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USGS Professional Paper 1697 - Alaska Resources Library

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ated subduction zone in the Wrangellia superterrane. Sedimentation<br />

continued along the passive continental margins of North<br />

Asia and North America. Out of the field of view of figure 33<br />

was formation of the Laoelin-Grodekovsk (LG) metallogenic<br />

belt, which contains granitic-magmatism-related deposits and<br />

that formed in the Laoelin-Grodekovsk island-arc terrane.<br />

Specific Events for Pennsylvanian<br />

(1) Along the margin of the North Asian Craton (NSC),<br />

dextral-slip occurred along the Mongol-Okhotsk suture (MO),<br />

resulting in displacement of its southern margin relative to the<br />

Mongol-Okhotsk Ocean.<br />

(2) Between the North Asian and North American<br />

Cratons, sporadic sea-floor spreading is interpreted as having<br />

enlarged the ancestral Pacific Ocean and formed the<br />

Oimyakon, Angayucham, and Goodnews Oceans. Forming<br />

during this event were the Aluchin (AC), and Ust-Belaya (UB)<br />

metallogenic belts, which contain podiform Cr deposits and<br />

are hosted mainly in fragments of ophiolites that are now pre-<br />

SKOLAI<br />

ARC<br />

?<br />

MO<br />

MONGOL-<br />

OKHOTSK<br />

OCEAN<br />

UB<br />

WRA<br />

(PE)<br />

NSC<br />

GL<br />

Position unknown<br />

relative to Stikinia and<br />

Quesnellia arcs<br />

ARW<br />

UNK<br />

OK<br />

NSV,<br />

KN<br />

?<br />

WRA<br />

(AX)<br />

60 o<br />

SKOLAI<br />

ARC<br />

KK<br />

NSC<br />

VL<br />

UNK<br />

UNK<br />

OM<br />

AK<br />

RA<br />

PR<br />

?<br />

?<br />

8-14 o<br />

(TA)<br />

OIMYAKON<br />

OCEAN<br />

COLL<br />

OL<br />

BE<br />

AC<br />

YA<br />

OV<br />

?<br />

AL<br />

AC<br />

KT<br />

ALAZEYA<br />

ARC<br />

Pennsylvanian Metallogenic Belts (320 to 286 Ma; figs. 31, 32) 77<br />

ANGAYU-<br />

CHAM<br />

OCEAN<br />

served in the Aluchin, and Penzhina-Anadyr, subduction-zone<br />

terranes. Fragments of the Oimyakon Ocean are preserved<br />

in the Debin and Garbyn’ya terranes (fig. 33). Fragments of<br />

the Angayucham and Goodnews Oceans are preserved in the<br />

Angayucham and Goodnews terranes, respectively (fig. 33).<br />

Within the Angayucham Ocean were the Kilbuck-Idono<br />

cratonal terrane (KI), derived from the North Asian Craton<br />

(NSC), and the Nixon Fork-Dillinger-Mystic passive continental-margin<br />

terranes (NX, DL, MY), derived from the North<br />

Asian Craton Margin (NSV). During this time span, before<br />

accretion to the present North American continent, the Nixon<br />

Fork-Dillinger-Mystic terrane may have experienced several<br />

post-rifting events that formed additional units, such as the<br />

siliciclastic rocks of the Sheep Creek Formation and the Mt.<br />

Dall Conglomerate.<br />

(3) The intraoceanic Omulevka Ridge, which separated<br />

the Oimyakon and ancestral Pacific Oceans, consisted of the<br />

Omulevka (OV), Prikolyma (PR), and Omolon (OM) terranes.<br />

These terranes were previously rifted from North Asian Craton<br />

and Craton Margin in the Early Mississippian. The Paleozoic<br />

ZL<br />

ANCESTRAL PACIFIC<br />

OCEAN<br />

KI<br />

GOOD-<br />

NEWS<br />

OCEAN<br />

YT<br />

NAM<br />

NX, DL,<br />

MY<br />

STIKINIA<br />

ARC<br />

0 800 km<br />

0 800 mi 320 to 286 Ma<br />

UNK<br />

NAC<br />

ST<br />

30 o<br />

SEVENTYMILE<br />

OCEAN<br />

METALLOGENIC BELTS<br />

AC - Aluchin<br />

ARW - <strong>Alaska</strong> Range-<br />

Wrangell<br />

Mountains<br />

KK - Ketchikan<br />

UB - Ust-Belaya<br />

NAM<br />

CACHE CREEK<br />

OCEAN<br />

NAC<br />

SLIDE MOUNTAIN<br />

OCEAN<br />

Figure 33. Pennsylvanian (320 to 286 Ma) stage of metallogenic-tectonic model for the Russian Far East, <strong>Alaska</strong>, and the Canadian<br />

Cordillera and adjacent offshore areas. Refer to text for explanation of metallogenic-tectonic events, to tables 3 and 4 for descriptions<br />

metallogenic belts and significant deposits, and to figure 18 for explanation of abbreviations, symbols, and patterns. Adapted<br />

from Nokleberg and others (1997b, 1998, 2000).<br />

KO

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