Natural analogue evidence for controls on radionuclide uptake by fractured crystalline rock

Metcalfe, Richard; Milodowski, Antoni E.; Field, Lorraine; Wogelius, Roy; Carpenter, G.; Yardley, B. W. D.; Norris, Simon

doi:10.1016/j.apgeochem.2020.104812

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…In this model, both fracture and wallrocks are fully saturated with water and the model predicts that species diffuse towards or away from the fracture at a rate that depends on the intrinsic properties of each species. Figure 1b is an alternative model (Alexander et al , 1990; Wogelius et al , 2020; Metcalfe et al , 2021), in which the fracture is surrounded by a damage zone with microcracks and enhanced porosity due to mineral reactions, resulting in higher permeability. Away from the fracture wall, the water content, saturation and transport properties of the wallrock change rapidly through the damage zone.…”

Section: Introductionmentioning

confidence: 99%

“…(a) Rock Matrix Diffusion model based on Baker et al (2002); the wallrocks are assumed to be water saturated throughout, permitting diffusive exchange between wallrock pores and fracture fluid. (b) Fracture Damage Zone model simplified from Metcalfe et al (2021). Water flows through microcracks and pores in a damage zone around the main fracture, as well as in the fracture itself.…”

Section: Introductionmentioning

confidence: 99%

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Groundwater–rock interactions in crystalline rocks: evidence from SIMS oxygen isotope data

Yardley

Milodowski

Field

et al. 2023

MinMag

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The diffusive exchange of dissolved material between fluid flowing in a fracture and the enclosing wallrocks (rock matrix diffusion) has been proposed as a mechanism by which radionuclides derived from a radioactive waste repository may be removed from groundwater and incorporated into the geosphere. To test the effectiveness of diffusive exchange in igneous and metamorphic rocks, we have carried out an investigation of veins formed at low temperatures (<100°C), comparing the oxygen isotopic composition of vein calcite with that of secondary calcite in the wallrocks. Two examples of veins from the Borrowdale Volcanic Group, Cumbria, and one from the Mountsorrel Granodiorite, Leicestershire, UK, have remarkably similar vein calcite compositions, ca. +20‰(SMOW) or greater, substantially heavier than the probable compositions of the host rocks, and these vein calcite compositions are inferred to reflect the infiltrating fluid and the temperature of vein formation. Calcites from the wallrocks are similar to those in veins, with little evidence for exchange with the wallrocks. The results support existing models for this type of vein which suggest low-temperature growth from formation brines originally linked to Permian or Triassic evaporites. The results are consistent with flow through fractures being attenuated through a damage zone adjacent to the fracture and provide no evidence of diffusional exchange with pore waters from wallrocks.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Groundwater–rock interactions in crystalline rocks: evidence from SIMS oxygen isotope data

Yardley

Milodowski

Field

et al. 2023

MinMag

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“…Such a high sorption capacity of these rock samples is due to the presence of chlorite, clay minerals and calcite in the material filler of the cracks. It was shown by digital radiography of a sample from the Toki Granite with fractured zones that alpha-emitting nuclides (uranium and thorium) are localized in the accessory minerals (apatite, orthite and zircon) in the zone of chloritized biotite, as well as in the clay matrix of the host rock [19]. Canadian researchers studied the sorption of Cs, Sr, Ce, Am, Se and Tc on thin sections of gabbroic rocks by digital radiography [20].…”

Section: Introductionmentioning

confidence: 99%

Sorption and Spatial Distribution of 137Cs, 90Sr and 241Am on Mineral Phases of Fractured Rocks of Nizhnekansky Granitoid Massif

et al. 2022

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The sorption behavior and spatial microdistribution of Cs-137, Sr-90 and Am-241 onto the surface of a fractured rock sample from the R-11 borehole of the exocontact zone of the Nizhnekansky granitoid massif were studied. The sorption efficiency of the fractured sample increases in the row of Sr < Cs < Am, where americium is the most retained radionuclide. Based on the image processing of radiograms and scanning electron microscopy data, the mineral relative sorption efficiency (RSE) values were determined to quantify the contribution of the mineral phases of the fractured sample to radionuclide retention. It was established that cesium and strontium are predominantly retained in cracks filled with secondary mineral chlorite. Zeolite is a less effective sorbent with respect to cesium and strontium. Americium sorption is uniform over the whole surface of the fractured sample, with close RSE values for all mineral phases (RSE ~1). The behavior of cesium in heterogeneous and monomineral systems of crushed mineral phases of quartz, biotite and zeolite NaA imitating minerals of the fractured rock sample R-11 was determined. It was shown that the fraction of the sorbed cesium in a heterogeneous system of two mineral phases—biotite and quartz—was larger than the sum of sorption values for the same separated mineral phases. Based on the models of radionuclide sorption on illite–smectite minerals, it was able to estimate the depth of the penetration of solution into the fractured rock sample R-11. The variations of penetration depths for solutions of specific radionuclide into the fractured rock sample were established.

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Geochemical approach to provenance, weathering, hydrothermal processes and tectonics in a continental basin: The Ferreira basin (NW Spain)

González-Menéndez

García

Martín-González

et al. 2022

CATENA

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Natural analogue evidence for controls on radionuclide uptake by fractured crystalline rock

Cited by 5 publications

References 25 publications

Groundwater–rock interactions in crystalline rocks: evidence from SIMS oxygen isotope data

Groundwater–rock interactions in crystalline rocks: evidence from SIMS oxygen isotope data

Sorption and Spatial Distribution of 137Cs, 90Sr and 241Am on Mineral Phases of Fractured Rocks of Nizhnekansky Granitoid Massif

Geochemical approach to provenance, weathering, hydrothermal processes and tectonics in a continental basin: The Ferreira basin (NW Spain)

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