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However, under slow lifting conditions
diamond-bearing magmas from
the upper mantle to the terrestrial surface there is a gradual decrease the
temperature of melts and at the presence of free oxygen the diamond
crystals begin oxidize and turn into curved facet forms. Right of way there
happened holocaust (“dissolution”) of diamond crystals in kimberlites of
diamond-pyrope subfacies ( Fersman, 1955; Orlov, 1963; Krutoyarskiy,
Milashev, 1964 ). If a diamond-bearing ultramafic melts slow rise to a
terrestriasl surface in environment without oxygen the diamond
crystals
transform in graphite right-of-way to total paramorphose graphite upon
diamond.
Figure 11. Thermodynamic conditions of formation the ophiolitic series of
ultramafic rocks. 1,2,3 – massifs of Koryak highland, NE Russia; 4. massifs
of New Zealand; 5.Adamsfield massif, Tasmania; 6. massifs of California; 7.
the evolutionary trends of massifs denoted as (I) - the first ( New Zeland
(NZ), California (CA), and (II) - the second (Koyak (KR), (Kaminsky,
1984). Reprinted with the permission of the Publishing House “Nedra”.
The exclusive interest represents the Beni Bousera peridotite massif in
NW Morocco, where mantle obduction slab, composed of altered spinel
lherzolite accompanied by rare harzburgites and dunite pods. The four
porphyroclastic eclogite layers within the massif are consisted by orange
pyrope-almandine garnet and omphacite-pyroxene. The former diamond-
bearing zones at Beni Bousera occur within garnet clinopyroxenites.
Graphite paramorph of diamonds were identified in the garnet
clinopyroxenite (Pearson et al. 1989).
116
necessary to take into account by mining and choice the most proved models
of crystallization diamonds in the ultramafic rocks and kimberlites
(Milashev, 1994).
Considering all of the above written, it is necessary to note, that the
kimberlites enriched with diamonds can’t be simple transporters of diamonds
from mantle ultramafic sources, but they are the genetic derivations of these
primary sources. As any rich deposit of minerals, the diamond-bearing
kimberlites are formed at the combination of the complex of favorable
factors, which should be revealed and taken into account at forecast and
searches a new diamond-bearing kimberlite provinces, fields and deposits
(Krutoyarskiy et al. 2000).
10. MODEL OF FORMATION DIAMONDIFEROUS KIMBERLITES OF THE
EARTH
1. At the passage of our Solar system through the magnetic and radioactive
belts of the Galaxy during the sidereal years (225-215 Ма) there was taken
periodic transfer of space energy to the Earth core. The results of these
processes were a warming up and melting of the external sphere Е of the core
(thickness about 2000 km) and the periodical pulsating-expanding growth of
the Earth volume (Krutoyarskiy at al. 2000). According to the primordial
hydridic hypothesis of the Earth, it was taking place the decomposition of
hydrides in the core on metals Fe, Mg, Si and others with dissolved protonic
hydrogen H
+1
in them (
Vernadsky, 1960; Larin, 1980).
2. On the basis of studying deep intratelluric mineralization, which were
forming inclusions in diamonds, it was established the places of diamond-
bearing magmatic centers in the upper mantle on depths about 240-170 km.
At these depths in ascending from decomposed hidridic core of
the streams of
hydrogen fluids there were generated of methane, water, carbon oxide and
carbon components in amounts, sufficient for partly melting of the mantle
substances. All these volatile components alongside with initial hydrogen
are containing in the fluid inclusions of diamond and its paragenetic mineral
sputniks.
3. Superheated volatile components was ascending through the mantle to the
Earth surface at first by disorderly jets, and then gathered in streams in more
top horizons, which in all probability formed “the hot spots and points " in
the upper mantle on the depths of 240-170 km. The centers of partly melting
mantle substratum have arisen in these “hot places” under the influence of
superheated volatile, especially hydrogen and hydrocarbon. Then these initial