Inverse Modeling to Constrain Composition of CO2-Rich Parental Melt of Kimberlite: Model Development and Application to the Majuagaa Dyke, Southern West Greenland.

This article focuses on developing and applying an inversion model to test the hypothesis that kimberlite magmas form by low-degree melting of asthenospheric mantle followed by entrainment and assimilation of lithospheric mantle xenocrysts. Using trace element mass balance equations and rare earth element data, the model quantifies the proportions of xenocrystic phases (olivine, orthopyroxene, clinopyroxene, garnet, ilmenite) and source mineralogy in the Majuagaa kimberlite dyke of southern West Greenland. Results indicate that the Majuagaa kimberlite magma contained approximately 41–51 wt% xenocrysts dominated by olivine and ilmenite, with a parental melt characterized as a hydrous magnesio-silico-carbonatite derived from a mantle source more enriched than typical depleted mid-ocean ridge basalt (MORB) mantle. The study highlights the model's ability to reconcile petrographic and geochemical data, while noting limitations such as uncertainties in orthopyroxene assimilation and the need for improved partition coefficient data to refine source and contaminant compositions.