Characterization of spatial porosity and mineral distribution of crystalline rock using X-ray micro computed tomography, C-14-PMMA autoradiography and scanning electron microscopy
Résumé
The spatial porosity and mineral distribution of geological materials strongly affects transport processes in them.X-ray micro computed tomography (X-μCT) has proven to be a powerful tool for characterizing the spatialmineral distribution of geological samples in 3-D. However, limitations in resolution prevent an accuratecharacterization of pore space especially for tight crystalline rock samples and 2-D methods such as C-14-polymethylmethacrylate (C-14-PMMA) autoradiography and scanning electron microscopy (SEM) are needed.The spatial porosity and mineral distributions of tight crystalline rock samples from Äspö, Sweden, andOlkiluoto, Finland, were studied here. The X-μCT were used to characterize the spatial distribution of the mainminerals in 3-D. Total porosities, fracture porosities, fracture densities and porosity distributions of the sampleswere determined using the C-14-PMMA autoradiography and characterization of mineral-specific porositieswere assisted using chemical staining of rock surfaces. SEM and energy dispersive X-ray spectroscopy (EDS) wereused to determine pore apertures and identify the minerals. It was shown that combination of the differentimaging techniques creates a powerful tool for the structural characterization of crystalline rock samples. Thecombination of the results from different methods allowed the construction of spatial porosity, mineral andmineral grain distributions of the samples in 3-D. These spatial distributions enable reactive transport modelingusing a more realistic representation of the heterogeneous structure of samples. Furthermore, the realism of thespatial distributions were increased by determinig the densities and porosities of fractures and by the virtualconstruction heterogeneous mineral distributions of minerals that cannot be separated by X-μCT.
Origine : Fichiers produits par l'(les) auteur(s)