In most cases, rocks and geomaterials are chemically and structurally inhomogeneous. The use of X-ray absorption spectro-microscopy is one promising solution, but the very long measuring time for scanning large samples with a tiny beam poses a limit for detailed analysis. At the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, scientists recently performed much more efficient and feasible experiments by coupling near-edge X-ray absorption spectroscopy and full-field transmission radiography with a large X-ray beam. The method basically consists of the repeated acquisition of X-ray images as a function of X-ray energy near the absorption edge (in the present case, iron K edge). The research group also combines this with polarization contrast imaging. By looking at the Fe3+/Fe(total) image, some redox variations were found in the single mineralogical phase of complex metamorphic rocks. The research group also analyzed bentonite analogue by separating the spectra into those of 5 simple minerals. The material is a candidate for the storage of nuclear waste and CO2, and the information is helpful in designing such applications. For more information, see the paper, "Submicrometer Hyperspectral X-ray Imaging of Heterogeneous Rocks and Geomaterials: Applications at the Fe K-Edge", V. De Andrade et al., Anal. Chem., Article ASAP (DOI: 10.1021/ac200559r Publication Date (Web) April 18, 2011).
