Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

Specific Events for Late Early Cretaceous
(1) AL about 50" paleolatitude, the Mainitskiy island arc (Mainitskiy teme, MAI) continued activiv, Associated wi&
this arc was subduction of part of the adjacent oceanic plate to form the Alkatvaam accretionary-wedge mane (AV). Thb arc and
companion subduction zone continued to migrate northwards towards the North Asian Craton Margin and outboard terranesarid
was accreted to the active continental margin at the end of the Early Cretaceous (about 100Ma). During this accreth, he Au
quartz vein and associated deposits of the Anadyr River (AD) metallogenic belt fod. The accretion is inmpreted RS oceuring
by the beginning of the Albian with deposition of the overlying Kuibiveemsechmtary assemblage (kb), which is iuterpd as a
forearc 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 tb\e coatinmtd
margin. This faulting resulted in structural interleaving of the previously active subduction-zone terranes. 'This strucRrral
interleaving 1s ~nterpreted as similar to the present-day region of Southern California and resulted in formation of thefault
bounded basln of marine turbidites now preserved in the Zhuravlesk-Twin hurbiditebasin terrane (ZT) (Ciolonrbov and
Khanchuk, 1996).
(3) The Khlngan continental margin arc (ko) started to fonn. Forming in the arc was the lhdzhd-EzopW$an (BZ-
KH) belt of grani tic-magmat lsrn-related deposits. Tectonically linked to the arc was oblique subduction dpmt of the Ancestral
Pacific Ocean plate to form the Amsv River (AM), Khabaro~sk W), and Kiselev~-~oma (KLM) subduction-me arrd
accretionary-wedge terranes. Also in lbe same region, the Samarka (SA) belt of gmnitic---~clated deposits* which b
hosted in the Samarka island-= terrae (SA), is interpratad as forming during anatectic plutanksm m~~~iatal with
thrusting of Kula-Farallon oceanic ridge under margin of southern Russian Far East.
(4) The continental margin Uda arc and associated subduction zones ceased activity with acmchn of the Bureya
superterrane and closure of the Mongol-OkhdPk Ocean along the ~&~ol-~khotsk suture (MO).
(5) The extemive Kooy-Murgal continental-margin and island an: and Pdahey hM an: continued to form. Associated
with thm arcs was subduction of part of the ancestral Pacific Ocean plate to faan the Talovakiy (n)* ~aazhina-~nahyr (PA), and
Pekulney (PK) tenanes.
(6) The final stages of accretion of the Kolyma-Ornolon superterrane is interpmed as &g a second p b of
deformation in the Verkhoyd fold and thrust-belt and formatian of the West Verkhoyansk colIhional grsnite belt (wk; 90 WI
120 Ma) aloog the Lena fad (LE). Forming in the associated Verkhoyansk granite belt and continuing on fiom the Early
Cretaceous was the Kulai (KU) metallogenic belt which contains Au quartz vein and granitic-magmatism-related deposit$.
(7) The Nutesyn and Koydcuk island arcs continued activity on the opposite sides of the South An* ami Ang~yuchm
Oceans. Parts of these arcs are gresesved in the Nutmyn @U), Koyukuk (KY), Togiak (TG), aad Nyac (NY) tarane;s. AssociaaGd
with lbcse arcs was subduction of par& of the South Anyui Anpyucham 0mw.1 piate thereby forming the V ehq (VE); and
(outer) Angayucharn (AG) lenanes, and subduction of the outbaud m qh oftbe Arctic Alaska temne. An extensive zone of
blueschist facies metamorphism occurs in this region in both the Angapcham and Arcejic Alaslra temraes. Forming Mng
extension which succeeded abduction were Nome (NO) and Southern Brooks Range (SBR) metallogenic bb which contain Au
quartz vein deposits, and are hosted in metamorphosed continmbd-margin tamus. These belts are mtmpcted heminas formkg
during regional metamorphism tusociated with extension.
(8) In the Arctic, sea-floor spreading and associated rifhng continued with forination J Iage sidrum Wins,
creation of a collage of passive continental-margin tcrranes derived from the Narth American Crataa. Margin (lUAh4; hwer and
Scotese, 1990; Grantz and others, 1990,1991, 1998). Continuing was closure of tbe Angayucham &em, subduction erhg the
North American continenhi margin, inme thrusting in the pive continental margin terranes, and deposition of Early to mid-
Cretaceous flysch.
(9) On the edge of the Wrangellii supertenme (WRA), the Gravina arc continued to fom Associated wictt the Gravina
arc was subduction of part of the Farallon Ocean plate to form the Cbugach (CG), Bridge River (BR), Easton @A), and Baker
(BA) terranes. Part of the arc was preserved in the Kahiltna (kh) and Gravina-Nutzotin-Gambier (gg) assemblages which occur
only on the Wrangeilia supcrtenane. The Gravina an: extended into the southern Canadian Cordillera with the fornation of the
Spences Bridge volcanic-plutonic klt (sb). Forming in the €hviifa arc, and continuiag on from the Early Cretaceous was the
Westem-Southeastem Alaska ( WSE) belt which contains granitic-r~gmatism-related deposits.
(1 0) The cenbal and northern parts of the Wrangllia swrrane (WRA) acweted to the Northem Canadian Copdillera
and southern Alaska. Along the acaeting edge of the suparteme, the intervening oceanic plate and thelbhiltna overlap
assemblage were t h t during the active continentd m;ugio of the Souh Alaska and the nonhem Camdian Cor&Ucm (Studey
and others, 1990). The small tectonic lenses of terranes of alphe u l e sod related rocks along the 8n- hnd faztlt (unit
UM; Nokleberg and otb, 1985,1994~~) may be rammts of this meaaic lithspbere.
(1 I) Coeval with accretion of the Wrangellia supeaeme was inbusion of the Omfneca-Selwyn mate& @te belt
(om) which occurs along the length of Canadian Cordillera and Alaska Fohg in or near the granite belt were the Bayonne
(BA), Cassiar (CA), Selwyn (SW), Tombstone (TS), and Whitehorse WH) metallogenic belts which coatfib grarutic-mxtgma69DP
related deposits.