Analysis of Crystalline Rock Permeability Versus Depth in a Canadian Precambrian Rock Setting

Abstract

Multiple countries (e.g., Canada, Finland, Sweden, and USA) around the world have undertaken studies regarding the management of used nuclear fuel. In Canada as well as globally, a solution for managing the long-term disposal of used nuclear fuel has been sought for several decades. Canada's management plans include the construction of a Deep Geologic Repository (DGR) to store the used nuclear fuel deep underground in stable rock settings. A DGR, according to Canada and Sweden, is a disposal area located deep underground (500-1,000 meters below the ground surface [mBGS]) in a suitable rock formation where used nuclear fuel could be isolated to minimize its impact on the environment and human health (Dixon &

Characteristics of hydraulic conductivity in mountain block systems and its effects on mountain block recharge: Insights from field investigation and numerical modeling

“…Although Bedrock K in our study area verified the assumption of a decreased trend with depth, the low predictive power (R 2 = 0.19) demonstrated the invalidity of a consistent and generalizable equation capable of describing the K-z relationship in a crystalline basement. Similar results were reported for the analysis of crystalline rock datasets (Ranjram et al, 2015;Snowdon et al, 2021;Stober and Bucher, 2007).…”

The Low Permeability of the Earth’s Precambrian Crust

“…cratons). The upper limit of permeabilities estimated here are slightly greater than those predicted by a relationship proposed for batholiths (large masses of relatively homogeneous intrusive igneous rock) 16 (Table 1; Figure 2), which likely reflect the lower-end of permeability 6 relative to Precambrian rock as a whole. Permeability is elevated in the upper 1 km in Precambrian rock, which supports the concept that enhanced permeability in shallow (<1 km) crystalline rocks is largely a function of weathering rather than unloading or tectonics 32,33 (Figure 3).…”

“…However, Ingebritsen and Manning 20 noted that stable tectonic settings ('cratons') where a significant proportion of the world's oldest rocks, including those of Archean age, are located, are likely to have even lower permeability values than the models they developed would predict. More recent studies based on compilations of permeability estimated from a range of in situ and laboratory hydraulic testing techniques 14,16 confirm the lower permeability values in crystalline rock down to depths of 1.3 km (Figure 2b), but, as previously noted, relatively few measurements are available from Precambrian rock at greater depths.…”

“…An upper limit of 10 km was used for L, based on the dimensions of regional groundwater flow in the Canadian Shield 27 and previous treatment of flow system dimensions in metamorphic and geothermal environments 15 .We assume a hydraulic gradient of 10 5 along with additional data on the depth of sample collection from the original studies (Table S1). Measurements for Precambrian rock in Canada 16 and globally 14 to depths of 1.3 km suggest that there is likely considerable variability in permeability at depth that may be difficult to capture with the approach used here.…”

“…The crystalline rocks of the Earth's Precambrian crust are inherently a low permeability hydrogeologic regime where what fluid flow occurs is primarily via fractured rocks. However, despite representing a significant proportion of the crust globally (Figure 1), detailed permeability measurements are few, particularly in deep (>1 km) crystalline rock [14][15][16][17] . These permeability values are necessary to constrain fluid and solute fluxes in the crust, to define the degree of interconnectivity that might occur between subsurface biomes, and to provide insights into the distribution and connectivity of fracture networks in deep Precambrian rock.…”