Central Anatolian Volcanic Province Research Articles

Hydrothermal fluid circulation within the restless structural frame of Hasandağ volcanic system (Central Anatolia, Türkiye) inferred from Self-potential, CO2, and temperature measurements

Hasandağ is an active composite volcanic system located in the Central Anatolian Volcanic Province (CAVP). A comprehensive field survey was conducted to reveal the hydrothermal activity within the Hasandağ volcanic system, with particular emphasis on Self-Potential (SP) mapping. The Hasandağ system is characterised by the presence of twin stratovolcanoes that arise from pre-existing partially buried calderas. In conjunction with the SP measurements, carbon dioxide concentration (CO2) and surface temperature (ST) measurements were taken. The temperature measurements were elaborated with thermal infrared remote (TIR) sensing methods. The SP results, with a peak-to-peak magnitude of 3.8 Volts, revealed the presence of a significant hydrothermal input in both of the twin cones, characterised by a typical W-shaped anomaly commonly observed in active volcanoes. The highest SP signal coincides with the active fumarole zone at the western flank of G. Hasandağ summit, where we measured ∼70 °C vapour temperatures and relatively high CO2 output (>100,000 ppm). The SP/elevation (Ce) gradient assisted in revealing the hydrothermal and hydrogeological zonation, providing substantial evidence of the relationship between hydrothermal circulation and the structural frame of the volcano. Integrated evaluation of SP, CO2, and temperature data revealed the structural control on the hydrothermal and hydrogeological circulation, with the contribution of Hasandağ, Karacaören, and Karkın Faults as major structural components. The partially buried rim of the Hasandağ caldera was revealed through the detection of a ‘double Ce-low’ signal, providing valuable insights on the dimensions of the structure and its role in the hydrogeological cycle of the system. The extent and magnitude of the hydrothermal activity observed, the Holocene eruptive history of the volcano, and its proximity to populated areas denote the requirement of further geophysical and geochronological research and the necessity of hazard assessment and instrumental monitoring.

Zircon grain shape parameters from ignimbrites of the Central Anatolian Volcanic Province (CAVP) with implications for petrogenetic processes

Zircon grain shape parameters from ignimbrites of the Central Anatolian Volcanic Province (CAVP) with implications for petrogenetic processes

Mineralogical and Geochemical Changes During Hydrothermal Alteration of Pyroclastic Rock in Central Anatolian Volcanic Province (CAVP): Simulating Natural Formation Condition

Orta Anadolu Volkanik Bölgesi’nde (OAVB) geniş alanlarda yayılım gösteren piroklastik akıntı birimleri çoğu zaman yer yer hidrotermal alterasyona maruz kalmış şekilde bulunmaktadır. Bu çalışma, bölgede farklı koşullar altında gerçekleşen hâkim alterasyon tipini saptamak, ikincil mineral oluşumunu etkileyen fizikokimyasal koşulları ortaya koymak ve hâkim jeolojik süreçlere yaklaşımda bulunmak amacıyla gerçekleştirilmiştir. Zelve ignimbiriti bölgede en fazla hidrotermal alterasyona uğramış piroklastik akıntı birimlerinden birini temsil etmektedir. Akıntı birimine ait ilksel pomza örnekler, alkali çözeltiler ile kontrollü koşullar altında tepkimeye sokulmuş ve alterasyon sonucu oluşan zeolit mineralleri incelenmiştir. Bu kapsamda yürütülen deneysel çalışmalar, bölgede etkin hidrotermal koşullar göz önünde bulundurarak, otojenik basınç altında ve yaklaşık 150 ºC sıcaklıkta NaOH, KOH ve NaHCO3 gibi alkali çözelti aktivite ajanları kullanarak gerçekleştirilmiştir. Deneyler sonucunda elde edilen reaksiyon ürünleri X-ışını difraksiyonu (XRD) ile tanımlanmış ve taramalı elektron mikroskobu (SEM) çalışmalarıyla oluşan ürünler karakterize edilmiştir. Sonuç olarak, filipsit (K- ve Na-), analsim, mordenit ve şabazit gibi zeolit mineralleri sentezlenmiştir. Gerçekleştirilen çalışmalar, ilksel camdan itibaren gerçekleşen hidrotermal alterasyonda NaOH alkali çözeltisinin, zeolit mineralinin oluşumunda etkin aktivite ajanı olduğunu ortaya koymaktadır. Bununla birlikte, bölgede doğal olarak oluşan zeolit mineralleri (analsim, filipsit, şabazit, mordenit, klinoptilolit ve eriyonit) ile deneysel çalışmalar sonucunda elde edilen ürünlerin örtüştüğü belirlenmiştir. Alterasyon ürünleri ana ve iz element bileşimleri başlangıç malzemesine göre belirgin farklılıklar göstermektedir. Ürünlere ait CaO, K2O ve Na2O ana oksit bileşimlerinde zenginleşme, Rb, Ba ve P gibi elementlerde tüketilme gözlenmiştir. Bu durum, özellikle zeolit oluşumu sırasında başlangıç malzemesi ile çözelti arasında gerçekleşen element değişimleri ile açıklanabilmektedir.

New findings on compositionally distinct maar volcanoes: A case study from Acıgöl (Nevşehir) caldera (Central Anatolia, Turkey)

Recent experiments have largely reshaped our knowledge of maar volcanism. A new evolutionary model promoting the role of explosion depth and vent migration during the formation of maars has provided an alternative approach to previous models. Despite a few attempts to test this model with real cases, there is still a need for field-based studies exploring the depositional characteristics of maars to better understand the factors affecting the model constraints. More investigations on less known felsic maars are required to elucidate the possible differences from their more common mafic counterparts. Here, we explore compositionally distinct monogenetic clusters within the Acıgöl caldera (NW of Central Anatolian Volcanic Province, CAVP), with four felsic maars (İnallı, Kalecitepe, Acıgöl, and Korudağ) and one mafic maar (İcik). Our field observations reveal a successive formation between rhyolitic maars and adjacent lava domes. The mugearitic İcik coalescent maar and the adjacent scoria cone are synchronously formed, which is disclosed by the intercalation of the maar and scoria cone deposits. The geochemistry of the maar juveniles suggests a parental basaltic magma source that has been possibly differentiated by varying degrees of fractional crystallization. Our findings identify the main factors in maar formation (i.e., optimum scaled depth-OSD, water-magma interaction, and basement lithology). We also determine some differences between the felsic and mafic maars in the region, such as higher juvenile content, less amount of sedimentary structure, and a clear transition from phreatomagmatic to magmatic explosions through the end of stratigraphy. All these reflect the complexity of maars, mainly formed by different depths of explosions that occurred in the shallowest few hundred meters rather than a systematic incremental decrease of the eruption locus. Further geophysical and geochronological studies will complete our proposed evolutionary model for the youngest monogenetic activity in the Acıgöl caldera that would also warrant volcanic hazard assessment due to the presence of low-velocity anomalies, shallow Curie depths, and prevalent geothermal activity.

Slab Induced Mantle Upwelling Beneath the Anatolian Plateau

AbstractThe subducting African Plate in the easternmost Mediterranean is actively tearing and deforming beneath the Anatolian Plate as the margin transitions from long‐lived subduction to collision. In central Anatolia, the subducting slab is characterized by both lateral and vertical slab tears. We investigate patterns of mantle flow around the edges of a contorting and fragmenting African slab segment, called the Cyprean slab, using measurements of shear wave splitting. We observe three distinct regions of coherent shear wave splitting that correlate with the segmentation boundaries of the Cyprean slab. Regionally coherent mantle flow occurs near both the eastern and western the edges of the slab. These regions of coherent splitting are separated by an area of null splitting that encompasses the Central Anatolian Volcanic Province near the easternmost edge of the slab. The null measurements likely result from mantle upwelling due to the displacement of asthenosphere from the vertical Cyprean slab.

Radiological assessment of urban soil samples in the residents of a central Anatolian volcanic province, Turkey

ABSTRACT The concentration of natural and anthropogenic radionuclides, emanation fraction (EF), and mass (χM) and area (χA) exhalation rate of 222Rn in urban soil samples collected from dwelling areas in Nevşehir city located in a region known as the central Anatolian volcanic province of Turkey were determined using gamma-ray spectroscopy. The average activity concentrations of 226Ra, 228Ra, 40K and 137Cs were measured as 60.2 ± 3.8, 50.1 ± 2.8, 631.0 ± 29.7 and 5.5 ± 0.4 Bq/kg, respectively. The average concentration of 222Rn in soil and air was estimated as 27 kBq/m3 and 84 Bq/m3, respectively. The average values of EF, χM and χA were found as 20%, 25.4 μBq/kg⋅s and 20.2 mBq/m2⋅s, respectively. The average values of outdoor absorbed gamma dose rate, external and internal annual effective dose and lifetime cancer risk estimated for radiological assessment were found as 85 nGy/h, 104 µSv/y, 797 µSv/y and 4.1 × 10−4, respectively.

Magnetotelluric imaging of the shallow-seated magma reservoir beneath the Karadağ stratovolcano, Central Anatolia, Turkey

The central Anatolian Volcanic Province encompasses many volcanoes elongated in a northeast-southwest direction. Karadağ is one of the dormant Quaternary stratovolcanoes of the region at the southern end of the province. We acquired broadband magnetotelluric (MT) data in the period range 0.0001–251 s at 124 locations to obtain a three-dimensional electrical resistivity model to identify the associated magmatic-hydrothermal system beneath the Karadağ stratovolcano. The resistivity model provides evidence for low resistivity anomalies that include (1) a near-surface localised low resistivity (~ 20 Ωm) zone situated directly beneath the crater centre that is interpreted to be lacustrine sediments of an extinct crater lake, (2) a shallow low resistivity (~ 10 Ωm) zone of probable hydrothermal alteration in the eastern part of the stratovolcano and (3) a deep and large zone of low resistivity (<10 Ωm) attributed to a shallow-seated magma reservoir at a depth of 3 to 7 km beneath the volcanic edifice. A few hundred meters thick resistive surface layer corresponds to the Karadağ adakitic volcanics (i.e., andesites and dacites), and a resistive basement representing Precambrian to Mesozoic high- and medium-grade metamorphic rocks on the flanks is observed in the resistivity model.

Investigating Stress Transfer Between the Tuz Gölü Fault Zone and Hasan Dağ Volcano (Turkey)

Faulting, magmatism and volcanism are intrinsically linked by plate tectonics. Fault slip imparts stress changes to the surrounding crust and other faults and fractures. Volcano-tectonic hazard assessment in areas with long recurrence intervals of volcanic and tectonic activity requires an assessment of current stress levels. Here we investigate stress transfer between the Akhisar-Kiliç fault segment (AKFS) of the seismically active Tuz Gölü fault zone in the Central Anatolian Volcanic Province and the active Hasan Dağ volcanic complex. Current stress accumulation by protracted gradual slip on the AKFS since its most recent rupture (5.45 ka±0.16 BP) is quantified using the Coulomb Failure Stress change (ΔCFS). We calculate currently accrued ΔCFS magnitudes of between 2.5±0.2 and 15±0.5 MPa on the fault plane for published lower and upper-bound estimates of right-lateral slip rates, respectively. These changes are sufficient to promote failure of the segment. The M5.1 September 20, 2020 earthquake SW of Hasan Dağ occurred in a volume predicted by this study to have undergone fault unclamping by gradual slip along the AKFS. We also show that gradual slip of the AKFS contributes to the progressive unclamping of fractures and transtensional opening of potential magma pathways oriented perpendicularly to the AKFS both above and below Hasan Dağ’s magma reservoir, while pathways oriented parallel to the AKFS are being clamped. Earthquake moment magnitudes of between Mw5.94 and Mw6.76 due to hypothetical partial or complete rupture of the segment exacerbate these trends. The spatial pattern of Coulomb failure stress changes on Hasan Dağ’s magma reservoir is predominantly controlled by the location of rupture relative to the reservoir with the magnitude of the earthquake playing a subordinate role. We explore implications of our findings for the assessment of interconnected seismo-volcanic hazards and associated risks.

The crustal structure of the Anatolian Plate from receiver functions and implications for the uplift of the central and eastern Anatolian plateaus

SUMMARYUnderstanding the crustal structure of the Anatolian Plate has important implications for its formation and evolution, including the extent to which its high elevation is maintained isostatically. However, the numerous teleseismic receiver function studies from which Anatolian Moho depths have been obtained return results that differ by ≤21 km at some seismograph stations. To address this issue, we determine Moho depth and bulk crustal VP/VS ratio (κ) at 582 broad-band seismograph stations, including ∼100 for which H–κ results have not been reported previously. We use a modified H–κ stacking method in which a final solution is selected from a suite of up to 1000 repeat H–κ measurements, each calculated using randomly selected receiver functions and H–κ input parameters. Ten quality control criteria that variously assess the final numerical result, the receiver function data set, and the extent to which the results are clustered tightly, are used to determine station quality. By refining Moho depth constraints, including identifying 182 stations, analysed previously, where H–κ stacking yields unreliable results (particularly in Eastern Anatolia and the rapidly uplifting Taurides), our new crustal model (ANATOLIA-HK21) provides fresh insight into Anatolian crustal structure and topography. Changes in Moho depth within the Anatolian Plate occur on a shorter length-scale than has sometimes previously been assumed. For example, crustal thickness decreases abruptly from &amp;gt;40 km in the northern Kirsehir block to &amp;lt;32 km beneath the Central Anatolian Volcanic Province and Tuz Golu basin. Moho depth increases from 30–35 km on the Arabian Plate to 35–40 km across the East Anatolian Fault into Anatolia, in support of structural geological observations that Arabia–Anatolia crustal shortening was accommodated primarily on the Anatolian, not Arabian, Plate. However, there are no consistent changes in Moho depth across the North Anatolian Fault, whose development along the Intra-Pontide and İzmir-Ankara-Erzincan suture zones was more likely the result of contrasts in mantle lithospheric, not crustal, structure. While the crust thins from ∼45 km below the uplifted Eastern Anatolian Plateau to ∼25 km below lower-lying western Anatolia, Moho depth is generally correlated poorly with elevation. Residual topography calculations confirm the requirement for a mantle contribution to Anatolian Plateau uplift, with localized asthenospheric upwellings in response to slab break-off and/or lithospheric dripping/delamination example candidate driving mechanisms.

Source constraints for the young basaltic rocks from the northernmost end of Cappadocian region, Turkey: Melting evidence from peridotite and pyroxenite source domains

Widespread magmatic activity developed in the Middle Miocene in the Cappadocian Region of Central Anatolia in Turkey. Despite several previous studies that focus on the geochemical features of the magmatic rocks, the source components and development of melting conditions are still a matter of debate.Recent basaltic rocks from Karaburna and Gülşehir (1228 and 96 Ka, respectively, Dogan, 2011) are considered as a part of the Central Anatolian Volcanic Province, situated at the northernmost end of the Cappadocian Region. These lavas have similar large ion lithophile (LIL) (except Rb) and high field strength (HFS) element abundances, however, Karaburna samples are more enriched in HFS elements, and both of the rocks suites reflect HFS depletions relative to the OIB signature.Karaburna and Gülşehir basalts have low Nb/La (0.45–0.5; 0.35–0.5), Nb/Th (2.75–4.61; 1.26–2.85) values, respectively, suggesting contributions from crustal sources, whereas Zr/Ba ratios of these samples range between 0.32–0.93 and 0.4–0.88 and imply that these rocks appear to be derived from asthenospheric sources. These incompatible element ratios can be attributed to either different geochemical processes, or are related to melting from different source component(s).The ambient mantle source of the Cappadocian region appears to be consistent with spinel peridotite, but this domain is not solely satisfactory to represent the melting conditions in the light of new elemental data. Values of Tb/Yb(N) and Zn/Fe provide new constraints suggesting the magmas were generated from the asthenosphere. Tb/Yb(N) ratio separates garnet – spinel transition Tb/Yb(N) (>1.8) and Zn/Fe ratio displays separation between the peridotite-derived (Zn/Fe <12) and pyroxenite-derived (13−20) melts.A melting model based on REE ratios and Zn/Fe, Co/Fe, Tb/Yb(N) values indicates that basaltic rocks were not derived from a single source component (peridotite). Instead, those values suggest substantial melting contributions from a pyroxenite source domain, which has not been discussed as a source component in previous studies. Melts, from both of the source domains, with the result of asthenospheric upwelling linked to the downgoing Aegean and Cyprean slabs, are distinct from the alkaline character frequently observed as the final products of recent volcanic activity in the Cappadocian region and also explains the different trace element variations observed in such a small scale.

Minimum Detectable Mass and Volume Fluxes During Magmatic Recharge at High Prominence Volcanoes: An Application to Erciyes Dağ Volcano (Turkey)

Magma reservoir recharge is widely recognised as a precursor of eruptive activity. However, the causative relationships between reservoir rejuvenation and surface observables such as gravitational potential field changes and ground deformation are still poorly understood. At intermediate and silicic intra-plate volcanoes where crustal mechanical heterogeneity combined with high-prominence are expected to fundamentally affect the crustal stress and strain relationship, protracted period of repose and absence of monitoring data raise questions about the detectability of magma recharge. Here we report results from integrated geodetic forward modelling of ground displacements and gravity changes from reservoir recharge at Erciyes Dağ, a large prominence (∼2,800 m), yet poorly studied, stratovolcano of the Central Anatolian Volcanic Province in Turkey. The most recent eruption at ∼7000 BC, close proximity to the Kayseri Metropolitan Area and absence of dedicated volcano monitoring set a precedent to explore stealth magmatic processes at the volcano. Using finite element analysis we systematically explore the influence of subsurface mechanical heterogeneities and topography on surface deformation and gravity changes from magmatic recharge of Erciyes Dağ’s reservoir. We show that whilst crustal heterogeneity amplifies ground displacements and gravity variations, the volcano’s substantial prominence has the opposite effect. For generic reservoir pressure and density changes of 10 MPa and 10 kg m−3 predicted vertical displacements vary by a factor of 5 while residual gravity changes vary by a factor of 12 between models ignoring topography or mechanical heterogeneity and those that do not. We deduce reservoir volume and mass changes of order 10–3 km3 and 1010 kg, respectively, at the detectability limit of conventional surveying techniques at the volcano. Though dependent on model assumptions, all results indicate that magma recharge at Erciyes Dağ may go undetected at fluxes 1) sufficient to maintain an active reservoir containing eruptable magma and 2) similar to those reported for intermediate/silicic volcanoes with repose times of 100–1,000s of years (e.g., Parinacota) and persistently active mafic volcanoes such as Mt. Etna and Stromboli. Our findings may be utilised to inform integrated geodetic and gravimetric monitoring at Erciyes Dağ and other large prominence silicic volcanoes and could provide early insights into reservoir rejuvenation with implications for the development of disaster risk reduction initiatives.

Morphological and multivariate statistical analysis of quaternary monogenetic vents in the Central Anatolian Volcanic Province (Turkey): Implications for the volcano-tectonic evolution

The interaction and competition between magmatic and tectonic processes mostly control the spatial distribution and morphology of monogenetic volcanoes. The Central Anatolian Volcanic Province, situated in a strike-slip environment, provides a remarkable opportunity to understand this relationship. We defined six monogenetic clusters and analyzed 540 Quaternary monogenetic volcanoes in terms of morphological and spatial characteristics. There is no distinct correlation among the morphological parameters of scoria cones or lava domes, possibly owing to the various factors and the sporadic nature of magmatic activity in the region. Our detailed multivariate statistical and vent alignment analyses together with several implications in the literature reveal that the CAVP is a tectonically-controlled intraplate volcanic field, which is mostly driven by regional deformations. The presence of both clustered and non-clustered vent distributions and the petrological characteristics of the volcanics within the region indicates that the dikes are derived directly by the pre-existing melt-bearing heterogeneous mantle (i.e., Eğrikuyu monogenetic field) or the independent and short-lived shallow or deep crustal magma reservoirs (i.e., Nevşehir-Acıgöl volcanic field). The local changes in the stress regimes and crustal lithology result in variations of field shape, spatial vent distribution, and vent alignments throughout the region. The triggering mechanisms for the initiation of the Quaternary volcanism in the region can be the lithospheric-scale Central Anatolian fault zone, here considered as an immature rift zone where Erciyes volcanic field is developed and behaves as a possible magmatic transfer zone. Tuz Gölü fault zone as a western border of the so-called rift basin in the region is mostly responsible for the crustal propagation of magma, and the kinematic changes along this fault zone (i.e., strike-slip to normal) mostly shaped the spatial vent distributions and alignments of the clusters in its close proximity (e.g., Hasandağ-Keçiboyduran volcanic field).

Zircon geochronology and O-Hf isotopes of Cappadocian ignimbrites: New insights into continental crustal architecture underneath the Central Anatolian Volcanic Province, Turkey

During the Mio–Pliocene between ca. 10 and 5 Ma, the Central Anatolian Volcanic Province (CAVP) formed as the focus of a high eruptive flux episode with voluminous high-silica, caldera-forming eruptions. Magmatic compositions of ignimbrites emplaced during this episode were uniformly rhyodacitic–rhyolitic, reflecting melt generation in an intracrustal hot zone heated by intrusions of basalt that were extracted from fertile asthenospheric mantle undergoing decompression. The clear imprint of crustal rocks on CAVP magmas provides unique opportunity to constrain the deep crustal architecture of central Anatolia. Here, we present a detailed study of zircon from key CAVP ignimbrites including U-Pb ages and the first coupled O- and Hf-isotopic compositions for this silicic igneous province, along with complementary whole-rock Nd isotope data. Ignimbrites with higher δ18O and lower εHf values (Zelve, Cemilköy, Gördeles) are typically compositionally more evolved compared to those with intermediate (Kavak, Kızılkaya) and more mantle-like compositions (Sarımadentepe, Sofular, Tahar), which is consistent with magmas acquiring their isotopic compositions through crustal assimilation coupled with fractional crystallization. Intriguingly, O-Hf-zircon compositions from Kızılkaya ignimbrite, one of the largest and youngest CAVP eruptions, cover almost the same isotopic range than all CAVP ignimbrites collectively. Despite evidence for a significant crustal influence revealed by O-Nd-Hf isotopic compositions of CAVP ignimbrites, inherited zircon is absent in all units. This is in stark contrast with previous studies of Kızılkaya ignimbrite for which abundant Proterozoic–Archean zircon populations have been reported. Isotopic compositions of evolved magmas in the CAVP can be explained by interaction of mantle-derived basalt with post-Archean crust, with minor contributions of hydrothermally altered rocks. No tangible evidence exists for a magmatic contribution of Archean crustal components to the Mio–Pliocene ignimbrite flare-up in Central Anatolia, suggesting that regional basement rocks largely represent Gondwanan crust that was originally consolidated and subsequently became reprocessed during post-Archean times.

Manifestations of Quaternary syn‐eruptive fluid circulations on carbonate veins, Central Anatolian Volcanic Province

ABSTRACTIn this study, we investigate the geochronological, geochemical and isotopic characteristics of two travertine sites surrounded by Quaternary eruption centres in central Anatolia with ample palaeo‐eruption records. High‐resolution carbonate precipitation records, revealed by U‐Th dating, are clustered around 5–35, 60–100 and 120–170 ka and are well correlated with the dataset on eruptions as well as the position of fractures related to the volcanic centres. Syn‐eruptive carbonate precipitation seems to occur due to the circulation of CO2‐rich fluids along the extensional fracture systems aligned tangentially to the related volcanic conduit and, therefore, the study of this system could be an alternative technique for the reconstruction of palaeo‐eruptions. δ18O values of the studied travertines are within the range of meteogene fluids. Oxygen isotope compositions at around 130 ka match well with Glacial Termination II that is also recorded by climate proxies in various cave and benthic deposits throughout the world. It is likely that the studied carbonates were precipitated under similar fluid circulation conditions which are represented by a high rate of dilatation followed by a meteoric water influx into the extensional fractures.

The late Miocene Öksüt high sulfidation epithermal Au-Cu deposit, Central Anatolia, Turkey: Geology, geochronology, and geochemistry

The Öksüt high sulfidation (HS) epithermal Au (-Cu) deposit (35.32 million tonnes of ore at 1.22 g/t Au) is located in the Central Anatolian Volcanic Province (CAVP) at the south-eastern segment of the Central Anatolian Crystalline Complex (CACC). The deposit is hosted by large hydrothermal breccia bodies and hornblende-rich basaltic andesite porphyry of the Develidag Volcanic Complex (DVC), which were pervasively altered to form silicification and argillic assemblages. The host rocks and mineralization are covered by post-mineral pyroxene-rich basaltic andesite of DVC. The volcanic rocks have a medium-K calc-alkaline affinity similar to regional volcanic rocks of the DVC. The gold and copper mineralization is mostly associated with quartz and primary sulfides hosted by silicification and argillic alteration particularly quartz-alunite cemented breccias and subsequently enriched by supergene oxidation processes causing destabilization of the primary sulfides.The LA-ICP-MS zircon U-Pb geochronology indicates a range of 206Pb/238U ages between 5.4 and 6.0 Ma with an average mean age of autocrystic grains of 5.73 ± 0.06 Ma for the host hornblende-rich basaltic andesite porphyry and 5.67 ± 0.07 Ma for the post-mineralization basaltic andesite cover. The high-precision CA-ID-TIMS analysis of the youngest grains from both rock types defines ages 5.778 ± 0.013 Ma and 5.700 ± 0.019, respectively, which bracket the ore mineralization between 5.791 and 5.681 Ma, including the error uncertainty. Consequently, the Öksüt gold mineralization took place in a very narrow lifetime of 78 ± 32 Ka. This is the youngest age for an economic gold deposit in Turkey.

Seismic Tomographic Imaging of the Eastern Mediterranean Mantle: Implications for Terminal‐Stage Subduction, the Uplift of Anatolia, and the Development of the North Anatolian Fault

AbstractThe Eastern Mediterranean captures the east‐west transition from active subduction of Earth's oldest oceanic lithosphere to continental collision, making it an ideal location to study terminal‐stage subduction. Asthenospheric‐ or subduction‐related processes are the main candidates for the region's ∼2 km uplift and Miocene volcanism; however, their relative importance is debated. To address these issues, we present new P and S wave relative arrival‐time tomographic models that reveal fast anomalies associated with an intact Aegean slab in the west, progressing to a fragmented, partially continental, Cyprean slab below central Anatolia. We resolve a gap between the Aegean and Cyprean slabs, and a horizontal tear in the Cyprean slab below the Central Anatolian Volcanic Province. Below eastern Anatolia, the completely detached “Bitlis” slab is characterized by fast wave speeds at ∼500 km depth. Assuming slab sinking rates mirror Arabia‐Anatolia convergence rates, the Bitlis slab's location indicates an Oligocene (∼26 Ma) break‐off. Results further reveal a strong velocity contrast across the North Anatolian Fault likely representing a 40–60 km decrease in lithospheric thickness from the Precambrian lithosphere north of the fault to a thinned Anatolian lithosphere in the south. Slow uppermost‐mantle wave speeds below active volcanoes in eastern Anatolia, and ratios of P to S wave relative traveltimes, indicate a thin lithosphere and melt contributions. Positive central and eastern Anatolian residual topography requires additional support from hot/buoyant asthenosphere to maintain the 1–2 km elevation in addition to an almost absent lithospheric mantle. Small‐scale fast velocity structures in the shallow mantle above the Bitlis slab may therefore be drips of Anatolian lithospheric mantle.

Sarıhıdır manganese mineralization related to travertine, Central Anatolian Volcanic Province, Turkey

ABSTRACT Sarıhıdır travertines and associated manganese mineralization are located in an area known as the Central Anatolian Volcanic Province (CAVP). The topic of the study, the Sarıhıdır manganese mineralization, was deposited in association with fault zones in this tectonically-active region. Paragenesis of the mineralization includes pyrolusite, rhodochrosite and goethite with gangue minerals of calcite and quartz observed. Diagrams drawn using major oxide and trace elements like Fe–Mn–(Ni+Co+Cu)×10, Fe-Si×2-Mn, Co/Ni vs Cu+Co+Ni, Si/Al, Na/Mg, Fe/Ti vs. Al/(Al+Fe+Mn), Co+Ni/As+Cu+Mo+Pb+V+ Zn and FeO–MnO2–10× MgO show the mineralization found in the region is sourced in the hydrothermal field. The low total REE values and LREE>HREE ratio indicate the effect of hydrothermal solutions. Additionally, Ce, Eu and Ceanom anomalies indicate the source of the mineralization was hydrothermal with oxic-anoxic formation environment. The Y/Ho ratio is mean 30.1 which is lower compared to hydrothermal fluids. Mean values are δ13CPDB 12.24‰ and δ18OPDB 10.87‰ indicating deposition from fluids with a deep CO2 component. In conclusion, the Sarıhıdır mineralization and travertine were determined to have formed about 50–53 ka (Upper Pleistocene) based on U-series age data, as fault-controlled, hydrothermal-sourced mineralization.

Application of zircon typology method to felsic rocks (Cappadocia, Central Anatolia, Turkey): a zircon crystallization temperature perspective

Zircon typology was developed nearly half a century ago as a tool for constraining the thermochemical conditions in granitic magmas from the morphology of zircon prismatic and pyramidal crystal surfaces. Although the method precedes experimentally constrained zircon-based thermometers (zircon saturation, Ti-in-zircon), the morphology of zircon remains an important criterion for zircon studies commonly relying on visual recognition of crystals during sample purification via hand-picking. This may introduce selection bias if morphologically distinct zircon crystals are present in a population. We conducted a comparison between zircon typology and thermochemical constraints from zircon thermometry and whole rock compositions. Therefore, we focused on zircon populations from diverse volcanic rocks from the Central Anatolian Volcanic Province (CAVP), which erupted during the Upper Miocene to Quaternary in a continental environment in a postcollisional extensional regime. Neogene rhyolitic volcanism produced widespread pyroclastic rocks (ignimbrites, and subordinate fall-out deposits), which are interstratified with fluviolacustrine sediments and local lava flows originating from various volcanic centers in the region. Zircon crystals from Neogene ignimbrites are mostly intermediate-temperature, calc-alkaline hybrid type, whereas zircons from Quaternary rhyolitic domes/lavas fall into typology trends assigned to subalkaline mantle-type granites with low temperatures and high alkalinity indices. Trends in zircon saturation and zircon crystallization temperatures in CAVP ignimbrites are broadly consistent with typology temperature estimates, but temperature differences between these estimates are slightly higher or lower. However, these deviations may partly result from zircon typology relying on crystal shape, and thus the latest crystallization event, which could result in bias between the granitic rocks used for the original typology development and the volcanic rocks investigated here. Our results show that typology differences exist between zircon populations from both Miocene ignimbrites and Quaternary rhyolitic domes/lavas of the CAVP. These differences affect the temperature values obtained from zircon typologies that also correlate with conventional quantitative thermometric calculations.

U-series dating and origin of Yaprakhisar (Güzelyurt-Aksaray) travertines in Central Anatolian Volcanic Province, Turkey

This study reveals the age, setting, and geochemistry of fissure ridge travertines outcropping in Yaprakhisar (Guzelyurt-Aksaray) that is located in the Central Anatolian Volcanic Province (CAVP) and investigates their relationship with main tectonic structures. Dating studies with the U-series analysis method identified that travertine formations were deposited from 3 to 147 ka BP. The travertines in the study area were divided into two groups based on the age and extension direction. The first group consists of fissure ridge travertines with 70° NE and deposited in the range of 126–147 ka BP. The second group has 10° NW strike and are fissure ridge travertines dated to 3–47 ka BP. The association between the travertine groups and the significant fault zones in the region was investigated, and three different formation models are presented. The relationship between the fissure ridge travertines and faults deforming the CAVP was determined using paleo-discontinuities. The Yaprakhisar travertines were determined to have Ce and Eu anomalies, along with low Ba and relatively low Sr values. When the trace element and REE content of the Yaprakhisar travertines are considered together, the travertines are concluded to have been deposited under oxic conditions from limestone-evaporite-dolomite-sourced hypogene water with low acidity and relatively low temperature.

U-Th age evidence from carbonate veins for episodic crustal deformation of Central Anatolian Volcanic Province

Central Anatolia represents one of the most outstanding examples of intraplate deformation related to both continental collision and back-arc extension generating non-uniformly distributed stress fields. In this study, we provide direct field evidence of various stress directions and investigate carbonate-filled fracture systems in the Central Anatolian Volcanic Province using U/Th geochronology and isotope geochemistry for evaluating the episodes of latest volcanic activity under regional stress. Field data reveal two independent fracture systems in the region. Successive fracture development has been controlled by two different volcanic eruption centers (Hasandağ Composite Volcano and Acıgöl Caldera). Trace element, and stable (C and O) and radiogenic (Sr) isotope compositions of carbonate veins indicate different fluid migration pathways for two different fracture systems. The U/Th age data for carbonate veins of two independent fracture systems indicate that the crustal deformation intensified during 7 episodic periods in the last 150 ka. The NNE-trending first fracture system was formed as a result of strain cycles in a period from 149 ± 2.5, through 91 ± 1.5 to 83 ± 2.5 ka BP. Subsequent deformation events represented by the ENE-trending second fracture zone have been triggered during the period of 53 ± 3.5, 44 ± 0.6 and 34 ± 1 ka BP before the first fracture zone resumed the activity at about 4.7 ± 0.15 ka BP. Although further studies are needed to evaluate statistical significance of age correlations, the periods of carbonate precipitation inferred from U-Th age distributions in this study are comparable with the previous dating results of surrounding volcanic eruption events.