Abstract We re-evaluate the Neoproterozoic, Pacific-type accretionary complex on Anglesey and in the Lleyn peninsula (Wales, UK), by reconstructing its ocean plate stratigraphy (OPS). Three types of distinctive OPS were successively emplaced downwards in an accretionary wedge: the oldest at the top formed when an ocean opened and closed from a ridge to a trench, the central OPS was subjected to deep subduction and exhumed as blueschists, and the youngest at the bottom is an olistostrome-type deposit that formed by secondary gravitational collapse of previously accreted material. The three types formed by successive eastward subduction of young oceanic lithosphere at the leading edge of Avalonia. The downward growth of the accretionary complex through time was almost coeval with exhumation of the blueschist unit at 550–560 Ma in the structural centre of the complex on Anglesey. From balanced sections we have reconstructed the ocean plate stratigraphy on Llanddwyn Island from which we calculate that about 8 km of lateral shortening of ocean floor took place during imbrication and accretion; this is comparable with the history of plate subduction around the Pacific Ocean. We also calculate that the age of the subducted lithosphere was very young, probably less than 10 Ma.

Abstract The North China Craton contains one of the longest, most complex records of magmatism, sedimentation, and deformation on Earth, with deformation spanning the interval from the Early Archaean (3.8 Ga) to the present. The Early to Middle Archaean record preserves remnants of generally gneissic meta-igneous and metasedimentary rock terranes bounded by anastomosing shear zones. The Late Archaean record is marked by a collision between a passive margin sequence developed on an amalgamated Eastern Block, and an oceanic arc–ophiolitic assemblage preserved in the 1600 km long Central Orogenic Belt, an Archaean–Palaeoproterozoic orogen that preserves remnants of oceanic basin(s) that closed between the Eastern and Western Blocks. Foreland basin sediments related to this collision are overlain by 2.4 Ga flood basalts and shallow marine–continental sediments, all strongly deformed and metamorphosed in a 1.85 Ga Himalayan-style collision along the northern margin of the craton. The North China Craton saw relative quiescence until 700 Ma when subduction under the present southern margin formed the Qingling–Dabie Shan–Sulu orogen (700–250 Ma), the northern margin experienced orogenesis during closure of the Solonker Ocean (500–250 Ma), and subduction beneath the palaeo-Pacific margin affected easternmost China (200–100 Ma). Vast amounts of subduction beneath the North China Craton may have hydrated and weakened the subcontinental lithospheric mantle, which detached in the Mesozoic, probably triggered by collisions in the Dabie Shan and along the Solonker suture. This loss of the lithospheric mantle brought young asthenosphere close to the surface beneath the eastern half of the craton, which has been experiencing deformation and magmatism since, and is no longer a craton in the original sense of the word. Six of the 10 deadliest earthquakes in recorded history have occurred in the Eastern Block of the North China Craton, highlighting the importance of understanding decratonization and the orogen–craton–orogen cycle in Earth history.

Abstract Mesozoic mafic magmatism in the North China Craton shows a clear temporal and spatial distribution. Mesozoic mafic volcanism occurred dominantly in the northern and southern margins of the craton, with episodic eruptions from Early Jurassic to Late Cretaceous time. In contrast, Mesozoic mafic magmatism, which produced gabbroic to dioritic intrusive complexes, occurred in the centre of the craton in areas such as the Taihang Mountains and the Luzhong region, and all the complexes were intruded at almost the same time in the Early Cretaceous. This temporal and spatial distribution of Mesozoic mafic magmatism shows a strong heterogeneity of the Late Mesozoic lithospheric mantle beneath the North China Craton and a secular evolution of the lithospheric mantle beneath it. The lithospheric mantle beneath the Luzhong region is slightly isotopically enriched; that beneath the Taihang Mountains has an EM1 character in Sr and Nd isotopic features ( 87 Sr/ 86 Sr) i =0.7050–0.7066; ɛ Nd(t) =−17 to −10); and it possesses EM2-like characteristics ( 87 Sr/ 86 Sr) i up to 0.7114) beneath the Luxi–Jiaodong region. The general enrichment suggests that the Mesozoic lithospheric mantle was distinctive compared with Palaeozoic and Cenozoic counterparts. The secular evolution of this variably enriched Mesozoic lithospheric mantle requires a considerable modification, transformation and reconstruction of the lithospheric mantle beneath the craton in Late Mesozoic time. The elemental and isotopic compositions and the coherence of the lithospheric changes with the formation of circum-craton orogenic mobile belts indicate that these rapid lithospheric changes and corresponding lithospheric thinning were tectonically related to the multiple subduction and subsequent collisions of circum-craton blocks. Dehydration melting of subducted oceanic and continental crustal materials produced silicic melts that migrated up and reacted with lithospheric peridotites to generate more fertile lithospheric mantle (‘wet’ low-Mg peridotites plus pyroxenite veins). This is demonstrated by the fact that beneath the southern and northern margins the mantle was strongly modified, but beneath the central craton the effects were less marked. Compositional mapping of olivine from mantle peridotitic xenoliths and xenocrysts entrained in Mesozoic and Cenozoic basalts and mafic rocks throughout the craton suggests a similar framework. The North China Craton provides convincing evidence that the nature of the refractory lithospheric mantle was considerably changed in chemical composition through time, and that the lithospheric destruction was triggered by multiple circum-craton subductions and collisions.

Abstract The lithospheric mantle underneath the North China Craton changed completely from the Palaeozoic to the Cenozoic. This study reviews geochemical data from Mesozoic mantle-derived mafic rocks from the North China Craton to investigate the role of mafic lower continental crust in lithosphere replacement. Samples from the North China Craton have typical ‘continental’ geochemical signatures, including depletion of high field strength elements, enrichment of large ion lithophile elements and Pb, unradiogenic Pb isotopes, and enriched Sr–Nd isotopic ratios. Positive correlation between initial 87 Sr/ 86 Sr and 206 Pb/ 204 Pb, low Ce/Pb and Nb/U, high Ba/Nb and La/Nb, and unradiogenic Pb isotopes of Mesozoic mafic rocks cannot simply be explained by derivation from a lithospheric mantle enriched by ancient (Archaean or Mesoproterozoic) fluid or melt metasomatism. Instead, they more probably result from a lithospheric mantle or upwelling asthenosphere underneath the North China Craton that was modified by the lower continental crust in the Mesozoic. Because oceanic plate subduction zones surrounded the North China Craton during the late Palaeozoic, the lithospheric mantle underneath the North China Craton was weakened by fluids derived from subducted slabs, and thus shortened and thickened by continent–continent collisions of the North China Block with the South China Block and the Siberian plate. Metamorphic reactions occurred in the mafic lower continental crust beneath the North China Craton, creating garnet-bearing assemblages (eclogite and garnet pyroxenite) with densities of up to 3.8 g cm −3 , which led to negative buoyancy in the over-thickened lithosphere. The unstable lithosphere was delaminated and subsided into the uppermost mantle. The delaminated lower crust partially melted, producing SiO 2 -rich melts that metasomatized surrounding asthenospheric mantle, which upwelled and replaced the volume formerly occupied by the delaminated lithospheric mantle, resulting in the ‘continental’ geochemical signatures widely observed in Mesozoic mantle-derived mafic rocks from the North China Craton. The ‘continental’ geochemical signatures of Mesozoic mantle-derived mafic rocks suggest that lithospheric delamination could have occurred by the time of volcanic eruption in the northern margin of the North China Craton in the mid-Jurassic and later in the southern margin and Dabie–Sulu Orogen in the early Cretaceous.

Abstract Available major, trace element and Sr–Nd isotope data for the late Mesozoic mafic rocks in the eastern North China Block (NCB) show chemical and isotopic differences between rocks from different tectonic units. Such differences are interpreted as signatures inherited from the melted mantle sources, which had experienced distinctive enrichment processes during lithospheric evolution. The subcontinental lithospheric mantle beneath the NCB interior is characterized by long-term light REE (LREE) enrichment and EM1-like Sr–Nd isotopic signatures. Such a lithospheric mantle is mainly composed of chemically refractory peridotites that are common in cratonic regions. In contrast to that of the NCB interior, beneath the northern part of the NCB a relatively chemically fertile mantle was enriched in large ion lithophile elements and LREE and depleted in Nb–Ta and Th–U. It has higher 87 Sr/ 86 Sr(i) and ɛ Nd ( t ) than that of the interior of the block, and is interpreted to have been modified by recycled lower continental crust components related to the palaeo-Asian Ocean subduction. The lithospheric mantle beneath the southern NCB has the highest 87 Sr/ 86 Sr(i) and the lowest ɛ Nd ( t ), and is chemically transitional between the interior and northern part of the block. Formation of such an enriched lithospheric mantle was closely associated with modification from the subducted Yangtze lower–middle crust during Triassic collision between the North China and Yangtze Blocks. A lithospheric extension–thinning model is proposed to explain the petrogenesis of these late Mesozoic mafic rocks in the eastern North China Block. This process was amplified by effects from surrounding plate interactions, including the rapid northward movement of the palaeo-Pacific Ocean, compressional forces from the Siberian plate, the Tethyan tectonic belt and possibly the Indo-China Block. The resultant forces triggered lithospheric extension, asthenospheric upwelling, and decompressional melting of the enriched mantle sources.

Abstract Major element, trace element and Sr–Nd isotope data for three suites of mafic volcanic rocks that erupted at c . 180 Ma (Group 1), c . 163–140 Ma (Group 2) and 136–110 Ma (Group 3) in the Yanshan belt in the northern margin of the North China Block (NCB) are presented in this paper. All the rocks show significant enrichment in large ion lithophile elements and light REE (LREE) but depletion in Nb–Ta and Th–U, and moderately radiogenic Sr ( 87 Sr/ 86 Sr(i)= 0.7052–0.7068) and unradiogenic Nd (ɛ Nd ( t )=−15.1 to −7.2) isotopic compositions. Sr–Nd isotopic modelling suggests an insignificant role of crustal contamination or assimilation fractional crystallization, and the geochemical variations in these rocks were mainly attributed to source heterogeneity and variable degrees of ferromagnesian, plagioclase and accessory mineral fractionation. The low Th/La (0.039-0.10) points to recycling of low-Th/La (e.g. Th/La <0.2) ancient crustal materials into the source region, probably related to the palaeo-Asian Ocean subduction. Compared with the late Mesozoic mafic rocks from the NCB interior, the Yanshan belt mafic lavas generally have higher Al 2 O 3 , TiO 2 , P 2 O 5 , LREE, high field strength elements, Sr and 87 Sr/ 86 Sr(i) but lower MgO and compatible elements. Major element extrapolation (MgO=8% normalization) reveals that the Yanshan belt mafic volcanic rocks have higher Ti 8 and Fe 8 , and lower Si 8 than those from the NCB interior, suggesting that they were probably derived from a relatively fertile mantle source, different from the Mesozoic chemically refractory lithospheric mantle beneath the NCB interior. Combining the geochemical features of the mafic rocks with Mesozoic deformation events in the northern NCB, we suggest that the three stages of mafic volcanism were caused by episodic lithospheric extension. The Group 1 rocks, which occur locally along major faults, were generated during a post-compressional extension related to the collision between the NCB and Mongolian Block; the Group 2 rocks formed as a result of post-collisional lithospheric extension related to the collision between the North China–Mongolian Block and the Siberian plate; and the Group 3 rocks were extruded in an extensional regime in response to lateral escape related to surrounding plate interactions.

Abstract Voluminous plutonic and volcanic rocks were emplaced in the eastern part of the North China Craton (NCC) in the Mesozoic. The Mesozoic igneous rocks include a variety of rock types ranging from monzogabbroic, through monzonitic to monzogranitic, and locally to syenitic. Monzonitic rocks are dominant, and frequently contain mafic enclaves (dioritic in composition). The principal geochemical signatures of these Mesozoic rocks include high-K calc-alkaline to shoshonitic affinity, high Sr–Ba abundances and high Sr/Y, La/Yb, and highly enriched Sr–Nd isotopic compositions with ɛ Nd ( t ) ranging from −8 to −20 and I Sr from 0.7053 to 0.710. Zircon sensitive high-resolution ion microprobe dating reveals that these Mesozoic rocks formed between 180 Ma and 120 Ma, but are predominantly confined to a narrow range of 135–127 Ma. The sudden surge of Mesozoic magmatism was genetically linked to the upwelling of asthenosphere in a back-arc extensional regime that was caused by subduction of the palaeo-pacific plate beneath the eastern NCC. Upwelling of hot asthenospheric mantle material triggered partial melting of enriched subcontinental lithosperic mantle, generating voluminous mafic magmas. The mafic magmas underplated in the lower crust and sparked melting of the latter, producting granitic melts. We suggest that the Mesozoic rocks in the NCC probably originated from mixing between the coeval mafic and granitic melts, followed by fractionation of ferromagnesian phases and subordinate plagioclase, rather than from melting of mafic lower crust as previously suggested by many others.

Abstract In Eastern China, the North China Block (NCB) has experienced a complex tectonic evolution during Late Palaeozoic to Mesozoic times. The unconformable sedimentary cover, which ranges in age from Neoproterozoic to Permian, underwent two tectonic episodes in Early Triassic and Cretaceous times. An early north–south compressional phase, D 1 , characterized by north-verging recumbent folds with east–west-trending axes and top-to-the-north ductile shear zones can be observed in a gabbroic pluton and the Neoproterozoic sedimentary host rocks. The available radiometric ages allow us to interpret this event as an Early Triassic back-thrusting related to the final stage of the collision between the North China and South China Blocks. During the Late Mesozoic, an extensional event characterized by (1) half-grabens filled by continental terrigeneous red beds and lava flows, (2) low-angle detachment faults, (3) synkinematic granitic plutons, and (4) metamorphic core complexes is widespread in the Eastern Liaoning Peninsula. This extensional D 2 event can be subdivided into a ductile deformation and a brittle deformation, corresponding to different expressions of crustal deformation. In every area studied in the Eastern Liaoning Peninsula, the ductile D 2 deformation is characterized by a NW–SE-trending stretching lineation with a top-to-the-NW sense of shear. Mica and amphibole from the metamorphic country rocks, granodioritic or monzogranitic plutons and their mylonitized margins yield 40 Ar/ 39 Ar ages ranging from 130 to 120 Ma. These dates support fast cooling and exhumation rates coeval with the extensional tectonics. The brittle D 2 deformation is responsible for the formation of high-angle normal faults marked by low-temperature cataclasites bounding half-grabens. During the Mesozoic, the tectonic regime of Eastern China experienced a significant inversion from compression to extension. The Eastern Liaoning Peninsula massif provides an example of this geodynamic transition.

Abstract The Jiao-Liao massif is located in the hanging wall of the north-dipping Dabie–Sulu suture zone and is an important part of the Eastern Block of the North China Craton. Several important tectonic models for the tectonic evolution of Eastern Asia rely on critical information from the Jiao-Liao massif. This paper combines new sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages of the Dandong Granite in the southern Liaoning Province, China, with extensive field data for the eastern North China Craton, including the Bohai Bay Basin. Combined with other recent SHRIMP dating, we use this information to summarize the Mesozoic tectonic reactivation and evolutionary processes of the Jiao-Liao massif of the Eastern Block of the North China Craton. In this study we identify a c . 160 Ma episode of partial melting of Palaeoproterozoic plutons in the Jiao-Liao massif. Cathode luminescence and backscatter electron imagery reveal c . 167–157 Ma magmatic euhedral single zircons and magmatic zircon rims surrounding c . 2100 Ma cores in the Dandong Granites near the Liaonan Neoarchaean terrane. This partial melting is probably related to in situ remelting of ancient lower continental material, mostly the North China Craton. The Dandong plutons are aligned in a NE–SW direction and are extensively deformed by subhorizontal ductile thrust-related shearing and subsequent NNE–SSW trending folds. Here, we show that for the Dandong area the first deformation occurred between 195 and 193 Ma, based on K–Ar and 40 Ar/ 39 Ar ages of muscovites from east–west-trending shear zones on the Liaodong Peninsula. Based on the field relationships between the plutons and structural fabrics, a range from 153 to 145 Ma is defined as the duration of the second deformation in the Dandong Granites. The third deformation is marked by the formation of NNE–SSW strike-slip faults between 135 and 95 Ma. This deduced age range is similar to an 40 Ar/ 39 Ar age range of 128–132 Ma of initial sinistral strike-slip faulting of the Tan-Lu fault in Anhui Province and to a biotite cooling age of 100±2.3 Ma of the Yilan–Yitong segment of the Tan-Lu fault in the Jilin Province. These faults are transtensive and controlled the formation of pull-apart basins. However, during the third deformation, some metamorphic core complexes in Eastern China formed in the overlapping area between the large-scale sinistral faults. Our SHRIMP data also indicate that the Liaodong basement and its Early Mesozoic magmatism are similar to the Jiaodong basement and its Mesozoic magmatism. Therefore, the Early Mesozoic evolution of the Liaodong area, similar to that of the Jiaodong area, was also closely related to the Sulu orogen in the Early Mesozoic and to the Pacific subduction throughout the Mesozoic.

Abstract The Mesozoic Yanshan intracontinental orogenic belt is developed in a weak zone on the northern margin of the North China Craton. We classify the Yanshan as an intracontinental orogen, as opposed to an intercontinental or pericontinental orogen, because of several geodynamic factors that differ from those of typical intercontinental orogens. These are: (1) reactivated tectonic activity on the lithospheric-scale faults since 1.8 Ga; (2) differential uplift of blocks during the Mesozoic, especially the great change of the elevation–subsidence framework at about 140 Ma, which induced building of the Yanshan Mountain and formation of the Cretaceous basins; (3) polycyclic evolutionary processes of active rift basins recorded by the Mesozoic volcanic and sedimentary strata; (4) Mesozoic tectonic regime reversion in the eastern North China Craton, demonstrated by petrological and geochemical evidence of crust–mantle interaction and supported by research on lithosphere thinning and ancient heat flow. Among these factors, the acute tectonic events of the lithosphere and evolution of active rift basins are directly affected by the upper mantle. The differential elevation of faulted blocks directly reflects the deep tectonic processes. Inherited features of the tectonic activities are characteristic of intracontinental orogenies and occur throughout all stages of the Yanshan movement but with different features. The deep controlling factors changed with time and combined with each other. The depth of tectonomagmatic activity became progressively shallower from 180 Ma to 130 Ma and then became deep again after 120 Ma. In the same period, extensional deformation was predominant in this area. The most important geodynamic characteristic of the Yanshan intracontinental orogeny is the tectonic regime inversion. Intracontinental orogeny is the response of the upper crust to the dramatic movements of the deep lithosphere. Its essential tectonic processes are thickening and subsequent thinning of the crust and lithosphere, which induces not only deformation of the rocks but also uplift of the mountain chain. Magmatic underplating is the most important factor of the Yanshan orogeny.

Abstract A widespread and well-documented episode of Late Jurassic–Early Cretaceous rifting followed multiple events of mid- to late Mesozoic crustal contraction in NE China. This extensional deformation was closely associated with widespread Mesozoic magmatism, thought to be related to lithospheric delamination and destabilization of the previously stable North China craton. Early Cretaceous rift-related sedimentary basins in the western Liaoning region of NE China comprise numerous discrete, largely lacustrine half-graben basins bounded by NW-rooting low-angle normal faults that sole into older thrusts or mid-crustal shear zones. These basins characteristically lack post-rift thermal subsidence and significantly postdate most of the Mesozoic volcanism in the region. Instead, magmatism that has been attributed to lower crustal foundering, and hence lithospheric delamination (perhaps as old as 160 Ma) accompanied continuing crustal thickening in eastern North China. Thus, although widespread magmatism plausibly played a role in thermally weakening the crust prior to extension, there is little upper crustal evidence that wholesale removal of the lithosphere and lower crust occurred during Mesozoic time. The expansive Cenozoic rift basins of Eastern China, which do contain thick post-rift sequences, constitute a more viable response to lithospheric delamination.

Abstract The Inner Mongolia–Daxinganling Orogenic Belt (IMDOB), located between the North China and South Mongolia Blocks, consists of several ENE–WSW- to NE–SW-trending zones including dismembered ophiolite blocks, metamorphic rocks and granitoids. Although numerous studies have been carried out on this belt, its tectonic evolution has been a subject of controversy, chiefly because of the lack of reliable geochronological data. Based on a synthesis of newly published geochronological data and our unpublished data for the IMDOB, we define two oceanic basins: Ondor Sum and Hegenshan. The former, probably the main one, was initiated during the Ordovician (>467 Ma) period, whereas the latter, representing a back-arc basin, opened on a pre-Permian basement at, or earlier than, Early Permian times ( c . 295 Ma). These two oceanic basins were separated by a magmatic arc (Sunid–Baolidao), and were probably closed simultaneously when the final orogenesis of the IMDOB occurred during the Triassic period (240–220 Ma). Importantly, the Triassic timing of the final orogenesis of the IMDOB due north of the North China Craton is essentially coeval with that of the Qinling–Dabie–Su–Lu orogenic belt on the southern margin of the North China Craton. It is inferred that this two-sided subduction–collision scenario in the Triassic may have contributed to the Mesozoic lithospheric thinning event of the North China Craton, although the details are unclear.

Abstract To better understand Mesozoic tectonic transition processes in Eastern China, this paper offers a comparison of Mesozoic basin-fill records around the eastern North China Craton. These Mesozoic basins have similar evolutionary features: inception since the Early Jurassic; basin-fills recording a tectonic evolution from compression and lithospheric thickening before Late Jurassic and/or Early Cretaceous time to intracontinental stretching and lithospheric thinning from Early Cretaceous time; tectonic transition during the late Jurassic with a time lag in shallow crust relative to deep lithosphere. However, basin-fill records reflect two distinct basin systems occurring in the southern and northern margins of the eastern North China Craton. First, varied volcanic rocks including mafic, intermediate–mafic and intermediate–felsic assemblages occur in the Yanshan–Liaoxi basins on the northern margin of the eastern North China Craton from the Early Jurassic to Cretaceous; in contrast, limited calc-alkaline volcanic rocks filled the Hefei basin system on the southern margin of the eastern North China Craton during the Late Jurassic–Early Cretaceous. Second, late Mesozoic lithospheric thinning began at about 163 Ma and 149 Ma in the northern and southern margins, respectively, culminating in basin-scale extensional events at about 145 Ma and 132 Ma, respectively. Third, coarse clastic sediments developed in the northern and southern basins during the tectonic transition phase reflect fluvial and alluvial systems, respectively, indicating greater topographic relief in the southern area than in the northern area. Fourth, Mesozoic depocentre migration was complicated in the Yanshan–Liaoxi basin but should a south to north trend in the Hefei basin system. Mesozoic basin-fill depositional and volcanic records in the southern margin of the eastern North China Craton were dominantly controlled by early Mesozoic deep subduction of the Yangtze block and subsequent post-orogenic extension of the Dabie Mountains. On the other hand, basin-fill evolution along the northern margin of the North China Craton was principally controlled by intensive crust–mantle and/or asthenosphere–lithosphere interactions, with regional transition from contractile to extensional strain during Mesozoic time. This study suggests that the late Mesozoic tectonic transition was first induced by crust–mantle interactions in the northern North China Craton and then it extended southwards. Late Mesozoic lithospheric thinning and subsequent tectonic transition are a linked systematic geodynamic process that has no direct relation to the Triassic plate convergence events around the North China Craton.

Abstract The palaeotemperature recorded by vitrinite reflectance ( R o ) in the pre-Cenozoic uplifted stratigraphic strata, and in Palaeozoic–Mesozoic remnant basins outside the Cenozoic depocentres, has not been overprinted by later thermal events in the eastern North China Craton (NCC). Based on downhole R o data from the Palaeozoic and the Mesozoic subsections, we reconstruct the temperature gradients when the subsections reached their maximum palaeotemperatures in the Middle Triassic and the Cretaceous, and calculate the corresponding heat flow histories since the early Mesozoic. The temperature gradient and heat flow were much higher in the Cretaceous (35–43 °C km −1 and 73–83 mW m −2 , respectively) than in the Middle Triassic and at the present. The high palaeo-heat flow during the Late Mesozoic implies that the thickness of the ‘thermal’ lithosphere at that time was c . 65 km, about half the thickness of c . 135 km estimated for the Early Mesozoic. The change from a stable thermal regime to an active thermal regime took place during the Late Jurassic–Early Cretaceous ( c . 110 Ma). This tectonothermal event was accompanied by extensive surface erosion, and is also evidenced in the areas adjacent to the NCC, such as the South Yellow Sea and East China Sea basins. Our study provides not only geothermal evidence for the Late Mesozoic lithospheric thinning, but also additional constraints on the thinning mechanism, which is currently being debated.

Abstract The conclusions of most previous studies on the eastward extension of the collision zone between the Sino-Korean and Yangtze Blocks can generally be divided into two categories: (1) the collision zone is connected to the Imjingang belt and crosses the Korean Peninsula; (2) the eastward extension of the collision zone does not enter the Korean Peninsula, nor is connected to the Imjingang belt. Recent geophysical studies on gravity and velocity tomography in the Yellow Sea and adjacent regions, respectively, have provided geophysical evidence for a nearly north–south-trading dextral strike-slip fault in the eastern margin of the Yellow Sea, which we have named the East Marginal Fault of the Yellow Sea (EMFYS). The geophysical evidence indicates that the EMFYS extends to great depth. It dips westward, and within 100 km depth the dip angle is very steep. The geophysical characteristics on its two sides show that they belong to different tectonic units. This fault is connected to the Wulian–Qingdao Fault in the north, and to the South Marginal Fault of Jeju Island (SMFJI) in the south (the SMFJI is a part of the collision zone). Therefore the EMFYS is considered as a part of the junction zone between the Sino-Korea and Yangtze Blocks, with the Korean Peninsula being part of the Sino-Korea Block. In the Late Triassic, it is inferred that dextral strike-slip movement took place on the EMFYS, and in the same geological period sinistral strike-slip took place on the Tan-Lu Fault Zone. Under north–south tectonic stress the Yangtze Block was translated northward and inserted into the Sino-Korea Block. Therefore the junction zone between the two blocks formed a gigantic Z-shaped tectonic belt. According to the gravity data and seismic tomography it is also inferred in this paper that the junction zone between the Yangtze and Cathaysia Blocks extends from the Jiangshao Fault eastward to the southern edge of the Hida Block, Japan.

Abstract We have collected seismic data, performed high-resolution seismic tomography in the North China Craton and analysed the relationships between crustal seismic velocity distributions and regional tectonics and metallogenesis. In the upper and middle crust velocity anomalies are distributed along east–west- and NNE–SSW-trending structures. Most belts of Cenozoic mineral deposits including gold in the North China Craton coincide with high-velocity anomalies, and the North China basin coincides with a low-velocity zone. Compared with the upper crust, the low-velocity anomalies in the lower crust are diffuse and extensive, which suggests that high-temperature material has upwelled from the mantle. High-temperature material in the lower crust provided buoyant, hot, mineralizing fluids that uplifted and formed the Cretaceous mineral deposits in the upper crust.

Abstract The Jiaodong Peninsula or eastern Shandong Province, the most important gold producing in region China, is located in the southeastern margin of the North China Craton. The gold deposits in the Jiaodong Peninsula are divided into three gold belts, from west to east, the Zhaoyuan–Laizhou, Penglai–Qixia and Muping–Rushan belts. The deposits occur as gold-bearing quartz veins and disseminated- and stockwork-style ores adjacent to fault zones. Most of the gold deposits can be classified in four stages: stage I, quartz–(minor) pyrite; stage II, pyrite–quartz–gold; stage III, quartz–base metal sulphide minerals; stage IV, quartz–carbonate. Ar–Ar ages, Rb–Sr isochrons, and hydrothermal zircon sensitive high-resolution ion microprobe U–Pb ages obtained from these deposits suggest a gold mineralization time of 120±10 Ma. The Sr–Nd isotopic compositions of pyrites and the associated rocks suggest that the ore-forming materials were probably derived from a mixed source. Fluid inclusion studies show that ore-forming fluids of gold deposits are consistent throughout the Jiaodong Peninsula, with similar mineralizing temperature and pressure conditions. Ore-forming fluids are characterized by H 2 O–CO 2 –NaCl±CH 4 . The optimal mineralizing temperature and pressure ranges are 170–335 °C and 0.7–2.5 kbar. Oxygen and hydrogen isotope data show that ore fluids are of magmatic origin. Gold deposits in the Jiaodong Peninsula formed in the same mineralizing–geodynamic conditions, and are related to the Mesozoic tectonic transition in the eastern North China Craton. Gold metallogeny is only one expression of the Mesozoic tectonic transition.

Abstract Two models have been proposed to explain lithospheric thinning of North Chinese cratonic lithosphere: (1) thermal erosion or/and chemical metasomatism, causing the lower part of the lithospheric mantle to be transformed into asthenosphere, a mechanism that implies thinning of relatively buoyant lithosphere; (2) the delamination of lithospheric mantle, in whole or part, along with the lowermost crust, as an effect of their increased densities relative to the underlying asthenosphere. This paper explores possible mechanisms whereby buoyant cratonic lithosphere might be transformed into a denser equivalent susceptible to delamination by the convecting asthenosphere. The Yanshan mobile belt in Eastern China developed in response to a combination of subduction and collision. Its apparent ‘counterclockwise’ P – T – t metamorphic evolution suggests that underplated basaltic magma may have heated and, in turn, weakened the cool, rigid crust, allowing for compressional deformation and crustal thickening. Based on three independent lines of evidence (compressional deformation, the record of igneous activity, and lower crustal xenoliths) the thickness of continental crust is estimated to be about 50–65 km. Along with petrological and geochemical studies, thermal modelling shows that large-scale input of asthenospheric basaltic magma leads to granitoid partial melts in the lower crust, and the dominance of high-pressure eclogitic products following orogenic thickening may be necessary for eventual delamination to occur.

Abstract The North China Craton (NCC) is the only place currently recognized where an Archaean craton developed a continental root in the Archaean, and subsequently lost half of that root in younger tectonism. In this volume, various authors have advanced different models of root loss, and provided geological, geophysical and geochemical data that help constrain the geometry and timing of root loss. Understanding why and how roots are lost may help us understand how often this process may have occurred in the geological past, and how much lithospheric material has been recycled to the convecting mantle through this mechanism, potentially drastically changing our current understanding of crustal growth rates and processes. With current data, there are several equally plausible possibilities that require further data collection for testing. There are several possible tectonic triggers that may have caused half the root to be lost, acting either separately or together. These include collisional, extensional, plume-related, fluid-weakening, spontaneous, and more complex hybrid mechanisms. We also do not know why only the eastern half of the root was lost, and not the root from beneath the whole craton. One tantalizing idea is that the root grew independently, by tectonic underplating of subducted buoyant oceanic lithosphere, beneath the previously separate eastern and western halves of the craton by 2.5 Ga, with modification at 1.8 Ga. If so, perhaps only the eastern half of the root was lost in younger tectonism because there was some physical or geometric difference between the two halves. Alternatively, collisional or subduction-related tectonic processes acting only on the Eastern Block may have caused the disruption of the tectosphere there in the Mesozoic. The timing of and mechanism for loss of the root is not uniquely resolvable with current data, but a solution to the problem is in reach. Possible triggering mechanisms include, but are not limited to, collision of the South China (Yangtze) and North China Cratons in the Triassic, the India–Asia collision, closure of the Solonker and Mongol–Okhotsk oceans, Mesozoic subduction of the Pacific plate beneath Eastern China, impingement of mantle plumes, mantle hydration from long-term subduction, and several rifting events. In this concluding review, we link studies of crustal tectonics with investigations aimed at determining the nature and timing of the formation and loss of the root, to better understand mechanisms of continental root formation, evolution and recycling–removal.