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Problems Associated with the Determination of Rare Earth Elements of a “Gem” Quality Zircon by Inductively Coupled Plasma‐Mass Spectrometry
Author(s) -
Jain Jinesh C.,
Neal Clive R.,
Hanchar John M.
Publication year - 2001
Publication title -
geostandards newsletter
Language(s) - English
Resource type - Journals
eISSN - 1751-908X
pISSN - 0150-5505
DOI - 10.1111/j.1751-908x.2001.tb00598.x
Subject(s) - zircon , inductively coupled plasma mass spectrometry , chemistry , nitric acid , zirconium , analytical chemistry (journal) , hydrofluoric acid , inductively coupled plasma , monazite , rare earth element , nuclear chemistry , mineralogy , mass spectrometry , rare earth , geology , inorganic chemistry , environmental chemistry , chromatography , geochemistry , physics , plasma , quantum mechanics
A gem quality zircon crystal from the Mud Tank Carbonatite, Australia, was carefully crushed, sieved, acid leached and hand‐picked to produce three different zircon fractions: 1) clear and apparently free of inclusions; 2) with inclusions; 3) with inclusions and adhering alteration/matrix material. Each separate and the bulk sample was dissolved by 1) lithium metaborate fusion and 2) Parr bomb digestion utilizing 29 mol l −1 hydrofluoric (HF) and 16 mol l −1 nitric (HNO 3 ) acids. In situ analyses were performed using laser ablation ICP‐MS and demonstrate that, on the basis of REE, two types of inclusions are present: 1) those with a positive Ce anomaly and 2) those with no Ce anomaly. The former type of inclusion appears to be smaller than the latter. Analysis of the digested samples for the rare earth elements (REE) was then performed using a quadrupole ICP‐MS. Comparison of the chondrite‐normalized REE patterns for the different fractions gave apparent positive anomalies at Sm and Eu in the acid digestions but not in the fused samples. Zirconium has five isotopes ( 90 Zr, 91 Zr, 92 Zr, 94 Zr and 96 Zr) and there is a strong tendency for Zr to combine with fluorine ( 19 F). Based on calculations and experiments, the increased levels of Sm and Eu in the acid digested samples were due to interferences of 90 Zr 19 F 3 on 14 7 Sm and of 94 Zr 19 F 3 on 151 Eu. Decreasing the ratio of HF:HNO 3 did not remove these interferences, nor did post‐treatment with perchloric acid. A mathematical method was developed to correct for these polyatomic interferences.