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Crystallization kinetics of silicate melts
Vrbenský, Adam ; Špillar, Václav (advisor) ; Trubač, Jakub (referee)
A process called crystallization is involved in the formation of most minerals and rocks on the Earth. This process further consists of two sub-processes, which are nucleation and growth of crystal. Crystallization is driven by kinetic factors which are still not fully understood. As it plays a significant role in global geological processes, it is very important to understand its mechanisms. The study of kinetic factors began in the 1970s and continues to some extent nowadays. The main aim of this work was to create an overview of available studies focusing on the crystal growth rate from a melt. Based on these studies, reliable kinetic data would be selected for creation of a general crystal growth rate model in the future. Data from the experiments that were performed under constant undercooling conditions and in which the growth rate remained constant (no influence of a diffusion or fractionation effects), were considered as a reliable source for a possible model. Relatively large amount of data is available for plagioclase only, with the growth rates ranging 10-6 -10-1 mm/s. Maximum plagioclase growth rates are generally reached at undercoolings from 100řC up to 200 řC, and it reaches the order of 10-3 -10-1 mm/s, depending on the system composition.
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Slags from copper processing at the Al Salili site, 2000 BC, Sultanate of Oman
Cseryová, Viktória ; Trubač, Jakub (advisor) ; Bursák, Daniel (referee)
Metallurgy in the Arab world has always been famous. Research is currently underway on the territory of Oman, which should reveal more details of the ore deposits that were used for the production of ancient artifacts. This work aims to describe appropriate methods that will allow us to gain insight into the secrets of processing copper deposits at the al-Ṣalaylī site in Oman. This bachelor thesis deals with the overall chemical and mineralogical composition of ancient copper metallurgical slags from the al-Ṣalaylī site in Oman (South-eastern Arabia). These slags can probably be dated in range from the Late Bronze Age, Early Iron Age to Middle Islamic Period. This work aimed to characterize collected slag using a combination of optical and scanning electron microscopy analysis, X-ray diffraction analysis and electron microanalysis, it has been possible to determine the composition and describe the mineral phases in the slag and to determine the conditions of the prehistoric metallurgical process. The results of analysis indicated that the samples were pieces of tapped slag and furnace slag from a production of copper. Examined slags are mainly composed from Ca-Fe-Mg olivine and clinopyroxene filled with silicate glass and spinel. Copper either occurs as metallic phase with small Cu grains or is...
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Mechanisms of differentiation and emplacement of peraluminic granite magma: Říčany pluton, Bohemian Massif
Trubač, Jakub ; Žák, Jiří (advisor) ; Závada, Prokop (referee)
English abstrakt This thesis is focused on emplacement mechanisms of granitic magma into upper continental crust. The studied area is the Říčany pluton due to its unusual and asymmetric shape. Therefore, it represents a suitable intrusion for interpretation different models referring to emplacement of granitic magma. Common model for ascent of magma is incremental diking in present. The Říčany pluton of the Central Bohemian Plutonic Complex is a post-tectonic elliptical shallow-level intrusion emplaced into low-grade Neoproterozoic and Lowe Carboniferous times (~337 Ma). It comprises of outer, more fractionated, strongly porphyritic granite and inner, less evolved, weakly porphyritic granite. Mesoscopic foliation represents an onion-skin pattern and corresponds well to the magnetic (AMS) foliations. Magnetic lineation has a gentle dip (0-20ř) and closely parallels with the pluton contact in its outer part whereas the lineation dips steeply (60-70ř) with a variable trend in the pluton interior. Author interprets these fabrics as a result of a helical flow, which is a faster subvertical flow in the low-viscosity pluton centre being accompanied by a subhorizontal flow in the outer, higher-viscosity (phenocryst-rich) margin. The proposed scenario of the helical magma flow can provide a viable mechanism for the...
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Quartz microchemistry as metallogenetic indicator
Pacák, Karel ; Zachariáš, Jiří (advisor) ; Trubač, Jakub (referee)
Region surrounding the Central Bohemian Plutonic Complex represents one of the most important gold bearing zones in the Czech Republic. Several types of gold deposits dominated by hydrothermal quartz gangue were explored here and distinguished: the Intrusion related gold deposits ("Petráčkova hora" and "Mokrsko") and the orogenic gold deposits ("Jílové u Prahy" and "Kasejovice" ). Deposits "Libčice u Nového Knína" and "Roudný u Vlašimi" are partially similar to the orogenic gold type, but are different from other orogenic type deposits in the region. All together 38 samples from these five deposits were analyzed with laser ablation technique (LA- ICP-MS) to produce 228 measurements. Selected samples were selected to represent both main quartz gangue carrying the Au ore and latter weakly mineralized quartz gangue. Samples representing hydrothermal quartz gangue with no direct relation to Au-ore deposits were also collected in order to compare chemical composition of both quartz types originating from the same area. Main concern of this work was in-situ analysis of chemical composition of different generations of quartz gangue and statistical comparison of differences within individual deposits as well as comparing the examined deposits themselves. Total 65 isotopes were measured, trace element...
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A correspondence seminar as a motivation for secondary school students to study Geology
Teliščaková, Martina ; Trubač, Jakub (advisor) ; Mourek, Jan (referee)
Master thesis is focused on how to promote secondary school students' interest in the next study of Geology as a subject of their future professional specialization. The convenient motivational tool seems to be the use of special correspondence seminar to gain and expand their knowledge. Experimental part of this thesis consists of the application the correspondence seminars through the current communication media (e.g. web portal or social network), directly in secondary schools. The results are statistically analysed and evaluated by a questionnaire at the model secondary school. Key words: motivation, Geology, correspondence seminar, secondary school, questionnaire
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Silver separation technique for isotopic measurement in archaeological samples
Venhauerová, Petra ; Trubač, Jakub (advisor) ; Vaněk, Aleš (referee)
Silver isotopes nowadays present a very fast evolving system. One of the field in which this isotopic system is used is archaeology where the silver isotopes are used as a tracer of monetary and power changes between geographical regions. Through statistical analysis of measured data and their comparison with so far published values can be estimated probability of common source area of metal used for coinage. On Celtic coin samples (180-70 BC) provided by the Institute of Archaeology of the CAS, Prague (A. Danielisová) the isotopic composition of silver was measured. Silver was separated from the matrix elements by a method which uses ascorbic acid to precipitate silver. However, the weights of samples commonly used for this method are generally distinctly higher than the amounts of the obtained fragments of Celtic coins. Regarding the differences in the method and low weights of fragments, tests with variable concentrations of ascorbic acid and amounts of silver were performed. The amounts of silver used for this method are commonly ~30x-70x higher. The results showed that this method effectively separates silver from matrix elements and is sufficient for higher concentrations of silver; with lower ones the yields are reduced. The separated silver was measured using MC-ICP-MS. The adjusted...
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Granite in the Světlá nad Sázavou area
Hájková, Věra ; Matějka, Dobroslav (advisor) ; Trubač, Jakub (referee)
The diploma thesis summarizes the basic data about the geological structure of the wider area of Světlá nad Sázavou, acquaints with the history of granite mining in this territory and deals with the didactic use of the information found in the school and in the field. Author performing an excursion to the active quarry Horka with pupils of the 6th and 9th year of elementary school. The pupils' current knowledge of geological structures in the vicinity of Světlá nad Sázavou was verified before the excursion and after graduation the levels of knowledge were determined again. We found that it is possible to see if it is possible to carry out an evaluation, to test whether any further information is available. It was prepared for the pupils on a worksheet for a project day. For a closer acquaintance with granite and their suitable mind maps and didactic games, to fulfill materials (crossword, quad, memory, domino). Key words: Světlá nad Sázavou, granite, Melechov massif, didactic games, school project
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Isotope alteration of carbonate component of Cretaceous sediments from xenolites and vicinity of selected neovolcanic bodies of the Jičín volcanic field
Konečný, Tomáš ; Zachariáš, Jiří (advisor) ; Trubač, Jakub (referee)
The diploma thesis deals with the study of stable isotopes of oxygen and carbon of Cretaceous rocks from the Jičín volcanic field. The aim of the thesis is to identify isotope alterations in Cretaceous sediments transported by basic magmas in the form of xenoliths and to determine the origin of oxygen and carbon of hydrothermal vein carbonates that penetrate the bodies of neovolcanites. The study is divided into two parts. The theoretical part summarizes in general the stratigraphy of the Czech Cretaceous Basin and Cenozoic volcanism of the Bohemian Massif, geochemistry of stable isotopes of oxygen and carbon and geology of studied localities in the Jičín volcanic field. The practical part presents a detailed isotope study of Hřídelec, Kulatý vrch, Zebín, Veliš and Kunětická hora localities. Cretaceous rocks from xenoliths in these neovolcanites show extreme variability in the isotopic composition of both carbon (from 0,15 to -11,1 ‰ V-PDB) and oxygen (from -5,4 to -22,9 ‰ V-PDB). They significantly exceed the variability of the isotopic composition of diagenetically altered Cretaceous rocks from the same area. The wide range of oxygen isotope composition is the result mainly of fluid temperature variability (approx. 300 - 20 řC), which isotopically altered Cretaceous sediments. Carbon isotope...
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