New spinel reference materials for oxygen isotopic microanalysis

Three natural spinels—MadSP (Mg₀. 75 Fe₀. 25 Al 2 O 4 ), TanzSP-1, and TanzSP-2 (both MgAl 2 O 4 )—are reported as SIMS oxygen isotope reference materials. Their recommended δ 18 O values are 11.94 ± 0.43‰, 23.40 ± 0.20‰, and 13.29 ± 0.48‰, respectively.