Natural Allanite Reference Materials for In Situ U-Th-Pb and Sm-Nd Isotopic Measurements by LA-(MC)-ICP-MS

Allanite is a common accessory mineral that generally incorporates considerable amounts of Th, U and light rare Earth elements in its structure, making it a useful mineral for in situ U-Th-Pb geochronology and Sm-Nd isotope measurements. Here, we present in situ U-Th-Pb ages and Sm-Nd isotopic compositions for nine allanite samples considered as potential reference materials (CAP(b), Tara, Daibosatsu, LE40010, LE2808, A007, A011, A012 and SQ-51), with ages ranging from similar to 2650 Ma to similar to 12 Ma. Our study indicates that Daibosatsu and LE40010 have relatively homogeneous Sm-147/Nd-144 and Nd-143/Nd-144 isotopic compositions (Sm-147/Nd-144 ratio variation is less than 2%) and, thus, can serve as primary reference materials for Sm-Nd microanalysis. In contrast, CAP(b), Tara, LE2808, A007, A011 and A012 all show homogeneous calculated initial Nd-143/Nd-144 isotopic compositions, but with variable Sm-147/Nd-144 compositions, and thus can be used only as secondary reference materials for Sm-Nd microanalysis. Of these materials, LE40010 allanite can serve as a suitable primary reference material for in situ U-Pb dating, CAP(b) allanite can serve as a suitable primary reference material for in situ Th-Pb dating, and LE2808, LE40010, A007, A011 and A012 can serve as suitable secondary reference materials for in situ U-Pb geochronology. In addition, Daibosatsu is suitable as a secondary reference material for Cenozoic Th-Pb dating to monitor data reproducibility.