1
Prof. Viktor I. Starostin, DSc (Geol. Miner.) is Head of the Department of GeoIogy
and Geochemistry of Mineral Resources,
Geological Faculty, Moscow State University. Не
is Academician of the Russian Academy of
Natural Sciences(RAEN), full member of the
International Academy of Sciences for Higher
Schools, аnd Honored Scientific Worker of the
Russian Federation. V. I. Starostin delivers
lectures оп Geology of Mineral Deposits,
Metallogeny,
and
Structural-Реtroрhysical
AnaJysis. Не has supervised dissertations of 28 PhD and DSc holders. Не has elaborated а
pioneer structural-petrophysical approach in Economic Geology. Не has pubIished mоге thaп
346 scientific works, including 9 monographs. Не is а mеmЬег of the working group of
UNESCO for РгесаmЬrian metallogeny, mеmЬег of editorial boards of scientific journals
"Vestnik MGU, Ser. Geology," "Rudу i Metally," аnd "Otechestvennaya Geologiya." V.I.
Starostin is chairman of the Academician Smirnov Foundation and editor -in-chief of Smirnov
Yeaгbook (scientific-literary anthology).
Tectonometallogenic Model of the Earth's Crust
V.I. Starostin
Department of Geology, Geochemistry and Economics of Mineral Resources, Faculty of
Geology, Lomonosov Moscow State University, Leninskie gory 1, Moscow, 119991 Russia
E-mail address: star@geol.msu.ru
Abstract
The Earth's crust includes three types of zones with contrast energy levels of tectonic and
metallogenic processes: (1) Type 1 - low-level energy (oceanic structures). Low magmatic
differentiation of mantle material; low endogenous metallogenic productivity; young (Mz-Kz)
age; depleted mantle devoid of anomalous concentrations of ore elements; lacks deposits of Sn,
Mo, W, Hg, Sb, U, Pb, diamond, as well as chalcophile and lithophile elements. (2) Type 2 middle-level energy (global megablocks with negative gravity anomalies). Wide development of
Precambrian tectonomagmatic processes; enrichment of the mantle with ore elements; formation
of siderophile deposits, pegmatites (with muscovite and Ве), and Cu-Ni ores (with PGE);
abundance of Cu-Pb-Zn deposits. (3) Type 3 - high-level energy (global megablocks with
positive gravity anomalies). Large-scale differentiation of magmatic formations; wide
distribution of all types of crustal structures: Archean cratons, epicratonic depressions,
Proterozoic mobile belts, zones of protoactivation, Caledonides, Hercynides, Mesozoides,
Alpides, and Cenozoides; maximal manifestation of the Phanerozoic tectonomagmatic
activation; formation of all known geological-commercial types of deposits. Types 2 and 3 are
2
characteristic of the continental crust. Global megablocks and first-order megablocks are
identified within the continental crust.
The Earth’s crust comprises zones of three types with different energy levels of tectonic
and metallogenic processes (Starostin et al., 2010): (1) low level (oceanic structures); (2) middle
level (global megablocks with negative gravimetric anomalies; and (3) high level (global
megablocks with positive gravimetric anomalies). Type 1 zone is represented by the World
Ocean. They are characterized by low magmatic differentiation of mantle material; low
endogenous metallogenic productivity; young (Mesozoic-Cenozoic) age; depleted mantle
(devoid of anomalous metal concentrations); and absence of tin, molybdenum, tungsten,
mercury, antimony, uranium, lead and diamond deposits. Type 2 zone is characterized by the
wide development of Precambrian tectonomagmatism, the concentration of metals in mantle and
the formation of deposits of siderophile elements and uranium, pegmatites (with muscovite and
beryllium), copper-nickel ores (with PGE), as well as copper, lead and zinc deposits. Type 3
zone demonstrates a large-scale differentiation of magmatic formations. It is characterized by the
wide distribution of all varieties of crustal structures (Archean cratons; epicratonic depressions;
Proterozoic mobile belts; protoactivation regions; Caledonian, Hercynian, Mesozoic, Alpian and
Cenozoic structures) and maximum Phanerozoic tectonomagmatic activation. The continental
crust includes global and first-order megablocks.
The present-day structure of the crust is related to long-term evolution of the Earth and its
shells. Different-scale geological structures observed now are composed of a heterogeneous
agglomerate of mineral complexes with appreciably different global geotectonic ensembles in
various parts of the Earth. Discrimination of the scale of these differences is essential from both
theoretical and practical points of view, because it will provide a prognostic appraisal of the
mineragenic potential of specified parts of our planet (Los, 2011; Martynov, 2010; Matveev and
Solovov, 2011).
It is very important now to provide metallogeny with precise quantitative methods.
Regional geochemistry and geophysics are most prepared in this respect. V. Los justly
formulated the group of problems in this path – formalization, mathematization,
computerization, and so on. His recommendations, however, are limited to regional
geochemistry. Metallogeny primarily needs a global-scale system study and development of
evolution models for both the entire planet and its separate parts (Historical Minerageny, 2005,
2007, 2008). There are many different-scale metallogenic schemes of the Earth's crust. The most
complete schemes are presented in (Rundquist et al., 2006).
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The territory of Kazakhstan, where prominent geologists of the Soviet Union carried out
investigation in the second half of the 20th century, is a unique site in this respect. The results
obtained were implemented successfully in this region and basic principles of the ore formation
analysis were refined. Modern schemes of metallogenic regionalization proposed by these
geologists (Bekzhanov et al., 1975; Mazurov, 2005; Metallogenic provinces..., 1983; Satpaev,
1968; Serykh, 2009; Shcherba et al., 1984; and others) have not yet lost the significance and
prognostic potential. However, despite replacement of the geosynclinal paradigm by the plate
tectonic version, large metallogenic belts and provinces identified earlier have retained their
significance, structure and ore specialization. Since regional special works were not carried out
in Kazakhstan and other regions of the Former Soviet Union in the recent 10-15 years,
replacement of paradigms was only expressed in a formal substitution of terminology in the
previous geological cartographic materials.
Basic Principles of the Systematics of Global Metallogenic Structures in the Earth’s
Crust
Taking these materials into consideration, we propose a theoretical model of the
formation of global metallogenic megaprovinces in the Earth’s crust.
Characteristics established in the whole volume of the Earth’s crust are needed as criteria
to identify such superensembles. At present, we can suggest the following criteria: (1) Differentage tectonomagmatic complexes; (2) global epochs of folding, magmatism, sedimentation and
minerageny (formation analysis of large regions); (3) geophysical parameters, such as globalscale gravimetric anomalies. According to M.E. Artemiev, averaged free-air gravity anomalies,
which record the zones with elevated tectonic activity and gravitational heterogeneity, are
sufficiently informative (Kozerenko, 1981).
At present, most researchers believe that the following postulates of evolutionary
metallogeny are sufficiently proved beyond doubt: (1) the Earth was homogeneous in the early
lunar period (until 3.8 Ga); (2) evolution of the Earth was marked by a differentiation of matter,
resulting in drastic differences in the Precambrian and Phanerozoic scenarios of metallogeny,
magmatism and sedimentation; (3) continental plates that appeared in the Early Precambrian
were continuously subjected to the impact of planetary processes and rotation. Lithospheric
plates merged periodically (approximately after every 800 Ma) into a single supercontinent.
Another specific feature is related to lineaments that dominated during different periods
of the Earth’s evolution: latitudinal lineaments in the Early Precambrian and meridional ones in
the Phanerozoic. A significant contribution to the structure of megablocks was made by
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supercontinent ensembles that appeared periodically: Monogea, Megagea, Rodinia (Mesogea)
and Pangea (Sorokhtin, 2007).
Evolution of mineragenic processes was appreciably influenced by planetary processes
(Urazaev, 1996; Pinsky, 2001): (1) global cyclicity of riftogenesis and fold-thrust deformations
related to acceleration and retardation of the Earth’s axial rotation (Urazaev, 1996); (2) moderate
pulsational expansion of the Earth (Milanovsky, 1991) is attributed to variations in the rotation
axis inclination and solar activity, lunar-solar tides and inversions of the magnetic field (Pinsky,
2001). Yu.V. Barkin (2011) developed a geodynamic model of the gravitational excitation of
planetary shells by external celestial bodies. He investigated the system of four gravitating
bodies: the Earth’s core and mantle, Moon and Sun. According to this model, compression and
expansion are cyclic processes that can take place in the Earth in one and the same geological
epochs but with different intensities and in specified zones. These processes are asymmetric
(contrast) relative to hemispheres. Displacements and oscillations are caused by cyclic
gravitational impacts of the Moon, Sun, planets and other external celestial bodies, gravity of
Galaxy included.
The onset of Phanerozoic was marked by great changes in the geological and
metallogenic processes. Until the Phanerozoic, the major ore components were mainly derived
from the mantle and endogenic ore formation was the dominating process. Subsequently, the
sources were exhausted (concentrations of ore components in the mantle became lower than the
background values in the continental crust). The mantle-crustal and crustal sources began to
dominate gradually, whereas the mantle processes (magmatism and fluid flows) mainly served as
energy for the metallogenic processes.
At present, it is believed that the Earth’s crust includes lithospheric plates that are
composed of fragments formed during different periods of its evolution. We identify the
fragments as global metallogenic megablocks.
In the pioneer work (Kozerenko, 1981), the continental crust was divided into two
categories of blocks: (i) global megablocks (superensembles) and (ii) first-order megablocks.
The global megablocks unite huge sectors of the crust based on the formation analysis of
continental and oceanic masses and data on the averaged free-air gravity anomaly. The firstorder megablocks represent a regular combination of various structures, such as platforms,
mobile belts and tectonomagmatic activation zones characterized by different styles and scales of
the manifestation of metallogenic processes.
Based on the formation analysis and averaged geological-geophysical characteristics, the
continental mass of the Earth’s crust is divided into five global megablocks: Eurafrican,
Siberian-Indostan-Madagascar-West
Australian,
Asian-Australian,
American,
American-
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Greenland. They are, in turn, subdivided into first-order megablocks with different structuralformational compositions and metallogenic specializations (Figs.1, 2).
Fig. 1. Sketch map of major structural-metallogenic subdivisions of continents.
Ancient platforms: 1 - stable (a - shields and massifs, b - plates); 2 - mobile (а - shields
and massifs, b - plates); 3 - low-mobile (a - shields and massifs, b - plates); 4-8 - foldbelts and
systems: 4 - Baikalides, 5 - Paleozoides (Salairides, Caledonides, Hercynides), 6 - Mesozoides, 7
- Alpides, 8 - Cenozoic tectogenesis zones; 9-11 - activation zones: 9 - Paleozoic stage, 10 Mesozoic stage (a - uplift zones, b - subsidence zones), 11 - Cenozoic stage (a - uplift zones, b subsidence zones); 12 - activation zones with residual degenerative (Mesozoic and Alpine)
geosynclines; 13 - Cenozoic activation zones of the Himalayan type; 14 - faults (a - inferred, b proven); 15 - boundary between global megablocks (a - inferred, b - proven); 16 - boundaries
between major structures in the Earth’s crust (a - inferred, b - proven); 17 - boundaries between
different-sign geophysical fields in global megablocks; 18 - free-air gravity anomaly zones (a positive, b - negative). Roman numerals designate global megablocks: I - Eurafrican, II Siberian-Indostan-Madagascar-West Australian, III - Asian-Australian, IV - American, V American-Greenland.
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Fig. 2. Schematic locations of global megablocks and first-order megablocks in the Earth.
Modified after V.N. Kozerenko (1981).
Global (Roman numerals) and first-order (Arabic numerals) megablocks: I - Eurafrican: 1
- European, 2 - North African, 3 - Central African, 4. South African; II - Siberian-IndostanMadagascar-West Australian: 1 - Siberian-Central Asian, 2 - Indostan, 3 - Madagascar-East
African, 4 - West Australian; III - Asian-Australian: 1 - Northern East Asian, 2 - Central East
Asian, 3 - Southern East Asian, 4 - Australian, 5 - Island-arc areas of the western Pacific; IV American: 1 - American-Mexican, 2 - Northern Antilles (Cuba, Haiti and others), 3 - Guiana, 4 South American; V - American-Greenland: 1 - Canadian-Greenland, 2 - NW Canada, 3 - Eastern
South American.
Supplementing and developing ideas of V.I. Kozerenko, let us describe the block
structures noted above. Comprehensive analysis of global megablocks revealed that they differ in
terms of evolution. From the viewpoint of metallogeny, the most important geochronological
boundaries are as follows: Lower Proterozoic, Late Riphean and Middle Paleozoic. They mark
an intensification of crust differentiation (thickening of the crust, its differentiation into the lower
basic and upper felsic portions, and thickening of the upper granitoid portion) аnd pulses of
expansion accompanied by vigorous trap effusions.
The megablocks differed in the scale of evolutionary events. For example, the SiberianIndostan-Madagascar-West Australian megablock was marked by the most complete
manifestation of Precambrian and Middle Paleozoic processes; the Asian-Australian megablock,
by the manifestation of all events that took place since the formation of the Earth’s crust,
7
although processes of the Phanerozoic megaperiod played a crucial role in the metallogeny of the
megablock.
According to fundamental studies by S.I. Andreev and I.S. Gramberg, a new stage in the
Earth's evolution began after the Middle Jurassic (170 Ma) –appearance of the global
talassogenic (marine) system (basic volcanoplutonic impulse) and formation of an oceanic type
of the Earth's crust. This process evolved in three megastages: (1) Mesozoic (50 Ma, Middle
Jurassic-Lower Cretaceous); (2) Cretaceous (40 Ma, Aptian-Campanian) and (3) Cenozoic (80
Ma, Pg-Q) (Fig. 3).
Fig. 3. Scheme of magmatic complexes in the World Ocean. According to S.I. Andreev
and I.S. Gramberg (1998). (1-19) Magmatic complexes of: (1) the initial pre-spreading ocean
formation stage, J (basalt); (2, 3) differently oriented spreading stage («old» oceanic plates, J2K1a): (2) tholeiite-basalt (dominant), (3) andesite-basalt (locally developed); (4, 5) the spreading
style alteration stage (K1a-K2km): (4) tholeiite-basalt (attenuating), (5) basalt-ferrobasalt
(dominant); (6, 7) the linear spreading stage («young» oceanic plates, К2km-Pg3): (6) basaltferrobasalt (attenuating), (7) ferrobasalt-basalt (dominant); (8-10) the linear spreading stage with
the simultaneous formation of mid-oceanic rise (Talassides, Pg3-Q): (8) ferrobasalt-basalt
(inherited), (9) ferrobasalt (dominant), (10) picroferrobasalt; (11-13) intraoceanic rises («oceanic
lands», K1a-K2km): (11) komatiite-tholeiite, (12) moderately alkaline basalt-trachyte, (13)
tephrite-phonolite; (14, 15) superimposed volcanic belts (K2km-Q): (14) moderately alkaline
basalt-trachyte, (15) tephrite-phonolite; (16-18) intrusive komatiites: (16) gabbro diabase, (17)
troctolite, (18) cumulative (olivine) gabbro; (19) protrusions (gabbro-peridotite); (20-22) other
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designations: (20) faults; (21) boundaries of magmatic complexes: (а) corresponding to the
replacement of ocean development stages, (б) confined to separate stages; (22) MAR axial rift.
Systematics of Global Megablocks and Mobile Belts
Taking into consideration the modern level of study of the Earth's crust, its
tectonometallogenic model can be presented in the following way (Fig. 4).
Fig. 4. Global megablocks and mobile belts of the Earth's crust. 1-9 - Continental
metallogenic structures. 1-6 - Global megablocks. 1-3 - Fragments of Gondwana: 1 - South
American, 2 - African, 3 - Indostan-Madagascar-West Australian; 4-6 - Fragments of Laurasia: 4
- American-Greenland, 5 - European, 6 -Siberian. 7-9 - Global mobile metallogenic belts: 7 Mediterranean-Central Asian (Tethys), 8 - Andean-Cordilleran, 9 - Asian-Australian. 10-12 Marine tectonic structures. According to S.I. Andreev and I.S. Gramberg (1998): 10 - Ancient
oceanic plates (J2-K1), 11 - Ancient-to-young plate transition zone (K1-K2), 12 - young oceanic
plates, flanks of Talassoids and riftogenic structures (K2-Plc). Other legends as in Fig. 3.
Global megablocks are subdivided into first-order megablocks–regular combinations of
platforms, mobile belts and tectonomagmatic activation zones of different types, scales and ore
genesis periods. First-order megablocks comprise regional metallogenic provinces and belts,
which appeared during the periods of a regular tectonomagmatic setting with a certain type of
magmatism, sedimentation and ore formation. Consequently, each global megablock and firstorder megablock acquired a specific modern composition, structure and mineragenic potential
(Figs. 1-).1. The South American global megablock includes the southwestern North America
(Cu, Pb, Zn), Guiana and Brazil shields (Fe, Mn, REE, diamond and pegmatites). The megablock
9
is characterized by an intricate gravity anomaly field. It comprises carbonatites, diamonds, Sn,
complex pegmatite deposits, ferruginous quartzites and gondites.
2. The African global megablock includes the following first-order megablocks: North
African megablock (Ta-Nb and base metal deposits); Central African megablock (Sn, Cr, Pt, Au
and U deposits); South African megablock (Pt, Au, U and diamond deposits). The positive freeair anomaly is typical of this global megablock. It is characterized by large Cr and Au deposits
(southern Africa). Volcanic-hosted deposits (base metals, Au-Ag), tin ores, diamonds in
kimberlite pipes and carbonatites are common. Pb, Zn, Ti, Fe and others are less common.
3. The Indostan-Madagascar-West Australian global megablock comprises the following
first-order megablocks: Siberian-Central Asian megablock (Siberian Platform, West Siberian
lowland, Kazakhstan, middle and northern Tien Shan) with Ni, Cu and Pb-Zn deposits; Indostan
megablock (Cu, Pb-Zn); East African-Madagascar megablock (Ni, U, diamonds), West
Australian megablock (Ni, Au, REE). The global megablock is characterized by negative free-air
anomalies. It typically includes pegmatite (with mica, Be and Li), Cu-Ni, Pb-Zn, Fe, Mn, Ti,
PGE, Ag and Au deposits.
4. The American-Greenland global megablock includes the following structures:
Canadian-Greenland Shield (U, Cu, Pb-Zn, Au deposits) and its folded framing; mid-continent
plates with the MV deposits (Pb-Zn); the Appalachia and Innuit folded systems (U, Fe); East
Greenland province (Li, Be). The gravity field is complicated. The Canadian Shield was
characterized by negative gravity anomalies until the Upper Proterozoic. Then the rock
complexes were developed under conditions of positive gravity anomalies. The megablock is
marked by wide development of Au deposits; Li-Be pegmatites; sulfide Cu-Ni deposits with
PGE; as well as W, Co, Ag, Mo, Ti (+ V) and U deposits. It also includes large reserves of Cu,
Pb, Zn and Fe.
5. The European global megablock comprises the Baltic Shield with the following
metallogenic provinces: East European, Svalbard, Kara and Pechora-Barents Sea. The
megablock includes siderophile element deposits, rare metal and
ceramic pegmatites, diamondiferous kimberlites and ferruginous quartzites. It is characterized by
negative gravity anomalies.
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Fig. 5. Sketch map of the North Asian Craton and its framing. According to L.M.
Parfenov (2000).
1-4 - Elements of craton: 1 - Siberian Platform, 2 - fold-thrust belts (VR - Verkhoyansk,
BP - Baikal-Patom, ST - South Taimyr, EA - East Angara), 3 - Riphean aulacogens, 4 Devonian aulacogens; 5-10 - orogenic belts of different ages: 5 - Circum-Siberian (CS) Late
Riphean (750-650 Ma), 6 - Yenisei-Transbaikal (YT) Late Cambrian-Early Ordovician (500-460
Ma), 7 - Altai (AL) Silurian (435-415 Ma), 8 - South Mongolian-Khingana (SMK) Late
Paleozoic (320-300 Ma), 9 - Mongolian-Okhotsk (МО) Late Paleozoic-Early Mesozoic (290-140
Ma), 10 - Verkhoyansk-Kolyma (VK) (145-100 Ma), South Anyui (SA), Badzhal (BD), HonsuSikhote Alin (HS) (140-95 Ma); 12 - Kolyma-Omolon (KO) superterrane formed at the terminal
Middle Jurassic; 13 -fragments of cratons: Okhotsk (ОK), Omolon (ОМ); 14 - fragments of Late
Riphean orogenic belts: Argun (AR) and Tuva-Mongolian (ТМ) superterranes; 15 - fragments of
Early Paleozoic orogenic belts: Bureya-Jiamusi (BJ) and Kara (КR) superterranes; 16 - thrusts;
17 - strike-slip faults; 18 - faults.
6. The Siberian global megablock is distinguished by the wide development of five major
groups of deposits: Au, Cu-Ni-PGE, iron ores and diamonds (Fig. 5). Their formation is closely
associated with the Precambrian history (primarily, Archean greenstone belts), mafic-ultramafic
magmatism and active geodynamics in the Late Cambrian-Early Phanerozoic. In the Aldan
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Shield, the latitudinal gabbro-anorthosite zone with titanomagnetite deposits is confined to
conjugation of the pre-Proterozoic consolidated structure of the shield with Karelides of the
Jugjur-Stanovik region.
7. The Mediterranean-Central Asian (Tethys) and Urals-Mongolia-Okhotsk belt is a
planetary zone with the highest ore concentration in the Earth. It appeared in the Middle
Paleozoic and actively evolved until the N-Q time in two megastages: Pz2-Mz3 and N-Q. The
first stage was marked by the formation of the planetary Urals-Mongolia-Okhotsk belt and
manifestation of the Late Caledonian, Hercynian and Early Cimmerian folding. These processes
were responsible for the formation of most ore provinces in West Europe, Urals and northern
Kazakhstan that accommodate approximately 140 unique ore deposits and fields.
8. The Andean-Cordilleran global megablock includes the Cordillera and Andes (Au, Sn,
Cu, Cu-Mo deposits), Alaska, tectonomagmatic reactivation zones, Basin and Range zone as
well as island arcs of the Greater and Lesser Antilles. This region accommodates up to 70% of
world reserves of Mo; hydrothermal volcanic-hosted deposits with complex ores (Au-Ag, Ag,
Sn-Ag, base metals); 60% of porphyry copper ores; various formation types of Pb-Zn deposits;
large Hg, Sb, W, U, Pt and Au deposits; as well as unique fluorite and Be deposits.
9. The Asian-Australian mobile metallogenic belt includes the following structures:
Mesozoic structures of Asia; Hercynian structures of Central Asia and Mesozoic
tectonomagmatic activation zones; Chukotka-Catasian volcanic belt; and Mesozoic orogenic
zone (Koryakia-Anadyr system, island-arcs in the western Pacific and other structures). Its
western boundary is represented by the Asian continental platforms. The global megablock also
includes the East Australian region (SE Australian Platform, Tasmania and New Zealand). On
the whole, the global megablock is characterized by positive free-air anomalies.
This region is characterized by the marginal-marine type of the Earth's crust with a wide
development of marginal-marine basins. They distinctly show deep structural elements that
extend down to the lithospheric boundaries, which coincide with the ancient or modern
seismofocal zones and outline autonomous lithospheric microplates. They reflect the internal
deep structure that differs basically from both oceanic and continental varieties. For example, the
Sea of Okhotsk Plate is an autonomous tectonic unit (precisely like the adjacent Sea of Japan and
Bering Sea plates, according to the same seismotomographic data). The marginal-marine type
includes separate blocks of the continental crust (the Precambrian consolidation block included)
and represents the site of mantle plumes that make up local riftogenic structures (depressions and
troughs).
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The Asian-Australian metallogenic belt comprises large reserves of Sn, Hg-Sb; W, Mo,
Au, Au-Ag, Pb-Zn, Cu and Ti; Precambrian iron ore deposits; and carbonatites (in eastern Asia).
Uranium, diamond, base metal and gold deposits are typical of Australia.
10. Ancient oceanic plates (J2 - K1). According to S.I. Andreev and I.S. Gramberg (1997),
this stage marks the beginning of the talassogenic system formation. It includes a large-scale
basification of the lithified upper mantle and the subsequent input of the mafic material along
disordered faults that made up the ancient oceanic plates. These processes were synchronous
with the continental Cimmerian activity.
11. The ancient-to-young plate transition zone (K1-K2) is characterized by wide
development of intraoceanic volcanic belts corresponding in age to the respective MesoCenozoic continental belts.
12. Young oceanic plates, flanks of Talassic structures, riftogenic zones (K2-Plc). The
terminal megastage of the oceanic crust formation, which coincided with the Alpine stage of
continents, was marked by the formation of young oceanic plates and the planetary system of
mid-oceanic ridges, resulting in the formation of the unique metallogenic zonality in the World
Ocean. The late stage produced provinces with ferromanganese nodules, Co-bearing
ferromanganese crusts and nodules, as well as hydrothermal sulfide occurrences in the midoceanic ridges.
General Features of Global Megablocks
Global megablocks are characterized by a specific association of typical metals, structure
of the Earth’s crust and set of geological formations. Blocks with positive gravimetric anomalies
Blocks with positive gravimetric anomalies comprise very large Cr, Hg, Sn and Ta-Nb pegmatite
deposits, large volcanic-hosted deposits (mainly massive sulfide). They incorporate up to 80% of
the world resources of gold (South Africa, Canadian Shield and Russian Far East). Large
uranium deposits are also found. Cu, Pb, Zn, Fe, Ti, V W show a transit character independent of
the megablock type. Megablocks with negative free-air anomalies enclose mainly siderophile,
rare earth and uranium deposits; pegmatites (with muscovite and Ве) and Cu-Ni ores (with
PGE). Cu, Pb, Zn, W, Mo and S deposits are widespread.
Thus, the continental part of the Earth’s crust includes two types of large global
megablocks. Type 1 (Eurafrican, American, Asian-Australian) is characterized by large-scale
differentiation of magmatic formations and positive gravimetric anomalies. They are
characterized by wide development of the whole ensemble of geotectonic structures in the
Earth’s crust: Archean cratons, epicratonic depressions, Proterozoic mobile belts, protoactivation
zones, Caledonides, Hercynides, Mesozoides, Alpides and Cenozoides. The Phanerozoic
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tectonomagmatic activation is widespread. The geological section is saturated with granitoid
complexes.
Type 2 (Siberian, European, Indostan-Madagascar-West Australian global megablocks) is
marked by active manifestation of early Precambrian tectonic processes, weak manifestation of
Phanerozoic processes and averaged negative gravity anomalies. Baikalides and Caledonides are
abundant, whereas Hercynides are subordinate. The platform structures incorporate crystalline
massifs. Granite gneisses, granulites, charnockites and granitoids are widespread. The
intermediate type is represented by the American-Greenland megablock. The early (Archean,
Early Proterozoic) history of the megablock followed the first scenario, whereas the history since
the Late Proterozoic followed the second scenario.
Based on analysis of a great body of empirical material, large areas of the World Ocean
are marked by low magmatic differentiation of mantle material and, consequently, low
endogenous metallogenic productivity. Sn, Mo, W, Hg, Sb, diamond and many other types of
deposits are absent.
The next (regional) scale of investigation of the Earth’s crust is aimed at subdivision of
first-order megablocks into metallogenic provinces, belts and ore districts. Regional metallogeny
studies regularities in the spatiotemporal distribution of mineral deposits in connection with
peculiarities of the development and structure of large territories. The main aim is to study
geodynamic settings of ore formation and accomplish metallogenic regionalization in order to
discriminate crustal sectors of certain period and tectonic evolution with typical associations of
mineral deposits. The regional metallogenic analysis includes the following three tasks: (1)
metallogenic regionalization based on hierarchic structural-metallogenic taxa; (2) compilation of
metallogenic maps and schemes; and (3) special metallogeny.
Regional metallogenic provinces, belts and ore districts were formed during a
homogeneous tectonomagmatic regime. They are characterized by certain type of magmatism,
sedimentation and ore formation. Specified metallogenic structures defined in this process are
investigated by the whole complex of modern prognostic-prospecting (geochemical, petrological,
formational and others) methods to assess their raw mineral potential. Since such investigations
have a very high theoretical and practical importance, issues of the metallogenic regionalization
should be handled very carefully. Regional taxa should be identified only after the global
metallogenic analysis with the identification of global (planetary) megablocks and first-order
megablocks therein.
Identification of large and superlarge deposits is a very important problem. It is
comprehensively investigated by special metallogeny. The point at issue is large mineral deposits
of separate types that are formed in (1) planetary-scale specific geological-metallogenic settings
14
or (2) unique combinations of such settings in first-order blocks. The first category includes
provinces with porphyry Cu-Mo and Sn-W-Mo, stratiform Pb-Zn, uranium-base metal, massive
sulfide and types of deposits. The second category includes polygenous and polychronous
complex (base metal) deposits with giant reserves.
When studying such metallogenic provinces, specific attention should be paid to global
geodynamic settings that promote the concentration of mineral matter: Precambrian cratons,
epicratonic depressions, Proterozoic mobile belts, as well as zones tectonomagmatic activation,
protoactivation, spreading, subduction, collision and others.
Further study of a crustal specified area should be corrected with the consideration of its
evolutionary maturity and mineral potential. Depending on the age and complex of geologicalgeochemical, petrological and sedimentary processes that took place in a specified structuralformational and geodynamic environment, we should significantly modify the known methods
and prospecting technologies.
Efficiency of the prognostic-prospecting method in modern conditions is demonstrated by
recommendations of the Canadian scientist F. Agterberg (2011) who studied the copper potential
of the Precambrian regional metallogenic province Abitibi in the Canadian-Greenland
megablock. Based on areal geochemical survey (grid 10 • 10 km), he compiled two series of
anomaly maps in 1968 and 2008. Prospecting and exploitation were carried out here during this
period. According to this researcher, the prognostic and proven reserves of Cu in 1968 and 2008
were estimated at 3.12 and 9.50 Mt, respectively. We believe that the growth in reserves and
excellent results of prospecting in this famous region were promoted by an accidental
coincidence of regional factors: (1) a uniform (with respect to geological structure and
metallogenic characteristics) territory of the Early Precambrian was studied; (2) the main ore
potential was related to volcanosedimentary massive sulfide copper formation; and (3) the
authors could empirically choose calculation parameters and coefficients that were most
appropriate for the hydrodynamic ore-forming systems functioning in the Early Precambrian in
the given block of the Earth’s crust.
Agterberg developed a specific prospecting method (complex Pareto and lognormal
geochemical models), which is highly efficient only for such geological-geochemical situations.
Its application to other geological-metallogenic conditions (particularly, Miocene massive
sulfide copper provinces in Japan) or prospecting for diverse deposits in China and other regions
(Singer, 2011) yielded more modest results.
15
Conclusions
In the Earth's crust, we can conditionally identify zones with contrast energy levels of
tectonic and metallogenic processes: low level (oceanic crust); medium and high levels
(continental crust). The latter group can be divided into two categories of planetary structure
ensembles (global and first-order megablocks): (1) megablocks with the formation history
terminating in the Precambrian (medium-energy level); (2) megablocks with a continuous
evolution during the whole geological history of the Earth (high-energy level).
The high-energy megablocks are characterized by large-scale differentiation of magmatic
formations and wide development of geotectonic structures: Archean cratons, epicratonic
depressions, Proterozoic mobile belts, protoactivation zones, Caledonides, Hercynides,
Mesozoides, Alpides and Cenozoides. Processes of the Phanerozoic tectonomagmatic activation
were most complete here. The geological section is saturated with granitoid complexes. The
crust is divided into the lower and upper parts. On the whole, these structures are characterized
by positive gravity anomalies.
Precambrian tectonic, magmatic, sedimentary and metallogenic processes were
widespread in the medium-energy megablocks. The mantle was enriched with ore elements. This
period is marked by the first fundamental phase of ore element concentration and formation of
the main volume of major metallogenic formations that served later as the source of ore material:
mainly siderophile and uranium deposits, pegmatites (with muscovite and Ве), and Cu-Ni ores
(with PGE). Cu, Pb, Zn deposits are widespread. Phanerozic metallogenic processes are weakly
manifested. Negative gravity anomalies are typical.
The low-energy level is recorded in large areas with the Mesozoic-Cenozoic oceanic
crust. This region is characterized by low magmatic differentiation and, consequently, low
endogenic metallogenic productivity. The depleted mantle could not serve as source for most ore
deposits. This level includes only endogenic deposits associated with the submarine
undifferentiated tholeiitic basaltoid formation (mainly massive sulfide ores). Sn, Mo, W, Hg, Sb,
U, Pb, diamond and many other deposits are absent here.
Ore components were concentrated in the Earth’s crust in three geological settings: (a)
hydrothermal rift systems of oceans and continents; (b) plate subduction zones beneath active
continental margins; (c) fluid systems in tectonomagmatic activation and protoactivation zones.
The geological history includes two maximums of ore formation: Early Proterozoic and
Phanerozoic. The Early Proterozoic period is marked by the formation of a single core of the
Earth and the formation of unique provinces with ores of siderophile elements. They were
accumulated in global megablocks with negative gravity anomalies. The ph Phanerozoic period
was marked by a new evolution level of the Earth and its crust: initiation of the cyclic
16
functioning of the mechanism lithospheric plate tectonics. The main role in ore formation
belonged to fluid systems in tectonomagmatic activation zones and mobile belts. This period is
characterized by global megablocks with positive free-air anomalies, unique (in terms of
diversity and intensity) ore provinces of chalcophile elements (Mo, Sn, W, Sb-Hg),
diamondiferous deposits associated with kimberlite and carbonatite and Ta-Nb deposits.
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