saxothuringian zone in germany and poland differences and common features the classical correlation by kossmat 1927 of the saxothuringian belt of germany with the west sudetes of poland is re evaluated with special reference to the crystalline massifs of munchberg and the gory sowie and the surrounding areas important common features are cambro ordovician magmatism and sedimentation silurian to devonian radiolarian cherts in the low grade to unmetamorphosed units early devonian and older pressure dominated metamorphism followed by rapid uplift the incorporation of high pressure and mantle rocks and early carboniferous mass flow deposits with saxothuringian clasts differing features in the west sudetes are tectonic contacts in and around the gory sowie are mostly subvertical and mainly semi brittle in contrast with subhorizontal and ductile contracts in the munchberg the gory sowie has undergone late re equilibration of the earlier tectonic fabrics an ophiolite juxtaposed with the gory sowie crystallized in devonian time and became only statically metamorphosed as opposed to the regionally metamorphosed cambro ordovician mafic rocks of the saxothuringian belt localized depocenters with upper devonian to lower permian elastic rocks relating to north west trending strike slip faults instead of the north east trending cylindroidal foreland basin in the saxothuringian it is possible that the west sudetes originated as an easterly continuation of the saxothuringian belt but then became involved from the late devonian onwards in a strike slip system parallel with the margin of the east european platform

the sudetes as a palaeozoic orogen in central europe two metasedimentary complexes are exposed in the sudetes mountains of poland germany and the czech republic succession i comprises pelites and greywackes of neoproterozoic cambrian age deformed and metamorphosed prior to intrusion by s type porphyritic granites at 515 480 ma succession ii comprises a sandstone mudstone chert sequence and turbidite sequence of ordovician early carboniferous age accompanied by bimodal volcanogenic rocks both successions were intruded by late to post orogenic granitoid intrusions at 340 300 ma the sedimentary rocks of succession ii show increasing maturity until mid late devonian times inversion of the basins commencing in late devonian early carboniferous times was reflected in the emplacement of turbidites and olistostromes concurrent with the uplift of a metamorphic core complex of succession i rocks the original stratigraphic order of the successions was maintained thus crustal imbrication was not significant instead extensional faulting became important followed by transpression on almost orthogonal fault zones resulting in the presently observed juxtaposition of crustal blocks the palaeozoic sequences developed in mainly ensialic basins on cadomian and older basement parts of which became strongly reworked 2 6 to 0 54 ga zircon inheritance ages and incorporated into the palaeozoic structures the orogen developed either on the rifted margin of peri gondwana or on a rifted away fragment of pre baltica the sudetic section of the variscan orogen is of broadly alpine style with significant basement involvement but apparently without evidence for long lived subduction of wide oceans or the accretion of numerous exotic terranes

primary nb ta minerals in the szklary pegmatite poland new insights into controls of crystal chemistry and crystallization sequences an assemblage of primary extremely as and sb rich nb ta minerals from the szklary pegmatite includes columbite fe columbite mn tantalite mn stibiocolumbite stibiotantalite an as yet unnamed as sb u rich ta ti oxide mn3uas2sb2ta2ti2o20 and holtite anomalous trends of mn fe and ta nb fractionation in the columbite group and crystallization sequences in the primary assemblage can be explained by the contamination of the pegmatite forming melt by ultramafic and mafic wall rocks the competition among these minerals for ta and sb and with biotite and tourmaline for mg fe and ti and local variations in melt composition a hot magmatic fluid exsolved from the parental melt reacted with the primary nb ta oxides inducing two different patterns of alteration the columbite group minerals were altered to fersmite pyrochlore and bismutopyrochlore locally grading to plumbopyrochlore whereas stibiocolumbite stibiotantalite and the as sb u rich ta ti oxide altered to stibiomicrolite uranmicrolite grading to betafite and then to bismutomicrolite or bi dominant betafite in all of the secondary pyrochlore group minerals ta nb fractionation is comparable to or only slightly greater than that in the primary nb ta oxides indicating a modest differentiation of the residual melt coexisting with the fluid

lepageite mn32 fe73 fe42 o3 sb53 as83 o34 a new arsenite antimonite mineral from the szklary pegmatite lower silesia poland

shrimp u pb zircon geochronology of the strzelin gneiss sw poland evidence for a neoproterozoic thermal event in the fore sudetic block central european variscides zircon ages recorded in gneissic rocks have recently been used as criteria to define and correlate various tectonic units and crustal blocks in the central european variscides a shrimp u pb zircon geochronological study of the strzelin gneiss in the fore sudetic block sw poland indicates the presence of 1 inherited zircon cores of palaeo to mesoproterozoic 206pb 238u ages between ca 2 000 and 1 240 ma and 2 zoned rims of neoproterozoic age with two distinct means of 600 7 and 568 7 ma the proterozoic age range of the cores suggests that different precambrian crustal elements were the source for the protolith of the gneiss a likely scenario is the erosion of various proterozoic granites and gneisses sedimentation after 1 240 ma and partial resistance of the original components to subsequent metamorphic dissolution and or anatectic resorption in neoproterozoic times the zoned zircon rims of both of the younger neoproterozoic ages are indistinguishable in the cathodoluminescence images the data are interpreted in terms of two different thermal events inducing zoned zircon overgrowth at ca 600 and 568 ma in general the new results confirm earlier assumptions of the proterozoic age of the gneiss protoliths and indicate their similarity to orthogneisses in the east sudetes tectonic domain e g the velke vrbno and desna gneisses the neoproterozoic dates are different from the age of 504 3 reported earlier for the go ciecice gneiss from a neighbouring locality in the strzelin massif the new data strongly indicate a moravo silesian bruno vistulian affinity for the strzelin gneiss and support the hypothesis that the strzelin massif lies within the tectonic boundary zone between the west and east sudetes domains which represents the northern continuation of the moldanubian thrust

potential field imaging of palaeozoic orogenic structure in northern and central europe abstract the trans european suture zone tesz is the most fundamental lithospheric boundary in europe separating the ancient crust of the fennoscandian shield east european craton from the younger crust of central europe and extending deep into the mantle geophysical potential field images provide an overview of the entire palaeozoic orogenic system of northern and central europe for the first time the tesz is largely concealed by sedimentary basins of permian cenozoic age geological observations are largely restricted to local basement highs and deep boreholes and the coverage of deep seismic surveys is widely spaced despite experiments recently acquired within the europrobe programme by contrast the potential field data offer a relatively detailed coverage of standardised observations throughout the tesz while some features of the images may be sourced in the near surface particularly in the gravity image much of their content reflects the structure of the underlying palaeozoic basement at the scale presented the images highlight the most fundamental features of the crustal structure of the tesz these include the strong contrast between the highly magnetic crust of the east european craton and the less magnetic palaeozoic accreted terranes of central europe the lateral continuity of terranes and their internal structure particularly where arc magmatic complexes are involved and the location and geometry of the terrane boundaries oceanic sutures and strike slip zones that separate them

high pressure granulites from the sudetes south west poland evidence of crustal subduction and collisional thickening in the variscan belt two high grade gneissic complexes of the western sudetes the gory sowie block and the nieznik area complex contain small predominantly felsic granulitic inliers with minor cpx bearing intercalations the p t conditions of the granulite facies events and of the subsequent re equilibration are estimated using the ternary feldspar thermometer and the geo calc computer program version twq jan 92 in the gory sowie granulites the peak granulitic event occurred at c 18 20 kbar and 900 c and the late decompressive re equilibration within a range of 4 10 kbar and temperatures decreasing to 600 700 c the latter event is thought to have coincided with the main metamorphic phase in the surrounding gneisses the p t estimates are more scattered in the nieznik granulites but the peak conditions for the granulitic event are estimated at pressure over 22 kbar possibly around 30 kbar and temperature exceeding 900 c the analysed samples from the nieznik area bear no significant evidence of lower pressure re equilibration integrating the thermobarometric data and some age constraints indicates that the gory sowie granulites belong to the early stage type i granulites of the variscan belt c 400 ma old which are interpreted as fragments of continental crustal materials subducted to mantle depths in the earliest stages of the variscan orogeny the nieznik granulites are more problematic they may belong to a younger high p suite c 350 ma old widespread in the southern and eastern parts of the bohemian massif and possibly related to the climax of the variscan continent continent collision

lower palaeozoic and precambrian igneous rocks from eastern england and their bearing on late ordovician closure of the tornquist sea constraints from u pb and nd isotopes the u pb isotope ages and nd isotope characteristics of asuite of igneous rocks from the basement of eastern england show that ordovician calc alkaline igneous rocks are tectonically interleaved with late precambrian volcanic rocks distinct from precambrian rocks exposed in southern britain new u pb ages for the north creake tuff zircon 449 13 ma moorby microgranite zircon 457 20 ma and the nuneaton lamprophyre zircon and baddeleyite 442 3 ma confirm the presence ofan ordovician magmatic arc tectonically interleaved precambrian volcanic rocks within this arc are verified by new u pb zircon ages for tuffs at glinton 612 21 ma and orton 616 6 ma initial end values for these basement rocks range from 4 to 6 consistent with generation of both c 615 ma and c 450 ma groups of rocksin continental arc settings the u pb and sm nd isotope data support arguments for an ordovician fold thrust belt extending from england to belgium and that the ordovician calc alkaline rocks formed in response to subductionof tornquist sea oceanic crust beneath avalonia

u pb ages from sw poland evidence for a caledonian suture zone between baltica and gondwana faunal and palaeomagnetic evidence suggests the existence of a c 3000 km wide tornquist sea between gondwana and baltica in early ordovician times which narrowed to 50 2 ma an unmetamorphosed ophiolite gives a 420 20 2 ma age whilst in two other terranes amphibolite facies island arc lavas have fossiliferous lower ludlow 424 415 ma sequences all are unconformably overlain by unmetamorphosed upper devonian conglomerates a sinistral transpressive regime is observed in regionally extensive mylonite zones titanite and zircon ages 338 2 3 and 339 4 ma record variscan magmatism the data suggest considerable narrowing of the tornquist sea during the ordovician continuing ocean floor and island arc activity in the silurian and final sinistral transpressive closure by the mid devonian

exhumation and metamorphism of an ultrahigh grade terrane geochronometric investigations of the sudete mountains bohemia poland and czech republic the sudete mountains ne bohemian massif czech republic and poland preserve abundant eclogitic and granulitic centimetre to decimetre scale boudins enveloped in a predominantly migmatitic matrix published geochronometry and thermobarometry from the uhp and uht rocks broadly constrain the crystallization and initial stage 1 exhumation history for these units however the timing of stage 2 metamorphism and associated unroofing is less well constrained new in situ ion microprobe th pb monazite results together with complementary u pb zircon and electron microprobe analyser total pb monazite results on 11 amphibolite facies gneissic to migmatitic samples place important temporal constraints on the second stage of uhp and uht metamorphism exhumation the orlica snieznik dome records uhp metamorphism occurring at 375 ma and subsequent exhumation to midcrustal levels in supra barrovian conditions at c 345 330 ma in contrast the western gory sowie block preserves evidence of hp granulite conditions at c 400 ma and exhumation to mid crustal levels at 380 370 ma revealing a c 30 million years difference in exhumation events between the neighbouring terranes the eastern gory sowie block preserves ages similar to the orlica sneiznik dome suggesting that different preserved metamorphic cooling histories are juxtaposed across the sudetic marginal fault the bounding niemcza shear zone yields preliminary th pb dates that range from 380 8 ma to 283 2 ma preserving a protracted metamorphic record that spans the exhumation history of the region the distinct collapsed geochronologies of both terranes probably reflect rapid vertical transport of low viscosity crust under supra barrovian conditions near the mid crustal high strength lid during oblique transpressional convergence

u pb geochronology and petrology of the late paleozoic gil marquez pluton magmatism in the variscan suture zone southern iberia during continental collision and the amalgamation of pangea the origin of plutonic complexes that stitch suture zones developed during collision is not well understood in southern iberia the pulo du lobo suture zone pdlz is intruded by the syn to postcollisional gil marquez pluton gmp thought to be part of the sierra norte batholith u pb la icpms zircon data on various phases of the gmp yield from oldest to youngest 1 a 354 4 7 6 ma unfoliated gabbro 2 a 345 6 2 5 ma foliated intermediate phase 3 a 346 5 5 4 ma unfoliated porphyritic granite 4 a 335 1 2 8 ma unfoliated biotite granite this sequence is consistent with cross cutting relationships observed in the field the range in ages is consistent with interpretations that the gmp is part of the composite ca 350 308 ma snb inherited ages preserved in the gmp intermediate and felsic phases indicate that its magmas traversed through south portuguese zone and pdlz crust during emplacement the ca 345 ma emplacement of the late kinematic foliated intermediate phase constrains the age of late stage strike slip deformation within the pdlz and the lack of a foliation in the older gabbro indicates that is was not proximal to a shear zone neither at the time of emplacement nor during its subsequent history the unfoliated porphyritic granite and unfoliated biotite granite cut the foliation of the intermediate phase indicating emplacement during the waning stages of collision while the ca 335 ma biotite granite intrudes the santa ira flysch thereby providing a tight constraint for the latest stage of deformation in the pdlz

pb u and th diffusion in natural zircon zircon zrsio4 is one of the most widely used minerals for determining the age origin and thermal history of rocks by u th pb geochronology but the parameters describing the solid state volume diffusion rates of these elements in natural zircon which are themselves important for establishing the limits on the applicability of zircon for geochronological studies have remained poorly quantified1 this is because of the measurement difficulties associated with the low p p m concentrations and low diffusion rates of these elements in natural zircon and the chemical and physical heterogeneity present in most crystals here we present direct measurements of the uranium thorium and lead loss from a thermally treated gem quality natural zircon and show that lead diffuses much faster than uranium or thorium we find that the u th pb isotopic system in natural zircon will typically have a closure temperature greater than 900 c which explains why zircon is apparently such a robust geochrometer and is capable of remaining isotopically closed through extended periods of high grade metamorphism and partial melting of the host rock

palaeozoic terrane amalgamation in central europe a ree and sm nd isotope study of the pre variscan basement ne bohemian massif

heterogeneous extrusion and exhumation of deep crustal variscan assembly geochronology of the western tatra mountains northern slovakia abstract the nature and style of mid crustal assembly and exhumation during continental collision has been investigated in the tatra mountains of the western carpathians the pre alpine basement of the western carpathians represents the easternmost exposure of the variscan orogen in europe which marks the collision of laurasia with gondwanian affiliated terranes during the palaeozoic the tatric crystalline unit of the western tatra in northern slovakia displays an inverted metamorphic sequence where a high grade unit comprising migmatites with relicts of eclogite has been thrust over a lower grade mica schist unit new geochronological and thermochronological data together with published thermobarometry illuminate the metamorphic history of the western tatra the upper unit eclogites with occasionally preserved omphacite record near isothermal decompression from 1 6 gpa to 1 0 1 2 gpa at 750 800 c which lead to intensive re equilibration at high pressure granulite facies conditions comparable to the peak metamorphic conditions of the host migmatite both eclogite and migmatite shared a retrograde p t path following the insertion of the eclogite assemblage into the migmatites the metamorphic evolution of the lower unit mica schist is constrained to peak p t conditions of 0 6 0 8 gpa and 640 and 660 c followed by retrogression this suggests that different rock types of the western tatra metamorphic core shared only their exhumation path from mid crustal levels id tims sm nd dating of garnet from eclogite yields a whole rock garnet isochron age of 337 10 ma with an initial e nd isotopic composition of 8 3 in situ u pb dating of monazite from a migmatite surrounding the eclogite shows one age population of c 380 ma whereas monazite from a migmatite away from the eclogite preserves a robust 340 11 ma age which is indistinguishable from sm nd garnet age and u pb age of zircons in the anatectic leucosome of the migmatite 347 7 ma a younger monazite age population from the migmatite of 300 16 ma is consistent with 40 ar 39 ar mica ages of c 310 ma this argues for a contemporaneous and likely shared exhumation path of the assemblage pair in situ monazite total pb analyses from the lower unit mica schists yields xenocrystic and c 370 ma ages but no geochronologic evidence for peak variscan tectonism exhumation of the deep crustal root occurred most probably in a two stage process the timing of the high pressure eclogite facies metamorphism before the onset of exhumation into the mid crust was likely between c 380 ma and 360 ma subsequent exhumation into the middle crust was coeval with migmatite generation at c 340 ma and garnet diffusion modeling suggest 30 c ma cooling rates the exhumation was likely tectonically forced by the action of a rigid indentor which prompted the weak lower crust to be heterogeneously extruded to mid crustal levels at a time coeval with anatexis and subsequently extruded with mid crustal material to the upper crust

new u pb monazite and zircon data from the sudetes mountains in sw poland evidence for a single cycle variscan orogeny new u pb monazite and zircon data combined with a study of their internal morphologies significantly clarifies the controversy surrounding the palaeozoic geodynamic evolution of the sudetes mountains in the northeastern bohemian massif variably thin rims of secondary magmatic overgrowth on zircons from an anatectic granite in the gory sowie block are dated by a u pb zircon lower intercept age of 353 61 ma by magmatic monazite growth at 378 2 ma and by xenotime crystallization at 383 370 ma in a late syntectonic pegmatite reflecting the anatectic event associated with a single cycle variscan orogeny in this area

terranes and terrane boundaries in the sudetes northeast bohemian massif in the sudetes seven distinct lithostratigraphic terranes exhibit a symmetric distribution a central region of basinal oceanic and ophiolitic rocks the central sudetic terrane is bordered respectively to the northwest and southeast by the sialic saxothuringian and moldanubian terranes these exhibit contrasting metasedimentary metavolcanic successions and tectonic metamorphic sequences but both are characterized by palaeozoic plutonism these are in turn bordered again respectively to the northwest and southeast by the lusatian and moravian terranes which are also sialic but contain cadomian granitoids and represent rifted and now widely separated fragments of gondwana along the southwestern flank of the sudetes the barrandian terrane largely covered by younger sediments extends to the southwestern margin of the bohemian massif the sowie gory terrane forms a klippe of high grade gneisses tectonically emplaced on top of low grade sheared ophiolites of the central sudetic terrane the sowie gory terrane exhibits a history of three distinct probably multi orogenic regional metamorphic events an early high pressure granulite eclogite metamorphism followed by medium to low pressure granulite and in turn by amphibolite facies metamorphism all the terrane boundaries are complex zones of ductile to brittle shearing modified by later brittle movements some such as the leszczyniec shear zone mark lines of old pre variscan rift and suture zones reactivated and overprinted during a series of variscan ductile to brittle events of extensional shearing with related metamorphism and plutonism

rb sr and u pb geochronology of migmatitic gneisses from the gory sowie west sudetes poland the importance of mid late devonian metamorphism the gory sowie block west sudetes sw poland consists of a gneiss migmatite complex with minor amphibolites calc silicate rocks ultrabasic rocks and granulites migmatitic gneisses underwent a complex polyphase history of deformation and metamorphism each deformation phase d1 to d5 being associated with synkinematic amphibolite facies metamorphism m1 to m5 for a better understanding of the p t t deformation path three types of gneisses which represent distinct stages of deformation and metamorphism d2 m2 d3 m3 and d5 m5 have been studied by means of the rb sr and u pb isotopic systems u pb monazite and xenotime ages of c 380 ma for rocks migmatized and deformed during the d3 m3 and d5 m5 stages constrain the timing of the last metamorphic migmatitic event in the gory sowie block rb sr thin slab and mica whole rock dating for samples with d2 d3 and d5 characteristics provide ages between 362 and 375 ma which overlap within error 2o no correlation between deformational characteristics and apparent rb sr ages was recognized the rb sr data are interpreted as time constraints for post peak metamorphic cooling the new geochronological data indicate the significance of devonian high temperature metamorphism in the sudetes and support a similar interpretation of earlier studies the isotopic results are also consistent with the interpretation based on field structural and petrological data that at least four d2 d5 structural episodes occurred in devonian times within a very short time interval the details of which cannot be further resolved with the methods used

space and time in the tectonic evolution of the northwestern iberian massif implications for the variscan belt recent advances in geochemical studies of igneous rocks isotopic age data for magmatism and metamorphism quantitative pressure temperature p t estimates of metamorphic evolution and structural geology in the northwestern iberian massif are integrated into a synthesis of the tectonic evolution that places the autochthonous

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

statistics and dynamics of persistent anomalies abstract persistent anomalies with recurrent spatial patterns play an important role in the atmosphere s low frequency variability we establish a connection between statistical and dynamical methods of description and prediction of persistent anomalies this is done by computing and analyzing the empirical orthogonal functions eofs in a simple deterministic model on the one hand and in southern hemisphere geopotential heights on the other the dynamical model is governed by the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography model solutions exhibit persistent anomalies identifiable with blocked zonal and wave train anomalies in northern hemisphere atmospheric data flow structures similar to the patterns above occur as high variance eofs of this nonlinear model the southern hemisphere data we analyze consist in gridded daily maps of 500 mb heights from june 1972 to july 1983 two types of persistent anomalies appear in t

kinematic data on major variscan strike slip faults and shear zones in the polish sudetes northeast bohemian massif the still highly disputable terrane boundaries in the sudetic segment of the variscan belt mostly seem to follow major strike slip faults and shear zones their kinematics expected to place important constraints on the regional structural models is discussed in some detail the most conspicuous is the wnw ese intra sudetic fault zone separating several different structural units of the west sudetes it showed ductile dextral activity and probably displacement magnitude of the order of tens to hundreds kilometres during late devonian to early carboniferous times in the late carboniferous to early permian the sense of motion on the intra sudetic fault was reversed in a semi brittle to brittle regime with the left lateral offset on the fault amounting to single kilometres the north south trending niemcza and north east southwest skrzynka shear zones are left lateral ductile features in the eastern part of the west sudetes similarly oriented northeast southwest to nne ssw regional size shear zones of as yet undetermined kinematics were discovered in boreholes under cenozoic cover in the eastern part of the sudetic foreland the nied wied and nysa brzeg shear zones one of these is expected to represent the northern continuation of the major stare mesto shear zone in the czech republic separating the geologically different units of the west and east sudetes the rudawy janowickie metamorphic unit assumed in some reconstructions to comprise a mostly strike slip terrane boundary is characterized by ductile fabric developed in a thrusting regime modified by a superimposed normal slip extensional deformation thrusting related deformational fabric was locally reoriented prior to the extensional event and shows present day strike slip kinematics in one of the sub units the sudetic boundary fault although prominent in the recent structure and topography of the region was not active as a variscan strike slip fault zone the reported data emphasize the importance of syn orogenic strike slip tectonics in the sudetes the recognized shear sense is compatible with a strike slip model of the northeast margin of the bohemian massif in which the kaczawa and gory sowie units underwent late devonian early carboniferous southeastward long distance displacement along the intra sudetic fault zone from their hypothetical original position within the northern phyllite zone and the mid german crystalline high of the german variscides respectively and were juxtaposed with units of different provenance southwest of the fault the intra sudetic fault zone together with the elbe fault zone further south were subsequently cut in the east and their eastern segments were displaced and removed by the younger early to late carboniferous nne ssw trending transpressional moldanubian stare mesto shear zone