Department of Geological Sciences and Geological Engineering Graduate Theses
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Item Chemistry of the pearl oyster Pinctada radiata and implications for palaeoceanography(2024-11-07) Yousif, Ruqaiya; Geological Sciences and Geological Engineering; Pufahl , Peir; James, NoelOyster shell chemistry offers major potential for palaeoceanographic studies and temperature reconstructions, particularly bimineralic oysters such as Pinctada radiata. This thesis explores the efficacy of using P. radiata shells from the shallow subtidal environment of the Qatari coast, Persian/Arabian Gulf, as recorders of oceanographic conditions. Collected from the Qatar coast, the chemistry of growth lines from calcitic and aragonitic layers within the shells was analysed and compared with known ocean buoy data (including temperature, salinity, and pH). The oxygen isotopic composition (δ18O) of calcite and aragonite ranges from -1.2 to 2.2‰ and -1.1 to 1.3‰, respectively, with seasonal δ18O temperatures derived from calcite mirroring recorded seawater temperatures. However, δ18O values in aragonite show no temperature correlation to seawater values, suggesting vital effects influence its composition. Carbon isotopic compositions (δ13C) for both minerals also indicate vital effects, with no direct correlation to buoy data. Trace element concentrations and ratios in both minerals correlate with salinity and pH, allowing for the reconstruction of Holocene and Pleistocene seawater conditions using fossilized P. radiata. Additionally, the application of carbonate clumped isotope (Δ47) thermometry to the bimineralic shells reveals discrepancies in temperature estimates. TΔ47 values from calcite layers accurately track seasonal temperature variations, while aragonite layers show consistently higher temperatures due to kinetic fractionation and vital effects. Elevated Ca and Mg concentrations further contribute to temperature overestimation. This thesis also examines the role of environmental stressors on living P. radiata, including temperature fluctuations and tidal exposure. These stressors affect the inner extrapallial fluid (iEPF), pH, and magnesium ion concentrations, facilitating dissolution and Mg-rich carbonate precipitation within the aragonite matrix. This research highlights that diagenesis is an active process throughout the organism's life and can be induced by the mantle itself. It offers new insights into biogenic carbonate preservation and diagenesis prior to its export to the geological record. Collectively, results highlight the potential of P. radiata shells as valuable proxies for understanding past environmental conditions and the complexities of carbonate chemistry in marine settings.Item Inorganic Thiolated Arsenic in Mine Wastewater: Sources, Stability, and Potential Environmental Impacts(2024-10-28) Ali, Jaabir Duunya; Geological Sciences and Geological Engineering; Vriens, Bas; Leybourne, Matthew; Harrison, AnnaAqueous inorganic thiolated As species (thio-As) can be essential for the biogeochemical cycling of As in both natural and engineered environments. Mine waste systems such as tailings ponds and waste rock piles may have the sub-oxic and pH conditions that allow for the formation and mobilization of thio-As, but there remains a paucity of quantitative data on the presence and kinetic stability of these forms of As. This thesis investigated the presence, behaviour, and stability of thio-As in mine waste systems across various environmental conditions and evaluated geochemical controls on their formation and degradation (oxidation kinetics). Laboratory column experiments were conducted with mine waste rocks from the Antamina mine, Peru, and processed tailings from Montague, Nova Scotia, to assess the production of thio-As. Drainage from column experiments contained thio-As concentrations up to 13 µg/L, primarily as monothioarsenate. Thio-As abundances were notably higher (<5% of total dissolved As) in drainages from enargite-rich materials compared to those of arsenopyrite-bearing materials (<0.5%). Investigation of legacy tailings in Ontario and Nova Scotia revealed significant thio-As in porewaters (up to 5 mg/L; 17% of total dissolved As), primarily as monothioarsenate, as well as lesser amounts of di- and tri-thioarsenates and methylated thioarsenates. Thio-As was most abundant in sub-oxic porewaters and tailings across the studied sites, and strongly related to the prevailing redox conditions and porewater hydrochemistry, less to the As-bearing mineralogy. The oxidation kinetics of thio-As at varying pH, dissolved Fe, and (thio-)As concentration were also examined. Thio-As oxidation rates increased at lower pH, reaching several μmoles/L/d at pH 3. Trithioarsenate oxidation was about two orders-of-magnitude faster than di- and mono-thioarsenate. Experimental data was used to parameterize rate equations and calibrate a kinetic model for rate constants, offering insights into thio-As mobility and its potential environmental impacts. This thesis demonstrates that thio-As can exist in mine waste systems and potentially influence As mobility in these and receiving downstream environments. This highlights the need for including thio-As in mine waste management, environmental assessment, and remediation strategies, particularly at high-As sites.Item The Neoproterozoic São Francisco Basin, central Brazil: tectonic evolution, paleoclimate, and mineral systems(2024-10-11) da Silva, Leandro Guimarães; Geological Sciences and Geological Engineering; Pufahl, Peir; James, NoelThe São Francisco Basin (SFB; ca. 950-550 Ma), central Brazil, hosts sediments deposited during most of the Neoproterozoic Era and so is a critical repository of information concerning the evolution of the late pre-Cambrian world. Detailed study and revision of existing stratigraphy reveals that deposition occurred during separate stages of a complete Wilson Cycle, three Neoproterozoic glaciations, and global changes in the biogeochemical cycling of nutrient elements. The basal Macaúbas Group (ca. 950-650 Ma), composed of rift-related sediments, accumulated during breakup of the supercontinent Rodinia. Deposition was punctuated by globally correlative Sturtian glacial deposits (ca. 717-660 Ma). Copious post-glacial organic matter and pyrite-rich siltstones formed during the subsequent passive margin stage. The overlying Bambuí Group is a Cryogenian-Ediacaran mixed biochemical-siliciclastic succession (ca. 650-550 Ma) composed of six stratigraphic sequences. Sequence 1 contains Marinoan glacial diamictites and cap carbonate (ca. 635 Ma) with distinctive barite and aragonite crystal fans. Sequence 2, composed of neritic limestone, siltstone, and phosphorite, is unconformably overlain by dolostone and stromatolitic reefs of Sequence 3. A karst unconformity with sulphide deposits caps Sequence 3. Organic-rich, pyritiferous, deep-water, marine siltstones of Sequence 4 are overlain by shallow water carbonates of Sequence 5 that accumulated as sea-level fell during the Gaskiers Glaciation (ca. 579 Ma). Post-glacial glauconitic siltstones form the lower portion of Sequence 6 and are evidence of marine transgression during the peak of oceanic ventilation. Greywackes and conglomerates in upper Sequence 6 record basin closure by ca. 550 Ma. The organic-rich, pyritiferous, deep-water siltstones are interpreted as the product of combined glacial grinding on land during the Cryogenian glaciations and subsequent eolian, oceanward, transport of silt and clay particles. Copious eolian dust is interpreted to have fertilized the surface ocean to stimulate primary productivity, increase photosynthetic oxygen, and contribute to atmospheric oxygenation. Combined analysis of modern analogs, paleogeographic reconstructions, global 87Sr/86Sr values, chemistry of Ediacaran zircons, and clay mineralogy support this interpretation. The revised stratigraphy of the SFB consolidates its correlation with paleoclimatic events worldwide. Finally, an eolian origin of organic-rich, pyritiferous siltstone provides a novel control reductants for sediment-hosted sulfide mineral deposits.Item Trace Elements and Sulfur Isotope Variations in Endowed and Non-Endowed Porphyry Systems of the Dawson Range Mineral Belt, Yukon Territory(2024-10-04) Akinleye, Funmilade Tobi; Geological Sciences and Geological Engineering; Leybourne, MatthewThe Dawson Range Mineral Belt (DRMB) in the Yukon Territory is a geologically complex region with significant potential for critical mineral exploration. This study addresses the challenges of exploring this area, focusing on select trace elements and sulfur isotope analyses to distinguish between endowed deposits and non-endowed occurrences. The remote location, poor access, and extensive glacial deposits complicate exploration efforts. The study analyzed fifty-six samples from eight porphyry systems, classifying them into endowed deposits (Casino, Cash, Revenue, Carmacks, and Minto) and non-endowed occurrences (Kerr, Cyprus, and Cockfield). Trace element analysis shows that endowed zones have higher concentrations of Cu, Mo, Au, Se and Re. Additionally, endowed samples had Cu concentrations ≥ 400 ppm, and non-endowed samples had Cu concentrations < 400 ppm. Sulfur isotope analysis of fifty-two sulfides from different mineral deposit/occurrence and host setting showed that the general δ³⁴S value in the region range from -6.6 to +5.8‰, with endowed deposits having a narrower range (-3.9 to +3.4‰) compared to non-endowed occurrences (-6.6 to +5.8‰). The alteration zones and weathering profiles of the samples were assessed, providing insights into genetic relationships of both sample groups. A sequence observed in the classified subgroups revealed δ³⁴S values in the order of ‘Argillic ≤ SCC (sericite-clay-chlorite) ≤ Potassic ≤ Phyllic ≤ Propylitic ≤ Argillic’ for alteration zones, and ‘Hypogene ≤ Supergene sulfide ≤ Supergene oxide’ for weathering profiles. Notably, the argillic alteration exhibited the widest δ³⁴S range, reflective of complex sulfur sources and processes. The δ34S values provide valuable insights into the provenance, geological and fluid evolution, as well as potential alteration and weathering zones within porphyry systems. They are, however, insufficient to definitively confirm the endowment criteria of mineral deposits, as fractionation factors are subject to changing conditions throughout the ore system's geological history. Understanding the regional zonation of δ34S can be a useful complementary tool in refining exploration findings, particularly when combined with other geological and geochemical data. This study emphasizes how integrating geochemical and isotopic data can refine exploration strategies, lower costs, and potentially identify new economically significant deposits, enhancing the global supply of critical minerals.Item Investigating the Occurrence and Effects of Fragmentation: Analysis of Rockfall Videos Captured During Slope Maintenance Campaigns(2024-10-02) MacPhail, Ruairidh; Geological Sciences and Geological Engineering; Hutchinson, JeanRockfall is a gravity-driven natural hazard common in mountainous areas, that poses a risk to infrastructure and human life. Understanding rockfall frequency and potential trajectories are essential for the safe design of roads and railways. This is traditionally through analysis of the slope and historical rockfall data. Fragmentation results in a spreading effect of the fragments, and alters most factors used to approximate rockfall behaviour and hazard calculations. Improved knowledge of fragmentation is vital for better protecting infrastructure in rockfall-prone areas. The focus of this research is to investigate factors influencing the occurrence of fragmentation and how fragmentation affects rockfall behaviour. Data was collected remotely due to issues with the COVID-19 pandemic. A methodology for collecting rockfall video data was developed and 218 videos from slope maintenance campaigns across the U.S. were analyzed. A fragmental video database was created, extracting 76 variables related to the slope, rockfall, and fragmentation from videos. Supplementary data (photos, notes, 3D models) is used to enhance video analysis, capturing key details such as slope conditions, slope geometry, and fragment locations. The following trends were discovered from the database analysis. Several factors were found to be associated with an increased chance of fragmentation: igneous rock type, a first impact on rock, bladed and platy rockfall shapes, rockfall exhibiting freefall, steep slopes and slopes with trees. Compact rockfalls fragmented less often than rockfall of any other initial shape. The rockfall, primary and secondary fragment shapes all seem to be influenced by the rock type, and the fragment shapes influenced by the initial rockfall shape. Most rockfalls fragmented only once, with fragment numbers showing a gap-graded pattern.