USGS Professional Paper 1697 - Alaska Resources Library

tion is interpreted as occuring by the beginning of the Albian
with deposition of the overlying Kuibiveem sedimentary
assemblage (kb), which is interpreted as a fore-arc unit to the
Okhotsk-Chukotka continental-margin arc (oc). Subduction
stepped outboard during accretion.
(2) At the end of the Neocomian, oblique subduction was
replaced by sinistral-slip faulting parallel to the continental
margin. This faulting resulted in structural interleaving of
the previously active subduction-zone terranes. This structural
interleaving is interpreted as similar to the present-day
region of Southern California and resulted in formation of the
fault-bounded basin of marine turbidites now preserved in the
Zhuravlesk-Tumnin turbidite-basin terrane (ZT) (Golozubov
and Khanchuk, 1996).
(3) The Khingan continental-margin arc (ko) started to
form. Forming in the arc was the Badzhal-Ezop-Khingan (BZ-
KH) belt of granitic-magmatism-related deposits. Tectonically
linked to the arc was oblique subduction of part of the
ancestral Pacific oceanic plate to form the Amur River (AM),
Khabarovsk (KB), and Kiselevka-Manoma (KLM) subduction-zone
and accretionary-wedge terranes. Also in the same
region, the Samarka (SA) belt of granitic-magmatism-related
deposits, which is hosted in the Samarka island-arc terrane
(SA), is interpreted as forming during anatectic granitic plutonism
associated with thrusting of Kula-Farallon oceanic ridge
under margin of southern Russian Far East.
(4) The continental-margin Uda arc and associated
subduction zones ceased activity with accretion of the Bureya
superterrane and closure of the Mongol-Okhotsk Ocean along
the Mongol-Okhotsk suture (MO).
(5) The extensive Kony-Murgal continental-margin and
island arc and Pekulney island arc continued to form. Associated
with these arcs was subduction of part of the ancestral
Pacific oceanic plate to form the Talovskiy (TL), Penzhina-
Anadyr (PA), and Pekulney (PK) terranes.
(6) The final stages of accretion of the Kolyma-Omolon
superterrane is interpreted as causing a second phase of deformation
in the Verkhoyansk fold and thrust-belt and formation
of the West Verkhoyansk collisional granite belt (wk; 90 to
120 Ma) along the Lena fault (LE). Forming in the associated
Verkhoyansk granite belt and continuing on from the Early
Cretaceous was the Kular (KU) metallogenic belt, which contains
Au quartz vein and granitic-magmatism-related deposits.
(7) The Nutesyn and Koyukuk island arcs continued
activity on the opposite sides of the South Anyui and Angayucham
Oceans. Parts of these arcs are preserved in the
Nutesyn (NU), Koyukuk (KY), Togiak (TG), and Nyac (NY)
terranes. Associated with these arcs was subduction of parts
of the South Anyui and Angayucham oceanic plate, thereby
forming the Velmay (VE) and (outer) Angayucham (AG) terranes
and causing 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. Forming during extension that
succeeded obduction were Nome (NO) and Southern Brooks
Range (SBR) metallogenic belts, which contain Au quartz vein
Late Early Cretaceous Metallogenic Belts (120 to 100 Ma; figs. 61, 62) 161
deposits and are hosted in metamorphosed continental-margin
terranes. These belts are interpreted herein as forming during
regional metamorphism associated with extension.
(8) In the Arctic, sea-floor spreading and associated
rifting continued with formation of large sedimentary basins,
creation of a collage of passive continental-margin terranes
derived from the North American Craton Margin (NAM;
Lawver and Scotese, 1990; Grantz and others, 1990, 1991,
1998). Continuing was closure of the Angayucham Ocean,
subduction along the North American continental margin,
intense thrusting in the passive continental-margin terranes,
and deposition of Early to mid-Cretaceous flysch.
(9) On the edge of the Wrangellia superterrane (WRA),
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. Part of the arc was preserved
in the Kahiltna (kh) and Gravina-Nutzotin-Gambier (gg)
assemblages that occur only on the Wrangellia superterrane.
The Gravina arc extended into the southern Canadian Cordillera
with the formation of the Spences Bridge volcanic-plutonic
belt (sb). Forming in the Gravina arc, and continuing
on from the Early Cretaceous was the western-southeastern
Alaska (WSE) belt, which contains granitic-magmatismrelated
deposits.
(10) The central and northern parts of the Wrangellia
superterrane (WRA) accreted to the Northern Canadian Cordillera
and southern Alaska. Along the accreting edge of the
superterrane, the intervening oceanic plate and the Kahiltna
overlap assemblage were thrust over the active continental
margin of the southern Alaska and the northern Canadian Cordillera
(Stanley and others, 1990). The small tectonic lenses
of terranes of alpine ultramafic and related rocks along the
ancestral Denali Fault (unit UM; Nokleberg and others, 1985,
1994a) may be remnants of this oceanic lithosphere.
(11) Coeval with accretion of the Wrangellia superterrane
was intrusion of the Omineca-Selwyn anatectic granite belt
(om), which occurs along the length of Canadian Cordillera
and Alaska. Forming in or near the granite belt were the Bayonne
(BA), Cassiar (CA), Selwyn (SW), Tombstone (TS), and
Whitehorse (WH) metallogenic belts, which contain graniticmagmatism-related
deposits.
Metallogenic Belt Formed in Late Mesozoic
Continental-Margin Arc, Russian
Southeast Badzhal-Ezop-Khingan Metallogenic
Belt of Sn Greisen, Skarn, and Sn Quartz Vein
Deposits (BZ-KH), Western Part of Russian
Southeast
The Badzhal-Ezop-Khingan metallogenic belt of Sn greisen
and Sn quartz vein deposits (fig. 61; tables 3, 4) occurs in
the western part of the Russian Southeast. The belt consists of