Plenary talk at the 7th Slag Valorization Symposium

Vojtěch Ettler will give a plenary lecture entitled “The leaching behavior of smelting slags: from contaminants to critical metals” on the 7th International Slag Valorization Symposium (SVS7). The conference, originally planned to take place in Leuven, Belgium, will finally run in a virtual mode. SVS7 is a major event on characterization and applications of metallurgical slags and will bring together people from R&D sector and industry.

Mobility of As in sulfidic gley soils during drought

We combined selective chemical extractions and S isotopes to examine the mobility of As and trace metals (Co, Cu, Ni) in two Czech wetland soils enriched in authigenic Fe-As sulfide minerals through the drying process. We found that As and trace metals released via oxidation of the sulfide phases (particularly Fe sulfides) were almost entirely sequestered by Fe(III) (oxyhydr)oxides, but concomitant acidification resulted in the pH-dependent release of the As(III) and trace metals. Although our results documented the relatively low As mobilization potential under relatively short droughts (several weeks), the preservation of the anoxic conditions must be regarded as a fundamental management strategy of these and other sulfidic wetlands enriched in As.

Drahota P., Peřestá M., Trubač J., Mihaljevič M., Vaněk A. (2021): Arsenic fractionation and mobility in sulfidic wetland soils during experimental drying. Chemosphere 277, 130306. (DOI)

Successful virtual PhD conference

We had a successful virtual conference, which has been jointly organized by PhD students associated to the Center for Geosphere Dynamics (UNCE/SCI/006 project) and SGA Student Chapter Prague. The morning of 15th April 2021 was full of exciting presentations (see program and abstracts here). Thanks go to all participants (we were up to 45), but especially to Rafael Baieta, Marine Jouvent and Marek Tuhý, who organized the conference and chaired individual sessions within the ZOOM platform!

Invasion to Carboniferous lakes makes horseshoe crabs look like babies

Today’s horseshoe crabs are often described as living fossils, mostly for their early appearance in the fossil record and their supposedly conservative morphologies. Nevertheless, after a careful investigation, one can find even peculiar species among this group of spider’s close relatives. Indeed, the recent marine representatives of horseshoe crabs (three genera, four species) are all members of one surviving clade called Limulidae. Deep in the past, during the Paleozoic and Mesozoic, some horseshoe crabs evolved into quite different morphologies and explored various environments. One group called Belinuridae comprises mostly late Paleozoic species that explored freshwater habitats. Lustri, Laibl and Bicknell, in their paper published recently in PeerJ (Lustri et al. 2021), redescribe small (about 3 cm long) and morphologically simple belinurid Prolimulus woodwardi. This species has been originally described by Antonín Frič, back in 1899, from the famous sapropelic coal of the Plzeň Basin. Based on numerous well-preserved specimens, the authors describe and clarify the species morphology, including such details as opercula and chelicerae. Phylogenetic analysis shows that Prolimulus is, together with some other morphologically similar genera, a member of highly paedomorphic (i.e., resembling juvenile stages of others closely related taxa) ingroup within Belinuridae. This discovery is further corroborated by morphometric results and by the fact that there are epibionts attached to some Prolimulus specimens. The presence of attaching organisms on the exoskeleton of Prolimulus suggests, that these small specimens are individuals that already stopped or significantly slowed the molting of their exoskeleton. In other words, they are adults that retain juvenile morphology. Such morphological and developmental plasticity, together with a successful exploration of freshwater habitats illustrates the horseshoe crab’s ability to adapt to various environmental conditions in the deep past.

Lustri L., Laibl L., Bicknell R. 2021. A revision of Prolimulus woodwardi Fritsch, 1899 with comparison to other highly paedomorphic belinurids. PeerJ 9, e10980. (DOI)

Carboniferous eruption covered central and western Bohemia with up to 1 m thick ash layer

The famous Bělka tuff is a widespread pyroclastic layer preserved elsewhere in the central and western Carboniferous late- to post-orogenic basins. This tuff represents a unique stratigraphic marker documented from tens of boreholes and numerous black coal mines within a large area between the southern edge of the Pilsen Basin in western Bohemia to the eastern part of the Kladno-Rakovník Basin over a distance of 100 km. However, its volcanic source was until now unclear. In a new study by Tomek et al. published in International Geology Review, a multidisciplinary approach using the LA-ICP-MS U/Pb zircon dating, thickness and grain size distribution analysis, and volume calculation suggested that the source volcano is the Altenberg–Teplice Caldera located at Czech-German border in the NW Bohemian Massif. In detail, this volcano erupted a major caldera-forming ignimbrite eruption with an estimated volcanic explosivity index 7 (out of 8) at 314 Ma. The pyroclastic density currents travelled over a distance of ca. 60 km towards the area of Oparno valley (Porta Bohemica). From here, the northeastern winds distributed the volcanic ash cloud towards the southwest, where the ash was deposited in the sedimentary basins. The isopach reconstruction indicate that for instance in Regensburg (Germany), there was a 10 cm thick ash layer that originated from the Altenberg–Teplice Caldera nearly 220 km away.

Tomek F., Opluštil S., Svojtka M., Špillar V., Rapprich V., Míková J. (2021): Altenberg–Teplice Caldera sourced Westphalian fall tuffs in the central and western Bohemian Carboniferous basins (eastern Variscan belt). International Geology Review in press. (DOI)

High scientific production in 2020 despite the COVID-19 pandemics

Despite the pandemic situation in 2020, the researchers of the Center for Geosphere Dynamics were highly productive. A total of 59 papers have been published (printed + in press) in 2020. Papers published in the first and second quartile journals according to Web of Knowledge accounted for 90% of the total. The numbers also include 13 papers in the D1 category and 5 papers in the Nature Index journals.

Successful online meeting of the Center

On Thursday, 19th November 2020, we organized a successful virtual meeting of the Center for Geosphere Dynamics with three lectures given by junior researchers: (1) Valéria Vaškaninová: Revival of our earliest ancestors by means of synchrotron tomography; (2) Jaroslava Hajná: Bohemian Massif records of Neoproterozoic to Lower Paleozoic geodynamic evolution of the northern Gondwanan margin and experimental modelling correlations and (3) Petr Tábořík: Hranice Abyss, the world’s deepest freshwater cave: a new evolutionary model.

Magmatic pulses during orogeny: when and how fast is magma added to the upper crust?

A new paper by Trubač et al. combines geochronologic data with a GIS-based spatial analysis of plutons in the Bohemian Massif, Variscan belt, to examine the magma fluxes and temporal pattern of plutonism during collisional orogeny. The collisional orogens differ from continental margin arcs, where the plutonic material is added in repeating cycles to the upper crust during protracted oceanic subduction. Instead, it was shown that the collisional plutonism reflects a secular thermotectonic evolution of the orogen, where magma sources change from mantle-dominated to intracrustal, paralleled by increasing significance of crustal recycling at the expense of crustal growth. The analysis also suggests that crustal thickening, commonly regarded as the main cause of plutonism in collisional orogens, may be of relatively lower significance than a late-stage mantle delamination.

Trubač J., Žák J., Kondrová L. (2020): Magmatic tempos in large hot orogens in comparison with continental margin arcs. Journal of Geology 128, 465-475. (DOI)