Assessing the U‐Pb, Sm‐Nd and Sr‐Sr Isotopic Compositions of the Sumé Apatite as a Reference Material for LA‐ICP‐MS Analysis
Cristiano Lana, G. Gonçalves, Ariela Mazoz, I. S. Buick, Sandra L. Kamo, Ricardo Scholz, Hao Wang, Hugo Moreira, Marly Babinski, Gláucia Queiroga
Abstract
This study has determined the trace element and the U‐Pb, Sm‐Nd and Sr‐Sr isotope composition of the Sumé apatite (from NE Brazil) to assess its suitability as a primary/secondary reference material for LA‐ICP‐MS. Reproducibility tests demonstrate that one batch (~ 100 g) of the Sumé apatite (Sumé‐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 (2 s ; 206 Pb*/ 238 U) and 0.06120 ± 0.00063 (2 s ; 207 Pb*/ 206 Pb*) and a weighted mean 206 Pb*/ 238 U date of 568 ± 3 Ma (95% c.l.). U‐Pb LA‐(SF/MC)‐ICP‐MS runs using Sumé‐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 Sumé‐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.