In situ U–Pb, Sr, Nd and Hf isotopic analysis of eudialyte by LA-(MC)-ICP-MS

Eudialytes are a group of complex Na–Ca zirconosilicate minerals that generally occur in peralkaline agpaitic syenites. Given that eudialytes are easily altered and commonly contain inclusions of earlier-crystallized minerals, in situ laser ablation is considered as the most suitable method to determine their U–Pb ages, and Sr, Nd and Hf isotopic compositions. Electron microprobe and LA-ICP-MS analysis of eudialytes from nepheline syenites from Ilímaussaq (Greenland), Khibiny and Lovozero (Russia), Saima (China), Tamazeght (Morocco), Kipawa and Mont Saint Hilaire (Canada), Poços de Caldas (Brazil) and Langesund Fjord (Norway), indicate that this mineral typically has high contents of U, Pb, Nb, Ta, Zr, Hf and rare earth elements (REE). is of an in-house standard eudialyte by both solution and laser ablation methods demonstrates that precise and accurate U–Pb ages can be obtained from eudialyte after correction for the common Pb content. The high Sr, Nd and Hf contents in eudialyte, coupled with the generally low Rb/Sr and Lu/Hf ratios, also permit the precise determination of in situ Sr, Nd and Hf isotopic ratios by LA-(MC)-ICP-MS methods. However, some eudialytes with Rb/Sr ratio of > 0.02 and Yb/Sr > 0.1, and Lu/Hf > 0.08 (or Yb/Hf > 0.4–0.5) cannot be used for in situ Sr and Hf isotopic measurement. Eudialyte is the only mineral investigated to date for which it is possible to determine simultaneously U–Pb ages and Sr, Nd and Hf isotopic compositions.