Browsing by Author "Oyan, Vural"

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Alkali Göllerden Elde Edilen Trona Madeninden Soda Külü Üretimi: Van ve Arin Gölü Örnekleri, Van Gölü Havzası, Türkiye
(2023) Oyan, Vural
Bu çalışmada, Van Gölü havzasındaki Van ve Arin Göllerinin trona ve soda külü zenginliği araştırılmıştır. Sodyum ve karbon yönünden zengin bu göllerde doğal buharlaşma ile mevcut trona çökelmesi gözlemlenmiş ve göl sularından kimyasal yöntemlerle trona ve soda külü elde edilmiştir. Göllerden alınan 400 ml su numunesi üzerinde buharlaştırma, kalsinasyon, liç ve santrifüjleme yöntemleri uygulanmıştır. Bu deneyler sonucunda Van ve Arin Gölü sularından sırasıyla 1 ve 3 gr trona ve soda külü elde edilmiştir. Bu veriler, 1 litre suda sırasıyla ortalama 2.5 ve 7.5 gr trona ve soda külü elde edilebileceğini göstermektedir. Nihai ürün olarak elde edilen soda külünün karakterizasyonunu belirlemek amacıyla X-ışınları kırınım (XRD), taramalı elektron mikroskobu (SEM-EDX) ve X-ışınları floresans (XRF) analizleri yapılmıştır. Nihai ürün üzerinde gerçekleştirilen XRD ve XRF analizleri, örneğin tamamına yakınının Na2CO3 (sodyum karbonat; soda külü) içerdiğini ve %65 oranında Na2O içeriğine sahip olduğunu göstermiştir. SEM-EDX analizleri ham trona örneğine göre nihai ürünün Na ve C elementlerince zenginleştiğini ve nihai ürünün %57-65 arasında Na2O içeriğine sahip olduğuna işaret etmiştir. Tüm bulgular, Van ve Arin göl sularının trona ve soda külü bakımından zengin olduklarını ve kimyasal yöntemlerle göl sularından soda külü elde edilebileceğini ortaya koymuştur.
Ar-Ar Dating and Petrogenesis of the Early Miocene Taskapi-Mecitli (ercis-Van) Granitoid, Eastern Anatolia Collisional Zone, Turkey
(Pergamon-elsevier Science Ltd, 2018) Oyan, Vural
The Early Miocene Taskapi-Mecitli granitoid that is located in the northern section of the Eastern Anatolia Collision Zone has typical I-type, metaluminous and calk-alkaline characteristics. It also contains mafic micro-granular / magmatic enclaves (MMEs). New Ar-Ar dating results show that the age of the Taskapi-Mecitli granitoid is similar to 23 Ma and it crystallised in the Early Miocene, in contrast to its previously known Cretaceous age. Identical crystallisation ages (similar to 23 Ma), similar mineral assemblages and geochemical compositions, and indistinguishable isotopic compositions of MMEs and host rocks imply that the MMEs are most consistent with a cumulate origin formed at earlier stages of the same magmatic system that produced the Taskapi-Mecitli granitoid. MELTS modelling suggests that magma of the Taskapi-Mecitli granitoid was the result of fractionation under a crustal pressure of 4 kbar, with a H2O content of 1.5%. EC-AFC model calculation reveals that the Taskapi-Mecitli granitoid includes from 0.5% to 2% crustal assimilation rates. These rates indicate that crustal contamination can be negligible when compared to fractional crystallisation in the evolution of the magma beneath the Taskapi-Mecitli granitoid. The partial melting model calculations and MORB-normalised trace element concentrations of the least evolved samples of the Taskapi-Mecitli granitoid are consistent with those of mafic melts obtained from partial melting of interacting mantle- lower crust with a melting degree of 18%. The age (23 Ma) of the post- or syn-collisional Taskapi-Mecitli granitoid suggests that the collision between Arabian and Eurasian plates could be before/around similar to 23 Ma (Late Oligocene to Early Miocene).
Au-Rich Bimodal-Mafic Type Volcanogenic Massive Sulphide Deposit Associated With Jurassic Arc Volcanism From the Central Pontide (Kastamonu, Turkey)
(Elsevier, 2022) Gunay, Kurtulus; Oyan, Vural; Donmez, Cahit; Cavdar, Bugra; Ciftci, Emin; Chugaev, Andrey V.; Ma, Chang-Qian
The central part of the Pontide Orogenic Belt, located in northern Anatolia, is a segment of the Alpine-Himalayan orogeny. Cangaldag Metamorphic Complex (CMC) occurs within this segment which consists of ensimatic island arc volcanics and deep sea sediments which occasionally cut cross by mafic sills/dykes. They were exposed to metamorphism under the greenschist facies conditions and remain in tectonic contact with each other. The Say yayla mineralization is one of the recently discovered volcanogenic massive sulfide (VMS) deposits in the CMC with a remarkable Au content. The mafic and felsic metavolcanic rocks are the host-rocks of the Say Yayla mineralization and the ages determined by U-Pb zircon grains of these felsic volcanic rocks range from 170 Ma to 165 Ma indicating Middle Jurassic time. At the 0.1% cut-off grade, 7.5 million tons of resource has been calculated with 0.75 ppm Au, 0.65 wt% Cu, and 0.35 wt% Zn grades. The Say Yayla mineralization consists of massive and semi-massive sulfide minerals and a mineral assemblage represented by predominantly pyrite and chalcopyrite and trace amounts of sphalerite, tennantite and galena. Average base and precious metal grades of the zones occur with >1 wt% Cu are 2 wt% for Cu, 0.7 wt% for Zn, 0.04 wt% for Pb and 1.5 g/t for Au. The sulfur isotope values (delta S-34 VCDT) range from 4.9 parts per thousand to 6.7 parts per thousand for pyrite grains and 4.2 parts per thousand was obtained from the one sphalerite sample. delta O-18 values for the quartz from quartz-rich ore samples were 10.6 parts per thousand and 11.7 parts per thousand delta O-18 (VSMOW)(qtz). delta O-18 (VSMOW)(fluid) values for the ore-forming fluids vary between 0 parts per thousand and 2.4 parts per thousand. Lead isotope compositions of the pyrite minerals were 18.148-18.150 (Pb-206/Pb-204), 15.548-15.550 (Pb-207/Pb-204) and 38.078-38.083 (Pb-208/Pb-204) The geological, geochemical, and isotopic data of the ore and host-rocks reveal that the mineralization is a bimodal-mafic type (Noranda type), which is classified into Cu-Zn group of volcanogenic massive sulfides. Geochemical and geochronological data from the wall rocks further show that mineralization was developed within an ensimatic island arc environment during the Middle Jurassic.
Bitlis Masifi' Nde (Yolcular Metamorfiti) Na-feldispat Bakımından Zengin Lökogranitik Kayaçlar: Feldispat Kaynağı Olarak Bir Potansiyel
(2005) Oyan, Vural; Tolluoğlu, A. Ümit
Bölükyazı-Hizan (Bitlis) arasında Yolcular Metamorfiti içinde gözlenen ve anateksi süreçlerinin etkisiyle gelişmiş granitik bileşimli lökokratik kayaçlar Na-feldispatça zenginleşme göstermektedirler. Bu çalışmada, Yolcular Metamorfiti içindeki lökogranitik kayaçların feldispat kaynağı olarak kullanılabilirliği araştırılmıştır. Yolcular Metamorfiti (Alt Birlik) almandin-amfibolit fasiyesindeki metamorfizma koşullarına sahip ve Bitlis Masifi'nin çekirdeğinde yüzeyleyen amfibolitler, mika minerallerince zengin paragnays/şistler, migmatit seviyeleri ve bunları kesen granitik kayaçlar içerirken, Masifin Üst Birliği metapelitler ve metakarbonatlarla karakterize edilirler. Lökokratik kayaçlar Yolcular Metamorfitinin içinde geniş bir alanda gözlenmektedir. Özellikle amfibolit ve biyotit-gnayslarla düzensiz sınır ilişkilerine sahip olan bu kayaçlar, çoğunlukla alterasyona uğramışlardır. Bu kayaç birimleri, mineralojik bileşim olarak kuvars ve feldispat minerallerince zengin olup, özellikle feldispat minerallerinin albit-oligoklaz bileşiminde plajiyoklaz serisi minerallerinden oluştuğu saptanmıştır. Çok ender oranda epidot, sfen ve mika gibi koyu renkli mineralleri içeren bu kayaçların, $Na_2O$ içerikleri %7-8, $Fe_2O_3$ içerikleri % 0.60-0.70 ve $TiO_2$ içerikleri % 0.2-0.3 arasında değişmektedir. Bu veriler, lökogranitik kayaçların Na-feldispatça zengin olduklarını göstermektedir. Örnekler yaş manyetik ayırma ve flotasyon deneylerine tabi tutulmuştur. Deneysel çalışmalar flotasyonla endüstrinin talebine uygun konsantre üretilebileceğini ortaya koymuştur. Granitik bileşimli lökokratik kayaçlarda $Na_2O$ içeriği % 11.30, $Al_2O_3$ içeriği % 21.60 ve ağırlık verimi %96.60 olan konsantre üretilmiş ve konsantrenin istenmeyen $TiO_2$ ve $Fe_2O_3$ içerikleri sırasıyla % 0.05 ve % 0.12'ye kadar düşürülmüştür.
Bölükyazı-hizan (Bitlis Masifi) Çevresindeki Na-k-feldispat Yataklarının Jeolojik Özellikleri ve Ekonomik Önemi
(2006) Tolluoğlu, Ümit; Oyan, Vural
Çalışma alanında yüksek-orta metamorfizma koşullarında oluşmuş çekirdek serisi (Alt Birlik), düşük-orta metamorfizma koşullarında oluşmuş örtü serisi (Üst Birlik) ve bu iki kayaç serisini kesen postmetamorfik aplit dayklan şeklinde 3 tip kayaç grubu tespit edilmiştir. Çekirdek serisi amfibolit, paragnays/şist, migmatit ve metagranitoyidlerden oluşmaktadır. Örtü birimleri çalışma alanında muskovit/klorit şistler ve mermer/dolomitik mermer, rekristalize kireçtaşı kütleleriyle karakterize edilmektedir. Amfibolitler masif ve yönlenmiş olarak iki ayrı parajenez sunmaktadır. Paragnays/şistler, biyotit gnays/şist ve muskovit gnays parajenezleri sunarlarken, çalışma alanında sillimanit-biyotit-gnays örneklerinin varlığı ve melanosom kısımlardaki amfibol mineralleri biyotit gnaysların ve amfibolitlerin anateksiye uğrayarak migmatitleri oluşturabileceği düşüncesini yaratmıştır. Çalışma alanındaki metagranitoyidler Hazo metagranodiyorit ve Doğruyol metagranitoyidi (lökogranit, granit ve tonalit) şeklinde petrografik ve jeokimyasal verilere göre ayırtlanmıştır. Örtü serisine ait muskovit/klorit şistler amfibolitleri uyumsuz olarak örterken, mermer/dolomitik mermer ve rekristalize kireçtaşları çekirdek kayaçlarmm üstüne bindirmeyle oturmaktadırlar. Jeokimyasal sonuçlar metagranitoyid kütlelerinin S ve I tipi olduklarını, subalkalin karakterli, kalkalkalin, kalsik ve yüksek alüminalı granitler olduklarını göstermektedir. I tipi karakteristiklerin amfibolitlerin özümlenmesi ile oluşabileceği de varsayılmış ve tektonik olarak metagranitoyidlerin çarpışma sonrası ve levha içi granitleri olduğu görülmüştür. Çalışma alanında feldispatça zengin kayaçlar lökogranitler, aplit dayklan ve granitik karakterli lökokratik kayaçlar (lökosom) olarak tespit edilmiştir. Çalışma alanında K-feldispatça zengin kayaçlar aplit dayklan ve Na-feldispatça zengin kayaçlar granitik bileşimli lökokratik kayaçlar olarak tespit edilmiştir. Lökokratik seviyeler üzerinde gerçekleştirilen zenginleştirme çalışmalan sonucunda V-5A nolu örneğin Na2O içeriği %11.25'e yükseltilmiş, $TiO_2$ içeriği %0.05'e, $Fe_2O_3$ içeriği %0.12'ye düşürülmüş ve V-93 nolu aplit daykı örneğinin $K_2O$ içeriği %7.5'a yükseltilmiş, $TiO_2$ içeriği < %0.1'e, $Fe_2C>3$ içeriği %0.10'a düşürülmüş ve TSE standartlanna uygun olduklan görülmüştür.
Composition, Pressure, and Temperature of the Mantle Source Region of Quaternary Nepheline-Basanitic Lavas in Bitlis Massif, Eastern Anatolia, Turkey: a Consequence of Melts From Arabian Lithospheric Mantle
(Elsevier Science Bv, 2019) Ozdemir, Yavuz; Mercan, Cagri; Oyan, Vural; Ozdemir, Ayse Atakul
The Quaternary (0.66-0.63 Ma) nepheline basanites (ne - basanite) are the firstly observed volcanic products of Arabia-Eurasia collision on Bitlis Pottirge Massif. They composed of clinopyroxene, olivine, Ti-magnetite, Cr spinel, and nepheline. The forsterite compositions of olivines range between 73 and 83%, calcic clinopyroxenes show modest variations in Wo(48-57)-En(37-45)-FS5-7 and nephelines occur as minor minerals within the networks of other groundmass minerals. They are characterized by low SiO2 (40.16-41.96 wt%), high MgO contents (8.54-9.73 wt%) and similar Sr-Nd isotopic compositions with Arabian Plate volcanics. Mineral and whole rock thermobarometry yield crystallization pressure and a temperature range between 8 and 20 kbar and 1301 degrees C - 1035 degrees C respectively. Lavas have high Mg -number (>0.58), high Cr and Ni contents and strong LREE enrichment but depletion in Rb, K, and Pb. Trace elements together with Sr isotopic compositions inferred negligible assimilation of the local upper crustal material. The calculated average pressure and temperature of mantle melting for ne-basanites is 2,85 kbar and 1353 degrees C respectively. FC3MS (wt% FeO/CaO-3*MgO/SiO2) parameter and melting models using REE data reveal catak basanites are products of amphibole and phlogopite bearing metasomatised lithospheric mantle in garnet stability field. They seem to originated from depths of similar to 85 km which corresponds to the base of the Arabian lithosphere in the region. (C) 2019 Elsevier B.V. All rights reserved.
Constraining the Timing of Lithospheric Thinning During Continental Collision: a Perspective of Cenozoic Basaltic Rocks From the Baltacik-Gunkoru (patnos-Malazgirt) Region in the East Anatolia, Turkey
(Elsevier, 2024) Oyan, Vural
Geochemical and isotopic markers of the most primitive basaltic melts allow us to understand the temporal evolution of the lithospheric mantle and geodynamic processes. This paper presents the geochemical, Sr-Nd-PbHf isotopic data, K-Ar dating and the petrological evolution of the petrogenesis of the late Miocene-early Pliocene basaltic volcanism observed in the Baltacik-Gunkoru region in the northeastern of Lake Van in Eastern Anatolia Collision Zone (EACZ). These data allow us to understand the origin of collision-related magmatism and the geodynamic processes in the late Miocene-early Pliocene in the EACZ. Geochronological age data (K-Ar) indicate that basaltic volcanism erupted between -7.63 and 5.24 Ma. Major-incompatible trace element contents, Sr-Nd isotopic compositions of the studied samples and EC-AFC (energy-constrained recharge, assimilation, and fractional crystallization), and MELTS model calculations point out that basaltic volcanism has undergone fractional crystallization but unaffected crustal contamination. Petrological models created using Sr-87/Sr-86, epsilon Nd and epsilon Hf isotopic data, together with calculated primary melt compositions of basaltic lavas, indicate that the DMM-type (Depleted Morb Mantle) mantle source is metasomatized by melts rather than fluids derived from subducted oceanic lithosphere. Combined trace element and isotopic modelling results indicate that the calculated primary melts were formed by 2.5-5% melting of a metasomatised spinel-garnet lherzolitic mantle source, including amphibole and 1% residual rutile. This mantle source has been metasomatised by a 1-3% contribution of subducted slab component, with a sediment melt/AOC (altered oceanic crust) melt ratio of about 90:10. Thermobarometric calculations based on calculated primary melts compositions indicate that the lithosphere-asthenosphere boundary (LAB) is a depth of 67 +/- 4 km for 7.53-5.24 Ma. Literature data and the findings obtained from this study indicate that the late Miocene to early Pliocene basaltic volcanism in the south of the EACZ) is progressed by the delamination of the mantle lithosphere. This delamination occurred in a fragmented/patched or dripping manner rather than whole-scale delamination in the 3-4 million years between similar to 9 Ma and 5-6 Ma.
A Debris Avalanche at Suphan Stratovolcano (Turkey) and Implications for Hazard Evaluation
(Springer, 2016) Ozdemir, Yavuz; Akkaya, Ismail; Oyan, Vural; Kelfoun, Karim
The Quaternary Suphan debris avalanche deposit is located in Eastern Anatolia, Turkey. The avalanche formed by the sector collapse of a major stratovolcano towards the north, possibly during a single catastrophic event. The deposit has an estimated volume of 4 km(3) and ran out over 25 km to cover an area of approximately 200 km(2). Products of the collapse are overlain by younger eruptive units from the Suphan volcano. We have tested the numerical code VolcFlow to first reproduce the emplacement of the Quaternary Suphan debris avalanche and then to develop a hazard assessment for potential future sector collapses and subsequent emplacement of debris avalanches and associated tsunami. The numerical model captures the main features of the propagation process, including travel distance, lateral spread, and run up. The best fit obtained for the existing flow has a constant retarding stress of 50 kPa and a collapse scar volume of 4 km(3). Analysis of potential future collapse scenarios reveals that northern sector debris avalanches (up to 6 km(3)) could affect several towns. In the case of a sector collapse towards the south, a tsunami will reach the city of Van and several of the biggest towns on the southern shoreline of Lake Van. Cities most affected by the larger amplitude waves would be Van, Edremit, Gevas, Tatvan, and, to a lesser extent, Ercis, with wave amplitudes (first waves after the onset of the collapse) between 8 and 10 m.
Doğu Anadolu Yüksek Platosundaki Olası Pliyosen? Yaşlı Plato ve Yerel Bazaltik Volkanizmanın Jeokimyasal ve Petrolojik Evrimi: Litosferik Ve/veya Astenosferik Mantonun Etkileri ve Magma Odası Evrim Süreçleri (FC, Afc, Mağma Karışımı)
(2017) Keskin, Mehmet Kürşat; Oyan, Vural; Güleç, Nilgün Türkan
Doğu Anadolu Bölgesi?nde çarpışmayla ilişkili Neojen volkanizması Arabistan ve Avrasya plkaları arasındaki kıta kıta çarpışmasından sonar başlamış ve kuzeyde Erzurum-Kars Platosu?ndan güneyde Karacadağ volkanına kadar geniş bir alana yayılmıştır. Bölgede volkanizma üzerine yaptığımız son çalışmalar ve bu proje çalışması volkanik aktivitenin Pliyosen zaman aralığında çıkan volkanik ürünlerin yayılımı ve hacmi açısından zirve yaptığını ve Kuvaterner boyunca aynı etkinlikte devam ettiğini göstermiştir. Yaş verileri bu Orta Mİoysen-Geç Pliyosen magmatik aktivitenin yaşının 12.5-2.5 milyon yıl arasında değiştiğine işaret eder. MELTS modellemesinin sonuçları Pliyosen bazaltik volkanizmasını oluşturan magmaların 1-5 kbar basınç ve % 0 ? 2 arasında değişen H2O içeriğiyle fraksiyonel kristallenmeye maruz kaldıklarına işaret eder. Iz element ve Sr,Nd, Pb ve ?O izotopik verileri kullanılarak elde ettiğimiz EC-AFCpetrolojik modelleme hesaplamaları bazaltik lavların kıtasal kirlenme ile birleşik fraksiyonel kristallenme süreçlerinden etkilenmediğini, bunun aksine evrmileşmiş lavların yaklaşık %2-7 arasında asimilasyon oranına sahip olduklarını ortaya çıkarmıştır. En az evrimleşmiş primitive bazaltik örneklerde Büyük iyon yarı çaplı elementlerin (LILs) ve hafif nadir toprak elementlerin (LREEs) yüksek alan şiddetli elementlere gore belirgin zenginleşmesi ve yüksek Sr, Hf ve Pb ile düşük 143Nd/Nd144 izotopik oranları Pliyosen bazaltik volkanizmasının manto kaynak alanının, alter okyanus kabuğu erigmeleri ve akışkanlardan ziyade dalmış sedimentin yaklaşık %2-7 arasında değişen ergimelerinden türeyen ergiyigler ile zenginleştiğine işaret eder. Pliyosen bazaltik volkanizması için yapılan ergime modellemelerinin sonuçları, söz konusu magmaların oluşumunda derin ve sığ kökenli mantoların farklı oranlarda ergimesinin belirleyici olduğunu ve kaynak alanın zaman içinde spinel peridotit bileşimine doğru değiştiğini; bu sırada türeyen magmaların ise alkaliden subalkali karakterine doğru yöneldiğini göstermiştir. Petrolojik modellerimiz, Pliyosen bazaltik volkanizmasında ergime derecelerinin yaklaşık % 0.8 ile % 5 arasında değiştiğine işaret etmektedir. Manto kaynağındaki spinel katkısı ve ergime derecesinin zaman içinde giderek artması, türeyen bazaltik magmaların karakterlerinin alkaliden subalkaliye değişmesine neden olmuştur. Bu Pliyosen?de metasomatize litosferik mantonun delaminasyonu ile derin astenosferik ve sığ litosferik mantoların kısmi ergimeleri ve sonra birbirleriyle karışmaları ile açıklanabilir.
Economic Geology of Pumice and Perlite Mines in the Van Lake Basin
(2017) Kılıçer, Ali; Örçen, Sefer; Oyan, Vural
Pomza ve Perlit kullanılarak üretilen ürünler inşaat sektöründe yapı elemanı olarak sıkça kullanılmaya başlamıştır. Pomza ve perlitin hafif, gözenekli ve yüksek silis içermesi; betonarme yapılarda yük ve enerji tasarrufu sağlamaktadır. Bu tez çalışmasında pomza ve perlit madenlerinin fiziksel, kimyasal ve mineralojik özelliklerinin tayini ile köpük ajanı kullanılarak köpük betonda agrega olarak kullanılabilirlikleri araştırılmıştır. Çalışmanın ilk bölümünde Van Gölü Havzası kuzey-kuzeybatı-güneybatı yönünde alınan pomza ve perlit madenlerinin XRD ve ince kesit analizleri yapılmış, pomza ve perlitin hangi tür malzemeden türediğinin ve kimyasal bileşenlerinin incelenmesi amacıyla jeokimyasal analizler yapılmıştır. Çalışmanın ikinci bölümünde pomza ve genleştirilmiş perlit kullanılarak köpük beton üretilmiştir. Elde edilen köpük betonların yapı sektöründe kullanılabilirliğini tespit etmek için köpük beton örnekleri üzerinde tek eksenli basınç deneyi, donma-çözülme ve ısı iletkenliği deneyleri yapılmıştır. Ayrıca çimento yerine belli miktarlarda pomza kullanılarak bu şekilde elde edilen köpük betonların basınç dayanım ve donma-çözülmeye karşı verecekleri reaksiyonlar tespit edilmiştir. Deneysel çalışmalarda 90 mikrondan küçük pomzanın % 30'a kadar çimento ile yer değiştirmesiyle nispeten daha iyi basınç dayanımına sahip olduğu ve donma çözülmeye karşı daha dirençli olduğu tespit edilmiştir. Pomza ve perlitin köpük beton içinde agrega olarak kullanılmasıyla birlikte 728 kg/m3'de 3.1 Mpa değerine ulaşılmıştır. Perlit agregalı köpük betonlarında ise 273 kg/m3'de 0,078 W/k ısı yalıtım değerine ulaşılmıştır.
Effect of Physical, Chemical and Electro-Kinetic Properties of Pumice on Strength Development of Pumice Blended Cements
(Springer, 2013) Tapan, Mucip; Depci, Tolga; Ozvan, Ali; Efe, Tugba; Oyan, Vural
In the present study, the potential effects of physical, chemical and electro-kinetic properties of pumice on the strength development of pumice blended cements (PBC) were examined and documented. A significant relationship between zeta potential of pumice samples, setting time and water demand of PBC was found. A relationship between the chemical content of pumice samples and compressive strength of PBC was also observed. However, zeta potential of the pumice samples was found to be less effective in strength development. Despite the lower clinker content, the setting time of the PBC samples was shorter than control specimen. 30 % pumice replacement by clinker resulted in 5-28 % reduction in 28-day strength depending on the characteristics of the pumice samples and grinding time.
Experimental Studies on Ignimbrite and the Effect of Lichens and Capillarity on the Deterioration of Seljuk Gravestones
(Elsevier, 2015) Ozvan, Ali; Dincer, Ismail; Akin, Mutluhan; Oyan, Vural; Tapan, Mucip
Ignimbrites are used extensively in masonry and decorative cladding not only in historical structures, but also in residential houses recently as well as monuments around Ahlat (Bitlis-Turkey) region because of their light weight, softness and insulating properties. The most famous architectural monument is the Ahlat Seljuk Tombs, in which ignimbrites were used for the structure. These are thousand year old gravestones that have been subjected to significant degradation over time caused by many physical and chemical effects. The aim of this study is revealing the mineralogical, petrographical, petrophysical and mechanical properties of fresh ignimbrites as well as determining the effect of lichens and capillarity on the deterioration of Seljuk gravestones in accordance with laboratory studies and field observations. A total of four different ignimbrite levels have been evaluated, which are widespread in the region and named as N1 (reddish brown), N2 (dark brown), N3 (yellowish gray) and N4 (black), respectively. Among these ignimbrites, the samples of N1 and N2 were employed in the construction of Seljuk gravestones. The lithic material content and welding degree are the main controlling factors of the engineering properties of ignimbrites. Laboratory test results indicate that high porosity of ignimbrites and transport of water mediated by capillarity accelerate the deterioration of ignimbrites. Furthermore, lichens play a preventive role in the deterioration mechanism of ignimbrites rather than disintegrating the tombstones. (C) 2014 Elsevier B.V. All rights reserved.
Geology and Geochemistry of Sediment-Hosted Hanonu Massive Sulfide Deposit (Kastamonu - Turkey)
(Elsevier, 2018) Gunay, Kurtulus; Donmez, Cahit; Oyan, Vural; Yildirim, Nail; Ciftci, Emin; Yildiz, Hayrullah; Ozkumus, Serkan
Hanonu massive sulfide (HMS) mineralization is the first sediment-hosted massive sulfide deposit discovered in Anatolia (Turkey). Containing more than 1% Cu and with more than 25 million tonnes reserve, the HMS mineralization is located in the Cangaldag Metamorphic Complex (CMC) in the central Pontides within metavolcaniclastic rocks with mafic sill and/or lava interlayers. Rocks related to mineralization were exposed to metamorphism under the greenschist facies conditions. Tectonism and metamorphic processes affected all units including ore. The HMS mineralization consists dominantly of Cu (0.2-6.9%) accompanied by Zn (239 ppm-1%) and comprises massive, banded and disseminated sulfide bodies. The main ore minerals include pyrite, chalcopyrite, with minor sphalerite and magnetite. The regular stratigraphy displaying uninterrupted layers of volcanoclastics contains mafic lava or sills within the sequence with the mineralization initially emplaced within immature clastics and then subjected to metamorphism as a package, which indicates that the ore and wall rocks formed in the same paleotectonic environment. Data obtained from melt models of mafic lava or sills related to the HMS mineralization indicate these rocks formed in back-arc basins from a mixture of 70% depleted MORE; mantle and 30% asthenospheric melt with melting degrees possibly of 8-15%. According to isotope data, lead from the HMS mineralization may be sourced from an arc-related environment, with magmatic activity in the lower crust and upper mantle. Geologic and geochemical data indicate that the HMS mineralization may have formed in a back-arc rift tectonomagmatic environment.
Geology, Geochemistry and Re-Os Geochronology of the Jurassic Zeybek Volcanogenic Massive Sulfide Deposit (Central Pontides, Turkey)
(Elsevier, 2019) Gunay, Kurtulus; Donmez, Cahit; Oyan, Vural; Baran, Cuneyt; Ciftci, Emin; Parlak, Osman; Ozkumus, Serkan
Located in the north of Anatolia, the Pontide Orogenic Belt hosts Turkey's most important volcanogenic massive sulfide (VMS) deposits. Studies completed in the last ten years have discovered new massive sulfide deposits in the Central Pontide zone. The Zeybek VMS deposit is one of these newly-discovered deposits found in the Central Pontides. This deposit is associated with the Cangaldag Metamorphic Complex occurring as east-west-striking tectonic slices. The Cangaldag Metamorphic Complex is an allochthonous mass of metavolcanic, metavolcanidastic and metaclastic rocks in the form of imbricated tectonic slices. Zeybek massive sulfide deposit is located within metaclastic rocks intercalated with mafic sills or lava flows in this complex. The major ore mineral paragenesis in the Zeybek VMS deposit comprises pyrite, chalcopyrite and sphalerite, with lower amounts of bornite, covelline, chalcocite and magnetite. With thirty thousand meters of drilling in the mineralized area, 20 million ton resources with 0.32 wt% Cu were determined. According to the wall-rock mineralization relationships, mineralization style and ore geochemistry of the Zeybek VMS mineralization, it is similar to a mafic-siliciclastic type volcanogenic massive sulfide formation. Re-Os geochronologic studies of chalcopyrites from the Cu-rich massive ore samples obtained a 178 +/- 2.2 Ma (MSWD: 4.1) Re-187/Os-188 against Os-187/Os-188 isochron. Geochemical and isotopical age data associated with the Zeybek VMS deposit indicate that the mineralization occurred in an arc-back arc tectonic environment, which developed in Middle Jurassic age intra-ocean as a result of the closure of north-ward subduction that resulted the closure of the Tethys ocean.
İgnimbiritlerdeki Kılcal Su Emme Özelliğinin Ahlat Selçuklu Mezar Taşlarının Bozunmasındaki Rolü
(2016) Oyan, Vural; Özvan, Ali; Tapan, Mücip; Akin, Mutluhan; Dinçer, İsmail
Selçuklular dönemine ait Ahlat Selçuklu mezar taşları, dünya üzerindeki bilinen en büyük Müslüman Mezarlığı olması ve taşıdığı tarihsel önem nedeniyle UNESCO'nun Dünya Kültür Mirası Geçici Listesi'nde yer almaktadır. Mezar taşı olarak, bölgede oldukça yaygın olarak bulunan ve piroklastik bir kaya türü olan ignimbiritler kullanılmış olup, yumuşak olmaları ve kolay işlenebilmelerini nedeni ile üzerlerine çeşitli motifler ve yazıtlar işlenmiştir. Ancak söz konusu mezar taşları, yaklaşık 800 yıllık süreç içerisinde bozunma etkilerine maruz kalmıştır. Mezar taşları incelendiğinde dikkati çeken en önemli unsur, birçok mezar taşının orta bölgelerine yakın kısımlarından kırılmış olmasıdır. Bu çalışma kapsamında Ahlat Selçuklu mezar taşlarının bozunmasına neden olan unsurların açığa çıkarılması amacıyla taze ignimbirit örnekleri üzerinde deneysel çalışmalar yapılmış ve özellikle kılcal su emmenin bozunma üzerindeki etkisi araştırılmıştır. Buna göre, ignimbiritlerin yüksek gözenekliliği ve kılcal su emme özelliği mezar taşlarının bozunmasındaki en önemli etkendir
Magmatic Evolution of the Early Pliocene Etrusk Stratovolcano, Eastern Anatolian Collision Zone, Turkey
(Elsevier, 2016) Oyan, Vural; Keskin, Mehmet; Lebedev, Vladimir A.; Chugaev, Andrey V.; Sharkov, Evgenii V.
The Pliocene Etrusk stratovolcano, located in the northeast of Lake Van (Eastern Anatolia; Turkey), is one of the important volcanic centres in the Eastern Anatolian collision zone. Mt. Etrusk overlies a widespread volcanic plateau, consisting of basaltic and hawaiitic lavas formed by fissure eruptions between 4.9-4.5 Ma. These basic lavas contain a phenocryst phase consisting of olivine, plagioclase and clinopyroxene. Trace element ratio diagrams imply that these basic magmas were generated from a mantle that contained a clear subduction component that is related to the subducted sediments rather than fluids or altered oceanic crust. Results of the melting models on the basaltic plateau lavas indicate that there was a marked variation both in the mantle source mineralogy (i.e. the ratio of garnet peridotite to spinel peridotite in the source varies between 60/40% and 40/60%) and the degree of melting (i.e. F between 0.8-4%). This can be explained by a model in which magmas were generated by partial melting of both metasomatised lithospheric and deeper asthenospheric mantle sources in an extensional setting in response to the partial delamination of the lithospheric mantle of Eastern Anatolia and then mixed with each other during Pliocene times. Central eruptions that formed the Etrusk volcano lasted similar to 600 kyr between 43-3.7 Ma during Zanclean times. The estimated depth of the Etrusk magma chamber is similar to 9-12 km. The volcano erupted lavas with a rather narrow compositional range from latite to rhyolite, which are either transitional or mildly alkaline in character. The Etrusk lavas contain plagioclase, clino- and orthopyroxene, biotite, K-feldspar and rarely, minor amounts of olivine and amphibole in the phenocryst phase. A composite chemo-stratigraphic section of the volcano and petrological models indicate that the evolved lavas of the Etrusk volcano differentiated from a parental magma composition, which is similar to that of the most primitive plateau basalt lavas underlying the volcano, via the AFC process, and experienced at least two major magma replenishment episodes at 4.1 Ma and 3.8 Ma during the magma chamber evolution. (C) 2016 Elsevier B.V. All rights reserved.
Origin and Petrogenesis of Magmatism in Collision-Related Environments: Evidence From the Melikler Volcanics on the Kars Plateau-Turkey in the Turkish-Iranian High Plateau
(Oxford Univ Press, 2023) Oyan, Elif; Oyan, Vural; Ozdemir, Yavuz; Gulec, Nilgun
The temporal distribution of enriched source components and magmatism in continental collision zones provides critical information about mantle dynamic processes in collision-related environments. This paper presents petrology, mineralogy, K-Ar ages and whole-rock major and trace elements, as well as Sr-Nd-Pb-Hf isotopic compositions of Melikler volcanism in Kars Plateau (KP) in the East Anatolia Collision Zone, NE Turkey, with the aim to understand the role of the subducting slab, the origin of magmatism and the geodynamic evolution in the collision-related environments. Our K-Ar dating results show the Melikler volcanism erupted between 5.29 and 1.7 Ma and allows us to divide it into an early (5.29-2.53 Ma) and a late (2.24-1.7 Ma) stage. Major-trace element abundances, isotopic compositions, EC(R) AFC (energy-constrained recharge, assimilation, and fractional crystallisation) and MELTS model calculations of both stages indicate that the least evolved samples were not affected by significant crustal contamination and fractional crystallisation. More evolved samples of the late stage underwent AFC processes with up to 6-9% crustal assimilation; however, those of the early stage were differentiated from a parental magma composition via AFC (up to 2-7.5% crustal assimilation) and experienced magma replenishment at pressure of 0.5 kbar; thus, both early and late stages have experienced open system conditions. The least evolved samples of both stages across the KP have arc-enriched geochemical and isotopic signatures, characterised by prevalent negative Nb-Ta anomalies and moderately radiogenic Sr, unradiogenic Nd-Hf and highly radiogenic Pb isotopic compositions. These primary melts could be derived from a depleted MORB mantle source metasomatised by sediment melt from the subducting Neotethys oceanic slab. Combined trace elemental and isotopic modelling results suggest that the least evolved samples of the early stage were formed by 2-4% melting of an amphibole-bearing garnet lherzolitic mantle source, which was metasomatised by 0.3-0.5% contribution of subducted slab component with a ratio of sediment melt/AOC (altered oceanic crust) melt about 90:10. A depleted lherzolitic mantle source containing apatite and garnet through inputs of 0.6-0.8% melts derived from the subducted oceanic slab, with 5-10% partial melting degree, could produce the least evolved samples of the late stage. Thermobarometric calculations reveal that the least evolved samples of the late stage are derived from the lithosphere-asthenosphere boundary at a depth of 77-82 km; in contrast, those of the early stage are produced from the lithosphere at a depth of 66-69 km. Literature data and the findings obtained from this study indicate that the onset of the Arabian-Eurasian collision may have occurred in the Oligocene and lithospheric dripping caused by the hard collision that occurred around the Late Miocene-Early Pliocene may produce the Melikler volcanic rocks.
Petrogenesis and the Evolution of Pliocene Timar Basalts in the East of Lake Van, Eastern Anatolia, Turkey: a Consequence of the Partial Melting of a Metasomatized Spinel-Rich Lithospheric Mantle Source
(Pergamon-elsevier Science Ltd, 2020) Aclan, Mustafa; Oyan, Vural; Kose, Onur
The Eastern Anatolian region provides a good example for collision-related volcanic activity. This activity started during the Middle Miocene and continued through the Pliocene and Quaternary. The new K - Ar ages reveal that the post-collisional Pliocene Timar basalts located in the East Anatolian Accretionary Complex (EAAC) erupted between 4.72 (Zanclean) and 3.29-2.93 Ma (Piacenzian). The Pliocene Timar basalts consist of plagioclase, clinopyroxene (augite), and olivine minerals and have glomeroporphyritic, intergranular, and ophitic textures. They display enrichment in light rare earth elements (LREEs) with (La/Yb)(N) values that range between 3.19 and 6.66 to 21.63-5.61. Sr-87/Sr-86(i) and Nd-143/Nd-144(i) isotopic ratios of the Timar basalts are 0.70599-0.70436 and 0.51277-0.51259, respectively. The epsilon Nd(t) values of these rocks range between 1.0116 and 1.0121. Sr-87/Sr-86(i) and Nd(t) contents indicate crustal contamination during the emplacement of the Timar basalts. According to the Energy Constrained-Assimilation Fractional Crystallization (EC-AFC) model, this contamination rate is between similar to 1.4 and 4.4%. The melting model shows that the least evolved samples of the Timar basalts were formed by similar to 0.1-2% partial melting of the lherzolitic source. Primitive melts that constituent Timar basalts were occurred with partial melting of a magma source that has predominantly spinel bearing mineralogy. All data indicate that the origin of the parental melts of the Timar basalts is metasomatized lithospheric mantle source and then these melts reached the surface from the fissures that is related to extensional tectonics in Pliocene.
Petrogenesis of Middle Miocene To Early Quaternary Basalts From the Karayaz?-G?ksu Plateau (Eastern Anatolia, Turkey): Implication for the Role of Pyroxenite and Lithospheric Thickness
(Elsevier, 2022) Ozdemir, Yavuz; Oyan, Vural; Jourdan, Fred
In Eastern Anatolia, the Karayazi-Go center dot ksu basaltic plateau is one of the basaltic eruption centers of post-collisional volcanism, located between the convergence zone of the Arabian and Anatolian plates. The geological and geochemical evolution of the plateau is documented using new 40Ar/39Ar age data, major-and trace element abundances, mineral geochemistry, and isotope compositions (Sr-Nd-Hf) for better understanding the petrogenesis and mantle source characteristics. Samples yield whole-rock 40Ar/39Ar ages of 12.53 +/- 0.05 and 12.68 +/- 0.05 Ma for transitional basalts (Middle Miocene), 5.88 +/- 0.20 Ma for tholeiitic lavas (Late Miocene), and 2.28 +/- 0.03 and 2.48 +/- 0.12 Ma for alkali members (Early Quaternary). The results suggest that the fractional crystallization of olivine and clinopyroxene in transitional, tholeiitic and lower alkaline lavas, and clinopyroxene in upper alkaline lavas, played a crucial role in their magmatic evolution without significant crustal contamination. Clinopyroxene-liquid equilibria indicate that the crystallization of transitional basalts occurred at the Moho and lower crust (temperature range 1157-1215 degrees C), tholeiitic basalts at the lower crust (temperature range 1154-1195 degrees C), alkaline basalts at lower to mid-crustal depths (temperature range 1083-1195 degrees C). The subduction-related metasomatism is in the form of melts derived from subducted sediments and decrease from Middle Miocene transitional to alkaline Early Quaternary basalts, as indicated by the Sr-Nd-Hf isotopes and Ba/ La and Th/Yb contents. The Early Quaternary alkaline basalts contain contributions from isotopically depleted but chemically enriched (enriched-MORB-like) asthenospheric mantle domain. Major elements-based parameters and olivine mineral chemistry yield that Karayazi-Go center dot ksu basalts could not be derived from a sole peridotite mantle source; the pyroxenite/eclogite-like mantle component would have contributed to the members of the plateau. Three-component mixing results using Sr-Nd isotopes indicate that the altered oceanic crust contributes to 0.5%-1% of the melt (crust vs. sediment about 65:35) for tholeiitic and alkaline basalts and reach up to 4% for transitional basalts (crust vs. sediment about 55:45). Melt equilibration depths of the basalts indicate that the lithospheric thickness of the region has not been changed on a large scale since the Middle Miocene to the Early Quaternary.
Petrogenesis of Miocene To Quaternary Primitive Basaltic Magmas in the Area of Lake Van (East Anatolia, Turkey): a Case for Relamination of Mantle Lithosphere After Lithospheric Delamination
(Springer, 2023) Oyan, Vural; Ozdemir, Yavuz; Chugaev, Andrey V.; Oyan, Elif; Chernyshev, Igor V.
We present the geochemical and Sr-Nd-Pb isotopic data and the petrological evolution of primitive basaltic lavas that erupted from the Miocene to Quaternary in the East Anatolia Collision Zone to understand the geodynamic conditions and the change in the lithospheric mantle over time. Major trace element abundances, Sr-Nd-Pb isotopic compositions and petrological models show that the primitive basaltic samples were not affected by crustal contamination and fractional crystallization. They are derived from a depleted MORB mantle modified by melts derived from subducted sediments. The primitive melts of the Miocene and Quaternary series were derived from an amphibole-bearing garnet lherzolitic mantle and an amphibole-bearing garnet-spinel lherzolite mantle source, respectively. In contrast, the Pliocene basaltic melts were formed by mixing melts originating from both an amphibole-bearing spinel and garnet lherzolite. Our thermodynamic calculations indicate that the lithosphere-asthenosphere boundary (LAB) is about 30 km shallower in the Pliocene than in the Miocene.This may be explained by lithospheric delamination in the Early Pliocene. In contrast, the LAB in the Quaternary is approximately 9 km deeper than in the Pliocene, which can be explained by relamination of the mantle lithosphere. Thermal calculations have shown that about 5-11 km of the relamination can occur within 5-6 Ma and that asthenospheric melts can relaminate the base of the thinned lithospheric mantle by cooling, and the presence of the relaminated mantle lithosphere is documented throughout the whole EACZ.