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

WTF and Red Mountain Kuroko Massive
Sulfide Deposit
The WTF and Red Mountain Kuroko massive sulfide deposits (Gilbert and Bundtzen, 1979; David R. Gaard, written
commun., 1984) consist of masslve pyrite, sphalerite, galena, and chalcopyrite in a quartz-rich gangue. The sulfides are hosted in
in felsic metavolcanic rock derived from crystal and lapilli tuff, minor flows, and metasedimentary rock. The stratiform massive
sulfide layers occur on both sides of a large. east-west trending synche. The massive sulfide layers at Red Mountain occur in a
proximal setting on the south limb of the antick, and occur in a sulfide-silica exhaIite which ranges up to 130 rn thick. An older,
southern horizon contains spbalerite and coarse pyrite in black chlorite schist. The WTF deposit occurs on the north limb of the
antifonn and consists of a thin blanket of fine-grained sulfides which are interpreted as having formed in a distal setting relative to
the vent. The WTF deposit contains an estimated 1.10 million tonnes @ng 0.15% Cu, 2.5% Pb, 7.9% Zn, 270 glt Ag, and 1.9
g/t Au. The deposits occur immediately below the Sheep Creek Member and above the Mystic Creek Member of the
Mississippian(?) Totatlanika Schist.
Delta District of Kuroko Masstve Sulfide DeposELr
The best-known kuroko massive sulfide deposits of the ALaska Range and Yukon-Tanana Upland metallogenic belt are
part of the Delta district in the eastern part of the Alaska Range (fig. 23). The district and large massive suEde deposits have been
described by several authors (Nauman and others, 1980; Lange and Nokleberg, 1984; C.R. Nauman and S.R. Newkirk, written
commun., 1984; Lange and others, 1990, 1993; Newberry and others, 1997a). The district comprises an area of about 1,000 km2.
The district contains about 26 deposits, many of which are sttatifom or transposed and some of which are replacement deposits
which occur along four regional trends. The deposits consist of varying amounts of pyrite, chalcopyrite, galena, spbale~ite, and
lesser malachite and bornite. The gangue minerals are mainly quartz, carbonate, and white mica Hydrothermal alteration consists
of chlorite, quartz, serici.te, pyrite, and Zn-Ag-Au sulfide mimds. The massive sulfides and adjacent disseminated sulfide layers
occur in zones which average 500 m long, 200 m wide, and 15 rn thick. The deposits are hosted in metamorpbd Devonian
spilite, andesite, and keratophyre suite, which initially formed in flows, W, and breccia, and in metamorphosedshallow- to deepmarine
sedimentary rocks; now mainly quartz schist, quartz-chlorite-feldspar schlSt, dc-schis1, and marble. The host rocks are
part of the extensive Devonian and Mississippian Yukon-Tmam terrane. Intruding the deposits are numerous tholeiitic greenstone
sills which are interpreted as Triassic(?) to Cretaceous(?). The largest deposit contains an estimated 18 million tonnes grading 0.3
to 0.7% Cu, 1 to 3% Pb, 3 to 6% Zn, 34 to 100 g/t Ag, 1 to 3.4 g/t Au.
Origin of and Tectonic Controls for Alaska Range and
Yukon-Tanana Upland Metallogenic Belt
The Alaska Range and Yukon-Tanana Upland metallogenic belt of kuroko massive sulfide d-its is hbskd in Devonian
metavolcanic and interlayered metasedimentcuy rocks of the swhem Yukon-Tanma ternme which which ia interpreted as a
fragment of metamorphosed Devonian and Mississippian continental-margin arc (Lange and others, 1990, 1993; Noklhg and
others, 1994c, 1997,2000). The metavolcanic rocks, which host most of the major base and precious metal depoeits, are derived
from a volcanic suite which varies in composition h m spilite to andndesite to keratophyre. Most studies of kwoko massive sulfide
deposits interpret a back-arc or arc-related rift origin for the deposits (Sawkins, 1990); however, in the eastera Alaska Range, the
lack of coeval mafic plutonic or volcanic rocks appears to preclude a rift origin. The Yukon-Tanana terrane in east-cenaal Alaska,
Southeastern Alaska, and the Canadian Cordillera, and tbe correlative Kootenay terrane in southern British Csluanbia are
interpreted to be fragments of the herein. informally named, Kootenay arc, a discontinuous Devonian continental-margin arc
which extended along the margin of the North American Cordillera from Arctic Alaska to Mfornia (Grma and others, 1991;
Rubin and others, 199 1 ; Mortmm, 1992; Plaiker and Berg, 1994; Noldeberg and others, 1994c, 1997~; Monger and Nokle-
1996; Nokleberg and others, 2000). Fragments of the Kootenay arc include several metallogenic bits which host kuroko d v e
sulfide and related depos~ts (Noklebetg and othus, 1997a, b, c): (I) The Arctic metallogenic belt in the &ldfi terrane in Arctic
Alaska; (2) the Frances Lake metallogenic belt (Murphy and Pierccy, 1999) in the Yukon-Tanam tenam in the southern Yukon
Territory; (3) the Tracey metallogenic belt in the Yukon-Tamma tenme in !hutheastern Alaska and westem British Coiumbia; and (4)
the Kootenay-Shuswap belt in the Kootenay terrane in the southern Canadian Cordillera
Dawson Metallogenic Bett of
Volcanogenic Pb-Zn-Cu Massive Sulfide and
SEDEX Pb-Cu-Zn-Ba Deposits (Belt DA)
Northwestern Yukon Territory
The Dawson metallogenic belt of volcanogenic Pb-Zn-Cu massive sulfide and SWEX Pb-Cu-Zh-Ba @CWC~$ is
located in the Yukon-Tanana terrane in the southern Yukon Territory (fig. 17; tables 2,3) (Noklebesg &nd others, 1997b, 1998).
Stratifonn massive sulfide occurrences exist in three sequences within the terrane. With more detajlkd stu*, ea6h of the thee
sequences and contained massive sulfide deposits might be designated as separate metallogenic belts.