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  • Rock matrix diffusion as a mechanism for radionuclide retardation : Natural radioelement migration in relation to the microfractography and petrophysics of fractured crystalline rock


Rock matrix diffusion is a potentially important radionuclide retardation mechanism. To predict retardation, mathematical models need data from actual sites. This study aims to provide such data by investigating the petrophysical, microstructural, geochemical and uranium series disequilibrium characteristics of rock adjacent to fractures in El Berrocal granite (Spain). Ultrasonic tests on cores EB4 and EB5 suggest microstructural changes adjacent to fractures. Acoustic microscopy has revealed anisotropy in surface wave velocity in thin sections; fluorescence microscopy has allowed quantification of microcrack orientation which appears anisotropic. Uranium microcartography (fission track analysis and alpha-autoradiography) has revealed three modes of U distribution: (i) dispersed within primary phases; (ii) point sources associated with accessory minerals; (iii) linear distributions associated within microfractures. Uranium series/geochemical work on EB4 has shown a correlation of U mobility with iron oxidation. The EB5 profile shows no chemical U enrichment but the activity ratio suggests recent 234U enrichment. The EB6 profile shows U enrichment on the fracture, but the activity ratios suggest geologically recent U mobilisation in the entire profile.

Additional information

Authors: HEATH M J ET AL., University of Exeter, Earth Resources Centre (GB)
Bibliographic Reference: EUR 15977 EN (1995) 128 pp., FS, ECU 15
Availability: (2)
ISBN: ISBN 92-827-0152-2
Record Number: 199411584 / Last updated on: 1995-03-21
Original language: en
Available languages: en
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