After partial melting, refractory peridotites may be modified via interaction with migrating MORB melts at the flanks of oceanic melting regions, thus affecting the chemical and isotopic evolution of large lithospheric mantle sectors. This study experimentally investigates the interactions between Enriched-MORB melts and modeled harzburgite at the oceanic asthenosphere-lithosphere boundary (1-2 GPa; 1150-1400°C). Harzburgite is made by depleted orthopyroxene (LaN/YbN = 0.004), San Carlos olivine (Fo90), homogeneously mixed to tholeiitic basaltic glass (XMg = 0.60, Na2O = 3.48 wt%, K2O = 0.81 wt%) with E-MORB signature (LaN/YbN = 5.39). High-temperature isothermal runs (1200-1350°C) simulate transient melt percolation and mostly results in orthopyroxene dissolution and olivine dissolution and reprecipitation. Some experiments cooled to 1150-1200°C experienced reactive melt crystallization that leads to clinopyroxene and orthopyroxene precipitation, associated with few modal garnets at 2 GPa or plagioclase at 1 GPa. After the reaction, rims of partially dissolved orthopyroxene and newly crystallized orthopyroxene are chemically modified compared to initial orthopyroxene composition. Olivine from high-T runs has high XMg (up to 0.95), high Ca, and low Ni, while cooling experiments results in lower XMg (up to 0.84), moderate Ca, and variable Ni. Several rims of orthopyroxenes relicts show selective LREE enrichment likely due to REE diffusion during the reaction. New orthopyroxenes exhibit LREE enrichments (LaN/SmN = 0.19-1.38) with respect to the initial orthopyroxene (LaN/SmN = 0.04). Accordingly, an unusual enrichment in orthopyroxenes has been recorded in abyssal peridotites metasomatized by moderately evolved melts. Clinopyroxenes have high convex upward LREE patterns with marked MREE/HREE fractionation. Reacted glasses show slight LREE/HREE fractionation and absolute REE at increasing extent of the interstitial melt crystallization. This study also provides “reaction” partitioning coefficients (KdREE = CREEsolid/CREEliquid), which allow to estimate the trace elements redistribution in mantle minerals during the reactive percolation of basaltic melts.