87
Most likely, it is connected with the decrease of the periods of tectono-magmatic
activity on the processes of irregular reduction of the volume of decomposed
hydridic core and increasing of the thickness of mantle during the pulsating-
expanding evolution of the Earth. The reduction intervals of the geological
tectonic cycles from the protoplanetary stage to
nowadays,
based on
Many researchers affirm, that all diamonds in kimberlite and lamproite are
xenocrysts and are formed in the garnet peridotites and eclogites in the upper
mantle and then picked up by the kimberlite magma during their ascent to the
Earth’s surface. Accordingly, there is no genetic connection between the time of
the formation of diamonds and the kimberlites (Gurney,1989; Kirkney et al.,
1991). However, the fact of the presence in kimberlites of pipe Premier (1200-
1180 Ма) diamonds (1200 Ма) with the identical absolute age, testifies to the
crystallization these diamonds from the same sources in the upper mantle, where
this kimberlite magma is generated.
Besides, if the kimberlite dikes, sills and pipes would be a simple elevators
for lifting diamonds from the mantle sources to the surface, then it is reasonable
to assume that in two coeval and adjacent kimberlite bodies the contents,
morphology and grade of diamonds should be identical. However, in real nature,
it has not been observed, behind a very rare exception. For example, in the
kimberlite field Kimberley (Southern Africa) there are more then 95 bodies, five
of which are the world famous diamond deposits of late Cretaceous age (95-84
Ма), there are pipes Kimberley, De Beers, Wesselton, Dutoitspan, and
Bultfontein. All of them are situated side by side on the area of 8х8 km
2
, with
intervals from 2 up to 4 km. But they have different chemical composition of
kimberlites; various contents, habits and the quality of diamond crystals (Du Toit,
1957). All this testifies to the advantage of crystallization diamonds from the
various sources at the evolution of kimberlite melts in each body.
2. DISTRIBUTION OF DIAMOND RESOURCES IN KIMBERLITES AND PLACERS
The distribution of established resources of the diamonds, which are
genetically connected to kimberlite and lamproite, represent practical and
scientific interest. The deposits of these specified types enriched
with diamonds are dated to the epochs of tectono-magmatic activity on the
platforms in mddle Riphean (1450-1400 and 1200-1100 Ma), lateDevon (370-350
Ma), late Mesozoic`(113-84 Ma) and Cenozoic (60-20 Ma). The total recovery of
diamonds from ancient to younger epochs from magmatic deposits and placers,
make accordingly 23.5%, 19%, 54% and 3.5% (Table 2). The finds of the
diamonds in late Archean and early Proterozoic conglomerates still have a
mineralogical interest (Krutoyarskiy, et al., 2000). In order to observe the more
objective picture of distributions diamonds in kimberlites and lamproites we had
calculated the reserves of diamonds that leftover in discovered fields. The total
amount of diamonds resources, including the crops and reserves that had been
found in the bowels of the Earth to 2000 year from late Proterozoic, middle