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
Shang et al. (Fri,) studied this question.