Diffusion pathways in crystalline rock - examples from Aspo-diorite and fine-grained granite

The influence of heterogeneous porosity, mineralogical composition and text ure on the diffusion of alkali and alkaline earth metals in water-saturated crystalline rock was studied. Through-diffusion technique was used, and th e concentration profiles in the rock samples were measured. The porosity di stribution was studied by the C-14-polymerhylmethacrylate (PMMA) impregnati on method. The distribution of the tracers was observed from autoradiograph s and was then compared to the mineralogical and structural composition of the rock. Radionuclides of the alkali and alkaline earth metals were used a s tracers, i.e. Cs-137(+), Ca-45(2+), and Ba-133(2+). A double porosity net work of slow and fast migration pathways, with different sorption capabilit ies was used to describe the diffusion results. (C) 1998 Elsevier Science B .V. All rights reserved.