Nuclear Microprobe analysis, which provides non-destructive,
quantitative, simultaneous multielement analysis and imaging at ppm sensitivity and micron resolution,
provides a complement to high sensitivity, but destructive, point analysis methods, such as
laser-ablation ICP/MS, and routine methods for major element analysis and imaging, such as the electron microprobe (EMP).
The CSIRO-GEMOC Nuclear Microprobe (NMP) is available for collaborative
research and commercial contract analysis and imaging.
Please make contact via email (or by the telephone and
fax numbers listed at the bottom of this page)
to discuss your particular geological problem or microanalytical requirements, or to develop new research proposals.
The guidelines and information below should help in sample selection and preparation. However, if something
is not clear, please send an email.
The NMP can accommodate the usual mineralogical samples that are used for EMP analysis. These include
thin-sections on 2" x 1" glass slides, and grain mounts set in 25 mm diameter polished epoxy blocks.
The NMP is less sensitive to surface roughness. Hence, samples need only be polished with diamond paste.
Note: Glass slides must not be wider than 26.0 mm.
There is no need for a tin-oxide or cerium-oxide polish step. Indeed, these should be avoided to reduce
contamination of the sample with these trace elements. Similarly, avoid using marker pens (possible Br,
Cu contamination) or silver-dag during EMP
analysis (use carbon dag instead); in practice, it is impossible to completely remove
Glass slides should be no wider than 26 mm. The stage can take a total slide length of 85 mm. So more
samples can be mounted together if they are shorter in length. However, a sample change takes only about 10 minutes
Generally, samples need a conductive carbon coating. But this can be done at the CSIRO.
Fluid Inclusion Samples
For convenience, it is best to glue quartz chips containing fluid inclusions onto a glass slide, or
set them in an epoxy block.
The stage can take a total slide length of 85 mm. So more
samples can be mounted together if they are shorter in length.
Note: Glass slides must not be wider than 26.0 mm.
The long range of 3 MeV protons, which makes fluid inclusion analysis possible, also means that the beam
can penetrate through a chip and burn the glue behind. This can impair the view through the microscope using
transmitted light illumination. Hence, choose chips with thicknesses of 100 µm or greater.
Some samples contain enormous numbers of solid phases, fluid inclusions and fractures. In these cases don't make the
chips too thick, as the view will be very cluttered and confused, particularly through our long working-distance
microscope. Around 100-150 µm is ideal.
Take care with sample mounting to ensure that the glue layer behind is clear, uniform and free of bubbles.
Bubbles here, as viewed through our long-working distance microscope can masquerade as a miriad of fluid inclusions.
Similarly, make sure the surface of the sample chip is free of any glue residues.
Preparation Prior to Fluid Inclusion Analysis
In order to guarantee
the analysis of selected fluid inclusions, it is necessary to bring
photomicrographs at low and high magnification. The low mag photos
should enable local navigation, and the high mag photos (x100 printed
on A4 paper is ideal) enables the correct identification of inclusions.
If possible, bring non-inverted images which will match the on-line
microscope. (Normal microscope images are inverted. These can be "mirrored"
in most image manipulation programs.)
Fluid Inclusion Selection
Ideally, select fluid inclusions in the size range 10-30 µm in diameter, and with depths of less than
20 µm; less than 10 µm is ideal. Inclusions down to ~3 µm in diameter can be analyzed,
but at reduced sensitivity, and only in clear samples. Measure inclusion depths prior to analysis on the
NMP, ideally using a spindle stage or confocal microscopy (or laser Raman in confocal mode).
inclusions are useful as they will provide better elemental images of their contents, but they are probably less
representative of a given inclusion population, and will be more difficult to make
Remember that the on-line microscope in the nuclear microprobe has a long working-distance and plane
transmitted light illumination, which make everything at all depths visible to varying degrees,
so avoid areas with great detail beneath the plane of the inclusions.
Fluid Inclusion Parameters
Measure the X,Y
dimensions of each inclusion. Estimate these as the dimensions of
an ellipse of the same area as the inclusion. Measure the depth to
the mid-plane focus of the inclusion. With the depth measurement,
remember that you need to scale your microscope Z scale by the refractive
index (eg. 1.54 for quartz).
For best results, use a spindle stage, confocal microscope, or laser
Raman microprobe used in confocal mode, to measure the depth (from
sample surface to the top of the inclusion) and its thickness.
Also provide an estimate of the homogeneous density of the inclusion
contents, and if available the microthermometry data (homogenization
temperature and equivalent salinity).
A spreadsheet listing all required parameters for PIXE analysis
is available from the CSIRO at this link.
Download a copy of this spreadsheet, to be completed before your analysis
session, to streamline analysis of your inclusions.
Fluid Inclusion Analyses
Depending on the sizes of inclusions, nature of the sample, concentration of fluids and sensitivity required,
between about 20 and 40 fluid inclusions can be analyzed typically per working day.
Quotations and Analysis Costs
Rates for NMP analysis vary according to the nature of the work and the form of collaboration. For
example, we can analyze between 20 and 40 fluid inclusions per day, depending on the size of the
inclusions and the nature of the sample, and between 2 and 12 images per day, depending on the
assemblage, required detection limits and image area.
Please contact the CSIRO for advice, for a quotation
or to discuss your research proposal.
Two basic styles of work are offered:
- Commercial analyses, in which the results remain confidential
for a time.
- Collaborative research projects, in which there is a sharing of information about the study area
and geology, joint publications and reduced rates.