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To paradigms 2,3.

  1. Basalts constitute the basis of all erupted volcanic rocks.Tholeiitic basalts constitute uptu 80-90% of all basalts of volcanic structures of continental plateau, oceanic islands and MOR, of main mantle matter suppliers.

  2. Tholeiitic basalts of all geodynamic conditions are relatively homogeneous and do not show meaningful differences in petrochemical composition and in elements and isotopic ratios. Basalts composition does not depend either on time and depth of eruption centres.

  3. Seismotomography data and mass-balance calculations show that in the crust extraction there should take part the whole mantle corresponding to homogeneous, non-chondritis, reservoir of primitive mantle with recent isotopes ratios as Sm/Nd = 0,350 и εNd = +9. These parameters are characteristic of tholeiitic basalts which constitute basic geochemical composition of always homogeneous and primitive mantle without meaningful indications of mantle differentiation.All the other variations of element and isotope ratios as well as variations of petrochemical compositions of all the other volcanogenic rocks are related with fluid-crust processes.

  4. More detailed cosiderations on this subject may be found in the works by A.F.Grachev, Yu.A.Kostitsin and others in the book "Mantle plumes and metallogeny", Petrozavodsk-Moscow 2002,515pp, and in the works by V.S.Gladkikh, A.V.Gushcin, G.S.Gusev and others in the book "Geological mapping of volcano-plutonic belts ",Moscow,1994,301pp.




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