Summary

The majority of inclusion-bearing alkaline rocks have a source region identical with that of ocean island basalts regardless of whether they were erupted through oceanic or continental crust. Models have been proposed where oceanic alkaline rocks are derived from the asthenosphere and during passage to the surface there have occurred variable amounts of interaction with lithosphere of the mid-ocean ridge basalt type. A similar scenario would account for most inclusion-bearing continental alkaline rocks. Genesis of micaceous kimberlites and lamproites, however, may require that asthenospheric plumes have impinged on ‘nuggets’ of aged heterogeneous enriched sub-continental lithosphere. This would lead to mixing of isotopically distinct asthenospheric and lithospheric melts.