new constraints on the pre permian continental crust growth of central asia west junggar china by u pb and hf isotopic data from detrital zircon in situ u pb geochronology of detrital zircons from various palaeozoic sedimentary rocks of west junggar accretionary complexes central asia suggests two distinct episodes of arc magmatism and an evolution in three steps i ordovician silurian subduction generating juvenile arc crust ii late silurian subduction jamming erosion and intraplate magmatism iii development of two new opposed devonian carboniferous subductions recycling the early palaeozoic crust zircon hf isotopes document three pre permian episodes of mantle derived magmatic input into the crust 1 neoproterozoic 850 550 ma 2 early palaeozoic 530 450 ma and 3 late palaeozoic 380 320 ma zircons also record the recycling of neoproterozoic and early palaeozoic juvenile crusts during the early and late palaeozoic these data support a model of episodic continental crust growth in central asia

metamorphic and tectonic evolution of the hwacheon granulite complex central korea composite p t path resulting from two distinct crustal thickening events of the hgc this decompressional process probably initiated in the hwacheon granulite complex hgc occupying the norththe kyanite stability field reached pressures of 3 6 kbar at eastern margin of the gyeonggi massif consists mainly of gar660 750 c the clockwise p t path may reflect the exhumation netiferous leucocratic gneiss and leucogranite together with minor of a deep seated crustal segment along discrete ductile shear zones kyanite garnet gneiss aluminous gneiss mafic granulite and garnet during the permo triassic collisional orogeny prevalent in far east amphibolite mineral assemblages and reaction textures in various asia rock types of the hgc document five distinct metamorphic stages pre m1 and peak m2 granulite facies metamorphism lower temperature high m3 and low m4 pressure upper amphibolitefacies metamorphism and local retrogression m5 producing andalusite bearing assemblages each metamorphic stage can be in

paleomagnetic results from the lower mesozoic daedong supergroup in the gyeonggi block korean peninsula an eastern extension of the south china block abstract lower mesozoic lake deposits in the daedong supergroup of the gyeonggi block were collected at 38 sites for paleomagnetic study a remanent magnetization component with unblocking temperatures of 635 660 c component a was isolated from four sites the directions of this component with both normal and reversed polarities yielded positive fold and reversal tests at the 95 confidence level component a is interpreted to be of primary origin of late triassic time the mean direction of component a d 82 2 i 23 1 with 95 4 1 together with previously reported primary directions yields a pole representative for the gyeonggi block at 31 9 n 220 2 e a 95 12 7 the paleomagnetic pole shows good agreement with that for the south china block suggesting that the gyeonggi block has been part of the south china block the gyeonggi block as the eastern part of the south china block is regarded to have thrust to its position at the present korean peninsula during the collision between the north and south china blocks

u pb ages of detrital zircons in lower cretaceous non marine successions of the gyeongsang basin northeast asia implications for sediment provenance abstract the cretaceous gyeongsang basin is the largest non marine mesozoic sedimentary basin of the korean peninsula the lower cretaceous successions of the gyeongsang basin are coevally correlated to those of the cretaceous gunsan basin in the yellow sea which is located far to the west of the gyeongsang basin this study presents u pb ages of detrital zircons to evaluate the sediment provenances of the gyeongsang basin the detrital zircon ages clearly show the different distributions between the northern uiseong area and southern jinju area areas of the gyeongsang basin the detrital zircons of the northern area have an age cluster in the jurassic or triassic whereas the detrital zircons of the southern area show a wide range of ages from early cretaceous to neoarchean in the gunsan basin detrital zircons from a core also yield ages ranging from early cretaceous to neoarchean the age distribution from the gunsan basin is similar to those of the southern gyeongsang basin except for the absence of jurassic detrital zircons the petrographic modal analysis of sandstones in the gyeongsang basin suggests a mixed provenance this study indicates that possible sediment provenances of the gyeongsang basin were shared with those of the gunsan basin we suggest that the sediment provenance of the northern gyeongsang basin was adjacent basement highs whereas sediments to the southern gyeongsang basin were probably derived from relatively distant source areas that possibly were located in the vicinity of the gunsan basin during the early cretaceous ca 113 ma

indosinian dextral ductile fault system and synkinematic plutonism in the southwest of the ogcheon belt south korea reply abstract the structure of the mylonite belt in the southwestern part of the ogcheon belt has been investigated and interpreted in the light of recent radiometric data the shear belt is composed of several en echelon dextral shear zones relayed by compressional or extensional tectonic bridges the dextral displacement along the fault system which may be extended to the hida zone of japan is of the order of 200 km it has brought into contact the ryeongnam block and its cambrian middle ordovician cover of north china affinity with the southwestern margin of the ogcheon belt characterized by cambrian middle silurian rift facies and shelf deposits of south china affinity synkinematic plutons are emplaced within the shear belt which is postdated by uppermost triassic unfoliated granitoids at the surface the shear belt generated elongated intermontane coal basins initiated as transtensional half grabens because of its post permian pre early jurassic age and its dextral kinematics we correlate the shear belt with the late stages of the akyioshi indosinian collisional orogeny of the east asian margin the synkinematic plutonism that accompanied the shear zone may be due to post collisional crustal stretching and subsequent anatexis at the mantle crust interface

first finding of eclogite facies metamorphic event in south korea and its correlation with the dabie sulu collision belt in china abstract metabasite lenses occur within granitic gneiss at bibong in the southwestern part of the gyeonggi massif south korea bibong metabasites experienced an initial eclogite facies metamorphism 17 0 20 9 kbar 835 860 c which was succeeded by a granulite facies metamorphism 11 5 14 6 kbar 830 850 c and finally overprinted by an amphibolite facies metamorphism 6 7 11 0 kbar 570 740 c the metabasites have sm nd internal isochron ages at 225 258 ma and the major elements of the metabasites display an island arc affinity the petrochemical and geochronological data suggest the southwestern part of the gyeonggi massif as an extension of the triassic dabie sulu collision belt in china

neoproterozoic bimodal volcanism in the central ogcheon belt korea age and tectonic implication abstract u pb zircon ages were determined for a metavolcanic rock from the munjuri formation in the central ogcheon belt korea four zircon fractions were analyzed of which three are nearly concordant the data define a discordia with an upper intercept at 755 8 1 3 ma and a lower intercept at 160 19 ma mswd 0 72 the upper intercept age is interpreted to indicate the timing of bimodal volcanism and the lower intercept age is interpreted to reflect jurassic thermal metamorphism this is the first definite evidence supporting the existence of a formation in the ogcheon belt that is at least in part late precambrian nd isotope and trace element geochemistry of the amphibolites and felsic metavolcanics suggests that they originated from a mantle source in a continental rift environment the rift does not appear to have matured enough to develop oceanic crust since rocks indicating deep sea environments are absent the possibility that the ogcheon belt is an extension of the east chinese collision belt as suggested by several authors is not supported by the available evidence

crustal evolution of northeastern yeongnam massif korea revealed by shrimp u pb zircon geochronology and geochemistry abstract paleoproterozoic igneous activity and metamorphism are widespread in north china and korean peninsula as a part of a precambrian tectonic unit located in the southeastern margin of korea the northeastern yeongnam massif consists mainly of metasedimentary rocks and granitoids such as the buncheon granite gneiss hongjesa granite and leucogranite here we present their shrimp zircon u pb ages and geochemical compositions magmatic oscillatory zones of zircon grains from the buncheon granite gneiss yielded a concordia age of 1990 5 ma the detrital zircon analyses of metasedimentary rocks tightly constrain the depositional age between 2 02 ga and 2 00 ga subsequently the igneous and detrital zircons were overgrown during a metamorphic overprint at ca 1 95 ga dark cathodoluminescent metamorphic rims of zircon grains from the metasedimentary rocks and buncheon granite gneiss are dated at 1 89 to 1 84 ga which is contemporaneous with the emplacement age of leucogranite all granitoids are peraluminous and show distinct eu negative anomalies also the initial whole rock end values of the granitoids are consistently negative such geochemical features are indicative of recycled crustal source rocks with residual plagioclase the granitoids are enriched in large ion lithophile elements and depleted in high field strength elements in their normalized trace element patterns which is typical of subduction zone magmas our compilation of the literature shows that the yeongnam massif lacks late archean and neoproterozoic igneous or metamorphic phases which are well recorded in the other two precambrian massifs in korea namely the gyeonggi and nangrim massifs all three massifs however show a strong metamorphic imprint at ca 1 85 ga possibly associated with the formation of the supercontinent columbia there remain ambiguities on the correlation between korean and chinese precambrian tectonic units considering discrepancies in the geochronological framework of magmatism and metamorphism

early triassic palaeomagnetic results from the ryeongnam block korean peninsula the eastern extension of the north china block greenish sandstones in the early triassic nogam formation of the ryeongnam block korean peninsula were collected at 23 sites for palaeomagnetic study a high temperature magnetization component with unblocking temperatures of 670 690 c was isolated from seven sites and yielded a positive fold test at the 95 per cent confidence level the high temperature component is interpreted to be of primary origin because the folding age is middle triassic the early triassic palaeomagnetic direction for the ryeongnam block after tilt correction is d 347 1 i 23 8 95 5 5 the palaeomagnetic pole 62 5 n 336 8 e a95 4 7 shows good agreement with the coeval pole for the north china block suggesting that the ryeongnam block has been part of the north china block at least since early triassic times a tectonic history of the korean peninsula includes obduction of the eastern part of the south china block onto the central part of the korean peninsula in the permian with the ryeongnam block geographically isolated from the main part of the north china block collision of the north and south china blocks commenced initially at the korean peninsula and suturing of the two blocks progressed westwards

timing duration and role of magmatism in wide rift systems insights from the jiaodong peninsula china east asia in east asia widespread extensional sedimentary basins together with the close association of metamorphic core complexes and magmatism are prominent features of the large scale wide rift system developed during late mesozoic times this region thus appears as a proper place to study continental extension as well as questions about the link between continental extension and magmatism this paper primarily provides pioneer exhumation time constraints on the linglong mcc jiaodong peninsula including cooling and deformation ages mcc cooling at mid crustal levels occurred at ca 143 ma besides last ductile deformation occurred at ca 134 ma while final exhumation stages under brittle 2 conditions occurred as late as ca 128 ma continuous crustal stretching were then recorded by the emplacement of a synkinematic pluton in the upper crust at ca 128 ma that cooled fast below an intracrustal shear zone crossing the ductile brittle transition at ca 123 ma the ca 120 118 ma age cluster is ascribed to the fast cooling of undeformed plutons marking the end of extension that lasted in the area over a minimum period of ca 30 my combining other mcc exhumation constraints and the onset of subsidence in the sedimentary basins total duration of late mesozoic extension in east asia could be estimated at ca 60 my related with a rather long process for extension from 160 to at least 100 ma east asian continental extension is heterogeneously distributed in space and time as revealed by fundamental differences between two end member classes of migmatite cored mcc already described in other wide rift systems extension seems to have first favoured partial melting which subsequently in turn maintained continental extension

pretectonic and posttectonic emplacements of the granitoids in the south central okchon belt south korea implications for the timing of strike slip shearing and thrusting structural analyses of three granitic plutons in the south central okchon belt of the korean peninsula reveal that the baegnok and cheongsan plutons are pretectonic with respect to right lateral strike slip ductile shearing along the cheongsan shear zone and later top to the ese thrusting whereas the boeun pluton is posttectonic with respect to these two deformation events u pb sphene age data from the three plutons indicate that the intrusion ages of the baegnok cheongsan and boeun plutons are 222 7 2 1 ma 216 9 2 2 ma and 171 7 1 4 ma respectively microstructural evidence preserved in deformed rocks from the ne striking cheongsan shear zone and adjacent nne striking thrusts suggests that the right lateral ductile shearing event along the shear zone occurred before the ese directed thrusting since these thrusts crosscut the late triassic early jurassic taedong group we estimate that the thrusts developed at 180 ma during the daebo tectonic event just prior to the intrusion of the boeun pluton we also constrain the age of the cheongsan shear zone at middle late triassic time corresponding to the songrim orogeny so that the shear zone is not related to deformation along the middle jurassic honam shear zone 176 ma the honam shear zone is not a simple tectonic boundary between the okchon belt and the yongnam massif but an anastomosing ductile shear zone not only affecting the okchon belt and the yongnam massif but also crosscutting the boundary between them at a low angle we suggest that the right lateral cheongsan shear zone is a major boundary between the okchon zone and the yongnam massif with paleozoic cover rocks the kyonggi massif and the okchon zone south china block were juxtaposed against the yongnam massif and taebaeksan basin north china block along the cheongsan shear zone during a late stage of the middle triassic songrim orogeny probably related to the late paleozoic early mesozoic collision between the north and south china blocks

spatial distribution of 1950 1800 ma metamorphic events in the north china craton implications for tectonic subdivision of the craton abstract great progress has been made in the last twenty years in understanding the unification of the north china craton according to a prevailing model it developed by amalgamation of four sub blocks by three spatially and temporally separate orogenic belts the first at 1950 ma formed the western block the second at 1900 ma created the eastern block and the third at 1850 ma unified the eastern and western blocks however new data show that the 1950 ma orogen was affected by granulite facies reequilibration at 1800 ma and parts of the 1850 ma orogen have evidence of metamorphism at 1950 1900 ma new zircon u pb ages enable the paleoproterozoic metamorphic events to be statistically sub divided into four at 1955 ma m 1 1920 ma m 2 1885 ma m 3 and 1850 ma m 4 the m 1 2 events always appear together mainly in two belt areas including the helanshan qianlishan northern ordos yinshan liangcheng huai an lushan jiaobei and liaodong regions whereas the m 3 4 events are distributed over larger areas and were superimposed on the m 1 2 activities this age distribution is inconsistent with previous models of three separate orogens it should also be noted that the igneous rocks contemporary with the regional ultra high temperature high pressure granulite facies metamorphisms m 1 2 were previously described as arc related series i e the gabbro norites i s type granites and trimodal volcanics based on the spatial distribution of the paleoproterozoic metamorphic events m 1 4 and of the coeval igneous rocks we speculate that the assembly of the ncc was created by one orogen which formed between the eastern and western cratons in two tectonic stages two marginal arcs the korean and xuwujia developed against both eastern sides of the two sub cratons and were both accreted and deformed at 1965 1900 ma m 1 2 subsequently the amalgamation of the two sub cratons resulted in metamorphism on the western side of the eastern craton and in metamorphism that was superimposed on both accreted arcs at 1900 1790 ma m 3 4

early cretaceous extensional reworking of the triassic hp uhp metamorphic orogen in eastern china corresponding to the early mesozoic continental subduction between the north china block ncb and the south china block scb the tongbaishan hong an dabieshan sulu massifs are famous for their hp uhp metamorphism more than 50 of the hp uhp orogenic belt was significantly reworked by early cretaceous extensional tectonics this early cretaceous event with a fast cooling period at 130 120 ma superimposed on the early mesozoic hp uhp orogenic belt and intensively changed the architecture of this orogen each individual segment documents different early cretaceous extensional structures namely the central tongbaishan domain is a metamorphic core complex mcc represented by an a type non cylindrical antiform the central dabieshan domain is a typical cordilleran type migmatite cored mcc the southern sulu uhp domain is a wedge shaped structure exhumed by a simple detachment fault these late stage extensional structures expose the previous hp uhp orogenic belt as fragments along the ncb scb boundary the geodynamic setting of this early cretaceous extensional tectonics along the hp uhp orogen is a part of a 1000km scale crustal extension belt that is widespread in eastern eurasia continent from trans baikal to the central part of scb convective erosion or delamination of the mantle lithosphere might be considered as a possible mechanism for mantle removal

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

nd isotopic constraints on crustal formation in the north china craton abstract recent tectonic analysis suggests that the north china craton consists of two archean continental blocks called the eastern and western blocks separated by the paleoproterozoic trans north china orogen although the published geochronological data are not sufficient to constrain the detailed tectonothermal evolution of the craton the available nd isotopic data show some important differences in nd model ages between the tectonic units the eastern block shows two main nd model age peaks one between 3 6 and 3 2 ga and the other between 3 0 and 2 6 ga limited nd isotopic data from the western block show a large range of model ages between 3 2 and 2 4 ga these differences are consistent with the recently proposed model the nd isotopic data from mantle derived mafic rocks indicate that the mantle beneath the north china craton was depleted in the archean consistent with major crustal growth during this period in the paleoproterozoic however the mantle derived mafic rocks show negative end t values implying crustal contamination this may have resulted from subduction and collision between the eastern and western block implying that the mechanisms of crustal formation and evolution may have been different between the archean and paleoproterozoic the north china craton was re activated by addition of mantle derived magma into the lower crust in the late mesozoic resulting in rejuvenation of the lower crust this indicates that underplating is also an important mechanism for continental addition although in this case it may not equate to crustal growth since it was preceded by removal of lithospheric mantle and possible some lower crust

clockwise rotations recorded in early cretaceous rocks of south korea implications for tectonic affinity between the korean peninsula and north china recent interest has focused on whether south korea may have undergone variable tectonic rotations since the cretaceous in an effort to contribute to the answer to this question we have completed a palaeomagnetic reconnaissance study of early cretaceous sedimentary and igneous rocks from the kyongsang basin in southeast korea stepwise thermal demagnetization isolated well defined characteristic magnetization in all samples the palaeomagnetic directions reveal patterns of increasing amounts of clockwise cw rotation with increasing age for aptian rock units palaeomagnetic declinations indicate clockwise vertical axis rotations of r 34 3 6 9 for the early aptian rock unit r 24 9 10 6 for the middle aptian and r 0 9 11 8 for the late aptian relative to eastern asia the new cretaceous palaeomagnetic data from this study are consistent with the hypothesis that korea and other major parts of eastern asia occupied the same relative positions in terms of palaeolatitudes in the cretaceous an analysis of and comparison with previously reported palaeomagnetic data corroborates this hypothesis and suggests that much of korea may have been connected to the north china block since the early palaeozoic a plausible cause of the rotation is the westward subduction of the kula plate underneath the asian continent which is inferred to have occurred during the cretaceous according to several geological and tectonic analyses

paleomagnetotectonics of east asia in the proto tethys ocean abstract seven paleomagnetic poles are obtained from early ordovician late carboniferous permo triassic jurassic early cretaceous miocene and quaternary rocks in korea these poles define the apparent polar wander path for the southern part of korean peninsula the comparisons of apwps from the north china block yangtze block and korea reveals that the east asia is comprised of two blocks the north sino korean and south sino korean which were parts of gondwana during the paleozoic time the north sino korean block was migrated northwards in late permian and accreted with laurasia in triassic time during middle late triassic time the north sino korean block collided with the south sino korean and subsequently divided into two the western part of the north sino korean block suffered counter clockwise rotation while the eastern part rotated clockwise until jurassic time complicated shear senses of the early mesozoic fault systems in east asia are well matched by this scenario

the kyonggi shear zone of the central korean peninsula late orogenic imprint of the north and south china collision abstract the crustal scale kyonggi shear zone of central korea has been identified as a major boundary between the precambrian kyonggi massif in the south and the imjingang belt in the north the latter is an eastward extension of the qinling dabie sulu collisional belt of china field observations and microstructural analysis indicate that the extensional shear zone evolved from a deep crustal ductile regime to a shallow crustal brittle regime associated with a rapid uplift of the kyonggi massif following the late permian early triassic collision between the sino korean and yangtze cratons a rb sr muscovite age documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 norm

shrimp u pb zircon ages of pyroclastic rocks in the bansong group taebaeksan basin south korea and their implication for the mesozoic tectonics abstract the bansong group daedong supergroup in the korean peninsula has long been considered to be an important time marker for two well known orogenies in that it was deposited after the songnim orogeny permian triassic collision of the north and south china blocks but was deformed during the early to middle jurassic daebo tectonic event here we present a new interpretation on the origin of the bansong group and associated faults on the basis of structural and geochronological data shrimp sensitive high resolution ion microprobe u pb zircon age determination of two felsic pyroclastic rocks from the bansong group formed in the foreland basin of the gongsuweon thrust in the taebaeksan basin yielded ages of 186 3 1 5 and 187 2 1 5 ma respectively indicating the deposition of the bansong group during the late early jurassic inherited zircon component indicates ca 1 9 ga source material for the volcanic rocks agreeing with known basement ages the bansong group represents syntectonic sedimentation during the late early jurassic in a compressional regime during the daebo tectonic event the northeast trending regional folds and thrusts including the deokpori gakdong and gongsuweon thrusts with a southeast vergence developed in the taebaeksan basin this is ascribed to deformation in a continental arc setting due to the northwesterly orthogonal convergence of the izanagi plate on the asiatic margin which occurred immediately after the juxtaposition of the taebaeksan basin against the okcheon basin in the late stage of the songnim orogeny thus the deokpori thrust is not a continental transform fault between the north and south china blocks but an intracontinental thrust that developed after their juxtaposition

contrasting plate tectonic styles of the qinling dabie sulu and franciscan metamorphic belts the dabie mountains are part of the 2000 km long qinling dabie sulu suture zone juxtaposing the sino korean and yangtze cratons an eastern extension apparently crosses korea and lies along the japan sea side of honshu as the imjingang and sangun terranes respectively a northeastern segment may be present in sikhote alin russian far east this orogenic belt records late paleozoic ocean floor consumption and the triassic collision of two precambrian continental massifs in east central china coesite and microdiamond inclusions in strong refractory minerals of eclogite facies ultrahigh pressure uhp metamorphic rocks in the dabie sulu area attest to profound subduction of a leading salient of the old cold yangtze craton now recovered through tectonic exhumation and erosion northward increase in intensity of subsolidus recrystallization of the suture complex is analogous to the internal progression in grade of high pressure hp and uhp metamorphism documented in the western alps in both regions subduction of narrow prongs of continental material uhp metamorphism and return toward midcrustal levels of relatively lower density buoyant microcontinental blocks resulted from delamination of these rocks from the descending higher density oceanic crust capped lithospheric plate such salients of continental crust represent an integral structural part of the downgoing slab remain intact and may be dragged to great depths before disengaging and rising differentially as coherent blocks uhp parageneses include trace mineralogic relics requiring peak metamorphic conditions of 700 900 c and 28 35 kbar or more in contrast pacific type hp metamorphic belts as represented by the franciscan complex of western california recrystallized under physical conditions up to 200 500 c 10 3 kbar in this setting voluminous quartzo feldspathic and graywacke debris was carried downward on oceanic crust capped lithosphere choking the subduction zone with incompetent material sited between both plates and strongly adhering to neither this buoyant largely sedimentary complex decoupled at 25 30 km depth and ascended toward the surface in both alpine type intracontinental collision and pacific type underflow light sialic material displaced dense mantle thus the return to midcrustal levels was propelled dominantly by body forces

late jurassic early cretaceous continental convergence and intracontinental orogenesis in east asia a synthesis of the yanshan revolution abstract the basic tectonic framework of continental east asia was produced by a series of nearly contemporaneous orogenic events in the late middle jurassic to early cretaceous commonly the late mesozoic orogenic processes were characterized by continent continent collision large scale thrusting strike slip faulting and intense crustal shortening crustal thickening regional anatexis and metamorphism followed by large scale lithospheric extension rifting and magmatism to better understand the geological processes this paper reviews and synthesizes existing multi disciplinary geologic data related to sedimentation tectonics magmatism metamorphism and geochemistry and proposes a two stage tectono thermal evolutionary history of east asia during the late middle jurassic to early cretaceous ca 170 120 ma in the first stage three orogenic belts along the continental margins were formed coevally at ca 170 135 ma i e the north mongol okhotsk orogen the east paleo pacific coastal orogen and the west bangong nujiang orogen tectonism related to the coastal orogen caused extensive intracontinental folding and thrusting that resulted in a depositional hiatus in the late jurassic as well as crustal anatexis that generated syn kinematic granites adakites and migmatites the lithosphere of the east asian continent was thickened reaching a maximum during the latest jurassic or the earliest cretaceous in the second stage ca 135 120 ma delamination of the thickened lithosphere resulted in a remarkable 120 km lithospheric thinning and the development of mantle derived magmatism mineralization metamorphic core complexes and rift basins the middle jurassic early cretaceous subduction of oceanic plates paleo pacific meso tethys and mongol okhotsk and continent continent collision e g lhasa and qiangtang along the east asian continental margins produced broad coastal and intracontinental orogens these significant tectonic activities marked by widespread intracontinental orogeny and continental reconstruction are commonly termed the yanshan revolution movement in the chinese literature

the geology of north korea an overview abstract the korean peninsula kp occupies a junction area of three big tectonic domains that are the paleo central asian orogenic belt paleo tethyan orogenic belt and the western pacific orogenic belt therefore the kp is a key area to understand the northeast asian and even global geotectonic evolution in terms of geological unit division the kp has long been thought to be closely tied with the mainland of china with using collective term the sino korea craton for the north china craton ncc however such correlation suffered from the absence of relevant geological information in north korea nk to bridge this knowledge gap our group carries out a long term collaborative study between the two sides of the kp and china and organized united field investigation in the north korea south korea sk and china as possible this paper introduces general geology in the north korea and simply make comparison with the ncc and south korea these pioneering works culminated in the following summaries 1 the kp comprises three major precambrian massifs i e rangnim gyeonggi and yeongnam massifs the rangnim and gyeonggi massifs are separated by the imjingang structural belt while the gyeonggi and yeongnam massifs are separated by the ogcheon structural belt 2 the basement of the rangnim massif is correlated with that of the ncc the characteristic metamorphic rocks of high temperature high pressure granulite facies including meta sedimentary rocks kondalites and meta sandstones and marbles with 1 9 1 8 ga metamorphic ages occur in the three massifs similar to the ncc 3 the proterozoic rift sedimentary sequences are developed in the ncc and north korea but lower paleoproterozoic strata are rare and neoproterozoic strata are more developed in north korea relative to the ncc 4 two main paleozoic basins within the rangnim massif and within the gyeonggi and yeongnam massifs are the phyongnam basin and taebaeksan basin both of them have a similar paleozoic tectono stratigraphy to the ncc 5 although the nature and tectonic significance of the imjingang belt remains controversial it doesn t show characteristics and natures of collisional orogenic belt 6 the eclogite bearing hongseong complex hsc is located in the southwestern part of the gyeonggi massif in south korea but no similar rock unit has been found in north korea 7 mesozoic igneous rocks are widespread throughout the northern and southern parts of the kp triassic magmatism is related to indosinian orogeny jurassic and cretaceous igneous rocks are different and irregular from those in the ncc on age and spatial temporal distribution this paper also suggests several key and controversial academic issues that are worthwhile to study in the future

trilobite faunal successions across the cambrian ordovician boundary intervals in korea and their correlation with china and australia abstract the cambrian ordovician boundary in korea lies within the choson supergroup exposed in the taebaeksan basin and has been recognized in the taebaek and yongwol groups the taebaek and yongwol groups show slightly different trilobite faunal successions across the putative cambrian ordovician boundary intervals in the taebaek group saukiid dominated missisquoia onychopyge and kainellid dominated faunas occur successively in the basal part of the tongjom formation while the remaining part of the tongjom formation is poorly fossiliferous the succeeding tumugol formation yields fairly diverse trilobite faunal assemblages of late tremadocian age this implies that the cambrian ordovician boundary in the taebaek group should be placed somewhere within the interval yielding the kainellid dominated fauna in the yongwol group an uppermost cambrian fatocephalus fauna is more or less contemporaneous with the saukiid dominated fauna of the taebaek group while three tremadocian trilobite faunas i e yosimuraspis kainella and shumardia zones in ascending order are well represented in the mungok formation the occurrence of jujuyaspis in the yosimuraspis zone provides a firm basis for locating the cambrian ordovician boundary at the base of the mungok formation these cambrian ordovician trilobite faunas of korea are in general well correlated with those of china and australia

the liaonan wanfu metamorphic core complexes in the liaodong peninsula two stages of exhumation and constraints on the destruction of the north china craton 1 the liaodong peninsula early cretaceous extension province lep located in the eastern part of the north china craton ncc was highly extended in early cretaceous the liaonan and the wanfu metamorphic core complexes mccs are two most important elements in the province both are typical cordilleran type core complexes that are composed of a general three layered structure but show various differences shearing along the jinzhou detachment fault zone in the liaonan mcc generated ductile to brittle tectonites various deformation microstructures and several types of quartz c axis fabrics implying that the mcc has a complicated progressive exhumation history however medium temperature microstructures and fabrics are superimposed by low temperature features along the wanfu detachment fault zone suggesting a relatively short and simple exhumation history of the wanfu mcc magmatic zircon u pb geochronological dating reveals that the early cretaceous extension of the lep began with the initiation of shearing along the jinzhou detachment fault zone and exhumation of the liaonan mcc before ca 134 ma subsequently relatively slow cooling and exhumation of the lower plate accompanied a giant magmatic event from 130 ma to 120 ma exhumation of a new mcc i e the wanfu mcc was triggered by progressive extension after ca 120 ma rapid cooling and exhumation of the metamorphic lower plate of the two mccs are attributed to coeval detachment faulting along both the jinzhou and wanfu faults from 120 ma to 113 ma the extension ended at ca 107 ma these data provide reliable evidence that the two mccs were exhumed progressively and sequentially during two stages of crustal extension of the lep our results indicates that heterogeneous lithosphere extension and upper middle crust upper mantle detachment possibly due to the interaction between the paleo pacific and eurasian plates are among the most important processes during the early cretaceous thinning of the lithosphere tectonic extension may have led to the detachment in east asia which contributed to the thinning of the lithosphere and the destruction of the ncc a phase of uniform and consistent wnw ese extension was responsible for the generation of the extensional structures in the eastern asia continent and the destruction of the ncc

correlation of paleoproterozoic igneous and metamorphic events of the korean peninsula and china its implication to the tectonics of northeast asia abstract correlation of the paleoproterozoic rocks of the korean peninsula and china has been considered to be important for the tectonic evolution of northeast asia yet it is still unclear recently considerable new data have been obtained from the korean peninsula and china providing a better opportunity to correlate the paleoproterozoic rocks of the korean peninsula and china intermediate p t metamorphism and post collisional magmatism have been found to have occurred during ca 1 95 1 83 ga not only in the jiao liao ji belt on the eastern north china craton but also in the nangrim and northern gyeonggi massifs within the korean peninsula representing that these paleoproterozoic rocks can be correlated these events occurred as a result of the collision between the longgang block of the eastern north china craton and the nangrim massifs of the korean peninsula on the other hand the southeastern gyeonggi massif underwent an arc related magmatic and metamorphic events during ca 1 96 1 91 ga suggesting that the paleoproterozoic rocks in southeastern gyeonggi massif cannot be correlated with those in northern gyeonggi massif the yeongnam massif is unlikely correlated to the nangrim and northern gyeonggi massifs and the eastern north china craton because arc related igneous activity occurred during ca 2 00 1 85 ga in the sobaeksan gneiss complex in the central to northeastern yeongnam massif the jirisan gneiss complex in the southwestern yeongnam massif underwent intermediate p t metamorphism that is followed by post collisional magmatic and low p t metamorphic events during ca 1 92 1 86 ga and these events may be correlated to those in the eastern cathaysia block on the south china craton the paleoproterozoic correlation between the korean peninsula and china in this study supports a tectonic model in which the permo triassic dabie sulu continental collision belt in china extends into the hongseong odaesan collision belt in the gyeonggi massif within the korean peninsula

in situ zircon u pb dating and whole rock geochemistry of metasedimentary rocks from south liaohe group jiao liao ji orogenic belt constraints on the depositional and metamorphic ages and implications for tectonic setting abstract the liaohe group is an important paleoproterozoic lithostratigraphic unit of the jiao liao ji orogenic belt and traditionally subdivided into the north and south liaohe groups however their tectonic setting and evolution are still a matter of debate the precise depositional and metamorphic data of the studied metasedimentary rocks from the south liaohe group provide important information on the controversial discussion of the tectonic setting and evolution based on cathodoluminescence cl imaging and connecting la icp ms u pb geochronology zircon grains separated from metasedimentary rocks of different formations of the south liaohe group were subdivided into detrital and metamorphic zircons or zircon domains igneous zircon cores of detrital zircons of the li eryu gaojiayu dashiqiao and gaixian formations yield u pb age peaks at 2130 ma 2520 ma 2160 ma 2500 ma and 2040 ma indicating that their sediments were transported from the liaoji granitoids the archean basement rocks of the adjacent complex in addition deposition age of the sedimentary precursors was investigated which must have taken place at some time after 2 05 ga 2 07 ga 2 04 ga and 1 92 ga respectively these new geochronological data can be well explained by 1 a continent arc collision model which suggests that the south liaohe group formed an intervening island arc and foreland basin sandwiched between the longgang and nangrim complexes and 2 a northward subduction of the nangrim complex source rocks of the south liaohe group these source rocks were successively deposited along the margin of the two complexes

formation of metamorphic core complexes in non over thickened continental crust a case study of liaodong peninsula east asia pre thickened hot orogenic crust is often considered a necessary condition for the formation of continental metamorphic core complexes mccs however the discovery of mccs in the liaodong peninsula where the crust has a normal thickness 35 km challenges the universality of this scenario therefore we implement a series of 2 d numerical thermo mechanical modeling experiments in which we investigate the conditions of mcc formation in normal crusts as well as the relationships between the underlying mechanisms and the syn rift basin evolution in these experiments we explore the impact of the lithostratigraphic and thermo rheological structure of the crust we also examine the lithosphere thickness strain softening extension rate and surface erosion sedimentation processes the experiments demonstrate that high thermal gradients and crustal heterogeneities result only in a symmetric spreading dome which is geometrically incompatible with the observations of the mccs in the liaodong peninsula according to our further findings the strain softening should play a key role in the development of asymmetric strain localization and domal topography uplift while synchronous surface erosion controls the polarity of the syn rift basin the synthetic model data are compatible with the geological observations and cooling history based on the thermo chronology for the eastern part of the east asia during the late mesozoic to the early cenozoic the model predicted p t t paths are essentially different from those inferred for the other known mccs confirming the exceptional character of the mcc formation in the wide rift system of the east asia

palaeozoic and mesozoic tectonic evolution and palaeogeography of east asian crustal fragments the korean peninsula in context east and southeast asia comprises a complex assembly of allochthonous continental lithospheric crustal fragments terranes together with volcanic arcs and other terranes of oceanic and accretionary complex origins located at the zone of convergence between the eurasian indoaustralian and pacific plates the former wide separation of asian terranes is indicated by contrasting faunas and floras developed on adjacent terranes due to their prior geographic separation different palaeoclimates and biogeographic isolation the boundaries between asian terranes are marked by major geological discontinuities suture zones that represent former ocean basins that once separated them in some cases the ocean basins have been completely destroyed and terrane boundaries are marked by major fault zones in other cases remnants of the ocean basins and of subduction accretion complexes remain and provide valuable information on the tectonic history of the terranes the oceans that once separated them and timings of amalgamation and accretion the various allochthonous crustal fragments of east asia have been brought into close juxtaposition by geological convergent plate tectonic processes the gondwana derived east asia crustal fragments successively rifted and separated from the margin of eastern gondwana as three elongate continental slivers in the devonian early permian and late triassic late jurassic as these three continental slivers separated from gondwana three successive ocean basins the palaeo tethys meso tethys and cenotethys opened between these and gondwana asian terranes progressively sutured to one another during the palaeozoic to cenozoic south china and indochina probably amalgamated in the early carboniferous but alternative scenarios with collision in the permo triassic have been suggested the tarim terrane accreted to eurasia in the early permian the sibumasu and qiangtang terranes collided and sutured with simao indochina east malaya in the early middle triassic and the west sumatra terrane was transported westwards to a position outboard of sibumasu during this collisional process the permo triassic also saw the progressive collision between south and north china with possible extension of this collision being recognised in the korean peninsula culminating in the late triassic north china did not finally weld to asia until the late jurassic the lhasa and west burma terranes accreted to eurasia in the late jurassic early cretaceous and proto east and southeast asia had formed palaeogeographic reconstructions illustrating the evolution and assembly of asian crustal fragments during the phanerozoic are presented d 2005 international association for gondwana research published by elsevier b v all rights reserved

possible eastward extension of chinese collision belt in south korea the imjingang belt structural petrological and geochronological data from the middle korean peninsula indicate that the qinling dabie sulu collisional belt of east central china crosses the yellow sea and extends into the imjingang belt the yeoncheon complex first identified as the western imjingang belt comprises primarily north dipping metamorphic sequences 1 the northern jingok unit consisting of barrovian type metapelites and 2 the southern samgot unit consisting of calc silicate and amphibolitic rocks south vergent structures with reverse sense shearing are dominant in the jingok unit whereas late normal sense shearing is pervasive in the samgot unit and the deformed granitoid to the south these structural patterns are interpreted to correspond to extensional deformation associated with uplift following compression in a collisional belt pressure temperature p t estimates from the amphibolites suggest a high p amphibolite facies metamorphism 8 13 kbar and 630 790 c possibly evolving from eclogite facies conditions along a clockwise p t path sm nd and rb sr geochronological data suggest that the amphibolites emplaced in late proterozoic time were metamorphosed during permian triassic time

early mesozoic alkaline complexes in the northern north china craton implications for cratonic lithospheric destruction abstract early mesozoic alkaline intrusive complexes are widespread in the northern north china craton ncc and constitute an e w trending alkaline magmatic belt that is more than 1500 km long along the northern sino korean craton our new zircon and baddeleyite u pb dating results of the yongfucun yaojiazhuang and sungezhuang alkaline complexes combined with previous geochronological data indicate emplacement of the e w trending alkaline belt in the northern ncc during the middle late triassic at around 235 220 ma geochemical and sr nd hf isotopic data suggest a common source region for the syenites pyroxene syenites and mafic rocks within the complexes they were mainly derived from a metasomatized enriched lithospheric mantle however some materials from depleted asthenospheric mantle have been involved during formation of these alkaline complexes involvement of depleted asthenospheric mantle materials indicates upwelling of the asthenospheric mantle and asthenosphere lithospheric mantle interaction in northern ncc during the early mesozoic initiation of lithospheric thinning and destruction of the northern ncc occurred in the middle late triassic which is much earlier than in other parts of the ncc during the late mesozoic delamination at the root of the subduction induced thick lithospheric mantle is likely main mechanism for the early mesozoic lithospheric thinning and destruction of the northern ncc multiple subduction of oceanic plates beneath the northern southern and eastern parts of the ncc and interactions of the surrounding orogenesis during the late paleozoic to mesozoic may play important roles on the late mesozoic lithospheric destruction of the ncc

la icp ms u pb zircon ages of the liaohe group in the eastern block of the north china craton constraints on the evolution of the jiao liao ji belt abstract as a major lithostratigraphic unit of the palaeoproterozoic jiao liao ji belt in the eastern block of the north china craton the liaohe group consists of an assemblage that is transitional from a lower arkose and volcanic rich sequence langzishan li eryu and gaojiayu formations through a middle carbonate rich sequence dashiqiao formation to an upper argillaceous sequence gaixian formation tectonically associated with the liaohe group are large volumes of granitoid rocks named the liaoji granite whose emplacement age has been dated at about 2 1 2 2 ga regionally the liaohe group and the associated liaoji granite extend along a nee trending belt that is flanked by 2 45 2 55 ga basement gneisses u pb zircon data and cathodoluminescence cl imaging are used to constrain the maximum depositional and metamorphic ages of the liaohe group which are critical in understanding the tectonic setting and history of the jiao liao ji belt cathodoluminescence images reveal that most detrital zircon grains from the liaohe group are characterized by concentric oscillatory zoning with comparatively low luminescence and high th u ratios suggesting magmatic origin but minor zircon grains have structureless overgrowth or recrystallization rims that are characterized by low th u ratio indicating metamorphic origin results of this study show that the detrital zircon grains of the langzishan formation the lowest sequence of the liaohe group have concordant u pb ages ranging from 2 05 to 2 24 ga suggesting that the liaohe group was deposited at some time after 2 05 ga although most overgrowth or recrystallization rims are too narrow to be analyzed some rims yield concordant or upper intercept ages around 1 93 ga interpreted as the peak metamorphic age of the liaohe group detrital zircon grains from the dashiqiao formation in the middle sequence of the liaohe group have concordant u pb ages ranging from 2 25 to 2 53 ga some of which are similar to those of the basement gneisses in the area this study indicates that the liaohe group was deposited after the emplacement of the liaoji granite and the latter may be a major component of the provenance for the langzishan formation in contrast the protoliths of the middle sequence of the liaohe group were most probably derived from the basement gneisses these new zircon ages for the liaohe group and recent data for the liaoji granite combined with lithological structural and metamorphic considerations support a rifting model for the evolution of the jiao liao ji belt

primary uranium sources for sedimentary hosted uranium deposits in ne china insight from basement igneous rocks of the erlian basin carboniferous permian triassic and jurassic igneous basement rocks around the erlian basin in northeast china have been investigated through detailed mineralogical whole rock geochemistry geochronological data and sm nd isotope studies carboniferous permian biotite granites and volcanic rocks belong to a calc alkaline association and were emplaced during the late carboniferous early permian 313 1 286 2 ma these rocks are characterised by positive end t 3 3 5 3 and fairly young t dm model ages 485 726 ma suggesting a dominant derivation from partial melting of earlier emplaced juvenile source rocks triassic biotite granites belong to a high k calc alkaline association and were emplaced during the middle triassic 243 3 233 2 ma their negative end t 2 to 0 1 and higher t dm model ages 703 893 ma suggest a contribution from precambrian crust during the magma generation processes leading to a strong enrichment in k and incompatible elements such as th and u highly fractionated magmas crystallised in u rich biotite up to 21 ppm u and two mica granites in biotite granite the major u bearing minerals are uranothorite and allanite they are strongly metamict and the major part of their uranium 90 has been released from the mineral structure and was available for leaching mass balance calculations show that the triassic biotite granites may have at least liberated 14 000 t u km3 and thus correspond to a major primary uranium source for the u deposits hosted in the erlian basin

metamorphic core complex dynamics and structural development field evidences from the liaodong peninsula china east asia metamorphic core complexes mcc constitute remarkable features within wide rifts based on analogue and numerical modelling mcc dynamics and structural development are mainly controlled by first geothermal gradient second the compositional layering and after the strain rate and partial melting in the late mesozoic continental extension occurred in east asia leading to the development of mcc magmatism and extensional sedimentary basins based on an integrated study i e structural and finite strain analysis petrofabrics anisotropy of magnetic susceptibility ams and u pb on zircon dating this paper aims at constraining the tectonic evolution and deformation mechanisms in the south liaodong peninsula ne china the gudaoling massif is identified as a migmatitic mcc developed from upper jurassic ca 157 154 ma to early cretaceous ca 128 113 ma intrusion of the yinmawanshan synkinematic pluton early cretaceous to the south of the dome marks out the final stages of shearing along the gudaoling detachment zone and of exhumation of the mcc into the upper crust the gudaoling mcc and the yinmawanshan pluton stay in line with the coeval south liaodong mcc to the south all making a 140x30km wide extensional band formed during a regional e w to nw se crustal stretching the area shows a bi phased development with a slow and a fast stage which correspond to 1 crustal necking and 2 dome amplification exhumation stages according to published thermo mechanical modelling results finally the gudaoling mcc lower unit almost exclusively displays migmatites and anatectic granitoids of late jurassic and early cretaceous respectively occurrence of partial melting during earlier stages of extension seems controlling the initiation of mcc as a soft anomaly within lower crust in east asia a regional scale thermal event during jurassic cretaceous times may have significantly reduced the bulk lithosphere strength and locally induced partial melting emphasizing pervasive deformations and development of a wide rift system

petrology of late paleozoic early mesozoic pyeongan group sandstones gohan area south korea and its provenance and tectonic implications abstract carboniferous to triassic strata of the pyeongan group crop out in the gohan area northeastern south korea these strata consist in ascending order of the hongjeom sadong gobangsan and nogam formations sandstones in these formations comprise three distinct framework mineral suites suite 1 sandstones hongjeom formation through the middle member of gobangsan formation are quartz and quartzose arenites wackes that contain abundant quartz little or no feldspar and few acid volcanic clasts heavy minerals are mainly tourmaline rutile and zircon suite 2 sandstones upper member of gobangsan formation are lithic arenites wackes characterized by moderate quartz content low amounts of feldspar and moderate to abundant volcanic clasts sphene is the predominant heavy mineral suite 3 sandstones nogam formation are feldspathic arenites wackes distinguished by low quartz content moderate to abundant feldspar and low amounts of acid volcanic clasts the heavy mineral assemblage of the nogam formation is characterized particularly by epidote and sphene feldspar poor suite 1 sandstones were derived from a source terrain rich in quartzite and quartzose sandstone abundant quartz and stable heavy minerals were supplied initially during late carboniferous time to a shallow marine shelf which changed gradually near the end of carboniferous time to a nonmarine paralic platform setting electron probe microanalysis shows that suite 1 tourmaline was derived originally from li poor granitoids pegmatites and ca poor aplite and metapsammite petrographic evidence demonstrates that the scarcity of feldspars in suite 1 sandstones is not the result of diagenetic intrastratal solution major changes in mineralogy from suite 1 into suite 2 and suite 3 sandstone indicate changes in provenance suite 2 sandstones were derived from diorite granodiorite acid volcanic rocks and possibly some metamorphic rocks which furnished feldspars and sphene the appearance of feldspars and volcanic rock fragments in these sandstones reflects orogenic changes and uplift resulting from incipient collision of the asian mainland and the honshu block of southwest japan compositionally immature suite 3 sandstones were derived mainly from granite granodiorite and granitic gneiss indicating continuing uplift these source rocks provided quartz k feldspar plagioclase epidote and sphene acid volcanic rocks supplied minor amounts of rock fragments

late mesozoic compressional to extensional tectonics in the yiwulushan massif ne china and its bearing on the evolution of the yinshan yanshan orogenic belt part i structural analyses and geochronological constraints abstract with a cratonic nucleus the north china craton ncc experienced a complex tectonic evolution with multiphase compressional and extensional events during mesozoic times along the northern part of the ncc the yinshan yanshan fold and thrust belt was a typical intraplate orogen jurassic and cretaceous continental sedimentation magmatism widespread intraplate characterize the yinshan yanshan orogenic belt the geodynamic significance of these tectonic events is still in dispute in the western part of the liaoning province the yiwulushan massif crops out at the eastern end of the yinshan yanshan orogenic belt the yiwulushan massif presents an elliptical domal shape with a ne sw striking long axis the structural evolution of this massif brings new insights for the understanding of the mesozoic plutonic tectonic history of the ncc a multidisciplinary study involving structural geology geochronology anisotropy of magnetic susceptibility ams and gravity modeling have been carried out the presentation of the new results splits into two parts part i this paper deals with field and laboratory structural observations and presents the main geochronological results the ams gravity modeling data will be provided in a companion paper part ii the early compressional deformation d1 corresponds to a late jurassic to early cretaceous southward thrusting the subsequent deformation is related to the early cretaceous exhumation of the yiwulushan massif a detailed structural analysis allows us to distinguish several deformation events d2 d3 and d4 the cretaceous extensional structures such as syntectonic plutons bounded by ductile normal faults metamorphic core complexes and half graben basins are recognized in many places in east asia these new data from the yiwulushan massif constitute a link between transbaikalia mongolia north china and south china indicating that nw se extensional mesozoic tectonics occurred throughout the entire region

mesozoic episodic magmatism in south korea and its tectonic implication 1 ne trending granitoid batholiths in south korea are part of the huge phanerozoic granitoid belt in east asia the crystallization ages of granitoid plutons show three episodes of mesozoic magmatism in south korea triassic 248 210 ma jurassic 197 158 ma and late cretaceous early tertiary 110 50 ma with a late jurassic early cretaceous 50 m y hiatus the granitoid ages and kinematic analyses of the mesozoic structures in south korea suggest that the middle jurassic 180 170 ma dextral strike slip ductile shear zones formed by the northwest orthogonal subduction of the izanagi plate whereas the cretaceous sinistral faults formed by the northward oblique subduction of the same plate which generally agree with proposed reconstruction of plate motions albeit uncertain around east asia among the models proposed to explain magmatic lull in a continental arc shallow angle subduction associated with high convergence rate and subduction of oceanic plateaus might be the probable cause for the magmatic hiatus in south korea and japan the huge width 500 km of the east asian granitoid belt may be explained by oceanward retreat of subduction zone in the cretaceous in association with change in the movement direction of the subducting plate

geochemistry zircon u pb ages and hf isotopic compositions of precambrian gneisses in the wonju jechon area of the southern gyeonggi massif implications for the precambrian tectonic evolution of korea and northeast asia abstract understanding the precambrian tectonic evolution of the gyeonggi massif in south korea can provide important insights into the tectonic evolution of korea and northeast asia and the geological relationship between korea and china the wonju jechon area is located in the southeastern part of the gyeonggi massif and is dominated by precambrian gneisses the protoliths of the granitic gneiss and migmatite in this area were emplaced in a collisional and or post collisional tectonic setting at ca 2 5 ga before the intrusion of the protolith of the two mica granitic gneiss in an arc related tectonic setting at 1 94 1 91 ga the intrusion of the two mica granitic gneiss was contemporaneous with the first stage of metamorphism of the granitic gneiss and migmatite in this area the protolith of the porphyritic gneiss then intruded into these granitic gneiss migmatite and two mica granitic gneiss in a post collisional tectonic setting at ca 1 79 ga the final major event recorded by these rocks is the second stage regional metamorphism at ca 285 ma zircons within the precambrian rocks in the wonju jechon area have e hf t values and isotopic model ages t dm2 that provide evidence of two stages of crustal growth at ca 3 3 and 2 7 ga and three periods of crustal reworking at ca 2 5 1 9 and 1 8 ga with generation of the protoliths of the two mica granitic and porphyritic gneisses in this area by the remelting of ancient crustal material the tectonic evolution of the southeastern gyeonggi massif differs from that of the northern gyeonggi and nangrim massifs both of which record continental collision related magmatism and metamorphism at 1 93 1 91 ga post collisional magmatism and metamorphism at ca 1 88 1 85 ga and within plate magmatism at ca 1 84 1 83 ga in comparison the tectonic evolution of the southeastern part of the gyeonggi massif is more similar to that of the northern yangtze block in the south china craton although more research is needed to confirm this relationship

frictionally modified continental shelf waves and the subinertial response to wind and deep 0cean forcing abstract analytic solutions am obtained for the barotropic shelf circulation caused by wind and deep ocean forcing at subinertial frequencies an inclined beach model of the continental shelf is used and only situations in which bottom friction is important are considered three different alongshore forces are considered pressure gradients and currents maintained by the deep ocean at the shelf break and wind stress over the shelf in each case the model is formulated as a boundary value problem in which the boundary conditions are determined by the forcing mechanism in general a damped resonant response occurs when the forcing function has the same longshore velocity as an unforced continental shelf wave and is most significant for the fim mode in the case of forcing by an alongshore pressure gradient at the edge of the shelf this leads to the amplification of the pressure signal toward the coast the model frequencies and structures are determined for various frictional values when friction is s

mesozoic terrane accretion in northeast china sikhote alin and japan regions abstract the nadanhada range in northeast china is composed of upper paleozoic limestone greenstone middle to late triassic bedded chert and middle jurassic siliceous shale these rocks are enclosed in post middle jurassic clastic rocks the lithologic association ages radiolarian assemblages and geologic structure of the nadanhada range are very similar to those of the tamba mino ashio terrane in southwest japan this indicates that the nadanhada range is the northern extension of the tamba mino ashio terrane mesozoic tectonostratigraphic terranes identified in northeast china sikhote alin and southwest japan are the khanka terrane a micro continent composed of precambrian metamorhic rocks and paleozoic to mesozoic sedimentary and volcanic covers the nadanhada western sikhote alin terrane a disrupted terrane composed of upper paleozoic to jurassic sedimentary rocks the eastern sikhote alin terrane a terrane composed mainly of early cretaceous clastics the tetyukhe terrane a disrupted terrane composed of upper paleozoic to early cretaceous sedimentary rocks the hida terrane a continent type stratigraphic terrane composed of precambrian and upper paleozoic basement covered with jurassic to cretaceous coarse clastics and the tamba mino ashio terrane a disrupted terrane composed of upper paleozoic to earliest cretaceous sedimentary rocks accretionary history of these terranes is discussed on the basis of paleomagnetic and paleobiogeographic data

cooling paths of the ne china crust during the mesozoic extensional tectonics example from the south liaodong peninsula metamorphic core complex abstract the south liaodong peninsula massif is the easternmost mesozoic metamorphic core complex recognized in eastern china it provides a good example of the combination of ductile shearing syn kinematic plutonism and polyphase exhumation the jurassic granodioritic plutons located at the footwall of the detachment normal fault and dated here at ca 160 ma recorded two different phases of cooling a slow cooling regime of about 3 10 c my prevailing before 122 ma was followed by a significant increase in cooling rate of about 40 55 c my after that time by contrast a single fast cooling path was recorded by the cretaceous monzogranite situated in the footwall of the detachment normal fault this result indicates that the jurassic and cretaceous plutons recorded different exhumation processes a jurassic slow or negligible exhumation and a cretaceous fast one assisted by normal faulting these two cooling stages correspond to distinct geodynamic processes during the jurassic and cretaceous extensional tectonics seems not significant before early cretaceous the second stage dominated by an extensional regime which develops after ca 120 ma is tentatively correlated to the lithosphere removal of the north china craton

isotopic and paleomagnetic constraints on the mesozoic tectonic evolution of south china in order to better constrain the paleogeographic evolution of south china we measured sm nd and rb sr isotopic compositions for 23 mesozoic granites that crop out throughout the area tightly grouped neodymium depleted mantle model ages 1 4 0 3 ga suggest the region is underlain by relatively homogeneous proterozoic crust and fail to define crustal provinces neither the isotopic nor geologic data suggest that a mesozoic suture exists however granites possessing anomalously high sm 8 ppm and nd 45 ppm concentrations relatively high initial epsilon neodymium 4 to 8 and high but variable initial 87sr 86sr 0 759 to 0 713 form a northeast trending zone that coincides with two prominent mesozoic basins southeast of the zone lie the majority of mesozoic intrusives and upper triassic to lower cretaceous extensional basins found in south china mesozoic paleomagnetic poles are well clustered northwest of the zone pre cretaceous poles southeast of it are discordant with respect to those from the northwest the only recognized tectonostratigraphic terrane in south china lies southeast of the zone the terrane is bordered by a northeast trending sinistral fault that was active in the mesozoic other faults in south china have similar attitudes ages and sense of shear together the observations suggest that the mesozoic tectonic regime in south china consisted of strike slip activity plus concomitant rifting as terranes or fragments of similar crust were transported north along sinistral faults the zone defined by the granites enriched in nd and sm demarcates displaced terranes to the southeast from relatively stable land to the northwest

clockwise rotation of the korean peninsula with respect to the north china block inferred from an improved early triassic palaeomagnetic pole for the ryeongnam block summary in order to detect a possible clockwise rotation of the korean peninsula with respect to the north china block early triassic rocks in the ryeongnam block korean peninsula have been restudied sandstones in the nogam formation were collected at four sites for palaeomagnetic study a high temperature magnetization component with an unblocking temperature of 690 c is isolated from all sites and yields a positive fold test at the 95 per cent confidence level this high temperature component is interpreted to be of primary origin because folding is middle triassic in age the primary directions together with previously reported ones give a new early triassic mean direction d 347 4 i 23 8 95 5 1 and corresponding palaeomagnetic pole 62 6 n 336 1 e a95 4 2 for the ryeongnam block this improved early triassic pole for the ryeongnam block is located to the west of the coeval poles for the north china block it is therefore concluded that the ryeongnam block underwent clockwise rotation of 10 15 with respect to the north china block because the amount of rotation observed in the present study is comparable with rotations observed in cretaceous results from the ryeongnam block and in the triassic cretaceous results from other blocks in the korean peninsula the whole of the korean peninsula appears to have been subjected to clockwise rotation in tertiary times

migration of igneous activities related to ridge subduction in southwest japan and the east asian continental margin from the mesozoic to the paleogene abstract in the inner zone of southwest japan the northern part of the median tectonic line mtl granites and their volcanic equivalents were formed in large quantities during the late cretaceous to early tertiary migration of magmatic activity related to ridge subduction is proposed to explain the widely distributed magmatism and its tectonics for this purpose the ages of granitic rocks were carefully inspected according to the criteria of the dating methods and procedures concerned and compiled with the sampling localities they clearly show a trend in rock ages along the mtl in agreement with the general direction of strikes in southwest japan from the trend of the ages and the cooling histories of the bodies it was concluded that the magmatism migrated eastward along the mtl with a rate of 30 km m y this migration concept is extended to the mesozoic igneous rocks of the east asian continental margin there two magmatic belts ranging in age from mesozoic to paleogene are found to become younger northeastward along the margins which is ascribed to the subduction of the farallon izanagi and kula pacific ridges

two episodes of paleoproterozoic mafic intrusions from liaoning province north china craton petrogenesis and tectonic implications abstract mafic dyke swarms constitute a common occurrence within the cratonic provinces in the world since the archean proterozoic boundary and their geneses harbor critical information for facilitating regional tectonic and supercontinental reconstruction this zircon u pb dating and geochemical study documents two episodes of paleoproterozoic mafic intrusions from liaoning province north china craton ncc the haicheng suite hcs with an emplacement age of ca 2125 ma from the liaodong peninsula and the guohua suite ghs with an age of ca 1816 ma from the western liaoning terrane the hcs meta gabbros are tholeiitic in composition with an sio 2 range from 46 to 52 modest enrichment in light rare earth elements lree and depletion in high field strength elements hfse and possess radiogenic whole rock nd nd t 1 91 to 4 21 and zircon hf hf t 4 02 to 8 48 isotopic compositions these features endow the hcs with a juvenile subduction fluid metasomatized lithospheric mantle source by contrast the ghs exhibits a meta gabbroic to dioritic composition and a transitional character from tholeiitic to calc alkali with variably enriched lrees and more evolved isotopic signatures nd t 0 20 to 5 82 zircon hf t 0 09 to 4 91 than the hcs while the relatively intact high fe gabbroic samples are supposed to represent partial melts from a fertile cratonic sub continental lithospheric mantle source in the garnet spinel stability field the low fe dioritic ones tend to bear the imprints of subsequent assimilation and fractional crystallization process apart from making an important contribution to the present archive of the paleoproterozoic mafic dyke swarms in the ncc the present two mafic magmatic suites witnessed a shift in tectonic setting from a subduction related continental arc environment to a post orogenic extensional regime synthesizing two suites with coeval felsic igneous episodes as well as concomitant episodic metamorphic events in the jiao liao ji belt leads to the characterization of a possible divergent double subduction system in the eastern ncc during the time span of ca 2 2 1 80 ga synchronized beating of episodic magmatic and metamorphic pulses in the constituent mobile belts of the ncc carries further implication of attesting to the ubiquity and importance of divergent double subduction system in the cratonic amalgamation and its incorporation within the supercontinent columbia

late cambrian biogeography conodont bioprovinces from korea abstract although the collisional belt between the north and south china blocks has been well defined in china the location of its eastward extension in the korean peninsula is highly controversial the cambro ordovician sedimentary rocks in south korea the joseon supergroup accumulated in the ogcheon belt which has been proposed as the suture zone between the north and south china blocks or the block boundary the joseon supergroup comprises five different lithostratigraphic units and may be divided into two tectonic blocks by the honam shear zone hsz in the ogcheon belt based on the affinities of the cambrian trilobite faunas previous studies correlated the yeongweol unit in the western part of the hsz with south china and the duwibong unit in the eastern part of the hsz with north china to test the above geodynamic interpretation this study analyzed and compared the degree of the provinciality of upper cambrian conodonts from the yeongweol and duwibong units and north and south china the quantitative test for the upper cambrian provincialism shows high bioprovincial affinities between the yeongweol and duwibong units and both conodont faunas from the two units display higher bioprovincial affinities with that of north china rather than with that of south china their high conodont faunal similarity suggests that the korean peninsula might have been included in a larger continental block including the north china and the korean peninsula the sino korean block in early paleozoic time this result is supported by recent studies on lower paleozoic biogeography stratigraphy and sedimentology that suggest that the yeongweol unit of the joseon supergroup is more closely correlated with north china than with south china

geochronology and geochemistry of early mesozoic magmatism in the northeastern north china craton implications for tectonic evolution abstract this paper reports geochronological geochemical zircon u pb and hf o isotopic data of the late triassic and early jurassic intrusive rocks in the northeastern north china craton ncc with the aim of reconstructing the tectonic evolution and constraining the spatial temporal extent of multiple tectonic regimes during the early mesozoic zircon u pb ages indicate that the early mesozoic magmatism in the northeastern ncc can be subdivided into two stages late triassic 221 219 ma and early jurassic 180 177 ma late triassic magmatism produced mainly granodiorite and monzogranite which occur as a ne sw trending belt parallel to the sulu jingji belt geochemically they are classified as high k calc alkaline and metaluminous to weakly peraluminous granitoids and are enriched in large ion lithophile elements liles and light rare earth elements lrees and depleted in high field strength elements hfses e g nb ta ti and p and heavy rare earth elements hrees indicating an affinity to adakite combined with their ehf t values 17 9 to 3 2 and two stage model ages 2387 1459 ma we conclude that the late triassic granitoid magma in the northeastern ncc was derived from partial melting of the thickened lower crust of the ncc and was related to deep subduction and collision between the ncc and the yangtze craton yc the early jurassic magmatism is composed mainly of monzogranites which are classified as metaluminous high k calc alkaline and i type granite their ehf t values and two stage model ages are 16 7 to 4 2 and 2282 1491 ma respectively compared with the late triassic granitoids the early jurassic granitoids have relatively high hree contents similar to calc alkaline igneous rocks in an active continental margin setting these early jurassic granitoids together with the coeval calc alkaline volcanic rocks and gabbro diorite granodiorite association in the northeastern ne asian continental margin comprise a nne ssw trending belt parallel to the ne asian continental margin indicative of the onset of paleo pacific plate subduction beneath eurasia

initial constraints on the timing of granitic magmatism in north korea using u pb zircon geochronology abstract the geology of north korea is very poorly known in this paper twenty seven granitic samples from the tumangang belt and the rangnim massif including diorite granodiorite and monzogranite were selected for in situ zircon u pb isotopic dating in the tumangang belt granites formed mainly in the jurassic with one sample giving a triassic age this is contrary to previous views that considered the granites to be permian to triassic in age in the rangnim massif precambrian granitic magmatism mainly took place at 2 1 and 1 9 1 8 ga no archean emplacement ages have been documented in this study although some inherited discordant zircon may be of this age mesozoic magmatism in this area can be divided into three stages with ages of 234 213 173 and 114 109 ma the triassic granites are mostly exposed in the north and the early cretaceous ones in the west the distribution of jurassic granites is less well documented and only one sample was identified in this study however previous data indicate they are more widely distributed in the area the 2 1 and 1 9 1 8 ga precambrian ages are comparable to paleoproterozoic magmatism in northeastern china indicating that the rangnim massif was most likely part of the north china craton during that time however the absence of 2 5 ga granites and the occurrence of 1 2 ga granites indicate that the rangnim massif was probably at the margin of the north china craton and affected by mesoproterozoic magmatism the similarity in age patterns of the mesozoic granites in north korea to surrounding areas of south korea and the liaodong peninsula of northeastern china indicate that they were controlled by subduction of the pacific ocean under eastern asia however roll back or retreat of the subduction zone resulted in a younging trend from northwest to southeast during the cretaceous

u pb ages of zircons from mesozoic intrusive rocks in the yanbian area jilin province ne china transition of the paleo asian oceanic regime to the circum pacific tectonic regime abstract geology in the yanbian area ne china is a key to understanding the relationship between the paleo pacific tectonic regime and the older paleo asian oceanic regime especially the transition between the regimes during the mesozoic a compilation of 131 u pb zircon ages including 18 obtained in the present study shows that the late paleozoic to mesozoic magmatism in the yanbian area took place from 285 to 105 ma mainly 205 160 ma and that there was a peak of activity at 175 ma and a hiatus from the late jurassic to early cretaceous 150 130 ma provisionally we subdivide the magmatic activity into four dominant stages middle permian to middle triassic 280 240 ma late triassic 230 205 ma early to middle jurassic 205 160 ma and early cretaceous 130 105 ma middle permian intrusive rocks including pyroxenite gabbro diorite granodiorite tonalite and monzogranite are interpreted to have been emplaced along an andean style continental margin in association with the subduction of the paleo asian oceanic plate the late permian middle triassic intrusive rocks are mainly quartz monzonite monzogranite and syenogranite and are considered to have been the result of syn orogenic post collisional activities the late triassic magmatism involved not only the emplacement of mafic ultramafic intrusive rocks but also coeval i and a type granitoids indicating an extensional environment after the final closure of the paleo asian ocean since the jurassic the tectonic setting has been dominated by subduction of the paleo pacific oceanic plate previously published data for the yanbian area and age data from surrounding regions show that the entire region from the yanbian area to the korean peninsula and the japanese islands experienced peaks in igneous activities that ranged from 200 to 165 ma during the jurassic and 120 to 110 ma and 90 to 65 ma during the cretaceous the jurassic intrusive rocks were emplaced mainly in the west and cretaceous intrusive rocks in the east in other words there is a southeastwards younging of mesozoic intrusive rocks that appears to have been closely associated with the evolution of the paleo pacific ocean taking all this into account we conclude that the transition from the paleo asian oceanic regime to the circum pacific tectonic regime took place during the late triassic to early jurassic

an integrated mineral system model for the gold deposits of the giant jiaodong province eastern china abstract the giant jiaodong gold province with more than 5000 t of proven gold resources is unique in that its mesozoic gold deposits are hosted in a precambrian basement block there has long been debate on the source of gold the mechanism for its extreme enrichment and a holistic genetic model for these spectacular deposits in order to improve understanding of these factors a mineral system model is proposed for the jiaodong gold deposits for the first time it is based on a detailed review of the architecture and composition of the underlying mantle lithosphere the geodynamic setting at the time of gold mineralization the geological and geochemical features of the deposits themselves and mechanisms of their preservation regional geodynamic reconstructions combined with the nature of mesozoic magmatic systems show that late mesozoic breakoff of the subduction slab and rollback of the paleo pacific plate caused asthenosphere upwelling and lithosphere extension and thinning robust geochronological studies demonstrate that the jiaodong gold deposits formed at ca 120 ma during a change of subduction direction of the paleo pacific plate and the synchronous transition of tectonic regime from regional compression to transpression or transtension prior to peak extension caused by thinning of the lithosphere geophysical exploration data and hf nd isotope mapping of the jiaodong peninsula reveal a relatively simple ancient crustal structure cut by near vertical shear or fault zones including the lithosphere scale tan lu and wulian yantai faults that provided the first order architecture for emplacement of mantle magmas and sub crustal fluids in terms of fertility the significant older pre mineralization crustal metamorphism combined with sulfur lead and strontium isotope ratios indicate a dominant sub crustal source for the ore components for the jiaodong gold deposits consistent with evidence for volatile and gold fertilized metasomatized mantle lithosphere beneath the north china block helium ar and c o isotope ratios implicate mantle sources of ore fluids with contamination by crustal components en route to crustal depositional sites in terms of crustal architecture combined geophysical structural mineralogical fluid inclusion and geochemical studies show that the deeply sourced ore fluids and metals advected upwards through lithosphere scale faults to deposit gold via sulfidation and phase separation in crustal scale nne ne trending fault systems at mid to upper crustal levels preservation of disseminated to stockwork style deposits and auriferous quartz pyrite vein deposits was enhanced by deep crustal formation combined with limited uplift and exhumation of the province the jiaodong gold deposits although commonly hosted in granite intrusions clearly post date them on the basis of robust and reliable geochronology the spatial but non temporal relationships of gold deposits with granites their strong structural control and their other characteristics clearly place them in the orogenic gold group it is suggested because of their uniqueness that they be termed jiaodong type orogenic gold deposits

petrogenesis of late triassic intrusive rocks in the northern liaodong peninsula related to decratonization of the north china craton zircon u pb age and hf o isotope evidence abstract major and trace element whole rock sr nd and hf isotopes and zircon u pb age and hf o isotope data have been determined for mafic to felsic intrusive rocks from the late triassic mayihe myh longtou chaxinzi xiaoweishahe lcx and nankouqian xidadingzi nx intrusions in the northern liaodong peninsula ne china in order to investigate their sources and petrogenesis related to decrationization of the north china craton the rocks include clinopyroxene diorite monzodiorite quartz diorite granodiorite monzogranite and mafic microgranular enclaves laser ablation inductively coupled plasma mass spectrometry la icpms and secondary ion mass spectrometer sims u pb analyses of zircon from myh lxc to nx intrusions yield late triassic ages of 224 218 ma establishing that the mafic and felsic magmas were coeval the clinopyroxene diorites from the myh pluton have high mgo concentrations at low silica contents with positive whole rock e nd t up to 3 8 and e hf t up to 6 2 and zircon e hf t values and some mantle like 18 o values they are enriched in large ion lithophile liles and light rare earth elements lrees and depleted in high field strength elements hfses which can be explained as melts derived from a depleted mantle with some subsequent crustal contamination however the diorites from the lxc and nx intrusions are high k rocks and have high mgo concentrations and mantle like 18 o values but with negative whole rock e nd t 12 9 to 7 6 and e hf t 14 0 to 5 6 and zircon e hf t values distinct from those of myh pyroxene diorites indicating that their parental magmas were derived from partial melting of an ancient lithospheric mantle the granitoids from three plutons have high sio 2 contents and low mgo concentrations suggesting they were mainly derived from crustal sources however the myh monzogranite and granodiorite have positive whole rock e nd t and e hf t up to 3 0 and zircon e hf t values indicating a juvenile crustal source whereas the lxc and nx granitoids have strong negative and variable whole rock e nd t and e hf t and zircon e hf t values indicating that they were derived from partial melting of ancient lower crustal materials with involvement of mantle components field observations geochronology geochemistry sr nd hf isotopic and zircon hf o isotopic compositions point to a complex petrogenesis where mantle and crust derived magma mixing was coupled with crystal fractionation thus explaining the genetic link between mafic and felsic rocks identification of four components i e depleted and enriched mantle and juvenile and ancient crust in the late triassic magmatism in the northern liaodong peninsula suggests a strong mantle crust interaction process related to decratonization of the north china craton

linking the sulu uhp belt to the korean peninsula evidence from eclogite precambrian basement and paleozoic sedimentary basins abstract considerable debate on whether and how the sulu orogenic belt extends eastward to the korean peninsula has remained over the past decade new results reported here include the following 1 an eclogite and retrograded eclogite bearing complex hongseong complex is discovered in south korea in which the eclogite occurs as lenses in circa 810 820 ma granitic gneiss shrimp zircon dating of the eclogite yields 230 ma for the metamorphic age and 880 ma for the protolith age 2 the basement of the rangnim gyeonggi and yeongnam massifs have affinities to the basement of the north china block ncb however the gyeonggi massif encloses a minor amount of large or small slabs of the hongseong complex that are similar to the rocks of the sulu belt 3 two main paleozoic basins within the rangnim and gyeonggi massifs have a similar paleozoic tectono stratigraphy to the ncb 4 the imjingang and ogcheon belts do not exhibit any metamorphic characteristics of collisional orogenic belts based on these facts we propose a crustal detachment and thrust model and suggest that the collision belt between the yangtze block yb and ncb sino korea craton is preserved along the western margin of the korean peninsula the lower part of the uhp metamorphosed lithosphere of the yb was subducted under the korean peninsula and not uplifted to the surface the lower crust of the yb the hongseong complex was detached from the subducted lithosphere and thrust over the korean peninsula and inserted into the basement rocks of the gyeonggi massif the upper crust of the yb possibly was detached from the lower crust and overthrusted along the honam and chugaryong shear zones the imjingang and ogcheon belts possibly represent the detached upper crust of yb and their present occurrences are controlled by a mesozoic strike slip shear structure all these detached lower and upper crustal slabs were strongly deformed during the late jurassic and early cretaceous tectonic event leading to their present geological distribution and characteristics

granulite facies metamorphism in the punggi area northeastern yeongnam massif korea and its tectonic implications for east asia abstract in the punggi area of the northeastern part of the yeongnam massif one of precambrian basement terrains in korean peninsular the metamorphic grade increases from the amphibolite to the granulite facies zones towards the southeast the boundary of the granulite facies zone is defined by the orthopyroxene opx in reaction in metabasites as metamorphic grade increases across the opx in isograd the mineral assemblage in calcic metabasites is changed from clinopyroxene amphibole plagioclase to orthopyroxene clinopyroxene amphibole plagioclase and that in alkali metabasites from garnet orthoamphibole plagioclase to garnet orthopyroxene plagioclase the metamorphic rocks in the granulite facies zone were overprinted by upper amphibolite facies retrograde metamorphism during retrograde metamorphism cordierite and spinel formed in the migmatitic gneiss the p t conditions of granulite facies metamorphism are 767 815 c and 6 0 8 4 kb and the p t conditions for the retrograde stage are 595 707 c 4 7 6 4 kb a u pb zircon age of 1904 9 ma has been obtained from a garnet granitic gneiss and is inferred to date the emplacement of its precursor this is consistent with the intrusion age of precursors to most orthogneisses in other parts of the yeongnam massif the same sample has yielded a sm nd whole rock garnet age of 617 38 ma which is inferred to represent a late proterozoic metamorphic event of upper amphibolite facies

a new concept on tectonic correlation between korea china and japan histories from the late proterozoic to cretaceous abstract the dabie sulu collision belt in china extends to the hongseong odesan belt in korea while the okcheon metamorphic belt in korea is considered as an extension of the nanhua rift within the south china block the hongseong odesan belt divides korea s gyeonggi massif into northern and southern portions the southern gyeonggi massif and the yeongnam massif are correlated with china s yangtze and cathaysia blocks respectively while the northern gyeonggi massif is part of the southern margin of the north china block the southern and northern gyeonggi massifs rifted from the rodinia supercontinent during the neoproterozoic to form the borders of the south china and north china blocks respectively subduction commenced along the southern and eastern borders of the north china block in the ordovician and continued until a triassic collision between the north china and south china blocks while subduction was occurring on the margin of the north china block high p t metamorphic belts and accretionary complexes developed along the inner zone of southwest japan from the ordovician to the permian during the subduction the hida belt in japan grew as a continental margin or continental arc collision between the north and south china blocks began in korea during the permian 290 260 ma and propagated westwards until the late triassic 230 210 ma creating the sinistral tanlu fault in china and the dextral fault in the hida and hida marginal belt in japan phanerozoic subduction and collision along the southern and western borders of the north china block led to formation of the qinling dabie sulu hongseong hida yanji belt

multiple deformations along the honam shear zone in southwestern korea constrained by rb sr dating of synkinematic fabrics implications for the mesozoic tectonic evolution of northeastern asia abstract the honam shear zone dextrally running along the southern margin of the ogcheon belt korea has drawn much attention in reconstructing the mesozoic tectonic framework of northeastern asia here we present rb sr data for the middle to southwestern part of the honam shear zone in an attempt to directly determine ages of deformation in the middle part the younger limit of deformation is constrained to be 162 11 ma by feldspar biotite rb sr dating of the deformed sunchang granodiorite on the other hand an early cretaceous deformation age is estimated for synkinematic fibers in ultramylonites from the southwestern part by two reproducible rb sr errorchrons at 138 4 and 139 23 ma this deformational time scale is consistent with earlier interpretations based on field evidence magnetic susceptibility data and age data for jurassic plutons within the shear zone our data demonstrate that the honam shear zone is not a permian to triassic tectonic feature related to the chinese continental collision

temporal and spatial variations of mesozoic magmatism and deformation in the north china craton implications for lithospheric thinning and decratonization abstract mesozoic triassic cretaceous magmatic rocks and structural deformation are widely distributed in the north china craton ncc and are crucial to understanding the timing location and geodynamic mechanisms of lithospheric thinning and decratonization of the ncc our new geochronological geochemical and structural data combined with previously published results on mesozoic magmatic rocks and deformational structures in the ncc indicate a temporal and spatial migration of magmatism and deformation from its margins to its cratonal interior triassic and early jurassic igneous rocks are only distributed along the northern southern and eastern margins of the ncc in contrast cretaceous magmatic rocks are widely distributed in whole eastern and central parts of the ncc there is a younging trend for mesozoic magmatic rocks from the northern and eastern parts yanshan jiaodong peninsula and liaodong to the central part of the ncc taihangshan mesozoic deformation in the ncc exhibits a similar migration trend from craton margins to its inland areas triassic early jurassic deformation mainly occurred in the margins of the ncc and transformed from compression during the early middle triassic to extension during the late triassic to early jurassic in its northern margin middle late jurassic to earliest cretaceous deformation is widely distributed in the ncc and exhibited non unique contractional directions usually perpendicular to boundaries of the ncc and its ordos block indicating that it was likely controlled by multiple tectonic regimes during the middle late jurassic to earliest cretaceous early cretaceous deformation was characterized by near unique nw se extension that was likely controlled by unique geodynamic regime that probably related to the far field effect of cretaceous paleo pacific plate subduction the above mentioned temporal and spatial migrations of mesozoic magmatic rocks and deformation indicate that lithospheric thinning and decratonization of the ncc was diachronous and complex the lithospheric thinning and decratonization of the ncc initially started from its northern and eastern margins as a result of post collisional post orogenic lithospheric delamination during the middle late triassic and then spread to the interior of the craton during the late mesozoic interactions of the surrounding orogenesis and the small size of the ncc may have played important roles on its late mesozoic lithospheric thinning and decratonization

early proterozoic granulites in central korea tectonic correlation with chinese cratons abstract a coherent granulite complex has been discovered in the central part of the korean peninsula formerly regarded as the eastern imjingang belt this granulite complex hwacheon granulite complex hgc experienced two cycles of tectonometamorphic events the first event corresponded to crustal thickening followed by peak granulite facies metamorphism and associated partial melting the quasi isobaric cooling path suggested by the occurrences of secondary garnet mantling orthopyroxene and secondary kyanite in mafic and pelitic granulites respectively indicates substantial residence time at midcrustal levels prior to exhumation of the hgc the timing of peak metamorphism was dated from the unzoned overgrowth rims on zircons in a migmatitic granulite at documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra

paleoproterozoic magmatic and metamorphic events in the hongcheon area southern margin of the northern gyeonggi massif in the korean peninsula and their links to the paleoproterozoic orogeny in the north china craton abstract the hongcheon area is located at the northern part of gyeonggi massif ngm in the korean peninsula the metamorphic rocks of the ngm at the hongcheon area are composed of the paleoproterozoic yongduri gneiss complex ygc euiam group eg and the euiam gneiss complex egc the quartz feldspathic gneisses in the northeastern part of the ygc record peak metamorphic temperature pressure condition of 790 840 c and 7 2 8 9 kbar whereas the granitic and garnet gneisses in the western part of the ygc record peak metamorphic temperature pressure conditions of 690 720 c and 6 1 6 9 kbar and 640 660 c and 5 0 5 4 kbar respectively the peak metamorphic conditions represent a regional low p t metamorphic event m2 in which metamorphic temperature and pressures increased towards the east shrimp zircon u pb age dating indicates that the m2 metamorphic stage occurred at ca 1886 1870 ma the presence of relict kyanite in the gneisses within the ygc suggests that the intermediate p t metamorphic stage m1 occurred in ca 1925 ma whole rock geochemistry of the metagranitoid in the egc indicates that they are originally post collision granitoid shrimp zircon u pb age dating indicates that the metagranitoid formed at ca 1885 1869 ma considering the similarity in age between the paleoproterozoic intrusion and the m2 low p t metamorphism the m2 metamorphism also occurred in a post collision tectonic setting and the m1 intermediate p t metamorphism with kyanite represents collision event further we suggest that the paleoproterozoic orogeny in the hongcheon area is closely linked to the paleoproterozoic orogeny in north korea and the jiao liao ji belt in the north china craton

neoproterozoic 900 ma sariwon sills in north korea geochronology geochemistry and implications for the evolution of the south eastern margin of the north china craton article the sariwon sills are distributed in the pyongnam basin at the center of the korean peninsula eastern part of the north china craton these sills are up to 150 m in thickness and up to more than 10 km in length baddeleyite grains separated from a 50 m thick sill give a sims 206 pb 207 pb age of 899 7 ma mswd 0 34 n 14 which is interpreted to be the crystallization age of this sill zircon grains from the same sill gives a lower intercept u pb age of 400 ma which is likely a close estimation of the greenschist facies metamorphism of this sill the sariwon sills are dolerites and have tholeiitic compositions they show enrichment of light rare earth element concentrations la ybn 1 4 2 8 and are slightly depleted in high field strength elements e g nb zr and ti in comparison to neighboring elements on the primitive mantle normalized spidergram the whole rock endt t 900 ma values are around 2 whereas in situ ehft t 900 ma values from zircon grains vary from 25 to 8 they are similar to the coeval sills in other parts of the north china craton e g the chulan sills xu huai basin shandong peninsula and the dalian sills lv da basin liaodong peninsula these sills possibly originated from a depleted mantle source e g asthenosphere rather than from the ancient lithospheric mantle of the north china craton and have experienced significant assimilation of lithospheric materials the strata and sills in the xu huai lv da and pyongnam basins are comparable moreover the three basins are geographically correlatable based on neoproterozoic geographical reconstruction we therefore propose that there is a xu huai lv da pyongnam rift system along the south eastern edge of the north china craton during neoproterozoic 900 ma with the closure of the rift at 400 ma as a result of a continent margin process it is possible that this southeastern margin of the ncc did not face the inland in the configuration of the supercontinent rodinia

formation and evolution of paleoproterozoic orogenic belt in southern jilin jiao liao ji belt north china craton constraints from geophysics abstract the tectonic setting and depositional environments of the laoling and ji an groups in the northeastern jiao liao ji belt northeastern china are controversial these paleoproterozoic stratigraphic units are exposed sporadically in baishan and tonghua beneath a thick cover of quaternary basalts meaning that only limited information can be obtained by traditional geological methods therefore using geophysical techniques in this region is pertinent here we present new data on the petrophysical properties density magnetic susceptibility and specific resistivity obtained from 2d cross gradient joint inversion profiles the results allow us to establish the relationships between the laoling and ji an groups interpret the tectonic setting of deposition and locate the subsurface margins of the jiao liao ji belt petrophysical parameters from the dataishan formation density of 2 58 g cm3 zero magnetic susceptibility and specific resistance of 103 04 m indicate that these rocks were derived predominantly from the longgang block in the north for the zhenzhumen formation the petrophysical parameters high density weak magnetic susceptibility and high specific resistivity are consistent with deposition in a passive margin that received detrital material sediments from the longgang block and the liaoji granitoids the mayihe and huangchagou formations intermediate to high density strong magnetic susceptibility and intermediate specific resistivity were deposited closer to a magmatic arc with the detritus derived from the liaoji granitoids the low to intermediate density stronger magnetic susceptibility and intermediate specific resistivity of the huashan linjiang dalizi and dadongcha formations indicate that these rocks were deposited in a pre orogenic setting with the detritus derived from the longgang block liaoji granitoids and other felsic igneous rocks based on the geophysical profiles we conclude that the jiao liao ji belt extends under quaternary basalt from linjiang to baishan and eastward towards north korea two basin controlling faults f1 and f2 represent the northern and eastern boundaries between the longgang block and the jiao liao ji belt we interpret geophysical anomalies and variations in the petrophysical parameters in the context of subduction and collision processes