Kuzey Kapıdağ Plütonu'nun (KB Anadolu) jeolojisi ve üç boyutlu gerilme analizi yöntemi ile yapısal özelliklerinin belirlenmesi
Geology of the Northern Kapıdağ Pluton and determination of its structural features using three-dimensional strain analysis method
Yazar: TUNAHAN ARIK
Danışman: PROF. DR. ŞAFAK ALTUNKAYNAK ; DR. ÖĞR. ÜYESİ ALP ÜNAL
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Jeoloji Mühendisliği Ana Bilim Dalı / Jeoloji Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2022
Konu: Jeoloji Mühendisliği = Geological Engineering
Dizin: Gerilme analizi = Stress analysis ; Kapıdağ yarımadası = Kapıdağ peninsula ; Petrografik özellikler = Petrographic properties ; Stratigrafi = Stratigraphy

Özet:
KUZEY KAPIDAĞ PLÜTONU'NUN (KB ANADOLU) JEOLOJİSİ VE ÜÇ BOYUTLU GERİLME ANALİZİ YÖNTEMİ İLE YAPISAL ÖZELLİKLERİNİN BELİRLENMESİ
ÖZET
Bu tez çalışması kapsamında Kapıdağ Yarımadası'nda (Kuzeybatı Anadolu) mostra veren plütonlardan biri olan Kuzey Kapıdağ Plütonu'nun (48 My) mezo ve mikro yapısal özellikleri incelenmiş ve üç boyutlu gerilme analizi yöntemi yardımı ile deformasyonun karakteri ortaya koyulmuştur. Kuzey Kapıdağ Plütonu yaklaşık 100 km2 alanı kapsamaktadır ve Erdek Kompleksi olarak isimlendirilen metamorfik temel kayalarının içerisine sokulmuştur. Erdek Kompleksi amfibolit fasiyesinde metamorfizmaya uğramış metaultrabazit, metabazit ve metapelitler ile temsil edilmektedir. Kuzey Kapıdağ Plütonu egemen olarak granodiyorit bileşimindedir. Plüton farklı alanlarda farklı mezo ve mikro yapısal özellikler sergiler. Buna göre ikiye ayrılmıştır: Bunlar homojen granodiyorit ve deforme granodiyorit'tir. Homojen granodiyorit plütonun güney kesimlerini oluşturur, holokristalen granüler ve yer yer porfirik doku sergiler. Deforme granodiyorit ise plütonun kuzey kesimini oluşturur, bu alanda birincil magmatik dokular çoğunlukla korunamamıştır. Birim, deformasyonun azalması ile dereceli olarak homojen granodiyorite geçer. İki kaya grubu da yaygın olarak mafik mikrogranüler anklavlar içerir ve aplit daykları ile kesilir. Petrografik incelemelere göre homojen granodiyorit %35-50 plajiyoklaz, %20-25 kuvars, %10-15 alkali feldspat, %5-10 biyotit ve %5 hornblend bileşimindedir. Deforme granodiyoritte ise bu bileşime epidot (%5-10) ve nadiren muskovit eşlik etmektedir. 
Kuzey Kapıdağ Plütonu kuzey kesimlerinde hem mezo hem de mikro ölçekli yapısal unsurları inceleme imkanı tanımaktadır. Kuzey Kapıdağ Plütonu mika ve feldspat minerallerinin uzaması ile gelişen foliasyon ve lineasyon gösterir. Yapılan ölçümler foliasyon düzlemlerinin baskın olarak doğu-batı doğrultulu ve kuzeye eğimli olduklarını göstermektedir. Lineasyon yönelimleri de benzer olarak doğu-batı yönlüdür ancak çok zayıf dalımlıdır (<10° D). Yönlü örnekler üzerinde yapılan mikro yapısal çalışmalar, Kuzey Kapıdağ Plütonu'nun sünekten kırılgana değişen deformasyondan etkilendiğini göstermektedir. Kuvars kristallerinde gözlemlenen satranç tahtası (chess-board) yapıları, tane sınır göçleri (grain boundary migration- GBM), kuvars ve feldspat kristallerinde gelişen tane dönme yeniden kristallenmeleri (subgrain rotation- SGR) sünek deformasyonu işaret eden yapılardır. Kuvars kristallerinde gelişen tane şişme yeniden kristallenmesi (bulging recrystallization- BLG) ve ince kesitlerde izlenen mikro faylar da deformasyonun kırılgan karaktere kadar sürekli olarak devam ettiğini göstermektedir. Bu dokusal özelliklere göre deformasyon sıcaklığı 600 ile <250°C arasında değişmektedir. Hem mezo hem de mikro ölçekte gözlemlenen C-S yapıları, mika balıkları ve σ-tipindeki feldspat kristalleri makaslamanın sağ yanal ve itilme yönünün doğuya doğru olduğuna işaret etmektedir. 
Kuzey Kapıdağ Plütonu'nda gelişen deformasyonun niteliğini ve makaslamanın karakterini anlamak amacıyla seçilen yönlü örnekler üzerinde üç boyutlu gerilme analiz yöntemi uygulanmıştır. Bu yöntem için kuvars kristalleri indeks mineral olarak seçilmiş ve Mathematica yazılım programı yardımı ile seçilen örneklerin kinematik vortisite değerleri (Wk), Flinn k değerleri, oktahedral kayma gerilmeleri ve Lode's oranları hesaplanmıştır. Bununla birlikte her örneğin temsili üç boyutlu gerilme elipsoidleri de çizilmiştir. Buna göre, örnekler 1.1 ile 5.32 arasında değişen Flinn k değerleri ve -0.64 ile +0.13 arasında değişen Lode's oranları sergilemektedir. Bu değerlere göre örneklerin büyük çoğunuğu Flinn ve Hsu diyagramlarında daralmalı (constrictional) deformasyon alanında kümelenmektedir. Örneklerin hesaplanan kinematik vortisite değerleri (Wk) 0.73 ile 0.99 arasında değişmektedir ve bu değerler örneklerin baskın olarak basit makaslama kuvvetleri altında deforme olduklarını göstermektedir. Elde edilen bütün bu veriler, Kuzey Kapıdağ Plütonu'nda gelişen deformasyonda basit makaslamanın baskın olduğuna ve deformasyonun sağ yanal transtansiyonel bir rejim altında geliştiğine işaret etmektedir.

Abstract:
GEOLOGY OF THE NORTHERN KAPIDAĞ PLUTON AND DETERMINATION OF ITS STRUCTURAL FEATURES USING THREE-DIMENSIONAL STRAIN ANALYSIS METHOD
SUMMARY
In this thesis, the meso and micro structural properties of the Northern  Kapıdağ Pluton were investigated. To better understand the character of the deformation, micro structural properties of the Northern Kapıdağ Pluton were studied by using the three dimensional strain analyses method. Northern Kapıdağ Pluton is located in the Kapıdağ Peninsula (NW Anatolia) and was intruded into the metamorphic basement rocks (Erdek Complex). It covers approximately 100 km2 area. The area is circumscribed by Turan and Ballıpınar village at the north, Ocaklar village at the south, Narlı and İlhanköy at the west and Kestanelik and the east. 
Three different rock types were identified in the field: basement rocks (Erdek Complex), Northern Kapıdağ Pluton, Southern Kapıdağ Pluton and Alluvium. The Erdek Complex consists of metaultrabasites, metabasites and metapelites which are pre-Permien in age. The metaultrabasites are formed from metaserpantinites, metapyroxenites and talcschists. Metapelites, on the other hand, are represented by micaschists, calcschists and phyllites. Metabasites are mostly consist of metabasalts and metagabbros and observed in dark grey and brown colors in the field. The mineral paragenesis of the metabasites is hornblend +plagioclase + epidote + biotite ± quartz ± alkali feldspar which indicates that the Erdek Complex was metamorphosed under amphibolite facies conditions. 
The plutonic rocks in the field are divided into two different associations. One is the Southern Kapıdağ Pluton which is upper Eocene in age and located at the south eastern part of the Kapıdağ Peninsula. It consists of granodiorite-monzogranite as the main plutonic body, with the accompany of microgranite, aplogranite and mafic microgranular enclaves. The other plutonic association that is located in the Kapıdağ Peninsula is the Northern Kapıdağ Pluton, which is the main focus of this thesis study. Northern Kapıdağ Pluton is located at the western and northern parts of the Kapıdağ Peninsula. The main plutonic body of the Northern Kapıdağ Pluton can be divided into two structurally different members. The southern part of the Northern Kapıdağ Pluton is formed from an isotropic granodiorite which presents holocrystalline granular and porphryitic texture. It shows % 35-50 plagioclase, %20-25 quartz, % 10-15 alkali feldspar, %5-8 biotite ve % 5 hornblend as the main mineral composition. Other member is the deformed granodiorite, which forms the northern part of the Northern Kapıdağ Pluton and located along norhtern shore line of the Kapıdağ Peninsula. It shows intense deformation which overprints the initial magmatic textures in most places. Deformed granodiorite shows similar mineral composition with isotropic granodiorite in which epidote (%5-10) and minor amount of muscovite are additionally observed. 
Northern Kapıdağ Pluton shows well displayed foliation and lineation developed by the elongation of feldspar and mica minerals. 101 foliation measurements were taken from the field from the Northern Kapıdağ Pluton and pole diagrams were prepared. The pole diagram show that the majority of the foliation plane have approximately east-west strike and their dip direction is towards the north. Along these foliation planes, the elongation of the mafic microgranular enclaves was observed. 54 lineation measurement were taken from the field studies. Pole diagram for the lineation indicate that the trend of the lineations are approximately east-west direction. A slight plunge in the linetaions were observed which is towards east. 
In order to conduct microstructural studies, 24 number of oriented samples were taken from the field. The microstructural studies indicate that the Northern Kapıdağ Pluton has experienced ductile and brittle deformation which developed at 600 C conditions below to the 250 oC. The highest deformation indicator in the Northern Kapıdağ Pluton is the chess-board extinction that is observed in the quartz crystals. This structure indicates that the deformation temperature of the Northern Kapıdağ Pluton has reached to the 600 oC conditions.  Another microstructre in the quartz and feldspar crystals is the myrmekite development. This structure also point out to a 600 oC of deformation temperature. The boundry between quartz crystals develop different structures under the influence of deformation. Grain boundary migration structures (GBM) were observed in the thin sections of the Northern Kapıdağ Pluton which develops between 450-550 oC temperatures. One of the other microstructures that is observed in the quartz crystals is the subgrain rotations (SGR). Subgrain rotations in quartz crystals point out to a deformation temperature between 400 and 300 oC. All these structures, together with the mesoscale foliation-lineations represent ductile deformation. Not only ductile structures were observed in the Northern Kapıdağ Pluton, but also brittle structures were common in the thin sections. The bulging recrystallization (BLG) of the quartz crystals of Northern Kapıdağ Pluton represent the 300-250 oC deformation temperatures indicating to a ductile-brittle transition. There are many microfaults and cracks observed in the thin sections which are the clear representatives of the birittle deformation. Therefore, it can be concluded that the Northern Kapıdağ Pluton has been subjected to ductile and overlaying brittle deformation, continuously.   
Both meso- and microstructural features of Northern Kapıdağ Pluton have shear sense indicators which show the direction of the movement. In mesoscale, one of the most distinctive structures is the C-S structure. C and S represent an individual plane and their angular relationship identifies the direction of the shear force. The C-S structures in the Northern Kapıdağ Pluton indicate a dextral movement, with top to east direction. Micro-scaled shear sense indicators point out to similar shear movement. The mica fish structures are one of the most important shear sense indicators. All mica fishes show top to east movement. Compatibly, the σ-type feldspar crystals also show similar sense of shear. 
Along the northeastern shoreline, the mylonitic zones are observed. These mylonitic zones are both clearly tracked in meso and micro-scale fault that is responsible from this mylonitizaion is a northwest-southeast oriented fault that is observed at the northeastern shoreline of the Kapıdağ Peninsula and elongates through the Marmara Sea. Geophysical studies and our micro-meso structural data collectively suggest that this fault is represented by a dextral normal oblique fault. 
In order to distinguish the deformation character of the Northern Kapıdağ Pluton, three-dimensional strain and kinematic vorticity analyses were conducted. These analyses were carried out on 8 different samples. Each sample were cut into three individual thin sections with perpendicular directions which makes total 24 thin sections. Quartz crytals were used as the deformation indicators and the boundaries of the crystals were drawn. By using Image J software, the perfect ellipses were drawn for each individual quartz crystal and their geometric data were generated. These data together with the foliation measurements were imported to a geological script in Mathematica software. With the aid of this script, the kinematic vorticity (Wk) numbers, Flinn k values, Lode's ratio and octahedral shear strains were calculated. The principal axes of foliation and also the deformation ellipsoids were generated. The results show that, the Flinn k values of the samples change between 1.1 and 5.32. In Flinn's diagram, the majority of the samples plot above the k=1 line which is defined as transtensional regime. Only one sample was ploted below k=1 line, indicating to a transpressional regime. Lode's ratios of the samples vary from -0.64 to +0.13. In the Hsu diagram, majority of the samples plot in the general constrictional field, only two of the samples are in the general flattening area. In order to identify the strain component of the Northern Kapıdağ Pluton, the kinematic vorticity numbers (Wk) were calculated. The Wk of the samples change between 0.73 to 0.99. The higer Wk numbers than the Wk=0.71 line points out to a simple shear domination in the deformation rather than the pure shear components. As a result, all structural properties of the Northern Kapıdağ Pluton, together with the three dimensional strain analyses indicate that the deformation of Northern Kapıdağ Pluton was developed under a simple shear dominated dextral transtensional regime.