49
geosynclinal-fold of the Pacific zone. This volcanogenic belt is extended
further to south along western coast of the Tatar channel and the East -
China sea, having the total expansion about 6,500 km and width from 100
up to 500 km. Metallogeny of Оkhotsko-Chukotskiy volcanogenic belt is
connected with effusives and extrusions, and also with granitoids of
Cretaceous and Paleogene ages. In the metallogenic respect it is necessary
to mark the leading value of molybdenum and tungsten, lead and zinc,
aluminium (аlunite); and minor value of gold, argentum, hydrargyrum,
antimony, tin;
and a very small role of iron, copper, arsenic.
V.2.2.3. E a s t - A s i a n (internal) мetallogenic belt is regarded
territorial to the transitive area between the Asian continent and the Pacific
ocean called t r a n s i t a l a c t i v e t y of type (Krasny, 1977). To
the same type of transital is referred also Australia-Pacific metallogenic
belt. The considering transitive area consists of marginal seas, hedge off
from ocean by island arc systems and deep-water valleys (troughs). The
marginal seas are underlaied one of continental (Bering, Okhotsk, East
China), and others by oceanic crust (Philippine, Fiji). There are seas with
bottom, under which occur crusts of transition type, and also of continental
and oceanic types (Japanese, Coral, Таsman). The total extent of Asian and
Australian transitive zones of the Pacific Ocean exceeds 20,000 km in
length with the width from 1,000 up to 3,000 km.
At the formation of shelf and deep-water depressions derived as well as
processes of downing and riftogen spreading. The island arcs differ on
length, types of volcanism and mineral resources. Volcanogenic rocks are
represented by tholeiite, andesite-basalt, less often by dacite-riolite and
alkaline-basalt magmas. Among the intrusive formations the granitoids and
basic-ultrаbasic intrusions and protrusions were developed. The generation
of these active transitive zones originated in Alpine and Pacific stages of
tectonogenes. At the expense of geosynclinal-fold systems of the transmital
areas there was upbuilding the territory of the Asian continent toward of the
Pacific Ocean, since Riphean time.
The entering in East - Asian and Australian-Pacific metallogenic belts
transital zones the Каmchatka-Koryaksky highland, islands of Japan,
Taiwan, Philippin, New Guinea, New Zealand, New Caledonia and Fiji are
characterized by one-type of miniralization. It expresses by domination of
copper-sulphide deposits (Кimlin, Krilyon, Oko, Kuroko) and low-
temperature hydrothermal gold - silver ores (Kusikino, Chinkushi, Morobe,
Khauraki, Vatukula); significant role of deposits of chromite (Khirako,
Masinloc, Santa-Craus); laterite ores of iron, hydrosilicates of nickel with
asbolane (Manikani, New Caledonia), and the presence of exhalyasion-
sedimentary ores of manganese. Less value has locally developed copper-
molybdenum ores, low-temperature hydrothermal deposits of hydrargyrum
(Puipui), antimony and arsenic, sedimentary phosphorites and placers
deposits of gold, platinum, magnetite and titanic minerals.
V.2.3. W e s t – A m e r i c a n
metallogenic megabelt is
asymmetric to the East - Asian megabelt, but the transferring zones from the
American continent to the Pacific ocean depression are principally differed.
50
The active transital zone here is completely absent and the continental crust
is contrasting osculated with oceanic crust. In west part of America there is
only the one Cordilleras-Andes volcanic belt on the type of magmatism and
metallogenic similar to internal island arc zone in East - Asian volcanic belt.
Just with this internal belt of geosynclinal fold systems of the Kimmerian,
Alpine and Pacific tectonic stages genetically connected the following
deposits, having world value of copper (Buitt, Climax, Chukikamato,
Potrerilyos); copper-molybdenum (Bingem, Chino, Cananeya, Braden, El-
Tenetye); gold (Mother vein, Grass-Valley, Cliff); gold - silver ores
(Коmstok, Kripa-Creek, El-Oro, Okampo, El-Rosario); argentum
(Моrocco); uranium (Мaryvill, Jilpin); hydrargyrum (Stimbot-Spring, New-
Almaden, Uitzuko); antimony (Santa-Lus-Potosy); polymetallic ores
(Ledvill, Tintic, San-Eulaliya, Durango, Santa-Barbara). These deposits are
disposed on Alaska, British Colombia, and Western states of USA, Mexico,
Peru and Chile.
The exterior West-American megabelt is well represented by the
Hertzian and Kimmerian geosynclinal-fold systems only in Bolivia and on
North-West Argentina, where they adjoin to the Brazilian shield, and they
are less exhibited in Alaska, British Colombia, Western states of USA on
the sites adjoining to Canadian shield. The exterior metallogenic belt in
Bolivia and North-West Argentina is most rich by deposits of tin, tungsten
and bismuth (Pepita, Antofagasta, Pakuni); tin and argentum (Chokaya,
Potosi, Orura); ligneous tin, polymetals (Коlkechaka); selenium
(Pakakhake) and especially of antimony (Tupisa, Orura) and on Alaska,
British Colombia and Western states of USA – of gold (Golden-Creek,
Yukon, Nome); chromite and platinum (Platinium); asbestos (Clinton-
Creek, Cassiar); magnesite and talc.
V.3. T r a n s i t i v e z o n e s f r o m c o n t i n e n t s t o
o c e a n s are well known in the geological literature as t r a n s i t a l s
(Krasny,1977; 1984). Depending on the regime of geodynamic
development there are two principally different types of them - the passive
and active transitals.
V.3.1. P a s s i v e t r a s i t a l s are represented by shelf’s plates,
overlaining on the heterogeneous folded granite-metamorphic foundation
and are bounded by continental slope of the ocean.
The continental structure
can be cut off by the continental slope or can have agreeable bedding,
extending the coastal plains. The power of sedimentary cover of passive
shelfs varies from several hundred meters up to many kilometers,
especially, in riftogenic uncompensated depression such as Mexican or
Laptevian (up to 15 km). Magmatic rocks occur seldom and are basically
represented by basalt dikes and volcanic overlying covers. The passive
transitals are referred to the stabilized areas with steady long-lived
submergences and low-grade structure of sedimentary cover at the
considerable disjointed relief of the foundation. By their geology-tectonic
structure, they resemble young platforms of the West-Siberian type. The
passive shelfs are widespread in the Arctic segment
of the Earth,
surrounded
by a narrow strip the Atlantic and places the Indian oceans, and also north