Contamination of seismicity catalogs by quarry blasts: An example from İstanbul and its vicinity,northwestern Turkey

Scientists have proposed two fault systems of different ages in the Sea of Marmara: the Thrace-Eski?ehir Fault Zone of Early Miocene–Early Pliocene age and the North Anatolian Fault Zone of Late Pliocene–Recent age. Different seismicity rates and extensions of these faults onto land near ?stanbul have been suggested. One of the reasons for these differences is the contamination of seismicity catalogs by seismic events from quarries operated in ?stanbul and its vicinity, including Gaziosmanpa?a (Cebeci and Kemerburgaz), Çatalca, Ömerli, Gebze, and Hereke.In this study, we investigated waveforms of 179 seismic events (1.8 < Md < 3.0) from the KOERI, NEMC digital database. We determined differences between earthquakes and quarry blasts based on time- and frequency-domain analyses of their seismograms (amplitude peak ratio, power ratio, and spectral amplitude ratio) and used these differences as discriminants. The results of this study indicate that 15% and 85% of the investigated seismic events are earthquakes and quarry blasts, respectively.     

The Zaghawa and the Midob of North Darfur – A comparison of migration behaviour

Two ethnic groups of North Darfur, the Zaghawa and the Midob, are being compared as regards their migration behaviour and their identification in their destination areas. Both groups have severely suffered as a result of the drought phase of the last three decades, during which more than half of the Zaghawa and Midob have migrated southwards and to the towns. Despite the similarity of the two ethnic groups, being non-Arab agropastoralists who are socially and politically marginalised both within Darfur and within the Sudan, they show marked differences in their migration behaviour and ethnic solidarity. The Zaghawa migrants are considerably more economically successful than the Midob migrants. The main reasons are: – The Zaghawa started their outmigration earlier than the Midob. Thus, they could establish ethnically-based networks in Libya and the Gulf countries, to which Zaghawa migrants can resort to make a good start in their destination areas. By the time the Midob started their migration in the 1980s, the conditions of employment in the Arab oil countries had worsened. – The Zaghawa show a strong clan solidarity. They readily lend money to young members of their clan to cover the high costs of travelling to the Arab oil countries for work, where many of them have already established themselves. – The Midob, both in the Sudan and abroad, have much less resources available. The only country open for them outside the Sudan is Libya. Lacking capital, the Midob go there on camels, mostly illegally. Having no connections in Libya, except those to other poor Midob there, they usually try to work in herding sheep and goats, which is not a lucrative profession. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimation of environmental impacts on the water quality of the Tahtalıdam watershed in İzmir, Turkey

Water pollution is a widespread problem in different areas of the world. Some of these problems originated from point contamination sources and widespread contaminant outlet sources which are observed in every country. The major elements and chemical loads of surface water have been dominated by constituents derived directly or indirectly from human activities and/or industrial practices that have increased additives in the last several decades. The point sources of contamination may result from the direct wastewater discharges to the dam sites, which are considered to be the most commonly encountered water pollution problems. One of these problems is the eutrophication process which usually occurs in the static water mass of lakes and other surface water reservoirs. This process may be caused by the continuous increase of nitrogen and phosphorus contents and decrease of O₂ level in water causing an anaerobic condition which may stimulate algae-growth flow in these water bodies, consequently reducing the quality of water. Of course, there are many research methods for determining the various kinds of water pollution. In this research, the hydrochemical parameters were evaluated to estimate the types of pollution sources, the level of pollution, and its environmental impacts on the Tahtal dam reservoir.     

REE and HFS element behaviour in the alteration facies of the Erenler Dağı Volcanics (Konya,Turkey) and kaolinite occurrence

Mainly high-K, calc-alkaline, Late Miocene to Pliocene volcanic rocks cropped out of the Konya area in Central Anatolia, Turkey. The volcanic rocks are predominantly andesitic to dacitic in composition and rarely basalt, basaltic andesite, basaltic trachyandesite and pyroclastics. Kaolinite, illite, Ca-montmorillonite, alunite, jarosite, minamiite and silica polymorphs were formed by widespread and intense hydrothermal alteration in or around the volcanic products. To investigate the effects of hydrothermal alteration on the chemistry of volcanic rocks, the whole rock chemical composition (major and trace elements, including rare-earth elements (REE) was analysed. The results of the study demonstrate notable differences in the REE behaviour in the different sample groups. REE trends of fresh parent rocks to weakly-, moderately-altered, kaolinitic and alunitic rocks are characterised by strong LREE enrichment ((La/Lu)_cn = 14.57, 11,8 to 15.20, 4.54 to 13.30, 12.5 to 24.2 and 34.6 to 47.26, respectively). Most of the samples have pronounced negative and/or weakly-negative Eu anomalies ranging from 0.75 to 0.98 while three samples have weakly-positive Eu anomalies. LRE element contents are higher than those of HREE in the samples. The LRE elements were strongly enriched in the kaolinitic and alunitic alteration; in weakly- and moderately-altered rocks. LREE are nearly immobile whereas HRE elements show different behaviour in different rock groups. The HFS and TRT elements are slightly mobilised in weakly-altered rocks, but enriched in other alteration types. Elements commonly assumed to be immobile (e.g. Y, Zr, Nb, Hf, TiO₂, Al₂O₃, REE) show variation in mass calculation. LIL elements showed enrichment over LREE and MREE, and similar behaviour, in contrast with HFSE. A clear increment of trans-transition elements (TRTE) was found mainly in alunitic and partly in kaolinitic samples.     

Gem-quality transparent diaspore (zultanite) in bauxite deposits of the İlbir Mountains, Menderes Massif, SW Turkey

Several m-thick, karst-unconformity-type metabauxite horizons in the İlbir Mountains of SW Turkey host open-space mineralization of gem-quality diaspore (trademarked as zultanite), associated with muscovite, hematite, ilmenite, chloritoid, and younger calcite. The hydrothermal-metamorphogenic mineralization occurs in fracture zones (veins and open structures) that crosscut the metabauxite horizons, but does not extend into the marble host rocks. The white to dark gray marble sequence (over 2,000 m in thickness) is of Cretaceous depositional age and was affected by Alpine (Paleogene) tectonometamorphism which caused the hydrothermal remobilization of primary bauxite components into crosscutting structures.     

Detrital zircon ages from a Lower Ordovician quartzite of the İstanbul exotic terrane (NW Turkey): evidence for Amazonian affinity

NW Turkey is a mosaic of several continental and oceanic units, that were amalgamated by collisional and strike–slip tectonics. One of the continental units is the İstanbul terrane, the Palaeozoic strata of which comprise an Early Ordovician to Early Carboniferous transgressive sedimentary sequence. The basement to the Palaeozoic succession is exposed in the Bolu Massif and is represented by a thick meta-volcanic unit intruded by Late Neoproterozoic (ca. 575 Ma) felsic magma. This meta-igneous basement is considered to be a sliver of the Cadomian magmatic arc. Unconformably overlying Early Ordovician strata start with red fluvial clastics (ca. 3,000 m), overlain by shallow marine quartzites (<250 m). Detrital zircons were separated from an Ordovician quartzite sample located 5 m above the contact with the underlying red fluvial clastics. We have dated a total of 99 zircon grains by U–Pb method using laser ablation-sector field-inductively coupled plasma mass spectrometer (LA-SF-ICP-MS). The ages (97% are >90% concordant) range from 530 to 2550 Ma. The dominance (44 grains) of Neoproterozoic zircon ages (around 540, 570, 600–640 and 700–800 Ma) rules out any link of the İstanbul terrane with Baltica. The large amount (40 grains) of Grenvillian and Meso- to Palaeo-proterozoic ages (around 1.0–1.2, 1.3–1.6, 1.7–1.8, and 1.9–2.1 Ga) in the zircon population further rules out a link to Cadomian and Minoan terranes, but is indicative for Amazonian source areas. The new age data suggest the İstanbul terrane to be a peri-Gondwanan terrane that was located at the northwestern margin of Gondwana close to Amazonia. This terrane should have travelled a large distance in the Phanerozoic times.     

Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir-Konya, Turkey

The Tepearasi Formation of the autochthonous Geyikdagi Group in the Central Tauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones and greyish dolomites occurring within the middle to upper sections. The total thickness of the dolomitic levels ranges from 100-300 m and laterally extends 500-700 m. Three types of dolomite were distinguished through petrographic analyses: homogeneous, mottled (saddle-crystalline) and joint-filling dolomite, which were interpreted to have formed in two different stages, early diagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage is light-coloured and monotonous-textured and shows the form of a dolosparite mosaic. The mottled dolomite formed in the late diagenetic stage is light- to dark-coloured and coarsely granular idiomorphic. The other type of late diagenetic dolomite, described as the joint-filling type, presents a crystal growth pattern from the joint walls towards the centre of the joint space. I     

Sedimentological,mineralogical and geochemical characteristics of the ooids in Cleopatra (Sedir Island,Gökova Bay,SW Turkey) and Alexandria (NW Egypt) Beach sediments: A comparison and reality of myth of the love

According to the myth, ooid-rich sediments in Cleopatra Beach (Sedir Island, Turkey) were brought by ships from Alexandria Beach (Egypt) by the Roman leader, Marcus Antonius, for his lover Cleopatra. Ooids of both beaches have been compared in terms of sedimentology, mineralogy and geochemistry to determine reality of the myth of love. Sieve analyses exhibit that sediments of Cleopatra Beach are slightly better sorted than Alexandria Beach sediments, and have relatively smaller sized ooids, interpreted to represent a relatively less agitated environment. All ooids are composed mainly of aragonite characterized by high Sr contents (>8600 mg/kg). Hierarchical Cluster Analysis, the cross-plot of δ¹⁸Oaragonite versus δ¹³C_aragonite values of ooids, and the presence of detrital grains such as gneiss and schist hint on two distinct groups of samples that correspond to the Cleopatra and Alexandria Beach ooids. These results suggest that the myth may not be realistic, and the ooids on the shore of Sedir Island were formed in-situ, e.g., during the Late Holocene.     

Hydrogeochemistry of thermal and mineralized waters in the Diyadin (Ağri) area,Eastern Turkey

The Diyadin Geothermal area, located in the eastern part of Anatolia (Turkey) where there has been recent volcanic activity, is favorable for the formation of geothermal systems. Indeed, the Diyadin geothermal system is located in an active geodynamic zone, where strike-slip faults and tensional cracks have developed due to N–S regional compression. The area is characterized by closely spaced thermal and mineralized springs, with temperatures in the range 30–64 °C, and flowrates 0.5–10 L/s. Thermal spring waters are mainly of Ca(Na)-HCO₃ and Ca(Mg)-SO₄ types, with high salinity, while cold groundwater is mostly of Ca(Na, Mg)-HCO₃ type, with lower salinity. High contents of some minor elements in thermal waters, such as F, B, Li, Rb, Sr and Cs probably derive from enhanced water–rock interaction.Thermal water samples collected from Diyadin are far from chemical equilibrium as the waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters. The temperatures of the deep geothermal reservoirs are estimated to be between 92 and 156 °C in Diyadin field, based on quartz geothermometry, while slightly lower estimates are obtained using chalcedony geothermometers. The isotopic composition of thermal water (δ¹⁸O, δ²H, δ³H) indicates their deep-circulating meteoric origin. The waters are likely to have originated from the percolation of rainwater along fractures and faults to the deep hot reservoir. Subsequent heating by conduction due to the presence of an intrusive cupola associated with the Tendurek volcano, is followed by the ascent of deep waters to the surface along faults and fractures that act as hydrothermal conduits.Modeling of the geothermal fluids indicates that the fluid is oversaturated with calcite, aragonite and dolomite, which matches travertine precipitation in the discharge area. Likewise, the fluid is oversaturated with respect to quartz, and chalcedony indicating the possibility of siliceous precipitation near the discharge areas. A conceptual hydro-geochemical model of the Diyadin thermal waters based on the isotope and chemical analytical results, has been constructed.     

Genetic investigation and comparison of Kartaldağ and Madendağ epithermal gold deposits in Çanakkale,NW Turkey

Two epithermal gold deposits (Kartaldağ and Madendağ) located in NW Turkey have been characterized through the detailed examinations involving geologic, mineralogical, fluid inclusion, stable isotope, whole-rock geochemistry, and geochronology data.The Kartaldağ deposit (0.01–17.65 ppm Au), hosted by Eocene dacite porphyry, is associated with four main alteration types with characteristic assemblage of: i) chlorite/smectite–illite ± kaolinite, ii) quartz–kaolinite, iii) quartz–alunite–pyrophyllite, iv) quartz–pyrite, the last being characterized by three distinct quartz generations comprising massive/vuggy (early), fine–medium grained, vug-lining (early), and banded, colloform, comb (late) textures. Observed sulfide minerals are pyrite, covellite, and sphalerite. Oxygen and sulfur isotope analyses, performed on quartz (δ¹⁸O_(quartz): 7.93 to 8.95‰ and calculated δ¹⁸O_(H2O): − 7.95 to 1.49‰) and pyrite (δ³⁴S_(pyrite): − 4.8‰ and calculated δ³⁴S_(H2S): − 6.08 to − 7.20‰) separates, suggest a meteoric water source for water in the hydrothermal fluid, and an igneous source for the sulfur dissolved in ore-related fluids. Microthermometric analyses of primary fluid inclusion assemblages performed on quartz (late quartz generation) yield temperatures (Th) dominantly in the range of 245–285 °C, and generally low salinity values at 0 to 1.7 wt.% NaCl eq. Based on the quartz textures and the associated base metal concentrations, along with fluid inclusion petrography, the early vug-lining quartz is considered to have been associated with the mineralization possibly through a boiling and a late mixing process at > 285 °C.The Madendağ deposit (0.27–20.60 ppm Au), hosted by Paleozoic mica schists, is associated with two main alteration types: sericite–illite–kaolinite, and quartz–pyrite dominated by two distinct quartz generations i) early colloform, comb and banded quartz and ii) late quartz, forming the cement in hydrothermal breccia. Whereas oxygen isotope analyses of quartz (δ¹⁸O_(quartz): 9.55 to 18.19‰ and calculated δ¹⁸O_(H2O): − 2.97 to 5.54‰) suggest varying proportions of meteoric and magmatic sources for the ore bearing fluid, sulfur isotope ratios (δ³⁴S_(pyrite): − 2.2‰ and calculated δ³⁴S_(H2S): (− 3.63) to (− 3.75) ‰) point to an essentially magmatic source for sulfur with or without contribution from sedimentary sources. Microthermometric analysis carried out on primary fluid inclusion populations of a brecciated sample (early quartz), give a temperature (Th) range of 235–255 °C and 0.0 to 0.7 wt.% NaCl eq. salinity. Based on the textural relationship, base metal and high gold contents, the ore precipitation stage is associated with late stage quartz formation via a possible boiling process.The presence of alunite, pyrophyllite and kaolinite, vuggy quartz and covellite suggest a high-sulfidation type of epithermal deposit for Kartaldağ. On the other hand, Madendağ is identified as an adularia-sericite type owing to the presence of significant sericite, neutral pH clays (mostly illite, chlorite/smectite, and kaolinite), low temperature quartz textures (e.g., colloform, comb, and banded quartz), and limited sulfide minerals.Given the geographical proximity of Kartaldağ and Madendağ deposits, the similar temperature and salinity ranges obtained from their fluid inclusions, and the similar ages of igneous rocks in both deposits (Kartaldağ: 40.80 ± 0.36 to 42.19 ± 0.45 Ma, Madendağ: 43.34 ± 0.85 Ma) the mineralizing systems in both deposits are considered to be genetically related.     

The Strandja Massif and the İstanbul Zone were once parts of the same palaeotectonic unit: new data from Triassic detrital zircons

Spatially continuous rock assemblages that share similar environmental evolution or structural features can be classified as a single tectonic unit. This approach enables to link dispersed units or massifs with each other and sometimes can be subjective, depending on the classification criteria. The relationship and the nature of the contact between the Strandja Massif and the ?stanbul Zone have been controversial due to the Cainozoic cover. Amalgamation of these units was claimed as early as the Aptian-Albian.

Lower Triassic sedimentary rocks, which are overlain by the Carboniferous flysch with a N-verging thrust fault are exposed NW of the ?stanbul Zone. This study reveals the spatial relationship between the Strandja Massif and the ?stanbul Zone deduced from the U-Pb dating and Lu-Hf isotopes of the detrital zircons from these Lower Triassic clastics. Our results show that the early Triassic basin was fed from a provenance that included arc-related Upper Carboniferous-Lower Permian magmatic rocks which is much more likely to be the Strandja Massif than the ?stanbul Zone. The second outcome of this study is that a unit that previously assigned to Palaeozoic turned out to be Triassic, which brings the Strandja Massif farther to the east, into the northern ?stanbul Zone.     

Landslide susceptibility assessment in the İzmir (West Anatolia,Turkey) city center and its near vicinity by the logistic regression method

A landslide susceptibility assessment for İzmir city (Western Turkey), which is the third biggest city of Turkey, was performed by a logistic regression method. A database of landslide characteristics was prepared using detailed field surveys. The major landslides in the study area are generally observed in the field, dominated by weathered volcanics, and 39.63% of the total landslide area is in this unit. The parameters of lithology, slope gradient, slope aspect, distance to drainage, distance to roads and distance to fault lines were used as variables in the logistic regression analysis. The effect of each parameter on landslide occurrence was assessed from the corresponding coefficients that appear in the logistic regression function. On the basis of the obtained coefficients, lithology plays the most important role in determining landslide occurrence and distribution. Slope gradient has a more significant effect than the other geomorphological parameters, such as slope aspect and distance to drainage. Using a predicted map of probability, the study area was classified into five categories of landslide susceptibility: very low, low, moderate, high and very high. Whereas 49.65% of the total study area has very low susceptibility, very high susceptibility zones make up 11.69% of the area.     

Middle Pleistocene bivalves of the İznik lake basin (Eastern Marmara, NW Turkey) and a new paleobiogeographical approach

?znik Lake is a tectonically originated basin mainly controlled by the E–W trending middle strand of the North Anatolian Fault (NAF) system. Pleistocene sediments occurring in front of the faults are well exposed both in the northern and in the southern shorelines of the basin. In this study, two endemic brackish water bivalve species, Didacna subpyramidata Pravoslavkev 1939 and Didacna nov. sp. were found in the oldest terrace of the northern Pleistocene sequence. Having characterized morphology, these species serve as stratigraphic indicators in the regional Pleistocene stratigraphy of the Ponto-Caspian region, and thus are well correlated to the assemblages of the early Khazarian subhorizon (Middle Pleistocene). Hence, these data demonstrate that the early Khazarian brackish water sea covered the study area. Additionally, a model for the formation of the basin is proposed: the ?znik lake basin was a gulf of the former Marmara Sea in the early Khazarian, connecting the Marmara to the Black Sea and the Caspian Sea. The subsequent regional prograding uplifts, main dextral strike-slip fault and many normal faults of the NAF Zone cut off the marine connections to the basin, leading to its present location and topographic level.     

Organic Material and Trace Elements of Bituminous Rocks in the Ozankiiy Field, Ankara, Turkey

Bituminous rocks in the Ozankoey （Ankara） field are different from those of the Paleocene- Eocene Mengen and Giineytepe （Bolu） regions in metal enrichment levels. Organic carbon （Corg） content of organic material-rich rocks in the Ozankoey （Ankara） field is 3.66-40.72% wt averaging 14.34%. The dominant organic materials are algae/amorphous accompanied by minor amount of herbaceous material （The dominant kerogen type is Type-I with a limited amount of Type-Ⅱ kerogen.）. The bituminous rocks in the Ozankoey field are enriched in heavy metals such as Ni, Mn, As and Cr. In comparison with the average enrichment values of dements, Ni, Mn, As and Cr in bituminous shales of the Ozankoey field are as about 4.38, 14.93, 10.90 and 5.58 times as average values. The average concentrations of these heavy metals are also as high as 215× 10^-6, 828 × 10^-6, 58.54 × 10^-6, and 148 × 10^-6 respectively. In addition, sorption properties of day and organic materials are also important for metal enrichments in the bituminous shales.     

Origin and geodynamic environments of the metamorphic sole rocks from the İzmir–Ankara–Erzincan suture zone (Tokat,northern Turkey)

ABSTRACT

The Late Cretaceous accretionary complex of the ?zmir–Ankara–Erzincan suture zone, near Artova, is composed mainly of peridotites (variably serpentinized), amphibolite, garnet-micaschist, calc-schist, marble, basalt, sandstones, neritic limestones. The metamorphic rocks were interpreted as the metamorphic sole rocks occurring at the base of mantle tectonites, because: (i) amphibolites were observed together with the serpentinized peridotites suggesting their occurrences in the oceanic environment; (ii) foliation in amphibolites and serpentinized peridotites run subparallel to each other; (iii) all these metamorphic rocks and serpentinized peridotites are cross-cut by the unmetamorphosed dolerite dikes with island arc tholeiite-like chemistry. Geochemical characteristics of the amphibolites display enriched mid-ocean ridge basalt (E-MORB)- and ocean island basalt (OIB)-like signatures. The dolerite dikes, on the other hand, yield an island arc tholeiite-like composition. Geothermobarometric investigations of the metamorphic sole rocks suggest that the metamorphic temperature was ~650 ± 30°C and the pressure condition was less than 0.5 GPa. Dating of hornblende grains from amphibolite yielded age values ranging from 139 ± 11 to 157 ± 3.6 Ma (2σ). The oldest weighted average age value is regarded as approximating the timing of the intra-oceanic subduction. These cooling ages were interpreted to be the intra-oceanic subduction/thrusting time of the ?zmir–Ankara–Erzincan oceanic domain.