亘ntroαuctio鷺to Geology of Mongolia · Mongolia is situated in the center of Asian continent....
Transcript of 亘ntroαuctio鷺to Geology of Mongolia · Mongolia is situated in the center of Asian continent....
Bulletin of the Geological Survey of Japan,voL43(12),p.735-744,1992
亘ntroαuctio鷺to Geology of Mongolia
Tsagaanbilegiin TsEDEN*,Satoshi MuRAo**
and,Dangind.orjiinDoRJGoTov*
TsEDEN Tsagaanbilegiin,MuRAo Satoshi and DoRJGoTov Dangindorjiin(1992)Intro- duction to Geology of Mongolia。j%ZZ,Gθo乙Sαro.」αpα1z,vol.43(12),p.735-744,
9fig.,3tab.
Abstract:Mongolia,situated between the Siberian pl&tform and Sino-Korean massif,
is divided into two large blocks by the Ural-Mongolian Lineament:North and South
Large Blocks.The North Large Block is composed of Ulaanbaatar and.North Mongo.
lia,n Folde(1Systems. Each fol(1ed system contains several folded,belts. The South
Large Block consists of Inner Mgngolian and Sout五Mongolian Folded Systems。These
systems are composed of some folded belts,but the detail has not known yet.The
:Khangai-Khentii Megazone,one of the megazones in the North Mongolian Folded
System,hosts the Kherlen Depression where intense meta.llic mineralizations are
noticed.The Mongon-Ondor and Ondor-tsagaan deposits were dated tO be174-175Ma,
but there is no information for the age of other mineral(1eposits.
1. 亙ntroduction
Recently,Mongolia has come to the atten-
tion of mining geologists by her politicaI
change(e.g.,Dorian,1991)but the geological
information on Mongolia presented in public is
Ilot enough。 Thus the authors will give a brief
summary about geology of Mbngolia and intro-
duce the mineralization of“Kherlen Depression”
which is one of the target for the ITIT project
of MITL
2.Geology of Mongolia
Mongolia is situated in the center of Asian
continent. Geologically,it is sandwitched by
the Siberian platform in north and Sino-
Korean massif in south,εしnd is roughly devided
into two“large blocks’7by the“Ural-Mongo-
lian Lineament”which is the largest overthrust
fault in.the country(Fig.1).
*Institute of Geology and Mineral Resources,
Mongolia
**Mineral Resources Department
2.1The North:Large Block
This block occupies large area of the nation
and is composed of two folded systems:
“North Mongolian”and“Ulaanbaatar”Folded
Systems(Fig.2and Table1).
The North Mongolian Folded System is of
Caledonian orogeny and is composed of“Cen-
tral Mongolian Median Mass”.,“Nuur-Altai
Megazone”,“Shishkhid-Zedin Megazone”and
“Khangai-Khentiin Megazone”.The Central
Mongolian Median Mass,occupying the central
part of the North Mongolian Folded System,
consists of polymetamorphic folded stratum of
upper Archean to lower Proterozoic age and
those of Precambrian to early Cambrian age.
The Nuur-Altai Megazone is widely developed
in the west of the Central Mongolian Median
M&ss.This megazone includes“Nuuriin”and“Altai(or Mongol-Altai)”folded belts.The
Nuuriin folded belt consists of ophiolite com-
plex (upper Riphean),spilite,keratophyre,
carbonate rocks and terrigenous se(iimentary
Keywords:Mongolia,Ur&1-Mongolian Linea-ment,Kherlen Depression,Mongon-Ondor pro.
spect,Ondor-tsagaanmine.
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FIG.2
1Tectonic map of Mongolia。(After Yanshin,1974)
1二Precambrian basement l2:Precambri&n anorthosite etc.;3:Ripheian strata l41Middle Ripheian ophiolite;
5:Middle Ripheian tonalite and plagiogranite;6:shelf and graben facies of Middle Ripheian to early Cambrian age l7:0phiolite of various ages and relic oceanic crust;8:1ate Ripheian to early Cambrian strata;
9middle to upper Cambrian system l10:early Cambrian system l11:middle Ordovician,Carboniferous, Permian and Triassic strata;12-13:middle Ordovician to lower Carboniferous rocks;14:Paleozoic tonalite
and plagiogranite l15-16:middle Paleozoic granitoids l17:middle Carboniferous to Permian marine sediments 18:middle Carboniferous to Permian rocks of micro-continents and island arcs;19:lower Triassic granitoids l
20:molasse of Silurian to lower Carboniferous age l21:Silurian to Devonian volcano-plutonic complex;22:
molasse of Carboniferous to lower Triassic age;23:volcano-plutonic complex of Carboniferous to lower Triassic age;24:molasse of middle Triassic to lower Jurassic age;25:Mesozoic granitoids;26:Jurassic strata;27:lower『Cretaceous strata l28:strata of upper Cretaceous to P&leogene age l29:Cenozoic basalt;301
0verthrust and thrust;31:0ther faults l UML:Ura1-Mongolian Lineament l KD:Kherlen Depression.
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Fi9.2Schematic map showing m&jor tectonic units of Mongolia. 1:Central Mongolian Median Mass l II a:Nuriin Folded Belt l II b:Altai Folded
Belt l III:Shishkhid-Zeddin Megazone;IV:Khangai-Khentiin Megazone l V:
Ulaanbaatar Folded System;VI:South Mongoli&n Folded System;VIL Inner Mongolian Folded System;UML:Ural-Mongolian Lineament。
rocks (upper Riphean to lower Cambrian),
carbonate and volcanic formation (lower
Cambrian)and tuff and terrigenous sedi-
mentary rocks(lower to middle Cambrian)。
The Altai Folded Belt is composed of middle to
upper Cambrian flysh.The Shishkhid-Zediin
megazone is of Caledonian orogeny and is
distributed north of the Central Mongolian
Median Mass,(Tes,Shishkhid,Eg and Uuriin
basins),andalsointheeasternsideoftheKhovsgol sea. The structure and geolog・ic
history are similar to those of the Nuuriin
Folded Belt of the Nuur-Altai Megazone.
Khangai-Khentiin Megazone of Caledonianorogeny is situate(l north-east of the Central
Mongolian Median Mass and is composed of
seven folded belts:“Tariat-Darkhan”,“Bayαn-
khongor”,“Adaatsag”,“South Khentii-Onon”
“Kherlen’ラ, “North Kherlen’ラ and ‘‘Zag-Khara-
agiin” Folde(l Belts。 The Zag-Kharεしagiin is
locate(i in the central part of the Khangai-
Khentiin Megazone.Ophiolite formations with
overthrust an(l thrust structures are observed
at Bayαnkhongor,Adaatsag and Kherlen foldedBelts.
Ulaanbaatar Folded System is of Variscan
orogeny and is subdivided into some smaller
units such as Tsetserleg Folded Belt,Ula、anba-
atar Folded Belt and Dochiin gol Depression.
But the system is not well understood yet.In
the Dochiin gol Depression,Permian to lower
Triassic sediments are distributed.
2.2TheSouthLargeBlock The South Large Block covers.the entire re-
gion of the Govi area an(1generally has linear
structures.Two folded systems, “South
Mongolian”(Variscan)and“lnner Mongolian”
(la、te Variscan),have been recognized in this
block but the(ietail of the geology has not been
well un(lerstood yet. These two folded
systems accompany smaller uplifted bodies of
Caledonian time.
The South Mongolian Folded System is
elongated from the west (Baruun-KhurainDepression)to the east(Kh&1khiin gol of the
country and is divided into the following
folded belts:“Khovd-Baruun-Urt”,“Edren”,
“Asgat(or Khalzan)”,“Goviin(or Govi)”,and
“Govi-Tjanshan-Uul-Nukhet-davaa”belts。 In
the Khovd-Baruun-Urt and Govi-Tjanshan-
Uul-Nukhet-davaa Fol(1ed Belts,volcanic rocks,
一737一
.B沼εむ加oμんeGεoZo9εcαZS乱rueッoゾ」αPαη,VoZ.43,No.12
Table l Tectonic framework of Mongolia.
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EdrenFoldedBelt
Asgat(Khalzan)Folded Belt
Goviin(Govi)FoldedBelt
Govi-Tjanshan-Uu1-NukheレdavaaFolded Belt
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Altai(orMongol,Altai)FoldedBelt
Shishkhid-ZαmnMegazone
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Tes-EgiingoIFoldedBelt
ZediinFoldedBelt
Dar㎞at,Khovsgol FoldedBelt
Shishkid董nFoldedBelt
Khangai-KhentHnMegazqne
丁短aレDarkhan Folded Belt
Bayankhongor Folded Belt
AdaatsagFoldedBelt
Omno Khentii-Opon Folded Belt
KherlenFoldedBelt
KhoitKherlenFoldedBelt
Zag-Kha㎜gi血Folded Belt
carbonate rocks and terrigenous sediments of
middle Ordovician to lower Carboniferous age
are underlain by the older folded basement.
Mongolian geologists believe that an original
continent was separated into some smaller
blocks (1uring the Cale(10nian orogeny. These
orogenic belts are marked by thrust an(l over-
thrust structures an(l carry various kinds of
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rock。For example,in Edren and Asgat ultrabasic rocks of unknown age are distin-
Belts,carbonate and volcanic rocks(middle guis五ed.The geology of this folded system
Ordovician to lower Cambrian)of island arc has not been well studied yet.
and VOICanO-Sedimentary fOrmatiOnS are Seen,
but in Goviin Folded Belt,ophiolite formation, 2.3 Superim夢osed Stmctures
volcanic rocks of island arcs,tuff of middle In additon to the structures mentioned
Ordovician to lower Carboniferous age are above,“super imposed structures”are observed
noticed. in Mongolia.This word includes(a)intra- In the Inner Mongolian Folded System,the deep basins and depressions filled with mollasse
autochthonous formation of middle Carbon- and volcanic rocks l(b)“Ulaanbaatar Variscan
iferous to Permian age臼and allochthonous System”;and(c)deep faults.Type(a)is
Table2Fault system of Mongoila.
FAULTOF 1:Turgen-go1, 2:Tolbo-nuur, 3:Khovd, 11:B勾ankhongor, 15:Edren, 37:(五khon,
NORTHWEST 38:Ulaanbaa倣, 39:Barkh
SYSTEM
FAULTOF 6:Agardag, 18:Khoit-Totoshan,201Bar帥n-Ovoo, 21:Modon-Ovoo, 24:Dund-govi,
NORTHEAST 25:漁taち 26:Delger, 27:陥oiトgovi, 28:】くherlen, 29=馳, 30:C㎞on,
SY㎝EM 31:αnn・紬en出・32:Ygr・(》9・1・33:B獅一9・1・34ゴSelenge・35:Zel曲・
36:Arg銭n-gol
FAULTOF 7:Khan-khokh銭, 8:Tam辻go1, 9:Shargi血ち 10:Bulga皿, 12:Ukh-Bogd,
SUELAT皿UDmAL 13:Alta血一tsaad舳 14:Gurbansaikhεm, 16:Tsagaam-Bogd, 17:Sulehkheer,
SYs肥M 19:㎜ai, 22:Sa舳an-dulaan, 23:0ndor-shil
FAULTOF 4:Deluun-sagsai, 5:Tsagaan-shiv㏄ち 40:】曲ovsgo1, 41:Dafkhaち 42:Zav㎞an
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Fig.3 Fault system of Mongoli&。Numbers’correspond to those in Table2.
一739一
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observed in most portion of the central Mongo-
1ia and south Mongolia.The crustal move-
ments responsible for these types took place in
Devonian,late Paleozoic and early Mesozoic
age. Type(b)is seen around Ulaanbaatar and
in souむhem Mongolia and is composed ofintra-deep depressions an(i volcano-plutonic
belt of Carboniferous and early Triassic ages.
Type(c)includes upthrust,displacement faults
an(i jointing. One of the(listinctive characters
of this structure is the exsistence of ultrabasic
rocks.In Mongolia,identified are the fo1-
lowing fault串ystems(Fig.3and Table2)North-West l North-East l sublatitudinal l and
submeridional systems.The North-West sys-
tem is developed in the Nuur-Altai Megazone
with the length of ca.600km.This system is
active from the Paleozoic age until present,
and is characterize(l by basic and ultrabasic
magmatism.The sublatitudinal fault system
has following Peculiarity:(a)the faults run
mostly parallel to the longitude in the central
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團 Middle to Late Carboniferous granitolds
固 EarIyPaleozoicdiorite and granite
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Fig.4 Geolog・ic map of the Kherlen Depression。
1:0ndor-tsagaan mine;2:Mongon-Ondor prospect l3:Mandaliin khuree deposit;4:Tsagaan-tschuluut deposit l5:Khoer zotlig deposit;6:0khaash deposit7:unnamed l81Uuluun raschaan deposit l9:unnamed;10-13:Nergui area;14:Ulaan-Ond.or d,eposit;15:Tsagaan-Ovoo d.eposit;16:Tuntger deposit l
17: 01ziitbulag depo$it; 18: unna.me(1; 19: Tugalgatain-nuruu (ieposit;20:
unnamed.
一740一
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part of the nation but ben(1to north direction
at the periphery l(b)metamorphic rocks(mica
schist,amphibolite,gameぴbearing gneiss)are
distributed along the faults l(c)most of the
faults are overthrusts;and (d)sometimesbreccia zone is(ievelope(l along faults。
2.4 Characters of Kherlen夏)epression
The Khangai-Khentiin Megazone of the
North Mongolian Folded System includes the
“Kherlen”Depression whi¢h is bounded by the
Onon,Kherlen and Barkh fαults,an(l has the
area of ca.130km by10-20km(Figs.1and4).
The depression exhibits synclinorium with NE-
trending fold axes,and is composed of the
following geologic bodies l metamorphic rocks
of upPer Proterozoic age,terrigenous and,vo1-
canic rocks of lower Cambrian age,gabbro and
granitoids of lower Paleozoic age,terrigenous
sedimentary rocks of lower to middle Devonian
age,vOICanOgeniC mOlaSSe fOrmatiOn Of IOwer
Permian,Triassic and middle to upper Jurassic
ages, an(1 granitoi(is of upper paleozoic to
Mesozoic ages.The Devonian terrigenous sedi-
mentary unit is called“Kherlen Group”and
contains clayey schists, siltstone, san(istone
(Fig.5),(iiabase,gabbro an(1且ne-grained green
rocks of intermediate composition.These green
rocks are deformed.Into the Kherlen Group,
1ate Paleozoic and Mesozoic granitoids have
been intruded.The former is called‘‘Tsenkher
gol complex”,while the latter is designated
“Bor-Ondor complex”.The Tsenkher gol com-
plex is mainly distributed at the marginal area
of the depression and is composed of coarse to
mediUm-grained granOdiOrite and mediUm-gra、ine(l biotite granite (Figs.6 and 7). The
Mesozoic granites ocωr along faults and are
mainly classified into late Triassic to early
Jurassic alkali granite an(l early to mi(ldle
Jurassic leucogranite. No petrochemica1 (iata
nor radiometric-age data have been known for
these granitoi(is but for one chemical analysis
of the sample from the Ondor-tsagaan mine
(Table3).
3.Mineral Deposits in the Kherlen
Depression
In the Kherlen Depression,there are a lot of
metallic
(Fig.4).
Ag veins(Fig.9),
therm撚,i Au and so on.
have not been studie(l yet from the geologica1,
mineralogical and geochemical point of view.
Tectonics of the depression has not been studi-
ed well neither.
Some of the metallic deposits seem to be
distributed near the contact between the
Kherlen Group and Paleozoic Tsenker gol
Ore depOSitS an(玉 minerεしliZed areaS
They are Pb veins,Zn veins,Pb-Zn一
(Fig.8),Mo-W veins or stockworks
Cu-Mo of porphyry type,hydro- Most of the deposits
Fig.5Sandstone(light-color band)and mudstone(dark-color portion)of the Kherlen Group.
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BωZZεあηo∫孟んεGθoZo8’‘cαZ Sαroθツo∫」αPαη, γoZ.43,1〉o.12
Fig.6 Microphotograph of a Paleozoic granite from Ts&gaan-tschuluut area.
No.0824-1.Qz:(luartz;Kf:alkali feldspar.
Fig’.
羅,喜瀟灘懸 轟戴
0 0。6・、,響
mm.雛
灘藩簿鰹繊
歌
琵《
鐸,豪
7Microphotograph of a granite of the Tsenkher gol Complex.No。0824-13。
Qz:quartz;Pl:plagioclase l Kf:alkali feldspar;My:myrmekite;Bt:biotite.
Complex,which implies the genetic relation
between the deposits and the compiex.But the
K-Ar dating of the mica concentrate from a
W-Mo stockwork(Ondor-tsagaan mine)and a
quartz-phlogopite vein (Mongon-On(lor pros-
pect)revealed that these deposits were deve1-
oped during the Jurassic ti亙ile(i.74-175Ma:
MuraoθむαZ.,in preparation).Thus(/etailed
petrochemical study and radiometric age dating
of the granites an(i ore(ieposits are necessary
to establish the guidline for the mineral ex-
ploration in the region.
4.ConcluαingRemarks
In Mongolia,two largb blocks are recognized.
These large blocks consist of several fol(1ed
systems.Each of them is subdivided intosome megazones and folded belts。Most of the
tectonic units have至!0t been well researched.
One of the tectonic ullits, Khangai-Khentii
megazone includes the Kherlen Depression which
is an expected area for mining.
In the Kherlen Depression,intense mineraliza-
tions of various kinds of useful metals are
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侃rod臨‘0瞬oGεoZO9ツ0/Moη8’oZ‘α‘Tsεdεπε孟αの
灘
Fig.8 Pb-Zn-Ag-ca.rbonate vein from the
Mongon-Ondor prospect. Sp:sphalerite l Cb:carbonate;
CR:country rock.
灘
藩灘と
鑛
Fig。9 Ad.it of the Ond.or-tsag・aan mine.
Analytical Result
Sio2
Tio2
A1203
Ee203
FeO
MnOCaONa20
K20P205
1g.Loss
Tota1
Table3
73.1
0.3
13.1
0,9
1.2
0.05
1.2
3.9
4.4
0.8
0.1
99.55%
Norma恒ve Cons亘tuent
il O.61
ap 6.05
or 26.16
&b 33.03
an 3.34
C O.71
mt 1.39
hy 2。13
Q 26.12
Total 99.54w%
D.1. 85.31
Chemical analysis of a granite from a drilling core at the
On(lor-tsagεしan ore且el(1.
Qbserved.Most of them are hydrothermaldeposits which are genetically related to acid
magmatism.But there is mostly no informa-
tion on the regional geology,mineral deposits
and granitoi(玉s, Bεlsic stu(1ies such as geo-
logical field survey,microscopic observation,
petrochemical analyses and radiometric dating
are required to discuss the mineralization and
to capture high-gra(1e ore bo(iies in this(iepres-
Slon.
Aknowleαgements:The authors would like to
thank Mr.Ch.Khurz,Dr.」.Biambaa,Dr.O.
Tomo-togoo and Mr.T.Battor of the Institute
of Geology and Mineral Resources,Prof.K
Fujii of Shizuoka Univ.and Dr。T.Nak:ajima
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BμZZ2む‘ηoゾリεん2G(30Zo9‘cαZ Sz4ruθツoゾ’」1αPαη, VoZ.43,〈τo.12
of the Geological Survey of Japan for thier
encouragement on the study,Secretaria玉assis-
tance by Ms.T.Hiroyama,Messers A.Seki-
guchi and S.Fujiwara,and technic&玉supPort
by Mr。T.Nogami are also appreciated.
Reference
minerals association about to end.
RθsoμrcεsPoZ‘cッ,vo1.17,P.42-53.
Tihonov,V。1.(1974) Faults。In Tee孟o痂cs
Oゾ ハ40η80屍αη Peoμε’S RθμめZ‘C.
N’auka,Moscow(in Russian).
Yanshin,A。1。.(1974)Tectonics of Mongolian
People’s Republic.Nauka,Moscow (in Russian).
Dorian,」。P. (1991) USSR-Mongolia:a
モンゴル国の地質区分の概要
T.ツェデン ・ 村尾 智 ・ D.ドルジゴトフ
要 旨
モンゴル国の地質区分にっいて概説した.同国は基本的にウラルーモンゴリアリニアメントによって
北ラージブロックと南ラージブロックに区分され,これらはさらに小さな地質単位(folded system,
megazone,median mass,folded belt)に分けられる,しかし各単位は経験的に設定されており定
義があいまいである.また,各単位の相互関係のほとんどは不明である,北ラージブロック内の
:Khangai-khentiinMegazoneにはKherlenDepressionと呼ばれる陥没地域があり,Au,Ag,
Pb,Zn,Moなどの金属鉱化作用がみられる.本地域はITITプロジェクトの対象区域であり,1991
年度の成果として,オンドルッァガンおよびモンゴンオンドル鉱床は174-175Maの生成である事が
明らかになっている.他の鉱床の詳細は不明である.
(受付:1992年6月5日;受理:1992年9月22日)
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