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

Alaska. For additional information the opening of the Canada Basin, whether by rifting and rotation, or by strike-slrp translation,
or by a o~mbinalion
of Ihc two processes, please refer to the analyses by Grantz and others (1990, 1998) or Lane (1 994, 1997).
FQure 63. Early Cretamus (Nemmian - 144 to 120 Ma) stage of rnetallogenic-tectonic model. Refer to text for explanation d
metallogefiic-lectonic events, to tables 3 and 4 for descriptions rnetallogenic belts and significant deposits, and lo figure 18 for
explenalion of abbrevlaliona, symbob, and patterns. Adapted from Nokleberg and others (1997b, 1998, 2000).
(9) Underthrusting in a suhction zone along the North American Craton Margin (NAM) resulted in consumptiol, of the
Farallon Ocean phte (FAR). Small tectonic lenses of terranes of alpine ultramafic and related rocks, whicb occur along the
anccstnl Dcnmki fault (f~. 63) (Nokleberg and others, 1985, 1994a), may be remnants of the subduction-zone assemblages whicb
may have been mostly thrust under b margin of what is now North America.
(10) The Gi-avina uc continued to form. Associated with the Gravina arc was subduction of pat of the Farallon Ocean
plate to form the Chugach (CG), Bridge River (BR), Easton (EA), and Baker (BA) terranes. The arc is preserved in the Kahiksa
(kh) and Grad-Nutzotin-Gambier (gg) assemblages which occur only on the Wrangellia superterrane. Forming in the Gmvb an was the Westem-Southeastern Alaska (WSE) metallogenic belt which contains granitic-magmatism-related deposits.
(1 1) The Wrangellia superterrane (WRA) started to accrete at about 60" paleolatitude. The continentward parl of the
Wrangelh supcrterrane impinging onto a collage of terranes previously accreted to the North American Craton Marwo (NAM).
During mctioa, the arc was extended to the south during the formation of two major overlap assemblages, the coeval Taistsa-
Tbrte Sisters magmatic assemblage (tt) and the Spences Bridge volcanic-plutonic belt (sb).
Metallogenlc Belb Formed Along
Late Meeonolu Continental-Margin
Transhm Faults in R ush Southeast
Samarka Metabgenic Bell of W Skarn, and
Pwphyry Cu-Mo Deposits (Belt SA)
\NeoCCmtml Part d Russian Southeast
The Sunaska mctsllogenic belt of W and Sn skarn and porphyry Cu-Mo deposits (fig. 61; tables 3,4) occurs in
aluminous, mainly Stype granitoid rocks of Early to mid-Cretaceous age which intrude the Samarka accrdicmary-wedge tarrand