Redox front penetration in the fractured Toki Granite, central Japan: An analogue for redox reactions and redox buffering in fractured crystalline host rocks for repositories of long-lived radioactive waste

The permeability (j[m 2 ]) of fractured crystalline basement of the upper continental crust is an intrinsic property of a complex system of rocks and fractures that characterizes the flow properties of a representative volume of that system. Permeability decreases with depth. Permeability can be derived from hydraulic well test data in deep boreholes. Only a handful of such deep wells exist on a worldwide basis. Consequently, few data from hydraulically tested wells in crystalline basement are available to the depth of 4-5 km. The permeability of upper crust varies over a very large range depending on the predominant rock type at the studied site and the geological history of the drilled crystalline basement. Hydraulic tests in deep boreholes in the continental crystalline basement revealed permeability (j) values ranging over nine log-units from 10 À21 to 10 À12 m 2 . This large variance also decreases with depth, and at 4 km depth, a characteristic value for the permeability j is 10 À15 m 2 . The permeability varies with time due to deformation-related changes of fracture aperture and fracture geometry and as a result of chemical reaction of flowing fluids with the solids exposed along the fractures. Dissolution and precipitation of minerals contribute to the variation of the permeability with time. The time dependence of j is difficult to measure directly, and it has not been observed in hydraulic well tests. At depths below the deepest wells down to the brittle ductile transition zone, evidence of permeability variation with time can be found in surface exposures of rocks originally from this depth. Exposed hydrothermal reaction veins are very common in continental crustal rocks and witness fossil permeability and its variation with time. The transient evolution of permeability can be predicted from models using fictive and simple starting conditions. However, a geologically meaningful quantitative description of permeability variation with time in the deeper parts of the brittle continental crust resulting from combined fracturing and chemical reaction appears very difficult.

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“…It is not a redox reaction front (e.g., Yamamoto et al . ) but rather a carbonation front (Priyatkina et al . ).…”

Section: Reactive Fluid Flow In the Crust And Its Effect On Permeabilitymentioning

confidence: 99%

Hydraulic conductivity of fractured upper crust: insights from hydraulic tests in boreholes and fluid‐rock interaction in crystalline basement rocks

Stober

Bucher

2014

Geofluids

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“…The study of thermal behavior of rocks at high temperatures is of great importance, as heating and cooling processes are relevant to their performance in geotechnical and engineering applications, such as radioactive waste storage (Liu et al, 2009;Yamamoto et al, 2013) and geothermal energy (Bartier et al, 2008;Marques et al, 2010). The effect of high temperatures is also essential when considering fire damage, both in forest fires or in the context of building stone.…”

Section: Introductionmentioning

confidence: 99%

Influence of mineralogy on granite decay induced by temperature increase: Experimental observations and stress simulation

Vázquez

Shushakova

Gómez-Heras

2015

Engineering Geology

131

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“…For example, in the context of a repository for radioactive waste, the host rock is one important barrier. A potential host type is crystalline rock, e.g., granite, which is considered for a repository in many countries including Germany, Finland, Russia, , Japan, Sweden, and the United States . Granite consists mainly of quartz, mica (e.g., muscovite), and feldspars.…”

Section: Introductionmentioning

confidence: 99%

Effect of Background Electrolyte Composition on the Interfacial Formation of Th(IV) Nanoparticles on the Muscovite (001) Basal Plane

et al. 2021

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Understanding the impact of actinide nanoparticle (NP) formation is important to assess radionuclide mobility in the environment. We combined surface X-ray diffraction (SXRD) and in situ AFM to investigate the previously reported unusual electrolyte effects on Th uptake on mica. At low [Th] (0.1 mM), interfacial structures show a broad Th electron density (∼50 Å). A linear decrease of Th uptake with decreasing hydration enthalpy of the electrolyte cation (Li+, K+, NH4 +, and Cs+) indicates a competitive effect between Th and the electrolyte cation. Na+ is a clear outlier from this trend. In situ AFM imaging confirms the results. Particles show a vertical size of ∼1–2 nm and larger lateral dimensions of ∼10–20 nm, which is typical for particles formed at interfaces (heterogeneous nucleation). At high [Th] = 1 and 3 mM, all investigated electrolytes (ACl, A = Li+, Na+, K+) show similar Th uptake, indicating a much smaller impact of electrolyte composition. The interfacial structures are dominated by a high Th loading at a distinct distance (∼6.5 Å) from the surface. Therefore, the main retention mechanism at high [Th] is suggested to be the sorption of Th NPs aggregated from Th oligomers present in solution (homogeneous nucleation).

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Redox front penetration in the fractured Toki Granite, central Japan: An analogue for redox reactions and redox buffering in fractured crystalline host rocks for repositories of long-lived radioactive waste

Cited by 23 publications

References 34 publications

Hydraulic conductivity of fractured upper crust: insights from hydraulic tests in boreholes and fluid‐rock interaction in crystalline basement rocks

Hydraulic conductivity of fractured upper crust: insights from hydraulic tests in boreholes and fluid‐rock interaction in crystalline basement rocks

Influence of mineralogy on granite decay induced by temperature increase: Experimental observations and stress simulation

Effect of Background Electrolyte Composition on the Interfacial Formation of Th(IV) Nanoparticles on the Muscovite (001) Basal Plane

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