On the origin of diamantiferous diatremes

Abstract

Diamantiferous diatremes usually occur in the old platforms and shields where deep fractures are «blind»,i.e., these fractures do not come out to the earth surface. Alkaline-ultrabasic magma ascending along these fractures and encountering an impervious cap of sedimentary and/or volcanic rocks had formed, between the cap and the basemnet rocks, intermediate chambers in which the crystallization of diamonds took place.

Under the influence of the increasing pressures in these chambers, the roofs were destroyed and diamantiferous diatremes, dykes and veins of kimberlite have been formed. These diatremes are filled with a typical eruptive breccia in which the fragmental material, formed by the destructive explosion of the magma chamber roof, is cemented by a porphyritic, alkaline-ultrabasic rock known under the name of kimberlite.