Determination of the concentrations of methane, carbon dioxide, nitrogen, oxygen, argon was performed with homemade NIER mass spectrometer. Isotopic composition of carbon dioxide, isotopic composition of methane, isotopic composition of deuterium in methane was determined with Europa-Scientific IRMS with an ANCA-TG preparation module and Thermo Delta XP GC-TC/CF-IRMS coupled to a TRACE GC analyzer. Total alkalinity of groundwater was measured by Gran titration. Major cations were analyzed by ICP-OES and anions by IC method. Isotopic composition of dissolved inorganic carbon was determined by MultiflowBio preparation module. The stable isotope composition of sulphur was determined with a Europa Scientific 20-20 continuous flow IRMS ANCA-SL preparation module. Concentrations of tritium were determined with the electrolytic enrichment method. PHREEQC for Windows was used to perform thermodynamic modelling. The average coalbed gas composition in the coalbed seam is approximately carbon dioxide: methane ) 2:1, where a high proportion of CO2 is adsorbed on the lignite structure, while methane is present free in coal fractures. It can be concluded that isotopic composition of carbon in methane from -70.4‰ to -50.0‰ is generated via acetate fermentation and via reduction of carbon dioxide, while isotopic composition of carbon in methane values range from -50.0‰ to -18.8‰, thermogenic methane can be explained by secondary processes, causing enrichment of residual methane with the heavier carbon isotope. Isotopic composition of deuterium in methane range from -343.9‰ to -223.1‰. Isotopic composition of carbon in carbon dioxide values at excavation fields range from -11.0‰ to +5‰ and are endogenic and microbial in origin. The major ion chemistry, redox conditions, stable isotopes and tritium measured in groundwater from the Velenje Basin, suggest that the Pliocene and Triassic aquifers contain distinct water bodies. Groundwater in the Triassic aquifer is dominated by hydrogen carbonate, calcium, magnesium and isotopic composition of dissolved inorganic carbon indicating degradation of soil organic matter and dissolution of carbonate minerals, similar to surface waters. In addition, groundwater in the Triassic aquifer has isotopic composition of oxygen and isotopic composition of deuterium values which plot near surface waters on the local and global meteoric water lines and detectable tritium reflects recent recharge. In contrast, groundwater in the Pliocene aquifers is enriched in magnesium, sodium, calcium, potassium, and silica and has alkalinity and isotopic composition of dissolved inorganic carbon values with low sulphate and nitrate concentrations. These waters have likely been influenced by sulfate reduction and microbial methanogenesis associated with coal seams and dissolution of feldspars and magnesium-rich clay minerals. Pliocene aquifer waters are also depleted in heavier oxygen isotope and heavier deuterium isotope and have tritium concentrations near the detection limit, suggesting these waters are older.
B.03 Paper at an international scientific conferenceCOBISS.SI-ID: 27659559
Diploma work was performed at Natural Science faculty in Ljubljana and describes different types of occurances of carbonate mineralizations (macroscopic and microscopic description) and their geocheical characteristics from excavation field -50C Velenje Basin. Besides occurances of mineralizations also description of petrological and microscopic characteristics of lignite from excavation field -50C are given. The intramontane Velenje coal basin located in N/NE part of Slovenia formed in Pliocene and Pleistocene as a result of multiphase strike-slip tectonics in the Periadriatic fault system. In the Velenje basin formed the biggest lignite seam in Slovenia that is also one of the world's biggest lignite seams. Lignite seam is located directly under groundwater discharging trhough Pliocene and Triassic strata. We suppose, that groundwater is connected to carbonate mineralization, but its precise age was still not determined. The collected samples originate mostly from the -50C excavation field, wich is located in the uppermost parts of the Velenje lignite seam. The interraction between the coalbed gas CO2 and the highly mineralized water from the pliocene aquifer has resulted in the precipitation of carbonate minerals forming various syngenetic crystalization forms: laminas, lenses, detrital matrix dispersed with carbonate , replacements of xilitic fragments, incrustrations around them and epygenetic flowstone. The highest carbonate content and lowest content of organic matter is found within the carbonate replacements of xilitic fragments. Incrustrations are formed around different organic pieces in the form of fibrous calcite minerals, which precipitated in the open area resulting from shrinking due carbonization process. Laminas are probably a shape of incrustrations, beacuse almost every laminae, has some kind of elongated organic matter in the ceneter. In almost every analyzed sample calcite spherules of different shapes and sizes are present. The chemical composition of the aquifer water played a vital part in the formation of spherules, because their formation requires the specific chemical environment. At least part of the mineralization took place already in the early digenesis, synchronous to shrinkage of organic matter.
D.10 Educational activitiesCOBISS.SI-ID: 1138782
Current research ongoing in the Velenje coal sedimentary basin were presented at Istituto Nazionale di Geofisica e Vulcanologia Italy (INGV), Palermo. INGV cooperates in the scope of research projects as partner and performs additional measurements to obtain QA/QC assuarance of results of coalbed gases. The topic included application of different geochemical methods to evaluate biogeochemical processes occurring in the Velenje coal sedimentary basin such as: 1) hydrogeochemical and isotopic characterization of groundwater and their interactions with surface waters, 2) distribution, composition and origin of coalbed gases in sedimentary basin, distribution of coalbed gases in advancement of working face, and 3) petrological, geochemical, microscopic and isotopic characteristics of lignite and carbonate mineralization from exit/delivery roadways and excavation fields.
B.05 Guest lecturer at an institute/universityCOBISS.SI-ID: 27958823