A Practical Preparation Method of Split Mounts in SIMS Analysis for Convenient Assembling Different Reference Materials

Secondary ion mass spectrometry (SIMS) is often the first choice to analyze precious samples because of its low sample consumption, high spatial resolution, and high sample throughput. However, samples subjected to SIMS analysis are conventionally prepared on the same mount with multiple reference materials (RMs) to monitor instrumental bias and to calibrate its accuracy. SIMS mounts prepared following this conventional protocol cannot fully satisfy requirements for analyzing different minerals containing a wealth of geological information. The limited amount of some RMs also makes it challenging to meet the demands of the increasing number of SIMS laboratories. To facilitate reuse and replacement of RMs, we tested assembling of two split-mounts into the sample holder to constitute a standard one-inch-diameter mount for further SIMS analysis. 91500 zircon, Plesovice zircon, Qinghu zircon, ZN3 zircon, and NIST SRM 610 glass RMs were used to evaluate the effects of differences in the electric field due to the gap between spliced parts by analyzing the U-Pb ages and oxygen isotopes on grains close to it. The results show that Pb-206/U-238 ages and oxygen isotopes of measured spots within a 1.5 mm distance from the spliced gap deviated from their recommended values to varying degrees. However, all spots beyond the 1.5 mm distance exhibited acceptable accuracy and reproducibility. Therefore, we propose a method that allows easy 1) reuse and 2) replacement of RMs during SIMS analysis to meet the modern analytical demands of SIMS laboratories. The proposed method will be useful, especially for the SIMS-based in situ analysis of precious samples limited in amount (e.g., lunar samples, meteorites, and others).