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

Monger and Nokleberg, 1996; Nokleberg and others, 2000). The SEDEX deposits of the Gataga metallogenic belt are interpreted
as forming during a relatively brief period immediately after rifting (Paradis and others, 1998; this study). However, other
metallogenic belts containing Devonian-Mississippian SEDEX deposits are interpreted as forming over a longer age range, from
Frasnian (early Late Devonian) at Macmillan Pass to Tournasian (Early Mississippian) in the Cassiar terrane.
Robb Lake Metallogenic Belt of
Southeast Missouri Zn-Pb Deposits (Belt RL)
Northern British Columbia
The Robb Lake metallogenic belt of Southeast Missouri Zn-Pb deposits occurs in northern British Columbia (fig. 17;
tables 3. 4) (Nokleberg and others, 1997b, 1998; Nelson and others, 2002) and is hosted in the Proterozoic to Devonian passive
continental units of the Rocky Mountains which constitute part of North American Craton Margin. The Southeast Missouri Pb-Zn
deposits in the Robb Lake metallogenic belt occur in secondary breccias of either solution or tectonic origin in folded dolostones
mainly of the Silurian and Devonian Muncho-McConnel Formation (Taylor and others, 1975; Nelson and othes, 2002).
Occurrences also are located in the underlying Silurian Wokkpash and overlying Devonian Stone,Dunedin, Pine Point, and Slave
Point Formations (Macqueen and Thompson, 1978; Nelson and others, 1999; Paradis and others, 1999). The significant deposit is
at Robb Lake.
Robb Lake Southeast Missouri Zn-Pb Deposits
The Robb Lake deposit consists of sphalerite, galena and pyrite which occur primarily in tabular and lenticular zones
parallel to bedding in dolomite collapse breccias of the Silurian and Devonian Muncho-McConnel Formation (EMR Canada,
1989; Dawson and others, 1991; Mining Review, 1992; Nelson and others, 2002). The deposit occurs on the west limb and crest
of a large south plunging anticline. The deposit occurs in an 8 krn' area, and consists of a series of interconnected, bedding-
parallel and crosscutting breccia bodies with a matrix of dolomite, sphalerite, galena, pyrite, quartz, calcite, and pyrobitumen, and
peripheral veins and stockwork. (Nelson and others, 2002). Estimated reserves are 7.1 million tonnes grading 4.7% Zn and 1.5%
Pb (Mining Review, summer, 2000). A significantly larger. but less defined resource for the district and belt is an estimated 20.1
million tonnes grading 5.1% combined Pb and Zn (Dawson and others, 1991).
Origin of and Tectonic Controls for
Robb Lake Metallogenic Belt
The southern part of the Robb Lake metallogenic belt occurs along a Devonian carbonate facies front in shales of the
Besa River Formation to the west for 250 km, extending from Mount: Burden on the south to the CTV and DODO deposits near
Tuchodi Lakes on the north. The stratigraphic setting for these occurrences, that consists of a carbonate front adjacent to the major
Great Slave Lake basin, is interpreted as analogous to that at Pine Polnt (Nelson, 1991). Some occurrences in the northern part of
the Robb Lake metallogenic belt contains fluorite, barite, and pyrobitumen and are poor in sphalerite, galena, and pyrite. This
feature suggests continuity with the southern end of the Liard metallogenic belt of Southeast Missouri Ba-F deposits which occurs
in similar Devonian host rocks (Nelson and others, 2002). The timing of mineralization is poorly constrained, but is interpreted as
pre-early Tertiary (pre-Laramide) on the basis of rotated geopetal structures (Manns, 198 1) or as Devonian or Missippian on the
basis of isotopic studies (Nelson and others, 2002).
The Robb Lake metallogenic belt exhibits characteristics similar to the Liard metallogenic belt of Southeast Missouri(?)
Ba-F deposits (described above), and to the Gataga Lake metallogenic belt of SEDEX deposit (described above). Sulphur isotope
analyses exhibit heavy values for barite in all three metallogenic belts (K.M. Dawson, unpublished data, 1995). These data and a
similar geologic setting suggest a genetic relation between the two deposit types and three metallogenic belts. A similar rifting
origin is interpreted for all three metallogenic belts. A major period of Late Devonian and Early Mississippian rifting along the
North American Craton Margin is interpreted with rifting away of the Yukon-Tanana and Kootenay continental margin terranes
and formation of the Robb Lake and coeval metallogenic belts (Nokleberg and others, 1994c, 1997c; Monger and Nokleberg,
1996; Nokleberg and others, 2000). Nelson and others (2002) propose a somewhat contrasting interpretation of back-arc and intra-
arc spreading, and exhalative activity for the genesis of the Robb Lake and related, coeval metallogenic belts. This back-arc and
intra-arc spreading would be coeval with the slightly older Kootenary arc as interpreted by Nokleberg and others (2000).
lngenika Metallogenic Belt of Southeast
Missouri Zn-Pb-Ag-Ba Deposits, and
Manto Zn-Pb-Ag Deposits (Belt IN)
Northern British Columbia
The Ingenika metallogenic belt of Southeast Missouri Zn-Pb-Ag-Ba deposits and manto Zn-Pb-Ag deposits occurs in
central British Columbia. The belt is hosted jn Late Proterozoic to Devonian carbonate-dominated strata of the proximal
pericratonic Cassiar terrane (fig. 17; tables 2, 3) (Nokleberg and others, 1997b, 1998). The significant deposits are in the Wasi
Lake area at Susie, Beveley, and Regent.