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Geochronology and Fluid Characterization of Gold Mineralization in the Yellowknife Gold Belt
No full textChapter 3: Titanite as a U-Pb geochronometer for gold mineralization in the Yellowknife Greenstone Belt
The age of mineralization events provides information on the regional and local processes responsible for their formation. The minerals associated with gold in orogenic gold deposits are typically quartz and sulfides. However, quartz is not a datable mineral whose deposition typically predates gold. Ages can be obtained from sulfides, which are linked to gold deposition primarily through a geochemical model that links sulfide and gold precipitation (Ridley and Diamond 2000) as well as by the systematic association of sulfur and gold geochemical anomalies (Langlois, 2020). However, multiple sulfide generations are common in orogenic gold deposits (Laflamme et al., 2018) and their paragenetic relationships to gold are not always clear. This is further complicated by the occurrence of multiple ore forming or remobilization (Mumin et al., 1994; Hastie et al., 2020) events within individual deposits and belts.
In the Yellowknife Greenstone Belt, gold is directly linked to lithogeochemical anomalies in titanium (van Hees et al., 1999) and there is textural evidence of replacement of ilmenite by titanite and/or rutile (Langlois, 2019). This has led to the suggestion that the alteration of ilmenite to titanium-bearing minerals (e.g. titanite and rutile) and the release of Fe2+ destabilizes the gold-transporting complex Au(HS)2- leading to precipitation of gold. In this study, we have attempted to use titanite (CaTiSiO5) as a U-Pb geochronometer for gold mineralization in the Crestaurum, Southbelt and Sam Otto claims. However, LA-ICP-MS analysis has revealed that titanites hosted within metamafic rocks from the YGB have low uranium concentrations typically below 2 ppm, making them unsuitable for U-Pb geochronology.
Chapter 4: Redox controls on gold mineralization at Discovery-Ormsby
The Yellowknife Greenstone Belt is host to numerous orogenic gold deposits and showings including the world-class Con and Giant deposits. The geochemical parameters including the composition of the mineralizing fluids and some of the controlling factors related to precipitation remain actively debated. Although mineralization styles within the YGB are highly variable, the presence of high-pressure volatile-rich (CO2±CH4±N2) fluid inclusions are typically an indication of gold within the belt, which suggests a genetic link between mineralization and carbonic fluids. Therefore, fluid inclusions from both auriferous and non-auriferous samples can be used to differentiate the characteristics of the fluids responsible for gold deposition and the potential triggers of ore formation.
In the Discovery-Ormsby property, mineralization systematically occurs in samples whose fluid inclusions are H2O-absent, CO2±CH4±N2. Carbonic fluids are also present in the unmineralized samples, but in the unmineralized samples the carbonic fluid inclusions are systematically end member CO2 or CH4 compositions, while mineralized samples present a range of CO2/CH4 ratios. The fH2 of the fluids in the mineralized samples varies systematically as a function of depth, transitioning from reduced to oxidized as the ore fluid migrates throughout the system. Based on these results, we suggest that gold precipitation at Discovery-Ormsby was triggered by redox changes. These changes may have been caused by (1) mixing of a reduced fluid generated from carbonaceous shales of the Burwash Formation with CO2-rich fluids produced from the mafic host rocks and/or (2) fluid-rock interactions between the reduced fluid derived from the Burwash Formation and a more oxidized mineral assemblage in the metamafics of the Banting Group. The geochemical changes associated with these redox-related processes are most likely responsible for producing the graphite-gold connection observed in some orogenic gold deposits in the Yellowknife Greenstone Belt
Methylmercury transformations in peatland-influenced beaver ponds on the Taiga Plains
No full textBeaver ponds are located at key hydrological areas on the landscape where they exert significant influence on downstream ecosystems. These ponds have previously been identified as sources of methylmercury (MeHg), a toxic pollutant of global concern due to its bioaccumulation potential and the associated ecosystem and human health risks. While several studies have documented net methylmercury production in beaver ponds, their impact in the Taiga Plains, which are rich in peatlands and known MeHg production hotspots, has yet to be studied. This study evaluated the effect of beaver ponds on MeHg dynamics in the Taiga Plains by examining the inflow and outflow water chemistry of 22 beaver ponds. The objectives were: 1) Identify whether beaver ponds in the Taiga Plains act as MeHg sinks or sources, and 2) Identify the conditions that drive MeHg transformations and understand the biogeochemical processes that dominate in the pond and control MeHg concentration delivery. By analyzing the concentrations and changes in dissolved organic matter, oxygen levels, pH, and other key water chemistry variables, I assessed the biogeochemical factors governing MeHg transformations. The results showed that beaver ponds in this peatland-rich landscape primarily functioned as net MeHg sinks. This effect was greater in beaver ponds with longer residence times and high initial MeHg concentrations, suggesting that photodemethylation was the primary driver of MeHg transformations. Strong relationships between MeHg and aromatic moieties of dissolved organic matter, and the influence of seasonal variations in water chemistry indicated that the elevated MeHg concentrations delivered to ponds originated from upstream peatlands. Consequently, the ponds acted as important biogeochemical filters that moderated MeHg levels before delivery to downstream aquatic ecosystems. This study supports the finding that mercury transformations in beaver ponds is shaped not only by internal pond processes but also by external factors such as peatland MeHg production upstream and seasonal variations in flow. The findings of this study recognize the complex interactions between landscape features and pond biogeochemistry, which drive mercury transportation and transformations together
A single-cell gene set analysis of differential expression in lung cells with the heritable risk of COVID-19
No full textUnderstanding the interplay between genetic predisposition and immune response is critical to deciphering the pathophysiology of COVID-19. This study explores heritable risk factors and gene expression differences in key lung cell populations—alveolar type 2 (AT2) epithelial cells, CD8⁺ T cells, and macrophages—by leveraging single-cell RNA sequencing (scRNA-seq) data derived from postmortem lung samples of individuals who succumbed to SARS-CoV-2 infection. Using data from over 106,000 cells across 16 donors, we applied the Linear Combination Test (LCT), a high-dimensional gene set analysis method robust to unbalanced case-control designs, to assess differential expression patterns associated with SARS-CoV-2 RNA presence. We identified 127 differentially expressed gene sets in CD8⁺ T cells, 13 in AT2 cells, and an extensive 4,829 in macrophages, with a comparable number of differentially expressed individual genes in AT2 cells and macrophages (54 each), and 28 in CD8⁺ T cells.
Subsequent pathway analysis of 20 highly significant gene sets revealed functional convergence into three interconnected immunological axes: 1) DUSP4-mediated T cell differentiation and inflammation, 2) regulatory CD8⁺ T cell activity and exhaustion, and 3) dendritic cell–toll-like receptor signaling driving innate immunity. These pathways reflect distinct yet overlapping aspects of COVID-19 immunopathogenesis and highlight the importance of early cytotoxic responses, T cell regulation, and the innate immune activation cascade in determining disease outcomes. Our results support prior findings identifying heritable risk in these specific lung cell types and extend them by mapping detailed expression-based mechanisms. While LCT offered computational advantages and sensitivity in detecting subtle signal changes, limitations emerged under highly skewed case-control distributions, suggesting the need for conservative interpretation in such contexts.\nAltogether, our findings contribute to a more granular understanding of how genetic susceptibility manifests at the cellular level during SARS-CoV-2 infection and offer insights into potential therapeutic targets. This study also underscores the importance of integrating heritability and single-cell transcriptomics to identify cell-type–specific mechanisms underlying severe COVID-19, with implications for precision medicine and future pandemic response strategies
Development of fricative speech sounds in French: A view through different acoustic and statistical analyses
No full textThe study of children's speech production contributes to our understanding of speech sound development. However, most studies on the development of speech sounds have been conducted in English-speaking children. This thesis explores the developmental path of French fricatives through the analysis of spectral moments, demonstrating that some of them are useful in revealing patterns of acquisition of fricatives in young children. Moreover, Bayesian Linear Mixed Models (LMMs) have emerged as an alternative to frequentist LMMs to describe child speech. We compared frequentist and Bayesian statistical frameworks using the same dataset to explore which one better fits the data. The findings suggest that Bayesian analysis has advantages compared to the traditional frequentist framework. Finally, as phonetic transcription is a method commonly used in clinical practice and research, but is affected by perceptual bias, we explored the relationship between phonetic transcriptions of children's fricatives and acoustic features, specifically the four spectral moments, intensity and duration. The study reveals that clear protocols of phonetic transcription supplemented by visual analysis of the speech signal (e.g. waveform and spectrogram) fulfill an accurate and reliable speech transcription
Saba Nisa - Abstract 28 - Innovate Conference 2025
No full textSafe spaces play a crucial role in providing support for the sexual and reproductive health (SRH) of youth. As young individuals undergo significant physical and emotional changes, they often encounter challenges such as societal taboos and a lack of accessible information related to their SRH needs. This scoping review explores the existing literature on using safe spaces to offer a supportive environment for adolescents SRH to navigate these complexities
Dr. Umar Yunusa - Abstract 45 - Innovate Conference 2025
No full textCatch-up vaccination is recommended for the increasing number of children who for whatever reason missed or have not received doses of vaccines for which they are eligible. While evidence suggests that catch-up vaccination strategies are being implemented, the existing evidence is fragmented and thus needs to be synthesized in order to inform policies and practices targeted at improving vaccine uptake
2025 WCHRI Research Day website and abstracts
No full textThe website, posters, and abstracts for the 2025 Women and Children's Health Research Institute Research Day event