New Quartz and Zircon Si Isotopic Reference Materials for Precise and Accurate SIMS Isotopic Microanalysis

Here we report the Si isotope compositions of four potential reference materials, including one fused quartz glass (Glass-Qtz), one natural quartz (Qinghu-Qtz), and two natural zircons (Qinghu-Zir and Penglai-Zir), suitable for in-situ Si isotopic microanalysis. Repeated SIMS (Secondary Ion Mass Spectrometry) analyses demonstrate that these materials are more homogeneous in Si isotopes (with the spot-to-spot uncertainty of 0.090-0.102 parts per thousand), compared with the widely used NIST RM 8546 (previously NBS-28) quartz standard (with the spot-to-spot uncertainty poorer than 0.16 parts per thousand). Based on the solution-MC-ICP-MS determination, the recommended delta Si-30 values are -0.10 +/- 0.04 parts per thousand (2SD), -0.03 +/- 0.05 parts per thousand (2SD), -0.45 +/- 0.06 parts per thousand (2SD), and -0.34 +/- 0.06 parts per thousand (2SD), for Glass-Qtz, Qinghu-Qtz, Qinghu-Zir, and Penglai-Zir, respectively. Our results reveal no detectable matrix effect on SIMS Si isotopic microanalysis between the fused quartz glass (Glass-Qtz) and natural quartz (Qinghu-Qtz) standards. Therefore, we propose that this synthetic quartz glass may be used as an alternative, more homogenous standard for SIMS Si isotopic microanalysis of natural quartz samples.