Lithium isotope composition of basalt glass reference material.

Area of Science:

• Geochemistry
• Analytical Chemistry
• Isotope Geology

Background:

• Accurate lithium isotope (⁷Li/⁶Li) measurements are crucial for various geochemical and geological applications.
• Standard reference materials are essential for validating analytical techniques and ensuring data comparability.
• Existing reference materials may exhibit matrix-dependent biases in lithium isotope determination.

Purpose of the Study:

• To assess the lithium isotope compositions of USGS and NIST glass reference materials.
• To compare data obtained from multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), thermal ionization mass spectrometry (TIMS), and secondary ionization mass spectrometry (SIMS).
• To identify suitable reference materials and potential biases in lithium isotope analysis.

Main Methods:

• Analysis of USGS and NIST glass reference materials using MC-ICPMS, TIMS, and SIMS.
• Determination of lithium isotope ratios (delta⁷Li) in various glass matrices.
• Statistical evaluation of data agreement and identification of systematic differences.

Main Results:

• USGS basaltic glass standards show agreement within 2‰ across different analytical techniques.
• Proposed USGS GSD-1G and BCR-2G as suitable SIMS standards for a broad range of lithium isotope compositions.
• MC-ICPMS and TIMS analyses of NIST silica-rich glasses agreed within 0.8‰, but SIMS showed systematic differences, indicating a matrix bias.

Conclusions:

• Lithium isotope analysis of USGS basaltic glasses is robust across MC-ICPMS, TIMS, and SIMS.
• SIMS analysis of high-silica materials exhibits a significant matrix bias, affecting accuracy.
• The presented data provide a reference for inter-methodological comparisons and microanalytical/bulk techniques.