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

segregations of hematite, magnetite, and pyrolusite, interpreted as volcanogenic(?) Fe and Mn deposits (American, Bear, Cub,
Monarch) which are hosted in calc-schist and marble.
Aurora Creek Massive Sulfide-Barite Deposit
The Aurora Creek massive sulfide-barite deposit (Herreid, 1968, 1970; Bundtzen and others, 1994, 1995; Schmidt,
1997b) consists of disseminated to massive sphalerite, galena, barite, pyrite, magnetite, and minor chalcopyrite in muscovitefeldspar
metavolcanic schist of Aurora Creek sequence, which is pad of the Late Proterozoic and early Paleozoic Nome Group.
Sulfide minerals occur for 2,400 m along strike. Significant dolomite formation is interpreted to have accompanied sulfide
deposition. The deposit has been explored by with limited drill cores and trenches. lntense alteration to toi~rmaline occurs in
feldspar-rich metavolcanic schists near massive sulfides and barite occurrences. Limited sulfur isotopic analyses indicate which
heavy sulfur probably formed in a seawater-contaminated, marine volcanogenic setting. Lead isotope analyses from the Aurora
Creek, Quarry, and Rocky Mountain Creek suggest either a kuroko massive sulfide and SEDEX deposit type (Bundtzen and
others, 1995). One zone in one drill core contains an average of 15.9% Zn, 1.38% Pb, 0.07 % Cu, 35% Ba, 2.6 g/t Au, 45 glt Ag.
Similar, but smaller occurrences are located at the Nelson, Rocky Mountain Creek, and Quarry prospects. The Aurora Creek and
nearby deposits are interpreted as similar to the Ansil mine and related deposits in the Noranda area of Quebec.
Origin of and Tectonic Controls for
Sinuk River Metallogenic Belt
The Sinuk River metallogenic belt, which contains the Aurora Creek, Quarry, Nelson, and Rocky Mountain Creek Zn-
Pb-barite-Ag deposits, is hosted in the Aurora Creek sequence of the Nome Group (Bundtzen and others, 1994; Schmidt, 1997b).
The Monarch, Quany, American, and Cub Bear Fe-Mn deposits are hosted in the overlying Mount Distan sequence. New U-Pb
zircon isotopic ages of 675 and 68 1 Ma were obtained from orthogneiss which intrudes the Mount Distan sequence (T.K.
Bundtzen, this study). This relation suggests which both the stratiform massive sulfide-barite and stratabound Fe and Mn deposits
of the Sinik River metallogenic belt are probably of Late Proterozoic or older age (Bundtzen and others, 1994, 1995; Patrick and
McClelland, 1995). Sulfur isotopic analyses of sulfides from the massive sulfide-barite deposits suggest formation in a seawater-
contaminated, marine volcanogenic rift(?) environment. The Aurora Creek sequence and the hosting Nome Group are part of the
Seward metamorphosed continental margin terrane that is interpreted as part of the North American Continental Margin
(Nokleberg and others, 2000). The Sinuk River metallogenic belt is interpreted as forming during marine volcanogenic rifting(?)
of the North American Continental Margin.
Gillespie Metallogenic Belt of
SEDEX Zn-Cu-Pb-Au-Ag Deposits
(Belt GM) Northern Yukon Territory
The Gillespie metallogenic belt of SEDEX Zn-Cu-Pb-Au-Ag deposits occurs in the northern Yukon Territory (fig. 3;
tables 3,4) (Nokleberg and others, 1997b, 1998). The belt is hosted in the Gillespie Lake Group which is the uppermost unit of
the Early Proterozoic Wernecke Supergroup of the North American Craton margin. The group is about 1 krn thick and consists
mainly of dolostones and dolomitic clastic rocks (Mustard and others, 1990). The major SEDEX occurrences are Blende in the
eastern Ogilvie Mountains, and Hart River.
Blende SEDEX Zn-Cu-Pb-Au-Ag Deposit
The East and West Zones of the Blende deposlt consist primarily of galena, sphalerite and pyrite, with lesser chalcopyrite
and tetrahedrite, in vein and breccia zones with siderite-dolomite-quartz gangue (NDU Resources, press release, 1993; Robinson
and Godwin, 1995). The deposit contains an estimated resource of 19.6 million tonnes grading 3.04% Zn, 2.81% Pb, 1.6% Cu, 56
g/t Ag, and 2.75 g/t Au. Ore horizons extend over 700 m vertically and 6 krn along strike along a structural zone of shears and
breccia. The mineralization is multistage. The deposits are hosted in stromatolite-bearing dolostone of the Middle Proterozoic
Gillespie Lake Group in the Wernecke Supergroup. Stocks, plugs, and dlkes of hornblende gabbro intrude the dolostone and
appear to be associated with mineralization (Robinson and Godwin, 1995).
Hart River SEDEX Zn-Cu-Ag Deposit
The Hart River SEDEX Zn-Cu-Ag deposit consists of pyrite and pyrrhotite and minor sphalerite, galena and tetrahedrite
which occur as a tabular mass along a facies change from dolomite to calcareous black argillite of the Early Proterozoic Gillespie
Lake Group (EMR Canada, 1989; Maclntyre, 1991). The host rocks are cut by numerous diabase sills and dikes which
metamorphose the dolomite to serpentinite-talc and the argillite to hornfels. The footwall is silicified and contains a stockwork of
sulfide veinlets, whereas the hanging wall contains thinly layered sulfides. The deposit has estimated reserves of 1.1 million
tonnes grading 3.6% Zn, 1.45% Cu, 0.9% Pb, 49.7 g/t Ag, and 1.4 git Au (MacIntyre, 1991; Abbott and others, 1994).