Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleYalnız künye2021Petrography, geochemistry and petrological characteristics of the Carboniferous Pamuktaş Pluton, Bayburt (NE Turkey)
Sari, Ekrem; Gücer, Mehmet Ali
The Eastern Pontides (NE Turkey) that formed during the Alpine-Himalayan orogeny\rin which geologically plays an important role in the formation of Anatolian Plate, is a\rsignificant area in term of containing different igneous rocks. Especially\rCarboniferous plutons are widely observed in the southern part of the Eastern\rPontides in larger outcrops and more commonly. This study presents new\rpetrography and whole-rock geochemistry data on granitic rocks in the Pamuktaş\rarea of Bayburt (NE Turkey). In addition, the source region of the magma,\rpetrological processes and geodynamic setting prevailing in the formation of these\rgranitic rocks are discussed. The Carboniferous Pamuktaş Pluton, which includes an\rarea of approximately 5 km2, represents the pre-Jurassic basement in the study area\rand is unconformably overlain by Lower-Middle Jurassic volcanoclastic and volcanic\rrocks and Upper Jurassic-Lower Cretaceous limestones. Pamuktaş Pluton mainly\rconsists of granite/granite porphyry and aplite (microgranite), to a lesser extent granodiorite and quartz microdiorite rocks. Granitic rocks mainly consist of alkali\rfeldspar (orthoclase), plagioclase feldspar, quartz, biotite, and amphibole\r(hornblende) minerals, as having euhedral and anhedral granular/microgranular\rtextures. The rocks have high SiO2 contents (65.62-75.09 wt.%) and a high K calc-\ralkali to shoshonitic affinities, and have been derived from an I-type source. The\rgranitic rocks are peralumine in character and are similar to post-collisional volcanic\rarc granitoids. Major and trace element trends show that the plagioclase, hornblende,\rapatite, and Fe-Ti oxide mineral fractionations play an important role in the formation\rof rocks. According to the petrological properties of the Pamuktaş Pluton, it has been\rrevealed that the fractional crystallization, magma mixing, and less assimilation and\rpartial melting processes play a role in the development of granites. The calculated\rzircon saturation temperatures (730-844°C) reflect lower initial magma temperatures.\rAll obtained data suggest that the parental magma of the Carboniferous Pamuktaş\rPluton has evolved from the mixing of lithospheric mantle and middle-lower crust-\rderived melts as a result of partial melting, differentiated and emplaced in the\rcontinental magma chamber.
- MakaleAçık Erişim2021Investigation of Hydrogeochemical Characteristics and Quality of the Water Resources in Şiran (Gümüşhane) District Center, Turkey
Alemdag, Selcuk; Semiz, Ümmühan; Gücer, Mehmet Ali
The study area is located of Şiran District Center in the southwest of Gümüşhane (NE Turkey). In this study, hydrogeochemical characteristics of water resources in district center were examined and metal element contents were determined. In the study area, the basement rocks are represented by Eocene Kelkit formation, which is composed of sandstone, claystone, marl, shale and tuff, and this unit is covered unconformably by the Quaternary aged alluvium. These units form granular porous unconfined aquifers according to the hydrogeological features. The pH, specific conductance (SC) and hardness (Fr°) values of the water resources in the study area varied between 5.41-7.48, 106.9-141.3 µS/cm and 4.72-6.78 (n= 18), respectively. According to the classification of Intra-Continental Water Resources, these data show that the samples are mostly class-I and II, rarely class-III water quality characteristics. The water resources in the study area are generally classified as Ca-Mg-HCO3 type carbonated (Ca+Mg>Na+K), and generally their weak acids are more than strong acids (HCO3>SO4+Cl). In the study area, (Ca+Mg)/(SO4+HCO3) ratios indicated the effect of silicate weathering in the waters, and the Cl/(Cl+HCO3) and (Na+K)/(Na+K+Ca) ratios show that the chemistry of waters is controlled by the chemical weathering of rock-forming minerals, hence, reflect the water-rock interaction. Except for a few, the concentration of dissolved potentially toxic elements in the water samples were distributed within acceptable limits. Consequently, the hydrogeochemical results showed that the water resources in the study area were in the category of good class waters in terms of drinking water
- MakaleYalnız künye2021Origin, petrogenesis and geodynamic implications of the early Eocene Altınpınar adakitic andesites in the eastern Sakarya Zone, northeastern Turkey
Gücer, Mehmet Ali
Early Cenozoic magmatism in the eastern Sakarya Zone (NE Turkey) provides an important constraint on the regional tectono-magmatic evolution of the region. Early Eocene syn-collisional adakitic rocks are observed as small stocks with outcropping areas commonly less than 10 km2. This study presents petrography, whole-rock geochemistry and Sr-Nd-Pb isotope data, as well as in-situ 40Ar/39Ar age constraints on one of these adakitic andesites in the Altınpınar area of Gümüşhane, and discusses source region, petrological processes and geodynamic setting prevailed during their genesis. Andesites commonly show microlitic porphyric and vitrophyric porphyric textures, and include significant amounts of mafic microgranular enclaves (MMEs). Plagioclase, hornblende, Fe-Ti oxides and minor pyroxene are the main mineral phases. In-situ 40Ar-39Ar amphibole dating constrains the cooling age of andesites into a time span from 52.8 ± 1.3–48.8 ± 1.9 Ma. Andesites are medium to high-K calc-alkaline and display most of the signatures typical of those of the adakites. They are characterized by moderate MgO (1.7–4.1 wt%), low Y (9−14 ppm), Yb (0.9–1.5 ppm), and HREE and high Sr (325−964 ppm) contents, and high Sr/Y (36–76) ratios. 87Sr/86Sr(t) (0.704948−0.705100) and 143Nd/144Nd(t) (0.512588−0.512628) ratios are in the isotopic range of the adakites. All these geochemical and isotopic data suggest that the parental magma of adakitic andesites has been produced by partial melting of oceanic basalts under amphibole-eclogite facies conditions during the breakoff of the northern Neotethyan oceanic slab.
- MakaleAçık Erişim2020Flotasyon Tesis Atıklarının Asit Üretme Potansiyeli ve Kirliliğin Önlenmesi, Gümüşhane, KD Türkiye
Alemdag, Selcuk; Akaryali, Enver; Gücer, Mehmet Ali
Madencilik faaliyetlerindeki çevre kirliliğinin birincil kaynağını, çoğunlukla metalik, kömür ve asfaltit madenlerinde meydana gelen asit drenajı oluşturmaktadır. Bu çalışmada, Pb-Zn cevherleşmesinin flotasyon tesisi atıklarının asit üretme potansiyelleri jeokimyasalanalizler, kısa-dönem temas sızıntı testleri ve Asit-Baz Muhasebesi (ABM) işlemlerini kapsayan statik testlerle incelenmiştir. İşlenen cevherin mineral parajenezini başlıca pirit, kalkopirit, sfalerit ve galen mineralleri oluşturmaktadır. Cevherli atık örneklerinin iz element konsantrasyonlarında, özellikle S, Zn, Cu, As, Sb, Cd, Hg, Ag ve Bi gibi potansiyel toksik metallerdeki yüksek zenginleşme cevherin türü ile doğrudan ilişkili olup, yeraltı suyunu kirletme potansiyeline sahiptir. Kısa-dönem temas sızıntı testlerine göre, örneklerin pH değerleri (9.55-10.60, n= 10), kıta içi su kaynaklarının kalite sınıflandırmasına göre, dördüncü-sınıf (IV) kalite sularını işaret etmektedir. Bununla birlikte, sülfit-sülfür (%S2: 2.92-3.98, n= 10), Net Nötralizasyon Potansiyeli (NNP; 32 kg CaCO3/t 149 kg CaCO3/t, n= 10) ve Nötralizasyon Potansiyel Oranı (NPO; 0.20-0.80, n= 10) değerleri cevherli atık malzemenin potansiyel asit üreticisi olduğunu göstermektedir. Baraj eksen yeri ve rezervuar alanında açılan sondaj kuyularında kaya kütle geçirimliliğini değerlendirmek için lugeon deneyleri yapılmış ve geçirgen özellikte (K= 2x10-6 m/s) olduğu belirlenmiştir.
- MakaleAçık Erişim2020Excess lifetime cancer risk due to natural radioactivity in Gümüşhane Province, NE Turkey
Maden, Nafiz; Akaryali, Enver; Gücer, Mehmet Ali
In this study, 162 in situ measurements of 238U, 232Th, and 40K radionuclide concentrations dataset taken by the gamma-ray spectrometer in Gümüşhane, Turkey are presented. The gamma ray measurements were performed by a 512-channel, three-window gamma-ray spectrometry equipment made by GF Instruments. We first observed the radionuclides of the 238U,232Th, and 40K values in Gümüşhane. We then calculated the hazard indices of gamma radiation such as annual effective dose equivalent (AEDE), internal and external hazard index (Hin, Hex), and excess lifetime cancer risk (ELCR) based on the radionuclide abundances of 238U, 232Th, and 40K for the first time. In Gümüşhane, the average activity concentrations of radionuclides 238U, 232Th, and 40K were measured as 58.7 ± 34.3 Bq kg-1, 62.7 ± 37.2 Bq kg-1, and 1026.8 ± 486.0 Bq kg-1, respectively. The average outdoor annual effective dose equivalent and ELCR values were 132.2 ± 63.2 mSv yr-1 and 0.40 ± 0.19 × 10-3, respectively. Numerical results indicate that the radiological parameters (AEDE and ELCR) obtained for Gümüşhane Province were greater than the world’s mean values.
- MakaleYalnız künye2020Prediction of mine drainage generation potential and the prevention method of the groundwater pollution in the Gümüşköy (Kütahya) mineralization area, NW Turkey
Alemdag, Selcuk; Akaryali, Enver; Gücer, Mehmet Ali
One of the leading factors of seepage contamination is mine drainage, which creates serious ecological risks on the environment both during operation and post-mining times. In this study, experimental processes have been carried out to determine the occurrence of mine drainage in the Gümüşköy (Kütahya) mineralization area (Northwest Turkey). The prevention method for potential mine drainage occurrence has been also discussed. High enrichment was observed which are directly related to mineralization in trace element concentrations, especially in potentially toxic metals such as Ag, Cd, Mo, Ba, Bi, and Zn. Based on short-term tests, mine drainage formation has not been expected according to the pH (7.36–9.38), contact leaching, and acid-base accounting studies. However, in the long-term, acid generation potential has been expected because of weathering and oxidation in terms of rock type and mineralization in the area. Therefore, in order to prevent groundwater contamination in the event of a possible formation of mine drainage, the hydraulic conductivity of the stock area bedrock was evaluated by the in situ tests performed in the field and it was found to be moderately permeable (K= 1.9 × 10−6 m/s). In order to make the stock area bedrock impermeable, natural clay will be laid and compressed at the base of the stock area. When the finite elements were modeled by seepage analysis, the seepage discharge to be formed on the base rock at a depth of 5 m was determined as 3.17 × 10−19 m3/s. Since the discharge value determined in the seepage analysis after modeling is very close to zero, contamination of possible ground and surface water will be prevented.
- MakaleAçık Erişim2020Nature of clays in late cretaceous dacitic rocks in the eastern sakarya zone (Ne turkey): A geochemical and isotopic approach
Sipahi, Ferkan; Gücer, Mehmet Ali; Sadiklar, Münür Burhan
Late Cretaceous felsic rocks are common in the eastern Pontides (NE Turkey). These rocks developed as an island arc from the Jurassic to the Miocene; they also host numerous volcanogenic massive sulfide deposits. The Late Cretaceous dacites that outcrop around Zigana Mountain (Gümüşhane, NE Turkey) were exposed to intensive hydrothermal alteration. Widespread hydrothermal alteration of Late Cretaceous dacite in Zigana Mountain has led to the formation of well-developed clay minerals. Their main alteration products are sericite, chlorite, and carbonates (ankerite and calcite). The clay minerals identified by X-ray diffraction and differential thermal analysis include illite, chlorite, small amounts of kaolinite, and smectite. The polytype of illite is 2M1. Illites formed as a result of hydrothermal alteration of feldspars; they are also Fe-and Mg-poor. Chlorite is characterized by decreasing Fe/(Fe+ Mg) ratio with increasing alteration grade and has a trioctahedral structure. Chlorite geothermometer calculations (100–300°C) reflect the activities of hydrothermal solutions. Chlorite forms in more alkaline conditions compared with illite, as its formation is associated with the presence of carbonates. Oxygen and hydrogen stable isotope values, K-Ar dating of illites, and textural and chemical evidence suggest that clays might have formed mainly by alteration of minerals in dacitic rocks with hydrothermal fluids of magmatic origin during the Campanian under acidic–weak alkaline conditions.
- MakaleAçık Erişim2020Assessment of acid mine drainage formation using geochemical and static tests in mutki (Bitlis, se Turkey) mineralization area
Gücer, Mehmet Ali; Alemdağ, Selçuk; Akaryali, Enver
In this study, geochemical analyses, as well as short-term contact leaching and acid-base accounting tests, were carried out to determine the occurrence of acid mine drainage (AMD) by static tests in the ore stockpile areas at the Mutki Cu-Fe-Cr deposit (Bitlis, SE Turkey). According to the short-term contact leaching tests, the high enrichment in trace element concentrations in ore-bearing samples, especially in potentially toxic metals such as Cr, Cu, Mn, and Zn, were directly related to sulphide and oxide mineralizations. The pH (3.27–4.05) values of water samples, together with the classification of the intracontinental water resources, indicated that the water quality is the fourth class. Leaching tests, paste pH (3.42–4.46) and sulphide-sulphur (3.9–13.4 wt%) values also suggested that there was AMD production potential in the mineralization area. The AMD production potential was supported by the high mobility of several elements, such as Fe, Mg, Cr, As, Cu, S, and Zn. In ore samples, net neutralization potential (NNP) and net potential ratio (NPR) values were less than –20 kg CaCO3 /t and 1, respectively. The basalts forming the basement rock of the stockpile area were characterized by permeable to slightly permeable properties that potentially increase the contamination risk of the groundwater due to seepage in the stockpile area. In order to prevent seepage in the stock area, geomembrane (synthetic waterproofing covers) should be laid at the base to ensure impermeability. The improvements planned in the stock area were modeled by the finite element method and seepage discharges at a depth of 5 m were determined as 1.34 × 10–17m3/s. Thanks to these planned applications, surface and groundwater pollution can be efficiently prevented.
- MakaleYalnız künye2020Geochemical composition of magnetite from different iron skarn mineralizations in NE Turkey: implication for source of ore-forming fluids
Sipahi, Ferkan; Gücer, Mehmet Ali; Saydam Eker, Çiğdem
Iron oxide mineralizations in the eastern part of the Pontides (NE Turkey) are hosted in the skarn environments which are the Pontide paleomagmatic arc. These mineralizations always occur in the contacts between granitoid and limestone. Magnetites are hosted in carbonate rocks and generally formed during garnet-magnetite-epidote-quartz phase. Magnetites have high Co (15.8–43.4 ppm for the Kopuz, 11–12.5 ppm for the Eğrikar, and 3.8–1266.7 ppm for the Karadağ) concentrations suggesting that the sulfide decreased from the early to the late phases in the iron skarn mineralization forming systems. The Co/Ni ratios in the magnetites (0.12 to 35.38 for Karadağ, 2.19 to 13.53 for the Kopuz, and 2.39 to 5.21 for the Eğrikar) show the hydrothermal effect on the magmatic source in iron skarns in the study area. Thus, variable Co/Ni ratios reflect interactions between the magma with the host rock during successive alteration stages. Magnetites in this study have Sc-Nb-Mg-Ti depletions and Ta enrichment. In this study, high Co, Ti, and V contents in magnetites suggest the high temperature (300–500 °C) and low ƒO2. The V contents of the magnetite in the Karadağ increase with the decreasing oxygen fugacity of fluid(s) forming magnetites, whereas the V contents of the magnetites in the Kopuz and Eğrikar decrease with increasing oxygen fugacity of fluid(s) forming magnetites. Element patterns and Ni/Cr ratio (< 1) of the magnetite are geochemically similar to those of magnetite in Fe-skarn deposits and partly magmatic accessory magnetite of I-type granites. As a result, the Co, Ni, V, and Ti elements of the magnetite have played an important role in the discriminating and interpreting of skarn mineralizations in the eastern Pontides and support a calcic skarn origin with studies of the mineralization geology.
- MakaleAçık Erişim2019Zigana Dağı (Gümüşhane, KD Türkiye) Dayklarının Jeokimyası ve Jeolojik Anlamı
Sadıklar, Münür Burhan; Gücer, Mehmet Ali; Sipahi, Ferkan
Eski bir magmatik yay olan Doğu Karadeniz Bölgesi (Pontidler) Sakarya Zonu içindeyer alan andezit ve porfirik dasit daykları Geç Kretase yaşlı volkanitleri kesmektedir.Andezit ve porfirik dasit daykları porfirik doku sergilemektedir. Andezitler başlıcaplajiyoklas ve ojit minerallerinden ibaret olup, plajiyoklaslar elek dokusu ve polisentetik ikizlenme göstermektedir. Ojit minerallerinin kenar kısımlarında opak mineral oluşumları yaygındır. Porfirik dasitler ise kuvars, plajiyoklas, amfibol ve biyotit minerallerinden oluşmakta olup, kuvars kristallerinin kenarları kısmen yenmiştir. Plajiyoklaslar yaygın olarak serizitleşmiş, daha az oranda kalsitleşmiştir. Amfiboller hidrotermal ayrışma sonucu klorit, karbonat (kalsit ve ankerit) ve opak minerallere, biyotitler ise genel olarak kloritlere dönüşmüştür. Ana oksit ve iz element değişim diyagramlarındaki düzgün yönsemeleri ve mineral ayrımlaşma diyagramlarındaki durumları, daykların gelişiminde fraksiyonel kristalleşmenin etkili olduğunu göstermektedir. Plajiyoklas ve ojit ayrımlaşmasının andezit daykların gelişiminde, hornblend ve plajiyoklas ayrımlaşmasının ise porfirik dasitlerin gelişiminde etkili olduğu belirlenmiştir. Zenginleşmiş okyanus ortası sırtı bazaltlara (Z-OOSB) göre normalleştirilmiş iz element diyagramında negatif Nb, P2O5 ve TiO2 anomalileri olup, büyük iyon çaplı elementler (BİYE) yüksek çekim alanlı elementlere (YÇAE) nazaran daha fazla zenginleşmiştir. Düşük Nb/U ile yüksek La/Nb ve Th/Nb oranları, andezit ve porfirik dasit dayklarının kıtasal kabuk kirlenmesinden etkilendiğini belirtmektedir. Sonuç olarak, daykların yay ortamında, Geç Kretase sonlarına doğru benzer kökenli ve yitim ilişkili metasomatize olmuş bir manto kaynağından türemiş oldukları düşünülmektedir.
- MakaleAçık Erişim2019Petrology and 40Ar-39Ar dating of paragneisses from the Devrekani Massif (Central Pontides, Northern Turkey): Implications for the Jurassic high-T metamorphism in an extensional tectonic environment
Gücer, Mehmet Ali; Arslan, Mehmet; Çimen, Okay; Sherlock, Sarah C.
The Devrekani Massif in the northern part of the Central Pontides (Northern Turkey) provides important clues to the regional tectonics and geodynamic processes associated with Jurassic high grade metamorphic conditions. This study reports new paragenetic assemblages, mineral compositions, whole-rock geochemistry and 40Ar-39Ar geochronological data from the paragneisses in the massif, and, discusses the P–T conditions and geodynamic implications of the Jurassic metamorphism during continental extension in the Central Pontides. Upper amphibolite to lower granulite facies paragneisses form one of the main lithological units in the massif. Within these, there are five different mineral parageneses with diagnostic mineral assemblages of: quartz, K-feldspar (An0-1Ab4-26Or73-96), plagioclase (An18-35), biotite [XPhl: 0.28–0.57; Mg/(Mg + Fe2+): 0.33–0.61], sillimanite, cordierite [Mg/(Mg + Fe2+): 0.48–0.71] and garnet (Alm43-80Grs0-18Prp5-23And0-4Sps10-33) with minor hercynite. Based on Na-in-Crd thermometry and GASP barometry results, the peak metamorphic conditions are 775 ± 25 °C and 6 ± 1 kbar in the massif. The field relations, petrography and bulk chemical data suggest that the paragneisses, derived from shale-wackestone and pelitic sedimentary protoliths, are typical rock lithologies of an active continental margin. They display enrichments in LILE over HFSE, coupled with negative Nb and Ti anomalies, which are geochemical signatures of subduction-related sources. It is likely that the peak metamorphism took place during the Middle–Upper Jurassic period (ca. 174–156 Ma), suggesting that the metamorphic rocks cooled to 300–350 °C at ca. 156 Ma. The mineral assemblages reveal that the prograde history passed from sillimanite zone conditions up to the cordierite-garnet-K-feldspar zone. The petrological and geochronological data indicate that the protoliths are related to multiple sources such as volcano-sedimentary successions. We conclude that the Devrekani Massif represents the products of pre-Jurassic sedimentation, and Permo-Carboniferous continental arc magmatism, overprinted by Jurassic metamorphism.
- MakaleAçık Erişim2018Atık Barajı Rezervuarı ve Cevher Stok Alanlarında Asit Maden Drenajı (AMD) Oluşumunun Değerlendirilmesi: Gümüşhane Örneği
Akaryali, Enver; Gücer, Mehmet Ali; Alemdag, Selçuk
Doğal kaynakların kullanımı ile ilgili işlemlerin başında gelen madencilik faaliyetleri, işletmenin türüne ve büyüklüğüne bağlı olarak farklı boyutlarda gelişen çevresel etkilere ve bozulmalara neden olmaktadır. Bu etkilerin başında, madencilik faaliyetleri sırasında ve sonrasında ciddi ekolojik riskler oluşturan Asit Maden Drenajı (AMD) gelmektedir. AMD, sülfür içeren (özellikle pirit, pirotin ve kalkopirit) cevher atıkların, tipik olarak hava (oksijen) ve su içeren ortamlarda, yeraltı suyu, yağmur ve akıntı nedeniyle oksitleyici koşullara maruz kalması sonucu meydana gelen asit oluşumunu ifade etmektedir. Bu çalışmada, Gümüştaş Madenciliğe ait işletme sahası, cevher stok ve atık depolama alanlarında AMD oluşumunu belirlemeye yönelik işlemler yapılmış ve AMD gelişme potansiyeli ile muhtemel AMD gelişmesi durumunda alınacak tedbirler ortaya konmuştur. Maden işletme alanı, Eosen yaşlı andezit ve bazalt ile bu kayaçların piroklastitlerinden oluşan Alibaba Formasyonu içerisinde yer almaktadır. Yapılan çalışmalarda pH değerleri tüm örneklerin I. sınıf kıta içi kaynak suyu özelliğinde olduğunu, macun pH ve sülfid (S-2) değerleri ise maden işletme sahasında AMD potansiyelinin bulunmadığına işaret etmektedir. Ana ve iz elementlerin düşük mobiliteye sahip olması ise bu durumu destekler niteliktedir. Tüm örneklerde Net Nötralizasyon Potansiyeli (NNP) değerlerinin 20 kg CaCO3/ton’dan ve Nötralizasyon Potansiyel Oranı (NPO) değerlerinin 2’den büyük olması da potansiyel asit üretmeyen karakterde olduğunu göstermektedir. S-2 değerlerinin çok düşük olması, söz konusu alanda kısa dönem içerisinde asit kaya drenajı potansiyeli gerçekleşmeyeceğini işaret etmektedir. Buna ek olarak, stok sahasını geçirimsiz hale getirmek için 50 cm kalınlığında geçirimsiz kil serilerek sıkıştırılmış, oluşan düşey profil sonlu eleman ağ sisteminde modellenerek su deşarjları belirlenmiştir. Yapılan tüm çalışmalar neticesinde maden işletme sahasında kısa sürede AMD oluşumu beklenmediği sonucuna varılmıştır. Ancak, maden işletme alanında, uzun sürelerde muhtemel AMD oluşumundan kaynaklanacak çevre kirliliği, yapılan çalışma kapsamında alınacak tedbirlerle önlenmiş olacaktır.
- MakaleYalnız künye2018Geochemical and Sr-Nd-Pb isotope characteristics of the Miocene to Pliocene volcanic rocks from the Kandilli (Erzurum) area, Eastern Anatolia (Turkey): Implications for magma evolution in extension-related origin
Kaygusuz, Abdullah; Aslan, Zafer; Aydınçakır, Emre; Yücel, Cem; Gücer, Mehmet Ali; Şen, Cüneyt
This paper presents Sr-Nd-Pb isotopic and whole-rock geochemical data of Miocene to Pliocene volcanic rocks in the Eastern Anatolia (Turkey) aiming to unravel their sources and evolutionary history. The wide compositional range of lavas and pyroclastics includes basaltic andesite, basaltic trachyandesite, trachyandesite, andesite and trachydacite. These calc-alkaline volcanics are enriched in large ion lithophile elements and light rare earth elements and depleted in the high field strength elements. Sr-Nd isotope data indicate low values for 87Sr/86Sr(i) (0.70432–0.70464) and high values for 143Nd/144Nd(i) (0.51272–0.51282). Further, these data are within the mantle array of the isotope ratio diagram. The lead (Pb) isotopic compositions (206Pb/204Pb(i) = 18.33 to 18.62, 207Pb/204Pb(i) = 15.51 to 15.60, 208Pb/204Pb(i) = 38.10 to 38.45) reveals the presence of an enriched source. The main petrological processes involved fractional crystallization and the mixing of at least two fractionated magmas having same source characteristics. All evidence supports the findings that the Kandilli volcanic rocks were derived from a partial melting of the both spinel and garnet bearing subcontinental lithospheric mantle, which had been previously metasomatized by mostly fluids derived from subducted slab during the collisional and post-collisional extension-related geodynamic setting in the Eastern Anatolia region of Turkey.
- MakaleYalnız künye2017Tersiyer Yaşlı Altınpınar Hornblendli Andezitlerinin (TorulGümüşhane) Petrografisi, Mineral Kimyası ve P-T Kristalleşme Koşulları
Yücel, Cem; Aydınçakır, Emre; Akaryali, Enver; Gücer, Mehmet Ali
Doğu Pontid orojenik kuşağında (KD Türkiye) farklı magma türleri altında oluşmuş farklı volkanikkayaçlar yüzeyleme vermektedir. Tersiyer volkanizması, Gümüşhane ve çevresinde asidik, nötr vebazik volkanik ve piroklastik kayaçlardan meydana gelmektedir. Bu volkanizma doğu Pontidler'inevriminde ise önemli bir rol oynamaktadır. Bu çalışma kapsamında Altınpınar (Torul/Gümüşhane)civarında yüzeyleme veren Tersiyer yaşlı hornblendli andezitik kayaçların petrografisi, mineralkimyası ve sıcaklık-basınç koşulları irdelenmiştir. Andezitler başlıca hornblend (amfibol),plajiyoklas (An40-61Ab38-57Or1-5), klinopiroksen (Wo44-45En43-44Fs12) ve opak (genellikle magnetit vepirit) mineralleri, ikincil kil, serizit, kalsit ve klorit mineralleri içerir ve mikrolitik-porfirik vevitrofirik porfirik dokular sergiler. Bazı hornblend mineralleri iri kristalli gelişmiş olup, plajiyoklasve opak mineral kapanımları içermektedir. Tüm hornblendler CaB >= 1.5, (Na+K)A <0.5 ve CaA <0.5parametrelerine sahip kalsik tip olup, magnezyohornblend bileşimi sunmakta, Mg# (Mg/Mg+Fe2+)ise 0.72-0.91 arasında değişmektedir. Andezitlerde kalsik amfibol jeotermobarometri denklemlerinikullanarak hesaplanan tahmini jeotermometre (T), jeobarometre (P) ve oksijen fugasitesi (?O2/ ?NNO) değerleri sırasıyla 765 - 867 °C (ort= 790±20 °C); 2.5 - 4 kbar ve -14.4 ile -11.1 olarakhesaplanmıştır. Elde edilen bu değerler hornblendlerin kıtasal kabukta 9 - 15 km derinliklerdekristallendiğini işaret etmektedir. Minerallerin kimyasal özellikleri inceleme alanındaki andezitlerinkalk-alkali bir ana magmadan itibaren kristallenmiş olduğunu göstermektedir.
- Proje2016Eosen Yaşlı Volkaniklerde (Gümüşhane, KD Türkiye) Gözlenen Hidrotermal Alterasyonlar ile Cevherleşmelerin, Jeolojik, Jeokimyasal, Kökensel ve Altın Potansiyeli Açısından İncelenmesi
Aydınçakır, Emre; Akaryali, Enver; Gücer, Mehmet Ali
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- MakaleYalnız künye2016Permo-Carboniferous granitoids with Jurassic high temperature metamorphism in Central Pontides, Northern Turkey
Gücer, Mehmet Ali; Arslan, Mehmet; Sherlock, Sarah; Heaman, Larry M.
In the northern part of the Central Pontides (N Turkey) there are different metamorphic rocks exposed, notably the Devrekani metamorphic rocks. Here, upper amphibolite-lower granulite facies metamorphic rocks contain predominantly paragneiss, orthogneiss and metacarbonate, and to a lesser extent, amphibolite and quartzite, with cross-cutting aplite, pegmatite and granite veins. This is the first report of these rocks and includes new data on the petrochemistry, geochronology and metamorphic evolution of the Devrekani orthogneisses from the Central Pontides. The orthogneisses show five different mineral parageneses with the characteristic mineral assemblage quartz + K-feldspar + plagioclase + biotite +/- hornblende +/- opaque (+/- ilmenite and +/- magnetite), and accessory minerals (zircon, sphene and apatite). These metamorphic rocks exhibit generally granoblastic, lepidogranoblastic and nematolepidogranoblastic with locally migmatitic and relic micrographic textures. They have well-developed centimeter-spaced gneissic banding and display gneissose structure with symmetric, asymmetric and irregular folds. The petrographic features, mineralogical assemblages and weak migmatization reflect high temperature conditions. Thermometric calculations in the orthogneisses indicate metamorphic temperatures reached 744 +/- 33 A degrees C. Field relations, petrography and petrochemistry suggest that the orthogneisses have predominantly granodioritic and some granitic protoliths, that show features of I-type, medium to high-potassic calc-alkaline volcanic arc granitoids. The orthogneisses have high contents of LILEs and low contents of HFSEs with negative Nb and Ti anomalies, which are typical of subduction-related magmas. The orthogneisses also show significant LREE enrichment relative to HREE with negative Eu anomalies (Eu-N/Eu* = 0.33-1.07) with La-N/Lu-N = 6.98-20.47 values. Based on U-Pb zircon dating data, the protoliths are related to Permo-Carboniferous (316-252 Ma) magmatism. It is likely that peak metamorphism took place during the Jurassic as reflected by the U-Pb zircon ages (199-158 Ma) and also 40Ar/39Ar from hornblende/biotite (163-152 Ma). The four biotite 40Ar/39Ar average ages from the rock samples are ca. 156 Ma, suggesting that the metamorphic rocks cooled to 350-400 A degrees C at ca. 156 Ma. Conclusively, the Devrekani metamorphic rocks can be ascribed as products of Permo-Carboniferous continental arc magmatism overprinted by Jurassic metamorphism in the northern Central Pontides.
- MakaleYalnız künye201440Ar-39Ar age, petrography and geochemistry of the Yoncayolu Metamorphic Rocks (NE Turkey): Subduction-related metamorphism under greenschist fades conditions
Gücer, Mehmet Ali; Aslan, Zafer
The Yoncayolu Metamorphic Rocks (YMR), exposed in the Sakarya zone (Erzincan, NE Turkey), consists mainly of greenschist rocks which are chlorite schists, muscovite-chlorite schists, metabasic rocks and lesser extent of pyhllites and calc-schists. All YMR are fine-grained, weakly foliated and often cut by quartz veins. The common mineral assemblage is chlorite+albite+epidote+quartz+/-clinozoisite+/-actinolite+/-opaques. Geochemically, protoliths of the YMR resemble calc-alkaline volcanic arc rocks. The YMR have high contents of large ion lithophile elements (LILEs) and low contents of high field strength elements (HFSEs) similar to mid-ocean ridge basalt (MORB). (La/Lu)(CN) values are between 0.26 and 6.16. The REE patterns show slight or no Eu anomalies (Eu-CN/Eu* of 0.48 to 1.13), suggesting minor plagioglase fractionation. 40Ar-39Ar dating on plagioclases from the metabasic samples of the YMR gave ages of 100.8+/-3.4 Ma (Albian) and 94.1+/-3.3 Ma (Cenomanian), suggesting that metamorphism was related to the closure of the Neo-Tethyan Ocean. Metamorphism took place during subduction of the Neo-Tethyan Ocean between similar to 90-70 Ma. Chlorite geothermometry yielded a temperature of 320-350 degrees C and a pressure around 4 kbar. All these findings lend support for greenschist facies metamorphic conditions during the formation of the YMR.