Revisiting zircon-melt REE partitioning systematics: new insight into shallow crustal melting on early Earth

Trace element abundances in ancient magmatic zircon could provide unique insights into Hadean and early Archaean felsic magmatism, yet the rare earth element (REE) partition coefficients (D REE ) between zircon and melt needed to translate zircon abundances to melt abundances remain poorly constrained. We combined results of eight new high-temperature partitioning experiments (1000–1400 °C) with prior data to quantify D REE systematics and show their strong dependence on both temperature and melt composition. An empirical lattice strain partitioning model for trivalent REEs was established, enabling re-assessment of reconstructed parental melt compositions from the REE abundances in ancient zircons. The inferred chondrite-normalized (La/Yb) N ratios in zircons from the Hadean and early Archaean are lower than those of later Archaean TTGs and adakites. This suggests a transition from garnet-absent, shallow crustal melting in the earliest Earth to later Archaean magmatism dominated by the involvement of deeper garnet signatures