A newly characterized natural sphalerite reference material (IGGSph-1) for in situ S and Zn isotope microanalysis

Abstract

Sphalerite has been extensively utilized for tracing geological processes through its zinc and sulfur isotopic microanalysis. However, the lack of matrix-matched reference materials with characterized zinc and sulfur isotopic compositions poses a challenge. In this study, we examined a natural sphalerite sample (IGGSph-1) to evaluate its potential as a matrix-matched reference material for in situ microanalysis of zinc and sulfur isotopes. Electron probe microanalysis (EPMA) confirmed the homogeneity of major elements without any growth zoning in sphalerite grains. Random spot isotopic analyses conducted using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) yielded variances in δ⁶⁶Zn and δ³⁴S of 0.07‰ (2S, N = 105) and 0.12‰ (2S, N = 105), respectively. Based on the results and statistical analysis, it was determined that the IGGSph-1 sample was isotopically homogeneous and had the potential to be used as a reference material. The δ³⁴S_VCDT value, measured using elemental analysis-isotope ratio mass spectrometry (EA-IRMS), was 16.35 ± 0.26‰ (2S, N = 6). Additionally, the δ⁶⁶Zn_JMC-Lyon value, measured using solution-nebulization multi-collector inductively coupled plasma mass spectrometry (SN-MC-ICP-MS), was 0.17 ± 0.04‰ (2S, N = 18). These values are recommended as the isotopic reference values for IGGSph-1.