Abstract: In this study the microstructural and thermobarometric investigation of the metapelitic sequence of the Horvát - hertelend Unit (borehole Hhm1; NW foreland of the Mecsek Mts., Hungary) were carried out. The well Hh–1 cuts through Cenozoic sediments and sedimentary rocks across 720 m. Below the depth 720 m a black slate sequence with metasandstone intercalations was drilled in a thickness of 70 m. The slate is underlain by a dark grey polymictic conglomerate-sandstone sequence. The slate and conglomerate bodies were correlated with the Silurian flysch-like Szalatnak Slate Formation, forming a unique low-grade metamorphic body in the region.
In this work the upper slate sequence was studied which consists of mainly black – dark grey, in the lower section pale grey, slate with metagreywacke and metasiltstone lenses. The studied rocks contain grain supported, well sorted arkose clasts from millimetre to centimetre scale. The studied slate samples have K-white mica + chlorite + quartz + albite + anatase ± tourmaline mineral assemblage. The metagreywacke lenses and laminas are often folded, and a moderately developed continuous foliation and pressure solution seams are also common. The arkose clasts are strongly flattened and boudinaged. Pretectonic quartz veins are systematically folded, dynamically recrystallized (low-T grain boundary migration recrystallization) and apparently sheared by pressure solution seams.
The full width at half maximum (FWHM) values of the 001 and 002 reflexion peaks of K-white mica and chlorite were measured by XRD in highly oriented <2 μm grain size fraction of the slate. The low FWHM values (Ms001:~0.117 h°2!, Chl002: ~0.147 h°2!) and the large crystallite sizes calculated using the Scherrer-equation (Ms001: 1121±70 Å, Chl002: 700±86 Å) suggest epizonal metamorphism. The b0=6d(060,331) value of K-white mica was determined in the unoriented <2 μm grain size fraction. In the investigated samples the average calculated b0 value ~9.022 Å suggests medium P-T gradients during metamorphism.
The rocks contain large amount of autochthonous carbonaceous material (CM) making possible to carry out Ramanspectroscopic thermometry based on the evolution of CM’s first order Raman bands. The calculated maximum temperature of the metamorphism can be estimated about 350 °C using three different empirical thermometers.
The presented observations and data suggest low-grade, medium pressure (chlorite zone ~350 °C) regional metamorphism and associated ductile deformation of the metapelitic sequence of the borehole Hh–1.
Keywords: Horváthertelend Unit, slate–metagreywacke, Raman-spectroscopy, phyllosilicates, FWHM, low-grade, medium pressure regional metamorphism
Összefoglalás: A 20. század második felében a permi Kővágószőlősi Homokkő uránércesedésének köszönhetően a Nyugati- Mecsek térsége intenzív földtani kutatások célpontjává vált. Miután az 1980-as évek végén az uránércbányászatot beszün tették, a terület a ’90-es években került újra az érdeklődés középpontjába, elsősorban a nagyaktivitású radioaktív hulladékok elhelyezésére alkalmas, szintén permi Bodai Agyagkő Formáció kapcsán. Ezen kutatás érdekében mélyí - tették 2014-ben Bodától délnyugatra a BAF–1 és BAF–1A mélyfúrásokat, amelyek vékony kvarter és pannóniai rétegeket követően a Kővágószőlősi Homokkő legalsó, Bakonyai Tagozatát érintették. A fúrás 474,6 m-es mélységben leállt a Kővágószőlősi Homokkőben, így nem érte el a Bodai Agyagkő Formációt. Bár ezt a tarka, durvaszemű, kavicsos, zömmel terresztriális homokkövet a Bakonyai Tagozatként azonosították, ez nem volt teljesen egyértelmű a riolit - kavicsok szinte teljes hiánya miatt, hiszen irodalmi adatok alapján a tagozat egyik jellemző törmelékanyaga a Gyűrűfűi Riolit. Legújabb tanulmányok ezt a főleg vörös színű, rosszul osztályozott kavicsos homokkövet a permi üledékes réteg - sor tagjaként értelmezik, bár jura mikrofosszíliák is előkerültek a rétegsor szürke szakaszaiból. További szokatlan jelen - ség volt a törmelékanyagban azono sí tott karbonátkavicsok jelenléte. Ahhoz, hogy eldöntsük, hogy a BAF–1 és BAF–1A fúrások valóban a Bakonyai Tagozatot érintették, olyan korábbi fúrások dokumentációival hasonlítottuk össze, amelyek biztosan megfúrták ezt a tagozatot. Ehhez 11, a MÉV (Mecseki Ércbányászati Vállalat) által az 1950-es és ’60-as években mélyített fúrás dokumentációját vizsgáltuk át, és számszerűsítettük az akkoriban Bakonyai Tagozatnak határozott réteg - sor kavicsban gazdag szakaszainak kavicsstatisztikáját. Eredményeinket térképen ábrázoltuk sávdiagramok formájában, hogy könnyebben meghatározható legyen az egyes kavicstípusok területi eloszlása a tagozaton belül. Az archív adatok alapján látható, hogy a permi lehordási terület igen nagy litológiai változatosságot mutatott, ahol a törmelékanyag egy viszonylag kis területen is erősen polimikt jellegű. Ez arra enged következtetni, hogy a Bakonyai Tagozat nem jelle mez - hető egyetlen jól meghatározott kavicstípus-eloszlással. A BAF–1 és –1A fúrásokban a karbonátkavicsok jelenléte meg - kérdőjelezi a homokkő Bakonyai Tagozat mivoltát.
Keywords: Kővágószőlős Sandstone Fm, Bakonya member, pebble distribution, Permian, West Mecsek, Hungary
Összefoglalás: Tanulmányunk a magyarországi egri korú tengeri molluszkafauna ismeretéhez járul hozzá egy újonnan feltárt rétegsor gastropodáinak leírásával. A lelőhely Esztergomtól északkeletre található a Duna jobb partján, kőzettípusa a Törökbálinti Formációt képviselő agyag és aleurolit. A gazdag fauna a Paratethysre jellemző egri taxonok mellett Magyarországról eddig nem ismertetett nemzetségeket és fajokat is tartalmaz, emellett négy új faj, Pugilina katalinae nov. sp., Dorsanum strigoniense nov. sp., Sveltia nemethi nov. sp. és Merica krocki nov. sp. leírását is lehetővé tette.
Keywords: Gastropoda, Paratethys, Esztergom Basin, Egerian Stage, Upper Oligocene, Lower Miocene
Abstract: Upper Miocene turbidites in the Transylvanian Basin are outcrop analogues to a number of hydrocarbon plays. These Late Miocene Lake Pannon and older Miocene turbidites are producing reservoirs in the subsurface in Romania and Hungary as well. In order to explore the reservoir quality of the turbidites, sedimentary facies and petrographic analyses were performed on two previously undescribed outcrops, with special focus on their depositional and diagenetic histories. The outcrops are near the eastern margin of the Transylvanian Basin, close to the source area, the Eastern Carpathians. Four facies associations were identified: thin-bedded, medium-bedded, thick-bedded sandstone and matrixsupported conglomerate facies associations. These were interpreted as low density turbidity currents, coupled high and low density turbidity currents and as debris flows. At Firtănu˛s, erosional surfaces are abundant, and overlain by upward thinning or thin bedded turbidites. These suggest a complex channel deposit subdivided by low relief scours. The outcrop at Medimoru Mic exposes laterally continuous beds and alternating thick and thin-medium bedded turbidites. These are interpreted as deposits that formed in the inner part of a lobe. The two outcrops are less than 4 km away, suggesting that the Firtănu˛sm channel might be eroding into the Medimoru Mic lobe, forming one system. Formerly studied outcrops in the vicinity and their sequence stratigraphic interpretation (KRÉZSEK 2005) enables us to draw paleogeographic maps for the systems tracts of the Late Miocene. The two exposures are assigned to the LST8 lowstand systems tract, sensu KRÉZSEK et al. (2010). At the time of deposition, several sandy lobes and channels developed in the deep basin which were fed by fandeltas and ultimately by the uplifting Carpathians. Immaturity of the sediments is reflected by poor to medium sorting, subangular to subrounded grains and abundance of lithoclasts, most of which are plastic grains that easily deform during physical compaction. The primary porosity and the mineral composition (i.e., abundance of lithics) predetermined the subsequent porosity changes. Physical and chemical compaction and calcite cementation had the most important role in destroying of the porosity, which is between 1–21% at present. Carbonate cementation was encountered in the channel deposits in form of concretions and cemented bedding planes, causing the compartmentalisation of the reservoir. The spatial distribution of the facies associations also influences the reservoir characteristics. The best porosity (21%) is encountered in the thin-bedded sandstone, but the thick-bedded sandstone is volumetrically more important, the noncemented parts still maintain 16% of porosity. Connectivity between sand bodies is enhanced by erosion in the channel fill. Laterally continuous mud and debrite layers of both the channel and lobe can create poor connectivity. The heterogeneous porosity distribution may also have affected diagenetic fluid flow, thus creating preferentially cemented layers. Additional high resolution investigations are necessary to model the complex fluid flow in these Transylvanian reservoirs.
Keywords: Transylvanian Basin, turbidite, reservoir quality, diagenesis, sedimentology, Late Miocene
Abstract: Geophysical anomaly can only be found where there is some-kind of change. Such change may be the variation of the physical parameter, the depth, or the spatial distribution. If there is no change, the field strength is also unchanged; it is a constant value without any anomalies. The Bouguer anomaly map shows the gravity effect of the changing rock density in a vertical extent of several tens of kilometres, because gravity is a long distance and always attractive force. So the Bouguer anomaly of a small exploration area will have some gravity effect of the deep crust too, even if we do not take it into account.
Magnetic anomalies are caused by mafic geological formations. These are the mafic magmatic rocks and their trans - formed metamorphic variants. The magnetic force may have both attractive and repulsive character (generally it is a dipole field), so the result of these strengths yields a much more complicated anomaly field. The penetration in this case is a few tens of kilometres, right down until the depth of the Curie-temperature. Geophysical interpretations are generally done in the range of the borehole’s penetration, although, some effects have obviously deeper origin. So the examination of bigger depth and elimination of deep effects are essential to have more accurate local interpretation of the geophysical measurements. Studying the area of Hungary requires knowledge about such deep effects in the entire Carpathian– Pannonian Region.
Keywords: Carpathian-Pannonian Region, exploration of crust, regional geophysical interpretation, gravity and magnetic anomalies
Abstract: The evaluation of recoverable resources and commercial reserves is probably the most important process of the publicly trading oil producers and mining companies. This is because the monetized value of reserves and resources is a key determinant with respect to market capitalization. For securing the interest of investors interest global guidelines have been made available to govern the disclosure of details about reserves and resources in both industries. The guidelines — Petroleum Resources Management System (SPE/AAPG/WPC/SPEE 2007); International Reporting Template for the Public Reporting of Exploration Results, Mineral Resources and Mineral Reserves (CRIRSCO 2004) — are underlain by methods for the assessment, classification and categorization of the resource volumes. The methods are similar given that volumes are considered to be estimations of an uncertain nature by both industries. However, the management of the uncertainty (as well as the terminologies applied) are different. Although this study focuses on the analyses of the similarities and differences, and concludes with the collation of certain petroleum and mineral resource and reserve classes or categories, it does not attempt to harmonize – definitely not standardize – the two naturally Concerning resources, the oil industry applies a two-dimensional classification and categorization system. This classification follows the current geological and reservoir engineering knowledge on the given accumulation and is indicated by the maturity of the resource volumes. There are five classes which are taken into account — (i) prognostic, (ii) prospective, (iii) contingent, (iv) undeveloped, and (v) developed. Categorization within each class is defined by the range of the uncertainty. With respect to the latter, the range is given by two extremes and one centrally-positioned value of the actual volumes: the “pessimistic”, the “optimistic” and the “best” estimates, respectively. In the mineral mining industry the re - source classification is uni-dimensiona. This is very similar to the oil industry classification in that it considers the geological knowledge; the respective resource maturity classes are named as (i) inferred, (ii) indicated, and (iii) measured. For minerals, a single volume representing the mathematical mean is given for each class.
Reserves are defined in both industries as commercial volumes and the commerciality criteria are almost identical, too. The monetized value of the reserves is given by the discounted cash-flow analyses. However, the discount rates seem to be approached in a different ways. While the mineral mining industry recognizes the uncertainty of the resource estimations with risk premium, in the oil industry the very same discount rate is applied for the economic evaluation of the resources characterized by different ranges of uncertainty. In line with the evaluation of the resources, the reserve classification is two-dimensional in the oil industry: maturity classes are termed as undeveloped and developed, while three probability categories are given in each class as Proved (1P), Proved and Probable (2P), and Proved, Probable and Possible (3P). The terminologies used for mineral reserve classes are probable and proved. Volumes in each class are numbered by the mathematical means and no further probability- based categorization is applied.
In the light of the above considerations it can be concluded that the “best” estimates of the (i) contingent, (ii) undeveloped, and (iii) developed petroleum resources may correspond with the mean volumes of the (i) inferred, (ii) indicated, and (iii) measured mineral resource classes, respectively. Analogically, undeveloped 2P and developed 2P petroleum reserves might be paired – under circumstances detailed in the study – with the respective means of the probable and proved mineral reserves.
Keywords: mineral and petroleum resource and reserves evaluation guidelines, resource and reserve classification and categorization, discount rates in resource economic evaluation, collation of petroleum and mineral resources and reserves
In memoriam