Zinc Isotope Measurement by MC‐ICP‐MS in Geological Certified Reference Materials

Here we present an analytical method for Zinc (Zn) isotopic measurements using “standard‐sample bracketing” on a Nu Sapphire multi‐collector inductively coupled plasma‐mass spectrometer. The effects of Zn mass fraction and HNO 3 molarity mismatch between the standard and the sample, as well as the presence of matrix elements have been evaluated. Long‐term reproducibility of better than ±0.03‰ for δ 66 Zn (2 s ) was routinely obtained. Accurate measurements were achieved when C Ni /C Zn < 0.001, C Ti /C Zn < 0.03, C Ba /C Zn < 0.05, C Na /C Zn and C Al /C Zn < 0.5, C Mg /C Zn < 0.1, C Fe /C Zn < 5 and C Cu /C Zn as well as C Cd /C Zn < 10. High‐precision Zn isotopic determination were performed on twenty‐one widely available geological certified reference materials, with an overall range of ~ 0.62‰ (0.15 to 1.07‰), which is nearly twenty times the current analytical precision (0.03), and the results are in agreement with most previously published data within 2 s . Among them, δ 66 Zn JMC 3‐0749L of eleven geological certified reference materials are reported for the first time: 0.22 ± 0.03‰ (dolerite, DR‐N), 0.23 ± 0.02‰ (gabbro, GSR‐10), 0.20 ± 0.04‰ (microgabbro, PM‐S), 0.15 ± 0.02‰ (andesite, GSR‐2), 0.22 ± 0.08‰ (diorite, GSR‐9), 0.19 ± 0.07‰ (syenite, GSR‐7), 0.30 ± 0.06‰ (granite, GSR‐1), 0.25 ± 0.00‰ (rhyolite, GSR‐11), 0.37 ± 0.01‰ (shale, GSR‐5), 0.21 ± 0.03‰ (limestone, GSR‐6) and 0.20 ± 0.03‰ (hornblendite, GSR‐15). The novel Zn isotopic data from these certified reference materials can be used for future interlaboratory comparisons.