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- Title
U-Th isotopic microanalysis of zircon reference materials and KBSI working standards.
- Authors
Jeong, Youn-Joong; Lee, Shinae; Kim, Sook Ju; Jo, Hui Je; Yi, Keewook; Cheong, Albert Chang-sik
- Abstract
Background: The 238U-230Th disequilibrium dating of the mineral zircon (ZrSiO4) provides an efficient tool for investigating the time scales of Quaternary magmatic processes. In situ mass spectrometric U-Th microanalysis of zircon requires careful calibration and correction of the measured isotope data, particularly for the instrumental fractionation of U and Th isotopes.Findings: For the selection of suitable calibration materials for U-Th isotopic analysis using a laser ablation multiple collector inductively coupled plasma mass spectrometer (LA-MCICPMS), we estimated the homogeneity of four reference zircons (91500, TEMORA 2, FC1, and Plešovice) and two zircon working standards (LKZ-1 and BRZ-1) in terms of their 232Th/238U ratios, based on the Pb isotopic compositions measured by a sensitive high-resolution ion microprobe (SHRIMP). The measured LA-MCICPMS 232Th/238U ratios of the zircons were calibrated externally using the SHRIMP 208Pb/206Pb-based average value of the 91500 zircon, 232Th/238U = 0.351 ± 0.035 (error corresponds to 1 standard deviation). The molecular interference-corrected 230Th/232Th ratios of the zircons were calibrated based on the assumption that the Plešovice zircon is in 238U-230Th secular equilibrium. After the calibration and correction, the activity ratios of 230Th/232Th and 238U/232Th for all reference zircons and working standards were plotted on the equiline.Conclusions: This study confirms that the 91500 zircon is relatively homogeneous in terms of U/Th ratios (relative standard deviation = ~ 10%) and does not support a recent claim that the Plešovice zircon is not in 238U-230Th radioactive equilibrium. The working standards LKZ-1 and BRZ-1 can be used to check the reliability of U-Th isotopic analyses for Quaternary zircons.
- Subjects
MICROCHEMISTRY; ZIRCON; MASS spectrometers; CALIBRATION; STANDARD deviations
- Publication
Journal of Analytical Science & Technology, 2018, Vol 9, Issue 1, p1
- ISSN
2093-3134
- Publication type
Article
- DOI
10.1186/s40543-018-0148-y