Zircon ZS - A Homogenous Natural Reference Material For U–Pb Age And O–Hf Isotope Microanalyses

Abstract

: A well-formed natural zircon crystal ~10 g in weight from Sri Lanka was introduced as a reference material for the geochemical microanalysis of U–Pb–O–Hf isotopes. For the U–Pb system, a total of 96 secondary ion mass spectrometry (SIMS) and 174 laser-ablation inductively coupled plasma mass spectrometry analyses showed that zircon ZS was homogeneous within a ~20 μm area level. According to chemical abrasion isotope dilution thermal ionization mass spectrometry, the U–Pb system is concordant within the uncertainties, yielding a weighted mean 206 Pb/ 238 U age of 560.6 ± 1.3 Ma (2 standard deviation (SD), n = 18) and a weighted mean 207 Pb/ 206 Pb age of 561.1 ± 3.5 Ma (2SD, n = 18). The U and Th concentrations were 570 ± 40 μg g -1 (1SD) and 132 ± 28 μg g -1 (1SD), respectively. The homogeneity of the O isotopes was confirmed by 261 SIMS analyses, and that of Hf isotopes was determined by 100 laser-ablation multi-collector inductively coupled plasma mass spectrometry (MC–ICP–MS) analyses. A weighted mean δ 18 O value of 13.69‰ ± 0.11‰ (2SD, n = 12) obtained by laser fluorination isotope ratio mass spectrometry (IRMS) and a weighted mean 176 Hf/ 177 Hf value of 0.281668 ± 0.000010 (2SD, n = 7) by solution MC–ICP–MS are recommended as the best reference values for zircon ZS.