37
The expansion of the Earth was accompanied by absorption of a great
quantity of heat, which was supposed to change the essential image of the
thermal regime of the internal spheres of the planet. Obviously, it is possible
to attract the given factor, alongside with cutting of volume of reactions of
acidification, for argument of sharp falling the geothermal gradient on the
frontier between Archean and Proterozoic and as a consequent of stabilizing
the lithosphere. The beginning of the process of the expansion of the Earth
at that time has determined all further evolution of the geodynamic regime
of the planet. The periodic expansion of the Earth is coupled with the cyclic
(temporary) cease of degassing protonal hydrogen from hydridic bowels of
the Earth, which stipulated disconsolidation of the exterior core,
magnification of power of the mantle and abatement
of radius of the internal
core, on what the huge consumption of energy and heat was required. As
an outcome, during late Archean and early Proterozoic, most probably, there
was an abatement of gravity of the Earth from 3.0 up to 2.75 g, began the
irrevocable lamination the upper mantle and earth crust on gypolite, pirolite,
basalt, granite and volcano-sedimentary layers. The upper mantle up to
depth of 110 km was represented by pyrolite of the pyroxene-olivine
composition, and lower up to depth of 400 km by the undepleted mantle –
gypolite make up of spinel-garnet (stratum В). The middle mantle (stratum
С),
since horizon Golitsyn, had an intermetallic composition (Larin, 1980).
Together with expansion of the Earth, decompression of gypolite of the
upper mantle takes place. When the pressure decreases lower 10 G
Pa the
transformation from spinel-garnet gypolite to pyroxene-olivine pyrolite
occurs. Such transformation should be conducted by «lattice downthrown»
of a lot of lithophile elements in connection with abatement of the
isomorphous capacity of lattices of olivine and pyroxene in comparison
with garnet and spinel. Such lithophile elements should be in the upper
mantle in the geochemical unstable state, which promotes their
mobilization. Most probably, they are the source of lithophile elements for
plutonic intertelluric fluid, inducing the granitization on the upper horizons
of the earth crust. As a result of the undepleted mantle during periods of
activating and degassing of protonic hydrogen, a gab in huge amounts of
lithophile elements and favorable conditions have arisen to bring about the
formation of large and rich deposits of uranium, gold, infrequent and rare-
earth elements, alongside with chalcophile and siderophile metals
. Thus, in
late Archean and early Proterozoic, the metallogeny sharply changes its
image, which is closely connected with the alteration of geodynamic regime
of development of the Earth (Krutoyarskiy et al., 2000).
Metallogeny of early Proterozoic has inherited from late Archean the
siderophile profile of giantest deposits of iron and titanomagnetite in
gabbro-anorthozite massive Sadberry (Canada), as well as greatest deposits
of nickel, copper, platinum, chrom, gold related to stratified intrusions of
ultrabasic-basic rocks (Bushveld, SAR), norite (Sadberry); chromite (Great
Dike, Southern Africa); chromite and platinum in the pluton Steelwater
(West of USA). Sulphide of copper-nickel ores is detected in ophiolites of
the belt Каtalakhti (Baltic shield) and in basic lopolite Sadberry (Canadian
38
shield). In connection with potassium granites, pegmatites and metasomatic
rocks, the largest deposits of the lithophile elements, in particular, uranium,
thorium, infrequent terrains, gold (uranium belt Аtabasca, Canada) and
uranium - thorium pegmatites were generated. The hydrothermal deposits of
cassiterite and infrequent terrains are coupled with the granite-rapakivi
(Baltic shield). The deposits of tin, tungsten and fluorite are connected to
granites of Bushveld complex; and the copper-molybdenum formation is
coupled with granite batholitic Fielsdreef (Africa).
In the protoplatform’s sedimentary rocks of early Proterozoic the
giantest deposits of iron jaspilites type are being detected in formations
Guron (Canada), Мinas (Brazil), Pretoria (Southern Africa), Hamersly
(Australia), Candina (China). The rich deposits of gold and uranium are
detected in the buried quartz conglomerates Tarqua (Gana), Jakobina
(Brazil), Wyoming and Guron (Canada); uranium and manganese - in red
color depositions Коngo (Africa) are marked.
In protogeosynclinal formations of early Proterozoic,
the rich deposits of
ferriferous quartzites and jaspilites have been detected (Canada, Baltic,
Ukraine, Australia). Sulfides deposits of iron are dated to the formation
Кuruna (Sweden). Coopers sandstones are opened in Udokan depression
(Aldan shield), in the copper belt Hindustan. The richest deposits of
uranium are connected with basal conglomerates Elliot-Lake, Haf-Lake
(Canada) and in the Hills-Creek complex (Northern Australia). The gold is
retrieved in molasses depositions of the formation Tarqua and together with
jaspilites in the Kape province (SAR).
With continental riftogen belts of early Proterozoic are connected the
intrusion of mantle magmatic melts, which have generated transcontinental
fields of dikes, large mafic-ultramafic laminated plutons such as Great Dike
and lopolith Bushveld (Southern Africa), and later the intrusions of alkaline
rocks and carbonatites, dated to the submeridional lineament of East Africa.
The giantest deposits of ingrained and massive chromit-platinum and
copper-nickel ores are coupled with laminated intrusions of the Great Dike
and lopolith Bushveld. The pluton Steelwater, dated to the rift Cuinoy
(West USA) is referred to the segregation type of chromit and platinum
deposits.
III. P r o t o c o n t i n e n t a l a n d p r o t o o c e a n i c c y c l e
(2,000-900 Ma) of geological development of the Earth also is divided
into three stages: 1. late Proterozoic (2,000-1,600 Ma), 2. early Riphean
(1,600-1,200 Ma) and 3. middle Riphean (1,200-900 Ma).
The community of conditions on all continents characterizes the end of
the early Proterozoic. To the frontier of 2,000 – 1,700 Ma all
protogeosynclinal basins practically have disappeared, all eocratons were
closed and there was the supercontinent Pangea I to start up. The drainage
of the overpowering parts of the marine basins at the end of early
Proterozoic and outgoing the water from the continents points out on the
formation already at this time alongside with Pangea I the image of the
future Pacific ocean – Panthalassa I. The early Riphean age of Panthalassa