USGS Professional Paper 1697 - Alaska Resources Library

62 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
Early(?) Devonian dolomite along a major north-south-trending
fault. The deposit is about 20 m long and 4 to 7 m thick.
The main ore mineral is cinnabar, which occurs with calcite
in masses and irregular veinlets. Pyrite, quartz, sphalerite,
and anthraxolite also occur. The deposit formed in several
stages—(1) pre-ore 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 the Givetian Formation that formed in a
shallow marine environment. The significant deposit is at Batko.
The Batko basaltic Cu deposit (Shpikerman and others,
1991) consists of disseminated and irregular masses of sulfides
that occur in subalkalic, amygdaloidal basalt flows as much
as 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 basalt flows.
The adjacent trachybasalt is intensely epidotized and carbonatized.
The upper mineralized horizon is no more than 2 to 3
m thick. The deposit is small with grab samples that contain as
much as 3.1 percent 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 that are intercalated
with tuff and diabase bodies. The Prizovoe bedded barite
deposit occurs in the Early and Middle Carboniferous Batko
Formation. Associated stratiform 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 exist between these formations
of sedimentary rocks.
Origin of and Tectonic Controls for Urultun and Sudar
Rivers Metallogenic Belts
Both the Southeast Missouri Pb-Zn and carbonate-hosted
Hg deposits are interpreted as forming in a middle Paleozoic
thermal artesian paleobasin in a major petroleum area (Shpikerman,
1998). Early and middle Carboniferous rifting is interpreted
as the source of mineralizing fluids. Similarly, the deep-marine
sedimentary and mafic volcanic rocks that host the basaltic
Cu, volcanogenic Mn, and associated deposits of the Urultun
and Sudar Rivers metallogenic belt are interpreted either as
allochthonous blocks of oceanic-floor sedimentary rocks or
as sedimentary and volcanic rocks that were deposited during
Devonian rifting of the North Asian Craton Margin to form the
Omulevka terrane (Nokleberg and others, 1994c, 1997c). Characteristic
pyroclastic debris in the sedimentary rocks indicates
that submarine volcanism and was associated with these SEDEX
deposits. This interpretation is supported by anomalous values of
Pb, Zn, Cu, Ag, and Hg in the host rocks. In spite of the variety
of mineral deposit types in this belt, a genetic relation is inter-
preted between most of the deposits. The sedimentary-exhalative
accumulation of Mn and barite ores, and anomalous Pb, Zn, Cu,
Ag, and Hg concentrations are interpreted as forming during
deposition of the Southeast Missouri Pb-Zn deposits in artesian
horizons. The younger parts of the Omulevka terrane consists
of Carboniferous and Permian fossiliferous tuff, chert, shale,
limestone, siltstone, and sandstone, and Triassic fossiliferous
siltstone, mudstone, marl, and shaley limestone.
Yarkhodon Metallogenic Belt of Southeast
Missouri Pb-Zn Deposits (Belt YR) West-Central
Part of Russian Northeast
The Yarkhodon metallogenic belt of Southeast Missouri
Pb-Zn-barite deposits occurs mainly in the Yarkhodon River
basin in the west-central part of the Russian Northeast (fig. 16;
tables 3, 4) (Nokleberg and others, 1997b, 1998). The belt is
hosted in the Yarkhodon subterrane in the eastern part of the
Prikolyma passive continental margin terrane. The belt is 330
km long and as much as 50 km wide. Most of the deposits occur
in the same stratigraphic level of the Yarkhodon Formation of
Givetian age and are hosted in diagenetic dolomite and dolomitized
limestone. Rare deposits occur in Proterozoic dolomite.
The depositional environment for the original limestone is
interpreted as a carbonate bank formed on a passive continental
shelf. The significant deposits are at Slezovka and Gornoe.
Slezovka Southeast Missouri Pb-Zn Deposit
The Slezovka Southeast Missouri Pb-Zn deposit (A.V.
Artemov and others, written commun., 1976; Davydov and
others, 1988) consists of vein, disseminated, and breccia
sulfides that occur in Middle Devonian a mineralized dolomite
sequence, which occurs in a sequence of clastic sedimentary
rocks and carbonate rocks. The deposit contains as much as
five mineralized beds, each 3 to 5 m thick that are separated by
barren interbeds ranging from 3 to 10 m thick. The ore minerals
are mainly galena, sphalerite, pyrite, and barite. The deposit
is cut by quartz and calcite veinlets. The deposit is small.
Origin of and Tectonic Controls for Yarkhodon
Metallogenic Belt
The Yarkhodon subterrane of the Prikolyma passive continental
margin terrane, which hosts the Yarkodon metallogenic
belt, consists of two major units (1) Givetian limestone, dolomite,
marl, and siltstone, and (2) Famennian to Early Permian
argillite, siltstone, volcaniclastic sandstone, rhyolite tuff, and
basalts. The sedimentary rocks are very thick are interpreted
as forming along continental-slope base of a rift-related trough
within a passive continental-margin area. The Prikolyma terrane
is interpreted as a rift-related fragment of the North Asia
Craton (unit NSC; Nokleberg and others, 1994c, 1997c). The
Southeast Missouri Pb-Zn-barite deposits of the Yarkodon
metallogenic belt are interpreted as forming during rifting during
the Late Devonian through the Mississippian.