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

1,079 significant mineral deposits in the region. Examples of metallogenic belts associated with each of the seven tectonic
environment are as follows: (1) An example of a subduction-related arc tectonic environment is the mid- and Late Cretaceous
Eastern Asia metallogenic belt of mainly epithermal and polymetallic vein deposits which is hosted by the Okhotsk-Chukotka
volcanic-plutonic belt. (2) An example of a collisional (anatectic)-related arc tectonic environment is the Late Jurassic-Early
Cretaceous Yana-Kolyma metallogenic belt of mainly Au quartz vein deposits which is hosted along the suture bordering Kolyma-
Omolon superterrane. (3) An example of a post-collisional extension tectonic environment is the Late Cretaceous and early
Tertiary Chugach Mountains metallogenic belt of Au quartz vein deposits which is associated with underthrusting of Kula-
Farallon oceanic ridge and post-underthrusting extension. (4) An example of an oceanic rifling tectonic environment is the Early
Tertiary Prince William metallogenic belt of Besshi and Cyprus massive sulfide deposits which is associated with the Kula-
Farallon oceanic ridge. (5) An example of a continental rifting tectonic environment is the Late Devonian Selennyakh
metallogenic belt of Southeast Missouri Pb-Zn deposits which is associated with rifting of North Asian craton margin. (6) An
example of a back-arc rifting tectonic environment is the Late Triassic Alexander metallogenic belt of Cyprus massive silltide
deposits associated with the back arc of Talkeetna-Bonanza arc. And (7) an example of a transform continental-margin arc
tectonic environment is the Early Tertiary Central Koryak metallogenic belt of polyrnetallic and epithermal vein deposits
associated with the Kamchatka-Koryak igneous belt. The tectonic controls for each of the metallogenic belts of the region are
listed in Table 3 and described in more detail in the below sections on descriptions and interpretations of origins of metallogenic
belts.
The tectonic classification of lode mineral deposits has been a topic of considerable debate (Sawkins, 1990); however
classification of lode mineral deposits by mineral deposit types and tectonic environment can be extremely useful. These
classifications are useful for regional mineral exploration and assessment, for research on the critical or distinguishing
characteristics of metallogenic belts, and for synthesizing of metallogenic and tectonic models. For this report in describing the
metallogenic belts of the region, the significant lode deposits are classified both according to mineral deposit type and tectonic
environment.
Metallogenic and Tectonic Definitions
Definitions for mineral deposit, metallogenic, and tectonic terms used in this report were adapted from Coney and others
(1980), Jones and others (1983), Howell and others (1985), Monger and Berg (1987), Nokleberg and others (1987, 1994a, c,
2000), and Wheeler and others (1988). In alphabetical order, these terms and their definitions are as follows.
Accretion. Tectonic juxtaposition of two or more terranes, or tectonic juxtaposition of terranes to a craton margin.
Accretionary wedge and subduction-zone terrane. Fragment of a mildly to intensely deformed complex : of varying
amounts of turbidite, hemipelagic, and pelagic deposits, and oceanic crust and upper mant le. This 0 .ane is divided
into units composed predominantly of turbidite deposits or predominantly of oceanic rock s. Units al :led to have
formed during tectonic juxtaposition in a zone of major thrusting of one lithospheric plate over another, generally along the
margin of a continent or an island arc. The terrane may include large fault-bounded units which contain a coherent internal
stratigraphy. Many subduction-zone terranes contain fragments of oceanic crust and associated rocks which exhibit a complex
structural history, occur in a major thrust zone, and possess blueschist-facies metamorphism.
Collage of terranes. A composite group of tectonostratigraphic terranes.
Craton. Regionally metamorphosed and deformed shield assemblages of Archean and Early Proterozoic sedimentary, volcanic,
and plutonic rocks, and overlying platform successions of Late Proterozoic, Paleozoic. and local Mesozoic and Cenozoic
sedimentary and lesser volcanic rocks.
Craton margin. Chiefly Late Proterozoic through Jurassic miogeoclinal units deposited on a continental shelf or slope. Locally
has, or may have had an Archean and Early Proterozoic cratonal basement.
Cratonal terrane. Fragment of a craton.
Continental-margin arc terrane. Fragment of an igneous belt of coeval plutonic and volcanic rocks, and associated sedimentary
rocks which formed on or close to a continent, above a subduction zone dipping beneath a continent. Inferred to possess a
sialic basement.
Deposit. A general term for any lode or placer mineral occurrence, mineral deposit, prospect, and (or) mine.
Island-arc terrane. Fragment of a belt of plutonic rocks, coeval volcanic rocks, and associated sedimentary rocks which formed
above an intraoceanic subduction zone.
Metallogenic belt. A geologic unit (area) which either contains or is favorable for a group of coeval and genetically-related,
significant lode and placer deposit models. Using this definition, a metallogenic belt is a predictive tool for undiscovered
deposits.
Metamorphic terrane. Fragment of a highly metamorphosed or deformed assemblage of sedimentary, volcanic, and (or) plutonic
rocks which cannot be assigned to a single tectonic environment because the original stratigraphy and structure are obscured.
Includes intensely-deformed struclural melanges which contain fragments of two or more terranes.
Metamorphosed continenfa1 rnargln terrane. Fragment of a passive continenlal margin, in places moderately to highly
metamorphosed and deformed, which cannot be linked with certainty to the nearby craton margin. May be derived either from
a nearby craton margin or from a distant site.