0 hot liquid rock found just below the surface of the earth --
1 melted rock under the surface of the earth --
The evidence, including that of xenoliths carried in the magmas, supports the idea of melting of old metasomatized lithospheric mantle, usually associated with rifting tectonics.
The magmas are of transitional (mildly alkalic) type, generated by relatively small-fraction (6-7 %) melting of a depleted mantle source.
The mafic magmas were probably derived from the upper mantle (spinel stability field) by 9 % partial melting.
However, the geochemical data are consistent with derivation of magmas from a mantle source modified by subduction processes.
With all these processes, interactions between mantle-derived and crustal-derived magmas control the nature of magmatism in the complex.
The role of mantle plumes, particularly in the generation of flood basaltic magmas, has been emphasized by many authors.
In particular, the heat for the melting may have been supplied by mafic mantle-derived magmas.
The rise of felsic magma to a high level in the crust without degassing or neutralization of the melt volatile phase suggests deep faulting.
