Ankara – Çubuk bölgesi agat oluşumlarının jeokimyasal ve mineralojik incelenmesi
Geochemical and mineralogical investigation of agate around Ankara – Çubuk
Yazar: ALEV KAN BOSTANCI
Danışman: PROF. DR. MEHMET SEZAİ KIRIKOĞLU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Jeoloji Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Jeoloji Mühendisliği = Geological Engineering

Özet:
Bu tez çalışması, Ankara ili Çubuk ilçesinin doğu ve kuzeydoğusunda yer alan Susuz, Kuyumcu, Bodurlar, Camili köylerinde ve çevresinde yataklanan agatların jeokimyasal ve mineralojik-petrografik özelliklerini kapsamaktadır.
Andezitik ve riyolitik birimlerde kanal dolgusu olarak gelişen ayrıca kendine özgü çubuksu kristalleri bulunan çubuk agatları volkanik istif içinde geneldedağınık ve düzensiz nodüller halinde yataklanmış olup, bölgede makroskobik özelliklerine gore farklı tiplerde agat belirlenmiştir.Belirlenen agatlar türlerinin isimleri Çubuk/Tüp agat, Yıldız agat, Thunder egg agat, Amigloidal (bademsi) agat, Uruguay tipi agat, Brazilya tipi agat olarak verilmiştir.Çatlak sistemleri içerisinde görülen agatların kalınlıkları 1mm.'den 20 cm. kalınlığına kadar, bağımsız nodüllerin büyüklükleri ise 5cm.-30cm. arasında değişmektedir.  İncelenmek üzere çalışma alanından ana kayaç ve agatlardan sistematik bir şekilde örnekler alınmıştır. Alınan bu örnekler uygulanacak analiz türüne gore numune hazırlama işlemlerinde geçmiştir. İnce kesit, asitte çözme ve pellet gibi işlemler uygulanarak numuneler analizlere hazırlanmıştır.
Yapılan optik-mineralojik analiz sonuçlarına gore, agatlarda ve bulundukları ana kayaçlarda incelemeler yapılarak tipik agat gelişimi görülmekte olup ana kayaçlarda feldispat, plajiyoklas, kuvars, biyotit ve opak mineraller, agat oluşumlarında opal-CT, kalsedon ve kuvars tespit edilmiştir.  Taramalı elektron mikroskop analiz sonuçlarına göre; agatların farklı SiO2 bantlarından oluştukları belirlenmeye çalışılmıştır.XRD (X-ışınları Difraktometresi) analizi ile agatların mineral bileşimleri tespit edilmiştir. Jeokimyasal  incelemelerle XRF (X-ışınları Fluoresansı) analizleri ile tüm kayaç analizleri yapılarak volkanik birimlerin major oksit, iz ve nadir toprak elementleri içerikleri belirlenmiştir.Ana kayaçlarda jeokimyasal sonuçların birbirleriyle uyumlu olduğuve böylece aynı kökene sahip oldukları görüşü ortaya çıkmıştır.13 adet farklı renklerdeagat bantları ayrılmış. Bu bantlarınICP-MS (Inductively Coupled Plasma – Mass Spectrometer) analiz sonuçlarına göre iz ve nadir toprak elementleri değişimleri ve dağılımları saptanmıştır.Bantlara göre farklı element dağılımları gözlenmiştir.Sıvı kapanım çalışmaları kapsamında incelemeler yapılmış, fakat hazırlanan kesitlerde sıvı kapanım oluşumları tespit edilememiştir.Sahada ekonomik olarak düzenli bir agat üretimi yapılmamaktadır.Fakat yöre halkı tarafından araziden toplanarak engelli vatandaşlar içim kurulan küçük atölyelerde işlenmekte ve ekonomiye kazandırılmaktadır.

Abstract:
This study comprises the determination of the geochemical and mineralogical-petrographicalcharacteristicsof agates deposited aroundSusuz, Kuyumcu, Bodurlar and Camili villages that are locatedto the northeastern and east part of the Çubuk district (Ankara).Agates have been used since the Chalcolithic period andhave come up today by not losing its significance. Alsothey have become more important gemstones for scientific envirenmet due to they could not be produced in the laboratory. They are typical with having significantly different color from each other and  matte layer, with banded or striped appearance. These different layers and transparency of the colors are similar banded appearance may be less obvious, although typical agate, always sharply contrasting colors indicate bands.
In this study, geochemical evaluation and characteristics of the causes of bands with different colors of agate coloration was targeted.This region has volcanic characterictics and lots of types of agates that are known by all world. Bu agates in the field are not producedregularly and economically.An important part of our country run gem isgemstones with SiO2 composition (quartz belongs to a group). This gem of the bedding area where mostly concentrated in the west of Turkey but also in areas of volcanic activity are observed. The most common and gem quality material in these units are agates.

Ankara-Çubuk region is the basin of aa compression. In eastern and western parts of the region are a major fault. Also available in small faults in the region and they are most likely formed by the influence of regional volcanism.Agate is disordered in the study area and are free. Volcanic units dissociate from the liberalization of the natural ways of the agate is processed in small workshops convened by the locals.
First of all, literature was searched and methods were determined in this study. Hoverwer, in our country, it is observed that there are limited studies about agates.After searching literature, the investigation field was visited and the samples for analyzingwere collected systematically.All samples were prepared according to analysis methods. For optical mineralogical and fluid inclusion investigation, thin sections were prepared properly. In addition, all samples were grinded until 40 micron. For geochemical analysises, the samples were solved within hydrochloric acite, nitric acid, hydrofluoric acid and boric acite in microwave device. Whereas the main rock samples were pressed and made pellets to analysis in X-Ray Fluorescence for identifying their major oxides. The geochemical composition of the host rocks of the study area has been identifiedas rhyolite, according to geochemical data. Optical mineralogy studies were identified the glassy matrix and mineral distribution indicates as trakianzite. This dilemma, giving rise to volcanism and create acidic composition and crystallization of magma high content of silica matrix is the participation of non-silica materials.So it is thought that the main rock compositon shows as rhyolite.
Suludere (1976), Ankara-Rod in Meşeli, Lower Orders, grandfathers vicinity geology of the working volcanic tuff, acid lava and basic lava flows as a group have also locally small-scale formation of pearlite have stated that.
Agates in the study area have been seen different forms due to theirmacroscopical features. Their names are stick/tube agates, star agates, thunder egg agates, amygdaloidal agates, Uruguay (gravitational) type agates and Brazilian type agates. Some of them are formed as their combination, like Uruguay (gravitational) type and thender egg.
Petronek J. (2004), found in basaltic rocks seen in agate banding, and gravitational (Uruguay type) as well as adezyonel (Brazilian type) banding, has argued that is controlled by the climate.The thickness of the agates in the veins and cracks in therock units vary from 1 mm to 20 cm whereas agates in the gas vesicles have athickness varying from 5 cm to 30 cm.
The optical - mineralogical analysis based on the results agate and their host rocks making the surveys typically agate development is evident on the main rocks feldspar, plagioclase, quartz, biotite and opaque minerals, agate formation in the opal- CT (C:cristobalite and T:tridimite), chalcedony and quartz have been identified. 
The study area compared to the host rocks of rhyolite composition is determined as geochemical data. Optical mineralogy studies identified the glassy matrix and with mineral distribution indicates trakianzit. This dilemma, giving rise to volcanism I create acidic composition and crystallization of magma high content of silica matrix is the participation of non-silica materials.
Mineralogical composition in the bands of the agates was determined by using XRD (X-Ray Diffractometer) analysis method. Their composition is generally consist of quartz, opal-CT (C:cristobalite and T:tridimite), chalcedony. All of them are polymorphous of SiO2. Their composition is same, on the other hand their sizes of crystals are different. Moreover, opal-CT has also H2O in its crystal structure.
According to analysis by scanning electron microscopy; they are composed of different types of agate band was to determine SiO2 .
With geochemical studies of whole rock analyzes were made by XRF (X-Ray Fluorescence)analysis of major oxides and trace element contents of volcanic units have been determined. Spider diagrams are formed with the result of these analysises. According to spider diyagrams, concentration of trace and rare earth elements in the main rock are generally compatible. So it is said that their origin is same. While some elements like Rb, Th, Ce, Pb, Y, Dy are growed rich, some elements like Nb, U, P,Eu, Ti become poor concentration.
Whereas by using some volcanic rock classification diyagrams such as TAS (Middlemost   1994), Jensen (1976) and AFM plot (Irvine and Baragar 1971),the main rock were identified asarhyolites. 
Whereas by using some volcanic rock classification diyagrams such as TAS (Middlemost 1994), Jensen (1976) and AFM plot (Irvine and Baragar 1971) ,the main rock were identified as a rhyolites.
The main chemical composition of rock samples as a result of taking into consideration the diagrams used has been found to be generally rhyolite. These cases do not overlap with the optical mineralogical studies are also consistent with previous studies.
According to the results of ICP - MS (Inductively Coupled Plasma – Mass Spectrometer)analysis of separated 13 different colored agate band elements in different variations and distribution were determined. Concentration of trace and rare earth elements in the agates are not compatible. Generally, Eu concentration of all samples becomes poor.Wang, Y. and Merino, E. (1995), in basalt formation of agate, chalcedony fibers and trace element geochemistry worked on bending. Also in basalts banding in agate and views on the origin of the fibrous structure, and have found that there are two mechanisms during the formation of agate have revealed.
Goetz, J. (2001), agate formation and agate forming the origin of fluids collected information about the world to different eighteen locations of different ages from the very acidic, intermediate and basic volcanic received from agate samples of trace elements and stable isotope analysis has worked with. As a result of agate and associated quartz shells isotope deuterium and oxygen isotopic composition of samples of different positions and individual differences in the samples revealed agate. Researchers, for different fluid compositions, nucleation temperatures calculated agate, consequently, from 50 ° C to 250 ° C as stated temperature scale.Gül B. (2006), Ankara-rod region of volcanic rock mineralogy, petrography and geochemistry accordingly prepared the master's thesis on the mineralogical and petrographic description Roseinecel. As a result, overall bütünvolkanik components of rock samples; plagioclase, amphibole, biotite, pyroxene and opaque minerals has indicated that. Pyroclastic rocks in his XRD studies, however, opal-CT, clinoptilolite, calcite, mica, quartz, feldspar, kaolin and clay presence was detected.
Goetz, J. (1999), agate structure and luminescence behavior across the globe, specific locations, different volcanic rocks, taking agate and quartz shell samples and the Electron Paramagnetic Resonance (EPR), katadolüminesans (CL) trace element analysis and examined. Goetz agate all the examples of the results of the research have been identified aparamanyetik centers and katadolüminesans microscopy and quartz agate shells have different internal structures and zoning studies have suggested.Fluid inclusion studies carried out within the scope views, but the formation of fluid inclusionswere not detected in the sections that were prepared.So, in the future, more samples will be prepared and searched for fluid inclusion to learn about temperature conditions of agates formation.A map of the study field was prepared by using the map of MTA (Mining Research and Exploration). Corel Draw X6 programme was used for mapping and other geological sectional shapes of figures, and also GCDKit for the preparation of geochemical and spider diagrams was used.