Hasandag Research Articles

Baseline monitoring of volcanic regions with little recent activity: application of Sentinel-1 InSAR to Turkish volcanoes

Volcanoes have dormancy periods that may last decades to centuries meaning that eruptions at volcanoes with no historical records of eruptions are common. Baseline monitoring to detect the early stages of reawakening is therefore important even in regions with little recent volcanic activity. Satellite techniques, such as InSAR, are ideally suited for routinely surveying large and inaccessible regions, but the large datasets typically require expert interpretation. Here we focus on Turkey where there are 10 Holocene volcanic systems, but no eruptions since 1855 and consequently little ground-based monitoring. We analyse data from the first five years of the European Space Agency Sentinel-1 mission which collects data over Turkey every 6 days on both ascending and descending passes. The high relief edifices of Turkey’s volcanoes cause two challenges: 1) snow cover during the winter months causes a loss of coherence and 2) topographically-correlated atmospheric artefacts could be misinterpreted as deformation. We propose mitigation strategies for both. The raw time series at Hasan Dag volcano shows uplift of ~ 10 cm between September 2017 and July 2018, but atmospheric corrections based on global weather models demonstrate that this is an artefact and reduce the scatter in the data to < 1 cm. We develop two image classification schemes for dealing with the large datasets: one is an easy to follow flowchart designed for non-specialist monitoring staff, and the other is an automated flagging system using a deep learning approach. We apply the deep learning scheme to a dataset of ~ 5000 images over the 10 Turkish volcanoes and find 4 possible signals, all of which are false positives. We conclude that there has been no cm-scale volcano deformation in Turkey in 2015–2020, but further analysis would be required to rule out slower rates of deformation (< 1 cm/yr). This study has demonstrated that InSAR techniques can be used for baseline monitoring in regions with few historical eruptions or little reported deformation.

Tectonic geomorphology and Plio-Quaternary structural evolution of the Tuzgölü fault zone, Turkey: Implications for deformation in the interior of the Central Anatolian Plateau

AbstractSituated within the interior of the Central Anatolian Plateau (Turkey), the 200-km-long Tuzgölü extensional fault zone offers first-order constraints on the timing and pattern of regional deformation and uplift. In this study, we analyze the morphometrics of catchments along the Tuzgölü range-front fault and the parallel, basinward Hamzalı fault using a variety of measured morphometric indicators coupled with regional geomorphic observations and longitudinal profile analysis. In addition, we use field and remote mapping to constrain the geometry of two key marker beds, the Pliocene Kızılkaya ignimbrite and Kışladaǧ limestone, in order to investigate deformation in the footwall of the Tuzgölü fault zone. The marker beds form a broad arch along the footwall of the fault, with greatest cumulative displacement along the central part of the fault zone, suggesting early Pliocene extensional reactivation of the Tuzgölü fault with a typical fault-displacement profile. However, a change in deformation pattern is marked by transient knickpoints along river channels; morphometric indicators sensitive to shorter (1−3 Ma) time scales, including river steepness, basin elongation, and mountain front sinuosity, indicate an overall southeastward increase in footwall uplift rate of the Tuzgölü fault zone, which could reflect block rotation or interaction with the Hasan Dag volcano. Basin asymmetry and basin-fault azimuth measurements indicate north-northwest tilting of footwall catchments, which may be linked to regional tilting across the Central Anatolian Plateau interior. Varying patterns of spatial and temporal deformation along the length of the Tuzgölü fault zone are likely due to the interference of crustal- and lithospheric-scale processes, such as rotation of crustal blocks, extrusion of the Anatolian microplate, crustal heating, gravitational collapse associated with plateau uplift, and mantle-driven vertical displacements.

Contemporaneous alkaline and calc-alkaline series in Central Anatolia (Turkey): Spatio-temporal evolution of a post-collisional Quaternary basaltic volcanism

This study focuses on spatio-temporal evolution of basaltic volcanism in the Central Anatolian post-collisional Quaternary magmatic province which developed along a NE-SW orientation in Turkey. This magmatic province consists of the stratovolcanoes Erciyes (ES) and Hasandag (HS), and the basaltic volcanic fields of Obruk-Zengen (OZ) and Karapınar (KA). The investigated samples range between basic to intermediate in composition (48–56wt% SiO2), and exhibit calc-alkaline affinity at ES whereas HS, OZ and KA are alkaline in composition. Based on new KAr ages and major element data, the oldest basaltic rock of ES is 1700±40ka old and exhibits alkaline character, whereas the youngest basaltic trachyandesite is 12±5ka old and calc-alkaline in composition. Most ES basaltic rocks are younger than 350ka. All samples dated from HS are alkaline basalts, ranging from 543±12ka to 2±7ka old. With the exception of one basalt, all HS basalts are ~100ka or younger in age. KAr ages range from 797±20ka to 66±7ka from OZ. All the basalt samples are alkaline in character and are older than the HS alkaline basalts, with the exception of the youngest samples. The oldest and youngest basaltic samples from KA are 280±7ka and 163±10ka, respectively, and are calc-alkaline in character. Based on thermobarometric estimates samples from OZ exhibit the highest cpx-liqidus temperature and pressure. For all centers the calculated crystallization depths are between 11 and 28km and increase from NE to SW. Multistage crystallization in magma chamber(s) located at different depths can explain this range in pressure. Harker variation diagrams coupled with least-squares mass balance calculations support fractional crystallization for ES and, to lesser extend for HS, OZ and KA. All basaltic volcanic rocks of this study are enriched in large-ion lithophile elements (LILE) and light rare earth elements (LREE). The lack of negative anomalies for high field strength elements (HFSE; Y, Yb) and the La/Nb >1 favor a shallow lithospheric source for ES, HS, OZ and KA basaltic volcanic rocks, whereas some samples bear the trace element signature of an asthenospheric mantle source. The lithospheric mantle beneath Central Anatolia may have not been affected from asthenospheric mantle directly. Negative Nb-Ta-Ti anomalies and a positive Pb spike of ES, HS, OZ and KA may be ascribed to crustal contamination or as the imprints of the previous subduction processes. According to this study, and previous studies, the effect of subduction and/or crustal contamination in Central Anatolia decreased from the Miocene to the Quaternary, and the origin of the Quaternary basaltic rocks mainly derived from subduction-related magmas enriched with sediment input rather than to slab-derived fluids. Our calculated eruption ages for the four basaltic complexes show that spatial differences predominate, whereas temporal trends are difficult to discern due to limited age resolution. According to the available geochronological, petrological and geochemical data, alkaline and calc-alkaline volcanism occurred simultaneously from distinct parental magmas.

Origin of carbon dioxide occurrences in Central Anatolia (Turkey)

Copyright © 2015 by The Geochemical Society of Japan. ignimbrite eruption (11–2.8 Ma), and c) the formation of stratovolcanoes, such as Erciyes, Melendiz Dag, and Hasan Dag, as well as numerous small monogenetic centers that erupted during the late Pliocene until recent times (Piper et al., 2002). The CO2 produced from different geological units and reservoirs exhibits different chemical characteristics. Previously published water chemistry data are presented in Table 1. The Karbogaz Field (Aksaray) is located in the eastern corner of the Tuz Golu Basin. Two superimposed aquifers are located within the field: the lower confined (gypsum, siltstone, and sandstone) and the upper unconfined (alluvium). The lower confined aquifer contains a high amount of dissolved CO2 (20–30 mg/L) (Geosan, 1998). According to their chemical composition, the wellhead waters are defined as Na–Ca–HCO3–Cl-type waters (Table 1). The wellhead waters within the Bozkar Field are defined as Na–Cl-type waters and the amount of dissolved CO2 is 469.45 mg/L (Table 1). The Guneygaz–Kemerhisar Field, located to the south of the city Nigde, consists of two aquifers: tuffites and alluvium. The Kemerhisar region wellhead waters have a similar chemical composition to the Na–Cl-type water. While shallow reservoir water contains only small amounts of dissolved CO2 (2–21 mg/L), the water within the tuffite aquifer has a high concentration of CO2 (102.8–1,280.7 mg/L) (Table 1) (Geosan, 1998). In the Karapιnar Field (Konya Province), water samples indicate predominantly Na–Cl/Ca–Mg–HCO3-type waters. The amount of dissolved CO2 varies in the range from 395.11 to 1,041.24 mg/L (Table 1). Origin of carbon dioxide occurrences in Central Anatolia (Turkey)

An isobaric–isenthalpic magma mixing model for the Hasan Dagi volcano, Central Anatolia, Turkey

Calc-alkaline rocks of the Hasan Dagi volcano (Central Anatolia, Turkey) are products of arc volcanism triggered by continental collision. Volcanic rocks of the Hasan Dagi range in composition from basalt to rhyolite but are dominated by andesite and dacite. Considering only the mass transfer part of the process leads to an incomplete picture of magma chamber processes. The exclusion of simultaneous calculations of heat and mass transfer between mixing magmas, however, has prevented petrologists from gaining new insights into the magma mixing process. Thus, we report our experimental results in conjunction with modeling with MELTS to test the ideas concerning the petrogenesis of Hasan Dagi volcanic rocks and quantitatively model the relevant petrogenetic processes. Our results demonstrate that the chemical diversity of Hasan Dagi volcano is inconsistent with the closed-system crystallization and differentiation. Thus, (1) our experimental modeling, (2) the agreement between the liquid line of descent defined by the natural rock data and the MELTS calculations, and (3) the agreement between the mineralogy of the rocks and calculated mineralogy corroborate the conclusion that the isobaric–isenthalpic magma mixing of basalt and rhyolite is the major controlling process in the petrogenesis of the Hasan Dagi magmas.

The Hasan Dagi stratovolcano (Central Anatolia, Turkey): evolution from calc-alkaline to alkaline magmatism in a collision zone

The Hasan Dagi volcano is one of the two large Plio-Quaternary volcanoes in Cappadocia (Central Anatolia, Turkey). Three stages of edifice construction have been identified for this volcano: Paleovolcano, Mesovolcano and Neovolcano. Most samples from Hasan Dagi volcano are calc-alkaline and define an almost complete trend from basaltic andesite to rhyolite. However, the more recent (Neovolcano) mafic samples are alkaline basalts. The mineralogical and geochemical characteristics of the oldest lavas (Keçikalesi (13 Ma) and Paleo-Hasan Dagi (7 Ma)) are significantly different from those of the younger lavas (Meso- and Neo-Hasan Dagi (<1 Ma)). Calcic plagioclase and pigeonite are typically observed in these older lavas. The Paleovolcano basalts are depleted in alkalis and display a tholeiitic tendency whereas the differentiated lavas are depleted in Na 2O but enriched in K 2O compared to younger lavas. There is an evolution through time towards higher TiO 2, Fe 2O 3 *, MgO, Na 2O and K 2O and lower Al 2O 3 and SiO 2 which is reflected in the basalt compositions. All the basalts display multi-element patterns typical of continental margin magmas with a significant enrichment in LILE (K, Rb, Ba and Th) and LREE and strong (Paleovolcano) to moderate (Meso- and Neovolcano) negative Nb, Zr and Ti anomalies. However, the younger basalts are the most enriched in incompatible elements, in agreement with their alkaline affinities and do not systematically display negative HFSE anomalies. REE data suggest an hydrous amphibole-bearing crystallization history for both Meso- and Neovolcano lavas. The distinction between the older and younger lavas is also apparent in trace element ratios such as Nb/Y, Ti/Y and Th/Y. These ratios indicate the role of a subducted component±crustal contamination in the genesis of the Hasan Dagi lavas, particularly for the oldest lavas (Keçikalesi and Paleo-Hasan Dagi). The decreasing influence of this component through time, over the last 6–7 m.y., has been accompanied by an increasing contribution of melt-enriched lithosphere. Although the range of variation of Sr, Nd and Pb isotopic ratios is small (0.70457–0.70515; 0.51262–0.51273; 18.80–18.94; 15.64–15.69; 38.87–39.10), it also reflects the evolution of the magma sources through time. Indeed, the youngest (Neovolcano) and most primitive basalts display significantly lower 87 Sr/ 86 Sr than the Paleo- and Mesovolcano basalts, whereas the Mesovolcano basalts display more radiogenic Pb than Paleovolcano samples. Magma mixing processes between initially heterogeneous and/or variably contaminated magmas may account for the genesis of the less differentiated and intermediate lavas (48–57% SiO 2). Meso- and Neovolcano differentiated lavas (60–68% SiO 2) are either derived from the analyzed basalts or from more primitive and more depleted magmas by fractional crystallization±some crustal contamination (AFC). Furthermore, the highly differentiated samples (72–75% SiO 2) are not strongly contaminated. The strong calc-alkaline character of Hasan Dagi lavas, in the absence of contemporaneous subduction, must reflect the heritage of the early subduction of the Afro–Arabian plate under the Eurasian plate. The evolution towards alkaline compositions through time is clearly related to the development of extensional tectonics in Central Anatolia in the Late Miocene.

Séquences volcanisées et corrélations téphrologiques au N-E du Hasan Dag (haut bassin de la Melendiz, Anatolie centrale, Turquie) [Volcanised sequences and tephrochronologic correlations in the area N-E of the Hasan Dag (upper basin of the river Melendiz, Central Anatolia, Turkey)

L'étude de nombreuses séquences quaternaires du bassin supérieur de la Melendiz permet de proposer une téphrostratigraphie de la bordure N-E du Hasan dag, important strato-volcan d' Anatolie centrale (Turquie). Les premières formations, localisées en bordure des gorges de la Melendiz, caractérisent un régime sédimentaire à dominante fluviatile (Belisirma) ou fluvio-lacustre (Ihlara), puis l'activité pyroclastique se développe à Test du volcan (Petit Hasan dag). Elle engendre quatre groupes de retombées cendro-ponceuses rhyodacitiques, séparées par des phases de colluvionnement et de pédogenèse marquées par le développement d'andosols. Une importante avalanche de débris issue du N-W du strato-volcan, comble ensuite les gorges de la Melendiz, puis une coulée de ponces ennoye sa bordure aux environs de Kitreli (bassin-affluent de la Gûvercilink). Le déplacement de l'activité vers l'ouest (coulées et nuées ardentes andésitiques du Grand Hasan dag), permet une reprise de l'incision et le dégagement des modelés actuels du secteur. Les niveaux-repères fournis par les téphras ou leurs produits de remaniement autorisent une corrélation précise des séquences en fonction de la texture, de la minéralogie ou de la géochimie des ponces. Ils corroborent la variété des stratigraphies et la multiplicité des hiatus en fonction de la position géomorphologique des témoins ou de leur éloignement par rapport au strato-volcan (domaine proximal à distal). Cette succession caractéristique reste malheureusement mal datée. Les datations C semblent situer l'avalanche de débris de la Melendiz et la coulée de Kitreli vers la fin du Pléistocène supérieur ; les paléosols antérieurs, sont plus âgés que 33 000 ans. Les datations K-Ar de 33 ± 2 et 29 ± 1 ka, corroborent l'importance de l'activité du Grand Hasan dag durant le Pleistocene supérieur et sa continuation probable durant l'Holocène (âge calculé d'une coulée «&lt; 0», soit «postérieur» au présent).

Le volcanisme quaternaire d'Anatolie centrale (Turquie): association de magmatismes calco-alcalin et alcalin en domaine de convergence

Collision volcanism in Central Anatolia (Cappadocia) began at least in the late Miocene. Because of the North–South Arabian-Eurasian convergence since this period, the Anatolian block is displaced towards the West along the North and East Anatolian strike-slip faults. Kinematic reconstructions show that the East Anatolian Fault is both sinistral and convergent. As a consequence, the Anatolian block is currently being deformed. Quaternary volcanism in Central Anatolia is represented by several hundreds of monogenetic scoria cones, lava flows, maars, and domes as well as two strato-volcanoes, Hasan Dag and Erciyes Dag. The monogenetic volcanism is bimodal (basalts and rhyolites), whereas the stratovolcanoes exhibit a complete calc-alkaline suite, from basalts to rhyolites. Most of the igneous products are calc-alkaline. Basalts erupted mainly from the monogenetic cones, lava flows, and maars. Andesites are encountered in the strato-volcanoes as lava flows, domes, and nuees ardentes deposits. Dacites and rhyolites occur as ignimbrites and dispersed maars and domes. Volcanic events were recorded up to historical times. Some basalts from monogenetic edifices, contemporaneous with the calc-alkaline suite, exhibit mineralogical and geochemical features that are typical of intraplate alkaline suites, such as normative nepheline, alkali feldspars, and Ti and Cr-rich Cpx. Euhedral microlites of aluminous garnet, although rare, have been observed in basalts, rhyodacites, and rhyolites. This association of contemporaneous calc-alkaline and alkaline suites may be related to collision tectonics.