Geochemistry of South African On- and Off-craton, Group I and Group II Kimberlites: Petrogenesis and Source Region Evolution

Bulk-rock geochemical compositions of hypabyssal kimberlites, emplaced through the Archaean Kaapvaal craton and Proterozoic Namaqua–Natal belt, are used to estimate close-to-primary magma compositions of Group I kimberlites (Mg-number = 0·82–0·87; ∼22–28 wt % MgO; ∼21–30 wt % SiO2; ∼10–17 wt % CaO; ∼0·2–1·7 wt % K2O) and Group II kimberlites (Mg-number = 0·86–0·89; ∼23–29 wt % MgO; ∼28–36 wt % SiO2; 8–13 wt % CaO; ∼1·6–4·6 wt % K2O). Group I kimberlites are distinguished from Group II by their lower Ba/Nb (