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Geochemistry of mantle xenoliths of the České středohoří Mts.
Kohoutová, Iveta ; Ackerman, Lukáš (advisor) ; Jelínek, Emil (referee)
The České středohoří Mts. forming the most important and active part of Ohře/Eger rift are formed by volcanic rocks of Tertiary age containing upper mantle xenoliths which can provide us information about internal structure of upper mantle. This diploma thesis is focused on the study of mantle xenoliths from this part of Bohemian massif close to the city Litoměřice (4 locations: Dobkovičky, Prackovice, Kuzov, Medvědí hill) and for comparison another 4 locations of mantle xenoliths from the northern Bohemia locaties Brtníky in Šluknovský ledge, Kraslice and Zámeček at Fláje in Krušné Mts. and Venuše volcano in Nízký Jeseník at Bruntálská Highlands. Almost all studied xenoliths are spinel harzburgites or lherzolites with mineral association olivine + orthopyroxene + clinopyroxene + spinel (the most often Cr-spinel). They have usually protogranular texture followed by porfyroclastic texture (porfyroclasts are represented by olivine, orthopyroxene and in some cases also by clinopyroxene, and fine-grained matrix of all these minerals with olivine showing undulose extinguishes). An equigranular texture is the least common. Host rock of the xenoliths is always basanite. The most abundant mineral in peridotite xenoliths is olivine with #Mg value 89,4-91,5; followed by orthopyroxene with #Mg value 90,8-92,1...
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Geochemistry of upper mantle rocks from Mohelno-Biskoupky locality
Kovács, Andrea ; Ackerman, Lukáš (advisor) ; Jelínek, Emil (referee)
Peridotites occuring in orogenic massifs provide important insights into geochemical processes of the Earth's upper mantle by providing direct evidence of mantle evolution throughout Earth history. It has been previously demostrated (e.g. Medaris et al., 1990, 2005) that the uppermost tectonic unit of the Bohemian Massif - the Gföhl Nappe hosts a variety of peridotites that originated from different sources, including subcontinental lithosphere, suboceanic asthenosphere, and possible ultramafic layered intrusive complex. The Czech peridotites of the Gföhl Nappe has been divided into three groups, defined by Medaris et al. (1999), according to their chemical compositions, identity and relations of the aluminous phases, ortopyroxen compositions and estimated P-T conditions. According to Medaris et al. (2005) "Type I" peridotites - represented by Mohelno and Biskoupky bodies - equilibrated in low P-T regime (recording the highest equilibration temperatures - up to 1335 ⁰C at 29 kbar - among the Gföhl peridotites) consist of spinel peridotite with garnet appearing only at its margins. Peridotites are enclosed in granulites that have been extensively recrystallized mostly at amphibolite-facies conditions. Many studies have been done on this locality and a wide range of mineralogy and P-T histories has...
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Fluid inclusion study of pegmatites from Skalsko near Jílové and Dolní Bory
Fenclová, Kateřina ; Zachariáš, Jiří (advisor) ; Ackerman, Lukáš (referee)
Fluid inclusions of pegmatites from two localities in the Moldanubina Zone were studied in order to constrain P-T conditions of their crystallization and enstablish composition and properties of fluids associated with pegmatite formation. The first locality Skalsko (near Jílové u Prahy) is located within the Central Bohemian Plutonic Complex (CBPC) of Variscian age.Pegmatitic dykes represent the late stage of magmatic evolution of the CBPC. Pegmatite is hosted by biotite-granodiorite of the "Požáry" and "Sázava" types and probably belongs to the muscovite class of the pegmatites. The other locality, Dolní Bory, is located within the Bory granullite Massif ( metamorphism is dated to about 340 Ma). Following types of pegmatite occur in this district: 1. barren to less evolved pegmatites; 2. more evolved phosphate-bearing pegmatites and 3. Li-complex, the most evolved pegmatites. The studied material comes from an andalusite-diaspore nodule hosted by blocky quartz of the barren pegmatite (pegmatite dike No. 3). Fluid inclusions were studied mostly in quartz (Skalsko, Dolní Bory), andalusite and diaspore (Dolní Bory). Fluids trapped in samples from Skalsko correspond to H2O-CO2 and H2O types. The H2O-CO2 fluid had relatively low salinity (4,1-5,9 wt.% NaCleq), contained from 20 to 5 mol.% CO2 and its...
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Geochemistry and petrology of plagiogranites from the Jílové belt
Santolík, Václav ; Ackerman, Lukáš (advisor) ; Jelínek, Emil (referee)
This thesis is focused on the study of the subvolcanic rocks from the northern part of the Jílové belt. The Jílové belt is a strip of magmatic rocks belonging to the Davle Volcanic Complex situated in the center of the Bohemian Massif, south of Prague, close to the border between the Teplá-Barandian and Moldanubian units. The sub-volcanic facies of its northern part has been previously ascribed to trondhjemite, alaskite or plagiogranite. In this study, we provide new geochemical data such as major and trace element analyses paralleled by Sr-Nd isotopic data, which indicate the origin of these rocks in the mantle wedge. They probably represent a final product of a magmatic differentiation of an island arc series. Here, we consider two possible models for their origin, according to which we could also choose the correct classification of these peculiar rocks: adakite, or plagiogranite. Adakites are rocks formed by melting of a subducted slab which are predominantly related to the volcanic arc settings. In comparison, plagiogranites are rocks formed by an extreme differentiation of a mantle- derived basaltic melt in the oceanic crust environment. Our new geochemical data, especially the low degree of light rare earth enrichment (LaN/YbN = 0.8-1.3), is clearly inconsistent with the genetic association...
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Geochemistry of upper mantle rocks from Kozákov and Horní Bory, Bohemian Massif
Ackerman, Lukáš ; Jelínek, Emil (advisor) ; Faryad, Shah Wali (referee) ; Becker, Harry (referee)
The purpose ofthis dissertation is geochemical study ofupper mantle rocks at two sites from diÍlěrent geological settings of the Bohemian Massif (Czech Repub|ic) - Koziíkov and Homí Bory. The first part of dissertation represents a review of petrological and geochemical studies of upper mantle Íocks found in the Bohemian Massi{ which have been pub|ished or presented so far' These include information about ýpe and occuÍTences of mantle{erived rock with individual Bohemian Massif units and summarized present state of knowledge on depletion and metasomatism ofthese rocks. The principal questions related to the mantle beneath the Bohemian Massif which remďn opened are presented at the end of this part. The most important paÍt of the dissertation represents three comprehensive papers on geochemical studies of upper mant|e rocks from Koziíkov and Horní Bory. In the second part, a geochemical study of major elements, trace elements, and Sr-Nd isotopes combined with mineral chemistry of upper mantle xenoliths from the Koziíkov volcano have been presented. This unique suite of xenoliths samples upper 2/3 of the upper mantle in this region and, therefore' provides a great possibility to study uppeÍ mantle composition variations with depth. The results show that upper mantle beneath Koziíkov volcano underwent...
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Mafic and intermediate intrusions accompanying peraluminious granites of the Krušné hory Mts.batholit
Holečková, Pavla ; Jelínek, Emil (advisor) ; Ackerman, Lukáš (referee) ; Leichmann, Jaromír (referee)
Mafic and intermediate intrusions commonly accompany Variscan granitoid plutons in Europe. They are documented from different localities of Iberian Peninsula, from the French Massif Central, Schwarzwald, from different parts of the Bohemian Massif, in Romania, Greece, Corsica and Sardinia. They comprise wide petrographic varieties from quartz gabbros, diorites, granodiorites to monzonites. They usually constitute small bodies or veins, they often occur as mafic microgranular enclaves (MME) in granodiorites and in some granites. Dioritic intrusions are characterized by a relatively high amounts of lithophile elements (Rb, Sr, Ba, Cs, LREE), and they are simultaneously high in compatible elements (Ni, Cr, V a Co). Their isotopic ratios 87 Sr/86 Sr are in all compared locations similar and are close to the Bulk Earth (0.704 - 0.708). εNd values show larger scatter, some intrusions have more crustal composition (to -8), on the other hand, another intrusions have εNd positive, that points to a contribution of basic magma. The age of dioritic intrusions differs according to individual locality suggesting more than one magmatic episode. The oldest occur in the French Massif Central (361 - 365 Ma), whereas the youngest are documented in Iberia (312 - 310 Ma). The oldest mafic intrusions in the Bohemian...
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Petrogenesis and evolution of the Davle Volcanic Complex
Santolík, Václav ; Ackerman, Lukáš (advisor) ; Krmíček, Lukáš (referee)
The Davle Volcanic Complex (DVC) situated in the Teplá-Barrandian unit (TBU) of the Bohemian Massif, is considered as a Neoproterozoic-Cambrian magmatic arc that developed on the northern active margin of Gondwana supercontinent during Cadomian accretionary orogeny. This study combines data obtained from fieldwork, petrography, rock-forming mineral microanalysis, major and trace element analysis, Sr-Nd-Pb isotopic systematics and U-Pb zircon geochronology in order to reveal the petrogenesis and evolution of the DVC. At least three-stage metamorphism including Cadomian seafloor alteration, Variscan regional metamorphism as well as contact metamorphism related to the emplacement of the Central Bohemian Plutonic Complex affected the DVC. The studied rocks follow calc-alkaline trend whereas tholeiitic trend previously reported is rather related to younger magmatic events. The northern part of the DVC is dominated by felsic subvolcanic (plagiogranite), volcanic (dacite- rhyolite) and pyroclastic (dacitic-rhyolitic tuffs and breccias) rocks with a few outcrops of basaltic andesite-andesite pillow lavas documenting the subaqueous activity of the DVC. These rocks are Na-rich, but K-poor, the plagiogranite contains albite most likely primary in origin, and exhibit highly radiogenic εNd values (~ +6 to +11),...
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Geochemistry and petrology of plagiogranites from the Jílové belt
Santolík, Václav ; Ackerman, Lukáš (advisor) ; Jelínek, Emil (referee)
This thesis is focused on the study of the subvolcanic rocks from the northern part of the Jílové belt. The Jílové belt is a strip of magmatic rocks belonging to the Davle Volcanic Complex situated in the center of the Bohemian Massif, south of Prague, close to the border between the Teplá-Barandian and Moldanubian units. The sub-volcanic facies of its northern part has been previously ascribed to trondhjemite, alaskite or plagiogranite. In this study, we provide new geochemical data such as major and trace element analyses paralleled by Sr-Nd isotopic data, which indicate the origin of these rocks in the mantle wedge. They probably represent a final product of a magmatic differentiation of an island arc series. Here, we consider two possible models for their origin, according to which we could also choose the correct classification of these peculiar rocks: adakite, or plagiogranite. Adakites are rocks formed by melting of a subducted slab which are predominantly related to the volcanic arc settings. In comparison, plagiogranites are rocks formed by an extreme differentiation of a mantle- derived basaltic melt in the oceanic crust environment. Our new geochemical data, especially the low degree of light rare earth enrichment (LaN/YbN = 0.8-1.3), is clearly inconsistent with the genetic association...
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New data on the origin of the Fe-Cu-As skarn deposit at Obří důl, West Sudetes, Bohemian Massif
Pašava, J. ; Veselovský, F. ; Dobeš, P. ; Erban, V. ; Pour, O. ; Žák, Karel ; Ackerman, Lukáš ; Haluzová, Eva ; Creaser, R. ; Tásler, R.
The Obří důl Fe-Cu-As sulfide deposit is hosted in metamorphosed lenses of marble, calc-silicate rocks and skarns. The deposit is located up to a few hundred meters away from the contact of the large, late-orogenic Variscan Krkonoše-Jizera Plutonic Complex (KJPC). Mineralogical and fluid inclusion studies of the Gustavská ore lens show that the main sulfide stage, dominated by pyrrhotite, chalcopyrite and arsenopyrite, originated from water-rich hydrothermal fluids with salinities up to 8 wt.% NaCl eq. at temperatures ranging from 324 to 358°C.These fluids replaced mainly the carbonate-rich lithologies. The 34S values indicate a magmatic source of sulfur and Re/Os dating of molybdenite are consistent with simultaneous formation of the main sulfide stage ore and the KJPC.
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