No abstract included. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Detailed mapping of the bedrock geology of the Brenda copper-molybdenum deposit has revealed a consistent sequence of geological events. Consolidation of the quartz diorite host rock that forms Brenda stock was followed by intrusion of small pegmatite and aplite dikes that probably relate to a residual fraction of the parent magma. Age dating of various quartz diorites (White and Harakal, unpublished) indicates that magma solidification occurred about 176 m.y. A concentration of biotite model ages at about 146 m.y. seems best interpreted as the time of ore mineralization. Mineralization occurred at the beginning of a continuous sequence of related structural events. All mineralized ore fractures and younger shears, faults and intramineral dikes exhibit similar, strongly preferred orientations that are unlike orientations of felsic dikes or primary foliations in the quartz diorite host rock. The ore occurs entirely in fractures as products of three sequential overlapping phases of mineralization and consists almost entirely of the ore minerals chalcopyrite and molybdenite with quartz gangue predominanting. Hydrothermal alteration products exist mostly as thin envelopes of potassium feldspar and/or biotite and propylitic alteration. Large argillic alteration zones also exist, however, and are associated commonly with extensively sheared zones. An effort was made at finding a zoning pattern of ore minerals, minor elements and alteration minerals. Ore mineral zoning in the classical sense appears to be absent at Brenda. Metal grades show a crude zonal distribution that correlates directly with density of ore fractures, Hydrothermal alteration minerals and minor elements in chalcopyrite also lack any obvious systematic zonation pattern on the scale of the mine pit. Intramineral dikes of various textures and compositions have been dated at about 130 m.y. They formed after ore mineralization yet before late minor veining not associated with ore-producing veins. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

An ap horizon of a soil collected from a highly mineralized area was fractionated into five organic and mineral components and the distribution of cu, zn, pb, ca and mg within these components was determined. Zn and ca were removed to a considerable degree in the 0.1n hcl extract. Of the five metals, cu and pb were the only ones present which combined with organic matter to any considerable degree. Of the five organic and mineral components, fulvic acid was shown to display the greatest complexing activity. Although gel filtration has been used extensively in the field of biochemistry, it was shown that the metal retaining properties of the various sephadex and agar gels used caused the technique to be unsuitable for the separation of naturally occurring metal-organic complexes. In addition the distribution of fe, cu and zn within the profiles of two soils from less mineralized areas was determined but the low levels of metal found did not permit a direct investigation of their metal-organic complexes. In order to study in detail metal-0rganic matter reactions, humic acids were extracted from several of the above soils. Functional group analysis coupled with elemental analysis for c, h, N and 0 in these humic acids revealed that a large percentage of the oxygen was unaccounted for in carboxylic acid and phenolic Hydoxylic groups, thus indicating the presence of other oxygen containing groups. Infrared spectra showed decreases in the amount of aliphatic material present with increasing maturity of the humic acids and also gave supporting evidence of complex formation upon the addition of cu. The humic acids were used in a series of incremental potentio- Metric titration experiments which monitored the pattern of proton release in response to copper additions at a series of ph levels. The resultant curves for humic acids of various origins were alike in their general shapes but displayed differences in detail which were especially marked between the juvenile and the more mature acids. Whereas in all cases of humic acids derived from mineral soils the proton release increased with ph, the peat humic acid displayed a greater proton release at ph 5.0 than at ph 6.0. The shapes of the curves obtained with humic acids were compared with those obtained in similar experiments from a series of model compounds of known chemical composition and were found to approximate most closely the patterns derived from salicylic acid and phthalic acid. This provides additional evidence for the hypothesis that salicylic and phthalic acid-like functional groups play a significant role in the formation of metal-organic complexes in soils. / Land and Food Systems, Faculty of / Graduate

The heterogeneity of the continental crust has a first order control on the dynamics of plate tectonic processes and the compositions of the Earth in both time and space. Heterogeneity can be characterized at a variety of scales and in a multitude of tectonic environments, but it is the links between seemingly disparate tectonic settings and crustal levels that are critical in understanding construction of the continents. The focus of this dissertation work is to apply microtextural, microgeochemical, whole rock geochemical and traditional petrographic techniques to study features in both deep and shallow crustal igneous rocks. The goal of these efforts is to better understand the roles that magmatic processes, mafic-felsic magma interaction, and partial melting have on the evolution of continental crust. Two principal field areas were selected, the Gouldsboro pluton in coastal Maine and the Fehr granite in northern Saskatchewan, Canada, because they each represent end-members of the processes involved with the generation, modification, transport, and emplacement of magmas that build continental crust. Evidence for bimodal magmatism preserved in the Silurian age Gouldsboro pluton has led to a refined model for the construction of shallow crustal magma chambers. Research efforts focused on the Neoarchean Fehr granite and Paleoproterozoic Chipman dike swarm have contributed to the current understanding of the links between high temperature metamorphism (migmitization) and the production of new felsic magmas as well as the rheological and chemical influences of mafic-felsic magma interaction in the deep crust. The results of these combined field and laboratory efforts have demonstrated the important role of mafic-felsic magma interaction on the strength and composition of both deep and shallow continental crust and have contributed to the current understanding of the complex links between deep crustal heterogeneity and bimodal magmatism at shallow crustal levels.

High-pressure granulite terranes are important sources of information for understanding deep-crustal architecture and processes related to the evolution and stabilization of continental lithosphere. However, one of the most critical challenges is to understand how, and on what timescales, large exposures of lowermost continental crust are exhumed to the Earth's surface. In the East Lake Athabasca region of the western Canadian Shield, high pressure granulites (∼1.0+ GPa) make up one of the largest exposed deep crustal terranes in the world (>20,000 km2). Important insight into the exhumation history of this region come from the study of the kinematics, timing, and metamorphic evolution of a several km-wide, oblique-slip, thrust-sense mylonitic shear zone (Legs Lake shear zone) that forms a major boundary of the high-pressure terrane. The juxtaposition of crustal levels across this structure is more than 20 km. Integrated structural and petrologic analysis of the shear zone and its wallrocks, combined with in situ electron microprobe monazite Th-U-Pb geochronology and U-Pb isotope geochronology, suggest a multi-stage exhumation history for the high-pressure region that occurred over a period of >100 million years. Similar studies of a second and younger fault zone and of the cross-cutting relationships between the two shear zone systems (with displacements of up to 110 km), provide an explanation for the present-day distribution of high pressure rocks in the region and have important implications for the early growth of this part of Laurentia.

The mining industry is under increased pressure from many stakeholders to be forward thinking in its approach to sustainability. This requires a holistic approach to address techno-economic, environment and social issues, rather than just focusing on individual aspects of sustainability practice. The ability to do so requires an integrated modelling framework, underpinned by mineralogy so that the effect of ore variability on one or more of these factors can be simultaneously evaluated and optimised. This study focuses on the steps towards the development of this proposed framework using a case study of a polymetallic sulfide ore flotation circuit. The initial focus in the framework development is on integrating the techno-economic and the environmental aspects of sustainability. Thereafter the framework is used to consider a variety of scenarios evaluating the balance between techno-economic value and environmental burden. A sampling exercise was conducted around the intermediate and terminal streams of the flotation circuit processing polymetallic sulfide ore. All samples were characterised using both chemical assays and mineralogy (QEMSCAN). This formed the input data for the development of an ore specific element to mineral conversion (EMC) recipe that converts chemical assays to mineral grades. The EMC technique has the advantage of being fast, inexpensive and can be used on a routine basis. The recipe for this specific polymetallic sulfide ore was designed to calculate nine minerals in four different rounds, using least square method in the first two rounds and non-negative least square in the last two rounds. Sulfide minerals (chalcopyrite, galena and sphalerite) were calculated in the first round, barite was estimated in the second round, silicate minerals (garnet, biotite and quartz) were determined in the third round and pyrrhotite and magnetite were calculated on the last round. Data validation for EMC was performed by comparing calculated mineral grades against the measured mineral grades obtained from QEMSCAN. The accuracy was determined by evaluating the R2 value, the results were comparable as the R2 value was above 0.95 for all minerals. Mineral grades obtained from EMC of the assayed streams were used to carry out a mineral mass balanced of the flotation circuit. From the results, mineral grade and recovery were calculated and were used to evaluate metallurgical performance across the flotation circuit. The chalcopyrite (copper) concentrate was diluted with pyrrhotite (26 wt. %). The sphalerite concentrate (zinc) had the highest grade (94 wt. %) followed by galena (lead) with a concentrate grade of 85 wt. %. Sphalerite and galena achieved high recoveries over 90 %. From analysis of the flotation performance of the circuit, the results demonstrate an opportunity to improve the copper (chalcopyrite) concentrate quality. The diluted concentrate is likely to attract penalties during downstream processing (e.g. smelter) due to the presence of impurities (pyrrhotite). The concentrate can be upgraded by rejecting pyrrhotite in the first stage of the copper circuit. In addition, the mass balanced mineralogy results were used to calculate a theoretical potential of the final tailings to generate acid rock drainage (ARD). The ARD method used is based on the relative abundance of acid generating sulfide minerals (chalcopyrite, galena, sphalerite and pyrrhotite) and other minerals with the theoretical potential to neutralise the acid generated. The net mineralogically calculated acid producing potential was estimated as 46.4 kg H₂SO₄/ton. To further demonstrate the usefulness of the framework, a mineral splitter function was used to model the flotation circuit and test different hypothetical scenarios. Two hypothetical scenarios were investigated relative to the current operating condition of the flotation circuit. A sensitivity analysis on both scenarios was conducted to assess the effect of feed ore variability. The pyrrhotite feed grade was varied between 10 and 100 % of the base case and all sulfide mineral recoveries were kept constant. Scenario I considered improving Cu (chalcopyrite) concentrate grade in the Cu circuit by rejecting pyrrhotite. A Monte Carlo simulation was carried out by varying the pyrrhotite recovery to concentrate from a minimum of 2 % to a maximum of 18 % in the mineral splitter function. The results showed an increase in pyrrhotite grade in the final zinc tailings and an increase in the mineralogically calculated ARD potential (up to 53.9 kg H₂SO₄/t for tailings). Scenario II considered the installation of a magnetic separator to concentrate pyrrhotite in the final tailings and achieved a net acid producing potential of 15.2 kg H₂SO₄/t, which was lower than scenario I. The sensitivity analysis of scenario I showed a correlation between increased pyrrhotite feed grade with mineralogically calculated ARD potential (89.6 kg H₂SO₄/t). The results from sensitivity analysis of scenario II were lower were than scenario I (28.6 kg H₂SO₄/t). This shows that installation of a magnetic separator has the potential to mitigate ARD formation and produce a potential economic magnetite concentrate by-product. In conclusion this study has shown how mineralogy can be integral in developing an integrated modelling framework for simultaneously assessing techno-economic and environmental performance. The developed framework demonstrated the possibility of simultaneously balancing the trade-off, improving grade and mitigating the risk of ARD formation. It is a conceptual starting point for a new approach to traditional process mineralogy studies to start implementing sustainable development aspects on the operational level.

The plutonic rocks of the Paleozoic Isle au Haut Igneous Complex, Maine (424 $\pm$ 1 Ma.), are a trimodal assemblage of granites, diorites, and gabbros. Exposed from the top to the bottom of the pluton, the complex consists of an enclave-bearing granite, a composite layered sequence of alternating gabbroic and dioritic units, a thick and massive gabbroic unit, and a base of an enclave-void granite. The composite layer shows a sequence of ten alternating gabbroic and dioritic units that were liquid or largely liquid contemporaneously. Complex hybridization has taken place between the lower massive gabbroic unit and the underlying granite, while both were liquid or largely liquid contemporaneously. The gabbros are compositionally similar to within-plate tholeiites and they are uniform in average composition throughout the stratigraphic succession. The interlayered dioritic units, on the other hand, change progressively from mafic quartz diorite to quartz monzodiorite with stratigraphic height. A comparison of their respective densities indicates a gravitationally unstable situation if both the gabbroic and dioritic units were simultaneously liquid. I contend that the composite layered sequence represents the successive invasion, or replenishment, of an evolving dioritic chamber by a compositionally uniform gabbroic magma that intruded sill-like between the cumulate floor of the chamber and the overlying melt. Petrography of the individual gabbroic units shows varying degrees of disequilibrium. These include crystals with heterogeneous dissolution textures and mineral assemblages. The hybrid compositions are typically skewed to one side or the other of a linear bulk mixing line between the two proposed end-members. Fractional Crystallization and Assimilation-Fractional Crystallization models are inconsistent with the observed geology, because $>$60-80% crystallization of the gabbroic melt would be required to account for the most silica-rich of the hybrid compositions. Moreover, in element-element comparisons, the hybrids tend to plot away from a linear bulk mixing line in the direction of the experimentally determined, slower diffusing element. The hybrid compositions, on the other hand, can be bounded, on element-element plots, between paths invoking simple diffusion in response to a compositional gradient. Selective contamination and effects of differing rates of diffusion between elements appear to progress in directions consistent with the hybrid samples. Compositionally, the layered dioritic units and the hybrid samples overlap in almost every major, minor, trace, and rare earth element analyses. The composition of the hybrid matrix and the dioritic units does not conform to processes which I examined for the hybrid rocks. Instead, I propose that the compositions of the large-scale dioritic layers are largely controlled by similar diffusion processes which effected the small-scale hybrid compositions. Selective contamination, effects of differing rates of diffusion between elements, and convective transport of those elements at the granite-gabbro contact appear to progress in directions consistent with the hybrid and diorite compositions. Relative diffusivity controlled the composition of a hybrid liquid which formed at both the top and base of the contact of the massive gabbroic unit overlying the granitic unit and collected to produce the composite layers sandwiched between the massive gabbro and the uppermost granite. (Abstract shortened by UMI.)

This dissertation presents the results of a collector - depressant equilibria study of the flotation systems potassium n-amyl xanthate - sodium cyanide - molybdenite and ethyl zanthate sodium sulfide - molybdenite and the study of conditions necessary for the selective flotation of covellite, tetra-hedrite, bornite, chalcopyrite, molybdenite, marcasite and pyrite in the system ethyl xanthate and sodium cyanide; the conditions necessary for the selective flotation of pyrite, covellite, bornite, galena, chalcopyrite, active sphalerite, and molybdenite in the system potassium ethyl xanthate and sodium sulfide; the conditions necessary for the selective flotation of molybdenite and pyrite in the system of potassium n-amyl xanthate and sodium cyanide; the condition necessary for the flotation of molybdenite and galena in the system potassium n-amyl xanthate and sodium sulfide.

Bibliography: pages 143-151. / Sugilite, a purple mineral belonging to the milarite group, occurs in the lower manganese orebody at Wessels Mine, in the Kalahari Manganese Field. This orebody was formed in the lowermost manganiferous horizon of the Hotazel Member of the Voelwater Jasper Formation, part of the volcanogenic sedimentary iron formation of the Griqualand West Sequence. At Wessels Mine, which is located northwest of Kuruman in the northwestern Cape Province, evidence of a widespread and pervasive hydrothermal event which took place around 1300 Ma is found in the form of upgrading of the manganese-ore horizons and the formation of zoned silicate-mineral assemblages. The presence of unusual minerals such as glaucochroite, iron akermanite, xonotlite and hydrogarnets of various types constrains the main phase of metamorphism to between 400 and 450 °C in a low pressure, hydrous environment with XCO2 ≤ 0,02. All the minerals which occur in these assemblages are described and discussed in terms of their chemistry and formation.

No description available.