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Acid leaching of different natural chrysocolla samples under ambient conditions demonstrated that the chemical and chrystallographic inhomogenity significantly affects the rate and that it is virtually impossible to use the mineral as a model for the kinetics of hydrometallurgical processing of copper ores.Dissolution experiments, stability diagrams,and X-ray powder diffraction studies are undertaken and studied in this research and results are given.It is found that a complete solid solution series exists in Nature with most tungstenian wulfenites and molybdenum stolzites containing a range of compositions. The first occurrence of a molybdenum stolzite from Broken Hill, Australia, which also contains small amounts of chromium is noted.Raman microprobe spectroscopy has proven to be a very quick and effective non-destructive method for semi-quantitative analysis of the wulfenite-stolzite and powellite-scheelite solid-solution series and in detecting very small amounts of substituted chromate in wulfenite, stolzite and anglesite / Doctor of Philosophy (PhD)

The solution geochemical conditions associated with the development of supergene copper mineralisation in the E22, E26 and E27 deposits at Northparkes, New South Wales, have been explored. Determination of a stability constant for sampleite [NaCaCu5(PO4)4Cl·5H2O], a conspicuous species in the upper oxidised zone of E26, has led to an understanding of the differences between the three deposits in terms of the influence of groundwater geochemistry on their mineralogical diversity. Modelling of copper dispersion from the three deposits using current ground water compositions as proxies for past solution conditions has shown that the elevated chloride concentrations associated with E26 have negligible influence on total dissolved copper concentrations over a wide pH range. The results are discussed with respect to applications in exploration geochemistry for the discovery of new ore deposits in the region. Determination of a stability constant for lavendulan [NaCaCu5(AsO4)4Cl·5H2O], the arsenate isomorph of sampleite, suggests that solid solution between lavendulan and sampleite is likely to be extensive and this has been established by reference to mineral compositions from a number of deposits. Activity-activity phase diagrams have been developed to explain the common mineral associates of lavendulan and differences between the analogous phosphate and arsenate systems. With respect to the occurrence of lavendulan in the oxidised zone of the Widgiemooltha 132 N ore body, Western Australia, its crystal chemistry explains why Ni does not substitute for Cu in the lattice. This is despite Ni being abundantly available in the deposit and substituting freely into other copper-based minerals. The substitution of Ni for Cu was explored in a study of supposedly Ni-rich paratacamite, Cu2Cl(OH)3, from the deposit. It transpires that much of this is a new mineral, gillardite, Cu3NiCl(OH)6, the isomorph of herbertsmithite, Cu3ZnCl(OH)6. The nature of gillardite was thoroughly investigated and the mineral was approved as a new species by the International Mineralogical Association. A high resolution single-crystal X-ray structure of gillardite has been completed. In addition, the substitution of Ni in simple carbonate lattices has been explored as gaspéite, NiCO3, Ni-rich magnesite, MgCO3, and calcite, CaCO3, are all common species in the oxidised zone of the Widgiemooltha 132 N deposit. Attention was subsequently focussed on the geochemistry of the element Bi, with special reference to deposits of the Kingsgate region, New South Wales. This study has led to a modern assessment of the Mo-Bi deposits in the area and new Bi sulfosalts from the Wolfram pipe at Kingsgate are described. A survey of secondary Bi minerals from a host of deposits has led to the development of a model for the dispersion of Bi in the supergene environment, which will have widespread applications in exploration geochemistry where Bi is used as a pathfinder element. Calculations of aqueous Bi species in equilibrium with bismite, Bi2O3, bismoclite, BiOCl, and bismutite, Bi2O2CO3, over a wide pH range show that the element is very insoluble under ambient oxidising conditions. It is noted that the results of previous geochemical exploration campaigns in the region will have to be reassessed. / Doctor of Philosophy (PhD)

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 179-192). Also available in print.

The Hekou Group in the Kangdian region, SW Yangtze Block is a metavolcanic-metasedimentary succession hosting the giant Lala Fe-Cu-(Mo, REE) deposit. Mafic volcanic rocks of the Hekou Group and nearby gabbroic intrusions have identical zircon U-Pb ages of ~1700 Ma. The sedimentary and mafic rocks are suggested to have formed in an intra-continental rift, similar to those of the North Australian Craton. Such a similarity suggests that the Yangtze Block was likely linked with the North Australian Craton in the Columbia supercontinent during late Paleoproterozoic. Overlying the Hekou Group is a thick sedimentary sequence of the Julin Group containing basaltic layers with zircon U-Pb ages of ~1050 Ma. The basalts and other coeval igneous rocks in the region have geochemical affinity of within-plate rocks, representing a ~1.05-1.1 Ga rifting event. Occurrence of the within-plate rocks does not support existence of a Grenvillian orogenic belt in the region, and thus agrues against previous hypothesis that proposed the Yangtze Block to be located in the interior of the Rodinia supercontinent on the basis of the so-called Grenvillian orogenic belt. The Lala deposit contains 200 Mt of ores with an average grade of 13 wt.% Fe, 0.92 wt.% Cu, 0.018 wt.% Mo, 0.022 wt.% Co, 0.25 wt.% REE2O3 and 0.16 ppm Au, and is one of the largest IOCG deposits in the region. The ores are hosted mostly in meta-vocalnic rocks (albitite) and schists, and are characterized by abundant low-Ti magnetite with subordinate chalcopyrite, pyrite, molybdenite and REE minerals. The paragenetic sequence includes Stage I of Na-alteration, Stage II of Fe mineralization, Stage III of Cu-Mo-REE mineralization, Stage IV of chalcopyrite-pyrite-calcite veins and Stage V of hematite-calcite-quartz veins. Molybdenite of Stage III has a Re-Os isotopic age of 1086 ± 8 Ma, similar to U-Pb ages of the primary allanite as 1067 ± 41 Ma, suggesting that mineralization of the Lala deposit is coeval with the ~1.05-1.1 Ga within-plate magmatism in the region. The secondary allanite has U-Pb ages of 880-850 Ma, comparable to Ar-Ar and Pb-Pb ages of undeformed Stage IV and V veins, representing a younger hydrothermal event. C-O-S isotopes suggest that the Fe and Cu mineralization stages (II and III) at Lala have formed from high temperature magmatic-hydrothermal fluids (385-430ºC). However, compositions of fluid inclusions and minerals demonstrate that the Fe and Cu mineralizing fluids have different compositions. Strontium isotopic compositions of apatite and calcite suggest that the Fe mineralizing fluid has formed from magmatic fluids interacted with late Paleoproterozoic host rocks, whereas the Cu mineralizing fluid with much higher 87Sr/86Sr ratios has possibly involved magmatic fluids that have interacted with older basement beneath. Close association of monazite-bearing apatite, Cu-sulfides and REE-minerals at Lala suggests that REE mobilization and mineralization is genetically related to the Cu mineralizing fluid. This study suggests that the Cu mineralizing fluid contains Cl-, K, CO2, F-, PO43- and CO32- with low Na activity, and is thus responsible for mobilization, transportation and deposition of LREEs in the Lala deposit. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

M. Tech. Metallurgical Engineering. / A novel process of leaching copper refractory ore from Nchanga mine, Zambia, in two stages consisting of a pre-oxidation step and an acid dissolution stage was investigated by means of a leach test rig.