Fig. 5: Li isotope–trace element covariations and REE concentrations in alkaline rocks.

A Ba/La ratios vs. δ7Li values, B Zr/Nb ratios vs. δ7Li values, C REEs vs. Th/Yb, and D REEs vs. Sr/Y. Data sources: MORB25,94; REE-fertile lamprophyres24,97; REE-fertile syenites67; Ba/La ratios from individual volcanic arcs98. AOC altered oceanic crust, MORB mid-ocean ridge basalt. The global dataset for arc lavas is from the PetDB Database (www.earthchem.org/petdb).