early devonian alkaline intrusive complex from the northern north china craton a petrological monitor of post collisional tectonics abstract laser ablation inductively coupled plasma mass spectrometry zircon u pb dating and geochemical data document the early devonian sandaogou alkaline complex 409 ma from the northern margin of the north china craton the rock suite includes pyroxene syenite quartz syenite and monzonite these rocks exhibit high contents of k 2 o 5 13 wt strong enrichments in large ion lithophile elements and light ree slightly negative eu anomalies and pronounced depletions in high field strength elements they are characterized by moderate 87 sr 86 sr i ratios of 0 7052 0 7071 low e nd t values of 12 7 to 17 9 and zircon e hf t values from 27 8 to 32 3 these geochemical features and quantitative isotopic modelling suggest that they might have been formed through simultaneous fractional crystallization and lower crustal assimilation of a metasomatized mantle derived alkali basaltic magma these trachytic rocks together with the middle devonian alkaline rocks and mafic ultramafic complex from neighbouring regions constitute a linear post collisional magmatic belt along the northern north china craton possibly formed under a tectonic regime of slab breakoff they serve not only as a magmatic milestone for marking the termination of early palaeozoic orogenic cycle around the northern north china craton but also as a spatial tracer for locating the position of the potential ancient slab breakoff at the surface supplementary material analytical methods mineral composition data field and zircon cathodoluminescence cl photographs are available at http www geolsoc org uk sup18403

long term ground displacement observations using insar and gnss at piton de la fournaise volcano between 2009 and 2014 abstract monitoring ground surface displacement of volcanoes over a long period of time helps improve understanding of the volcano structure dynamics and mechanisms in this paper we investigate the spatio temporal behavior of the long term displacement field at piton de la fournaise volcano la reunion island by means of x band insar and gnss time series analysis from 2009 to 2014 we propose a new correction approach based on principal component analysis to mitigate the long wavelength artifact in the interferograms over the study area our results show that most of the volcanic edifice including the central cone the eastern flank and recent lava flow fields was affected by varying degrees of ground motion more importantly a widespread sector 20 km2 affected by time dependent downward and eastward motion was observed on the eastern flank of piton de la fournaise the combined analysis of insar and gnss time series and previous studies allows us to confirm that this large mobile sector on the eastern flank underwent deformation for at least 7 years following the end of the large march april 2007 eruption including a stage of transient strain from the end of eruption to february 2011 followed by a stage of steady state strain until late 2014 several possible origins including a pre existing structural discontinuity summit stress associated with magmatism and activated fault movement are explored to explain the observed widespread long term seaward motion that is considered to be direct evidence of potential flank instability

persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

zircon u pb chronology of the jianping complex implications for the precambrian crustal evolution history of the northern margin of north china craton abstract the neoarchean to paleoproterozoic jianping complex in the western liaoning province is an important component of the precambrian basement of the north china craton this region connects the neoarchean fengning chengde complex in the west the neoarchean to paleoproterozoic north chaoyang complex in the northeast and the yixian fuxin archean greenstone belt in the east the precambrian jianping complex is dominantly composed of metamorphosed supracrustal sequence and dioritic to granitoid gneisses tonalite trondhjemite granodiorite ttg here we present results from la icpms zircon u pb isotope dating from the various lithological units in this complex which reveal that the magmatic precursors of the metavolcanic rocks associated with the supracrustal sequence were generated during 2555 2550 ma and up to 2615 ma a major magmatic pulse of dioritic to granitic suite occurred during 2538 to 2495 ma this was followed by ca 2485 ma granulite facies metamorphism and a retrograde event at ca 2450 2401 ma our data also reveal a major charnockite emplacement event in this region at ca 1694 ma integrating our new results with the available geologic and previous geochronological data we identify three major growth stages in the crustal evolution history of the northern margin of the eastern continental block of the north china craton at ca 2550 2495 ma ca 2403 2394 ma and ca 1700 ma the la icp ms zircon data provide new insights on the neoarchean to paleoproterozoic tectonothermal evolution history in the northern margin of the eastern continental block of the north china craton

monitoring volcano slope instability with synthetic aperture radar a review and new data from pacaya guatemala and stromboli italy volcanoes abstract volcano slope instability manifests in many forms ranging from steady state to punctuated movement or shallow erosion to deep seated spreading the interplay of gravity magmatic or hydrothermal fluids and often active tectonics on a volcanic edifice results in complex spatial and temporal variations in deformation kinematics while this makes the recognition assessment and monitoring of volcano slope instability challenging advancements in synthetic aperture radar sar technology have significantly accelerated our knowledge of instability phenomena and our ability to assess their hazards this review discusses the applications and challenges of sar imagery to various slope instabilities at volcanoes around the world sar amplitude images are powerful tools for mapping areas of geomorphological changes these snapshots can be combined using interferometric sar insar to create multi temporal deformation maps that provide unique information on the evolution of slope failures space borne insar has become an economic way to detect changes at volcanoes at very high resolution ground based insar gbinsar can produce frequent sar images on the order of seconds to minutes propelling insar from monitoring to surveillance and early warning applications however interpreting insar derived ground deformation signals related to volcano slope instability is still challenging deformation from magma rise or variations in hydrothermal systems may be inseparable from persistent deep seated flank motion similarly shallow or localized ground motion may occur in overlap with thermal contraction or subsidence of newly emplaced lava or tephra deposits if triggered to failure landslides can vary over several magnitudes from small volume rock falls that pose only a localized hazard to large volume debris avalanches capable of travelling tens of kilometers away from the source these collapses can have cascading hazards if accompanied by directed blasts or tsunamis emphasizing the need for continued advancement of our understanding of these events and their consequences to highlight the utility of sar for measuring and monitoring mass movement two case studies of stromboli italy and pacaya guatemala volcanoes are discussed in detail where recent instability events persistent volcanic activity and ground truth constraints have resulted in excellent case histories in applying sar imagery to understand these potentially hazardous slope instabilities

from oblique arc continent collision to orthogonal plate subduction in the southeastern central asia orogenic belt during paleozoic evidence from superimposed folds at the northern margin of the north china craton abstract accretionary kinematic history of the central asia orogenic belt caob remains unclear in previous geological studies based on detailed structural analysis of newly identified folds on the northern margin of the north china craton ncc we propose a tectonic model suggesting that paleozoic accretion of the orogenic belt includes two phases of deformation the first phase of deformation is oblique collision of the bainaimiao arc and the ncc which was followed by orthogonal subduction of the paleo asian ocean in the second phase of deformation the change of plate kinematics is supported by two generations of folding namely d1 db and d2 da both d1 db and d2 da folds developed in the bayan obo group bog a meso and neoproterozoic rift sequence deposited on the passive continental margin of the ncc d1 db folds were superimposed by the east west trending d2 da folds the d1 db folds developed as a result of oblique collision of the bainaimiao arc and the ncc the d2 da folds developed in response to the southward orthogonal subduction of the paleo asian ocean plate they formed between latest silurian and early permian coeval with the two accretion events at the northern edge of the ncc our study suggests that multiphase deformation of sedimentary layers on the subducting plates provide important constraints for kinematic evolution of plate tectonics

psinsar as a new tool to monitor pre eruptive volcano ground deformation validation using gps measurements on piton de la fournaise 1 the permanent scatterers synthetic aperture radar interferometry psinsar is a technique which aims at ground deformation mapping with millimetric precision in the framework of the globvolcano esa project we evaluated a psinsar derived approach to monitor ground deformation in highly active volcanic areas based on the example of piton de la fournaise the permanent scatterer ps velocities show two main areas of deformation 1 the eastern flank displaying old lava flow subsidence 0 05 0 13 m y 1 and 2 the summit cone highly disturbed by eruptions the ps time series for the summit area agree with the cgps trends with small long term weeks months ground displacements preceding eruptions 0 05 0 35 m y 1 and large rapid ground displacements linked to eruptions despite some limitations such as the loss of coherence during the most rapid ground displacements and lava flow emplacement psinsar and its derived approach provide a reliable inference of the volcano ground deformation over large areas

petrogenesis of the middle devonian gushan diorite pluton on the northern margin of the north china block and its tectonic implications the gushan diorite pluton located at the northern margin of the north china block was emplaced during middle devonian times shrimp u pb zircon age of 390 5 ma rocks from the pluton are characterized by low sio 2 and high alkali contents and they show monzodiorite compositions in a total alkali v silica tas plot they exhibit light ree enrichment no to slightly positive eu anomalies strong depletion in rb th u nb ta p zr hf and ti enrichment in ba k and sr low contents of y and yb and high sr y ratios they have a relatively narrow range of isotopic compositions with initial 87 sr 86 sr ratios of 0 7050 e nd t values of 9 5 to 7 5 and zircon e hf t values from 11 8 to 5 8 these features are remarkably similar to another middle devonian intrusion the shuiquangou syenitic complex at the northern margin of the north china block these similarities suggest that the two intrusions probably have a common origin they were considered to be derived from a type i enriched mantle ultimately with some involvement of ancient lower crustal components and were likely emplaced in a back arc extension environment related to southward subduction of the palaeo asian oceanic plate or during the cessation of the subduction aluminium in hornblende barometry studies of the middle devonian gushan pluton yielded emplacement depths of about 18 km combined with previous geobarometry results on the carboniferous plutons within the inner mongolia palaeo uplift on the northern margin of the north china block it is inferred that the uplift and exhumation of the plutons within the inner mongolia palaeo uplift during middle devonian to late carboniferous times were not as distinct as those during late carboniferous to early jurassic times and the strong uplift and exhumation of the inner mongolia palaeo uplift were achieved during late carboniferous to early jurassic times

early soil consolidation from magnetic extensometers and full resolution sar interferometry over highly decorrelated reclaimed lands abstract reclaimed lands account for a large portion of the developable territories in hong kong towards better construction planning for the follow up civil works stability monitoring is usually required at these artificial sites the synthetic aperture radar interferometry insar technique can provide bi weekly updates of high resolution up to 1 m and high precision millimeter level ground motion maps at low costs which overcomes the limitations of ground based instruments however rapid settlement during the early stage of soil consolidation can result in significant temporal decorrelation to phase signals and impact insar detection especially over newly reclaimed areas here we give a first demonstration on how the introduction of in situ extensometer measurements can help improve insar capabilities for signal recovery of the early consolidation process we integrate persistent scatterers ps and distributed scatterers ds in our processing chain to establish a two tier monitoring network magnetic extensometers are used to estimate local consolidation models which are then utilized to replace the linear part in the conventional functional phase model for nonlinear deformation both hyperbolic and exponential models were considered the proposed method was applied to 61 terrasar x images covering the penny s bay reclamation stage 2 pbr2 in hong kong the consolidation history of the new reclamation site has been successfully extracted with cumulative subsidence exceeding 1 6 m between may 2008 and dec 2011 approximately 84 of the settlement of the non dredged region was found to be from compaction of underlying soft marine deposits not the filling materials in addition to highlighting the spatiotemporal characteristics of the deformation insar also helps reveal the compaction evolution of the underlying deposit the results benefit our understanding of the early consolidation process in pbr2 and inform extra reinforcement plans if necessary

high resolution altimetry reveals new characteristics of the december 2004 indian ocean tsunami 1 the indian ocean tsunami which occurred on december 26 2004 was the first to be clearly observed using satellite altimeters the wave amplitude observed in deep ocean by topex and jason 1 was close to 60 cm about 2 hours after the earthquake envisat crossed the tsunami wave 3h15 after the earthquake and measured a 35 cm wave even though it flew over the tsunami 7h20 after the earthquake gfo still observed a wave close to 20 cm to better extract the tsunami signal from altimeter measurements a specific ocean variability mapping technique is used this technique proves to be mandatory for discriminating tsunami waves from other ocean signals altimeter signals are then compared with those derived from the cea commissariat a l energie atomique model outputs for the first time with altimeter data peculiar short wavelengths signals along jason 1 and envisat profiles have been detected from the analysis of 20 hz altimeter measurements such high wavenumber signals can be explained by the dispersive propagation of tsunami waves these observations highlight the essential role of satellite altimeter measurements to better understand and to improve models of tsunami wave propagation and dissipation

bainaimiao arc as an exotic terrane along the northern margin of the north china craton evidences from petrography zircon u pb dating and geochemistry of the early devonian deposits

provenance of meso to neoproterozoic cover sediments at the ming tombs beijing north china craton an integrated study of u pb dating and hf isotopic measurement of detrital zircons and whole rock geochemistry abstract the north china craton ncc was subjected to an extensional regime after the luliang movement at 1 8 ga and then was covered by an extensive meso to neoproterozoic sedimentary succession namely the changcheng jixian and qingbaikou groups in ascending order we report age spectra for detrital zircons and monazites hf isotopic systematics of detrital zircons and whole rock chemical and nd isotopic compositions for sediments from the succession in the ming tombs area beijing one of the typical meso to neoproterozoic areas in the ncc detrital zircons of six sedimentary samples have two distinct age peaks at 2 52 ga and 1 85 ga there are some detrital zircons at 2 4 2 0 ga but none at 2 3 ga and only a few 2 7 ga the detrital zircon age spectra change with time sediments in the lower succession changcheng group and in the upper successions jixian and qinbaikou groups are dominated by significant detrital zircon populations of late neoarchean and late paleoproterozoic ages respectively the 2 5 ga detrital zircons of the changcheng group have ehf 2 5 ga values and tdm hf model ages mainly ranging from 2 to 7 and 2 8 to 2 7 ga respectively detrital monazites of a sample from the jixian group exhibit a major age peak between 1 95 and 1 80 ga with some data between 2 0 and 1 95 ga the sedimentary rocks of the changcheng group are characterized by high k2o contents mostly 7 09 15 20 and insignificant eu anomalies eu eu 0 71 1 16 they have tdm nd model ages ranging from 2 70 to 2 43 ga being older than the tdm nd ages 2 11 and 1 99 ga of sedimentary samples from the qingbaikou group based on a comparison with ages for the early precambrian 1 8 ga basement of the ncc it can be concluded that 1 the sediments of the meso to neoproterozoic cover were undoubtedly derived from the ncc itself or once neighboring terranes 2 variations in the detrital zircon age spectra from the lower to the upper successions reflect provenance evolution in that the lower crustal late paleoproterozoic rocks were exposed at the surface after the upper crustal late neoarchean rocks had already been eroded

reassessment of continental growth during the accretionary history of the central asian orogenic belt we argue that the production of mantle derived or juvenile continental crust during the accretionary history of the central asian orogenic belt caob has been grossly overestimated this is because previous assessments only considered the palaeozoic evolution of the belt whereas its accretionary history already began in the latest mesoproterozoic furthermore much of the juvenile growth in central asia occurred in late permian and mesozoic times after completion of caob evolution and perhaps related to major plume activity we demonstrate from zircon ages and nd hf isotopic systematics from selected terranes within the caob that many neoproterozoic to palaeozoic granitoids in the accreted terranes of the belt are derived from melting of heterogeneous precambrian crust or through mixing of old continental crust with juvenile or short lived material most likely in continental arc settings at the same time juvenile growth in the caob occurred during the latest neoproterozoic to palaeozoic in oceanic island arc settings and during accretion of oceanic island arc and precambrian terranes however taking together our data do not support unusually high crust production rates during evolution of the caob significant variations in zircon ehf values at a given magmatic age suggest that granitoid magmas were assembled from small batches of melt that seem to mirror the isotopic characteristics of compositionally and chronologically heterogeneous crustal sources we reiterate that the chemical characteristics of crustally derived granitoids are inherited from their source s and cannot be used to reconstruct tectonic settings and thus many tectonic models solely based on chemical data may need re evaluation crustal evolution in the caob involved both juvenile material and abundant reworking of older crust with varying proportions throughout its accretionary history and we see many similarities with the evolution of the sw pacific and the tasmanides of eastern australia

phanerozoic magmatic tempos of north china abstract detrital zircons from northeast china record cyclic magmatism along the northern and eastern margins of the north china block during late paleozoic time and mesozoic time respectively the late paleozoic zircons record three magmatic flare ups with a period of 60 m y that occurred within a magmatic arc constructed along the paleoasian northern margin of north china and are accompanied by negative e hf t excursions representing shortening and increased crustal melting over the duration of each flare up the intervening magmatic lulls are accompanied by rapid positive e hf t excursions signifying influxes of juvenile magma into the arc probably during extension and foundering of underlying melt residua the lack of similar isotopic patterns in zircons derived from contemporaneous intrusions into older continental settings inboard of the arc indicate that this process was restricted to the arc itself mesozoic magmatism in north china occurred along the paleo pacific margin following closure of the paleoasian ocean and exhibits a 50 m y periodicity that is out of phase with that of the paleozoic arc although the tectonic setting of north china during mesozoic time is complex and still controversial it is possible that this younger periodicity is governed by similar processes as those that dominated the paleozoic arc this is a testable hypothesis that warrants further attention crustal shortening was widespread in north china during mesozoic time and documented lithosphere removal events in eastern north china occurred during the mesozoic magmatic lulls lithospheric thickening foundering cyclicity well documented in cordilleran arc systems may be a common process in continental arcs through space and time

a phase altimetric simulator studying the sensitivity of earth reflected gnss signals to ocean topography this paper presents a simulation study on global navigation satellite system gnss reflections focusing on a phase altimetric method for ocean topography retrieval it examines carrier phase residuals of earth reflected gnss signals in preparation for the gnss reflectometry radio occultation and scatterometry experiment aboard the international space station geros iss the residuals sensitivity to ocean topography maximum of 2 m amplitude variation of global sea level is shown a trigonometric approach to determine the specular reflection point is proposed reflection events are simulated assuming different low earth orbit receivers and gnss type transmitters suitable events for phase altimetry are assumed between 5 and 30 elevation lasting between 10 and 15 min with ground tracks length of 3000 km typical along track footprints 1 s integration time have a length of about 5 km within the assumed elevation range the coherent footprint ellipse has a major axis between 1 and 6 km a master slave sampling is proposed to approximate large scale delay and doppler variations of the reflected signal slave channel relative to the direct signal master channel slave residuals of an example event are simulated to retrieve a small scale phase delay for ocean topography inversion the signal to noise ratio restricts the quality of the topography results height precision on sub decimeter level for 30 db snr is degraded up to a meter level for 20 db snr ionosphere free linear combination allows keeping the precision level troposphere refraction degrades precision particularly at the low elevation limit precision improves toward higher elevations the tolerance to ocean roughness decreases in the same way

subsidence in the paricutin lava field causes and implications for interpretation of deformation fields at volcanoes abstract assessment of volcanic hazards includes interpretation of ground deformation signal which at polygenetic volcanoes often results from the superposition of deformation due to pressure changes in the magmatic system and due to surficial processes such as cooling of emplaced lava the deformation signal associated with emplaced lava is sometimes considered negligible if fields are decades old but if the lava thickness is great deformation may still be occurring possibly leading to misinterpretation of the observed deformation here i evaluate the 2007 2011 ground motion of the 1943 1952 lava field of the paricutin monogenetic cinder cone mexico interferometric synthetic aperture radar insar time series reveal patchy subsidence restricted to the lava field and following linear rates up to 5 5 cm year there is a clear correlation between subsidence rates and topography suggesting a causal relationship with deposits or lava thickness i estimate these thicknesses in the subsiding areas using pre and post eruption topographic maps and show that they reach up to 200 m a numerical model for lava flow cooling was developed considering radiation and convection from the surface conductive transfer inside the flow and to the ground and vesiculation and latent heat generation at the top and bottom of the flow the model shows that compaction induced by cooling of the thick deposits emplaced 60 years ago explains the observed subsidence when conductive transfer to the ground is considered these results demonstrate that thick deposits can keep deforming significantly even decades after their emplacement emphasizing the importance of considering cooling processes when interpreting deformation fields at polygenetic volcanoes producing massive lava fields

end permian to mid triassic termination of the accretionary processes of the southern altaids implications for the geodynamic evolution phanerozoic continental growth and metallogeny of central asia the altaids is one of the largest accretionary orogenic collages in the world with the highest rate of phanerozoic continental growth and significant metallogenic importance it is widely accepted that subduction related orogenesis of the altaids started in the late precambrian and gradually migrated southward present coordinates however it is uncertain when and how the building of the altaids was finally completed based on structural geology geochemical geochronological and paleomagnetic data this paper presents late paleozoic to early mesozoic accretionary tectonics of two key areas north xinjiang in the west and inner mongolia in the east together with neighboring mongolia the late paleozoic tectonics of north xinjiang and adjacent areas were characterized by continuous southward accretion along the wide southern active margin of siberia and its final amalgamation with the passive margin of tarim which may have lasted to the end permian to early mid triassic in contrast in inner mongolia and adjacent areas two wide accretionary wedges developed along the southern active margin of siberia and the northern active margin of the north china craton which may have lasted to the mid triassic the final products of the long lived accretionary processes in the southern altaids include late paleozoic to permian arcs late paleozoic to mid triassic accretionary wedges composed of radiolarian cherts pillow lavas and ophiolitic fragments and high pressure ultrahigh pressure metamorphic rocks permian alaskan type zoned mafic ultramafic complexes intruded along some major faults of the tien shan we define a new tarim suture zone immediately north of the tarim craton that is probably now buried below the tien shan as a result of northward subduction of the tarim block in the cenozoic the docking of the tarim and north china cratons against the southern active margin of siberia in the end permian to mid triassic resulted in the final closure of the paleoasian ocean and terminated the accretionary orogenesis of the southern altaids in this part of central asia this complex geodynamic evolution led to formation of giant metal deposits in central asia and to substantial continental growth

multidimensional time series analysis of ground deformation from multiple insar data sets applied to virunga volcanic province summary a novel multidimensional small baseline subset msbas methodology is presented for integration of multiple interferometric synthetic aperture radar insar data sets for computation of 2 or 3 d time series of deformation the proposed approach allows the combination of all possible air borne and space borne sar data acquired with different acquisition parameters temporal and spatial sampling and resolution wave band and polarization the produced time series have improved temporal resolution and can be enhanced by applying either regularization or temporal filtering to remove high frequency noise we apply this methodology to map 2003 2010 ground deformation of the virunga volcanic province vvp north kivu democratic republic of congo the horizontal and vertical time series of ground displacement clearly identify lava compaction areas long term deformation of mt nyamuragira and 2004 2006 and 2010 pre and coeruptive deformation providing that enough sar data is available the method opens new opportunities for detecting ground motion in the vvp and elsewhere

polarity reversal in the solomon islands arc mckenzie1 proposed that the direction of subduction beneath an island arc will reverse following arc continent collision dewey and bird2 suggested that such an arc polarity reversal occurred in northern new guinea johnson and molnar3 however proposed two alternative models of plate convergence that could explain the observed seismicity we present here a spatial seismicity study of the solomon islands region which has revealed the existence of two juxtaposed wadati benioff w b zones of opposite polarity shallow and intermediate foci define a north east dipping w b zone associated with active subduction along the new britain and san cristobal trenches and a south west dipping w b zone associated with the inactive north solomon trench nst these data provide the first direct seismic evidence of a reversal in subduction polarity at an island arc

post eruptive deformation associated with the 1986 87 and 1989 lava flows of etna detected by radar interferometry we analysed 92 interferograms produced using ers1 sar images taken on etna between may 1992 and october 1993 nineteen show a local subsidence in the eastern flank of the volcano correlated with the location of the 30 october 1986 1 march 1987 and 27 september 9 october 1989 lava flows using fringe unwrapping and data gridding techniques and assuming that over the sampled time window deformation was a linear function of time we derive a map of along range rate of motion the correlation between the deformation field and the area covered by recent lavas suggests that compaction of the lava flows continues several years after the eruptions the area of maximum subsidence 47 mm yr is localised at the narrowing of the 1989 flow between 1500 and 1700 m a s l we observe that subsidence extends outside the lava flows accounting for at least 12 mm yr assuming a relaxation process of the substrate in response to loading produced by recent lavas a simple 1d maxwell visco elastic model predicts a maximum subsidence rate of 25 mm yr and a relaxation time of about 3 5 years the relaxation time agrees with those derived from post eruptive displacements observed by levelling on etna and piton de la fournaise after several eruptions we conclude that at the time of our measurements 25 to 50 of the deformation was related to relaxation of the substrate and the other part due to compaction of the lava flows

assessing the reliability and consistency of insar and gnss data for retrieving 3d displacement rapid changes the example of the 2015 piton de la fournaise eruptions abstract insar and gnss are now the best and most developed techniques in the earth sciences to track deformation especially in volcanology in this study we assess the reliability and consistency of these two techniques for measuring 3 d ground displacements and not only the displacement in the direction of the insar line of sight on volcanoes during rapid changes the use of a large amount of satellite data x c l band as well as right and left looking acquisitions made it possible to retrieve the 3 d displacement components with an unprecedented accuracy we carry out this evaluation on the piton de la fournaise volcano where four eruptions occurred in 2015 the comparison between gnss and insar allows us i to describe the deformation pattern associated with these eruptions ii to quantify the discrepancies between insar and gnss and iii to discuss the limits and the complementarities of insar and gnss the ground deformation patterns associated with the four eruptions of piton de la fournaise in 2015 are typical of this volcano with decimeter ground displacements asymmetrically distributed along the dike path evidencing a preferential eastward motion particularly visible thanks to the broad spatial coverage of insar except for the ns component insar and gnss data are in overall agreement with most of the gnss insar residuals

altimetric analysis of the sea surface gps reflected signals we describe the development and implementation of a method for extracting altimetric information using the passive reflectometry and interferometry system paris i e from gps signals after their reflection off the sea surface we have formalized one idea laid out in the description of a bistatic system for ocean altimetry using the gps signal by hajj and zuffada jet propulsion laboratory and have extended it to real situations encountered in paris aircraft experiments second we have developed the corresponding algorithms to produce real time altimetric observables to be used in dedicated digital signal processors finally we have applied this method to estimate sea surface height from one flight experiment in the north sea off the coast of norway

the deformation field of the august 2003 eruption at piton de la fournaise reunion island mapped by asar interferometry 1 three independent asar interferograms spanning the august 2003 piton de la fournaise eruption reveal a 3 by 3 km asymmetric pattern of range changes centred on the dolomieu crater northern flank it corresponds to 30 cm of displacement towards the satellite east of the eruptive fissures and 7 cm away from the satellite west of the fissures displacements are caused by dyke emplacement below fissures we model the deformation using a 3d mixed boundary element method for elastic media this consists of a dyke defined by six geometric parameters and an overpressure gradient a neighbourhood algorithm was applied to explore this 7 dimensional parameter space the best fit model is a 57 eastward dipping dyke with a base lying around 1520 m a s l the model provides new evidence of the dyke intrusion related seaward displacements of the volcano eastern flank

structural and kinematic analysis of the early paleozoic ondor sum hongqi melange belt eastern part of the altaids caob in inner mongolia china we present a structural and kinematic study of an early paleozoic subduction melange and a magmatic arc that form the main elements of the southern orogen belt of inner mongolia which lies in the eastearn part of the altaids or central asia orogenic belt the structural analysis of the melange conducted in the hongqi and ondor sum areas western inner mongolia shows two phrases of ductile deformation the d1 event is responsible for the pervasive s1 foliation nw se striking l1 stretching lineation and f1 intrafolial folds these microstructures are coeval with a greenschist facies metamorphism during d2 nw verging f2 folds associated with a s2 axial planar cleavage deformed s1 and l1 the d1 kinematic criteria indicate a top to the nw sense of shear d1 and d2 developed before the unconformable deposition of the early devonian shallow water sandstone a lithosphere scale geodynamic model involving an early paleozoic southeast directed subduction beneath the north china craton and late silurian collision of the north china craton with an hypothetical microcontinent is proposed to account for the microstructural evolution

rapid magma emplacement in the karoo large igneous province abstract understanding the dynamics of continental large igneous provinces lips relies on precise dating of basaltic rocks lip research has traditionally focused on dating lavas often neglecting the volumetrically important sill intrusions in underlying sedimentary basins here we present u pb zircon and baddeleyite ages for fourteen new samples of karoo lip sills and dykes spaced by as much as 1100 km across the half million square kilometer karoo basin the samples yield remarkably coherent ages ranging from 183 0 0 5 to 182 3 0 6 myr probability modeling indicates that basin scale emplacement took place within an interval of about 0 47 myrs less than 0 90 myrs with 95 confidence and could even have represented a single magma emplacement event combining the new ages with the estimated volume of sills in the karoo basin gives an emplacement rate of 0 78 km3 yr which is higher than previous estimates upper crustal magma storage may account for these high rates the results challenge the view that melt emplacement in a sedimentary basin is a prolonged process support a scenario of pulsating catastrophic events within a narrow time frame and strengthens the hypothesis linking lips and sill emplacement to global environmental crises

reconstructing late paleozoic exhumation history of the inner mongolia highland along the northern edge of the north china craton abstract the inner mongolia highland imh along the northern edge of the north china craton was considered to be a long standing topographic highland whose exhumation history remains elusive the aim of this study is to reveal late paleozoic exhumation processes of the imh based on an integrated analysis of stratigraphy petrography of clastic rocks and u pb ages and hf isotopes of detrital zircons from permian triassic succession in the middle yanshan belt the results of the study show that the benxi formation which was originally regarded as a late carboniferous unit proves to be early permian in age because it contains detrital zircons as young as 298 ma the lower shihezi formation is demonstrated to be a unit whose age spans the boundary of the middle and upper permian constrained by a u pb age of 260 2 ma from a dacite layer clastic compositions of conglomerate and sandstone change markedly characterised by the predominance of sedimentary components in the benxi shanxi formations by large amounts of volcanic clastics in the lower and upper shihezi formations and by the presence of both metamorphic and igneous clastics in the sunjiagou ermaying formations sedimentary clastics include chert carbonate sandstone and quartzite which may have been derived from proterozoic to lower paleozoic sedimentary covers volcanic clasts were directly related to volcanic eruptions while granite and gneiss grains were sourced from exhumed late paleozoic intrusive rocks and basement rocks detrital zircon u pb ages can be divided into five populations 2 6 2 4 ga 1 9 1 7 ga 400 360 ma 325 290 ma and 270 250 ma precambrian detrital zircons are typically subrounded to rounded in shape implying a recycling origin late paleozoic zircons show oscillatory zones and their th u ratios 0 4 suggesting a magmatic origin most phanerozoic zircons have negative e hf t values of 3 2 to 25 5 which are compatible with those of late paleozoic plutons in the imh the results indicate that the imh may have been covered with proterozoic to lower paleozoic sedimentary strata which then underwent subsequent erosion and served as provenances for adjacent late paleozoic basins vertical changes in both clastic compositions and detrital zircon ages in permian triassic strata imply an unroofing process of the imh three phases of the imh uplift are distinguished the first phase uplift commenced 325 312 ma and resulted from magmatic intrusion related to southward subduction of the paleo asian ocean the second phase uplift took place in the middle permian and may be attributed to crustal contraction related to the collision of the north china craton and the southern mongolia terrane the third phase uplift happened at the end of the permian and may have been induced by upwelling of calc alkali magma under an extensional setting

phase altimetry with dual polarization gnss r over sea ice this paper evaluates the potential use of reflected signals from global navigation satellite systems as a source of opportunity for the retrieval of absolute ellipsoidal heights over sea ice accurate estimation of the surface level would be helpful for the determination of the ice thickness a key parameter for classification and characterization of sea ice masses our analysis is based on altimetric estimations from the coherent differential phase between direct and both cross and co polar reflected signals for this purpose gps waveforms have been collected from a fixed platform in greenland monitoring the complete process of sea ice formation and melting during a 7 month period the variability of coherent phase samples and polarimetric measurements are compared with in situ observations to make a realistic rough characterization of the ice cover the retrieved sea ice surface height estimates are then evaluated against an arctic tide model ice surface temperature from moderate resolution imaging spectroradiometer and the laser altimetry product from icesat

investigation of surge derived pyroclastic flow formation by numerical modelling of the 25 june 1997 dome collapse at soufriere hills volcano montserrat deposits from ash cloud surges associated with dome collapse can under certain conditions be remobilised to form surge derived pyroclastic flows sdpfs using numerical modelling we reproduce the emplacement of these flows and investigate the conditions that favour their genesis we use the new version of the numerical model volcflow which simulates the two components of a pyroclastic flow the basal avalanche and the overriding ash cloud surge the basal avalanche primary block and ash flows and sdpfs are simulated using three previously published rheological laws plastic frictional and frictional velocity weakening rheologies applied to the 25 june 1997 dome collapse at soufriere hills volcano the models reproduce to different degrees the deposit footprints formed by the block and ash flows the ash cloud surges and the sdpfs in the plastic model sdpfs occur if the ash cloud surge deposit exceeds a threshold thickness that allows it to remobilise and flow in the frictional models sdpfs occur only if ash cloud surge deposition takes place on a slope exceeding the friction angle of the ash results also highlight that sdpfs appeared so clearly in 1997 at montserrat due to a combination of topographic factors i a bend in the mosquito ghaut drainage that allowed the ash cloud surges to detach ii a depositional area on the watershed between the eastern and western drainage channels and iii a network of tributaries that drained all the remobilised mass into dyer s river to form a single large sdpf our model could be a promising tool for the future forecasting of hazards posed by surge derived pyroclastic flows

sea surface topography retrieved from gnss reflectometry phase data of the geohalo flight mission sea surface topography observations are deduced from an airborne reflectometry experiment a gnss global navigation satellite system receiver dedicated for reflectometry was set up aboard the german halo high altitude long range research aircraft flights were conducted over the mediterranean sea about 3500 m above sea level a signal path model divided into large and small scale contributions is used for phase altimetry the results depict geoid undulations and resolve anomalies of the sea surface topography for the whole experiment 65 tracks over the mediterranean sea are retrieved and compared with a topography model tracks differ between right handed and left handed circular polarization the difference however is not significant for this study precision and spatial resolution decrease disproportionately at low elevations eight tracks with centimeter precision are obtained between 11 and 33 of elevation at higher elevation angles the number of tracks is significantly reduced due to surface roughness in future such retrievals could contribute to ocean eddy detection

long term dynamics of piton de la fournaise volcano from 13 years of seismic velocity change measurements and gps observations we study the piton de la fournaise pdf volcano dynamics through the observation of continuous seismic velocity changes from 2000 to 2013 we compute the cross correlations of ambient seismic noise recorded at more than 30 short period and broadband stations of the undervolc temporary seismic experiment and of the pdf volcano observatory network the velocity changes are estimated from the travel time delay measured on the cross correlations computed between pairs of stations we average the relative velocity changes for all pairs of stations and obtain a time series of the velocity change of piton de la fournaise volcano over 13 years from the period 0 5 to 4 s the depth sensitivity of the velocity change is ranging from approximately 100 m to 2500 m a slow decrease of velocity is measured from 2000 and ends with a major eruption that occurred in april 2007 this eruptive episode is followed by an increase of the velocity these long term changes are compared to the deformation of the piton de la fournaise edifice estimated from geodetic measurements an analysis of baseline change between gps stations indicates an inflation of the volcanic edifice prior to april 2007 followed by a deflation since then this deflation predominantly affects the terminal cone seismic velocity changes and deformation have similar long term trends with velocity decrease observed during inflation and velocity increase during deflation however the velocity change magnitude is about 2 orders of magnitude greater than the deformation this suggests nonlinear relation between velocity changes and deformation

multiple metamorphic events recorded in the metamorphic terranes in central inner mongolia northern china implication for the tectonic evolution of the xing an inner mongolia orogenic belt abstract the tectonic evolution of the xing an inner mongolia orogenic belt ximob in the southeastern segment of the central asian orogenic belt is not well understood it is arguable whether the paleo asian ocean was closed in devonian or early mesozoic and whether the tectonic regimes during carboniferous and permian were operated by continuous subduction arc systems or extension after the orogenic process comprehensive studies of metamorphism for four metamorphic terranes including the ondor sum group baoyintu group xilingol complex and early triassic metamorphic sequences in central inner mongolia provide good constraints on the arguable issues about the ximob according to the zircon u pb dating analyses in this study quartz schists of the ondor sum group in the northern and southern orogenic belts nob and sob have a broad detrital zircon age range from late archean to early paleozoic with a similar youngest deposition age of 434 430 ma but have different zircon age populations with a 650 ma peak for the nob but not for the sob biotite gneisses of the xilingol complex have age populations and the youngest deposition age of 436 ma similar to the ondor sum group in the nob amphibolites in the complex have a metamorphic zircon age of 321 3 ma and hornblende 40ar 39ar age of 309 2 ma the early triassic metamorphic sequences metabasites in wulangou and mica schists in shuangjing both have broad zircon age ranges from the late archean to late paleozoic their protoliths are constrained to have formed later than 258 ma and 261 ma respectively and the metamorphism occurred soon afterwards in the early triassic constrained by an actinolite 40ar 39ar age of 241 19 ma in metabasite and a muscovite 40ar 39ar age of 240 2 ma in mica schist combined with the results previously published this study identified four phases of metamorphism in central inner mongolia since paleozoic the silurian 430 426 ma high p t metamorphism of the ondor sum group was related to bidirectional subduction processes the devonian 400 ma medium p t metamorphism of the baoyintu group suggests a crustal thickening orogeny the carboniferous 337 321 ma low p t metamorphism of the xilingol complex is indicative of an extension process of a previous orogen the early triassic 240 ma extensive medium low p t metamorphism along the solonker suture zone was attributed to the closure of limited ocean basins thus an alternative tectonic scenario for the metamorphic terranes in central inner mongolia involves i the early paleozoic trench arc system 500 425 ma ii the devonian collisional orogeny due to closure of the paleo asian ocean 400 360 ma iii the carboniferous and permian extension after the collision 350 250 ma and iv the early triassic within plate orogeny due to the closure of limited ocean basins 240 ma

analysis of surface deformations over the whole italian territory by interferometric processing of ers envisat and cosmo skymed radar data abstract interferometric processing of series of data acquired over time by synthetic aperture radar sar satellites makes it possible to measure millimetric deformations typically due to landslides subsidence and earthquake or volcanic phenomena and to monitor the stability of terrain and infrastructures despite the unique capability to observe very large areas this technology has been typically applied to the analysis of relatively small sites or specific geophysical phenomena in this work we present the first application of this technology to a national scale project which required the processing through advanced persistent scatterer interferometry psi techniques of about 20 000 sar images acquired from 1992 to 2014 over the whole italian territory by the ers envisat and cosmo skymed satellites the obtained results provide a huge database of surface deformation measurements covering the last 20 years and the whole italian territory which represents an extremely useful and pioneering service for geo hazards mapping and prevention

airborne gravimetry of geohalo mission data processing and gravity field modeling airborne gravimetry is a crucial method to improve our knowledge about the earth gravity field especially in hard to access regions generally the accuracy of airborne gravimetry is several milligals which is suitable for filling the so called polar gaps in satellite derived global gravity field models here some investigations based on airborne gravity measurements from the geohalo mission over italy are presented to subtract the vertical accelerations from the values measured by the gravimeter four different versions of kinematic accelerations were derived from global navigation satellite systems gnss recordings to remove the high frequency noise a low pass filter with a cutoff wavelength of 200 s was applied to both chekan am measurements and kinematic accelerations from gnss to investigate how future airborne gravity campaigns could be designed a dedicated flight track was repeated two times showing that the equipment worked well also at higher altitude and speed from the final best results follows an rms of gravity differences at crossover points of 1 4 mgal which according to the law of error propagation implies the accuracy of a single measurement to be 1 4 2 1 mgal to demonstrate how a satellite only gravity field model can be improved by airborne measurements a gravity field model for the geohalo region has been computed to compute also an improved regional geoid model the point mass modeling pmm and the remove compute restore rcr technique using a recent satellite only model and residual terrain modeling rtm were applied finally gnss leveling points have been used to check the quality of the regional point mass model

magma transport and storage at piton de la fournaise la reunion between 1972 and 2007 a review of geophysical and geochemical data abstract since the middle of the 20th century improvement in volcano monitoring techniques has provided large data sets that can be used to evaluate the evolution of magma plumbing systems at piton de la fournaise volcano abundant eruptive activity and a dense monitoring network are especially conducive to such research analysis of the extensive set of geophysical and geochemical data associated with the last 35 years of activity provides new insights into magma transport and storage at piton de la fournaise two periods of frequent eruptions separated by 6 years of inactivity can be distinguished 1972 1992 and 1998 2007 considering these two periods we show evidence of major changes in the shallow plumbing system in 2000 during 1972 1992 and 1998 2000 lava compositions and weak long term eruptive precursors lasting few days to three weeks characterized by no significant summit inflation and about ten volcano tectonic earthquakes per day suggest that eruptions were fed by the progressive drainage of an occasionally recharged shallow magma reservoir geophysical evidence of shallow magma reservoir recharge was only recorded in 1986 and 1998 in contrast from 2000 to 2007 geophysical data highlight the appearance of long term precursors 1 to 5 months of summit inflation and strong seismicity up to one hundred events per day preceding cycles of successive eruptions each cycle of eruptions was characterized by a sequence 3 to 10 months in duration of summit and near summit proximal eruptions and ended with a distal low altitude oceanite olivine abundances 20 vol eruption on the eastern flank of the volcano within each of these eruptive cycles lavas became progressively more magnesian over time the preferential motion of the eastern flank caused by continuous recharging of the shallow reservoir since 2000 would favour the occurrence of distal eruptions towards this flank at the end of a cycle

subduction polarity reversal at the junction between the western alps and the northern apennines italy abstract the controversial relationship between the orogenic segments of the western alps and the northern apennines is here explored integrating recently published 3d tomographic models of subduction with new and re interpreted geological observations from the eclogitic domain of the voltri massif ligurian alps italy where the two belts joint each other the voltri massif is here described as an extensional domain accommodating the opposing outward migration of the alpine and apennine thrust fronts since about 30 35 ma using tomographic images of the upper mantle and paleotectonic reconstructions we propose that this extensional setting represents the surface manifestation of an along strike change in polarity of the subducted oceanic slab whose polarity changed laterally in space and in time our tectonic model suggests that the westward shift of the alpine thrust front from the oligocene onward was the consequence of the toroidal asthenospheric flow induced by the retreat of the apenninic slab

gondwana derived microcontinents the constituents of the variscan and alpine collisional orogens abstract the european variscan and alpine mountain chains are collisional orogens and are built up of pre variscan building blocks which in most cases originated at the gondwana margin such pre variscan elements were part of a pre ordovician archipelago like continental ribbon in the former eastern prolongation of avalonia and their present day distribution resulted from juxtaposition through variscan and or alpine tectonic evolution the well known nomenclatures applied to these mountain chains are the mirror of variscan resp alpine organization it is the aim of this paper to present a terminology taking into account their pre variscan evolution at the gondwana margin they may contain relics of volcanic islands with pieces of cadomian crust relics of volcanic arc settings and accretionary wedges which were separated from gondwana by initial stages of rheic ocean opening after a short lived ordovician orogenic event and amalgamation of these elements at the gondwanan margin the still continuing gondwana directed subduction triggered the formation of ordovician al rich granitoids and the latest ordovician opening of palaeo tethys an example from the alps external massifs illustrates the gradual reworking of gondwana derived pre variscan elements during the variscan and alpine tertiary orogenic cycles

slab breakoff as a mechanism for flipping of subduction polarity in taiwan we propose a model that involves breakoff of the east dipping eurasian slab beneath the taiwan orogen to account for the flipping of subduction polarity in northern taiwan the breakoff was initiated in southern ryukyu in the early pliocene and then propagated southwestward into taiwan like an opening zipper detachment of the eurasian slab has created a mantle window for the north dipping philippine sea plate to move in laterally causing a switch in the subduction polarity slab breakoff not only provides a testable model for the lithospheric structure of taiwan but also accounts for the high heat flow rapid uplift synorogenic extension deep focus earthquakes and north diminishing crustal contraction in the taiwan mountain belt

inversion of geohalo aerogravimetry to infer ocean bottom topography application to the tyrrhenian ionian and adriatic seas

squeesar and gps ground deformation monitoring of santorini volcano 1992 2012 tectonic implications abstract the santorini volcanic complex svc has been in a dormant state for the last 60 years until january 2011 when upward influx of magma reawakened the volcano with intense radial ground deformation and inter caldera seismicity that lasted until january 2012 but declined afterwards this paper aims to study the ground deformation and the inferred tectonic implications of the svc for the period 1992 2012 mainly based on the squeesar technique and dgps campaign results of our local network which incorporates available data on internet from several continuous gps stations established on the island the spatial deformation of the svc during the quiet period 1992 2010 was deduced by joint analysis of ers1 and 2 and envisat it was found that the intra caldera palaea kammeni shield volcano was being uplifted 2 3 mm yr with increasing rate whilst the adjacent nea kammeni shield volcano was being subsided up to 6 mm yr with increasing rate the rest of the svc showed a velocity field varying from 1 to 2 mm yr indicating a rather linear deformation during that period the results from the gps network are in full agreement with the squeesar results based on the results of squeesar analysis of 12 envisat images and dgps cgps data to end 2012 the deformation for the unrest period 2011 2012 was non linear being characterized by strong radial deformation in the northern part of the caldera 50 120 mm yr and accelerating values 130 mm yr 2 combined gps squeesar mogi modeling indicated a source located north of nea kammeni at a shallow depth however a progressively decreasing rate in deformation was noted at most gps cgps station components after january 2012 indicating magma settlement consistent with the constantly decreasing rate of the inter caldera seismicity the faulting features seem to have a key role in the evolution of the deformation which continues up the end 2012 but at a very low level

landslide susceptibility map refinement using psinsar data abstract landslide susceptibility maps lsm are commonly used by local authorities for land use management and planning activities representing a valuable tool used to support decision makers in urban and infrastructural planning the accuracy of a landslide susceptibility map is affected by false negative and false positive errors which can decrease the reliability of this useful product in particular false negative errors are generally worse in terms of social and economic losses with respect to the losses associated with false positives in this paper we present a new technique to improve the accuracy of landslide susceptibility maps using permanent scatterer interferometric synthetic aperture radar psinsar data the proposed approach uses two different data sets acquired in ascending and descending geometry the ps velocity measured along the line of sight is re projected into a new velocity along the steepest slope direction v slope integration between the lsm and the ground deformation velocity map along the slope was performed using an empirical contingency matrix which takes into account the average v slope and the susceptibility degree obtained using the random forests algorithm the results show that the susceptibility degree increased in 56 41 km 2 of the study area the combination of psinsar data and the landslide susceptibility map lsm improved the prediction reliability of slow moving landslides which particularly affect urbanized areas the use of this procedure can be easily applied in different areas where psi data sets are available this approach will help planning and decision making authorities produce reliable landslide susceptibility maps correcting some of the lsm errors

late paleozoic early mesozoic magmatic history of central inner mongolia china implications for the tectonic evolution of the xingmeng orogenic belt the southeastern segment of the central asian orogenic belt abstract the tectonic setting and location of the southernmost boundary of the central asian orogenic belt caob in the late paleozoic early mesozoic era and the history evolution for the xingmeng orogenic belt xmob are sources of debate within the scientific community this paper presents new geochronological petrological and geochemical data for late paleozoic early mesozoic intrusions from the siziwangqi region in the southeastern caob and discusses the tectonic setting for that area using zircon la mc icpms u pb dating intrusions can be broadly grouped as late carboniferous amphibolite with an age of 323 1 3 4 ma middle late permian granitoids with ages of 271 3 1 5 ma 261 3 3 8 ma 260 6 4 8 ma 259 9 3 5 ma 253 3 4 8 ma and 249 6 4 8 ma early triassic k feldspar granite with an age of 235 0 1 8 ma these studies by interaction of regional geology provide new constraints on the tectonic evolution of the southeastern central asian orogenic belt during the late paleozoic early mesozoic and we predict five stages of tectonic evolution during the late paleozoic early mesozoic 1 the early carboniferous early permian 298 ma which is the active continental margin stage and the exit of the back arc basin during the late carboniferous 2 the early permian middle permian 298 271 ma where there was continued subduction of paleo asian oceanic lithosphere and the solonker ophiolite emplacement at the end of early permian 3 the middle permian 271 261 ma which had continent continent collision between the siberian plate and the north china craton 4 the middle permian middle triassic 261 235 ma which was the collisional orogeny stage with few intermountain basin deposition and the disappearance of marine strata and 5 late triassic

early paleozoic magmatic history of central inner mongolia china implications for the tectonic evolution of the southeast central asian orogenic belt to provide insights into the early paleozoic tectonic evolution of the southern portion of the long lived central asian orogenic belt we have conducted major and trace element analyses and zircon u pb dating of granitoid samples from central inner mongolia our study area covers three pre mesozoic tectonic units from north to south the wenduermiao subduction accretionary complex the bainaimiao magmatic belt and the northern margin of the north china craton our new geochronological and geochemical data show the temporal and genetic relationships between the three tectonic units accordingly we suggest that the wenduermiao subduction accretionary complex developed in the middle cambrian late silurian 509 421 ma comprising of coeval oceanic crust arc magmatism and forearc deposits the bainaimiao continental arc was developed during the late cambrian to early silurian 501 437 ma which superposed on the basement with the affinity of the north china craton the back arc basin opened prior to early silurian and lasted to the late silurian which is slightly younger than bainaimiao island arc the wenduermiao ocean between the wenduermiao subduction accretionary complex and the bainaimiao continental arc existed in early paleozoic

carrier phase delay altimetry with gps reflection occultation interferometry from low earth orbiters 1 gps signals reflected off the surface of the earth can be detected by receivers aboard occulting low earth orbiters leos in this work carrier phase interferometry between the reflected and direct occultation signals is performed to infer its relative delay at centimetric error our analysis shows that submeter sensitivity on the surface heights can formally be reached with this technique the potential applications to polar ice altimetry are discussed

geodynamic processes of taiwan arc continent collision and comparison with analogs in timor papua new guinea urals and corsica abstract the taiwan arc continent collision involves four geodynamic processes intra oceanic subduction initial arc continent collision advanced arc continent collision and arc collapse subduction these processes now occur simultaneously in 19 24 30 n but have operated sequentially southward since the late miocene although the geological and geophysical features appear to change progressively from north to south across the island they are distinct within individual tectonic regimes using the present scenario as a basis for comparison it is suggested that timor is at the initial arc continent collision stage while papua new guinea and urals proceeded to the advanced arc continent collision stage however corsica represents an even more advanced stage than in taiwan where a previously accreted arc has collapsed and been totally removed

devonian alkaline magmatic belt along the northern margin of the north china block petrogenesis and tectonic implications abstract some devonian magmatic rocks have been identified from the northern margin of the north china block ncb in recent years however their petrogenesis and tectonic setting are still highly controversial here we present new geochronological sr nd hf isotopic and whole rock chemical data on several newly identified and previously reported devonian alkaline complexes including mafic ultramafic rocks pyroxenites and gabbros alkaline rocks syenites monzonites and alkaline granites in the northern ncb we firstly identified some mafic ultramafic rocks coeval with monzonite and quartz monzonite in the sandaogou and wulanhada alkaline intrusions new zircon u pb dating of 16 samples from the baicaigou gaojiacun sandaogou wulanhada and chifeng alkaline intrusions combined with previous geochronological results indicate that the devonian alkaline rocks emplaced during the early middle devonian at around 400 380 ma and constitute an e w trending alkaline magmatic belt that extend ca 900 km long along the northern margin of the ncb whole rock geochemical and sr nd hf isotopic data reveal that the devonian alkaline rocks were mainly originated from partial melting of a variably enriched lithospheric mantle with different involvement of ancient lower crustal component and fractional crystallization the devonian alkaline magmatic belt rocks in the northern ncb are characterized by very weak or no deformations and were most likely related to post collision extension after arc continent collision between the bainaimiao island arc and the northern margin of north china craton during the latest silurian partial melting of subcontinental lithospheric mantle to produce the devonian alkaline magmatic rocks suggests that the northern north china craton has an inhomogeneous variably enriched subcontinental lithospheric mantle and was characterized by significant vertical crustal growth during the devonian period

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

insar monitoring using radarsat 2 data at piton de la fournaise la reunion and karthala grande comore volcanoes piton de la fournaise la reunion and karthala grande comore are the two active volcanoes of the southwestern indian ocean a 14 month april 2013 to june 2014 monitoring period was carried out at both volcanoes using synthetic aperture radar interferometry insar techniques on radarsat 2 data thanks to the seas oi survey of environment assisted by satellite in the indian ocean station 21 sar scenes were acquired over this period and insar results revealed the slow subsidence of the dolomieu caldera floor at piton de la fournaise following the 2009 and 2010 eruptions and the subsidence of the whole cone between april and july 2013 at karthala no evidence of any volcanic activity was found for the period april 2013 to june 2014 the use of systematic insar for volcano monitoring is an efficient tool to study effusive eruptions we showed that during periods of unrest insar is able to pick up early signs of a future eruption and monitor secondary phenomena that require no real time data during an effusive crisis it is still difficult to carry out fully operational insar monitoring but using the example of the june 2014 eruption at piton de la fournaise we show that sar data can help with the detection and tracking of lava flows and active flow paths during effusive eruptions based on sar coherence and sar amplitude these preliminary results are very promising for the future of insar monitoring of active volcanoes and highlight the need for near real time access to sar data in the mapping of active lava flows during effusive eruptions this study also revealed the major role of ground stations like seas oi in the efficiency of this monitoring supplying free near real time remote sensing data to the scientific and institutional communities

the eddy experiment accurate gnss r ocean altimetry from low altitude aircraft 1 during the eddy experiment two synchronous gps receivers were flown at 1 km altitude to collect l1 signals and their reflections from the sea surface for assessment of altimetric precision and accuracy wind speed u10 was around 10 m s and swh up to 2 m a geophysical parametric waveform model was used for retracking and estimation of the lapse between the direct and reflected signals with a 1 second precision of 3 m the lapse was used to estimate the ssh along the track using a differential model the rms error of the 20 km averaged gnss r absolute altimetric solution with respect to jason 1 ssh and a gps buoy measurement was of 10 cm with a 2 cm mean difference multipath and retracking parameter sensitivity due to the low altitude are suspected to have degraded accuracy this result provides an important milestone on the road to a gnss r mesoscale altimetry space mission

gold mineralization in the northern margin of the north china craton influence of alkaline magmatism and regional tectonic during middle paleozoic mesozoic abstract the northern margin of north china craton nncc has undergone multiple tectonic and magmatic episodes associated with numerous gold mineralization during devonian to cretaceous the origin of gold mineralization is a subject of debate in the nncc but there is a consensus on a metamorphic hydrothermal origin and a magmatic hydrothermal origin for this study we focused on four gold districts including the daqingshan zhangjiakou west liaoning and changbaishan from west to east we specifically constrain the link between the hadamengou dongping jinchanggouliang erdaogou and haigou gold deposits and their magmatic episodes the dahuabei and haigou granites and dongping syenite rocks have an alkaline affinity in contrast the xitaizi jinchanggouliang and xiaoxigou granites as well as the duimiangou quartz monzonites are calc alkaline with high alkaline rocks they are predominantly metaluminous and high fractionated i type granites except the xiaoxigou granite which is a type granites with peraluminous nature this indicates a variable mixing between depleted mantle derived mafic magma and ancient crust derived magma the magmatic events overlap the gold mineralization episodes in the nncc we have identified four magmatic episodes during middle paleozoic to mesozoic at 400 320 ma 245 221 ma 199 161 ma and 143 125 ma on the other hand gold mineralization was emplaced from carboniferous to cretaceous 390 110 ma with a peak in the middle jurassic 170 160 ma the available sulfur oxygen and carbon isotopic data from the studied nncc gold deposits suggest that the ore forming fluids were derived from a mixture of magmatic fluids and meteoric waters that flow in the wall rocks except for the hadamengou and jinchanggouliang gold deposits both late deposits present a multi source involving organic matter and other regional crustal rocks as shown by their positive 34s values 0 6 18 5 the intrusive rocks and sulfides in the nncc display similar lead isotope data suggesting that the lead isotopes might have similar origin the gold forming materials resulting from the mixing of these fluids are the product of several alkaline magmatism activities in this region hence this study has proved that gold mineralization is spatially and temporally related to the alkaline magmatism in the nncc the dominant tectonic events in the nncc are marked by post collisional or anorogenic geodynamical setting which is characterized by high alkaline features and andean type arc related to subduction geodynamical setting and characterized by calc alkaline features of the studied rocks both tectonic events are controlled by 1 the collision between the ncc and the bainaimiao arc 2 the subduction of the paleo asian ocean plate beneath the ncc 3 the collision between the siberian craton and the ncc and 4 the subduction of the western paleo pacific beneath the ncc these tectonic regimes are expressed by a transitional regime changing from compression to extension at western and an extensional regime at western and eastern parts of the nncc respectively

carrier phase ambiguity resolution for the global positioning system applied to geodetic baselines up to 2000 km the global positioning system gps carrier phase data are biased by an integer number of cycles a successful strategy has been developed and demonstrated for resolving these integer ambiguities for geodetic baselines of up to 2000 km in length resulting in a factor of 3 improvement in baseline accuracy and giving centimeter level agreement with coordinates inferred by very long baseline interferometry in the western united states for this experiment a method using pseudorange data is shown to be more reliable than one using ionospheric constraints for baselines longer than 200 km an automated algorithm exploits the correlations between the many phase biases of a gps receiver network to enable the resolution of ambiguities for very long baselines a method called bias optimizing has been developed which unlike traditional bias fixing does not require an arbitrary confidence test bias optimizing is expected to be preferable to bias fixing for poorly configured networks in order to enable ambiguity resolution for long baselines it is recommended that future gps networks have a wide spectrum of baseline lengths ranging from 1000 km and that gps receivers be used which can acquire dual frequency p code data

5 cm precision aircraft ocean altimetry using gps reflections 1 we present the first two aircraft global positioning system gps reflection altimetry measurements the most precise gps ocean altimetry measurement and demonstrate the altimetric precision and spatial resolution necessary to map mesoscale eddies our first experiment demonstrated a 14 cm precision single satellite ocean altimetry measurement while our more recent experiment demonstrates 5 cm altimetric precision with 5 km spatial resolution the new results show significant improvement over our previous effort due to improved modeling greater aircraft altitudes and velocities improved receiver positioning and better experimental control plans to further reduce speckle and refine models to obtain 5 cm altimetric accuracy are presented

first spaceborne phase altimetry over sea ice using techdemosat 1 gnss r signals a track of sea ice reflected global navigation satellite system gnss signal collected by the techdemosat 1 mission is processed to perform phase altimetry over sea ice high precision carrier phase measurements are extracted from coherent gnss reflections at a high angle of elevation 57 the altimetric results show good consistency with a mean sea surface mss model and the root mean square difference is 4 7 cm with an along track sampling distance of 140 m and a spatial resolution of 400 m the difference observed between the altimetric results and the mss shows good correlation with the colocated sea ice thickness data from soil moisture and ocean salinity this is consistent with the reflecting surface aligned with the bottom of the ice water interface due to the penetration of the gnss signal into the sea ice therefore these high precision altimetric results have potential to be used for determination of sea ice thickness

rapid tectonic exhumation detachment faulting and orogenic collapse in the caledonides of western ireland collision of the oceanic lough nafooey island arc with the passive margin of laurentia after 480 ma in western ireland resulted in the deformation magmatism and metamorphism of the grampian orogeny analogous to the modern taiwan and miocene new guinea orogens after f470 ma the metamorphosed laurentian margin sediments dalradian supergroup now exposed in connemara and north mayo were cooled rapidly 35 jc m y and exhumed to the surface we propose that this exhumation occurred mainly as a result of an oceanward collapse of the colliding arc southwards probably aided by subduction rollback into the new trench formed after subduction polarity reversal following collision the achill beg fault in particular along the southern edge of the north mayo dalradian terrane separates very low grade sedimentary rocks of the south mayo trough lough nafooey forearc and accreted sedimentary rocks of the clew bay complex from high grade dalradian meta sedimentary rocks suggesting that this was a major detachment structure in northern connemara the unconformity between the dalradian and the silurian cover probably represents an eroded major detachment surface with the renvyle bofin slide as a related but subordinate structure blocks of sheared mafic and ultramafic rocks in the dalradian immediately below this unconformity surface probably represent arc lower crustal and mantle rocks or fragments of a high level ophiolite sheet entrained along the detachment during exhumation orogenic collapse was accompanied in the south mayo trough by coarse clastic sedimentation derived mostly from the exhuming dalradian to the north and to a lesser extent from the lough nafooey arc to the south sediment flow in the south mayo trough was dominantly axial deepening toward the west volcanism associated with orogenic collapse rosroe and

2 cm gps altimetry over crater lake dierences in electromagnetic path delay be tween direct global positioning system gps signals and those reflected from the surface of crater lake have led to lake surface height estimates with 2 cm precision in 1 sec ond this is the rst high precision altimetric demonstra tion with gps from sucient altitude 480 m to probe fundamental experimental errors which bear on future air and spaceborne passive gps altimetry it also serves as the rst demonstration of a new approach to altimetric remote sensing in the coastal region an area that is poorly mea sured by conventional radar altimetry time series analy sessuggest thattroposphericandthermalnoisefluctuations dominate the altimetric error in this experiment estimat ing the dierential delay from several simultaneously visi ble satellites may enable tropospheric error estimation and correction thermal noise on the reflected signal will be reduced with fully polarimetric observations and larger an tenna apertures

finding realistic dike models from interferometric synthetic aperture radar data the february 2000 eruption at piton de la fournaise dike intrusions often cause complex ground displacements that are not sufciently explained by simple analytical models we develop a method to nd complex and realistic dike geometries and overpressures from interferometric synthetic aperture radar insar data this method is based on a combination of a boundary element method with realistic topography and a neighbourhood algorithm inversion dike model geometry is roughly a quadrangle with its top reaching the ground the inversion has two stages search and appraisal the appraisal stage involves calculations of model marginal probability density functions using mist val ues calculated during the search stage the mist function takes into account the variance and correlation of data noise synthetic tests show that a model is successfully retrieved within predicted narrow condence intervals we apply the method on insar data of the february 2000 ank eruption at piton de la fournaise and get a trapezoid dike dipping seaward 61 0 n 67 3 with its bottom passing 800n1000 m beneath the summit a model with a basal slip plane does not better explain observed asymmetric displacements and thus this asymmetry is solely attributed to the dipping dike the dike lies above a narrow band of pre eruption seis micity suggesting that lateral magma propagation occurred neglecting topography results in poor modeling at depth and in overestimations of overpressure or opening height both about 30 and volume about 20

carboniferous granitic plutons from the northern margin of the north china block implications for a late palaeozoic active continental margin we report four late palaeozoic zircon sensitive high resolution ion microprobe shrimp u pb ages for granitic plutons from the inner mongolia palaeo uplift on the northern margin of the north china block these cast a new light on the poorly understood tectonic history of the northern margin of the north china block and the central asian orogenic belt during the late palaeozoic the plutons have for a long time been considered to belong to the early precambrian basement of the north china block our new shrimp u pb zircon dating of four plutons at longhua daguangding boluonuo and hushiha has yielded intrusive ages of 311 2 ma 324 6 ma 302 4 ma and 310 5 ma respectively geochemical data suggest that these granitoids have a calc alkaline subduction related i type signature indicating the existence of an andean style continental arc along the northern margin of the north china block during the late palaeozoic our results also indicate that the palaeo asian ocean still existed during latest carboniferous earliest permian time and that the final collision between the southern mongolia composite terranes and the north china block occurred later than c 290 ma we suggest that the northern margin of the north china block was an active continental margin and the inner mongolia palaeo uplift is a deeply exhumed mid crustal root of a late palaeozoic andean style continental arc

sedimentological and geochronological constraints on the carboniferous evolution of central inner mongolia southeastern central asian orogenic belt inland sea deposition in a post orogenic setting handling editor s j liu keywords central asian orogenic belt central inner mongolia carboniferous sedimentary detrital zircon sedimentological and geochronological analyses were performed on carboniferous strata from central inner mongolia china to determine the tectonic setting of the southeastern central asian orogenic belt caob sedimentological analyses indicate that the widespread late carboniferous strata in central inner mongolia were dominated by shallow marine clastic carbonate deposition with basal conglomerate above the precambrian basement and early paleozoic orogenic belts based on lithological comparison and fossil similarity five sedimentary stages were used to represent the carboniferous deposition the depositional stages include from bottom to top 1 basal molassic 2 first carbonate platform 3 terrigenous with coeval intraplate volcanism 4 second carbonate platform and 5 post carbonate terrigenous these five stages provide evidence for an extensive transgression in central inner mongolia during the late carboniferous detrital zircon geochronological studies from five samples yielded five main age populations 310 ma 350 ma 400 450 ma 800 1200 ma and some meso proterozoic to neoarchean grains the detrital zircon geochronological studies indicate that the provenances for these late carboniferous strata were mainly local magmatic rocks early paleozoic arc magmatic rocks and carboniferous intrusions with subordinate input of precambrian basement combining our sedimentological and provenance analyses with previous fossil comparison and paleomagnetic reconstruction an inland sea was perceived to be the main paleogeographic feature for central inner mongolia during the late carboniferous the inland sea developed on a welded continent after the collision between north china craton and its northern blocks

dnsc08 mean sea surface and mean dynamic topography models 1 the danish national space center data set dnsc08 mean sea surface mss is a new enhanced mapping of the mean sea surface height of the worlds oceans derived from a combination of 12 years of satellite altimetry from a total of eight different satellites covering the period 1993 2004 it is the first global mss without a polar gap including all of the arctic ocean by including laser altimetry from the icesat mission the mean dynamic topography mdt is the quantity that bridges the geoid and the mean sea surface constraining large scale ocean circulation here we present a new high resolution 1 min global mdt called dnsc08 mdt derived from the slightly smoothed difference between the dnsc08 mss and the egm2008 geoid the derivation and quality control of the new dnsc08 mss and dnsc08 mdt is presented in this paper along with suggestions for time period standardization of the mss and mdt models this way a consistent modeling of the interannual sea level variability is carried out before different mss and mdt models are compared altimetric derived physical mss can be converted into an inverse barometer corrected mss by correcting the altimeter range for the inverse barometer effect of the atmosphere on the sea surface height it is demonstrated that it is important to choose the right version of the mss when comparing with hydrodynamic models and gps measured tide gauges

evolution of the solonker suture zone constraints from zircon u pb ages hf isotopic ratios and whole rock nd sr isotope compositions of subduction and collision related magmas and forearc sediments abstract the solonker zone in northern inner mongolia china is considered as the suture between the north china craton and the south mongolian microcontinent two magmatic belts are recognized along the suture zone a subduction related magmatic belt represented by the baolidao arc rocks and a younger collision related granite belt represented by the halatu granites we use zircon u pb ages zircon in situ hf isotopic analyses and whole rock nd sr isotopic data of the two magmatic belts and related forearc sediments the xilinhot metamorphic complex to constrain timing of the suturing and to discuss the petrogenesis of the magmatic rocks a gabbroic diorite bld 1 of the baolidao arc was dated at 310 5 ma by shrimp this sample shows an e nd t value of 2 5 and i sr of 0 7052 hf isotopic analyses on 25 zircons from the same sample show e hf t 5 4 to 11 5 another diorite sample xh 2 of the same arc from south of xilinhot displays even more depleted isotopic compositions with e nd t 5 6 and i sr 0 7037 the main population of zircons from this sample have highly variable and depleted hf isotopic compositions e hf t 0 18 3 the large variation in hf isotopic composition of zircons with largely the same crystallization age from a single pluton is explained by a mixing process between depleted mantle derived magma and continental crust in an active continental arc setting the halatu granite hlt 2 was dated at 234 7 ma by shrimp zircons from the granite also show a large variation of e hf t values 9 1 to 26 despite most samples having whole rock e hf t 2 the large variation in e hf t values suggests that the granite formed probably by partial melting of two source regions a dominant juvenile crust and a subordinate old continental crust most zircons from the xilinhot metamorphic complex show ages comparable with those of the baolidao arc rocks suggesting that the protolith of the metamorphic complex was probably deposited during or after arc magmatism some zircons however show precambrian ages that fall into two groups one with ages of 780 900 ma resembling those from the south mongolian microcontinent and the other with ages of 1524 2900 ma similar to those of the north china craton thus the protolith of the metamorphic complex probably formed in a forearc basin during convergence of the two continents and metamorphosed subsequently during collision in the late paleozoic our zircon age data thus constrain timing of collision between the south mongolian microcontinent and the north china craton to have been between 296 and 234 ma

widespread uplift and trapdoor faulting on galapagos volcanoes observed with radar interferometry volcanic uplift caused by the accumulation of magma in subsurface reservoirs is a common precursor to eruptions1 2 but for some volcanoes uplift of metres or more has not yet led to an eruption3 here we present displacement maps of volcanoes in the galapagos islands constructed using satellite radar interferometry that might help explain this dichotomy we show that all but one of the seven volcanoes on the islands of isabela and fernandina deformed during 1992 99 cerro azul and fernandina erupted4 5 6 during the observation period and show evidence of inflation co eruptive deflation and shallow dyke intrusion in contrast the largest volcano sierra negra has not erupted yet exhibits spatially and temporally variable deformation with a maximum uplift of 2 7 m between 1992 and 1999 which can be modelled by a shallow inflating sill inflation during 1997 98 however was accompanied by trapdoor faulting on a steeply dipping fracture system within the caldera repeated trapdoor faulting over geological time has formed an arcuate intra caldera ridge within sierra negra and may have acted to relax stresses above the magma chamber inhibiting summit eruptions similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes

tectonic environment of the devonian gramscatho basin south cornwall framework mode and geochemical evidence from turbiditic sandstones the portscatho formation within the allochthonous unit of the middle and upper devonian gramscatho group is a thick sequence of deep water sandstones and interbedded slates deposited by southerly derived turbidity currents into the gramscatho basin of south cornwall throughout an approximately 3 5 km thick sequence the portscatho formation is petrographically and chemically coherent except that the upper section shows a higher proportion of metamorphic clasts high but variable cr and low uniform zr abundances complementary framework mode and bulk geochemistry indicate that the sandstones were derived from a dissected continental magmatic arc of predominantly acidic composition similar to average upper continental crust but with an admixture of minor intermediate basic material flysch deposition took place in a fore arc setting the presence of an arc to the south of cornwall during the devonian implies that there was subduction at the margin of the gramscatho basin whose ultimate closure was accommodated by the northward stacking of flysch ophiolite nappes

permian geodynamic setting of northeast china and adjacent regions closure of the paleo asian ocean and subduction of the paleo pacific plate abstract northeast china and adjacent regions are located in the central east asian continent and consist tectonically of both the paleo asian and paleo pacific orogens between the siberian platform and sino korean north china block this paper discusses some hotly debated issues concerning the permian geodynamic setting of these regions based on a comprehensive analysis of available geological geochemical paleobiogeographical and paleomagnetic data spatial and temporal distribution of ophiolites and associated continental marginal sequences permian sedimentary sequences spatial distribution and geochemistry of permian magmatic rocks and the evolution of paleobiogeographical realms imply 1 that the permian marine basins in northeast china and adjacent regions include remnants of the paleo asian ocean in southeastern inner mongolia and central jilin province and active continental margins of the paleo pacific ocean 2 that the suture between the siberian and sino korean paleoplates was finally emplaced in the permian and is located in areas from suolunshan solonker eastwards through regions north to the xar moron river in southeastern inner mongolia and then central jilin province to the yanji area and 3 that the permian crustal evolution of northeast china and adjacent regions as well as parts of the siberian paleoplate was influenced by subduction of the paleo pacific oceanic plate finally the permian tectonic framework and paleogeography of northeast china and adjacent regions in central east asia are discussed briefly and early and late permian palinspastic reconstruction maps are provided

ordovician 40ar 39ar phengite ages from the blueschist facies ondor sum subduction accretion complex inner mongolia and implications for the early paleozoic history of continental blocks in china and adjacent areas we obtained 453 21 8 ma and 449 41 8 ma 2 laser step heating 40 ar 39 ar plateau ages for phengite from quartzite mylonites from the blueschist facies ondor sum subduction accretion complex in inner mongolia northern china these ages are within error of the inverse isochron ages calculated using the plateau steps and the weighted mean ages of total fusion of single grains the compositional change from glaucophane in the cores to crossite in the rims of blue amphiboles as revealed by electron microprobe analysis points to decompression probably caused by progressive exhumation of the subducted material the late ordovician ages were not affected by excess argon incorporation because in all likelihood the oceanic sediments were wet on arrival at the trench and free of older detrital mica the ca 450 ma ages are hence interpreted as the time of crystallization during mylonitization under high fluid activity at fairly low temperatures this means that accretion of the quartzite mylonite unit occured about 200 ma before final closure of the paleo asian ocean amalgamation of the siberian tarim and north china cratons and formation of the end permian solonker suture zone we argue that the early paleozoic evolution of the ondor sum complex occurred along the northeastern cimmerian margin of gondwana which was composed of micro continents fringed by subduction accretion complexes and island arcs the later evolution took place during the building of the eurasian continent following middle devonian and younger rifting along the east gondwanan margin and northward drift of the detached north china craton an extensive review shows that this type of two stage scenario probably also applies to the geodynamic evolution of other micro continents like south china tarim a number of kazakh terranes alashan qaidam and kunlun as well as south kitakami and correlatives in japan and probably indochina like the north china craton these were bordered by early paleozoic subduction accretion complexes island arcs or contained calc alkaline volcanic mar gins like for example the central tienshan north qinling north qaidam altun north qilian and kunlun belts in china as well as the oeyama and miyamori ophiolites and matsugadaira motai blueschist belt of japan and the dismembered sergeevka ophiolite of the southern part of the russian far east this implies that a vast orogenic system comprising an archipelago of micro continents seems to have existed along the cimmerian margin of east gondwana in early paleozoic time in which the ultrahigh pressure metamorphism that characterizes the early evolution of many of the asian micro continents occurred introduction and aim

u pb 39ar 40ar geochronology of the metamorphosed volcanic rocks of the bainaimiao group in central inner mongolia and its implications for ore genesis and geodynamic setting abstract the greenschist facies volcano sedimentary sequence of the bainaimiao group in central inner mongolia hosts the bainaimiao cu mo au deposit and the bainaimiao lode gold deposit but the ore classification and genetic process of the bainaimiao cu mo au deposit is still disputed in this study we have selected the interbedded metamorphosed volcanic rocks of the bainaimiao group for la icp ms zircon u pb analysis 17 analyses form a tight cluster on the concordia and yield a weighted mean 206 pb 238 u age of 465 1 ma 95 confidence level mswd 0 95 n 17 which represents the best estimate of the crystallization age of the volcanic rocks of the bainaimiao group biotite from the greenschist of the bainaimiao group yielded a well defined plateau with an age of 429 2 4 1 ma the inverse isochron age is 429 1 4 2 ma with an elevated 40 ar 36 ar i ratio of 299 9 22 7 which represents the time of regional greenschist facies metamorphism previous studies showed that the re os isochron age of the molybdenite from the bainaimiao cu mo au deposit is 445 0 3 4 ma and the mineralized granodiorite porphyry yielded a weighted mean 206 pb 238 u age of 445 6 ma these data indicate that the bainaimiao volcanic rocks were formed at about 465 ma and the porphyry cu mo au mineralization took place at about 445 ma volcanic rock emplacement is 20 ma older than the cu mo au mineralization indicates it is a porphyry deposit rather than vms deposit the dynamic setting for the porphyry mineralization is the paleo asian oceanic plate subduction along the northern margin of the north china craton in early paleozoic subsequently the collision between the bainaimiao arc and the north china craton led to regional metamorphism and deformation at about 430 ma and the old porphyry system may have been overprinted during this metamorphic process

early permian plutons from the northern north china block constraints on continental arc evolution and convergent margin magmatism related to the central asian orogenic belt recent zircon dating identified several late carboniferous to early permian hornblende gabbro diorite quartz diorite granodiorite tonalite granite plutons in lithological assemblages at the northern margin of the north china block ncb that were previously regarded as archaean to palaeoproterozoic our geochronological results indicate that emplacement of these plutons was a continuous process during the late carboniferous to early permian from 324 6 to 274 6 ma and lasted for at least 50 ma in this paper the early permian components with compositions from gabbro to granite within the intrusive complex were studied the early permian plutons exhibit calc alkaline or high k calc alkaline metaluminous geochemical features and highly variable sio2 contents they have no significant eu anomaly in their ree patterns and in primitive mantle normalized spidergrams they display depletion in th u nb ta p and ti and enrichment in ba k pb and sr the granitoid bodies within these plutons display i type and adakitic geochemical signatures the early permian rocks exhibit low whole rock initial 87sr 86sr ratios from 0 70520 to 0 70615 and have negative whole rock e nd t values ranging from 17 4 to 9 3 and zircon e hf t values of 23 2 to 10 5 the gabbros exhibit higher e nd t values from 11 1 to 9 3 and e hf t values from 16 5 to 10 5 and one granodiorite exhibits an even lower e nd t value of 17 4 and zircon e hf t values of 23 2 to 15 1 geochemical sr nd and in situ zircon hf isotopic compositions suggest that the hornblende gabbros were derived from a metasomatized lithospheric mantle and the diorite and quartz diorite were generated from a gabbroic magma by fractional crystallization coupled with differential assimilation of ancient lower crustal material the granodiorite was likely derived from partial melting of ancient lower crust with involvement of some mantle components involvement of both lithospheric mantle and ancient lower crust in the generation of the early permian plutons indicates strong crust mantle interaction in the northern ncb petrological associations as well as geochemical and sr nd hf isotopic results show that the early permian plutons were emplaced along an andean type active continental margin during southward subduction of the palaeo asian oceanic plate beneath the ncb integration of our results with previously published data for late carboniferous and late permian to middle triassic intrusions suggests that the continental arc on the northern margin of the ncb existed for at least 50 ma during the late palaeozoic and final amalgamation of the mongolian arc terranes with the northern ncb likely occurred during a period from 270 to 250 ma i e in the late permian to earliest triassic

arc continent collision and subduction reversal in the cenozoic evolution of the northwest pacific an example from kamchatka ne russia abstract the principal new feature in the cenozoic evolution of the northwest pacific is based on the fact that two arc terranes of upper cretaceous paleogene age were incorporated in the kamchatka orogen during the early tertiary and at the end of the miocene respectively these two arc terranes so called achaivayam valaginskaya campanian lower paleocene and kronotskaya coniacian eocene arcs are separated by a suture zone that contains deformed slices of young paleocene lower eocene oceanic crust paleomagnetic data on the original paleolatitudes of the arc positions as well as geochemical data characterized the arcs as intraoceanic originated in the northwest pacific the arcs were separated by the vetlovka oceanic plate suggested to be a trapped fragment of the kula plate in which a new spreading zone developed in the early tertiary the principal event in the reconstructed evolution is the eocene collision of the extended achaivayam valaginskaya arc terrane with the continental margin of asia the margin is interpreted as the southeastern facing the pacific cretaceous accretionary boundary of the okhotsk microplate docked against the asian continent at 55 65 ma the arc continent collision developed progressively northward from the end of the paleocene early eocene in southern kamchatka to the middle eocene in the olutorka region the different stages of the collision occurred simultaneously along strike of the achaivayam valaginskaya arc according to the geodynamic model based on geological data for southern kamchatka collision included 1 the entrance of the continental margin in the subduction zone deformation of the overriding plate and subduction of fore arc block 2 arc obduction on the continental margin blocking of continental margin subduction and 3 subduction reversal with onset of oceanic subduction at the eastern side of the deformed arc this subduction reversal produced deformation and reverse faulting along the eastern side of the arc thus allowing accretion of tectonic slices of young oceanic crust of the vetlovka plate which began to subduct during the subduction reversal the subducted plate dipping to the southeast was broken off and detached at depth under the arc area the subduction polarity reversal the most characteristic feature of the collision model is strongly supported by structural and geologic data of southern kamchatka and explains the main tectonic metamorphic and magmatic events related to and postdating the collision

provenance and tectonic setting of clastic deposits in the devonian xicheng basin qinling orogen central china abstract the qinling orogenic belt is one of world s great collisional orogenic belts which extends from the pamirs west kunlun to the korean peninsula and occupies a key position in understanding of the evolution and assembly of asia this belt separates the north china and south china blocks extensive thick devonian clastic rocks sandwiched between the shangdan and mianlue suture zones are mainly infills of the xicheng basin and provide the principal sedimentary record of tectonism in the qinling orogen devonian infills were subdivided into three subunits the upper devonian dacaotan group the middle upper devonian shujiaba group and the lower upper devonian xihanshui group their provenance and tectonic setting are critical to understanding not only the tectonic evolution of asia but also the global aspects of collisional regions compared with devonian strata in the eastern part of the qinling orogen the xicheng basin was not seriously modified by mesozoic tectonism petrologic studies demonstrate that the dacaotan group consists mainly of feldspathic litharenite with abundant volcanic fragments in contrast the shujiaba and xihanshui groups contain more metamorphic and sedimentary fragments and fewer magmatics than other lithic fragments these relations demonstrate that magmatic plutons were not extensively exposed at the time of deposition of these groups on q f l plots sandstones fall into the field of transitional arcs but on qm p k and lm lv ls diagrams they plot in the fields of continental arc and continental suture rocks the presence of volcanic lithic grains in the sandstones suggests they were derived mainly from a continental arc major element geochemistry of siltstones and mudstones demonstrate that most were derived from a continental arc but some from an oceanic island arc trace element geochemistry favors a continental arc provenance mostly from felsic rocks a high cr content of siltstones and mudstones demonstrates that some mafic or ultramafic rocks were exposed in the source area and provided some detritus rare earth element patterns are very similar to those of sandstones in modern continental arcs devonian paleocurrent indictors demonstrate that this continental arc was located at the northern edge of the basin this deduction demonstrates that the qinling arc in the southern margin of the north china block was the major source of clastic debris in the devonian xicheng basin these relationships suggest that the sediments were most probably deposited in a forearc basin