The main problem in the study of mantle petrology is that the primary mantle matter is inaccessible to direct research. The only direct “witnesses” of the conditions prevailing in deep mantle horizons are crystallization products of deep-seated magmas. These are minerals of the most deep-seated, intratelluric, crystallization (diamond and its accessory minerals) and products of final crystallization of these magmas in the higher horizons of the mantle and in the crust. Deep-seated magmas which completed crystallization in the crust gave rise to gabbro (eclogite)-peridotite massifs, such as Rondo in Spain and Beni Boushera in Morocco, and to some other magmatic structures which could undergo tectonic deformations and metamorphism similar to those in diamondiferous and/or coesite-bearing eclogite-pyroxenite-peridotitic rocks of the Dabie Shan massif in China and the Kokchetav massif in Kazakhstan. The depth and conditions of origin of initially diamondiferous magmas were determined by the transformation of fluids H2 and CO, which, probably, ascended from the Earth’s core, into H2O and CO2, which stimulated the mantle substrate melting. Kimberlitic and lamproitic magmas have an acquired diamond-bearing capacity. Their chambers expanded in the peridotite substrate of plutons of deep-seated magmas. In doing so, kimberlitic and lamproitic melts inherited the diamond and other (in particular, Cr-spinel) kinds of deep mineralization of replaced rocks and underwent alkalization. This concept is based on analysis of clinopyroxene-garnet parageneses and the compositional peculiarities of clinopyroxene and spinel from the above massifs. It provides additional criteria for the diamond-bearing capacity of kimberlites and lamproites.

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