Thesis (M.Sc.)(Geology)--University of Pretoria, 1985. / Summaries in English and Afrikaans. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 116-137). Also available in print.

The accretion of the Earth was marked by the high-pressure segregation of most of its core, accompanied by dissolution of about 10% of one or more “light” elements into the metallic phase. Various light elements have been proposed including S, Si, C and O, with each having an effect on the partitioning behaviour of the trace elements. Metallurgical data indicate that dissolution of even small amounts of light elements in liquid Fe can have profound effects on the activities of some trace components. For instance, significant partitioning of Si into the core of the growing Earth should have affected the observed Mo content of the mantle (Ono-Nakazato et al., 2007). Here, I use the epsilon model of non-ideal interactions in Fe liquids (ε. I present interaction parameters (ε, derived from 1.5GPa, 1550-1650oC metal-silicate equilibration experiments, for W, Ni, Co and Mo in liquid Fe alloyed with C, and W, Ni, Co, Mo, Cu, Mn, Ag, Sb, Cd, In, Tl, Pb, Ga, Ge, Cr, V and Zn in liquid Fe alloyed with S. Additional epsilon values were taken from the steelmaking sourcebook when necessary. I used this new data in conjunction with published metal–silicate partitioning results to develop a model of continuous accretion and core segregation taking explicit account of the partitioning of Si (this study) and O (from Ozawa et al., 2008) between metal and silicate and their effects on metal–silicate partitioning of siderophile elements. The best model for explaining the Earth’s formation including the Mo:W ratio of the silicate Earth posits that the Earth’s oxidation state increased in steps from 1 to 6.26% FeO, increasing Si in the Earth’s core and the light elements C and S being added to the planet in the last ~20% of accretion material.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves R-1-R-17. Also available online.

Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography : leaves 175-189. Also available online.

Subvulcanics rocks of the Roztoky volcanic centre consists of trachytic and phonolitic intrusions, accompanied by hypabyssal intrusions of trachybasaltic (essexite, monzodiorite) and syenitic (sodalite syenite) charakter and dyke swarm of lamprophyres > semilamprophyres. Intrusions of the hypabyssal faintly alcalic series (essexite, monzodiorite, sodalite syenite) are 33-28 Ma old, the lamprophyres of greatly alcalic series (monchiquite, camptonite) are 31-26 Ma old and the semilamprophyres of faintly alcalic series (gauteite, bostonite) are 28-24 Ma old (sensu Ulrych, 1998). The datas corresponds to the trachybasalt - basaltit - trachyandesite suite of the Děčín Formation and the interval of České středohoří Mts. volcanic activity to (42-16 Ma, Eocene -Miocene). 14 samples plutonic rocks of the essexite-monzodiorite-sodaliticsyenite suite and 10 samples of theirs venous equivalents from (semi)lamprophyres and tinguaites groups were withdrawaled in the Roztoky nad Labem area. I analyzed in detail 5 essexite samples and 6 (semi)lamprophyres samples in those study. I studied the sampels using polarization microscope and subsequently elektron micro-analyzer in the analitic metods laboratory of the Geologic institute of Academy of Science, Czech Republic. All analyzed samples belong to II., hypabysal,...

Subduction zone volcanoes are a major natural hazard, frequently endangering lives and livelihoods. The eruptive history of many subduction zone volcanoes includes the extrusion of blocky, silicic lava that forms domes or flows, but we do not yet understand what determines the duration of dome-forming behaviour, what path magma may take to the surface, or how these systems may change over time. This thesis presents an investigation of the Santiaguito complex of lava domes and flows in Guatemala, which has been erupting continuously since its inception in 1922. The Santiaguito lavas are predominantly dacitic to andesitic, with a gradual reduction in SiO2 content from ~66 wt% in the 1920s, to ~62 wt% in 2002. This is consistent with a ~15% decrease in the extent of fractional crystallization over that time. The compositions of plagioclase phenocryst cores indicate a diminished role for magma mixing after the 1940s. I model the Santiaguito system as progressively extracting magma from an extensive, chemically-stratified storage zone. Petrological data are consistent with a storage zone extending from ~25 to ~12 km depth, and magma storage temperatures of ~940 to ~980°C. Phenocryst-hosted apatites suggest melt in this storage zone contained 401 to 1199 ppm S, 600 to 1300 ppm F, and 4100 to 6200 ppm Cl. Ascending magma may pass slowly through a conduit bottleneck, or plug, at shallow depths; groundmass texture suggests that melt rigidifies at or near the base this plug. Pre-eruptive melt volatile concentrations suggest time-averaged fluxes of 40 to 263 Mg d-1 SO2, 32 to 145 Mg d-1 HF, and 247 to 708 Mg d-1 HCl, giving ratios of 0.6 to 0.8 HF/SO2, and 2.7 to 6.2 HCl/SO2. These results are consistent with the few direct measurements of SO2 at Santiaguito, and with measured halogen emissions from other silicic dome-forming systems.

The Palaeoproterozoic Birimian terrane of the West African Man Shield is a gold province of global importance. Gold mineralization at the Damang deposit, however, is unique amongst known gold deposits in Ghana. It comprises a stratigraphically controlled auriferous quartz-pebble conglomerate, which is overprinted by later orogenic gold contained in a sub-horizontal fault-fracture quartz vein array. Furthermore, this gold mineralization is hosted in sediments of the Tarkwaian System, rather than volcanics of the underlying Birimian Supergroup. This thesis integrates petrological, geochemical, thermodynamic and geochronological data to investigate the Damang deposit in the context of the regional tectonic and metallogenic framework. Staurolite-grade, amphibolite facies peak metamorphism at Damang occurred at around 595ºC and 5.5 kbar at 2005±26 Ma. This was immediately followed by a short period (~ 5 Ma) of rapid exhumation, at a rate of approximately 2.6 mm/yr. This decompression led to the formation of the fault-fracture mesh, which was enhanced by the silicification of host rocks during an earlier ‘Pink Haematite’ hydrothermal event that was associated with the intrusion of voluminous dolerite bodies. Orogenic gold mineralization occurred at the end of this exhumation period at conditions of 400–450ºC and 1–2 kbar. These conditions are in broad agreement with other Ghanaian deposits. A gold-bearing, CO₂-rich (X(CO₂) ~ 0.7), aqueous fluid generated through metamorphic devolatilization reactions close to peak metamorphism and during the subsequent exhumation fed the fault-fracture mesh. This fluid imparted a potassic–carbonation–sulphidation alteration overprint similar to that seen at orogenic gold deposits globally. This alteration signature is characterized and identified with portable infrared spectroscopic techniques. Exhumation rates following gold mineralization were less than 0.01 mm/yr, while ⁴⁰Ar/³⁹Ar dating of biotites give ages ranging between 1978.8±6.2 Ma and 1898±11 Ma, indicating extremely prolonged (~ 80 Ma) cooling through the interval 300–250ºC. Ultimately, this thesis demonstrates that the Damang deposit is part of the same regional metallogenic event that formed the other Ghanaian deposits. This implies that the Tarkwaian System elsewhere in Ghana may be prospective for orogenic gold mineralization.

Structural field observations, combined with petrological, isotopic and geochemical analysis of metamorphic and igneous rocks associated with the Semail ophiolite of Oman and the United Arab Emirates, have been used in conjunction with geochronology and estimates of metamorphic conditions and PT paths to constrain the ophiolite emplacement history. The ophiolite metamorphic sole was formed at peak conditions of 840 ± 70°C and 11.6 ± 1.6 kbar (THERMOCALC) and 840-870°C and 11.8-13.9 kbar (conventional thermobarometry) and is characterised by an anticlockwise PTt path. Further analysis and structural constraints imply an apparent inverted sole gradient of ~2°C m-1 and ~3.7 MPa m-1. In conjunction with existing geochronology, a peak sole exhumation rate of ~12.5 mm yr-1 is indicated. Geochemical analysis and tectonic constraints suggest that the Semail ophiolite sole formed from neo Tethyan MORB crust similar in composition to the preserved Triassic-Jurassic Haybi tholeiites and Masirah ophiolite crust. The Bani Hamid granulite facies sole metamorphism peaked at ~96.5 Ma and exhibits a similar PTt path and peak conditions, but formed from oceanic island igneous, volcanoclastic and sedimentary protoliths. Anatectic granitoids in the ophiolite mantle sequence have geochemical and isotopic (Rb-Sr and Sm-Nd) characteristics compatible with derivation from the Bani Hamid sole granulites during prograde metamorphism and have ages of 98.8 ± 9.5 Ma, 93.0 ± 10.0 Ma (Sm- Nd) and 105 ± 4 Ma (U-Pb). The Saih Hatat high pressure metamorphic terrane beneath the ophiolite consists of two contrasting structural levels juxtaposed during exhumation following the subduction of the Arabian continental margin beneath the advancing ophiolite. PT analysis shows the HP event culminated at 450-550°C and 20.0 ± 1.5 kbar (THERMOCALC) and was characterised by a clockwise PTt path. In conjunction with ambiguous existing geochronology, a peak exhumation rate of ~4-12 mm yr-1 is indicated, followed by erosion at ~0.5 mm yr-1.

Thèse (D.R.M.)--Université du Québec à Chicoutimi, 1995. / Document électronique également accessible en format PDF. CaQCU