<p> Metagreywackes of the Goldenville Formation, Nova Scotia, possess a well developed spaced cleavage. Petrographic evidence suggests that the dominant mechanism producing this cleavage has been pressure solution, involving the dissolution of quartz from cleavage zones. A large amount of shortening occurs during cleavage development due to this volume loss of quartz. Based on a simple comparison of amounts of mica in cleavage and lithon zones shortenings of 50 - 60% have been found.</p> <p> Cleavage zones are marked by distinct mineralogical variations, notably a high content of white mica, and a low quartz content. Trends for all components have been documented to characterize the cleavage and lithon zones.</p> / Thesis / Bachelor of Science (BSc)

Historical gold mine tailings at several sites in Nova Scotia, Canada are publicly accessible and may pose a threat to human and ecosystem health because of high arsenic (As) concentrations in the tailings (max 25 wt.%) and associated pore waters (up to 100 mg/L). Two of these sites, Montague and Goldenville, are under consideration for remediation. Similar tailings sites have been cleaned up by covering the mine wastes with soil. However, the tailings at Montague and Goldenville have been weathering for at least 70 years, leading to a wide range of As-bearing secondary minerals which may dissolve under a soil cover, releasing As to local waters. The challenge of remediating these heterogeneous tailings lies in the different Eh-pH niches in which iron arsenates (oxidizing, acidic), calcium-iron-arsenates (oxidizing, alkaline), and sulfides (reducing) are stable. The main objectives of this study were to: 1) characterize pre-remediation geochemical controls on As mobility in subsurface tailings; 2) establish hydrogeological influences on As mobility; and 3) identify geochemical changes that result when a low organic soil cover is applied to the tailings. Pore water measurements were combined with bulk chemistry, scanning electron microscopy, and synchrotron micro-X-ray diffraction analyses, which were used to characterize the mineralogical composition of the tailings. Groundwater and surface water flow regimes throughout the tailings were defined through the use of piezometers and hydraulic conductivity measurements. Laboratory leaching experiments were used to assess the effects of a soil cover on the tailings. Variable weathering conditions over time have resulted in a continuum of saturation and redox environments and a range of As hosts in the tailings. In some areas, tailings pore waters are mixing with stream waters leading to As transport beyond the tailings. Applying a low organic soil cover does not induce reducing conditions in the tailings or cause dissolved As concentrations to increase compared to field pore water concentrations. This type of soil cover is effective in slowing sulfide mineral oxidation while maintaining stable conditions for secondary As-phases. The results of this research can be used to inform remediation decisions and guide ongoing environmental management of historical gold mine sites. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2014-06-04 10:22:43.838

<p> The greywackes of the Goldenville Formation, Meguma Group, Nova Scotia display a well developed spaced cleavage. The cleavage is characterized by zones of mica enrichment and associated quartz depletion and forms a network of anastomosing cleavage rhombs. Parallelism between cleavage and water escape structures suggests that the cleavage was emplaced perpendicular to bedding early in the deformational history of the rocks. Subsequent passive rotation of cleavage and water escape structures reduced the bedding-cleavage angle to its present values.</p> <p> XRF whole rock analyses of cleavage planes and lithons from two different sample locations show that the cleavage is depleted in SiO2, CaO, Na2O and enriched in Al2O3, Fe2O3, MgO, K2O, TiO2, MnO and P2O5 relative to lithons. Mass balance calculations based on the Gresens (1967) approach indicate that the cleavage with respect to the lithon represents a 40%-60% volume loss. Using the volume loss it can be shown that the cleavage lost SiO2, Na2O, CaO, MnO, P2O5, Pb, Sr, Nb, and Y and gained MgO, K2O, Ba, Rb, and W during its formation. TiO2, Al2O3, Fe2O3 and Zr remain relatively immobile during the cleavage forming processes. The behavior of Au, Sb, As, Ce, Nd, and La can not be discerned.</p> <p> The cleavage was initiated by pressure solution at grain contacts. However, several of the above mentioned chemical migrations increased the solubility of quartz and therefore greatly enhanced the development of the cleavage.</p> / Thesis / Master of Science (MSc)