North and SouthChina collision along the eastern and southern NorthChina margins

Ž.
Tectonophysics2701997145–156
North and South China collision along the eastern and southern
North China margins
K.-J.Zhang
Department of Earth Sciences,Nanjing UniÕersity,Nanjing210093,China
Received3January1996;accepted23August1996
Abstract
Ž.
Lithofacies distribution and petrography and intracontinental deformation in the North China block NCB and the South Ž.
China block SCB show an active continental margin flanked by the eastern NCB,and a passive continental margin was present along the west side of the SCB,both margins initially trending N-NE.The Tanlu fault possibly initiated as part of the subduction zone during Paleozoic time along the eastern margin on the NCB.The NCB and the SCB were divided along the eastern–southern North China margin by the Qinling–Dabie–Tanlu–Sulu–Imjingang–Yanji zone from southwest to northeast.These two continental blocks made contact first in the northeast during late Early Permian time,finally in the southeast at Late Triassic time,and the clockwise collision probably lasted to Middle Jurassic time.The eastern suture,the Yanji–Imjingang–Sulu–Tanlu zone,was dominated by contractional deformation.The southern suture,the Qinling–Dabie zone,was a transpression belt dominated by right-lateral strike-slip.
Keywords:tectonic reconstruction;kinematics;Tanlu fault;North China block;South China block
1.Introduction
ŽThe North and South China blocks NCB and .
SCB located in eastern China are two of the major
Žcontinental blocks of the Eurasian continent Fig. .
1a.The collision between these two subcontinents
Žduring late Paleozoic to middle Mesozoic time e.g.,
.ŽYin and Nie,1993,or middle Paleozoic time e.g.,
.
Mattauer et al.,1985,formed one of the most spectacular tectonic landscapes on Earth,including the Sulu–Dabie ultra-high-pressure metamorphic Ž.
belts e.g.,Wang et al.,1989and the eastern China
Žintracontinental deformation belts e.g.,Guo et al.,
.Ž.
1988;Zhang,1994Fig.1b.The collisional tecton-ics between these two continental blocks is a key to understanding the framework of the Eurasian conti-nent.
Nearly all the previous tectonic models of the collision between the North and South China blocks are based upon the knowledge of a north-directed collision along the Qinling–Dabie–Sulu–Imjingang Ž
zone e.g.,Cluzel et al.,1990,1991;Cluzel,1991; Okay and Sengor,1992;Yin and Nie,1993;Li, .
1994,and allegedly E–W-trending continental mar-gins of both North China and South China blocks Ž.
e.g.,Yin and Nie,1993;Li,1994.In this paper,the initially N-NE-trending geometries and extent of the SCB and the diachroneity of the collision between
0040-1951r97r$15.00Copyright q1997Elsevier Science B.V.All rights reserved.
Ž.
PII S0040-19519600208-9
()K.-J.Zhang r Tectonophysics 2701997145–156
146the NCB and the SCB are shown.Subsequently,detailed intracontinental deformational and sedimen-tologic evidence for contraction along the eastern Ž.suture zone including the Tanlu fault and right-lateral transpression along the southern suture zone is presented.Finally,a clockwise collision tectonic model is proposed that best explains the intensive Mesozoic intracontinental deformation in the eastern Asian continent and the diachroneity of the collision.
2.Geologic setting 2.1.North China Block
The locus of the North China–South China colli-sion is constrained in east-central China along the Qinling–Dabie–Tanlu–Sulu zone and extends along the Imjingang belt of central Korea into the Korea Ž.Žpeninsula Fig.1b e.g.,Cluzel et al.,1990,
1991;
Ž.Ž.Ž.Fig.1.a Tectonic position of studied area,revised after Ernst and Liou 1995.The black zones are sutures.b Simplified geologic map of eastern China.NCB North China block,SCB South China block,XPB Xinkai-southeastern Primoria block,T Tarim block,CSAT central-eastern Sikhote–Alin terranes.I Yanshan fold and thrust belt,II Taihan–Luliang fold and thrust belt,III Xuzhou–Huainan fold and thrust belt,VI Lower Yangzi fold and thrust belt,V Sichuan fold and thrust belt.HFB Hefei Triassic basin,YJB Yanjiang Triassic basin.
()
K.-J.Zhang r Tectonophysics2701997145–156147
Hsu et al.,1990;Cluzel,1991;Yin and Nie,1993;
.
Li,1994;Yang et al.,1994.The eastern or north-
eastern extension of the collision belt prior to
Ž
Miocene initiation of the Japan Sea Jolivet et al., .
1994has not been discussed in detail in the context of the North China–South China collision.
The general N-NE trend of sedimentary facies in the NCB from Early Neoproterozoic to Late Permian Ž.Ž. time Guang,1986;Fong,1990a Fig.2a,c,d,f with extensive N-NE-trending synsedimentary faults Ž.
Tiang,1992shows the initial geometry of the NCB was possibly a N-NE-trending subcontinent.
Remarkably,numerous Chinese publications on the late Paleozoic coal-bearing series in the NCB detailed the late Paleozoic widespread andesitic vol-
Ž. canism in the eastern half of the NCB Fig.3.There spread andesitic pyroclastic breccias,sedimentary pyroclastic breccias and tuffs ca.150m thick in the Ž.
Jinan area Wang,1988,1990,in the Beijing–Tian-Ž.
jin area Zhang,1984,and in the Shenyang area Ž.Ž.
Hang and Yang,1980,p.123Fig.3.The an-desitic volcanic rocks cover more than50,000km2. All the volcanic layers are interbedded with clastic rocks of the coal-bearing series,and are limited to the Taiyuan,Shanxi and Shihezi formations of Mid-dle Carboniferous to Early Permian age.The main compositions of the pyroclastic breccias based on a
preliminary analysis are on average SiO65.15%,
2
TiO0.58%,Al O15.86%,Fe O 2.34%,FeO 22323
2.38%,MnO0.08%,MgO1.76%,CaO4.21%,Na O
2 3.69%,K O2.27%.
2
Moreover,in the eastern half of the NCB east of Xian,within the same strata,also exist numerous tonsteins up to2m thick with single layers thicker Ž
than0.01m Fong,1986;Liang et al.,1986;Zheng et al.,1986;Li and Jia,1988;Zao,1988;Chen,
.Ž.
1989;Liu,1990Fig.3.The rocks nearly consist of only one mineral,such as kaolinite.These later-ally extensive tonsteins contain andesine-labradorite, biotite,epitone,ilmenite,magnetite,b-quartz,rutile, sanidine,tourmaline,zircon,all idiomorphic and even shards,and thus are believed to be the product of
Ž
weathered volcaniclastic ash Fong,1986;Liang et al.,1986;Li and Jia,1988;Zao,1988;Chen,1989;
.
Liu,1990.
The andesitic volcanism can not be attributed to post-Mesozoic circum-Pacific andesitic volcanism Ž.
e.g.,Yang and Yang,1988because the volcanic layers are contained within strata rich in Late Car-boniferous and Early Permian fossils and were de-
Žposited during Late Paleozoic sedimentation Zhang,
.
1984;Wang,1988,1990;Liu,1991.Further,the andesitic volcanism cannot be local in view of the areal extent of the volcanism as above-mentioned. Apparently,on the eastern flank of the NCB a late Paleozoic N-NE-trending volcanic arc existed;that is,it was an active continental margin that flanked the eastern NCB before Late Permian time.In fact, the late Paleozoic eastern North China coal basin
Ž.
east of Taiyuan–Xian Fig.3is filled with a mo-
Ž
lasse assemblage thicker than1300m e.g.,Hang
.
and Yang,1980;Yang and Yang,1988,contains scattered andesitic debris,crystal,and glass shards Ž.Ž
at least10% e.g.,Zhang,1984;Yang,Q.,1987; Yang,X.,1987;Wang,1990;Liu,1991;Jia and Li, .
1993,and may be a retroarc foreland basin.The analysis of sedimentary structures show that the up-per Paleozoic terrigenous sediments in North China
Ž
were derived mainly from the east Fig.3;e.g.,Lan,
.
1982;Wang,1988;Zhang and Li,1988.During the same period,the eastern part of the NCB,such as in the Beijing area,was mainly covered by continental sediments,but in the western part,such as in the Taiyuan–Xian area,it often underwent marine trans-Ž
gressions e.g.,Guang,1986;Yang and Yang,1988;
.
Tong,1994,all implying a topographic high to the east.
2.2.South China Block
There is a notably consistent NE trend in the sedimentary facies of the Sinian to the Upper Per-
Ž.
mian rocks in the entire SCB Fig.2b–g,which indicates the initial geometry of the SCB was a
Ž
passive continental margin e.g.,Okay and Sengor,
.
1992;Yin and Nie,1993that probably trended also
Ž.Ž. N-NE,just as shown by Fong1990b,Tong1994Ž.Ž.
and Guang1986.Ernst and Liou1995speculated a possible extension of the suture zone between the NCB and the SCB into the Permian high-pressure zone of Sikhote–Alin,Russian Far East.Further,I tentatively propose the Xinkai–southeastern Primoria Ž.
block XPB,a borderland among northeastern China, northwestern Korea,and Russian Far East in the northeastern Asia,possibly formed the northeastern-most part of the SCB,where the existence of Car-
()
K.-J.Zhang r Tectonophysics2701997145–156 148
boniferous and Permian fauna and flora of close South China affinity has been known since the early Ž. 1980’s e.g.,Huang et al.,1981;Sun,1988.The
Ž
marine index Permian fauna in the XPB Sao et al., .
1995could not have been derived from the NCB,whose Permian sediments were nearly entirely ter-Ž
rigenous e.g.,Hang and Yang,1980;Yang and .
Yang,1988.The XPB is divided from the central-eastern Sikhote–Alin terranes to the east,from the Sibria platform to the north,and from the NCB
to
()
K.-J.Zhang r Tectonophysics2701997145–156
149
Fig.3.Distribution of Late Paleozoic andesitic volcanic rocks and current directions of Late Paleozoic sediments in North China.
the southwest by the Yanji belt containing the asso-
Žciations of high-pressure rocks and melanges Fig.
.
1b;Sao et al.,1995;Tang et al.,1995.The XPB contains a west-facing Paleozoic passive continental Ž.
margin Sao et al.,1995.I also agree that southwest Japan containing Paleozoic rocks of South China Ž
affinity e.g.,Yang and Yang,1988;Yang et al.,
.Ž
1994was rifted part of the SCB Jolivet et al.,1994;
.
Ernst and Liou,1995.
ŽOphiolites have been discovered in the Yanji Sao .Ž.Ž
et al.,1995,Sulu e.g.,Liu,1989,Dabie e.g.,Xu,
.Ž
1987;Xu et al.,1992and Qinling e.g.,Zhang et .Žal.,1995belts,but not in the Imjingang belt e.g., .
Lee,1987.However,sutures do not always abso-
Ž.
Fig.2.Isopach and marine sedimentary facies map of Sinian s Late Precambrian to Lower Triassic sequences in eastern China,revised ŽŽ.2
after Guang1986,Guang1986.Z is Lower Sinian;Z is upper Upper Sinian;is Middle–Upper Cambrian;O is Middle
122–32 Ordovician;S is Silurian;e is Middle–Upper Carboniferous;P is Lower Permian;T is Lower Triassic.Isopach lines are in meters.
2–311
Ž.
Sedimentary facies:I is shallow-sea basin facies;II is marginal platform facies;III is platform facies undivided;III is depressed
platform facies;III is open platform facies;III is semi-closed platform facies;III is closed platform facies;III h is high-energy platform 123
Ž.
facies;IV is epicontinental facies;O is trough facies undivided;O is deep trough facies;O is shallow trough facies.The shadow is
12
land.The thick line with bars is the boundary between the North and South China blocks.Note that both the isopaches and facies of Lower Precambrian to Lower Permian sequences in both North and South China blocks kept stable northeastern trends that may indicate northeastern trends of margins of both North and South China blocks.
()K.-J.Zhang r Tectonophysics 2701997145–156
150lutely contain ophiolites,and they may be marked only by deformation and metamorphism,a view Ž.shared by Yin and Nie 1993.Consequently,I pro-pose the Tanlu–Sulu–Imjingang–Yanji zone is the eastern suture,and the Dabie–Qinling zone is the Žsouthern suture between the NCB and the SCB Fig..1b .
2.3.Timing of North China–South China collision On the basis of the youngest strata involved in the tectonic melanges formed during the collision and the Early to Late Permian foreland molasse in the Ž.XPB,Sao et al.1995suggested the XPB,the northeasternmost part of the SCB,came into contact with the NCB in late Early to early Late Permian time.The transition from marine to terrestrial deposi-tion immediately north of the Imjingang belt during Ž.the latest Early Permian Reedman and Um,1975indicates a latest Early Permian collision event in Ž.Korea Yin and Nie,1993.The time of the collision along the Dabie–Tanlu zone is well illustrated by sedimentological records.Fig.4includes four maps detailing terrigenous clastics in the marine strata from Permian to Early Triassic time east of the Tanlu fault.Ages of units in these maps are well constrained because they contain a rich fossil record.Apparently,during the Permian time the terrigenous clastics were derived exclusively from an area within Ž.the SCB southeast of the Tanlu fault Fig.4a,b ,and during early to middle Early Triassic time from the Ž.NCB northwest of the Tanlu fault Fig.3c,d .The initial sedimentation in the SCB of the terrigenous clastics from the NCB marks the onset of collision between the NCB and the SCB.Furthermore,in the two sides of the Tanlu fault there existed a series of Triassic contractional foreland basins,such as the ŽHefei basin on the NCB Fig.1b,e.g.,Lu and Dou,.1982;Okay and Sengor,1992and the Yanjiang Žbasin on the SCB Fig.1b,Dong et al.,1994;Zhang,.1994.All indicate the NCB and SCB collided along the Tanlu fault at about early Early Triassic time.Apparently,the trends of lithofacies in the SCB since Early Triassic time had been disturbed by the initial Ž.collision Fig.2h .
It has long been intensively debated whether the SCB and the NCB collided along the Qinling belt Žduring middle Mesozoic time e.g.,Sengor,1985;.ŽYin and Nie,1993,or middle Paleozoic time e.g.,.Mattauer et al.,1985.And there are various divi-Žsions to the subunits of the Qinling belt e.g.,Gao et .al.,1995;Zhang et al.,test understanding about the Qinling belt is that there are both collisions along the Qinling belt,a middle Paleozoic in
the
Ž.Ž.Ž.Ž.Ž.Ž.Fig.4.Terrigenous clastic constituents %maps in the marine sediments in eastern South China,a and b after Fong 1990b ,c and d Ž.after Fong 1988.NCB North China block,SCB South China block,TL Tanlu fault.The shadow is land;the arrow shows the flow direction of terrigenous clastic constituents.P 2is upper Lower Permian;P 1is lower Upper Permian;T 1is lower Lower Triassic;T 2is 1211middle Lower Triassic.
()
K.-J.Zhang r Tectonophysics2701997145–156151
northern Qinling and a Mesozoic in the southern
ŽQinling with a Qinling block between them e.g.,
.
Zhang et al.,1995.An explanation by Zhang et al.Ž.
1995for the middle Paleozoic collision in the northern Qinling is that it might have been caused by the middle Paleozoic collage between the Qinling block and the NCB.The Qinling block possesses similar basement,sedimentation,and close affinity
Ž
during early Paleozoic time to the SCB Gao et al.,
.
1995;Zhang et al.,1995,is partly covered by the
Ž. Devonian foreland molasse e.g.,Du,1986,1995 and is believed to be a rifted part of the SCB during
Ž
early Paleozoic time Chen,1994;Zhang et al., .Ž. 1995.The South Qinling in Gao et al.1995’s Fig. 2is well-matched to the Qinling block in Zhang et Ž.
al.1995’s Fig.1.Therefore,the possibility remains that the provenance change in the Silurian–Devonian
Ž. clastic sediments in the Qinlin Gao et al.,1995 probably marks a middle Paleozoic collision not between the NCB and the SCB,but the NCB and the Qinling block,because it is extremely difficult to geochemically distinguish the Qinling block and the SCB due to their similarity in sedimentation.In fact, the northern margin of the SCB south of the Qinling belt experienced virtually continuous passive-margin sedimentation during nearly entire Paleozoic time Ž.
e.g.,Yang and Yang,1988;Fong et al.,1994. Also,abundant geological and paleomagnetic evi-
Ždence suggests that in Paleozoic time the NCB in-
.
cluding the Qinling block and the SCB that did not join possibly each other until Permo-Triassic time, and that there is a diachroneity in the suturing be-
Ž
tween these two continental blocks Lin et al.,1985; Zhao and Coe,1987;Li et al.,1989;Enkin et al., 1992;Fang and Yang,1992;Yin and Nie,1993;
.
Zhang et al.,1995.The transition from marine to terrestrial deposition in the SCB south of the western
ŽQinling belt during latest Late Triassic time e.g.,
.
Yang and Yang,1988suggests the NCB and the SCB sutured there at that time,similar to the conclu-
Ž.
sion of Zhang et al.1994based upon the study of isotopic geochronology.
I conclude that the NCB and the SCB possibly made contact by clockwise rotation along the suture zone,first at the northeast end in late Early Permian time,then in early Early Triassic time along the Tanlu fault,and finally in latest Late Triassic time at the southwest end,thereby in accord with the rota-tion model based on paleomagnetic data for the convergence of these two continental blocks pro-
Ž.
posed by Zhao and Coe1987and Enkin et al.Ž.
1992.The collision could have lasted to Middle
Ž.
Jurassic time e.g.,Li,1994and thus the duration of the collision was about100Ma.
2.4.Collision-related deformation
The folds and thrusts related to the collision in the NCB display a general N-NE-trend with the excep-tional E–W trend of the Yanshan fold and thrust belt Ž.
I in Fig.1b.The major fold and thrust belts are the Yanshan belt,the Taihan–Luliang belt and the
Ž. Xuzhou–Huainan belt I,II,III in Fig.1b.The surficial fold and thrust structures in these belts are well controlled and in the subsurface they are re-vealed by numerous boreholes.I select a few typical structural cross-sections of these belts to show their general outlines.The Yanshan fold and thrust belt, involving the Sinian and Paleozoic cover,is consis-
Ž.
tent with thrusting to the north Fig.5a,b and may extend far into northeastern China and north Korea Ž.
Fig.1b and5a.The Taihan–Luliang belt also involved the Proterozoic and Paleozoic cover and
Ž
was dominated by thrusting to the WNW e.g.,Ma,
.Ž. 1986;Tiang,1992;Tong,1994Fig.1b and5c. The Xuzhou–Huainan belt can be considered as the counterpart in the NCB of the Lower Yangzi fold
Ž.
and thrust belt Fig.1b.It involved the Sinian and Paleozoic cover of the North China facies,clearly
Ž.
related to the collision Xu et al.,1993.Its arcuate Ž.
appearance Fig.1b indicates its consistent thrusting
Ž. towards the WNW Fig.1b and5d;Xu et al.,1993. It was shortened about240km or74%over a325
Ž.
km wide deformation zone Xu et al.,1993.Seismic profiling revealed the flat detachment between the cover and the metamorphic basement in the eastern half of the NCB east of the Taihan–Luliang belt Ž.
e.g.,Xu,1985;Zheng and Ma,1991.I think these intracontinental deformational belts in the NCB should not be attributed to post-Mesozoic subduction
Ž. of the Pacific plate e.g.,Yang and Yang,1988 despite the local involvement of the Middle Jurassic volcanic rocks in the Yanshan,Taihan–Luliang and
Ž.
the northeastern China belts because:1they con-
Ž
tain synorogenic granites of220–240Ma e.g.,Yang
.Ž.Ž.
and Yang,1988Fig.1b;2they are best related
()K.-J.Zhang r Tectonophysics 2701997145–156
152to the stress field of the North China–South China Ž.collision,not the subduction of the Pacific;and 3if otherwise,the NCB and the SCB must have under-gone unified deformation related to the Pacific sub-duction.However,the respectively distinctive defor-mation in the NCB and the SCB discussed in this paper is contrary to such a conjecture.I postulate that in the NCB the crustal contractional deformation related to the collision verged toward the WNW along the sole detachment,with the Yanshan belt possibly acting as a large-scale lateral ramp struc-tural zone.The deformation due to the collision in the SCB is nearly as pervasive,and is characterized by changing trends of the folds and thrusts,from the N-NE east of the Tanlu fault,the E–W south of the Dabie belt,to Ž.the NE south of Qinling belt Fig.1b .However,the trends are continuous and are not truncated by the Ž.Qinling–Dabie zone or the Tanlu fault Fig.1b .The major fold and thrust belts in the SCB are the Sichuan and the Lower Yangzi belts from west to Ž.east Fig.1b .The general NE trend of the Sichuan fold and thrust belt distinctly intersects the WNW Ž.trend of the Qinling–Dabie zone Fig.1b indicates
a
Ž.Ž.Fig.5.Schematic deformational cross-sections in North China and South China.See Fig.1b for locations.a ,b revised after Tiang Ž.Ž.Ž.Ž.Ž.Ž.Ž.Ž.Ž.1992,c revised after W.Y.Zhang unpubl.,1991,Tiang 1992,Chen 1994and Tong 1994,d revised after Xu et al.1993,e Ž.after Zhang 1994.The black is Carboniferous–Permian;the shadow is Lower Sinian.HP high-pressure metamorphic rocks;Z Lower 1Sinian;Z Upper Sinian;e Cambrian;O Ordovician;S Silurian;D Devonian;T Triassic;K Cretaceous.The vertical lines with triangles 2are boreholes.
()
K.-J.Zhang r Tectonophysics2701997145–156153
synchronous right-lateral strike-slip or transpression along the Qinling–Dabie zone during the collision, consistent with the structural analysis within the
Ž.
Qinling belt Suo et al.,1992.The Lower Yangzi fold and thrust belt displays a N-NE trend parallel to
Ž.
the Tanlu fault Fig.1b and underwent intense and typical contractional deformation,involving the Sinian to Triassic cover of the South China facies,
Žincluding the high-pressure metamorphic rocks Fig. .
5e.The deformation is consistent with thrusting to
Ž.Ž
the SE and S Fig.5e Guo et al.,1988;Zhang, .Ž.
1994.Zhang1994estimated that,in the Lower Yangzi fold and thrust belt,crustal shortening was about220km or58%over a380km wide deforma-tion zone.
2.5.The Tanlu fault
The Tanlu fault begins at Tancheng in the north, and terminates at the east end of the Dabie belt
Ž. immediately east of Hefei Fig.1b.Diverse opin-ions exist about the extension and nature of the Tanlu fault.Its extension far to the Russian Far East
Ž
and its postulated huge magnitude of slip Xu et al., .Ž.
1987were intensely doubted because:1it did not apparently dislocate the precollisional Paleozoic sed-
Žimentary facies of the NCB and the SCB Fig.
.Ž.
2a,c–f,e.g.,Guang,1986;Qiao,1986;2the Tanlu fault was dominated by consistent thrusting to the Ž.ŽSEE Xu,1987;Xu et al.,1993;Zhang,1994Fig.
.Ž.
1b,5d,e;and3on both sides of the Tanlu fault exist a series of Late Triassic contractional foreland
Žbasins,such as the Hefei basin in the NCB e.g.,Lu
.
and Dou,1982;Okay and Sengor,1992and the
Ž
Yanjiang basin in the SCB Dong et al.,1994;
.Ž. Zhang,1994,all parallel to the Tanlu fault Fig.1b. Furthermore,the fault contains blueschist assem-
Ž. blage rocks dated at220Ma Li et al.,1989.The seismic profiling across the Tanlu fault reveals that the whole Tanlu fault zone dips at about558toward Ž.
the WNW Chen,1988,identical to the definite
Ž
NCB-ward subduction of the SCB e.g.,Okay and
. Sengor,1992;Yin and Nie,1993;Li,1994,and is
Ždominated by contractional deformation Chen, .
1988.The gradually eastward increase of terrige-nous clastics from the NCB during Early Triassic Ž.
time Fong,1988,1990b implies a distinct conver-gent movement of E–W direction between the NCB
Ž.
and the SCB Fig.4.Based upon the parallelism among the lithofacies of the NCB and the SCB during the Proterozoic to Paleozoic time and the dominance of contractional deformation along and on both sides of the Tanlu fault in the NCB and the Ž.Ž.
SCB Fig.2Xu et al.,1993,I suggest that the Tanlu fault initiated as part of the subduction zone during Paleozoic time along a N-NE-trending active continental margin on the NCB.The Tanlu fault,just as the Sulu belt,developed as part of a convergent continent–continent boundary N-NE-trending be-tween the NCB and the SCB,subjected to high-pres-sure metamorphism,and dominated by contractional deformation during the late Paleozoic to middle Mesozoic collision.It was not dominated by left-
Ž. lateral strike-slip faulting e.g.,Xu et al.,1987.The extension far to the Russian Far East could result
Ž
from thrusting related to the collision Xu et al., .
1993and intracontinental deformation due to the
Ž. India–Tibet collision e.g.,Tapponnier et al.,1982. The rifting along the Tanlu fault in Late Mesozoic Ž.
time Xu,1982may be related to the breakup of the contractional orogen.
3.Tectonic model
The lithofacies distribution and petrology in the NCB and the SCB may be interpreted that an active continental margin flanked the eastern NCB and that the western SCB was a passive continental margin prior to the contact of these two subcontinents in late Paleozoic time.Both margins initially trended N-NE. The SCB possibly extended N-NE far into the north-eastern Asia,and the NCB and the SCB were di-vided along the southern and eastern North China margin by the Qinling–Dabie–Tanlu–Sulu–Im-
Ž.
jingang–Yanji zone Fig.1b.These two continental blocks collided,and rotated relatively clockwise, starting from the northeast in late Early Permian time and ending in the southeast in Late Triassic time Ž.
Fig.6.Although transform faulting along the Yanji–Imjingang–Sulu–Tanlu zone could cause jux-taposition of the two different plates,the consequent initiation of the collision between the two continental
Ž. margins almost perpendicular to each other Fig.2 along the Qinling–Dabie zone was extremely diffi-cult in geometry and mechanics.The amount of
()K.-J.Zhang r Tectonophysics 2701997145–156
154Fig.6.Schematic tectonic model for initial geometry of both North and South China blocks,and collision between them.The latitude data Ž.1after Fang and Yang 1992.NCB North China block,SCB South China block.P early Early Permian;P Late Permian;T Middle 122Triassic;J Late Jurassic.
3intracontinental deformation also suggests a domi-nance of convergence along the eastern suture or the Yanji–Imjingang–Tanlu zone.In the SCB,many more facies types were absent east of the Tanlu fault Ž.than south of the Qinling–Dabie zone Fig.2.This situation cannot be considered as a hiatus represent-ing facies changes because the SCB had been sub-ducted earlier and by a greater amount east of the Tanlu fault than south of the Qinling belt.The most intense intracontinental subduction along the Ž.Dabie–Sulu zone Fig.6could result in the ultra-Ž.high-pressure metamorphism there Fig.1b .The penetration of the rigid NCB into the softer SCB,which possesses much thinner basement than the Ž.NCB e.g.,Yang and Yang,1988could have modi-fied the tectonic configuration,especially in the east-Ž.ern half of the China continent Zhang,1994.The Ž.irregular suture zone Fig.1b could be the result of the irregular geometry of the passive northeastern Žmargin of the SCB prior to the collision e.g.,Yin .and Nie,1993.4.Summary
A tectonic model is proposed for the North China and South China collision.Lithofacies distribution and petrography in the NC
B and the SCB show an active continental margin flanked the eastern NCB and a passive continental margin formed on the west side of the SCB prior to contact of the two subconti-
nents in Late Paleozoic time;both margins originally trended N-NE.The NCB and the SCB were sepa-rated by the Qinling–Dabie–Tanlu–Sulu–Im-jingang–Yanji zone from southwest to northeast.These two continental blocks rotated relatively clockwise and made contact,first in the northeast at late Early Permian time,and finally in the southeast at Late Triassic time.Convergence probably lasted to Middle Jurassic time.The eastern suture,or the Yanji–Imjingang–Sulu–Tanlu zone,was dominated by contractional deformation.The southern suture or the Qinling–Dabie zone was a transpression belt dominated by supposed right-lateral strike-slip fault-ing.In particular,I suggest the Tanlu fault was part of an initial suture zone between the NCB and the SCB,best explaining its abrupt termination at both ends and the contractional deformation within and on both sides of the fault zone.Also,my model pro-vides a more reasonable interpretation for the Meso-zoic intracontinental deformation within the eastern Eurasian continent.
Acknowledgements
I owe the paper to Prof.Y.S.Shi’s enthusiastic encouragement.I thank W.Y.Zhang in Hebei Geo-logical Bureau of Coal,L.Q.Ding in Jiangsu Geo-logical Bureau of Coal,D.K.Qian in Anhui Geologi-cal Bureau of Coal,Z.F.Lu in Shandong Geological Bureau,C.T.Chen in Anhui Geological Bureau,and。