Apatite Reference Materials for SIMS Microanalysis of Isotopes and Trace Elements

Twelve apatite samples have been tested as secondary ion mass spectrometry (SIMS) reference materials. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) analysis shows that the SLAP, NUAN and GR40 apatite gems are internally homogeneous, with most trace element mass fractions having 2 standard deviations (2 s ) ≤ 2.0%. BR2, BR5, OL2, AFG2 and AFB1, which have U > 63 μg g ‐1 , 206 Pb/ 204 Pb > 283, and homogeneous SIMS U‐Pb data, have respective isotope dilution thermal ionisation mass spectrometry (ID‐TIMS) ages of 2053.83 ± 0.21 Ma, 2040.34 ± 0.09 Ma, 868.87 ± 0.25 Ma, 478.71 ± 0.22 Ma and 473.25 ± 0.09 Ma. Minor U‐Pb heterogeneity exists and accurate SIMS results require correction with the 3D Concordia‐constrained common Pb composition. Among the studied samples, AFG2 and BR5 are the most homogeneous U‐Pb reference materials. The SIMS sulfur isotopic compositions of eight of the apatites shows they are homogeneous, with 2 s for both 10 3 δ 34 S and 10 3 δ 33 S < 0.55‰. One apatite, BR96, has Δ 33 S = ‐0.36 ± 0.2‰. The apatite samples have ID‐TIMS 87 Sr/ 86 Sr between 0.704214 ± 0.000030 and 0.723134 ± 0.000035.