minerology

CLAY MINERALOGY AND DIAGENESIS OF K-BENTONITES OCCURRING IN THE DEVONIAN YILANLI FORMATION FROM NORTH WESTERN ANATOLIA (BARTIN-ZONGULDAK) &Uuml / nl&uuml / ce, &Ouml / zge M. Sc., Department of Geological Engineering Supervisor: Prof. Dr. Asuman G&uuml / nal T&uuml / rkmenoglu January 2013, 80 pages Yellowish brown and gray-green colored K-bentonite horizons revealing thicknesses up to 60 cm are exposed within the limestone-dolomitic limestone successions (Middle Devonian-Lower Carboniferous Yilanli formation) deposited on a shallow marine carbonate platform at Zonguldak and Bartin area in the western Black Sea region. In this study, bentonite samples collected from two different locations / Gavurpinari quarry and Yilanli Burnu quarry are investigated by means of optical microscopy, X-ray powder diffraction analyses (XRD), both scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis, high resolution transmission electron microscopy (HR-TEM) and inductively coupled plasma mass spectrometry (ICP-MS) in order to reveal their mineralogicalgeochemical characteristics and understand their origin and evolution. Illite is determined as the major phyllosilicate mineral in K-bentonites. Additionally, kaolinite and illite-smectite mixed-layer clay minerals are also detected in some samples. As non-clay minerals calcite, dolomite, quartz, gypsum, feldspar, pyrite and zircon are present in these K-bentonites. Crystal-chemical characteristics (K&uuml / bler index-KI, intensity ratios (Ir), illite polytypes (%2M1), (d060) of illite minerals from the two different sampling locations were investigated. Their KI values (for Yilanli Burnu sampling location varying between 0.47-0.93 (with an average of 0.71 &Delta / &deg / 2&theta / ) / for Gavurpinari quarry sampling location varying between 0.69-0.77 (with an average of 0.72 &Delta / &deg / 2&theta / )) / % of swelling component (smectite-max 5%) and crystallite thickness (N=10-20 nm) indicate that these illites were affected by high-grade diagenetic conditions. Similarly, illite polytype ratios (%2M1/(2M1+1Md)) range between 20-50% (with an average of 36%) for the Yilanli Burnu quarry samples, whereas, these ratios are between 25-45% (with an average of 37%) for the Gavurpinari limestone quarry samples. Illite polytpe data also supports a high-grade diagenetic origin possibility of K-bentonites. Illite d060 values ranges between 1.491-1.503 &Aring / , (with an average of 1.499 &Aring / ) which reflect the octahedral Mg+Fe compositions are varying between 0.27-0.51 and thus approach the ideal muscovite-phengite values close to dioctahedral muscovite composition. Based on the data obtained from this study, volcanic ash was firstly transformed into a smectitic I/S mineral in early stages of sedimentation and burial diagenesis. This initial smectite was then be transformed into a highly illitic I/S, and finally illite by diffusion of elements into and out of the bed, during Devonian. Mineralogical-petrographical data points out that these K-bentonites evolved in a high-grade diagenetic environment (approximately 100-150 &deg / C) from the products of volcanic eruptions having yet unknown source and distance during Middle-Late Devonian time.

This thesis investigates the morphological, chemical and growth characteristics of zircon mineral in relation with the granitoid petrology. Physical and chemical variations recorded within zircon crystals during evolution of the Central Anatolian Granitoids are discussed. The thesis focuses on twelve granitoid samples from the Ekecikdag, Aga&ccedil / &ouml / ren and Terlemez regions from western part of central Anatolia. These granitoids are differentiated into S- and H-type granitoids on the basis of field, petrographical and whole-rock geochemical aspects. In granitoids concerned, zircon is associated with biotite, allanite and plagioclase, and zircon populations mainly comprise P- and S-type zircon crystals, with rare G-, L- and J-types. Typology method combined with cathodoluminescence imaging revealed that S- and H-type granitoids show intrusive aluminous autochthonous and hybrid character, respectively. Zircons generally have euhedral to subhedral cores exhibiting zoning, although sometimes faint, but inherent and embayed cores also exist. Large scale, first order, and/or small-scale second order oscillatory zoning and effects of late stage recrystallization are observed within zircon crystals. Multi-corrosion zones within zircons are characterized by sharp changes in crystal forms with decreased Zr and Si, and increased U, Th and REE+Y contents, beside infrequent increase in Hf, Sc, Ta, Ti, Ca, Al and Fe elements. These zones are interpreted to be formed by transient heating of the resident felsic magma due to mafic melt contribution, at the time of mixing/mingling processes of the H-type granitoids, and then zircons re-grow in magma source reflecting a mafic character. Corrosion stages within zircons of S-type granitoids, on the other hand, were probably formed by mantle-derived melts producing heat for resorption of zircons without direct contribution.

The purpose of this study is to understand the geological, petrographical, mineralogical and geochemical characteristics of analcime-bearing tuffs in the Biga Peninsula and to determine formation process of these tuffs. The study area lies between Ayvacik and K&uuml / &ccedil / &uuml / kkuyu. The rock units are pre-Eocene basement rocks, Miocene Behram Volcanics (Arikli Tuff, andesite, andesitic agglomerate), Pliocene volcanics, Miocene lacustrine sediments (K&uuml / &ccedil / &uuml / kkuyu Formation) and Quaternary alluvium. Analcimes which are found in Arikli Tuff are the main objective of this study. Detailed petrographical, mineralogical and geochemical studies were caried out on the Arikli Tuff samples by using petrographical microscope, X-ray diffractometry, scanning electron microscopy, diffrential thermal analyses inductively coupled plasma &amp / #8211 / mass spectrometry and optical emission spectrometry. Fine-grained and coarse-grained analcime crystals in Arikli Tuff were determined by their colorless, isotropic, trapezohedral and low relief. In addition to petrographic study, SEM and XRD methods also confirmed the presence of analcime. Two modes of occurrences were determined by the petrographical and mineralogical studies / coarse-grained euhedral or anhedral crystals in cavities and pumice fragments and single crystals or clusters of fine-grained analcimes embedded in the matrix. It was stated that there are two types of formation of analcime / alteration of volcanic glass and precipitation from alkaline solution based on petrographical and SEM studies. Geochemical methods, moreover, support the formation types.

The aim of this study is to extract information about mineral distribution and percentages of Oymaaga&ccedil / granitoid (Beypazari-Ankara) by using remote sensing techniques. Two methods are applied during the studies which are spectral analysis and Crosta techniques. Spectral measurements are done for fresh and weathered samples collected at 32 locations. Mineral percentages are calculated using spectral mixture analysis for each sample by considering main, accessory and secondary mineral content of granodiorite. A total of 10 endmembers for fresh samples and 15 for weathered samples are used. USGS spectral library data is utilized through the analyses. For Crosta technique (image analysis) the multispectral ASTER satellite image is used. Five alteration minerals are discriminated and their maps are generated during this analysis. Interpretation and comparison of the results of both methods and testing these results with the existing petrographical and geochemical data indicate that: 1) according to the results of both spectral analyses and Crosta technique a zonation is not observed in the granitoid, 2) comparison of the results for alteration minerals of these two analyses are partly compatible but not exactly similar, 3) Results of spectral analysis do not fit geochemical nor modal analyses because of inconsistency of the data sets.