a seismic discontinuity in the upper mantle between the eastern alps and the western carpathians constraints from wide angle reflections and geological implications abstract seismic investigation of the lithosphere by means of active source experiments is mostly confined to the crust and the moho structures in the upper mantle are more likely to be discovered by analyses of teleseismic data although these methods are restricted in their resolution capabilities the relatively rare evidence for upper mantle refractors or reflectors in active source data enables challenging and interesting studies of the lower and not so well known part of the lithosphere we present such an example from the tectonically complex region between the eastern alps and the western carpathians this area was covered by several extensive 3d wide angle reflection refraction experiments within the last decade and their layout was designed to illuminate the crustal structure and in particular the moho discontinuity in some areas reflections from below the moho are also recorded these reflections occur at recording offsets between 200 and 500 km and they are particularly strong in cross line recordings we derive a set of travel times from the data and perform a tomographic inversion for the depth and shape of the reflecting interface the inversion makes use of an existing 3d crustal model which also includes the moho topography since the upper mantle velocities are poorly constrained and the azimuthal distribution of the rays is biassed several tests are applied to investigate the reliability of possible solutions the results from the tomographic inversion indicate an overall horizontal and radially dipping reflector the average depth of the reflector is 55 km which is about 25 km below the crust mantle transition and amplitude modelling suggests that the reflecting interface represents a velocity increase the investigated area is further characterised by deep sedimentary basins high heat flow high velocities in the lower crust diffuse moho signature and a strong positive bouguer anomaly nearby xenolith outcrops exhibit a pronounced change in anisotropy and indicate the presence of two distinct layers in the lithospheric mantle whereas the deeper layer is thought to present more juvenile lithosphere derived from thermal relaxation in the post extension phase most likely the upper mantle reflector also represents this change in anisotropy though other scenarios are also possible we conclude that the entire lithosphere is significantly shaped by extensional processes which affect the area since the late oligocene early miocene

crustal structure due to collisional and escape tectonics in the eastern alps region based on profiles alp01 and alp02 from the alp 2002 seismic experiment 1 alp01 and alp02 are the longest profiles recorded during alp 2002 a large international seismic refraction and wide angle reflection experiment undertaken in the eastern alps in 2002 alp01 crosses the alpine orogen from north to south thus providing a cross section mainly affected by the collision between europe and the adriatic microplate alp02 extends from the eastern alps to the pannonian basin supplying evidence on the relation between alpine crustal structure and tectonic escape to the pannonian basin during this experiment 363 single channel recorders were deployed along these profiles with an average spacing of 3 2 km recordings from 20 inline shots were used in this study two dimensional forward modeling using interactive ray tracing techniques produced detailed p wave velocity models that contain many features of tectonic significance along alp01 the european moho dips generally to the south and reaches a maximum depth of 47 km below the transition from the eastern to the southern alps the adriatic moho continues further south at a significantly shallower depth moho topography and a prominent south dipping mantle reflector in the alpine area support the idea of southward subduction of the european lithosphere below the adriatic microplate the most prominent tectonic feature on the alp02 profile is a vertical step of the moho at the transition between the alpine and pannonian domains suggesting the existence of a separate pannonian plate fragment the development of the pannonian fragment is interpreted to be a consequence of crustal thinning due to tectonic escape from the alpine collision area to the pannonian basin

3 d modelling of the crustal s wave velocity structure from active source data application to the eastern alps and the bohemian massif summary here i present results from 3 d modelling of crustal s wave velocities in the eastern part of the eastern and southern alps and the southern part of the bohemian massif data were acquired between 2000 and 2003 during three large 3 d wide angle reflection and refraction experiments the surveys aimed at the p wave velocity structure of the crust and uppermost mantle and therefore only vertical component geophones were used nevertheless many shot gathers show strongs waves in particular refractions from the crust sg waves and reflections from the moho discontinuity sms waves compared to p wave arrivals the traveltimes of s waves can only be picked with a relatively large uncertainty furthermore approximately 80 per cent of the data represent crossline recordings on which it is more difficult to assign certain phases to the arrivals for these reasons i apply signal detection and stacking routines to put the 3 d data set to best possible use concerning the crust a smooth 3 d velocity model is based on refractions from within the crust sg whereas the crust mantle boundary is modelled by reflections sms from the moho discontinuity considering that the projects were designed for p wave studies the proposed methodology provides surprisingly detailed images s wave velocities and poisson s ratio correlate with tectonic units and show significant features in the upper crust a high poisson s ratio is observed in the moravian part of the bohemian massif in the southern alps and in the northern calcareous alps and their basement within the eastern alps the middle and lower crust are only covered in the moldanubian part of the bohemian massif where poisson s ratio is low this would favour a felsic composition the evaluation of sms waves is in accordance with previously proposed p wave velocity models which indicate a fragmentation into three crustal blocks in the centre of the eastern alps

climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

crustal velocity structure of the british isles a comparison of receiver functions and wide angle seismic data summary magmatic underplating at the base of the continental crust is thought to be an important consequence of mantle plume activity geochemical evidence supports the hypothesis of underplating beneath the british tertiary igneous province during palaeocene times a process that has been invoked to explain at least part of the observed pattern of cenozoic denudation and consequent offshore deposition this study uses receiver functions to independently test the results of modelling of four wide angle seismic lines across the british isles several of which indicate the presence of a lens of high velocity material at the base of the crust this lens has been interpreted as evidence of palaeogene magmatic underplating receiver functions were calculated for three permanent and two temporary three component broad band seismometers in order to detect p to s conversions from intracrustal velocity discontinuities high frequencies were preserved in the calculation of the receiver functions receiver functions were modelled using the delay times of the p to s converted arrivals only with constraints on the vp and vp vs structure imposed from controlled source data this pragmatic method of interpreting receiver function data agrees well with the results of applying an established inversion technique resulting crustal velocity models are broadly consistent with the velocity models from the wide angle lines showing evidence for a four layer crust with laterally varying moho depths of between 33 2 5 km beneath southwest ireland 32 2 5 km beneath northern and eastern ireland 31 2 km beneath the isle of man and 35 3 km beneath northern england while these velocity models are consistent with the presence of a lower crustal layer receiver functions are insensitive to the p wave velocity structure and so unfortunately they cannot be used to independently constrain the p wave velocity of the lower crust which is an important diagnostic of the presence of magmatic underplating

the cold bay volcanic center aleutian volcanic arc the cold bay volcanic center has experienced two major stages of eruptive activity early m series acitivity produced bimodal hi alumina basalt and calc alkaline andesite lavas while later fpk series activity produced only calc alkaline andesite the spectrum of basalt compositions is believed to be due to high pressure 8 kb fractionation at or near the base of the crust abundant mineralogical and geochemical evidence support a lower pressure mixing origin for all andesites inspection of the mineralogical data has shown that the earliest m series andesites were produced by mixing of basalt 53 wt sio2 and silicic andesite 60 5 to 62 5 wt while later fpk series andesites resulted from the mixing of basaltic andesite 53 to 56 wt and less silicic andesite 58 5 to 60 0 wt the major element and trace element geochemical data are consistent with a low pressure fractionation origin for the silicic endmember magmas and support the temporal variations in both mafic and silicic endmember compositions the complete lack of crustal inclusions in all lavas is taken as evidence for a minimal crustal melting and or assimilation role in the origin of the silicic endmembers many of the features of all andesites including the important long term convergence of endmember magma compositions are consistent with the process of liquid fractionation accompanied by large scale magma mixing a deduced upper limit of 62 5 wt sio2 for the silicic endmember magmas suggests that liquid fractionation in the absence of major crustal melting cannot produce more silicic magmas a possible explanation is the presence of a rheological barrier based on the concept of critical crystallinity marsh 1981 which prohibits more silicic liquids from being extracted from a crystal liquid suspension

density log of a 181 m long ice core from berkner island antarctica a 181 m long ice core was drilled at 79 36 51 s 45 43 28 w near the summit of berkner island antarctica 886 m a s l berkner island is located between the filchner and ronne ice shelves and the ice near the summit shows little lateral flow the density of the ice core was measured every 3 mm along its length using attenuation of a gamma ray beam which gave an absolute accuracy of 2 as expected there is a general density increase with depth the maximum densities of 900 kg m 3 being reached just above 100 m depth comparison with the electrical conductivity method ecm shows density variations with the same wavelength as the annual signals which can be seen in the ecm log higher acidity during summer in the shallowest part of the core the density of winter layers is higher than that of summer layers a relationship which is reversed at greater depth we assume that the densification rates for the two types of firn are different similar density phenomena were observed on ice cores from greenland showing that such phenomena are not a local effect

the development of magmatism along the cameroon volcanic line evidence from teleseismic receiver functions 1 the cameroon volcanic line cvl in west africa is a chain of cenozoic volcanism with no clear age progression the reasons for its existence are unclear and the nature of its magmatic plumbing system is poorly understood specifically whether or not the cvl crust presently contains melt and or mafic intrusions as is often observed at hot spots and rifts elsewhere is presently unknown to address this issue we present a receiver function study of crustal structure using earthquakes recorded by the cameroon broadband seismic experiment in regions of the cvl unaffected by cretaceous extension associated with the breakup of gondwana e g the garoua rift vp vs ratios are markedly low network average 1 74 compared to hot spots elsewhere providing no evidence for either melt or cooled mafic crustal intrusions due to cvl magmatism the character of p to s conversions from beneath the cvl also indicates that lower crustal intrusions often termed underplate are not present beneath the region our observations thus corroborate earlier petrological studies that show cvl alkaline magmas fractionate in the mantle not the crust prior to eruption hypotheses for the formation of the cvl should not include markedly elevated upper mantle potential temperatures or large volumes of partial melt both of which can explain observations at hot spots and rifts worldwide the protracted yet sporadic development of small volume alkali melts beneath the cvl may instead be explained better by lower melt volume mechanisms such as shear zone reactivation or lithospheric delamination

new unspiked k ar ages of volcanic rocks of the central and western sector of the aeolian islands reconstruction of the volcanic stages abstract a geochronological study of the filicudi salina lipari and vulcano islands aeolian archipelago using the unspiked potassium argon technique provides new age data which combined with stratigraphic correlation better constrain the temporal evolution of volcanism the unspiked k ar age of the oldest exposed lavas on filicudi 219 5 ka is significantly younger than the previous estimation of 1 02 ma in the general context of aeolian volcanism this new date suggests that the volcanism of the western sector of the aeolian archipelago is younger than previously thought geochronological data point out on the rapid transition from calc alkaline to potassic volcanism the distribution of the k ar ages within the salina lipari vulcano group shows that the volcanism started on lipari and propagated over time northward on salina and southward on vulcano geochronological and geophysical data suggest that the onset of volcanism in the central sector of the aeolian arc may be due to a mantle upwelling structure located below lipari a change in the style of the eruptions occurred in the salina lipari vulcano system at about 100 ka from the present low energy magmatic eruptions occurred between 188 and about 100 ka from about 100 ka to the present higher energy eruptions and low energy events due to magma water interaction also occurred this change in the style of activity together with the appearance of evolved products i e rhyolites during the last 50 ka is consistent with the formation of magmatic reservoirs located at shallower depth with respect to those of the 188 100 ka period the new geochronological data and available petrological models reveal that a change in the deep source of the primary magmas occurred in a relatively short time interval

a new seismic data set on the depth of the moho in the alps we present the results from receiver function analysis applied to a comprehensive data set in the eastern alps teleseismic events were recorded at 70 stations with an average deployment of 1 year the investigated area includes the eastern part of the eastern alps and their transition to the bohemian massif the pannonian domain and the southern alps the crustal structure at each station is examined with the zhu kanamori zk method which yields well resolved interface depths in laterally homogeneous media with limited layering the application of the zk technique is challenged because of the complex tectonic setting therefore we include additional constraints from recent active source seismic studies in particular the well known crustal p wave velocity and where available the vp vs ratio are kept fixed thus reducing the ambiguity in determining moho depths individual depth values vary strongly between adjacent stations showing that the employment of the zk technique in tectonically complex settings is limited we therefore avoid interpreting the results in detail but rather compare them to existing crustal models of the eastern alps we regard this receiver function study in the easternmost part of the alps as a documentation of a data set that has potential to be exploited in the future

volcanological implications of crystal chemical variations in clinopyroxenes from the aeolian arc southern tyrrhenian sea italy crystal chemistry and structural data for clinopyroxene from the aeolian islands southern tyrrhenian sea italy were determined with the aim of obtaining geobarometric information and exploring implications for the structure of volcanic plumbing systems cell and m1 site volumes for clinopyroxenes which are known to decrease with increasing pressure of crystallization revealed variable values both within some single islands and along the entire arc indicating polybaric conditions of crystallization the lowest cell and m1 volumes were found at filicudi plotting close to values of clinopyroxenes from high pressure ultramafic xenoliths entrained in alkali basalts indications of high pressure crystallization were also found at salina and to a lesser extent at alicudi all situated in the western sector of the aeolian arc the central and eastern islands of lipari vulcano panarea and stromboli generally show higher values of cell parameters suggesting crystallization in shallow magma chambers these islands are characterized by the occurrence of large calderas which are apparently lacking at salina and filicudi time related variations were observed for cell and m1 volumes of clinopyroxene for some islands at salina the early erupted products display low values of cell parameters with respect to later activity thus indicating a decrease in crystallization pressure with time a similar although less striking pattern is observed at alicudi and lipari an overall increase in cell parameters with time was observed at the scale of the entire arc the observed variations in clinopyroxene structural parameters highlight the significance of pyroxene crystal chemistry for petrogenetic and volcanological interpretation correlation with time and the structural characteristics of volcanoes suggest significant regional and temporal modifications in the plumbing systems of aeolian volcanoes clinopyroxenes from filicudi and the older salina crystallized at high pressure in deep magma chambers in the lower crust or at the mantle crust boundary the lower crystallization pressure in the younger salina is interpreted as evidence of upward migration of magma chambers with time similar evolution can be envisaged for alicudi instead the entire evolutionary history of the central and eastern islands was dominated by low pressure crystallization with formation of calderas and generation of abundant acid products that are scarce or absent in the western islands evolution of the plumbing system of single volcanoes and of the aeolian arc in general is probably related to modification of stress regimes and or thinning of the arc basement due to the effect of uprising mantle material above the ionian subduction zone

the transition from calc alkaline to potassic orogenic magmatism in the aeolian islands southern italy the aeolian volcanic arc displays a wide range of magmatic products mafic lavas range from hypersthene normative calc alkaline basalts to silica undersaturated potassic absarokites although the former are spatially and temporally dominant consistent with the subduction zone tectonic setting in addition intermediate and acidic members of the various fractionation series may be recognised large variations in trace element and isotope ratios accompany the rapid calc alkaline to potassic transition and it is argued that these may be largely explained in terms of subduction zone mantle enrichment involving components derived from both basaltic ocean crust and subducted sediments in addition it seems that the mantle wedge itself was substantially heterogeneous prior to the onset of subduction zone processes not only are these subduction components similar to those proposed in a number of island arcs but they also resemble those recognised in the ultra potassic lavas of the roman province supporting recent subduction related petrogenetic models of the roman magmatism although subducted sediment plays an important role in the generation of some potassic magmatism it is not uniquely responsible for k2o rich lavas which are also produced without a large sediment contribution

transition from calc alkaline to potassium rich magmatism in subduction environments geochemical and sr nd pb isotopic constraints from the island of vulcano aeolian arc the problem of mantle metasomatism vs crustal contamination in the genesis of arc magmas with different potassium contents has been investigated using new trace element and sr nd pb isotopic data on the island of vulcano aeolian arc the analysed rocks range in age from 120 ka to the present day and cover a compositional range from basalt to rhyolite of the high k calc alkaline hkca to shoshonitic sho and potassic ks series older vulcano products 30 ka consist of hkca sho rocks with sio2 48 56 they show lower contents of k2o rb and of several other incompatible trace element abundances and ratios than younger rocks with comparable degree of evolution 87sr 86sr ranges from 0 70417 to 0 70504 and increases with decreasing mgo and compatible element contents 206pb 204pb ratios display significant variations 19 31 to 19 76 and are positively correlated with mgo 143nd 144nd 0 512532 0 512768 207pb 204pb 15 66 15 71 and 208pb 204pb 39 21 39 49 overall geochemical and isotopic data suggest that the evolution of the older series was dominated by assimilation fractional crystallisation afc with an important role for continuous mixing with mafic liquids magmas erupted within the last 30 ka consist mostly of sho and ks intermediate and acid rocks with minor mafic products except for a few acid rocks they display moderate isotopic variations e g 87sr 86sr 0 70457 0 70484 206pb 204pb 19 28 19 55 but 207pb 204pb 15 66 15 82 which suggest an evolution by fractional crystallisation or in some cases by mixing with little interaction with crustal material the higher sr isotopic ratios 87sr 86sr 0 70494 0 70587 of a few low volume intermediate to acid rocks support differentiation by afc at shallow depths for some magma batches new radiogenic isotope data on the aeolian islands of alicudi and stromboli as well as new data for lamproites from central italy are also reported in order to discuss along arc compositional variations and to evaluate the role of mantle metasomatism geochemical and petrological data demonstrate that the younger k rich mafic magmas from vulcano cannot be related to the older hkca and sho ones by intra crustal evolutionary processes and point to a derivation from different mantle sources the data from alicudi and stromboli suggest that even though interaction between magma and wall rocks of the calabrian basement during shallow level magma evolution was an important process locally a similar interpretation can be extended to the entire aeolian arc

estimating crustal seismic anisotropy with a joint analysis of radial and transverse receiver function data summary we developed an integrated technique for estimating crustal anisotropy with a horizontal axis using radial r and transverse t receiver functions the technique includes computing three individual and one joint objective function jof and a reliability analysis of the estimated anisotropy the individual objective functions iofs are designed to 1 maximize the peak energy of the stacked r receiver function after a cosine moveout correction in the ps arrival time 2 to maximize the correlation of the radial receiver functions after a full correction of anisotropy or 3 to minimize the total energy of transverse receiver functions stacked after a removal of crustal anisotropy the jof was computed by a weighted average of the three iofs and the reliability analysis uses the principle that stacking coherent signals can lead to an increase of signal to noise ratio we applied the technique to synthetic receiver functions generated with 30 60 per cent white noise from a variety of anisotropic and heterogeneous models the synthetic tests indicate that the proposed technique has good capability to recover the input models despite the presence of random and other coherent noises such as those caused by inhomogeneous structures in the data the technique can always provide accurate estimates of crustal anisotropy we applied the technique to two permanent seismic stations in western china and found significant crustal anisotropy beneath one station located at the northern edge of the tibetan plateau the observed fast polarization direction at this station follows the direction of the maximum horizontal tensile stress suggesting that the observed seismic anisotropy is likely caused by mineral alignment in the lower crust the station situated in the sichuan basin on the other hand shows little to no seismic anisotropy which may suggest that the crust beneath the basin is nearly rigid with very little deformation the developed technique can be applied to any broadband seismic stations that have a good backazimuthal coverage of teleseismic events

crustal assimilation during turbulent magma ascent ata new isotopic evidence from the mull tertiary lava succession n w scotland assimilation of crustal rocks with concomitant fractional crystallisation afc is a well documented phenomenon in many igneous suites but geochemical evidence from the tertiary mull lava succession suggests that in these magmas crustal contamination occurred by a distinctly different mechanism lavas from the lower half of the mull plateau group mpg can be divided into two broad sub types high 8 mgo basalts with elevated ba and k and lower mgo 8 basaltic hawaiites with lower ba and k the lower crust and most of the upper crust beneath mull is probably of lewisian age the sr nd and pb isotope compositions of local lewisian crustal samples yield the following ranges 87sr 86sr 0 71002 0 72348 143nd 144nd 0 51045 0 51058 and 206pb 204pb 14 0 14 6 ten lavas have also been analysed and yield the following ranges 87sr 86sr 0 7028 0 7042 143nd 144nd 0 51214 0 51230 and 206pb 204pb 15 1 17 9 however within this range it is predominantly the more primitive mafic compositions with elevated mg ba and k that show the lowest nd and pb and the highest sr isotope values modelling of these isotopic results in conjunction with major and trace element data show that 1 contamination by lewisian lower crustal material does occur 2 that the process involved was not one of assimilation with concomitant fractional crystallisation afc the proposed contamination process is one whereby the hottest most mgo rich magmas have assimilated acidic partial melts of lewisian lower crust during turbulent ascent ata through thin poorly connected dyke and sill like magma chambers the chemical composition of the contaminated lavas can be modelled successfully through addition of 5 acidic lewisian crust to an uncontaminated lava in contrast the more evolved magmas which probably fractionated at sub crustal levels were either not hot enough to molt significant amounts of crust or did not ascend turbulently because of their higher viscosity and so are less contaminated with crust

orogenic structure of the eastern alps europe from transalp deep seismic reflection profiling abstract the transalp group comprising of partner institutions from italy austria and germany acquired data on a 340 km long deep seismic reflection line crossing the eastern alps between munich and venice although the field work was split into four campaigns between fall 1998 and summer 2001 the project gathered for the first time a continuous profile across the alps using consistent field acquisition and data processing parameters these sections span the orogen itself at its broadest width as well as the editor fred davey and the two adjacent basins vibroseis and explosion data complementary in their depth penetration and resolution characteristics were obtained along with wide angle and teleseismic data the profile shows a bi vergent asymmetric structure of the crust beneath the alpine axis which reaches a maximum thickness of 55 km and 80 100 km long transcrustal ramps the southward dipping sub tauern ramp and the northward dipping sub dolomites ramp strongly reflective patterns of these ramps can be traced towards the north to the inn valley and towards the south to the valsugana thrust belt both of which show enhanced seismicity in the brittle upper crust the seismic sections do not reveal any direct evidence for the presence of the periadriatic fault system the presumed equivalent to the insubric line in the western alps according to our new evolutionary model the sub tauern ramp is linked at depth with remnants of the subducted penninic ocean the crocodile type model describes an upper lower crustal decoupling and wedging of both the european and the adriatic african continents

crustal thickness and vp vs variations in the grenville orogen ontario canada from analysis of teleseismic receiver functions abstract we have developed a simple semblance weighted stacking technique to estimate crustal thickness and average vp vs ratio using teleseismic receiver functions we have applied our method to data from 32 broadband seismograph stations that cover a 700 400 km2 region of the grenville orogen a 1 2 0 98 ga himalayan scale collisional belt in eastern north america our seismograph network partly overlaps with l ithoprobe and other crustal refraction surveys in 8 out of 9 cases where a crustal refraction profile passes within 30 km of a seismograph station the two independent crustal thickness estimates agree to within 7 our regional crustal thickness model constructed using both teleseismic and refraction observations ranges between 34 0 and 52 4 km crustal thickness trends show a strong correlation with geological belts but do not correlate with surface topography and are far in excess of relief required to maintain local isostatic equilibrium the thickest crust 52 4 1 7 km was found at a station located within the 1 1 ga mid continent failed rift the central gneiss belt which contains rocks exhumed from deep levels of the crust is characterized by vp vs ranging from 1 78 to 1 85 in other parts of the grenville orogen vp vs is found to be generally less than 1 80 the thinnest crust 34 5 37 0 km occurs northeast of the 0 7 ga ottawa bonnechere graben and correlates with areas of high intraplate seismicity

the mohorovicic discontinuity beneath the continental crust an overview of seismic constraints abstract the seismic signature of the moho from which geologic and tectonic evolution hypotheses are derived is to a large degree a result of the seismic methodology which has been used to obtain the image seismic data of different types passive source earthquake broad band recordings and controlled source seismic refraction densely recorded wide angle deep seismic reflection and normal incidence reflection using vibroseistm explosives or airguns have contributed to the description of the moho as a relatively complex transition zone of critical importance for the quality and resolution of the seismic image are the acquisition parameters used in the imaging experiments a variety of signatures have been obtained for the moho at different scales generally dependent upon bandwidth of the seismic source this variety prevents the development of a single universally applicable interpretation in this way source frequency content and source and sensor spacing determine the vertical and lateral resolution of the images respectively in most cases the different seismic probes provide complementary data that gives a fuller picture of the physical structure of the moho and its relationship to a petrologic crust mantle transition in regional seismic studies carried out using passive source recordings the moho is a relatively well defined structure with marked lateral continuity the characteristics of this boundary change depending on the geology and tectonic evolution of the targeted area refraction and wide angle studies suggest the moho to be often a relatively sharp velocity contrast whereas the moho in coincident high quality seismic reflection images is often seen as the abrupt downward decrease in seismic reflectivity the origin of the moho and its relation to the crust mantle boundary is probably better constrained by careful analysis of its internal details which can be complex and geographically varied unlike the oceanic moho which is formed in a relatively simple well understood process the continental moho can be subject to an extensive variety of tectonic processes making overarching conclusions about the continental moho difficult speaking very broadly 1 in orogenic belts still undergoing compression and active continental volcanic arcs the moho evolves with the mountain belt 2 in collapsed phanerozoic orogenic belts the moho under the collapse structure was formed during the collapse often by a combination of processes 3 in regions having experienced widespread basaltic volcanism the moho can result from underplated basalt and basaltic residuum in precambrian terranes the moho may be as ancient as the formation of the crust in others precambrian tectonic and magmatic processes have reset it we note that seismic reflection data in phanerosoic orogens as well as from precambrian cratonic terranes often show thrust type structures extending as deep as the moho and suggest that even where crust and mantle xenoliths provide similar age of formation dates the crust may be semi allochothonous

teleseismic tomography of the mantle in the carpathian pannonian region of central europe summary subducted slab roll back lithospheric instability and asthenospheric extrusion have all been proposed as mechanisms that explain the evolution of the extensional pannonian basin within the convergent arc of the alpine carpathian mountain system in central europe we determine the p and s wave velocity structure of the mantle to depths of 850 km beneath this region using tomographic inversion of relative arrival time residuals from 225 p waves and 124 s waves teleseismic earthquakes recorded by 56 stations of the carpathian basins project cbp temporary seismic network 16 month duration and 44 permanent seismic stations the observed median p wave relative arrival time residuals vary between 1 13 s early in the alps and 1 12 s late at the western end of the carpathians s wave relative arrival time residuals are about twice as large 2 13 s and 3 39 s we tested the effect of deterministic corrections on our relative arrival time residuals using crustal velocity models from controlled source experiments but show that the use of station terms in the inversion provides a robust method of correcting for near surface crustal variation our tomographic models reduce the p wave rms residual by 71 per cent to 0 130 s and our s wave rms residual by 59 per cent to 0 624 s at shallow sublithospheric depths we image several localized lower velocity regions correlated with higher heat flow and interpreted as upwelling asthenosphere we image a high velocity structure down to depths of about 350 km beneath the eastern alps further east beneath the pannonian basin a deeper continuation of the eastern alps fast anomaly is imaged trending e w from 300 km depth and extending into the mantle transition zone mtz in the mtz we image a fast anomaly extending outwards as far as the carpathians the dinarides and the eastern alps this higher velocity mantle material is interpreted as being produced by a mantle downwelling whose detachment from the lithosphere above may have triggered the extension of the pannonian basin

regional ambient noise tomography in the eastern alps of europe we present results from ambient noise tomography applied to temporary seismological stations in the easternmost part of the alps and their transition to the adjacent tectonic provinces vienna basin bohemian massif southern alps dinarides by turning each station into a virtual source we recover surface waves in the frequency range between 0 1 and 0 6 hz which are sensitive to depths of approximately 2 15 km the utilization of horizontal components allows for the analysis of both rayleigh and love waves with comparable signal to noise ratio measured group wave dispersion curves between stations are mapped to local cells by means of a simultaneous inverse reconstruction technique the spatial reconstruction for love wave velocities fails in the central part of the investigated area and we speculate that a heterogeneous noise source distribution is the cause for the failure otherwise the obtained group velocity maps correlate well with surface geology inversion of rayleigh wave velocities for shear wave velocities along a vertical n s section stretching from the bohemian massif through the central alps to the southern alps and dinarides reveals a mid crustal low velocity anomaly at the contact between the bohemian massif and the alps which shows a spatial correlation with the p wave velocity structure and the low frequency component of the magnetic anomaly map our study is validated by the analysis of resolution and accuracy and we further compare the result to shear wave velocity models estimated from other active and passive experiments in the area

alpine mantle transition zone imaged by receiver functions abstract assessing the thermal state of the mantle is essential to understand mantle dynamics and provides important clues about present and past tectonic regimes the tectonic processes related to the cenozoic subduction of the alpine tethys likely affected the regional upper mantle structure we use receiver functions to determine the mantle transition zone thickness beneath the greater alpine region as a proxy for its current thermal state compilation of a dataset of nearly 7000 high quality receiver functions from 98 stations yields a reliable and stable image of the alpine mantle transition zone significant signal from p to s conversions at the 410 and 660 km discontinuities is clearly observed the 410 km discontinuity is found at a depth close to that predicted by the iasp91 global model its seismic signature is generally strong except south of the alps signal from the 660 km discontinuity is strong continuous and emerges throughout the whole alpine region at depths greater than predicted by the global model the mantle transition zone is not or only slightly thickened 10 km north of the alps but is up to 40 km thicker than normal south of the alps and in the western alps outlining a roughly 300 km wide and 800 km long ene wsw directed anomaly thickening assuming conversions are due to olivine phase transformations suggests that the alpine mantle transition zone is at least 300 k colder than normal if the thickness anomaly were caused by equal amounts of shallowing and deepening of the 410 and 660 km discontinuity respectively however the thickness anomaly seems mainly due to depression of the 660 km discontinuity which suggests that temperature at the bottom of the mantle transition zone could actually be up to 800 k cooler than ambient mantle while temperatures at 410 km depth may be close to normal both location and amount of suggested thermal anomaly agree with tectonic reconstruction and large scale tomography models of the euro mediterranean region the cold material accumulated at the 660 km discontinuity is interpreted as remnants from the oceanic mantle lithosphere that detached from the eurasian plate after closure of the alpine tethys

andesites from northeastern kanaga island aleutians kanaga island is located in the central aleutian island arc northeastern kanaga is a currently active late tertiary to recent calc alkaline volcanic complex basaltic andesite to andesite lavas record three episodes series of volcanic activity series i and series ii lavas are all andesite while series iii lavas are basaltic andesite to andesite four series ii andesites contain abundant quenched magmatic inclusions ranging in composition from high mgo low alumina basalt to low mgo highalumina basalt the spectrum of lava compositions is due primarily to fractional crystallization of a parental low mgo high alumina basalt but with variable degrees of crustal contamination and magma mixing the earliest series i lavas represent mixing between high alumina basalt and silicic andesite with maximum sio2 contents of 65 67 wt later series i and all series ii lavas are due to mixing of andesite magmas of similar composition the maximum sio2 content of the pre mixed andesites magmas is estimated at 60 63 wt the youngest lavas series iii are all non mixed and have maximum estimated sio2 contents of 59 wt the earliest series i lavas contain a significant crustal component while all later lavas do not it is concluded that the maximum sio2 contents of silicic magmas the contribution of crustal material to silicic magma generation and the role of magma mixing all decrease with time furthermore silicic magmas generated by fractional crystallization at this volcanic center have a maximum sio2 content of 63 wt all of these features have also been documented at the central aleutian cold bay volcanic center brophy 1987 based on data from these two centers a model of aleutian calc alkaline magma chamber development is proposed the main features are 1 a single low pressure magma chamber is continuously supplied by primitive low alumina basalt 2 non primary high alumina basalt is formed along the chamber margins by selective gravitational settling of olivine and clinopyroxene and retention of plagioclase 3 sidewall crystallization accompanied by crustal melting produces buoyant silicic 63 wt sio2 liquids that pond at the top of the chamber and 4 continued sidewall crystallization now isolated from the chamber wall produces silicic liquids with 63 wt sio2 that increase the thickness and lowers the overall sio2 content of the upper silicic zone it is suggested that the maximum sio2 content of 63 imposed on fractionation generated magmas is due to a rheological barrier that prohibits the extraction of more silicic liquids from a crystal liquid mush along the chamber wall

mechanical erosion of xenoliths by magmatic shear flow 1 we focus on the role of mechanical erosion by magmatic shear flow in the formation of xenoliths occurring in lava flows the process is analyzed by combining the physics of fragmentation and erosion to the concept of rock mass the conditions for the country rock fragmentation are analyzed as a function of the magma viscosity strain rate and tensile strength of the rock mass in reservoirs mechanical processes play a subordinate role and thermal erosion processes prevail in conduits intermediate and silicic magmas may erode and eventually fragment good to poor quality country rock masses basalts may erode poor quality country rocks a crystal rich magma has more chance to break up the conduit walls with respect to a vesiculated melt the variety of xenoliths of a lava reflects a set of wall rocks with similar mechanical properties and may not mirror the stratigraphy of the substratum of a volcanic area

joint inversion of long period magnetotelluric data and surface wave dispersion curves for anisotropic structure application to data from central germany geophysical datasets sensitive to different physical parameters can be used to improve resolution of earth s internal structure herein we jointly invert long period magnetotelluric mt data and surface wave dispersion curves our approach is based on a joint inversion using a genetic algorithm for a one dimensional 1 d isotropic structure which we extend to 1 d anisotropic media we apply our new anisotropic joint inversion to datasets from central germany demonstrating the capacity of our joint inversion algorithm to establish a 1 d anisotropic model that fits mt and seismic datasets simultaneously and providing new information regarding the deep structure in central germany the lithosphere asthenosphere boundary is found at approx 84 km depth and two main anisotropic layers with coincident most conductive seismic fast axis direction are resolved at lower crustal and asthenospheric depths we also quantify the amount of seismic and electrical anisotropy in the asthenosphere showing an emerging agreement between the two anisotropic coefficients

receiver functions of seismic waves in layered anisotropic media application to the estimate of seismic anisotropy abstract we investigate the effect of seismic anisotropy on p wave receiver functions calculating synthetic seismograms for p wave incidence on multilayered anisotropic structure with hexagonal symmetry the main characteristics of the receiver functions affected by the anisotropy are summarized as 1 appearance of seismic energy on radial and transverse receiver functions 2 systematic change of p to s ps converted waveforms on receiver functions as ray back azimuth increases and 3 reversal of the ps phase polarity on the radial receiver function in a range of the back azimuth another important influence is shear wave splitting of the ps converted waves and other later phases reverberated as s wave by numerical experiments using synthetic receiver functions we demonstrate that the waveform cross correlation analysis is applicable to splitting ps phases on receiver functions to estimate the seismic anisotropy of layer structure advantages to utilizing the ps phases are 1 they appear more clearly on receiver functions than on seismograms and 2 they inform us about what place along the seismic ray path is anisotropic real analysis of shear wave splitting is executed to the moho generated ps phases that are identified on receiver functions at six seismic stations in the chugoku district southwest japan the time lags between the two arrivals of the split ps phases are estimated at 0 2 0 7 sec and the polarization directions of the fast arrival components are from north south to northeast southwest this result is consistent with recent results of shear wave splitting measurements and the trend of linear epicenter distributions of crustal earthquakes and active fault strikes in the chugoku district

moho map of south america from receiver functions and surface waves 1 we estimate crustal structure and thickness of south america north of roughly 40 s to this end we analyzed receiver functions from 20 relatively new temporary broadband seismic stations deployed across eastern brazil in the analysis we include teleseismic and some regional events particularly for stations that recorded few suitable earthquakes we first estimate crustal thickness and average poisson s ratio using two different stacking methods we then combine the new crustal constraints with results from previous receiver function studies to interpolate the crustal thickness between the station locations we jointly invert these moho point constraints rayleigh wave group velocities and regional s and rayleigh waveforms for a continuous map of moho depth the new tomographic moho map suggests that moho depth and moho relief vary slightly with age within the precambrian crust whether or not a positive correlation between crustal thickness and geologic age is derived from the pre interpolation point constraints depends strongly on the selected subset of receiver functions this implies that using only pre interpolation point constraints receiver functions inadequately samples the spatial variation in geologic age the new moho map also reveals an anomalously deep moho beneath the oldest core of the amazonian craton

from mountain summits to roots crustal structure of the eastern alps and bohemian massif along longitude 13 3 e abstract the crustal structure of the eastern alps and adjacent tectonic units investigated in this work sheds new light on the relationship of surface geology to geodynamic processes operating at depth of particular interest are the nature of a previously proposed moho gap south and east of the tauern window the plate tectonic affinity of the steeply dipping eastern alpine slab and the relationship of the alps to the neogene sedimentary basins and the bohemian massif to address these questions we use various seismological approaches based on converted waves from the temporary passive experiment easi eastern alpine seismic investigation a complementary experiment of the alparray project the easi is a densely spaced 540 km long seismic network along 13 3 e we operated for more than a year the uppermost crustal structures in and near the alps exhibit dipping layers and or tilted anisotropy that correlate well with surface geology observations the moho despite its variable appearance is clearly identified along most of the swath the variscan lithospheric blocks beneath the bohemian massif are imaged with sub vertical boundaries beneath the eastern alps the shape of the moho is consistent with bi vergent orogenic thickening with a steeper and deeper reaching adriatic plate plunging northwards beneath the european plate in the north at the junction of these plates at depth around the previously proposed moho gap the root of the eastern alps is a broad trough characterized by a zone of low velocity gradient that is up to 20 km thick transitioning between crust and mantle our receiver function results corroborate earlier lithosphere upper mantle seismic tomography images and highlight the adriatic affinity of the eastern alpine slab the zigzag deployment pattern of stations in the easi experiment also allows distinction of short wavelength variations perpendicular to the profile both within the shallow and the deep crust this underlines the importance of applying 3d imaging in complex geodynamic systems

crustal structure of the eastern alps and their foreland seismic model beneath the cel10 alp04 profile and tectonic implications summary the subject of this paper concerns the seismic modelling of the crustal structure in the transition zone from the bohemian massif across the molasse basin and the eastern alps to the southern alps mainly on the territory of austria the cel10 alp04 profile crosses the triple point of the european plate adriatic microplate and the recently identified pannonian fragment the seismic data along the presented profile originate from two large experiments celebration 2000 and alp 2002 the wavefield observed in the eastern alps is more complex than in the bohemian massif strong first arrivals pg are distinct up to 60 90 km offset and are characterized by large variations in apparent velocity and amplitude the contact between the molasse basin and the eastern alps represents a barrier for seismic waves midcrustal reflections pc are usually recorded at short distance intervals 20 50 km and are also characterized by variations in apparent velocity and amplitude the moho reflections are usually strong and well correlated while pn arrivals are only fragmentarily recorded detailed 2 d forward modelling of all refracted post critical and reflected phases identified in the correlation process was undertaken using a ray tracing technique the p wave velocity in the crystalline upper crust of the bohemian massif and molasse basin is about 6 15 km s 1 which is slightly higher than in the alpine area about 6 0 km s 1 below the northern accretionary wedge of the eastern alps low velocity sediments penetrate towards the southwest sw down to about 10 km depth in the middle crust of the alpine part a reflective zone was modelled by a lamellae structure with alternating high and low velocities and thicknesses of about 2 3 km the lower crust in this part of the model is more homogeneous with a velocity of about 6 9 km s 1 in the bohemian massif a high velocity hv body vp 7k m s 1 o f af ew kilometres thickness was delineated in the depth interval 18 23 km the crustal thickness along the cel10 alp04 profile changes from about 42 44 km in the sw alpine part to around 40 km in the central part of the profile molasse basin and 38 40 km in the ne bohemian massif the velocity in the uppermost mantle determined from pn wave traveltimes is about 8k m s 1 along the whole profile the interpretation of the seismic wavefield is supplemented by an existing 3 d p wave velocity model of the area main features derived by 2 d modelling low velocities beneath the accretionary wedge high velocities in the lower crust of the bohemian massif moho topography well correlate with the 3 d model furthermore the 3 d model allows assessing the lateral extent of significant features alongside the cel10 alp04 profile this area is affected by both collision and escape tectonics the high reflectivity zone

volcanological and geochemical evolution of filicudi aeolian islands south tyrrhenian sea italy this paper reports on field petrological geochemical and isotopic characteristics of volcanic rocks from filicudi island aeolian arc southern tyrrhenian sea with particular attention to the recognition of temporal and geochemical variations of magma activity the filicudi volcano consists of basaltic basaltic andesitic and high k andesitic lavas and pyroclastic deposits it represents the emergent part of a complex structure parallel to the main regional structural lineaments stratigraphic investigations and dating have defined four main cycles of activity interrupted by periods of quiescence the main stratigraphic sequences reconstructed on filicudi display irregular variations of rock evolution over time with recurrent reversals to more basic compositions magmas erupted from different vents during the first three cycles of activity display overall similar petrological and geochemical characteristics some major and trace elements define slightly scattered correlations with silica sr abundances are particularly scattered with a large range of values in basic rocks sr isotope ratios range between 0 704270 and 0 704740 and do not exhibit good correlations with geochemical parameters fractional crystallization associated with several episodes of mixing processes and crust assimilation are considered to be responsible for the complex evolution of the filicudi magma mafic magmas erupted during the last cycle of activity at la canna centre show increasing k na mg al rb sr and decreasing ba nb ba rb ratios in respect to the older basalts these characteristics are considered to reflect a derivation from a different mantle source

seismic velocities in southern tibet lower crust a receiver function approach for eclogite detection summary beneath the tibet plateau the deficit of crustal thickening with respect to what is expected from the plate tectonic constraints is thought to be absorbed either by lateral extrusion or by vertical rock mass transfer to nourish the unsettled debate of the relative importance of these two processes we propose a new approach based on the s to p and the p to s wave conversions enabling the precise determination of the seismic velocities the weighted amplitudes of the direct conversion and of reverberations are stacked at their predicted arrival times for various values of layer thickness and vp vs ratio separately for two sets of p and s receiver functions for each set of receiver functions coherent stack gives the vp vs ratio and thickness for the considered layer the grid search stacking method the values of vp vs ratio and layer thickness are functions of the velocity used for stacking the set of receiver functions but using the p and s receiver functions allows us to solve this indetermination and to find the effective parameters of the layer velocity vs vp vs ratio and thickness we use a bootstrap resampling of the receiver function data sets to estimate the parameters uncertainties for the southern lhasa block the migrated sections of both p and s receiver functions hi climb experiment data show a layer in the lower crust that may be related to the lower indian crust underplated beneath tibet with the grid search stacking method high shear wave velocities vs 4 73 km s 1 and low vp vs ratios 1 69 are detected in this layer such values are typical for high grade eclogites and the low vp vs ratio precludes the confusion with mafic granulites there is no evidence for partial eclogitization near and south of the yarlung tsangpo suture and the about 19 km thick eclogitic layer extends northwards only to about the middle of the lhasa terrane

shape and origin of the east alpine slab constrained by the alpass teleseismic model abstract during the last two decades teleseismic studies yielded valuable information on the structure of the upper mantle below the alpine mediterranean area subducted oceanic lithosphere forms a broad anomaly resting on but not penetrating the 670 km discontinuity more shallow slabs imaged below the alpine arc are interpreted as subducted continental lower lithosphere substantial advances in our understanding of past and active tectonic processes have been achieved due to these results however important issues like the polarity of subduction under the eastern alps and the slab geometry at the transition to the pannonian realm are still under debate the alpass teleseismic experiment was designed to address these open questions teleseismic waveforms from 80 earthquakes recorded at 75 temporary and 79 permanent stations were collected during 2005 and 2006 from these data a tomographic image of the upper mantle was generated between 60 km and 500 km depth crustal corrections additional station terms and ray bending caused by the velocity perturbations were considered a steeply to vertically dipping shallow slab below the eastern alps is clearly resolved down to a depth of 250 km it is interpreted as european lower lithosphere detached from the crust and subducted during post collision convergence between adria and europe below the pannonian realm low velocities or high mantle temperatures prevail down to 300 km depth consistent with the concept of a pannonian lithospheric fragment which underwent strike slip deformation relative to the european plate and extension during the post collision phase of the alpine orogeny between 350 km and 400 km depth a deep slab extends from below the central eastern alps to under the pannonian realm it is interpreted as subducted lithosphere of the alpine tethys at greater depth there is a continuous transition to the high velocity anomaly above the 670 km discontinuity

evolution of the pannonian basin system 1 tectonics the carpathian arc formed during cretaceous to miocene time by continental collision between europe and smaller continental fragments following southward and westward subduction of ocean floor during the last stages of thrusting in the outer carpathians a set of discrete basins formed behind the carpathian loop these basins are regions of middle to late miocene extension and are connected to each other and to areas of coeval shortening in the outer carpathian thrust belt by a system of strike slip faults sinistral northeast trending and dextral northwest trending sets of conjugate shears reflect overall east west extension of the intra carpathian region during middle to late miocene time palinspastic reconstruction of the basins indicates about 100 50 km of east west extension across the intra carpathian region during this time we interpret the vienna basin which is superimposed partly on the flysch nappes of the outer west carpathians as the result of thin skinned extensional tectonics above a shallow detachment surface within the crust extension of upper crustal rocks above this detachment was probably accomodated by thrusting of the outermost nappes of the west carpathians over the european platform extension of basins farther inside the carpathian loop probably involved rocks at deeper crustal levels and within the upper mantle the most internally situated basins formed by extensional processes that involved the entire lithosphere thus the depth to which extension occurred seems to be closely related to the proximity of each basin to the active thrust front in the carpathians this can be related to the geometry of the subduction zone extension within the intra carpathian basins began first in the northernmost basins and migrated southward and eastward over a ten million year period palinspastic reconstruction of the basins at three different times during the miocene 17 5 16 5 and 13 0 ma predicts eastward migration of the zone of thrusting and shortening within the carpathian mountains to accomodate the synchronous eastward and southward migration of areas of extension from these reconstructions about 120 60 km of east west shortening is predicted across the outer east carpathians from about 17 5 ma until present both predictions are in good agreement with the timing and magnitude of shortening in the carpathian thrust belt as determined directly from rocks within the belt from this we infer a close relationship for middle to late miocene extension of the intra carpathian region and middle to late miocene crustal shortening within the outer carpathians during middle and late miocene time deformation of the pannonian fragment was dominated by extensional and wrench tectonics except along a narrow zone in the outer carpathian thrust belt middle and late miocene thrusting in the carpathians is interpreted as the result of simple shear caused by relative motion between europe and the overriding pannonian fragment at the subduction boundary rather than of regional compression of lithospheric rocks at depth the initiation of extensional tectonics within the intra carpathian region in middle miocene time can be related to reorganization of major fragment boundaries of the eastern european alpine system

moho depth and poisson s ratio in the western central alps from receiver functions summary current knowledge about deep crustal structure of the alpine orogen has mainly been derived from p wave velocity models obtained from active and passive seismic experiments a complementary s wave model to provide lithological constraints necessary for unique structural interpretation has been missing to date in this paper we present important new information on s wave velocity model in the alps we applied the receiver function method using 6 yr of high quality data from 61 permanent and temporary stations sampling the western central alps we determined first order crustal features moho depth h and average vp vs ratio with the h stacking technique that uses timing of direct and multiple p to s converted phases from the moho interface synthetic tests reveal a dipping moho interface expected beneath an orogen causes a systematic bias of h and potentially leading to misinterpretation we thus applied corrections determined from synthetic data to remove the bias providing better fit of recovered moho depths with active seismic estimates for each site we also obtained independent h and estimates based on the timing of the strong ps phase our results show a gently south southeast dipping european moho at a depth of 24 30 km beneath the northern alpine foreland steepening rapidly towards the europe africa suture zone to reach a maximum depth of 55 km south of the suture the moho of the adriatic crust promontory of the african plate is at 35 45 km depth in the previously ill constrained western alps we found the european moho at 30 km depth beneath the more external units dipping east northeast to reach 50 55 km in the inner core of the alps the poisson s ratio clearly correlates with the tectonic units that comprise the alps average crustal values in the european alpine foreland are close to 0 25 in the alps we observe low values 0 22 in the highly deformed nappes of the mesozoic helvetic and southern alps indicating a thickening of felsic upper crustal material in contrast the poisson s ratio is significantly higher 0 26 in the penninic and austroalpine units near the suture zone this rapid and significant change marks a clear rupture between the alpine forelands and the suture domain we assign this high poisson s ratio to doubling of mafic lower crust consistent with results from previous active seismic experiments a continuation of the lower crustal wedge into the central part of the western alps however seems unlikely based on low observed poisson s ratios

rhyolites contaminated with metapelite and gabbro lipari aeolian islands italy products of lower crustal fusion or of assimilation plus fractional crystallization pleistocene lavas from monte s angelo and chiesa vecchia volcanoes on lipari contain two suites of inclusions a metapelitic suite consists of gneisses and granulites with combinations of cordierite garnet corundum hercynite andalusite sillimanite orthopyroxene ilmenite magnetite biotite plagioclase and quartz a gabbroic suite has cumulus texture and contains plagioclase orthopyroxene clinopyroxene and magnetite all megacryst phases in the lavas appear to be derived from rock fragments with the exception of euhedral strongly zoned calcic plagioclase and none has grown by homogeneous nucleation from liquid represented by the groundmass which is peraluminous rhyolite 70 wt sio2 6 wt k2o ground mass microcrysts were nearly all derived from disaggregated metapelites overgrowths of alkali feldspar on plagioclase and of orthopyroxene on clinopyroxene and quartz intergrown with alkali feldspar are the only phases that grew from the rhyolitic liquid euhedral cordierite hercynite and plagioclase at the margins of some rock fragments grew by reaction of metapelite with liquid

from basalt to dacite origin and evolution of the calc alkaline series of salina aeolian arc italy the island of salina comprises one of the most distinct calc alkaline series of the aeolian arc italy in which calc alkaline high k calc alkaline shoshonitic and leucite shoshonitic magma series are developed detailed petrological geochemical and isotopic sr nd pb o data are reported for a stratigraphically well established sequence of lavas and pyroclastic rocks from the middle pleistocene volcanic cycle 430 127 ka of salina which is characterized by an early period of basaltic volcanism corvo capo rivi fossa delle felci group 1 and a sequence of basaltic andesites and andesites and dacites in the final stages of activity fossa delle felci groups 2 8 major and trace element compositional trends rare earth element ree abundances and mineralogy reveal the importance of crystal fractionation of plagioclase clinopyroxene olivine orthopyroxene titanomagnetite amphibole apatite in generating the more evolved magma types from parental basaltic magmas and plagioclase accumulation in producing the high al2o3 contents of some of the more evolved basalts sr isotope ratios range from 0 70410 to 0 70463 throughout the suite and show a well defined negative correlation with 143nd 144nd 0 51275 0 51279 pb isotope compositions are distinctly radiogenic with relatively large variations in 206pb 204pb 19 30 19 66 fairly constant 207pb 204pb 15 68 15 76 and minor variations in 208pb 204pb ratios 39 15 39 51 whole rock 18o values range from 6 4 to 8 5 and correlate positively with sr isotope ratios overall the isotopic variations are correlated with the degree of differentiation of the rocks indicating that only small degrees of crustal assimilation are overprinting the dominant evolution by crystal liquid fractionation afc type processes the radiogenic and oxygen isotope composition of the salina basalts suggests derivation from primary magmas from a depleted mantle source contaminated by slab derived fluids and subducted sediments with an isotopic signature of typical upper continental crust these magmas then evolved further to andesitic and dacitic compositions through the prevailing process of low pressure fractional crystallization in a shallow magma reservoir accompanied by minor assimilation of crustal lithologies similar to those of the calabrian lower crust

structure of the lithosphere beneath the eastern alps southern sector of the transalp transect abstract the interpretation of the seismic vibroseis and explosive transalp profiles has examined the upper crustal structures according to the near surface geological evidences and reconstructions which were extrapolated to depth only the southern sector of the transalp transect has been discussed in details but its relationship with the whole explored chain has been considered as well the seismic images indicate that pre collision and deep collision structures of the alps are not easily recognizable conversely good records of the neo alpine to present architecture were provided by the seismic sections two general interpretation models crocodile and extrusion have been sketched by the transalp working group 2002 both illustrate the continental collision producing strong mechanical interaction of the facing european and african margins as documented by giant lithosphere wedging processes arguments consistent with the extrusion model and with the indentation of adriatic southalpine lithosphere underneath the tauern window tw are according to the previous dss reconstructions the bouguer anomalies and the receiver functions seismological data the european moho descends regularly attaining a zone south of the periadriatic lineament pl the moho boundary and its geometry appear to be rather convincing from images of the seismic profile the tauern window intense uplift and exhumation is coherent with the strong compression regime which acted at depth thus originating the upward and lateral displacement of the mobile and ductile penninic masses according to the extrusion model the indentation of the penninic mobile masses within the colder and more rigid adriatic crust cannot be easily sustained wedging of the adriatic stiffened lower crust under high stresses and into the weaker penninic domain can be a more suitable hypothesis furthermore the intrusion of the european penninic crustal wedge underneath the dolomites upper crust is not supported by any significant uplifting of the dolomites the total average uplift of the dolomites during the neogene appears to be 6 7 times smaller than that recognized in the tw markedly the northward dip of the pl reaching a depth of approximately 20 km is proposed in our interpretation finally the adriatic upper crustal evolution points to the late post collision change in the tectonic grow up of the eastern alps orogenic chain the tectonic accretion of the northern frontal zone of the eastern and central alps was interrupted from the late miocene serravallian tortonian onward as documented by the molasse basin evolution on the contrary the structural nucleation along the s vergent tectonic belt of the eastern southern alps montello friuli thrust belt severely continued during the messinian and the plio pleistocene this structural evolution can be considered to be consistent with the deep under thrusting and wedge indentation of the adriatic lithosphere underneath the southern side of the eastern alps thrust and fold belt similarly the significance of the magmatic activity for the construction of the southern alps crust and for its mechanical and geological differentiation which qualified the evolution of the thrust and fold belt is highlighted starting with the permian triassic magmatism and progressing with the paleogene occurrences along the periadriatic lineament and in the venetian magmatic province lessini euganei hills

moho depth and vp vs ratio in peninsular italy from teleseismic receiver functions 1 we present a new data set of moho depth estimates for peninsular italy obtained from receiver functions analysis and a grid search approach teleseismic records from 174 broadband seismic stations were used to compute the receiver function data set in general our results agree well with previous knowledge adding original information in many regions where previous data were lacking or uncertain we find broad regions with consistent moho depth namely 1 the peri tyrrhenian areas bordering the homonymous sea have a 20 to 25 km deep moho 2 the foreland regions adriatic apulia iblean with 30 35 km deep moho 3 the apennines belt where we find westward deepening of the adriatic moho down to 50 km depth that well delineate the westward adria subduction overlayed by the shallow tyrrhenian moho 4 calabria shows a flat 40 km deep moho suddenly dipping at high angle from the tyrrhenian coast westward defining the ionian subduction and 5 a clear separation between northern and southern apennines is marked by a region of almost flat moho possible evidence of a detached slab in between we also find that in the northern apennines the shallow tyrrhenian moho is continuous for more than 200 km from the sea to under the northern apennines with a generally flat geometry and a few undulations suggesting either the boudinage or episodic pulses of extension of the tyrrhenian crust during its pliocene quaternary stretching the eastward extent of the tyrrhenian moho below the apenninic belt approximately corresponds to the eastward extent of the observed extension in the upper crust as mapped by the normal faulting earthquakes in this portion of the apennines we interpret an intracrustal discontinuity sw dipping below the belt parallel to the adria moho as the top of the lower crust being subducted beneath the apennines the subcrustal earthquakes of this region down to 80 km depth seem to be located within this subducted crustal layer the southern apennines show the same general geometry of subduction as the northern arc although the former have a less defined on land extended region and no earthquakes in the lower crust uppermost mantle in between the central apennines present a different moho geometry no clear doubling of the two plates but rather a constant bilateral deepening possibly associated to a crustal root with no evidence of a subduction setting this reinforces the hypothesis of a detached slab in this area we also present the first large scale mapping of average crustal vp vs ratios for peninsular italy the results although representing averages over the whole crust enhance some interesting features the most evident are belts of high vp vs in the thinned crust of the apennines where extension has long been active in the quaternary probably as an effect of highly fractured rocks with abundant fluid circulation strong correlation exists between areas of high vp vs and quaternary volcanoes suggesting the presence of fluids at depth

a crustal model for the eastern alps region and a new moho map in southeastern europe in the last two decades south central europe and the eastern alps have been widely explored by many seismic refraction experiments e g celebration 2000 alp 2002 sudetes 2003 although quite detailed images are available along linear profiles a comprehensive three dimensional crustal model of the region is still missing this limitation makes this region a weak spot in continental wide comprehensive representations of crustal structure to improve on this situation we select and collect 37 published active source seismic lines in this region after geo referencing each line we sample them along vertical profiles every 50 km or less along the line and derive p wave velocities in a stack of homogeneous layers separated by discontinuities depth of crystalline basement top of lower crust and moho we finally merge the information using geostatistical methods and infer s wave velocity and density using empirical scaling relations we present here the resulting crustal model for a region encompassing the eastern alps dinarides pannonian basin western carpathians and bohemian massif covering the region within 45 circ text 51 circ hbox n and 11 circ text 22 circ hbox e with a resolution of 0 2 circ times 0 2 circ we are also able to extend and update the map of moho depth in a wider region within 35 circ text 51 circ hbox n and 12 circ text 45 circ hbox e gathering moho values from the collected seismic lines other published dataset and using the european plate reference epcrust as a background all the digitized profiles and the resulting model are available online

the problem of the moho in the alps abstract the tertiary alps are the product of continental collision and material balance estimates require the subduction of continental crust and the underlying moho the present moho in the alpine region consists of three parts that of the european plate me that of the adriatic african plate ma and a new moho m2 believed to have developed in the subducted continental crust by high pressure metamorphism at 40 60 km depth the fate of m2 however is uncertain some of it is apparently destroyed subsequently as some eclogite facies and even highest p coesite bearing rocks somehow find their way to the surface where they form exotic bodies from microscopic to nappe size on the other hand the continental moho exposed in the ivrea body tells a different story here continental granulite facies rocks are intruded by ultramafic and mafic masses this suggests an origin in an extensional environment possibly in subduction related gravitational collapse basins such successor basins succeed the basins of the original tethys that had been largely consumed by the late cretaceous they puncture the 1000 2000 km wide belt of africa europa collisional interaction e g the aegean the tyrrhenian and the pannonian basins although in some ways similar to the back arc basins of the pacific these mostly intracontinental basins differ in important aspects such as their small size in these basins asthenospheric upwelling replaces m2 by a new moho m3 and the eclogitic rocks underlying m2 by the ultramafic mafic intrusions of the ivrea type material balance considerations suggest that most of the eclogues remain part of the mantle for some time on the other hand recent deep reflection seismic surveys in several places indicate delamination of a part of the lower crust and the uppermost mantle with the formation of imbrications and duplexes some of which are wedged into the middle crust of the opposite plate they may be the first stage in the formation of granulite and eclogite nappes

lithospheric wedging in the western alps inferred from the ecors crop traverse the ecors crop traverse integrates vertical and wide angle seismic reflection gravity and magnetic studies along a 190 km profile across the western alps the combination of geophysical and geologic data constrains the deep structure along the traverse although alternative models are not excluded the model that best fits the data of crustal accretion implies that after the consumption of the piemontese ocean continental collision proceeded by lithospheric wedging of the subducting european continental foreland in the internal zones further shortening may have been achieved by an unknown amount of penetrative deformation and by back thrusting

morphostructural features and some petrochemical data from the submerged area around alicudi and filicudi volcanic islands aeolian arc southern tyrrhenian sea abstract during several oceanographic surveys of the submarine area surrounding the aeolian islands attention was focused on the western sector which is occupied by the alicudi and filicudi volcanic complexes several kilometres of electroacoustical and high resolution seismic reflection profiles and several submarine samples collected by dredging or directly by diving allowed us to draw the following conclusions on the morphostructural and volcanological evolution of the area 1 1 the structural evolution of the volcanic complex of alicudi a regular subconical volcanic edifice with a stable feeding system is not influenced by regional tectonics a slight southeastward migration of the volcanic focus is evident in the activity of the subaerial summit of the complex where remnants of the oldest submarine volcanic portions lie northeast of the more recent subaerial apparatus 2 2 unlike alicudi the filicudi complex is strongly influenced by nw se oriented structural lineaments the most important feature is represented by a volcanic belt which starting from the subaerial volcanic centres of the island and passing northwest through the submarine centres of la canna and banco di filicudi continues down to the alicudi north seamount for a total length of about 35 km a submerged marine terrace average depth of 100 m surrounds all the coast line of filicudi and covers the top of the banco di filicudi indicating that almost all the volcanic activity was coeval the only exception being represented by la canna centre 3 3 the structural evolution of the large area between the filicudi and salina islands is affected by two different structural systems oriented nne ssw and nw se respectively the only volcanic manifestation of this area is represented by the nw se oriented filicudi north seamount which along with the alicudi north seamount must be considered to be among the oldest volcanic edifices in the whole area 4 4 petrochemical data for two samples from the submarine portion of the oldest alicudi edifices show calcalkaline character and compositions ranging from basalt to basaltic andesite which are similar to those of the subaerial rocks the submarine samples of filicudi have geochemical patterns indicating a good similarity with the calcalkaline trend of the filicudi subaerial rocks the only exception is represented by samples from la canna which show high potassium calcalkaline features the evolution trends are mainly controlled by crystal fractionation processes and subordinately by assimilation of crustal rocks

the moho depth map of the european plate summary the european plate has a 4 5 gy long and complex tectonic history this is reflected in the present day large scale crustal structures a new digital moho depth map is compiled from more than 250 data sets of individual seismic profiles 3 d models obtained by body and surface waves receiver function results and maps of seismic and or gravity data compilations we have compiled the first digital high resolution map of the moho depth for the whole european plate extending from the mid atlantic ridge in the west to the ural mountains in the east and from the mediterranean sea in the south to the barents sea and spitsbergen in the arctic in the north in general three large domains within the european plate crust are visible the oldest archean and proterozoic crust has a thickness of 40 60 km the continental variscan and alpine crust has a thickness of 20 40 km and the youngest oceanic atlantic crust has a thickness of 10 20 km

nd and sr isotope systematics of clastic metasediments from isua west greenland identification of pre 3 8 ga differentiated crustal components recent field work on the isua metasediments has established that there are two lithological sequences a and b which are divided into a number of distinct formations each clastic metasedimentary unit has a relatively unique trace element signature the depleted mantle sm nd model ages of samples from all major units range from 3 59 to 3 98 ga whereas rb sr model ages cover a very wide range 1 9 4 6 ga the samples from the sequence a felsic gneiss formation a6 yield a relatively good rb sr isochron age of t 3 71 0 07 ga the sequence b samples do not yield a rb sr isochron however some of the samples plot close to the a6 rb sr isochron and sequences a and b appear to have essentially the same deposition age the sm nd data for both sequences yield initial end values in the range 1 to 3 for a deposition age tstrat 3 64 ga if tstrat 3 81 ga the range is 0 4 this range appears to reflect real variability of initial end values corresponding to the time of deposition data trends in end versus 1 nd diagrams suggest at least three distinct components in each of sequences a and b model age calculations suggest that some of these components must be derived from continental crustal sources that predate the time of deposition of these sediments by as much as 0 4 b y other components appear to be derived from volcanic sources that are roughly coeval with sediment deposition the very high initial end values implied for early depleted mantle sources 2 to 4 suggest a very large pre 3 8 ga continental crust alternatively these high values could reflect an early terrestrial mantle with highly fractionated cumulate layers that formed in a 4 5 ga magma ocean

upper mantle and lithospheric heterogeneities in central and eastern europe as observed by teleseismic receiver functions summary data from 90 permanent broad band stations spread over central and eastern europe were analysed using ps receiver functions to study the crustal and upper mantle structure down to the mantle transition zone receiver functions provide valuable information on structural features which are important for the resolution of european lithospheric dynamics moho depths vary from less than 25 km in extensional areas in central europe to more than 50 km at stations in eastern europe craton and beneath the alpine carpathian belt a very shallow moho depth can be observed at stations in the upper rhine graben area ca 25 km whereas for example stations in the sw bohemian massif show a significantly deeper moho interface at a depth of 38 km vp vs ratios vary between 1 60 and 1 96 and show no clear correlation to the major tectonic units thus probably representing local variations in crustal composition delayed arrivals of converted phases from the mantle transition zone are observed at many stations in central europe whereas stations in the cratonic area show earlier arrivals compared with those calculated from the iasp91 earth reference model differential delay times between the p410s and p660s phases indicate a thickened mantle transition zone beneath the eastern alps the carpathians and the northern balkan peninsula whereas the transition zone thickness in eastern and central europe agrees with the iasp91 value the thickening of the mantle transition zone beneath the eastern alps and the carpathians could be caused by cold deeply subducted oceanic slabs

volcanological evolution of the rivi capo volcanic complex at salina aeolian islands magma storage processes and ascent dynamics lava flows and pyroclastic deposits from strombolian fallout related to the activity of the rivi and capo volcanoes which are representative of early subaerial volcanoes on salina aeolian islands have been investigated through a geological petrological approach our geological field survey shows that rivi and capo volcanoes are part of a single n50 e aligned volcanic complex here named rivi capo volcanic complex rcvc stratigraphically specific rock sampling has allowed reconstruction of the magma feeding processes through time whole rock major element compositions together with core to rim profiles of plagioclase and clinopyroxene crystals show a general evolution toward more basic compositions through the three formations constituting the capo volcano and within the rivi center melts simulations and mass balance modeling suggest that the rcvc rocks are the result of fractional crystallization of plagioclase clinopyroxene and olivine ca 45 of solid removed from a primary magma in addition to fractional crystallization continuous recharge and mixing with more basic magma coming from deeper parts of the magmatic plumbing system contributed to the final volcanic rock compositions our textural and microanalytical data on plagioclase and clinopyroxene crystals allow the definition of a multilevel magmatic storage system with reservoirs at 20 and 3 km below sea level when processes of magma differentiation ascent and storage are considered together with the stratigraphic position of each sample a history of continuous modification of the rcvc plumbing system can be constructed volcanism may have been characterized by fissure type eruptions during the early stages lower capo lower rivi and middle capo formations gradually changing later to central type volcanism upper capo and upper rivi formations

application of stacking and inversion techniques to three dimensional wide angle reflection and refraction seismic data of the eastern alps summary we present new methods for the interpretation of 3 d seismic wide angle reflection and refraction data with application to data acquired during the experiments celebration 2000 and alp 2002 in the area of the eastern alps and their transition to the surrounding tectonic provinces bohemian massif carpathians pannonian domain dinarides data was acquired on a net of arbitrarily oriented seismic lines by simultaneous recording on all lines of seismic waves from the shots which allows 2 d and 3 d interpretations much 80 of the data set consists of crossline traces low signal to noise s n ratio in the area of the young orogens decreases the quality of travel time picks in these seismically heterogeneous areas it is difficult to assign clearly defined arrivals to the seismic phases in particular on crossline record sections in order to enhance the s n ratio signal detection and stacking techniques have been applied to enhance the pg pn and pmp phases further inversion methods have been developed for the interpretation of war r data based on automated 1 d inversion pg and the application of the delay time concept pn the results include a 3 d velocity model of the crust based on pg waves time and depth maps of the moho and a pn velocity map the models based on stacked data are robust and provide a larger coverage than models based on travel time picks from single fold unstacked traces but have relatively low resolution especially near the surface they were used as the basis for constructing models with improved resolution by the inversion of picks from single fold data the results correlate well with geological structures and show new prominent features in the eastern alps area and their surrounds the velocity distribution in the crust has strong lateral variations and the moho in the investigation area appears to be fragmented into three parts

evolution and genesis of calc alkaline magmas at filicudi volcano aeolian arc southern tyrrhenian sea italy petrological trace element and sr nd pb isotopic data are reported for volcanic rocks from the island of filicudi aeolian arc southern tyrrhenian sea the volcano consists of several monogenic and polygenic centres built up through four major phases of explosive and effusive activity started before 1 ma rock composition ranges from calc alkaline basalts to high k andesites there is a negative correlation between silica and mgo cao tio2 feototal and a positive trend for k2o na2o and p2o5 lile and hfse increase with silica whereas ferromagnesian trace elements have an opposite tendency incompatible elements such as zr ba rb la display well defined positive correlations on elemental variation diagrams weak correlations are shown by the other incompatible elements sr and compatible elements define negative roughly curvilinear trends with incompatible elements 87 sr 86 sr is poorly but significantly variable 0 704016 0 704740 and shows overall higher values in the mafic than in the sialic rocks nd isotope ratios range from 0 512670 to 0 512760 and are negatively correlated with 87 sr 86 sr pb isotope ratios cluster around 206 pb 204 pb 19 31 19 67 207 pb 204 pb 15 64 15 69 208 pb 204 pb 39 11 39 47 major trace element and isotopic variations reveal complex multistage polybaric evolutionary processes for the filicudi magmas it is clear that crystal liquid fractionation processes determined many of the petrologic and geochemical characteristics of these magmas however elemental variations when coupled with isotopic variations in particular sr isotopes demonstrate that mixing processes and interaction of the magmas with older crustal material also played an important role when compared with other aeolian arc volcanoes filicudi shows petrological and geochemical characteristics similar to those of the nearby islands of salina and alicudi the three islands consist of calc alkaline rocks but the degree of magma evolution increases going from the alicudi to salina these variations are likely related to the plumbing system of the three volcanoes however trace element and isotopic evidence also suggests significant variations of primary magmas which reveal a zoned source which suffered different types of metasomatism d 2003 elsevier b v all rights reserved

temporal evolution of a three component system the island of lipari aeolian arc southern italy the volcanic products from lipari define an evolutionary trend with a high gradient of k enrichment similar to the calc alkaline to potassic volcanism of other islands in the aeolian arc stratigraphic reconstruction of the island based on field and geochronological data indicate that the volcanic activity can be subdivided in two stages the first stage from 223 to 42 ka consists of six eruptive cycles and is characterized by basalts and basalt andesites showing progressive increase in both sio2 and k2o contents with time the second stage consists of four cycles erupted since 42 ka and is marked by an apparent rejuvenation of the geochemical system with the appearance of the first rhyolitic products fractional crystallization assimilation and mixing models suggest that the geochemistry of lipari volcanism evolved with time by a complex interplay between two mantle derived components one sub alkaline and the other alkaline in addition to crustal melts and or crustally derived materials a petrogenetic model in which fractional crystallization was subordinate to mixing best fits the geochemical data and petrographic observations of macro and microscopic features melts from the crustal and mantle end members are almost always present in the system but the relative proportions appear to vary with time the sub alkaline mantle component source of tyrrhenian tholeiites is an important contributor to the early evolution of the volcanism in lipari input from the alkaline mantle component source of the roman comagmatic province increases with time and the crustal component becomes dominant in the later activity the preferred petrogenetic model for the temporal evolution of the volcanic system in lipari involves melting initially caused by an increase in the thermal input related to the opening of the tyrrhenian sea and or to subduction processes the quick rise of the isotherms and almost contemporaneous melting of source materials with different compositions favored complex mixing during ascent of the melts

upper mantle structure beneath the alpine orogen from high resolution teleseismic tomography 1 to understand the evolution of the alpine orogen knowledge of the actual structure of the lithosphere asthenosphere system is important we perform high resolution teleseismic tomography with manually picked p wave arrival times from seismograms recorded in the greater alpine region the resulting data set consists of 4199 relative p wave arrivals and 499 absolute p wave arrivals from 76 teleseismic events corrected for the contribution of the alpine crust to the travel times the three dimensional 3 d crustal model established from controlled source seismology data for that purpose represents the large scale alpine crustal structure absolute p wave arrival times are used to compute an initial reference model for the inversion tests with synthetic data document that the combination of nonlinear inversion high quality teleseismic data and usage of an a priori 3 d crustal model allows a reliable resolution of cells at 50 km 50 km 30 km hence structures as small as two cells can be resolved in the upper mantle our tomographic images illuminate the structure of the uppermost mantle to depth of 400 km along strike of the alps the inversion reveals a high velocity structure that dips toward the se beneath the adriatic microplate in the western and central alps in the eastern alps we observe a northeastward dipping feature subducting beneath the european plate we interpret this feature in the western and central alps as subducted mainly continental european lower lithosphere for the east we propose that parts of the vardar oceanic basin were subducted toward the ne forcing continental adriatic lower lithosphere to subduct northeastward beneath the european plate

a natural and controlled source seismic profile through the eastern alps transalp abstract the combined passive and active seismic transalp experiment produced an unprecedented high resolution crustal image of the eastern alps between munich and venice the european and adriatic mohos em and am respectively are clearly imaged with different seismic techniques near vertical incidence reflections and receiver functions rfs the european moho dips gently southward from 35 km beneath the northern foreland to a maximum depth of 55 km beneath the central part of the eastern alps whereas the adriatic moho is imaged primarily by receiver functions at a relatively constant depth of about 40 km in both data sets we have also detected first order alpine shear zones such as the helvetic detachment inntal fault and sub tauern ramp in the north apart from the valsugana thrust receiver functions in the southern part of the eastern alps have also observed a north dipping interface which may penetrate the entire adriatic crust adriatic crust interface aci deep crustal seismicity may be related to the aci we interpret the aci as the currently active retroshear zone in the doubly vergent alpine collisional belt

complex layered deformation within the aegean crust and mantle revealed by seismic anisotropy continental lithosphere can undergo pervasive internal deformation often distributed over broad zones near plate boundaries however because of the paucity of observational constraints on three dimensional movement at depth patterns of flow within the lithosphere remain uncertain endmember models for lithospheric flow invoke deformation localized on faults or deep shear zones or alternatively diffuse viscous fluid like flow here we determine seismic rayleigh wave anisotropy in the crust and mantle of the aegean region an archetypal example of continental deformation our data reveal a complex depth dependent flow pattern within the extending lithosphere beneath the northern aegean sea fast shear wave propagation is in a north south direction within the mantle lithosphere parallel to the extensional component of the current strain rate field in the south central aegean where deformation is weak at present anisotropic fabric in the lower crust runs parallel to the direction of palaeo extension in the miocene the close match of orientations of regional scale anisotropic fabric and the directions of extension during the last significant episodes of deformation implies that at least a large part of the extension in the aegean has been taken up by distributed viscous flow in the lower crust and lithospheric mantle

a fine structural section through the crust and lower lithosphere along the axial region of the alps summary a unified two dimensional lithospheric model has been derived for the p wave velocity structure beneath the alpine longitudinal profile alp 75 main line by making new phase correlations and using ray tracing and ray theoretical seismogram calculations in laterally inhomogeneous media due essentially to an increase in thickness of the lower crust the total crustal thickness increases from 30 40 km in the peripheral regions to about 50 km in the central region of the alps the thickness change is more abrupt at the eastern end than at the western end of the line the boundary between the upper and lower crust occurs at 18 20 km depth except in the peripheral region at the eastern end of the line where it occurs at 14 16 km depth along the whole line the seismic basement has velocities averaged over some tens of kilometres of 5 85 6 15 km s 1 with individual values having uncertainties of 0 05 0 1 km s 1 at least east of shot point b the lower part of the upper crust has been modelled as a low velocity layer which is most pronounced beneath the peripheral regions and which is generally underlain by a transition zone at the base of which the top of the lower crust occurs the top of the lower crust has been modelled with velocities ranging from 6 25 6 5 km s 1 beneath the peripheral regions to 6 5 6 65 km s 1 beneath the central alps velocity uncertainties at the top of the lower crust are estimated to be around 0 2 km s 1 beneath the central alps a low velocity layer has also been modelled in the lower crust the top 6 km of the mantle has been modelled with velocities of 8 0 8 2 km s 1 with individual estimates having uncertainties of 0 15 km s 1 below this the upper mantle down to almost 100 km depth has been modelled as a series of high velocity layers embedded in material with lower velocities of 8 0 8 2 km s 1 the combined effects of tectonic overthrusting and uplift and erosion have probably led to the lower crust being apparently thicker than the upper crust in the central alps at the present day

three dimensional moho topography in italy new constraints from receiver functions and controlled source seismology in complex tectonics regions seismological geophysical and geodynamic modeling require accurate definition of the moho geometry various active and passive seismic experiments performed in the central mediterranean region revealed local information on the moho depth in some cases used to produce interpolated maps in this paper we present a new and original map of the 3 d moho geometry obtained by integrating selected high quality controlled source seismic and teleseismic receiver function data the very small cell size makes the retrieved model suitable for detailed regional studies crustal corrections in teleseismic tomography advanced 3 d ray tracing in regional earthquake location and local earthquake tomography our results show the geometry of three different moho interfaces the european adriatic ionian and tyrrhenian the three distinct moho are fashioned following the alpine and apennines subduction collision and back arc spreading and show medium to high frequency topographic undulations reflecting the complexity of the geodynamic evolution

phase relations of a high mg basalt from the aleutian island arc implications for primary island arc basalts and high al basalts many volcanic centers in the aleutian islands have erupted lavas that range in composition from high mg basalt mgo 9 wt to more fractionated and voluminous high al basalts and basaltic andesites the petrogenetic relationships between these rock types and the composition of primary magmas has been vigorously debated the phase relations of a typical high mg basalt from the makushin volcanic field on unalaska island provide important constraints on petrogenetic models results of one atmosphere and moderate to high pressure 5 20 kb anhydrous experiments are similar to results obtained from primitive morb at low pressures olivine is the liquidus phase joined by plagioclase and clinopyroxene at progressively lower temperatures clinopyroxene is the second phase to crystallize at pressures greater than 5 kb and replaces olivine on the liquidus at approximately 10 kb above 10 kb the liquidus pyroxene is aluminous augite and orthopyroxene is the second phase to crystallize glasses in equilibrium with olivine and clinopyroxene at intermediate pressure 5 to 10 kb are similar in composition to high al basalt plagioclase is not involved and most likely does not become a liquidus phase until the liquid has evolved significantly although our studies do not confirm the primary nature of high mg basalts they do support a model in which high al basalts are generated by moderate amounts of crystal fractionation from more primitive high mg mg fe lower al2o3 basaltic magmas near the arc crust mantle boundary

mapping seismic anisotropy using harmonic decomposition of receiver functions an application to northern apennines italy 1 isotropic and anisotropic seismic structures across the northern apennines italy subduction zone are imaged using a new method for the analysis of teleseismic receiver functions rfs more than 13 000 p wave coda of teleseismic records from the 2003 2007 retreating trench extension and accretion tectonics retreat experiment are used to provide new insights into a peculiar subduction zone between two continental plates that is considered a focal point of mediterranean evolution a new methodology for the analysis of receiver functions is developed which combines both migration and harmonic decomposition of the receiver function data set the migration technique follows a classical common conversion point scheme and helps to focus on a crucial depth range 20 70 km where the mantle wedge develops harmonic decomposition of a receiver function data set is a novel and less explored approach to the analysis of p to s converted phases the separation of the back azimuth harmonics is achieved through a numerical regression of the stacked radial and transverse receiver functions from which we obtain independent constraints on both isotropic and anisotropic seismic structures the application of our method to the retreat data set succeeds both in confirming previous knowledge about seismic structure in the area and in highlighting new structures beneath the northern apennines chain where previous studies failed to clearly retrieve the geometry of the subducted interfaces we present our results in closely spaced profiles across and along the northern apennines chain to highlight the convergence of the tyrrhenian and the adriatic microplates which differ in their crustal structure where the adriatic microplate subducts beneath tuscany and the tyrrhenian sea a signature of the dipping adriatic moho is clearly observed beneath the tyrrhenian moho in a large portion of the forearc region in the area where the two mohos overlap our new analysis reveals the presence of an anisotropic body above the subducted moho there is a strong ps converted phase with anisotropic characteristics from the top of the adriatic plate to a depth of at least 80 km because the ps conversion occurs much deeper than similar ps phases in cascadia and japan dehydration of oceanic crust seems unlikely as a causative factor rather the existence of this body trapped between the two interfaces supports the hypothesis of lower crustal delamination in a postsubduction tectonic setting

thermal evolution of a rift basin the tyrrhenian sea existing geological and geophysical data support the view that the opening of the tyrrhenian sea was by rifting of a formerly continuous continental lithosphere which began in upper miocene on the upper sardinian margin and migrated southeastward to the calabria margin heat flow across the tyrrhenian sea shows a pronounced asymmetry from about 50 70 mw m 2 over the sardinian margin to more than 150 mw m 2 over its southeastern margin off southern italy and calabria in this study we use the newly acquired data from ocean drilling program leg 107 heat flow seismic velocity and bathymetric data to constrain a group of models that supposes the tyrrhenian sea opened by detachment of a formerly continuous lithosphere along a southeastern facing low angle normal fault specific models tested include 1 the wernicke model in which thinning and extension of the continental lithosphere are supposed to be accomplished by simple shear along a large scale gently dipping detachment fault zone which cut through the entire lithosphere and 2 the delamination model in which the low angle detachment fault is supposed to cut only the upper and middle crust but to merge subhorizontally into the lower crust below which concurrent pure shear may occur a versatile two dimensional finite element procedure is used to evaluate the tectonic and thermal evolution of these models and the results are compared with observations to test the validity of the models delamination models with large pure shear components in the lower lithosphere and the wernicke model predict heat flow within 1 of the measurements the wernicke model however predicts a basin configuration much too deep in comparison with bathymetry and a subbasinal lithospheric thickness substantially different from rayleigh wave dispersion results the delamination model with a large component of pure shear in the subbasinal lower lithosphere on the other hand predicts satisfactorily both the bathymetry and the lithospheric thickness beneath the basin

volcanological and petrological evolution of vulcano island aeolian arc southern tyrrhenian sea petrological and geochemical data are reported for volcanic rocks from vulcano island the subaerial volcanism 120 ka to present built up a nw se elongated composite structure affected by two intersecting multistage calderas volcanics older than 20 ka consist mostly of high k calc alkaline hkca to shoshonitic sho mafic rocks these magmas interacted significantly with the continental crust which generated variable sr isotopic ratios 0 70412 0 70520 however a major role was also played by input of parental liquids into the magma chamber which prevented further evolution of the magmas hkca sho and potassic ks rocks formed from 20 to 8 ka display a much larger range of sio2 from shoshonites to rhyolites and higher concentrations of incompatible elements with respect to the previous stage sr isotopic ratios show small variations 0 70448 0 70486 mixing of silicic and mafic liquids and fractional crystallization processes fc were the main evolutionary processes during this stage volcanics younger than 8 ka consist of sho and leucite bearing ks mafic rocks with abundant intermediate and silicic products mafic and intermediate rocks display similar incompatible element abundances and sr isotopic ratios as the previous stage volcanics whereas higher 87sr 86sr 0 70494 0 70583 are observed in some rhyolites these products originated from a complex interplay of fc crustal assimilation and magma mixing processes the most mafic rocks show increasing incompatible element abundances rb sr rb ba mg al mg ca and a decrease in large ion lithophile to high field strength element ratios passing from older hkca sho to the younger sho ks volcanics these variations suggest a shifting of magma sources from a slightly metasomatized asthenosphere fertile peridotite to a more strongly metasomatized lithospheric mantle residual peridotite time related petrological and geochemical variations have been used to develop a model for the evolution of the vulcano plumbing system

crustal structure and active tectonics in the eastern alps 1 during the last decade a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the eastern alps and their adjacent tectonic provinces a fragmentation of the lithosphere into three blocks europe eu adria ad and the new pannonian fragment pa was interpreted and a triple junction was inferred the goal of this study has been to relate these deep crustal structures to active tectonics we used elastic plate modeling to reconsider the moho fragmentation we interpret subduction of eu below ad and pa from north to south and underthusting of ad mantle below pa from southwest to northeast the moho fragmentation correlates well with major upper crustal structures and is supported by gravity seismic and geodetic data an analysis of crustal thickening suggests that active convergence is associated with continued thrusting and lateral extrusion in the central eastern alps and thickening of the adriatic indenter under the southern alps according to the velocity relations at the triple junction pa moves relative to eu and ad along ene and se striking faults mainly by strike slip an eastward directed extensional component is compensated by the lateral extrusion of the central eastern alps the periadriatic insubric line east of the triple junction and the mid hungarian fault zone have relatively recently lost their role as first order active structures we favor the idea that the pannonian fragment and the tisza block merged to a soft microplate surrounded by the eastern and southern alpine carpathian and dinaric orogens

crustal structure of the eastern alps along the transalp profile from wide angle seismic tomography abstract the objective of the transalp project is an investigation of the eastern alps with regard to their deep structure and dynamic evolution the core of the project is a 340 km long seismic profile at 12 e between munich and venice this paper deals with the p wave velocity distribution as derived from active source travel time tomography our database consists of vibroseis and explosion seismic travel times recorded at up to 100 seismological stations distributed in a 30 km wide corridor along the profile in order to derive a velocity and reflector model we simultaneously inverted refractions and reflections using a derivative of a damped least squares approach for local earthquake tomography 8000 travel time picks from dense vibroseis recordings provide the basis for high resolution in the upper crust explosion seismic wide angle reflection travel times constrain both deeper crustal velocities and structure of the crust mantle boundary with low resolution in the resulting model the adriatic crust shows significantly higher p wave velocities than the european crust the european moho is dipping south at an angle of 7 the adriatic moho dips north with a gentle inclination at shallower depths this geometry suggests s directed subduction azimuthal variations of the first break velocities as well as observations of shear wave splitting reveal strong anisotropy in the tauern window we explain this finding by foliations and laminations generated by lateral extrusion based on the p wave model we also localized almost 100 local earthquakes recorded during the 2 month acquisition campaign in 1999 seismicity patterns in the north seem related to the inn valley shear zone and to thrusting of austroalpine units over european basement the alignment of deep seismicity in the trento vicenza region with the top of the adriatic lower crust corroborates the suggestion of a deep thrust fault in the southern alps