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Assessment of USGS BCR‐2 as a Reference Material for Silicate Rock U‐Pa Disequilibrium Measurements
Author(s) -
Prytulak Julie,
Elliott Tim,
Hoffmann Dirk L.,
Coath Christopher D.
Publication year - 2008
Publication title -
geostandards and geoanalytical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.037
H-Index - 73
eISSN - 1751-908X
pISSN - 1639-4488
DOI - 10.1111/j.1751-908x.2007.00868.x
Subject(s) - disequilibrium , geological survey , silicate , geology , mineralogy , reference values , chemistry , geophysics , medicine , organic chemistry , ophthalmology
The accuracy of 231 Pa‐ 235 U measurements can be readily assessed using a secular equilibrium reference material (RM), but a secular equilibrium RM is also required to calibrate the 233 Pa spike used in 231 Pa determinations. The only silicate RM commonly accepted to be in secular equilibrium is Table Mountain Latite (TML) and so an additional reference is required. Our measurements on the widely available USGS BCR‐2 (Basalt Columbia River) rock powder yielded ( 231 Pa/ 235 U) = 0.997 ± 0.013 2s (n = 10), indicating its value as a secondary reference to test the fidelity of U‐Pa determinations. Such a reference material additionally provides a useful check on data reduction, which our literature survey highlights can lead to discrepancies of up to 53% between reported ( 231 Pa/ 235 U) activity ratios and corresponding U and Pa concentration data.