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Late Mesozoic extensional tectonics in the North China block: a crustalresponse to subcontinental mantle removal?

WEI LIN1 and QINGCHEN WANG1

Key words. – Continental extension, Synkinematic plutonism, Metamorphic core complex, Half-grabens, Lithosphere delamination,Cretaceous, North China Block.

Abstract. – In the North China block, Cretaceous extensional tectonics is expressed by numerous syntectonic plutonsbounded by ductile normal faults and several metamorphic core complexes (MCC). Cretaceous half-grabens filled bycontinental terrigenous deposits are widespread. The examples of MCC from South Liaoning Peninsula, Yiwulüshan,Hohhot as well as the Yunmengshan syntectonic pluton spread along ca 2000 km suggest that the early Cretaceous ex-tensional tectonics in the North China block is globally symmetric. The geodynamics setting of this continental-scaleextension remains disputed. It is not satisfactorily explained by back-arc rifting related to the Paleo-Pacific subductionor crustal “unthickening”. Mantle lithosphere removal is, however, considered. Upwelling of asthenosphere may be theorigin of heat advection and fluid transfer from mantle to lower crust, thus triggerring the Cretaceous magmatism, crus-tal softening and diffuse continental stretching. Several possible lithosphere-scale models, such as convective removalof mantle lithosphere and detachment of a large piece of mantle, are discussed.

La tectonique extensive fini-mesozoïque du bloc de Chine du Nord : une réponse crustale àl’enlèvement du manteau sous-continental ?

Mots clés. – Extension continental, Plutons synkinématic, Métamorphic core complex, Demi-grabens, Délamination lithosphérique,Crétacé, Bloc Chine du Nord.

Résumé. – Dans le bloc de Chine du Nord, la tectonique extensive se caractérise par de nombreux plutons syntectoni-ques bordés par des failles normales ductiles et plusieurs dômes extensifs (« metamorphic core complex »). Desdemi-grabens intracontinentaux sont aussi très répandus. Les exemples des dômes situés au sud de Liaoning, Yiwulü-shan, Hohhot et du pluton syntectonique de Yunmengshan distribués sur une distance de 2000 km suggèrent que l’exten-sion d’âge crétacé en Chine du Nord est globalement symétrique. Le contexte géodynamique de l’extension demeurecontroversé. Elle n’est pas expliquée de façon satisfaisante par le rifting d’arrière-arc lié à la subduction d’une plaquePaléo Pacifique, ou le « desépaississement crustal post-orogénique ». Les processus d’ablation de manteau lithosphé-rique sont considérés. La remontée d’asthénosphère peut être à l’origine d’advection de chaleur et de transferts de flui-des depuis le manteau vers la croûte inférieure et ainsi déclencher le magmatisme crétacé, l’amollissement de la croûteet l’étirement diffus de la croûte continentale. Plusieurs modèles comme l’ablation convective du manteau lithosphé-rique et le détachement de grands panneaux de manteau sont discutés.

INTRODUCTION

There is a general agreement to consider that during the lateCretaceous, eastern Eurasia was an Andean-type active con-tinental margin below which a “Paleo-Pacific” oceanic platewas subducting [e. g. Uyeda and Miyashiro, 1974; Klimetz,1983; Faure and Natatal’in, 1992]. In China, Cretaceousplutons are widespread not only near the presumed site ofsubduction, but also several hundreds of kilometers inland.Moreover, late Mesozoic continental extension characterizedby extensional basins, volumetrically important plutonismand volcanism, and several metamorphic domes, is widelyrecognized from the Korea Peninsula to Baikal Lake andGobi Desert, and from the Siberia-China border to SouthChina (fig. 1) [e. g. Faure et al., 1996; Allen et al., 1997;Ratschbacher et al., 2000; Ren et al., 2002; Meng et al.,

2003; Darby et al., 2004]. These late Mesozoic events thataffect the entire East China are known as the “Yanshan cy-cle” [Wong, 1929].

Numerous syntectonic plutons and several metamorphiccore complexes (MCC) as well as numerous extensionalbasins have accommodated a large amount of crustal exten-sion. However, the relationship between extensional tecto-nics and lithosphere behavior is not well understood be-cause of lack of detailed data such as extension direction,kinematics, ductile or brittle regimes. In this paper, we pres-ent new structural observations from different plutons in theNorth China block (NCB), namely the South Liaoning Penin-sula, Yiwulüshan, Yunmengshan and Hohhot in order toconstrain the geodynamic setting of the extension in this re-gion. Several possible lithosphere-scale models are thendiscussed.

Bull. Soc. géol. France, 2006, t. 177, no 6, pp. 287-297

Bull. Soc. géol. Fr., 2006, no 6

1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 10029, ChinaManuscrit déposé le 22 mars 2006 ; accepté après révision le 13 juin 2006.


288 LIN W. and WANG Q.

FIG. 1. – Distribution of geological elements related to the late Mesozoic extension along the eastern margin of Eurasia: i) extensional domes formedaround 115-130 Ma: Yagan-Onch Hayrhan [Zheng et al., 1991; Webb et al., 1999; Wang et al., 2004]; Hohhot [Davis et al., 2002]; Yunmengshan [Davis etal., 1996; Zhang et al., 1997] and Yiwulüshan [Ma et al., 1999; Darby et al.,2004]; Kalaqin [Han et al., 2001]; Luotian [Eide et al., 1994; Hacker et al.,1998; Faure et al., 1999]. Hongzhen [Luo et al., 1992]; Lushan [Lin et al., 2000]; Wugongshan [Faure et al., 1996]; ii) Late Jurassic to early Cretaceousvolcanics, iii) Late Mesozoic continental red beds basin. Modified from Allen et al. [1997], Ren et al. [2002], Meng et al. [2003].FIG. 1. – Distribution des éléments géologiques associés à l'extension fini-Mésozoïque le long de la marge orientale de l'Eurasie.

CRETACEOUS CONTINENTAL EXTENSION INNORTH CHINA

The South Liaoning Peninsula metamorphic corecomplex

The South Liaoning Peninsula is a NNE-SSW trendingdome coeval with syntectonic plutonism [Lin et al., 2007](figs. 1 and 2). The Proterozoic gneiss that forms the core ofthe dome is heterogeneously deformed with a weakly folia-ted core and a marginal mylonitic shear zone (fig. 2). Thefoliation exhibits a conspicuous mineral and stretchinglineation with a dominantly NW-SE trend. A top-to-the-NWshearing is unambiguously determined by quartz, biotiteand amphibole pressure shadows, feldspar or amphibole

sigma or delta type porphyroclast systems, and shearbands. In granite, S-C structure complies with other kine-matic criteria. Proterozoic dykes are also asymmetricallyfolded or boudinaged by this top to the NW shearing. Twogenerations of Mesozoic granite are recognized. Jurassicgranodiorites (ca. 175-160 Ma) are widely foliated andlineated like their host rocks. Conversely, Cretaceousmonzogranites, dated around 130-120 Ma by SHRIMPU-Pb method on zircon [Wu et al., 2005], exhibit amagmatically foliated core and a mylonitic rim. Since themineral lineation developed under subsolidus and post-solidus conditions in the Cretaceous plutons have the sametrend as those observed in the metamorphic host rock, thesegranites are considered as syntectonic bodies. This interpre-tation complies with radiometric data [Lin et al., 2007].


LATE MESOZOIC EXTENSIONAL TECTONICS IN THE NORTH CHINA BLOCK 289

FIG. 2. – Structural geological map of the South Liaoning Peninsula metamorphic core complex (located in fig. 1) and its cross-section drawn parallel tothe direction of the main stretching lineation (the pluton roots are hypothetic) [Modified from Lin et al., 2007].FIG. 2. – Carte structurale du dôme métamorphique de la péninsule du Sud-Liaoning (localisée sur la figure 1) et coupe correspondante parallèlement àla direction de la linéation d'étirement (les racines des plutons sont hypothétiques) [Modifié de Lin et al., 2007].

Biotites collected in the mylonitic shear zone, Cretaceousmonzogranite and host gneiss yield 40Ar/39Ar plateau agesranging from 122 Ma to 116 Ma.

In the south and southeast parts of the dome, metamor-phism is absent or very weak in the Neoproterozoic and Pa-leozoic series, but a slight recrystallization of sericite orchlorite may be observed in the pelitic layers. Near thedome, the sedimentary rocks are folded by north-west-vergent folds. In some parts, the bedding is over-printed by an axial-planar slaty cleavage and a NW-SElineation marked by elongated and recrystallized chloriteand quartz grains. Along this lineation, top-to-the-NWshearing is indicated by sericite and chlorite shear bands.

These features allow us to interpret the South LiaodongPeninsula as a Cretaceous metamorphic core complexformed in response to a NW-SE extension [Liu et al., 2005;Lin et al., 2007]. The mylonitic zone corresponds to a de-tachment normal fault that strikes NNE and dips NW-wardsin the western part and strikes ENE and dips to ESE in theeastern part (fig. 2). As observed in many MCC [e.g. Listerand Davis, 1989], the detachment fault of the SouthLiaoning Peninsula dome is arched with a NE-SW axis dueto the isostatic equilibration. As a result, the SE dome limbsuggests an apparently top-to-the-NW thrust, which is in rea-lity a tilted normal fault. SE of Fuxian city, a west-dippinghigh angle brittle normal fault overprints the ductile fault(fig. 2), and controls the opening and sedimentary infill of aCretaceous half-graben. Sedimentary rocks in the basinyield early Cretaceous fossils [LBGMR, 1989]. This basinis similar to other half-graben basins found in the wholenorthern parts of the North China block (fig. 1). Extensionalbasins overly the mylonitic rocks formed at an early stageduring the exhumation of the metamorphic core complex.Although both faulting events are due to the same tectonicphenomena, our field observations allow us to derive a rela-tive timing. The brittle extensional deformation follows theductile one.

The Yiwulüshan dome

At the eastern limit of the Yanshan fold belt and CenozoicLiaohe rift, the Yiwulüshan massif is a NNE-SSW trendingantiform (figs. 1 and 3). East of Beining city, Archean-Pro-terozoic gneiss and undeformed Mesozoic monzograniteform the core of the dome [LBGMR, 1989; Ma et al., 1999].Along the western boundary of the massif, a kilometer-thickmylonitic zone separates the metamorphic and plutonicrocks from an early Cretaceous terrigenous red series ofsandstones, pelites and conglomerates with intercalations oflava flows and tuffs (fig. 3). A part of these mylonites areorthogneiss that might be highly sheared Mesozoic graniticintrusions. The west to northwest dipping foliations exhibita conspicuous mineral and stretching lineation with aNW-SE trend and dips ranging from 20o-60o. A top-to-the-northwest shearing is determined by quartz, biotite andamphibole pressure shadows, feldspar or amphibole sigma,delta type porphyroclast systems as well as shear bands.Previous workers considered the Yiwulüshan massif as asymmetric MCC [Ma et al., 1999] or a SE-directed thrust[Zhang et al., 2002]. Because the western boundary of themassif was considered as a top-to-the-West low angle detach-ment, Darby et al. [2004] renamed the Yiwulüshan massifthe “Waziyu MCC”. According to our field observations, the

deformation in the eastern part of the massif does not corre-spond to the exhumation of the metamorphic rocks andpluton, the Yiwulüshan massif is rather an asymmetricalMCC with a syntectonic pluton of which the margins andcontact aureole were ductilely deformed during its emplace-ment. Thus we prefer to keep the original name ofYiwulüshan for the whole massif.

Samples collected from Waziyu ductile normal faultyield 40Ar/39Ar biotite plateau ages ranging from 116 ± 2 Mato 126.6 ±1.1 Ma [Zhang et al., 2002; Zhai et al., 2004];(fig. 3). These ages allow us to assess an early Cretaceousage for this ductile extensional event.

A west to northwest-dipping high angle brittle normalfault overprints the ductile Waziyu fault and controls theopening and sedimentary infill of the MesozoicFuxin-Yixian basin (fig. 3). Early Cretaceous fossils arefound in the sedimentary series of the basin, and mafic lavaflows intercalated in the series are dated around 129.8-135.0 Ma [LBGMR, 1989; Ma et al., 1999]. Although bothductile and brittle faulting events are due to the same tec-tonics, our structural observations show that the brittle de-formation follows the ductile one. Conglomerate withmylonitic pebbles, coming from the ductile normal fault,can be found close to the basin boundary [LBGMR, 1989;Ma et al., 1999 and our field survey]. Conversely to thehalf-grabens in the eastern part of the Liaoning Peninsula,the Fuxin-Yixian basin is a symmetric graben similar to theSong-Liao rift [Cheng et al., 1999]. These extensional basinsoverly the mylonitic rocks formed at an early stage of theexhumation of the Yiwulüshan massif.

The syntectonic pluton of Yunmengshan

Quite similar to the South Liaoning Peninsula and Yiwulüshanmassifs, the bulk architecture of Yunmengshan, situated inthe north of Beijing in the middle part of Yanshan fold belt,is dominated by an NNE-SSW trending dome cored byArchean and early Mesozoic metamorphic rocks intrudedby late Jurassic to early Cretaceous plutons (figs. 1 and 4).In the granitic plutons, a post-solidus foliation developswell around the margins and progressively grades in asub-solidus mineral preferred orientation in the plutoniccore. Mylonites are widespread in the SE part (fig. 4). Pre-vious works argue that the Yunmengshan pluton experien-ced a complicated history with a Mesozoic compressioncoeval with magmatism followed in the early Cretaceous byextensional tectonics [Zheng et al., 1988; Davis et al.,1996]. The structure of the Yunmengshan dome was ex-plained by gravity sliding, thrusting and extensional col-lapse caused by thermal uplift [Zheng et al., 1988],metamorphic core complex formation [Davis et al., 1996]or granite dome emplacement [Zhang et al., 1997]. South-east of the Yunmengshan massif, the Shuiyu-Hefangkoufault separates this massif from the late Mesozoic-CenozoicBohai Bay sedimentary basin (fig. 4). Most of the myloniticorthogneiss that develop along the fault are highly shearedMesozoic granitoids. The SE-dipping foliation contains aNW-SE stretching lineation with dips ranging from 10o to50o. Ductile shear criteria, such as S-C fabrics, quartz pressureshadows, feldspar sigma-type porphyroclast systems andshear bands, indicate a clear top-to-the-SE sense of shear.The Shuiyu-Hefangkou normal fault exhibits transitionalfeatures from ductile to brittle [Davis et al., 1996; Zhang et



al., 1997]. In the brittle fault zone, slickenline parallel tothe mineral lineation indicates that the hanging wall was

displaced southeastwards. Away from the ductile fault, theYunmengshan granodiorite is magmatically deformed, as shown



FIG. 3. – Structural geological map of the Yiwulüshan metamorphic core complex (located in fig. 1) and its cross-section drawn parallel to the direction ofthe main stretching lineation (the pluton roots are hypothetic; top to the south-southwest contractional deformation is not presented here, for clarity. Thestructure of basin was demonstrated by seismic profiles).FIG. 3. – Carte structurale du dôme métamorphique de Yiwulüshan (localisée sur la figure 1) et coupe correspondante parallèlement à la direction de lalinéation d'étirement (les racines des plutons sont hypothétiques ; pour simplifier, la déformation compressive vers le SW n'est pas représentée ici. Lastructure du bassin sédimentaire est établie à partir de profils sismiques).

by high temperature fabrics [Wang, 1985; Zhang et al., 1997].According to our understanding, the Yunmengshan massif isa Cretaceous syntectonic pluton and experienced succes-sively magmatic, ductile and brittle deformations during itscooling and exhumation. On the hanging wall, cataclasticNeoproterozoic and Paleozoic sedimentary rocks and Mid-dle Jurassic volcanic rocks indicate a brittle overprint alsodeveloped in an extensional setting.

The Yunmengshan granodiorite yields a zircon U-Pbearly Cretaceous age [Davis et al., 1996]. Biotite and K-feld-spar from the Shuiyu-Hefangkou normal fault provide

40Ar/39Ar cooling ages comprised between 126 Ma and116 Ma [Davis et al., 1996]. This result is quite similar withour work in the South Liaoning Peninsula MCC and theYiwulüshan massif. This suggests that these massifs proba-bly underwent the same geodynamic background in Creta-ceous time.

The Hohhot metamorphic core complex

About 400 km west of Beijing, in the western part of theYanshan fold belt, the kilometer-scale Daqinshan anticlineforms the Hohhot metamorphic core complex of late



FIG. 4. – Structural geological map of the Yunmeng-shan metamorphic core complex (located in fig. 1)and its cross-section drawn parallel to the directionof the main stretching lineation [Modified from Da-vis et al., 1996; Zhang et al., 1997]. The pluton rootsare hypothetic; top to the south-southwest contrac-tional deformation is not presented here.FIG. 4. – Carte structurale du dôme métamorphiquede Yunmengshan (localisée sur la figure 1) et coupecorrespondante parallèlement à la direction de la li-néation d'étirement [modifié d'après Davis et al.,1996 (les racines des plutons sont hypothétiques ;pour simplifier, la déformation compressive vers leSW n'est pas représentée ici).

Jurassic to early Cretaceous age [Darby et al., 2001; Daviset al., 2002] (fig. 1). The massif is an E-W trending dome(fig. 5). The metamorphic core consists of Archean gneiss,Proterozoic orthogneiss, garnet micaschist, marble andphyllite [NBGMR, 1989]. These rocks are intruded bysynkinematic plutons. Monzogranite, granodiorite andquartz diorite present a magmatically oriented core and anouter augen gneiss or mylonitic rim [Wang et al., 2002].The planar structure exhibits a NW-SE trending minerallineation (fig. 5). Ductile shear criteria indicate a top-to-the-SE displacement. A south dipping, low-angle (25o in ave-rage) normal fault bounds the southern margin of theHohhot MCC [Davis et al., 2002]. Different from otherMCC, Davis et al. [2002] have identified two stacked andfolded detachment faults on the northern flank of HohhotMCC (figs. 5). Red terrigenous sandstone with conglome-rate and some non-mylonitic gneiss form the hanging wallof the detachment fault. Near the ductile detachment fault,brittle deformation has been evidenced by cataclastic gneissand breccias. Striae in the brittle fault surface indicate thatthe hanging wall moved to the southeast. Below the southerndetachment, biotite and hornblende from amphibolite schistyield 121.4 ± 0.9 Ma and 121.5 ±1.3 Ma that are interpretedas the cooling age of this fault [Davis et al., 2002].

DISCUSSION AND CONCLUSIONS

Regional pattern of the Mesozoic extensionalstructure in North China

The NCB is characterized by two major NE-SW trendingdiscontinuities, namely the Tanlu and Taihangshan-Nenjiang faults (fig. 1). To the east, the Tanlu fault extendsin a NNE-SSW direction over more than 1500 km. The sur-face structural features correspond to Mesozoic and Ceno-zoic grabens filled by terrigenous deposits. Geophysics datashow that the Tanlu fault turns to vertical at depth and thetwo sides are quite different in terms of crustal velocity androck magnetism. To the west, the Taihangshan-Nenjing faultseparates Meso-Cenozoic basins from the Archean-Protero-zoic metamorphic rocks. To the north this fault separatesearly Jurassic volcanic rocks. It controls the sedimentarybasins at the surface and turns to subvertical at depth(fig. 1). Between these two faults, the basins of Songliao,Xialiaohe and Bohai Bay form the largest extensional struc-tures of eastern China [Lin et al., 2003 and referencetherein].

Although preliminary, since only a few number of MCCare presently documented, our work in the South Liaoning



FIG. 5. – Structural geological map of the Hohhotmetamorphic core complex (located in fig. 1) and itscross-section drawn parallel to the direction of themain stretching lineation [Modified from Davis etal., 2002; Wang et al., 2002]. The pluton roots arehypothetic; top to the south contractional deforma-tion is not represented here.FIG. 5. – Carte structurale du dôme métamorphiquede Hohhot (localisée sur la figure 1) et coupe cor-respondante parallèlement à la direction de la linéa-tion d'étirement [modifié d'après Davis et al., 2002et Wang et al., 2002 (les racines des plutons sonthypothétiques; pour simplifier, la déformation com-pressive vers le SW n'est pas représentée ici).

Peninsula, Yiwulüshan, Yunmengshan and Hohhot massifssuggests that the early Cretaceous extensional tectonics inthe North China block is globally symmetric. The centralzone of extension is situated between the Taihangshan-Nenjiang and Tanlu faults (fig. 1). Near the central zone ofextension, most of the basins are graben [Cheng et al.,1999], and as a whole they form the Songliao rift [Lin et al.,2003]. Syntectonic plutons and MCC like Yiwulüshan andYunmengshan massifs are well developed in the normalfault footwalls.

In the east of the central zone, the South Liaoning Penin-sula MCC is driven by a west-dipping asymmetric detach-ment fault. Brittle normal faults overprint the ductile one,and control the development of half-graben basins in thewest of the dome (fig. 2). Meanwhile, in the western part ofthe NCB, the Hohhot MCC with a SE-dipping detachmentfault examplifies asymmetric extensional deformation. Thehalf graben basins are controlled by dominantly SE-dippingbrittle normal faults. However, at depth, at the scale of thewhole NCB, the ductile kinematics related to the exhuma-tion of the middle crust seem to exhibit a bulk symmetricalpattern. The extension direction is indicated by a NW-SElineation. In the eastern part, the ductile normal faults of theSouth Liaoning Peninsula MCC and Yiwulüshan massif areassociated with a top-to-the-NW shearing. In contrast, inthe western area, top-to-the-SE kinematics characterizes theHohhot MCC and Yunmengshan syntectonic pluton. Allthese available data indicate that early Cretaceousextensional tectonics in the North China block is globallysymmetric along the central zone of extension, and this cen-tral zone complies well with a lithosphere removal centeraccording the geophysical and geochemical data [Deng etal., 2004; Zhou et al., 2003].

NCB extensional tectonics related to lithosphereremoval ?

In eastern China, early Cretaceous sinistral strike-slip faultingalong the Tanlu fault is consistent with NW-SE convergencealong the Eurasian plate boundary [e. g. Kimura et al.,1990; Xu and Zhu, 1994; Song and Dou, 1997;Ratschbacher et al., 2000; Mercier et al., 2007]. Paleo-magnetism indicates that in late Cretaceous, the easternLiaoning Peninsula-Korea block has underwent a clockwise

rotation of ca 20o since the late Cretaceous with respect toEurasia [Lin et al., 2003]. The Songliao rift developed duringthis rotation (fig. 1) [Lin et al., 2003]. Moreover, althoughnot always clearly identified in the geological maps, Creta-ceous syn-kinematic plutons of granodiorite, monzogranite,tonalite, gabbro and two micas leucogranites are wide-spread in the eastern margin of Eurasia continent [Deng etal., 2004]. Most of these plutons exhibit a magmatically orien-ted core and a mylonitic rim with down-dip lineation andnormal sense of shear. Late Mesozoic extensional domes,syn-tectonic plutons and extensional basins are prominentgeological features related to the “Yanshan Movement”[Wong, 1929; Zhao et al., 2004 and reference therein] buttheir geodynamic setting is still controversial. Several hy-potheses have been put forward.

Back-arc extension related to subduction of a “Paleo-Pa-cific plate’’ [Watson et al., 1987; Traynor and Sladen, 1995;Ratschbacher et al., 2000; Ren et al., 2002] is often consid-ered as the driving force of extension. But this mechanismfails to account for the fact that the late Mesozoic extensionspreads over a so vast area. Extensional basins with rift-re-lated volcanics, plutons and MCC crop out up to 2500 kmeast of the Pacific margin (fig. 1). Webb et al. [1999], Wanget al. [2002] and Meng [2002] attributed the Cretaceous ex-tension to the gravitational collapse of the Mongol-Okhotskbelt. However, the geologic evolution of this belt remainspoorly known and crustal “unthickening” along the Mon-gol-Okhotsk belt is unable to account for the Cretaceous ex-tension in the south part of the East Eurasian continent. Moregenerally, in NCB, the youngest events responsible forcrustal thickening took place in the early Triassic along theQinling-Dabie belt or the Solonker belt. The large time span,around 100 Ma, between the Triassic thickening and Creta-ceous extension makes this explanation unlikely.

Thus, the difficulty to reasonably explain the continen-tal-scale extension by plate margin or crustal processes,leads us to consider an asthenospheric cause. As a matter offact, although somewhat enigmatic, mantle lithosphere re-moval might explain the large area of extensional tectonicsoccurring in a quite short time of the early Cretaceous(116-126 Ma), at least for the peak events. Upwelling of theasthenosphere may be the origin of heat advection and fluidtransfer from mantle to lower crust and necessary to trigger



FIG. 6. – Schematic crustal scale section showing the regional Cretaceous extensional tectonics, magmatic dome, metamorphic core complexes and halfbasins in inner Mongolia and northern China (Dome locations have been displaced to make it clear, basins were interpreted according to Chen et al.,[1999]; Peng et al. [1995]; Cheng et al. [1999] and Liu [1994]; the Cenozoic extension is neglected).FIG. 6. – Coupe schématique d'échelle crustale montrant la tectonique extensive crétacée, les dômes magmatiques et métamorphiques et les bassins sédi-mentaires en demi-grabens en Mongolie intérieure et Chine du Nord. Les bassins sont interprétés selon Chen et al. [1999]; Peng et al. [1995] et Liu[1994]; l'extension cénozoïque est négligée.

the Cretaceous magmatism, crustal softening as well as con-tinental break up. Lithosphere removal is supported by petro-logical studies of mantle xenoliths. The occurrence of earlyPaleozoic diamond-bearing kimberlites at Mengyin in thewestern of Shandong province and Fuxian in the south ofLiaoning province requires the presence of a thick(�200 km) Archean or Proterozoic lithospheric mantlewhen they were emplaced (fig. 1). But the xenoliths recove-red in the Cenozoic basalts indicate that the present litho-sphere is about 65-120 km thick [Menzies and Xu, 1998;Zhang and Zheng, 2003]. These findings imply that the sub-continental lithospheric mantle underwent extensive thinningand lost more than 100 km of thickness, at some period be-tween the Ordovician and the Mesozoic [Menzies et al., 1993;Griffin et al., 1998; Flower et al., 1998; Gao et al., 2002].

Schematically, two possibilities can be put forward.Thermo mechanical convective ablation of the lithosphere,as suggested for the North American cordilleras [e. g. Bird,1979], appears as a very attractive process (fig. 7A). An-other possibility is the detachment of a large piece oflithospheric mantle [e. g. Houseman et al., 1981] (fig. 7B).

Nevertheless, whatever the model, the partial loss of mantlewould be also responsible for a significant uplift and therise of a high elevation plateau like in Tibet [e. g. Turner etal., 1996]. Although such a Cretaceous plateau is suggestedfor Mongolia and NE China [e. g. Meng et al., 2003], thistopographic effect is not well recorded in the sedimentationsince the amount of terrigenous material deposited in theCretaceous basins does not comply with the important ero-sion associated to such uplift. Nevertheless, paleotopo-graphic reconstructions for the Cretaceous NCB remainpoorly studied. A detailed discussion of the models of litho-sphere removal is beyond the scope of this paper. In thepresent state of knowledge, we consider that additional geo-physical data such as seismological tomography are neces-sary in order to reach a satisfactory understanding of thegeodynamic significance of the continental-scale Mesozoicextension in the North China block.

Acknowledgements. – This work has been supported by NSFC grantsno 40202021 and 40472116. MOST Project 2005CB422101 is also acknow-ledged.



FIG. 7. – Conceptual models that might account for lithospheric-scale continental extension in different tectonic settings. A. Convective removal of the li-thospheric mantle triggered by slab break off [Bird, 1979]; B. Delamination of a large piece lithospheric mantle triggered by slab break off [adapted fromHouseman et al., 1981].FIG. 7. – Modèles conceptuels susceptible d'expliquer l'extension continentale à l'échelle lithosphérique. a : ablation convective du manteau lithosphé-rique déclenchée par la rupture de la planque plongeante [Bird, 1979] ; b : délamination d'un grand morceau de manteau lithosphérique, possiblementdéclenchée par la rupture de la plaque plongeante [adapté de Houseman et al., 1981].

References

ALLEN M. B., MACDONALD D. I., ZHAO X., VINCENT S. & BROUET-MENZIES

C. (1997). – Early Cenozoic two-phase extension and late Ceno-zoic thermal subsidence and inversion of the Bohai basin, Nor-thern China. – Mar. Petrol. Geol., 14, 951-972.

BIRD (1979). – Continental delamination and the Colorado plateau. –J. Geophys. Res., 84, 7561-7571.

CHEN J., CAI X., LIN C., WANG H. & LEI M. (1999). – Tectonic characteris-tics and episodic evolution of the northern fault depression inSongliao basin. – Acta Petrol. Sin., 20, 14-18 (in Chinese withEnglish abstract).

CHENG R., CAO S., WANG D. & LIAO X. (1999). – The basement structuresand tectonic patterns of the Mesozoic basins in West Liaoningprovince and its northern adjacent area. – J. Changchun Univ.Sci. and Tec., 29, 29-32.

DARBY B. J., DAVIS G. A., ZHANG X., WU F., WILDE S. & YANG J. (2004). –The newly discovered Waziyu metamorphic core complex, Yi-wulüshan, western Liaoning province, Northwest China. – EarthScience Frontiers, 11, 145-155.

DARBY B. J., DAVIS G. A. & ZHENG Y. (2001). – Structure evolution of thesouthwestern Daqingshan, Yinshan belt, inner Mongolia, China,In: M.S. HENDRIX & G.A. DAVIS, Eds., Paleozoic and Mesozoictectonic evolution of central and eastern Asia. – Continental as-sembly to intracontinental deformation, Boulder, Colorado. –Geol. Soc. Amer. Mem., 194, 199-214.

DAVIS G.A., DARBY B. J., ZHENG Y. & SPELL T.L. (2002). – Geometric andtemporal evolution of an extensional detachment fault, Hohhotmetamorphic core complex, Inner Mongolia, China. – Geology,30, 1003-1006.

DAVIS G.A., QIAN X., ZHENG Y., YU H., WANG C., MAO T.H., GEHRELS

G.E., MUHAMMAD S. & FRYXELL J.E. (1996). – Mesozoic defor-mation and plutonism in the Yunmeng Shan: A Chinese meta-morphic core complex north of Beijing, China. In: A. YIN &T.A. HARRISON, Eds., The tectonic evolution of Asia. – Cam-bridge University Press, New York, 253-280.

DENG J.F., MO X.X., ZHAO H.L., WU Z.X., LUO Z.H. & SU S.G. (2004). –A new model for the dynamic evolution of Chinese lithosphere:‘continental roots-plume tectonics’. – Earth-Science Reviews,65, 223-275.

EIDE E.A., MCWILLIAMS M.O. & LIOU J.G. (1994). – 40Ar/39Ar geochrono-logy and exhumation of high-pressure to ultrahigh-pressure me-tamorphic rocks in east-central China. – Geology, 22, 601-604.

FAN W.M. & MENZIES M.A. (1992). – Destruction of aged lower lithosphereand asthenosphere mantle beneath eastern China. – Geotectonicaand Metallogenia, 16, 171-179 (Chinese with English abstract).

FAURE M., LIN W., SHU L., SUN Y. & SCHÄRER U. (1999). – Tectonics of theDabieshan (eastern China) and possible exhumation mechanismof ultra-high pressure rocks. – Terra Nova, 11, 251-258.

FAURE M., SUN Y., SHU L., MONIÉ P. & CHARVET J. (1996). – Extensionaltectonics within a subduction-type orogen. The case study of theWugongshan dome (Jiangxi Province, SE China). – Tectonophy-sics, 263, 77-108.

FAURE M. & NATAL’IN B. (1992). – The geodynamic evolution of the eas-tern Eurasian margin in Mesozoic times. – Tectonophysics, 208,397-411.

FLOWER M., TAMAKI K. & HOANG N. (1998). – Mantle extrusion: A modelfor dispersed volcanism and DUPAL-like asthenosphere in EastAsia and the western Pacific. In: M.F.J. FLOWER, S.L. CHUNG,C.H. LO, & T.Y. LEE, Eds., Mantle dynamics and plate interac-tion in East Asia. – Geodynamics Series, 27, 67-88.

GAO S, RUDNICK R.L., CARLSON R.W., MCDONOUGH W.F. & LIU Y.S.(2002). – Re-Os evidence for replacement of ancient mantle li-thosphere beneath the North China craton. – Earth Planet. Sci.Lett., 198, 307-322.

GRIFFIN W.L., ZHANG A., O’REILLY S.Y. & RYAN C.G. (1998). – Phanero-zoic evolution of the lithosphere beneath the Sino-Korean cra-ton. In: M.F.J. FLOWER, S.L. CHUNG, C.H. LO & T.Y. LEE, Eds.,Mantle dynamics and plate interaction in East Asia. – Geodyna-mics Series, 27, 107-126.

HACKER B.R, RATSCHBACHER L., WEBB L., IRELAND T., WALKER D. &DONG S. (1998). – U/Pb zircon ages constrain the architecture ofthe ultrahigh-pressure Qinling-Dabie orogen, China. – EarthPlanet. Sci. Lett., 161, 215-230.

HAN B., ZHENG Y., GAN J. & CHANG ZH. (2001). – The Luozidian normalfault near Chifeng, Inner Mongolia: master fault of a quasi-me-tamorphic core complex. – Int. Geology Rev., 43, 254-264.

HOUSEMAN G., MCKENZIE D.P. & MOLNAR P. (1981). – Convective instabi-lity of a thickened boundary layer and its relevance for the ther-mal evolution of continental convergent belts. – J. Geophys.Res., 86, 6115-6132.

KIMURA G., TASAKI T. & KONO M. (1990). – Mesozoic collision–extrusiontectonics in eastern Asia. – Tectonophysics, 181, 15-23.

KLIMETZ M.P. (1983). – Speculations on the Mesozoic plate tectonic evolu-tion of eastern China. – Tectonics, 2, 139-166.

LBGMR – Liaoning Bureau of Geology and Mineral Resources (1989). –Regional geology of Liaoning Province. – Geological Publis-hing House, Beijing (in Chinese), 856p.

LIN W., CHEN Y., FAURE M. & WANG Q. (2003). – Tectonic implications ofnew late Cretaceous paleomagnetic constraints from easternLiaoning Peninsula, NE China. – J. Geophys. Res., 108(B6),2313, doi: 10.1029/2002JB002169.

LIN W., FAURE M., MONIÉ P., SCHÄRER U. & PANIS D. (2007). – Mesozoicextensional tectonics in eastern Asia: The South-Liaodong Pe-ninsula metamorphic core complex (NE China). – Tectonics(submitted).

LIN W., FAURE M., MONIÉ P., SCHÄRER U., ZHANG L. & SUN Y. (2000). –Tectonics of SE China, new insights from the Lushan massif(Jiangxi Province). – Tectonics, 19, 852-871.

LISTER G. S. & DAVIS G.A. (1989). – The origin of metamorphic core com-plexes and detachment faults formed during Tertiary continentalextension in the northern Colorado River region, USA. – J.Struct. Geol., 11, 65-94.

LIU J., DAVIS G., LIN Zh. & WU F. (2005). – The Liaonan metamorphiccore complex, southeastern Liaoning Province, North China: Alikely contributor to Cretaceous rotation of eastern Liaoning,Korea and contiguous areas. – Tectonophysics, 407, 65-80.

LIU Y. (1994). – The late Mesozoic fault coal basins and the stretchingstructure in eastern Inner Mongolia. – Mineral Deposits, 13,212-220.

LUO Q., LIU G. & WANG B. (1992). – The research of metamorphic corecomplex of Hongzhen-Anqing area, Lower Yangtze. – J. Nan-jing Uni. (Natural Sciences), 4, 14-25 (In Chinese with Englishabstract).

MA Y., CUI S., WU G., WU H., ZHU D., LI X. & FENG X. (1999). – Thestructural feature of metamorphic core complex in Yiwulüshanmountains, West Liaoning. – Acta Geoscientia Sinica, 20,385-391.

MENG Q. (2002). – What drove late Mesozoic extension of the northernChina-Mongolia tract? – Tectonophysics, 369, 155-174.

MENG Q., HU J., JIN J., ZHANG Y. & XU D. (2003). – Tectonics of the lateMesozoic wide extensional basin system in the China-Mongoliaborder region. – Basin Res., 15, 397-415.

MENZIES M. A. & XU Y. (1998). – Geodynamics of the North China craton.In: M.F.J. FLOWER, S.L. CHUNG, C.H. LO & T.Y. LEE, Eds.,Mantle dynamics and plate interaction in East Asia. – Geodyna-mics Series, 27, 155-165.

MENZIES M. A., FAN W. M. & ZHANG M. (1993). – Palaeozoic and Ceno-zoic lithoprobes and the loss of 120 km of Archean lithosphere,Sino-Korean craton, China. In: H.M. PRICHARD, T. ALABASTER,N.B.W. HARRIS & C.R. NEARY, Eds., Magmatic processes andplate tectonics. – Geol. Soc. London Spec. Publ., 76, 71-81.

MERCIER J., HOU M., VERGELY P. & WANG Y. (2007). – Structural and stra-tigraphical constraints on the kinematics of the southern Tan Lufault during the Mesozoic. – Tectonophysics (in press).

NBGMR– Nei Mongol (Inner Mongol) Bureau of Geology and Mineral Re-sources (1989). – Regional geology of Nei Mongol Province. –Geological Publishing House, Beijing (in Chinese), 725p.

PENG Z., ZHENG J., HUANG H. & LIU Z. (1995). – Classification of the chiefsedimentary basin in China. – Acta Sediment. Sin., 13, 150-159.



RATSCHBACHER L., HACKER B.R., WEBB L., MCWILLIAMS M.O., IRELAND

T., DONG S., CALVERT A., CHATEIGNER D. & WENK H. (2000). –Exhumation of ultrahigh-pressure continental crust in east cen-tral China: Cretaceous and Cenozoic unroofing and the Tan-Lufault. – J. Geophys. Res., 105, 13303-13338.

REN J., KENSAKU T., LI S. & ZHANG J. (2002). – Late Mesozoic and Ceno-zoic rifting and its dynamic setting in eastern China and adja-cent areas. – Tectonophysics, 344, 175-205.

SONG J. & DOU L. (1997). – Mesozoic-Cenozoic tectonics of petroliferousbasins in eastern China and their petroleum systems. – Petro-leum Industry Press, Beijing. 182 pp.

TRAYNOR J. J. & SLADEN C. (1995). – Tectonic and stratigraphic evolutionof the Mongolian People’s Republic and its influence on hydro-carbon geology and potential. – Mar. Petrol. Geol., 12, 35-52.

TURNER S., ARNAUD N., LIU J., ROGERS N., HAWKESWORTH C., HARRIS N.,KELLEY S., VAN CALSTEREN P. & DENG W. (1996). – Post-colli-sion, shoshonitic volcanism on the Tibetan Plateau implicationsfor convective thinning of the lithosphere and the source ofocean island basalts. – J. Petr., 37, 45-71.

UYEDA S. & MIYASHIRO A. (1974). – Plate tectonics and the JapaneseIsland; a synthesis. – Geol. Soc. Amer. Bull., 85,1159-1170.

WANG P., LIU W., WANG S. & SONG W. (2002). – 40Ar/39Ar and K/Ar da-ting on the volcanic rocks in the Songliao basin, NE China:Constraints on stratigraphy and basin dynamics. – Int. J. EarthSci., 91, 331– 340.

WANG T., ZHENG Y., LI T. & GAO Y. (2004). – Mesozoic magmatism in ex-tensional tectonics near the Mongolian border in China and itsimplications for crustal growth. – J. Asian Earth Sci., 23,715-729.

WANG X., ZHENG Y., ZHANG J., DAVIS G.A. & DARBY B. J. (2002). – Exten-sional kinematics and shear type of the Hohhot metamorphiccore complex, Inner Mongolia. – Geol. Bull. China, 21,238-245.

WANG Y. (1985). – On features of quartz fabric of mylonite in the Shuiyuductile fault, Huairou, Beijing. – Collective struct. Geol., 5,77-85.

WATSON M. P., HAYWARD A. B., PARKINSON D. N. & ZHANG Z. M. (1987). –Plate tectonic history, basin development and petroleum sourcerock deposition onshore China. – Mar. Petrol. Geol., 4, 205-225.

WEBB L.E., GRAHAM S.A., JOHNSON C.L., BADARCH G. & HENDRIX S.(1999). – Occurrence, age, and implications of the Yagan-OnchHayrhan metamorphic core complex, southern Mongolia. – Geo-logy, 27, 143-146.

WONG W.H. (1929). – The Mesozoic orogenic movement in eastern Asia. –Bull. Geol. Soc. China, 8, 33-44.

WU F., LIN J., WILDE S.A., ZHANG X. & YANG J. (2005). – Nature and si-gnificance of the early Cretaceous giant igneous event in easternChina. – Earth Planet. Sci. Lett., 233, 103-119.

XU J. & ZHU G. (1994). – Tectonic models of the Tan-Lu fault zone, eas-tern China. – Int. Geol. Rev., 36, 771-784.

ZHAI M., ZHU R., LIU J., MENG Q., HOU Q., HU S., LIU W., LI ZH. & ZHANG H.(2004). – Time range of Mesozoic tectonic regime inversion ineastern North China block. – Science in China (Series D), 47,151-159.

ZHANG H F. & ZHENG J. P. (2003). – Geochemical characteristics and petro-genesis of Mesozoic basalts from the North China craton: Acase study in Fuxin, Liaoning Province. – Chinese Sci. Bull., 48,924-930.

ZHANG J., ZENG L. & QIU X. (1997). – Granite dome and extensional tecto-nics in the Yunmeng Mountain, Beijing. – Geol. Rev., 43,232-240 (in Chinese with English abstract).

ZHANG X., LI T. & PU Z. (2002). – 40Ar/39Ar thermochronology of twoductile shear zones from Yiwulüshan, west Liaoning region:Age constraints on Mesozoic tectonic events. – Chinese Sci.Bull., 47, 13, 1113-1118.

ZHAO Y., XU G., ZHANG Q., YANG ZH., ZHANG Y. & HU J. (2004). – Yans-hanian movement and conversion of tectonic regimes in easternAsia. – Earth Science Frontiers, 11, 328 (in Chinese withEnglish abstract).

ZHENG Y., WANG Y., LIU R. & SHAO J. (1988). – Sliding-thrusting tectonicscaused by thermal uplift in the Yunmeng Mountains, Beijing,China. – J. Struct. Geol., 10, 135-144.

ZHENG Y., WANG S. & WANG Y. (1991). – An enormous thrust nappe andextensional metamorphic core complex newly discovered inSino-Mongolian boundary area. – Science in China (Series B),34, 1145-1152.

ZHOU X.H., YANG J.H. & ZHANG L.C. (2003). – Metallogenesis of super-large gold deposits in Jiaodong region and deep processes ofsubcontinental lithosphere beneath North China Craton in Meso-zoic. – Science in China (D), 46 (Sup.), 14-25.

