Open AccessSynchrotron scanning photoemission microscopy of homogeneous and heterogeneous metal sulfide minerals
Author(s) -
Acres Robert George,
Harmer Sarah Louise,
Shui Hung Wei,
Chen ChiaHao,
Beattie David Allan
Publication year - 2011
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049511007175
Subject(s) - synchrotron , homogeneous , materials science , microscopy , metal , sulfide minerals , synchrotron radiation , sulfide , mineralogy , chemical engineering , chemistry , analytical chemistry (journal) , metallurgy , optics , environmental chemistry , physics , thermodynamics , engineering
Scanning photoemission microscopy (SPEM) has been applied to the investigation of homogeneous and heterogeneous metal sulfide mineral surfaces. Three mineral samples were investigated: homogeneous chalcopyrite, heterogeneous chalcopyrite with bornite, and heterogeneous chalcopyrite with pyrite. Sulfur, copper and iron SPEM images, i.e. surface‐selective elemental maps with high spatial resolution acquired using the signal from the S 2 p and Cu and Fe 3 p photoemission peaks, were obtained for the surfaces after exposure to different oxidation conditions (either exposed to air or oxidized in pH 9 solution), in addition to high‐resolution photoemission spectra from individual pixel areas of the images. Investigation of the homogeneous chalcopyrite sample allowed for the identification of step edges using the topography SPEM image, and high‐resolution S 2 p spectra acquired from the different parts of the sample image revealed a similar rate of surface oxidation from solution exposure for both step edge and a nearby terrace site. SPEM was able to successfully distinguish between chalcopyrite and bornite on the heterogeneous sample containing both minerals, based upon sulfur imaging. The high‐resolution S 2 p spectra acquired from the two regions highlighted the faster air oxidation of the bornite relative to the chalcopyrite. Differentiation between chalcopyrite and pyrite based upon contrast in SPEM images was not successful, owing to either the poor photoionization cross section of the Cu and Fe 3 p electrons or issues with rough fracture of the composite surface. In spite of this, high‐resolution S 2 p spectra from each mineral phase were successfully obtained using a step‐scan approach.