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Zsolt Benko

Zsolt Benko. Photo: Åsa Brandt

Zsolt Benko. Photo: Åsa Brandt

Zsolt Benko from Budapest in Hungary visited the Laboratory for Isotope Geology for six weeks during October and November 2007. This was his first trip to Sweden and the Swedish Museum of Natural History. He was impressed by NRMs exhibitions and their interactive parts, unusual in Hungary, as well as the number of families with children he saw visiting the museum. Zsolt experienced Stockholm as a beautiful town and had been to Gamla stan (Old Town) and to many of Stockholm´s other museums, to mention some things.
Zsolt´s main reason for coming to the museum as a guest researcher was the high quality of the equipment, especially the mass spectrometers, which were critical for his research. He highly appreciated the support and friendliness of his host, Kjell Billström. Zsolt said that the museum's “calm and quiet atmosphere is perfect for research".
Wobbly rocks in the Velence Mountains, Hungary

Wobbly rocks in the Velence Mountains, Hungary

Project summary

The Periadriatic-Balaton Lineament is a major tectonic fault system, which forms part of the Pannonian-Carpathian Region, in the Eastern Alps and in the Carpathian Basin. Along this fault system several allochtonous Palaeozoic magmatic and sedimentary series can be found which have undergone very intense Variscan (≈300 Ma) and Alpine (≈30 Ma) tectonic, magmatic and fluid circulation processes. Due to the superimposed magmatic and hydrothermal events related to the evolution of the Alpine system, these rock bodies often have suffered a complex geological history. One of these allochtonous bodies is the monzo-granite of the Velence Mountains.
After its formation at around 300 Ma ago, this granite was affected by younger regional Triassic fluid circulation, local Cretaceous magmatism and regional Palaeogene magmatism and related hydrothermal fluid flow. The Velence Mountain granite hosts quartz-molybdenite, quartz-base metal sulphide, quartz-fluorite and quartz-barite vein mineralizations, which by several workers are believed to be genetically related to the stage of Variscan magmatism. However there are also certain tectonic, geochemical and structural evidence, which suggest that these formations could be related to younger (Triassic, Cretaceous or Palaeogene) fluid mobilization processes.

There are several K/Ar (of illite from hydrothermally altered wall rocks) and fission track age data available from the study area, but these data do not point unequivocally to a common age, and there is a risk that younger thermal processes could have affected K-Ar ages as these are relatively easy to disturb. Moreover, such data have no direct bearing on the timing of ore-forming processes.

One basic goal is to use isotope geochemical methods as a finger-print technique; i.e. to obtain isotopic signatures for ore minerals, valid at the time of ore formation, and to compare these with calculated isotopic signatures for potential source rocks, thereby constraining the type of rocks supplying metals to the ores. Fortunately, the ore mineralogy of the studied deposits is well suited for an isotopic study, and analyses will be carried out on a suite of ore and alteration mineral phases as well as on the host rock and potential source rock candidates.

In the light of new isotope data we will have a much improved picture about the mineralization processes in the Variscan granite of the Velence Mountains, and their possible links with younger hydrothermal/magmatic processes. A prime aspect of my PhD work is to investigate the tectonic control of fluid circulation processes. As the formation of mineralized veins is most likely related to tectonic activity, a knowledge of mineralization age(s), together with structural orientation data, will thus help me to model the fracture forming events in the Velence Mountains.
Another aspect of the new data is related to ore prospecting. Given that Palaeogene magmatic complexes (locally found at E-VelenceMountains, and at Recsk), in general, often are associated with gold mineralization, this knowledge may also have implications for the exploration for gold in the study area.

Finally, apart from comparisons on a regional scale, the new isotope data set in combination with other evidence available for Variscan and Alpine metallogenetic events in the Alp-Carpathian-Dinaride systems will also enable a large scale correlation and geodynamic interpretation of tectonic processes affecting the Central European region during the Alp-Carpathian orogeny.