Journal article
Improvements in 230Th dating, 230Th and 234U half-life values, and U-Th isotopic measurements by multi-collector inductively coupled plasma mass spectrometry
H Cheng, R Lawrence Edwards, CC Shen, VJ Polyak, Y Asmerom, J Woodhead, J Hellstrom, Y Wang, X Kong, C Spötl, X Wang, E Calvin Alexander
Earth and Planetary Science Letters | Published : 2013
Abstract
We have developed techniques for measuring 234U and 230Th on Faraday cups with precisions of 1-3 epsilon units (1 ε-unit=1 part in 104) using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Using a Thermo-Scientific Neptune with desolvation nebulization, we obtained ionization/transmission efficiencies of 1-2% for both U and Th. We set up protocols to correct for tailing, prepared U and Th gravimetric standards, tested a Th mass fractionation correction procedure based on U isotopes, and identified natural calcite samples likely to be in U-Th isotopic secular equilibrium. The measured atomic ratios, 234U/238U=54.970 (±0.019)×10-6 and 230Th/238U=16.916 (±0.018)×10-6,..
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Awarded by National Science Foundation
Funding Acknowledgements
We are grateful to the valuable support of Prof. Alexander Klimchouk for sample Kr3, and Mr. Peter Giangrande for all green calcites; Dr. Stephan Richter for providing detailed information about the U standard IRMM-074/10; Prof. Randall R. Parrish for providing detailed instruction for zircon dissolution; and Yu-Te Hsieh for laboratory assistance. This work was supported by US NSF 0502535, NBRPC 2013CB955902, NSFC 41230524, US NSF 0902867, 0908792, 1103320, and 1103403, Gary Comer Science and Education Foundation Grants CC8 and CP41, and NSC Grants 97-2745-M-002-009 and 100-2116-M-002-009.