Stable chromium isotopic variations in peridotite mantle xenoliths: Metasomatism versus partial melting

Chromium isotope compositions have been determined for 42 mantle-derived xenoliths from Cameroon, France, Mongolia, Russia and the USA. The samples are mainly spinel garnet lherzolites, or harzburgites, yield ?53CrNIST979 ?0.33 to 0.43‰, within range of previously reported compositions, ?0.51 0.74‰ (Xia et al., 2017). Partial melting has proposed as a process that alters ?53Cr mantle residue. New non-modal models show compatible nature Cr is inconsistent with large changes in residue’s isotopic composition. fractionation during constrained by calculated ?53Crmantle-melt-values <0.09 measured ?53/52Cr mantle-melt ? 0.07‰, which too small generate observed at low medium degrees melting. Fertile melt-depleted, unmetasomatised peridotite no correlations between indicators partial Almost all LREE-enriched studied here define correlation (La/Yb)N. This consistent alteration some related interactions degree melts. content melts renders metasomatism via such liquids difficult explanation effects found. A possible form disequilibrium loss isotopically light into their percolation through mantle. similar mechanism kinetic associated silicate peridotitic