USGS Professional Paper 1697 - Alaska Resources Library

etrograde minnesotaite (Fe talc), Fe-, Mn-, and Mg-carbonate,
chlorite, calcite, and quartz. A K-Ar isotopic age of 59 Ma for
vein muscovite that cuts a gabbro dyke indicates an Eocene
age of mineralization for the Riondel deposit and possibly
for the district (Beaudoin and others, 1992). The mine at the
deposit attained the largest production from a Canadian Zn-
Pb-Ag skarn mine. Between 1895 and 1971 estimated production
was 4.82 million tonnes of ore, and estimated reserves are
0.35 million tonnes grading 6.3 percent Zn, 5.2 percent Pb,
and 45 g/t Ag.
Highland Bell (Beaverdell) Ag-Polymetallic Vein Deposit
The Highland Bell (Beaverdell) Ag-polymetallic vein
deposit consists of sphalerite, pyrite, galena, arsenopyrite,
chalcopyrite, and minor pyrargarite in quartz-calcite veins that
occur along a northeast-trending, 3 km by 800 m belt on the
west slope of Mt. Wallace (Watson and others, 1982; MIN-
FILE, 2002). The deposit was notably rich in Ag, and the mine
at the deposit had the longest continuous operating life of any
mine in British Columbia. Between 1901 and 1992, estimated
production was 941,644 tonnes grading 1,060 g/t Ag, 1.14 percent
Pb, and 1.37 percent Zn. The majority of the production
(1,166 tonnes of Ag) was from the upper and lower Lass vein
systems, which occur in Jurassic granodiorite and adjacent
turbiditic clastic and pyroclastic rocks of the Permian Wallace
Formation. However, the Highland Bell deposit is interpreted
as forming during intrusion of the Eocene quartz monzonitic
Beaverdell stock that has a K-Ar isotopic age of 50 Ma (Christopher,
1975; Watson and others, 1982).
Carmi Moly Porphyry Mo-Cu (U-F) Deposit
The Carmi Moly porphyry Mo-Cu (U-F) deposit consists
of molybdenite and chalcopyrite that are disseminated in
brecciated Early Jurassic granodiorite that was intruded by a
Mohican Formation
(Lower Cambrian)
Badshot Formation
(Lower Cambrian)
(lower 50 ft)
Index Formation
(Middle Cambrian)
Comfort Ore
Zone
Contact
Orebody
Late Cretaceous and Early Tertiary Metallogenic Belts (84 to 52 Ma) (figs. 102, 103) 261
Quartzite-mica schist
Bluebell Ore
Zone
~1,700 m
alkalic to calc-alkalic Eocene quartz monzonite porphyry Beaverdell
stock with a K-Ar isotopic age of 50 Ma (Eocene) that
also contains part of the deposit (Dawson and others, 1991;
MINFILE, 2002). The deposit occurs in a 2-km-diameter
annular-shaped pyrite zone. The stock is part of the Coryell
Plutonic Suite. Estimated reserves are 44.5 million tonnes
grading 0.13 percent Mo.
Lassie Lake and Hydraulic Lake Paleoplacer U Deposits
The Lassie Lake and Hydraulic Lake paleoplacer U
deposits consist of autunite and saleeite that occur in paleostream
channels in Paleogene continental sedimentary rocks
or basins that overly quartz monzonite of Cretaceous Valhalla
pluton, which is part of the alkaline Coryell Plutonic Suite
and calc-alkalic plutons of the Okanagan composite batholith
underlie the paleoplacer U deposits. (Sawyer and others, 1981;
MINFILE, 2002). Secondary U minerals, autunite and saleeite,
derived from underlying uraniferous quartz monzonite of the
Cretaceous Valhalla pluton, are concentrated in early Tertiary
paleochannel sediments where oxidation was retarded by
a capping of plateau basalt of the Pliocene Chilcotin Group.
Estimated reserves are 2.1 million tonnes containing 4,000
tonnes of U and grading 0.227 percent U3O8 (Bell, 1991;
Sawyer and others, 1981). The uranium minerals occur in
oxidized facies of coarse-grained fluvial sedimentary rocks
and in disseminated organic material in reduced, fine-grained
sedimentary rocks.
Origin of and Tectonic Controls for Nelson Metallogenic Belt
The Nelson metallogenic belt contains a wide variety of
Ag polymetallic vein, Ag-Pb-Zn manto, Au-Ag epithermal
vein, porphyry Mo, paleoplacer U, and related deposits (tables
3, 4). Some deposits occur to the east, in or near the Middle
Jurassic Nelson Batholith, which is part of the Nelson plutonic
Bluebell Limestone
Kootenay Chief
Ore Zone
Upper Limestone
~700 m
Quartzite-mica schist
(+ pegmatite)
Figure 122. Bluebell (Riondel) Zn-Pb-Ag skarn and manto deposit, Nelson metallogenic belt, Canadian Cordillera.
Schematic block diagram. Host Bluebell limestone occupies western limb of a north-trending antiform. Adapted from
Hoy (1980) and Dawson (1996a). See figure 103 and table 4 for location.
~100 m