) North China Craton within the Paleoproterozoic Columbia supercontinent (after Kusky and Santosh, 2009). (b) Tectonic framework of China illustrating the major Precambrian cratons and younger orogens (after Zhao et al., 2005).

Geologic and tectonic map of the North China Craton (compiled and revised after [83], [87], [27], [50] and [51]), showing the distribution of the main tectonic subdivisions. The locations of ultrahigh-temperature and high pressure orogens are also shown. The collision zone between the Yinshan and Ordos Blocks has been recently defined as the Inner Mongolia Suture Zone (Santosh et al., 2010). The Eastern Block is renamed in the present study as the Yanliao Block

(a) Geological map of NCC showing four seismic profiles discussed in this study (AбьбьCAЎбьз╖, BбьбьCBЎбьз╖, CбьбьCCЎбьз╖, DбьбьCDЎбьз╖). (b) Migrated S-RF image for profile AбьбьCAЎбьз╖. (c) Migrated S-RF image for profile BбьбьCBЎбьз╖. (d) Synthetic model simulating the structure imaged from profile AбьбьCAЎбьз╖. Upper dashed line indicates Moho. (aбьбьCc) After Chen et al. (2008).

(a) Seismic profile along transect CззCCЎз╒ (after Zheng et al., 2009) showing the crustal structure beneath Ordos Block, Central Orogenic Belt and Yanliao Block. (b) Interpretative sketch of tomographic profile along longitude 108Ўз╘E down to a depth of 600 km (transect AззCAЎз╒ in Fig. 3a, after Tian et al., 2009). (c) Interpretative sketch of seismic traverse along latitude 37Ўз╘N (after Xu and Zhao, 2009). This transect down to 800 km depth is approximately parallel to the AззCAЎз╒ profile of Chen et al. (2008) for the shallower region. The dashed line indicates the 410 km discontinuity defining the top of the mantle transition zone.

The distribution of major lithological units within the Inner Mongolia Suture Zone (bound by the Yinshan Block to the north and Ordos Block to the south). The main lithological units in the Central Orogenic Belt (along which the Ordos Block to the west and the Yanliao Block to the east were amalgamated) are also shown. The base map is modified with new data (M. Santosh and S.J. Liu, unpublished) from the version compiled by Kusky et al. (2007a). The various localities discussed in the text are also marked

Representative field photographs of the major lithological units from the Khondalite Belt within the Inner Mongolia Suture Zone. (a) North-verging thrust sheets of interlayerd metapelite and quartzite in the Hoh-hotбкHeligбпer section. (b) Metagabbros interlayered with quartzties and metapelites in the Xinghe section. (c) Ultrahigh-temperature granulite facies rocks interlayered with metagabbros showing imbricate structures around Danqingshan. (d) Hand specimen photograph showing the association of ultrahigh-temperature (UHT) granulite and metagabbro in the Daqingshan section. (e) Thick metagabbro layers and blocks south of the khondalite-leptynite sequence in Tuguiwula

Field photographs of representative lithological units from the Inner Mongolia Suture Zone. (a and b) Sapphirine-bearing ultrahigh-temperature granulites from Tuguiwula. These rocks occurs as thin extruded belts in association with metagabbros within Jining khondalite unit. (c) TTG (tonalite-trondhjemite-graniodiorite) gneisses in the Xinghe section. (d) Sheet-like intrusion of calc-alkaline granites within the ultrahigh-temperature granulite section in Tuguiwula. (e) Extensive charnockite outcrops forming large hillocks in the Xinghe section. These are incorporated within a regional mega-sheath fold. (f) Banded iron formation with alternating iron-rich and silica-rich laminae from the Xinghe section

. Cartoon sketch illustrating the proposed plate tectonic model for the formation of the Inner Mongolia Suture Zone through southward subduction of the Archean Yinshan Block with a possible thick lithospheric keel. The various lithological units in the khondalite belt are thought to represent an oceanic plate stratigraphy incorporated within an accretionary complex. According to this model, the high pressureиCultrahigh-temperature rocks were generated in a subduction setting which subsequently extruded as thin layers or were incorporated as disrupted blocks within the accretionary sequence. The association of amphibolites and metagabbros with quartzites is interpreted to represent an underplated sequence of oceanic lithosphere and sediments as schematically shown in the figure. According to this model, the TTG gneisses, charnockites and associated intrusives represent the deeply eroded root of a magmatic arc

Interpretative sketches of seismic images. (a) Profile CиCCбф (after Zheng et al., 2009) showing the detailed crustal structure. (b) Migrated S-RF image along profile BиCBбф (after Chen et al., 2009) showing the topology of the subcontinental mantle down to 250 km. The various units shown envisage successive underplating and an eastward migration of the trench.

The model proposed in this study to explain the formation of the layered structure of the sub-continental mantle lithosphere beneath the Ordos Block through westward subduction. (a) In the initial stage, the various units (units 1Ц11) were accreted by progressive subduction from the east during the Archean/Paleoproterozoic. Subsequently, extensive thermal and material erosion of the tectosphere occurred towards the east through asthenospheric upwelling and removal of units 7Ц11. The thick broken line marks the Сerosional planeТ as interpreted from the present day seismic data from Chen et al. (2009). (b) Successive underplating of younger oceanic slab (units AЦG) through subduction from the east resulting in the development of a layered structure similar to that observed for the tectosphere

a) Cartoon illustrating the concept of double-sided subduction discussed in the text (after Santosh et al., 2009a). (b) Double-sided subduction in the Western Pacific region, considered as the frontier of a future supercontinent (after Maruyama et al., 2007).

Geological map of the North China Craton showing the proposed subduction zones and inferred subduction polarity (thick arrows).

(a) Cartoon illustrating the concept of double-sided subduction discussed in the text (after [51] and [87]). (b) Geological and tectonic framework of the North China Craton showing the assembly of crustal blocks through opposing subduction as interpreted from a recent synthesis of S-wave receiver functions, S-wave velocities and two versions of P-wave tomographic images along various transects in this craton (after Santosh, 2010). The assembly of the major crustal blocks within the North China Craton during the Paleoproterozoic and their incorporation within the Columbia supercontinent are correlated to double-sided subduction history. (c) The Central India Tectonic Zone (CITZ) that sutures the South and North Indian blocks. The major cratons are also shown. A combined geological and geophysical synthesis suggests double-sided subduction as a trigger for the Mesoproterozoic suturing event (after Naganjaneyulu and Santosh, in press).http://www.sciencedirect.com/science/article/pii/S0264370710000700