Zircon water content: reference material development and simultaneous measurement of oxygen isotopes by SIMS

Zircon water content is an important physicochemical parameter for many geological processes, yet its measurement by the secondary ion mass spectrometry (SIMS) technique is hampered by the lack of suitable reference materials and high water background, especially if large-geometry (LG)-SIMS is used. Here we have described a suite of newly developed reference materials for SIMS zircon water content analysis and a modified micro-analytical technique (using a CAMECA IMS 1280-HR SIMS) that can simultaneously measure the zircon water content and oxygen isotopes. A total of 20 natural zircon grains/sherds were analyzed via Fourier transform infrared spectroscopy (FTIR), among which 8 (with good water content result reproducibility) were further analyzed by SIMS. Before the SIMS analysis, FTIR analyzed sample blocks were mounted with a Sn-based alloy to minimize degassing and background water. As in routine SIMS oxygen isotope measurement, 16 O − and 18 O − were collected using two Faraday cups, and in addition 16 O 1 H − was simultaneously measured using an electron multiplier. The measured 16 O 1 H/ 6 O ratio was converted into water content, using a calibration line established based on SIMS 16 O 1 H − / 16 O − ratios vs. the FTIR water content. Both the internal and external precisions of corrected δ 18 O are