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

GEKON, Ltd. Prague, Project No. 7106: Kaolinitic sandstones. Nekmíř – Horní Bělá (J.K. Novák, J. Bek, P. Bosák, J. Pavková, J. Straková & J. Dobrovolný)

The upper Carboniferous kaolinitic sandstones with a different proportion of clayey-silty and quartzose clasts were studied to show the grain-size distribution as well as chemical and mineralogical compositions of the following grain-size fractions: (i) smaller than 25 μm (clayey silt), and (ii) 25–63 μm (silt). Clay minerals and micas of those fractions include dominant kaolinite, mostly well ordered, besides muscovite/illite and minor biotite flakes. Unlike at the Kaznějov kaolin deposit, kaolinite pseudomorphs after feldspar clastic grains are mostly absent in sandstones studied and the post-sedimentary kaolinization process in situ is improbable. Rather, attention was paid to the relationship between abundance and mineralogical composition of the clayey-silty clasts and to petrographical properties of the matrix. Sometimes, secondary alteration of clasts involves the precipitation of released silica. In general, these kaolinitic sandstones can be considered an example of redeposited saprolite from the Upper Carboniferous regoliths outside the Plzeň Basin.

Micropaleontological examination of one sample from siltstone intercalation indicates a close relationship to the Nýřany Member of the Kladno Formation (Bolsovian to Westphalian D). The miospore assemblage is composed of the genus Verrucosisporites (dominant one) as well as genera of Savitrisporites, Lundbladispora, and Latensina. This assemblage bears a close relation to the lowermost level of the Nýřany Member of the Kladno Formation. Further identified spores, such as Granulatisporites, Cyclogranisporittes sp., Calamospora, Leiotriletes, and Laevigatosporites, appear to show a wider extent, from Westphalian to Lower Stephanian. In comparison with them, the genera of Punctatosporites, Laevigatisporites, Latosporites, and species Raistrickia crinita display a relatively great richness in one sample. It means that they represent the assemblage of the uppermost Westphalian D – Cantabrian, i. e. to Nevřeň Coal Seams. Because of the presence of xylofilous floras and that of tree-ferns (Marattiales), a remarkable change in dry climatic condition and in miospore assemblage is suggested.

It is difficult to decide whether or not the sample with spore genera of Potoniesisporites a Florinites represents the Týnec Fm. (Lower Stephanian). Less plentiful are, however, genera such as Laevigatosporites and Leiotriletes.

The oceanic crust was previously known as the Amaime Fm., the Lara Nappes, Villa de Cura Klippe, etc., which crops out on the northern border of Barquisimeto Basin. Pebbles and ks of mafic volcanic blocks of various dimensions are rather mixed in the allochtonous Matatere Fm. than emplaced in original setting. This turbidite formation also includes (i) serpentinized peridotite, spilitic basalts, tuffs, gabbros at Siquisique and Río Tocuyo, and (ii) pebbles of chert, limestones, shales, and phyllites. The successive allochtonous slabs inverted the original sequences and caused low-grade metamorphism. It is suggested that the larger blocks of slightly altered peridotite and basaltic rocks could be investigated for the use as rock aggregates.

The northeastern segment of the Venezuelan Andes between towns of El Tocuyo and Quibor hosts the Caribbean (Lara) nappes (i) with Upper Cretaceous Barquisimeto Fm. (clay, clayey schist, marl, dark-gray and black limestone, and phtanite), (ii) with Paleocene Matatere Fm. (sandy turbidites with conglomerate intercalations), and (iii) with strongly deformed Eocene Morón Fm. (clastic sediments). All are juxtaposed to Andean autochtonous units consisting of Precambrian, Paleozoic and Jurassic rocks. There are no known metallic deposits.

Severočeské doly, Inc., Doly Bílina. Project No. 7109: Evaluation of geochemical and mineralogical data of carbonate concretions and of hard carbonate-cemented layers in the Miocene sediments of the Bílina Quarry, Northern Bohemia (K. Žák)
Abundant carbonate concretions and carbonate-cemented beds occur in the coal-bearing freshwater Miocene sedimentary fill of the Most Basin, northern part of Bohemia. Most of these carbonates were formed during diagenetic processes. Primary syngenetic carbonates are rare and are represented only by shells of mollusks and by rare occurrences of freshwater carbonates and clays with calcite content. These syngenetic carbonate types occur at several rare sites in the sedimentary sequence below the main coal seam.

Interpretation of geochemical and mineralogical data from the prevailing diagenetic carbonate types requires very detailed approach, since even within a single siderite concretion an evolution of diagenetic conditions and processes from early to late diagenesis can be recorded. Concretion centre-to-rim profiles in carbonate C and O isotope composition, carbonate chemistry and in carbonate/clay ratio showed that centers of some concretions are characterized by the highest Mn content, high carbonate/clay ratio and by high carbonate δ¹³C values. These carbonate types were formed during early diagenesis and very shallow burial, in the zone of bacterial fermentation (methanogenesis). Outer concretion zones frequently reflect conditions of deeper burial, higher compaction of the hosting sediment, and higher temperatures, with dominance of thermal decomposition of the organic matter as a source of CO₂ for the carbonate growth. In between the diagenetic carbonates the dolomitic sandstone cements represent the latest diagenetic phase. Calculations based on carbonate δ¹⁸O data of these cements indicate diagenetic temperatures up to 50 °C.

The results of petrographical investigation show that bioclastic carbonates from the Santa Cruz Mts. localities are free of siliciclastic admixtures. Some exceptional chemical purity and brightness remain preserved, because the shallow water limestone fragments are cemented repeatedly by pure calcite mud. The majority of limestone fragments consist of (1) biomicrosparite with algal and foraminiferal bioclasts, (2) biomicrite, and (3) oosparite. From the chemical point of view, the average content of CaO is 55.5 wt. % (representing 98.9–99 wt. % low-Mg calcite) in nearly all samples, satisfying specific requirements for industrial applications, e. g., as white cement mix with silica sand and kaolin as well as finely ground limestone filler for the Portland limestone cement. The use of both products seems to have many benefits, mainly positive effect of limestone filler on the water demand in concrete.

Volcanic rocks – basalts, melaphyre, phonolite, spilite, porphyry, and diabase – from various localities of the Bohemian Massif were investigated. Basalts from Měrunice, Smrčí and Všechlapy show the best quality of the strength properties. Their values of the simple compressive strength oscillate about 350 MPa and values of cross-tensile strength range from 14 to 17 MPa. On the contrary, basalts from locality of Dolánky, melaphyre, spilite, porphyry, and diabase have the smallest values of the strength properties – up to 160 MPa for simple compressive strength and 6–13 MPa for cross-tensile strength, respectively. Only diabase revealed a very high value of cross-tensile strength – 19 Mpa. The obtained results serve for consequential research at the Faculty of Science.

A new method for the determination of seismic hazard was developed. This method is based on the extrapolation of regression polynomial distribution function of seismic vibration acceleration in the NPP Temelín site. Developed method is non-zonal and its input data are only values of seismic vibration acceleration in NPP Temelín site. Method yet demands fulfilment series of conditions for input data, namely their stacionarity and allocation of earthquakes zones. The obtained results by new method were compared with yet results obtained by various previous methods. Up to now accepted values were confirm also by new simple method.

The new method based on the extrapolation of regression polynomial distribution function of seismic vibration acceleration was applied for NPP Temelin site. Developed method is non-zonal and its input data are only values of seismic vibration acceleration in NPP Temelín site. The obtained results by new method were compared with yet results obtained by various previous methods. Up to now accepted values were confirm also by new simple method.
Masaryk University, Faculty of Science, Brno, Project 7144: Micromorphology of samples from locality Tel Abrid, SE Syria (L. Lisá)
Micromorphological descriptions and interpretations of eight samples from Tel Abrid 2007 season were elaborated. Two samples are made from mudbricks, three samples from plaster, one sample was described macroscopically as a typical floor deposit, sample from the layer below described macroscopically as probably buried soil, sample macroscopically described as “virgin soil”, and residuum of mudbrick found in upper layer disturbed by ploughing. Additional analyses are loss of ignition (LOI) (carbonates and organic matter).

The mudbrick samples show slight differences (Fig. 78); one sample contains material with different color and is moderately sorted while the other one is well sorted. Both samples contain added organic matter. The basic matrix stays the same, the differences are probably only in the general inhomogenity and by unsorting of samples. Another sample shows significant differences represented for example by anthropogenetically influenced material (partly burned piece of matrix, a piece of bone), the different porosity and more intensive corrosion of pedogenetically originated carbonates. One sample was macroscopically interpreted as a typical floor, but microscopically is visible just increase of coarse fraction, decomposed organic matter and a piece of bone. There were no features typical for floor deposits identified. The sample below floor layer is probably an example of primary material not influenced by man or by erosion. The typical layering can be interpreted as storm events connected with increased humidity. The primary structure was probably preserved by human activity (building works). One sample was macroscopically described as a virgin soil and as the only one shows the features typical for pedological process (moderately developed A horizon). One sample was macroscopically described as a residuum of mudbrick in a layer influenced by ploughing. It was micromorphologically interpreted as a mix of material of different composition and provenance.

The graywacke-like sandstone is slightly affected by weathering and remains sufficiently strong and durable in Jamaican tropical climate. Aggregate characteristics, particularly angular shape of grits and grading of processed rocks, should be improved in artificial aggregates.

Weakly cemented quartzose conglomerate with calcite clasts is considered as the appropriate raw material for manufacturing coarse sand. The potential deficiencies are consistent with a gap-grading, a reduced strength (due to variation in calcite content and low percentage of argillized lithoclast). For satisfactory particle size distribution this material should be mixed with alluvial silica sand.

A series of the XRF chemical analysis was performed in order to clarify the chemical composition of calcarenite and biosilica-bearing limestone from new localities within the Santa Cruz Mts. and Northern Coastal belt. Vein barite from the Benbow Inlier is particularly well suited for barium chemicals and as white pigment, because it is clean.

Among the main monitored parameters in atmospheric precipitation belongs pH values and fluxes of the main acidificants such as S and N. In this chapter we evaluated the fluxes at site DM before all due to existing data from 90ties of the past century. Comparing the values from 90ties of the previous century with the current pH values it is remarkable that in 21^st century samples with pH < 4.2 are exceptional, while samples with pH > 5.0 became very common. This is a result of desulphurization of coal heated powerplants that has been completed in the Czech Republic in year 2002.

On the other hand, deposition fluxes of nitrogen in form of NO₃ did not change as dramatically but still high monthly deposition fluxes over 3.0 kg.ha^-1 were not detected either. The decrease of NO_x emissions from the burning of fossil fuels was compensated by increasing vehicular emissions.

Czech Geological Survey, branch Brno, Projects Nos. 7217, 7245: Triaxial strengths of selected types of rocks (R. Živor)
Triaxial strengths of andesite, claystone and two types of limestones were measured and compared using by a conventional triaxial test. Ten various levels of confining pressures up to 50 MPa were used during the tests. In the case of one type of limestone the effect of water saturation of sample on the triaxial strength was also studied. Triaxial strengths of limestones and claystone were found to markedly increase under lower values of confining pressure. The increase is not so strong under higher confining pressures (25–35 MPa approximately). This trend is very distinct in the case of claystone when the triaxial strength value reached under confining pressure of 25 MPa has not almost changed by the growing confining pressure. On the other hand, the triaxial strengths of andesite shows a contrary trend. The strength accrual is very slowly under lower values of the confining pressure while a marked triaxial strength accrual comes up after transcendence of confining pressure value of 25 MPa.

The trends of triaxial strength accruals of limestone with natural moisture and fully water-saturated limestone are very similar. However, saturated limestone shows about 20 % lower triaxial strength values on average than limestone with natural moisture.

Of special interest is the recognition of hyaloclastite-rich lapilli tuff and some of the spilitic glassy tuffs which may serve as pozzolanic admixture for both the production of blended Portland cement and pozzolanic concrete/mortar. Pozzolans are not cementitious by themselves, but form a hydraulic alumosiliceous compounds when mixed with lime hydrates. The active pozzolanic components in studied rocks refer to authigenic zeolites (analcime or gismondite), basic glass, and smectite. The pozzolanic activity is also enhanced due to the high microporosity and specific surface area of hyaloclasts.

The essential requirements of foundry sand for casting is that those sand-sized grains are stable in bituminous mixtures, and resistant to stripping, i. e., that they maintain adhesion to binder agents. Certain aggregate properties, such as grain macroporosity, resistance to periferial grain alteration, and workability of mixtures have greater significance in some context than chemical aggregate purity.

The apatite fission-track data documenting a rapid decrease in temperature from 120 ºC (PAZ) to 20 ºC in the gneisses already between 3.0–2.0 Ma suggest the existence of dissected mountain relief at that time which probably developed (in a substantially lower elevation above the sea level) during the Pliocene. The rapid decrease in temperature of the exhumed crystalline rocks can evidence one of the substantial periods of rapid erosion and denudation of the paleorelief of the High Himalayan nappe which were stimulated by the integration of its tectonic uplift with the increasing of intensity and range of exogenous geomorphological processes as a consequence of global climatic change.

Gneisses have the highest value of the simple compressive strength in parallel direction to foliation surprisingly (265 MPa). Simple compressive strength found in direction of 25° to the foliation is the lowest (178 MPa) when a foliation angle is closed to the future fracturing surface. The simple tensile strength was the highest in the parallel direction to the foliation and the lowest in the perpendicular direction to the foliation (11 MPa and 9 MPa, respectively). On the other hand, the shear strength determined by a punch test method was the highest in the perpendicular direction to the foliation and the lowest in the parallel direction to the foliation (32 MPa and 29 MPa, respectively). Parameters of the shear properties – angle of shear resistance and shear strength – were also determined by calculation from compressive and tensile strength values by Mohr envelope method. By this way determined shear strength value varies from 21 MPa (in the sideways direction to the foliation) to 27 MPa (in the parallel direction to the foliation). The angle of shear resistance oscillates about 66°. The deformational characteristics – Young’s and deformation moduli are significantly higher in the parallel direction to the foliation (45 GPa and 51 GPa, respectively) then ones determined in the parallel direction to the foliation (22 GPa and 30 GPa, respectively).