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

Origin of and Tectonic Controls for
Tommot River Metallogenic Belt
The intrusion of alkal~c igneous rocks which host the Nb, Ta and REE deposits of the Tommot River metallogenic belt
are interpreted as forming during Late Devonian rifting of the North Asian Craton and the formation of the Omulevka Ornulevka
passive continental margln terrane (Nokleberg and others, 1997b, 1998). The alkalic igneous rocks, that host the Tommot River
metallogenic belt, are part of a sequence of Mississippian igneous rocks in the terrane. The Omulevka ternerne is herein interpreted
as rifted fragment of the Paleozoic passive continental margin of North Asian Crato~l (Nokleberg and others, 1994c, 1997c, 2000)
which in the Khamna River area contains a possibly similar belt of carbonatite-related Nb, Ta, and REE deposits.
Urultun and Sudar Rivers Metallogenic Belt of
Southeast Missouri Pb-Zn, Carbonate-Hosted Hg,
Basaltic Cu, and Volcanogenic Mn Deposlts
(Belt URS) West-Central Part of Russian Northeast
The Urultun and Sudar Rivers metallogenic belt of Southeast Missouri Pb-Zn, volcanogenic-sedimentary Mn, basaltic
Cu, bedded barite, and carbonate-hosted Hg deposits (fig. 16; tables 3,4) occurs in three discontinuous fiapnts which extend
northwesterly for 170 km in the west-central part of the Russian Northeast (Shpikerman, 1998. The southeastern portion of the
belt is in the Si~dar River basin, and the northwestern portion of the belt is in the Late Taskan and Umlhln Rivers. The deposits
occur in various parts of the Pakeozoic Sudar rift sequence in the Omulevka passive continental margin terrane (Nokleberg and
others, 1994c, 1997~). Southeast Missouri Pb-Zn-fluorite deposits, as at Urultun, are most prevalent, and occur in Late Ordovician
through Middle Devonlan strata (Shpikerman, 1987, 1988). The significant deposits are the Urultun Southeast Missouri Pb-Zn
deposit; the Uochat carbonate-hosted Hg deposit, the Batka basaltic Cu deposit, the Lygiykhtakh volcanogenic M.n deposit, and
the Prizovoe bedded barite deposit (table 4) (Nokleberg and others 1997a. b, 1998).
Urultun Southeast Missouri Pb-Zn Deposit
The Urultun Southeast Missouri Pb-Zn deposit (fig. 27) (Shpikerman, 1987, 1998) consists of disseminated veinlets and
brecciated ore which occur in Early Devonian dolomite overlain by Middle Devonian (Givetian) marl. The ore bodies are
composed of dolomite, calcite, fluorite, galena, sphalerite, and anthraxolite. Barite, pyrite, and cinnabar are present locally. The
deposit is interpreted as forming in two stages: (1) an early sphaleritefluorite stage which resulted in disseminated metasomatic
ore; and (2) a galena-fluorite-calcite stage which resulted in brecciated and veinlet ores. The orebearing dolomite sequence is up
to 240 m thick and occurs along a synclinal limb of a fold which generally trends northwesterly. Two to five conformable ore
horizons, varying in thickness from 1 to 10 m, occur in the dolomite sequence. The ore bodies are sporadic within a given horizon.
The deposit occurs over an area of about 20 by 4 krn. This and other deposits and host rocks are stratigraphically overlapped by
deep-sea argillaceous and carbonaceous sedimentary rocks. The deposit contains an estimated resource of 23 million tomes with
an average grade of about 2.85% Pb, 6.74% Zn, and 10% fluorite.
Carbonate-Hosted Hg Deposits
The carbonate-hosted Hg deposits of the Urultun and Sudar Rivers metallogenic belt are interpreted as forming in the
same event as the Southeast Missouri Pb-Zn deposits. The signjficaot deposit at Uochat (Babkin, 1975) consists crfdisseminated,
cinnabar-bearing veinlets which occur in brecciated Early(?) Devonian dolomite along a major north-south-trendjag fault. The
deposit is about 20 m long and 4 to 7 m thick. The main ore mineral is cinnabar, which occurs with calcite h masses and irregular
veinlets. Pyrite, quartz, sphalerite, and anthraxolite also occur. The deposit formed in several stages: (I) presre silicification; (2)
pre-ore calcite alteration; (3) deposition of cinnabar and calcite; and (4) post-ore deposition of calcite. The deposit is small.
Basaltic Cu, Volcanogenic Mn, and
Bedded Barite Deposits
The stratabound basaltic Cu deposits occur in rift-related trachybasalt flows of Lhe Givetian Formation which formed in a
shallow marine environment. The significant deposit is at Batko.
The Batko basaltic Cu deposlt (Shpikennan and others, 1991) consists of disseminated and irregular masses of sulfides
which occur in subakalic, amygdaloidal basalt flows up to 200 m thick, within folded red beds of Middle Devonian (Givetian)
age. The ore minerals are bornite, chalcocite, and covellite. The deposit occurs at the tops of the basdt flows. The adjacent
trachybasalt is intensely epidotized aad carbonatized. The upper mineralized horizon is no more than 2-3 rn thick. The deposit. is
small with grab samples which contain up to 3.1% Cu and 13.7 g/t Ag. Ag and Ba are associated with the Cu.
The stratiform volcanogenic Mn deposits, as at Lyglykhtakh, and the bedded barite deposits occur in folded Early
Carboniferous (Mississippian) through Late Permian siliceous shales, cherts and siliceous-carbonate rocks which are intercalated
with tuff and diabase bodies. The Priwvoe bedded barite deposit occurs in the Early and Middle Carboniferous Batko Formation.
Associated stratifom rhodochrosite deposits, at Lyglykhtakh and elsewhere in the Sudar and nearby river basins, occur in the
lower part of the Late Permian Turin Formation. Stratigraphic breaks may exisl between these formations of sedmentary rocks.