Felsic granulites from the Kutná Hora complex in the Moldanubian zone of central Europe preserve mineral assemblage that record transition from early eclogite to granulite facies conditions, and exhibit discordant leucocratic veining, which is interpreted as evidence for melt loss during the decompression path. The granulites are layered and consist of variables proportions of quartz, ternary feldspar, garnet, biotite, kyanite, and rutile. In the mesocratic layers, garnet grains show relatively high Ca contents corresponding to 28-41 mol. % grossular end member. They have remarkably flat compositional profiles in their cores but their rims exhibit an increase in pyrope and a decrease in grossular and almandine components. In contrast, garnets from the leucocratic layers have relatively low Ca contents (15-26 mol. % grossular) that further decrease towards the rims. In addition to modelling of pressure-temperature pseudosections, compositions of garnet core composition, garnet rim- ternary feldspar-kyanite-quartz equilibrium, ternary feldspar composition, and the garnet- biotite equilibrium provide five constraints that were used to constrain the pressure- temperature path from eclogite through the granulite and amphibolite facies. In both layers, garnet cores grew during omphacite and phengite dehydration...

The study of fluid inclusions proved the metamorphic origin of the cinnabar-pyrite mineralization at the deposit of Horní Luby. In addition, thermal conditions of the mineralization formation were determined. During the deposit forming processes, the primary homogenous H2O-CO2 fluid of the temperature of about 300řC was differentiated to fractions rich in H2O or CO2. The differentiation took place in several stages in the temperature range between 200 to 150řC. Quartz crystallized from the parent fluid at the temperature about 300řC, pyrite at temperatures in the range of 220řC to 210řC and cinnabar at temperatures in the range of 195řC to 160řC. The cinnabar is thus the youngest mineral at the deposit (crystallization succession. quartz - pyrite - cinnabar). At the deposit of Jedová hora, quartz crystallized at the temperature of about 160řC to 150řC, barite at temperature of about 115řC (the fluid boiling point) and cinnabar in the range between these temperatures. The origin of mercury at all Czech historical deposit of cinnabar can be very likely related to Lower Paleozoic submarine volcanism. In all cases, the pre-concentrated mercury was remobilized during the Variscian metamorphosis, followed by precipitation in form of veins with cinnabar or as cinnabar impregnation. Study of tetrahedrite...

Ore deposits of the Krásná Hora ore district are the main representative of the Sb-Au mineralization in the Czech Republic. It can be classified genetically as epizonal subtype of orogenic gold deposits. Spatially and partly temporally are associated with the intrusion of the Central Bohemian Pluton. The ore bodies are related to quartz veins that follow the course of E-W striking lamprophyre dykes, which are usually heavily crushed and altered. Ore shoots with massive stibnite are located mainly at the intersections of these E-W trending veins with the NW-SE striking tectonic fault zones. Au-Sb ores at Krásná Hora ore district formed in an area of repeatedly activated fault zones. Three generations of hydrothermal quartz were identified on microscopic scale. Earliest quartz (Qtz1), which was considered in the literature auriferous originated from low-salinity H2O - CO2 fluids at ~350 řC and at a depth of about 5 km. The younger quartz (Qtz2) originated at lower temperatures of about 260 řC and lower depth of about 3-4 km from low/saline aqueous fluids. Both older (Qtz1) and younger quartz (Qtz2) are not auriferous. The gold is associated with younger paragenetic formation (Anti + Au + Cc + Qtz3) that fills in intergranular spaces and fractures in Qtz1 and Qtz2 . Due to the partial exhumation of the...

III Summary This thesis is focused on crystal chemistry and crystal structure of apatites from alkaline rock of the Bohemian Massif. Fifteen samples of volcanic rocks, mostly of the Cenozoic age was selected for the study. Sample No. 5 is of the Silurian age. Sample No. 15 originates from volcanic rock of the Cenozoic age from the Slovak Western Carpathians. This sample was chosen for this study due to its substantially different chemical composition. The contents of major and minor elements in apatites were measured on an electron microprobe, the contents of some minor and trace elements were determined by laser ablation inductively coupled plasma mass spectrometry. Selected samples were investigated by cathodoluminescence (CL) spectrometry. Crystal structure of studied apatites was characterized by X-ray diffraction and Raman spectroscopy. It was found that dominant anion at position X is fluorine. The OH content calculated on the basis of the fully occupied position X is significant in some samples. The amount of Cl is generally low. The exception is the sample No. 15 where Cl reached up to 0.6 apfu (Z = 2). Studied apatites contain many substitutions but they are generally of minor extent. Strontium, iron and REE at position M belong to the most common and most important substituents for calcium in...

English abstract This diploma thesis is concerned with the brief introduction to the structures and fabrics in granitoid plutons. In the next part of this work are sumarized results of structural analyses of Weinsberg-type granite intrusion (Prášily and Strážný pluton) located in the SW part of high-grade rocks of the Moldanubian Zone. This research proceeded based on a combination of field structural data and results of AMS (Anisotropy of magnetic susceptibility) method. The emplacement and crystallization of both studied magmatic bodies took place in cooperation with the final phases of S3-fabrics development. This "bavarian phase" has a character of heterogenous deformation with indications of the dextral subhorizontal shear (WNW-ESE strike). During this event, syntectonic emplacement and internal fabrics development of strážný pluton took place at ~322 Ma. The transpression was followed by the localized transtension tectonics in NE direction, probably in cooperation with exhumation of high-grade metamorphic rocks of Bavarian terrane. In this phase, at ~320 Ma, the granitoids of Prášily pluton were emplaced into the considerably exhumed crust of the Moldanubian region.

Fabrics and geodynamic evolution of Moldanubian orthogneisses English abstract The aim of this paper is a structural analysis of selected mostly Cambro-Ordovician orthogneisses cropping out in a part of high-grade rocks of western Moldanubian Zone. These rocks have been affected by HT-MP/LP metamorphism and the polyphase deformation during the Variscan orogeny. In the blaník orthogneisses, (Qtz + Kfs + Plg + Bt ± Ms ± Sill ± Ky) an early deformation banding dips steeply to SSE to ESE. These fabrics were overprinted by NW to N gently dipping foliation with well developed stretching lineations plunging to W. Rare kinematic indicators (e. g. fold and pressure shadows asymmetry) reveal a strong subvertical contraction and stretching in the ~N-S direction. Based on the microstructural analysis this contractional event was connected with the activity of "Grain Boundary Migration Recrystallization" (GBM). Ductile shear zones dipping to E, locally ESE or ENE were identified. Bechyně orthogneisses (Qtz + Kfs + Plg + Bt ± Ms) is a N-S elongated body with the presence of regional pervasive metamorphic foliation dipping homogenously under low angles from SSW to WNW . These foliations bear well developed mineral or stretching lineation of quartz, biotite and feldspar aggregates plunging to ~SW. In the blaník orthogneiss...

English abstract This diploma thesis deals mainly with identification of magmatic (respectively magnetic) fabrics, geodynamical aspects of emplacement and geochronology of the Eisgarn granitoids. For the analysis Klenov and Mrákotín pluton were chosen, which is placed in the eastern part of the Moldanubian Batholith. This thesis contains petrological and mezoscopic structural analysis of the host metamorphic rocks of the Moldanubian Unit and it includes calculation of P-T conditions of the main mineral assemblage. This is followed by petrological, geochemical and mezoscopic structural analysis of the Klenov and Mrákotín pluton and analysis of the anisotropy of magnetic susceptibility, geochronology of the Klenov pluton, gravimetry analysis and determination of the orientation of density interfaces in different depths. Granitoids of the Klenov and Mrákotín pluton are characterized as S-type granitoids, whose protolith were probably metasedimentary rocks. From the analysis it is also evident that the Klenov pluton records lower degree of magma fractionation than the Mrákotín pluton. The emplacement and crystallization of both studied magmatic bodies took place in cooperation with a development of regional metamorphic fabrics, which originate between 329 and 327 Ma. During this period a rapid exhumation of...

The Bohemian Massif was consolidated during the Variscan orogeny (~400-300 Ma), which involved several oceanic subductions and collisions of continental micro-plates. The central part of the Bohemian Massif, the Moldanubian domain, shows a large accumulation of felsic high-pressure metamorphs. We present a numerical model of exhumation of these rocks due to continental collision and underthrusting. The key feature of the model is a felsic (light, rheologically weak and rich in radioactive elements) material in the lower crust of one of the colliding blocks. We examine the influence of the rate of convergence of the two blocks, radiogenic heating in the felsic lower crust and efficiency of erosion, on the model evolution and pressure-temperature conditions in the lower-crustal material. The models where the material is sufficiently weakened due to radiogenic heating show formation of an orogenic plateau, sedimentation in a foreland basin, and crustal thickening accompanied by gravity-driven exhumation of the lower crust and subsequent sub-horizontal flow in the middle crust. In colder and/or faster models, the thickening is dominated by folding. We correlate the tectonic style of these two types of models with differences between the high-grade rocks in the southern (Moldanubian) and northern (Sudetic) parts...

English Abstract The Dunkelsteiner Wald granulite massif in Lower Austria belongs to the Gföhl unit of the Moldanubian zone of the Bohemian Massif. Predominant rocks are felsic granulites which in some places contain garnet pyroxenites and peridotites. There are positions of mafic and intermediate granulites on their intersection. Primary mineral association of mafic granulites is garnet, clinopyroxene rich on Jd and Ca-Tschermack component and kyanite. These rocks probably represent Ca-richer variant of pyroxenites. Contemporary mineral association is make by garnet, clinopyroxene, plagioclase and orthopyroxene. Accessory there is amphibole, spinel, rutile and Ilmenite in the rocks. Sapphire inclusion in garnet cores close to kyanite inclusions has been observed in several cases. Decompression of these rocks creates specific symplectite textures in mafic granulites characterized by plagioclase inclusions. These inclusions are partly or fully surrounded by garnet porphyroblasts on their edges and coarse grain symplectics of plagioclase and pyroxene in matrix. A possible explanation of emergence of this specific texture in rocks on intersection with felsic granulite is an infiltration of melt from felsic lithology. Proof can be the enrichment of K component on edges of plagioclase grains. On the other hand,...

No description available.