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

Metallogenesis and Tectonics of the Russian Far East, Alaska, and
the Canadian Cordillera
Abstract
The Proterozoic and Phanerozoic metallogenic and tectonic evolution of the Russian Far East. Alaska, and the Canadian
Cordillera is recorded in the cratons, craton margins, and orogenic collages of the Circum-North Pacific mountain belts which
separate the North Pacific from the eastern North Asian and western North American Cratons. The collages consist of
tectonostratigraphic terranes and contained metallogenic belts which are composed of fragments of igneous arcs, accretionary-
wedge and subduction-zone complexes, passive continental margins, and cratons. The terranes are overlapped by continental-
margin-arc and sedimentary-basin assemblages and contained metallogenic belts. The metallogenic and geologic history of
terranes, overlap assemblages, cratons, and craton margins has been complicated by post-accretion dismemberment and translation
during strike-slip faulting which occurred subparallel to continental margins.
Seven processes overlapping in time were responsible for most of metallogenic and geologic complexities of the region.
(1) In the Early and Middle Proterozoic, marine sedimentary basins developed on major cratons and were the loci for ironstone
(Superior Fe) deposits and sediment-hosted Cu deposits which occur along both the North Asia Craton and North American
Craton Margin. (2) In the Late Proterozoic, Late Devonian, and Early Carboniferous, major periods of rifting occurred along the
ancestral margins of present-day Northeast Asia and northwestern North American. The rifling resulted in fragmentation of each
continent, and formation of cratonal and passive continental-margin terranes which eventually migrated and accreted to other sites
along the evolving margins of the original or adjacent continents. The rifting also resulted in formation of various massive-sulfide
metallogenic belts. (3) From about the late Paleozoic through the mid-Cretaceous, a succession of island arcs and contained
igneous-arc-related metallogenic belts, and tectonically paired subduction zones formed near continental margins. (4) From about
mainly the mid-Cretaceous through the present, a succession of continental-margin igneous arcs (some extending offshore into
island arcs) and contained metallogenic belts, and tectonically paired subduction zones formed along the continental margins. (5)
From about the Jurassic to the present, oblique convergence and rotations caused orogen-parallel sinistral, and then dextral
displacements within the plate margins of the Northeast Asian and North American cratons. The oblique convergences and
rotations resulted in the fragmentation, displacement, and duplication of formerly more continuous arcs, subduction zones, passive
continental margins, and contained metallogenic belts. These fragments were subsequently accreted along the margins of the
expanding continental margins. (6) From the Early Jurassic through Tertiary, movement of the upper continental plates toward
subduction zones resulted in strong plate coupling and
accretion of the former island arcs, subduction zones, and contained metallogenic belts to continental margins. In this region, the
multiple arc accretions were accompanied and followed by crustal thickening, anatexis, metamorphism, formation of collision-
related metallogenic belts, and uplift; this resulted in the substantial growth of the North Asian and North American continents.
And (7) in the middle and late Cenozoic, oblique to orthogonal convergence of the Pacific Plate with present-day Alaska and
Northeast Asia resulted in formation of the present ring of volcanoes and contained metallogenic belts around the Circum-North
Pacific. Oblique convergence between the Pacific Plate and Alaska also resulted in major dextral-slip faulting in interior and
Southern Alaska and along the western part of the Aleutian-Wrangell arc. Associated with dextral-slip faulting was crustal
extrusion of terranes from Western Alaska into the Bering Sea.
Introduction
This report provides an analysis of the metallogenesis and tectonics of significant metalliferous lode deposits, selected
major nonmetalliferous lode deposits, and host rocks in the Russian Far East, Alaska, and the Canadian Cordillera. The report is
based on a series of published terrane and overlap assemblage maps, mineral deposit and metallogenic belt maps, and mineral
deposit databases, and interpretive articles for the region (Nokleberg and others, 1987, 1993, 1994a, b, c, d, 1995a, 1996, 1997a,
b, c, 1988a, b, 1989a, b, 2000). For the analysis, this report synthesizes and combines coeval and genetically-related groups of
significant lode mineral deposits into metallogenic belts. Each section on a specific metallogenic belt contains: (1) a description of
the significant mineral deposits; (2) a description of the host rocks for the significant lode deposits; and (3) an interpretation of the
origin of, and tectonic controls for the host rocks and contained deposits and metallogenic belt(s). The report also provides: (1)
metallogenic and tectonic definitions; (2) explanation of methodology; (3) list of mineral deposits models; (4) an integrated
metallogenic and tectonic model for the Phanerozoic geologic history of the region; and (5) an extensive list of cited references for
the geology, mineral deposits, metallogenesis, and tectonics of the region. The descriptions of sigrllficant mineral deposits in this
report are adapted from Nokleberg and others (1997a), with additional data and revision from the authors. For British Columbia
(southwest Canadian Cordillera), descriptions of significant mineral deposits are also revised with new data from MlNFlLE
(2002).
The Russian Far East, Alaska, and the Canadian Cordillera are commonly regarded as frontier areas in the world for the
discovery of metalliferous lode and placer deposits. During the late 1800's and early 1900's, the region was subject to recurring
ncvhes or sfnmpedes to sites of newly discovered deposits. During the last few decades, the region has been substantially explored