Thesis (M.Phil.) - University of Queensland, 2005. / Includes bibliography.

No description available.

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1928. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed October 8, 2009) Includes bibliographical references (p. 38).

The Old Hickory is the largest of a series of Pliocene (?) age heavy mineral sand deposits in Virginia and North Carolina. The high density of heavy minerals allows for selective concentration during transport and deposition. Under the right conditions, placers of considerable size can be formed. The elliptically shaped ore body of the Old Hickory Deposit extends in a North - South direction and is approximately 13 km (8 miles) long and up to 2.5 km (1.5 miles) wide, with an average thickness of 6.5 m (20 feet). The deposit lies along the Fall Zone, where a thin wedge of Cenozoic Coastal Plain sediments unconformably overlies the older rocks of the Piedmont. The principal minerals of economic interest found in the heavy mineral sands at the site are ilmenite (FeTiO₃), leucoxene (Fe<SUB>2-x</SUB>Ti<SUB>3+x</SUB>O<SUB>9+x/2</SUB>) where x is less than or equal to 2, rutile (TiO₂), and zircon (ZrSiO₄). An important focus of this study is the alteration of ilmenite by leaching away of iron, which results in enrichment in titanium. Titanium metal is highly valued for its light weight and high strength. In terms of total economic value, however, the use of titanium dioxide pigments for paint, coated paper, and other products is far more important. As the value of the ore is heavily dependent on the titanium content, the weathering process is a matter of considerable interest to the mineral industry. Analysis of ilmenite grains using reflected light microscopy revealed a wide range of alteration textures. Quantitative analysis and mapping of trace elements showed altered areas with enrichment in Ti and depletion in Fe, Mn, Mg, and Cr. It is believed that the weathering process took place in a reducing environment prior to final deposition according to the reaction: Fe²⁺TiO₃ + 2H⁺ --> Fe²⁺ (aq) + TiO₂ + H₂O Reducing environments are found in water-logged soils such as floodplains and other low-lying areas. Repeated cycles of burial and exhumation during transport would have created conditions ideal for the removal of iron from the ilmenite. / Master of Science

This thesis focuses on heavy mineral species found in a unique carbonate assemblage in the Mt. Mica pegmatite in order to determine the conditions of their formation and their mineral paragenesis as well as to gain insight on the origin of this very unusual carbonate-rich unit.

No description available.

Rutile, although not a major component of detrital heavy mineral deposits, is a valuable source of titanium oxide. Theoretically rutile is pure titanium dioxide (TiO2) and should form white or colourless tetragonal crystals with a density of 4.25gm/ml. However, natural rutile although tetragonal, displays a variety of colours ranging from red through brown to black, yellow or blue, variable density between 4.23 to 5.50g/ml as well as a range in the magnetic susceptibility and electrical conductivity. In addition to these variations exhibited by natural rutile, samples from detrital heavy mineral deposits normally contain, in addition to homogenous grains, composite grains, in which rutile is intergrown with one or more mineral species, commonly quartz, feldspar and ilmenite. The Sibaya Formation, like most detrital heavy mineral deposits, has a polymictic source, and as such contains rutile grains formed in many different chemical environments. Homogenous rutile grains display a chemical variation with a preference for the select few elements, which are compatible with the rutile cyrstallographic structure. The ions that substitute for titanium (Ti4+) in the crystal lattice are a reflection of chemical environment in which the crystal formed. The size and charge of the Ti4 + ion greatly restricts the species that may enter the rutile crystal lattice, with Sb3 +, V3 +, Fe3 +, Cr3 +, Sn4 +, M04+, W4+, Mn4+, 8i5+, Nb5+, Ta5 +, Sb5 +, V5 +, being theoretically compatible with the size and charge of the Ti4+ ion. Electron microprobe analysis of detrital rutile grains from the Sibaya Formation, KwaZulu-Natal show that elements, Nb5 +, Ta5+, A13+, Zr4+, Si4+, Fe3+, Cr3 +, and V5 +, commonly substitute for the Ti4 + ion. However, Sb3+, Sn4+, M04+, W4 + and 8i5 + were not present at detectable levels implying that the provenance area is not enriched in these elements. Although the high Fe3+ values were expected in the rutile grains, as Fe3 + is common in many rocks, the high Si4+ values encountered were not expected, as Si4 + is not normally compatible with Ti4 + ion, as noted by their distinct separation in rutilated quartz. The anomalous Si4 + content of certain grains suggests that within the provenance area rutile bearing rocks formed under unusual conditions, such as high pressure, temperature and silicon activity where the high charge density of the Si4 + ion would favour the inclusion of Si4 + into the rutile lattice. The chemical variation of the rutile grains causes significant variation in the magnetic susceptibility and electrical conductivity, and thus has marked effects on mineral processing, which relies heavily on magnetic and electrostatic separation techniques. The data presented indicates that individual homogenous rutile grains displays significant range of chemical composition, commonly containing other oxides from a fraction of a weight percent to well over 10wt%. Data plots of TiO2, FeO and 'other' oxides (Nb2O5, Ta2O5, A12O3, ZrO2, SiO2, Cr2O3 and V2O3), showed that many of the more magnetic rutile grains appeared to be FeO enriched and contained a higher proportion of 'other' oxides. However, some grains that just had higher proportions of 'other' oxides and a lower FeO content were also magnetic. Thus magnetic susceptibility although strongly influenced by the presence of FeO, can also be enhanced by the substitutions of other oxides. The vast majority of rutile grains from the electrostatic fractions were relatively TiO2 pure, and contained low concentrations of 'other' oxides. However, some grains did have slightly enhanced SiO2 and V2O3 concentrations, which appear to enhance the conductivity of the grains. Four main colour groups were differentiated from the population of rutile grains from the Sibaya Formation, these being, reddish brown, black, blue and yellow. No single oxide seemed solely responsible for the colour of rutile grains. However, the red rutile grains had a slightly but significantly higher Cr2O3 and Nb2O5 content, whereas black rutile grains appeared to be V2O3 and Nb2O5 enriched. The blue colour of rutile grains appears to be influenced by a combination of SiO2, Al2O3 and Nb2O5 substitutions. The yellow rutile grains had slightly enhanced FeO and Nb2O5 concentrations. Although these differences are very small, trace quantities of certain elements and different combinations of elements can have a strong effect on colour. Apart from Fe3+, no single element; appears to be solely responsible for variations noted in the physical characteristics (magnetic susceptibility, electrostatic conductivity and colour) of homogenous rutile grains from the Sibaya Formation. However a combination of substituting elements appears to influence magnetic susceptibility and electrical conductivity. An enhanced Fe3+ content normally increases the magnetic susceptibility although combinations of other elements may have the same effect on Fe3+ poor grains. In general terms, the purer the rutile grain, the more likely it is, to be non-magnetic and conductive. Substitutions of 'other' oxides appear to decrease the conductivity of rutile grains. The relationship between grain colour and chemistry is also not very clear, verifying the widely held view that grain colour is often the result of more than just mineral chemistry. / Thesis (M.Sc.)-University of Durban-Westville, 2002.

This thesis examines the mineral suite of undeveloped heavy-mineral deposits in the Cretaceous of the Northern Mississippi Embayment and compares them to the developed deposits of the Atlantic Coastal Plain. The hypothesis presented here is that Cretaceous heavy-mineral deposits of the eastern Mississippi Embayment had the same provenance, the Appalachian Piedmont, as did the younger sediments of the U.S. Atlantic Coast. Kyanite/sillimanite and staurolite were recognized in all samples, and represent strong evidence for an Appalachian Provenance. Alternatively, the overall lack of epidote in the HM suite points away from a Mississippi River related provenance. The dominant heavy minerals found in the Mississippi Embayment samples are ilmenite, leucoxene, zircon, rutile, kyanite/sillimanite, staurolite, and monazite. This suite of heavy minerals compares favorably to those represented along the Atlantic Coastal Plane, and supports an Appalachian Provenance. Southwest trending Paleozoic paleovalleys were likely sedimentation pathways from the Appalachian region.

This thesis reviews heavy mineral separation techniques for red-bed heavy mineral provenance studies. It demonstrates the effectiveness of automated mineralogy for mineral comparisons and targeted mineral analysis, resulting in new provenance history conclusions for the Permo-Triassic of SW England. The methodology was developed to remove iron-oxide coatings from grains and provide optimal separation of heavy mineral concentrates in comparison to hydroseparation and panning. Step-wise methodology iterations were validated at each stage using the QEMSCAN (Quantitative Evaluation of Minerals by SCANing electron microscopy). The QEMSCAN works in a similar way to the SEM (scanning electron microscope) and electron-microprobe. Four EDS (energy dispersive spectroscopy) detectors measured X-rays, secondary electrons and back-scattered electrons from the sample. The software allocated these to defined geochemical SIP (species identification protocol) categories. The SIP was back-validated using the electron-microprobe, XRD (X-ray diffraction), microscopy and SEM. QEMSCAN was the primary analysis technique. The results included false colour mineral maps and semi-quantitative statistics for the SIP categories. This enabled targeted mineral analysis with supporting techniques. The methodology was applied to the Permo-Triassic of SW England. The QEMSCAN was able to pick up small scale and large scale heavy mineral provenance trends. Case study 1 showed regional heavy mineral trends and allowed lithological correlation of outliers. Case study 2 used heavy minerals to confirm contemporaneous structural evolution and the base of the Upper Permian in South Devon. Case study 3 allowed a re-evaluation of the base Triassic. Case study 4 targeted biotite minerals at Corbyn's Head. Case study 5 reviewed local vertical and horizontal trends in comparison to regional trends. This has significant oil and gas exploration implications as it gives confidence in correlating deposits over 10s km and can be applied to North Sea barren red-beds. Finally, some mineral firsts, including rammelsbergite and a topaz rhyolite were identified.

The objective of this review is to summarise the characteristics, significance and evolution of heavy minerals and their accumulations, and to identify the key controls on the development and distribution of heavy mineral concentrations in alluvial systems. These controls can be broadly classified as tectonic setting, geomorphic setting and grain-scale concentrating processes, each of which is discussed. Based on this review, exploration models are developed which are designed to indicate favourable localities for the accumulation of heavy minerals, and trends likely to be exhibited within these accumulations. The models are structured from the broadest scale of target selection, down to the local scale of sample site selection. The major conclusion of this work is that an understanding of process geomorphology is required to develop genetic models of placer development, including a detailed evaluation of climatic fluctuations throughout the Caenozoic. Palaeoplacers such as the Witwatersrand goldfield, are inferred to have formed under similar circumstances of tectonic setting as genetically comparable Caenozoic placers such as those of Otago, New Zealand. The means of preservation of such major basins is however poorly understood.