Research Reports 2007 & 2008 Institute of Geology as cr, V v. I. Nějaká linka Titulní foto

Modelling of Mg–Fe exchange between Mg-pd and Fe-rich melts coupled with Sr-Nd isotopic modelling revealed that modal and chemical compositions of dunite-wehrlites from Horní Bory can be produced by melt-rock reactions between lherzolites and SiO₂-undesaturated melts of basaltic composition at variable melt/rock ratios. In such model, pyroxenites represent crystalline product (± trapped liquid) of melt migrating along conduits in the peridotite. Thus, Mg-lherzolite from Horní Bory has been transformed to Fe-dunite-wehrlite, similar in many respects to the modification of lherzolite to Fe-rich lherzolite-wehrlite series found in several mantle xenolith localities sampled subcontinental lithospheric mantle (Lee & Rudnick 1999; Peslier et al. 2002; Ionov et al. 2005). However, in contrast to these studies, the calculated trace element compositions of melts equilibrated with pyroxenites and Sr-Nd composition of Horní Bory peridotites point to a significant contribution of crustal material in interacted melts. Therefore, melt-rock reactions were probably associated with melt percolation in a mantle wedge above the subduction zone, which could be driven by the infiltration of subduction-related melts/fluids, if the melt/fluid flux was high enough to enhance partial melting in the mantle wedge.

The differences between the Kozákov and Horní Bory upper mantle suites revealed complex heterogeneity of upper mantle beneath the Bohemian Massif. Different types of metasomatism (melt-rock reactions) which reflect sources of metasomatic agents (subcontinental vs. subduction-related) at these two localities suggest different evolutions of mantle beneath the Bohemian Massif. In turn, this means that upper mantle beneath the Bohemian Massif should comprise mantle domains with different evolution histories (i. e. ancient partial melting) which survived even the Cadomian/Variscan orogeny. This is supported by Re–Os data from Kozákov (see above) as well as by the different orientation of anisotropy (Babuška & Plomerová 2006). On the other hand, the geochemical study on Kozákov and Horní Bory suggests that secondary processes (metasomatism, melt-rock reactions) are probably associated with Variscan orogeny and Neogene magmatism.

The highly siderophile element (HSE) and Re–Os isotopic study on pervasively metasomatized mantle xenoliths from Kozákov provide insights into the behaviour of these elements and Os isotopes during melt percolation. In agreement with other studies, it has been shown that HSE systematics is highly dependent on removal/addition of sulphides (represents their principal hosts) and S-saturation of percolating melt. On the other hand, we reported addition of I-PGE from a S-undersaturated percolating melt, suggesting a possibility of precipitation of I-PGE-bearing alloys during melt percolation. In the case of Kozákov, this was not coupled with an import of radiogenic Os, but is of high importance due to the possible I-PGE enrichment in the upper mantle and its possible effect on Re-Os isotopic geochemistry.

Babuška V. & Plomerová J. (2006): European mantle lithosphere assembled from rigid microplates with inherited seismic anisotropy. – Physics of the Earth and Planetary Interiors, 158, 2–4: 264–280.

Büchl A., Brügmann G., Batanova V. G., Münker C. & Hofmann A. W. (2002): Melt percolation monitored by Os isotopes and PGE abundances: a case study from the mantle section of the Troodos Ophiolite. – Earth and Planetary Science Letters, 204, 3–4: 385–402.

Chesley J. T., Rudnick R. L. & Lee C. T. (1999): Re-Os systematics of mantle xenoliths from the East African Rift; age, structure and history of the Tanzanian Craton. – Geochimica et Cosmochimica Acta, 63, 7–8: 1203–1217.

Ionov D. A., Chanefo I. & Bodinier J.-L. (2005): Origin of Fe-rich lherzolites and wehrlites from Tok, SE Siberia by reactive melt percolation in refractory mantle peridotites. – Contributions to Mineralogy and Petrology, 150, 3: 335–353.

Kelemen P. B. (1990): Reaction between ultramafic rock and fractionating basaltic magma I. Phase relations, the origin of calc-alkaline magma Series, and the formation of discordant dunite. – Journal of Petrology, 31, 1: 51–98.

Kelemen P. B., Hart S. R. & Bernstein S. (1998): Silica enrichment in the continental upper mantle via melt-rock reaction. – Earth and Planetary Science Letters, 164, 1–2: 387–406.

Lee C.-T. & Rudnick R. L. (1999): Compositionally stratified cratonic lithosphere: petrology and geochemistry of peridotite xenoliths the Labait volcano, Tanzania. – In: Gurney J.J., Gurney J.L., Pascoe M.D. & Richardson S. H. (Eds.): Proceedings of the 7th International Kimberlite Conference, vol 1.: 503–521. RedRoof Design, Cape Town.

Luguet A., Lorand J. -P., Alard O. & Cottin J. Y. (2004): A multi-technique study of platinum group element systematic in some Ligurian ophiolitic peridotites, Italy. – Chemical Geology, 208, 1–4: 175–194.

Peslier A. H., Francis D. & Ludden J. (2002): The lithospheric mantle beneath continental margins: melting and melt-rock reactions in Canadian Cordillera xenoliths. – Journal of Petrology, 43, 11: 2013–2047.

van Acken D., Becker H. & Walker R. J. (2008): Refertilization of Jurassic oceanic peridotites from the Tethys Ocean-implications for the Re-Os systematics of the upper mantle. – Earth and Planetary Science Letters, 268, 1–2: 171–181.

Zanetti A., Mazzucchelli M., Rivalenti G. & Vannucci, R. (1999): The Finero phlogopite-peridotite massif: an example of subduction-related metasomatism. – Contributions to Mineralogy and Petrology, 134, 2–3: 107–122.

Borovička J. (2008): Geochemical and ecological aspects of trace elements content in macrofungi.
Fungi have important biogeochemical roles in the biosphere and are intimately involved in the cycling of elements and transformations of both organic and inorganic substrates (Fig. 85). The research area of geomycology is focused on the interactions of fungi with geological environment.
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Fig. 85. Proton- and organic acid ligand-mediated dissolution of metals of soils componets and minerals (Gadd 2004, Mycologist 18: 60–70). Proton release results in cation exchange with sorbed metal ions on clay particles, colloids etc. and metal displacement from mineral surfaces. Released metals can interact with biomass and also be taken up by other biota, and react with other environmental components. Organic acids anions, e. g., citrate, may cause mineral dissolution or removal by complex formation. Metal complexes can interact with biota as well as environmental constituents. In some circumstances, complex formation may be followed by crystalization, e. g., metal oxalate formation.
Many macrofungal species (macromycetes, mushrooms) are capable of accumulating high concentrations of certain trace elements (including heavy metals, noble metals and metalloids) in fruit-bodies and thereby affect elemental geochemical cycling. Many studies focused on trace elements content in macrofungal fruit-bodies have been published to date. Most of them deal with heavy metals (Hg, Pb, Cd), essential elements (Fe, Co, Se, Zn) or radionuclides (¹³⁷Cs) and consider environmental aspects (biomonitoring of artificial pollution) and/or health risks for mushroom consumers. Detailed data on chemical form of arsenic in macrofungal fruit-bodies are available and preliminary results on some other elements have been published. Factors that influence the trace element content in fruit-bodies and the biological importance of the accumulation process itself are poorly known. However, many elements attain elevated concentrations in polluted areas.

My PhD study has focused on several aspects that have not been considered to date (ecological strategy of macrofungi, antimony pollution) and, moreover, some interesting results on noble metals – gold and silver – content in macrofungi are presented and discussed.

My data indicating high gold concentrations in fungal fruit-bodies from both auriferous and non-auriferous areas suggest that macrofungi might play a significant role in gold cycling in the environment. The reported gold contents in macrofungi are the highest ever recorded among eukaryotic organisms under natural conditions. Recent studies have shown an important role of microbiota in gold mobilization in rocks and soils. According to several authors, gold tends to be enriched in organic soil layers; gold accumulation in fungal mycelia might represent a retention factor of gold in organic soil horizons.

Two ectomycorrhizal macrofungal Amanita species of the section Lepidella – Amanita strobiliformis (Fig. 86) and A. solitaria were found to hyperaccumulate silver. The silver contents of both Amanita species that were collected in non-argentiferous areas with background silver content in soils (0.07 to 1.01 mg.kg^-1 Ag) were mostly in the range of 200–700 mg.kg^-1 with the highest content of 1,253 mg kg^-1 in one sample of A. strobiliformis. Silver concentrations in macrofungal fruit-bodies were commonly 800–2,500 times higher than in underlying soils. A. strobiliformis and A. solitaria are the first eukaryotic organisms known to hyperaccumulate silver.

In general, antimony contents of ectomycorrhizal and saprobic macrofungi from clean areas are mostly below 100 µg.kg^–1. No appreciable difference between saprobic and ectomycorrhizal fungi was found. Antimony contents of macrofungi from polluted areas are approx. 100 timěs higher than those from the clean areas.

Kvaček Z., Dašková J. & Zetter R. (2004): A re-examination of Cenozoic Polypodium in North America. - Review of Palaeobotany and Palynology, 128: 219–227. The sterile holotype of Polypodium fertile MacGinitie 1937 was re-examined together with other fertile type specimens from the Miocene Weaverville Formation at Redding Creek (California, western USA). In its leaf morphology, venation and in situ spores Polypodium fertile MacGinitie 1937 matches the extant Polypodium vulgare Linnaeus 1753 complex. The spores belong to the verrucose type. In view of discrepancies between the original description and the real morphology of the sterile frond of ‘Polypodium’ alternatum Pabst 1968 from the Chuckanut Formation of northwestern Washington (Eocene), this fern must be excluded from the record of Polypodium Linnaeus 1753.

Kvaček J. & Dašková J. (2007): Revision of the type material in the genus Nathorstia Heer (Filicales). – Journal of the National Museum (Prague), Natural History Series, 176 (7): 117–123. Nathorstia angustifolia Heer 1880 from the Lower Cretaceous of Greenland has been revised and the true status of the genus Nathorstia Heer 1880 has been verified. Nathorstia Heer 1880 is redefined here as a morphogenus of fern foliage recalling the family Matoniaceae, but lacking diagnostic characters of this family: sori consisting of radially arranged sporangia having Matoniaceaeporites spores in situ. All the type material has been restudied and documented, including unsuccessful attempts in sampling for spores in situ. The lectotype of Nathorstia angustifolia Heer 1880 is designed and its status is discussed.

Kvaček J., Falcon-Lang H. & Dašková J. (2005): A new Late Cretaceous ginkgoalean reproductive structure Nehvizdyella gen. nov. from the Czech Republic and its whole-plant reconstruction. – American Journal of Botany, 92, 12: 1958–1969. During the Mesozoic Era, gingkoaleans comprised a diverse and widespread group. Here we describe ginkgoalean fossils in their facies context from the Late Cretaceous (Cenomanian) Peruc–Korycany Formation of the Czech Republic and present a reconstruction of tree architecture and ecology. Newly described in this study is the ovuliferous reproductive structure, Nehvizdyella bipartita gen. et sp. nov. (Ginkgoales). Monosulcate pollen grains of Cycadopites Wodehouse 1933 are found adhering to the seeds. Facies analysis of plant assemblages indicates that our Cretaceous tree occupied a water-stressed coastal salt marsh environment. It therefore represents the first unequivocal halophyte among the Ginkgoales.

Libertín M., Bek J. & Dašková J. (2005): Two new species of Kladnostrobus nov. gen. and their spores from the Pennsylvanian of the Kladno-Rakovník Basin (Bolsovian, Czech Republic). – Geobios, 38: 467–476. A new lycopsid family Kladnostrobaceae is proposed, based on the type of sporangia, their attachment by a pedicel and the type of reticulate spores enclosed. All these characteristics distinguish the Kladnostrobaceae from all other lycopsid families. A new lycopsid genus Kladnostrobus nov. gen., consisting of two new species Kladnostrobus clealii nov. sp. and Kladnostrobus psendae nov. sp., is described from the Kladno–Rakovník Basin (Lower Bolsovian) of the central and western Carboniferous continental basins of the Czech Republic. Helically arranged distal laminae and pedicels are relatively primitive, suggesting that Kladnostrobus may represent a new, primitive type of lycopsid cone produced by some unknown, probably arborescent lycopsid parent plant. Spores of Kladnostrobus are about 90–100 μm in diameter, and possess reticulate sculpture. The proximal contact area of spores is laevigate. In situ spores can resemble some dispersed species.

Bek J., Drábková J., Dašková J. & Libertín M. (2008): The sub-arborescent lycopsid of the genus Polysporia Newberry and its spores from the Pennsylvanian (Bolsovian-Stephanian B) continental basins of the Czech Republic – Review of Palaeobotany and Palynology, 152: 176–199. About fifty compression specimens belonging to four species of Polysporia (Newberry 1873) DiMichele, Mahafy et Phillips 1979 from the Kladno–Rakovník Basin of the central and western Bohemian Carboniferous continental basins and Intra-Sudetic Basin of the Czech Republic were studied macromorphologically and for in situ spores. Their stratigraphic range is from the Bolsovian to the Stephanian B. Polysporia rothwellii sp. nov., P. drabekii sp. nov. and P. radvanicensis sp. nov. are proposed as new species. Polysporia (Newberry 1873) DiMichele, Mahafy et Phillips 1979 is reconstructed as a sub-arborescent plant with a principal axis with sterile and fertile apical portions. P. rothwellii sp. nov. and P. drabekii sp. nov. are preserved only as clusters of micro- and megasporophylls on specimens not in connection to an axis, and their identification and classification is based mainly on in situ spores.

Drahota P. (2008): Geochemical model of arsenic at the Mokrsko gold deposit.
In addition to As contamination of shallow aquifers in the areas such as mentioned above, highly localized sources of As can present health hazards to individuals and local communities. Contamination from natural sources or former industrial sites is of serious concern, and as seen in many articles published in this subject, a fundamental understanding of how As moves through soils and watercourses is critical to assessing the environmental risks.

Relevant As contamination in the Czech Republic is restricted only to the highly localised sources. These mainly include As concentrations related to historical mining operations, where mine wastes or wastes from mineral processing are the sources. A specific feature associated with high As contamination is represented by natural sources in mineralised rocks or sediments. Arsenic in the biogeochemical systems is usually in stationary state with different sensitivity to change of external conditions, and may thus represent possible environmental risk for the surroundings. The study of quantitative biogeochemical cycles and explanation of the possible As mobility at such sites are for these reasons very challenging and important from many practical aspects.

The dissertation contributes to the As mobility at the naturally contaminated site of Mokrsko gold deposit in central Czech Republic that has been studied by many authors in many publications during the last decade. We have attempted to fill some gaps in previous research in order to complete the quantitative biogeochemical model of As at this site. The particular main objectives included: (1) a brief summary of previous environmental As-related research at the study site; (2) a description of biogeochemical processes controlling precipitation and dissolution of As-bearing secondary minerals in soils and sediments under different redox conditions at the study site; (3) a description of hydrobiogeochemical processes controlling seasonal variations of dissolved As and metal concentrations in stream waters at the study site, and (4) a quantification of the role of bedrock weathering in mass budget of As in two watersheds located within the study site.
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