Analyses

Ion probes allow three types of analyses:

  • Point analysis : a stationary or rastering primary beam is used to know the composition in a point with a spot size between 5-20µm
  • Depth profiling: the progressive erosion of the sample surface using a scan of a small surface (raster) allows monitoring of the variations of composition as a function of depth
  • Imaging : an image of either elemental or isotopic variations in composition with a spatial resolution of roughly 1µm

As CASA center is equipped with a NanoSIMS instrument with a high spatial resolution, by far higher than the SIMS, we usually do not do imaging. 

The measurements accuracy allowed by the IMS 1280 HR can be as low as conventional bulk technique (e.g. 2SD for oxygen isotopes is 0.2-0.3‰).

Accurate isotopic analysis requires matching of the chemical matrix composition (to a few % weight) and the unknown sample, as well as a match of the structure. Chemical variations due to solid solutions, present in many glasses and crystals, requires a series of standards wich cover the range in composition to be analyzed (with respect to major elements).

SwissSIMS analytical portofolio:

Material Elements/isotopes routinely analyzed Development in progress
Quartz d18O, d30Si, traces elements (Li, Al, Ti, Fe)  OH
Glass d18O, d7Li, d11B, d30Si, d37Cl, volatile contents, dD  d56Fe
Biotite d18O, volatile contents dD
Sulfure D34S, d56Fe  
Micas d18O OH
Feldspars d18O  
Graphite d13C  
Organic matter d13C, D33S  
Calcite, dolomite d13C, d18O d11B
Olivine d18O, d56Fe  
Diamonds d13C  
Zircon d18O, U-Pb dating  
Monazite d18O, U-Pb dating
Tourmaline d18O, d11B OH
Garnet d18O, d7Li

SwissSIMS precisions for regular (~10-15µm) spot size

  • δ7Li: ± 1‰ 2SD or better for [Li] > 20 ppm
  • δ11B: ± 1‰ 2SD or better for [B] > 20 ppm; ± 0.3‰ 2SD in tourmaline
  • δ13C: ~ ± 1‰ 2SD
  • δ18O: ± 0.3‰ 2SD
  • δ30Si: ± 0.3‰ 2SD
  • δ34S: ± 0.3‰ 2SD
  • δ37Cl: ± 0.4‰ 2SD for [Cl] > 100 ppm
  • δ56Fe: ± 0.3‰ 2SD
  • Cl, F, H2O: F-H2O: 0.3 – 0.6% s.e., Cl: 1% s.e. (F-OH-rich minerals)
  • Trace elements: ~ ± 10 %