Primary basaltic magmas are accumulated after they have migrated through extensive regions of residual mantle. The migrating magma may react to various degrees with the residuum, so that the composition of the primary magma ...
Abyssal tholeiite is generated by partial melting of the upper mantle. The mantle sections of ophiolite complexes show that partial melting leaves mantle residua that are lherzolitic or harzburgitic, harzburgite being the ...