A new potential synthetic pyrrhotite reference material for Fe–S isotope microanalysis

Abstract

Pyrrhotite is a common Fe sulfide mineral in meteorites and magmatic sulfide ore deposits. It can be used to trace the origin of metals, as well as the formation and evolution of ore deposits. The natural pyrrhotite reference materials have been extensively consumed with the development of in situ techniques. In this study, we synthesized pyrrhotite by the hydrothermal method and evaluated its suitability as a reference material for in situ Fe and S isotope analysis. The synthetic pyrrhotite obtained through a hydrothermal experiment exhibits uniform surfaces and dense structures. The electron probe microanalysis (EPMA) verified the homogeneity of the major elements. The results of laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) for the iron isotopes and secondary ion mass spectrometry (SIMS) for the sulfur isotopes demonstrate the homogeneity of Fe and S isotopes, respectively. For in situ microanalysis, the two standard deviations (2SD) of iron and sulfur isotope compositions of SY-Po are 0.47‰ (2SD, n = 30) and 0.53‰ (2SD, n = 133), respectively. The solution MC-ICP-MS analyses and isotope ratio mass spectrometry (IRMS) results for SY-Po determined that the best recommended δ⁵⁶Fe value is 0.39 ± 0.03‰ (2SD, n = 3) and δ³⁴S value is −1.16 ± 0.23‰ (2SD, n = 11). Synthetic pyrrhotite SY-Po is a new potential reference material for in situ Fe and S isotope microanalysis, intended for tracing the formation processes of Fe sulfide minerals in magmatic sulfide ore deposits and meteorites.