Séminaire de Margherita Martini

Résumé :

Quantitative X-ray tomography provides new opportunities to investigate the internal structure and composition of objects in three dimensions. In this context, dual-energy X-ray computed tomography (DECT), originally developed for medical imaging, has been adapted to geological materials through a
stoichiometric calibration framework enabling the quantitative estimation of chemical composition (expressed as effective atomic number, Zeff) and density (specifically electron density, ρe).
This methodological development was first applied to the identification of common minerals and subsequently extended to the non-destructive characterization of complex sedimentary archives. In particular, the approach was applied to a varved sediment core retrieved from South Sawtooth Lake
in the Eastern Canadian High Arctic, a well-preserved lacustrine archive providing a continuous paleoclimate record spanning approximately 2900 years. By combining effective atomic number and electron density derived from DECT, distinct sedimentary facies could be quantitatively discriminated within the sequence. As illustrated in the Figure, this information can be used to reconstruct the three-dimensional spatial organization of sedimentary facies throughout the entire core, revealing the internal architecture of the archive and allowing contrasting depositional facies to be quantitatively discriminated within the sequence.
However, the potential of quantitative dual-energy X-ray tomography remains largely unexplored. In particular, this approach could provide new opportunities to investigate diagenetic processes by identifying heterogeneities within sedimentary materials in three dimensions prior to geochemical analyses. Such developments may ultimately contribute to improve the interpretation of paleoclimate proxies and to better constrain the role of diagenesis in geological archives.