Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

Origin of and Tectonic Controls for
Omulevka River Metallogenic Belt
The Omulevka River metallagenic belt of stratabound Audrian Alps W and Kipushi Cu-Pb-Zn deposits consists mainly
of vein deposits which are hosted in the Omukvka passive continental margin terranc (Shpikeman, 1998).
The stratabound Austrian Alps W mineralization deposits are hosted in the lower part of the Middle Ordovician
(Llanvirnian) Krivun Formation which ranges from 600 to 700 m hick and conrists of flysch composed of rhythmically-
Interbedded black clay-carbonaceous limestone, calcareous siltstone ad phytlitu. ore-bearing rock hrkm ranges from 10 to
15 rn thick and is composed of black calcarem sillstone with clastic. rowd grains ~f calcite ( 55-7W), quartz ( 20-30%), and
graphite (3-5%). Metarnorph~srn has produced a fine-gmined granoblaftic and lapidogr~oblasic textwe. Former interstitial clay is
metamorphosed to a fine-grained epidote aggregate.
The Vesnovka and related Kipushi Cu-Pb-Zn deposita art hasted in the Mi#le Ordovician hhutka Fmtion which is
about 325 m thick and consists of rhythmically interlayered black clay limtstane and ehale wit beds of siltstone and cdcareous
sandstone. The sulfide deposits are beds of saRdslonc aod calcareous siltstone. The deposits and host rocks are interpreted as
having been regionally metamorphosed in the Late Silurian for seveml reasons. (1) The Ordovician and Silurian sedimentary rock
of Rassokha terrane and the northern pan of the Chndevka terrane arc unconfombly overlapped by Lower Devonian
conglomerates, and pebbles of the m ~rpbic rocks occur in these cmgfomtratcs. And (2) a model Pb age of 410 to 432 Ma is
obtained for the galena from the sulficte oras of the Omulcvka Austrian Alps W deposit { Shpikffman, 1998).
Because the stratabound Austrian Alps W and Kipushi Cu-Pb-Zn deposits mur as veins and replacements, the
Omulevka River metallogenic belt is interpreted as brming during regi.ona1 rncbmorphism. The regional metamoxphhn is
interpreted as occurring during accretion of tbe s~nall Rassdcha oceanic crust krrane to the North Asian Craton Margin 0 in
the Late Silurian (Shpikeman, 1998), The host Omulevka continental margin krrane is interpreted as a dked fragment of the
North Asian Craton Margin (Nokleberg and others, 19!24c, 1997~). IU%ng is interpreted as occurring in the Late Devonian and
Early Carboniferous.
Rassokha Metallogenic Belt of Basdtk Cu and
Sediment-Hosted Cu Deposit3 (Belt RA)
Northern Part of Russian Northeast
The Rassokha metallogenic belt of basaltic Cu and sediment-hosted Cu deposits (fig. 2; tableg 3,4) occurs in tbQ uorthem
part of the Russian Northeast (Shpikerman, 1998). The bdt is 80 km long and 20 km wide and is hmkd in the Rassokha passive
continental-margin terrane of the Kolyrna-Omoh supertenanc (Nokleberg and others, 19%, 1997~). The aaetahgezh belt also
contains sparse Pb-Zn vein deposits which occur in the Middle a d Late Ordovician Bulkui Formation. This volcanic-rockdominated
unit consists of potassic trachybasalt, trachyandesite, basalt, and tracbyte flows, interbedded tuff, siiicmtis shale, red
sandstone, conglomerates and gray limestone, md hypabyssal shoshanite bodies. The Pb-Zo vein deposits sre intwptetd aa
forming during a period of post-volcanic, hydrothermal activity. The B&t F~mtion is interpd M of a distal(?) oceanic
island arc volcanic assemblage. The significant deposit is tht basaltic Cu and sediment-hosted Cu Apdja deposit (table 4)
(Nokleberg and others 1997a, b, 1998).
Agyndja Basaltic Cu and Sediment-Hosted Ou lkposlt
The basaltic Cu and sediment-hosted Cu Agyndja deposit (Shpikcrrnan and others, 1988) consists of disseminsted and
vein-like ore bodies, and sparse breccia ores which are hosted i~ amygdaloidai trachybasait and &tone of Middle to Late
Ordovician age. The ore minerals are bornite, chalcocite, chalcqyrite, covelllte, and local native copper. The lowerparl of the
stratified deposit is commonly composed of mineralized h-achybasait which overlain by Ch-bearing sandstone. The Cu minerals in
trachybasalt occur in amygdules and synvokanic fissures in tbc ufrp# portion of lava flows. The (=u eera.ls a h occur botb as
cemenr and as clasts in sandstone. Tbe deposit ocem ovw an area dabout 100 km2. hdivibual om horizons are 1 to 30 m thick
and trend northwest. The Cu sulfide depovits occur in nubmarhe law flows, subvolcanic p~phyry fntausiow, and %h&ow-water
sandstones. The Agyndja deposit 1s large with an average gtade of about 1% Cu.
Origin of and Tectonic Controls for
Rassokha Metallogenic Belt
The Rassokha passive continental-margin terrene, which host the Rassokha metallogenic belt, consist of two stnxc-1
complexes (Shpikerman, 1998). A lower cornplax consists mainly of Qrdavicim marhe sedimentary and volcanic rock is about
5,000 m thick. The major lithologies are Cambrian eandstatle and congkmcrate with round clads of serpentinite, Whybasalt,
tuff, volcaniclastic sandstone, mmor tracbyte. The basaltic Cu and sediment-hosted Cu deposits ofthe Rasokha metallogenic belt
are hosted in the Middle and Late Ordovician Agyndja Formation whlch contains s&edw arrd vol&c rbcb and rattgcs from
800 to 1000 m thick. The major litbologics in the fonnation ara interbeddad lava flows (10-30 m thick), mainly red porphyry
trachybasalt, rare trachyte, trachyandesik, tuff, volcaniclastic srrnbtone, and conglomerate. Locd l ktone md dolomite with
marine fauna occur ( Shpikerrnan, 1998). The lower complex is intruded by sills of K-rich basalt, momnite, and syenite porphyry