U Series Concentration Distributions Around Rock Fractures—Qualitative Indication of Matrix Diffusion

Abstract

Concentrations of U series nuclides (238U, 234U, 230Th, 226Ra and231Pa) across secondary U accumulations in rock matrix around water-carrying fractures were examined to find records of radionuclide movement. The accumulations, loaded in rock pores, were separated without dissolving the host rock. The concentration profiles observed, form patterns which point to both “old” and “young” U accumulations and, moreover, post accumulation movement of certain radionuclides. In the case of the young U accumulation, shown to have occurred between 10, 000 and 33, 000 years ago, the apparent diffusivity of Da=6.10-15 m2/s for U could be calculated.

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Correspondence to Juhani Suksi.

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Suksi, J., Saarinen, L., Ruskeeniemi, T. et al. U Series Concentration Distributions Around Rock Fractures—Qualitative Indication of Matrix Diffusion. MRS Online Proceedings Library 353, 441–448 (1994). https://doi.org/10.1557/PROC-353-441

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