Application of Cryo-SIMS to the analysis of polar ice

The suitability of secondary ion mass spectrometry (SIMS) for the analysis of polar ice is assessed. A magnetic sector SIMS instrument, modified to permit analysis of cryogenically prepared specimens, was used to analyze a sample of naled ice from in front of midre Lovénbreen, Svalbard. The ion-induced secondary electron imaging capability of the instrument permitted identification of features such as grain boundaries, triple junctions, filaments, pore spaces and cracks. Secondary ion maps were acquired with sub-micron resolution, permitting the characterization of chemical impurities at grain boundaries. Two regions of interest were analyzed and are described in detail. In the first, discrete particles of impurity (possibly precipitates) containing Na, Mg, K and Cl were identified along a grain boundary. Additionally, Mg was found to be present along the full length of the boundary. In the second analysis, impurity containing Na, Mg, K and Cl was found at a triple junction and some evidence for segregation of impurity to grain boundaries was gained. In both regions of analysis, Na, K and Cl were more apparent in grain interiors than Mg, despite the presence of the latter element at the boundaries. Results corroborate previous scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS) observations.