Assessing the U-Pb, Sm-Nd and Sr-Sr Isotopic Compositions of the Sume Apatite as a Reference Material for LA-ICP-MS Analysis

This study has determined the trace element and the U-Pb, Sm-Nd and Sr-Sr isotope composition of the Sume apatite (from NE Brazil) to assess its suitability as a primary/secondary reference material for LA-ICP-MS. Reproducibility tests demonstrate that one batch (similar to 100 g) of the Sume apatite (Sume-570) is uniform in terms of Nd-Nd and U-Pb isotope compositions. Bulk isotope dilution TIMS/ICP-MS and LA-MC-ICP-MS analyses confirm that the apatite is well suited for use as quality control material for Nd isotopes and U-Pb geochronology. U-Pb ID-TIMS analyses yield weighted mean ratios of 0.09211 +/- 0.00053 (2s; Pb-206*/U-238) and 0.06120 +/- 0.00063 (2s; Pb-207*/Pb-206*) and a weighted mean Pb-206*/U-238 date of 568 +/- 3 Ma (95% c.l.). U-Pb LA-(SF/MC)-ICP-MS runs using Sume-570 as a primary RM and reproduces the dates of other established RMs within 1% deviation (except for Durango 2-4%). Major and trace element abundances show that Sume-570 is a fluorapatite derived from a syenitic source. It also strongly shows LREE-enriched chondrite-normalised REE patterns with significant negative Eu anomalies, due to crystallisation of plagioclase in the residue.