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ÖgeWinClbclas, a Windows program for columbite-supergroup minerals(Cambridge University Press, 2024)A Microsoft® Visual Basic software, WinClbclas, has been developed to calculate the chemical formulae of columbite-supergroup minerals based on data obtained from wet-chemical and electron-microprobe analyses and using the current nomenclature scheme adopted by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (IMA) for columbite-supergroup minerals. The program evaluates 36 IMA-approved species, three questionable in terms of their unit-cell parameters, four insufficiently studied questionable species and one ungrouped species, all according to the dominant valance and constituent status in five mineral groups including ixiolite (MO2), wolframite (M1M2O4), samarskite (ABM2O8), columbite (M1M2O6) and wodginite (M1M2M32O8). Mineral compositions of the columbite supergroup are calculated on the basis of 24 oxygen atoms per formula unit. However, the formulae of the five ixiolite to wodginite groups can be estimated by the program on the basis of their cation and anion values in their typical mineral formulae (e.g. 4 cations and 8 oxygens for the wodginite group) with normalisation procedures. The Fe3+ and Fe2+ contents from microprobe-derived total FeO (wt.%) amounts are estimated by stoichiometric constraints. WinClbclas allows users to: (1) enter up to 47 input variables for mineral compositions; (2) type and load multiple columbite-supergroup mineral compositions in the data entry section; (3) edit and load the Microsoft® Excel files used in calculating, classifying, and naming the columbite-supergroup minerals, together with the total monovalent to hexavalent ion; and (4) store all the calculated parameters in the output of a Microsoft® Excel file for further data evaluation. The program is distributed as a self-extracting setup file, including the necessary support files used by the program, a help file and representative sample data files.
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ÖgeThrace basin—an oligocene clastic basin formed during the exhumation of the rhodope complex(Wiley, 2023)Some orogenic sedimentary basins are difficult to assign to a particular category. An example is the hydrocarbon-bearing Thrace Basin in the northern Aegean. It has more than 9-km-thick Cenozoic clastic sediment, and is spatially associated with the Rhodope metamorphic core complex in the west, and with the Tethyan subduction-accretion complexes in the south, and is cut by the North Anatolian Fault and its precursors. It has been interpreted variously as an intramontane, a forearc, or an orogenic collapse basin. Here, we provide new geochronological and biostratigraphic data to constrain the tectonic evolution of the Thrace Basin. The new data indicate that as an individual depocenter the Thrace Basin has a short age span (late Eocene—Oligocene, 36–28 Ma) and more than 90% of the basin fill consists of early Oligocene (34–28 Ma) siliciclastic turbidites, deposited at rates of 1.0 km/my. Paleocurrents and new detrital zircon U-Pb ages show that the Rhodope Complex was the main sediment source. The exhumation of the northern Rhodope Complex (36–28 Ma) was coeval with the main subsidence in the Thrace Basin (34–28 Ma), and involved clockwise crustal rotation in the northern Aegean and possibly crustal flow from underneath the Thrace Basin. Crustal rotation is indicated by the paleomagnetic data, regional stretching lineations in the Rhodope Complex, and the triangular shape of the Thrace Basin. The rotating crustal block must have been bounded in the south by a sinistral fault zone; the location of which corresponds largely with the present day North Anatolian Fault. Key Points Thrace Basin is a late Eocene - Oligocene clastic basin with >90% of the sedimentary fill deposited in the early Oligocene at rates of 1.0 km/my The main subsidence in the Thrace Basin (34-28 Ma) was coeval with the exhumation of the northern Rhodope Complex (36-28 Ma), which was the major sediment source The exhumation of the Rhodope Complex and the formation of the Thrace Basin involved crustal rotation and possibly crustal flow
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ÖgeMicrobialites on the northern shelf of Lake Van, eastern Türkiye : morphology, texture, stable isotope geochemistry and age(Wiley, 2024)Lake Van, the world's largest alkaline lake, hosts some of the largest microbialite towers worldwide, which are considered as modern analogues of ancient stromatolites. This study investigates the links between microbialite evolution, geology, climate and hydrology, and the role of biotic and abiotic processes in microbialite growth and morphology. For these objectives, the northern shelf of Lake Van was surveyed by sub-bottom seismic profiling and diving, and two 9 m and 15 m high microbialite chimneys were sampled at 25 m water depth. Samples were analysed for stable oxygen and carbon isotopes, X-ray diffractometry, scanning electron microscopy and U/Th age dating. Lake Van microbialites precipitate wherever focused Ca-rich groundwater flows onto the lake floor to mix with alkaline lake water. Variable columnar, conical and branching morphologies of the microbialites indicate various processes of formation by groundwater channelling within the chimneys. Collectively, our data suggest that the microbialite chimneys have formed within the last millennium, most likely starting during the warm and humid Medieval Climate Anomaly (ca ad 800–1300), when lake level rose approximately to the present level due to enhanced Inputs of riverine Ca-rich freshwater and groundwater. Our new scanning electron microscopy observations indicate that the internal structure of the microbialites below the outer cyanobacteria-covered crust is constructed by calcified filaments, globular aggregates and nanocrystals of algal, cyanobacterial and heterobacterial origins and inorganically precipitated prismatic calcite crystals. These textural features, together with dive observations, clearly demonstrate the important role of inorganic carbonate precipitation at sites of groundwater discharge, followed by cyanobacteria and algal mucilage deposition and microbially meditated calcification in the photic zone in the rapid growth of the microbialite chimneys. Considering the close similarities of some textures with those of ancient stromatolites and meteorites, the results of this study provide new insights into the environmental conditions associated with stromatolite formation and extra-terrestrial life evolution.
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ÖgeSlope stability analysis applied to the 5th section of the Northern Marmara Motorway, İzmit, Türkiye(Springer, 2024)The Northern Marmara Motorway is a project that aims to alleviate the heavy traffic congestion in the provinces of İstanbul, Tekirdağ, Kocaeli and Adapazarı. Within the 5th section bounded by “the Motorway Port Connection Road” and “İzmit Intersection”, mass movements of slide (Y1, Y2) and flow (Y3) types were observed along the route. This study investigated the causes of mass movements in the Korucu Formation, which consists of sandstone and shale alternation. It also evaluated the support systems to prevent these movements. The analysis considered project criteria, both static and dynamic conditions, types of mass movements and triggering factors. The study identified a combination of factors, including the water table and surface waters, which lead to progressive weathering and mass movement. Stability analyses were conducted for specific right-cut slope sections. These analyses included assessments of soil structure, soil–rock mechanics, engineering geology and geotechnics, as well as examination of field and laboratory test results. These analyses aimed to comprehensively investigate and understand the factors influencing the occurrence of mass movements, particularly for km: 170 + 300–170 + 400, km: 170 + 640 and km: 175 + 297–175 + 463. At Y1, pile retaining walls are proposed using Slide2 software to reduce the slope angle from 22° to 17°. At Y2, a translational landslide occurred with recommendations for the adjustment of the slope angle and protective measures considering the disturbance factors (D = 0.3 and D = 0.5). Y3 was a flow-type movement that required protection of the slope with riprap due to the different geological conditions and disturbance factors. This study underlines the need for a comprehensive geological analysis and structural measures to ensure safety in these areas.
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ÖgeUluslararası katılımlı 9. jeokimya sempozyumu bildiri özetleri kitabı: Aydın, 17–20 Ekim 2022(İTÜ Yayınevi, 2022-11-20)