USGS Professional Paper 1697 - Alaska Resources Library

to form along the leading edge of the superterrane. Forming
in the Uyandina arc was the Chersky-Argatass Ranges (CAR)
metallogenic belt, which contains kuroko massive sulfide
deposits, and the Yasachnaya River (YS) metallogenic belt,
which contains granitic-magmatism-related deposits. Tectonically
linked to the Uyandina arc was subduction of the oceanic
crustal rocks preserved in the Garbyn’ya (GA) and Debin
(DB) ophiolite belt (and corresponding terranes, fig. 48) of
Oxman and others (1995) that are herein interpreted as a remnants
of the Oimyakon oceanic plate.
(7) On the opposite side of the Kolyma-Omolon superterrane
(KLO), the Oloy island arc (ol) formed in response to
subduction of part the South Anyui oceanic plate. Forming in
the arc was the Oloy (OL) metallogenic belt that contains granitic-magmatism-related
deposits. Along one part of the North
Asian Craton Margin (NSV), the Svyotoy-Nos continentalmargin
arc formed along the margin of the Taymyr Peninsula
collage (TA) in response to subduction of another part of the
South Anyui oceanic plate to form the South Anyui subduction-zone
terrane (SA). Forming in the arc was the Svyatoy-
Nos (SVN) metallogenic belt that contains Au-Ag epithermal
vein deposits and is hosted in the Svyatoy-Nos volcanic belt.
The Angayucham Ocean continued to exist along with the
South Anyui Ocean.
(8) Outboard of the Oloy arc was the minor Pekul’ney
island arc. Incorporated into the tectonically linked Pekul’ney
subduction-zone terrane was the basaltic Cu deposits of the
Pekulney metallogenic belt that formed in a primitive island
arc and neighboring sea-floor environment.
(9) Adjacent to the North American Craton Margin
(NAM) two extensive arcs formed. The Nutesyn continental-margin
arc formed in response to subduction of part of
the South Anyui oceanic plate to form the Velmay subduction-zone
terrane (VE). The Koyukuk (KY), Togiak (TG),
and Nyac (NY) island-arc terranes formed in response to
subduction of an (inner) Angayucham oceanic plate to extend
the Angayucham (AG) subduction-zone terrane and opening
of the Aerasia and Canada Basins. Outboard of the island arc
were the outer Angayucham and the Goodnews Oceans. Forming
in the basal parts of the Koyukuk (KY), Togiak (TG), and
Nyac (NY) island arcs were the Eastern Seward Peninsula and
Marshall (ESM), Klukwan-Duke (KL), Kobuk (KB), Kuyul
(KUY), southwestern Alaska (SWA), and Yukon-River (YR)
metallogenic belts, which contain podiform Cr and related
deposits and zoned mafic-ultramafic PGE deposits, and are
hosted in mafic-ultramafic plutons. The polarity of the island
arc was continentward, toward the North American Craton
Margin (NAM).
(10) The Kilbuck-Idono cratonal (KI) and the Nixon
Fork-Dillinger-Mystic passive continental-margin terranes
(NX, DL, MY) accreted onto the North American Craton
Margin (NAM) at about the same time as obduction of the
Stikinia-Quesnellia island arc described below.
(11) Rift grabens, depicted as rifting associated with
sea-floor spreading, began to open the Amerasia and Canada
Basins (Grantz and others, 1998). These grabens were an early
Late Jurassic Metallogenic Belts (163 to 144 Ma; figs. 48, 49) 113
stage of creation of new oceanic crust in the Early Cretaceous,
as described below.
(12) A subduction zone (UNK) having a component of
oblique sinistral-slip is inferred to have formed along and
parallel to the continental margin in order to accomplish
migration of the Wrangellia superterrane toward the North
American Craton Margin. Remnants of the subduction zone
may be preserved in the terrane of ultramafic and related rocks
that occurs discontinuously along the Denali strike-slip fault
(DE, fig. 50) for several hundred kilometers (Nokleberg and
others, 1994b). The mafic and ultramafic rocks may in part be
derived from the Farallon oceanic plate (FAR) that separated
the Wrangellia superterrane from the North American Craton
Margin.
(13) Regional thrust faulting occurred with obduction of
the Stikinia (ST), Quesnellia (QN), Cache Creek (CC), Slide
Mountain (SM), Yukon-Tanana (YT), Seventymile (SM), and
Kootenay (KO) terranes over the Cassiar (CA) terrane and the
North American Craton Margin (NAM). This compressional
event marked the beginning of a major orogenic event, including
regional metamorphism, deformation, crustal thickening,
anatectic magmatism, and uplift in the core of the Canadian
Cordillera (Monger and Nokleberg, 1996). Forming during
the regional metamorphism, or during younger hydrothermal
alteration, were the serpentinite-hosted asbestos deposits of the
Cassiar (CS) and Fortymile metallogenic belts (FM) that are
hosted in ultramafic rock in the Slide Mountain (SM) and (or)
Seventymile (SV) terranes. The Nelson plutonic suite (ns, fig.
50), which intrudes the Stikinia, Quesnellia, Kootenay, Cache
Creek, and Slide Mountain terranes, and the coeval Francois
Lake plutonic suite formed during this compressional event.
The Nelson plutonic suite consists chiefly of granodiorite,
quartz monzonite, and local monzonite plutons that yield isotopic
ages mainly of 185 to 155 Ma and exhibit local crustal
inheritance (Parrish and others, 1988; Woodsworth and others,
1992). Formed in the Nelson plutonic suite was the Rossland
(RL) metallogenic belt of Au-Ag polymetallic vein deposits.
Forming nearby in the Francois Lake plutonic suite was the
Francois Lake (FL) metallogenic belt of porphyry Mo deposits.
Forming in the nearby Kootenay terrane was the Cariboo
(CB) belt of Au quartz vein deposits. By the Late Jurassic
(about 155 Ma), detritus from this emergent orogenic welt in
the eastern Canadian Cordillera was shed eastwards onto the
North American Craton Margin (Cant, 1989).
(14) The extensive Gravina island arc was initiated along
the length of the Wrangellia superterrane. Remnants of the arc
are preserved in the Kahiltna (kh) and Gravina-Nutzotin-Gambier
(gg) overlap assemblages that occur only on the Wrangellia
superterrane. Forming in the Gravina arc were the Eastern-Southern
Alaska (ESA) metallogenic belt, which contains
granitic-magmatism-related deposits, and the continuity of the
Island Porphyry (IP) belt, which contains granitic-magmatismrelated
deposits. Tectonically linked to the arc was subduction
of part of the Farallon oceanic plate (FAR) to form the
Chugach (CG), Bridge River (BR), Easton (EA), and Baker
(BA) terranes.