USGS Professional Paper 1697 - Alaska Resources Library

24 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
and Kootenay (KO) belts, which contain SEDEX Zn-Pb-Ag
deposits, are hosted in the North American Craton Margin
or in the Yukon-Tanana and Kootenay continental-margin
terranes, which are interpreted as having been rifted from the
North American Craton Margin. These belts are interpreted as
forming during rifting of early Paleozoic (Cambrian) North
American Continental-Margin. (6) In southeastern Alaska, the
Prince of Wales Island (PW) porphyry Cu and polymetallic
vein deposits, which are hosted in the Alexander sequence of
the Wrangellia superterrane, are interpreted as forming in a
short-lived continental-margin arc. In the below descriptions
of metallogenic belts, a few of the notable or significant lode
deposits are described for each belt. table 4, which is adapted
and revised from Nokleberg and others (1997a), provides a
complete listing of significant lode deposits in each metallogenic
belt.
Metallogenic Belts Formed During Early Paleozoic
Marine Sedimentation in Rifted Fragments
of Gondwandaland Supercontinent
Voznesenka Metallogenic Belt of Korean Pb-Zn
Deposits (Belt VZ), Southern Russian Southeast
The Voznesenka metallogenic belt of Korean Pb-Zn
massive sulfide deposits (fig. 2; tables 3, 4) occurs in the
southern part of the Russian Southeast. The belt is hosted in
the Voznesenka terrane of the Khanka superterrane, a fragment
of a Paleozoic active continental-margin arc (Androsov and
Ratkin, 1990; Nokleberg and others, 1994c, 1997c; Khanchuk
and others, 1996, 1998; Ryazantseva, 1988). The significant
deposits are at Voznesenka-I and Chernyshevskoe (table 4)
(Nokleberg and others 1997a,b, 1998). The massive sulfide
ores generally occur conformable to organic-rich, bituminous
limestones near a contact with overlying marl. Banded magnetite
ore associated with algae bioherms is a peculiarity of the
stratiform deposits of the Voznesenka metallogenic belt.
Voznesenka-I Korean Pb-Zn Deposit
The Voznesenka-I (Korean Pb-Zn deposit (fig. 8) (Androsov
and Ratkin, 1990; Ryazantseva, 1988) consists of massive
and thick-banded sphalerite and magnetite-sphalerite layers in
bedded Early Cambrian limestone turbidite. The ore bodies are
lenticular, 1-2 m thick, 20 to 100 m long, and occur in dolomitic
limestone and marl. The sulfide bodies and host rocks are folded
and regionally metamorphosed. The sulfide bodies were locally
altered to skarn and greisen during emplacement of a Silurian
granitic stock that intrudes the carbonate unit. The deposit is of
medium size with an average grade of 4 percent Zn.
Chernyshevskoe Korean Pb-Zn Deposit
The nearby Chernyshevskoe Korean Pb-Zn deposit
(Bazhanov, 1988; Ryazantseva, 1988) consists of sheeted
pyrrhotite-arsenopyrite-pyrite-galena-sphalerite bodies that
occur at the contact of a limestone sequence with overlying
Early Cambrian siltstone. Rare conformable zones of disseminated
sulfide mineralization occur within the limestone away
from the contact. The sulfide bodies are 1 to 2 m thick, with a
surface exposure 100 to 200 m long. The deposit was drilled to
a depth of about 100 m. The deposit is small with an average
grade of 1.5-6.5 percent Pb and 0.7 to 2.5 percent Zn. Both
the Voznesenka-I and Chernyshevskoe deposits were formerly
interpreted as skarns and were previously not evaluated properly.
Locally abundant sedimentary-exhalative siliceous rocks
have anomalously high F, B, and Zn values.
Origin of and Tectonic Controls for Voznesenka
Metallogenic Belt
The Cambrian through Silurian units of the Voznesenka
terrane consists are (Nokleberg and others, 1994c, 1997c;
Khanchuk and others, 1996, 1998) (1) Cambrian sandstone,
pelitic schist, rhyolite, felsic tuff, and limestone and dolomite
that together are as much as several thousand meters thick,
are intensely deformed, (2) Ordovician collision-related
biotite and Li-F protolithionite granitoid rocks with Rb-Sr and
Sm-Nd ages 450 Ma (Belyatsky and others, 1999), and (3)
Ordovician to Early Silurian conglomerate and sandstone with
questionable-age flora. The limestone turbidites hosting the
Voznesenka-I and Chernyshevskoe Korean Zn-Pb deposits are
interpreted as forming on the upper part of an Early Cambrian
continental slope. The limestone turbidite and other Cambrian
sedimentary and volcanic units of the Voznesenka terrane are
interpreted as a fragment of a Late Proterozoic to early Paleozoic
carbonate-rich sedimentary rock sequence that formed
on a passive continental margin. Archaeocyathid fauna in
Cambrian limestone is related to the Australia paleogeographic
province. The Voznesenka terrane probably was a part of the
passive continental margin of Gondwanaland (Khanchuk and
others, 1998). Similar stratiform Cambrian Zn deposits occur
in fragments of Gondwanaland in Africa and South America.
Kabarga Metallogenic Belt of Ironstone Superior
Fe) Deposits (Belt KB), Southern Russian Southeast
The Kabarga metallogenic belt of ironstone (Superior Fe)
deposits (fig. 2; tables 3, 4) occurs in the southern part of the
Primorye province in the Russian Southeast and is hosted in
the Kabarga terrane of the Khankha superterrane (Nokleberg
and others, 1994c, 1997c). The belt is defined principally by
a group of ironstone deposits at Ussuri that consist of beds of
magnetite- and hematite-magnetite-bearing chert that occur
in a sequence of Early Cambrian clastic-carbonate rocks that
overlie Early Cambrian dolomite (Denisova, 1990; Nokleberg
and others 1997a,b, 1998). Magnetite and hematite layers also
occur along the layering planes between chert and intercalated
with quartz-sericite-chlorite and quartz-sericite schist
and dolomite. The upper part of the Fe deposit is oxidized,
and contains Mn deposits, mainly pyrolusite, which occur