SIMS determination of mu g g(-1)-level fluorine in geological samples and its concentration in NIST SRM 610

The fluorine concentration in NIST SRM 610 was determined by SIMS to be 295 +/- 16 mu g g(-1) (5.40% relative standard deviation). Accuracy of the mea surement was determined from a calibration involving the synthesis of glass calibration samples doped with varying concentrations of fluorine and char acterized by electron microprobe analysis and SIMS. The calibration was acc urate to about +/-5%. Multiple analyses of the calibration samples and SRM 610 in three different analytical sessions combine to produce a low relativ e standard deviation of the mean (0.23% RSD) in the mean fluorine value for SRM 610. Analytical uncertainty in the fluorine value was 5.40% (RSD), ori ginating from a combination of calibration and ion counting uncertainties a s determined from multiple analyses. Evaluation of the SIMS technique using the new fluorine value in SRM 610 shows that this element can be determine d with a precision and accuracy superior to that of EPMA. Measurements of f luorine in igneous and hydrothermal zircon suggest that F-ligands may have been responsible for Zr transportation in hydrothermal fluids also responsi ble for W-Au mineralisation. Other applications for low-level fluorine dete rminations may include melt inclusions and nominally anhydrous mineral phas es, particularly mantle phases.