“…In combination with the high δ 65 Cu value for eclogite RC‐1J (Liu et al., 2015), our new data for the GVF Type II xenoliths suggest that such high δ 65 Cu values may predominate among pyroxenite metasomes in the mantle. If correct, this has implications for models of basalt petrogenesis that infer the existence of pyroxenite metasomes in their mantle source region (Basch et al., 2019; Howarth & Harris, 2017; Kempton et al., 2021; Lambart et al., 2016; Lassiter et al., 2000; Matzen et al., 2017), for example, basalts derived from such a source might be expected to have higher δ 65 Cu than those derived from depleted peridotitic upper mantle. But how do these pyroxenites inherit their heavy δ 65 Cu compositions?…”