USGS Professional Paper 1697 - Alaska Resources Library

logenesis of the region (1) subduction-related arc, (2) collisional
(anatectic)-related arc, (3) post-collisional extension,
(4) oceanic rift, (5) continental rift, (6) back-arc rift, and (7)
transform continental-margin arc. Each tectonic environment
provides a unique interpretation for the origin of the 144 major
metallogenic belts and 1,079 significant mineral deposits in
the region.
Examples of metallogenic belts associated with each of
the seven tectonic environments 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-rifting
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 sulfide deposits
associated with the back arc of Talkeetna-Bonanza arc. (7) An
example of a transform continental-margin arc tectonic environment
is the Early Tertiary Central Koryak metallogenic belt
of polymetallic 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,
Figure 1. Generalized theoretical example illustrating the methodology for metallogenic analysis of cratons, terranes,
accretionary assemblages, overlap assemblages, and contained metallogenic belts. Refer to text for discussion.
Introduction 5