pre alpine history of the pennine zone in the tauern window austria u pb and rb sr geochronology zircon ages from major lithologies of the zentralgneis suggest that much of the variscan magmatism in the tauern window is older than previously suggested in the southeast tauern window a tonalite has been dated at 314 7 m y and a granodioritic biotite augen gneiss at 313 10 m y two granodiorites from the granatspitzkern yielded zircon data consistent with a similar age these zircon data require re interpretation of some previously published rb sr whole rock ages and raise the possibility that alpine metamorphism caused more widespread disturbance of rb sr whole rocks than commonly supposed

carbo permian pteridophyll leaf fragments from an amphibolite facies basement tauern window austria graphitic schists from the pennine basement tauern window austria contain fragments of pteridophyll leaves they are preserved despite the overall strong deformation and metamorphism at amphibolite facies conditions 525 c 750 100 mpa due to a particular strain path with volume loss by pressure solution they were determined as cf callipteridium sp indicating a permo carboniferous age this depositional age is similar to radiometric age data obtained for the intrusion of nearby metagranitoids indicating either tectonic contacts between the metagranitoids and the graphite schists or a very active and rapidly changing tectonic regime during the hercynian event

replacement of primary monazite by apatite allanite epidote coronas in an amphibolite facies granite gneiss from the eastern alps accessory monazite crystals in granites are commonly unstable during amphibolite facies regional metamorphism and typically become mantled by newly formed apatite allanite epidote coronas this distinct textural feature of altered monazite and its growth mechanism were studied in detail using backscattered electron imaging in a sample of metagranite from the tauern window in the eastern alps it appears that the outer rims of the former monazites were replaced directly by an apatite ring with tiny thorite intergrowths in connection with ca supply through metamorphic fluid around the apatite zone a proximal allanite ring and a distal epidote ring developed this concentric corona structure with the monazite core regularly preserved in the center shows that the reaction kinetics were diffusion controlled and relatively slow quantitative electron microprobe analyses suggest that the elements released from monazite breakdown p ree y th u were diluted and redistributed in the newly formed apatite allanite and epidote overgrowth rings and were unable to leave the corona this supports the common hypothesis that these trace elements are highly immobile during metamorphism furthermore microprobe data suggest that the preserved monazite cores lost little possibly none of their radiogenic lead during metamorphism thus metastable monazite grains from orthogneisses appear to be very useful for constraining u th pb protolith ages on the basis of these findings and a review of literature data it seems that monazite stability in amphibolite facies metamorphic rocks depends strongly on lithologic composition while breaking down in granitoids monazite may grow during prograde metamorphism in other rocks such as metapelites

geomorphology and neogene tectonic evolution of the palomares continental margin western mediterranean abstract the palomares continental margin is located in the southeastern part of spain the margin main structure was formed during miocene times and it is currently part of the wide deformation zone characterizing the region between the iberian and african plates where no well defined plate boundary occurs the convergence between these two plates is here accommodated by several structures including the left lateral strike slip palomares fault the region is characterized by sparse low to moderate magnitude mw

slab rupture and delamination under the betics and rif constrained from receiver functions abstract we map the lithospheric structure under the westernmost mediterranean convergent setting interpreting p receiver functions obtained from a dense seismic network no orogenic root occurs under the eastern and great part of the central betics however the subducted south iberian continental lithosphere is found beneath the western betics where the iberian moho reaches depths of approximately 65 km dipping gently towards the se meanwhile at the rif strong crustal and lithospheric thickness contrasts occur across the nekor nw se sinistral fault that overlies the region of present slab tearing east of the nekor fault there is no orogenic root and the crust has been thinned to approximately 22 km whilst to the west the crust reaches 55 km thickness and the maghrebian continental lithosphere is attached to the lithospheric slab imaged by tomography under the alboran basin these data suggest that subduction rollback under the alboran and algerian basins together with continental slab tearing or detachment producing edge delamination under the betics and rif have been the main tectonic mechanisms driving extension magmatism and regional uplift in the westernmost mediterranean since the late miocene until present the surface expression of edge delamination and slab tearing is marked by regional uplift denudation of hp rocks in elongated core complex type domes late miocene volcanism in the eastern betics and rif and by large ne sw strike slip transfer faults like the alpujarras crevillente torcal or nekor faults that accommodate strong gradients in crustal displacements the iberian slab is still attached to the oceanic slab imaged under the alboran basin at the western betics where intermediate depth seismicity recent dextral strike slip faulting and folding could reflect slab tearing meanwhile active faulting and differential gps measured displacements would mark slab tearing beneath the rif coinciding with the trace of the sinistral nekor fault

crystallization and deformation of amphiboles and cummingtonite forming reactions in the garbenschists of the western tauern window eastern alps northeast italy western austria abstract a detailed microscopic study of the amphiboles crystallized during the late alpine metamorphism in the hornblende garbenschists of the western tauern window reveals sevesal stages of crystallization cr1 cr3 and deformation d1 d3 during the first stage of crystallization cr1 poikiloblastic green hornblende of tschermakitic composition overgrew a matrix showing a strong s1 foliation a slight tendency towards increasing tschermak s and edenite exchange with glaucophane component decreasing towards the rim suggests amphibole growth during heating and decompression this prograde metamorphism leads to simultaneous formation of cummingtonite and hornblende in 3 out of 16 studied samples the cummingtonite forming reactions are discussed both hornblende and cummingtonite show microcracks forming s2 which is oblique to s1 s2 is missing in quartz and feldspar and also in some cases in the rims of the hornblende but is traceable through trails of fluid inclusions the last deformational event d3 is a tensional one producing s3 as large cracks in the amphiboles correlation of deformation and exchange components with published p t paths suggests growth of amphibole cores at amphibolite facies conditions hornblende and cummingtonite rims formed at decreasing pressures but still rising temperatures s2 microcracks are due to tectonic deformation d2 while the s3 extensional cracks were formed by ductile thinning d3 at rising temperatures as revealed by the mineral parageneses found in the cracks this paper presents the petrological framework for detailed geochronological investigations giving the time calibration of the p t path of the alpine metamorphism of the western tauern window

active shallow extension in central and eastern betic cordillera from cgps data abstract the betic cordillera is an alpine belt formed in the western mediterranean by the westward displacement of the alboran domain in between the eurasian and african convergent plates new cgps data from the central and eastern betic cordillera and its foreland obtained mainly from the topo iberia project allowed us to precisely determine the rate of tectonic deformation most of the displacements of the central and eastern betics are westward with a variable southwestward component in relation to the eurasian stable plate while in the iberian foreland the displacements are extremely low some deformation related to low compressional deformation occurs in the easternmost foreland basin and eastern betic cordillera the displacement increases substantially southwards and westwards in relation to present day extensional deformation major active discontinuities correspond to the nw se normal fault zones which dip westwards they are located in almeria tabernas balanegra and western sierra de gador whereas the padul fault zone located west of sierra nevada extends northwards to the granada basin nw se extensional faults are also observed to the north in the baza basin moreover the activity of dextral faults along the sorbas tabernas alpujarras guajares band generally considered as a transfer fault zone is evidenced by the displacement data these results come to demonstrate the low activity or inactivity of the large northern e w oriented folds of the central and eastern internal zone such as the sierra de los filabres antiform they also point to the possible residual activity of the northern part of the ne sw sierra nevada antiform where the maximum relief of the cordillera is found altogether our data support a heterogeneous present day westward extension that affects the upper crust of the betic cordillera and increases towards the thinned continental crust of the alboran sea and towards the west which is compatible with roll back subduction along the gibraltar arc

understanding the pre variscan and variscan basement components of the central tauern window eastern alps austria constraints from single zircon u pb geochronology new single grain and within grain u pb zircon ages from the central tauern window help sorting out the time dimension among the various variscan and pre variscan basement components that were strongly overprinted by alpine orogeny single grain isotope dilution id tims u pb zircon geochronology of three basisamphibolit samples yield protolith formation ages of 351 2 349 1 and 343 1 ma laser ablation icp ms and id tims u pb detrital zircon dating of the biotitporphyroblastenschiefer constrained the maximum time of sedimentation to between 362 6 ma and 368 17 ma paragneisses from the zwolferzug yield maximum sedimentation ages from 345 5 ma ion microprobe data to 358 10 ma zircons from gabbroic clasts and detrital zircons from a meta agglomerate from the habach phyllite give an upper intercept age of 536 8 ma and a near concordant age of 506 9 ma respectively hence apart from the habach phyllite the maximum sedimentation ages of the metasediments investigated range from upper devonian to lower carboniferous consequently the basisamphibolit the biotitporphyroblastenschiefer and the paragneisses of the zwolferzug form parts of the variscan basement series the basisamphibolit 351 343 ma is distinct both in space and time of formation from the zwolferzug garnet amphibolite c 486 ma which forms part of the pre variscan basement

distribution of variscan i and s type granites in the eastern alps a possible clue to unravel pre alpine basement structures abstract meta granitoid rocks with variscan intrusion ages have been investigated in the three large austroalpine basement massifs of the schladminger tauern the seckau bosenstein tauern and the semmering raabalpen the first two massifs are dominated by calc alkaline i type granitoids mainly granodiorites tonalites and are thus similar to most other intra alpine variscan granitoid massifs while the semmering raabalpen area is one of the rare examples of an intra alpine s type batholith this confirms previous concepts according to which the semmering raabalpen area is part of a separate variscan terrane within the austroalpine basement it is suggested that this basement terrane already had some affinities to the thick mature crust that is typical for the internal moldanubian zone of the variscides the widespread occurrence of carboniferous i type plutons suggests the presence of a less evolved or newly underplated variscan lower crust in most other parts of the eastern alps this kind of crust was probably typical for the former southern flank of the variscan orogen

u pb zircon rb sr and sm nd geochronology of high to very high pressure meta acidic rocks from the western alps three meta acidic rocks from the western italian alps a magnesiochloritoid bearing metapelite from the monte rosa massif a coesite pyrope quartzite from the dora maira massif and the monte mucrone granite in the sesia zone have been studied by u pb zircon rb sr on whole rock apatite and phengite and sm nd wholerock methods the mineral parageneses of the investigated rocks indicate high to very high pressure and medium to high temperature metamorphism this combined isotopic study has enabled us to constrain the ages of magmatic and metamorphic events and also to compare the behaviour of u pb zircon systems in three intensely metamorphosed areas of the pennine domain the u pb zircon data have yielded a magmatic age for the monte mucrone granite at 286 2 ma this result confirms the occurence of late hercynian magmatism in the sesia zone as in other austro alpine units and in other areas of the european crystalline basement in the monte rosa massif a geologically meaningless lower intercept age of 192 2 ma has been interpreted as an artefact due to a complex evolution of the u pb zircon system the magmatic shape of the zircons implies a magmatic or volcano sedimentary protolith for this rock originally considered as a metasediment the very high pressure metamorphism in the dora maira quartzite has produced an opening of the u pb zircon system at 121 12 29 ma the rb sr data support the occurence of high grade metamorphism during cretaceous times phengites model ages are slightly younger than the u pb zircon lower intercept ages due to cooling phenomena or possible response of the phengites to a later deformation the nd model ages from the whole rock samples as well as the u pb upper intercept ages from zircons of all three investigated rocks indicate the presence of proterozoic crustal components inherited from the precursors of these meta acidic rocks the studied zircon populations and their u pb systems apparently showed open system behaviour only when affected by extreme metamorphic conditions 700 750 c 28 kbar whereas eclogite facies conditions of 500 550 c and 14 16 kbar were not enough to disturb significantly the u pb zircon evolution it is also probable that the sedimentary or magmatic origin of the protoliths of these meta acidic rocks which involved different characteristics such as grain size and fluid phase concentration and composition could be another important factor controlling the u pb zircon system behaviour during metamorphic events

modelling floodplain flows using a two dimensional finite element model a prototype two dimensional finite element flow model for depth averaged free surface flows was developed for floodplain environments limited refinement of the model s physical representation was undertaken and the enhanced scheme applied to an 11 km river channel floodplain reach in the u k preliminary model results indicate that this modelling approach can be used to identify dynamic variations in the flow field parameters over length scales of the order of 10 100 m potentially such data have the ability to permit detailed analysis of short term floodplain sedimentary dynamics

footwall uplift in an orogenic wedge the tauern window in the eastern alps of europe abstract in the tauern window tw the deepest structural units of the eastern alps are exposed in a 30 160 km antiform european basement and cover occur under nappes of oceanic penninic units and continental origin austroalpine nappes the tertiary structural history of the tw is related to a rapid uplift of 20 30 km since oligocene times structural mapping revealed 1 detachment and folding of the cover units and stacking of orthogneiss sheets 2 constrictional folding of the entire duplex with amplitudes and half wavelengths of several kilometres 3 backthrusting and backfolding along the northern margin of the tw and 4 displacement along steep dip divergent strike slip faults the strain history is complex and related to all these deformation phases the most uniform structural element is a stretching parallel to the long axis of the tw and its major fold axes strain did not contribute to tw uplift because ductile n s shortening was compensated by e w extension restoration of the tw shows that the exposed structures are not sufficient to explain the tw uplift by analogy with the engadine window and the western alps where seismic data are available a deep seated duplex is suspected the tw uplift is best explained in a dextral transpressive regime

geodetic evidence for continuing tectonic activity of the carboneras fault se spain abstract the carboneras fault zone cfz is a prominent onshore offshore strike slip fault that forms part of the eastern betic shear zone ebsz located in se spain in this work we show for the first time the continuing tectonic activity of the cfz and quantify its geodetic slip rates using continuous and campaign gps observations conducted during the last decade we find that the left lateral motion dominates the kinematics of the cfz with a strike slip rate of 1 3 0 2 mm yr along the n48 direction the shortening component is significantly lower and poorly constrained recent onshore and offshore paleoseismic and geomorphic results across the cfz suggest a minimum late pleistocene to present day strike slip rate of 1 1 mm yr considering the similarity of the geologic and geodetic slip rates measured at different points along the fault the northern segment of the cfz must have been slipping approximately at a constant rate during the quaternary regarding the eastern alpujarras fault zone corridor afz located to the north of the cfz our gps measurements corroborate that this zone is active and exhibits a right lateral motion these opposite type strike slip motion across the afz and cfz is a result of a push type force due to nubia and eurasia plate convergence which in turn causes the westward escape of the block bounded by these two fault zones

interactions between serpentinite devolatilization metasomatism and strike slip strain localization during deep crustal shearing in the eastern alps the greiner shear zone in the tauern window eastern alps changes from a zone of distributed dominantly sinistral shear in supracrustal rocks to a series of narrow gully forming dextral splays where it enters basement gneisses within these splays granodiorite is transformed into quartz poor biotite and or chlorite schists reflecting hydration removal of si ca and na and concentration of fe mg and al stable isotope analyses show a prominent increase in d and a decrease in 18o from granodiorite into the shear zones these changes indicate significant channelized flow of an externally derived low 18o high d fluid through the shear zones the shear zone schists are chemically similar to blackwall zones developed around serpentinite bodies elsewhere in the greiner zone and the stable isotope data support alteration via serpentinite derived fluid monazite in schist from one shear zone yields spot dates of 29 20 ma indicating that the fluid influx and switch from sinistral to dextral shear occurred at or shortly after the thermal peak of the alpine orogeny c 30 ma we suggest that alpine metamorphism of serpentinites released large amounts of high d low 18o si undersaturated fe mg saturated fluids that became channelized along prior zones of weakness in the granodiorite infiltration of this fluid facilitated growth of chlorite and biotite which in turn localized later dextral strain in the narrow splays via cleavage parallel slip this dextral strain event can be linked to other structures that accommodated tectonic escape of major crustal blocks during dextral transpression in the eastern alps this study shows that serpentinite devolatilization can play an important role in modifying both the chemistry and rheology of surrounding rocks during orogenesis

oligocene range uplift and development of plateau morphology in the southern central andes 1 the puna altiplano plateau in south america is a high elevation low internal relief landform that is characterized by internal drainage and hyperaridity thermochronologic and sedimentologic observations from the sierra de calalaste region in the southwestern puna plateau argentina place new constraints on early plateau evolution by resolving the timing of uplift of mountain ranges that bound present day basins and the filling pattern of these basins during late eocene miocene time paleocurrent indicators sedimentary provenance analyses and apatite fission track thermochronology indicate that the original paleodrainage setting was disrupted by exhumation and uplift of the sierra de calalaste range between 24 and 29 ma this event was responsible for basin reorganization and the disruption of the regional fluvial system that has ultimately led to the formation of internal drainage conditions which in the salar de antofalla were established not later than late miocene upper eocene oligocene sedimentary rocks flanking the range contain features that suggest an arid environment existed prior to and during its uplift provenance data indicate a common similar source located to the west for both the southern puna and the altiplano of bolivia during the late eoceneoligocene with sporadic local sources this suggests the existence of an extensive longitudinally oriented foreland basin along the central andes during this time citation carrapa b d adelmann g e hilley e mortimer e r sobel and m r strecker 2005 oligocene range uplift and development of plateau morphology in the southern central andes tectonics 24 tc4011 doi 10 1029 2004tc001762

systematics of internal zircon morphology in major variscan granitoid types the internal morphologies of zircon crystals from different types of granitoids alkaline calcalkaline and anatectic are revealed by cathodoluminescence imaging and are described in terms of growth rates of the crystal faces relative to each other zircons in the alkaline granitoids are characterized by high and constant growth rates of 010 relative to the pyramidal forms and by symmetric grwoth of 011 zircons in the calcalkaline and anatectic granitoids are characterized by fluctuating or gradually decreasing relative growth rates of 010 by asymmetric and highly variable growth of 011 and by a tendency of 110 to become grwoth inhibited corrosion events are interspersed during zircon growth in the calcalkaline magmas in the calcalkaline and anatectic magmas a discontinuity breaks the morphological evolution at late stages of crystallization the discontinuity coincides with a sharp drop in cathodoluminescence the growth behaviour of each crystal form is analysed and compared with predictions made by the periodic bond chain pbc theory it is argued that the relative growth rate of 010 depends on supersaturation that the growth rates of 011 faces are changed in response to different ratios of adsorbing cations na k al and that 110 faces become growth inhibited by the adsorption of h2o or trace elements enriched in the residual liquid morphological and chemical discontinuities at late stages of crystallization are reasonably explained by the formation of larger growth units from smaller ionic entities in the residual liquid important factors controlling the zircon morphology in different types of granitoids are high cooling rates alkaline magmas magma mixing calcalkaline magmas enrichment of h2o and trace elements in residual liquids calcalkaline and anatectic magmas and the major element chemistry of the magma possibly the ratio of na and k to al agpaicity

isotopic dating in metamorphic belts isotopic dating in metamorphic rocks is concerned with the timing of processes whose operation is controlled by continually changing physical conditions of these temperature has a pervasive influence and the use of physical models to elucidate the ways in which temperature is likely to vary is briefly reviewed the central concept of closure temperature is critically discussed and quantitative estimates for biotite and hornblende are evaluated in order to illustrate the factors which control closure temperatures and limit their application in practice the possibility of dating crystallization using minerals which crystallize below their respective closure temperatures is examined taking examples involving k ar rb sr sm nd and u pb analyses the indirect dating of metamorphism via structurally dated plutons is briefly considered and the problems of interpreting both discordant u pb zircon ages and rb sr whole rock isochrons in metamorphosed granites are discussed the value of near concordant zircon ages is emphasized the extent of isotopic equilibration during metamorphism specifically of sr isotopes in metasediments is shown not to be a simple function of metamorphic grade the flow of fluids produced by metamorphic reactions appears to be crucial and there is a potential for dating metamorphism using whole rock samples where such flow can he demonstrated independently the concluding discussion briefly examines existing data for the dalradian and indicates the potential for further progress using both well established and novel approaches

cathodoluminescence studies and u pb dating of zircons in pre mesozoic gneisses of the tauern window implications for the penninic basement evolution the pre mesozoic basement in the eastern and central part of the tauern window eastern alps consists mainly of anatectic plagioclase gneisses and amphibolites intruded and migmatized by carboniferous granitoids the gneisses are geochemically similar to calcalkaline dacites of modern primitive island arcs cathodoluminescence investigations and u pb data on zircons indicate an uppermost proterozoic or cambrian extrusion age of the dacitic protoliths and a carboniferous syngranitoid anatexis around 320 ma high k calcalkaline meta rhyolites in the north central tauern window form a separate part of the basement not affected by carboniferous anatexis and plutonism their protoliths extruded in the lower carboniferous in the permian high k granitoids intruded the anatectic basement

time calibration of a pt path from the western tauern window eastern alps the problem of closure temperatures new hornblende k ar and 39ar 40ar and mica rb sr and k ar ages are used to place specific timemarks on a well constrained pressure temperature path for the late alpine metamorphism in the western tauern window after identification of excess 40ar the closure behavior of ar in hornblende is compared with that of sr and ar in phengite and biotite samples were collected in three locations whose maximum temperatures were 570 c zemmgrund 550 c pfitscher joch and 500 540 c landshuter hutte

evidence from rb sr microsampling geochronology for the timing of alpine deformation in the sonnblick dome se tauern window austria

tourmaline geochemistry and δ11b variations as a guide to fluid rock interaction in the habachtal emerald deposit tauern window austria tourmalines from the habachtal emerald deposit in the eastern alps formed together with emerald in a ductile shear zone during blackwall metasomatism between pelitic country rocks and a serpentinite body electron microprobe and secondary ion mass spectrometric sims analyses provide a record of chemical and b isotope variations in tourmalines which represent an idealized profile from metapelites into the blackwall sequence of biotite and chlorite schists tourmaline is intermediate schorl dravite in the country rock and become increasingly dravitic in the blackwall zones while f and cr contents increase and al drops metasomatic tourmaline from blackwall zones is typically zoned optically and chemically with rim compositions rich in mg ti ca and f compared with the cores the total range in 11b values is 13 8 to 5 1 and the within sample variations are typically 3 5 both of these ranges are beyond the reach of closed system fractionation at the estimated 500 550 c conditions of formation and at least two boron components with contrasting isotopic composition are indicated a key observation from tourmaline core analyses is a systematic shift in 11b from the country rock 14 to 10 to the inner blackwall zones 9 to 5 we suggest that two separate fluids were channeled and partially mixed in the habachtal shear zone during blackwall alteration and tourmaline emerald mineralization a regional metamorphic fluid carried isotopically light boron as observed in the metapelite country rocks the other fluid is derived from the serpentinite association and has isotopically heavier boron typical for morb or altered oceanic crust

u pb zircon and sm nd geochronology of mafic and ultramafic rocks from the central part of the tauern window eastern alps geochronological and geochemical analyses were carried out in order to identify the pre variscan basement of the tauern window eastern alps maficultramafic rocks from the central part of the tauern window have been studied by ree analysis and u pb and sm nd isotopic analyses on whole rock zircons garnets and sphene u pb and sm nd zircon dating define both magmatic pan african and cambro ordovician events from 650 ma to 486 ma within the alpine fold belt this indicates a time span of 150 ma for magmatic activities in the tauern window of the eastern alps the ages of 657 ma u pb zircon and 644 sm nd zireon obtained from an amphibolite are the oldest dates of the eastern alps they may be related to the pan african orogeny and imply an early cycle of magmatic intrusion before major activity started at around 500 ma sm nd whole rock analyses of the precambrian rocks do not define an isochron reflecting heterogenities within the mantle source the initial end values 1 2 to 4 7 are very low implying an enrichment of the magma source the second main phase of magmatic activity 539 486 ma is characterized by the emplacement of mafic ultramafic rock sequences as no ophiolitic relies are observed in these domains the early paleozoic magmatism was likely associated with extensional tectonics obtained ages of 301 3 and 314 4 3 ma point to a variscan metamorphism the first combined u pb zircon sm nd zircon data for an amphibolite from the basal amphibolite formation baf favoured the sm nd zircon isochron age as a magmatic age whereas the low initial end value point to an enriched magma source as well as to heterogenities within the magma source the obtained ages suggest that parts of the pre variscan basement within the alpine fold belt were formed during the pan africa cycle the detection of pre variscan ages within the alpine basement must reffect a complex history involving significant pre variscan activity

thrust regime and transpression regime tectonics in the tauern window eastern alps below the penninic nappes of the tauern window the deepest level of the alpine thrust system is exposed in the parautochthonous sedimentary sequence of helvetic facies

quaternary landscape evolution driven by slab pull mechanisms in the granada basin central betics abstract the granada basin is one of the largest neogene quaternary intramontane basins of the betic cordillera in se spain the landscape evolution in this basin is complex and does not respond to a simple model of headward erosion following river capture of a former endorheic catchment in the ne border of the basin the drainage network is highly incised and reveals two different stages of river development since the pleistocene the older drainage network presents low incision being locally controlled by ene wsw open folds the present day drainage network features deep incised valleys with a well defined local base level controlled by nw se normal faults the ene wsw open folds were generated by compressional stresses and affect a geomorphic surface that caps the local sedimentary sequence these folds are thought to reactivate a pliocene roll over formed in the hanging wall of ene wsw normal faults that bound the granada basin to the north and the deepest pliocene depocenter on the contrary quaternary depocenters are located in the hanging wall of the nw se oriented normal faults that control the present day drainage network nw se oriented the activity of these faults also contributes to the erosion of the pliocene depocenter located to the north thus suggesting a southwestward migration of the loci of extension to the center of the basin the broad scale scenario envisaged to explain the pliocene quaternary evolution of the ne border of the granada basin is one dominated by mantle slab pull coeval with the africa iberia continuous convergence

alpine metamorphism in the south east tauern window austria 1 p t variations in space and time the pennine rocks exposed in the south east tauern window austria contain mineral assemblages which crystallized in the mid tertiary late alpine regional metamorphism the pressure and temperature conditions at the thermal peak of this event have been estimated for rocks at four different structural levels using a variety of published and thermochemically derived geobarometers and geothermometers the results are a in the garnet chlorite zone 2 5 km structurally above the staurolite biotite isograd t 490 50 c p 7 1 kbar b within 0 5 km of the staurolite biotite isograd t 560 300c p 7 1 kbar c in the staurolite biotite zone c 2 5 km structurally below the staurolite biotite isograd t 610 30 c p 7 6 1 2 kbar d in the staurolite biotite zone 3 4 km structurally below the staurolite biotite isograd t 630 40 c p 6 6 1 2 kbar the pressure estimates imply that the total thickness of overburden above the basement cover interface in the mid tertiary was c 26 4 km this overburden can only be accounted for by the austro alpine units currently exposed in the vicinity of the tauern window if the altkristallin the middle austro alpine nappe was itself buried beneath an upper austro alpine nappe or nappe pile which was 7 4 km thick at that time the occurrence of epidote margarite quartz pseudomorphs after lawsonite in garnet indicates that part of the mesozoic pennine cover sequence in the south east tauern experienced blueschist facies conditions t 450 c p 12 kbar in early alpine times evidence from the central tauern is used to argue that the blueschist facies imprint post dated the main phase of tectonic thickening d1a and was thus a direct consequence of continental collision combined oxygen isotope and fluid inclusion studies on late stage veins thought to have been at lithostatic pressure and in thermal equilibrium with their host rocks during formation suggest that they crystallized from aqueous fluids at 1 1 0 4 kbar and 420 20 c early alpine late alpine and vein formation p t constraints have been used to construct a p t path for the base of the mesozoic cover sequence in the south east tauern window the prograde part of the p t path between early and late alpine metamorphic imprints is unlikely to have been a smooth curve and may well have had a low dp dt overall the decompression presumably due to erosion which occurred immediately before the thermal peak and possibly also earlier in the tertiary was probably partly or completely cancelled by the effects of early to mid tertiary d2a tectonic thickening the thermal peak of metamorphism was followed by a phase of almost isothermal decompression which implies a period of rapid uplift in the middle tertiary the peak metamorphic p t estimates are compared with the solutions of england s 1978 one dimensional conductive thermal model of the eastern alps and are shown to be consistent with the idea that the late alpine metamorphism was caused by tectonic burial of the pennine zone beneath the austro alpine nappes in the absence of extraneous heat sources such as large intrusions at depth

pre alpine eclogites in the pennine basement complex of the eastern alps an occurrence of quartz eclogite is described from the inner schieferhulle unit of the pennine basement complex in the se tauern window austria field relations strongly suggest a pre alpine age for the primary eclogitic mineral assemblage garnet omphacite quartz rutile this implies that there was no connection between the formation of these eclogites and the late cretaceous and tertiary tectonic evolution of the eastern alps the quartz eclogite mineral assemblage crystallized under conditions of 620 100 c and at pressures in excess of 12 kbar and suffered amphibolitic overprinting of alpine and possibly hercynian age a four stage polymetamorphic history is proposed for the inner schieferhulle

alpine metamorphism in the south east tauern window austria 2 rates of heating cooling and uplift existing geochronological data are reviewed and new rb sr k ar and 39ar 40ar ages are presented including a suite of 33 mica ages from a 20 km north south tunnel section these data are discussed in relation to the thermal history from the overthrusting of the autroalpine nappes c 65 myr ago to the present the earliest phase of metamorphism involving lawsonite crystallization is associated with emplacement of these nappes subsequently temperatures in the rocks beneath rose at a mean rate of 3 6 c myr until the climax of metamorphism at high structural levels published data indicate an age 35 myr for the metamorphic climax in contrast a new 39ar 40ar step heating age of 23 8 0 8 myr on amphibole from near the base of peripheral schieferhulle closely approximates the age of metamorphism and provides the first clear indication that the climax of metamorphism occurred later at deeper structure levels following the climax near isothermal uplift and erosion reduced pressure to c 1 kbar before white mica closure at 19 myr this implies uplift at 3 mm yr along the tunnel section white mica k ar ages vary systematically from 24 myr to 16 5 myr with position relative to a late 4 km amplitude dome whereas biotite rb sr ages are uniform at 16 5 myr across the whole profile doming is thus dated at 16 5 myr with transient uplift rates 5 mm yr at other times uplift rates were 1 mm yr

moment tensor solutions for the iberian maghreb region during the iberarray deployment 2009 2013 abstract we perform regional moment tensor inversion for 84 earthquakes that occurred in the iberian maghreb region during the second and third leg of iberarray deployment 2009 2013 during this period around 300 seismic broadband stations were operating in the area reducing the interstation spacing to 50 km over extended areas we use the established processing sequence of the iag moment tensor catalogue increasing to 309 solutions with this update new moment tensor solutions present magnitudes ranging from mw 3 2 to 6 3 and source depths from 2 to 620 km most solutions correspond to northern algeria where a compressive deformation pattern is consolidated the betic rif sector shows a progression of faulting styles from mainly shear faulting in the east via predominantly extension in the central sector to reverse and strike slip faulting in the west at the sw iberia margin the predominance of strike slip and reverse faulting agrees with the expected transpressive character of the eurasian nubia plate boundary new strike slip and oblique reverse solutions in the trans alboran shear zone reflect its left lateral regime the most significant improvement corresponds to the atlas mountains and the surroundings of the gibraltar arc with scarce previous solutions reverse and strike slip faulting solutions in the atlas system display the accommodation of plate convergence by shortening in the belt at the gibraltar arc several new solutions were obtained at lower crustal and subcrustal depths these mechanisms show substantial heterogeneity covering the full range of faulting styles with highly variable orientations of principal stress axes including opposite strike slip faulting solutions at short distance the observations are not straightforward to explain by a simple geodynamic scenario and suggest the interplay of different processes among them plate convergence in old oceanic lithospheric with large brittle thickness at the sw iberia margin as well as delamination of thickened continental lithosphere beneath the betic rif arc

role of topography in isotherm perturbation apatite u th he and fission track results from the malta tunnel tauern window austria 1 apatite u th he and fission track age determinations of samples from a 20 km long near horizontal tunnel in the hochalm ankogel dome eastern tauern window austria are presented in order to determine the role of paleo topography in perturbing isotherms in the shallow crust apatite fission track ages 26 8 ma show no systematic correlation with distance along the tunnel or elevation two age components in the fission track data indicate cooling through 120 c at approximately 20 ma and 80 c at approximately 6 ma surface and tunnel u th he ages 17 9 ma and 13 5 ma respectively are consistently younger than the equivalent fission track ages u th he ages vary systematically along the tunnel with older ages at the northern and southern tunnel portals and younger ages in the central section geological factors faulting lithology appear to have had little effect on this age distribution the u th he age pattern is inconsistent with rock cooling underneath the present day hochalm ankogel dome topography the age minimum is interpreted to coincide with a paleotopographic maximum in the hochalm ankogel dome and suggests that the 40 60 c isotherms were warped sufficiently to affect apatite u th he ages the tunnel apatite u th he ages match synthetic he ages derived from a two dimensional numerical model of landscape evolution integrating the thermal model results with the data allows the relief development to be constrained and we calculate that the present day hochalm ankogel dome topography was formed at 7 to 10 ma

eocene high pressure metamorphism in the penninic units of the tauern window eastern alps evidence from 40 ar 39 ar dating and petrological investigations the40ar 39ar degassing spectra of white micas and amphiboles from three tectonic units of the central tauern window pennine basement and cover in the eastern alps have been measured white micas are classified as 1 pre alpine low si relic micas with an age value of 292 ma variously disturbed by the alpine metamorphism 2 alpine phengitic micas of variable composition with an age between 32 and 36 ma 3 alpine low si micas with a maximum age of 27 ma we attribute the higher alpine ages to a blueschist facies event whereas the lower age reflects the late cooling of the nappe pile blueschist facies phengites from the basement lower schieferhulle and the tectonic cover upper schieferhulle crystallized at a temperature below the closure temperature tc for argon diffusion in white mica and record ages of 32 to 36 ma at the same time a thin eclogite facies unit eclogite zone was thrust between the lower and the upper schieferhulle and cooled from eclogite facies conditions at about 600 c at 20 kbar to blueschist facies conditions at 450 c or even 300 c at 10 kbar eclogite facies phengites closed for argon diffusion and record cooling ages coinciding with the crystallization ages in the hanging and the footwall unit amphibole age spectra actinolite glaucophane barroisite are not interpretable in terms of geologically meaningful ages because of excess argon

thermal history of the sonnblick dome south east tauern window austria implications for heterogeneous uplift within the pennine basement the sonnblick dome is one of several domal structures affecting the interface between basement and cover within the pennine zone of the tauern window in the eastern alps rb sr isotopic data comprising 19 biotite and 22 white mica ages from variably deformed granitic gneisses provide new evidence of the thermal and tectonic history of the dome and its relationships with other parts of the south east tauern window white mica ages generally cluster between 26 and 30 ma although there are values up to 82 ma which appear to reflect incomplete equilibration during tertiary metamorphism under low amphibolite facies conditions six closely spaced samples from an intensely sheared gneiss lamella are more tightly grouped between 26 and 27 6 ma and provide the best estimate of the age of syntectonic crystallization biotite ages are systematically younger ranging from 19 to 23 5 ma reflecting closure during post metamorphic cooling sonnblick dome and the hochalm dome approximately 20 km further east where closure of rb sr in biotite did not occur until 16 5 ma the metamorphic peak here is also probably younger possibly as late as 22 ma the sonnblick dome was formed before 27 ma and the deformation style had changed to extension before biotite closure by 19 ma in contrast rapid updoming in the hochalm dome was previously dated at 16 5 ma and the differences in thermal history can be linked to differences in deformation history overall the geochronological data from the south east tauern window demonstrate the heterogeneity of thermal history on a geographical scale of 10 km and emphasize the importance of tectonic displacements in controlling temperature within orogenic belts