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

Origin of and Tectonic Controls for
Chersky-Argatass Ranges Metallogenic Belt
The Chersky-Argatass Ranges metallogenic belt is hosted in the Indigirka-Olay sedimentary-volcanic assemblage which
consists chiefly of shallow-marine and n o d late Middk Jurassic to Neocomian formations wbich overly various accreted
terranes of the-~ol~ma-0molon superterrane (Nokleberg and others, 1994c, 1997~). The Indigirka-Oloy is chased mainly of
sandstone, s~ltstone, shale, conglomerate, and volcanic rocks of varying composition. The igneous rocks of the Indigirka-Oloy
assemblage ~nclude coeval plutonic rocks and mainly shallow-marine, rarely nonmarine basalt, andesite, rhyolite, and tuff with
interlayered sandstone, conglomerate, siltstone, and shale. The belt also contains small bodies of granite, granodiorite, and
monzogranlte. The igneous rocks of Ibe Indigirka-Oloy sedimentary-volcanic assemblage are interpreted as part of the Jurassic
Uyandina island arc which formed on margin of the Kolyrna-OrnoJon superterrane during fmd stages of migration towards, but
before accretion the northeastern North Asian Craton (Nokleberg and others, 2000).
Yassachnaya River Metallogenic Belt of Pb-Ln
Skarn, Porphyry Cu, and CU-4 Vein Deposb
(Belt YS) Western Part of Russlan Northeast
The Yasachnaya River metaltogenic beh of Pb-Zn skam, porphyry Cu, and Cu-Ag vein deposits (fig. 48; tables 3,4)
occurs in the Yasachnaya River basin in the western part of the Russian Northeast. The belt extends in two branches to the
northwest for nearly 500 kin and ranges up to 100 km wide. The deposits are hosted in or near Late Jurassic granitic and
subvolcanic intrusive bodies which are associated with the Uyandin-Yassachny volcanic-plutonic belt, part of the Migirh-Oloy
overlap assemblage (unit io, fig. 48) (Nokleberg and others, 1994c, 1997~). The significant Pb-Zn slcarn deposits are at Terramot
and Kunarev (table 4) (Nokleberg and others 1997a, b, 1998). A porphyry Cu stockwork deposit at Datsytovoe is spatially
associated with the Pb-Zn skam deposit at Kunarev. Thcse relation8 define a complex mineral deposit district where Pb-Zn skarn
and porphyry Cu deposits are closely associated.
Terrassnoe Pb-Zn Skarn Deposit
The Terrassnoe Pb-Zn skam deposit (Shpikerman, 1987; V.I. Shpikemmn and others, wrilten commun, 1988) occurs
along a fault between Late Devonian (Framian) Limestone and late Paleozoic pelitic and chert in the bottom of a Late Jurassic
volcanic depression intruded by bypabyssal dikes which overly a hied late Mesozoic granitic intrusion. The skam consists of
hedenbergite, gamet (andradite-grossular), and ilvaite. The main me minerals are sphdtrite, galena, chalcopyrite, and magnetite.
Silver occurs mainly with sulfide minerals and Ag-plymetalk ~~ predominate. Ag Einedbation was later than the &am
formation. The deposit conlains a probable resource of 5.2 million tonnes with an avmge pk of about 1% Pb, 5% Zn, and 140
g/t Ag. The deposit extends for 700 rn.
Kunarev Porphyry Cu and Pb-Zn-Cu-Ag Skarn Deposit
The Kunarev deposit (fig 52) (Shpikerman, 1987; V.I. Shpikerman and N.E. Sawa, written commun., 1988) is a
composite deposit containing both porphyry Cu, PbZn-Cu-Ag skam, and polym~c replacement deposits. In the middle oftha
host volcanic sequence is a Ag-Cu-Bi s-ork related to a porphyry tmchyrhyolite dike and to a quartz diorite stock, Quartzcarbonate
veinlets in the stockwork contain pyrite, chalcopyrite, spblerite, galma, fieihgite, d Ag-Pb-Bi sulfosalts. Tfie host
rhyolite and quartz diorite exhibit an intense pyrile alteration, and the quartz diorite is propylitically altered. lXa part of the
deposit is known as the Datsytovoc porphyry Cu occuneace.
To the west and soutb is the Kunaryov Pb-Zn-Cu-Ag skarn deposit. The skams ~ ccm as sheet-like replacements in
Middle and Late Jurassic calcareous conglomerate, and in fissure veins above and beneath the conglomerate. The skarns C O~S~S~S
of hedenbergite and gamet, along with pymhotite, sphalerite, and chalcopyrite. The centpal part of the deposit consists of relatively
younger quartz-carbonate veins and veinlets which contain sphalerite, galena, chalcopyrite, pyrite, cobaltite, matildite, and galenabismuthite.
Average grades are 0.7-1.1% Pb, 1.15-10.5% Zn, and 47-170 g/t Ag. Further to south, skauns in the cob~omerale are
replaced by epidote- and jasper-bearing melasomatic rocks. In addition are polymetallic replwtcemenls with a thickness $wn 10 uj
25 m which occur in several places at the southern end of the deposit. The ore minerals are pyrite, sphalerite, chalcopyrite, and
marcasite.