Analysis of graphite orientation and crystallinity

The sample was sourced from the Epanko deposit Tanzania, located within the Mahenge Inlier in the Eastern Granulite terrane of the East African Orogen, where the host rocks consist of anorthosite basement and a sequence of sediments including shales, with a variable organic carbon content, and limestones that have been metamorphosed to high temperature and pressure as graphitic schists and marbles. The phases present in the sample were determined by clustering the X-ray hyperspectral map which was collected in parallel to the SEXS and CL datasets.

C Kα spectra from distinctively different carbon-rich grains, measured using the SXE spectrometer are shown to the right. The graphite spectra are equivalent to those observed on HOPG graphite and attributed to 2p(x+y) and 2pz orbitals. The C Kα second order peak at 281 eV is attributed to π bond, whereas the peak at 271 eV is attributed to σ bond. The presence of π and σ bonding indicates the highly crystalline graphitic nature of the carbon, as these would not be present if it was amorphous.