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 (2s) <= 2.0%. BR2, BR5, OL2, AFG2 and AFB1, which have U > 63 mu g g(-1), Pb-206/Pb-204 > 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 2s for both 10(3)delta S-34 and 10(3)delta S-33 < 0.55 parts per thousand. One apatite, BR96, has Delta S-33 = -0.36 +/- 0.2 parts per thousand. The apatite samples have ID-TIMS Sr-87/Sr-86 between 0.704214 +/- 0.000030 and 0.723134 +/- 0.000035.