Mafic rocks of the Ukaliq supracrustal belt display negative 142Nd anomalies.
BIFs interleaved in the sequence show no evidence for in situ decay of 146Sm.
30">142Nd anomalies are likely inherited from a metasomatically enriched mantle source.
Sm–Nd systematics imply preservation of Earth's protocrust for >600 Myr.
This suggests inefficient lithospheric recycling in the post magma ocean Earth.