We present in this paper Fe isotope compositions for magnetite and pyrite mineral separates from banded iron formations in the Anshan-Benxi area, where green schistlower amphibolite facies metamorphism has occurred. Both pyrite and magnetite show heavy Fe isotope enrichment relative to IRMM014; furthermore, Fe isotope compositions of pyrite are systematically heavierthan those of corresponding magnetite from the same samples (Δ57Fepyrite－magnetite＝2.23～5.13). These features cannot be explained if they represent the primary signatures inherited from their sedimentary precursors, but can be reconciled if Fe isotope exchange reequilibrium have been taking place duringregional metamorphism. The equilibrium mass fractionation factor of 57Fe/54Fe in green schist-to lower-amphibolite facies conditions is αpyrite－magnetite≈1.000?4‰±0.06‰(2σ). This study represents a significant advance in understanding the behaviour of Fe isotopes during metamorphism. 