Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 374-384). Also available for download via the World Wide Web; free to University of Oregon users.

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Diamonds have been discovered in a variety of potassic ultramafic rocks including group-I and group-II kimberlites, olivine lamproites and aillikites, all of which are macroscopically similar and can be difficult to differentiate when viewed under the microscope. However, group-I kimberlites, and to a much lesser extent group-II kimberlites and olivine lamproites, are known to contain economic concentrations of diamonds. This study addresses the problem of distinguishing among different types of kimberlitic and related rocks by developing a geochemically-based method for classifying them. / Geochemical methods have been largely ignored in the classification of kimberlites and related rock types due to high concentrations of xenoliths. However, this problem can be largely overcome by only selecting matrix material for analysis. An evolving kimberlitic magma will become enriched or improvished in Si due to the fractionation of olivine and phlogopite, depending on the initial Si concentration of the magma. As they have low Si concentrations, group-I kimberlites and aillikites can be separated from group-II kimberlites and meimechites, which have higher Si concentrations for any Mg content. Furthermore, since aillikites and meimechites are relatively rich in Fe compared to group-I and group-II kimberlites, these rock types form four separate fields on a Si vs. Fe discrimination diagram. Similar rock-type separation is observed when the ratio of La to Yb is plotted against the ratio of Sm to Yb. Kimberlite and other potassic ultramafic rocks were sampled from nine areas in Quebec: the Otish Mountains, Wemindji, Torngat Mountains, Desmaraisville, Temiscamingue, Ile Bizard, Lac Leclair, Baie James and Ayer's Cliff regions. Major and selected trace element concentrations were determined by XRF analysis for all samples, while a subset of representative samples was selected for trace element analysis by ICP-MS. Electron microprobe analyses of unaltered olivine and phlogopite were also conducted. / Of the 37 samples that were classified both mineralogically and chemically, 23 or 62% were correctly classified using Fe and Si. This number increases to 84%, if the REE are used in conjunction with Si and Fe. The Si vs. Fe discrimination diagram separates group-I kimberlite from most aillikite and meimechite rocks and group-II kimberlite/olivine lamproite rocks from most aillikite and meimechite rocks. Therefore, major and trace element geochemistry offers an important tool for the classification of kimberlitic rocks. / Vasilenko et al. (2002) and Francis (2003) both suggested that diamond grades can be correlated with the major element compositions of the kimberlites. The data collected in this study confirm the inverse relationship between TiO2 concentration and diamond grade. The lowest TiO 2 values were obtained on samples from the Otish Mountains and Renard samples in particular. Other areas of Quebec are characterized by higher TiO2 contents with most samples containing greater than 2 wt% TiO 2. Therefore, the kimberlitic rocks from the Renard locality have the greatest potential for an economic diamond deposit. The origin of this correlation needs to be explored, however, because it is unclear whether this is a feature of the mantle source, or reflects the survivability of diamonds within the kimberlites.

This thesis is a palaeoenviromnental investigation into possible non-climatic effects on the environment from volcanic ash fall and toxic emissions outside the blast zone of a volcanic eruption. These effects are determined from palynological and geochemical changes following tephra fall at a range of sites across the North Island of New Zealand which were located at increasing distances from the main volcanic source, the Taupo Volcanic Zone. These sites collectively covered a wide variety of habitats existing under different climatic regimes. The first site is a peat bog at a warm temperate, comparatively unstable coastal location, Matakana Island. The peat profile extends to 1000 yrs BP and contains the Kaharoa Tephra layer, erupted around the time of early human settlement in New Zealand. The second study site is Kaipo peat bog which, in contrast to Matakana Island, is an upland sub-alpine site existing under a harsher climatic regime with cool temperatures, strong winds and heavy rainfall. The Kaipo record covers the Holocene period up to recent times. Lake Rotoroa is the third site which is located inland, sheltered within the Waikato valley, an area of rich fertile soils and mild temperate climate. The Lake Rotoroa record extends to approximately 15,000 yrs BP including the end of the last glacial period and the Holocene. The final site investigated, Kohuora bog, is situated in an extinct late Quaternary volcanic crater within Auckland urban area, a region of warm temperate climate. This record extends from the last glacial period to the present. Fine resolution sampling methods were employed above tephra layers preserved at each of these sites to examine the immediate short-term palaeoenvironmental impacts from volcanic tephra deposition. The methods used included pollen analysis, and the relatively new technique of Energy Dispersive X-ray Micro Analysis (EDMA) which investigated changes in sediment geochemistry to provide further information on local environmental change following tephra impact. The use of pollen analysis together with EDMA proved beneficial in assessing overall short term environmental impacts from tephra fell. Results revealed that thicker tephra layers did not always cause extensive environmental damage, as impacts seen above the 0.5 cm thick Egmont 15 Tephra at Lake Rotoroa were among the most significant recorded at this site. Instead, the contributing factors of prevailing climate and local site factors (e.g. drainage, soils, vegetation cover and shelter) at the time of an eruption, together with local forest diversity and species sensitivity to tephra deposition, proved more important in determining the degree of tephra impact. Taxa found to be particularly sensitive to tephra deposition included Halocarpus, with inconsistent impacts from tephra fell on Dacrydium and Metrosideros. Duration of tephra impacts varied between sites, but broad estimates from the results showed the time taken for recovery of forest vegetation following an eruption was >100 years, with environmental stability returning after a minimum period of 50 years. The results from Matakana Island revealed that any possible tephra impacts from deposition of the Kaharoa Tephra were obscured owing to large-scale deforestation following Polynesian settlement on the island around the time of the Kaharoa eruption. This study indicates the importance of investigating distal volcanic impacts prior to human settlement to eliminate ambiguity in interpretation of palaeoenvironmental data.

Thesis (M.Sc.) -- University of Adelaide, 1992. / Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 1998. / Title from document title page. Document formatted into pages; contains ix, 137 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 117-124).

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1927. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed October 12, 2009)

Thesis (Ph.D.)--University of Tulsa, 1992. / Bibliography: v.1, leaves 268-296.

Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2007. / Includes bibliographical references (p. 55-56).

A database containing previously published geochronologic, geochemical, and isotopic data on Mesozoic to Quaternary igneous rocks in the Himalayan-Tibetan orogenic system are presented. The database is intended to serve as a repository for new and existing igneous rock data and is publicly accessible through a web-based platform that includes an interactive map and data table interface with search, filtering, and download options. To illustrate the utility of the database, the age, location, and Hf-t composition of magmatism from the central Gangdese batholith in the southern Lhasa terrane are compared. The data identify three high-flux events, which peak at 93, 50, and 15 Ma. They are characterized by inboard arc migration and a temporal and spatial shift to more evolved isotopic compositions. Plain Language Summary A new database with a web-based interface is presented that contains compiled geochronologic, geochemical, and isotopic data on igneous rocks in the Himalaya-Tibetan orogen.