement of Plio-Pleistocene Na-alkali basalts in Karakoçan (4·1 Ma) and Elazığ (1·7 Ma). The oldest samples are characterized by large ion lithophile element (LILE) enrichment (e.g. Ba/Nb = 32–76) with high 87Sr/86Sr (0·7052–0·7065) and low 143Nd/144Nd isotopic ratios (0·51246–0·51262). The late Miocene basalts display variable geochemical characteristics, including large variations in 87Sr/86Sr (0·7039–0·7068) and LILE/HFSE (high field strength element) ratios (e.g. Ba/Nb = 13–36). The Plio-Pleistocene alkali basalts have higher LILE and HFSE contents and lower LILE/HFSE ratios (Ba/Nb = 8–21) compared with the two previous groups, low 87Sr/86Sr (0·7033–0·7038) and high 143Nd/144Nd (0·51270–0·51290), with compositions similar to those of oceanic intraplate magmas. Pb isotopes vary slightly: 206Pb/204Pb ranges from 18·66 to 19·11, 207Pb/204Pb from 15·64 to 15·72 and 208Pb/204Pb from 38·67 to 39·24, with the calc-alkaline early–middle Miocene rocks characterized by higher 207Pb/204Pb and 208Pb/204Pb at a given 206Pb/204Pb. The evolution of volcanic activity is strictly linked to the geodynamic scenario. The early–middle Miocene magmas, emplaced in a convergent setting, indicate derivation from mantle sources modified by subduction components, whereas the late Miocene Tunceli transitional basalts mark the change from compressional to strike-slip tectonics. During the development of the NAF and EAF, passive upwelling of the sub-slab mantle, favoured by the formation of small pull-apart basins, led to the onset of Na-alkali basaltic activity.
The Elazığ and Tunceli provinces in eastern Anatolia host a complex succession of Miocene-Pleistocene effusive and explosive volcanic rocks, divided into four distinct volcanic phases. The most abundant and widespread products are the calcalkaline Mazgirt volcanic rocks, characterized by wide Sr isotope variations (87Sr/86Sr ~0.7054-0.7077) and narrower 143Nd/144Nd (~0.51246-0.51260) and Pb isotopes (e.g., 206Pb/204Pb ~18.89-19.13). New 40Ar-39Ar ages indicate that Mazgirt volcanic activity occurred between ~16.3 and 15.1 Ma. The other three volcanic phases are represented by the Tunceli mildly alkaline basaltic lavas (~11.4-11.0 Ma), the Pliocene Karakoçan (~4.1 Ma) and Pleistocene Elazığ (~1.9-1.6 Ma) Na-alkali basaltic lavas with clear OIB-like geochemical signature.Mazgirt volcanics can be subdivided on the base of mode of emplacement into lava flows and lava domes units characterized by petrographic, chemical and isotopic differences: lava flows are calcalkaline, whereas lava domes mostly belong to a high-K calcalkaline series and are, on average, more LREE- and 87Sr-enriched. Lava domes are more porphyritic, with a phenocryst assemblage dominated by amphibole, whereas plagioclase and clinopyroxene are the most abundant phenocryst phases in lava flows, pointing out that evolution of dome magmas occurred in conditions of slightly higher pressure, favouring the crystallization of hydrous phases.The Karabakır Formation, previously reported as late Miocene- Pliocene, encloses Mazgirt volcanics and is capped by Tunceli basalts. These new age data constrain the Karabakır Formation emplacement from early to late Miocene.The evolution of this igneous activity mirrors the geodynamic framework of the region: the early-middle Miocene Mazgirt volcanics represent arc volcanism related to Eurasia-Arabia convergence. The late Miocene Tunceli basalts postdate the onset of post-collisional tectonics in Eastern Anatolia, whereas the Karakoçan and Elazığ volcanic rocks were emplaced after the initiation of strike-slip motion on the North Anatolian and East Anatolian Fault systems.
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