An evaluation of precision and accuracy of SIMS oxygen isotope analysis

In this study, a high-precision secondary ion mass spectrometry (SIMS) zircon oxygen isotope ratio analytical protocol is described. The analysis is conducted using a Cameca IMS 1280-HR at the SIMS Laboratory of Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS). Four reference zircons (91,500, Qinghu, TEMORA 2 and Penglai) have been chosen to evaluate the reproducibility (precision) and accuracy. An identical protocol is used for the analyses, with unchanged instrumental parameters and with ion beam intensities kept as identical as possible. The Penglai zircon is used as an external reference material to calibrate the instrumental mass fractionation. The 91,500, Qinghu and TEMORA 2 zircons are used as the unknown samples, which yielded 10.15 ± 0.26‰ (2SD), 5.46 ± 0.24‰ (2SD) and 8.33 ± 0.29‰ (2SD), respectively, all consistent with the recommended values within error (2SD). A half-year long-term precision of 0.44‰ (2SD) is achieved using the Qinghu zircon as a monitoring sample for the routine measurement of zircon 18O/16O ratio, which demonstrates the reliability of this analytical protocol.