Developments in the Understanding and Application of Lithium Isotopes in the Earth and Planetary Sciences

The significant relative mass difference (c. 16%) between the two stable isotopes of Li (approximately ⁶Li 7.5%, ⁷Li 92.5%), coupled with broad elemental dispersion in Earth and planetary materials, makes this a system of considerable interest in fingerprinting geochemical processes, determining mass balances, and in thermometry. Natural mass fractionation in this system is responsible for c. 6% variation among materials examined to date (Fig. 1¹). Although the “modern era” of Li isotope quantification has begun, there are still many questions about the Li isotopic compositions of fundamental materials and the nature of fractionation by important mechanisms...