Dunkl István: Quo vadis U-Pb geochronology? Online előadás, március 22.

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Tisztelettel hívunk minden érdeklődőt a Litoszféra Fluidum Kutató Laboratórium (LRG) online szeminárium sorozatának keretében

Dunkl István, a Göttingeni Egyetem (Németország) kutatójának előadására:

Quo vadis U-Pb geochronology? What can we expect from the current developments?

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Időpont: 2021. március 22. 17.00

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Quo vadis U-Pb geochronology? What can we expect from the current developments?
István Dunkl
Sedimentology & Environmental Geology, Geoscience Center, University of Göttingen

The classical application of the U-Pb geochronology was concentrated on the zircon and the aim of such analyses was to determine high temperature crystallization processes - mostly from melt. These zircon-based applications experienced significant improvement thanks to the better sensitivity of the analytical technique, better spatial resolution and the simultaneous application of other mapping and spot analytical methods like the determination of Li-, Hf- or O-isotope ratios or the REE anomalies of the dated crystals.
However, beyond the high-temperature crystallization from magma other processes that happen in lower temperature, in metamorphic or diagenetic environments became also datable by the U-Pb technique in the last decades. One of the approaches is in the metamorphic petrochronology, when temporal development of relatively long-lasting processes can be described by the combined application of mineral pT stability analyses, mineral-specific trace element analyses and in-situ U- Pb geochronology of minerals having different textural contexts. By the evaluation and modelling of the U-Pb ages and zonation in apatite, rutile or titanite crystals "high-T thermochronology" was developed, that contributes to the recognition of the time-temperature trajectories in mid-crustal conditions.
When we observe the shallower levels, the low temperature and the short duration of the processes often do not allow growing minerals in equilibrium conditions. The dating toolkit for these, low- T environments is rather poorish - although many, crucial geological processes happen on the surface and in shallow depths. The enhanced sensitivity and the new U-Pb techniques allow to date "non-conventional" phases like carbonate minerals, opal, goethite, hematite, anatase and Mn- hydroxides. We can gain now time constraints that were formerly unimaginable for formation ages of these minerals precipitated in hydrothermal, ore-bearing regimes, in veins along active faults, in syn-sedimentary and diagenetic processes, but also in weathering zones allowing to date the circulation of descendent, meteoric fluids and the development of local relief.