where was south china in the rodinia supercontinent evidence from u pb geochronology and hf isotopes of detrital zircons abstract u pb geochronology and lu hf isotopic studies on detrital zircons from late neoproterozoic sediments of the cathaysia block south china show abundant grenville age 1 0 ga and neoarchaean populations and minor eoarchaean 3 8 ga paleo to mesoarchaean 3 3 3 0 ga mesoproterozoic 1 7 1 4 ga and pan african 0 70 0 54 ga populations this is the first report of 3 8 ga material in the crust of the cathaysia block the presence of euhedral 1 0 ga zircons indicates that a grenville orogenic belt was within or very close to the southern cathaysia block however the provenance containing the 3 8 ga 3 3 3 0 ga 2 5 ga 1 0 ga and 0 70 0 54 ga zircon populations cannot be found in the south china block the combination of zircon age distributions and the rounded strongly abraded shapes of the archean zircons suggesting long transport is consistent with derivation from other continental terranes previously linked with the southern part of the south china block comparison with the tectono magmatic history and compositions of rocks in western laurentia eastern australia and eastern india east antarctica western australia we suggest that these late neoproterozoic sediments may have originated mainly from eastern india east antarctica this indicates that the south china block was linked with the eastern india east antarctica continents in the late neoproterozoic rather than being located between the western laurentia and eastern australia continental blocks u pb and hf isotope studies on detrital zircons provide an important independent constraint on the palaeogeography of the south china block in the context of the breakup of rodinia and the subsequent assembly of gondwana in late neoproterozoic time and insights into the relationship between the cathaysia and yangtze blocks

permo carboniferous magmatism of the northeast german basin abstract variscan continent continent collision in central europe was followed by a period of syn to late tectonic magmatism involving the extrusion of large volumes of permosilesian age volcanic rocks particularly in the northeast german basin the volcanic suite up to ca 2000 m thick comprises rhyolites acid and basic andesites and tholeiitic and alkali basalts tectono geochemical analysis in conjunction with volume calculations and petrography reveals changes in volcanic activity over time a total of five eruptive stages are recognised beginning in the stephanian and extending up into the upper rotliegend permian these include the stephanian late carboniferous andesite pre ignimbrite stage i lower rotliegend permian age explosive ignimbrite stage ii post ignimbrite stage iii late rhyolite stage iv and upper rotliegend permian age late basalt stage v in addition several volcanic centres including at least two large caldera like structures are recognised the total calculated volume for the northeast german basin volcanics is ca 48 000 km3 comprising rhyolitic rocks and ignimbrites ca 70 andesitic rocks ca 26 and basalts with cogenetic dolerites ca 4 regional variations in composition and geochemistry are related to diverse crust mantle regimes which correlate with differing positions relative to the heterogeneous basement of the variscan foredeep or within the rhenohercynian orogenic zone the crustal thickening and increasing generation depth of the mafic magmas from north to south may reflect the presence of a pre existing subduction influenced basaltic magma source

composite nature of the north china granulite facies belt tectonothermal and geochronological constraints granulite facies rocks are intermittently exposed in a roughly e w trending belt that extends for approximately 2000 km across the north china craton from the helanshan qianlishan wulashan daqingshan guyang and jining complexes in the western block through the huai an hengshan xuanhua and chengde complexes in the trans north china orogen to the jianping western liaoning eastern hebei northern liaoning and southern jilin complexes in the eastern block the belt is generally referred to as the north china granulite facies belt previously interpreted as the lowest part of an obliquely exposed crust of the north china craton recent data indicate that the north china granulite facies belt is not a single terrane instead it represents components of three separate terranes the eastern and western blocks and trans north china orogen each of these units records different metamorphic histories and reflect the complex tectonic evolution of the ncc during the late archean and paleoproterozoic mafic granulites in the eastern block and the yinshan terrane western block underwent medium pressure granulite facies metamorphism at about 2 5 ga with anticlockwise p t paths involving near isobaric cooling following peak metamorphism reflecting an origin related to intrusion and underplating of mantle derived magmas pelitic granulites in the khondalite belt western block underwent medium pressure granulite facies metamorphism at about 2 0 1 9 ga with clockwise p t paths which record the paleoproterozoic amalgamation of the yinshan and ordos terranes to form the western block mafic and pelitic granulites in the trans north china orogen experienced high to medium pressure granulite facies metamorphism at 1 85 ga with clockwise p t paths involving nearly isothermal decompression following peak metamorphism which are in accord with the final collision between the eastern and western blocks to form the north china craton at 1 8 ga the ncgb cannot therefore represent a separate unique terrane instead it reflects the amalgamation of three separate granulite terranes that evolved independently and at different times d 2005 international association for gondwana research published by elsevier b v all rights reserved

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

shrimp u pb zircon geochronology of the fuping complex implications for formation and assembly of the north china craton abstract the fuping complex located within the central zone of the north china craton is composed of amphibolite to granulite facies orthogneisses interleaved with minor supracrustal rocks at similar metamorphic grade the oldest components recognised are hornblende gneiss enclaves within the predominant biotite orthogneiss which have a shrimp u pb zircon age of 2708 8 ma we consider these enclaves to represent fragments of 2 7 ga continental materials incorporated in the biotite gneiss the biotite gneiss has a shrimp u pb zircon age of 2513 12 ma interpreted to be time of magmatic crystallisation of the igneous precursor based on the igneous characteristics of the zircons this indicates a major magmatic episode at 2 52 ga in the fuping complex identical to the age of felsic volcanism within the low grade wutai complex which crops out immediately to the west a gneissic granite that intrudes the biotite gneisses has a poorly defined 207pb 206pb age of 2045 64 ma this is within error of the age of 2097 46 ma obtained from a fine grained gneiss interlayered with amphibolite of the wanzi supracrustal suite wss interpreted to be volcanic in origin zircons from both these samples have strong oscillatory zoning and provide the first indication of a palaeoproterozoic magmatic event in the area again similar in age to magmatic events recently recognised in the adjacent wutai complex these data indicate a comparable history for the fuping and wutai complexes and support geochemical evidence that they had a common origin and formed part of a late archaean arc affected by later palaeoproterozoic re activation low uranium zircons without oscillatory zoning separated from a sample of biotite gneiss yield data clustered at 1817 26 ma which is interpreted to reflect a period of new zircon growth during a major metamorphic event these data support the recently proposed tectonic model that amalgamation of the north china craton occurred due to collision of the eastern and western blocks along the central zone at 1 8 ga ago

coastal quaternary morphologies on the northern coast of the south china sea china and their implications for current tectonic models a review and preliminary study marine terraces tidal notches and sediments along a 1200 km long stretch of the northern coast of the south china sea passive margin were studied and divided into five areas with varying tectonic characters up to three marine terraces occur that have elevations reaching up to 60 m above mean sea level amsl and two marine notches occur up to 11 m amsl chronology of the morphologies and deposits was obtained mainly by comparison with quaternary sea levels derived from the oxygen isotope curve however prior to the last interglacial highstand mis 5e c 125 ka evidence of history of events is less well constrained leading to less precision on sea level positions prior to mis 5e using the morphological features of mis 5e as a marker mean coastal uplift rates in the last c 125 ka range from 0 07 mm yr to 0 18 mm yr the pattern of deformations is slightly higher than those observed on passive margin coasts in other parts of the world the cause of uplift of the south china coastline is not clear but may relate to the himalayan collision zone or any other large scale phenomena

ephemeral liquid water at the surface of the martian north polar residual cap results of numerical modelling abstract gypsum a mineral that requires water to form is common on the surface of mars most of it originated before 3 5 gyr when the red planet was more humid than now however occurrences of gypsum dune deposits around the north polar residual cap nprc seem to be surprisingly young late amazonian in age this shows that liquid water was present on mars even at times when surface conditions were as cold and dry as the present day a recently proposed mechanism for gypsum formation involves weathering of dust within ice e g niles p b michalski j 2009 nat geosci 2 215 220 however none of the previous studies have determined if this process is possible under current martian conditions here we use numerical modelling of heat transfer to show that during the warmest days of the summer solar irradiation may be sufficient to melt pure water ice located below a layer of dark dust particles albedo 0 13 lying on the steepest sections of the equator facing slopes of the spiral troughs within martian nprc during the times of high irradiance at the north pole every 51 ka caused by variation of orbital and rotational parameters of mars e g laskar j et al 2002 nature 419 375 377 this process could have taken place over larger parts of the spiral troughs the existence of small amounts of liquid water close to the surface even under current martian conditions fulfils one of the main requirements necessary to explain the formation of the extensive gypsum deposits around the nprc it also changes our understanding of the degree of current geological activity on mars and has important implications for estimating the astrobiological potential of mars

geochronological and geochemical constraints on the luliang group in the luliang complex implications for the tectonic evolution of the trans north china orogen abstract the luliang complex is located at the western margin of the middle segment of the trans north china orogen along which the western and eastern blocks amalgamated to form the basement of the north china craton the complex consists of the late neoarchean to paleoproterozoic granitic plutons and meta supracrustal rocks of which the latter are subdivided into the jiehekou luliang yejishan and heichashan lanhe groups the luliang group is composed mainly of siliciclastic rocks in the lower part and volcanic rocks in the upper part all of which have been metamorphosed from greenschist to amphibolite facies u pb ages of detrital zircons from meta sedimentary rocks in the luliang group yield four populations of 3061 2920 ma 2790 2600 ma 2599 2280 ma and 2211 2202 ma suggesting that their provenances were derived mainly from the luliang and taihua complexes in the trans north china orogen the meta volcanic rocks give igneous zircon u pb ages of 2209 2178 ma and e hf t values of 0 8 to 3 6 geochemically they are subalkaline basalts and andesites that can be classified into two groups of which one group has flat lrees weak enrichment in lrees relative to hrees and flat hrees and displays e morb like spider diagrams with the exception of insignificantly negative nb ta zr hf and ti anomalies in contrast the other group displays stronger lree fractionation stronger enrichment in lrees relative to hrees and mildly fractionated hrees and is characterized by spiky spider diagrams similar to arc volcanic rocks the first group is interpreted to have originated from a neoarchean e morb source whereas the second group shows inputs of newly subduction derived fluids in the mantle source these geochronological and geochemical signatures indicate the existence of an 2 2 2 1 ga continental back arc system in the luliang complex of the trans north china orogen which is consistent with the model that the collision between the eastern and western blocks to form the coherent basement of the north china craton in the paleoproterozoic not at the end of neoarchean

a late tournaisian synmetamorphic folding and thrusting event in the eastern variscan foreland 40 ar 39 ar evidence from the phyllites of the wolsztyn leszno high western poland a variscan foreland in western poland comprises two nw trending basement highs which are concealed under carboniferous through triassic strata of the fore sudetic monocline fsm both highs consist of multiply deformed quartz sericite albite chlorite phyllites of unknown protolith age 40ar 39ar laser probe dating of white micas in up to 0 5 mm thick mica layers which form the s2 axial plane foliation in phyllites of the wolsztyn leszno high yielded an age of 340 1 2 6 ma for the lower greenschists facies metamorphism and probably also for the f2 folding this deformation was associated and followed by thrusting which brought about the basement highs the latter delivered clasts to overlying late visean early namurian flysch basin that was mainly sourced from the saxothuringian sudetes in which most of the deformation occurred between 345 335 ma the fsm basement may represent an independent terrane referred to as the wielkopolska terrane belonging to the armorican terrane assemblage

late paleozoic volcanism in the central part of the southern permian basin ne germany w poland facies distribution and volcano topographic hiati based on facies analysis of more than 5 500 m cores of 45 deep wells three large sub provinces have been defined for the lower rotliegend volcanic rocks in the central southern permian basin spb in northeastern germany and western poland additional data came from unpublished descriptions of more than 200 wells the three sub provinces are a the mecklenburg vorpommern sub province mvsp dominated by silica rich lava domes and subvolcanic intrusions b the eastern brandenburg sub province ebsp dominated by a mg andesite shield volcano complex which extends into western poland and c the flechtingen altmark sub province fasp with prominent ignimbrite sheets punctuated by lava domes and flows whereas in ne germany thickness of up to 2 300 m have been found in places in western poland ignimbrites and other pyroclastic deposits as well as andesitic and silica rich lava complexes accumulated successions of a few hundreds of meters a hiatus of up to 30 ma occurs between the lower rotliegend volcanic and sedimentary rocks asselian sakmarian and upper rotliegend ii sediments upper wordian capitanian upper rotliegend i deposits are known from a few wells and outcrops only previous studies postulated solely intrabasinal tectonics to account for this major unconformity however under semiarid to arid conditions as assumed for the rotliegend of the spb both sio2 rich lava complexes and silica poor shield volcanoes can be expected as being extremely resistant to weathering and erosion most probably these bodies drowned in a regolith formed by physical weathering rarely removed by torrential rain thus the silica rich lava complexes and the shield volcanoes in the central european basin system cebs can be viewed as long living morphological highs with intervolcanic depressions in between in these intervolcanic depressions syn to postvolcanic successions of conglomeratic to sandy alluvial fan sediments and lake to mud flat deposits accumulated during the upper rotliegend i they show numerous pedogenic horizons representing times of non deposition during the upper rotliegend ii the remaining volcano topography was filled up with alluvial eolian and playa deposits in some places in western poland covering was not complete until the zechstein latest permian at the same time soil formation and or erosion in the upper part of sio2 rich complexes and shield volcanoes remained subordinate consequently the volcano topographic hiatus on top of the volcanic complexes comprises the maximum period of time whereas in the intervolcanic depressions this time splits into periods of deposition and numerous minor intraformational hiati intrabasinal tectonic activity cannot be ruled out as one major control of the rotliegend depositional evolution in the subsiding spb however the presence of weathering resistant volcanic edifices led to the formation of long lasting depositional gaps in many regions of the central spb

note on the paper by guochun zhao simon a wilde sanzhong li min sun matthew l grant and xuping li 2007 u pb zircon age constraints on the dongwanzi ultramafic mafic body north china confirm it is not an archean ophiolite

mapping seismic anisotropy of the lithospheric mantle beneath the northern and eastern bohemian massif central europe abstract we evaluate 3d body wave anisotropic parameters shear wave splitting fast s polarizations and delay times of the split slow shear waves and directional terms of relative p wave residuals from data of passive seismic experiment bohema ii 2004 2005 data from 34 temporary stations increased substantial density of observations in the bohemain massif bm and allowed us to scan in detail the upper mantle structure of its northern and eastern parts for the first time we delimit domains of the mantle lithosphere in this part of the bm and infer 3d self consistent models of their fabrics by a joint inversion of the body wave anisotropic parameters fabrics of the northern and north eastern parts of the bm are approximated best by peridotite aggregates with the a c foliations dipping approximately to the n and ne respectively whereas a model with the westerly dipping a lineation fits best the fabric of the south eastern domain the saxothuringian fabric nw of the eger rift extends to the east across the elbe fault zone and continues along this zone to the southeast beneath the cretaceous basin the south eastward continuation of the elbe fault zone seems to be related to the boundary between two different fabrics of the northern and southern brunovistulian domains below the moravo silesian zone this study shows an underthrusting of the brunovistulian micro plate beneath the eastern rim of the bm and indicates that its northern and southern fragments might have originally belonged to baltica and to gondwana respectively according to a zone of distinctly decreased anisotropic signals the brunovistulian micro plate extends at least about 100 km westward beneath the moldanubian with these new findings we update the domain like mantle structure of the bm and compare the results with inferences from the upper mantle velocity tomography and depth changes of the lithosphere asthenosphere boundary retrieved in a detailed model from relative residuals and from the receiver functions inferences on anisotropic structure beneath the permanent observatories included in different experiments are stable and are validated by the bohema ii experiment

erratum to marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece mar geol 179 2001 213 228 in the above paper there were the following errors references to notches in the heraion localities cut into mesozoic bedrock in the captions to figures 2 and 4 and on page 221 line 2 are incorrect the notches in the photographs are cut into pleistocene cyanobacterial mounds which are exposed in the cliis of heraion harbour and heraion north not the mesozoic limestones which are exposed in nearby locations the publisher would like to apologise for any inconvenience caused by this error

uplift and late orogenic deformation of the central european variscan belt as revealed by sediment provenance and structural record in the carboniferous foreland basin of western poland the carboniferous foreland basin of western poland contains a coherent succession of late visean through westphalian turbidites derived from a uniform group of sources located within a continental magmatic arc detrital zircon geochronology indicates that two main crustal components were present in the source area of namurian a sediments they represent late devonian and early carboniferous ages respectively the detritus from westphalian d beds is much more diversified and contains admixture of late carboniferous zircons suggesting rapid unroofing of variscan igneous intrusions in the hinterland between namurian a and westphalian d times tectonic repetitions of tens of metres thick fault bounded stratigraphic intervals recorded in several wells provide evidence for compressional regime that occurred in the sw part of the carboniferous basin not earlier than during the westphalian c and produced nw se trending folds concordant with the structural grain of the adjacent ne part of the bohemian massif

evolution and assembly of archean gneiss terranes in the godthabsfjord region southern west greenland structural metamorphic and isotopic evidence the godthabsfjord region of southern west greenland comprises several terranes that were assembled between 2750 and 2550 ma and folded during amphibolite facies metamorphism the terranes which are dominated by gneisses of different ages and show different preassembly metamorphic and structural histories are 1 the faeringehavn terrane containing the 3820 3600 ma amitsoq gneisses with granulite facies metamorphism at circa 3600 ma 2 the akia terrane containing the 3070 2940 ma nuk gneisses with granulite amphibolite facies metamorphism at circa 2980 ma 3 the tasiusarsuaq terrane containing circa 2900 ma gneisses with granulite facies metamorphism at circa 2800 ma and 4 the tre brodre terrane containing the 2800 2750 ma ikkattoq gneisses with amphibolite facies metamorphism at 2800 2750 ma metamorphic assemblages and structures formed prior to terrane assembly were variably overprinted during amphibolite facies metamorphism and heterogeneous strain associated with assembly recognition of the region as consisting of several terranes indicates that the anatomy of some archean high grade gneiss complexes may resemble that of orogens of proterozoic and phanerozoic age that formed as a consequence of plate tectonic processes

contrasting sources of late paleozoic rhyolite magma in the polish lowlands evidence from u pb ages and hf and o isotope composition in zircon the polish lowlands located southwest of the teisseyre tornquist zone within trans european suture zone were affected by bimodal but dominantly rhyolitic magmatism during the late paleozoic thanks to the inherited zircon they contain these rhyolitic rocks provide a direct source of information about the pre permian rocks underlying the polish lowland this paper presents zircon u pb geochronology and hf and o isotopic results from five drill core samples representing four rhyolites and one granite based on the ratio of inherited vs autocrystic zircon the rhyolites can be divided into two groups northern rhyolites where autocrystic zircon is more abundant and southern rhyolites where inherited zircon dominates we suggest that the magma sources and the processes responsible for generating high silica magmas differ between the northern and southern rhyolites isotopically distinct sources were available during formation of northern rhyolites as the hf and o isotopes in magmatic zircon differ between the two analysed localities of northern rhyolites a mixing between magmas formed from baltica derived mudstone siltstone sediments and avalonian basement or mantle can explain the diversity between the zircon compositions from the northern localities daszewo and wysoka kamienska conversely the southern rhyolites from our two localities contain zircon with similar compositions and these units can be further correlated with results from the north east german basin suggesting uniform source rocks over this larger region based on the ages of inherited zircon and the isotopic composition of magmatic ones we suggest that the dominant source of the southern rhyolites is variscan foreland sediments mixed with baltica avalonia derived sediments

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

foraminifera and tidal notches dating neotectonic events at korphos greece abstract fossil assemblages of foraminifera and thecamoebians from three salt marsh cores recovered at korphos greece provided evidence for five transgression events since the mid holocene marsh accretion rates based on radiocarbon dated peat and geomorphic evidence from a series of discrete v shaped submerged tidal notches indicated that these transgression events were rapid and episodic correlation of the tidal notches with the transgression horizons in the salt marsh stratigraphy revealed a stepwise pattern of relative sea level change at korphos which is best explained by coseismic subsidence related to fault displacement earthquakes associated with the hellenic subduction zone a comparison between the korphos data and a model of holocene sea level change for the peloponnesus reinforces this interpretation as sea level rose in a series of jumps by amounts greater than accounted for by eustatic and glacio hydro isostatic factors up to 2 0 m this study illustrates that by combining microfossil sedimentary and geomorphic records of past sea level change problems frequently encountered with each record individually e g dating submerged notches and autocompaction of marsh sediments may be overcome

an updated database of holocene relative sea level changes in ne aegean sea abstract the reconstruction of holocene relative sea levels has several implications ranging from the investigation of coastal vertical movements to the calibration of earth rheology models and ice sheet reconstructions the north eastern aegean sea is among the tectonically complex sectors of the eastern mediterranean mainly influenced by the activity of the north anatolian fault in this paper we created a relative sea level rsl database by expanding upon the previous compilation with recently published geological and archaeological data we reconstruct the rsl history in those aegean coastal sectors located within the south marmara microplate a broad shear zone located between western anatolia and central greece and affected by dominant strike slip faulting at times combined with a normal component then we compared it with the rsl histories obtained for the surrounding coastal sectors the analysis of the database indicated that it is not possible to define a common holocene rsl curve for the entire ne aegean as rsl history here is majorly influenced by changes in deformation patterns in addition data in our database are consistent with a continuous rsl rise in the last 6 0 ka bp in the whole ne aegean sea and cannot support the hypothesis of a mid holocene rsl highstand in the area finally we present our best estimates of late holocene rates of rsl prior to any possible acceleration during the twentieth century in the broad area of ne aegean here we identified the fastest rising rate 0 9 mm a 1 in that sector whose active tectonic deformation is mainly controlled by the north anatolian fault activity

high resolution 3d seismic model of the crustal and uppermost mantle structure in poland abstract in the area of poland a contact between the precambrian and phanerozoic europe and the carpathians has a complicated structure and a complex p wave velocity of the sedimentary cover crystalline crust moho depth and the uppermost mantle the geometry of the uppermost several kilometers of sediments is relatively well recognized from over 100 000 boreholes the vertical seismic profiling vsp from 1188 boreholes provided detailed velocity data for regional tectonic units and for stratigraphic successions from permian to the tertiary and quaternary deposits these data however do not provide information about the velocity and basement depth in the central part of the trans european suture zone tesz and in the carpathians so the data set is supplemented by 2d velocity models from 32 deep seismic sounding refraction profiles which also provide information about the crust and uppermost mantle together with the results of other methods vertical seismic profiling magnetotelluric allow for the creation of a detailed high resolution 3d model for the entire earth s crust and the uppermost mantle down to a depth of 60 km the thinnest sedimentary cover in the mazury belarus anteclise is only 0 3 to 1 km thick which increases to 7 to 8 km along the east european craton eec margin and 9 to 12 km in the tesz the variscan domain is characterized by a 1 4 km thick sedimentary cover while the carpathians are characterized by very thick sedimentary layers up to about 20 km the crystalline crust is differentiated and has a layered structure the crust beneath the west european platform wep variscan domain is characterized by p wave velocities of 5 8 6 6 km s the upper and middle crusts beneath the eec are characterized by velocities of 6 1 6 6 km s and are underlain by a high velocity lower crust with a velocity of about 7 km s a general decrease in velocity is observed from the older to the younger tectonic domains the tesz is associated with a steep dip in the moho depth from 30 35 km in the paleozoic platform to 42 52 km in the precambrian craton the new model confirms the moho depth derived from previous compilations in the tesz the lower crust has a very high seismic velocity 7 0 km s which correlates to the high p wave velocity about 8 4 km s in the uppermost mantle beneath the polish basin the cratonic area is generally characterized by high p wave velocities 8 2 km s while the phanerozoic area is characterized by velocities of 8 0 km s in the tesz very high velocities of 8 3 8 4 km s are observed and the southwestern limitation of this area coincides with a high velocity lower crust and could be continued to the nw toward the elbe line the influence of the structure for teleseismic tomography time residuals of seismic waves traveling through the 3d seismic model was analyzed lithological candidates for the crust and uppermost mantle of the eec and wep were suggested by comparison to laboratory data the presented 3d seismic model may make more reliable studies on global dynamics and geotectonic correlations particularly for sedimentary basins in the polish lowlands the napped flysch sediment series in the carpathians the basement shape the southwestern edge of the eec a high velocity lower crust and the high velocity uppermost mantle in the tesz finally the new 3d velocity model of the crust shows a heterogeneous structure and offers a starting point for the numerical modeling of deeper structures by allowing for a correction of the crustal effects in studies of the mantle heterogeneities

the timing of metamorphism in the odenwald spessart basement mid german crystalline zone new in situ electron microprobe monazite and white mica 40ar 39ar step heating ages support the proposition that the odenwald spessart basement mid german crystalline zone consists of at least two distinct crustal terranes that experienced different geological histories prior to their juxtaposition the monazite ages constrain tectonothermal events at 430 43 ma 349 14 ma 331 16 ma and 317 12 ma 316 4 ma and the 40ar 39ar analyses provide white mica ages of 322 3 ma and 324 3 ma granulite facies metamorphism occurred in the western odenwald at c 430 and 349 ma and amphibolite facies metamorphism affected the eastern odenwald and the central spessart basements between c 324 and 316 ma we interpret these data to indicate that the otzberg michelbach fault zone which separates the eastern odenwald spessart basement from the western odenwald basement is part of the rheic suture which marks the position of a major variscan plate boundary separating gondwana and avalonia derived crustal terranes the age of the carboniferous granulite facies event in the western odenwald overlaps with the minimum age of eclogite facies metamorphism in the adjacent eastern odenwald the granulite and eclogite facies rocks experienced contrasting pressure temperature paths but occur in close spatial proximity being separated by the rheic suture as high pressure and high temperature metamorphisms are of similar age we interpret the odenwald spessart basement as a paired metamorphic belt and propose that the adjacent high pressure and high temperature rocks were metamorphosed in the same subduction zone system juxtaposition of these rocks occurred during the final stages of the variscan orogeny along the rheic suture

syn collisional channel flow and exhumation of paleoproterozoic high pressure rocks in the trans north china orogen the critical role of partial melting and orogenic bending within the paleoproterozoic trans north china orogen the high pressure belt hpb is made of high pressure 15 kbar mafic granulites hosted in migmatitic gneisses in this contribution we document a set of structural analyses acquired over the whole hpb we also proposed a morphological subdivision of the partially molten rocks that compose the hpb according to changes in melt fraction a compilation of the p t and radiochronological data carried out over the last 15 years is presented the results highlight the concurrent effect of oroclinal bending and partial melting in controlling the exhumation of the deeply buried continental crust during ongoing compression of the thickening orogenic root onset of partial melting at peak metamorphism is responsible for a first strength drop that enhanced an eastward lateral flow radiometric ages show that the deep crust was partially molten over a 50 ma lasting period during which it evolved in a diatexite core mantled by metatexites this was responsible for a second strength drop with strain concentrated along the diatexite metatexite boundaries as exemplified by the newly documented datong chengde shear zone a 400 km long normal shear zone with a sinistral strike slip component that accommodated the final uprise of the high pressure rocks

petrochemistry and sr pb and nd isotopic geochemistry of early precambrian rocks wutaishan and taihangshan areas china abstract in the wutaishan and taihangshan region china the lowermost high grade metamorphic complex of grey gneiss and amphibolite the fuping complex gives a 2 2 0 2 ga pb pb isochron age with a first stage growth 7 73 and a 2 37 0 07 ga sm nd isochron age with 143nd 144nd 0 0 50963 0 00005 or nd t 1 50 nd depleted mantle model dates tdm of amhibolites 2 48 to 2 60 ga those of gneisses are 2 43 to 2 46 ga the unconformably overlying medium to low grade metavolcanic complex the wutai complex gives a 2 0 0 1 ga rb sr isochron age with 87 86sr 0 0 7025 2 a 2 27 0 02 ga pb pb isochron date with afirst stage growth 7 73 and a 2 26 0 06 ga sm nd isochron first stage 143nd 144nd 0 0 5097 2 or nd t 1 08 individual sample nd depleted mantle model date are 2 5 ga metavolcanic samples from low grade metasedimentary rocks of the hutuo group all lie close to a 2 3 ga reference line on a rb sr isochron plot have nd tdm 2 32 2 34 and 2 62 ga from previous geological work published u pb zircon dating and ourisotopic and geochemical results we infer that the fuping rocks formed 2 6 ga ago in an environment like a modern island arc the wutai complex formed by 2 5 ga ago mostly formed in a tectonic setting similar to that of the fuping complex with the exception that one volcanic cycle formed in an environment like a modern mor and one unit formed in an environment transitional between modern within plate and plate margin settings the hutuo group formed 2 4 ga ago in a within plate tectonic environment there is no evidence for continental crust before 2 6 ga in the wutaishan and taihangshan region this contradicts previous assignment of the fuping complex to 2 8 ga ol older the fuping complex is not an early nucleus of the sino korean craton the new data also confirm that the wutai complex is older than its original assignment as early proterozoic the sm nd systems for metabasaltic rocks in the region either in amphibolite facies or in greenschist facies are all significantly disturbed in contrast with the undisturbed sm nd reported in previous studies of the sino korea craton this study provides further evidence that the archean igneous rocks in china formed at different times from heterogeneous and depleted mantle sources

depositional age and provenance of the wutai group evidence from zircon u pb and lu hf isotopes and whole rock geochemistry abstract the hengshan wutai fuping area is situated in the middle segment of the trans north china orogen and consists of the upper amphibolite to granulite facies hengshan and fuping complexes and the intervening greenschist to lower amphibolite facies wutai complex the wutai complex is composed of neoarchean to paleoproterozoic granitoids and low grade metamorphosed supracrustal rocks of which the latter are further divided into the wutai and hutuo groups geochemistry of the meta sedimentary samples from the wutai group indicates weak to moderate source weathering dominantly compositional variation trend and major felsic with few mafic source rocks on the tectonic discrimination plots most of the samples display continental island arc and active continental margin features u pb ages of detrital and xenocrystic zircons from the wutai group yield two major age populations of 2565 2465 ma and 2729 2676 ma and a subordinate age population of 2372 2331 ma the major 2522 ma and 2699 ma zircons were most likely derived from the wutai meta volcanic rocks the minor 2348 ma zircons are only found from the upper gaofan subgroup and most likely sourced from the 2360 2330 ma orthogneisses in the hengshan complex the maximum depositional ages of 2535 2516 ma from the meta sedimentary rocks are consistent with the eruption ages of 2548 2513 ma from meta volcanic rocks in the lower shizui and middle taihuai subgroups indicating coeval sedimentation and volcanism in a fore arc or intra arc basin this favors a tectonically juxtaposed contact rather than a layer cake model however the maximum depositional age of 2348 ma and the 2176 2161 ma felsic intrusions suggest a much younger formation age for the gaofan subgroup

is the teisseyre tornquist zone an ancient plate boundary of baltica the teisseyre tornquist zone ttz is generally regarded as a fossil plate boundary in europe that extends 2000 km from the baltic sea to the black sea we used an integrated approach merging potential fields and seismic data to explore crustal architecture across the ttz in central poland the aim of the study was to test whether the ttz coincides with an early paleozoic caledonian suture formed through the closure of the tornquist ocean along the sw baltica margin the suture is presumed to separate the east european craton eec from the paleozoic terranes of western europe two seismic reflection lines from the polandspan experiment were used to image the deep structure at the sw margin of the eec lines pl 5300 and pl 5400 run ne sw in central and northern poland respectively the seismic interpretation down to top of basement was integrated with 2 d gravity and magnetic modeling to highlight the structure of the deep crust both the gravity and magnetic models show a suture that welds together two blocks at the base of crust however top of basement above the suture dips uniformly to the sw and is overlain by undisturbed lower paleozoic and younger sediments by implication the suture must have developed in the precambrian and both crustal blocks amalgamated belong to the eec consequently the caledonian suture formed by the closure of the tornquist ocean between avalonia and baltica must be located farther southwest beneath thick upper paleozoic and mesozoic sediments

late paleoproterozoic 1900 1800ma nappe stacking and polyphase deformation in the hengshan wutaishan area implications for the understanding of the trans north china belt north china craton abstract the hengshan wutaishan area forms part of the trans north china belt developed in response to the final amalgamation of the north china craton the hengshan wutaishan domain and the adjacent fuping massif constitute the largest and the most representative rock exposure of the belt a structural study allows us to redefine the lithological and tectonic units that compose the architecture of the hengshan wutaishan domain and to propose that the trans north china belt was built up through a polyphase tectonic evolution within the period 1900 1800 ma the first event d1 corresponds to the emplacement of lower and upper nappes herein called the orthogneiss and volcanites unit ovu and the low grade mafic unit lgmu respectively the ovu mainly consists of rocks formed in an arc system and metamorphosed under amphibolite facies conditions whereas the lgmu represents oceanic crust rocks with an arc component that underwent greenschist facies metamorphism the syn metamorphic d1 deformation is characterized by a nw se stretching and mineral lineation with a top to the se sense of shear that corresponds to the sense of nappe motion u th pb epm chemical dating on monazite from three metapelites of the ovu gives isochron ages of 1884 11 ma 1886 5 ma and 1887 4 ma interpreted as the age of the prograde amphibolite facies metamorphism coeval with nappe stacking during the d1 event the d2 event corresponds to a widespread crustal melting of the ovu and underlying basement rocks in hengshan related to the exhumation of deep structures about 20 30 ma after nappe emplacement the migmatite contains blocks of retrograded eclogite or hp granulitic restites and is characterized by the development of a pervasive foliation and lineation a late d2 event represents the folding stage of the migmatitic foliation during the completion of a dome the orthogneiss and volcanics unit and the low grade mafic unit are unconformably covered by weakly metamorphosed to unmetamorphosed sediments belonging to the hutuo supergroup these rocks were deformed by a ductile d3 event characterized by a nw se trending stretching lineation south verging folds associated with an axial planar slaty cleavage and an e w crenulation lineation lastly a left lateral wrenching along the zhujiafang shear zone separates the northern and southern parts of hengshan our structural study shows that there is no significant difference between the southern part of hengshan and the lower part of wutaishan both areas belong to ovu and show a structural continuity we suggest that this polyphase deformation developed in response to a north westward subduction of an old ocean named the luliang ocean beneath the western block followed by collision with a micro continent named the fuping block at 1890 1880 ma

topography of the variscan orogen in europe failed not collapsed the variscan orogenic collage consists of three subduction collision systems rheno hercynian saxo thuringian and massif central moldanubian devonian to early carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts but also in post tectonic basins within these foreland belts and on the cadomian crust of peri gondwanan microcontinental fragments which represent the upper plates of the subduction collision zones these marine basins preclude high elevations in the respective areas and also in their neighbourhood widespread late carboniferous intra montane basins with their coal bearing sequences are likewise incompatible with high and dry plateaus while narrow belts with high elevations remain possible along active margins within the orogen comparison of the variscides with the himalaya tibetan plateau is unfounded plausible reasons for the scarcity of high variscan relief include subduction of oceanic and even continental crust subduction erosion orogen parallel extension and most important lithospheric thinning accompanied by high heat flow and magmatism in many areas timing and areal array of magmatism and ht metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse it is suggested instead that lithospheric thinning and heating are due to mantle activities caused by the tethys rift the lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift in terms of topography the variscides represent a failed orogen the ht regime also explains the abundance of granitoids and ht lp metamorphic rocks typical of the variscides melting in the ht regime extracted mafic components from variscan and cadomian crust as well as from cadomian metasomatized lithospheric mantle thus mimicking subduction related magmatism the onset of the ht regime at c 340 ma may also have triggered the final ascent of hp uhp felsic metamorphic rocks

seismic basement in poland the area of contact between precambrian and phanerozoic europe in poland has complicated structure of sedimentary cover and basement the thinnest sedimentary cover in the mazury belarus anteclize is only 0 3 1 km thick increases to 7 8 km along the east european craton margin and 9 12 km in the trans european suture zone tesz the variscan domain is characterized by a 1 to 2 km thick sedimentary cover while the carpathians are characterized by very thick sediments up to c 20 km the map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles these maps do not provide data about the basement depth in the central part of the tesz and in the carpathians therefore the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high resistivity low conductivity layer from magnetotelluric soundings identified as a basement all of these data provide knowledge about the basement depth and of p wave seismic velocities of the crystalline and consolidated type of basement for the whole area of poland finally the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area

remnants of an archean oceanic plateau belingwe greenstone belt zimbabwe stratigraphic and structural data from the archean zimbabwe craton suggest that a major detachment surface exists within the belingwe greenstone belt the surface separates ultramafic and mafic magmatic rocks of the upper greenstones in the hanging wall from an ancient gneiss complex older volcanic sedimentary rocks and a shallow water sedimentary sequence in the footwall rocks dated at ca 2 7 ga above the detachment surface form the proposed mberengwa allochthon the regionally extensive upper greenstone succession represents tectonically emplaced allochthonous sheets not indigenous magmas erupted within autochthonous continental rifts magmatic rocks of the mberengwa allochthon resemble oceanic plateaus preserved in younger mountain belts comparison of the zimbabwe craton with the proterozoic birrimian terranes of west africa leads us to suggest that precambrian continental growth may have been characterized by intense structural imbrication related to the difficulty of subduction of buoyant oceanic lithosphere

different modes of the late cretaceous early tertiary inversion in the north german and polish basins several selected seismic lines are used to show and compare the modes of late cretaceous early tertiary inversion within the north german and polish basins these seismic data illustrate an important difference in the allocation of major zones of basement thick skinned deformation and maximum uplift within both basins the most important inversion related uplift of the polish basin was localised in its axial part the mid polish trough whereas the basement in the axial part of the north german basin remained virtually flat the latter was uplifted along the sw and to a smaller degree the ne margins of the north german basin presently defined by the elbe fault system and the grimmen high respectively the different location of the basement inversion and uplift within the north german and polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the wnw ese trending elbe fault system and by the nw se striking teisseyre tornquist zone the latter underlying the mid polish trough therefore the inversion of the polish and north german basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis the inversion of the mid polish trough was connected with the reactivation of normal basement fault zones responsible for its permo mesozoic subsidence these faults zones inverted as reverse faults facilitated the uplift of the mid polish trough in the order of 1 3 km in contrast inversion of the north german basin rarely re used structures active during its subsidence basement inversion and uplift in the range of 3 4 km was focused at the elbe fault system which has remained quiescent in the triassic and jurassic but reproduced the direction of an earlier variscan structural grain in contrast n s oriented mesozoic grabens and troughs in the central part of the north german basin avoided significant inversion as they were oriented parallel to the direction of the inferred late cretaceous early tertiary compression the comparison of the north german and polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field a thick zechstein salt layer in the central parts of the north german basin and the mid polish trough caused mechanical decoupling between the sub salt basement and the supra salt sedimentary cover resultant thin skinned inversion was manifested by the formation of various structures developed entirely in the supra salt mesozoic cenozoic succession the zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution only in parts of the ngb and mpt characterised by either thin or missing zechstein evaporites thick skinned inversion directly controlled inversion related deformations of the sedimentary cover inversion of the permo mesozoic fill within the mid polish trough was achieved by a regional elevation above uplifted basement blocks conversely in the north german basin horizontal stress must have been transferred into the salt cover across the basin from its sw margin towards the basins centre this must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion related basement faults are seismically detected apart from the basin margins this strain decoupling in the interior of the north german basin was enhanced by the presence of the elbe fault system which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred late cretaceous early tertiary far field compression

upb zircon geochronology of late archaean metamorphic rocks in the taihangshan wutaishan area north china abstract a geochronological study has been made in the taihangshan wutaishan area shanxi province on a sequence of precambrian supracrustal rocks and stratigraphically related intrusives these constitute part of the north china basement block the oldest rocks of the fuping group consist predominantly of mafic granulites paragneisses quartzites and amphibolites this group was always considered archaean and early k ar measurements yielded some minimum ages as old as 2300 ma and others as young as 1500 1900 ma the unconformably overlying wutai group is considered as the base of the proterozoic succession and consists of amphibolite grade paragneisses carbonates and amphibolites in its lower part and greenschist grade clastic sediments and volcanics in its upper part it has given apparent k ar mineral ages between 1500 and 2000 ma present investigations have employed the u pb zircon approach on selected parts of the sequences to provide direct depositional ages or age constraints for the fuping and wutai groups and to find the age s of subsequent metamorphic processes a minimum age for the fuping group and maximum age for the wutai group has been derived from zircon age measurements on the lanzhishan granite 2560 9 ma which intrudes the fuping group and is unconformably overlain by the wutai group this late archaean result can be interpreted as the age of an igneous crystallization event and therefore a maximum for the depositional age of the wutai group the above result is well substantiated by zircon dating of the wutai group itself zircons from a low grade metamorphosed keratophyric lava in the upper part of the group give a volcanic crystallization age of 2520 17 ma this provides close constraints for the age of deposition of the wutai group at between 2560 and 2520 ma ago if the wutai group is indeed basal proterozoic the archaean proterozoic boundary in this part of china is also dated at between 2560 and 2520 ma further evidence as to the antiquity of the wutai group comes from a u pb zircon age of 2520 30 ma for the ekou granite which intrudes the wutai group sequence the age of the underlying late archaean rocks in the tainhangshan wutaishan area the fuping group could not be directly determined because of the paucity of volcanic markers and the higher grade of metamorphism its minimum age is 2560 ma see above but only an approximate maximum age can be gleaned from the zircon systematics in granulite and amphibolite grade paragneiss samples these data indicate a degree of pb inheritance which combined with metamorphic disturbance and more recent pb loss inhibit any further interpretation other than that they indicate an approximate maximum age of around 2800 ma several of the paragneisses and one amphibolitic schist contain zircon systems which are interpreted as having completely responded to a well defined amphibolite facies metamorphic event at 2500 ma ago a younger but less well defined metamorphism caused complete pb loss from zircon and recrystallization in the amphibolite and granulite facies terrains at between 2000 and 1800 ma ago rocks which show evidence of this younger metamorphic event were not recognized from the field or structural data base but from the distribution of the few such samples analyzed it seems possible that this younger terrain may now be interpretable as a cross cutting proterozoic mobile belt this proterozoic metamorphic province is also reflected by k ar mica ages between 1600 and 2000 ma and some preliminary rb sr total rock ages at 1700 ma on nearby paragneisses whose u pb zircon age is 2500 ma

deep temperature distribution along three profiles crossing the teisseyre tornquist tectonic zone in poland abstract the teisseyre tornquist tectonic zone is a large deep fracture zone separating the precambrian east european craton from the variscan system of central europe with the use of ample deep seismic sounding data the detailed crustal temperature distribution was calculated for three profiles crossing this zone in its northern central and southern segments the conversion technique of transforming the reported seismic velocities p into heat production values a was used together with the temperature dependent thermal conductivity structure and the observed surface heat flow pattern in addition to the obtained 2 d temperature distribution this work allowed a more reliable estimate of the crustal contribution to the surface heat flow and thus the characteristic moho heat flow q m 26 mw m 2 to be assessed in this region the results can also serve as an independent confirmation of the necessity of applying the p a conversion separately for phanerozoic and for precambrian rocks

determining precambrian crustal evolution in china a case study from wutaishan shanxi province demonstrating the application of precise shrimp u pb geochronology

geochemical constraints on the genesis of the ekou banded iron formation shanxi province north china the ekou banded iron formation bif in the wutai area is hosted within the late archean baizhiyan formation the mineral assemblage is used to identify oxide and silicate facies the oxide facies is composed of magnetite and quartz and the silicate facies is characterized by the presence of silicate minerals a geochemical analysis shows that the major elemental compositions are dominantly sio2 and fe2o3t with very little al2o3 and tio2 and minor abundances of incompatible elements and transition elements these results indicate that negligible terrigenous materials were involved in the bif deposition the rare earth elements rees normalized by post archean australian shale exhibit the characteristics of light ree lree depletion heavy ree hree enrichment and positive la y and eu anomalies the y ho ratios are superchondritic these results indicate that the material that formed the ekou bif originated from the mixing of seawater and submarine hydrothermal fluids a ce anomaly deficiency and heavy fe isotope enrichment indicate that the ekou bif formed in an anoxic marine environment the 30sinbs 28 values for quartz in the ekou bif are similar to those of other bifs with distribution ranges of modern sinters and black smokers the 18ov smow distribution is similar to that of hydrothermal sedimentary siliceous rocks these results suggest that the formation of the ekou bif was closely connected to submarine volcanic exhalation activity

the wutaishan orogenic belt within the shanxi province northern china a record of late archaean collision tectonics abstract the archaean crust of northeastern shanxi province northern china is dominated by three distinct terranes the high grade gneiss terranes hengshan in the north and fuping in the southeast and the intervening low grade terrane of the wutaishan belt the 2 5 ga beitai arc complex which constitutes the major part of the wutaishan belt is interpreted as a pre collision magmatic arc there was a marginal sea basin between the beitai arc and the fuping terrane at the fore arc collision stage the passive margin deposits which occurred along the western margin of the fuping terrane became a foreland fold thrust belt after the closure of the marginal sea basin the remnants of sea floor occur as a melange zone along the suture zone between the beitai arc and fuping terrane nearly at the same time at 2 5 ga the back arc oceanic lithosphere started to subduct beneath the hengshan terrane then the hengshan terrane came into collision with the arc and the fuping terrane some dismembered sea floor rocks are preserved as a back arc melange zone between the hengshan terrane and the beitai arc the term wutaishan orogeny should be reserved for the processes which lasted from 2600 to 2450 ma

variability of trace element uptake in marine reptile bones from three triassic sites s poland influence of diagenetic processes on the host rock and significance of the applied methodology abstract diagenetic alternation of apatite building vertebrate bioclasts is a complex process it is influenced by numerous factors but the impact of diagenetic processes affecting the host rock is commonly underestimated the present study aims at identifying the causes of different concentration levels and distribution patterns of ree and at examining the significance of the material chosen for normalisation we measured ree and other trace element concentrations in three bone assemblages of triassic marine reptiles using la icp ms and in the host rocks using icp ms two groups of hard parts reveal clearly different trace element contents and distribution patterns the remains from gogolin show a distinct mreen enrichment which must have been caused by replacement involving numerous substitutions that was possible due to a relatively high porosity of the host rocks and the presence of pore water the mreen enrichment and low concentrations of mg and sr combined with a relatively high content of u in these bones indicate solutions derived from meteoric water as the source of the incorporated ions the reductive dissolution of fe oxyhydroxides that are abundant in the host rock matrix and that likely were an important source of ree may have influenced and controlled the ree uptake the significant hreen enrichment over lreen as revealed in the rust coloured bones from raciborowice gorne is likely connected with local acidification of the pore water resulting from aqueous oxidation of pyrite infilling the pore spaces in the bones the material selected for normalisation of the chemical composition of apatite can have a significant impact on values of the normalised data used further for interpretations particularly when vertebrate bioclasts from carbonate host rocks are involved the carbonate rocks have element ratios that differ from those characterising the commonly used paas and nasc normalisation materials in particular ce anomaly values can distinctly vary depending on the applied normalisation procedure vertebrate hard parts that definitely spent more time in a host rock than in an animal body must be rigidly handled as a constituent of a specific rock never as a separate item

accretion of japanese island arcs and implications for the origin of archean greenstone belts the present day region of arc arc collision between the izu bonin arc and mainland japan honshu arc in the western pacific called the izu collision zone or icz provides a useful kinematic model for the development of many archean greenstone belts the compositional assemblage thermal structure and structural style of the crust in the icz are very similar to those inferred for many archean greenstone belts in both cases thick young and flaky arc crust with a high heat flux is in collision with another crustal block the icz has resulted in the imbrication of very thick slices of crust and associated sediments juxtaposed against older accretionary prisms many archean greenstone belts show similar geological features and we suggest that the incremental imbrication of the crust was a common tectonic style in some archean convergent margins

deformation history of the hengshan complex implications for the tectonic evolution of the trans north china orogen structural analysis indicates that the hengshan complex underwent five distinct episodes of deformation d1 d5 the d1 episode formed small isoclinal folds f1 penetrative axial planar foliations s1 and mineral stretching lineations l1 d1 fabrics were reworked by following d2 deformation associated with d2 was the development of nw verging asymmetric folds and accompanying thrust faults both d1 and d2 resulted from crustal thickening and coherent with prograde and peak metamorphism d2 deformation was followed by transpressional dextral shearing d3 including top to nw oblique slip shearing and nne ssw dextral strike slip shearing ongoing collision led to development of the zhujiafang ductile shear zone d4 a near e w trending high strain belt across the hengshan complex d5 deformation is characterized by f5 open folds and associated normal faults probably related to exhumation of the complex structural patterns of the hengshan complex can place important insights into a recently proposed tectonic model suggesting that an ocean between the eastern and western blocks underwent eastward directed subduction beneath the western margin of the eastern block and closure of this ocean finally led to collision between the two blocks to form the coherent north china craton

age and tectonic setting of the jingangku besshi type volcanogenic massive sulfide deposit from the northern shanxi north china craton abstract the jingangku volcanogenic massive sulfide deposit is one of the largest archean deposits in china it is located in the wutai greenstone belt in the northern part of the central orogenic belt in the north china craton the deformed deposit is hosted in a suite of neoarchean metamorphosed volcano sedimentary rocks mica quartz schist plagioamphibolite plagioclase schist and bif the orebodies are characterized by massive pyrite and contain varied amounts of chalcopyrite pyrrhotite and sphalerite the country rock of the jingangku vms ores shows intense chloritization silicification sericitization and carbonation the vms hosted pyrite and copper deposit is represented by the jingangku deposit that yielded a la icp ms zircon age of 2500 15 ma mswd 0 87 the other two vms hosted pyrite and copper deposits are represented by the houping and haoditang deposits that formed between 2494 ma and 2507 ma the late neoarchean vms deposits can be interpreted to have formed in a forearc setting and subsequently tectonically transported in melange belts during continental collision quite similar to the younger besshi type deposits in japan analyses of fluid inclusions from ore bearing magnetite quartzite showed the composition of metamorphic fluid to be h2o nacl co2 ch4 n2 h2 the analysis also showed that during the peak of metamorphism the fluid was characterized by medium high temperature 322 473 and low salinity 2 2 6 74 sulfide orebodies are closely associated with the magnetite quartzite and therefore it is proposed that both the sulfide and magnetite quartzite were derived from the same material source and have the same formation age and underwent the same history of deformation and metamorphism consequently the jingangku deposit most likely formed from submarine exhalative sedimentation and later superimposed and transformed by metamorphic fluid

nd isotopic and geochemical constraints on the provenance and tectonic setting of the low grade meta sedimentary rocks from the trans north china orogen north china craton abstract in the trans north china orogen tnco of the north china craton low grade supracrustal successions extensively occur in the wutai luliang zanhuang zhongtiao and dengfeng complexes from north to south meta sedimentary samples from the wutai and zhongtiao complexes were collected for geochemical and nd isotopic studies and several samples from the zanhuang and dengfeng complexes were also analyzed for nd isotopic studies for comparative purpose most of the meta siltstones and meta sandstones from the wutai and zhongtiao complexes are characterized by depletions in mobile elements like cao sr and na2o high chemical index of weathering ciw values and strong positive correlation between al2o3 and tio2 indicating intense weathering conditions significant post depositional k metasomatism is indicated in the a cn k diagrams for most of the analyzed samples and the relatively high pre metasomatized chemical index of alteration cia values 43 87 also imply a high degree of source weathering depleted transitional trace elements ni cr co and sc fractionated light rare earth elements patterns mild negative eu anomalies in the majority of these meta sedimentary samples point toward felsic source rocks including the 2 5 ga granitics ttg gneisses and the paleoproterozoic granitics in the tnco minor contribution from mafic rocks is evidenced from relative high contents of mgo fe 2 o 3 t sc and lower la ybn ratios in some older sequence set samples from the zhongtiao complex our geochemical and nd isotopic data combined with previous studies in the lithostratigraphic sequence provenance and depositional age suggest that the older and younger sequence sets of the low grade supracrustal successions in the tnco were deposited in the different depositional environments the older sequence set was deposited in a back arc basin between the andean type continental margin arc and the eastern block after 2 1 ga whereas the younger sequence set formed in a foreland basin between 1 88 and 1 80 ga which is consistent with the model that the collision between the eastern and western blocks to form the trans north china orogen occurred at 1 85 ga

tomography study of the upper mantle around the tesz based on passeq experiment data abstract we present a detailed velocity perturbation model of the earth s upper mantle in the area around the trans european suture zone tesz imaged by the teleseismic tomography the model is based on 12473 p wave arrival times measured on recordings of 273 stations of the passive seismic experiment passeq which was active during 2006 and 2008 station and teleseismic event distribution is sufficient to resolve the structure below the passeq array down to a depth of 350 km the velocity perturbation model clearly shows a 250 km thick uniform layer of positive velocity perturbations north east of the teisseyre tornquist zone ttz and 150 km thick layer south west of the ttz characterized by relatively lower velocity perturbations the former we associate with the precambrian mantle lithosphere of the european plate while the latter represents the much younger phanerozoic lithosphere in the uppermost layer of the model 40 km the boundary between the two regions closely follows the crustal trace of the ttz in deeper layers the boundary shifts south westward at a depth of approximately 120 km the region with positive perturbations reaches the northern part of the bohemian massif bm the shift suggests that the phanerozoic part of the european plate thrusts over the precambrian lithosphere the upper mantle below a depth of 250 km lacks the pronounced division between the two regions around the tesz which allows us to associate these depths with asthenospheric part of the upper mantle

age geochemistry and sm nd isotopic signature of the 0 76 ga burin group compositional equivalent of avalonian basement abstract the ca 760 ma burin group occurs in a well exposed 60 km long northeasterly trending belt on the burin peninsula in the avalon zone of the southeastern newfoundland appalachians this lithologically distinctive tectonically bounded succession is characterized by low grade massive and pillowed basalts abundant gabbro and diabase dykes and sills mafic pyroclastic and epiclastic rocks and stromatolitic carbonate bearing rocks the burin group preserves the oldest known magmatic event in the avalon terrane but its tectonic evolution and its relationship to the voluminous 640 570 ma arc related magmatism that typifies avalonia is uncertain geochemical analyses confirm that the basalts are predominantly low k tholeiites they are characterized by high ratios of lil hfs elements and display depletion to slight enrichment in lree sm nd isotopic data reveal that most basalts have juvenile compositions with nd values similar to contemporaneous depleted mantle indicating that high lil hfs elemental ratios were probably due to coeval subduction which contaminated the mantle source other basalts have lower nd values and the negative correlation of nd with la sm together with a positive correlation of nd with 147 sm 144 nd suggest that their isotopic signatures have been modified by a mesoproterozoic older oceanic crust or mantle into which the burin group mafic magmas were emplaced the isotopic signature of the burin mafic rocks is similar to that inferred for the source of the main phase of avalonian magmatism these data together with paleocontinental reconstructions for ca 760 ma suggest that the burin group is a local representative of ensimatic arcs within the panthalassa type ocean that surrounded rodinia possibly as a far field response to the breakup of rodinia although its low metamorphic grade precludes it being the basement from which avalonian magmas were extracted the burin group may be representative of the geochemical and isotopic composition of that basement

amphibole sponge in arc crust pressure temperature time paths followed by arc magmas ascending through the lithosphere dictate the phase assemblage that crystallizes and hence the compositions of liquid fractionates here we use la yb and dy yb versus sio 2 relationships from selected volcanoes to show that amphibole is an important mineral during differentiation of arc magma production of intermediate and silicic arc magmas occurs as magmas stall and cool in the mid lower crust where amphibole is stable because amphibole is rarely a phenocryst phase we term this cryptic amphibole fractionation if this process is as widespread as our investigation suggests then 1 amphibole cumulates may act as an effective filter for water dissolved in mantle derived magmas 2 amphibole cumulates may act as a fertile source of intracrustal melts and fluids and 3 recycling of amphibole cumulates has the potential to return incompatible trace elements and water to the mantle

late archaean terrane accretion in the godthab region southern west greenland tectono stratigraphic terranes fault bounded blocks of the earth s crust characterized by a geological history distinct from that of adjacent terranes1 are now widely recognized in phanerozoic and proterozoic orogenic belts and their present configurations are thought to result from plate tectonic processes similar to those in operation today2 4 there has been much debate about whether such processes operated in archaean times5 6 here we present new data from the archaean high grade gneiss complex of the godthab now nuuk region of southern west greenland which show that discrete tectonic units recognized in the south of the region7 can be more widely identified at least four terranes are recognized each of which evolved separately until their juxtaposition in the late archaean this suggests that at least some archaean high grade gneiss complexes may resemble more recent orogenic belts formed by plate tectonic processes

precambrian tectonic evolution of part of gondwana southwestern australia southwestern australia has a long dynamic precambrian history of crustal fragmentation and aggregation by continental collision and accretion this interpretation contrasts with the widely held belief that most of australia was part of a proterozoic supercontinent in which all tectonic magmatic and metamorphic activity was intracontinental the pilbara and yilgarn cratons are two quite different fragments of archean continental crust that collided to form the capricorn orogen between 2000 and 1600 ma the albany fraser orogen formed along the southern margin of the yilgarn craton during another major continental collision at 1300 to 1100 ma rifting removed the northeastern part of these combined cratons and orogens between 1100 and 700 ma subsequent continental collision along this rifted margin formed the paterson orogen at 700 to 600 ma therefore the assembly of this considerable part of gondwana may not have been completed until about 600 ma

pervasive near surface stratal disruption in an accretionary prism setting kaczawa complex sw poland the tectonized and metamorphosed mudrocks within the variscan accretionary prism of the kaczawa mountains in sw poland comprise sedimentary melanges together with more coherent stratigraphic units some represent large olistoliths deposited in a submarine trench we infer a trend of progressive near surface stratal disruption in mud dominated deposits due to dewatering that forms a continuum with subduction related tectonic structures imposed on unconsolidated sediment during deeper burial the assemblage of characters suggests that an accretionary prism environment can influence and leave characteristic traces of the total burial history of a trench succession

geophysical and petrological modeling of the lower crust and uppermost mantle in the variscan and proterozoic surroundings of the trans european suture zone in central europe abstract high quality seismic data on the lower crust and uppermost lithospheric mantle in the central european part of the trans european suture zone together with thermal and gravimetric data enables the quantitative modeling of the rocks occurring in those parts of the lithosphere including their mineral compositions and the chemical composition of individual minerals the p3 seismic profile is located at the sw margin of the east european craton the lower crust is dominated by gabbronoritic intrusions plagioclase an 45 ab 55 clinopyroxene di 80 hed 20 orthopyroxene en 74 fs 26 and the uppermost mantle is harzburgitic olivine and orthopyroxene mg 0 91 the lower crust and upper mantle of the p1 seismic profile belong to the trans european suture zone albeit the upper crust is of variscan affinity the p1 lower crust has gabbronoritic composition which is layered from plagioclase rich compositions on the top to the orthopyroxene rich ones at the bottom plagioclase an 45 ab 55 clinopyroxene di 80 hed 20 orthopyroxene en 85 fs 15 and is lithologically different proterozoic and variscan surroundings the 100 200 km eclogite slice garnet alm 48 gr 25 py 27 clinopyroxene di 51 hed 10 jd 39 with a thickness of 5 10 km occurs in the uppermost mantle sampled by the p1 profile the nied wied massif is located at the ne margin of the bohemian massif which shows an exposed variscan basement the lower crust beneath the nied wied massif consists of gabbroic rock of variable proportions of plagioclase an 45 ab 55 and clinopyroxene di 80 hed 20 whereas the uppermost mantle is supposedly spinel harzburgite olivine ortho and clinopyroxene mg 0 90 our models show that the lowermost crust and uppermost mantle of the east european craton do not continue to the sw into the trans european suture zone in its central european section in poland

rb sr and sm nd isotopic dating of an early precambrian spilite keratophyre sequence in the wutaishan area north china preliminary evidence for nd isotopic homogenization in the mafic and felsic lavas during low grade metamorphism the spilite keratophyre sequence in the wutaishan area north china has been dated by zircon from the quartzkeratophyre and a volcanic crystallization age of 2522 ma liu dunyi et al 1985 was obtained this volcanic rock sequence experienced a low grade metamorphism of greenschist facies during 1800 2000 ma however combined sm nd whole rock data from the volcanic rock sequence if interpreted in terms of an isochron gives a younger age of 2250 182 ma if separately calculated sm nd isochrons for quartz keratophyre and spilite yield two consistently younger ages of 1977 385 ma and 1981 178 ma these sm nd isochron ages are consistent with a rb sr age of 1871 98 ma and with the time of regional greenschist facies metamorphism consequently we interpret the 2250 ma alignment on the sm nd diagram as an errorchron the two sm nd metamorphic ages suggest that partial homogenization of nd isotopic composition in water rich spilite keratophyric meta volcanics can be achieved during low grade metamorphism as a result of ree mobility using the nd values at the time of metamorphism and the average 147sm 144nd ratios of the spilite and the quartzkeratophyre initial nd values of 2 6 3 5 and 3 0 6 1 respectively are estimated at the time of volcanic eruption 2522 ma similar positive initial nd values for the spilites and quartz keratophyres suggest that they might have been derived from the same depleted mantle source or that the quartz keratophyres are derived from a short lived mafic source

shrimp u pb zircon ages of the fuping complex implications for late archean to paleoproterozoic accretion and assembly of the north china craton the fuping complex is situated in the central part of the north china craton and consists of four major lithological assemblages fuping tonalitic trondhjemitic granodioritic gneisses longquanguan augen gneisses wanzi supracrustal assemblage and nanying granitic gneisses shrimp u pb geochronology combined with u th and cathodoluminescence cl imaging of zircon enables resolution of magmatic and metamorphic events that can be directed towards understanding the late archean to paleoproterozoic history of the fuping complex cl images reveal the coexistence of magmatic and metamorphic zircons in nearly all rock types of the fuping complex the metamorphic zircons occur as either single grains or overgrowth or recrystallization rims surrounding and truncating oscillatory zoned magmatic zircon cores and are all characterized by nebulous zoning or being structureless with extremely high luminescence and very low th contents these features make them distinct from magmatic zircons that are characterized by concentric oscillatory zoning comparatively low luminescence and high th and u contents shrimp u pb analyses on magmatic zircons reveal that the tonalitic trondhjemitic and granodioritic plutons of the fuping gneisses were emplaced at 2523 14 ma 2499 10 ma and 2486 8 ma respectively whereas the monzogranitic and granitic plutons of the longquanguan augen gneisses were intruded respectively at 2510 22 ma and 2507 11 ma prismatic and oscillatory zoned zircons dominate in the pelitic rocks of the wanzi supracrustal assemblage and are interpreted as detritus from igneous source rocks the concordant and discordant u pb ages of 2502 5 ma and 2507 14 ma obtained from two pelitic rock samples indicate these rocks must have been deposited no earlier than 2507 ma ago in addition a zoned zircon grain in one pelitic rock sample has a near concordant age of 2109 5 1 ma which may provide a maximum depositional age for the wanzi supracrustal rocks shrimp results also reveal that granitic magmatism assigned to the nanying granitic gneisses occurred over a protracted interval from 2077 13 ma to 2024 21 ma the nebulously zoned zircon grains and overgrowth recrystallization zircon rims from different rocks yielded similar concordant 207pb 206pb ages in the range 1875 to 1802 ma interpreted as approximating the age of regional metamorphism of the fuping complex timing of primary zircon crystallization and regional metamorphism of the fuping complex is in general agreement with recent u pb zircon ion probe results for the wutai and hengshan complexes that bound the fuping complex to the northwest these areas are characterized by the emplacement of major granitoid bodies at around 2 50 ga to 2 48 ga ago deposition of supracrustal rocks in the paleoproterozoic intrusion of paleoproterozoic granitic bodies at 2 1 to 2 0 ga and regional metamorphism at 1 875 to 1 802 ga these data indicate that the fuping and hengshan complexes do not represent an older crystalline basement to the wutai complex as suggested in previous tectonic models but together with the wutai complex represent elements of a single late archean to paleoproterozoic magmatic arc system that has been subsequently tectonically disrupted and juxtaposed during the collision of the eastern and western north china blocks at 1 85 ga which resulted in the final assembly of the north china craton

geochemical changes in baslts and andesites across the archean proterozoic boundary identification and significance abstract to identify accurately changes in rock composition across the archean proterozoic boundary it is necessary to compare rocks from similar lithologic associations to constrain the effect of tectonic setting most basalts and andesites from the greenstone association volcanic dominated submarine supracrustal rocks possess a geochemical subduction zone component similar to their counterparts from modern arc systems basalts with island arc geochemical affinities dominate in archean greenstones while those with calc alkaline affinities are most abundant in proterozoic greenstones basalts with morb or oceanic within plate geochemical characteristics are rare in precambrian greenstones of all ages preserved early archean greenstone basalts 3500 ma reflect mantle sources less depleted than late archean greenstone basalts 2500 3500 ma proterozoic greenstone basalts are derived from relatively enriched mantle sources compared to all archean sources a feature which may be due to recycling of continental sediments into the mantle following rapid late archean continental growth precambrian andesites are geochemically similar to andesites from modern arcs but archean andesites are unique in that they are depleted in heavy ree and y results are consistent with archean andesite production by partial melting of descending mafic crust with amphibole garnet remaining in the residue while proterozoic and younger andesites are produced by fractional crystallization of basalts

heat flow and lithospheric thermal regime in the northeast german basin abstract new values of surface heat flow are reported for 13 deep borehole locations in the northeast german basin negb ranging from 68 to 91 mw m 2 with a mean of 77 3 mw m 2 the values are derived from continuous temperature logs measured thermal conductivity and log derived radiogenic heat production the heat flow values are supposed free of effects from surface palaeoclimatic temperature variations from regional as well as local fluid flow and from thermal refraction in the vicinity of salt structures and thus represent unperturbed crustal heat flow two d numerical lithospheric thermal models are developed for a 500 km section along the dekorp basin 9601 deep seismic line across the basin with a north eastward extension across the tornquist zone a detailed conceptual model of crustal structure and composition thermal conductivity and heat production distribution is developed different boundary conditions for the thickness of thermal lithosphere were used to fit surface heat flow the best fit is achieved with a thickness of thermal lithosphere of about 75 km beneath the negb this estimate is corroborated by seismological studies and somewhat less than typical for stabilized phanerozoic lithosphere modelled moho temperatures in the basin are about 800 c heat flow from the mantle is about 35 to 40 mw m 2 in the southernmost part of the section beneath the harz mountains higher moho temperatures up to 900 to 1000 c are shown while the relatively high level of surface heat flow in the negb obviously is of longer wave length and related to lithosphere thickness changes in crustal structure and composition are responsible for short wave length anomalies

archean geodynamics in the central zone north china craton constraints from geochemistry of two contrasting series of granitoids in the fuping and wutai complexes abstract the archean to paleoproterozoic central zone of the north china craton is situated between the eastern and western archean continental blocks and contains two contrasting series of neoarchean granitoids the 2523 2486 ma tonalite trondhjemite granodiorite ttg gneisses in the fuping complex and the 2555 2525 ma calc alkaline granitoids tonalite granodiorite granite and monzogranite in the wutai complex the fuping ttg gneisses most likely formed from partial melting of 2 7 ga basalts at 50 km with an involvement of 3 0 ga crustal material the wutai granitoids have higher k 2 o lile and rb sr but lower sr y and la n yb n than the fuping ttg gneisses are characterized by nd t dm from 2 5 to 2 8 ga and e nd t from 0 49 to 3 34 and are derived from partial melting of a juvenile source at the geochemistry of these two contrasting series of neoarchean granitoids provides further evidence that the wutai complex originated and evolved separately from the fuping complex the wutai complex most likely formed as an oceanic island arc with volcanism and synvolcanic granitoid intrusions at 2555 2525 ma the wutai complex was subsequently accreted onto the eastern archean continental block and was probably responsible for crustal thickening and ttg magmatism at 2523 2486 ma in the fuping complex as part of the taihangshan hengshan block at the western margin of the eastern archean continental block

crustal lithology vs thermal state and moho heat flow across the ne part of the european variscan orogen a case study from sw poland geotherms of four crustal profiles across the variscan orogen in sw poland have been constructed to better understand the variation in thermal state of the region seismic and drilling data as well as rock sequences in exposed parts of the orogen were used for wilcza gora sudetic block polkowice rudna middle odra horst wieciechowa wolsztyn leszno horst and wrze nia szczecin miechow synclinorium within tesz profiles the palaeoclimate corrected surface heat flow map and the heat production calculations based on literature data enabled the construction of geotherms and estimation of moho heat flow exception is the polkowice rudna profile where the surface heat flow was calculated using temperature measurements in underground copper mines and k u and th contents and density heat conductivity measurements in rocks drilled in the middle odra horst were used to calculate geotherm the basaltic lava migration through the lithospheric mantle and its effect on crustal geotherm in wilcza gora area of cenozoic alkaline volcanism at ca 30 18 ma was shown to increase slightly both current surface and current moho heat flow by ca 4 mw m2 the presented approach couples geological and geophysical information and thus differs from standard purely geophysical assessment of lithosphere thermal state it shows that surface heat flow is enlarged to 84 mw m2 by granitic plutons in the upper crust in the lubin polkowice site heat flow on the moho varies from 28 to 34 mw m2 in sites located in the sudetic fore sudetic blocks middle odra horst and wolsztyn leszno horst locally it may slightly increase because of extraneous heat input by cenozoic basaltic volcanism but the values close to 30 mw m2 are specific for mantle root of saxothuringian zone in sw poland mantle heat flow is 36 mw m2 in wrze nia site and supposedly is a manifestation of different nature of lithospheric mantle underlying tesz

a late archean foreland fold and thrust belt in the north china craton implications for early collisional tectonics abstract the archean north china craton is divided into the western and eastern blocks along the central orogenic belt a 1600 km long archean foreland basin and thrust belt fringes the eastern side of the central orogenic belt rocks in the orogen form tectonically stacked east vergent fold and thrust sheets including foreland basin sediments 2 50 ga ophiolitic melange and an island arc complex foreland basin sediments overlie a passive margin sequence and include a 2 50 ga deep water turbidite sequence that grades upward and westward into shallow water molasse now disposed in structurally imbricated east verging thrusts and asymmetric folds that gradually migrated craton ward with deformation uplift and erosion of the orogen there is a strong linked relationship of the formation of the foreland basin to collision of the east and west blocks of the north china craton along the central orogenic belt at 2 50 ga the qinglong foreland basin and central orogenic belt of the north china craton represents one of the best preserved archean orogen to craton transitions in the world its classic internal to external zonation and flexural response to loading demonstrate that convergent tectonics in the archean were broadly similar to phanerozoic convergent margin processes

geochemical evidence for progressive rift related early palaeozoic volcanism in the western sudetes the volcanigenic rocks of the kaczawa mts western sudetes poland in the eastern variscides show changing geological and geochemical evolution during early palaeozoic time the lower part of the succession cambrian ordovician has three components 1 shallow marine to subaerial metabasalts associated with limestones and volcaniclastics the lavas are dominantly of a transitional tholeiitic alkaline type and their trace element patterns typically represent a rift related environment they pass laterally and upwards into more depleted basalts resembling enriched morb with nd isotopic characteristics indicating contamination by continental crust 2 interlayered rhyodacitic lavas and volcaniclastics which show negative nd values suggesting formation of the original magma by crustal melting 3 an overlying alkaline bimodal suite of lavas and volcaniclastic rocks as well as alkaline metabasites of shallow intrusive character the geochemistry of the latter resembles oceanic island volcanics but they may well have been emplaced in the same evolving rift environment the upper part of the kaczawa succession ordovician silurian in age comprises a thick and monotonous sequence of deep marine pillowed and massive metabasalts associated with black shales and cherts these lavas exhibit morb trace element characteristics with minor evidence of crustal contamination during this stage of rifting true oceanic crust probably formed it is thus suggested that the studied part of the kaczawa succession developed in a progressively evolving rift initially within an ensialic environment and finally reaching the stage of a basin underlain by oceanic type crust together with similar cambrian ordovician volcanic sedimentary associations widely distributed in western europe from portugal through france and germany they represent a record of the early palaeozoic rifting in the northern periphery of gondwana

new terrestrial heat flow map of europe after regional paleoclimatic correction application heat flow variations with depth in europe can be explained by a model of surface temperature changes 10 c new heat flow map of europe is based on updated database of uncorrected heat flow values to which paleoclimatic correction is applied across the continent correction is depth dependent due to a diffusive thermal transfer of the surface temperature forcing of which glacial interglacial history has the largest impact it is obvious that large part of the uncorrected heat flow values in the existing heat flow databases from wells as shallow as few hundreds of meters is underestimated this explains some very low uncorrected heat flow values 20 30 mw m2 in the shields and shallow basin areas of the craton also heat flow values in other areas including orogenic belts are likely underestimated based on the uncorrected and corrected heat flow maps using 5 km 5 km grid we have calculated average heat flow values uncorrected heat flow 56 0 mw m2 sd 20 3 mw m2 vs corrected heat flow 63 2 mw m2 sd 19 6 m wm2 and heat loss for the continental part total heat loss is 928 e09 w for the uncorrected values versus corrected 1050 e09 w

formation of an archaean continent about 30 of the earth is covered by continents but only about 10 small kernels of these continentsae known as archaean cratonsae are continental fragments formed before 2 5 gyr ago the kaapvaal craton of south africa which formed and stabilized between 3 7 and 2 7 gyr ago is one of the oldest reasonably sized examples of these continental fragments it consists of a mosaic of subdomains that have been welded together by processes similar to those of modern day plate tectonics the earliest subdomains may have owed their origin to the onset of efficient recycling from the earth s hydrosphere into the mantle

early palaeozoic crustal melting in an extensional setting petrological and sm nd evidence from the izera granite gneisses polish sudetes the izera block in the west sudetes which is composed of granites gneisses and transitional granite gneisses and minor mica schists is one of the largest outcrops of early palaeozoic ca 500 ma metagranitoid rocks in the basement units of the variscides of central europe the izera granites show s type features magmatic cordierite relict garnet and sillimanite lack of mafic enclaves and absence of coexisting tonalites and diorites the paucity of pegmatites indicates that the granitic magma was relatively dry the s type character of these granites is further supported by their peraluminous character a cnk 1 0 1 63 high content of normative corundum up to 3 5 and relatively high 87sr 86sr initial ratio the chemical variation of these rocks was controlled by the fractional crystallization of plagioclase cao sr eu eu biotite and cordierite al2o3 mgo feo zircon zr hf and monazite ree initial end values range from 5 2 to 6 9 mean 5 9 sd 0 6 these largely negative end values imply that the granitic magmas emplaced ca 500 ma were extracted from a source reservoir that was strongly enriched in lree i e with low sm nd ratio on a time integrated basis the relatively consistent depleted mantle model ages 1 730 2 175 ma mean 1 890 ma is in agreement with the earlier reported presence of ca 2 1 ga old inherited pb component in zircon from the closely related rumburk granite this points to an old early proterozoic crustal residence age of the inferred metasedimentary protoliths of the izera granitoids with only minor contribution to their protoliths of juvenile components of late proterozoic early palaeozoic age although the izera granites show some trace element features reminiscent of syn collisional or post collisional granitoids they more likely belong to the broad anorogenic class our data corroborate some previous interpretations that granite generation was connected with the early palaeozoic rifting of the passive margin of the saxothuringian block well documented in the region by bimodal volcanic suites of similar age kaczawa unit eastern and southern envelope of the karkonosze izera block in this scenario granite magmatism and bimodal volcanism would represent two broadly concomitant effects of a single major event of lithospheric break up at the northern edge of gondwana

geochemistry of the paleoproterozonic nanying granitic gneisses in the fuping complex implications for the tectonic evolution of the central zone north china craton abstract the nanying granitic gneisses represent a major 2 0 ga magmatic event in the fuping complex of the central zone of the north china craton they occur in the chengnanzhuang shear zone which is chiefly developed along the contact between the neoarchean fuping tonalite trondhjemite granodiorite ttg gneisses and the wanzi paragneisses the nanying granitic gneisses were derived from monzogranite and syenogranite with minor amounts of quartz diorite and granodiorite and belong to the metaluminous to peraluminous high potassium calc alkaline series correlations between major and trace elements and similarities in chondrite normalized rare earth element ree patterns support field relationships e g gradational contacts indicating that the nanying granitic gneisses originated from similar magmas the granodioritic monzogranitic and syenogranitic gneisses have similar ranges of initial 87sr 86sr values 0 7030 0 7093 0 7021 0 7193 and 0 7049 0 7111 respectively although these variations are partly attributable to local resetting of the isotopic system during late deformation hydrothermal alteration the whole rock 208pb 204pb 206pb 204pb and 207pb 204pb values of the nanying granitic gneisses are 37 32 76 8 15 24 23 82 and 14 92 17 92 respectively these sr pb isotope systematics together with previously published nd isotope compositions suggest that the nanying granitic gneisses were derived from partal melting of the 2 50 ga fuping ttg gneisses with local assimilation involving the wanzi paragneisses the nanying granitic gneisses are geochemically similar to the cca and ccl groups of granitoids except for a few samples which plot in the hlo group the nanying granitic gneisses exhibit depletion in rb sr ba ti and u and enrichment in th nb zr hf and ree similar to those of syn shear high potassium calc alkaline granitoids and late shear alkaline granitoids they therefore represent the product of a syn collisional to post collisional magmatic event this collisional event which is significantly older than the 1 84 1 80 ga event that has been proposed for the juxtaposition of the eastern and western archean continental blocks in the final stabilization of the north china craton supports a tectonic model involving multiple collisional events for the amalgamation of the internal lithotectonic domains within the central zone and the assembly of the north china craton as a whole

the palaeozoic variscan oceans revisited abstract geological evidence supported by biogeographical data and in accord with palaeomagnetic constraints indicates that one ocean models for the variscides should be discarded and confirms instead the existence of three gondwana derived microcontinents which were involved in the variscan collision avalonia north armorica franconia and thuringia subdivided by a failed vesser rift and south armorica central iberia armorica bohemia all divided by small oceans in addition parts of south eastern europe including adria and apulia are combined here under the new name of palaeo adria which was also peri gondwanan in the early palaeozoic oceanic separations were formed by the break up of the northern gondwana margin from the late cambrian onwards most of the oceans or seaways remained narrow but much like the alpine cenozoic oceans gave birth to orogenic belts with hp uhp metamorphism and extensive allochthons the saxo thuringian ocean between north and south armorica and the galicia moldanubian ocean between south armorica and palaeo adria only the rheic ocean between avalonia and peri gondwana was wide enough to be unambiguously recorded by biogeography and palaeomagnetism and its north western arm closed before or during the emsian in europe ridge subduction under the northernmost part of armorica in the emsian created the narrow and short lived rheno hercynian ocean it is that ocean and not the rheic whose opening and closure controlled the evolution of the rheno hercynian foldbelt in south west iberia south west england germany and moravia czech republic devonian magmatism and sedimentation set within belts of early variscan deformation and metamorphism are probably strike slip related the first arrival of flysch on the forelands and or the age of deformation of foreland sequences constrains the sequential closure of the variscan seaways galicia moldanubian in the givetian saxo thuringian in the early famennian rheno hercynian in the tournaisian additional mid to late devonian and partly early carboniferous magmatism and extension in the rheno hercynian saxo thuringian and galicia moldanubian basins overlapped with variscan geodynamics as strictly defined the early carboniferous episode was the start of episodic anorogenic heating which lasted until the permian and probably relates to tethys rifting

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

development of the north china craton during the late archaean and its final amalgamation at 1 8 ga some speculations on its position within a global palaeoproterozoic supercontinent abstract new data obtained over the past few years indicate that by the end of the archaean the north china craton consisted of two major crustal entities identified as the eastern and western blocks the formation of island and magmatic arcs along the western margin of the eastern block record the latest archaean events so far identified the location of the western block at this time is unknown however the occurrence of palaeoproterozoic passive margin sediments similar in age to those occurring in the eastern block indicates essentially similar conditions and possible separation by an ocean of unknown dimensions re initiation of east dipping subduction beneath the western margin of the eastern block resulted in closure of this palaeoproterozoic ocean bringing the western block into close proximity continued subduction resulted in a major continental continental collision and the western margin of the eastern block was again reactivated leading to extensive thrusting high pressure metamorphism and the generation of crustal melts this occurred between 1 88 and 1 79 ga ago resulting in the formation of the trans north china orogen and final amalgamation of the north china craton although information is sparse to non existent we have reviewed the possible location of the north china craton at the time of collision and note a similarity in terms of age lithology and distribution of major crustal components between the north china craton and baltica although speculative we present this model in the hope that it will stimulate debate and lead to further research in these areas

tectonic evolution in the archaean and proterozoic kre high heat flow probably favoured global hotspot activity with crustal growth of iceland type through vertical magmatic accretion the tectonic environment for the generation of about 3 9 2 5 ga granite gneiss greenstone terrains with volurnlnous production of tonalite trondhjemite granodlorite magmas is still uncertain and both piate ma and intrapiate scenarios arc possible deformanon atylea in greenstones and adjacent high grade orthognersses with intercalated shallow water supracrustal assemblages suggest extensive horizontal shortening and crustal interstacking this probably resulted from collisional and or rotational motion and produced significant intracrustal melting as early as 3 9 ga by the end of the archaean and locally much earlier crustal thicknesses reached 35 50 km or more and the cxtl aordinary hhlding to erogenic deformation may have been due to delamination and crustal subduction towards the end of the proterozoic evidence for modern style plate tectonics becomes abundant through the recognition of laland a16 accretion ophiolite obducdon foreland thrust and fold belts and exotic terranes one of the best documented example for this tectonic environment is the arabian nubian shield 4lthough it is doubtful whether modern plate tectonic settings can serve as analogues for all precambrian tectonic styles it i clear that global crustal evolution since the early archaean was governed by the motion of plates which repeatedly came togethel tv fotm supercontinents and then dlspersetl again we shall not understand the detailed mechanism of precambrian crustal itlton cs before we learn horn lo irltejpret recent large scale crustal deformation and its causes

zircon u pb and lu hf isotopic and whole rock geochemical constraints on the lanhe and heichashan groups implications for the paleoproterozoic tectonic basin evolution of the luliang complex abstract the luliang complex is located at the western margin of the middle segment of the trans north china orogen along which the western and eastern blocks collided to form the north china craton the complex mainly consists of metamorphosed granitic plutons and supracrustal rocks of which the latter are subdivided into the jiehekou luliang yejishan lanhe and heichashan groups the lanhe group is composed of meta conglomerates quartzites and phyllites with minor meta basalts whereas the heichashan group consists of molasse like meta conglomerates and coarse grained quartzites geochemistry of the yejishan meta sedimentary rocks indicates weak source weathering and dominantly chemical immature features whereas the lanhe and heichashan samples display opposite features u pb ages of detrital zircons from the lanhe groups yield four age peaks at 2180 ma 2370 ma 2520 ma and 2700 ma the former three peaks coincide with ages of the chijianling guandishan ttg gneisses 2199 2151 ma and meta volcanic rocks from the luliang and yejishan groups 2213 2156 ma age of the gaijiazhuang porphyritic gneisses 2375 2364 ma and age of the yunzhongshan ttg gneisses 2499 ma respectively whereas detrital zircons forming the oldest age peak were most likely derived from the early neoarchean crust of the eastern block for the heichashan group the dominant 2 2 2 0 ga detrital zircons were probably recycled from the underlying jiehekou group and the minority is directly derived from the early paleoproterozoic granitoids in the luliang complex the youngest detrital zircon age peaks of 2 17 ga and 1 82 ga place maximum depositional ages on the lanhe and heichashan groups respectively whereas the local 1 81 1 79 ga massive granites place constraint on their minimum depositional ages taking into account the lithostratigraphic features provenance and formation ages we suggest that the lanhe group formed in a shrinked remnant back arc basin and the heichashan group was deposited in a foreland basin conversion of the tectonic basin from the middle paleoproterozoic back arc basin to the late paleoproterozoic foreland basin is well consistent with the model that the single collision to form the basement of the north china craton happened at 1 85 ga

european mantle lithosphere assembled from rigid microplates with inherited seismic anisotropy abstract we have modelled three dimensional seismic anisotropy of the mantle lithosphere from anisotropic parameters of teleseismic body waves we invert jointly shear wave splitting parameters and p residual spheres based on data from dense networks of temporary and permanent stations in four european regions ranging from the variscan belt to the baltic shield changes in orientation of the large scale anisotropy caused by systematic preferred orientation of olivine identify boundaries of domains of mantle lithosphere individual domains are characterized by a consistent large scale orientation of anisotropy approximated by hexagonal or orthorhombic symmetry with generally inclined symmetry axes the domains are separated by mapped tectonic boundaries sutures which cut the entire lithosphere besides the change of anisotropy orientation at domain boundaries we often observe a change of the lithosphere and or crust thicknesses we do not detect any fabric of the mantle lithosphere which could have been produced by a collision of microcontinents in a volume detectable by large scale seismic anisotropy the observations of consistent anisotropy within individual blocks of the mantle lithosphere reflect frozen in olivine preferred orientation most probably formed prior to the assembly of microcontinents that created the modern european landmass therefore our findings support a plate tectonic view of the continental lithosphere as a mosaic of rigid blocks of the mantle lithosphere with complicated but relatively sharp contact zones these contacts are blurred by the easily deformed overlying crust terranes

shrimp u pb zircon geochronology of the huai an complex constraints on late archean to paleoproterozoic magmatic and metamorphic events in the trans north china orogen the huai9an complex is situated in the northern segment of the trans north china orogen tnco a continent continent collisional belt along which the discrete archean eastern and western blocks amalgamated to form the basement of the north china craton the complex consists of six distinct lithologic units the huai9an ttg gneisses the manjinggou high pressure mafic granulites the khondalite series the dongjiagou granitic gneiss the huai9an charnockite and the dapinggou k feldspar granite shrimp u pb geochronology combined with th and u data and cathodoluminescence cl imaging of zircons enables resolution of magmatic and metamorphic events that can be directed towards understanding the late archean to paleoproterozoic history of the tnco cl images reveal the coexistence of magmatic and metamorphic zircons in most lithologies of the huai9an complex of which the metamorphic zircons occur as either single grains or overgrowth rims surrounding and truncating oscillatory zoned magmatic zircon cores shrimp u pb analyses on magmatic zircons reveal that the tonalitic trondhjemitic and granodioritic protoliths of the huai9an ttg gneisses were emplaced at 2515 20 ma 2499 19 ma and 2440 26 ma respectively much earlier than the emplacement of the dongjiagou granitic gneiss dated at 2036 16 ma however their metamorphic zircons yield similar concordant 207pb 206pb ages of 1847 17 ma 1842 10 ma and 1847 11 ma for the tonalitic trondhjemitic and granodioritic gneisses respectively and 1839 46 ma for the dongjia granitic gneiss these ages demonstrate that the huai9an complex underwent a regional metamorphic event at 1850 ma which is further supported by a mean 207pb 206pb age of 1848 19 ma for metamorphic zircons in the manjinggou high pressure mafic granulite and 1849 10 ma and 1850 17 ma for igneous zircons in the anatectic huai9an charnockite and dapinggou garnet bearing s type granite respectively the timing of late archean to paleoproterozoic magmatism and regional metamorphism in the huai9an complex is in general agreement with recent shrimp zircon data for other metamorphic complexes in the tnco these data prove that the high grade gneiss complexes were not the basement to the low grade granite greenstone terranes in the tnco furthermore the lithologies of the orogen are considered to have developed as a long lived magmatic arc that was subsequently tectonically disrupted and juxtaposed during the collision of the eastern and western blocks at 1 85 ga leading to final assembly of the north china craton

deformation history of the hengshan wutai fuping complexes implications for the evolution of the trans north china orogen abstract the trans north china orogen separates the north china craton into two small continental blocks the eastern and western blocks as one of the largest exposure in the central part of the orogen the hengshan wutai fuping complexes consist of four lithotectonic units the wutai hengshan and fuping complexes and the hutuo group the hengshan complex contains high pressure mafic granulites and retrograded eclogites structural analysis indicates that most of the rocks in these complexes underwent three distinct episodes of folding d 1 to d 3 and two stages of ductile thrust shearing stz 1 between d 1 and d 2 and stz 2 after d 3 the d 1 deformation formed penetrative axial planar foliations s 1 mineral stretching lineations l 1 and rarely preserved small isoclinal folds f 1 in the hengshan and fuping complexes in the wutai complex however large scale f 1 recumbent folds with sw vergence are displayed by sedimentary compositional layers penetrative transposition resulted in stacking of thrust sheets which are separated by ductile shear zones stz 1 the kinematic indicators of stz 1 in the hengshan and wutai complexes show top to the s230 w thrusting likely related to northeastward oblique pre collisional subduction d 1 resulted in crustal thickening with resultant prograde peak metamorphism the hutuo group did not undergo the d 1 deformation either because sedimentation was coeval with the d 1 deformation or because it was at a high structural level and was not influenced directly by the early deformation the d 2 deformation produced nw verging asymmetric and recumbent folds the d 2 deformation is interpreted to have resulted from collision between the eastern and western blocks of the north china craton in the hutuo group and the fuping complex the development of ese verging asymmetric tight folds is associated with d 2 the structural pattern resulting from superimposition of d 1 and d 2 is a composite synform in the hengshan wutai fuping complexes all four lithotectonic units were superposed during the later d 3 deformation the d 3 deformation developed nw trending open upright folds ongoing collision led to development of transpressional ductile shearing stz 2 forming the transpressional zhujiafang dextral ductile shear zone between the northern hengshan complex and the southern hengshan complex and generating the sinistral longquanguan ductile shear zone between the fuping complex and the wutai complex respectively the stz 1 and d 2 deformation were possibly responsible for fast syn collisional exhumation of the high pressure mafic granulites and retrograded eclogites the structural patterns and elucidation of the deformation history of the hengshan wutai fuping complexes places important constraints on the tectonic model suggesting that an oceanic lithosphere between the eastern and western blocks underwent northeastward directed oblique subduction beneath the western margin of the eastern block and that the final closure of this ocean led to collision between the two blocks to form the coherent basement of the north china craton

thermal evolution of two textural types of mafic granulites in the north china craton evidence for both mantle plume and collisional tectonics mafic granulites from the north china craton can be divided into two textural types referred to as a and b types a type mafic granulites display garnet quartz symplectic coronas and outcrop in the eastern and western zones of the craton whereas b type mafic granulites exhibit orthopyroxene plagioclase clinopyroxene symplectites or coronas and are mainly exposed in the central zone of the craton most a type mafic granulites preserve the prograde m 1 peak m 2 and post peak near isobaric cooling m 3 assemblages which are represented respectively by inclusions of hornblende plagioclase quartz a peak mineralogy of orthopyroxene clinopyroxene plagio clase quartz garnet and overprinted by garnet quartz symplectic coronas these mineral assem blages and their p t pressure temperature estimates define anticlockwise p t evolutionary paths the b type mafic granulites preserve the peak m 1 post peak near isothermal decompression m 2 and cooling m 3 assemblages which are represented by the peak assemblage of orthopyroxene clinopyroxene plagioclase quartz garnet hornblende post peak orthopyroxene plagioclase clinopyroxene symplectites or coronas and later hornblende plagioclase magnetite symplectites respectively these mineral assemblages and their p t estimates define clockwise p t paths the anticlockwise p t paths of the a type mafic granulites in the eastern and western zones of the north china craton are consistent with a model of underplating and intrusion of mantle derived magmas in combination with lithological structural and geochronological data the eastern and west ern zones of the north china craton are considered to represent two continental blocks that devel oped through the interaction of mantle plumes with the lithosphere from the palaeoarchaean to the neoarchaean era the b type mafic granulites and associated rocks in the central zone represent a magmatic arc that was metamorphosed and deformed during amalgamation of the eastern and west ern continental blocks in the late palaeoproterozoic era the mineral reaction relations and clockwise p t paths of the b type mafic granulites from the central zone record the tectonothermal history of the collision that resulted in the final assembly of the north china craton at c 1800 ma

variscan granitoids related to shear zones and faults examples from the central sudetes bohemian massif and the middle odra fault zone the granitoid intrusions of the central sudetes cs and of the middle odra fault zone mofz ne part of the bohemian massif are both spatially and temporally related to large scale shear zones and faults including possible terrane boundaries that provided effective channels for melt migration summarizing common features of the cs and mofz granitoids we have delineated a set of characteristics of the fault related and shear zone related granitoids 1 they are mainly generated by partial melting of crustal sources with variable contribution or no contribution of mantle materials 2 the sheet like steeply inclined narrow and rather small granitoid intrusions are emplaced within shear zones at mid crustal level c 20 km depth whereas the larger flat lying plutons intrude into the upper crust outside or above these shear zones 3 the magmatic foliation and lineation in granitoids of the deeper sheet like intrusions are concordant with those in the surrounding metamorphic rocks suggesting that the solidification of granitoids was coeval with the deformation in the shear zones instead the magmatic foliation in the shallower and larger dome like plutons reflects magma flow 4 ductile transcurrent movements along the shear zones postdate medium pressure regional metamorphism and are accompanied by an increase in the local thermal gradient as documented by the crystallization of cordierite andalusite and sillimanite 5 the increase in the thermal gradient precedes the emplacement of granitoids and their concomitant thermal influence on the country rocks the granitoids related to the final stages of tectonothermal activity of the shear zones are good time markers of their evolutionary path

a late archean tectonic melange in the central orogenic belt north china craton abstract laterally extensive belts of melange characterize phanerozoic convergent plate margins but are rare in archean terranes we document a late archean melange in the zanhuang massif of the north china craton ncc the zanhuang melange separates a passive margin to foreland basin sequence developed on the western edge of the eastern block of the ncc from an arc terrane consisting of trondhjemitic tonalitic and granodioritic ttg gneisses in the central orogenic belt cob of the ncc the melange belt contains a structurally complex tectonic mixture of metapelites metapsammites marbles and quartzites mixed with exotic tectonic blocks of ultramafic and metagabbroic rocks metabasalts that locally include relict pillow structures and ttg gneisses all units in the melange have been intruded by mafic dikes that were subsequently deformed and are now preserved as garnet amphibolite boudins we interpret the melange to mark the suture zone between the eastern block and the arc terrane in the cob field relationships and geochemistry suggest that the exotic ultramafic metagabbroic metabasaltic blocks are possible slivers of an intra oceanic arc or fore arc ophiolite incorporated into the melange during the arc continent collision process a circa 2 5 ga granitic pluton intrudes the melange and undeformed circa 2 5 ga pegmatites cut the melange tectonic models for the evolution of the cob are varied but include models that favor collision at 2 5 ga 2 1 ga and 1 8 ga this work shows clearly from field structural relationships and geochronology that the first collision must have occurred prior to 2 5 ga consistent with late archean suturing of the western margin of the eastern block with an arc terrane fuping terrane during an arc continent collision the presence of an archean melange with exotic blocks in a suture zone between an archean arc and continental margin is clear evidence for the operation of plate tectonics at circa 2 5 ga

the proterozoic ophiolite problem continental emergence and the venus connection to account for the lack of preservation of ophiolites fragments of oceanic crust and mantle in old orogenic belts age 1000 to 2500 million years a hypothesis proposes that the magmatic oceanic crust formed during sea floor spreading was thicker during the cited time interval this thickening led to reduced contrast between the elevation of continental and oceanic regions and to greater average flooding of the continents the resultant distribution of elevation may have resembled modern venus more than modern earth

tournaisian age of granitoids from the odra fault zone southwestern poland equivalent of the mid german crystalline high the odra fault zone of southwestern poland is a nw trending horst marked by gravimetric and magnetic anomalies and composed of high to low grade metamorphic and igneous rocks which are only known from boreholes this zone embraces a concealed border between variscan internides and externides it also contains an array of several i type metaluminous to peraluminous high potassic granitoid bodies which intruded earlier metamorphosed rocks except for one case they remain unfoliated and undeformed and presumably play a role of stitching plutons at the suture between two obliquely colliding terranes u pb tims dating of single zircons from one foliated and one unfoliated granitoid samples yielded identical concordant ages of 344 1 ma tournaisian they resemble a pb pb age of 350 5 ma obtained for s type granitoids from the luckau area further west in germany which is generally regarded as an eastern segment of the mid german crystalline high carboniferous granitic intrusions in the high are generally younger 340 290 ma correlations of the the odra fault zone with the mid german crystalline high appear plausible but by no means certain and require further confirmation

the late paleozoic felsic lava dominated large igneous province in northeast germany volcanic facies analysis based on drill cores in the deep subsurface of the northeast german basin products of extensive volcanism are present that formed during the waning phase of the variscan orogeny permian carboniferous boundary large volumes 48 000 km3 of dominantly felsic magma were emplaced in the northern foreland of the variscan mountains in a terrestrial semi arid environment most of these units were inferred by previous authors to represent the products of explosive volcanic eruptions such as ignimbrites however a detailed analysis of the volcanic texture and lithofacies association shows that most units are best interpreted as coherent lavas emplaced either as extrusive units or as shallow intrusions with important implications for the reconstruction of the paleo environment this study shows that detailed textural examination of drill cores provide important observations which can be applied as criteria for the interpretation of the mode of volcanic eruptions furthermore phenocryst logging and geochemical fingerprinting based on immobile element ratios can be employed for the classification and discrimination of individual emplacement units

granitoid evolution in the late archean wutai complex north china craton abstract two temporally discrete episodes of granite magmatism have been identified in the wutai complex of the north china craton based on shrimp u pb zircon dating of all major granitoid bodies in the area the older period is latest archean and ranges in age from 2560 to 2515 ma whereas the younger episode is paleoproterozoic with magmatism at 2170 and 2120 ma archean magmatism can be further separated into two pulses based on geochemistry and the association of the younger plutons with extensive coeval volcanic activity in the wutai complex the early phase of archean activity is represented by the lanzhishan ekou and portions of the chechang betai granites with ages ranging from 2560 to 2540 ma the lanzhishan granite is the only one at wutaishan that contains inherited zircon with a number of cores and individual grains giving ages in excess of 2700 ma these are relatively evolved granitoids interpreted to be derived from older basement of the eastern block of the north china craton the shifo guangmingshi the main grey phase of the wangjiahui granite and the major components of the chechang betai granite have ages of 2540 2515 ma and are coeval with felsic volcanism in the wutai complex which is a consequence of subduction and related arc magmatism the dawaliang granite and pink phase of the wangjiahui granite are considerably younger with paleoproterozoic ages of 2170 and 2120 ma respectively these are also evolved granitoids most likely derived by partial melting of the older basement although we have found no evidence of inheritance the petrogenesis of the granitoids reflects the precambrian amalgamation history of the north china craton indicating derivation along the western edge of the eastern block during development and amalgamation of the wutai arc and prior to collision with the western block of the craton 1 8 ga ago

lithosphere thickness from new heat flow data of the odra variscan area s w poland equilibrium temperature data from shafts in a mining area of sw poland in the paleozoic platform were used for heat flow calculations a new technique to calculate paleoclimatic correction for heat flow determination from single deep temperature data and equilibrium surface temperatures was applied elevated surface heat flow of 82 87 mw m 2 and mantle heat flow of some 37 41 mw m 2 were found this high heat flow zone spreads from s w poland in the variscan deformation front towards the german part of the polish german basin calculations of geotherms for a variety of heat production models of the crust and upper mantle point to lithosphere asthenosphere boundary depths of about 80 90 km compared to seismologically determined depths of 90 120 km

late carboniferous early permian events in the trans european suture zone tectonic and acid magmatic evidence from poland abstract the trans european suture zone tesz links the east and west european platforms it is concealed under meso cenozoic cover available seismic data show that the lower crustal layer in the tesz is an attenuated 200 km wide sw margin of baltica the attenuation occurred when rodinia broke up which gave rise to evolution of the thinned thus relatively unstable margin of baltica it accommodated accretions during phanerozoic events we focus on acid magmatism specifically granitoid observed close to the sw border of the tesz in poland this border is defined by the dolsk fault zone dfz and the krakow lubliniec fault zone klfz on which dextral wrenching developed as a result of the variscan collision between laurussia and gondwana the granitoids at the dfz and klfz were dated at 300 ma in the variscan foreland that overlaps the tesz orogenic thickening continued to 307 306 ma possibly contributed to melting of the thickened upper continental crust end300 6 0 to 4 5 and triggered the tectonically controlled magmatism the wrenching on the tesz border faults caused tensional openings in the basement which promoted magmatic centers with extrusions of rhyolites and extensive ignimbrites the chrzypsko paproc and malopolska magmatic centers were developed at the dfz and klfz respectively the magmatic edifices commenced at 302 ma with relatively poorly evolved granites which carried both suprasubduction and anorogenic signatures then followed by more evolved volcanic rocks up to 293 ma their geochemistry and inherited zircons suggest that the felsic magmas were mainly derived from upper crustal rocks with some mantle additions which included sveconorwegian and older baltican components the complex tesz with baltica basement in the lower crust was susceptible to transient effects of mantle upwelling that occurred by the end of the variscan orogeny and resulted in an episode of the flare up magmatism in the north german polish basin

single zircon u pb ages and geochemistry of granitoid gneisses from sw poland evidence for an avalonian affinity of the brunian microcontinent seven granitoid gneisses from the contact zone between the eastern margin of the variscan belt and the brunian microcontinent in sw poland have been dated by ion microprobe and 207 pb 206 pb single zircon evaporation methods the zircons define two age groups for the gneiss protoliths 1 late neoproterozoic c 576 560 ma and 2 early palaeozoic c 488 503 ma granites the granitoid gneisses belonging to the basement of the brunian microcontinent contain abundant mesoproterozoic to latest palaeoproterozoic inherited material in the range of 1200 1750 ma the gneisses of the variscan crustal domain lack mesoproterozoic inherited zircon cores trace element geochemistry of proterozoic gneisses reveals features resembling either volcanic arc or post collisional granites the studied rocks are geochemically similar to other proterozoic orthogneisses derived from the basement of the brunian microcontinent gneisses with early palaeozoic protolith ages are geochemically comparable to granitoid gneisses widespread in the adjacent sudetic part of the bohemian massif and are considered characteristic of peri gondwanan crust our data prove the dissimilarity between the brunia plate and the westerly terranes of the variscan belt the occurrence of granitic gneisses with late neoproterozoic protolith ages and widespread mesoproterozoic inheritance in our dated samples support an east avalonian affinity for the brunian microcontinent in contrast the abundance of gneisses derived from an early palaeozoic granitic protolith and devoid of mesoproterozoic zircon cores supports the armorican affinity of the variscan domain bordering on the brunia plate from the west structural evidence shows that the eastern segment of the variscan belt is juxtaposed against the brunian microcontinent along a n s trending tectonic contact possibly equivalent to the rheic suture