SIMS Laboratory CNR-IGG Pavia

Typical SIMS analysis

 

REE and other trace elements are generally monitored all together during a SIMS analysis. Several acquisition lists have been developed over these years in order to allow for the choice of the various isotopes, optimise the analytical sensitivity and correct for residual interferences (if any) as a function of the sample composition.

Our SIMS methodology is characterised by a great flexibility in adjusting the measurement parameters to the chemical characteristics of the sample, and in providing, at the same time, with all the relevant geochemical data on the selected microspot area (~ 5-20 mm Ø ).

The duration of a SIMS analysis is a function of the number of elements to be analysed, acquisition times for all the isotopes selected and deconvolution procedures involved, spanning in all cases between 20 to 40 min.

The possibility to reduce up to few microns the diameter of the primary ion beam (O^- is generally used for the analysis of geologic samples) makes the ion microprobe essential in the study of tiny crystals, zoned minerals, interstitial glasses and melt inclusions.

 

 

Sample preparation

Minerals and glasses are analysed both as separate grains, embedded in epoxy resin (2.54-cm Ø ) and in rock thin section (30-mm thickness) mounted on glass and polished. Since the sample holder can contain only circular mounts by 2.54-cm Ø, it is necessary to follow duly this specification.

Working with embedded materials, the thickness cannot overcome 1 cm.

In order to get the best accuracy of analysis, both embedded grains and thin sections must be accurately polished (as for the EMP analysis). It is recommended an accurate washing (possibly in ultrasonic tank) in order to remove any residual contamination deriving from polishing or previous carbon coating.

All the areas of interest must be accurately studied preliminarily at the optical and electron microscope. It is very advisable to prepare maps or micrographs at different magnification, with a clear indication of the areas to be investigated.

Since the quantification is done relative to an inner standard (generally Si, but in some case also Ca or Al), all the samples shall be preliminarily analysed at the electron microprobe. The major-element composition (by EMPA) is required in order to choose the most suitable standard for the SIMS analysis. In the general case, it is advisable that SIMS analysis is done as close as possible to previous EMP investigation so that the match among major, minor and trace elements is maximum. In some cases and with particularly complex samples, an additional EMP analysis may be required proxy or at the SIMS crater.

The final preparation of the sample before SIMS analysis (gold coating and mapping of the coated sample surface) may be done directly at the SIMS lab.

H analysis requires a preliminary sample degassing overnight. All the samples (unknowns and calibration standards) are placed in the dual sample holder of the ion-probe sample chamber.

In the following, we list the price per day (in Euros)*:

 

 

* Vat Excluded

** Eventually including some light or volatile elements