Major-element ratios in synthetic fluid inclusions by synchrotron X-ray fluorescence microprobe

Abstract

Individual fluid inclusions in quartz were investigated by synchrotron radiation X-ray fluorescence (SXRF) microprobe to develop protocols for major-element microanalysis. Studies were conducted of synthetic fluid inclusions in Brazilian quartz that contain fluids of known NaClCaCl 2H 2O and KClH 2O compositions. Inclusions were irradiated by synchrotron X-rays and the resulting energy-dispersive spectra were corrected for fluorescence yield and absorption effects to obtain Ca/Cl and K/Cl ratios. Results are commonly better than ±30% relative to the nominal ratio. Element ratios obtained by SXRF may be combined with results of heating and freezing studies to characterize non-destructively the bulk major-element composition of individual inclusions. Extension of the analytical protocol to elements of higher atomic number (e.g., trace and transition elements) will result in better precision as absorption effects and peak overlaps become less problematic.