Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8910688 | Geochimica et Cosmochimica Acta | 2018 | 48 Pages |
Abstract
Lithium isotopes are important geochemical tracers for many geological processes. Knowledge of Li isotope fractionation factors is essential for understanding the behavior of Li isotopes. On the basis of density functional perturbation theory (DFPT), we calculate Li isotope fractionation parameters of α-eucryptite (LiAlSiO4), β-eucryptite (LiAlSiO4), lithiophilite (LiMnPO4), montebrasite (LiAlPO4OH), petalite (LiAlSi4O10), bikitaite [Li2(Al2Si4O12)·2H2O], spodumene (LiAlSi2O6), lithiophosphate (Li3PO4) and amblygonite (LiAlPO4F). The reduced partition function ratios of 7Li/6Li (103 ln β7-6) for these minerals decrease in the order petaliteâ¯>â¯lithiophosphateâ¯>â¯bikitaiteâ¯>â¯Î±-eucryptiteâ¯>â¯Î²-eucryptiteâ¯>â¯montebrasiteâ¯>â¯amblygoniteâ¯>â¯lithiophiliteâ¯>â¯spodumene, agreeing with the observations on granitic pegmatites. Li isotope fractionations in these Li-rich minerals have a notable linear correlation with the average LiO bond lengths, and are significantly influenced by Li coordination number. Furthermore, we calculate Li isotope fractionation factors of Li-bearing forsterite (Mg2SiO4) and diopside (CaMgSi2O6). It is found that forsterite is enriched in heavy Li relative to diopside, and both minerals' 103 ln β7-6 values depend on Li contents. These results allow for better understanding Li isotope fractionations in natural systems and provide a theoretical basis for Li isotope applications to understand geological processes.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Shanqi Liu, Yongbing Li, Jie Liu, Yiwen Ju, Jianming Liu, Zhiming Yang, Yaolin Shi,