National Repository of Grey Literature 20 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Silica sinter as a source of paleoenvironmental information
Sobek, Ondřej ; Hošek, Jan (advisor) ; Rapprich, Vladislav (referee)
Hydrotermální prameniště s alkalicko-chloridovými a SiO2 přesycenými vodami jsou ojedinělým typem terestrického prostředí, vyznačujícím se tvorbou chemogenního sedimentu, nazývaného křemenný sintr. Na termálním a chemickém gradientu, od ústí vývěrů až po distální části prameniště, lze vyčlenit několik litofaciálních typů křemenných sintrů (např. gejzírit, packed fragmental sinter, palisádový sintr aj.), jejichž výsledná textura je ovlivněna řadou abiotických a biotických faktorů. Ve vzdálenějších oblastech od hydrotermálních vývěrů se nachází mokřadní prostředí s druhově pestrým zastoupením vyšších rostlin a asociované fauny. V těchto částech hydrotermálního systému vzniká tzv. plant-rich sinter, který umožňuje studovat anatomii silicifikovaných rostlin a dalších organismů na velmi vysoké úrovni, což činí tuto litofacii cenným zdrojem paleobotanického materiálu a paleoenvironmetnálních informací. Předkládaná práce poskytuje ucelený přehled o křemenných sintrech s důrazem na využití těchto specifických sedimentů při rekonstrukci lokálních paleoenvironmentálních podmínek. Klíčová slova: hydrotermální prameniště, křemenný sintr, silicifikace, rostlinný materiál, paleoenvironmentální rekonstrukce
Quantitative description of textures in volcanic rocks: Case study of trachybasalt from Dubičná
Ditterová, Hana ; Dolejš, David (advisor) ; Rapprich, Vladislav (referee)
- iii - ENGLISH ABSTRACT Quantitative description of textures, in particular, the distribution of grain sizes, is becoming a powerful tool for interpreting kinetic processes that govern crystallization of igneous rocks. Variation in grain size are frequently represented by logarithm of population density vs. linear crystal size, where the majority of igneous rocks forms a linear trend. Its slope provides an estimate of characteristic grain size, or growth rate and crystallization time, whereas the intercept provides the nucleation density. The log-linear trend is predicted to result from kinetic nucleation and growth processes only, whereas its modifications such as kinks or curvature are due to mechanical separation or accumulation of crystals, magma mixing or Ostwald ripening (coarsening) in the presence of melt. In order to investigate the true, three-dimensional crystal size distribution, the raw two-dimensional data acquired from thin sections or rock slabs must be processed by various stereological methods. We illustrate application of quantitative textural measurements to distribution and origin of clinopyroxene crystals in a trachybasaltic lava flow from Dubičná near Úštěk. This effusion belongs to Cenozoic volcanic products in the Bohemian Massif, specifically to its main Eocene-Miocene stage in...
Magmatic and Volcanic Evolution of the Doupovské hory Volcanic Complex
Rapprich, Vladislav ; Holub, František (advisor) ; van Wyk de Vries, Benjamin (referee) ; Renno, Axel D. (referee)
The Doupovské hory Volcanic Complex (DHVC) occupies the western part of the northeast- southwest trending Eger Graben in northwestern part of the Bohemian Massif. The Graben follows the older Variscan suture between the Saxothuringian and Teplá-Barrandian Domains. The rocks of the DHVC are alkaline with setting and composition similar to other Cenozoic intraplate volcanic complexes of the Central and Western Europe (CIMACi). The Doupovské hory Volcanic Complex started the activity in the Lowermost Oligocene and lasted until Lower Miocene. The volcanic activity resulting in accumulation of the Doupovské hory Volcanic Complex was several times interrupted by periods of volcanic edifice decay and sector collapses. The magmatic activity lasted for ca. 14 M.y. and built a volcanic complex of total thickness 600-1000 m. The earliest volcanic activity was explosive in style and the eruptions could be classified as Strombolian to Sub-plinian and phreatomagmatic. The eruptions deposited about 80 m of volcaniclastics. This initial activity was dated by paleontology to the Lowermost Oligocene. The volcanic activity subsequently became calmer and lava flows dominated over explosive events. The growth of the early DHVC edifice culminated with intrusions of the Flurbühl intrusive complex by about 30-29 Ma. The...
Volcanism of Large Igneous Provinces in Earth's history; possible impacts on global ecosystem
Zajícová, Jana ; Holub, František (advisor) ; Rapprich, Vladislav (referee)
Large igneous provinces (LIPs) are huge accumulations of magmatic rocks originated during unusually short time and characterized by extremely high magma productivity. Among them, namely the continental flood basalts (traps) cover very extensive areas and may or may not be associated to rifting and breakup of continents. However, also highly voluminous oceanic plateaus were recognized and some authors count to LIPs even some other types of huge magmatic complexes. A large amount of gases is released with escaping magma, usually oxides of carbon, sulfur and nitrogen. These gases more or less have impact on the environment and thus also influence organisms. The formation of magmatic provinces repeated many times in the past. The best known are continental Deccan Traps in India and the most voluminous Siberian Traps. Oceanic LIPs are represented, e.g., by the Ontong Java Plateau in the west Pacific Ocean. There is a link in dating the emergence of large igneous provinces and mass extinctions. As an example, the largest known extinction at the end of Permian, which was broadly contemporaneous with the formation of the Siberian traps (approximately 250 Ma ago), or extensive loss of species on the boundary of Cretaceous / Tertiary, which coincides with the formation of the Dekkan in India (before about 65...
Reconstruction of volcanic processes in the Komárov Complex: case from the Zaječov volcanic centre
Machalová, Jitka ; Rapprich, Vladislav (advisor) ; Fediuk, Ferry (referee)
Reconstruction of volcanic processes in the Komárov Complex: case from the Zaječov volcanic centre Summary Sheet lava flows with pillow breccias and hyaloclastites are interbedded agglomerate and volcaniclastics. This is the basic interpretation of rocks exposed in quarry near the town Zaječov. Rocks are part of geological area called Barrandien. Resediment volcaniclastic particles were transfer by sediment gravity flows. Agglomerates were deposited from volcaniclastic debris flow and fine grain volcanoclastics sediments from turbidity currents or hyperconcentrated flows. These types of flows named as eruption-fed aqueous density current are directly initiated by subaqueous volcanic eruption. One volcaniclastics strata set on the south wall of quarry was formed from subaquatic eruption plume, called steam copula. Steam copula created under the eruptive vent is water exclusion zone. Accretion lapilli can be formed in this zone if the copula is stable for a longer time. Accretion lapilli were generally considered to be able to form only in subaerial conditions, during the phreatomagmatic eruption till lately. Rocks exposed in quarry were probably formed during the Surtseyan eruption in shallow subaqueous setting. According to thin section lava flows are containing pseudomorphosis phenocrysts of olivine and...
Mineral and chemical changes of magma crystallization during formation of post-Variscan intrusions and veins in the Moldanubian Zone of the Bohemian Massif
Kubínová, Šárka ; Faryad, Shah Wali (advisor) ; Rapprich, Vladislav (referee) ; Moyen, Jean-François (referee)
- 1 - English abstract The late-Variscan magnesium-rich potassic to ultrapotassic igneous rocks create numerous dykes, dyke swarms and several plutonic bodies at the boundary between the Moldanubian Zone and the Teplá-Barrandian Block of the Bohemian Massif. They represent a volumetrically smaller group of igneous rock but they are the key to understand generation of melt and processes of mantle metasomatism and shallow-level magma differentiation. In addition, they are considered as an indicator of the tectonic evolution of this part of the Bohemian Massif during the final stages of the Variscan orogenesis. Currently, they are the subject of discussion by several authors in terms of their genesis, emplacement time and geodynamic significance. The presented thesis is a compilation of four scientific publications that are aimed at the petrological study of selected (ultra)-potassic dyke rocks from several localities at the western border of the Moldanubian Zone. The study of mineral textures, mineral chemistry and whole-rock geochemistry together with magnetic fabrics, structural field relations and age determinations allowed us to describe the crystallization history of these rocks, discuss their evolution from melt generation to magma ascent and emplacement, and form the model of sequence of Variscan...

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