Van Gölü civarının (Doğu Anadolu) tektonik gelişiminin ve deformasyonunun paleomanyetik çalışmalar ile incelenmesi
Investigation of the tectonic evolution and deformation around the Lake Van (Eastern Anatolia) using palaeomagnetic studies
Yazar: SERCAN KAYIN
Danışman: DOÇ. DR. TURGAY İŞSEVEN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Jeofizik Mühendisliği Ana Bilim Dalı / Jeofizik Mühendisliği Bilim Dalı
Derece: Doktora, 2019
Konu: Jeofizik Mühendisliği = Geophysics Engineering

Özet:
Arap ve Avrasya levhaları arasındaki yakınlaşma sebebiyle Neotetis okyanusunun kuzey ve güney kollarının kapanmasının ardından, bölgede kıta kıta çarpışması meydana gelmiştir. Çarpışmanın ardından bölge yükselmeye başlamış, takiben geniş alanlar kaplayan bir volkanizma hüküm sürmüştür. Doğu Anadolu yüksek platosunda çarpışmaya bağlı olan bu volkanik ürünlerin hacim ve bileşimleri zamansal ve mekânsal olarak farklılık göstermekte olup, Neojenden Kuvaterner'e kadar geniş bir zaman yelpazesine sahip ürünlerin bulunması bölgenin yerbilimleri açısından bir inceleme alanı olmasını sağlamaktadır. Bu tez çalışmasının amacı, bölgedeki tektonik deformasyonları paleomanyetik açıdan incelemek ve bölge tektoniğinin gelişimini açıklamaya katkı koymaktır. Bu bağlamda, Van Gölü kuzeyinden 145, Karlıova üçlü eklemi civarından 43 olmak üzere toplam 188 mevkiden yönlü paleomanyetik numune toplanmıştır. Bu örneklerin standart paleomanyetik laboratuvar çalışmaları Boğaziçi Üniversitesi Kandilli Rasathanesi ve İstanbul Teknik Üniversitesi ortak paleomanyetizma laboratuvarı olan "KANTEK Paleomanyetizma Laboratuvarı"nda gerçekleştirilmiş olup, kaya manyetizması çalışmaları İstanbul Üniversitesi, Jeofizik Mühendisliği Bölümü'nde bulunan Doç.Dr. Yılmaz İspir Paleomağnetizma Laboratuvarı'nda yapılmıştır.
Van Gölü kuzeyinde yer alan Miyosen-Holosen ve Karlıova üçlü eklemi civarındaki Miyosen-Pliyosen yaşlı volkanik kayaçların büyük çoğunluğunun güvenilir kalıcı mıknatıslanmaya sahip olduğu belirlenmiştir. Tez kapsamında yapılmış olan Eş-Isıl Kalıntı Mıknatıslanma çalışmalarında, mıknatıslanmadan sorumlu minerallerin genelde çok domen yapılı Manyetit (Ti-Manyetit) ve Manyetit+Hematit olduğu saptanmıştır. Yüksek sıcaklık süseptibilite ölçümleri ile kayaçların mıknatıslanmasından sorumlu minerallerin sıcaklığa bağlı olarak herhangi bir alterasyon geçirip geçirmediği, Curie sıcaklıkları ve domen yapıları gibi kaya manyetizması özellikleri belirlenmiştir. Paleomanyetizma çalışmalarından elde edilen ortalama mıknatıslanma doğrultularının eğim açılarının bölge için beklenen değerde (I=58°) olduğu, Van Gölü civarında Miyosen'den günümüze bölgede enlemsel bir hareketin olmadığı ortaya çıkarılmıştır. 
Miyosen – Pleyistosen zaman aralığında, Erciş Fayı / Fay Zonu'nun doğusunda (~27±8°) ve kuzeydoğusunda (~8,8±7,72°) kalan bölgenin saat yönünde, batısında ve fayın güneyinde kalan bölgenin ise saatin tersi yönünde (~18±4°) rotasyona sahip olduğu belirlenmiştir. Fay zonuna çok yakın veya fay zonu arasında kalan mevkilerde ise net bir gruplaşma olmaksızın çok az da olsa (~5±4.9°) saatin tersi yönünde rotasyonun etkin olduğu görülmüştür. Bu sonuçlara göre, Van Gölü kuzeyinde bulunan Erciş Fayı / Fay Zonu bölgenin genel tektoniğini şekillendiren ana unsur olduğu ifade edilebilir. Nemrut Dağı ve civarından elde edilen paleomanyetik sonuçlar ise (~4.5±6.9°) olup, 95 emniyet çemberi de düşünüldüğünde, Holosen sonrası güncel şiddetli bir deformasyonun olmadığını göstermektedir.
Karlıova – Varto – Solhan bölgesinden elde edilen paleomanyetik sonuçlara göre; KAF ve DAF'a yakın bölgelerde saatin tersi yönünde aktif bir deformasyonun olduğu görülmektedir. Varto Fay Zonu'nun batı taraflarında bulunan mevkilerden, doğrultu atımlı faylar arasında gelişen blokların saatin tersi yönünde (~22±13°) dönmüş olduğu, VFZ'nin doğu kesimlerinde bulunan mevkilerde ise saat yönünde rotasyonlar (~22±11°) görülmüştür. Elde edilen bu rotasyonlara göre yakın zamanda bölgenin oluşumu ve gelişimi hakkında öne sürülen modeller karşılaştırılmış, VFZ'nin gelişimi hakkında literatüre değerli bilgiler sunulmuştur. 
Tunceli – Elazığ civarında bulunan Miyosen ve Pleyistosen yaşlı volkanik kayaçlardan elde edilen paleomanyetik sonuçlar, Miyosen Pleyistosen arasında saat yönünde rotasyonların gerçekleştiği, Pleyistosen sonrası bölge tektoniğinde yaşanan değişikliğe bağlı olarak araştırma bölgesinin saatin tersi yönünde bir rotasyona maruz kaldığı belirlenmiştir.

Abstract:
Due to the convergence between the Arabian and Eurasian plates, the continent-continent collision occurred in the region after the northern and southern branches of the Neotethys ocean were closed. This collision caused a large plateau formation about 2 km elevation and Eastern Anatolian Region still continuous to evolve as a young mountain belt. In the Eastern Anatolia east-west trending folds, thrusts and strike-slip fault systems were developed due to the compressional tectonic regime. Also, it can be observed from seismicity of the area. In the Late Miocene, Anatolian plate started to move westward along the North Anatolian Fault Zone (NAFZ) and East Anatolian Fault Zone (EAFZ). This movement continues today. Volcanic activity has started in the region after the collision. This volcanism took place occupying large areas and the thickness of this volcanic series reaches to 1 km. It continued from the Miocene to Holocene. Eastern Anatolia High Plateau yielding time and location dependent varieties in volumes and compositions of volcanic products resulting from the collision and producing from Neogene to Quaternary times show region's importance in geo-scientific aspect.
The aim of this thesis is to determine the tectonic deformations in the region in paleomagnetic aspects and contribute explaining region's tectonic development. In this context, oriented palaeomagnetic samples were collected from a total of 188 sites, including 145 from the north of Lake Van and 43 from the Karlıova triple junction. Paleomagnetic samples in the Lake Van are consist of around Nemrut Volcano 7 sites from Holocene and Upper Pleistocene volcanics, around NE of Lake Van 38 sites from Pleistocene lavas, 82 sites from Pliocene volcanic rocks, 14 sites from Miocene volcanic rocks. Also, paleomagnetic samples, which collected from near the Karlıova triple junction consist of in the Karlıova-Varto region 16 sites from Pliocene volcanics and vicinity of the Solhan 8 sites from Pliocene volcanics and 19 sites from Miocene Pleistocene volcanics of near the Tunceli-Elazığ. The rocks where paleomagnetic sampling are taken are the products of different volcanic series which are related to volcanic centers such as Tendürek, Aladağ, Etrüsk Mountain, Pliocene plateau basalts, Girekol, Yüksektepe, and Karnıyarık Hill in the North of the Lake Van. Also, their ages have already known in previous studies. Paleomagnetic samples were collected using a portable motorised core drill. Orientations were determined using both magnetic and sun compasses. The paleomagnetic laboratory studies of these samples were carried out in the Paleomagnetism Laboratory of KANTEK, a paleomagnetism laboratory under the auspices of the Boğaziçi University Kandilli Observatory and Istanbul Technical University. Rock magnetism studies were carried out at the Doç.Dr. Yılmaz İSPİR Paleomagnetism Laboratory of Geophysical Engineering Department of Istanbul University. 
Paleomagnetic samples in the Lake Van are consist of around Nemrut Volcano 7 sites from Holocene and Upper Pleistocene volcanics and around NE of Lake Van 38 sites from Pleistocene lavas, 82 sites from Pliocene volcanic rocks, 14 sites from Miocene volcanic rocks.
In order to control and supporting the paleomagnetic data and specify the different magnetic properties of the rocks, rock magnetic studies have also been carried out such as Isothermal Remanent Magnetization, Anisotropy of Magnetic Susceptibility and High-Temperature Susceptibility.
In the anisotropy of magnetic susceptibility (AMS) studies; The k1 (kmax) component of the rock is determined by measuring 18 different directions with respect to the reference line of the sample. In this way, magnetic anisotropy direction (paleo-flow direction) was determined. In this thesis study, volcanic centers of the Miocene, Pliocene and Pleistocene volcanics in the North of the Lake VAN were identified (crater and/or cracking).
For IRM (Isothermal Remanent Magnetisation) studies, samples from 33 sites were selected at least one of each of the rock types sampled from the north of Van Lake. It has been determined that only Hematite is not responsible alone for the magnetization of any selected sample. On the other hand, it was found that from 21 sites at 33 locations, magnetization is reached saturation in the sample, thus responsible mineral for magnetisation is the "Magnetite". In the remaining 12 sites, it was first observed a rapid rise associated with magnetite, followed by a relatively less steep increase associated with hematite, and the sample did not reach the saturation. In this samples, it was determined that the mineral responsible for magnetization is both "Magnetite" and "Hematite". As a result, in the IRM studies, it is determined that the minerals of magnetizations are domain-structured Magnetite (Ti-Magnetite) and Magnetite+Hematite for the most part.
In this thesis study, 16 sites were selected to represent different age and rock types for high temperature susceptibility studies. The magnetic susceptibility of the rocks during the heating and cooling steps is examined in the high temperature susceptibility measurements. High temperature susceptibility measurements were used to determine whether the minerals responsible for magnetization in the rock underwent any alteration depending on the temperature, Curie temperatures and the structure of the structure were determined. It is seen that the heating curves are mostly over the cooling curves. It can be said that the rocks are rich in "Ti-Magnetite" and it has a multidomain magnetic structure.  As a result of heating processes, it is seen that in some of rocks the mineral phase transformation is carried out. 
A high percentage of Miocene-Holocene aged volcanic rocks located at the north of Lake Van and Miocene-Pleistocene aged volcanic rocks located around Karlıova triple junction found to have reliable permanent magnetization. Because only 17 of 188 paleomagnetic sites have reliable mean direction could not be obtained. 
It was observed that the inclination angles of the mean magnetization directions obtained from paleomagnetism studies were in the expected value (I = 58 °) for the region and there have been no latitudinal movement in the region from Miocene to the present day.

The youngest (Holocene and Upper Pleistocene) volcanic rocks around Lake Van are ignimbrites around the Mount Nemrut and rhyolitic domes in Nemrut Caldera. Paleomagnetic analysis results from Nemrut Mountain and surrounding area show that there are no any contemporary deformations (~4.5±6.86°) occurred after Holocene. Paleomagnetic rotations of the Pleistocene volcanic rocks show that whole region rotated ~ 10° counter-clockwise and moved as a mono-block.
A widespread volcanism dominated the Pliocene and these volcanic products spread over large areas to the north of Lake Van. Therefore, the highest paleomagnetic sites were obtained from these volcanic rocks (82 sites). In the Pliocene, the area to the east and northeast of the Erciş fault zone rotated clockwise (~ 27.1±8.17° and ~ 8.8±7.72° respectively), the area on the west of the fault zone rotated counter clockwise (~18.3±3.9°). Despite there are not any clear grouping, very close to the fault zone or inside the fault zone are affected by very small amounts of counter clockwise rotations (~5±4.9°). According to these results, the Erciş Fault / Fault Zone at the north of Lake Van may be the main factor shaping the general tectonics of the region. 
It is not possible to say a clear result due to the non-homogeneous distribution and the necessity of adequate sampling in the rotations of the Miocene aged, when the paleomagnetic results obtained from Miocene rocks are investigated.
There are remarkable differences in the rotation of the eastern, western and northern part of the Erciş fault. It is known that the north and south sides divided by the Erciş fault. However, the rotation on the eastern side of Erciş Fault may be due to the sinistral Çakırbey fault, which is not included in the recently prepared "Active Fault Map of Turkey".
Also when we made the reconstruction of the region with the obtained rotations, while counter-clockwise rotations are observed in the Miocene, clockwise rotations are seen in the Pliocene. This result indicates a change in the tectonic regime between Miocene Pliocene ages in the region.
According to the paleomagnetic results obtained from the Karlıova - Varto - Solhan region, active deformation is observed counterclockwise in the regions closer to the NAF and DAF. While the sites, which is located on the western side of the Varto Fault Zone was shown counterclockwise (~ 22±13°) rotations, the sites in the eastern side of the VFZ was shown clockwise rotations (~ 22±11°). According to these rotations, recently proposed models of development and development of the region were compared and valuable information was presented to the literature about the development of VFZ.
The paleomagnetic results obtained from the volcanic rocks of Miocene and Pleistocene around the vicinity of Tunceli – Elazığ, it is seen that clockwise rotation between the Miocene Pleistocene times. It was determined that the region was subjected to a counter-clockwise rotation due to the change in the tectonism of the region after Pleistocene.