Genesis of diamonds revealed by in metamorphic rocks of Northern Kazakhstan is argumentative. We made an attempt to find the correlation between regularities of the distribution of helium's isotopes in rocks and the mechanism of the diamonds' formation from the Kokchetav diamonds bearing province.
The concentration and isotopic composition of helium were studied in the fractions of diamonds of different grain size from metamorphic rocks of the Kokchetav massif. This fractions were derived using the method of the alkaline floating.
The ratio 3He/4He for this diamonds varies 1.8¥10-7 to 3.1¥10-4 and the concentration of helium: for 4He from 1.7¥10-4 to 9.2¥10-4ccSTP/g; for 3He from 3.1¥10-11 to 2.8¥10-7. A correlation between the isotopic composition of helium and the grain size has been established.
The stepwise heating of carbonado from Ubangi, Central Africa was performed for investigation of dependence between isotopic composition, the diffused characters and the crystal's size. The kinetics of the extraction of helium isotopes from carbonado and Kokchetav diamonds are differ.
Isotopic composition of helium was studied in the carbonat-pyroxene, the garnet-pyroxene rocks and the fractions of garnet and pyroxene. The some 3He-bearing and 4He-bearing phases and unhomogenious distribution of helium's isotopes were found in these rocks.
The garnet-pyroxene rock was subjected to the consistent acid treatment for the study of regularities of distribution of helium's isotopes in the diamonds bearing garnet-pyroxene rock. The isotopic analysis of helium was made in the acid-unsoluble residues. It is shown that the considerable variations of ratio 3He/4He in diamonds bearing rock were caused by the presence (or absence) of 4He-bearing phase and in a smaller degree presence (or absence) of some 3He-bearing phases. Zircon was revealed as 4He-bearing phase.
The anomalous excess of the light helium's isotope in the diamonds of fine grain size has the local character. It is suppose, on resulting grounds, that the excess of helium in diamonds is the consequence of metasomatism. To account for the anomalous relative and absolute 3He enrichment, the hypothesis of the chemical fractionation of helium's isotopes in consequence of concentration of radioactive precursor - 3H in the composition of hydrogen on the frontier of microblocks in diamond's
crystals must be proposed.