Mid-oceanic ridge basalts (MORBs) are depleted in incompatible elements, but ridge segments far from mantle plumes frequently erupt chemically enriched MORBs (E-MORBs). Two major explanations of E-MORBs are that these basalts are generated by the melting of entrained recycled crust (pyroxenite) beneath ridges or by the melting of refertilized peridotites. These two hypotheses can be discriminated with compatible element abundances from Sc to Ge, here termed the ScGe elements. Here, we demonstrate that E-MORBs have systematically lower Ge/Si and Sc contents and slightly higher Fe/Mn and Nb/Ta ratios than depleted MORBs (D-MORBs) due to the mixing of low-degree pyroxenite melts. The Ge/Si ratio is a new tracer that effectively discriminates between melts derived from peridotite sources and melts derived from mixed pyroxenite-peridotite sources. These new data are used to estimate the distribution of pyroxenite in the mantle sources of global MORB segments.

中洋海脊玄武岩（MORB）的元素不相容，但远离地幔柱的脊段经常喷出化学富集的MORB（E-MORB）。E-MORB的两个主要解释是，这些玄武岩是由山脊下方夹带的再循环地壳（辉石）融化或由溶化橄榄岩融化而产生的。这两个假设可以通过从Sc到Ge的兼容元素丰度（在此称为ScGe元素）来区分。在这里，我们证明，由于低度黄铁矿熔体的混合，E-MORBs与贫化MORB（D-MORBs）相比，系统地具有较低的Ge / Si和Sc含量，而Fe / Mn和Nb / Ta比则稍高。Ge / Si比是一种新的示踪剂，可以有效地区分来自橄榄岩来源的熔体和源自混合的辉石岩-橄榄岩的来源的熔体。