This study is intended to clarify the depositional environment of a 180-m-thick, immature, limy Middle Miocene oil source rock interval, cored in the Zala Basin, western Hungary. For this purpose, a highly interdisciplinary approach was applied combining simple, standard micropaleontological, isotopic, and organic geochemical methods, rarely applied together. Foraminifera were studied for estimating bottom oxygenation and water depth, while nannoplankton biostratigraphy permitted for estimating the rate of sedimentation. The studied source rocks were deposited in a rather shallow sea, below well-oxygenated bottom water. The abundant epiphytic foraminiferal fauna proves that the bottom was densely inhabited by benthic algae, while the high δ13Corg (>–22‰) clearly indicates massive benthic algal contribution to the kerogen. Mass accumulation rate of the limy upper part of the NN5 nannoplankton biozone, the oil source interval included, was very high (551 t/m2/Ma). In spite of moderate productivity and good oxygenation of the bottom, rapid accumulation of carbonate, produced partly by benthic algae, assured both the great relative weight of the marine organic components and their good preservation. Our results provide the first proof for the possibility of a major contribution of benthic algae to oil-prone kerogen.
The pre-Cenozoic basement of central Hungary is partly made up of different types of carbonate rocks. These carbonates are often good hydrocarbon reservoirs, and hydrocarbon production is significant in this region in Hungary. Nonetheless, the petrography of the reservoir rocks has not yet been investigated in detail. In this study, the results of the investigations of the lithology of a carbonate hydrocarbon reservoir from central Hungary (Gomba Field) are presented. Based on this work, two types of pure limestone, a dolomitic limestone and a polymictic breccia, could be distinguished in the study area. The limestone types are similar to the Kisfennsík Limestone Member and the Berva Limestone of the Bükk Mountains, but they contain significant amounts of framboidal pyrite and dead oil as vein fillings. The breccia is predominantly composed of angular carbonate clasts and minor metamorphic and sedimentary rock fragments in a chaotic pattern. The breccia has some grains that may be speleothems (e.g., stalactite or stalagmite) based on their structure and isotopic compositions. The fabric of the breccia suggests that it may have been formed by fluid-related processes. Cross-cutting relationships of the veins and petrography of the vein fillings suggest that there are four different fracture generations and two different hydrocarbon migration phases to be distinguished. The composition of the hydrocarbon-bearing fluid inclusions related to the second migration event is similar to the crude oil currently produced from the Gomba Field. During the Eocene, the Triassic basement was buried and brecciated. Subsequently, a primary hydrocarbon migration can be assumed, but the hydrocarbons became overmature, apparently due to the high temperatures of the burial environment. Finally, an uplift phase began and the youngest fracture generation formed, which serves as a primary pathway for the more recent hydrocarbon migration.
Mantle peridotites are interpreted as either residues after partial melting and melt extraction or products of igneous refertilization of refractory peridotites. The simple distinction between these models is difficult to assess because in chemical variation diagrams, both processes lead essentially to the same results. The only exception is the Ti-in-Cpx versus Ti-in-whole-rock plots, which can successfully discriminate between these models. In this study, a modified version of Ti-in-Cpx versus Mg#-in-olivine plots was applied to ∼1,500 spinel peridotite xenoliths from worldwide localities. The results showed that the vast majority of shallow mantle samples are consistent with the partial melting model; however, a minority of samples may indicate refertilization of formerly refractory mantle domains.
The Zagros Orogenic Belt includes the Fold and Thrust Belt, the High Zagros Belt, the Outer Zagros Ophiolitic Belt, the Sanandaj–Sirjan Metamorphic Belt, the Inner Zagros Ophiolitic Belt, and the Urumieh–Dokhtar Magmatic Belt. We divide the High Zagros evolutionary history into five stages: (1) triple junction formation, (2) continental lithosphere rifting, (3) generation, spreading, and maturation of the Neotethys Ocean, (4) subduction of the oceanic lithosphere, and (5) collision. The Neotethys triple junction, located at the southeastern corner of the Arabian Plate, formed during the Late Silurian–Early Carboniferous. Subsequently, this triple junction became a rift basin due to normal faulting and basalt eruption. The rifting stage occurred during the Late Carboniferous–Early Permian. Thereafter, extension of the basin continued, leading to spreading and maturation of the Neotethys oceanic basin during the Late Permian–Late Triassic. Probably at the end of the Late Triassic, closure of the Paleotethys Basin caused the initiation of two northeastward subductions: (1) oceanic–oceanic and (2) oceanic–continental. Oceanic–oceanic subduction continued until the Late Cretaceous and was terminated by the emplacement of the Outer Zagros Ophiolites, whereas oceanic–continental subduction continued until the Middle Miocene. Subduction in the southern Neotethys Basin between the Arabian and Central Iran Plates caused a tensional regime between Sanandaj–Sirjan and Central Iran, and the formation of a back-arc basin that by its closing led to the emplacement of the Inner Zagros Ophiolites during the Late Cretaceous.
Stone masonry arch bridges in North Hungary represent cultural heritage values. For the maintenance and preservation of these bridges detailed mapping of lithologies and weathering forms are required. The purpose of this paper is to present the identified lithotypes, their conditions (weathering grade) and their petrophysical properties by using in situ lithological mapping, documentation of weathering forms, non-destructive tests and laboratory analyses. Furthermore these analyses demonstrate the difficulties of characterization and diagnostics of the historical construction materials. Additionally the results of condition assessments and the properties of the four different dimension stones from four different sites provide examples for the large dissimilarities regarding the strength parameters. The above-listed parameters are required as input data for stability calculations and modeling of these structures.
The paper provides information on the mechanical properties of granitic rocks that were subjected to heat. Two types of granitic rocks were tested under laboratory conditions at temperatures of 23 °C, 300 °C and 600 °C. The granitic rock from Bátaapáti (Mórágy Granite) is a pinkish leucocratic monzogranitic type while the second type is grey granite from Mauthausen (Austria). The samples were placed in furnace and temperature raised to 300 °C. Other set of samples were heated to 600 °C. Mechanical tests were performed on non-heated and heated samples and the test results were compared. Heating to 300 °C caused a slight increase in the uniaxial compressive strength and in indirect tensile strength, with reference to the samples kept at 23 °C. A drastic drop in both values was observed when samples were heated to 600 °C. The density of the samples did not show a major change up to 300 °C. On the contrary, a decrease in ultrasonic pulse velocity was observed, with an additional significant loss when samples subjected to 600 °C were compared to the reference samples of 23 °C. This decrease can be related to the initiation of micro-cracks. With increasing temperature the Young modulus of both granites was reduced.
This paper aims at determining the behavior of thermal water brought to surface and how this might impact reinjection wells and the rock during reinjection. The biggest problem is that reinjection wells are predisposed to choking. We searched for a method to examine this process, including a model for physico-chemical changes in the water—rock interaction. Two different samples of powdered rock (designated α and β) were analyzed using thermal water samples from production and reinjection wells. The pH shows significant differences between the samples from wells where free water treatment was carried out, and those from the aerated thermal waters, as well as for the rock sample. Basically, a decrease in sediment volume can be obtained by increasing the pH. The salt effect was more coherent. Its result was an interesting case of W-shaped graphs from the producing well. On the other hand there is virtually no difference between the samples with acid titration.
This article evaluates the known rare earth elements (REE), Ti and Li occurrences and exploration potential in Finland, based on existing data combined with new geochemistry and mineralogy, heavy mineral studies, geophysical measurements, geologic mapping and recent drilling of new targets.
The potential rock types for REE include carbonatite (Sokli, Korsnäs), alkaline rocks (Otanmäki, Lamujärvi, and Iivaara), rapakivi granite and pegmatite (Kovela), and kaolin-bearing weathering crusts in eastern and northern Finland. The highest REE concentrations occur in late magmatic carbonatite veins in the fenite area of the Sokli carbonatite complex. Detailed mineralogical investigations have revealed three distinct types of REE mineralization as phosphates, carbonates and silicates in the studied areas. Mineralogical and mineral chemical evidence demonstrates that hydrothermal processes are responsible for the REE mineralization in the studied rocks and confirms that such processes are predominant in the formation of REE minerals in carbonatite, calc-silicate rocks and albitite. Titanium occurs as ilmenite in hard rock deposits in Paleoproterozoic subalkaline mafic intrusions. The Otanmäki ilmenite was mined together with vanadium-rich magnetite from 1953 to 1985 from a small gabbro—anorthosite complex, which still contains potential for Ti resources. Other major ilmenite deposits are within the Koivusaarenneva ilmenite gabbro intrusion and Kauhajärvi apatite—ilmenite—magnetite gabbro complex. Possible Ti resources are included in Ti-magnetite gabbro of the large layered mafic intrusions in northern Finland, such as at the former Mustavaara vanadium mine. For several years, Rare Element (RE)-pegmatite of the Kaustinen and Somero—Tammela areas has been the objective of Li exploration by the Geological Survey of Finland (GTK). At Kaustinen, Li-pegmatite occurs as subparallel dyke swarms in an area of 500 km2 within Paleoproterozoic mica schists and metavolcanic rocks. Li pegmatite contains more than 10% spodumene as megacrysts (1–10 cm), albite, quartz, K-feldspar, muscovite and accessory minerals such as columbite-group minerals, apatite, tourmaline, beryl, Fe-oxide minerals and garnet. The Kaustinen spodumene pegmatite and Somero—Tammela petalite—spodumene pegmatite contain potential Li resources for the battery industry in EU countries.
Magma/wet sediment interaction (e.g. autobrecciation, magma-sediment mingling, hyaloclastite and peperite-forming, etc.) is a common phenomenon, where hot magma intrudes into unconsolidated or poorly consolidated water saturated sediment. In the Eastern Borsod Basin (NE-Hungary) relatively small (2–30 m) subvolcanic bodies, sills and dykes with contact lithofacies zones were found generated by mechanical stress and quenching of the magma, and interacting with unconsolidated wet andesitic lapilli-tuff and tuff-breccia. Close to the contact between sediment and intrusions, thermal and mechanical effects may occur in the host sediment. Hydrothermal alteration and stratification of the host sediment were developed only locally along the contact zone, probably due to the paleo-hydrogeologic and paleo-rheological inhomogeneities of the lapilli-tuff–tuff-breccia deposits. Processes of magma/wet sediment interaction may be difficult to recognize because of limited exposure and/or certain similarities of the brecciated intrusions to the characteristics of the host sediment; hence detailed field work (geologic mapping or profiling) was required to demonstrate the subvolcanic origin of the brecciated andesite bodies.
Quartz grains from the Ries impact structure containing shock-induced microstructures were investigated using Scanning Electron Microscopy in cathodoluminescence (SEM-CL), secondary electron (SEM-SE) and back-scattered electron (SEM-BSE) modes as well as Mott–Seitz analysis. The purpose of this study is to evaluate the mechanism by which CL detects Planar Deformation Features (PDFs) in quartz, which is one of the most important indicators of shock metamorphism in rock-forming minerals. PDFs are micron-scale features not easily identified using optical microscopy or scanning electron microscopy. The CL spectrum of PDFs in quartz that has suffered relatively high shock pressure shows no or a relatively weak emission band at around 385 nm, whereas an emission band with a maximum near 650 nm is observed independent of shock pressure. Thus, the ~385 nm intensity in shocked quartz demonstrates a tendency to decrease with increasing shock metamorphic stage, whereas the 650 nm band remains fairly constant. The result indicates that the emission band at 385 nm is related to the deformed structure of quartz as PDFs.