Összefoglalás: A Preluca-hegységben (ÉNy-Erdély, Románia), a Măgureni-domb területén proterozoos metamorfizált karbonátos kőzetek (dolomitok és mészkövek) ismertek. A késői, hercíniai regionális metamorfózis alkalmával nagyszámú pegma - tit test nyomult be a metamorf összletbe. A pegmatitok képződését diopszid-tremolit-flogopit összetételű szkarn kiala - kulása, majd hidrotermás folyamatok kísérték. A SiO2-tartalmú, alkáli, illetve semleges vizes oldatoknak a Mg-dús kőzetekkel való reakciója következtében magnéziumos agyagásvány-társulás képződött. Ezek közül mind ásványtani, mind gazdasági szempontból a szepiolit-előfordulások a legfontosabbak.
A lelőhely szepiolitja vékony teléreket és lencséket képez. Kísérő ásványai a talk, szaponit, klorit, kaolinit, markazit, kalcit és opál. Kémiai, röntgendiffrakciós, termoanalitikai, infravörös spektroszkópiai és elektronmikroszkópos vizsgá - latok igazolták a majdnem tiszta Mg-szepiolit jelenlétét, kis mennyiségű alumínium- és vas-oxid beépüléssel. Ugyancsak kimutatható a Mg-ot koordináló és a szabad (zeolitos) víz jelenléte.
Végül bemutatjuk a technológiai kísérletek eredményeit is a szepiolit kitermelése, dúsítása és alkalmazása tekin - tetében.
Keywords: Romania, Preluca Mts, Măgureni Carbonate Formation, dolomite, pegmatite, sepiolite, analytical data
Abstract: The Permian Gyűrűfű Rhyolite Formation is the only volcanic association within the Palaeozoic sequence of Southern Transdanubia which outcrops in the western foreland of the Mecsek Mts. Furthermore, this formation has long been well-known as the source of the gravel material of the younger sedimentary siliciclastic formations in the area. Due to the uranium ore exploration deep drillings of the second half of the 20th century, details about the subsurface regions of the formation are also well-documented; these regions include the Western Mecsek Mts, the northern foreland of the Villány Mts and the Máriakéménd–Bár–Báta Range.
According to the previous reports of uranium ore exploration and other studies based on them (SZEDERKÉNYI 1962, BARABÁSNÉ STUHL 1988, FÜLÖP 1994, BARABÁS & BARABÁSNÉ STUHL 1998, JAKAB 2005), the material of the outcrop is a lava rock. In the early stage of the research only PANTÓ (in BOCZÁN et al. 1966) mentioned the possibility of a pyroclastic (ignimbrite) origin. The later petrographic descriptions of the rocks recognised the common appearance of flattened, oriented pumices and this made it necessary to implement a process of reambulation. As the first step in this process, HIDASI et al. (2015) documented detailed petrographic descriptions of the deep-drilling and gravel material of the formation and, according his work, many textural features indicate a pyroclastic flow origin.
In this study, detailed macroscopic and microscopic documentation is given of surficial samples of Gyűrűfű Rhyolite (from area between the villages of Gyűrűfű and Dinnyeberki, Western Mecsek Mts). Many textural features (e.g. devitrified pumices, former glass shards, poor sorting, fragmented phenocrysts) of the pyroclastic flow deposits were also observed. In this paper the surficial rock material of the formation is presented as an altered, locally strongly-welded, crystal-rich, pumice-bearing lapilli tuff. According to the intensity of the welding, 2 lithofacies were distinguished. The eutaxitic, strongly-welded rock samples could have their origin in the medium or greater depth of the proximal part of the pyroclastic flows; the latter filled a former valley in the area of Gyűrűfű. The non-welded material is probably derived from the lowermost, upper, sideward or distal part of the pyroclastic flows.
Alongside the petrographic description, this study was supplemented with preliminary zircon examinations as part of the preparations for U-Pb radiometric dating. From the examined samples more than 200 pieces of zircon grains were documented. Based on this database, the respective zircon populations of the two lithofacies were analysed and compared (using statistical parameters). Zircon crystals were found both in the matrix and within the phenocrysts of the rock samples. The high amount of idiomorphic and hipidomorphic zircon grains that appear in the groundmass shows the possibility of zircon crystallization within the rock-forming magma. Most of the zircon grains are fragmented and this fact serves as further evidence of a pyroclastic origin. The examined zircon crystals often show zonation and contain xenocrystic cores; these details need to be taken into account when carrying out U-Pb radiometric dating.
Keywords: Mecsek Mountains, Gyűrűfű Rhyolite, Permian, pyroclastic flow deposit, pumice, volcanic glass shard, eutaxitic texture, devitrification, zircon
Abstract: The Veszprém Plateau is situated on the south-eastern flank of the Transdanubian Range Unit. The most typical structural elements of the study area are the SE verging Litér, Veszprém and Hajmáskér Thrusts. These thrusts were formed during the Eoalpine stage in the mid- Cretaceous. During the work we carried out a detailed structural analysis of the study area. This area is built up by Middle Triassic basin and platform sediments. The stratigraphy of these features has been investigated in detail, but modern structural analysis has not yet been performed. The Middle Anisian Tagyon Formation is overlain by basinal sediments of the Late Anisian to Ladinian Buchenstein Group. The Group was thought to be subdivided into two parts by a dolomite rock mass. In previous studies concerning this subject, this dolomite was depicted as a prograding wedge of a Ladinian carbonate platform. The present work took on the task of clarifying the stratigraphical and structural position of these units. South of Öskü and in the Kikeri quarry, Tagyon Dolomite underlies the Buchenstein Group. The Upper Anisian – Ladinian cherty, crinoidal limestones and tuffitic clays are moderately folded and affected by reverse faults and detachments along bedding planes. The Tagyon Dolomite was thrust onto the Buchenstein Group along the newly-defined Öskü Thrust. This south-east-verging, NE–SW striking thrust could be traced alongstrike into the village of Öskü, and it resulted in a repetition of the narrow stripe of basinal formations. Between these two belts the platform dolomite was gently folded as part of a ramp or fault-propagation anticline and its lower contact is tectonically truncated. This structural scenario suggests that the intervening platform dolomite between the two belts of the Buchenstein Group is the Middle Anisian Tagyon Formation. The structural model presented in this paper shows that within the study area the intervening platform dolomite unit does not stratigraphically subdivide the stripes of the basinal formations; in other words, it does not appear as a prograding wedge of a Ladinian carbonate platform. The Öskü Thrust is coeval with the major, SE verging thrusts of the Veszprém Plateau and it is Cretaceous in age. The thrust could be the same structure as the Hajmáskér Thrust because it has the same strike and is collinear with that thrust. However, the junction of the two thrusts is covered by Miocene rocks.
During the work which underpins the present study some Triassic structural elements were identified, such as neptunian dykes, and outcrop- and map-scale normal faults; furthermore, the slide direction of the already identified slump folds was measured. Based on these observations we suggest that the Middle Triassic platforms were disintegrated by a NE–SW extension. This direction is in good agreement with the previous works which envisaged NW–SE striking normal faults at the platform margins.
Keywords: Transdanubian Range, Eoalpine deformation, thrust, Middle Triassic, basin, platform
Abstract: The precise dating of the Upper Triassic pelagic dolomites in the Buda Hills has always been a problematic point in the geologic research of the area. Previously found fossils were mostly unsuitable for the exact stratigraphic assignment of these formations due to their low number and poor preservation. Recently, sparse samples were collected from the dolomite sequence of the northern and southern ranges for conodont biostratigraphic investigations. The standard processing technique of dilute acetic acid provided a rich and diverse conodont fauna which enabled the chrono - stratigraphic subdivision of the Sashegy Dolomite Member of the Mátyáshegy Formation. Samples of the northern range yielded a Lower to Upper Norian conodont assemblage consisting mainly of the genera Epigondolella and Mockina beside the genera Metapolygnathus, Norigondolella and Parvigondolella. The western part of the southern range is Upper Carnian in age indicated by genus Carnepigondolella and early epigondolellids. Eastwards, genera Epigondolella and Mockina suggest Lower to Middle Norian age. From the central part of the range towards the east the recurrence of the Upper Carnian to Lower Norian sequence was observed. The easternmost segment of the range is Upper Norian based on the genera Mockina and Parvigondolella. According to the new conodont biostratigraphic results, the Mátyáshegy Formation is confirmed to be coeval with the Csővár Formation that occurs on the east side of the River Danube. Detailed studies on the conodont assemblages of the Buda Hills might offer a solution for the problems of Upper Triassic conodont phylogenesis and conodont zonation.
Keywords: Upper Triassic, conodont biostratigraphy, Buda Hills, Transdanubian Range, Hungary
Abstract: In connection with Earth Sciences, amateur mineral and fossil collecting in Hungary has a long tradition. Amateur, collectors have not only enriched our knowledge about the geology of Hungary but, without their enthusiasm, the collections of museums and natural history departments would also be more modest. In this paper, after a concise presentation of the concomitant legal background to this hobby, a short summary of the collectors’ activities is given. This is based on interviews made with a number of amateur collectors. The existence of restrictive points in current legislation — related to environmental protection, forestry, etc. — and the importance of a constructive and ongoing relationship between the collectors and the professionals are pointed out. Furthermore, the relevance of a precise system of identification of sampled quarries, the necessity of keeping and updating a register of observations and findings, and the significance of the publication of results are emphasized. It is a significant point that half of the internationally registered but, in Hungary, earlier undetected mineral species were recognised and collected by amateurs. Not only is this impressive but also the fact that five of seven new mineral species (according to the IMA register) were discovered in Hungary by such enthusiasts. This article asserts that the majority of amateurs play a very positive role in the development of Earth Sciences in Hungary. However, mention also is made of the dubious activities of other so-called “amateur gatherers” who build their collections using unfair practices and acting against the rules laid down in official regulations. Obviously, the attitude of such individuals is not supported in this paper and their methods are treated negatively and discouraged.
Keywords: mineral, fossil, rock, act, amateur collevtor