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The absence of lithium isotope fractionation during basalt differentiation: New measurements by multicollector sector ICP-MS

January 1, 1999

We report measurements of the isotopic composition of lithium in basalts using a multicollector magnetic sector plasma-source mass spectrometer (MC-ICP-MS). This is the first application of this analytical technique to Li isotope determination. External precision of multiple replicate and duplicate measurements for a variety of sample types averages ±1.1‰ (2σ population). The method allows for the rapid (∼8 min/sample) analysis of small samples (∼40 ng Li) relative to commonly used thermal ionization methods. The technique has been applied to a suite of samples from Kilauea Iki lava lake, Hawaii. The samples range from olivine-rich cumulitic lava to SiO2− and K2O-enriched differentiated liquids, and have δ7Li (per mil deviation of sample 7Li/6Li relative to the L-SVEC standard) of +3.0 to +4.8. The data indicate a lack of per mil-level Li isotope fractionation as a result of crystal–liquid fractionation at temperatures greater than 1050°C. This conclusion has been tacitly assumed but never demonstrated, and is important to the interpretation of Li isotope results from such geochemically complex environments as island arcs.

Publication Year 1999
Title The absence of lithium isotope fractionation during basalt differentiation: New measurements by multicollector sector ICP-MS
DOI 10.1016/S0016-7037(98)00318-4
Authors P.B. Tomascak, F. Tera, Rosalind Tuthill Helz, R.J. Walker
Publication Type Article
Publication Subtype Journal Article
Series Title Geochimica et Cosmochimica Acta
Index ID 70021512
Record Source USGS Publications Warehouse