# Terrane Map of Northeast Asia:

# Principles of Compilation and Major Subdivisions of the Legend

# 

# By Leonid M. Parfenov (Institute of Geological Sciences, Siberian Branch,

# Russian Academy of Sciences, and Academy of Sciences of the Sakha Republic (Yakutia), Yakutsk), Alexander I. Khanchuk (Far East Geological Institute, Russian Academy of Sciences, Vladivostok, Russia), and Warren J. Nokleberg (U.S. Geological Survey, Menlo Park, California, USA).

**ABSTRACT**

A terrane map being compiled for Northeast Asia at a scale of
1:5,000,000 covers the territories of eastern and southern Siberia,
Mongolia, northeast China, southern Russian Far East, South Korea and
Japan. The compilation of the map is part of an international scientific
project on metallogenesis and tectonics of the region. This paper
discusses the principles and contents of terrane analysis on which the
map is based; provides definitions of key terms such as craton, terrane,
accretion, amalgamation, dispersion, etc.; describes different types of
terranes, overlap and stitch assemblages that are classified on the
basis of actualistic (tectonic) principles. A possibility of recognizing
terranes within the Early Precambrian basement of cratons is also
discussed.

**INTRODUCTION**

Studies in the 1970's, based on the new concepts of plate tectonics,
established that ophiolites of orogenic belts are former fragments of
oceanic crust that floored oceans, which subsequently disappeared. Also
recognized within orogenic belts were fragments of island arcs,
continents, and microcontinents. Also at this time, initial global and
regional paleotectonic reconstructions were made. At the time, it seemed
that the new paradigm would allow for quick resolution, because on the
basis of relatively limited initial data, all the global problems would
be quickly solved concerning the structure and evolution of Phanerozoic
orogenic belts and the accretion of continents. Consequently, future
generations of geologists would have little to accomplish (Howell,
1989).

However, detailed investigations carried out in the early 1980's,
primarily, in Alaska and the North American Cordillera (Coney and
others, 1980; Howell, 1985, 1989; Howell, and others, 1985; Jones and
others, 1983; Wheeler and others, 1991), revealed that orogenic belts
consist of a collage, or mosaic of fault-bounded crustal blocks known as
terranes. Terranes are fragments derived from larger tectonic units,
such as craton, passive and active continental margins, oceanic crust
(ophiolites), intraoceanic assemblages of various types and island arcs.
All these fragments are

interpreted as having formed at distances of hundreds to thousands of
kilometers from their present location, from each other, and from
adjacent cratons. Accretion (collision) of these fragments onto
continental margins produced orogenic belts and were accompanied by
regional thrust and strike-slip faulting. These accretions caused
dismembering of previously single tectonics units, their dispersion and
formation of new tectonic fragments along orogenic continental margins.
These fragments, now defined as a mosaic of terranes, defines the
structure of orogenic belts in Alaska and the North American Cordillera
(Coney and others, 1980; Howell, 1985, 1989; Howell, and others, 1985;
Jones and others, 1983; Monger and Nokleberg, 1996). These studies
clearly show that paleotectonic reconstructions must be preceded by hard
work that consists of recognizing terranes, establishing their
geodynamic nature, etc., a type of study now defined as terrane
analysis. A terrane analysis, now accepted as an efficient method of
regional tectonic study of orogenic belts, combines regional geological
mapping and detailed scientific investigations (structural, geochemical,
paleomagnetic, paleobiogeographic, etc.) with regional and global
paleotectonic reconstructions based on plate tectonic models. Also
linked to terrane analyses are metallogenic analyses of orogenic belts.

**PREVIOUS REGIONAL TERRANE ANALYSIS STUDIES**

In the 1980s, terrane maps of Alaska and North American Cordillera
(Jones and others, 1987; Monger and others, 1987; Silberling and others,
1987; Wheeler and others, 1988), and other regions (Howell, 1985) were
compiled and published. The terrane maps, in contrast to geodynamic maps
that are similar to geologic maps, show a mosaic of major tectonic units
in orogenic belts that formed by tectonic juxtaposition (accretion) of
terranes.

One of the first terrane maps for the territory of Russia was compiled
within the framework of an International Project on Metallogenesis and
Tectonics and of the Circum-North Pacific (Parfenov and others, 1993;
Monger and Nokleberg, 1996). The project was completed in the period
from 1990 to 1998 by geologists of the Russian Academy of Sciences (Far
Eastern and Siberian Branches) and the \"Roskomnedra\" (now Russian
Ministry of Natural Resources) in cooperation with geologists from U.S.
Geological Survey, the Geological Survey of Canada, the Alaska Division
of Geological and Geophysical Surveys, and the Geological Survey of
Japan. The results of the work were the terrane, mineral deposit, and
metallogenic maps published at scales of 1:5,000,000 to 1:10,000,000 of
the region and companion explanations (Nokleberg and others, 1994, 1997,
1998). The obtained data and interpretative analyses were reported and
appreciated at many international meetings in Russia, Japan, Alaska,
Canada, and the conterminous USA. As a successor to this first study, a
new similar international project of type was started on the to
metallogenesis and tectonics and of Northeast Asia (specifically Eastern
and Southern Siberia, Mongolia, Northeast China, South Korea, and Japan.
The terrane map discussed here is part of this new project that involves
geologists from all these countries and the USA. The terrane map for the
new project overlaps the western part of the former study, and a
continuation of the previous project (Figure 1). The new project is
scheduled to be completed in 5 years (1997-2002).

**PURPOSE OF THE MAP**

This paper discusses the principles of compilation of terrane maps in
connection with development of the legend of the terrane map of
Northeast Asia at a scale of 1:5,000,000. This discussion is
particularly important, because in Russian geological literature, such
terms and concepts such as terrane and terrane analysis are understood
differently than in North American (Gusev and Khain, 1995).

The terrane map of Northeast Asia is based on the principles developed
for the prior project on the Circum-North Pacific (Nokleberg and others,
1994, 1997, 1998) and on previously published terrane maps of other
regions (Jones and others, 1987; Monger and Berg, 1987; Silberling and
others, 1987; Wheeler and others, 1988). At the same time, additional
development of the legend is needed. These additions are required, on
the one hand, by the necessity of further refining the principles and
methods of tectonic cartography and, on the other hand, by a great
variety and complexity of tectonic structures for the new project area.
For instance, the Circum-North Pacific terrane map only delineates
Mesozoic and Cenozoic orogenic belts, whereas the new map will include,
in addition to Mesozoic and Cenozoic orogenic belts of Sikhote-Alin,
Japan and Russian Northeast, the various Paleozoic orogenic belts of
Central Asia, the Taimyr Peninsula, as well as the whole of the Siberian
platform and part of the North China platform. These areas contain
extensive outcrops of Early Precambrian crystalline rocks. The legend of
the previous map must be substantially supplemented to describe ancient
Archean and Proterozoic craton and young platform covers, Early
Precambrian cratonal formations, magmatic rocks of cratons, and
granitoids and metamorphic rocks within variously-aged orogenic belts.

The 1:5,000,000 terrane map of Northeast Asia is planned as a major
source of information on the geology and tectonic structures of the
region. Within the limits of the project, the map will serve as a
tectonic basis for analyzing the occurrence and formation of mineral
resources and metallogenesis of the region. The map may also be used for
other purposes, including regional tectonic analyses as well as analysis
of neotectonics, seismicity, recent volcanism, etc. The terrane map will
serve as a basis for paleotectonic reconstructions, showing ancient
continents, their passive and active margins, ancient oceans, island
arcs, microcontinents, and other intraoceanic formations.

Within the framework of the new project, regional problems and
fundamental geologic, tectonic, and metallogenic problems will be
addressed. These problems include: (1) comparatively analyzing the
structure, paleogeodynamics and metallogenesis of Mesozoic-Cenozoic,
Paleozoic and Late Precambrian orogenic belts in relation to the opening
and evolution of the Pacific and Paleoasian oceans; (2) analyzing the
tectonics and metallogenesis of Precambrian and Phanerozoic rocks within
the limits of ancient platform shields; (3) recognizing specific events
of metallogenesis and crustal formation; (4) determining the origin and
evolution of major sedimentary basins within ancient platforms and in
variously-aged orogenic belts on the periphery of the Pacific and Arctic
oceans; and (5) determining the nature of magmatic activity and
associated mineralization within platforms.

**TERRANE ANALYSIS CONCEPTS**

Terrane analysis includes the following concepts: (1) recognition of
terranes, their overlap units (sedimentary and volcanic-sedimentary) and
\"stitching\" assemblages (magmatic and metamorphic); (2) definition of
terrane boundaries and types (thrust, strike-slip, or normal faults);
(3) classification of terranes and their overlap and \"stitching\"
assemblages on an actualistic or tectonic basis (island-arc formations,
accretionary wedge complexes, active and passive continental margins,
fragments of oceanic crust, etc., and magmatic formations related to
rifting, collision, subduction, and other processes); (4) recognition
and classification of post-accretionary faults that formed after the
accretion of terranes to a continental margin and which caused
dismembering and dispersion of terranes; and (5) analysis of
paleobiogeographic and paleomagnetic data to clarify the origin of
terranes.

**KEY TERMS FOR TERRANE ANALYSIS**

Key terms of terrane analysis are craton, tectonostratigraphic terrane
(or simply \"terrane\"), accretion, amalgamation, dispersion,
overlapping and \"stitching\" assemblages.

**Craton** is defined as a large (several million sq. km), rigid part of
the continental crust that formed in the Precambrian (e.g., North Asian,
Sino-Korean, and North American Cratons). A craton includes ancient
platform and outer zones (fold-and-thrust belts) of contiguous orogenic
belts. The platform and outer zones of orogenic belts have the same
Precambrian crystalline basement, and thick, deformed sedimentary
sequences that overlap the basement of the outer zones that laterally
grade into synchronous formations of the ancient platform cover. For
example, North Asian Craton (Kosygin and others, 1964) includes the
Siberian Platform and variously-aged, marginal fold- and thrust-belts,
including the Verkhoyansk, Baikal-Patom, Yenisey Ridge and Southern
Taimyr fold- and thrust-belts. The outer zones of orogenic belts are
separated from the platform by frontal thrusts or frontal monoclines.
The character of deformations within the outer zones of orogenic belts
is defined by thrusts, including regional tectonic decollements
(sedimentary sequences detached from the crystalline basement), and by
major folds. These zones are called \"miogeoclines\" (Dietz and Holden,
1966) because their stratigraphic section and thickness increase with
distance from the front of the orogenic belt and \"fold-and-thrust
belts\". Paleotectonically, a craton with a miogeoclinal margin
corresponds to a continent with the miogeocline corresponding to passive
margins of the modern continents. A craton (continent) increases in size
with time due to attachment (accretion) of various terranes.

**Tectonostratigraphic terrane** (terrane) occurs beyond a craton margin
and is defined as a fault-bounded body of the Earth\'s crust, large
enough to be mapped at a scale of 1:5,000,000, that greatly differs in
its geologic history from that of adjacent terranes. A combination of
terranes with complex structural relationships comprises an entire
orogenic belt. Recognition of a terrane is based not on the idea of
possible large horizontal movements, but on the analysis of
stratigraphic, paleontologic, structural, magmatic and metamorphic data
that indicate a difference in geologic history compared to that of
adjacent terranes.

The term \"tectonostratigraphic terrane\" implies that terranes
recognized in Phanerozoic orogenic belts are characterized first of all
as a distinctive stratigraphy and stratigraphic sequence of geologic
complexes that formed in specific geodynamic settings (geodynamic
complexes), as well as by the time and peculiarities of deformational,
metamorphic, and magmatic events. A terrane may include one or more
geodynamic complexes. In the explanatory note to the Circum-North
Pacific terrane map (Nokleberg and others, 1994) each terrane is
illustrated by a tectonostratigraphic column that portrays a sequence of
geodynamic complexes, major stratigraphic breaks and unconformities,
fossils (macrofauna, microfauna, or flora), isotopic ages, and age of
deformational, metamorphic, and magmatic events. Terranes in many of the
orogenic belts are interpreted as having migrated several thousands of
kilometers before accretion to a continent, and having traveled on \"the
back\" of oceanic lithosphere that was subducted beneath a continental
margin or an island arc. Such terranes are called **exotic**. Examples
of such terranes are those occurring in the Koryak Highland and
Sikhote-Alin regions of the Russian Far East, as well as the Wrangellia,
Quesnellia, and Stikinia terranes of southern Alaska and the western
Canadian Cordillera. All contain remnants of late Paleozoic and early
Mesozoic Tethyan fauna. In general, all recognized terranes must be
checked for the degree of exotic nature by examining paleomagnetic and
paleobiogeographic data. Sometimes such terranes are called \"suspect\"
(Howell, 1989).

In addition, some terranes may have been fragments of larger tectonic
units that disintegrated and were dispersed during accretion and
post-accretion faulting. Such dispersal may create a collage of terranes
derived from many various tectonic origins, including cratonal,
miogeoclinal (passive continental margins), continental margin magmatic
arc (active continental margins), island-arc, accretionary wedge,
oceanic environments. Some terranes include geologic formations of
various geodynamic or tectonic nature, i.e., different geodynamic
complexes. For example, a terrane may consist of a
continental-margin-arc or rift-volcanic sequence that formed an Early
Precambrian crystalline basement. In this case the nature of a terrane
is defined by the upper (younger) geodynamic complex (tectonic
environment).

About twenty terranes occur within the Mesozoic orogenic belts of the
Russian Northeast on the Circum-North Pacific terrane map (Nokleberg and
others, 1994, 1997) with each terrane defined by a unique name and map
unit, and a distinct geologic history. The terranes vary in size from
several kilometers to 350 km across. The smallest are ophiolite sheets,
representing fragments of oceanic crust and lithosphere. Most of the
terranes are rather large (tens to hundreds of kilometers across) and
are variously shaped. In plan view, there exist equidimensional
terranes, e.g., Okhotsk (300 by 350 km) and Omolon (250 by 350 km)
cratonal terranes; narrow (several tens of kilometers) linear terranes
that extend for many hundreds of kilometers, e.g., the South-Anyui
accretionary wedge terrane, Koni-Murgal island-arc terrane, Omulevka
miogeoclinal (passive continental margin) terrane and others. Terranes
are subdivided into subterranes defined as fault-bounded parts of
terranes with similar but not identical geologic history (Nokleberg and
others, 1994).

In the analysis of orogenic belts in the context of plate tectonics the
term \"suture\" (or \"suture zone\") is widely used and is defined as a
tectonic expression of the zone of collision (Howell, 1989). A suture
zone normally includes ophiolites and (or) high-pressure metamorphic
rocks. On the Circum-North Pacific terrane map, ophiolites and
high-pressure metamorphic rocks with glaucophane and lawsonite comprise
parts of some accretionary wedge terranes. Many of these terranes, with
a ribbon-like plan view, are described in the literature as suture
zones, e.g., the Angayucham terrane in Alaska, the South-Anyui terrane
in Chukotka, and the Tukuringra-Djhagdi terrane in the Mongol-Okhotsk
belt. Consequently, no need exists to separately delineate suture zones
as independent tectonic units. In the past, many of the terranes were
separated by vast expanses of oceanic crust. Consequently, ophiolites,
and sometimes high-pressure metamorphic rocks tend to occur at the
boundaries of many terranes; however this occurrence is not a necessary
condition for defining terranes boundaries. Rather the boundaries of the
terranes are marked by major thrust, strike-slip, and, less frequently,
by normal faults, and tectonic melange zones.

Some authors criticize the term \"terrane\" without apparent good basis.
Sengör (1990, 1991) expresses concerns that the term \"terrane\" might
be emasculated and reduced to a tectonic nappe or even smaller tectonic
units. In fact, it is difficult to set size limits of a terrane.
Recognition of a terrane must be guided by the ultimate aim of research
which is to make global and regional paleotectonic reconstructions on
the basis of a terrane map. These aims include reconstructions of an
orogenic belt as a whole, e.g. North American Cordillera, or those of a
number of orogenic belts, e.g. in the Russian Northeast. In this case,
recognition of numerous, small terranes is not useful. It should be
noted that in his works devoted to tectonic evolution of Asia, Sengör
(1990, 1991 presents \"a generalized tectonic map\" showing present
location of \"the first-order tectonic units\" (Figure 2 in (Sengör and
others, 1993)). Subsequent paleotectonic reconstructions are based on
these first-order tectonic units from which island arcs,
microcontinents, etc. are reconstructed. As can be easily seen, these
first-order tectonic units are the same as terranes.

**Accretion** is defined as tectonic attachment of one or more terranes
to a craton (continent) margin. It is a cardinal event in tectonic
evolution of a terrane and a craton margin. Geologic assemblages that
formed before the accretion are defined as preaccretion assemblages,
whereas those that formed afterwards as postaccretion assemblages.
Accretion may result from subduction, for example collision of an island
arc with a passive or active continental margin, from obduction of
oceanic crust onto a continent, or from large strike-slip motions
parallel to a continent margin.

**Amalgamation** is defined as tectonic combination of two or more
terranes into a single larger tectonic unit prior to their attachment to
a craton. Amalgamation produces either a composite terrane or a
superterrane or. A composite terrane consist of terranes of the same
nature, say, two or more island arc terranes. A superterrane includes
terranes of different nature such as island-arc, passive continental
margin, oceanic terranes, etc. For example, the Mesozoic Kolyma-Omolon
superterrane in the Russia Northeast includes the Omolon cratonal
terrane, the Omulevka and Prikolyma miogeoclinal (passive continental
margin) terranes, the Alazeya, Khetachan, and Oloy island-arc terranes,
the Munilkan oceanic terrane, etc. The superterrane formed as a single
unit in the late Middle Jurassic. Upper Jurassic rocks rest with an
angular unconformity on different-aged deposits of terranes making up
the superterrane. According to paleomagnetic data, the superterrane was
at a distance of 1,500-2,000 km from the North Asian craton in the early
Late Jurassic. The superterrane accreted to the craton margin only in
the late Late Jurassic to Early Cretaceous as indicated by the formation
of collisional granites of 140-130 Ma as dated by incremental Ar
techniques.

In addition to \"accretion\" and \"amalgamation\", terrane analysis
involves such terms as \"collision\" and \"docking\". The term
\"collision\" is used in the English geologic literature in a general
sense as \"impact\". This may explain its absence in the basic Glossary
of Geology edited by Bates and Jackson (1990). One can speak of
collision of terranes with one another or with a craton, collision of
continents, island arcs, etc. The term \"docking\" denotes attachment of
terranes to a craton (continent) (Twiss and Moores, 1992) and is
synonymous with \"accretion\".

**Dispersion** is defined as tectonic dismemberment of previously
accreted or amalgamated terranes and occurs in three different ways
(Howell, 1989):

\(1\) By translation of terrane fragments along major strike-slip faults
over a distance of hundreds to thousands of kilometers; (2) By rifting
leading to divergence of fragments of previously single terrane or
terranes; the amount of displacement may be very large if rifting
develops into the opening of a new ocean; And (3) by dismembering of
terranes by deep-seated thrusting that causes sheets of lower crustal
(or even upper mantle) rocks coming to the surface. One example of a
terrane dispersion as a result of strike-slip tectonics is the
Wrangellia terrane in North American Cordillera which was accreted to
the continent in the mid-Cretaceous (Monger and Nokleberg, 1996).
Subsequently in the Late Cretaceous and Cenozoic the terrane was
dismembered into fragments and was dispersed over a distance of 24^°^ of
latitude as a result of large-scale strike-slip faults that occur
parallel to the continent margin. Another example is the San Andreas
fault in California along which dispersion of terranes on the continent
margin occurred over the last several million years and continues to the
present (Crowell, 1985). Similar examples are known from eastern Asia
(the Tanlu fault in China and the Central Sikhote-Alin fault, each with
displacements of hundreds of kilometers). The Avekova terrane within the
Mesozoic rocks of northeast Asia, which is comprised of Early
Precambrian metamorphic rocks, is an example of terranes detached from
the structurally similar Omolon terrane. Detachment is interpreted as
occurring in the Late Paleozoic due to rifting that formed the so-called
Gizhiginsk fold zone that separates the two terrane (Parfenov, 1984).
Examples of deep thrusts are known from the southern Alps and the
Grenville province in the Canadian shield (Howell, 1989). **Terrane
fragments** are parts of terranes that formed by dispersion.

**Overlap and stitch assemblages** form after the accretion and
amalgamation of terranes and define the maximum age limit of such
events.

Overlap assemblages consist of sedimentary, volcanic-sedimentary and
volcanic rocks that accumulated after amalgamation or accretion of
terranes. These assemblages stratigraphically overlie two or more
adjacent terranes or a terrane and a craton margin. Overlap assemblages
include ancient and young platform covers, marginal and intermontane
basins, molasses, etc. Stitch assemblages are represented by plutonic
rock belts or dike swarms and metamorphic belts of various geodynamic
nature that pierce the adjacent terranes and a craton (continental)
margin.

Stitch assemblages may form during accretion and amalgamation of
terranes, rifting, subduction, or other processes. Plutonic rocks may be
genetically related to volcanic rocks overlying terranes. An example in
the Russian Northeast is the granitoids of the Cretaceous
Okhotsk-Chukotka continental-margin volcanic-plutonic belt. As with
terranes, overlap and \"stitch\" assemblages are classified on the basis
of actualistic principles.

Key terms of terrane analysis are schematically illustrated in Figure 2A
where an orogenic belt, formed of terranes 1, 2, 3, and 4, occurs
between two cratons (A and B). A corresponding tectonostratigraphic
diagram (Figure 2-B) shows ages of rocks comprising terranes, and
postamalgamation and postaccretion overlap and stitch assemblages. As
seen from the diagram, terranes 3 and 4, that formed after intrusion by
pluton **a** of Early Jurassic age, formed a single tectonic unit,
superterrane I, that was accreted to craton B in Middle Jurassic time,
as indicated by the age of the lower horizons of their overlying
deposits **b**. Terranes 1 and 2 were amalgamated into superterrane II
in Late Jurassic time, and subsequently, in the early Cretaceous, were
accreted to craton B. Formation of an orogenic belt in the Cenozoic
occurred as a result of collision of cratons A and B. In the Cretaceous
time, accretion of superterrane II to craton B was followed by
dispersion of terranes 2 and 4 along a strike-slip fault.

**TERRANES IN PRECAMBRIAN BASEMENT OF CRATONS**

Early Precambrian structures in the basement of cratons which are
exposed within the limits of shields represent a mosaic of blocks as
large as hundreds of kilometers across that are separated and surrounded
by linear belts of folded rocks that are metamorphosed to varying
degrees (in some cases, up to granulite facies). The craton of the
Canadian Shield is divided into provinces, subprovinces, orogenic, and
granulite belts. The cratons of Africa and Australia are composed of
granite-greenstone formations and mobile belts composed of granulite and
amphibolite facies rocks. The Aldan Shield is described as fold areas,
systems, and zones.

In recent years the term \"terrane\" has found wide use for describing
these large Early Precambrian tectonic units or smaller structures
within them (Dobretsov and others, 1997; Dook, 1989; Frost and others,
1997; Glover and Ho, 1992; Howell, 1989; Moscovchenko and others, 1993;
Rosen and others, 1990). We find it reasonable to apply the term
\"terrane\" to Early Precambrian fault-bounded tectonic units that
differ in their geologic features and, hence, in their geologic history.
Where not affected by high-grade metamorphism, a general mosaic pattern
of Early Precambrian structures in many ways is similar to the
structures of some Phanerozoic orogenic belts. An example is the
Paleozoic structures of Central Kazakhstan or Mesozoic units of the
Russian Northeast, that all exhibit a \"block-mosaic\" pattern. At first
glance, plate tectonics models are also readily applicable for
interpreting Early Precambrian structures of cratons, provided that
original composition of high-grade rocks could be restored on the basis
of geochemical and other data. However, it is not always possible to
reconstruct unambiguously original composition of metamorphic rocks and,
moreover, it is still unclear whether plate tectonics operated in the
same sense in Early Precambrian time. Kevin Burke, former editor of
\"Tectonics\" wrote, in the foreword to the book *Greenstone Belts*,
that plate tectonics is a basic property of the present Earth and it
would be interesting to know if the Earth was different during Archean
times. Unfortunately this is not an easily answered question (Burke,
1997).

For compilation of the terrane map of Northeast Asia, we suggest that
terranes be identified in the Early Precambrian cratons in a manner
similar to that for Phanerozoic orogenic belts, i.e. as large (tens and
first few hundreds of kilometers across) fault-bounded tectonic units
differing in their geologic history, and classified on the basis of
their rock composition. Unlike Phanerozoic terranes, Early Precambrian
terranes can not be classified as stratigraphic sequences, in most
cases, due to their high-grade metamorphism. In recognizing Early
Precambrian terranes, the most important things to consider are the
types and combination of their metamorphic and magmatic rocks, age of
protolith, age and type of the main and superimposed metamorphism, and
age of magmatic events.

Within the Aldan-Stanovoy Shield various Early Precambrian terranes have
been recognized. These terranes include the Olekma and Batomga
granite-greenstone terranes, the Nimnyr charnockite-granite gneiss
terrane, the Seimsko-Sutam quartzite-paragneiss terrane, the
Timpton-Uchur quartzite-carbonate-paragneiss terrane, the Tynda
tonalite-trondhjemite terrane, and the Chogar amphibolite-diorite gneiss
terrane. Just like in Phanerozoic orogenic belts, Early Precambrian
terranes can amalgamate into a composite terrane or superterrane. For
example, the Nimnyr and Seimsko-Sutamsk terranes comprise the
Central-Aldan superterrane. The Seimsk thrust separating these two
terranes is dated at 2.3 Ga which is much earlier than the time of
accretion of the superterrane to the Olekma terrane to the west (1.85
Ga) and the time of accretion of the Timpton-Uchur terrane to the east
(1.75 Ga). According to interpretations of Smelov (1996), the
Central-Aldan superterrane is separated from adjacent terranes to the
west, south, and east by wide (up to 100 km) zones of tectonic melange,
respectively the Amga, Kalar and Tyrkanda tectonic melanges. Within
these melange zones are tectonically juxtaposed sheets comprised of
adjacent terranes and high-pressure granulites and anorthosites from the
lower crustal levels. In the Anabar Shield, similar melange zones, up to
several tens of kilometers wide, separate blocks (terranes) of
compositionally various granulites, and are described as deeply eroded
fault zones (Lutz and Oxman, 1990).

Assuming plate tectonics operated in Early Precambrian time in a manner
similar to modern plate tectonics, attempts can be made to find possible
Phanerozoic analogs of geodynamic settings in which Early Precambrian
terranes formed. For example, granite-greenstone terranes may be
highly-metamorphosed units that formed from the island-arc or oceanic
tectonic environments. Tonalite-trondhjemite terranes may be the
highly-metamorphosed, root zones of continental-margin magmatic arc.
Charnockite-granite gneiss terranes may be the highly-metamorphosed,
miogeocline (passive continental margin), forearc or backarc basins of
island arcs. Of course, these correspondences are highly speculative and
many specialists of Early Precambrian geology would not agree to these
interpretations. Because of these considerations, for compiling the
Northeast Asia terrane map, we decided to classify Early Precambrian
terranes on the basis of generalized compositional data and have map
users formulate their interpretations of the nature of the terranes.

**MAIN DIVISIONS OF MAP LEGEND**

The legend of the 1:5,000,000 terrane map of Northeast Asia includes
three divisions: (1) terranes, (2) overlap and \"stitch\" assemblages,
and (3) other symbols.

**Tectonic Environments for Terranes**

Terranes of Phanerozoic and Late Precambrian orogenic belts are defined
and interpreted as forming in the following tectonic environments
(Nokleberg and others, 1994). Terranes are colored according to tectonic
environment and not according to age.

***Cratonal terrane*** is defined as a fragment of a craton, composed of
Early Precambrian crystalline rocks, sometimes with a thin Late
Precambrian and (or) Phanerozoic cover (e.g., Gardan terrane in Eastern
Sayan region or Muya terrane in Transbaikal region (Parfenov and others,
1996)).

***Miogeoclinal terrane*** is defined as a fragment of a miogeocline
(passive continental margin), composed of thick shallow-water (shelf)
sedimentary series deposited on a thinned continental crust (e.g.,
Omulevka and Chukotka terranes in Russian Northeast (Parfenov and
others, 1993)).

***Continental margin terrane*** is defined as a fragment of a
continental slope and adjacent rise and is composed of distal turbidites
and hemipelagic deposits formed deposited on a thinned continental or
oceanic crust (e.g., Kular-Nera, Rassokha and West Kamchatka terranes in
Russian Northeast (Parfenov and others, 1993)).

***Continental margin arc terrane*** is defined as a fragment of an
Andean-type continental margin arc and includes calc-alkaline volcanic
and (or) plutonic rocks unconformably overlying or intruding units below
the arc. This type of terrane may also include forearc basins
represented by thick (measured in kilometers), deep-water,
shallow-water, and continental deposits formed near of the front of a
magmatic arc (e.g., Sergeevka and Kabarga terranes in Sikhote-Alin
region (Nokleberg and others, 1994)).

***Island arc terrane*** is defined as a fragment of a volcanic island
arc and adjacent forearc basin, and is composed of island-arc
volcanic-sedimentary and intrusive rocks. Various types of ophiolites,
representing subjacent oceanic crust, may also occur (e.g., Alazeya and
Khetachan terranes in the Russian Northeast, and the Iruneiskiy and
Olyutorka-Kamchatka terranes in Kamchatka (Parfenov and others, 1993;
Nokleberg and others, 1994), the Eravnya and Djida terranes in
Transbaikal (Parfenov and others, 1996)).

***Oceanic terrane*** is defined as a fragment of oceanic crust obducted
onto continental crust and is composed of MORB-type ophiolites. This
type of terrane may also include fragments of submarine volcanic
islands, guyots, etc. (e.g., Munilkan and Econay terranes in the Russian
Northeast (Parfenov and others, 1993)).

***Accretionary wedge terrane (type A*)** is defined as a fragment of
the accretionary wedge of a continental margin or island magmatic arc
made mainly of turbidites with minor amounts of oceanic rocks or without
them (e.g., Prince Williams terrane in southern Alaska (Nokleberg and
others, 1994)).

***Accretionary wedge terrane (type* B)** is defined as a fragment of
the accretionary wedge of a continental margin or island magmatic arc
made chiefly of oceanic rocks with subordinate turbidites (e.g., South
Anyui terrane in the Russian Northeast, and the Samarka terrane in the
Sikhote-Alin region (Nokleberg and others, 1994)).

***Flysch** or **turbidite basin terrane*** is defined as a fragment of
thick flysch (turbidite) series of unclear origin. This type of terrane
may form on a continental slope and its rise, or in forearc or backarc
basins related to continental-margin or volcanic island arcs, or in
narrow troughs in the front of advancing tectonic nappes (e.g.,
Beryozovka terrane in the Russian Northeast (Nokleberg and others,
1994), and the Barguzin terrane in Transbaikal (Parfenov and others,
1996)).

***Rift terrane*** is herein defined as a fragment of a rift zone
composed of sedimentary and magmatic rocks associated with regional
normal faults and (or) basin and range structures in intracontinental
rifting conditions. Such terranes were not recognized for the
Circum-North Pacific; however, a careful investigation of Northeast Asia
may reveal their presence.

***Crystalline Cratonal Basement*** terranes of Early Precambrian age
are classified on the basis of their generalized present-day rock
composition. These terranes include granite-greenstone,
charnockite-granite gneiss, quartzite-paragneiss, enderbite gneiss and
other terranes.

**Tectonic Environments for Overlap and Stitch Assemblages**

Overlap and \"stitch\" assemblages are defined and interpreted as
forming in the following tectonic environments (Nokleberg and others,
1994).

***Continental margin and island arc assemblages*** (undifferentiated).
These assemblages consist of which volcanic-plutonic belts, formations
of backarc and forearc basins. Tectonically-linked (paired) and
accretionary wedge or subduction zone assemblages are excluded. Examples
of continental margin assemblages are; (1) the Cretaceous
Okhotsk-Chukotka and East Sikhote-Alin volcanic-plutonic belts in which
granitoids and volcanics are shown; (2) the adjacent Penzhina and West
Sakhalin forearc basins; (3) the modern Kuril-Kamchatka volcanic arc
with the associated South Okhotsk backarc basin and adjacent forearc
basins on the Pacific side of the arc; and (4) the Kuril-Kamchatka arc
composed of the Kuril Islands arc and the onstrike East Kamchatka
volcanic belt that unconformably overlying previously accreted terranes.

***Miogeoclinal (passive continental margin) assemblages***.

***Intracontinental assemblages.*** These assemblages include rifts,
aulacogens, platform covers of different age, and magmatic formations
(massifs, pipes, alkali ultramafic dike complexes, carbonatites,
gabbros, alkali granites, kimberlites, plato-basalts, etc.).

***Assemblages related to orogenic belts***. These assemblages include
foreland molasse, hinterland and intermountain basin deposits,
collisional granite belts and dikes, and various metamorphic belts.

***Assemblages related to large-scale transform motions of crustal
blocks.*** These assemblages include fields and belts of bimodal
volcanic rocks, alkali to subalkalic granites, mafic to ultramafic
rocks, pull-apart sedimentary basins, etc).

***Colors, symbols, and faults.*** Ages of overlap and \"stitch\"
assemblages are colored by age whereas their geodynamic nature (tectonic
environment) is indicated by patterns. Ancient and modern overlap
assemblages (including modern-day island arcs, passive continental
margins, etc.) are also defined as overlap assemblages. Overlap and
stitch assemblages are marked by low-intensity yellow and light-brown
colors that differ sharply from the intense red, green, violet, and blue
colors of tectonic environments for terranes. This practice permits
recognition of terranes and determination of the timing of accretion and
amalgamation of terranes. Other symbols include stratoisohypses along
the sole of platform covers, boundaries of major sedimentary basins,
astroblemes, and faults. Faults are differentiated into terrane-bounding
faults and postaccretion faults causing dispersion of terranes. Faults
types are subdivided into thrusts, strike-slips, and normal faults.

**CONCLUSIONS**

The terrane map of Northeast Asia at a scale of 1:5,000,000 will display
present-day locations of terranes, overlap and \"stitch\" assemblages
within Cenozoic, Mesozoic, Paleozoic and Late Precambrian orogenic belts
located along the margins of the North Asian and Sino-Korean cratons,
and the Arctic and Pacific oceans. Both the terranes and their overlap
and \"stitch\" assemblages are classified on the basis of the plate
tectonic models. An effort has been made to recognize terranes in the
Early Precambrian basement of cratons. These terranes are classified on
generalized compositional data of crystalline rocks. By showing terranes
and the overlap and \"stitch\" assemblages, the map will demonstrate
major structures of orogenic belts and time of their formation, age of
accretion, as well as postaccretion and postamalgamation modifications.

The map is a major prerequisite for performing a regional metallogenic
analysis, for determining relationships of metallogenic belts and zones
with geodynamic complexes of various type and geodynamic processes that
have formed orogenic belts and contained mineral deposits. The map will
also yield valuable initial information for palinspastic (tectonic)
reconstructions that will also utilize paleomagnetic and
paleobiogeographic data.

**ACKNOWLEDGEMENTS**

The authors have discussed the preliminary legend of the terrane map of
Northeast Asia with N.A. Berzin, and M.I. Kuzmin. A section devoted to
the problem of terranes in the Early Precambrian basement of cratons is
the result of discussions with A.P. Smelov, V.F. Timofeev, A.N.
Zedgenizov and V.S. Oxman. M.I. Kuzmin and A.V. Prokopiev made valuable
remarks which were taken into consideration in preparing the final
version of the paper. The preliminary legend of the terrane map of
Northeast Asia is partly derived from the Circum-North Pacific terrane
map. For this map and corresponding legend, discussions with J.W.H.
Monger, Boris A. Natalin, George Plafker, D.W. Scholl, and Arthur Grantz
were very helpful. We are indebted to all of the above mentioned
geologists for fruitful discussions and help.

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**FIGURE CAPTIONS**

Figure 1. Areas covered by the previous project on metallogenesis and
tectonics of the Circum-North Pacific and the new project on
metallogenesis and tectonics of Northeast Asia.

Figure 2. Key concepts of terrane analysis.