Anal. Chem. 2005, 77, 5251-5257
Lithium Isotope Composition of Basalt Glass Reference Material Simone A. Kasemann,*,† Alistair B. Jeffcoate,‡ and Tim Elliott‡
Grant Institute of Earth Science, Ion Microprobe Unit, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, U.K., and Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, U.K.
We present data on the lithium isotope compositions of glass reference materials from the United States Geological Survey (USGS) and the National Institute of Standards and Technology (NIST) determined by multicollector inductively coupled plasma mass spectrometry (MCICPMS), thermal ionization mass spectrometry (TIMS), and secondary ionization mass spectrometry (SIMS). Our data on the USGS basaltic glass standards agree within 2‰, independent of the sample matrix or Li concentration. For SIMS analysis, we propose use of the USGS glasses GSD-1G (δ7Li 31.14 ( 0.8‰, 2σ) and BCR-2G (δ7Li 4.08 ( 1.0‰, 2σ) as suitable standards that cover a wide range of Li isotope compositions. Lithium isotope measurements on the silica-rich NIST 600 glass series by MC-ICPMS and TIMS agree within 0.8‰, but SIMS analyses show systematic isotopic differences. Our results suggest that SIMS Li isotope analyses have a significant matrix bias in high-silica materials. Our data are intended to serve as a reference for both microanalytical and bulk analytical techniques and to improve comparisons between Li isotope data produced by different methodologies. Improvements in the accuracy and precision of lithium isotope ratio measurements over recent years has led to an increasing interest in lithium isotope analyses in many fields of science and technology, including biomedicine, the nuclear industry, and geology.1 The geological interest in lithium arises from its use as a powerful tracer of recycled crustal materials (e.g., oceanic crust, sediments) that find their way back into the source regions of mantle-derived melts. Li isotope measurements, therefore, show great potential in the study of mantle dynamics and global recycling processes.2 Together with a rapid increase in the number of lithium isotope studies, there has been a growth in the variety of chemical extraction techniques and mass spectrometric procedures employed to measure Li isotope ratios.3-12 The increasing variety of * To whom correspondence should be addressed. E-mail: Simone.Kasemann@ ed.ac.uk. Fax: +44 (0)131 668 3184. † University of Edinburgh. ‡ University of Bristol. (1) Tomascak, P. B. Rev. Mineral. Geochem. 2004, 55, 153-195. (2) Elliott, T.; Jeffcoate, A.; Bouman, C. Earth Planet. Sci. Lett. 2004, 220, 231245. (3) Chan, L. H.; Edmond, J. M.; Thompson, G.; Gillis, K. Earth Planet. Sci. Lett. 1992, 108, 151-160. 10.1021/ac048178h CCC: $30.25 Published on Web 07/26/2005
© 2005 American Chemical Society
geological samples and applications has required studies to be performed on a range of length scales. Hence, this requires integration of data sets obtained from bulk analyses of separated lithium and microanalytical, in situ techniques. However, to ascertain the accuracy of the isotope data obtained by the different laboratories and techniques, homogeneous lithium reference materials with internationally accepted Li isotope data are required. Recently, some effort has been invested in characterizing lithium isotope reference materials, processed using a range of bulkanalytical procedures and analyzed by both thermal ionization mass spectrometry (TIMS) and several multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) methods.6-9,11,12 However, little work has been done toward establishing reference materials for microanalytical techniques4,13 e.g., secondary ionization mass spectrometry (SIMS) or laser ablation inductively coupled plasma mass spectrometry. Such reference materials are needed to allow both interlaboratory and methodical comparisons. To initiate such work, we present the lithium isotope compositions of basaltic glass reference materials from the United States Geological Survey (USGS) that have been measured using bulk analyses (MC-ICPMS, TIMS) and in situ techniques (SIMS) at the Universities of Bristol and Edinburgh, respectively. To increase the range of sample matrices beyond that of basaltic glass, we also analyzed synthetic, silica-rich glass reference materials from the National Institute of Standards and Technology (NIST). MATERIALS AND METHODS Samples. Natural and synthetic glass reference materials of basaltic composition were supplied by the USGS. The natural glass samples BHVO-2G, BCR-2G, and BIR-1G were produced from the same material used in the preparation of the respective rock powders (BHVO-2, BCR-2, BIR-1) at USGS. The materials for these reference powders are a basalt collected from Columbia River, (4) Decitre, S.; Deloule, E.; Reisberg, L.; James, R.; Agrinier, P.; Mevel, C. Geochem. Geophys. Geosyst. 2002 3:10.1029/2001GC000178. (5) Hoefs, J.; Sywall, M. Geochim. Cosmochim. Acta 1997, 61, 2679-2690. (6) James, R. H.; Palmer, M. R. Chem. Geol. 2000, 166, 319-326. (7) Jeffcoate, A. B.; Elliott, T.; Thomas, A.; Bouman, C. Geostand. Geoanal. Res. 2004, 28, 161-172. (8) Moriguti, T.; Nakamura, E. Earth Planet. Sci. Lett. 1998, 163, 167-174. (9) Nishio, Y.; Nakai, S. Anal. Chim. Acta 2002, 456, 271-281. (10) Qi, H. P.; Taylor, P. D. P.; Berglund, M.; De Bievre, P. Int. J. Mass Spectrom. 1997, 171, 263-268. (11) Bryant, C. J.; McCulloch, M. T.; Bennett, V. C. J. Anal. At. Spectrom. 2003, 18, 734-737. (12) Millot, R.; Guerrot, C.; Vigier, N. Geostand. Geoanal. Res. 2004, 28, 153159. (13) Chaussidon, M.; Robert, F. Earth Planet. Sci. Lett. 1998, 164, 577-589.
Analytical Chemistry, Vol. 77, No. 16, August 15, 2005 5251
Table 1. Major Element Composition of Certified Reference Glasses oxide, wt %
GSE-1Ga
GSD-1Ga
GSC-1Ga
GSA-1Ga
BHVO-2b (1σ)
BCR-2b (1σ)
BIR-1b (1σ)
SRM 610c
SRM 612c
SRM 614d
SiO2 TiO2 Al2O3 Fe2O3tot MnO MgO CaO Na2O K2O P2O5
50.4-54.6 0.07-0.1 7.6-11.3 12.1-15 0.052-0.077 1.7-5 5.6-8.4 1.4-4 1.2-2.4
