Synthetic Fluid Inclusion Tests The method for PIXE microanalysis of fluid inclusions has been tested by the direct analysis of synthetic fluid inclusions in quartz (Ryan et al., 1995).

Method Synthetic inclusions in quartz were produced from undersaturated aqueous solutions of NaCl and various metal chlorides. The cations K, Zn, Rb and Cs were chosen to yield X-rays, together with Cl, that span a major part of the PIXE spectrum at a range of concentrations. Inclusions, selected to lie at depths of 2-17 µm, were probed using a 3 MeV raster- scanned proton beam. The geometry of each inclusion was determined by optical microscopy, and the depth was inferred, from the fit to the Cl K alpha/beta ratio in the PIXE spectrum.

Accuracy Using these geometry parameters, expected X-ray yields per ppm were calculated with the CSIRO model for X-ray production from fluid inclusions. The results of the PIXE microanalysis of these synthetic inclusions demonstrated an accuracy of ~10-15% (Ryan et al., 1995). Natural inclusions with daughter crystals show increased scatter due to the positioning of the crystals within the inclusion cavity (up to ~30% for Cl). Application The scanning beam method for fluid inclusion analysis is now in routine use in the Fluid Inclusion Project. and is capable of detecting ore elements (such as Cu, Zn, Pb and Bi) at concentrations down to ~20 ppm.

For further information contact: Dr. Chris Ryan via email: (Chris.Ryan@csiro.au) +61-2-9490 8673 +61-2-9490 8909 CSIRO Exploration and Mining PO Box 136 North Ryde NSW 2113 Australia

CSIRO-GEMOC Nuclear Microprobe CSIRO Exploration and Mining

References

• Ryan, C.G., Heinrich, C.A., Van Achterbergh, E., Ballhaus, C., and Mernagh, T.P., (1995), Nucl. Instr. Meth. B104, 182-190.