USGS Professional Paper 1697 - Alaska Resources Library

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140 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera duction of parts of the South Anyui and Angayucham oceanic plate, thereby forming the South Anyui (SA), Velmay (VE), and (inner) Angayucham (AG) terranes, and subduction of the outboard margin of the Arctic Alaska terrane. An extensive zone of blueschist facies metamorphism occurs in this region in both the Angayucham and Arctic Alaska terranes. After initial accretion of the Koyukuk arc with the Arctic Alaska superterrane, beginning in the Late Jurassic at about 160 to 145 Ma (Moore and others, 1994a,b), subduction flipped to outboard of the new continental margin of this part of Alaska. (8) At about 140 to 135 Ma, sea-floor spreading and associated rifting, which started with the formation of grabens in the Late Jurassic or earlier (Lawver and Scotese, 1990; Grantz and others, 1990, 1991, 1998) formed (1) new oceanic crust and the large proto-Amerasia (ab) and proto-Canada (cb) basins, and (2) a collage of passive continental-margin terranes derived from the North American Craton Margin (Artis Plateau (AP), Chukchi Cap (CK), Chukchi Spur (CS), and Northwind Ridge (NR) terranes). Sea-floor spreading and opening of the Amerasia and Canada Basins is herein interpreted as causing (1) closure of the inner Angayucham Ocean, (2) subduction of the North American continental margin 60 o o At 30 latitude MAI-MAINITSKIY ARC AV MO 80 o LS ? ? (Chukotka terrane, CH, and the Arctic Alaska superterrane, AA), (3) beginning of closure of the South Anyui Ocean, (4) intense deformation and metamorphism of the southern margin of the eastern Chukotka terrane (CH) and southern Arctic Alaska superterrane (AA) to form the Seward (SD), Coldfoot (CO), and Ruby (RB) terranes, (5) formation of an extensive blueschist facies belt in both the subducted continental margin (Arctic Alaska superterrane (AA), and Seward (SD), Coldfoot (CO), and Ruby (RB) terranes) and in the overthrust Angayucham terrane (AG), and (6) deposition of synorogenic Early to mid-Cretaceous flysch in the Koyukuk Basin in what became western Alaska. For additional information the opening of the Canada Basin, whether by rifting and rotation, or by strike-slip translation, or by a combination of the two processes, please refer to the analyses by Grantz and others (1990, 1998) or Lane (1994, 1997). (9) Underthrusting in a subduction zone along the North American Craton Margin (NAM) resulted in consumption of the Farallon oceanic plate (FAR). Small tectonic lenses of terranes of alpine ultramafic and related rocks, which occur along the ancestral Denali Fault (fig. 63) (Nokleberg and others, 1985, 1994a), may be remnants of the subduction-zone SOUTH ANYUI & ANGAYUCHAM OCEANS NU OPENING OF PROTO- AMERASIA BASIN SA NSS SK uz COLL (BU) KHINGAN ARC - ko ST NSC NSV UDA VK ARC ud TO tr no AL KO ma AY VE (TA, KT) COLL YP, ZL KU OLOY ARC LO KY UNK UNK CH AA B B B B B AA COLLAGE OF RIFTED TERRANES: NR, CK, CS, AP OPENING OF PROTO- CANADA BASIN NAC ZT AM, KB, KLM TD UL DP (KLO) ol SH OL AG KOYUKUK ARC B B B YA KM TL KONY-MURGAL ARC COLL PA WP PK PEKUL’NEY ARC KI GOOD- KY NEWS OCEAN NX, DL, MY TG, NY NAM ANCESTRAL PACIFIC OCEAN WSE GRAVINA ARC UNK MA, TAM LE AD kh WRA (PE) gg CG 144 to 120Ma WRA (WR) FAR gg CG 60 o WRA (AX) FARALLON OCEAN METALLOGENIC BELTS AL - Algama AY - Allakh-Yun DP - Darpir CB - Cariboo KO - Kondyor KU - Kular LO - Left Omolon NB - North Bureya OL - Oloy TAM - Tamvatney-Mainits SA - Samarka SH - Shamanikha SK - Selemdzha-Kerbi ST - Stanovoy TAMTamvatney-Mainst TO - Tompon VK - Verkhoyansk WSE - Western- Southwestern Alaska YA - Yana-Kolyma YP - Yana-Polousnen COLL CBsb gg tt BR,EA MT BA WRA (WR) NAC gg NAM 0 800 km 0 800 km Figure 63. Early Cretaceous (Neocomian—144 to 120 Ma) stage of metallogenic-tectonic model for the Russian Far East, Alaska, and the Canadian Cordillera and adjacent offshore areas. Refer to text for explanation of metallogenic-tectonic events, to tables 3 and 4 for descriptions metallogenic belts and significant deposits, and to figure 18 for explanation of abbreviations, symbols, and patterns. Adapted from Nokleberg and others (1997b, 1998, 2000).
assemblages, which may have been mostly thrust under the margin of what is now North America. (10) The Gravina arc continued to form. Associated with the Gravina arc was subduction of part of the Farallon oceanic plate to form the Chugach (CG), Bridge River (BR), Easton (EA), and Baker (BA) terranes. The arc is preserved in the Kahiltna (kh) and Gravina-Nutzotin-Gambier (gg) assemblages, which occur only on the Wrangellia superterrane. Forming in the Gravina arc was the western-southeastern Alaska (WSE) metallogenic belt, which contains granitic-magmatism-related deposits. (11) The Wrangellia superterrane (WRA) started to accrete at about 60° paleolatitude with the continentward part of the Wrangellia superterrane impinging onto a collage of terranes previously accreted to the North American Craton Margin (NAM). During accretion, the arc was extended to the south during the formation of two major overlap assemblages, the coeval Tahtsa-Three Sisters magmatic assemblage (tt) and the Spences Bridge volcanic-plutonic belt (sb). Metallogenic Belts Formed Along Late Mesozoic Continental-Margin Transform Faults in Russian Southeast Samarka Metallogenic Belt of W Skarn, and Porphyry Cu-Mo Deposits (Belt SA), West- Central Part of Russian Southeast The Samarka metallogenic belt of W and Sn skarn and porphyry Cu-Mo deposits (fig. 61; tables 3, 4) occurs in aluminous, mainly S-type granitoid rocks of Early to mid-Cretaceous age that intrude the Samarka accretionary-wedge terrane in the west-central part of the Russian Southeast. The belt contains major W skarn deposits at Benevskoe and Vostok-2, small porphyry Cu-Mo deposits at Khvoshchovoe, Kafen, and Malakhitovoe, and a porphyry Mo deposit at Skalistoe (table 4) (Nokleberg and others 1997a,b, 1998). The deposits are hosted in Early to mid-Cretaceous granodiorite porphyry, granite, and gabbro-diorite. The southern-most part of the Samarka metallogenic belt occurs in a displaced fragment of the Samarka terrane, which is displaced along a left-lateral, north-east-trending strike-slip fault (fig. 61). The small W skarn deposit at Benevskoe occurs in this displaced fragment. Also possibly part of the same Samarka metallogenic belt is a younger, Paleocene porphyry Cu-Mo deposit at Skalistoe (fig. 61). This deposit consists of veinlet molybdenum ore and wolframite that occur in a subvolcanic granite porphyry. Alternatively, the Skalistoe deposit may be part of postaccretionary Luzhkinsky metallogenic belt described below. Vostok-2 W Skarn Deposit The major productive Vostok-2 deposit (fig. 64) (Stepanov, 1977; Rostovsky and others, 1987) consists of vein Early Cretaceous Metallogenic Belts (144 to 120 Ma; figs. 61, 62) 141 and sheet skarn that formed in several stages. An older stage consists dominantly of pyroxene, plagioclase, amphibole, and garnet. A subsequent stage consists of greisen alteration of skarn and granitoid rocks with formation of quartz, feldspar, and muscovite, along with minor chlorite and biotite that contains scheelite and apatite, and minor arsenopyrite, pyrrhotite, and chalcopyrite. A late stage consists of scheelite and quartz followed by crystallization of low temperature scheelite and arsenopyrite. The deposit occurs along the flat to steeply dipping contacts of granitoid plutons that intrude olistostromes of large, Carboniferous-Permian limestone and calcareous-shale. Successive skarn and greisen alternation of limestone preceded the deposition of scheelite and other minerals, including gold and apatite, locally as much as a few tens of percent. Plagiogranite with an approximate K-Ar age of 110 ma is interpreted as forming with the deposit. The deposit is large with average grades of 0.65 percent W 2O 3 and 1.64 percent Cu. The deposit has been mined since the 1980’s. The olistostromes that host the Samarka belt of Sn and W skarn deposits are derived from the caps of guyots that are enclosed in a matrix host of highly deformed Jurassic sedimentary rocks in the accretionary-wedge complex of the Samarka terrane. The skarns are hosted in limestone layers and occur along the contacts of calcareous and alumosilicate clastic rock. Benevskoe W Skarn Deposit The small Benevskoe W skarn deposit (V.D. Shlemchenko and others, written commun., 1983) occurs along the margin of an Early Cretaceous biotite, peraluminous granite that intrudes olistoliths of Permian sedimentary shales and interbedded with limestone. The skarn occurs in altered limestone. Various mineral assemblages are magnetite, garnet, pyroxene-garnet, garnet-epidote, and garnet-orthoclase. Late-stage quartz-feldspar and quartz-amphibole overgrowths replace the skarns and locally contain disseminated scheelite. Late-stage quartz-sericite and zeolite alterations also occur. The major ore minerals are scheelite with minor magnetite, arsenopyrite, pyrite, and rare cassiterite. Gangue minerals are quartz, feldspar, amphibole, epidote, biotite, and tourmaline. Easily concentrated apatite also exists. The deposit is small with average grades of 0.44 to 3.15 percent W2O3. As to the north, small porphyry Cu-Mo occurrences also occur in this part of the metallogenic belt. Origin of and Tectonic Controls for Samarka Metallogenic Belt The W skarn deposits of the Samarka metallogenic belt occur near mainly Early Cretaceous, S-type granitoid rocks that intrude the Samarka accretionary-wedge terrane. The host granitoid rocks and associated deposits are herein interpreted as forming in underthrusting of the Kula oceanic ridge and resultant genesis of bimodal igneous activity along the transform continental margin of the Russian Southeast (A.I. Khanchuk, written commun., 1997; Khanchuk and others, 1998).
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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
Page 121 and 122: ers, 1994c, 1997c). In southern Bri
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Page 125 and 126: a resource of 34.3 million tonnes o
Page 127 and 128: potassic zone. Combined estimated p
Page 129 and 130: and quartz monzodiorite stock and s
Page 131 and 132: and Omolon (OM) cratonal terranes,
Page 133 and 134: in volcanic and volcaniclastic rock
Page 135 and 136: minor calcite, and sporadic pyrite
Page 137 and 138: supergene blanket are interpreted a
Page 139 and 140: deposits and occurrences consist of
Page 141 and 142: onto the Omulevka terrane to form t
Page 143 and 144: superterrane. This belt is interpre
Page 145 and 146: to form along the leading edge of t
Page 147 and 148: quartz, and is virtually not associ
Page 149 and 150: deposits are at Terrassnoe and Kuna
Page 151 and 152: Peschanka Porphyry Cu-Mo Deposit Th
Page 153 and 154: The belt is hosted in the Late Jura
Page 155 and 156: in a island arc that was tectonical
Page 157 and 158: and Early Cretaceous Koyukuk island
Page 159 and 160: The deposit consists of disseminate
Page 161 and 162: The Orange Hill deposit contains an
Page 163 and 164: 49; tables 3, 4) (Foley and others,
Page 165 and 166: locally Late Triassic marine volcan
Page 167 and 168: gold in a gangue of quartz, calcite
Page 169 and 170: Verkhoyansk granite belt, which int
Page 171: metallogenic belts are interpreted
Page 175 and 176: during hypogene and supergene alter
Page 177 and 178: collision and regional thrusting, t
Page 179 and 180: Yur Au Quartz Vein Deposit The smal
Page 181 and 182: phase has a Rb-Sr isotopic age of 1
Page 183 and 184: sian Northeast. The belt is hosted
Page 185 and 186: Host Granitoid Rocks and Associated
Page 187 and 188: that are up to 600-1,500 m long, av
Page 189 and 190: 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
Page 197 and 198: and comagmatic with volcanic rocks;
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
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quartz-arsenopyrite-pyrrhotite, pol
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thermally altered to siliceous and
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These ore bodies are as much as 1 m
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Eastern Asia-Arctic Metallogenic Be
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Demin, and Krasilnikov, 1974; Nekra
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10 percent Cu, as much as 0.92 perc
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pyrite, pyrite, galena, sphalerite,
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content decreases with depth, as do
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azdelnoye, (2) porphyry Sn deposits
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Karalveem Au Quartz Vein Deposit Th
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Democrat (Mitchell Lode) Granitoid-
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with high-temperature and high-pres
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chalcocite and covellite and also h
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cum-North Pacific, (2) completion o
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(6) In the Paleocene (about 56 to 6
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sists of cinnabar and metacinnabari
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Eastern Asia-Arctic Metallogenic Be
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groups of deposits are interpreted
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Indian Mountain and Purcell Mountai
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and southeastern Alaska (Moll and P
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Nokleberg and others, 1995a; Bundtz
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g/t Au or 368.2 Au gold. The deposi
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wim Group and altered mafic dikes.
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Mount Nansen porphyry Cu-Mo deposit
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A Map 450 500 550 Cross section Dik
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Cretaceous and early Tertiary conti
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deposits, at Chichagoff and Hirst-C
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others, 1994c, 1997c). The signific
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tonnes grading 0.53 percent Ni, 0.3
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with a 0.25 percent cut-off. The de
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Bulkley Metallogenic Belt of Porphy
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Red Rose W-Au-Cu-Ag Polymetallic Ve
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ish Columbia and consists of severa
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during back-arc extension or transt
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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.,
Page 335 and 336:
Grove, E.W., 1986, Geology and mine
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Høy, T., 1982a, Stratigraphic and
Page 339 and 340:
Jones, D.L., Silberling, N.J., Cone
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Kutyev, F. Sh., Baikov, A.I., Sidor
Page 343 and 344:
Shield—Ultramafic magma and its m
Page 345 and 346:
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
Page 355 and 356:
Perello, J.A., Fleming, J.A., O’K
Page 357 and 358:
Far East—Mineralogical criteria f
Page 359 and 360:
Roeske, S.M., Mattinson, J.M., and
Page 361 and 362:
Schmidt, J.M., and Zierenberg, R.A.
Page 363 and 364:
formation occurrences: Materialy po
Page 365 and 366:
Struik, L.C., 1986, Imbricated terr
Page 367 and 368:
Valuy, G., and Rostovsky, F., 1988,
Page 369 and 370:
Wolfe, W.J., 1995, Exploration and
Page 371 and 372:
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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