Exploring the application of dual-energy CT to discriminate sediment facies in a varved sequence

Abstract

Dual-energy X-ray computed tomography consists of imaging objects using two incident X-ray beams of different energy to distinguish the different compounds within a sample based on their density (electron density, ρ_e) and elemental composition (effective atomic number, Z_eff). The stoichiometric calibration for dual-energy X-ray computed tomography was already successfully implemented to identify single and homogeneous minerals easily and non-destructively. It is here applied for the first time to a more complex and heterogeneous sample, a varved sediment core with three distinct facies. The output of dual-energy X-ray computed tomography was compared against elemental geochemistry obtained at the same resolution using a micro-XRF core scanner. The three individual facies can be successfully differentiated using dual-energy X-ray computed tomography because their range of ρ_e and Z_eff values allow their discrimination. Correlations with elemental geochemistry are also discussed but are less conclusive, probably because of variations in grain size and porosity, and because these high resolution analyses were not performed at the exact same location. The paper not only eventually discusses the limitations when using dual-energy X-ray computed tomography on sediments but also demonstrates its potential to quantitatively study sediment cores in a non-destructive way.