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

P.B. Tomascak·F. Tera·Rosalind Tuthill Helz·R.J. Walker
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Abstract

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 SiO 2 − and K 2 O-enriched differentiated liquids, and have δ 7 Li (per mil deviation of sample 7 Li/ 6 Li 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.

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Geochimica et Cosmochimica ActaArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 19.389757323349656° to 19.4323753918207° latitude; -155.30239350719927° to -155.23861852271375° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeXRIS

P.B. Tomascak, F. Tera, Rosalind Tuthill Helz, R.J. Walker. 1999. The absence of lithium isotope fractionation during basalt differentiation: New measurements by multicollector sector ICP-MS. https://doi.org/10.1016/s0016-7037(98)00318-4

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