Temporal and spatial variations of Mesozoic magmatism and deformation in the North China Craton: Implications for lithospheric thinning and decratonization Shuan-Hong Zhang, Yue Zhao, Gregory A. Davis, Hao Ye, Fei Wu PII: DOI: Reference:
S0012-8252(13)00219-5 doi: 10.1016/j.earscirev.2013.12.004 EARTH 1939
To appear in:
Earth Science Reviews
Received date: Accepted date:
16 August 2013 16 December 2013
Please cite this article as: Zhang, Shuan-Hong, Zhao, Yue, Davis, Gregory A., Ye, Hao, Wu, Fei, Temporal and spatial variations of Mesozoic magmatism and deformation in the North China Craton: Implications for lithospheric thinning and decratonization, Earth Science Reviews (2013), doi: 10.1016/j.earscirev.2013.12.004
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Temporal and spatial variations of Mesozoic magmatism
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and deformation in the North China Craton: Implications
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for lithospheric thinning and decratonization
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Shuan-Hong Zhang1, Yue Zhao1, Gregory A. Davis2, Hao Ye1, Fei Wu1
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1 Institute of Geomechanics, Chinese Academy of Geological Sciences, MLR Key Laboratory of Paleomagnetism and Tectonic Reconstruction, Beijing 100081, China
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90089-0740, USA
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2 Department of Earth Sciences, University of Southern California, Los Angeles, CA
Corresponding Author. Tel: (86-10) 88815058; Fax: (86-10) 68422326; E-mail:
[email protected] (S. H. Zhang) Address: No. 11 South Minzudaxue Road, Haidian District, Beijing 100081, China
ACCEPTED MANUSCRIPT Abstract Mesozoic (Triassic-Cretaceous) magmatic rocks and structural deformation are
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widely distributed in the North China Craton (NCC) and are crucial to understanding
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the timing, location, and geodynamic mechanisms of lithospheric thinning and decratonization of the NCC. Our new geochronological, geochemical and structural data combined with previously published results on Mesozoic magmatic rocks and
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deformational structures in the NCC indicate a temporal and spatial migration of
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magmatism and deformation from its margins to its cratonal interior. Triassic and Early Jurassic igneous rocks are only distributed along the northern, southern and
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eastern margins of the NCC. In constrast, Cretaceous magmatic rocks are widely
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distributed in whole eastern and central parts of the NCC. There is a younging trend
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for Mesozoic magmatic rocks from the northern and eastern parts (Yanshan, Jiaodong Peninsula and Liaodong) to the central part of the NCC (Taihangshan).
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Mesozoic deformation in the NCC exhibits a similar migration trend from craton margins to its inland areas. Triassic-Early Jurassic deformation mainly occurred in the margins of the NCC and transformed from compression during the Early-Middle Triassic to extension during the Late Triassic to Early Jurassic in its northern margin. Middle-Late Jurassic to earliest Cretaceous deformation is widely distributed in the NCC and exhibited non-unique contractional directions usually perpendicular to boundaries of the NCC and its Ordos block, indicating it was likely controlled by multiple tectonic regimes during the Middle-Late Jurassic to earliest Cretaceous. Early Cretaceous deformation was characterized by near unique NW-SE extension
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ACCEPTED MANUSCRIPT that was likely controlled by unique geodynamic regime that probably related to the far-field effect of Cretaceous Paleo-Pacific plate subduction. The above mentioned
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temporal and spatial migrations of Mesozoic magmatic rocks and deformation
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indicate that lithospheric thinning and decratonization of the NCC was diachronous and complex. The lithospheric thinning and decratonization of the NCC initially started from its northern and eastern margins as a result of
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post-collisional/post-orogenic lithospheric delamination during the Middle-Late
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Trisssic, and then spread to the interior of the craton during the Late Mesozoic. Interactions of the surrounding orogenesis and small size of the NCC may have
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decratonization.
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played important roles on its Late Mesozoic lithospheric thinning and
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Key Words: magmatism, deformation, Mesozoic, decratonization, lithospheric thinning, North China Craton (NCC)
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1. Introduction
The North China Craton (NCC) has become famous in geological research in recent years due to its significant lithospheric thinning and decratonization (or destruction) during the Mesozoic and Early Cenozoic eras (e.g., Fan and Menzies, 1992; Menzies et al., 1993, 2007; Griffin et al., 1998; Fan et al., 2000; Xu, 2001; Gao et al., 2002, 2004; Zhang et al., 2002a, 2011a; Wilde et al., 2003; Rudnick et al., 2004; Gao et al., 2004; Zhai et al., 2004a, 2004b, 2007; Zheng et al., 2007; Wang et al., 2007a; Deng et al., 2007; Dong et al., 2008a, 2008b; Kusky et al., 2007; Wu et al., 2006a, 2008; Ji et al., 2008; Liu et al., 2008a; Yang et al., 2008a, 2010a; Zhou,
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ACCEPTED MANUSCRIPT 2009; Xu et al., 2010; Zhu et al., 2011, 2012a, 2012b; Li et al., 2012a). It is widely acknowledged that a thick and cold cratonic lithospheric mantle remained intact
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through the Paleozoic, but by the Cenozoic its eastern parts had been replaced by a
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thinner and hotter lithospheric mantle with oceanic affinitities, as evidenced by constrasting data from mantle xenoliths captured in the Paleozoic kimberlites and Cenozoic basalts (e.g., Fan and Menzies, 1992; Griffin et al., 1998; Menzies et al.,
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1993; Menzies and Xu, 1998; Fan et al., 2000; Xu, 2001; Zheng et al., 2001;
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Rudnick et al., 2004; Menzies et al., 2007). The timing of initiation and the geodynamic factors inducing the NCC lithospheric conversion are still highly
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controversial (e.g., Ji et al., 2008; Wu et al., 2008, and references therein). Such
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initiation has been variably considered as Late Carboniferous-Late Triassic (Xu et al.,
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2009), Late Triassic (Han et al., 2004; Yang et al., 2007a, 2010a; Yang and Wu, 2009; Zhang et al., 2009a, 2012a), Late Jurassic (Gao et al., 2004), Early Cretaceous (Wu
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et al., 2003, 2005b, 2008; Zhu et al., 2012a), or as young as Late Cretaceous-Cenozoic (Lu et al., 2006; Li et al., 2012a, 2012b). Although the Late Mesozoic is believed to be the most important period for lithospheric thinning and decratonization of the NCC (e.g., Wu et al., 2008, and references therein; Zhu et al., 2012a), some evidence suggests that decratonization of the NCC is diachronous (Xu, 2007; Yang et al., 2010a). Lithospheric thinning of its eastern and northern parts started most likely during the Early Mesozoic (Han et al., 2004; Yang et al., 2007a, 2010a; Yang and Wu, 2009; Zhang et al., 2009a, 2012a), and lithospheric thinning and decratonization of the NCC probably initially started at its northern and eastern
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ACCEPTED MANUSCRIPT margins as a result of post-collisional/post-orogenic lithospheric delamination, and then spread to the interior of the craton (Zhang et al., 2009a, 2012a).
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Principal mechanisms proposed for lithospheric destruction include delamination
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(e.g., Deng et al., 1994, 2007; Gao et al., 2002, 2004; Wu et al., 2003, 2005b; Xu et al., 2006a, 2006b, 2008a, 2013; Lin and Wang, 2006; Windley et al., 2010; Li et al., 2012a), thermo-chemical erosion from below (e.g., Fan and Menzies, 1992; Menzies
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et al., 1993; Griffin et al., 1998; Xu, 2001; Xu et al., 2004, 2008b; Zheng et al.,
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1998a, 2006, 2007), peridotite-melt interaction (e.g., Zhang et al., 2002a, 2005a, 2007a; Tang et al., 2006), lower crustal detachment (e.g., Liu et al., 2008a),
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subduction dehydration (e.g., Niu, 2005) or lithospheric folding-induced removal of
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lithospheric mantle (Zhang, 2012). Contrasting tectonic models for loss or
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conversion of the NCC cratonic lithosphere invoke breakup and dispersal of Gondwanaland (e.g., Wilde et al., 2003), Triassic collision of the South China
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(Yangtze) and North China cratons (e.g., Gao et al., 2002; Xu et al., 2006a), Mesozoic subduction of a Paleo-Pacific plate beneath eastern Asia (e.g., Wu et al., 2000, 2003, 2005b; Zheng et al., 2006, 2007; Sun et al., 2007; Xu et al., 2008b; Zhu et al., 2011, 2012a), hydration caused by long-term multiple subduction from the Paleozoic to Mesozoic (e.g., Kusky et al., 2007; Windley et al., 2010), multi-direction subduction of Paleo-Pacific, Neo-Tethys and Mongolia-Okhotsk oceans around East Asia during the Late Jurassic (e.g., Dong et al., 2000, 2008a, 2008b; Zhang et al., 2007b, 2008a, 2011b), multiple rifting events in the Late Mesozoic to Cenozoic (e.g., Ren et al., 2002), or ridge subductions (Ling et al.,
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ACCEPTED MANUSCRIPT 2013). Magmatism plays critical roles in defining and influencing the timing, mechanism
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and processes of lithospheric thinning and cratonic destruction (e.g., Hawkesworth et
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al., 1995; Wells and Hoisch, 2008; Wu et al., 2008, and references therein; Yang and Wu, 2009; Xu et al., 2009; Zhu et al., 2012a). North China decratonization involved considerable thinning and loss of the subcontinental lithospheric mantle, perhaps
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through upwelling of the convective asthenosphere and modification of the thermal
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structure of the overlying lithosphere (Xu et al., 2009). Resulting geological processes could be expected to include the generation of large volumes of
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magmatism, tectonic exhumation of deep-seated rocks, extensional tectonics such as
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metamorphic core complex, and the development of extensional sedimentary basins
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(Wu et al., 2008, and references therein). The involvement of mantle components in magmatism can be considered to be a fundamental expression of cratonic
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modification (Xu et al., 2009), most markedly the switch in magmatic source regions from an enriched lithosphere mantle to depleted asthenosphere mantle (Menzies et al., 2007; Yang et al., 2007a; Wu et al., 2008; Xu et al., 2009). The relationship between lithospheric removal and igneous activity, especially asthenospheric mantle-derived magmatism can, therefore, provide a means of constraining the timing, location, and geodynamic mechanism of lithospheric thinning and decratonization (e.g., Wu et al., 2008; Yang and Wu, 2009). Moreover, the NCC lithospheric thinning and decratonization were also accompanied by significant crustal deformation (e.g., Wang et al., 2007a, 2011a; Wu et al., 2008; Liu et al.,
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ACCEPTED MANUSCRIPT 2011a; Zhu et al., 2012b), which provides additional constraints on the nature and timing of decratonization. In this paper, we review previously published results on
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Mesozoic magmatism and deformation in the NCC, and present new structural,
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geochronological, geochemical and Sr-Nd-Hf isotopic data on these topics. The major goal of this paper is to evaluate the temporal and spatial distribution and migration of magmatism and crustal deformation in the NCC, in order to provide
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new constraints on timing, mechanism and processes of cratonic lithospheric
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thinning and decratonization. 2. Geological setting
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The NCC was one of the oldest cratons in the world, with crustal rocks as old as
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3.8 Ga (Liu et al., 1992). However, compared with other Precambrian cratons (e.g.,
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Africa, Siberia, Antarctica, North America, South America, India, etc.), the NCC is really very small in area and was therefore much more easily destroyed by
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surrounding plate collisions and pre-collisional subductions beneath it. The NCC is bordered by the Central Asian Orogenic Belt (CAOB) to the north, the Qinling-Dabie-Sulu high-ultrahigh pressure metamorphic belt to the south and a Pacific convergent system on the east (Fig. 1). The northern NCC was strongly influenced by the Paleo-Asian tectonic system during the Carboniferous to Permian because the Paleo-Asian oceanic plate was subducted southward beneath the NCC (e.g., Wang and Liu, 1986; Davis et al., 2001; Xiao et al., 2003, Li, 2006a; Zhang et al., 2007c, 2009a) with the development of an Andean-style continental margin during the Late Carboniferous-Early Permian (Zhang et al., 2007c, 2007d, 2009a,
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ACCEPTED MANUSCRIPT 2009b). The Solonker-Xar Moron-Changchun-Yanji suture marks final closure of the Paleo-Asian ocean and amalgamation of the North China block and the southern
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Mongolian composite terranes during Late Permian to earliest Triassic (e.g., Wang
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and Liu, 1986; Xiao et al., 2003, Sun et al., 2004a; Li, 2006a; Li et al., 2007a; Wu et al., 2007a; Zhang et al., 2007c, 2009a). The Qinling-Dabie-Sulu high-ultrahigh pressure metamorphic belt was formed as a result of the Triassic subduction of the
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continental crust of the Yangtze Craton beneath the NCC and continent-continent
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collision of the South China (Yangtze) and North China cratons (e.g., Li et al., 1993). During the Jurassic and Cretaceous, the NCC was influenced by southward
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movement of the Siberian plate and closure of the Mongol-Okhotsk suture, westward
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subduction of the Paleo-Pacific plate beneath the eastern Asian continent and
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probablly northward movement of the Indian plate (or Neo-Tethys block) and opening of the Indian Ocean (Dong et al., 2000, 2008a, 2008b, Zhai et al., 2007).
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After its final cratonization in the Paleoproterozoic at around 1.85 Ga (Zhao et al., 2001; Wilde et al., 2002), the NCC experienced several stages of rifting related to the breakup and dispersal of the NCC from other parts of Columbia and Rodinia supercontinents during Late Paleoproterozoic, Mid-Mesoproterozoic and Early Neoproterozoic (e.g., Peng et al., 2011; Zhang et al., 2012b; Xia et al., 2013). The basement of the NCC is, thus, composed of highly metamorphosed Archean and Paleoproterozoic rocks, which were covered by Meso-Neoproterozoic and Cambrian-Ordovician marine clastic and carbonate platformal sediments, Middle-Late Carboniferous interactive marine and terrestrial deposits, Permian to
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ACCEPTED MANUSCRIPT Triassic fluvial and deltaic sediments, and Jurassic-Cretaceous and younger continental sediments and volcanic rocks. Prior to Triassic period, most parts of the
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NCC remain almost stable with no regional angular unconformities between these
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rock units. Since Middle-Late Ordovician period, the NCC was uplifted and a significant sedimentation gap occurred until the Middle-Late Carboniferous, coinciding with emplacement of the Mengyin and Fuxian diamondiferous
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kimberlites during the Middle-Late Ordovician at ca. 460~470 Ma (e.g., Dobbs et al.,
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1994; Lu et al., 1998; Li et al., 2005a; Zhang and Yang, 2007; Yang et al., 2009). During the Late Mesozoic, the eastern part of the NCC was strongly remobilized
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with intense deformation (e.g., Ge, 1989; Zhao, 1990, Davis et al., 1998, 2001;
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Zheng et al., 2000; Zhang et al., 2011a), widespread magmatism (e.g., Wu et al.,
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2005a, 2005b; Deng et al., 2007; Wan and Zhao, 2012) and metallic mineralization (e.g., Hua and Mao, 1999; Yang et al., 2003; Mao et al., 2003a; Li and Santosh, 2013;
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Zhai and Santosh, 2013).
3. Distribution of the Mesozoic magmatic rocks Mesozoic magmatic rocks are widely distributed in the NCC (Figs. 2 and 3). Our new SHRIMP and LA-ICP-MS zircon U-Pb dating results (Supplementary Tables 1 and 2, Fig. 4) and previously published zircon U-Pb and 40Ar/39Ar ages (Supplementary Table 3) indicate that the formation of Mesozoic magmatic rocks can be divided into several stages including Early Triassic, Middle-Late Triassic, Early Jurassic-earliest Middle Jurassic, Middle-Late Jurassic, Early Cretaceous and Late Cretaceous. Fig. 2 shows distribution of exposed Mesozoic magmatic rocks in
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ACCEPTED MANUSCRIPT the NCC and Fig. 3 represents stragraphic sections of volcanic-bearing sequences at
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spatial distributions of Mesozoic magmatic rocks in the NCC.
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different locations in the NCC. These figures illustrate the significant temporal and
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3.1. Early Triassic magmatic rocks (Fig. 2b)
Early Triassic intrusive rocks are widely distributed in the east-west-trending Yinshan and Yanshan belts along the northern margin of the NCC. Typical plutons
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from west to east include the Hailiutu granite (25011 Ma, Wang et al., 2009), the
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Baihuagou granite (2523 Ma, Wang et al., 2009), the Yunwushan granite (2472 Ma~2442 Ma, Table 1, Fig. 4), the Liangjia quartz syenite (2462 Ma, Yang et al.,
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2012a), the Hanjiadian granite (2504 Ma~2473 Ma, Mao et al., 2003b), the
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Louzidian granite (2533 Ma, Davis et al., 2001) and the Shijiafang
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monzonite-granite (2492 Ma~2482 Ma, Zhang et al., 2010a). Several Early Triassic plutons include the Dakai and Bailiping granites (2494 Ma and 2482
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Ma~2456 Ma, Zhang et al., 2004a) and the Jianpingzhen biotite monzogranite (2491 Ma, Cao et al., 2013) in southern Yanbian-Liaobei area in northeastern NCC and Buryong granodiorite pluton (2461 Ma, Wu et al., 2007b) in northernmost North Korea were reported. Early Triassic volcanic rocks with one zircon SHRIMP U-Pb age of 2486 Ma exist near Liaoyuan in the southern Yanbian-Liaobei area in NE China (GSIJP, 2004a). Emplacement of the Early Triassic magmatic rocks is a continuum of the latest Permian magmatism in the northern margin of the NCC (Zhang et al., 2010b) and is probably related to post-collisional lithospheric extension after final collision and suturing of the Mongolian arc terranes with the
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ACCEPTED MANUSCRIPT NCC (Zhang et al., 2009b, 2010b). 3.2. Middle-Late Triassic magmatic rocks (Fig. 2c)
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Middle-Late Triassic magmatic rocks are widely distributed in the Yinshan and
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Yanshan belts in the northern NCC, the Liaodong and the southern Yanbian-Liaobei area in the eastern NCC and Korean Peninsula (e.g., Wu et al., 2005a, 2005b, 2007a; Yang and Wu, 2009). Typical plutons in the Yinshan and Yanshan belts include: the
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Shadegai granite (2353 Ma, Table 1, Fig. 4); the Yongfucun alkaline complex
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(2337 Ma~2242 Ma, Zhang et al., 2012a); the Yaojiazhuang alkaline complex (2344 Ma~2215 Ma, Zhang et al., 2012a); the Xiaozhangjiakou ultramafic-mafic
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complex (2205 Ma, Tian et al., 2007); the Guzuizi granite (2362 Ma, Miao et al.,
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2002); Honghualiang granite (2352 Ma, Jiang et al., 2007); the Fanshan alkaline
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complex (2182 Ma, Ren et al., 2009); the Jizhazi granite (2295 Ma, Table 1, Fig. 4); the Guangtoushan alkaline granite complex (2201 Ma, Han et al., 2004); the
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Sungezhuang alkaline complex (2312 Ma, Zhang et al., 2012a); the Panshan monzonite-granite (2035 Ma~2084 Ma, Ma et al., 2007); the Dushan granite-granodiorite (2232 Ma, Luo et al., 2003); the Baizhangzi granite (2223 Ma, Luo et al., 2004); the Hekanzi alkaline complex (2263 Ma~2242 Ma, Yang et al., 2012a); the Dashaoleng and Sijiazi granite (ca. 220 Ma, Zhang et al., 2012d); the Jianping granite (2412 Ma~2371 Ma, Zhang et al., 2009e) and the Xiaofangshen gabbro (2416 Ma, Zhang et al., 2009c). Late Triassic magmatic rocks in the Liaodong area mainly include: the Xiuyan granite (213±1 Ma~210±1 Ma, Wu et al., 2005a; Yang et al., 2007a); the Tongjiapuzi diorite (2142 Ma, Wu et al., 2005a); the
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ACCEPTED MANUSCRIPT Shuangyashan granite (2241 Ma, Wu et al., 2005a); the Laojiandingzi diorite (2201 Ma, Wu et al., 2005a); the Yujiacun syenite (2191 Ma, Wu et al., 2005a);
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the Saima alkaline complex (2331 Ma, Wu et al., 2005a); the Bailinchuan alkaline
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complex (2311 Ma, Wu et al., 2005a); the Shuangdinggou granite (224±1 Ma, Duan et al., 2012), the Longtou quartz diorite-granodiorite-granite (224±2 Ma~203±9 Ma, Lu et al., 2003; Yang et al., 2012b); the Xiaoweishahe granodiorite
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(220±2 Ma~217±7 Ma, Lu et al., 2003; Yang et al., 2012b); the Chaxinzi granite
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(222±2 Ma~216±6 Ma, Lu et al., 2003; Yang et al., 2012b); the Mayihe diorite-granite (226±3 Ma~220±2 Ma, Pei et al., 2008; Yang et al., 2012b); the
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Xidadingzi granite (221±2 Ma~220±2 Ma, Yang et al., 2012b) and the Nankouqian
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granite (224±2 Ma~221±2 Ma, Yang et al., 2012b). Typical Middle-Late Triassic
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magmatic rocks in the southern Yanbian-Liaobei area include the Hongqiling mafic-ultramafic complexes (217±3 Ma~216±5 Ma, Wu et al., 2004) and the
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Bakeshu mafic-ultramafic complex (2223 Ma, Cao et al., 2013). Typical Middle-Late Triassic magmatic rocks in North Korean Peninsula include: the Tokdal alkaline complex (224±4 Ma, Peng et al., 2008); Unsan syenite (2342 Ma, Wu et al., 2007b); Taepyeongli granite (2131 Ma, Wu et al., 2007b); the Kangseo granite (2151 Ma, Wu et al., 2007b) and North Korean kimberlite intrusions (ca. 223 Ma, Yang et al., 2010a). Other areas in the NCC include the Xiaoqinling area in its southern margin with only a few intrusions such as the Laoniushan diorite-monzonite-granite complex (2281 Ma~2081 Ma, Ding et al., 2011; Wang et al., 2012a) and the Zhaiwa syenogranite pluton (2184 Ma, Li et al., 2012c), and
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2011c). Although some Late Triassic syenite, alkaline gabbro and alkaline granite
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intrusions exist in the Sulu Orogenic Belt (e.g., Chen et al., 2003b; Guo et al., 2005; Yang et al., 2005; Chen and Jiang, 2011), no Late Triassic magmatic rocks have been indentified from the Jiaodong Peninsula (NCC part).
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Although there is no source outcrop exposed, some Middle Triassic volcanic
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cobbles with biotite 39Ar-40Ar plateau age of 241.10.8 Ma have been indentified from the Late Triassic-Early Jurassic conglomerate in Chengde area (Cope et al.,
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2007), indicating existence of some Middle Triassic volcanic rocks in the northern
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margin of the NCC. Late Triassic volcanic rocks are mainly distributed in the
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southern Yanbian-Liaobei area (Pei et al., 2004, Fig. 3k–l), although their ages are not well constrained. Some Late Triassic volcanic rocks of the Shuiquangou
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Formation with a zircon U-Pb age of 2303 Ma are present in the Lingyuan area of the eastern Yanshan belt (Hu et al., 2005, Fig. 3g). 3.3. Early Jurassic-earliest Middle Jurassic magmatic rocks (Fig. 2d) Early Jurassic-earliest Middle Jurassic intrusive rocks are mainly distributed in the southern Yanbian area in the northeastern NCC (Zhang et al., 2004a, Wu et al., 2011) and the Yanshan belt and the Western Hills of Beijing in the northern NCC (e.g., Davis et al., 2001; Wu et al., 2006b; Dai et al., 2008; Liu et al., 2012b). Other areas include the Liaodong area in the eastern NCC (e.g., Wu et al., 2005a, 2005c; Yang et al., 2007c), the Korean Peninsula (Wu et al., 2007b), and western Shandong in the
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ACCEPTED MANUSCRIPT eastern NCC (e.g., Xu et al., 2007a; Lan et al., 2012). Typical Early Jurassic-earliest Middle Jurassic intrusions in the Liaodong area include: the Xiaoheishan
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diorite-granodiorite-granite pluton (177±2 Ma~170±4 Ma, Wu et al., 2005c; Yang et
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al., 2007c) and the Southern Hanjialing granodiorite pluton (179±3 Ma, Wu et al., 2005c). The southern Yanbian area is represented by the Huangniling granodiorite-granite (171±5 Ma~168±3 Ma, Zhang et al., 2004a), the Mengshan
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granodiorite-granite (184±2 Ma~174±3 Ma, Zhang et al., 2004a), the Gaoling
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granodiorite-granite (192±2 Ma~170±3 Ma, Zhang et al., 2004a) and the Bailiping diorite-syenogranite (187±3 Ma~178±2 Ma, Zhang et al., 2004a). Early Jurassic
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intrusions in the northern Korean Peninsula include the Sonbong granodiorite
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(193±1 Ma, Wu et al., 2007b) and the Hoesan granodiorite (182±2 Ma, Wu et al.,
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2007b). Early Jurassic plutons in the Yanshan belt include the Wangtufang granite (191±1 Ma, Liu et al., 2012b) and the Jianchang-Yangjiazhangzi-Lanjiagou
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monzodiorite-granite (190±3 Ma~182±2 Ma, Wu et al., 2006b; Dai et al., 2008). The only recognized Early Jurassic intrusion in western Shandong in the eastern NCC is the Tongshi monzonite-syenite-granite complex with zircon U-Pb ages ranging from 185±1 Ma to 177±4 Ma (Xu et al., 2007a; Lan et al., 2012). Early Jurassic volcanic rocks, assigned to the Nandaling and Xinglonggou formations in the northern NCC, are distributed only locally in the Western Hills of Beijing, the Chengde area in northern Hebei province (biotite 40Ar-39Ar plateau age of 180±2 Ma, Davis et al., 2001) and the Beipiao and Nanpiao areas in western Liaoning province (40Ar-39Ar plateau age of 188±7 Ma, Chen et al., 1997; Fig. 3e–f, h).
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ACCEPTED MANUSCRIPT 3.4. Middle-Late Jurassic magmatic rocks (Fig. 2e) Middle-Late Jurassic intrusive rocks are widely distributed in the Yanshan Belt in
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the northern NCC, the Liaodong area and Jiaodong Peninsula in the eastern NCC
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and the southern Yanbian-Liaobei area in northeastern NCC and northern North Korea (Wu et al., 2011). Typical Middle-Late Jurassic intrusions in the Yanshan Belt include: the Shicheng diorite (159±2 Ma, Davis et al., 2001); the Changyuan diorite
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(151±2 Ma, Davis et al., 2001); the Siganding diorite-mozonite-granite (159±4 Ma,
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Table 1, Fig. 4); the Qianzhangzi diotite-syenite (166±2 Ma, Table 1, Fig. 4); the Nianziyu diorite (165±2 Ma, Table 1); the Xingzhangzi granite (165±2 Ma, Table 1,
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Fig. 4); the Zhoujiawopi diorite (159±2 Ma, Table 1, Fig. 4); the Daheishan
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monzonite (164±1 Ma, Table 1, Fig. 4); the Jianchang monzodiorite (157±1 Ma, Wu
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et al., 2006b) and Yiwulüshan granite (163±3 Ma~153±3 Ma, Wu et al., 2006b; Du et al., 2007; Zhang et al., 2008e). Among the Middle-Late Jurassic intrusions in the
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Liaodong area are: the Dandong (or Jiuliancheng) granite (157±6 Ma~156±3 Ma, Li et al., 2004a; Wu et al., 2005c); the Gaoliduntai granite (156±5 Ma, Li et al., 2004a); the Heigou granite (173±6 Ma, Wu et al., 2005c); the Lianhuapei granite (160±5 Ma, Wu et al., 2005c); the Northern Hanjialing granite (164±4 Ma, Wu et al., 2005c); the Wulong granite (163±7 Ma, Wu et al., 2005c) and the Yutun diorite (157±3 Ma, Wu et al., 2005c). Middle-Late Jurassic intrusions in the Jiaodong Peninsula include: the Linglong granite (160±4 Ma~153±4 Ma, Miao et al., 1998; Wang et al., 1998a; Qiu et al., 2002); the Lujiahe granite (154±4 Ma~152±10 Ma, Miao et al., 1998; Wang et al., 1998a; Qiu et al., 2002) and the Kunyushan granite complex (160±3 Ma~141±3
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ACCEPTED MANUSCRIPT Ma, Hu et al., 2004; Guo et al., 2005; Zhang et al., 2010c). Several Late Jurassic plutons occur in the Xiaoqinling area in the southern margin of the NCC including
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the Balipo granite (156±2 Ma, Jiao et al., 2009), the Wuzhangshan granite (157±1
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Ma, Mao et al., 2005), the Nanjihu porphyritic granite (158±3 Ma, Mao et al., 2005), the Shangfanggou granite (158±3 Ma, Mao et al., 2005), the Lantian granite (154±1 Ma, Ding et al., 2010), the Muhuguan granodiorite-granite (151±2 Ma, Ding et al.,
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2010; 150±1 Ma, Wang et al., 2011b) and the Xiaxie and Mulonggou granitoid
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plutons (154±2 Ma~151±1 Ma, Ke et al., 2013). A Middle Jurassic Jingshan garnet-bearing granite pluton is present in the Bengbu uplift in the southeastern NCC
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(166±2 Ma~160±1 Ma, Xu et al., 2005; Li et al., 2010; Yang et al., 2010b).
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Middle-Late Jurassic volcanic rocks, including those of theTiaojishan and Lanqi
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formations, are widely distributed in the Yanshan Belt, the Western Hills of Beijing in the northern NCC (Fig. 3e–h) and the southern Yanbian-Liaobei area in
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northeastern NCC (Fig. 3k–l). Although Jurassic sedimentary rocks are locally distributed in the western Yinshan belt, central Taihangshan, Bohai Bay Basin, Luxi (western Shandong Province), Hefei Basin, Jiaodong Peninsula, Liaodong, Korean Peninsula, and Xiaoqinling, no Jurassic volcanic rocks have been recognized in these areas (Fig. 3a–d, i–j, m–o). 3.5. Early Cretaceous magmatic rocks (Fig. 2f) Unlike the Triassic-Jurassic magmatism that was concentrated near craton margins, the Early Cretaceous magmatic rocks are widely distributed throughout the eastern and central NCC, but show a decrease trend of magmatism from eastern to central
15
ACCEPTED MANUSCRIPT NCC. Over 80 percent of the Phanerozoic intrusive rocks in the NCC were formed during this period and the Early Cretaceous magmatism is considered to be a “giant
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igneous event” in eastern China (Wu et al., 2005b). As with the intrusive rocks, Early
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Cretaceous volcanic rocks are widely distributed in the Yanshan Belt, the Western Hills of Beijing and northern Taihangshan, western Shandong, Liaodong, Huanghua depression in the Bohai Bay Basin (Fig. 3b, d–o). The westernmost areas with the
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Early Cretaceous volcanic rocks (131±2 Ma~128±1 Ma, Table 1, Fig. 4) in the NCC
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are located north and south of Bayan Obo in the far western segment of the Yinshan belt (Figs. 2f and 3b). No volcanic rocks have been identified from the Early
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Cretaceous strata within the Ordos Basin (Fig. 3a).
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3.6. Late Cretaceous magmatic rocks (Fig. 2g)
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Late Cretaceous volcanic rocks are relatively minor and scarcely distributed in the eastern part of the NCC including the Jiaodong Peninsula, Bohai Bay Basin, Liaoxi
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(western Liaoning Province), Qujiatun in the Liaodong Peninsula, Laohutai in eastern Liaoning and Datun area near Changchun in NE China (Xu et al., 1999; Wang et al., 2002, 2006a; Yan et al., 2003; Meng et al., 2006; Hua et al., 2006; Ling et al., 2007; Tang et al., 2008; Zhang et al., 2006a, 2011c). Late Cretaceous volcanic rocks in western Liaoning Province of the Daxingzhuang Formation are composed mainly of intermediate-silicic and silicic lavas, pyroclastic rocks and minor mafic lavas with K-Ar ages of ca. 81 Ma (Bing et al., 2003; Li, 2011, Fig. 3h) and Fuxin trachybasalt with K-Ar ages from 92.12.1 Ma to 84.81.7 Ma (Xu et al., 1999; Wang et al., 2002). Eruption of basalts in Datun area near Changchun and in
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ACCEPTED MANUSCRIPT Laohutai near Fushun in NE China occurred around 92.50.5 Ma (40Ar-39Ar age, Zhang et al., 2006a) and 70.10.9 Ma to 60.11.5 Ma (40Ar-39Ar age, Kuang et al.,
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2012b), respectively. The Qujiatun basalt near Pulandian in the Liaodong Peninsula
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yield a Late Cretaceous K-Ar age of 81.62.5 Ma (Wang et al., 2006a). Late Cretaceous basaltic rocks in the Jiaodong Peninsula with a 40Ar-39Ar age of 73.50.3 Ma exist within the Wangshi Group in the Jiaolai Basin (Yan et al., 2003, 2005, Fig.
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3n). Late Cretaceous rhyolitic lavas with zircon U-Pb age of 723 Ma have been
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recovered from drilling holes in the Huanghua depression of the Bohai Bay Basin (Zhang et al., 2011c). Late Cretaceous intrusive rocks are rarely reported in the
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NCC.
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4. New zircon U-Pb ages of the Mesozoic magmatic rocks
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Newly obtained zircon SHRIMP and LA-ICP-MS U-Pb ages of the Mesozoic magmatic rocks in the NCC (30 samples) are listed Table 1 and their U-Pb concordia
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diagrams are presented in Fig. 4. Together with the previously published geochronological results of 938 samples (zircon U-Pb data for intrusive and felsic volcanic rocks and 40Ar-39Ar data on mafic volcanic rocks) on the Mesozoic magmatic rocks in the NCC and North Korea (Supplementary Table 3), the ages of the Mesozoic magmatic rocks in the Sino-Korean Craton are summarized in Figs. 5 and 6. Fig. 5 clearly indicates episodic magmatism in the Sino-Korean Craton during Mesozoic time and the magmatism reached its peak during the Early Cretaceous. Because Late Cretaceous magmatism was very weak in the NCC and its ages are not well constrained, it is not included in the following discussion. Cluster ages of Early
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ACCEPTED MANUSCRIPT Triassic, Late Triassic, Early Jurassic-earliest Middle Jurassic, Middle-Late Jurassic and Early Cretaceous magmatic rocks are 254–247 Ma, 231–221 Ma, 190–174 Ma,
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165–157 Ma and 136–115 Ma, respectively (Fig. 5). Clearly, there are major
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differences between ages of the Mesozoic magmatic rocks in different portions of the Sino-Korean Craton (Fig. 6). 4.1. Yinshan
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The Triassic and Cretaceous are very important periods for magmatism in the
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Yinshan belt along the northern margin of the western NCC (Fig. 6a). Ages of the Early Triassic and Middle-Late Triassic magmatic rocks are 248 Ma and 239–211
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Ma, respectively. Ages of the Early Cretaceous magmatic rocks in Yinshan belt range
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from 142 Ma to 114 Ma with main peaks at 142 Ma, 131 Ma, 125 Ma, 119 Ma and
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114 Ma, respectively. Jurassic magmatism is very weak in the Yinshan belt with only a few samples that are latest Late Jurassic in age (ca. 148 Ma).
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4.2. Yanshan-Liaoxi (Western Liaoning Province) The Yanshan belt and Liaoxi area along the northern margin of the central-eastern NCC are the most studied areas of Mesozoic magmatism in the Sino-Korean Craton with abundant high-precision zircon SHRIMP and LA-ICP-MS U-Pb and 40Ar-39Ar ages. Almost all periods of Mesozoic magmatism in the Sino-Korean Craton can be found in these areas and the most intensive magmatism occurred during Early Triassic, Middle-Late Triassic, Middle-Late Jurassic and Early Cretaceous, respectively (Fig. 6b). The Early Triassic magmatism exhibits main age peaks of 254 Ma and 248 Ma. The Middle-Late Triassic magmatism displays main age peaks at
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ACCEPTED MANUSCRIPT 231 Ma, 227 Ma, 220 Ma and 206 Ma. The Early Jurassic-earliest Middle Jurassic magmatism exhibits main age peaks of 196 Ma, 190 Ma and 173 Ma. The
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Middle-Late Jurassic magmatism displays main age peaks of 166 Ma, 159–161 Ma
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and 152 Ma. The Early Cretaceous exhibits main age peaks at 138 Ma, 133 Ma, 129 Ma, 125 Ma, 120 Ma and a minor peak of 106 Ma. 4.3. Liaodong
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The Liaodong area is another well studied area for Mesozoic magmatism in the
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Sino-Korean Craton. No Early Triassic magmatism has been indentified, but the Late Triassic and Early Cretaceous were very important periods for magmatism there (Fig.
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6c). Ages of the Middle-Late Triassic magmatism range mainly from 233 Ma to 210
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Ma with main peaks at 222–221 Ma and 214–210 Ma. Ages of the Early Cretaceous
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magmatism range mainly from 130 Ma to 115 Ma with main peaks at 128 Ma, 121 Ma and 115 Ma. The Middle-Late Jurassic magmatism exhibits main age peak at 157
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Ma. Ages of the Early Jurassic magmatism range mainly from 185 Ma to 174 Ma with main peak at 174 Ma. 4.4. Southern Yanbian-Liaobei Neighboring on the northern Korean Peninsula, the southern Yanbian-Liaobei area is located at the northeasternmost NCC (Fig. 1). Main stages of magmatism in the southern Yanbian-Liaobei area occurred in the Early Triassic, Jurassic and Early Cretaceous periods (Fig. 6d). Ages of the Early Cretaceous magmatism range mainly from 138 Ma to 108 Ma with main peaks at 130 Ma, 127–125 Ma, 123 Ma, 119 Ma and 108 Ma. The Middle-Late Jurassic magmatic rocks display main age peaks of
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ACCEPTED MANUSCRIPT 172–170 Ma, 163 Ma and 159 Ma. Ages of the Early Jurassic magmatism range from 192 Ma to 178 Ma with main age peaks of 186–182 Ma and 178 Ma. Ages of
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the Late Triassic magmatism range mainly from 229 Ma to 222 Ma. Ages of the
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Early Triassic magmatism range mainly from 251 Ma to 247 Ma with main peaks at 249–247 Ma.
4.5. Western Hills of Beijing and northern Taihangshan
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Mesozoic magmatism in the Western Hills of Beijing and northern Taihangshan
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occurred in the Jurassic and Early Cretaceous periods (Fig. 6e). No Triassic magmatic rocks were indentified in this area. The Early Jurassic magmatic rocks in
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the Western Hills of Beijing exhibit an age peak at 177 Ma. Ages of the Middle-Late
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Jurassic magmatic rocks range mainly from 157 Ma to 147 Ma and have a main peak
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at 147 Ma. Ages of the Early Cretaceous magmatism range from 142 Ma to 126 Ma and peak at 139 Ma, 134 Ma, 130 Ma and 126 Ma, respectively.
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4.6. Luxi (western Shandong Province) The Luxi area is a large uplifted region in the eastern NCC (Fig. 1). Mesozoic magmatic rocks in the Luxi area are almost all Early Cretaceous in age with only one Early Jurassic monzonite-syenite-granite complex (ca. 190–176) in Tongshi near the Tan-Lu fault zone (Fig. 6f). No Triassic and Middle-Late Jurassic magmatic rocks were indentified from this area. Ages of the Early Cretaceous magmatic rocks range from 144 Ma to 113 Ma with main peaks at 133–130 Ma, 125 Ma and 115 Ma. Ages of the Early Jurassic Tongshi monzonite-syenite-granite complex range from 190 Ma to 176 Ma with main peaks at 190 Ma and 180 Ma.
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ACCEPTED MANUSCRIPT 4.7. Jiaodong Peninsula (NCC part) The most intensive magmatism in the Jiaodong Peninsula (NCC part) occurred in
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the Early Cretaceous contemporaneously with large-scale gold mineralization (Fig.
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6g). Ages of the Early Cretaceous magmatism range from 128 Ma to 100 Ma with main peaks at 128 Ma, 124 Ma, 119–115 Ma, 111 Ma and 100 Ma. An earlier stage of magmatism occurred with ages ranging from 161 Ma to 152 Ma and age peaks at
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161 Ma and 157 Ma. No Triassic and Early Jurassic magmatic rocks have been
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identified in this area. 4.8. Northern Korean Peninsula
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Although Mesozoic magmatic rocks are widely distributed in the northern Korean
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Peninsula, their ages are not as well constrained as for the NCC due to the absence of
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high-precision geochronological data. Recently, about 20 zircon LA-ICP-MS U-Pb ages on Mesozoic granitoids have been published (Wu et al., 2007b). The present
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data show that granitic magmatism occurred mainly in the Triassic, Early Jurassic-earliest Middle Jurassic and Early Cretaceous periods (Fig. 6h). Ages of Early Cretaceous magmatism range from 115 Ma to 106 Ma with main peaks at 113 Ma, 111 Ma and 109 Ma. Ages of Early Jurassic-earliest Middle Jurassic plutons range from 193 Ma to 173 Ma with peaks at 193 Ma, 182 Ma and 173 Ma. The Triassic magmatism exhibit age peaks at 246 Ma, 234 Ma and 213–215 Ma. It seems that Late Jurassic is a silent period for magmatism in the northern Korean Peninsula. 4.9. Southern Taihangshan All Mesozoic magmatic rocks in the southern Taihangshan are Early Cretaceous in
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ACCEPTED MANUSCRIPT age. Their ages range from 139 Ma to 125 Ma with main peaks at 132 Ma, 127–125 Ma and minor peaks at 139 Ma and 134 Ma (Fig. 6i).
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4.10. Xiaoqinling
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The Xiaoqinling area is located at the southern margin of the central NCC (Fig. 2). Magmatism in this area occurred in the Late Triassic, Late Jurassic and Early Cretaceous (Fig. 6j). Ages of Late Triassic magmatism range from 228 Ma to 205
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Ma with main peaks at 228 Ma, 217 Ma and 208 Ma. Ages of the Late Jurassic
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magmatism range from 158 Ma to 148 Ma with main peaks at 157 Ma and 149 Ma. Ages of the Early Cretaceous magmatism range from 142 Ma to 112 Ma with main
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peaks at 141 Ma, 131–129 Ma and 117 Ma. No Early-Middle Jurassic magmatism
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was indentified from this area.
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4.11. Xuhuai-Bengbu
The Xuhuai-Bengbu area is located near the Tan-Lu fault zone in the southeastern
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NCC with exposure of several Mesozoic intrusions (Fig. 1). Most the Mesozoic magmatic rocks in the Xuhuai-Bengbu area are Early Cretaceous in age with only one Middle Jurassic garnet-bearing granite pluton in Jingshan in the Bengbu uplift (Fig. 6k). Ages of the Early Cretaceous magmatic rocks range from 132 Ma to 112 Ma with main peaks at 131 Ma, 127 Ma, 118 Ma and 112 Ma. Ages of the Middle Jurassic Jingshan granite pluton ranges from 166 Ma to 160 Ma. 4.12. Southern Songliao Basin Because of a thick Cenozoic strata cover (Fig. 2a), the ages of most Mesozoic magmatic rocks in the southern Songliao Basin were obtained from drill hole
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ACCEPTED MANUSCRIPT samples encountered during oil exploration. Results show that the southern Songliao Basin has a Precambrian crystalline basement as the NCC (e.g., Pei et al., 2007).
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Mesozoic magmatism in the southern Songliao Basin occurred primarily in the
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Middle-Late Jurassic and the Early Cretaceous periods (Fig. 6l). Ages of the Early Cretaceous magmatic rocks range from 133 Ma to 110 Ma with main peaks at 133 Ma, 127 Ma, 118 Ma and 115–113 Ma. Ages of the Middle-Late Jurassic magmatism
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range from 166 Ma to 160 Ma with main peaks at 169 Ma and 165 Ma. Moreover,
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minor Middle Triassic magmatism at ca. 236 Ma has also been indentified. 5. Petrological, geochemical characterics and origin of the Mesozoic magmatic
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rocks
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Major and trace element data of representative Mesozoic magmatic rocks in the
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NCC (37 samples) are listed in Table 2 and plotted in Figs. 7 and 8. 5.1. Early Triassic magmatic rocks
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Early Triassic intrusive rocks in the NCC are mainly composed of monzogranite, syenogranite and monzonite, with minor mafic-ultramafic rocks and granodiorite. Early Triassic volcanic rocks consist mainly of dacite and rhyolite. They display similar petrological and geochemical features to the latest Permian magmatic rocks and are considered as a continuum of latest Permian magmatism in the northern NCC. Most of the Early Triassic magmatic rocks are characterized by high contents of SiO2, low initial 87Sr/86Sr ratios and low negative Nd(t) and Hf(t) values (Figs. 9 and 10). Granites belong to highly fractionated I-type to A-type (Zhang et al., 2009e). Geochemical and isotopic data indicate that the felsic rocks were produced by partial
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ACCEPTED MANUSCRIPT melting of ancient lower crust and that the mafic-ultramafic rocks are derived from partial melting of a metasomatized enriched lithospheric mantle. Formation of these
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rocks is likely related to post-collisional extension following final closure of the
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Paleo-Asian Ocean and amalgamation between the Mongolian arc terranes and the NCC along the Solonker suture during latest Permian to earliest Triassic (e.g., Zhang et al., 2009e, 2010b).
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5.2. Middle-Late Triassic magmatic rocks
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Middle-Late Triassic intrusive rocks in the northern NCC consist mainly of diorite, granodiorite, monzogranite, syenogranite, monzonite and syenite. From Middle-Late
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Triassic, alkaline intrusive complexes including nepheline syenite, aegirine-augite
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syenite, pyroxene syenite, quartz syenite, syenite, alkaline granite and associate
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mafic-ultramafic rocks are also quite common (Zhang et al., 2012a; Yang et al., 2012a). Middle-Late Triassic volcanic rocks in the NCC are composed mainly of
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rhyolite, andesite and andesitic tuff. They display a very wide range of SiO2 compositions and high content of alkali (Na2O+K2O). As is the case for to the latest Permian-Early Triassic igneous rocks, the Middle-Late Triassic magmatic rocks are also characterized by low initial 87Sr/86Sr ratios and negative Nd(t) and Hf(t) values (Figs. 9 and 10). Geochemical and Sr-Nd-Hf isotopic data show that the alkaline and mafic-ultramafic rocks were derived mainly from a previously subduction-modified enriched lithospheric mantle (e.g., Yan et al., 1999; Mu et al., 2001; Niu et al., 2012; Zhang et al., 2012a; Yang et al., 2012a). In contrast, the felsic rocks were mainly produced by partial melting of the ancient lower crust. However, compared with Late
24
ACCEPTED MANUSCRIPT Carboniferous-Early Permian and Early Triassic ultramafic-mafic rocks that were derived from an enriched lithospheric mantle, Nd(t) and Hf(t) values of the
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Middle-Late Triassic alkaline and mafic-ultramafic rocks are much higher (Figs. 9
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and 10), which requires input of some depleted asthenospheric mantle components. The Late Triassic magmatic rocks in Xiaoqinling area in the southern margin of the NCC consist of hornblende monzonite, quartz monzonite, quartz diorite,
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syenogranite and monzogranite (Ding et al., 2011; Wang et al., 2012a; Li et al.,
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2012c). They exhibit a wide range of SiO2 compositions and high content of alkali (Na2O+K2O) and belong to high-K calc-alkaline to shoshonitic series. They are
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characterized by moderate initial 87Sr/86Sr ratios of 0.7061 to 0.7075, low negative
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Nd(t) values of -9.2 to -17.0 and low negative zircon Hf(t) values of -9.0 to -17.0
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(Ding et al., 2011). The above geochemical and isotopic characteristics indicate that the Late Triassic magmatic rocks in the southern margin of the NCC were likely
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produced mainly by partial melting of ancient thickened lower continental crust of the NCC in a post-collisional setting following slab break-off (Ding et al., 2011; Wang et al., 2012a), which is similar to origin of the Late Triassic magmatic rocks in the Qinling Orogenic Belt (e.g., Qin et al., 2007a, 2007b; Qin and Lai, 2011; Liu et al., 2011b, 2011c). 5.3. Early Jurassic-earliest Middle Jurassic magmatic rocks Early Jurassic-earliest Middle Jurassic intrusive rocks are composed mainly of granite, monzodiorite, monzonite and syenite. Early Jurassic-earliest Middle Jurassic volcanic rocks consist mainly of basalt, andesitic basalt, andesite, dacites and minor
25
ACCEPTED MANUSCRIPT trachyte. Most of the Early Jurassic-earliest Middle Jurassic intrusive rocks belong to high-K calc-alkaline or shoshonitic series. They are characterized by a wide range of
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Nd(t) and Hf(t) values from low negative to low positive (Figs. 9 and 10), indicating
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interaction of various crustal and mantle sources including lower to upper crust, lithospheric mantle and asthenospheric mantle in their generation (Lan et al., 2012). The Nandaling basalts and basaltic andesites of the Beijing area are characterized by
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low contents of SiO2, LREE (light rare earth element) enrichments and by Nd, Ta,
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Th, U and Ti depletions (Li et al., 2004b; Wang et al., 2007b). They exhibit low initial 87Sr/86Sr ratios and variable negative Nd(t) values from -13.8 to -5.0 and, thus,
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were produced by upwelling of asthenosphere and decompressional melting of early
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subduction-metasomatized continental lithospheric mantle (Li et al., 2004b; Wang et
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al., 2007b; Guo et al., 2007). The Xinglonggou volcanic rocks consists of high-Mg andesites, adakites and dacites and are characterized by high contents of MgO, Sr, Cr
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and Ni, high Mg numbers (Mg#>50), high Sr/Y and LaN/YbN ratios, low initial Sr/86Sr ratios and slightly negative to low positive Nd(t) values from -2.2 to 2.5,
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and young Nd model ages from 1.06 Ga to 0.78 Ga (Gao et al., 2004; Li, 2006b; Yang and Li, 2008). They have been considered to be derived from ancient mafic lower crust that foundered into the convecting mantle and subsequently melted and interacted with peridotite (Gao et al., 2004) or to have been generated from partial melting of subducted oceanic slab of the Paleo-Asian Ocean (Li, 2006b; Yang and Li, 2008). However, high Nd(t) values and young Nd model ages of the Xinglonggou volcanic rocks indicate significant involvement of depleted asthenosphere mantle
26
ACCEPTED MANUSCRIPT materials in formation of these Early Jurassic magmatic rocks. Although some researches suggest that the Early Jurassic-earliest Middle Jurassic
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magmatic rocks and associated Mo deposits in the eastern part of the NCC were
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related to the subduction of a Paleo-Pacific plate (Han et al., 2009), others have attributed the Early Jurassic-earliest Middle Jurassic magmatic rocks in northern and eastern parts of the NCC to the post-orogenic extension or collapse of the CAOB and
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Sulu Orogenic Belt, respectively (e.g., Wang et al., 2007b; Lan et al., 2012). From
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their spatial distribution in the NCC (Fig. 2c), most of the Early Jurassic-earliest Middle Jurassic magmatic rocks are closely associated with the Middle-Late Triassic
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magmatic rocks in the northern NCC and less so in the eastern margin of the NCC.
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Therefore, we proposed that most of the Early Jurassic-earliest Middle Jurassic
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magmatism in the NCC was a continuum of Middle-Late Triassic magmatism and was related to the post-orogenic extension or collapse of the CAOB and Sulu
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Orogenic Belt, not of Paleo-Pacific subduction. However, for the Early Jurassic-earliest Middle Jurassic magmatism in the Yanbian area and northern North Korea (Fig. 2d), it could related to subduction of the Mudanjiang oceanic plate (Wu et al., 2011) or Paleo-Pacific plate (Xu et al., 2013) similar as the contemporaneous magmatism in NE China. 5.4. Middle-Late Jurassic magmatic rocks Middle-Late Jurassic intrusive rocks consist mainly of monzodiorite, syenite, diorite, mozonite and granite. Middle-Late Jurassic volcanic rocks are mainly composed of andesite, basaltic andesite, andesitic tuff, trachyteandesite with minor
27
ACCEPTED MANUSCRIPT basalt, rhyolite and rhyolitic tuff. These rocks are mainly calc-alkaline in composition and exhibit similar petrological and geochemical characteristics to those
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in the Andes arc and the active continental margin of western North America (Deng
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et al., 2000, 2007). Most of the Middle-Late Jurassic magmatic rocks exhibit adakite-like geochemical signatures with high contents of Al2O3, Na2O and Sr, low contents of MgO, Y and Yb, high Sr/Y and LaN/YbN ratios, depletions of high field
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strength elements (HFSE, e.g., Nb, Ta, Ti, Zr, Hf), low to moderate initial 87Sr/86Sr
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ratios and significant negative Nd(t) values (Table 3). They have been generally considered to be derived from the partial melting of a thickened mafic lower crust
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(e.g., Zhang et al., 2001; Rapp et al., 2002; Davis, 2003; Li et al., 2001, 2007b).
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Middle-Late Jurassic granites in the NCC are mainly classified as I-type with minor
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as A-type. Some of the granites in the Jiaodong Peninsula belong to S-type (Zhang and Zhang, 2007). Geological and Sr-Nd-Hf-Pb isotopic data indicate that the
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intermediate-felsic magmatic rocks are mainly crustal-derived (e.g., Zhang et al., 2001; Yang et al., 2006b; Yang and Li, 2008; Li et al., 2001, 2007b, 2010) and scarce exposure of basaltic rocks might be a result of mafic cumulates emplaced at crustal levels (e.g., Guo et al., 2007) or partial melting of an EMI-type subcontinental lithospheric mantle (e.g., Yang and Li, 2008). Unlike the Triassic-Early Jurassic igneous rocks that are only distributed along craton margins (Fig. 2b–d), Middle-Late Jurassic magmatism affected a broader region of the eastern NCC (Fig. 2e). Considering its predominant calc-alkaline compositions and strict distribution in eastern NCC, the Middle-Late Jurassic
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ACCEPTED MANUSCRIPT magmatism was most likely formed in an active continental margin during Paleo-Pacific subduction (e.g., Wu et al., 2000, 2003, 2008; Zhao et al., 1994, 2004a,
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2004b, 2010). It was produced by partial melting of thickening lower continental
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crust (e.g., Li et al., 2001, 2007b, 2010; Zhang et al., 2001; Yang and Li, 2008) and may represent the emergence of a continental arc on the East Asian continental margin in response to westward subduction of the Paleo-Pacific plate (e.g., Zhao,
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1990; Zhao et al., 1994, 2004a, 2004b, 2010). Inception of Paleo-Pacific plate
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subduction beneath East Asian continent is also supported by Jurassic accretionary complexes in Jiamusi Massif (Wu et al., 2007c) and Japan (e.g., Isozaki et al., 1990;
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Isozaki, 1997; Taira, 2001).
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5.5. Early Cretaceous magmatic rocks
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Early Cretaceous intrusive rocks consist mainly of syenite, granite, granodiorite and diorite. Early Cretaceous volcanic rocks are mainly basalt, rhyolite, rhyolitic tuff,
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trachyte and trachyteandesite. Most of the Early Cretaceous granites in the NCC are of A-type (e.g., Wu et al., 2005b; Sun and Yang, 2009). Mafic microgranular enclaves (MME) are very common in most of the Early Cretaceous granitoid intrusions, indicating magma mixing or intense crust-mantle interaction during the Early Cretaceous. Although some Early Cretaceous magmatic rocks exhibit similar geochemical characterics as the Middle-Late Jurassic rocks (Fig. 7, Fig. 8g–h), alkaline rocks and basalts are very common within the Early Cretaceous (e.g., Zhang et al., 2002a, 2004b, 2005a; Guo et al., 2007; Yang et al., 2007b, 2008b; Yang and Li, 2008; Ying et al., 2011). The Early Cretaceous mafic rocks are characterized by low
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ACCEPTED MANUSCRIPT content of SiO2, high content of MgO and high Mg numbers (Mg#), low to moderate initial 87Sr/86Sr ratios and Nd(t) values increasing from early low negative to late
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positive (Figs. 9 and 10), indicating derivation varying from enriched lithospheric
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mantle materials during early periods to depleted lithospheric mantle in later periods (Zhou et al., 2001; Zhang et al., 2002a, 2004b, 2010e; Yang et al., 2004, 2008c, 2012c; Qiu et al., 2005; Guo et al., 2007; Yang and Li, 2008; Liu et al., 2009, 2010a;
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Wang et al., 2006b, 2011c; Kuang et al., 2012a). The alkaline rocks (syenite,
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monzonite and trachyte with alkaline affinity) exhibt low to moderate initial 87Sr/86Sr ratios and variable Nd(t) and Hf(t) values from low negative to low positive (Figs. 9
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and 10), indicating they were derived mainly from an enriched lithospheric mantle
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(Zhang et al., 2005a; Yang et al., 2007b; Yan et al., 2008; Ying et al., 2007, 2011).
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However, the most depleted Sr, Nd and Hf isotopic compositions of some syenites indicate a considerable contribution of asthenosphere materials during formation of
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these alkaline rocks (e.g., Yang et al., 2007b; Ying et al., 2007). The felsic rocks are characterizied by variable initial 87Sr/86Sr ratios and low negative to high negative Nd(t) and Hf(t) values (Figs. 9 and 10) and were formed via a complex process involving mixing of magmas derived from mantle and crustal sources, crystal fractionation and intracrustal melting (e.g., Yang et al., 2008b; Sun and Yang, 2009). Formation of the voluminous Early Cretaceous igneous rocks in the eastern and central NCC has generally been considered to be related to lithospheric thinning and decratonization (e.g., Deng et al., 2000, 2007; Chen et al., 2003a; Qian et al., 2002, 2003; Wu et al., 2005b; Luo et al., 2006; Xu et al., 2006a, 2006b; Su et al., 2007;
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ACCEPTED MANUSCRIPT Yang et al., 2008b; Sun and Yang, 2009; Liu et al., 2012a). Although most researchers have proposed that the Early Cretaceous igneous rocks in eastern NCC
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were related to the Paleo-Pacific subduction (e.g, Chen et al., 2003a, 2005, 2013; Wu
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et al., 2005b; Sun et al., 2007; Zhu et al., 2011, 2012a), others recognize no genetic links between Early Cretaceous magmatism and Paleo-Pacific subduction (e.g., Shao et al., 2001; Xiao et al., 2010; Wan and Zhao, 2012; Zhang, 2013). The existence of
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Early Cretaceous intermediate-mafic lavas in Suhongtu north to the Alashan block
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(40Ar/39Ar ages of six samples ranging from 113.11.4 Ma to 106.51.3 Ma, Zhong et al., 2011) and granitoids with zircon U-Pb age of 1352 Ma in Yagan near the
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Mongolian border in China (e.g., Wang et al., 2004a, 2012b) indicate that nor all of
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the Early Cretaceous igneous rocks can be attributed to Paleo-Pacific subduction;
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some were probably related to late-orogenic extensional collapse of previously thickened continental crust (e.g., Meng, 2003; Zheng and Wang, 2005; Xu et al.,
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2007b).
5.6. Late Cretaceous magmatic rocks Late Cretaceous magmatic rocks consist mainly of alkali basalts or trachybasalts with minor intermediate-silicic and silicic lavas in western Liaoning Province and Huanghua depression in the Bohai Bay Basin. The alkali basalts or trachybasalts are characterized by low SiO2 contents from 44.4% to 52.3%, high contents of MgO and high Mg values, enrichments of light rare earth elements (LREE) and large ion lithophile elements (LILE), no deleption of high field strength elemennts (HFSE), low initial 87Sr/86Sr ratios and high negative to high positive Nd(t) values ranging
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ACCEPTED MANUSCRIPT from -5.1 to 7.6 (Yan et al., 2003, 2005; Meng et al., 2006; Zhang et al., 2006a; Kuang et al., 2012b). These geochemical and isotopic characteristics indicate
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derivation from a depleted asthenospheric mantle or from magmas of asthenosphere
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origin that were mixed with magma of enriched lithosphere origin (Yan et al., 2003, 2005; Meng et al., 2006; Zhang et al., 2006a). Late Cretaceous felsic lavas are characterized by moderate initial 87Sr/86Sr ratios and low negative Nd(t) values. They
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are considered to have been derived from the partial melting of ancient lower crust
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(Li, 2011; Zhang et al., 2011c).
6. Temporal and spatial differences of the Mesozoic deformation patterns in the
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NCC
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During the Mesozoic, the NCC underwent several stages of contractional and
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extensional deformation both at its margins and interior. Preliminary results show that there are significant temporal and spatial differences of deformation patterns in
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the NCC during this time.
6.1. Early-Middle Triassic deformation (Fig. 11a) Early-Middle Triassic deformation occurred mainly in the northern NCC Yinshan and Yanshan belts. Mylonite 40Ar-39Ar dating results indicate that compressional deformation of the E-W-trending Shangyi-Chicheng, Fengning-Longhua, Heilihe-Songsanjia and Faku ductile shear zones in the northern NCC occurred during Early-Middle Triassic (Wang, 1996; Liu et al., 2003; Zhang et al., 2005b; Zhang, 2008; Wan, 2012). E-W-trending folds and angular unconformities between Late Triassic and pre-Late Triassic strata in the Yinshan and Yanshan belts indicate
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ACCEPTED MANUSCRIPT N-S contraction prior to the Late Triassic (e.g., HBGMR, 1989; Liu and Xu, 2003). Early-Middle Triassic NW-W thrust faulting older than the Shuiquangou Formation
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with a zircon U-Pb age of 2303 Ma, was reported in the Lingyuan area of the
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eastern Yanshan belt (Hu et al., 2005, 2010). Formation of the E-W-trending Malanyu anticline and Jixian thrust fault in southeastern Yanshan belt may occur during this period (Ma et al., 2007; Li et al., 2008a). In the Liaodong Peninsula in
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the eastern NCC, large folds within Neoproterozoic-Permian strata indicate near N-S
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contraction at ca. 250–219 Ma, a deformation that had been attributed to continental-continental subduction/collision between the Yangtze plate and NCC
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along the Sulu belt (Xu et al., 1991; Yang et al., 2002, 2011; Bing and Wang, 2004).
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Initiation of the Xuzhou-Suzhou thrust nappes in the southeastern margin of the
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NCC occurred during the Middle Triassic as a result of the subduction and collision between the Yangtze and North China cratons (e.g., Xu et al., 1987b, 1993; Shu et al.,
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1994; Wang et al., 1998b; Chen and Shu, 2000). 6.2. Late Triassic-Early Jurassic deformation (Fig. 11b) From the Early-Middle Triassic to latest Triassic, the deformation patterns in the northern NCC changed from N-S or NE-SW contraction to extension. Late Triassic extension has been reported in the NW Ordos Basin and controlled Triassic sedimentation in the Helan Shan and Zuozi Shan (Liu, 1998; Ritts et al., 2004). A Late Triassic metamorphic core complex was reported south of Sonid Zuoqi in the vicinity of the Solonker suture zone north to the northern margin of the NCC (Davis et al., 2004). Late Triassic NE-SW extension indicated by the L-tectonites exists near
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ACCEPTED MANUSCRIPT Chifeng area in eastern northern NCC and geochronological results on syntectonic diorite plutons and mylonitic rocks indicate deformation at ca. 228–219 Ma (Liu et
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al., 2011d). In contrast, the southern margin of the NCC was characterized by
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Middle-Late Triassic contraction as indicated by E- to NWW-trending thrust faults and folds in the southern North China Basin (e.g., Xu et al., 2003a; Sun et al., 2004b). The Luxi area in the eastern NCC was characterized by E-W-trending open
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to tight folds and related small-scale reverse faults during Late Triassic period (Li et
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al., 2004c, 2005b, 2009a). Deformation of the large folds within Neoproterozoic-Permian strata in the Liaodong Peninsula probably continued to
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earliest Late Triassic period (Xu et al., 1991; Yang et al., 2002, 2011; Bing and Wang,
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2004). Some Late Triassic to earliest Jurassic E-W-trending folding and NWW
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thrusting was reported in eastern Jiaodong Peninsula (Zhang et al., 2007e; Li et al., 2009a). The Xuzhou-Suzhou thrust nappes in the southeastern margin of the NCC
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were probably active during this period (Shu et al., 1994; Chen and Shu, 2000). Whether the Tan-Lu fault zone in the eastern NCC was active during the Triassic, or not, is still highly controversial (e.g., Zhang and Dong, 2008, and references therein). Although many researchers believe that sinistral strike-slip motion of the Tan-Lu fault zone in the eastern NCC was initiated during the Late Triassic-Early Jurassic as a result of collision between the South and North China blocks (e.g., Xu et al., 1987a; Lin and Fuller, 1990; Okay and Sengor, 1992; Yin and Nie, 1993; Li, 1994; Wan and Zhu, 1996; Wang et al., 2000b; Chen et al., 2000a; Zhang and Dong, 2008; Zhu et al., 2009), others have proposed that initial large-scale sinistral
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ACCEPTED MANUSCRIPT strike-slip motion occurred no earlier than the Middle-Late Jurassic (e.g., Xu and Zhu, 1994; Zhu et al., 2005; Wang, 2006).
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Early Jurassic deformation, which is considered as a continuum of Triassic
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(Indosinian) deformation, is locally existed in the northern and eastern NCC. Although some Early Jurassic thrusting was reported in the Yanshan belt (e.g., Xu et al., 2003b; Davis et al., 2009; Liu et al., 2012b), the Early Jurassic deformation in
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the northern NCC was mainly characterized by extension (Zhang et al., 2008a; Davis
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et al., 2009). Late Triassic to Early Jurassic extensional deformation and large-scale gravity sliding has been indentified in western Liaoning Province in eastern part of
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the northern NCC (e.g., Hu et al., 2005, 2010; Davis et al., 2009). Ma and Liu (1986)
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proposed that the Late Triassic-Early Jurassic NEE-trending sedimentary basins in
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the northern NCC are rift-controlled. Early Jurassic rift-controlled E-W-trending basins were also recognized in the Daqingshan area in the middle northern NCC
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(Ritts et al., 2001; Darby et al., 2001; Meng, 2003). Recent studies suggest that the Late Triassic-Early Jurassic Dengzhangzi Formation in western Liaoning Province was deposited in a NE-trending half-graben (Davis et al., 2009; Hu et al., 2010). Structural analyses and geochronological results show that deformation of the E-W-trending ductile shear zones in the Liaodong Peninsula occurred in Early Jurassic time (Wang et al., 2000a; Li et al., 2004c, 2007c). 6.3. Middle-Late Jurassic to earliest Cretaceous deformation (Fig. 11c) Middle-Late Jurassic to earliest Cretaceous deformation in the NCC is mainly characterized by contraction with development of large-scale thrust faults and folds
35
ACCEPTED MANUSCRIPT (Fig 12a–h; Table 4). The Middle-Late Jurassic to earliest Cretaceous fold and thrust belts are mainly distributed in the Yinshan and Yanshan belts along the northern
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NCC (e.g., Ge, 1989; Zhao, 1990; He et al., 1998; Chen, 1998; Davis et al., 1998,
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2001; Zheng et al., 1998b; Ma et al., 2002; Cui et al., 2002; Zhang et al., 2002b, 2011a; Du et al., 2005; He et al., 2007; Li and Liu, 2009), the Western Hills of Beijing and northern Taihangshan (e.g., Xu and Hong, 1996; Sun et al., 2004c;
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Zhang et al., 2006b, 2011a; Zhao and Du, 2007), circum-Ordos Basin in the
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middle-western NCC (e.g., Tang et al., 1988; Chen and Zhou, 1994; Liu, 1998; Darby and Ritts, 2002; Zhang et al., 2004c, 2008a, 2009f), the southern margin of
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the NCC (e.g., Liu et al., 2001; Gao et al., 2006), the Xuzhou-Suzhou area in the
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southeastern margin of the NCC (e.g., Xu et al., 1987b, 1993; Shu et al., 1994; Wang
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et al., 1998b) and the Liaodong area and Jiaodong Peninsula in the eastern NCC (e.g., Yang et al., 2000; GSILP, 2002; Zhang and Zhang, 2007, 2008). Commonly,
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Middle-Late Jurassic sedimentary and volcanic rocks were involved in deformation and thrust faults of that age have been covered by Early Cretaceous volcanic and sedimentary rocks or intruded by Early Cretaceous intrusions. The controversical Tan-Lu fault in the eastern NCC was characterized by thrust faulting or sinistral transpression during the Middle-Late Jurassic (e.g., Ge, 1989; Wan and Zhu, 1996; Zhang and Dong, 2008; Zhu et al., 2010). The NW-trending faults in the Luxi area was characterizied by dextral transpression during this period (Wang et al., 2008, 2010). Although Middle-Late Jurassic to earliest Cretaceous contractional deformation is
36
ACCEPTED MANUSCRIPT widespread in the NCC, it was spatially partitioned. The timing of deformation is broadly similar, but thrust vergence and orientations are not unique, indicating they
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are likely controlled by multiple tectonic regimes during the Middle-Late Jurassic to
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earliest Cretaceous. Large-scale basement-involved E- to NEE-NE-striking thrust tectonics are common in the Yinshan and Yanshan fold and thrust belts (Table 4). From west to east, strikes of the thrust faults and folds in the Yinshan and Yanshan
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belts change from E-W to NE-SW, but vergence is not systematic. The thrust faults
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and folds in the Western Hills of Beijing and northern Taihangshan are mainly E-W or NE-SW in strike and the deformation intensity decreases from north to south.
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Strikes of Middle-Late Jurassic thrust faults and folds in the circum-Ordos Basin are
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usually parallel to the boundary of the Ordos Basin. Strikes of the Middle-Late
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Jurassic thrust faults and folds in the southern margin of the NCC are mainly NWW and parallel to the Qinling-Dabie Orogenic Belt (e.g., Liu et al., 2001; Gao et al.,
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2006) as well as the thrust faults and folds within the belt (e.g., Liu and Wang, 1999; Sun et al., 2004b, 2004d; Dong et al., 2005). The Xuzhou-Suzhou thrust nappes in the southeastern margin of the NCC are large scale thin-skin contractional tectonics with the movement direction from SE to NW (e.g., Shu et al., 1994; Wang et al., 1998b). The thrust nappes were strongly reactivated and the Middle Jurassic was an important period for formation of the Xuzhou-Suzhou thrust nappes (e.g., Xu et al., 1987b, 1993; Shu et al., 1994; Wang et al., 1998b; Chen and Shu, 2000). 6.4. Early Cretaceous deformation (Fig. 11d) Early Cretaceous deformation in NCC was mainly characterized by extension with
37
ACCEPTED MANUSCRIPT development of rift basins (e.g., Ren et al., 2002; Cope et al., 2010; Li et al., 2012a; Zhu et al., 2012b) and metamorphic core complexes in Xiongershan, Xiaoqinling,
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Linglong, Liaonan, Yiwulüshan, Louzidian, Yunmengshan and Hohhot areas (e.g.,
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Hu and Tian, 1994; Davis et al., 1996, 2002; Davis and Darby, 2010; Darby et al., 2004; Yang et al., 1996, 2007d; Liu et al., 1998, 2005, 2011a; Ma et al., 1999; Han et al., 2001; Zhang et al., 2003, 2012e; Wang et al., 2004b, 2011b, 2012b; Wang and
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Zheng, 2005; Lin et al., 2008, 2011; Charles et al., 2011; Guo et al., 2012a, 2012b).
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Similar extensional deformation was very common throughout NE Asia and is regarded comprising a NE Asian extensional province (Darby et al., 2004; Daoudene
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et al., 2009; Wang et al., 2011b and references therein; Zhou et al., 2012). The
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Tan-Lu fault was mainly characterized by normal faulting and extension during the
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Early Cretaceous (e.g., Wang et al., 2000b; Chen et al., 2000a; Zhang and Dong, 2008; Zhu et al., 2010). Unlike the Middle-Late Jurassic to earliest Cretaceous
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contraction deformation with its non-consistent shortening directions, the Early Cretaceous NCC extension is characterized by steady NW-SE extensional direction that is similar to that of the NE Asian extensional province (Daoudene et al., 2009; Wang et al., 2011b; Zhou et al., 2012). Although some Late Jurassic thrusting continued into the Early Cretaceous and could have been synchronous with extension elsewhere (e.g., Qi et al., 2007; Zhang et al., 2009d), much evidence demonstrates that late Mesozoic NCC extension occurred later than contraction (e.g., Davis et al., 2010; Wang et al., 2011b; Zhang et al., 2011a, 2011b, Lin et al., 2013a, 2013b). In the Yinshan belt in the northern NCC,
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ACCEPTED MANUSCRIPT the Late Jurassic-earliest Cretaceous Daqingshan thrust plate was cut by a low angle normal fault (Fig. 12i), which clearly indicates that the extension is later than
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thrusting deformation.
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7. Temporal and spatial variations of the Mesozoic magmatism and deformation in the NCC
7.1. Temporal and spatial variations of magmatism
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As previously discussed, Mesozoic magmatic rocks are widespread within the
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NCC, but with significant differences in their temporal and spatial distribution. Early Triassic magmatic rocks are only distributed in the northern margin of the NCC and
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the CAOB north to it (Fig. 2a). Middle-Late Triassic and Early Jurassic magmatic
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rocks are primarily distributed in the northern, eastern and southern margins and the
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surrounding orogenic belts such as the CAOB, Sulu and Qinling-Dabie (Fig. 2bc). Ages of the Mesozoic magmatism became younger and magmatic intensity became
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much weaker from the northern and eastern parts (Yanshan, Jiaodong and Liaodong Peninsula) to the central part of the NCC (Taihangshan). This temporal and spatial migration of Mesozoic magmatism from craton margins to its interior indicates that Mesozoic mobilization of the NCC was diachronous and interactions of the NCC-surrounding orogenesis may have played important roles in Mesozoic magmatism and destruction of the NCC. Ages for the widely distributed Early Cretaceous magmatic rocks appear to exhibit a slightly younging trend from the central to the eastern NCC. This apparent migration could be the result of eastward migration of lithospheric delamination
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ACCEPTED MANUSCRIPT associated with rollback of the subducted Paleo-Pacific oceanic plate (e.g., Wu et al., 2007b; Zhang et al., 2010d).
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7.2. Temporal and spatial variations of deformation
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There are many differences in the temporal and spatial distribution of Mesozoic deformation in the NCC. Early-Middle Triassic deformation is only present of the Yinshan and Yanshan belts in the northern NCC and is mainly characterized by
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deep-seated N-S-trending compressional ductile shear zones and folds (Fig. 11a).
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Middle Triassic-earliest Late Triassic deformation in the Liaodong Peninsula is characterized by E-W-trending folds within the Neoproterozoic-Permian strata (Fig.
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11a). Late Triassic-Early Jurassic deformation is largely restricted to the northern,
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eastern and southeastern parts of the NCC (Fig. 11b). Among them the Late
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Triassic-Early Jurassic deformation in the Yinshan and Yanshan belts in the northern NCC are characterized by NEE to NE-trending normal faults indicating SEE- to
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SE-directed extension. The Jiaodong Peninsula was characterized by E-W-trending folding and NWW thrusting during the Late Triassic to earliest Jurassic (Zhang et al., 2007e; Li et al., 2009a). Some Late Triassic E-W-trending open to tight folds and related small-scale reverse faults may exist in the Luxi area (Li et al., 2004c, 2005b, 2009a). Initiation of an arcuate thrust nappe in the Xuhuai-Bengbu area in the eastern NCC likely occurred during the Middle-Late Triassic and is probably related to subduction/collision and convergence between the North China plate and the Yangtze plate (e.g., Shu et al., 1994; Wang et al., 1998b). Some Middle-Late Triassic E-W- to NWW-striking thrust faults and parallel to folding may exist in the Hebfei
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ACCEPTED MANUSCRIPT Basin in southeastern NCC as indicated by geophysical studies (e.g., Xu et al., 2003a; Sun et al., 2004b). Sinistral strike-slip displacement of the southern Tan-Lu fault
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zone in the eastern NCC was probably initiated during the Late Triassic to Early
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Jurassic as a result of collision between the South and North China blocks (e.g., Xu et al., 1987a; Lin and Fuller, 1990; Okay and Sengor, 1992; Yin and Nie, 1993; Li, 1994; Wan and Zhu, 1996; Wang et al., 2000b; Chen et al., 2000a; Zhang and Dong,
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2008; Zhu et al., 2009).
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Contractional deformation during the Middle-Late Jurassic to earliest Cretaceous periods included widespread large-scale thrust faults and folds in the Yinshan and
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Yanshan belts along the northern NCC, the Western Hills of Beijing and northern
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Taihangshan, the circum-Ordos Basin in the middle-western NCC, the southern
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margin of the NCC, the Xuzhou-Suzhou area in the southeastern margin of the NCC and the Liaodong and Jiaodong peninsulas (Fig. 11c). Structures of this age
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commonly exhibit non-unique contractional directions usually perpendicular to boundaries of the NCC and the Ordos block, indicating they are likely controlled by multiple tectonic regimes during the Middle-Late Jurassic to earliest Cretaceous. The Tan-Lu fault zone was characterized by thrust faulting and/or sinistral transpression during this time and probablly absorbed most of the contractional deformation in the eastern NCC. Extensional deformation in the Early Cretaceous is widespread in the eastern and central parts of the NCC with development of metamorphic core complexes and rift basins (Fig. 11d). The Tan-Lu fault zone was characterized by extension during this
41
ACCEPTED MANUSCRIPT period. Unlike the varied trends of Middle-Late Jurassic to earliest Cretaceous contractional deformation in the NCC, the Early Cretaceous deformation was
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characterized by a surprisingly homogeneous NW-SE extensional direction. It’s
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cause is one of the most controversial topics in northeast Asian tectonics, versial but is widely perceived to be related to the far-field effect of Cretaceous Pacific plate subduction (e.g., Wu et al., 2005b; Sun et al., 2007; Wang et al., 2011b; Zhu et al.,
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2012a). Although the Middle-Late Jurassic to earliest Cretaceous contraction
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deformation is considered to be responsible for the Early Cretaceous extension in the NCC (e.g., Wang et al., 2011b; Zhang et al., 2011b), there is no consistent spatial
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relationship between earlier contractional and younger extensional structures; the
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later are common in some places that are not strongly influenced by earlier
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contraction. For example, most of the Early Paleozoic strata in the Luxi area of the eastern NCC and southern Taihangshan remain horizontal or nearly horizontal and
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the Mesoproterozoic mafic dykes emplaced into the Archean-Paleoproterozoic basement rocks remain vertical or nearly vertical (Fig. 12j–l), indicating no strong contractional deformation during the Mesozoic; however, this area was strongly influenced by Early Cretaceous extension (Li et al., 2008b, 2009b). Distribution of the Mesozoic deformation (Fig. 11) indicates that Mesozoic deformation in the NCC initiated along its northern, eastern and southern margins during the Triassic period then spread to more wide areas including the interior of the NCC during Middle-Late Jurassic to Early Cretaceous. This temporal and spatial migration of Mesozoic deformation from craton margins to its interior also indicates
42
ACCEPTED MANUSCRIPT that Mesozoic mobilization of the NCC was diachronous and interactions of NCC-surrounding orogenesis may have played important roles in Mesozoic
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deformation and decratonization of the NCC.
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8. Implications for cratonic lithospheric thinning and decratonization Temporal and spatial variations of Mesozoic magmatism and deformation in the NCC indicate that lithospheric thinning and decratonization of the NCC was
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diachronous. Thinning and decratonization of the NCC lithosphere was initiated
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from its eastern and northern margins during the Middle-Late Triassic as a result of post-collisional/post-orogenic lithospheric delamination. Delamination of the
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lithosphere was accompanied by (1) the generation of large volumes of Middle-Late
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Triassic A-type granites, alkaline rocks and related mafic-ultramafic rocks in its
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eastern and northern margins (Fig. 2c), and by (2) Late Triassic-Early Jurassic extensional deformation in the northern NCC and southern CAOB (Fig. 11b). It has
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also been suggested that thinning of the craton lithosphere in the eastern NCC during the Late Triassic was induced by delamination of the thickened continental crust during deep subduction of Yangtze continental crust and the continent-continent plate collision between the Yangtze Craton and the NCC (e.g., Yang et al., 2007a, 2010a; Yang and Wu, 2009). Initiation thinning of the craton lithosphere in the northern NCC during the Middle-Late Triassic is related to delamination at the root of the subduction-induced thick lithospheric mantle after final closure of the Paleo-Asian Ocean and the amalgamation of the Mongolian arc terranes with the NCC along the Solonker suture (e.g., Zhang et al., 2009e, 2012a). Early Mesozoic
43
ACCEPTED MANUSCRIPT lithospheric thinning and decratonization is also supported by recently recognized Early Mesozoic extensional faulting, extensional sedimentary basins, rapid
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exhumation of crustal rocks, and metallic mineralization in the northern NCC
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(Zhang et al., 2012a, and references therein). In contrast to the Early Mesozoic destruction that only occurred near the craton margins, the eastern and central parts of the NCC were affected later in the late Mesozoic. The Yanshan belt in the
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northern NCC and the Liaodong and North Korean peninsulas were likely affected
Early Cretaceous, respectively.
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by two stages of lithospheric modifications during the Middle-Late Triassic and
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During the Middle-Late Jurassic period, the NCC was characterized by
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lithospheric thickening with development of extensive multi-directional
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contractional deformation and adakitic rocks mainly derived from thickened ancient lower continental crust. This multi-directional intracontinental shortening resulted in
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thickening of the continental crust (e.g., Dong et al., 2008a, 2008b; Zhang et al., 2007b, 2008a), which may have played important roles on the lithospheric thinning and decratonization in the Late Mesozoic. Lithospheric decratonization of the NCC reached its peak in the Early Cretaceous with extensive magmatism including A-type granites, alkaline rocks and related mafic-ultramafic rocks (e.g., Zhang et al., 2002a, 2005a; Wu et al., 2005b; Yang et al., 2008b, 2008c; Zhu et al., 2012a), metamorphic core complex (e.g., Davis et al., 1996, 2002; Liu et al., 2005; Lin et al., 2008; Wang et al., 2011b, and references therein), metallic mineralization (e.g., Hua and Mao, 1999; Yang et al., 2003; Mao et al., 2003a) and extensional sedimentary basins (e.g.,
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ACCEPTED MANUSCRIPT Ren et al., 2002; Meng, 2003; Cope et al., 2010; Graham et al., 2012; Li et al., 2012a; Zhu et al., 2012b). Diachronous decratonization of the NCC from Early Mesozoic in
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its eastern and northern margins to Late Mesozic in whole eastern and central NCC
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and temporal and spatial variations of the Mesozoic magmatism and deformation indicate that interactions of the surrounding orogenesis and small size of the NCC may have played important roles on its lithospheric thinning and decratonization.
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9. Concluding remarks
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Our new structural, geochronological and geochemical data integrated with the previously published results on Mesozoic magmatism and deformation in the NCC
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allow us to draw the following preliminary conclusions:
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1) Mesozoic magmatic rocks can be divided into several stages including Early
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Triassic (254–247 Ma), Middle-Late Triassic (231–221 Ma), Early Jurassic-earliest Middle Jurasssic (190–174 Ma), Middle-Late Jurassic (165–157 Ma), Early
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Cretaceous (136–115 Ma) and Late Cretaceous (90–70 Ma), respectively. From the northern and eastern parts to the central part of the NCC, the ages of the Mesozoic magmatism became younger and its intensity became much weaker, indicating temporal and spatial migration of the Mesozoic magmatism from craton margins to its inland areas. 2) Mesozoic deformation in the NCC exhibits similar migration from craton margins to its inland areas. Triassic-Early Jurassic deformation occurred mainly in the margins of NCC and transformed from compression during the Early-Middle Triassic to extension during the Late Triassic to Early Jurassic. Middle-Late Jurassic
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ACCEPTED MANUSCRIPT to earliest Cretaceous deformation in the NCC exhibits non-unique contractional directions usually perpendicular to boundaries of the NCC or Ordos block, indicating
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they are likely controlled by multiple tectonic regimes during the Middle-Late
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Jurassic to earliest Cretaceous. In contrast, Early Cretaceous deformation was characterized by strongly consistent extension in the NCC and elsewhere in northeastern Asia. This regional strain pattern indicates a unique geodynamic regime
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that was probably related to the far-field effect of Cretaceous Paleo-Pacific plate
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subduction.
3) Lithospheric thinning and decratonization of the NCC was diachronous and
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complex. Decratonization of the NCC lithosphere was initiated from its northern and
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eastern margins during the Middle-Late Triassic by post-collisional/post-orogenic
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lithospheric delamination and then spread to its interior during the Late Mesozoic. Interactions of the surrounding orogenesis and small size of the NCC may have
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played important roles on its Late Mesozoic lithospheric destruction. Acknowledgements This research was financially supported by the SinoProbe Program of China (SinoProbe-08-01-03), the National Natural Science Foundation of China (40972149) and the China Geological Survey (1212011085476). We thank B. Song, X.M. Liu, Y.S. Liu, Z.C. Hu, L.W. Xie, Y.H., Yang, C.F. Li, H. Li and X.D. Jin for their analytical assistance. Constructive criticism and detailed comments by three anonymous reviewers and editorial handling by Prof. Gillian R. Foulger are greatly appreciated.
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ACCEPTED MANUSCRIPT Appendix A. Methods and analytical procedures Sample preparation and imaging
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Zircons were separated using conventional crushing and separation techniques and
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were then handpicked under a binocular microscope. They were mounted in epoxy resin together with zircon standards and polished to expose the cores of the grains in readiness for photomicrograph, cathodoluminescence (CL), SHRIMP or LA-ICP-MS
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U-Pb and in-situ Lu-Hf isotopic analyses. Zircons were imaged using the HITACHI
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S3000-N electron microscope attached with GATAN Chroma CL detector at the Beijing SHRIMP Center.
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SHRIMP and LA-ICP-MS U-Pb analysis
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Zircon SHRIMP U-Pb dating was performed on the SHRIMP II at the Beijing
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SHRIMP Center following the method of Williams (1998). The mass resolution was ca. 5000 at 1% peak height. The spot size of the ion beam was 25–30 m, and five
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scans through the mass range were used for data collection. The M257 (561 Ma, U=840 ppm, Nasdala et al., 2008) and TEMORA (417 Ma) standards (Black et al., 2003) were used in the analyses for U concentration and age calibration, respectively. Sites for dating were selected on the basis of CL and photomicrograph images. Ages and concordia diagrams were produced using the programs SQUID 1.03 (Ludwig, 2001) and ISOPLOT/Ex 3.23 (Ludwig, 2003). Zircon LA-ICP-MS U-Pb dating was performed on an excimer (193 nm wavelength) LA-ICP-MS at the State Key Laboratory of Continental Dynamics, Northwest University, Xi’an and State Key Laboratory of Geological Processes and
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ACCEPTED MANUSCRIPT Mineral Resources, China University of Geosciences, Wuhan following the method described by Yuan et al. (2004) and Liu et al. (2008b, 2010b). The ICP-MS used is
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an Agilent 7500a. The GeoLas 2005 laser-ablation system was used for the laser
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ablation experiments. Nitrogen was added into the central gas flow (Ar+He) of the Ar plasma to decrease the detection limit and improve precision (Hu et al., 2008). Sites for dating were selected on the basis of CL and photomicrograph images. The
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spots used were 30–32 m in diameter. Common Pb corrections were made using
MA
the method described by Andersen (2002). U, Th and Pb concentrations were calibrated by using 29Si as an internal standard and NIST SRM 610 as the reference
D
standard. Isotopic ratios were calculated using GLITTER 4.0 (Macquarie University)
TE
and ICPMSDataCal 5.0 (Liu et al., 2008b, 2010b), which were then corrected for
CE P
both instrumental mass bias and depth-dependent elemental and isotopic fractionation using Harvard zircon 91500 as an external standard. Concordia
AC
diagrams and weighted mean ages were produced using the program ISOPLOT/Ex 3.23 (Ludwig, 2003). Major and trace element geochemistry Major elements except FeO were analyzed on fused glass discs by X-ray fluorescence spectrometry and FeO contents by classical wet chemical analysis at the National Research Center of Geoanalysis, Beijing and State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. Trace elements (including REE) were determined by ICP-MS (VG Plasma Quad PQ2 Turbo ICP-MS) at the State Key Laboratory of Lithospheric
48
ACCEPTED MANUSCRIPT Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing and State Key Laboratory of Geological Processes and Mineral Resources,
IP
T
China University of Geosciences, Wuhan. The U.S. Geological Survey (USGS)
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reference materials AGV-2 (andesite), BHVO-2 (basalt), BCR-2 (basalt), RGM-1 (rhyolite) and Chinese national standards GSR-1 (granite) and GSR-3 (basalt) were used to monitor analyses. Errors for major element analysis are within 1%, except
NU
for P2O5 (5%), and analyses for most trace elements (including REE) are within
MA
10%. Rb-Sr and Sm-Nd isotopic analyses
D
Samples for Rb-Sr and Sm-Nd isotopic analyses were dissolved in Teflon bombs
TE
after being spiked with 84Sr, 87Rb, 150Nd and 149Sm tracers prior to HF+HClO4
CE P
dissolution. Rb, Sr, Sm and Nd were separated using conventional ion exchange procedures and measured using a VG IsoProbe-T and a Finnigan MAT 262
AC
multi-collector mass spectrometer at the State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. Procedural blanks were
