The shape of a chondrite-normalized rare earth element (REE) pattern of an igneous rock reflects the mineralogy retained in its residual source during partial melting: a steep, LREE-enriched/HREE-depleted overall slope indicates that garnet (which strongly retains heavy REE, particularly Lu, in its crystal structure) remained in the residual source rather than entering the melt, while a distinct negative Eu anomaly indicates that plagioclase (which strongly retains Eu2+ in its crystal structure under reducing conditions) also remained in the residual source rather than melting into the liquid.