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

(4) The Angayucham Ocean (Kobuck Sea of Plafier and Berg, 1994), along with the South Anyui Ocean, continued to
receive sparse continental-derived detritus. Previously rified terranes, including the Kilbuck-ldono cratonal (KI) and the combined
Nixon Fork-Dillinger-Mystic passive continental-margin (NX, DL. MY) terranes were near the North American Craton Margin.
(5) The dextral-slip imbrication of the Stikinia-Quesnellia arc and associated subduction-zone terranes continued along
the Tally Ho shear zone (Hansen and others, 1990; Hart, 1995) (inset, fig. 43). Part of the Tally Ho shear zone may occur be
defined by a string of fault-bounded(?) ultramafic rocks which occur within the Yukon-Tanana temne in northern Southeastern
Alaska (Himmelberg and others, 1985). Alternatively, the present-day configuration of the Stikinia-Quesnellia island-arc and
associated subduction zone terranes may have formed by oroclinal warping in response to a combination of oblique convergence
and arc migration toward the companion subduction zone of the Cache Creek terrane (Mihalynuk and others, 1994) (not depicted
in fig. 43). Oroclinal warping is interpreted as forming in response to: (I) oblique-sinstral convergence between the ancestral
Pacific Ocean plate and the Stikinia-Quesnellia arc; and (2) arc migration toward the companion subduction zone (trench
rollback), similar to tectonics of the present-day Banda arc in Southeast Asia (McCaffrey and Abers, 1991; Mihalynuk and others.
1994). Migration of the Stikinia-Quesnellia arc and associated terranes toward North America was accomplished by subduction
and (or) obduction of the Seventymile Ocean plate along the continental margin.
(6) The Stikinia part of the arc consisted of the extensive suite of the subduction-related volcanic and plutonic arc rocks
of the Hazelton Group which also formed in response to subduction of the Cache Creek Ocean plate (CC). In central part of the
Stikinia-Quesnellia island arc, coeval subduction-related granitic plutonic rocks also intruded the previously-accreted passive
continental-margin Yukon-Tanana terrane (YT), which may have been the stratigraphic basement for part of the Stikinia island arc
(Mihalynuk and others, 1994).The plutonic rocks also intrude the structurally overlying Slide Mountain (SM) and Seventymile
(SV) terranes. The subduction-related volcanic and plutonic arc rocks of the Quesnellia part of the arc, consisting of the Takla and
Rossland Groups, and the coeval igneous belts formed in response to continued subduction of part of the Cache Creek Ocean plate
(CC; Mihalynuk and others, 1994).
(7) In the axial parts of the Stikinia-Quesnellia island arc, continuing on from the Late Triassic, were the Coast (CM),
Copper Mountain (North; CMN), Copper Mountain (South; CMS), Galore (GL), Guichon (GU), Klotassin (KL), and Texas Creek
(TC), and Toodoggone (TO) belts which contain granitic magmatism-related deposits
(8) Also occurring was obduction of parts of the Seventymile and Slide Mountain Ocean plates onto the North American
Craton Margin (NAM; Mihalynuk and others, 1994). Part of the obduction occurred by the Late Triassic and (or) Early Jurassic
when granitic plutons of the Stikinia-Quesnellia island arc intruded across an intervening fault. During the final st age of ob duction
of the Slide Mountain terrane (SM) over the Kootenay metamorphosed continental-margin terrane (KO), these ter Tanes star ted to
obduct onto the North American Craton Margin (NAM). Migration of the Stikinia-Quesnellia arc and associated t erranes to )ward
-A: ---a- I -- - - -. -
the North American Craton Margin was accomplished by subduction of the Seventymile Ocean plate along the conunenml-rnargln
and by obduction.
(9) Outboard and perhaps at a lower paleolatitude (either 25" or 4S0), the Talkeetna and Bonanza arcs continued activity
in the Wrangellia superterrane (WRA). This extensive arc formed along most of the length of the Wrangellia superterrane with
coeval equivalents in the Cadwallader (CD) island arc and Methow (MT) turbidite-basin terranes. Forming in the arcs were the
Talkeetna Mountains-Alaska Range metallogenic belt, which contains kuroko massive sulfide deposits, the Alaska Peninsula
metallogenic belt (AP), which contains Cu- and Fe-skam deposits, and the Island Porphyry metallogenic belt (IP), which contains
granitic-magmatism-related deposits. Associated with the Talkeetna and Bonanza arcs was subduction of part of the Cache Creek
Ocean plate to form the Chugach (CG), Bridge River (BR), and possibly Baker (BA) terranes.
Metallogenic Belts Formed in
Middle Mesozoic Talkeetna-Bonzana
Island Arc in Wrangellia Superterrane
Alaska Peninsula Metallogenic Belt of
Granitic Magmatism Deposits (Belt AP)
Alaska Peninsula
The Alaska Peninsula metallogenic belt of granitic magmatism deposits (fig. 42; tables 3,4), mainly Cu- Au, Cu-21 n, and
Fe skarn deposits, occurs on the northeastern Alaska Peninsula. The metallogenic belt is hosted in the central and northwesl tern
part of the Peninsular sequence of the Talkeema-Bonanza island in the Wrangellia superterrane where intruded by Julamlr. ..----.- g~anitoid --
plutons (Nokleberg and others, 1994c, 1997~). The significant deposits in the belt are the Crevice Creek, Glacier Fork, Kasna
Creek Cu-Fe skarn deposits, and the Magnetite Island Fe skam deposit (table 4) (Nokleberg and others 1997a. b, 1998).
Crevice Creek Cu-Au Skarn Deposit
The Crevice Creek Cu-Au skam deposit (Martin and Katz, 1912; Richter and Herreid, 1965) consists of at least ten
epidote-garnet skarn bodies which occur in limestone over a 2 krn' area adjacent to the Jurassic(?) granodiorite stock of Pilot
Knob. The skarn bodies vary from 3-800-m long and from a few centimeters to 60 m wide. Local magnetite-rich skam occurs in
isolated pods in nearby metavolcanic rocks, and local disseminated magnetite zones occur in epidote-garnet skams. The garnet