68
intervals were distributed a little differently, because the richest late
Cretaceous deposits of Southern China, containing about 77 % of world
reserves of antimonies, whereas 19 % of antimony is related to the Alpine
stage. However, it is not excluded, that the age of the Chinese deposits of
antimony is more ancient (late Hersynian), since their presence between
Devonian and Triassic depositions without any clear connection with
Cretaceous granites and are controlled by large breaks zones.
As a result of the spent analysis of the distribution reserves of metals of
the chalcophile group, it is possible to make a conclusion, that maximum
resources of these metals are connected with the late stages of the two last
cycles of geodynamic development of the Earth (late Hercynian and
Alpine), that was caused by epoch of the maximum expansion of the Earth
and activity of tectono-magmatic processes. The exception makes the
unique richest Witwatersrand deposit of gold of late Archean age and,
perhaps, the antimony deposits of Cretaceous age (?) on Southern China.
5. 3. L i t h o p h i l e elements are represented by tin, wolfram,
aluminium, uranium, thorium, niobium, tantalum, fluorine, potassium,
sodium, barium, lithium, rubidium, cesium, beryllium, strontium, radium,
yttrium, cerium, zirconium and other rare metals, the reserves of which are
given in the Table 9 and Figure 5.
Tin and tungsten are complementary metals and more often usually
found in the deposits of hydrothermal, greisens, pegmatite, stockwork and
skarn types genetically connected with acid granitoides. The maximum
reserves of tin (60 %) and tungsten (73 %) are dated to Cimmerian stage of
tectogenesis, less - to Alpine (10 % and 15 %) and the late Hercynian (18 %
and 9 %) stages, the deposits of which are territorially disposed in external
zones of the Pacific Ocean metallogenic megabelt.
Aluminium, basically, is extract from bauxites, which formed at lateral
chemical weathering of various rocks in conditions of the humid tropical
climate on the continents, or from deposition of weathering products in the
littoral zone of the seas. Four epochs of weathering of bauxites are known
in the geological history of the Earth. The reserves of the bauxites were
distributed in such manner that the most productive of them appear to be the
late Palaeogene-Holocene bauxites, containing 88 % of the world reserves,
less in the middle Devonian-Carbon - 7 %, Cretaceous - 4 % and early
Cambrian bauxites- 1 %. The formation of bauxites originated at the times
of tectonic rest and formation of the peneplains.
Uranium. More than
half account reserves of U
3
O
8
on the planet is dated
to Precambrian epoch – 54%, and less in Paleozoic - 12 %, then in
Mesozoic - 24 % and in Cenozoic formations - 10 % are included. To
magmatic deposits of uranium (mainly in acid and alkaline granites and
pegmatites) are related 6-7 % of reserves. In the late Archean and early
Proterozoic uranium - gold metamorphic conglomerates and quartzstones
are included 15 %; in the hydrothermal and infiltrational stratiformal
deposits of discordant type there are more than 48 % reserves of uranium.
The remain resources of uranium are contented in carbonatites, skarns,
71
according to the data of М.V.Schumilin (1996), only 63 % of the
world resources of uranium are connected to Protozoic epoch.
The significance of the geological history of the Earth in Proterozoic
period from positions of uranium metallogeny are the level of "maturity" of
continental crust, shielding of cratogenic fundament by powerful cover of
sedimentary rocks and increasing of partial pressure of oxygen in the
atmosphere. The cosmos rhythms are not crucial for formation of large
deposits of uranium (Lyachnitskiy, Markov, 1996). It is characteristically
the connection of uranium epoch to the marked above final stages of
geotectonic cycles. They are accompanied by raising the continents and
regressing the seas, that is to say, with geocratonic conditions, especially at
formation the supercontinents of Pangea I, II, III, accordingly, after Karelian
(1,900-1,700 Ma), Grenville (1,100-900 Ma) and Hercynian (290-230 Ma)
epochs of foldering. It is necessary to note, that 63 % of large deposits of
uranium is located on the supercontinent Laurasia and only - 37 % on the
Gondwana.
Thorium is genetically connected to sodium granites, syenites and
pegmatites, in which it is attended as accessory thorium contents minerals.
Besides, there are rare pneumatolytic and hydrothermal deposits of thorite
in association with barite, fluorite, hematite and other minerals. The
industrial contents of thorium are established in some gold – uranium
metamorphic conglomerates and quartzstones of early Proterozoic age, for
example, in the deposit Blind-River (Canada), where the reserves of ThO
2
about 3,300 t are calculated. For the account of denudation all primary
sources of thorium are formed rich alluvial and seacoast placers deposits of
monazite in Southern India and Brazil, which are the basic raw material for
manufacture of thorium. It is interesting to note, that 75 % of the
discovered large deposits of thorium are located on the continents
Gondwana, whereas 25 % - on the continents of Laurasia.
Rare, dissipated and terra-rare elements have brightly expressed
lithophile geochemical specialization. The rare metals Ta, Nb, Be, Li, Rb,
Ce, Sc, Zr, Hf, B; dissipated elements - Cd, Ga, Ge, Tl, Re, Se, Te, In; terra-
rare elements №№ 58-71 lanthanum both cerium groups and Y are
represented. General part of these specified elements is dated to the crust
alaskites and subalkalines granites and genetically connected with them
pegmatites, greisens and metasomatites with raised alkaline. The next
one of most significant sources of these elements is geocratonic conditions,
especially at formation of uniform supercontinents Pangea I, II, III,
accordingly, after Karelian (1,900-1,700 Ma), Grenville (1,100-900 Ma),
Rare, dissipated and terra-rare elements have brightly expressed
lithophile geochemical specialization. The rare metals Ta, Nb, Be, Li, Rb,
Ce, Sc, Zr, Hf, B; dissipated elements - Cd, Ga, Ge, Tl, Re, Se, Te, In; terra-
rare elements №№ 58-71 lanthanum both cerium groups and Y are
represented. The most part of these specified elements is connected with
alaskites and subalkalines granites and genetically connected with them
pegmatites, greisens and metasomatites with raised alkaline. The next one