Biga Peninsula Research Articles

Significance and Petrochemistry of Upper Mantle–mantle Transition Zone Metaperidotites and Oceanic Crust Metagabbros within the Kazdağı Metaophiolite: Implications for the Geological Evolution of the Izmir–Ankara–Erzincan Ocean, Northwestern Turkey

AbstractThe Kazdağı metaophiolite crops out in the Kazdağı (Ida) Mountains in the Biga Peninsula in northwestern Turkey. It is in stratigraphic contact with the high–grade metamorphic rocks of the Kazdağı Massif. Metaophiolitic and high–grade metamorphic rocks are tectonically overlain by low–grade metamorphic units of the Permo‐Triassic Karakaya Complex of the Sakarya Zone. Late Oligocene‐Early Miocene granites intruded these tectonic units (Okay and Satır, 2000; Duru et al. 2012).In the Kazdağı metaophiolitic sequence, upper mantle peridotites are represented by metaharzburgite and metadunite, whereas the mantle transition zone metaperidotites are composed of metadunite, metapyroxenite and minor plagioclase‐bearing metalherzolite. The upper part of the metadunites in the mantle transition zone show intercalation with metagabbros. Gabbros of oceanic crust experienced amphibolite facies metamorphism and are transformed into amphibolite, garnet amphibolite and migmatitic gabbros. The metagabbros and amphibolites display MORB‐ and IAT‐like geochemical features.The Kazdağı metaophiolite is conformably overline by basal conglomerates and hemi‐pelagic carbonate rocks continuing upward into forearc‐type flysch–like detrital sedimentary rocks interspersed with mafic volcanic intervals. These cover units underwent high–grade metamorphism into gneisses, migmatites, amphibolites and marbles in a compressional regime during the Alpine orogeny. New U–Pb zircon data from the metagabbros show two crystallization peaks at ∼52 Ma and ∼73 Ma. This has implications for the age of subduction of the Izmir–Ankara–Erzincan Ocean, generally assumed to be northward under the Sakarya Zone. During the Triassic to Middle Eocene, progressive overthrusting of the Sakarya Zone via a N–S compresional regime created by the Alpine orogeny onto subduction–accretion‐ and forearc‐units resulted in high–grade metamorphic conditions in the Biga Peninsula.

Opportunities of electrokinetics for the remediation of mining sites in Biga peninsula, Turkey

This study investigated the geological conditions of Biga Peninsula. There are metamorphic rocks, ophiolitic melange, plutonic rocks, subvolcanics, volcanic rocks and volcanoclastics along with marine and terrestrial sediments in the region. This variety of rocks and the associated minerals resulted in many interesting metallic ores and coal for commercial exploitation. The mining exploitations in Biga Peninsula (Turkey) pose an environmental risk due to the release of contaminants, metals and arsenic, to the soil and waterbodies. This study analyzed the potential release of As and metals (Al, Fe, Mn) from a sediment sampled in a mine pond. The extraction column tests proved that those contaminants can be dissolved from the sediment using deionized water as eluent. The electrokinetic treatment of the sediment was able to remove Al and Mn, but the removal of Fe and As was negligible. The fractionation of As and metals in the sediment confirmed that the electrokinetic treatment was able to mobilize the contaminants. Based on the results of this study, it has been hypothesized that the toxic elements could be removed by electrokinetics using facilitating agents, neutralizing the alkaline environment of the cathode and increasing the treatment time.

Geochemical Features and Petrogenesis of Gökçeada Volcanism, Çanakkale, NW Turkey

Gökçeada Island, which is situated west of Biga Peninsula, has widespread magmatism with variable ages. Lower-Middle Eocene Dağiçitepe volcanics are the oldest volcanic unit in the island and consist of lavas, tuff-tuffites. They are influenced by alteration and almost all minerals, except quartz, are transformed into other minerals. Lower Oligocene Gökçeada andesitic lava/ domes exhibiting hypocrystalline porphyric texture, are the products of NE-SW trending domes/ cryptodomes. The phenocrysts assemblages consist of plagioclase, hornblende, clinopyroxene ± biotite and quartz. Middle Miocene Eşelek volcanics, which occur as lavas and pyroclastic rocks, exhibit hypocrystalline porphyric and intersertal textures. They are composed of plagioclase, hornblende and clinopyroxene crystals. Rhyolitic Dağiçitepe volcanics and andesitic Gökçeada lava/domes have calc-alkaline, andesitic Eşelek volcanics have tholeiitic character. They have geochemical features similar to subduction-related magmas. Lower-Middle Eocene Dağiçitepe volcanics are the products of syn-collisional magmas that have undergone processes of crustal contamination due to thickened crust. Whereas, Lower Oligocene Gökçeada andesitic lava/domes are the products of post-collisional magmas and were derived from metasomatized lithospheric mantle. Middle Miocene Eşelek volcanics were also derived from lithospheric mantle but, the mantle source generating Eşelek volcanics were relatively depleted over time. Geochemical data demonstrate the decreasing role of subduction signature and crustal contamination during the genesis and evolutionof Gökçeada volcanics from Lower-Middle Eocene to Middle Miocene.

Analysis of local site conditions through geophysical parameters at a city under earthquake threat: Çanakkale, NW Turkey

Çanakkale is the second province, after Istanbul, that has territories in both Asia and Europe. The city, also known as Dardanelles, is located on the Gallipoli peninsula in the northwest of Turkey, and the Biga peninsula which is an extension of Anatolia at the west. The region is tectonically quite active and it has high earthquake generation potential. The city has experienced a significant earthquake (Mw = 6.8) once again that occurred on May 24, 2014. In addition to these challenges, remarkable part of the city's territory and also potential new settlement areas are located on thick alluvium. Thus, mentioned-above disadvantages clearly increase the importance of this study, which focuses on determining the areas having different earthquake hazard potentials with regard to local site conditions by performing seismic risk assessments, as well as providing a basis for the preparation of settlement suitability maps on different scales that will lead knowledge for zoning plans. To that end, an integrated geophysical and geotechnical study was performed in a detailed manner. Multi-channel analysis of surface waves (MASW) and microtremor (MT) measurements were carried out at properly distributed 110 stations representing the whole survey area. The geotechnical study, planned to contribute geophysical interpretation, involved the drilling of 110 boreholes that are close to geophysical measurement stations. In addition to examining Vs30 variations based on the MASW, the ground dominant vibration period maps were also produced through MT time series analysis. In particular, the mean Vs velocity (Vs30) up to the first 30 m and the ground oscillation period change based on spectral amplitude ratios (HVSR) yielded substantial information that helped generate the seismic microzonation maps and also make the ground classification. These outputs contributed to exhibit the risk zones in the coastal city that has a dense and narrow settlement plan.

Singularity mapping of bulk leach extractable gold and −80# stream sediment geochemical data in recognition of gold and base metal mineralization footprints in Biga Peninsula South, Turkey

Stream sediments remain the preferred geochemical sampling media for regional mineral exploration programs in most parts of the world where there is a well-defined drainage system. In Au exploration the analysis of either Bulk Leach Extractable Gold (BLEG) or acid-extractable Au in the −80# (<180 μm) stream sediment fraction are the two most common approaches. Western Turkey contains a variety of mineral deposit types and geological settings. Using a geochemical database derived mainly from company exploration programs, a study is made on the efficiency of singularity mapping technique in detecting the known mineral deposits or prospects.The composite media of samples are representative of sampling locations but also are extremely diluted. Therefore, recognition and mapping of significant geochemical anomalies of composite media still remains a challenge. In this study, geochemical assay results were subjected to multifractal analyses to detect gold geochemical anomalies, which are related to gold mineralization. In this regard, a singularity mapping technique was applied to enhance the single element geochemical signatures of BLEG sand −80# stream sediment data. Since the singularity mapping technique does not define threshold values for delineation of anomalies, number-size (N-S) and concentration-area (C-A) fractal models were applied to delimit the geochemical anomalies as target areas for further exploration. A hundred percent of the known gold deposits and prospects discovered in the study area are delineated by BLEG Au stream sediment anomalies by N-S and C-A multifractal modeling. Moreover, 89% of known gold prospects of the study area are delineated within the recognized anomalous zones of Au in −80# stream sediment data. The comparison of the delineated geochemical anomalies of BLEG and −80# stream sediment with those of rock chip samples demonstrated the efficiency of the applied methodology.

RESIDUE ANALYSIS OF GRINDING STONES FROM CHALCOLITHIC GÜLPINAR

This study presents the preliminary results of residue analysis of grinding stones recovered from the Early Chalcolithic 2 and Middle Chalcolithic period settlements (Gülpınar II and Gülpınar III) in the Sanctuary of Apollo Smintheus (Smintheion), located in the southwestern corner of the modern Biga Peninsula (Ancient Troad) in north-western Anatolia. The Early Chalcolithic 2 period settlement at Gülpınar II has been dated to 5320-4940 BC, while the Middle Chalcolithic period settlement at Gülpınar III superimposing it has radiocarbon dates ranging between 4930 and 4450 BC. Excavations at Chalcolithic Gülpınar between 2004 and 2014 revealed a total of 453 ground stone tools. This work in this context residue analyze of total of 28 grinding stones that were uncovered from these two Early Chalcolithic 2 and Middle Chalcolithic cultural levels. Chemical analysis of residue on stone tools has become a common research technique used in archaeology science. Chemical residues in and on the working surface of used grinding tools lead us to consider the context of the tool usage. The widely-used Gas Chromatography–Mass Spectrometry (GC-MS) method was selected for analyses of the grinding stones from Chalcolithic Gülpınar. The chemical analysis and preliminary results obtained from Gülpınar samples are outlined in this study. Results show evidence of the distinctive lipid organic residues pentacosane and heptacosane as minor and trace constituents in some of the essential oils of edible crops and the major fatty acids of octadecanoic (stearic) and palmitic (oleic). Palmitic acid is also a major component of the oil found in dairy products and abundant in animal fat. These results may contribute to approaches that aim to explain how prehistoric societies carried out processing of organic and inorganic raw materials.

KALKOLİTİK GÜLPINAR TAŞ AĞIRLIKLARININ İŞLEVİNE YÖNELİK ÖNERİLER

The Early Chalcolithic 2 (Gulpinar II) and Middle Chalcolithic period (Gulpinar III) settlements identified at Smintheion (Sanctuary of Apollo Smintheus) in the southwestern corner of the modern Biga Peninsula (ancient Troad) in north-western Anatolia have revealed new evidence regarding ground stone tool typology. Evaluation of the ground stone tool assemblages from these two consecutive Chalcolithic phases at Gulpinar have resulted in identification of a unique class of tools that could be considered as stone weights or net sinkers. Such tools were previously unknown in the archaeological record of northwestern Anatolia. This assemblage of ground stone tools is examined here via ethnographic analogy based on parallels with North America and Oceania, where they were mainly classified as sinkers for fishing lines and nets. The function of these tools is controversial because they have often been identified as loom weights or miscellaneous objects in studies of western Anatolian archaeology because direct evidence for fishing gear is relatively scarce. For the first time, these Chalcolithic Gulpinar stone weights, found in situ along with a pile of shells, support the opinion of them being used as net sinkers. Beside ethnographic analogy, other examples reported from various sites in the Near East, Aegean, and Anatolia were also examined in order to explain the function of these ground stone tools. This study also proposes that the sinker stones of Chalcolithic Gulpinar could be added to Anatolian ground stone typology. It is hoped that these tools will contribute to our understanding of long-term conventions in the fishing methods of prehistoric people and in the functional use and variability of these objects.

Love and Rayleigh waves inverted for vertical transverse isotropic crust structure beneath the Biga Peninsula and the surrounding area in NW Turkey

Love and Rayleigh waves inverted for vertical transverse isotropic crust structure beneath the Biga Peninsula and the surrounding area in NW Turkey

Evaluation of Çanakkale Kilitbahir Castle in the Context of Refunctioning

The Dardanelles Strait functions as a bridge between Biga and Gelibolu peninsulas, connecting the Aegean Sea and the Marmara Sea. Many defences have been built on the Dardanelles Strait, which has hosted many civilizations from the past to the present day, in line with the needs of the time. Kilitbahir Castle, which has a three-leaf clover plan and is located on a slope rising on the Gallipoli peninsula in the narrowest part of the Bosphorus after the conquest of Istanbul by Mehmet the Conqueror; manifests itself as a pioneering structure of the military architecture of the era with the developing artillery technology. In terms of protecting the physical environment, it is observed that the defensive buildings which survived up to today are not adequately protected, losing their historical and architectural values. In this context, the restoration of Kilitbahir Castle dating back to Ottoman Period defence structures on the Dardanelles Strait was evaluated. Its phases throughout the process along with the current location and architecture were evaluated by using written and visual resources. European Archives, BNF Archives, Topkapi Palace Archives and Istanbul University Archives were utilized for reaching the castle engravings. In accordance with the information obtained in the historical research process, the exhibition arrangement and environment planning project of the structure, which serves as a museum, was prepared.

ACTIVE TECTONIC AND PALEOSEISMOLOGIC CHARACTERISTICS OF THE YENİCE-GÖNEN FAULT, NW TURKEY, IN LIGHT OF THE 18 MARCH 1953 YENİCE-GÖNEN EARTHQUAKE (Ms=7.2)

The Yenice-Gönen Fault (YGF) is located in the central part of the Biga Peninsula between Gönen and Yenice and is a right-lateral strike-slip active fault with general trending N65°E. On 18 March 1953 there was an earthquake on the YGF that died 263 people (Ms=7.2) and a 70 km surface rupture developed during this earthquake. In this study measurements of slip distribution were performed on the surface rupture of the Yenice-Gönen Earthquake (YGE) and the annual slip rate on the YGF was calculated. Right-lateral displacements of between 1.70±0.1 and 3.20±0.2 metres were measured on the surface rupture of the YGE. The maximum displacements were in an area close to the central part of the YGF (between Çakır and Karaköy village) and these values decreased relatively in NE and SW directions, documenting that was the bilaterally surface rupture propogation during the YGE. In the last 300.000 years, a total offset of 800±50 metres was measured on Gönen River and annual slip rate of 2.65±0.15 mm was calculated along the YGF. Current GPS studies show right-lateral strike-slip faults in the South Marmara region have slip rates of 6-8 mm/year. This slip rate is assessed as being partitioned between the YGF, Sarıköy Fault and Çan-Biga Fault zones which represent extensions of the North Anatolian Fault system within the South Marmara region. Paleoseismology studies determined that in the last 6200 years 6 earthquakes resulting in surface ruptures have occurred on the YGF, including the 1953 earthquake. According to the 14C and OSL dating results, the variable and irregular earthquake recurrence interval of YGF is ranging from 505 to 1793 years. In this study average earthquake recurrence interval of YGF was determined as 1180 years.

EVALUATION OF SOIL GEOCHEMISTRY DATA OF CANCA AREA (GÜMÜŞHANE, TURKEY) BY MEANS OF INVERSE DISTANCE WEIGHTING (IDW) AND KRIGING METHODS- PRELIMINARY FINDINGS

In Northwest Anatolia, widespread magmatism developed due to collision between Anatolide-Tauride platform and Sakarya continent during Late Cretaceous-Early Tertiary period. The granitoids in Biga Peninsula are products of post-collisional magmatism following the convergence of the northern branch of Neotethyan Ocean and developed in two different stages as Eocene and Oligo-Miocene. Eocene Karabiga, Gureci, Kuscayir and Dikmen granitoids are granite and diorite-granodiorite; Oligo-Miocene Sarioluk, Yenice, Kestanbol, Eybek, Evciler, Camyayla and Alankoy granitoids are diorite, granodiorite, monzonite and Q-monzonite in composition. Metaluminous and peraluminous granitoids have similar geochemical variations and exhibit post-collisional geochemical signatures. Trace element patterns are almost similar to those observed in upper crust and GLOSS (Global Subducting Sediment) patterns with depletion in high field strength (HFS) elements (Nb, Ta, Ti, Zr, Hf). But, Oligo-Miocene Sarioluk, Yenice-Cakiroba, Kestanbol, Evciler, Camyayla, Alankoy and Eocene Karabiga, Gureci and Kuscayir granitoids have higher Th and U contents relative to upper crust and GLOSS. Dikmen, Yenice-Hamdibey, Yenice-Eskiyayla and Eybek granitoids have lower Th content. Geochemical variations indicate that partial melting and fractional crystallisation- crustal contamination processes are effective in their genesis and evolution. Trace element ratios also indicate subduction signatures in their genesis and Rb/Ba, Rb/Sr ratios suggest mantle melting rather than crustal melting. Accordingly, post-collisional Biga Peninsula granitoids were derived from a previously metasomatised lithospheric mantle source, which was enriched during northward subduction and closure of the northern branch of Neo-Tethys Ocean beneath the Sakarya continent, since variations in Rb, Cs, Th, La and Sm reveal that lithospheric mantle was mesomatised by both aqueous fluids and sediment melts.

Estimation of optimum velocity model and precise earthquake locations in NE Aegean: Implications for seismotectonics and seismic hazard

This study relocates the seismicity in NE Aegean during the period 2011–2017 using data recorded by the Hellenic Unified Seismic Network (HUSN) in order to elucidate the relationship between seismicity and active faults in this area. P- and S-phase travel times of well-recorded events were first inverted in order to derive a minimum 1D velocity model with station delays using VELEST. Absolute locations of 4450 events were obtained by use of the nonlinear probabilistic algorithm NLLOC and the newly derived velocity model. Precise relative locations with horizontal and vertical uncertainties that do not exceed 1.2 km were calculated for 3354 events using the double-difference algorithm. The relocated seismicity delineates active faults to the south of Lesvos island, at the tip of Biga peninsula in Turkey and along the parallel strands of strike-slip faults that accommodate the westward motion of Anatolia. The comparison of the seismicity distribution with known active faults and the regional stress field shows that the strike-slip faults represent either principal shear zones, or Riedel shears oriented obliquely to the minimum stress axes. Normal faults are oriented almost perpendicular to the direction of the minimum stress axes in accordance with the transtensional deformation model. The seismogenic layer thickness derived from the depth distribution of relocated seismicity was found to be in the range of 14.8–15.8 km. By combining this thickness with geometrical characteristics of active faults and with a relationship that connects moment magnitude with rupture area, it is possible to estimate expected magnitudes of earthquakes. These magnitudes range from 6.3 to 7.2 depending on the rupture scenario that is considered for each fault. Of particular concern are the faults of Agia Paraskevi in Lesvos and Mastichochoria in Chios island that traverse densely populated areas and can produce large events with magnitudes from 6.4 to 6.9. Very little seismicity can be observed along these faults in the past 7 years, which may indicate either that they are creeping, or that they are locked and accumulate strain energy.

Geochemical and Sr-Nd-Pb isotopic characteristics of extrusive rocks within the Çetmi Ophiolitic Mélange, Biga Peninsula

The different geochemical characteristics of the extrusive rocks of the Cetmi Ophiolitic Melange (COM) a remnant of the Intra-Pontide Suture (IPS) in the Biga Peninsula, NW Turkey, evidence the episodic formation of oceanic crust. Geochemically, volcanic rocks are divided into three groups: ocean island basalts (OIB), enriched mid-ocean ridge basalts (E-MORB) and basalts with supra-subduction zone (SSZ) affinity. While the OIB type samples were produced by small degrees partial melting from an enriched source, the E-MORB type samples point to mixing of enriched and depleted sources. In the OIB-type samples, the depletion of Zr and Hf compared to Nd as well as enrichment of Nb-Ta are attributed to presence of the amphibole in the mantle source. Radiogenic Pb isotope compositions towards EMII support metasomatic processes related to fractionation in the mantle reservoir. The SSZ samples are characterized by enriched light rare earth elements (LREE) and depleted high field strength elements (HFSE). The trace element characteristics of the SSZ samples indicate that a depleted MORB mantle source interacted with subduction-derived fluids due to the slab dehydration processes. Besides, the Sr-Nd-Pb isotope characteristics suggest that these samples originated from a MORB-type mantle source metasomatized by fluids or melts from subducted sediments. The major, trace element and isotopic data of the volcanic rocks in the COM indicate that the oceanic lithosphere is generated along a SSZ-type spreading centre at an arc-basin system within the Intra-Pontide Ocean.

Coseismic Displacements from Moderate-Size Earthquakes Mapped by Sentinel-1 Differential Interferometry: The Case of February 2017 Gulpinar Earthquake Sequence (Biga Peninsula, Turkey)

We study the tectonic deformation from the February 2017 shallow earthquake sequence onshore Biga Peninsula (NW Turkey, NE Aegean region). We use InSAR interferograms (Sentinel-1 satellites) to identify the seismic fault (striking N110°E) and seismological data (parametric data and Moment Tensor solutions from NOA and KOERI catalogues) so as to refine its geometry and kinematics using inversion techniques. Despite the moderate magnitudes of the main events of the sequence (5.0 ≤ Mw ≤ 5.2), the total surface deformation is 2.2 fringes (or maximum 6.2 cm along LOS) and it is well visible with InSAR because of the shallow depth of the four main events (6–8 km) and the good coherence of the signal phase. Our geodetic inversion showed that the fault has normal-slip kinematics, dimensions of 6 by 6 km (length, width) and dips at 45°. The InSAR data are fitted by a uniform slip of 28 cm. In addition, 429 earthquakes were relocated with the HypoDD software and the use of a 1-D velocity model. The dip-direction of the fault is not retrievable from InSAR, but a south-dipping plane is clear from seismology and the aftershocks distribution. The spatial distribution of relocated events indicates the activation of one fault with a rupture zone length of about 10 km, a result of the occurrence of off-fault aftershocks along strike the main rupture. A stress inversion using 20 focal mechanisms (M ≥ 3.6; NOA solutions) indicates that faulting accommodates a N196°E extension. It is confirmed that moderate (5.0 ≤ M ≤ 5.2) shallow events can be traced in InSAR studies and can produce surface displacements that provide useful data in fault inversion.

Middle-Late Eocene marine record of the Biga Peninsula, NW Anatolia, Turkey

The Eocene shallow marine deposits marking the first marine incursion in the Biga Peninsula (NW Turkey) after the collision of the Sakarya and Anatolide-Tauride plates were investigated based on paleontological, litho- and chrono-stratigraphic data. Larger Benthic Foraminifera (LBF) from patchily distributed outcrops were studied in order to i) revise the stratigraphy of Eocene shallow marine units, and ii) establish a modern biostratigraphic setting and a correlation scheme. The Sevketiye Formation (Fm.) is herein defined as a predominantly shallow marine clastic deposit with subordinate carbonates overlying the Camlica metamorphic rocks, and passing laterally to the Sogucak Fm., a carbonate unit that is widely represented in the Thrace Basin. The record of alveolinids, primitive developmental stages of heterosteginids, and orthophragminids in the Sevketiye Fm. suggests that this formation is part of the Shallow Benthic Zones (SBZ) 16?/17 (Late Lutetian?/Early Bartonian), SBZ17?/18 and SBZ19A (Early Bartonian/earliest Priabonian). The Sogucak Fm., which overlies the Eocene volcanics, on the other hand, yielded advanced developmental stages of heterosteginids, Spiroclypeus sp. and Nummulites fabianii lineages, implying a younger marine incursion during the Late Eocene (earliest Priabonian; SBZ19A). A drastic shift in the depositional regime is marked amid Priabonian by the deposition of deep-marine clastics and volcanoclastics of the Ceylan Fm. In conclusion, the Eocene Sea transgressed first Gokceada (in the Aegean Sea) during the Late Lutetian, then reached the Biga and Gelibolu peninsulas in the Bartonian, and finally led to the widespread deposition of carbonate and siliciclastic rocks in the Biga Peninsula and the Thrace Basin during the Late Bartonian and Priabonian.

PETROGRAPHY AND PETROLOGY OF THE YÜREKLİ (BALIKESIR) VOLCANICS: AN EXAMPLE OF POST-COLLISIONAL FELSIC VOLCANISM IN THE BIGA PENINSULA (NW TURKEY)

In this study, the aim was to determine the petrography, geochemistry and source of the Yürekli volcanics (Biga Peninsula, NW Turkey). Tertiary volcanism is widespread in Western Anatolia (NW Turkey), which is an important area where tectonic and magmatic events are observed together. Yürekli volcanic rocks comprise dacitic lavas and pyroclastics. Dacitic lavas show porphyric and hyaloporphyric texture, and consist of plagioclase, quartz, amphibole, biotite, sanidine and Fe-Ti oxide minerals with apatite and zircon accessory minerals. Petrologically, they have high-potassic and calc-alkaline characteristics. Yürekli volcanics show enrichment in large ion lithophile elements (LILE) and are depleted in high field strength elements (HFSE) on the N-MORB normalized diagram. On the chondrite-normalized rare earth element (REE) plot, light rare earth elements are enriched but heavy rare earth elements are depleted in the rocks. REE patterns are concave shaped (mean LaN/LuN=16–25) and show slight negative Eu anomalies (0.66–0.81). Plagioclase, amphibole and biotite fractional crystallisation and crustal assimilation are important in the evolution of the Yürekli volcanics. According to all data, it can be argued that the Yürekli volcanics formed in a post-collisional setting, and the parental magmas were derived from the melts of enriched lithospheric mantle.

Preliminary Observations and Assessment of Çanakkale-Ayvacık Earthquake Activity

A project was begun to monitor earthquake activity at the southwest branch of the Biga Peninsula in Ayvacık and close surroundings beginning on 14 January 2017 with Mw=4.6 and continuing through 6 February 2017 with Mw=5.5 (Mw=5.5 Kandilli Observatory and Earthquake Research Institute – KOERI - , Mw=5.3 AFAD, Mw=5.4 ÇOMÜ). The region has active seismicity and includes portions of the significant tectonic elements of the northwest Aegean region. Due to the continuation of earthquake activity, in addition to permanent stations linked to the national networks (KOERI and AFAD) in the region 10 continuous-form recording 3-component temporary stations were set up with the aim of observation for at least 1 year. The distances between these stations varied from 6 to 12 km. In addition to the intensity and continuity of microearthquake activity in the region, and the inclusion of geothermal fields in the region, the necessity to investigate the seismotectonic character of the region in detail came to the agenda. Together with permanent stations belonging to national observatories in the study area, the station density was insufficient to reveal these details. As a result, data from both national network and temporary stations will contribute to understanding the tectonic character of the region. When temporary stations at close proximity to the main shock and epicenter distribution are compared with the national network primary results indicate there were significant improvements in identifying microearthquakes especially and in determining their locations. Additionally, and in source mechanism solutions belonging to earthquake data with moderate magnitude, faulting with a dominantly NW-SE oriented normal offset component was observed. This study aims to reveal the time and spatial distribution, frequency content and source mechanisms for earthquakes occurring in the southwest of the Biga Peninsula near Ayvacık and surroundings, in addition to determining a detailed velocity model with local tomography.

Repeated reactivation of clogged permeable pathways in epithermal gold deposits: Kestanelik epithermal vein system, NW Turkey

This study presents a detailed study of the dimensions, geometry, textures and breccias of a well-exposed epithermal vein system, the Kestanelik gold deposit in the Biga Peninsula, NW Turkey, and investigates the permeability enhancement mechanisms in epithermal gold deposits. Here mineralization is associated with quartz veins up to 13.6 m thick. Vein textures and breccia components indicate repeated sealing and subsequent brecciation of wall rock and pre-existing vein infill. Field and petrographic analyses characterize east–west-trending veins as left lateral faults, whereas NE–SW-trending veins are extensional (Mode I) fractures. Cataclasite and tectonic breccia of wall rocks and early quartz, hydrothermal crackle breccias, and matrix-supported chaotic breccias of pre-existing vein infill, all of which are cemented by late iron-oxide-bearing quartz, indicate that co-seismic rupturing and hydraulic fracturing are two major permeability enhancement mechanisms. In addition, transient variations in local stress direction, caused by syn-mineralization dyke intrusion, may have enhanced permeability on misoriented surfaces and at locations where the dip changes. This study emphasizes the importance of understanding structural geology and kinematics as controls on the location of boiling and mineralization mechanisms in epithermal gold deposits.

Tectonic implications of the 2017 Ayvacık (Çanakkale) earthquakes, Biga Peninsula, NW Turkey

The west to southwestward motion of the Anatolian block results from the relative motions between the Eurasian, Arabian and African plates along the right-lateral North Anatolian Fault Zone in the north and left-lateral East Anatolian Fault Zone in the east. The Biga Peninsula is tectonically influenced by the Anatolian motion originating along the North Anatolian Fault Zone which splits into two main (northern and southern) branches in the east of Marmara region: the southern branch extends towards the Biga Peninsula which is characterized by strike-slip to oblique normal faulting stress regime in the central to northern part. The southernmost part of peninsula is characterized by a normal to oblique faulting stress regime. The analysis of both seismological and structural field data confirms the change of stress regime from strike-slip character in the center and north to normal faulting character in the south of peninsula where the earthquake swarm recently occurred. The earthquakes began on 14 January 2017 (Mw: 4.4) on Tuzla Fault and migrated southward along the Kocaköy and Babakale's stepped-normal faults of over three months. The inversion of focal mechanisms yields a normal faulting stress regime with an approximately N-S (N4°E) σ3 axis. The inversion of earthquakes occurring in central and northern Biga Peninsula and the north Aegean region gives a strike-slip stress regime with approximately WNW-ESE (N85°W) σ1 and NNE-SSW (N17°E) σ3 axis. The strike-slip stress regime is attributed to westward Anatolian motion, while the normal faulting stress regime is attributed to both the extrusion of Anatolian block and the slab-pull force of the subducting African plate along the Hellenic arc.

Hydrogeological Modelling of Some Geothermal Waters of Ivrindi, Havran and Gönen in the Province Capital of Balikesir, Western Anatolia, Turkey

In this study, hydrogeological, hydrogeochemical and isotope geochemical features of Havran, Gönen and Ivrindi within the province capital of Balıkesir, Turkey were investigated in detail. The Early Triassic Karakaya formation in the study area of Havran forms the oldest rocks consisting of spilitic basalts, diabases, gabbros, mudstones, cherts and radiolarites. There are limestone blocks in this formation with intercalations with sandstones and with feldspar contents, quartzite, conglomerates and siltstones. Oligocene to Miocene granodiorite intrusions were generated in association with intensively volcanic events in the area. Between Upper Oligocene and Early Miocene, andesitic and dacitic pyroclastic rocks cropped out due to intensively volcanism. Later, conglomerates, sandstones, claystones, marls and limestones as lacustrine sediments formed from Middle to Upper Miocene in the study area. In the study area of Gönen, the Lower Triassic Karakaya formation consists of basalts, diabases, gabbros, mudstones, cherts and radiolarites and forms the basement rocks overlain by Upper Jurassic to Lower Cretaceous sandy limestones. Upper and Middle Miocene volcanics which can be considered intensive Biga Peninsula volcanos outcrop in the area. These andesitic lava flows are of black, gray and red color with intensive fissures. Neogene lacustrine sediments consist of conglomerates, sandstones, marl, claystone and clayey limestones. Upper Miocene to Pliocene rhyolitic pyroclastics and dacitic lava flows are the volcanic rocks which are overlain by Pliocene conglomerates, sandstones and claystones. In the study area of Ivrindi, the Çaldağ limestones are the oldest formation in Permian age. Çavdartepe metamorphic rocks are of Lower Triassic in which can be observed marbles sporadically. The Kınık formation consisting of conglomerates, sandstones, siltstones and limestones are of Lower Triassic age and display a lateral Stratigraphic progress with volcanic rocks. Upper Miocene to Pliocene Yürekli formation consists of dacites and rhyodacites. Upper Miocene to Pliocene Soma formation is composed of clayey limestone, marl, siltstone, intercalations of sandstone, agglomerate and andesitic gravels and blocks cemented by tuffs. Quaternary alluvium is the youngest formation. The samples of geothermal waters in the area of Havran can be considered as Na-Ca-(SO4)-HCO3, Na-(SO4)-HCO3 and Na-SO4 type waters. In comparison, the geothermal waters in Gönen are of Na-(SO4)-HCO3 and Na-HCO3 type waters. The geothermal waters of Ivrindi are considered as Na-Ca-HCO3 type waters. In the area, a groundwater sample is of Ca-Mg-HCO3 type water.The geothermal waters belong to the cations of Na+K>Ca>Mg in Havran, Gönen and Ivrindi and to the anions of SO4>HCO3>Cl in Havran, HCO3>SO4>Cl in Gönen and SO4>HCO3>Cl in Ivrindi. In the diagram of Na-K-Mg1/2, the geothermal waters in Havran, Gönen and Ivrindi of the province capital of Balıkesir can be classified as immature waters.