MICROANALYSIS OF ORE-FORMING FLUIDS USING THE SCANNING PROTON MICROPROBE

Much of the uncertainty in our early method of microanalysis of fluid inclusions using PIXE stemmed from the heterogeneous internal structur e of each inclusion, which typically contains a vapor bubble and daugh ter crystals, and the non-uniform beam dose distribution. This paper r eports on recent work to improve the accuracy of quantitative analysis through the use of beam-scanning techniques which provide a controlle d beam-dose distribution. Improvements have been made to the PIXE yiel d modelling to better account for large vapor bubbles, and all fluid i nclusion analysis routines have been incorporated as standard features of the GeoPIXE software package, The method has been tested using syn thetic fluid inclusions in quartz (solutions of Na, K, Zn, Rb and Cs c hlorides). The results demonstrated an accuracy improved to similar to 10-15%. Examples show the application of the method for the analysis of ore-forming fluids in magmatic hydrothermal systems.