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

Mastadon SEDEX Pb-Zn(?) Deposit
The Mastadon SEDEX Pb-Zn (?) deposit consists of pyrite, arsenopyrite, sphalerite, galena and sulfosalts which occur in
bands, lenses and stringers from 0.1 to 12 meters wide (Mining Review, 1992). The hanging wall part of deposit consists of
disseminated sphalerite, galena and pyrite; footwall part of deposit consists of massive arsenopyrite, sphalerite and pyrite. Ore
minerals are concentrated along the contact between phyllite and limestone. Au is refractory and associated with arsenopyrite. The
deposit contains estimated production and reserves of 12.27 million tonnes grading 4.9% Zn, 2.3% Pb, and 62 g/t Au. The deposit
is hooted in Early Cambrian Hamill Formation quartzite and Badshot Formation with limestone forming the footwall. The deposit
origin is poorly understood.
Jersey SEDEX Pb-Zn Deposit
The Jersey deposit consists of fine grained sphalerite and galena with pyrite, pyrrhotite and minor arsenopyrik in five ore
bands ranging from 0.30 to 9 meters thick (Fyles and Hewlett, 1959; Sangster, 1986; Maclntyre, 1991). Sulfides occur more
abundantly in fold troughs relative to fold crests. Cd is associated with sphalerite, Ag with galena. The deposit bas produced 7.7
million tonnes grading 3.49% Zn, 1.65% Pb, 3.08 g/t Ag. The deposit is hosted in the folded Reeves Member dolomite of the
Early Cambrian Laib Formation, and may be a SEDEX Pb-Zn deposit.
H. B. (Zincton) Pb-Zn SEDEX Deposit
The H.B. (Zincton) Pb-Zn SEDEX deposit consists of pyrite and sphalerite which occur in narrow bands, irregular lenses
or disseminations in dolomite of the Early Cambrian Reeves Formation (Sangster, 1986; MacIntyre, 1991; Hoy, 1982b; MINFLLE,
2002). Local cross-zones contain fine-grained massive sulfides which commonly occur as matrix in a coarse breccia. Tbe breccia
zones are related lo thrust faults and are interpreted as secondary structures. Much of the dolomite in the West orebody is altered
to talc The dcposlt has produced 6.7 rnillion tonnes grading 3.91% Zn, 0.74% Pb, 4.42 g/t Ag.
Origin of and Teotvnic Setting for
Komnay ldetallogenic Belt
The Kootenay metallogtnic belt of Zn-Pb SEDEX deposits is hosted in platformal, Early Cambrian carbcmate rocks in the
Kootenay metamorphosed continental margi.n terrane. The deposits commonly consist of bands and lenses of rphderite, galena
and pyrite both conformable and discordant 10 often isoclinally folded and regionally metamcuphosed dolostone of the Badshat,
Reeves and Laib formations. Mong with their host rocks, these deposits were deformed prior to deposition of uncdormably
overlying strata of the Carboniferous Milford Assemblage (Monger and others, 1991). The age of the carbonate-hosed deposits is
not hown with certainty, and may be either SEDEX, or highly-deformed replacement deposits in Ea~ly Cgmbrian carbonate rock.
The mineral msemblagu, host rock age, and geologic setting for the Kootenay metallogenic belt are similar to those for the Anvil
and Howards Pass metallogenic belts of the northern Canadian Cordillera as described above. All three belts are interpreted as
fofilling from Pb- and Zn-rich fluids resulting during rifting, volcanism, basinal subsidence, bcal marine trulsgrcssion, and related
hydrothermal activity aloag the passive continental margin of the North American Craton. Episodic rifling in the Cambrian
through Ordovician is interpretd as opening several sedimentary basins in the Canadian Cordillera, such as the Selwyn Basin,
with related formation of Zn-Pb SSEDEX deposits which are similar to those in the Kootenay metallogenic belt.
Prtnce of Wales Island Metallogenio Belt of
Coniinental-Margin ArcRelated Deposits (Belt PW)
Southeastern Naska
The Prince of Wales Island metallogenic belt occurs in Southeastern Alaska and consists mainly of a suite &porphyry
Cu-Mo, polyrnelallic vein, and skarn deposits (fig. 3; tables 3,4) which occur mainly in alkalic Orodovian and Silurian piutons in
the Alexander sequence of the Wrdngellia superterrane. The deposits and metallogenic belt occw on central and southeno Prince
of Wales Island, and to a much lesser extent on Chichagof, Annette, and Gravina Islands in central- southeastern Alaska
(Nokleberg and others, 199%). These alkalic plutons range in age from Late Ordovician to EarIy Silurian. The plutans intrude the
meramorphosed Devonian(?) St. Joseph Island Volcanics (Eberlein and others, 1983; D.A. Brew, oral ccrmmun., 1995), Early and
Middle(?) Devonian Karheen Formation (Gehrels, 1992; D.A. Brew, oral commun., 1995), Middle to Late Ordovician to Early
Silurian Descon Formtion (Herreid and others, 1978; D.A. Brew, oral commun., 1995), and metamorphosed Latc Proterozoic and
Early Cambrian(?) Wales Group (Gehrels and Berg, 1992; D.A. Brew, oral commun., 1995). The plutons and rnetasedimentary
rocks form the older pail of the Alexander sequence in the region. The major granitic-magmatism-related deposits are represenlad
by deposits in four areas: (1) several deposits in the McLean Arm porphyry Cu-Mo district; (2) the Klaka Inlet plymetallic skun
and vein +sit; (3) the Kassan Peninsula Cu-Fe skarn deposit; and (4) the major zoned mafic-ultramafic Cu-Au-PGE depoail at
Salt Chuck (table 4) (Nokleberg and others 1997a, b, 1998).