Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 58-61).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 73-75).

Undergraduate honors paper--Mount Holyoke College, 2007. Dept. of Earth and Environment. / Includes bibliographical references (leaves 44-50).

Lithium and tantalum mineralization in rare-element pegmatites has been studied in 4 field areas. Three field areas are within a pegmatite belt which stretches for 450 km from Steinkopf, Namaqualand in the west, to Kenhardt in the east along the Orange River in South Africa, incorporating Tantalite Valley, Namibia in the central area. This Belt is considered to be of 1200 my age. The 4th field area is in central Namibia in the Karibib-Usakos region of 500 my age. Lithium mineralization involves primary minerals, petalite and spodumene (crystallizing< 650&deg; C) and amblygonite which crystallize from a magma +/- an aqueous fluid, and lithian mica which along with cleavelandite is one of the last mineral assemblages to form, probably these last two assemblages are replacement in origin. Petalite is dominant in the Karibib area and spodumene in Steinkopf, Namaqualand and Tantalite Valley. The Kenhardt area is poor in lithium in comparison with the western and central portions of the Pegmatite Belt. Amblygonite-montebrasite is present in Karibib and Tantalite Valley usually in association with cleavelandite and lithian mica. Hydrothermal low temperature replacements, < 400&deg;C occur in spodumene in the Steinkopf and Tantalite Valley pegmatites, being pseudomorphed by albite and mica +/- sericite. Amblygonite-montebrasite in Karibib displays replacements of natromontebrasite (the first occurrence in Karibib, Namibia), crandallite, brazilianite and possibly cookeite. Apatite is always prominent at the contact. An unusual occurrence of Mn-tantalite lamellae, primarily parallel, lying in microlite, is intergrown with montebrasite at the Rubicon pegmatite, Karibib, suggesting simultaneous crystallization of these three minerals, i.e. Ta-dominated tantalite and microlite and LiAl(F/P04) involving late fluids rich in F, P and Ta. Mn-tantalite and Ta-rich microlite are the dominant Ta-minerals in the rare-element Li-rich pegmatites of Namaqualand, Tantalite Valley and Karibib. In contrast, columbite (Nb-rich) is prevalent in the Li-poor, less differentiated pegmatites in the eastern Pegmatite Belt near Kenhardt. Microlite replaces Mn-tantalite in Li-rich rare-element pegmatites in all three field areas. A uranmicrolite from Karibib, Namibia contains 14.35% UO2, 1.03% PbO, 56.12% Ta205, 13.18% Nb205, 0.58% Fe203, 6.87% CaO, 0.54% SrO, 0.59% MnO, 0.86% Na2O and 0.47% F. U-plumbomicrolite or Pb-uranmicrolite is intergrown with manganotantalite from the same pegmatite. Throughout one aggregate of microlite PbO varied from 21.98 to 1.57% and UO2 from 12.89 to 16.20%. Pb appears to be concentrated around the periphery of the crystal. Backscattered electron images reveal metamict textures in radioactive microlites and distinctive subspheroidal features. A uranoan microlite from Tantalite Valley, Namibia, revealed two essentially different compositions; a more hydrated rim area of 200 mum radius containing 7% higher Ta2O5, 10% lower CaO and 1.3% lower F than a main central area of slightly variable composition. Crystals of uranoan microlite from Steinkopf, Namaqualand contain remnants of a bismuth phase. Bismuth intergrowths with quartz reveal the presence of two rare-minerals, pyromorphite [Pb5(PO4) 3 C1] and m0ttramite[PbCu(VO4)OH], new data is given for these minerals. Ferro tantalite occurs at Rubicon mine. A schematic diagram is produced for the paragenetic sequence of mineral assemblage in each of the pegmatite areas in Karibib, Tantalite Valley, and Steinkopf, Namaqualand in relation to T and P of formation, and the magma and fluids effecting the crystallization sequence. Finally different fractionation trends of Ta-Nb, Mn-Fe, Rb-K and Cs-K in columbite-tantalites and lithian mica have highlighted variable paths of differentiation in contrasting rare-element pegmatites which may reflect different sources of original parental magma.

No description available.

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 30, 2007) Includes bibliographical references.

Thesis (M.Sc.(Geology))--University of Pretoria, 2008. / Abstract in English. Includes bibliographical references (leaves 123-126).

Review of literature shows that rocks of all ages from the Archaean to the early Phanerozoic host pegmatite-based mineralisation in the central and southern region of the African continent. The greatest concentrations occur in the Archaean and late Proterozoic orogenic belts, while early to middle Proterozoic granites do not, in general, host mineralisation. Pan-African mineralisation is present, but is not widespread. Some deposits previously considered to be of Pan-African have been shown to be of Proterozoic age. In common with occurrences of other regions, the deposits are closely associated with small, late- to post-tectonic granites. Therefore, preliminary assessment of the potential of granites as sources of pegmatite mineralisation should utilise satellite data or aerial photographs. The granites also tend to be alkaline and peraluminous. Thus, in the next stage, chemical analysis for selected major and trace elements should be conducted directly on granites if they occur as small plutons. For large granitic batholiths or terranes, preliminary stream-sediment surveys may be necessary to reduce the size of the target area. Subsequently, pegmatite zonation around suitable granites should be assessed as it allows attention to be focussed on areas likely to host the specific type of mineralisation being explored for.

High Purity Quartz (HPQ; quartz containing less than 50 ppm trace elements) is of increasing economic significance due to its use in certain high-tech components (computer chip/semiconductor manufacture) and in green technologies (silicon wafer production). Current HPQ deposits (hydrothermal veins/leuco-granites/alaskites) are rare and volumetrically small. Unless significant new deposits are found, increasing demand will raise its prices, elevating the strategic nature of this limited commodity. The large volumes and simple mineralogy of pegmatites and the high chemical purity of their constituents make them an attractive target for HPQ. PhD studies are being carried out on quartz from the Evje-Iveland pegmatite field of the Bamble-Evje pegmatite cluster, southern Norway. The area was targeted due to its well constrained geological setting and previously identified potential for HPQ. The aim of the investigation is to develop exploration tools for HPQ by determining the genetic history of the pegmatites and mode of HPQ formation. The study is focussing on 7 pegmatites and their country rocks. Each shows typical pegmatite zonation, with quartz/feldspar intergrowths at the margins, a massive quartz core and a variety of accessory (including REE-bearing) phases. The proximal Høvringsvatnet granite was previously suggested to have supplied late-stage, highly fractionated melts to form the pegmatites. However, from their trace element systematics (no relationship was observed between trace element content and degree of fractionation in each pegmatite body), and a difference in U/Pb age of approximately 70 Ma, the pegmatites cannot be related to the granites. From field evidence (corroborated by geochemical modelling) the pegmatites formed by ‘in situ’ anatexis of country rocks; some locally, some from distal sources. Some pegmatites contain brecciated feldspar and replacement quartz. From LA-ICP-MS analyses, hydrothermal quartz, compared with magmatic quartz, typically contains lower quantities of trace elements. Hydrothermal material shows relatively elevated levels of Al and Li, low Ge and a complete absence of Ti, indicating relatively low temperature hydrothermal formation. Different quartz domains (from SEM-CL imaging) show distinct δ18O values; late stage low trace element zones show values consistent with meteorically derived fluids. In situ LA-ICP-MS studies will provide further information about the characteristics of the fluids which have replaced/refined magmatic quartz to form HPQ. This beneficiation process is a potential mechanism for the generation of economically significant HPQ deposits.