USGS Professional Paper 1697 - Alaska Resources Library

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210 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera parts, an older, mid-Cretaceous part, described and interpreted herein, and a younger Late Cretaceous and early Tertiary part, described in a subsequent section. The mid-Cretaceous part contains a wide variety of granitoid-related Au, Sb-Au vein, Pb-Ag-Zn-Au polymetallic vein, and W-Au skarn deposits (table 4). The East-Central Alaska belt is hosted mainly by mid Cretaceous granitoid rocks in the Yukon-Tanana Upland (Miller, 1994; McCoy and others, 1997), which are part of the Yukon-Tanana igneous belt (Moll-Stalcup, 1994). Recently, the name was described in a series of papers in the volume edited by Tucker and Smith (2000). However, their usage was for both granitoid-related Au deposits and occurrences in the East-Central Alaska metallogenic belt and in the correlative Tombstone metallogenic belt that is described above. Three major groups of deposits occur in the East-Central Alaska metallogenic belt (table 4): (1) In the north-central part of the belt, in the Manley and Livengood area, the significant lode deposits are a Pb-Ag-Zn-Au polymetallic vein deposit at Hot Springs Dome (mid-Cretaceous?), an Sb-Au vein deposit at Sawtooth Mountain (mid-Cretaceous), and Sb-Au and Au quartz vein deposits at Gertrude Creek, Griffen, and Ruth Creek (table 4) (Nokleberg and others 1997a,b, 1998). (2) In the central part of the belt are a variety of granitoid-related deposits in the Fairbanks area. (3) In the southern part of the belt are polymetallic and Sb-Au vein deposits in the Kantishna area in the northern Alaska Range (Bundtzen, 1981; McCoy and others, 1997). Described below are the major granitoidrelated deposits at Fort Knox, Democrat, and Pogo, in the Fairbanks area, and vein deposits in the Kantishna district. The Fairbanks area is underlain by multiply metamorphosed and penetratively deformed, middle Paleozoic and older quartzmetasedimentary, sparse metavolcanic, and rare metagranitoid rocks of the Yukon-Tanana continental-margin terrane (Nokleberg and others, 1994c, 1997c). The characteristics and origin of the mid-Cretaceous granitoid-related Au deposits in this area are described by McCoy and others (1997). S N 0 60 m Fairbanks Area In the eastern and southern parts of the belt in the Fairbanks area, a wide variety of granitoid-related deposits (table 4) are spatially associated with mid-Cretaceous plutons. These deposits are (1) Sb-Au vein deposits at Dempsey Pup and Scrafford, (2) a Sn polymetallic vein deposit at Table Mountain, (3) polymetallic vein deposits at Cleary Summit, Ester Dome (Ryan Lode), Democrat (Mitchell Lode), Blue Lead, Tibbs Creek, and Gray Lead, (4) a major granitoid-related Au deposit at Fort Knox, (5) a high-grade, granitoid-related Au quartz vein deposit at Pogo, and (6) an Au-As vein deposit at Miller House. The deposits at Scrafford, Cleary Summit, Gilmore Dome, Ester Dome, and Democrat are in the Fairbanks district. Fort Knox Granitoid-Related Au Deposit The Fort Knox granitoid-related Au deposit (fig. 99) (Blum, 1985; Robinson and others, 1990; A.A. Bakke, written commun., 1991; Bakke, 1995; Hollister, 1992, McCoy and others, 1997) occurs northeast of Fairbanks and consists of free gold, bismuthinite, and minor to trace molybdenite and chalcopyrite that occur in a sulfide-poor, quartz vein stockwork in the Fort Knox (porphyritic granodiorite) pluton. The stockwork is preferentially emplaced along a steeply dipping fracture system that trends 290°. The deposit is at least 1,500 m long by 300 m wide and 250 m deep and contains an estimated reserve of 186.5 million tonnes grading 1.6 g/t Au (Bakke, 1995, 2000). The gold is remarkably pure (greater than or equal to 980 fine). The Fort Knox pluton is alkali-calcic and peraluminous. Mineralization is interpreted to have occurred either during the late stages of emplacement of the nearby Gilmore Dome stock, which has a K-Ar biotite age of 92 Ma (McCoy and others, 1997). However, a younger, early Tertiary heating event that post-dates the older porphyry Mo-Bi-Cu-mineralization may have also introduced Au (Bakke, 1995). Coarse-grained granite Medium-grained granite Fine-grained granite Schist and quartzite Contact Late Cretaceous Devonian or older Shear zone showing sericite halos Pegmatite/aplite showing mostly feldspar halos Stockwork veining showing feldspar-quartz and/or white mica quartz halos Figure 99. Fort Knox granitoid-related Au deposit, east-central Alaska metallogenic belt, east-central Alaska. Schematic cross section looking west. Adapted from Bakke (1994). See figure 80 and table 4 for location.
Democrat (Mitchell Lode) Granitoid-Related Au Deposit The Democrat (Mitchell Lode) granitoid-related Au deposit (fig. 100) (Bundtzen and Reger, 1977; T.K. Bundtzen and R.B. Forbes, written commun., 1990) occurs in the Richardson district south of Fairbanks, and consists of disseminated and stockwork tetrahedrite, galena, acanthite, owyheeite, RL See inset map below 50 0 2 km Tanana Shaft River 10 53 Democrat Lode 0 30 m RL 28 Early Late Cretaceous Metallogenic Belts (100 to 84 Ma; figs. 79, 80) 211 Tenderfoot other Ag-sulfosalts, free gold, and quartz in a hydrothermally altered granite porphyry. A strong sericite alteration halo surrounds the porphyry, which intrudes sillimanite-bearing metasedimentary schists of the Yukon-Tanana terrane. The granite porphyry has a K-Ar biotite age of 89.1 Ma and is part of a 35-km-long sill complex that intruded along the Creek RL 10 Undifferentiated bedrock (Unmapped orcovered) Stream alluvium and alluvialcolluvial deposits Epidote-hornblende skarn Granite porphyry sill (Late Cretaceous) Granite and granodiorite gneiss (Devonian?) Garnet biotite muscovite schist and meta-felsite (greenschist facies) Sillimanite bearing schist and gneiss (amphibolite facies) Silicified zone (silicic with Ag/Au pods)alteration Argillic alteration Sericite alteration with Mn patina Potassic alteration High angle fault or prominant linear feature 'Richardson Lineament' / fault Placer mine tailings Edge of open pit or mine cut Foliation Caved portal with timbers Figure 100. Democrat granitoid-related Au deposit, east-central Alaska metallogenic belt, east-central Alaska. A, Schematic geologic map of part of surrounding Richardson district. B, Schematic geologic map of Democrat deposit. Adapted from Bundtzen and Reger (1977), T.K. Bundtzen (written comm., 1989), and Nokleberg and others (1995). See figure 80 and table 4 for location.
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USGS Prepared in collaboration with
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U.S. Department of the Interior Gal
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iv Hart River SEDEX Zn-Cu-Ag Deposi
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vi Specific Events for Middle Throu
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viii Metallogenic Belts Formed Duri
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x Origin of and Tectonic Controls f
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xii Toodoggone Metallogenic Belt of
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xiv Slate Creek Serpentinite-Hosted
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xvi Left Omolon Belt of Porphyry Mo
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xviii Origin of and Tectonic Contro
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xx Chukotka Metallogenic Belt of Au
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xxii Plutonic Rocks Hosting East-Ce
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xxiv Skeena Metallogenic Belt of Po
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xxvi Bee Creek Porphyry Cu Deposit
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xxviii 36. Wellgreen gabbroic Ni-Cu
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xxx 87. Partizanskoe Pb-Zn skarn de
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Metallogenesis and Tectonics of the
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format (Nokleberg and others, 1996)
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logenesis of the region (1) subduct
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Subterrane—A fault-bounded unit w
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dilemma consists of two conflicting
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2 to 20 m thick. A related dolomite
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Lantarsky-Dzhugdzhur Metallogenic B
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Origin of and Tectonic Controls for
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Metallogenic Belts Formed During Pr
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as at Oz, Monster, and Tart, may al
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Monashee Metallogenic Belt of Sedim
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Clark Range Metallogenic Belt of Se
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in addition to the Fe deposits. Min
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study) consists of lenses, from 100
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Omulev Austrian Alps W Deposit The
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ock, including coarse clastic rock,
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lative metalliferous brines in a re
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Prince of Wales Island Metallogenic
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suite of deposits and host rocks ar
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margin of the North American Craton
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newly created terranes migrated int
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(Ryazantzeva and Shurko, 1992). The
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tonnes Au and an average grade of a
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mafic and felsic metavolcanic rocks
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intrusion from about 402 to 366 Ma
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mentary rocks of the Cambrian to De
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(Preto and Schiarizza, 1985; Schiar
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ate and clastic rocks and volcanicl
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(Nokleberg and others, 1994c, 1997c
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Berezovka River Metallogenic Belt o
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Finlayson Lake Metallogenic Belt of
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and barite in siliceous black turbi
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Windermere Creek (Western Gypsum) C
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(NX, DL, MY), Viliga (VL), and Zolo
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South of the main east-west-trendin
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ated subduction zone in the Wrangel
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icite-biotite-quartz bodies in frac
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Canada Cordillera. The granitoid ro
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Viliga (VL) passive continental-mar
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32; tables 3, 4) occurs along the n
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superterrane, consists mainly of ma
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ers, 1994c, 1997c). In southern Bri
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mental volcanic rocks of intermedia
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a resource of 34.3 million tonnes o
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potassic zone. Combined estimated p
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and quartz monzodiorite stock and s
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and Omolon (OM) cratonal terranes,
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in volcanic and volcaniclastic rock
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minor calcite, and sporadic pyrite
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supergene blanket are interpreted a
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deposits and occurrences consist of
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onto the Omulevka terrane to form t
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superterrane. This belt is interpre
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to form along the leading edge of t
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quartz, and is virtually not associ
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deposits are at Terrassnoe and Kuna
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Peschanka Porphyry Cu-Mo Deposit Th
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The belt is hosted in the Late Jura
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in a island arc that was tectonical
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and Early Cretaceous Koyukuk island
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The deposit consists of disseminate
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The Orange Hill deposit contains an
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49; tables 3, 4) (Foley and others,
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locally Late Triassic marine volcan
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gold in a gangue of quartz, calcite
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Verkhoyansk granite belt, which int
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metallogenic belts are interpreted
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assemblages, which may have been mo
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during hypogene and supergene alter
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collision and regional thrusting, t
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Yur Au Quartz Vein Deposit The smal
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phase has a Rb-Sr isotopic age of 1
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sian Northeast. The belt is hosted
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Host Granitoid Rocks and Associated
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that are up to 600-1,500 m long, av
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Metallogenic Belts Formed During La
Page 191 and 192: y partly coeval plutons that range
Page 193 and 194: tion is interpreted as occuring by
Page 195 and 196: the Badzhal-Ezop and Khingan parts
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Page 199 and 200: as interpreted for the Rock Creek d
Page 201 and 202: source (Yeo, 1992). The Blow River
Page 203 and 204: 2000). The spatial location of the
Page 205 and 206: to the east in the central Yukon Te
Page 207 and 208: occur in a 30-km-long belt along ir
Page 209 and 210: The Emerald deposit has produced ap
Page 211 and 212: Metallogenic-Tectonic Model for Ear
Page 213 and 214: cham oceans were closed, and the Ch
Page 215 and 216: greisenized Mesozoic granite that i
Page 217 and 218: composition magmatic bodies (with a
Page 219 and 220: Origin of and Tectonic Controls for
Page 221 and 222: to Albian pelecypods (Nokleberg and
Page 223 and 224: quartz-arsenopyrite-pyrrhotite, pol
Page 225 and 226: thermally altered to siliceous and
Page 227 and 228: These ore bodies are as much as 1 m
Page 229 and 230: Eastern Asia-Arctic Metallogenic Be
Page 231 and 232: Demin, and Krasilnikov, 1974; Nekra
Page 233 and 234: 10 percent Cu, as much as 0.92 perc
Page 235 and 236: pyrite, pyrite, galena, sphalerite,
Page 237 and 238: content decreases with depth, as do
Page 239 and 240: azdelnoye, (2) porphyry Sn deposits
Page 241: Karalveem Au Quartz Vein Deposit Th
Page 245 and 246: with high-temperature and high-pres
Page 247 and 248: chalcocite and covellite and also h
Page 249 and 250: cum-North Pacific, (2) completion o
Page 251 and 252: (6) In the Paleocene (about 56 to 6
Page 253 and 254: sists of cinnabar and metacinnabari
Page 255 and 256: Eastern Asia-Arctic Metallogenic Be
Page 257 and 258: groups of deposits are interpreted
Page 259 and 260: Indian Mountain and Purcell Mountai
Page 261 and 262: and southeastern Alaska (Moll and P
Page 263 and 264: Nokleberg and others, 1995a; Bundtz
Page 265 and 266: g/t Au or 368.2 Au gold. The deposi
Page 267 and 268: wim Group and altered mafic dikes.
Page 269 and 270: Mount Nansen porphyry Cu-Mo deposit
Page 271 and 272: A Map 450 500 550 Cross section Dik
Page 273 and 274: Cretaceous and early Tertiary conti
Page 275 and 276: deposits, at Chichagoff and Hirst-C
Page 277 and 278: others, 1994c, 1997c). The signific
Page 279 and 280: tonnes grading 0.53 percent Ni, 0.3
Page 281 and 282: with a 0.25 percent cut-off. The de
Page 283 and 284: Bulkley Metallogenic Belt of Porphy
Page 285 and 286: Red Rose W-Au-Cu-Ag Polymetallic Ve
Page 287 and 288: ish Columbia and consists of severa
Page 289 and 290: during back-arc extension or transt
Page 291 and 292: stocks and dikes, is associated wit
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etrograde minnesotaite (Fe talc), F
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Specific Events for Early to Middle
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of fractured and faulted Permian-Tr
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sists of a mineralized fracture zon
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dolomite. Wall rock alteration incl
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elt of late Tertiary plutons that a
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plates that exhibit magnetic anomal
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stages (Petrenko, 1999): (1) In the
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mon. The deposit is of medium size
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Metallogenic-Tectonic Model for Lat
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The origin of the Hg deposits of th
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margin or island-arc tectonic envir
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Columbia: Implicatons for the Middl
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Bazard, D.R., Butler, R.F., Gehrels
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Bradley, D.C., Haeussler, P.J., and
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Bundtzen, T.K., Laird, G.M., Caluti
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Cecile, M.P., 1982, The lower Paleo
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Debari, S.M., and Coleman, R.G., 19
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U.S. Bureau of Land Management Open
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Cordilleran Orogen in Canada: Geolo
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Goldfarb, R., Hart, C., Miller, M.,
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Grove, E.W., 1986, Geology and mine
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Høy, T., 1982a, Stratigraphic and
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Jones, D.L., Silberling, N.J., Cone
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Kutyev, F. Sh., Baikov, A.I., Sidor
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Shield—Ultramafic magma and its m
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Manns, F.T., 1981, Stratigraphic as
Page 347 and 348:
Miller, M.L., and Bundtzen, T.K., 1
Page 349 and 350:
Mortimer, N., 1987, The Nicola Grou
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Noble, S.R., Spooner, E.T.C., and H
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Canada Annual Meeting, Saskatoon, S
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Perello, J.A., Fleming, J.A., O’K
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Far East—Mineralogical criteria f
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Roeske, S.M., Mattinson, J.M., and
Page 361 and 362:
Schmidt, J.M., and Zierenberg, R.A.
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formation occurrences: Materialy po
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Struik, L.C., 1986, Imbricated terr
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Valuy, G., and Rostovsky, F., 1988,
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Wolfe, W.J., 1995, Exploration and
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Appendix Table 1. Mineral deposit m
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Table 2 Summary of correlations and
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Table 2—Continued Unit(s) and Cor
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Table 2—Continued Unit(s) and Cor
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Table 3—Continued Metallogenic Be
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Table 4. Significant lode deposits,
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Table 4—Continued Appendix 369 De
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Table 4—Continued Tracy Metalloge
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Table 4—Continued Appendix 373 In
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Table 4—Continued Deposit Name Mi
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Table 4—Continued Mainits Metallo
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Table 4—Continued Whitehorse Meta
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Table 4—Continued Appendix 389 LA
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Table 4—Continued Surprise Lake M
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Table 4—Continued Sredinny Metall
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