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İstanbul Boğazı batısında gözlenen magnetik kayaçların petrografik ve jeokimyasal olarak incelenmesi

Başlık çevirisi mevcut değil.

  1. Tez No: 55827
  2. Yazar: A.BORA YALÇIN
  3. Danışmanlar: PROF.DR. IŞIK ÖZPEKER
  4. Tez Türü: Yüksek Lisans
  5. Konular: Jeoloji Mühendisliği, Geological Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1996
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 50

Özet

ÖZET Bu çalışma İstanbul'un batı bölgesinde gözlenen, nötr ve bazik magmatik kayaçların petrografik ve jeokimyasal olarak incelenmesini içerir. İstanbul Boğazı'nın batı bölgesi, güncel yüzeysel çökeller dışında, Silüriyen'den Karbonifer'e kadar yayılımını sürdürmüş olan İstanbul-Kocaeli Paleozoyik istifi, Üst Kretase yaşlı tüfit, aglomera, lav ve kireçtaşı ardışımından oluşan Sanyer formasyonu ile Pliyokuvaterner yaşlı karasal çökellerden oluşmuştur. İnceleme alanındaki magmatik kayaçlar, Paleozoyik istifti dayklar şeklinde kesen andezitik ve diabazik kayaçlar ile stok şeklinde yerleşmiş diyoritik kayaçlardan, Sanyer Formasyonu'nda ise tüfitlerle arakatkılar şeklinde gözlenen andezitik kayaçlardan oluşmuştur. Kayaçlarda yapılan mikroskopik incelemelerde, hidrotermal alterasyon sonucu mafik minerallerde kloritleşme, plajioklaslarda ise epidotlaşma gözlenmiştir. Paleozoyik istifi kesen andezitik ve diyabazik kayaçlar ile Sarıyer Formasyonu içindeki andezitik kayaçlar aynı tektonik oluşumun ürünleri olup, yitim zonu ile ilişkili, kalkalkalen ve sialik malzemece zengin bir magmadan türemiş ada yayı volkanitleridir. Palezoyik istifi kesen diyoritik kayaçlar da aynı tektonik oluşumun ürünleri olup, olgunlaşmakta olan bir ada yayı ortamında oluşmuş, yitim kökenli S-Tipi granitoyidlerdir. VII

Özet (Çeviri)

PETROGRAPHIC AND GEOCHEMICAL INVESTIGATION OF THE IGNEOUS ROCKS LOCATED AT THE WEST OF THE BOSPHORUS - ISTANBUL SUMMARY This study covers petrographic and geochemical investigation of intermediate and basic igneous rocks observed at the western side of the Bosphorus - İstanbul. The western side of the Boshporus consists of Paleozoic, Upper Cretaceous and Plio-Quaternary aged units; including recent surficial sediments. Stratigraphic sequence begins with the Paleozoic aged rocks of istanbul-Kocaeli region which are made up mainly of Upper Ordovician- Upper Silurian aged laminated shale named as the Büyükdere Shale Unit, Upper Silurian-Lower Devonian aged limestones named as the Dolayoba Limestone Unit, Lower - Middle Devonian aged shales named as the Kartal Formation, Middle-Upper Devonian aged limestones named as the Büyükada Formation, Lower Carboniferous aged cherts named as the Baltalimani Formation and Lower Carboniferous aged sandstones and shales named as the Trakya Formation. The Paleozoic aged rocks of Istanbul-Kocaeli region are unconformibly overlain by the Sarıyer Formation that consist of tuffites and agglomerates with intercalation of andesites and limestones. This unconformity is seen as thrusts but regionally observed as angular unconformity. The Sarıyer Formation is overlain by the Belgrad Formation with an angular unconformity that is made up of Plio-Quaternary aged various continental sediments such as clay, sand, gravel. Quaternary aged alluvium covers all of these formations. In this study, investigated igneous rocks are observed as andesitic and diabasic dykes and a dioritic stock in the Paleozoic aged rocks and observed as intercalations with tuffites in the Sarıyer Formation. The tunnel excavations of the Taksim-Levent subway were chosen as an investigation area for the investigation of andesitic and diabasic dykes and an a dioritic stock that cut the Paleozoic aged rocks. The width of andesitic and diabasic dykes along the tunnel section is between 5-20 m. These intrusions were observed at every 100-150 m along the tunnel section. Only one dioritic stock was observed which has 200 m width in Gayrettepe-Levent part of tunnel section. VIIIThe coast line between Sanyer-Rumelifeneri was chosen as an investigation area for the investigation of andesitic rocks in the Sanyer Formation. These andesitic rocks are intercalated with tuffites in this area. The age of tuffites in the Sanyer Formation was determined as Upper Cretaceous by paleontological examinations of fossils found in limestones lenses in the tuffites. The age of andesitic rocks was attained as Upper Cretaceous because they are intercalated with tuffites. For the purpose of petrographical and geochemical investigation 9 samples were collected from diabasic dykes, 3 samples from andesitic dykes and 16 systematic samples from dioritic stock that cut the Paleozoic rocks and 3 samples were collected from andesites in the Sanyer Formation. Totally 30 samples were collected. All samples were examined under polarisan microscope for petrographic investigations. For geochemical investigations, 14 samples were chosen out of 30 for chemical analyses. Diabasic rocks that cut the Paleozoic rocks have green-gray colored matrix with disseminated very small ferromagnesian mineral particles which black colored in the hand specimen observations. Thin section examinations indicate that elongated semi-rectangular plagioclases are surrounded by mafic minerals in ophitic texture. Samples contain 45 % of plagioclase in mineralogical composition and type of plagioclases were determined as labradorite. Diabases have chloritization of mafic minerals and epidotization of plagioclases have also quartz due to hydrothermal alteration. Andesitic rocks that cut the Paleozoic rocks were seen in gray colored matrix with disseminated medium grained plagioclases and fine grained mafic minerals in the hand specimen observations. Thin section examinations indicate that rocks are made up of matrix that consists of tiny plagioclases and phenocrysts that consist of plagioclases and mafic minerals in porphyritic texture. Samples contain over than 40 % of plagioclase in mineralogical composition and types of plagioclases were determined as oligoclase and andesine. Andesites have also chloritization of mafic minerals and epidotization of plagioclases have also quartz due to hydrothermal alteration. Dioritic rocks that cut the Paleozoic rocks have white colored matrix with disseminated mafic minerals in the hand specimen observations. Thin section examinations indicate that rocks are made up of fine and medium grained plagioclase, amphibole and quartz phenocrysts in granular texture. Mineralogical composition of dioritic sock changes from outside to inside. On the inside of stock, content of quartz is 35-40 % while 15-20 % on the outside. On the inside of stock, content of mafic minerals ( determined as amphibole due to cleavages with 124° angle) is 15-20 % while 30-40 % on the outside. As a result of these determinations, rocks are named as tonalite on the inside of the stock, and named as quartz diorite on the outside of the stock. IXAndesites that are found as intercalation in the Sarıyer Formation have gray colored matrix with disseminated fine grained plagioclases in the hand specimen observations. Thin section examinations indicate that rocks contain phenocryst of plagioclase in a fine grained of plagioclases and mafic minerals in porphyric texture. Samples contain 35-40 % of plagioclase in mineralogical composition and type of plagioclases is andesine. Samples contain percentage 30-40 of mafic minerals that completely altered to chlorite. In this study, the igneous rocks were investigated under 2 groups. The first group is named as the volcanic rocks. These rocks are diabases and andesites that cut the Paleozoic rocks and andesites that are intercalated with tuffites in the Sarıyer Formation. The second group is named as plutonic rocks. These rocks are dioritic rocks that cut the Paleozoic rocks. In the first group, all the volcanic rocks were evaluated in the same diagrams. But they were shown by different symbols to make correlations. The rocks that cut the Paleozoic rock were shown as“o”and the rocks that are intercalated with tuffites were shown as 8+" in the diagrams. The results of the correlation show that all the volcanic rocks have similar chemical properties and occurred from same magma. The results obtained from investigation of volcanic rocks are as follows. All the volcanic rocks were derived from calcalkaline magma that has sialic origin according to total alkali-silica diagram (Figure 1) and the Gottini (1969) diagram ( Figure 2). The Rittmann and Villan (1979) diagram indicates that all the volcanic rocks are orogenic region volcanics that occurred at compressional areas.( Figure3). When F1 and F2 functions of basaltic (diabasic) rock samples located at the Pearce (1976) diagram, the diagram shows that all these rocks occurred during island arc volcanism. (Figure 4) U5 50 55 60 65 70 Figure 1. Total Alkali-Silica Diagram of the Volcanic Rocks x SiO,log t °-4 0 04 08 log a Figure 2. Gottini (1969) diagram of the Volcanic Rocks OROGENİC REGION VOLCANİCS POST OROGENİC VOLCANİCS CRATONIC REGION VOLCANİCS Q2 0A 0,6. 6,8 a Figure 3. Rittmann and Villari (1979) diagram of the Volcanic Rocks 0.1 0.2 0.3 0.4 0.5 -I 1 T-» 1 ^ 1.6 4 Figure 4. Pearce (1976) diagram of the Basaltic Volcanic Rocks XIIn the second group 5 samples collected from the dioritic stock that cut the Paleozoic rocks were investigated. 4 of these samples show that these rocks are derived from calcalkaline magma and one of these shows tholeiitic magma according to total alkali-silica diagram(Figure 5). The Peacock (1931) diagram shows that these rocks have alkalic-calcic characters, alkali-lime index of rocks is 54.5 and rocks had occurred in mature consumption (Figure 6). When R1 and R2 functions of plutonic rock samples located at the Batchelor and Bowden (1985) diagram, 3 of these samples had occurred at pre-plate collision, 2 of them had occurred at post - collision uplift (Figure 7). All these properties mentioned above indicate that the plutonic rocks are the S-Type granitoids according to Bowden and oth. (1982). 65 50 55 60 70 */. SlOr Figure 5. Total Alkali Silica Diagram of the Plutonic Rocks. Normal Collision 13 O + O ğ 11 î o O I Mature Consumption + Collision I 1 1 I Early Consumption 1 A,kali J Alkali-Calcic j Calc-Alkali ' Calcic Figure 6. Peacock (1931) diagram of the Plutonic Rocks. XII< + O) (M + CO 10 ıı Pre-Plate Collision Mantle Fractionates -t.r \, \ \ \ \ \ Syn-Collision. \ \ Post-Orogenic. 1000 2000 Rl = 4Si - 11 ( Na+K ) - 2 ( Fe+Tı ) Figure 7. R1-R2 diagram (Batchelor and Bowden (1985)) of the Plutonic Rocks For the conclusions, the volcanic rocks are island arc volcanics and are derived from calcalkaline magma with sialic origin and are related with consumption. The plutonic rocks are also derived from calcalkaline magma like volcanic rocks. They are S-Type granitoids and ocurred at mature consumption. XIII

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