Natural Allanite Reference Materials forIn SituU‐Th‐Pb and Sm‐Nd Isotopic Measurements by LA‐(MC)‐ICP‐MS

Abstract

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 forin situU‐Th‐Pb geochronology and Sm‐Nd isotope measurements. Here, we presentin situU‐Th‐Pb ages and Sm‐Nd isotopic compositions for nine allanite samples considered as potential reference materials (CAPb, Tara, Daibosatsu, LE40010, LE2808, A007, A011, A012 and SQ‐51), with ages ranging from ~ 2650 Ma to ~ 12 Ma. Our study indicates that Daibosatsu and LE40010 have relatively homogeneous147Sm/144Nd and143Nd/144Nd isotopic compositions (147Sm/144Nd ratio variation is less than 2%) and, thus, can serve as primary reference materials for Sm‐Nd microanalysis. In contrast, CAPb, Tara, LE2808, A007, A011 and A012 all show homogeneous calculated initial143Nd/144Nd isotopic compositions, but with variable147Sm/144Nd 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 forin situU‐Pb dating, CAPballanite can serve as a suitable primary reference material forin situTh‐Pb dating, and LE2808, LE40010, A007, A011 and A012 can serve as suitable secondary reference materials forin situU‐Pb geochronology. In addition, Daibosatsu is suitable as a secondary reference material for Cenozoic Th‐Pb dating to monitor data reproducibility.