Extended Data Fig. 5: The composition of natural carbonatites and kimberlites, with the composition of experimental melts formed by incipient melting of mantle peridotites/eclogites.
From: Carbon concentration increases with depth of melting in Earth’s upper mantle
These are used to constrain the C, S and Sr composition of the mCm(s) (Cb1-2 and, Kb1-3). (a) CO2 vs. Sr global distribution of natural carbonatitic and kimberlitic rocks (source GeoRoc; http://georoc.mpch-mainz.gwdg.de/georoc/). These define a compositional array overlapping (but extending to more enriched compositions) the compositional array exhibited by our parental CO2 (inferred, Fig. 1 and Extended Table 3) vs. Sr trend for the 12 hot-spot/rift volcanoes (symbols are as in Fig. 1); (b) The derived Sr/Sm ratios are similar in the 5 mCm model scenarios; (c) Global datasets (GeoRoc) demonstrate that Ca and Sr are globally correlated in natural carbonatitic and kimberlitic rocks, suggesting that calcic (dolomitic) incipient mantle melts are very likely to be Sr-rich, too; (d and e) Global correlations of CO2 vs. SiO2 and CO2 vs. S in natural carbonatitic and kimberlitic rocks, compared with the composition of experimentally derived mantle melts4,105. From data in plot (e), we infer a characteristic (GeoRoc mean) S content of 1000-2000 ppm in carbonatitic to carbonated silicate melts in the mantle105.
