Abstract
The subject of the doctoral thesis is the investigation of the genesis mechanism of palygorskite-smectite deposits in the Ventzia basin, located in the Western Macedonia region, between the prefectures of Grevena and Kozani. In total, 81 samples were collected, including samples from fieldwork and two core drillings from the Pefkaki, Piloroi, and Harami mine/sites. Sampling was conducted in a manner that allowed for the most effective and precise selection of samples from all sides toward the center of the basin. Field samples and drillings were obtained from GEOELLAS-S.A. mines, with the necessary permits, and also from their peripheral areas, as deemed necessary. The samples underwent lithological and granulometric analysis. Specifically, the laser diffraction method was applied to the<2mm fraction. The results of the granulometric analysis indicate that the samples are primarily composed of silt, followed by sand, and clay as the least dominant component. Mineralogical analysis of t ...
The subject of the doctoral thesis is the investigation of the genesis mechanism of palygorskite-smectite deposits in the Ventzia basin, located in the Western Macedonia region, between the prefectures of Grevena and Kozani. In total, 81 samples were collected, including samples from fieldwork and two core drillings from the Pefkaki, Piloroi, and Harami mine/sites. Sampling was conducted in a manner that allowed for the most effective and precise selection of samples from all sides toward the center of the basin. Field samples and drillings were obtained from GEOELLAS-S.A. mines, with the necessary permits, and also from their peripheral areas, as deemed necessary. The samples underwent lithological and granulometric analysis. Specifically, the laser diffraction method was applied to the<2mm fraction. The results of the granulometric analysis indicate that the samples are primarily composed of silt, followed by sand, and clay as the least dominant component. Mineralogical analysis of the total samples was conducted using X-ray diffraction(XRD). The mineralogy of the clay minerals was determined through oriented, glycolated, and heated samples using XRD. The quantitative determination of mineral phases was performed using the method of the external standards. Five external standards were prepared with the participation of palygorskite-smectite-serpentinite-quartz, as well as six external standards with the participation of palygorskite-smectite-calcite and palygorskite-smectite-dolomite in specific ratios. The chemical composition of the bulk samples was determined in a certified laboratory abroad. The determination of the chemical composition of the clay fraction(<2μm) of the samples was performed using a portable X-ray fluorescence device(pXRF). The results of mineralogical and chemical analyses reveal a clear influence of ultramafic rocks and formations of the Mesohellenic Trough on the clastic materials of the deposition basins. To detect the morphology and mineralogy of the clay samples(<2μm), samples rich in palygorskite, rich in smectite, and mixed samples from the three locations/mines were selected. The analysis was conducted using field emission scanning electron microscopy(FESEM-EDS). A representative mixed sample with grain size<2μm, was studied using transmission electron microscopy(TEM) in order to identify genetic or other relationships between palygorskite-smectite crystals. To evaluate the diagenesis of the examined sedimentary formations, the δC13and δO18 isotopes were determined in selected grains of secondary carbonate minerals (calcite, dolomite ,and/or aragonite) that were isolated from the examined samples. Fourier-Transform-Infrared-Spectroscopy (FTIR) was applied to representative samples rich in smectite, palygorskite, and mixed samples for the precise determination of their di-or trioctahedral character. The results of the mineralogical analysis indicate a close geochemical relationship between smectite and palygorskite. The chemical formula of smectite was found to be:[Na(0,000-0,425)Ca(0,000-0,142)K(0,000-0,036)][Ti(0,023-0,770)AlVI(0,251-1,195)Fe2+(0,481-0,770)Mg(0,588-1,508)][Si(3,960-3,981)AlIV(0,019-0,040)]4O20(OH)2, while that of palygorskite is:[Na(0,297-2,848)K(0,000-0,004)][Ca(0,141-0,844)AlVI(0,250-0,745)Fe2+(0,254-0,676)Mg(1,633-3,022)][Si(7,932-7,989)AlIV(0,011-0,068)]8O20(OH). Scanning and transmission electron microscopy images demonstrate the direct genetic origin of smectite from palygorskite. The FTIR results reveal that palygorskite exhibits both di-tri-octahedral character, while smectite is characterized as di-octahedral. Finally, the results of the C13and O18 isotopes indicate that the paleoenvironment conditions of the study area is characterized by alternating warm and wet periods with dry to semi-arid periods. Finally, the depositional environment is characterized as a distall lower fan–lacustrine margin(of an alkaline lake).
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