Dissertations / Theses on the topic 'Base-metal ores'

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)

Thesis (PhD) -- University of Western Sdyney, 2001.
"A thesis presented in accordance with the regulations governing the award of the degree of Doctor of Philosophy, University of Western Sydney" "November 2001" Bibliography: leaves 249 - 254.

This thesis focuses on platinu'm group element (PGE) mineralization in the Unki Section of the Selukwe Subchamber of the Great Dyke (Zimbabwe), and is based on drill hole intersections and underground and surface exposures of the Main Sulphide Zone (MSZ) which hosts significant concentrations of PGE. The petrological and geochemical data presented are part of a broader study currently underway and the present are restricted to the 2m section of the PGE-rich MSZ encountered in drill hole MR126. The PGE-rich MSZ at Unki is unique in having a shear, locally referred to as the Footwall Shear, developed at or close to its base . It is however, similar to the other PGE occurrences on the Great Dyke (MSZ) in having its hanging-wall restricted to within 1m of the websterite/bronzitite contact. Slight axial tilting to t he west is indicated by steeper dips on the eastern flank. The sulphide concentration wit hin the MSZ can be used as a rough guide to the PGE-rich zone, but is not sufficiently precise to be used in stope control. The visual identification of the potentially mineable zone remains a problem that is unlikely to be solved. Based on petrological evidence, the bulk of the sulphides with which the PGE are associated, are cumulus in status. This provides unequivocal evidence for an orthomagmatic origin of the MSZ. The dominant platinum group mineral (PGM) phase is the Arsenide/Sperrylite group which is most commonly found at the contact zones between base metal sulphides (BMS) and gangue. The PGM range up to 90 ~m in length. Geochemical evidence from the analyses of cumulate orthopyroxenes through the 2m PGE-rich MSZ interval at Unki reveals a trend of arked Fe enrichment upwards which corresponds to an enrichment in sulphide. This indicates that precipitation of sulphide was caused by fractionation with lowering of temperature in the magma. The Fe enrichment is followed by a reversal in Mg# of orthopyroxene which corresponds to the decrease in sulphide content, suggest i ng that the termination of the PGE-rich MSZ was due to an increase in temperature associated with an influx of new magma. Coupled with these magmatic events are a complex interplay of chemical and physical processes occurring at a critical stage in the overall fractionation of the Great Dyke magma chamber. The overall persistence and continuity of t he PGE zone as observed in the Unki area is consistent with the inferred orthomagmatic origin of the mineralization

The Big Horn Mountains are a geologically complex range that extends over 500 square km in west-central Arizona. Three major lithologic terranes outcrop: (1) Proterozoic amphibolite, phyllite, schists, gneiss, and granite; (2) Mesozoic monzonite to diorite intrusives; and (3) Cenozoic mafic to silicic volcanic rocks and clastic rocks. The entire area is in the upper plate of a detachment fault and, consequently, contains many low- to high-angle normal faults. Each lithologic terrane has its associated mineral occurrences. The Big Horn district is exclusively hosted in the pre- Tertiary terrane. Most of its mineral occurrences are spatially related to the Late Cretaceous intrusive rocks. One occurrence, the Pump Mine, may be a metamorphic secretion deposit, and therefore, would be middle Proterozoic. The vast majority of the mineral occurrences in the Big Horn Mountains are middle Tertiary in age and occur in three districts: the Tiger Wash barite - fluorite district; the Aguila manganese district; and the Osborne base and precious metal district. Fluid inclusions from Tiger Wash fluorite (T(h) 120 to 210° C, NaCl wt. equivalent 17 to 18 percent not corrected for CO₂) and nearby detachment - fault- hosted Harquahala district fluorite (T(h) 150 to 230° C., NaC1 wt. equivalent 15.5 to 20 percent not corrected for CO₂) suggest cooling and dilution of fluids as they are presumed to evolve from the detachment fault into the upper plate. Mass-balance calculations suggest that the proposed evolution of fluids is sufficient to account for the observed tonnage of barite and fluorite. The Tiger Wash occurrences grade directly into calcite- gangue-dominated manganese oxides of the Aguila district. A wide range of homogenization temperatures (T(h) 200 to 370° C.), an absence of CO₂ and low salinities (NaC1 wt. equivalent 1 to 2 percent) in the Aguila district calcite-hosted fluid inclusions argue for distillation of fluids during boiling or boiling of non saline-meteoric waters. Mass - balance calculations modeling the evolution of Ca and Mn during potassium metasomatism of plagioclase in basalt suggest that little if any influx of these cations is necessary to form the calcite –dominated manganese oxide tonnage observed. The Aguila district grades directly to the east into the base-metal and precious-metal occurrences of the Osborne district. Preliminary data describing geological settings, fluid inclusions, and geochemistry suggest that the Osborne district has a continuum between gold-rich to silver-rich epithermal occurrences. The gold-rich systems have dominantly quartz gangue, with or without fluorite, and are hosted in a variety of rocks, but are proximal to Precambrian phyllite or mid-Tertiary rhyolite. Fluid inclusions from two occurrences representative of the gold -rich systems spread across a minor range (T(h) 190 to 230° C., NaC1 wt. equivalent 17 to 23 percent not corrected for CO₂). Dilution of highly saline fluids is the inferred mechanism for precipitation of gold in the gold-quartz systems. The silver-rich systems have dominantly calcite gangue with or without quartz, and are hosted in mid-Tertiary basalt. Calcite fluid inclusions from a representative high-silver occurrence display a wide range of homogenization temperatures and salinities (T(h) 120 to 370° C., NaC1 wt. equivalent 7 to 23 percent). Boiling and consequent neutralization of acidic solutions is the inferred mechanism for the silver-rich, calcite gangue systems. A model inferring a regional fluid-flow regime and local sources of metals is proposed. Four possible regional and local causes of fluid flow in upper-plate detachment regimes are proposed: (1) regional elevation of geothermal gradients as a result of middle-crustal, lower-plate rocks rising to upper crustal levels; (2) meteoric water recharge along the southeast flank of the Harquahala antiform and consequent displacement of connate waters in the upper-plate of the Big Horn Mountains; (3) local emplacement of feeder stocks to rhyolitic flows; (4) and tilting of major upper-plate structural blocks.

Late-stage fissure-filling ore at the world class Bingham Canyon, Utah, porphyry copper deposit has long been recognized, but poorly studied. Physical and chemical characterization of the Pb-Zn-Cu-Ag-Au mineralized fissures in the porphyry-epithermal transition zone provides insight into the origin, timing, and controls of ore deposition. These sheared sulfide-rich fissures are dominated by pyrite and multiple generations of quartz, with lesser amounts of other sulfides and gangue minerals. Au (0.27 to 4.61 ppm) provides the most value to the ore in the transition zone. Host rocks include Eocene monzonite and Paleozoic limestone and quartzite"”all of which can contain economic ore bodies. Associated alteration is predominantly sericitic and argillic. Mineralization into the wall rocks is restricted, not exceeding 1.5 m from the fissure margins. Mineral assemblages vary with distance from the center of the main Cu-Mo deposit and the modal abundances are dependent on host rock. The appearance of both galena and sphalerite (and tennantite to an extent) mark the transition from a porphyry to an epithermal environment. This is accompanied by an increased concentration of chalcophile trace elements in sulfides as determined by EMPA and LA-ICP-MS. Significant hosts of Ag include galena and tennantite, while Cu is hosted primarily in chalcopyrite, tennantite, and sphalerite. Gold does not appear to be hosted in solid solution, but may be focused along fractures or inclusions in pyrite. δ3434S values of fissure pyrite has a narrow range (+2.3 to 3.4‰), while δ18O of quartz is more variable and high (+11.5 to 14.0‰) relative to typical hydrothermal quartz. This can be explained by increased fractionation at lower temperatures in the magmatic fluids, which could have additionally mixed with exchanged 18O-rich meteoric water. Ore grades improve with distance from the center of the deposit; however, this is accompanied by higher concentrations of elements (Pb, As, Bi, etc.) undesirable for downstream processing. The mineralized fissures were created sequentially throughout the formation of the deposit. Initial joints probably formed as a result of the intrusion of a barren equigranular monzonite. The NE orientation of the joints was controlled by the regional stress field, which is more apparent distal to the center of the deposit. A quartz monzonite porphyry then intruded, dilating the joints to allow precipitation of quartz and then pyrite during the Cu-Au-stage of mineralization in the main ore body. After dike-like intrusions of latite porphyry and quartz latite porphyry intruded, galena, sphalerite, and pyrite precipitated to form the Pb-Zn-Ag mineralization. This was followed by late precipitation of chalcopyrite and tennantite (and likely Au mineralization).

The optimisation and process development surrounding the beneficiation of nickelcopper sulphide ores is of fundamental importance when considering the continued rise in global demand for base metals. The selective sequential flotation of these ores is accompanied with various processing challenges due to the low-grade and mineralogical complexity associated with such deposits. One of the greatest challenges faced during the flotation stage is the successful separation of the nickel and copper valuable minerals from the pyrrhotite gangue, significantly decreasing the grade and recovery of the final products. Utilisation of the TETA/sulphite depressant system has proven to significantly improve the flotation process, however its dosage requirements have been found to vary extensively between ore types. The investigations undertaken throughout this thesis project and the subsequent findings discussed in this report have allowed for a greater insight involving this system and its influence on the selective sequential flotation process. The research undertaken throughout this project focuses on the mineralogy of nickelcopper sulphide ores and their subsequent concentration. Mineralogical and metallurgical analysis of this work has found that the individual mineral compositions within an ore have a large impact of its response to flotation processes and the successful separation of copper and nickel concentrates. This thesis paper emphasises the fundamental importance of a holistic approach in order to understand the interactions and mechanisms involved in the selective flotation of nickel-copper sulphides. This will allow for the optimisation and development of operations with improved process control systems and the ability to predict mineral flotation behaviours with variations in ore type.

This study addresses trace element concentrations and distributions in hydrothermal base metal sulphide (BMS) ores using samples from a wide variety of ore deposits and conditions of ore formation. The ranges of trace elements that can be incorporated into natural sphalerite, galena, chalcopyrite and tetrahedrite-tennantite are determined, as are the preferred equilibrium trace element partitioning trends among these sulphides. The previously documented coupled substitution Ag⁺+(Bi, Sb)³⁺↔2Pb²⁺ in galena is confirmed, yet should also be modified to include Cu⁺ and Tl⁺. However, when Bi and/or Sb are present at concentrations above ~2000 ppm, incorporation likely includes the creation of site vacancies. Thallium is always principally hosted in galena when BMS assemblages including sphalerite and chalcopyrite are mapped with LA-ICP-MS. Trace element mapping also reveals oscillatory and sector compositional zoning of various elements in galena for the first time. It is inferred that the partitioning of certain minerals between galena and sphalerite pairs is both predictable and systematic. This systematic partitioning is explored and it is shown that the primary factors controlling the preferred BMS hosts of almost all trace elements in sphalerite-galenachalcopyrite assemblages are element oxidation state, ionic radii of the substituting elements, element availability and the maximum trace element budget that a given sulphide structure can accommodate. In contrast, it is revealed that temperature, pressure, redox conditions at time of crystallization and metal source, do not significantly affect the preferred BMS host of almost all trace elements. The only exceptions to this recognized in the study are the critical metals Ga, In and Sn in assemblages recrystallized at high metamorphic grades. Observed partitioning patterns can be used to assess whether a particular BMS assemblage cocrystallized. Compared to sphalerite and galena, trace element concentrations in chalcopyrite are typically quite low (tens to hundreds of ppm). Nevertheless, it is shown that chalcopyrite can host a wide range of trace elements, and the concentrations of such elements generally increase in chalcopyrite in the absence of other co-crystallizing sulphides. Importantly, chalcopyrite is generally a poor host for most elements considered harmful or unwanted in the smelting of Cu (except for Se and Hg on occasions), which suggests it is rarely a significant contributor to the presence of such elements in copper concentrates. The concentrations of Zn and Cd in chalcopyrite show systematic variation that depends, at least in part, on the temperature of BMS crystallization. The Cd:Zn ratios in coexisting chalcopyrite and sphalerite may be used to assess if the physiochemical conditions remained constant during BMS crystallization. Since minerals of the tetrahedrite isotypic series are also common components in base metal ores, investigation into the trace element chemistry of tetrahedrite-tennantite is relevant to understanding the controls on trace element partitioning in such ores. It is shown that tetrahedrite-tennantite will always be the primary host of Ag, Fe, Cu, Zn, As and Sb, and will be the secondary host of Cd, Hg and Bi in co-crystallizing BMS assemblages. Conversely, tetrahedrite-tennantite is a poor host for the critical metals Ga, In and Sn, all of which will prefer to partition to co-crystallizing BMS.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 2017.

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Garnetiferous rocks show a spatial association with several base metal deposits in the Early Cambrian Kanmantoo Trough. These rocks include coticules (garnet-quartz rocks) and banded iron formation (BIF) and are hosted by pelitic metasediments of the Tapanappa Formation. Petrological and geochemical investigations have been made of garnetiferous rocks associated with the Scotts Creek Ag-Pb-Zn and Angas Pb-Zn deposits and in the vicinity of the Kanmantoo Cu deposit. Geochemical features indicate variations between coticules from the three localities but general similarities with coticules from Broken Hill, N S. W. BIF from the Kanmantoo area is also comparable to the equivalent lithologies in the Willyama Complex, at Olary and Broken Hill. Geochemical diagrams (Fe-Mn-(Co+Cu+Ni), Al/(Al+Fe+Mn ) vs Fe/Ti, Ti02 vs Al203 and chondrite-normalised rare earth element (REE)) for coticules and iron formations suggest variable contributions of detrital and hydrothermal components. The hydrothermal component, is generally 30 to 50 wt. percent for coticules, and >70 wt percent for BIF. The stratigraphic position, layer parallel banding and unusual geochemistry suggest the coticules associated with Scotts Creek, Kanmantoo and Angas deposits are exhalative in origin, and may be termed "meta-exhalites". The Kanmantoo BIF appears to have formed from high temperature submarine hydrothermal fluids and metalliferous sediments analogous to those of the Red Sea and the East Pacific Rise. Coticules and BIFs are indicators of hydrothermal activity and may be local guides to base­ metal mineralisation. The Mn content of garnet in coticules reflects proximity to Pb-Zn ore, and may be a useful exploration tool.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 1998