TY - JOUR
T1 - Synchrotron PEEM and ToF-SIMS study of oxidized heterogeneous pentlandite, pyrrhotite and chalcopyrite
AU - Acres, Robert
AU - Harmer-Bassell, Sarah
AU - Beattie, David
PY - 2010/9/1
Y1 - 2010/9/1
N2 - Synchrotron-based photoemission electron microscopy (PEEM; probing the surface region) and time-of-flight secondary ion mass spectrometry (ToF-SIMS; probing the uppermost surface layer) have been used to image naturally heterogeneous samples containing chalcopyrite (CuFeS2), pentlandite [(Ni,Fe)9S8] and monoclinic pyrrhotite (Fe7S8) both freshly polished and exposed to pH 9 KOH for 30 min. PEEM images constructed from the metal L 3 absorption edges were acquired for the freshly prepared and solution-exposed mineral samples. These images were also used to produce near-edge X-ray absorption fine-structure spectra from regions of the images, allowing the chemistry of the surface of each mineral to be interrogated, and the effect of solution exposure on the mineral surface chemistry to be determined. The PEEM results indicate that the iron in the monoclinic pyrrhotite oxidized preferentially and extensively, while the iron in the chalcopyrite and pentlandite underwent only mild oxidation. The ToF-SIMS data gave a clearer picture of the changes happening in the uppermost surface layer, with oxidation products being observed on all three minerals, and significant polysulfide formation and copper activation being detected for pyrrhotite.
AB - Synchrotron-based photoemission electron microscopy (PEEM; probing the surface region) and time-of-flight secondary ion mass spectrometry (ToF-SIMS; probing the uppermost surface layer) have been used to image naturally heterogeneous samples containing chalcopyrite (CuFeS2), pentlandite [(Ni,Fe)9S8] and monoclinic pyrrhotite (Fe7S8) both freshly polished and exposed to pH 9 KOH for 30 min. PEEM images constructed from the metal L 3 absorption edges were acquired for the freshly prepared and solution-exposed mineral samples. These images were also used to produce near-edge X-ray absorption fine-structure spectra from regions of the images, allowing the chemistry of the surface of each mineral to be interrogated, and the effect of solution exposure on the mineral surface chemistry to be determined. The PEEM results indicate that the iron in the monoclinic pyrrhotite oxidized preferentially and extensively, while the iron in the chalcopyrite and pentlandite underwent only mild oxidation. The ToF-SIMS data gave a clearer picture of the changes happening in the uppermost surface layer, with oxidation products being observed on all three minerals, and significant polysulfide formation and copper activation being detected for pyrrhotite.
KW - chalcopyrite
KW - heterogeneity
KW - oxidation
KW - PEEM
KW - pentlandite
KW - pyrrhotite
KW - sulfide mineral
KW - ToF-SIMS
UR - http://www.scopus.com/inward/record.url?scp=77955976627&partnerID=8YFLogxK
U2 - 10.1107/S0909049510026749
DO - 10.1107/S0909049510026749
M3 - Article
VL - 17
SP - 606
EP - 615
JO - Journal of Synchrotron Radiation
JF - Journal of Synchrotron Radiation
SN - 0909-0495
IS - 5
ER -