Earth and Environmental Sciences

Permanent URI for this collectionhttps://uwspace.uwaterloo.ca/handle/10012/9943

This is the collection for the University of Waterloo's Department of Earth and Environmental Sciences.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

Waterloo faculty, students, and staff can contact us or visit the UWSpace guide to learn more about depositing their research.

Browse

Browsing Earth and Environmental Sciences by Author "Frape, Shaun"

Filter results by typing the first few letters
Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Chlorine and Bromine Isotopic Analyses of Groundwaters and Porewaters from the Bruce Nuclear Site
    (University of Waterloo, 2017-10-23) Wang, Yinze; Frape, Shaun
    This study reports chlorine (δ37Cl) and bromine (δ81Br) isotopic values for groundwaters and pore fluids from early Paleozoic (Cambrian to Devonian) sedimentary rocks at the Bruce Nuclear Site near Kincardine, Ontario, Canada. The Cl and Br isotope data, in conjunction with their concentration data, are used to ascertain fluid origins as well as to identify processes responsible for isotopic fractionation. The sampled groundwaters and porewaters (from boreholes DGR-3/4) have isotopic and geochemical signatures similar to formation fluids from the same geological units elsewhere in the Michigan Basin, based on comparison with regional sedimentary formation water databases. The Silurian Salina A1 and Guelph Formation groundwaters, sourced within the Michigan Basin, have low δ81Br. The Salina A1 samples appear to have been altered by halite dissolution and mixing with cold climate recharge. In contrast, the Cambrian groundwaters have high δ37Cl and δ81Br values that are similar to Cambrian brines found in the Appalachian Basin to the east and south. The halide isotopic signatures of the Cambrian groundwaters suggest that these fluids may be very old, and their isotopic compositions have been preserved since emplacement during basinal fluid migration events in the early Paleozoic. In general, Devonian to Cambrian porewaters at the site have similar δ37Cl and δ81Br values as fluid samples from equivalent geological units listed in the combined regional database compiled from Shouakar-Stash (2008), Hobbs et al. (2011) and Skuce et al. (2015). However, some Cambrian and Ordovician porewater samples have δ37Cl and δ81Br values that are distinctive from regional sedimentary groundwaters found in the equivalent units. The Early Silurian to Late Ordovician stratigraphic sequence (~400 m thick) at the site has been effectively defined as a diffusion-dominated system (Clark et al. 2013; Al et al. 2015). However, δ37Cl and δ81Br values of the porewater samples at the site are not easily explained by a simple diffusion process across multiple geological layers of highly variable sedimentological characteristics. The halide isotopic profiles throughout the stratigraphic sequence was potentially impacted by several fractionation mechanisms over long geologic time frames. These physical or biological processes include organic and/or microbial halide gas production and degassing, salt dissolution, diagenesis/dolomitization (early Phanerozoic), tectonically-driven fluid migrationand/or hydrothermal fluid mixing (late Phanerozoic) as well as localized diffusional migration of porewater solutes within stratigraphic units. In addition, the initial depositional environment may have influenced the δ37Cl and δ81Br isotopic signatures of the sedimentary porewaters from the site. This depositional influence can be tied to temporal variations in the relative fluxes of continental weathering inputs and mantle inputs (degassing from ocean volcanic sources) of Cl and Br to seawater. This study shows that an increased understanding of transport processes, and the origin and relative ages of potential end-member fluids, can be gained through the analyses of porewater Cl and Br isotope compositions together with chemical and isotopic parameters already used to assess solute longevity.
  • Thumbnail Image
    Item
    Geochemical Characterization of Groundwaters, Surface Waters and Water-Rock Interaction in an Area of Continuous Permafrost Adjacent to the Greenland Ice Sheet, Kangerlussuaq, Southwest Greenland
    (University of Waterloo, 2016-01-21) Henkemans, Emily; Frape, Shaun
    Continental scale glaciations, such as those that covered much of Canada and Northern Europe during the last glacial maximum (26,000 to 19,000 y BP), can be expected to cause large disturbances to both the surficial and subsurface environments. The Greenland Ice Sheet (GrIS) provides a modern, natural analogue for past continental scale glaciations, allowing the extent and nature of the impact on ground and surface waters in the vicinity of the ice sheet to be studied. Currently, geochemical and isotopic information concerning groundwater chemistry and movement adjacent to a continental scale ice sheet is very limited. In areas of continuous permafrost, available knowledge is based on springs, open pingos and fluids from underground openings such as mines. Properly instrumented boreholes can provide additional insight into geochemical processes affecting groundwaters in cryogenic environments next to ice sheets. As part of the Greenland Analogue Project (GAP), three deep, inclined boreholes were drilled in crystalline bedrock in the Kangerlussuaq Region of southwest Greenland and two of these were successfully instrumented with sampling systems: i) Borehole DH-GAP01 intercepting a talik beneath a lake located less than 2 km from the Greenland ice sheet; and ii) Borehole DH-GAP04 was completed adjacent to the ice sheet in order to sample groundwaters from the bedrock below the ice. Drill core from the GAP boreholes was used to study fracture mineralogy, matrix pore fluids and whole rock chemistry. Geochemical studies were conducted on the borehole groundwaters and aimed to determine the depth of meltwater penetration beneath the ice sheet and the relative impact of cryogenic processes such as in-situ freeze out versus water-rock interaction on groundwater salinity. Surface water studies, including lakes and meltwaters in the Kangerlussuaq region, were also undertaken. Understanding the role of taliks, unfrozen conduits through the permafrost, in the groundwater system was an important goal of both surface and groundwater studies. Groundwater discharge significant enough to impact lake chemistry was not observed in any of the lakes studied, suggesting little groundwater-surface water interaction occurs in the study area. Recharge conditions between lakes and the groundwater system could also be an ongoing process and therefore help explain the lack of observable groundwater discharge into lakes. Evaporation is a key process impacting surface water chemistry. Lakes had enriched δ¹⁸O/δ²H isotopic signatures and fall along local evaporation lines. Consistent with previous work (e.g. Blum & Erel, 1995) on increased biotite weathering in glaciated environments, ⁸⁷Sr/⁸⁶Sr isotopic ratios were found to be more radiogenic (>0.73) in lakes in more recently glaciated terrain. In more recently deglaciated areas, sulfide oxidation was the main source of sulfur (as sulfate) in lakes, while the influence of marine aerosols and bacterial sulfate reduction increased further away from the ice sheet around Søndre Strømfjord. Groundwater sampled beneath the margin of the ice sheet (DH-GAP04) had highly depleted isotopic signatures (δ¹⁸O -23.5 to -24.4‰), similar to values observed for some regional meltwaters (-23.4 to -30.5‰). Meltwater recharging beneath the ice evolves from dilute Ca, Na, K-HCO₃ type waters to the brackish Ca-Na-SO₄ waters observed in the DH-GAP04 borehole. Gypsum is found as a ubiquitous fracture and rock matrix infilling in some borehole sections and has an isotopic composition of 3.2 to 10.7‰(δ³⁴S-SO₄), 4.5 to 9.1‰ (δ¹⁸O-SO₄) and ⁸⁷Sr/⁸⁶Sr ratios of 0.7022 to 0.7093. Recharging meltwater interacts with gypsum resulting in groundwaters with SO₄²- concentrations up to 1880 mg/L and groundwaters had similar isotopic signatures to fracture infillings: δ³⁴S-SO₄ (4.5 to 5.0‰), δ¹⁸O-SO₄ (2.9 to 5.9‰) and ⁸⁷Sr/⁸⁶Sr (0.7033 to 0.7075). The origin of the gypsum is believed to be due to an older hydrothermal event and not related to solute exclusion during freezing of fracture and matrix fluids. The continued presence of such a soluble mineral phase suggest that ice sheet induced meltwater circulation has not disturbed large sections of the rock matrix porosity and parts of the groundwater system sufficiently to dissolve gypsum and activate gypsum sealed fractures. Isotopic evidence for bacterial sulfate reduction was not observed. Groundwater from the talik lake borehole had a more enriched isotopic signature (δ¹⁸O -21.6‰) than the deeper groundwaters obtained from DH-GAP04, reflecting mixing with evaporatively enriched surface water. Solute exclusion due to permafrost formation was not observed to impact groundwater or matrix porewater chemistry. A perennially flowing spring located at the front of nearby Leverett Glacier was found to be geochemically unique from the borehole groundwaters. The source of the spring water could not be confirmed but was isotopically enriched (average δ¹⁸O -18.5‰) relative to meltwaters and the borehole groundwaters. High abundances of rare earth elements in the spring waters suggest a higher temperature origin for the spring.
  • Thumbnail Image
    Item
    Geochemical Evolution of Fracture Filling Minerals from the Chalk River Laboratory Site, Ontario, Canada
    (University of Waterloo, 2016-02-18) Tian, Long; Frape, Shaun
    The isotope geochemistry combined with fluid inclusion studies of several generations of fracture minerals from the Chalk River Laboratory site (CRL) has been applied to investigate the past fluid evolution including hydrothermal processes and hydrogeochemical evolution of the rock mass. Typical fracture minerals found at the CRL site include chlorite, quartz, dolomite, and calcite. Fracture mineral investigations use oxygen and carbon isotopes from calcites combined with fluid inclusion information such as homogenization temperatures (Th), and melting temperatures (Tm) to calculate temperature and salinity of calcite forming fluids. By combining Th with oxygen isotopic data, we were able to use δ18O geothermometry calculations to estimate past isotopic characteristics and composition of the fluids responsible for calcite precipitation. From petrologic evidence, calcite from the CRL site mainly includes four varieties: fibrous calcite, metasomatic calcite, crystal calcite, and vuggy calcite. Fibrous calcite precipitated at a temperature of 78 to 128 oC with a δ13C signature of -4.91 to -7.88 ‰ (VPDB) and a δ18O signature of -9.36 to -17.34 ‰ (VPDB). These calcites were formed at an elevated temperature, in a low salinity, Na-Cl fluid that could have been a mixture of hydrothermal water derived from meteoric fluids or seawater. Metasomatic calcite precipitated at 62.1 to 90.0 oC with a δ13C signature of -4.64 to -8.59 ‰ (VPDB) and a δ18O signature of -11.98 to -15.08 ‰ (VPDB). These fluids were elevated in temperature, had higher salinity and a Ca-Na-Cl composition similar to a sedimentary basinal brine. Crystal calcite separated into three groups according to fluid inclusion analyses and results, which are (a) elevated-temperature (67 to 113 oC) low-salinity calcite (lower than 15.14 wt. %), (b) elevated-temperature (73.7 to 91.7 oC) high-salinity (30 to 40 wt. %) calcite, and (c) higher-temperature (179.6 to 199 oC) low-salinity (lower than 7.33 wt. %) calcite. Group (a) has a δ13C isotopic signature of -5.61 to -10.42 ‰ (VPDB) and a δ18O signature of -8.35 to -16.04 ‰ (VPDB), Group (b) has a δ13C isotopic signature of -4.64 to -8.60 ‰ (VPDB) and a δ18O signature of -12.34 to -15.04 ‰ (VPDB), and Group (c) has δ13C signature of -5.59 to -8.06 ‰ (VPDB) and a δ18O signature of -10.03 to -16.17 ‰ (VPDB). Group (a) most likely formed from a hydrothermal fluid with a meteoric water origin, Group (b) could have formed during hydrothermal fluid mixing with an evaporated seawater or basinal brine, and group (c) seems to have formed as a result of a mixture of meteoric and lower salinity metamorphic or crystalline rock fluids. Vuggy calcite precipitated at 85 to 89 oC with a δ13C signature of -7.47 to -9.04 ‰ (VPDB) and a δ18O signature of -9.32 to -10.59 ‰ (VPDB). This case is from a high temperature, high Ca-Na-Cl salinity fluid which is hydrothermal fluids mixed with basinal brines. Strontium isotopic ratios, thorium-uranium ratios and REE data associated with the fracture calcites show that they have a limited water/rock interaction with the host bedrock. Some elevated thorium or uranium concentration were sourced from specific rock types such as pegmatite intrusions in the site.
  • Thumbnail Image
    Item
    Integration of Geochemical and Isotopic Analyses of Fracture Minerals and Fluids to Assess the Deep Geological Stability at Chalk River Laboratories, Chalk River, Canada
    (University of Waterloo, 2019-09-30) Gwynne, Rhys; Frape, Shaun; Yakymchuk, Chris; Kendall, Brian
    The crystalline bedrock underlying the Chalk River Laboratories (CRL) at Canadian Nuclear Laboratories (CNL) provides a valuable analogue for potential nuclear waste storage sites. As the main pathways for fluid flow in crystalline rock are facilitated by interconnected fracture networks, it is especially important to study and understand the timeline of fracture formation, the subsequent precipitation and stability of fracture sealing minerals, as well as the glacial, tectonic and geological history of the site as it relates to the local and regional hydrological stability. Previous studies were integrated with new data that was primarily focused on the discrete groundwater sampling of a series of boreholes at the CRL site as well as porewater analyses. Utilizing major ion geochemistry as well as stable isotopic analyses, several trends were noted in order to infer the fluid history at the CRL as well as the theoretical influence of the different possible water types on hydrological and fracture mineral stability. The groundwaters of the CRL were found to be a mixture of mostly meteoric recharge with a smaller glacial meltwater component. A more saline endmember was noted in certain locations thought to originate from mixing with a high conductivity fluid at depth (paleoseawater, rock porewaters, etc.). Meteoric and glacial meltwaters after infiltration from the surface follow typical evolution trends due to mineral dissolution and water-rock interaction progressing from Ca-HCO3 to Na-HCO3 to Na-HCO3-Cl type waters as available minerals are dissolved and longer timescale exchange reactions occur. No evidence of the influence of shield brines or recent hydrothermal waters was noted. Despite the geochemical variability documented there were no significant concerns that could be noted when considering their influence on calcite stability at depth. This supports the findings of previous studies that the crystalline bedrock fracture calcites of the CRL have been stable for more than 250 ka.