National Repository of Grey Literature 11 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
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...
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.
Highly siderophile element and Re-Os isotopic geochemistry of carbonatites and associated alkaline rocks from selected occurrences in India
Polák, Ladislav ; Ackerman, Lukáš (advisor) ; Krmíček, Lukáš (referee)
Carbonatites are intrusive and extrusive rocks with content of carbonate minerals > 50% predominantly derived from upper mantle. They represent a potential economical source for platinum- group elements as can be seen on actively mined sites like Phalaborwa in South Africa or Ipanema in Brazil. The first complete dataset for highly siderophile element (HSE) abundances along with their 187 Os/188 Os compositions for carbonatites, silicocarbonatites and associated alkaline rocks (pyroxenite, syenite, monzogabbro and tonalite) from two Neoproterozoic (~ 800 Ma) suites from Samalpatti and Sevattur, Tamil Nadu region in south India is presented. The data were obtained by a standard methods in involving decomposition of samples in Carius Tubes, Os separation by CHCl3 following microdistillation and Ir, Ru, Pt, Pd isolation by anion exchange chromatography. The data show that carbonatites from Samalpatti and Sevattur are characterized by very low HSE contents, lower than other mantle-derived mafic melts such as basalts or komatiites. Suprachondritic OsN/IrN ratios might suggest that carbonatites are able to concentrate not negligible amount of Os. Due to high, non-uniform 187 Os/188 Os ratios, we suggest that the source of carbonatitic melts was largely heterogeneous with high contribution of crustal...
Trace element and Re-Os geochemistry of mantle pyroxenites from the Bohemian Massif
Haluzová, Eva ; Ackerman, Lukáš (advisor) ; Jelínek, Emil (referee)
Mantle pyroxenites are important components of mantle rocks, because they provide important insights into bulk composition and heterogeneity of the Earth's upper mantle and therefore, direct evidence of mantle evolution throughout the Earth history. Studied pyroxenites from localities Bečváry (the Kutná Hora Complex), Níhov, Nové Dvory, Mohelno, Horní Kounice, Karlstteten and Meidling (the Gföhl Unit of the Moldanubian Zone) occur as dykes and/or layers within spinel and garnet peridotites from the Bohemian massif. Whole-rock concentrations of rare earth (REE) and other trace elements in studied pyroxenites yield extreme variability, which most likely reflect: 1) variable garnet/clinopyroxene ratios in bulk rocks, 2) different degree of fractionation of parental melts and 3) different concentrations trace elements in the source host material. Pyroxenites from locality Mohelno (LREE-depleted) may be derived from depleted or only slightly enriched suboceanic mantle. In contrast, pyroxenites from Karlstetten, Meidling, Horní Kounice and Nové Dvory (LREE-enriched) crystallized from the melts derived from enriched mantle source with possibly significant contribution of recycled crust. Studied pyroxenites are characterized by extremely variable 187 Os/188 Os ratios. While the pyroxenites from Mohelno and...
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...
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...
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...
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...
Historical cinnabar deposits in Bohemia - genetic study.
Velebil, Dalibor ; Ackerman, Lukáš (referee) ; Zachariáš, Jiří (advisor)
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...

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