USGS Professional Paper 1697 - Alaska Resources Library

(Preto and Schiarizza, 1985; Schiarizza and Preto, 1987; Høy,
1997. The deposit occurs in two parts (1) the East Zone with
reserves of 42.5 million tonnes grading 0.39 percent Cu, 2.4
g/t Ag, and 0.044 g/t Au; and (2) the West Zone with reserves
of 53.5 million tonnes grading 0.42 percent Cu, 2.6 g/t Ag and
0.047 g/t Au. The deposit has estimated reserves of 96 million
tonnes grading 0.41 percentCu, 2.5g/t Ag, 0.04g/t Au, and
0.016 percent Mo. A skarn or porphyry origin was interpreted
by Schiarizza and Preto (1987) with a relation to Devonian
intrusive rocks that are now metamorphosed to orthogneiss
and are interpreted as derived from bimodal, calcalkaline
volcanic rocks. The deposit is herein interpreted as a kuroko
massive sulfide deposit.
The Chu Chua Cyprus Cu-Zn volcanogenic massive
sulfide consists of pyrite with chalcopyrite and minor sphalerite
that occur in two major and several smaller stratiform
massive sulfide lenses associated with pyritic, cherty sediments
and pillow basalt of the late Paleozoic (Devonian to
Permian) Fennel Formation (McMillan, 1980; Schiarizza and
Preto, 1987). Chalcopyrite and sphalerite occur interstitially to
pyrite. Basalt is locally extensively altered to talc and carbonate
in structures interpreted as vents. The deposit contains
estimated reserves of 2.5 million tonnes grading 2 percent Cu,
0.5 percent Zn, 0.5 g/t Au, 9 g/t Ag. The deposit is interpreted
as a Cyprus(?) massive sulfide deposit (Høy, 1991).
Adams Plateau SEDEX Zn-Pb-Ag Deposits
Several SEDEX Zn-Pb-Ag deposits that occur in the
Adams Plateau area are hosted in clastic metasedimentary
sequences of probable Cambrian age and lower Eagle Bay
Assemblage (Schiarizza and Preto, 1987; Høy, 1991) in the
Kootenay terrane, and in Devonian and older magmatic arc
rocks in the Yukon-Tanana terrane in the Canadian Cordillera.
The assemblage is correlative in part with the Nisutlin Assemblage
of the Yukon-Tanana terrane (Wheeler and McFeely,
1991). The significant deposits are two previously-producing,
small mines at Mosquito King and Lucky Coon.
Origin of and Tectonic Setting for Kootenay-Shuswap
Metallogenic Belt
A diverse group of volcanogenic and related mineral deposits
occur in the Kootenay-Shuswap metallogenic belt. Because
of a wide age range of host rocks and deposits, this metallogenic
belt may be divided into two metallogenic belts, one of Cambrian
age and the other of Devonian and Mississippian age.
The Kuroko massive sulfide deposits in the Kootenay-
Shuswap metallogenic belt are hosted in Devonian and Mississippian
felsic to intermediate metavolcanic units. The calc-alkaline
igneous-arc rocks are interpreted as part of the extensive middle
Paleozoic continental-margin arc that extends for several thousand
km along the North American Craton Margin (Grantz and others,
1991; Rubin and others, 1991; Plafker and Berg, 1994; Nokleberg
and others, 1994c, 1997c; Monger and Nokleberg, 1996). Fragments
of the continental-margin arc include several metallogenic
belts hosting the kuroko massive sulfide and related deposits
Middle and Late Devonian Metallogenic Belts (387 to 360 Ma; figures 16, 17) 55
(Nokleberg and others, 1997a,b,c)—(1) The Arctic metallogenic
belt hosted in the Coldfoot terrane in Arctic Alaska, (2) Alaska
Range and Yukon-Tanana Upland metallogenic belt hosted in the
Yukon-Tanana terrane in central and eastern Alaska, and (3) the
Frances Lake and Finlayson Lake metallogenics belt hosted in the
Yukon-Tanana terrane in the southern Yukon Territory.
The Cyprus massive sulfide deposits in the Kootenay-
Shuswap metallogenic belt are hosted in Devonian mafic
volcanic and associated metasedimentary rocks. The deposits
and host oceanic assemblages, together with SEDEX sulfide
deposits and their host rocks, occur in imbricated thrust sheets
within other assemblages in the Kootenay terrane. These oceanic
assemblages and deposits, which are interpreted to have
formed in the back-arc of the Kootenay arc and were subsequentally
structurally emplaced within shelf and continentalmargin
arc parts of the Kootenay terrane during accretion of
the outboard Slide Mountain oceanic terrane in the Jurassic
(Monger and Nokleberg, 1996; Nokleberg and others, 2000).
The Besshi Cu-Zn-Ag deposits in the Kootenay-Shuswap
metallogenic belt are hosted in Cambrian tholeiitic metavolcanic
and associated rocks that constitutes the older part of
the Kootenay terrane. The Besshi Cu-Zn-Ag deposits in the
Kootenay-Shuswap metallogenic belt are herein interpreted as
forming in a short-lived Cambrian continental-margin arc.
The Adams Plateau SEDEX Zn-Pb-Ag deposits in the
Kootenay-Shuswap metallogenic belt are hosted in Cambrian
metasedimentary rocks. The deposits are correlated with
similar SEDEX deposits in the Kootenay metallogenic belt
to the east, and with deposits in the Anvil and Howards Pass
metallogenic belts to the north in the Selwyn Basin of the
northern Canadian Cordillera. All three metallogenic belts are
interpreted as forming from Pb- and Zn-rich fluids during rifting,
volcanism, basinal subsidence, local marine transgression,
and related hydrothermal activity along the passive continental
margin of the North American Craton.
Metallogenic Belts Formed During Middle
Paleozoic Rifting of North Asian Craton Margin
Khamna River Metallogenic Belt of Carbonatite-Related
Nb, Ta, and REE Deposits (Belt KR)
Southern Part of Eastern Siberia
The Khamna River metallogenic belt of carbonatiterelated
Nb, Ta, and REE deposits (tables 3, 4) occurs in the
southern part of eastern Siberia in the North Asian Craton
Margin (fig. 16; Verkhoyansk fold belt, unit NSV) (Nokleberg
and others, 1994c). The belt strikes north-south, is about 300
km long, and varies from 20 to 60 km wide. The significant
deposits are at Khamna and Gornoye Ozero (table 4) (Nokleberg
and others 1997a,b, 1998). These deposits consist of
pyrochlore, orthite, perovskite, and monozite that occur in
halos adjacent to or around alkalic igneous rocks. The Khamna
River metallogenic belt is similar to the Tommot River metal-