Fig. 4: Bulk rare-earth element (REE) concentrations of cratonic peridotites.
From: The role of C-O-H-F-Cl fluids in the making of Earth’s continental roots
a Orthopyroxene-rich garnet harzburgites and b other types of peridotites in mantle xenolith suites from the Kaapvaal craton of southern Africa. Elements increase in incompatibility during mantle melting from right to left. The orthopyroxene-rich garnet harzburgites exhibit sinusoidal REE patterns when normalised to the MORB source mantle. These patterns vary with the amounts of orthopyroxene. As the amount of orthopyroxene increases, the contents of light and heavy REEs decrease and middle REEs increase (as illustrated by the black arrows). The most extreme example of this in our sample suite is the diamondiferous orthopyroxene-rich harzburgite BD2125 from Lesotho. This xenolith equilibrated just below the graphite-diamond boundary (1060 °C and 4.4 GPa). Data are from this work (Supplementary Data 1) unless stated otherwise in the legend. A MORB-source normalisation36 is used because cratonic mantle is widely believed to represent aggregated residues of large amounts of melting.
