the penetration of kuroshio water into the sea of japan abstract the nonlinear leakage of kuroshio water via the tsushima strait into the sea of japan is examined using a reduced gravity analytical model the flow in our conceptual model results from the zonal sea level difference between the pacific ocean and the sea of japan the landmasses separating the pacific from the adjacent sea of japan are represented by thin walls and the tsushima strait whose width is larger than the rossby radius is represented by a gap the gap is initially closed and the problem is treated as an adjustment process resulting from an abrupt opening of the gap steady analytical solutions for the final state associated with the adjustment are constructed using the integrated momentum equation on a plane conservation of energy and potential vorticity also a perturbation expansion in l f0 the ratio of the change in the coriolis parameter as one moves from the gap to the boundary current separation latitude to the coriolis parameter at the center of the gap is used

destruction of ancient lower crust through magma underplating beneath jiaodong peninsula north china craton u pb and hf isotopic evidence from granulite xenoliths abstract zircons from granulite xenoliths entrained in a late cretaceous mafic dike in the jiaodong peninsula north china craton ncc show three distinct u pb age populations part of the old zircon grains yield discordant data that project to ages of about 2 4 to 2 5 ga a few grains indicate growth at about 2 0 ga and a third group yield cretaceous ages with peaks at 120 and 90 ma the oldest zircons give hf t dm model ages of 2 6 2 8 ga these results demonstrate the existence of original archean lower crust in the jiaodong region zircons of 2 0 ga have similar hf t dm model ages as the neoarchean paleoproterozoic grains suggesting that these zircons were products of metamorphic recrystallization due to thermal event without juvenile input early cretaceous zircons yield ehf t values of 21 to 12 and late cretaceous zircons large variable ehf t from 4 to 50 these data suggest that magmatic underplating occurred in the neoarchean to earliest proterozoic lower crust of the ncc both in the early and late cretaceous it is suggested that the mesozoic magma underplating which also provided the heat source for the voluminous mesozoic magmatism in the ncc significantly modified the composition of the archean to paleoproterozoic lower crust of the ncc

evolution of the archean and paleoproterozoic lower crust beneath the trans north china orogen and the western block of the north china craton abstract we report u pb ages and hf isotopes of zircons in granulites from two continental suture zones in the north china craton ncc from granulite xenoliths entrained in the cenozoic hannuoba basalts within the trans north china orogen tnco that amalgamates the western and eastern blocks and from a mafic granulite associated with ultrahigh temperature uht granulites within the inner mongolia suture zone imsz that welds the yinshan and ordos blocks the zircons in these rocks together with the inherited zircons from mesozoic subalkalic intrusives of these regions show several distinct u pb age populations and provide constraints on the evolution of the lower crust beneath the ncc parts of the older zircons from the tnco yield discordant data that project to ages of about 2 5 to 2 7 ga these old zircons show hf tdm model ages of 2 6 2 9 ga suggesting the existence of archean lower crust beneath the tnco which is coupled with the neoarchean metamorphic basement and greenstone belt a major zircon population grew at 1 75 2 0 ga consistent with the timing of the paleoproterozoic collision between the various crustal blocks within the ncc suggesting that this event had a significant effect on the archean lower crust the older inherited zircons from the western block also yield discordant data that project to younger ages of about 1 8 to 1 9 ga this age is consistent with the timing of intrusion of the mafic magmatic protoliths of the granulites associated with the uht rocks in the khondalite belt within the imsz these older zircons yield hf tdm model ages of 2 0 2 5 ga suggesting that the lower crust beneath the western block in the ncc to be dominantly paleoproterozoic and decoupled with the archean metamorphic basement of the region yet another population of zircons from the hannuoba banded granulite xenoliths garnet bearing pyroxenite cumulate and dark pyroxenite xenoliths yield a large spread of phanerozoic concordant ages ranging from 470 ma to 40 ma with peaks at 315 ma 220 230 ma 120 ma and 46 ma the late paleozoic zircons predominantly occur in the garnet bearing pyroxenite xenoliths and yield variable ehf t values of 24 to 18 triassic cretaceous zircons mainly occur in the banded granulite xenoliths and yield highly variable ehf t values ranging from 48 to 16 the tertiary zircons occur only in the dark pyroxenite xenoliths and show a restricted ehf t with a dominant range from 0 to 18 these data suggest episodic magmatic underplating in the ancient lower crust of the ncc lasting continuously throughout phanerozoic producing zircons from the underplated magmas or providing the heat source for the recrystallization of zircons from the ancient crust our data clearly demonstrate the important events of phanerozoic magmatic underplating beneath the neoarchean paleoproterozoic crust of the ncc

effect of the change of bottom depth on the penetration of kuroshio water onto the east china sea shelf 1 a theoretical problem of the penetration of a western boundary current driven by a cross stream sea level difference onto a shallow basin to the west of the current is put forth to account for the penetration of the kuroshio onto the east china sea ecs shelf and formation of the tsushima warm current different from previous studies this study assumes that the change of bottom depth is the primary factor determining the penetration for a given depth of the shallow basin the penetration depends on two external parameters speed of the western boundary current v0 and surface elevation of the current at the edge of the shallow basin z0 two penetration modes emerge depending on the magnitude of the inertia of penetration for sufficiently large inertia which is favored by large z0 and hindered by large v0 penetration occurs in the form of a free jet mode j otherwise it is in the form of a coastal current mode c volume transport of the penetration is maximized in mode j in general volume transport width and speed of the penetrating current increase with z0 although the latter two are slightly more dependent on v0 in mode c the model considered in this study predicts that the penetration of the kuroshio onto the ecs shelf is of mode j as indicated by observations the volume transport of the penetration is somewhat overestimated possibly because bottom friction is ignored in this model although this model is highly idealized it allows one to gain insight into the behavior of the kuroshio penetrating onto the shallow ecs shelf

on the kuroshio branch in the taiwan strait during wintertime abstract past investigations reported that warm and saline waters originating from the kuroshio region occupied the northern south china sea nscs during wintertime these waters were called a branch of the kuroshio and an offshoot of them was long believed to flow persistently along the west coast of taiwan contrary to the winter ne monsson however these descriptions are not completely consistent with recent evidence field measurements in the eastern taiwan strait now available display a quasi stationary oceanic front whose alignment is roughly normal to the transverse of the strait which separates the warmer more saline water to the south from the colder fresher china coastal water in the north during most of the winter this feature implies the further northward movement of southeasterly kuroshio water having been stagnated by cold waters to the north of the front therefore the intruded kuroshio water driven by the ne monsoon tends to accumulate in the nscs and eventually establishes an anti cyclonic warm core eddy there the first event of the intrusion of warm waters from the eddy into or even through the taiwan strait usually appears when the ne wind weakens from a strong cold air outbreak in winter or early spring we believe the inception of the kuroshio branch in the strait starts from such an intrusion event

on the branching of the kuroshio west of kyushu trajectories of satellite tracked surface drifters released in the continental margin area west of kyushu indicate a separation of the inshore side of the kuroshio that appears to form the beginning of the tsushima current the trajectories also indicate an anticyclonic sense of circulation in the area between the separated branch and the eastward directed kuroshio main stream consistent with long term geomagnetic electrokinetograph measurements of surface currents which show a broad southward flow along the west kyushu coast a theory is put forth that ties together these observed flow features in the theory the incidence is considered of an inertial current upon a step rise in topography characterized by a step depth of h0 to simulate the west kyushu coastal bathymetry in an f plane two layered inviscid ocean with a quiescent lower layer the inertial current is of a constant potential vorticity f h where h h0 is the undisturbed upper layer depth and is bounded inshore by a free streamline along which the upper layer depth is a constant hc h the steady state downstream configuration of a separation branch and a deflected main stream along the step is connected to the upstream approach current through the consideration of the constancy of the bernoulli function and the conservation of potential vorticity and mass in the immediate neighborhood of the incidence a complicated flow region is anticipated in which recirculation is featured and an anticyclonic gyre is expected further onto the step the volume integrated balance of along step momentum of the constant potential vorticity flow allows the determination of the angle the branch current makes with the step as a function of the angle of incidence and two depth ratios hc h and h0 h the bifurcation quotient defined as the ratio of the branch current transport to that of the approach current is found to be also such a function except it is independent of the incidence angle these functions yield results that are qualitatively in agreement with the observed bifurcation of the kuroshio west of kyushu that gives rise to the tsushima current

neoarchean 2 7 2 8 ga accretion beneath the north china craton u pb age trace elements and hf isotopes of zircons in diamondiferous kimberlites abstract zircon xenocrysts from the early paleozoic mengyin and fuxian diamondiferous kimberlites on opposite sides of the translithospheric tanlu fault in the north china craton have been used to probe the deep crust based on detailed studies of external forms and internal structures the zircons can be roughly divided into magmatic and metamorphic zircons there are no consistent differences in u th or th u between the two zircon populations the trace element affinities of the igneous zircons vary widely from mafic through intermediate to felsic rocks with minor populations similar to zircons from carbonatite and syenite in situ isotopic analysis for u pb and lu hf reveals that all zircons both from mengyin and fuxian kimberlites regardless of their chemical affinities have similar formation ages 2 5 2 7 ga and depleted mantle model ages t dm 2 7 2 8 ga these ages are also similar within error to those of zircons in mafic granulite xenoliths from the fuxian kimberlites implying that the lower crust was similar neoarchean cratonic basement beneath the mengyin and fuxian areas but the latter experienced stronger thermal modification in proterozoic time the magmatic zircons may be derived from late differentiates of underplated mafic magmas with some contamination by crustal components and the metamorphic populations developed during heating events linked to the ongoing underplating the addition of juvenile material up to 9 5 e hf at this time 2 7 2 8 ga corresponds to a known major episode of global crustal formation

seasonal exchanges of the kuroshio and shelf waters and their impacts on the shelf currents of the east china sea previous in situ observations and modeling studies have indicated that through mass and momentum exchanges across the shelf edge the kuroshio can significantly influence the shelf currents of the east china sea ecs here instead of localized observations this study uses 25yr of drifter data supported by satellite and other data to identify seasonal cross shelf exchanges along the entire shelf edge the authors show that kuroshiomeandersonshorefromfalltowinterandoffshorefromspringtosummer withthelargestamplitude northeast of taiwan the influence is limited to the shelf edge when the kuroshio meanders offshore in spring and summer by contrast strong onshelf intrusions and cross shelf exchanges occur when the kuroshio meanders onshore in fall and winter drifters intrude onshelf northeast of taiwan and spread as far north as 308n against the strong northeasterly wind the forcing on the shelf is identified as a northward downsloping of the sea level that is steepest north of taiwan at 258 288n but which is 3 times weaker farther north the vorticity budget computed from a numerical model indicates that intrusion during fall andwinter is primarily a result of balancebetweenonshelfadvectionofambientpotentialvorticityandvorticityproductionbythealong isobath pressure gradient acting on the changing mass of water column across the continental slope

sea surface height variations in the yellow and east china seas 1 linear response to local wind stress the sea surface height ssh variations observed by the topex poseidon satellite in the yellow and east china seas are examined over the 3 years from 1993 through 1995 assuming a linear response to wind stress across the region the transfer function relating wind stress to ssh is modeled by a series of increasingly complex functions that gradually allow wind stress over successively broader regions and time periods to influence the ssh solution at a particular point the ssh response to instantaneous wind stress at the same point in space implies an ekman transport but the response explains only a small fraction of the ssh variability relating ssh to wind stress averaged over two subregions and including both instantaneous and 12 hour lagged wind stress indicates that a significant portion of ssh variability responds to winds that are remote in both space and time an optimal estimation of the transfer function by minimizing the error variance leads to an extended empirical orthogonal function eeof analysis of the wind stress field the ssh response to each wind mode is determined the analysis shows the principle variations in the wind stress to consist of northerly wind bursts during winter which produce large ssh drops in the bohai bay and northern yellow sea region the principal wind mode also is significantly related to variations along the shelf break near the kuroshio current the third and fourth wind stress modes indicate the passage of typhoons

shrimp u pb zircon ages of granitoid rocks in the luliang complex implications for the accretion and evolution of the trans north china orogen abstract the luliang complex is situated in the central segment of the trans north china orogen tnco a continent continent collisional belt along which the discrete eastern and western blocks amalgamated to form the basement of the north china craton the complex consists of supracrustal and granitoid rocks of which the latter can be subdivided into pre tectonic ttg gneisses including the yunzhongshan guojiazhuang and chijianling guandishan gneisses syn tectonic gneissic granites represented by the huijiazhuang gneissic granite and post tectonic granites including the luyashan charnockite luchaogou porphyritic granite and tangershang guandishan massive granite the pre tectonic ttg gneisses are mostly calc alkaline and considered to have formed in a magmatic arc environment shrimp u pb analyses reveal that the yunzhongshan gneisses were emplaced at 2499 9 ma representing the earliest arc related magmatic event in the luliang complex this was followed by the intrusion of the guojiazhuang gneisses at 2375 10 ma the most widespread arc related magmatic event in the region was the emplacement of the chijianling guandishan granitoid gneisses of which the tonalitic granodioritic and monzogranitic gneisses were emplaced at 2199 11 ma 2180 7 ma and 2173 7 ma respectively metamorphic zircon overgrowth rims from a tonalitic gneiss yielded a weighted mean 207 pb 206 pb age of 1872 7 ma consistent with the metamorphic age range of 1880 1820 ma defined by metamorphic zircons from various high grade rocks in the tnco thus the evolution of the luliang complex involved emplacement of the yunzhongshan granitoids at 2499 ma the guajiazhuang granitoids at 2375 ma and the chijianling guandishan granitoids at 2199 2173 ma with the final collision between the eastern and western blocks in this area occurring at 1872 7 ma the whole series of magmatic events lasting nearly 650 ma this suggests that the trans north china orogen represents a long lived magmatic arc the new shrimp zircon data combined with structural and petrological studies also reveal the existence of both syn and post collisional granites in the luliang complex the former is represented by the huijiazhuang gneissic granite that was emplaced at 1832 11 ma whereas the latter include the 1815 5 ma luyashan charnockite 1807 10 ma luchaogou porphyritic granite 1798 11 ma guandishan massive granite and 1790 14 ma tangershan massive granite

tectonic evolution of the tancheng lujiang tan lu fault via middle triassic to early cenozoic paleomagnetic data the north striking tancheng lujiang tan lu fault is a conspicuous and controversial feature of the eastern asian landscape near the southeast extremity of the fault in anhui province we collected paleomagnetic samples at 17 middle triassic t2 and 10 upper cretaceous k2 to lower cenozoic e1 sites t2 remanent magnetizations are interpreted as primary in two of three areas the three areas are rotated 37 to 137 counterclockwise with respect to the south china block scb reference direction k2 e1 remanent magnetization directions pass regional fold and reversals tests and are not rotated with respect to surrounding areas counterclockwise rotation of t2 strata therefore ended before k2 and is attributed to left lateral shear acting along tan lu during the north china block ncb scb collision in shandong province 700 km north of the anhui sites four areas containing 33 upper jurassic j3 and cretaceous sites have negligible declination differences except for one which has dispersed directions the fold test is inconclusive for this latter area and positive for the other three regional concordance of the j3 e1 paleomagnetic data including paleolatitudes together with observed deformation patterns suggest that an extensional regime prevailed in the late cretaceous and cenozoic euler pole positions that constrain the north south china collision and account for tan lu motion suggest at least 500 km of sinistral shear took place along the fault and either 1 subduction and related ultrahigh pressure uhp metamorphism occurred near the present location of the qinling dabieshan and sulu uhp belts while tan lu acted as a transform fault that connected the two subduction zones or 2 tan lu and sulu were parts of the same transform fault system and no uhp rocks formed in situ at sulu in either case uhp rocks originally exhumed near dabieshan could have been transported by plate capture toward sulu along tan lu after north and south china impacted near dabieshan the tan lu fault grew within the scb as the dabieshan corner indented the scb causing folds in scb cover rocks to conform to the ncb margin late cretaceous to cenozoic reactivation of tan lu with both right lateral strike slip and normal fault motion occurred as the scb extruded east relative to the ncb under the influence of the india asia collision

inter annual and decadal sea level variations in the north western pacific marginal seas abstract long term sea level changes in the okhotsk japan east east china and yellow seas have been explored based on mean monthly values of sea level from tide gauge and altimetry measurements the analysis of low frequency sea level variability reveals clearly differentiated areas the okhotsk sea and the northern sector of the japan east sea display lower sea level variances and no sea level rise the southern japan east sea presents larger sea level variability associated with the circulation regime of the warm current entering through the tsushima strait and inter annual sea level variations that are driven by steric and atmospheric changes the largest sea level variances are found in the yellow sea due to the effect of atmospheric forcing over the continental shelf inter annual variability is spatially varying within the yellow sea and the east china sea and is mainly related to the steric sea level changes regional mean sea level indices have been synthesized for each area using the longest tide gauge records and have revealed correlations between the southern japan east and yellow seas with pdo and np climatic indices linear trends at coastal sites in the japan east east china and yellow seas show a rather heterogeneous pattern with values between 1 5 and 5 5 mm yr for the period 1960 2000 during the period 1993 2008 linear trends derived from coastal tide gauges and from altimetry observations are coherent and reveal a southwards increasing pattern with maximum averaged values reached at the yellow sea 4 9 1 9 mm yr followed by the japan east sea 3 8 0 9 mm yr decadal rates of sea level change show distinct behaviour among basins as well as with the global average the southern japan east sea the east china sea and the yellow sea display decadal variability which is out of phase with respect to the global values

sea surface height variations in the yellow and east china seas 2 ssh variability in the weekly and semiweekly bands two types of models are used to examine the sea surface height ssh variability at the principle short time frequency bands in the yellow and east china seas the models are a primitive equation numerical model and a statistical model based on topex poseidon altimeter data in situ pressure gauge measurements at two mooring locations are first used to evaluate each model in addition a comparison of the numerical and statistical models is made through duplicate analysis of the response to the main extended empirical orthogonal function wind stress modes in the northern yellow sea the wind stress pressure gauge data numerical model and statistical model all indicate local spectral maxima in bands centered on the weekly and semiweekly periods the coherence of the two models with the in situ data is significant down to 3 day periods at the northern mooring and down to 5 day periods at the southern mooring the meridional wind stress variability in the semiweekly band is higher than the weekly band energy in the northern yellow sea and bohai bay and lower than the weekly band energy across the east china sea the ssh variability contained in the weekly and semiweekly bands is largest in the bohai bay and northern yellow sea with a region of high energy along the chinese coast the spatial structure of the weekly and semiweekly ssh variability is similar to the wind stress variability at these bands with semiweekly variability higher in the bohai bay and northern yellow sea and weekly variability dominant in the east china sea

two layer tidal modeling of the yellow and east china seas with application to seasonal variability of the m2 tide 1 the baroclinic response of tide and tidal currents in the yellow and east china seas is investigated using a two layer numerical model seasonal variability in the m2 tide especially the smaller summer amplitudes prevailing along the korea tsushima strait kang et al 1995 is investigated by a series of numerical experiments with varying degrees of stratification specific to winter and summer model results show that the summer amplitudes of the m2 tide around the southwestern tip of the korean peninsula and korea tsusima strait decrease with a peak decrease of about 14 cm off the southwestern tip of the korean peninsula while the summer amplitudes in other coastal regions tend to increase this seasonal variability generally coincides with the observations these models results indicate that seasonal stratification has several noticeable effects on the tides including varying degrees of current shear varying frictional dissipation and varying barotropic energy flux in particular it drives complicated seasonal variability in the m2 tide with a peak amplitude modulation of nearly 5 off the southwestern tip of the korean peninsula the seasonal variation of barotropic m2 energy flux through the eastern entrance of the yellow sea is thought to induce the corresponding variability in the m2 amplitude in the korea tsusima strait with smaller amplitudes found in the summer

discovery of sapphirine bearing mg al granulites in the north china craton implications for paleoproterozoic ultrahigh temperature metamorphism abstract we report here for the first time the occurrence of mg al granulites within the khondalite belt of the north china craton and provide robust evidence for extreme crustal metamorphism at ultrahigh temperature uht conditions in this region the uht indicator assemblages in these rocks include equilibrium sapphirine quartz high alumina orthopyroxene sillimanite quartz and high temperature perthites the surrounding khondalites also carry spinel quartz equilibrium assemblage the sapphirines occurring in various microstructural associations are markedly magnesian x mg 0 69 0 77 with a composition varying from 7 9 3 to 2 2 1 end members spinel is a solid solution of mg spinel and hercynite x mg 0 41 0 54 with zno content varying from 0 48 to 1 79 wt garnet shows a compositional range between pyrope and almandine x mg 0 39 0 48 with minor grossular 2 6 3 8 mol and spessartine 0 5 1 8 mol the orthopyroxenes display marked compositional variations in terms of al 2 o 3 content with the core of the medium grained orthopyroxene adjacent to sillimanite in the matrix showing the highest al 2 o 3 content 8 4 wt the history of prograde to peak metamorphism of these rocks is indicated by inclusions of sapphirine spinel quartz and sillimanite within garnet sapphirine formed during the peak stage through the reaction spl qtz sil spr occurrence of sapphirine and quartz inclusions trapped in sillimanite suggests the reaction spr qtz grt opx sil a series of retrograde reactions are observed in these rocks as corona and symplectite textures around early coarse grained minerals such as opx sil qtz crd grt sil qtz crd grt qtz crd opx grt o 2 crd qtz fe 2 o 3 in mag or ilm and finally opx kfs h 2 o bt qtz whereas the stability of sapphirine quartz and orthopyroxene sillimanite quartz in the matrix assemblage suggests t 1000 c and p 10 kbar peak metamorphism conventional geothermobarometric estimates confirm the ultrahigh temperature nature and also trace the retrograde conditions 930 970 c at p 10 kbar al in opx 900 1000 c perthite 930 990 c grt opx and 910 940 c sapphirine spinel electron microprobe dating of monazites in textural association with the uht assemblages yield a sharply defined isochron age of 1917 48 ma which correlates with the 1927 11 ma obtained in a previous study from monazites in the surrounding khondalites carrying spinel quartz assemblage an evaluation of the assemblages and textures using appropriate petrogenetic grids indicate that following peak ultrahigh temperature conditions the rocks underwent initial isobaric cooling and subsequent isothermal decompression and we interpret these trajectories to be part of an overall anti clockwise p t evolution the study area located within the northern margin of the north china craton defines a collisional orogenic belt where continental collision and deep subduction was possibly followed by extensional collapse of the orogen evidence for the extensional phase is provided by the several mafic magmatic intrusives of paleoproterozoic age occurring in the region which suggest a possible link between the thermal anomaly associated with extreme crustal metamorphism in this region with mantle derived magmas the uht metamorphism in north china craton coincided with the assembly of the paleoproterozoic supercontinent columbia

collision between the north and south china blocks a crustal detachment model for suturing in the region east of the tanlu fault a crustal detachment model based on the interpretation of linear aeromagnetic anomalies surface geological observations and deep seismic profiles is proposed for the continent continent collision between the north and south china blocks east of the tanlu fault the model suggests that during the mid mesozoic collision between the two continental blocks the upper crust of the south china block in the subei yellow sea region was detached from the lower crust and thrust over the north china block for 400 km whereas the lower part of the lithosphere was subducted under the north china block along a subsurface suture running east from nanjing the sinistral offset of the qinling suture by the tanlu fault is only 110 120 km in the deep crust much less than previously suggested

where is the north china south china block boundary in eastern china the qinling dabieshan belt results from the collision of the north china and south china blocks the eastern extension of the belt the sulu area consists of several stacked units from top to bottom these are 1 a weakly metamorphosed slate sandstone unit of neoproterozoic paleozoic age 2 a gneiss quartzite unit metamorphosed under high pressure p conditions 3 a marble amphibolite unit 4 an ultrahigh p unit that was very deeply subducted and then exhumed and 5 a migmatitic dome resulting from the melting of ultrahigh p rocks all these units underwent the same deformation which was characterized by a top to the northwest extensional ductile shearing during their exhumation granulite facies restites in the migmatite are not significantly different from granulitized eclogites derived from the ultrahigh p rocks the migmatite exhibits the same structural and petrologic evolution as that determined for the other units the resemblance of petrologic and structural features and the lack of ocean basin rock shows that the boundary between the north china block and south china block must be placed north of the sulu area

zircon u pb and trace element data from rocks of the huai an complex new insights into the late paleoproterozoic collision between the eastern and western blocks of the north china craton abstract the trans north china orogen tnco is interpreted as a continent continent collisional belt along which the discrete archean eastern and western blocks amalgamated to form the basement of the north china craton the timing of its formation has not been precisely constrained yet six samples including five high grade metamorphic rocks and a pegmatite dike from the huai an complex in the northern segment of the tnco were selected for zircon u pb dating and trace element analysis a tonalite trondhjemite granodiorite ttg gneiss sample and a high pressure hp mafic granulite sample contain magmatic zircon cores yielding protolith formation ages of 2503 17 and 1964 38 ma respectively detrital zircons of magmatic origin in two metasedimentary rocks show concordant or moderately discordant u pb ages of 2683 22 to 1964 13 ma indicating that they were mainly derived from the tnco with some possibly derived from the archean continental rocks of the north china craton metamorphic zircons in the ttg gneiss and two metasedimentary rocks exhibit low hree contents flat hree patterns and negative eu anomalies implying their formation coeval with garnet and feldspar under grannulite facies conditions metamorphic zircons in an hp mafic granulite and a sample of leucosome from a ttg gneiss also have depleted hree contents flat hree patterns but only weak negative eu anomalies which may also indicate formation under granulite facies conditions whereas the weak eu anomalies may be due to the whole rock composition all these metamorphic zircons have formation temperatures of 702 749 c approaching the peak metamorphic temperatures of hp granulite rocks in this area they have identical ages of ca 1845 ma within analytical errors which is the best estimate age for hp granulite facies metamorphism of the huai an complex these results confirm previous models proposing late paleoproterozoic collision between the eastern and western blocks of the north china craton along the tnco on the other hand some metamorphic zircons in the leucosome sample show planar or polygonal zoning high th u contents and high th u ratios high ree contents and steep hree patterns indicating that they crystallized during partial melting with abundant garnet decomposition they yielded a weighted mean age of 1819 13 ma which we interpret to register the time of retrograde metamorphism combined with previously published data there are three age peaks at 1876 6 1849 2 and 1814 4 ma for metamorphic zircons from high grade metamorphic rocks in the tnco these may indicate either a protracted event or at least three peaks of metamorphism a pegmatite dike cutting the foliation of a mafic granulite boudin was dated at 1806 15 ma which signifies termination of collision between the eastern and western blocks in the huai an area

crustal growth in the north china craton at 2 5ga evidence from in situ zircon u pb ages hf isotopes and whole rock geochemistry of the dengfeng complex abstract the dengfeng complex is located on the southern margin of the north china craton ncc and belongs to the southern portion of the trans north china orogen this terrane is important to understand the formation and evolution of ncc during late neoarchean 2 5 ga the dengfeng complex is well exposed in the junzhao region and comprises two distinct lithologic units supracrustal assemblage and plutonic rocks la icpms magmatic zircon u pb age data shows that the rocks formed within the range of 2547 2504 ma the available hf isotope data indicate that the majority of ca 2 5 ga zircons from the dengfeng complex have high e hf t values close to the initial hf isotope ratios of the contemporaneous depleted mantle these data indicate that the rocks in the dengfeng represent juvenile crust the ttg gneisses in the dengfeng complex display low mg 41 48 mgo 59 69 mgo 3 5 6 6 wt ni 82 130 ppm and cr 148 237 ppm abundances elevated sr 1759 1927 ppm and ba 1742 2289 ppm concentrations and high lree la n 38 487 such geochemical features are similar to archean sanukitoids a two stage model is applied here to explain the genesis of metadiorites of dengfeng complex 1 firstly the mantle is metasomatized either by melts or by aqueous fluids from a subducted slab 2 subsequently sanukitoid magmas were produced by partial melting of the hybridized mantle furthermore the amphibolites of supracrustal rocks have a mixture of morb and arc like geochemical affinities suggesting the development of a back arc in the southern ncc at ca 2 5 ga the contemporary late neoarchean ttgs sanukitoids and morb back arc association may represent a late neoarchean tectonic melange implying a neoarchean subduction accretion process which would suggest that modern style plate tectonics processes was probably initiated in the southern ncc by 2 5 ga

precise determination of phanerozoic zircon pb pb age by multicollector sims without external standardization 1 zircon has long been recognized as the best geochronometer and the most important timekeeper in geosciences modern microbeam techniques such as sims and la icpms have been successfully applied to in situ u pb zircon age determinations at spatial resolutions of 20 30 m or less matrix matched calibration by external standardization of well characterized natural zircon references is a principal requirement for precise microbeam u pb zircon age determination due to fractionation effects between pb and u which usually result in an external age error exceeding 1 alternatively zircons with a closed u pb system can be directly dated by measurement of 207pb 206pb isotopic ratio without external standardization which has been a common practice for zircons older than 1 0 ga but not for relatively young 1 0 ga and particularly phanerozoic ones because of limitations of analytical precision we describe in this paper a method of 207pb 206pb measurement on phanerozoic zircons using a new generation of large radius magnetic sector multicollector cameca ims 1280 sims in combination with multicollector mode a nuclear magnetic resonance nmr magnet controller and oxygen flooding techniques we achieve precisions of 207pb 206pb ratio of 0 1 and 0 1 0 2 propagating to pb pb age errors 0 4 and 1 3 excluding u decay constant uncertainties for zircons of latest neoproterozoic and late paleozoic to mesozoic age respectively therefore the multicollector sims is capable of direct determination of zircon pb pb ages as young as mesozoic age with uncertainties of geological significance this technique is useful for direct dating of zircons in thin sections moreover it has significance for dating of some other u rich minerals i e baddeleyite and zirconolite that are not suitable for sims u pb dating by external standardization

two layer model on the branching of the kuroshio southwest of kyushu japan observations suggest that a separation branch of the kuroshio appears southwest of kyushu japan the observed density and surface current fields clearly show a separation branch in autumn however the separation branch disappears in winter and spring when the relatively homogeneous structure develops due to the intense surface cooling a scenario generating a separation branch is examined using simple two layer model the northward kuroshio along the shelf slope turns to the east abruptly and leaves the shelf slope around tokara strait a hump local increase of the upper layer thickness is made by the lower layer flow impinging on the bottom slope this hump extends to the shallow shelf region due to the combined effect of advection and dissipation of the upper layer thickness then the cross isobath flow that is the separation branch appears around the hump when the thin upper layer obstructs the advection process in winter and spring a separation branch disappears moreover the separation branch disappears when a small damping coefficient is used

a morb arc basalt adakite association in the 2 5 ga wutai greenstone belt late archean magmatism and crustal growth in the north china craton abstract the wutai fuping and hengshan complexes form part of a major 2 5 ga late archean arc system in the northern part of the north china craton the wutai complex is a well preserved greenstone belt dominated by mafic intermediate and felsic volcanic rocks with a mid ocean ridge basalt morb arc back arc basalt adakite association multi element plots for morb type mafic volcanic rocks are characterised by depletion of th nb ta and la nearly flat or lree depleted ree patterns and nb u and nb th ratios greater than primitive mantle values back arc basin basalt babb type rocks have nearly flat trace element patterns with nb ti and y troughs and lree depleted or near flat ree patterns island arc basalt iab type rocks are characterized by negative anomalies of nb ta zr hf ti and y and by lree enrichment the felsic volcanic rocks conform to most compositional criteria for cenozoic adakites including low y and yb high la smn la yb and zr sm ratios and similar trace element and ree patterns trends defined by the association are consistent with magma mixing between morb like melts and subduction slab related melts intra oceanic subduction coupled with contemporary morb type mantle upwelling related to back arc basin extension can account for the interaction between the two components subduction accretion or back arc basin collapse led to accretion of the wutai intra oceanic arc back arc complexes with the magmatic arcs of the fuping and hengshan terranes that are dominated by high grade tonalite trondhjemite granodiorite ttg gneisses this geodynamic interpretation is different from many tectonic models for archean greenstone belts in which magmatism and crustal growth were dominated by mantle plumes or interaction between subduction zones and mantle plumes the final disposition of the arc complexes was controlled by the collision of the eastern and western blocks of the north china craton during the paleoproterozoic resulting in extensive tectonic interleaving within a major orogenic belt that extended throughout the central portion of the north china craton

heat advection processes leading to el nino events as depicted by an ensemble of ocean assimilation products the oscillatory nature of el nino southern oscillation results from an intricate superposition of near equilibrium balances and out of phase disequilibrium processes between the ocean and the atmosphere the main objective of the present work is to perform an exhaustive spatiotemporal analysis of the upper ocean heat budget in an ensemble of state of the art ocean assimilation products we put specific emphasis on the ocean heat advection mechanisms and their representation in individual ensemble members and in the different stages of the enso oscillation leading to en events our analyses consistently show that the initial subsurface warming in the western equatorial pacific is advected to the central pacific by the equatorial undercurrent which together with the equatorward advection associated with anomalies in both the meridional temperature gradient and circulation at the level of the thermocline explains the heat buildup in the central pacific during the recharge phase we also find that the recharge phase is characterized by an increase of meridional tilting of the thermocline as well as a southward upper ocean cross equatorial mass transport resulting from ekman induced anomalous vertical motion in the off equatorial regions although differences between data sets are generally small and anomalies tend to have the same sign the differences in the magnitude of the meridional term are seen to be key for explaining the different propagation speed of the subsurface warming tendency along the thermocline the only exception is gecco which does not produce the patterns of meridional surface ekman divergence subsurface sverdrup convergence in the western and central equatorial pacific

an estimate of the cross frontal transport at the shelf break of the east china sea with the finite volume coastal ocean model 1 the finite volume coastal ocean model fvcom is used to estimate the onshore cross frontal transport at the shelf break of the east china sea boundary conditions of fvcom are provided by the princeton ocean model simulating ocean currents in the yellow sea and east china sea realistically one advantage of this study is that the unstructured triangular cell grid of fvcom resolves complex bottom topography that may trigger kuroshio frontal waves it is anticipated that these nonlinear frontal waves enhance the exchange of seawater between the kuroshio and shelf regions kuroshio frontal waves in the model are excited around the location where the bottom slope changes abruptly and have the phase speed and amplitude consistent with those observed in the east china sea in addition the model reproduces the onshore transport associated with growing frontal waves in the upper and lower layers on the basis of passive tracer experiments the annually averaged onshore transport integrated along the shelf break is estimated to be 0 85 106 m3 s

th u pb monazite geochronology of the luliang and wutai complexes constraints on the tectonothermal evolution of the trans north china orogen abstract recent lithological metamorphic and geochronological studies show that the basement of the north china craton ncc formed by collision of two discrete archean to paleoproterozoic blocks eastern and western blocks along a paleoproterozoic orogen named the trans north china orogen however the timing of the collision is controversial and post collisional exhumation has not been precisely dated this study applies the electron microprobe th u pb monazite dating technique to determine the ages of the peak metamorphic event and subsequent exhumation of the low to medium grade luliang and wutai complexes in the trans north china orogen electron microprobe th u pb monazite data for the luliang complex reveal five tho 2 pbo age ranges 1 1940 1938 ma 2 1880 1847 ma 3 1795 1755 ma 4 1720 1703 ma and 5 1648 ma of these age ranges the first four have also been recorded in the wutai complex which yields tho 2 pbo ages of 1 1930 ma 2 1838 1822 ma 3 1793 ma and 4 1719 ma the oldest age range of 1940 1930 ma is interpreted to record the widespread emplacement of mafic dikes in rocks of the luliang and wutai complexes the age range of 1882 1822 ma is in accord with the shrimp u pb ages of metamorphic zircons and mineral sm nd and 40 ar 39 ar ages obtained for other complexes in the orogen and is interpreted as the age of the major metamorphic event caused by amalgamation between the eastern and the western blocks the age range of 1795 1755 ma is consistent with emplacement of large scale unmetamorphosed mafic swarms at 1800 1765 ma interpreted as the time of post orogenic extension the 1720 1703 ma and 1648 ma ages are considered to date later multiple stages of hydrothermal alteration since monazites with such young ages only occur along fractures in older monazite grains and at the rims these new monazite tho 2 pbo ages support the tectonic model for the evolution of the north china craton that envisages discrete eastern and western blocks colliding along the trans north china orogen at 1 85 ga and then undergoing post collisional extension in the period 1795 1755 ma

assembling north china craton within the columbia supercontinent the role of double sided subduction abstract an evaluation of recent s wave receiver functions s wave velocities and two versions of p wave tomographic images along various transects in the north china craton provides some clues on the subduction collision history of the different crustal blocks and their final amalgamation within the paleoproterozoic columbia supercontinent interpretation of a n s seismic section of the craton suggests thick slab debris sinking to various depths in the mantle the w e seismic corridors show the preservation of a thick 200 km lithospheric root tectosphere beneath the ordos block and its variable and extensive erosion towards the yanliao block eastern block this zone is characterized by layers with marked velocity contrast and suggests repeated stacking of the remnants of underplated and accreted paleoproterozoic oceanic lithosphere the present day lithosphere asthenosphere boundary beneath this region probably marks the erosional plane along which decratonization occurred through subduction erosion from the east and thermal and material erosion by upwelling asthenosphere from below resulting in the partial destruction of the tectosphere and its thinning towards the east within the asthenosphere below the yanliao block younger and thinner slabs predominate in the absence of any prominent thick high velocity layers these younger slabs define a westward polarity and constitute a mega scale duplex formed by underplating through phanerozoic subduction process particularly the pacific plate subduction from the east the lithologic associations within the inner mongolia suture zone dividing the yinshan block to the north and ordos block to the south correspond to an accreted ocean plate stratigraphic sequence with the tonalite trondhjemite granodiorite ttg gneisses charnockites and calc alkaline granites representing a continental arc built up through subduction from the north the seismic transects bring out a contrasting polarity in the subduction regime with an oblique east to southward subduction of the yinshan block and a westward subduction of the yanliao block here i propose a double sided subduction history for the ncc similar to the ongoing subduction process in the western pacific such double sided subduction is considered to promote rapid amalgamation of continental fragments within supercontinents and the subduction polarities and mantle dynamics of ncc are therefore considered to be critical in evaluating the final assembly of the paleoproterozoic supercontinent columbia

seasonal circulation patterns of the yellow and east china seas derived from satellite tracked drifter trajectories and hydrographic observations abstract we investigated seasonal circulation patterns of the yellow and east china seas yecs by reviewing previous works on the circulation and its dominant currents and taking into account newly compiled trajectories of satellite tracked drifters collected between the 1980s and 2000s the circulation patterns suggested before the 1990s can be categorized into two groups depending on the identified origin of the tsushima warm current in the korea tsushima straits i branching from the kuroshio southwest of kyushu or ii northeastward continuation of the taiwan strait throughflow the branching of the kuroshio southwest of kyushu and northeast of taiwan was clearly evidenced by current measurements and concurrent hydrographic surveys however there is still no clear evidence for the northeastward pathway of taiwan strait throughflow across the mid shelf area of the east china sea target oriented surveys in the 1990s and 2000s employing advanced instruments such as drifter tracking and acoustic doppler current profiler measurements now provide decisive proof of the clockwise rounding of the cheju warm current around jeju do throughout the year of the northeastward extension of changjiang discharge in summer and of the presence of the yellow sea warm current only in winter thus both coastal currents in shallow water and secondary branch currents of the kuroshio such as the yellow sea warm current are found to significantly change from winter to summer to better present the basic pattern of yecs circulation and its seasonality we have constructed seasonal circulations patterns based on review results on the newly compiled drifter trajectories and on hydrographic observations further investigations should be carried out in future with support of comprehensive current measurements on shelf areas and through elaborate numerical modeling

spring season flow of the tsushima current and its separation from the kuroshio satellite evidence attempts to determine where and how separation between the kuroshio and tsushima current occurs have been inconclusive spring season satellite data acquired over a number of years reveals two conditions important to this question 1 an areally extensive zone of mixing between the kuroshio and shelf waters occurring along the edge of the east china sea shelf and 2 plumes of warm water from the kuroshio extending into the mixed water west of kyushu this mixed water is observed to form the tsushima current in the outer shelf of the northern east china sea and korea strait warm plumes branching from the north wall of the kuroshio are seen with particular clarity in imagery of april 23 1981 and february 21 1982 details of the split suggest that branching was a transient event

trace element and isotope characteristics of cenozoic basalts around the tanlu fault with implications for the eastern plate boundary between north and south china a reply abstract cenozoic intraplate basalts in eastern china show variations of pb sr and nd isotope ratios that essentially correspond to major lithospheric domains with distinct tectonic histories whereas an enriched mantle em1 type isotope signature is commonly observed in basalts from the north china block an em2 type isotope signature appears to dominate in those from the south china block this study reports new trace element data for cenozoic basalts occurring around the tanlu fault zone a sinistral translithospheric fault related to the triassic continental collision between the north and south china blocks combining published isotope data basalts from the subei basin in the east of the tanlu fault exhibit the em1 type geochemical and isotopic features implying that their lithospheric mantle source region is structurally affiliated with the north china block this is consistent with the crustal detachment collision model that suggests a subsurface suture between the north and south china blocks

shrimp u pb zircon geochronology of palaeoproterozoic metasedimentary rocks in the north china craton evidence for a major late palaeoproterozoic tectonothermal event abstract although metasedimentary successions are widely distributed across the north china craton those of palaeoproterozoic age are restricted to three orogenic belts namely the trans north china orogen the khondalite belt and the jiao liao ji belt prior to this work some of those successions were considered to be archaean in age the palaeoproterozoic metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 0 to 2 1 ga with the majority recording an age between 2 3 and 2 0 ga this latter group define a series of magmatic events that occurred between formation of the archaean basement and deposition of the metasedimentary rock protoliths the metasedimentary rocks occur as two associations older volcano sedimentary units that formed between 2 37 and 2 0 ma and younger sedimentary units that formed mainly between 2 0 and 1 88 ga all these rock associations were then subjected to metamorphism during the late palaeoproterozoic 1 88 and 1 85 ga tectonothermal event named the luliang movement in early chinese literature which was a continent continent collision that led to the amalgamation of the north china craton

cenozoic volcanic rocks of eastern china secular and geographic trends in chemistry and strontium isotopic composition abstract the cenozoic volcanic rocks of eastern china are subalkalic to alkalic basalts erupted in an early tertiary back arc rift environment and from scattered late tertiary and quaternary volcanic centers in a continental area crossed by active faults driven by subduction of the pacific plate and the collision of india and eurasia immobile trace elements and major elements conform very well to each other in classification of the 59 rocks for which complete data are reported and they correctly identify the tectonic setting lil element enrichments of the basalts lie between those of p morb and ocean island alkalic basalts and show a secular increase 87sr 86sr ratios of basalts vary from 0 7029 to 0 7048 alkalic basalts are systematically less radiogenic than geographically coextensive and contemporaneous tholeiitic basalts increase of radiogenic sr with increasing crustal thickness and crustal age and with silica enrichment of the magmas suggests crustal contamination but this is inadequate to explain the lil element enrichment patterns and variable lil element enrichments the preferred hypothesis is that the alkalic magmas come from a deeper source with long term lil element depletion and low rb sr ratio but relatively recent lil element enrichment conversely the tholeiitic magmas are melts of subcontinental mantle lithosphere that is more lil element depleted than the alkalic source at the time of magma genesis but has had an elevated rb sr ratio for much of its post consolidation history

water mass and throughflow transport variability in the taiwan strait 1 variability of water mass and throughflow transport in the taiwan strait are analyzed using strait wide conductivity temperature depth 1985 2003 and sectional acoustic doppler current profiler 1999 2001 data results from a cluster analysis temperature salinity diagrams and direct transport calculations indicate that the strong northeast monsoon drives the brackish mixed china coastal water into the northern strait and hinders the northward intruded saline kuroshio branch water kbw in the southeastern strait from december to january the mean throughflow transport across the central strait is about 0 1 sv southward during this period thus supporting previous observations that there is no persistent northward flowing current throughout the strait in winter the weakening of the northeast monsoon in february march however emancipates the kbw to intrude northward into the east china sea ecs in june the increase in this northward transport accompanied by the decrease in the westward intrusion of kuroshio through the luzon strait leads to the replacement of the kbw by the less saline south china sea water scsw the northward transports ranging from 1 16 to 2 34 sv between march and august yield 0 131 0 238 1015 w and 53 33 81 74 106 kg s of temperature and salt transports respectively toward the ecs the inception of the northeast monsoon in october marks both the change of water mass from fall to winter patterns and the decrease of the northward throughflow transport our results also reveal that the subsurface kbw and scsw remain consistent throughout the observation periods between 100 and 200 m and below 200 m depths respectively in the southeastern strait

a peritidal evaporite environment in the neoproterozoic of south gabon schisto calcaire subgroup nyanga basin the neoproterozoic 630 ma nsc3 or sciii formation schisto calcaire subgroup of the nyanga basin is a muddy peritidal carbonate dolomite shelf succession that is exposed in the old mouila quarry keri quarry south gabon its 20 m thick lower member is dominated by microbially laminated dolomites and domal stromatolites representing shallow subtidal to supratidal environments abundant pseudomorphs after gypsum and anhydrite relicts indicate carbonate precipitation in sulphate rich hypersaline environments dolomitization of the muddy microbial sediments probably occurred by the evaporite reflux of groundwaters silica precipitates constitute the ultimate diagenetic phase dolomites of the nsc3 formation retain a pattern of oxygenic isotopic variation that reflects the depositional environment shallow subtidal microbialites and stromatolites record the lightest values 18o 5 1 consistent with the isotopic values of neoproterozoic marine waters whereas strongly dolomitized facies display heavier oxygen isotope values 18o 1 3 with the heaviest values in subaerially exposed caps enrichment of 3 8 fungal hyphae and spores have been discovered in these upper parts the 18o pattern through the plurimetric recognized sequences thicknesses from 2 to 6 m suggests a constant exposure in a sabkha like environment although the timing of the series is poorly constrained the c isotopic values of the nsc3 carbonates with values of 2 and 3 approximate depositional conditions minor variations in c isotopes have been observed the evolution of the succession from the stromatolitic lower member to the oolitic upper member of the nsc3 formation could record the progradation of a low energy evaporitic tidal flat that migrated seaward from oolitic shoal crests

comparison of wind and tidal contributions to seasonal circulation of the yellow sea 1 seasonal circulation of the yellow sea ys in response to wind and tidal forces is examined using a three dimensional numerical model wind forcing affects the wintertime circulation of the ys on the other hand the summer southerly monsoon is weak and therefore has little impact on the circulation on the basis of comparative experiments with and without wind conditions results indicate that the yellow sea warm current yswc along the ys trough exists regardless of wind forcing however strong winter northerly winds intensify the southward coastal flows along both coasts of the ys and therefore the northward intrusion of the yswc becomes stronger these flows in the ys are substantially weakened when wind forcing is not applied to the model in addition to wind driven circulation tide induced circulation is also dominant in the ys particularly in summer in winter the tidal effect weakens the upwind and downwind flows in response to the strong northerly winds while in summer tidal forcing induces a strong southward residual flow along the western slope and a cyclonic gyre with a bottom cold water dome at the central region of the ys the southward residual current possibly explains the southward movement of the yellow sea bottom cold water as observed in summer comparison to the effects of parameterized tidal mixing suggests that residual flow driven by explicit tidal forcing plays an important role in the summertime circulation of the ys

tectonothermal history of the basement rocks in the western zone of the north china craton and its tectonic implications the basement of the north china craton can be divided into the eastern central and western zones based on lithological structural metamorphic and geochronological data the western zone comprises two different petrotectonic units archaean tonalitic trondhjemitic granodioritic ttg grey gneisses and metamorphic mafic rocks and palaeoproterozoic khondalite series the former is characterized by isobaric cooling ibc type anticlockwise p t paths in the north northwestern part of the zone and near isothermal decompression itd type clockwise p t paths in the eastern part adjacent to the central zone on the other hand the tectonothermal evolution of palaeoproterozoic khondalite series rocks is characterized exclusively by nearly isothermal decompression following the peak of metamorphism and then cooling defining clockwise p t paths the archaean ttg gneisses and associated mafic rocks with anticlockwise metamorphic p t paths reflects an origin related to underplating and intrusion of mantle derived magmas which may be derived from mantle plumes they represent a late archaean continental block in the western part of the north china craton the palaeoproterozoic khondalite series rocks represent passive continental margin deposits they were metamorphosed and deformed in the late palaeoproterozoic during the amalgamation of the western continental block with another continental block in the east part of the north china craton the itd type clockwise p t t paths of the palaeoproterozoic khondalite series rocks record the tectonothermal histories of the collision of the western and eastern continental blocks which resulted in the final assembly of the north china craton at c 1800 ma

current distributions in the southern east china sea in summer current measurements using a shipboard acoustic doppler current profiler adcp and two satellite tracked buoys together with conductivity temperature depth ctd casts were carried out over the continental shelf in the southern east china sea in july 1995 two transects for adcp measurements were defined and divided into segments of 56 km in order to remove diurnal and semidiurnal tidal flows from observed flows four round trip adcp surveys were conducted along each segment over diurnal tidal periods of 24 hours and 50 min the outflow through the taiwan strait i e the taiwan current with velocities of 35 40 cm s 1 was clearly observed to flow northeastward along the coast of china the volume transport was estimated as at least 1 sv the taiwan current probably increased width and decreased velocity in the central east china sea bifurcation into two branches of the taiwan current shown by previous studies was not observed another current entering onto the continental shelf northeast of taiwan i e the kuroshio branch was found with velocities 15 cm s 1 in the surface and it helped to make an anticyclonic eddy the main portion of the kuroshio branch flowed northeastward along the 100 m isobath with a volume transport of 0 3 sv the taiwan current was clearly separated from the kuroshio branch by the area of very weak or southward reverse flows

episodic surface intrusions in the yellow sea during relaxation of northerly winds the surface currents over the yellow and east china seas are mapped from the geostationary ocean color imager goci based on a composite of six intrusion events in january april the strong northward surface current in the yellow sea is shown to be concentrated along the deep trough accompanied by a broad northward surface current over the east china sea from the corresponding surface winds the episodic northward surface flow bursts appear to be associated with abrupt changes from the strong northerly winds to weak southerly winds during cold front passages a three dimensional model driven with observed surface winds is used to simulate the observed shelf wide response to northerly winds there is an outstanding agreement between the simulated and observed surface currents the surface intrusion in the yellow sea is shown to be driven primarily by a barotropic longitudinal surface slope while the strong northward current in the east china sea is associated with a coastal trapped wave moreover the surface intrusion is associated with a large volume transport suggesting that the transient intrusions could be important in the northward heat transport the unprecedented capability of goci satellite in providing a regional circulation pattern in conjunction with complementary model simulations could contribute greatly to understanding of the dynamics of the yellow and east china seas

separation of the kuroshio water and its penetration onto the continental shelf west of kyushu the separation of kuroshio water west of kyushu and its penetration onto the continental shelf of the east china sea were investigated by analyzing trajectories of satellite tracked surface drifters deployed during 1989 1996 conductivity temperature and depth ctd data collected in the eastern east china sea in december 1993 and late april early may 1995 were also analyzed composite trajectories of 172 drogued drifters provided direct evidence of the separation of the northeastward flowing kuroshio into two parts at the western mouth of the deep trough southwest of kyushu the kuroshio main stream turns to the east toward the tokara strait and a northward flowing branch current penetrates onto the shelf across the continental slope west of the trough analysis of the ctd data and drifter trajectories concurrently observed shows that the branch current was part of the inshore kuroshio just upstream before its separation during the periods of ctd observations the separated inshore kuroshio water intruded northward in a tongue shape along the shelf break of the trough and penetrated onto the shelf after crossing obliquely the western continental slope of the trough the water that penetrated onto the shelf continued to flow northward toward the korea strait the main path of this water was easily traced by its high salinity which is characteristic of the inshore kuroshio water application of an inverse method to the observed ctd data also supports the separation and penetration of the kuroshio and calculates the volume transport of the northward branch to be about 4 0 106 m3 s for the two different surveys the tongue shaped intrusion of the inshore kuroshio water onto the outer shelf may take place in close association with the eastward turning of the kuroshio main stream and it might be caused by the vorticity adjustment created by the eastward turning of the kuroshio

lithotectonic elements and geological events in the hengshan wutai fuping belt a synthesis and implications for the evolution of the trans north china orogen the hengshan wutai fuping belt is located in the middle segment of the trans north china orogen a palaeoproterozoic continental collisional belt along which the eastern and western blocks amalgamated to form the north china craton the belt consists of the medium to high grade hengshan and fuping gneiss complexes and the intervening low to medium grade wutai granite greenstone terrane and most igneous rocks in the belt are calc alkaline and have affinities to magmatic arcs previous tectonic models assumed that the hengshan and fuping gneiss assemblages were an older basement to the wutai supracrustal rocks but recent studies indicate that the three complexes constitute a single long lived neoarchaean to palaeoproterozoic magmatic arc where the wutai complex represents an upper crustal domain whereas the hengshan and fuping gneisses represent the lower crustal components forming the root of the arc the earliest arc related magmatism in the belt occurred at 2560 2520 ma marked by the emplacement of the wutai granitoids which was followed by arc volcanism at 2530 2515 ma forming the wutai greenstones extension driven by widespread arc volcanism led to the development of a back arc basin or a marginal sea which divided the belt into the hengshan wutai island arc japan type and the fuping relict arc at 2520 2480 ma subduction beneath the hengshan wutai island arc caused partial melting of the lower crust to form the hengshan tonalitic trondhjemitic granodioritic ttg suites whereas eastward directed subduction of the marginal sea led to the reactivation of the fuping relict arc where the fuping tonalitic trondhjemitic granodioritic suite was emplaced in the period 2360 2000 ma sporadic phases of isolated granitoid magmatism occurred in the hengshan wutai fuping region forming 2360 ma c 2250 ma and 2000 2100 ma granitoids in the hengshan complex the c 2100 ma wangjiahui and dawaliang granites in the wutai complex and the 2100 2000 ma nanying granitoids in the fuping complex atc 1920 ma the hengshan wutai island arc underwent an extensional event possibly due to the subduction of an oceanic ridge leading to the emplacement of pre tectonic gabbroic dykes that were subsequently metamorphosed together with their host rocks to form medium to high pressure granulites at 1880 1820 ma the hengshan wutai fuping arc system was juxtaposed intensely deformed and metamorphosed during a major and regionally extensive orogenic event the l uliang orogeny which generated the trans north china orogen through collision of the eastern and western blocks the hengshan wutai fuping belt was finally stabilized after emplacement of a mafic dyke swarm at 1780 1750 ma

evolution of late quaternary mud deposits and recent sediment budget in the southeastern yellow sea abstract analysis of high resolution seismic reflection profiles and sediment samples has revealed the evolution and sediment budget of the southeastern yellow sea mud belt seysm along the southwestern korean peninsula the seysm up to 50 m thick over 250 km long and 20 55 km wide can be divided into three stratigraphic units a1 a2 and b from oldest to youngest unit a1 overlying the acoustic basement comprises the northern part of the seysm unit a2 comprises the southern part of the seysm much of unit a2 is exposed at the seafloor unit b completely covers unit a1 and pinches out southward 14c data suggest that evolution of each unit is closely related to the postglacial sea level changes unit a1 consists of estuarine deltaic or shallow water muds deposited during the early to middle stage of postglacial sea level rise ca 14 000 7000 yr b p unit a2 corresponds to relict muds deposited during the last deceleration stage of sea level rise ca 7000 3 500 yr b p unit b consists of shelf muds deposited during the recent sea level highstand ca very low background activities of 210pb of the surface sediment of unit a2 suggest that the present day sediment accumulation is negligible in the southern seysm on the other hand 210pb excess activity profiles in unit b yield an average sediment accumulation rate of 3 9 mm yr indicating active sediment accumulation in the northern seysm the annual sink 3 0 10 7 tons yr of fine grained sediment in unit b is about an order of magnitude greater than can be explained by the sediment input from the korean rivers alone we propose that reworking of unit a2 has provided large volumes of muds to unit b resulting in excessive sediment accumulation in the northern seysm much of unit a2 in turn is likely to have originated from erosion of unit a1 in the north this rather unique erosional depositional regime of the seysm is probably owing to the tidal and regional currents characteristic in the southeastern yellow sea

on the origin of the tsushima warm current the origin of the tsushima warm current referred to as twc was investigated by surface drifter experiments and conductivity temperature and depth ctd surveys in the northeastern east china sea ecs at three different times july 1991 and april and november 1992 trajectories of 10 satellite tracked drifters provide direct information for the first time on the surface flow patterns in each season and ctd observations allow identification of warm and saline twc waters the results of the experiments argue against two historical concepts of twc origins i e 1 a northward flow transporting warm and saline water through the deep trough southwest of kyushu toward the korea strait after separation from the kuroshio and 2 a northeastward continuation of the taiwan current tc on the shelf of ecs after passing through the taiwan strait a persistent northward current was found to exist both on the shelf west of the trough and on the western flank of the trough the northward flow seems to bifurcate around the northwestern corner of the trough splitting into a northward continuing flow on the shelf of 100 150 m and an eastward flow along the northern wall of the trough the northward flow on the shelf which might be the shore fringe of the kuroshio corresponds to the origin of twc entering the korea strait the eastward flow on the northern slope turned back to the south along the west coast of kyushu and eventually joined the kuroshio this structure was accompanied by an anticyclonic eddy in the northern trough the second concept that of twc originating from tc contradicts the observed differences in physical properties between twc and tc waters the saline water in the taiwan strait flows out intermittently only during late winter early spring and its salinity during other seasons is lower than that of the twc water in the korea strait experiments also indicated a seasonal shift of drifter paths in the northeastern ecs and coexistence of cyclonic and anticyclonic eddies in the trough during the cold season

timing of metamorphism in the paleoproterozoic jiao liao ji belt new shrimp u pb zircon dating of granulites gneisses and marbles of the jiaobei massif in the north china craton abstract the paleoproterozoic jiao liao ji belt lies in the eastern block of the north china craton with its southern segment extending across the bohai sea into the jiaobei massif high pressure pelitic and mafic granulites have been recently recognized in the paleoproterozoic jingshan group jiaobei massif new shrimp u th pb geochronology combined with cathodoluminescence cl imaging of zircon has been applied to the determination of the timing of the metamorphism of the high temperature and high pressure granulites and associated gneisses and marbles metamorphic zircons in these high pressure granulites gneisses and marbles occur as either single grains or overgrowth or recrystallization rims surrounding and truncating oscillatory zoned magmatic zircon cores metamorphic zircons are all characterized by nebulous zoning or being structureless with high luminescence and relatively low th u values metamorphic zircons from two high pressure mafic granulites yielded 207pb 206pb ages of 1956 41 ma and 1884 24 ma one metamorphic zircon from a garnet sillimanite gneiss also gave an apparent 207pb 206pb age of 1939 15 ma these results are consistent with interval of ages of c 1 93 1 90 ga already obtained by previous studies for the north and south liaohe groups and the laoling group in the northern segment of the jiao liao ji belt metamorphic zircons from a high pressure pelitic granulite and two pelitic gneisses yielded weighted mean 207pb 206pb ages of 1837 8 ma 1821 8 ma and 1836 8 ma respectively two diopside olivine phlogopite marbles yielded weighted mean 207pb 206pb ages of 1817 9 ma and 1790 6 ma these paleoproterozoic metamorphic ages are largely in accordance with metamorphic ages of c 1 85 ga produced from the ji an group in the northern segment of the jiao liao ji belt and c 1 86 1 80 ga obtained for the high pressure pelitic granulites from the jingshan group in the southern segment as this metamorphic event was coeval with the emplacement of a type granites in the jiao liao ji belt and its adjacent areas it is interpreted as having resulted from a post orogenic or anorogenic extensional event

archean blocks and their boundaries in the north china craton lithological geochemical structural and p t path constraints and tectonic evolution an examination of lithological geochemical geochronological structural and metamorphic p t path data suggests that the basement of the north china craton can be divided into eastern and western blocks separated by major crustal boundaries that roughly correspond with the limits of a 300 km wide zone called the trans north china orogen the eastern block consists predominantly of late archean domiform tonalitic trondhjemitic granodioritic ttg batholiths surrounded by anastomosing networks and linear belts of open to tight synforms of minor volcanic and sedimentary rocks metamorphosed from greenschist to granulite facies at 2 5 ga with anticlockwise p t paths some early to middle archean rocks are locally present in the eastern block but their tectonic history is unclear due to reworking by the 2 5 ga tectonothermal event the western block has a late archean assemblage structural style and metamorphic history similar to that of the eastern block but it differs in the absence of early to middle archean assemblages and in being overlain by and interleaved with paleoproterozoic khondalites which were affected by a 1 8 ga metamorphic event involving clockwise p t paths a mantle plume model is proposed for the formation and evolution of late archean basement rocks in the eastern and western blocks based on a combination of extensive exposure of ttg gneisses affinities of mafic rocks to continental tholeiitic basalts presence of voluminous komatiitic rocks dominant diaprism related domiform structures anticlockwise p t paths and a short time span from the primary emplacement of ttg and ultramafic to mafic rocks until the onset of regional metamorphism between the two blocks is the trans north china orogen which is bounded by two major fault systems and is composed of late archean to paleoproterozoic ttg gneisses and granitoids interleaved with abundant sedimentary and volcanic rocks that are geochemically interpreted as having developed in magmatic arc and intra arc basin environments these rocks underwent multiple phases of compressional deformation and peak high pressure metamorphism followed by rapid exhumation during the late paleoproterozoic at 1 8 ga as a result of collision between the eastern and western blocks resulting in the amalgamation of the north china craton

single zircon grains record two paleoproterozoic collisional events in the north china craton abstract the western block of the north china craton consists of the yinshan block in the north and the ordos block in the south which were amalgamated along the east west trending khondalite belt at 1 95 ga the western block then collided with the eastern block to form the coherent basement of the north china craton along the north south trending trans north china orogen at 1 85 ga the huaian complex a high grade terrrane located at the conjunction of the khondalite belt and trans north china orogen records metamorphic events associated with both collisions the complex consists of lithologies from both the khondalite belt and trans north china orogen of which the former consist of graphite garnet sillimanite gneiss garnet quartzite felsic paragneiss calc silicate rock and marble together called the khondalite series zircons in the graphite garnet sillimanite gneiss can be divided into three types 1 spherical grains without internal structures 2 grains with a core and rim structure and 3 grains with a dark core surrounded by double rims except for the dark core in type 3 all other types of zircon domains are structureless and highly luminescent with very low th u ratios typical of a metamorphic origin analyses on the cores of type 2 and the inner rims of type 3 from two samples yield upper intercept ages of 1946 26 and 1947 22 ma similar to previously determined metamorphic ages from the khondalite belt and thus interpreted as the time of collision between the yinshan and ordos blocks analyses on type 1 zircons rims of type 2 and the outer rims of type 3 from the same two samples give ages of 1850 15 and 1857 16 ma interpreted as the time of collision between the eastern and western blocks thus zircons in the graphite garnet sillimanite gneiss of the huaian complex record both of the paleoproterozoic collisional events in the north china craton

yellow and east china seas response to winds and currents the influences of the kuroshio current kuc taiwan warm current twc and surface wind stress on the yellow and east china seas yes are examined using tracers in a princeton ocean model two experiments are performed one with wind stress and one without seasonal variations in the inflow and outflow of the twc and tsushima current are specified to examine the effects of the current transports two separate tracers are inserted into each model experiment to track the pattern of kuc and twc waters into the yes the two main areas of kuc and twc water movement into the yellow sea are the southern entrance to the yellow sea trough and the yangtze relict river valley results indicate that kuc and twc waters advect into the yellow sea regardless of wind stress however in the yellow sea during winter the wind stress increases kuc and twc concentration at 20 m the wind stress also produces short time period events that horizontally advect water masses and spatially smooth seasonally averaged water mass concentrations the bottom ekman layer appears to be one of the mechanisms driving the northward bottom flow across the east china sea shelf the bottom friction layer is stronger in summer when the twc velocity is high the bottom friction layer draws kuc water across the bottom of the continental shelf into the yangtze relict river valley and generates upwelling along the chinese coast

evidence for intracontinental thrust related exhumation of the ultra high pressure rocks in china coesite and diamond bearing ultra high pressure metamorphic rocks produced during the triassic continental collision between the sino korean and yangtze plates are offset by about 530 km along the sinistral tanlu fault in eastern china the tanlu fault terminates abruptly south of the ultra high pressure metamorphic terrain in dabie shan and does not extend into the foreland fold belt along the yangtze river this suggests that in this region the mesozoic major sinistral displacement along the tanlu fault was transferred to southward directed thrusting which led to the exhumation of the ultra high pressure metamorphic rocks formed earlier postcollisional himalayan type intracontinental thrusting and concomitant erosion appear to be the main agents in the exhumation of the very high pressure metamorphic rocks in china

on kuroshio front fluctuations in the east china sea using satellite and in situ observational data fluctuations of the kuroshio front in the east china sea and their relation to variations of the kuroshio stream around the tokara strait are investigated using consecutive satellite images sea level data as well as water temperature records from a japan meteorological agency buoy station and a ferryboat which crosses the tokara strait meanders of the kuroshio front with typical horizontal scales of 100 to 150 km and wave periods of 14 to 20 days are found to appear ubiquitously in the east china sea the front meanders originate upstream over the continental slope and evolve rapidly while propagating downstream at speeds of 20 to 26 cm s 1 downstream southwest of kyushu the fully developed meanders sometimes take the form of warm filaments and when the volume transport of the kuroshio is large they may develop into shed off warm eddies previous observations based on ferryboat temperature records have revealed the repeated northward migration of a clear sea surface temperature sst front across the tokara strait it is shown that this northward migration of the sst front corresponds to the passage of the kuroshio front meanders across the tokara strait and that the unclear southward migration of the sst front is due to the presence of mixed water behind each meander the kuroshio front meanders in the east china sea are further found to be closely related to the north southward movement of the entire kuroshio stream in the tokara strait a lag of about 10 days exists between the time the front meanders reach the tokara strait and the kuroshio stream there shifts to its northernmost position

zircon geochronology and metamorphic evolution of mafic dykes in the hengshan complex of northern china evidence for late palaeoproterozoic extension and subsequent high pressure metamorphism in the north china craton abstract magmatic and metamorphic zircons have been dated from ductilely deformed gabbroic dykes defining a dyke swarm and signifying crustal extension in the northern part of the hengshan complex of the north china craton these dykes now occur as boudins and deformed sheets within migmatitic tonalitic trondhjemitic granodioritic and granitic gneisses and are conspicuous due to relics of high pressure granulite or even former eclogite facies garnet pyroxene bearing assemblages shrimp ages for magmatic zircons from two dykes reflect the time of dyke emplacement at 1915 ma whereas metamorphic zircons dated by both shrimp and evaporation techniques are consistently in the range 1848 1888 ma the youngest granitoid gneiss yet dated in the hengshan has an emplacement age of 1872 17 ma these results complement recent geochronological studies from the neighbouring wutai and fuping complexes to the se of the hengshan showing that a crustal extension event occurred in the late palaeoproterozoic this preceded a major high pressure collision type metamorphic event in the central part of the north china craton that occurred in the palaeoproterozoic and not in the late archaean as previously thought our data support recent suggestions that the north china craton experienced a major craton wide orogenic event in the late palaeoproterozoic after which it became cratonized and acted as a stable block

an open ocean forcing in the east china and yellow seas 1 recent studies have demonstrated that the annual mean barotropic currents over the east china and yellow seas ecys are forced primarily by the oceanic circulation in the open ocean basin through the kuroshio current kc the western boundary current of the subtropical gyre in the north pacific ocean the local wind stress forcing plays an important but secondary role those previous results were mainly qualitative and from a simple barotropic model forced by a steady wind stress field they remain to be tested in a more complete 3 d model with both wind stress and buoyancy fluxes in addition the seasonal variability of major ecys currents may involve different forcing mechanisms than their annually averaged fields do and this can only be addressed when a seasonally varying forcing is used in the model in this paper we will address these issues by using a 3 d baroclinic model our results confirm the finding from the previous studies that the kc is the primary forcing mechanism for major annually mean currents in the ecys which include the taiwan strait current the tsushima warm current and the yellow sea warm current yswc etc however the local monsoonal forcing plays a prominent role in modulating the seasonal variability of all major currents in the region a deep northwestward intrusion of the yswc in winter for instance is mainly due to a robustly developed china coastal current and korea coastal current which draw water along the yellow sea trough to feed the southward flows along the west and east coasts of the yellow sea

geophysical and geological tests of tectonic models of the north china craton abstract the geometry and timing of amalgamation of the north china craton have been controversial with three main models offering significantly different interpretations of regional structure geochronology and geological relationships one model suggests that the eastern and western blocks of the ncc formed separately in the archean and an active margin was developed on the eastern block between 2 5 and 1 85 ga when the two blocks collided above an east dipping subduction zone a second presumes the eastern block rifted from an unknown larger continent at circa 2 7 ga and experienced a collision with an arc perhaps attached to the western block above a west dipping subduction zone at 2 5 ga and the 1 85 ga metamorphism is related to a collision along the northern margin of the craton when the ncc joined the columbia supercontinent a third model suggests two collisions in the central orogenic belt at 2 1 and 1 88 ga but recognizes an early undated deformation event recent seismic results reveal details of the deep crustal and lithospheric structure that support both the second and third models showing that subduction beneath the central orogenic belt was west directed and that there is a second west dipping paleosubduction zone located to the east of the cob dipping beneath the western block ordos craton the boundaries identified through geophysics do not correlate with the boundaries of the trans north china orogen suggested in the first model and the subduction polarity is opposite that predicted by that model high pressure granulite facies metamorphism at 1 85 ga is not restricted to the tnco as suggested by the first model but is documented across the ncc as predicted by the second model suggesting a major continent continent collision along the north margin of the craton at 1 85 ga further it has recently been shown that in the southern tnco there is no record of metamorphism at circa 1 85 ga but only at 2 7 2 5 ga showing that the tnco as defined as a circa 1 85 ga orogen does not exist this is further confirmed by recent re os isotopic studies which show that the subcontinental lithospheric mantle beneath the southern cob is late archean in age and that a province in the northern ncc is circa 1 8 ga correlating with the proposed collision belt of the ncc with the columbia supercontinent across the entire ncc the cob is an archean convergent belt re worked in the paleoproterozoic and the paleoproterozoic tectonism is widespread across the ncc as predicted by the model whereby the previously amalgamated eastern and western blocks experienced a continental collision with columbia at circa 1 85 ga but uplift exhumation rates are slow necessitating a re evaluation of the tectonic models of the ncc

summertime hydrographic features in the southeastern hwanghae abstract ctd casts in the southeastern hwanghae yellow sea were made in august 1983 and 1984 to describe the spatial structure of the summertime hydrographic features cold coastal water appeared around the southwestern coast of korea which was formed by strong tidal stirring tidal mixing in the study area seems to have been enhanced by the presence of many small islands in the deeper region beyond the tidal front stratification became much stronger and the bottom layer below seasonal thermocline was occupied mostly by the hwanghae cold water characterized by a temperature lower than 10 c and salinity of 32 5 33 0 the northeastward extension of the changjiang diluted water was shown by a tongue like plume of relatively warm fresh water confined to the thin surface layer 10 m thick there was no evidence for the hwanghae warm current carrying high salinity water into the eastern hwanghae along the korean coast the warm current was found to flow in a narrow band close to the west and north coast of chejudo cheju island and then to pass eastward through the cheju strait thus the eastern part of the cyclonic circulation in the surface layer cannot be considered to be a northward continuation of the hwanghae warm current the local salinity maximum in the lower layer off kunsan and the higher salinity on the west side of the central trough than on the east side would imply a northward flow on the west flank of the trough to compensate for the southward intrusion of the hwanghae cold water from which an anticyclonic circulation could be expected in the lower layer

a review of the geodynamic setting of large scale late mesozoic gold mineralization in the north china craton an association with lithospheric thinning abstract abundant gold deposits are distributed along the margins of the north china craton ncc occurring throughout the precambrian basement and located in or proximal to mesozoic granitoids these deposits show a consistent spatial temporal association with late jurassic early cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock their ages are mainly early cretaceous 130 110 ma and constrain a very short period of metallogenesis sr nd pb isotopic tracers of ores minerals and associated rocks indicate that gold and associated metals mainly were derived from multi sources i e the wall rocks precambrian basement and mesozoic granites and associated mafic rocks previous studies including high surface heat flow uplift and later basin development slow seismic wave speeds in the upper mantle and a change in the character of mantle xenoliths sampled by paleozoic to cenozoic magmas have been used to suggest that ancient cratonic mantle lithosphere was removed from the base of the ncc some time after the ordovician and replaced by younger less refractory lithospheric mantle the geochemistry and isotopic compositions of the mafic rocks associated with gold mineralization 130 110 ma indicate that they were derived from an ancient enriched lithospheric mantle source whereas the mafic dikes and volcanic rocks younger than 110 ma were derived from a relatively depleted mantle source i e asthenospheric mantle according to their age and sources relation to magmatism and geodynamic framework the gold deposits were formed during lithospheric thinning the removal of lithospheric mantle and the upwelling of new asthenospheric mantle induced partial melting and dehydration of the lithospheric mantle and lower crust due to an increase of temperature the fluids derived from the lower crust were mixed with magmatic and meteoric waters and resulted in the deposition of gold and associated metals

shrimp u pb zircon dating of the wulian complex defining the boundary between the north and south china cratons in the sulu orogenic belt china abstract neoproterozoic metasedimentary and metavolcanic rocks of the wulian group are associated with gneissic granitoids at the northern margin of the sulu uhp belt adjacent to the wulian yantai fault and are collectively referred to as the wulian complex shrimp u pb dating of detrital zircon from the metasedimentary rocks of the wulian group indicates a range in age from 3478 to 625 ma based on zircons 3000 ma with the oldest age being 3339 ma 2700 2400 ma with a peak at 2436 ma 2200 1800 ma with a peak at 2156 ma and at 770 ma these results indicate that deposition of the wulian group was after 770 ma and that some detrital material most likely came from neoproterozoic sources in the south china craton scc shrimp u pb zircon dating of a metavolcanic rock defines a weighted mean 206 pb 238 u age of 761 8 ma which is consistent with other rocks of south china affinity and can be correlated with syn rift magmatism during the breakup of the supercontinent rodinia the wulian group together with neoproterozoic granites of the wulian complex constrains the location of the triassic suture zone between the north china and south china cratons based on our new data the suture must lie north of the wulian complex and is marked by the baichihe yantai fault