Thesis (doctoral)--Technische Universität Carolo-Wilhelmina zu Braunschweig, 1983. / Abstract also in English. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 137-141).

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1904. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed December 22, 2008) Includes bibliographical references (p. 18).

Thesis (Ph. D.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Oct. 16, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geology, Department of Earth and Atmospheric Sciences, University of Alberta." Includes bibliographical references.

Mantle xenoliths allow us to investigate the geochemical and dynamic evolution of the mantle beneath the western margin of Antarctica and reconstruct a timeline of geologic events that are obscured on the surface. For this study, mantle xenoliths, brought to the surface by recent volcanism, were collected along a transect from the rift shoulder and into the rift basin in the western margin of the West Antarctic Rift System (WARS), thus providing a recent snapshot of the lithospheric mantle after major episodes of rifting. The second chapter of my thesis focuses on determining the age and persistence of the mantle within the rift. The rhenium-osmium (Re-Os) isotope system has proven to be an invaluable tracer of the tectonic history of the lithospheric mantle and can constrain the age of melt extraction and subsequent stabilization of the lithospheric mantle. This allowed us to track the age of the lithospheric mantle across this rifted margin. Os isotopes, combined with major element compositions, reveal widespread Paleoproterozoic (1.7-2.4 Ga) stabilization of the lithosphere and subsequent preservation, suggesting the lithosphere has dynamically thinned in response to rifting. Major element data allowed us to place temperature (T) constraints on the mantle and characterize the thermal history in the WARS. This study also revealed the oldest lithosphere ages recorded in Antarctica (3.3 Ga) and is the first to report ages that coincide with adjacent crustal ages, thus confirming the coupled relationship between the lithospheric mantle and continental crust. An integral factor controlling the composition of magmas generated at Earth’s surface is the composition of the SCLM. Magmas generated at depth must pass through it, and subsequently may take on geochemical signatures of the lithosphere, or may leave behind geochemical imprints of the migrating magma in the SCLM. Trace elements provide a means to investigate both the depletion and re-enrichment history of the SCLM. The third chapter of my thesis investigates the metasomatic overprinting of the Paleoproterozoic SCLM. Metasomatism, which is the chemical alteration of a rock by a migrating melt and/or fluid, leaves behind diagnostic signatures of the metasomatizing agent (e.g. subduction related fluids or carbonated melts). This can occur cryptically, where a melt percolates through the rock, changing the composition of the rock, but not the lithology. Modal metasomatism produces new mineral phases that are not typically expected in the rock. In xenoliths, trace elements enable us to decode geochemical signatures, and determine the sources of metasomatism. The WARS lithosphere has experienced varying degrees of re-enrichment, broadly characterized by low high field strength element (HFSE) abundances and rare earth element (REE) enrichments that correspond with carbonatite metasomatism. In addition, the presence of secondary hydrous phases (e.g. amphibole and phlogopite) imparted distinct geochemical signatures, revealing that the SCLM beneath the WARS was modified by reactive porous flow with an evolving metasomatic fluid/melt. Widespread Cenozoic rift-related volcanism (<20 Ma) is observed throughout the western margin of the East Antarctic Craton. It has been proposed that the Cenozoic basaltic volcanism in the region of our study site originated from a SCLM source that had been metasomatized during subduction along the paleo-Pacific margin of Gondwana, and subsequent extension in the WARS during the Late Cretaceous (~90 Ma). The fourth chapter of my thesis utilizes strontium (Sr), neodymium (Nd), and hafnium (Hf) isotopes to date depletion and refertilization events in the lithosphere, as well as understand the role of the SCLM in the formation of WARS volcanism. Together with lithologic features (e.g. presence of hydrous phase additions), Sr and Nd isotopic ratios in WARS xenoliths provide a geochemical link to the Cenozoic rift-related magmatism, and supports the SCLM’s role in the formation of diffuse alkaline magmatism throughout the region. Lu-Hf isotope model ages add a constraint on the timing of melt depletion, and establish a relationship between depleted and refertilized domains. Sr isotopes constrain a genetic link between the metasomatized Archean lithosphere sampled on the rift shoulder and the highly radiogenic character of the Ferrar flood basalts, and indicate long-term storage of subduction modified mantle domains in the SCLM. The Sm-Nd isotope system is variably overprinted by metasomatism throughout the WARS. The most highly metasomatized location produces a well-correlated isochron that indicates that the SCLM acquired its trace element metasomatic signature about 130 Ma ago, during the late stages of subduction along the paleo-Pacific margin of Gondwana.

No description available.

Thèse (M.sc.A.)-- Université du Québec à Chicoutimi, 1981. / "Thèse présentée à Chicoutimi en vue de l'obtention d'une maîtrise en science appliqué (géologie)" CaQCU Document électronique également accessible en format PDF. CaQCU

>Magister Scientiae - MSc / This study is focused on the Akanani prospect area, approximately 25 km north-west of the town of Mokopane, Limpopo Province where exploration geologists at the study area have classified the ‘pyroxenitic’ units into P1, P2, P3 and P4 units upward in order of succession with height based on their textures, mineralogy and colour. The primary aim of this study is to distinguish the distinctive geochemical and mineralogical characteristics that can be used to identify each unit (P1 to P4) and in so doing create major geochemical, petrographic and mineralogical variables that will help or facilitate the exploration for and recovery of PGE and BMS mineralisation. Geochemical and mineralogical variation studies were carried out on the cores from ZF044, ZF045, ZF048, ZF057, ZF078, ZF082 and M0023, located in the Platreef at the Akanani Prospect area on the farms Moordkopje 813LR and Zwartfontein 814LR. Using a combination of various multivariate statistical techniques (factor, cluster and discriminant analysis) and mineralogical studies (CIPW norm, microprobe analysis, petrography), the outcomes of the study have demonstrated that the Platreef at Akanani comprise at least four lithological units i.e. the basal pyroxenite portion referred to as the P1 unit comprises chromitite, pyroxenites and feldspathic pyroxenites with associated Cr, TiO2, chromite, pyroxenes, hematite and Fe2O3, the mineralized section of the P2 unit is characterized by harzburgite, serpentinized harzburgite and in places orthopyroxenites are present consistent with high MgO and LOI contents, the feldspathic portion referred here as the P3 unit is characterized by a feldspathic pyroxenite containing higher Al2O3, Na2O, K2O, albite, hypersthene and SiO2 and the top most portion of the P4 unit comprising CaO, Diopside, ilmenite, anorthite, apatite and P2O5 that can be interpreted to have formed by three separate magma pulses. Considering the possibility that the P4 unit is a hybrid melt of assimilated Platreef that interacted with intruding Main Zone magma, this reduces the number of magma pulses to two. The classification of P1, P2, P3 and P4 units of the Platreef at Akanani shows that the criteria used by mining personnel to classify the four lithological units is not definitive and therefore are not highly reliable. Although various multivariate statistical techniques were employed relatively similar elemental associations were obtained highlighiting the importance of this approach. The strongly positive correlation between sulphides, PGEs and chromite at Akanani is consistent with an orthomagmatic deposit that had been disturbed by significant hydrothermal activity, while in places a good BMS-PGE relationship is commonly associated with the main chromitite stringers in P1. Mineral and whole rock compositions of silicate rocks highlight the strongly magnesian nature of the ultramafic P2 unit. Mineral chemistry studies of chromite, orthopyroxene, olivine, clinopyroxene and plagioclase are consistent with the multi- emplacement model. Convective exchange resulted in the enrichment of iron at the bottom of the stagnant chamber, while incompatible elements migrated upwards consistent with iron depletion with stratigraphic height. Injection of P1 magma and subsequent mixing with country rocks gave rise to the formation of chromitites and addition of plagioclase component to the intruding magma. A normal fractionation trend is suggested between P2 and P3 consistent with enrichment of MgO in P2 and enrichment of Al2O3, Na2O, SiO2 and K2O in P3. The An% of 84.4 of plagioclase coupled with CaO enrichment in P4 is suggestive of some Main Zone influence and can be interpreted as resulting from partial melting and recrystallization of P3 in response to the intrusion of the Main Zone magma is suggested for the formation of the P4 unit. There exists a good correlation between the modal mineralogy and mineral chemistry as determined optically, the norm as determined by the CIPW norm and the whole-rock geochemical results as determined by multivariate statistics and conventional methods.

>Magister Scientiae - MSc / The Platreef is known for its complexity and its heterogeneous lithologies, coupled with an unpredictable PGE and BMS mineralisation. The motivation behind this study was to aid mining geologists in targeting mineralisation irrespective of the farm. It is known that the Platreef generally overlies different footwall lithologies at individual farms. Thus, the aims of this study were firstly to investigate the potential of chemostratigraphy by delineating indices indicative of distinctive lithological layers. These indices were then tied to the second aim; which were to use geochemical vectoring, which is process-based, to target the PGEs at two different farms. This study included three drillcores: from the farms Sandsloot (SS339) and Tweefontein (TN754 and TN200). The footwall units at Tweefontein are shales of the Duitschland Formation and the Penge banded iron formation; and at Sandsloot it is the Malmani Subgroup dolomites. Samples included 121 quarter cores, used for petrographical and geochemical studies. The elemental rock composition was determined by XRF and ICP-OES analyses. The approach also included statistical and mass balance methods to understand the geological and geochemical controlling processes. Initially, the Platreef package at both farms was petrographically divided into three main layers: pyroxenite, and two distinctive feldspathic pyroxenites (FP-I and FP-II). However, the pyroxenites were also further separated as P-I and P-II, because of a higher notable difference in the degree of alteration within P-I. Progressive degrees of metasomatism were further observed in the lithologies, e.g. within the Platreef package, where feldspathisation was potentially the main metasomatic process. Many geochemical plots (corroborated by the petrographical and mass balance results) illustrated that the feldspathisation were linked to an increase in the content of Al₂O₃ and CaO, and coupled with a decrease in content of Fe₂O₃ and MgO. Together with other geochemical trends, geochemically distinct units of the Platreef package could be discriminated with a metasomatism index (MI; CaO + 10Na₂O / CaO + 10Na₂O + Fe₂O₃ + MgO). The ensuing MI is lowest for the P-II pyroxenite and shows a progressive increase through FP-I, P-I to the highest values in FP-II. Geochemical layering were also observed in the calcsilicates and hornfels; e.g. a progressive decrease in the content of Fe₂O₃, Al₂O₃, Ce, Co, Cu, Ni, Zn, Zr, Au, Pd and Pt from the hornfels subunits H-I, H-II to H-III and an increase in of SiO₂, Fe₂O₃, TiO₂, SO₃, Co, Cu, Ni, Rb, V and Zn content from CS-I, CS-II to CS-III. Correlating the pyroxenites and feldspathic pyroxenites spatially from one drillcore to another were hindered, hence, chemostratigraphy were not completed. In terms of vectoring, it was essential to establish a possible link between the metasomatism index and the nature and style of the PGE and/or BMS mineralisation. The Hornfels subunit H-I and calcsilicate subunit CS-III were the main carriers of BMS and PGE. The Platreef package were more complicated: P-I (low PGE, low BMS); P-II (low PGE, high BMS); FP-II (high PGE, low BMS); and FP-I (high PGE, high BMS). Element indices (e.g. Cu+Ni and Co+Zn) were developed to define a consistent gradient indicative of these ore subunits. A validation process to assess the metasomatism index (MI), base metal indices and PGE distribution within the individual drillcores (TN754, TN200 and SS339) were then undertaken. The results were that the MI ranges were similar in all drillcores, and discriminated the subunits of the Platreef package, gabbronorites and even the calcsilicates. The base metal ratios (e.g. Ni/Co and Cu/Co) were indicative of the PGE rich zones. Trends of the base metal ratios reflected a strong positive relationship with the MI within the Platreef package and the calcsilicates. However, the opposite trend is observed with the hornfels. In conclusion, the MI could potentially be a strong vector of high PGE and BMS mineralisation. It is also possible to discriminate lithologies within the Platreef package with the MI. However, it should be noted that the limitation of this study is that the results are based on three drillcores. The Platreef is heterogeneous at individual farms and extremely diverse across the northern limb. Therefore, future research could be undertaken to validate these findings, by using a bigger drillcore database. / National Research Foundation

M.Sc. / Please refer to full text to view abstract