LAUSR

A field emission electron probe microanalyser (FEG-EPMA) equipped with traditional wavelength and energy dispersive spectrometry, together with soft x-ray emission spectroscopy (SXES) and a cathodoluminescence (CL) spectrometer has been used to investigate a geological sample from a Tanzanian deposit containing graphite, quartz and a number of other minerals. One of the aims of this study was to understand the crystallinity of the graphite, as the geology indicated the ore has been subjected to a heating event up to 800°C. At these conditions the carbon should be fully crystalline graphite. Initial Raman analysis had shown a mixture of signals indicating the possibility of different crystallinities of graphite. The SXE spectrometer equipped with a Princeton CCD [1, 2] was used to investigate whether different graphite or carbonaceous forms were present while the CL together with trace Ti analysis, was used to determine the maximum heating temperature using the Tin quartz geothermometry [3]. The sample was mounted in a 25mm round, then mechanically polished with a 1μm final lap and to finish the surface, it was ion beam milled at 2kV, 5°, for 10 minutes using a Technoorg Linda model SEM Prep2. Prior to examination the sample had a 5nm carbon coat applied. Cathodoluminescence maps were spectrally examined and the Ti4+ CL peak identified and fitted at each pixel and trace Ti levels measured to calibrate the CL levels as described previously.