USGS Professional Paper 1697 - Alaska Resources Library

mafic and felsic metavolcanic rocks and associated carbonate,
pelitic, and graphitic metasedimentary rocks of the Devonian
and Mississippian Ambler sequence (Hitzman and others,
1982, 1986; Newberry and others, 1997) that forms part of
the informally named Ambler schist belt or Coldfoot metamorphosed
continental margin terrane of the southern Brooks
Range (Moore and others, 1992; Nokleberg and others,
1994c, 1997c). On the basis of local bimodal volcanic rocks,
a back-arc rift environment is interpreted by some workers in
the southern Brooks Range belt for the origin of kuroko massive
sulfide deposits and host rocks (Hitzman, 1986; Newberry
and others, 1997; Schmidt, 1986; Moore and others,
1994; Goldfarb, 1997). However, this belt shares many characteristics
with the broadly coeval Eastern Alaska Range belt
of kuroko massive sulfide deposits, described below, which is
interpreted as forming in a submerged continental-margin arc
environment (Lange and others, 1993). In addition, regional
tectonic analyses interpret the Devonian submarine and
associated volcanic rocks of the southern Brooks Range and
the belt of Devonian granitoid plutons, which occur along the
southern flank of the Brooks Range, are part of a discontinuous
Devonian continental-margin arc that extended along the
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Aurora Mountain
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Gabbro (Tertiary and
Cretaceous)
Angayucharn metabasalt
(Jurassic to Devonian)
Beaver Creek phyllite
(Devonian?)
Bornite carbonate
sequence (Devonian
and Silurian)
Anirak (pelitic) schist
(Devonian?)
Hydrothermal dolostone
Middle and Late Devonian Metallogenic Belts (387 to 360 Ma; figures 16, 17) 47
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Pardners Hill
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margin of the North American Cordillera (Rubin and others,
1991; Plafker and Berg, 1994; Goldfarb, 1997; Nokleberg and
others, 2000). The Arctic metallogenic belt is herein interpreted
as forming in the back-arc of the same continentalmargin
arc in which formed the Brooks Range metallogenic
belt of granitic magmatism deposits, described below (fig.
17). With this interpretation, the SEDEX deposits formed
later in the Late Mississippian and Early Pennsylvanian and
in a distinctly different tectonic environment. This interpretation
differs from Goldfarb (1997) who interprets that the
Arctic metallogenic belt as forming during a long-protracted,
100-m.y.-long event that included formation of SEDEX zinclead
deposits in the Northwestern Brooks Range metallogenic
belt (described below).
Brooks Range (Chandalar) Metallogenic Belt of
Granitic Magmatism Deposits (Belt BR) Northern
Alaska
The Brooks Range metallogenic belt of granitic magmatism
deposits (fig. 17; tables 3, 4), mainly porphyry, polyme-
Strike and dip
Contact
Fault
0 1 2 km
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Ruby Creek
Figure 22. Ruby Creek (Bornite) Kipushi Cu-Pb-Zn deposit and related deposits, Cosmos Hills area, Arctic
metallogenic belt, northern Alaska. Schematic geologic map. Except where noted, all faults are downthrown
to the east. Adapted from Hitzman (1986) and Schmidt (1997). See figure 17 and table 4 for location.
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