highly fractionated i type granites in ne china ii isotopic geochemistry and implications for crustal growth in the phanerozoic ne china is the easternmost part of the central asian orogenic belt caob the area is distinguished by widespread occurrence of phanerozoic granitic rocks in the companion paper part i we established the jurassic ages 184 137 ma for three granitic plutons xinhuatun lamashan and yiershi we also used geochemical data to argue that these rocks are highly fractionated i type granites in this paper we present sr nd o isotope data of the three plutons and 32 additional samples to delineate the nature of their source to determine the proportion of mantle to crustal components in the generation of the voluminous granitoids and to discuss crustal growth in the phanerozoic despite their difference in emplacement age sr nd isotopic analyses reveal that these jurassic granites have common isotopic characteristics they all have low initial 87 sr 86 sr ratios 0 7045f0 0015 positive end t values 1 3 to 2 8 and young sm nd model ages 720 840 ma these characteristics are indicative of juvenile nature for these granites other late paleozoic to mesozoic granites in this region also show the same features sr nd and oxygen isotopic data suggest that the magmatic evolution of the granites can be explained in terms of two stage processes 1 formation of parental magmas by melting of a relatively juvenile crust which is probably a mixed lithology formed by pre existing lower crust intruded or underplated by mantle derived basaltic magma and 2 extensive magmatic differentiation of the parental magmas in a slow cooling environment the widespread distribution of juvenile granitoids in ne china indicates a massive transfer of mantle material to the crust in a post orogenic tectonic setting several recent studies have documented that juvenile granitoids of paleozoic to mesozoic ages are ubiquitous in the central asian orogenic belt hence suggesting a significant growth of the continental crust in the phanerozoic d 2003 elsevier science b v all rights reserved

reservoir assessment using non invasive geophysical techniques this paper describes the use of three geophysical techniques to detect potential seepage that could jeopardise the integrity of reservoir embankments could induce partial or total collapse and pose a risk to the population nearby a fast scanning geophysical technique using two dipole electromagnetic em profile apparatus gem2 provided the first step to detect the weakest points on the selected dams in order to proceed to a more detailed analysis and visualisation of the soil erosion fissuring or piping using electrical resistivity tomography ert finally self potential surveys were carried out to relate to the em and ert anomalies that could be pathways for seepage and changes of the water displacement inside the embankment the three geophysical techniques used were evaluated in one case study of reservoir in a location relevant to flooding issues in czech republic a risk approach based on the geophysical results was undertaken for the reservoir embankment the three techniques together were compared for the same problematic section and confirmed seepage by showing similar results conclusions were also drawn on the efficiency of using these three techniques as a package to give a comprehensive non invasive assessment to be used as common practice by local authorities and environment agencies whereby remedial action could be recommended to protect assets and civilians

tectonic erosion of the peruvian forearc lima basin by subduction and nazca ridge collision 1 subsidence of lima basin part of the peruvian forearc is controlled by tectonic erosion by the subducting nazca plate multichannel seismic reflection data coupled with age and paleowater depth constraints derived from ocean drilling program odp coring now allow the rates of erosion to be reconstructed through time in trenchward locations the forearc has experienced limited recent relative uplift 700 850 m likely due to preferential basal erosion under the center of lima basin long term subsidence driven by basal tectonic erosion dominates and is fastest closest to the trench since 47 ma eocene up to 148 km of the plate margin have been lost at an average rate of up to 3 1 km myr 1 appoximately 110 km of that total appears to be lost since 11 ma implying much faster average rates of trench retreat 10 km myr 1 since collision of the nazca ridge with the lima basin at 11 ma although there is no clear subsidence event at odp site 679 during the time at which nazca ridge was subducting beneath this part of the forearc 4 11 ma the more trenchward odp sites 682 and 688 show significant deepening after 11 ma indicating that subduction of the ridge accelerates tectonic erosion long term rates of crustal erosion in the region of lima basin are greater than estimates of regional arc magmatic productivity implying that such margins are net sinks of continental crust

zircon u pb dating and the petrological and geochemical constraints on lincang granite in western yunnan china implications for the closure of the paleo tethys ocean abstract lincang granite is a batholith located in the sanjiang region and is an important research subject for understanding subduction and collision during the paleo tethyan period it is widely exposed in the lincang terrane and extends south into burma based on various petrological and geochemical investigations performed from south to north across the lincang granite a new set of data which includes zircon chronological and hf isotopic data is presented to discuss the origin of the lincang granite and its tectonic significance the lincang granite is a peraluminous high k calc alkaline body with sub parallel ree patterns and a strong negative eu anomaly this anomaly is characteristic of a post collision peraluminous s type granitic batholith the 200 230 ma formation age of the lincang granite was determined using la icp ms zircon u pb dating thus it has been confirmed that the granite formed during the late triassic period and the formation process lasted for approximately 30 ma geochemical and isotopic compositions indicate that the primary magma of lincang granite most likely originated from a crustal source and possibly underwent an assimilation fractionation crystallization afc process during its emplacement the lincang granite formed during the continental collision between the baoshan gengma terrane and the lanping simao terrane after the northeast subduction of the paleo tethyan oceanic plate therefore the late triassic lincang granite is important evidence for the closure of the paleo tethyan ocean

boundary lines within petrologic diagrams which use oxides of major and minor elements use of some petrologic diagrams applied to analyses of volcanic rocks is unnecessarily difficult due to lack of data for construction of discriminant lines between rock series coordinates are provided for sufficient points to enable accurate plotting of the boundary lines within seven diagrams viz 1 tas total alkalies na2o k2o vs sio2 2 k2o vs sio2 3 afm 4 jensen 5 ktp k2o tio2 p2o5 6 fms feo mgo vs sio2 and 7 taktip k2o na2o k2o vs tio2p2o5 different versions of these boundaries are collated to indicate their variable position and it is demonstrated that inter laboratory analytical precision suffices to account for almost all of their spread on the tas and k2o vs sio2 diagrams

magma chambers at oceanic ridges how large seismic models of magma chambers at fast spreading oceanic ridges predict small perched magma chambers above a wide low velocity zone seismic attenuation in a low velocity zone allows for 10 melt in hot gabbros in order to reconcile these data with a structural model of magma chambers that is supported by compelling field data in the oman ophiolite we propose that the low velocity zone belongs to the magma chamber in such a dynamic magma chamber gabbros develop strong shape fabrics during magmatic flow in a concentrated suspension this process results in a drastic reduction of the melt fraction that is compatible with magmatic flow as confirmed by preliminary experiments we propose here that dynamic magma chambers below ridges may contain as little as 10 melt

slab breakoff a model for syncollisional magmatism and tectonics in the alps slab breakoff is the buoyancy driven detachment of subducted oceanic lithosphere from the light continental lithosphere that follows it during continental collision in a recent paper davies and von blanckenburg 1994 have assessed the physical conditions leading to breakoff by quantitative thermomechanical modeling and have predicted various consequences in the evolution of mountain belts breakoff will lead to heating of the overriding lithospheric mantle by upwelling asthenosphere melting of its enriched layers and thus to bimodal magmatism breakoff will also lead to thermal weakening of the subducted crustal lithosphere thereby allowing buoyant rise of released crustal slices from mantle depths in this paper we present a test of this model in the tertiary evolution of the european alps in the alps both basaltic and granitoid magmatism occur between 42 and 25 ma following the closure of oceanic basins by subduction and continental collision the granitoids are now well established to result from mixing of basalt with assimilated continental crust to identify the tectonically crucial origin of the partial mantle melts we have compiled all published geochemical and isotopic data of numerous mafic dykes occurring throughout the whole alpine arc their trace element and isotopic composition suggests that they have been formed by low degree melting of the mechanically stable lithospheric mantle we see no evidence for melting of asthenospheric mantle it was thus not decompressed to depths shallower than 50 km once initiated rapid lateral migration of slab breakoff will result in a linear trace of magmatism in locally thermal weakened crust this explains why all alpine magmatic rocks intruded almost synchronously along a strike slip fault the periadriatic lineament a compilation of ages from penninic high pressure rocks subducted to depths of up to 100 km shows that subduction took place at circa 55 40 ma followed by uplift at 40 35 ma from the short time interval between their uplift and the onset of magmatism we infer that both processes have been induced by the breakoff the slab breakoff model fulfills its predictions in the case of the alps and therefore supports the assumptions made in the theoretical model on a geological basis we believe that the characteristic association of magmatic activity with the return of high pressure rocks to the surface allows the identification of this process in the earth s mountain belts

shear wave velocity imaging of the avignonet landslide france using ambient noise cross correlation 1 the avignonet landslide affects a 2 by 2 km area covered by clayey deposits this paper presents the use of the seismic ambient noise cross correlation technique to retrieve a 3 d model of the shear wave velocity of the area seismic ambient noise was recorded during 15 days at 13 stations located on the landslide cross correlations computed between the vertical components of all station pairs allow the retrieval of the rayleigh wave green s functions and the estimation of their group velocity dispersion curves in the 1 7 5 hz frequency range at frequencies lower than 1 5 hz the anisotropy of the wavefield strongly influences the apparent rayleigh wave velocities moreover the analysis of the convergence of the cross correlations shows that at frequencies higher than 5 hz the recording time length was not sufficient for the cross correlation to be stable these 1 7 5 hz passive group dispersion curves are complementary to the ones computed from shot signals in the 3 7 hz frequency range a tomographic inversion of the resulting 1 7 7 hz rayleigh wave group dispersion curves provides local group dispersion curves at each cell of the tomographic grid these are inverted with a neighborhood algorithm to retrieve the 3 d model of the landslide despite the complex wave propagation in the eastern part of the landslide and the sparse ray coverage estimated velocities and first order features are in good agreement with previous investigations

triassic subduction of the paleo tethys in northern tibet china evidence from the geochemical and isotopic characteristics of eclogites and blueschists of the qiangtang block abstract a 500 km long high pressure metamorphic belt occurs in the qiangtang block of northern tibet the occurrence of high pressure metamorphic rocks eclogite and blueschist has a significant bearing on the paleo tethys subduction and plate suturing processes a few studies have been conducted on petrology mineralogy and geochronology of high pressure rocks in this paper we present the results of a geochemical and isotopic investigation on eclogite and blueschist from this belt and discuss the probable geodynamic implications geochemical analyses show that the two rock types eclogite and blueschist have grossly similar bulk compositions but they can be subdivided into two groups based on their tio 2 contents the low tio 2 2 2 75 wt rocks are more akin to ocean island basalts oib the positive e nd t values ranging from 0 4 to 6 3 for all samples suggest that the basaltic protoliths of the eclogites and blueschists were derived from a long term depleted mantle source however their geochemical characteristics require that the source be metasomatized and enriched in large ion lithophile and light rare earth elements shortly before the formation of these basaltic protoliths like for most oib and e morb of the world the recognition of oceanic basalts suggests that a paleozoic ocean should be present in the central qiangtang block this ocean was hypothesized to be the western extension of the changning menglian paleo tethys ocean in the eastern margin of the tibetan plateau the eclogite and blueschist were formed by northward subduction of this paleozoic ocean in the triassic

fifteen new discriminant function based multi dimensional robust diagrams for acid rocks and their application to precambrian rocks abstract for the discrimination of four tectonic settings of island arc continental arc within plate continental rift and ocean island together and collision we present three sets of new diagrams obtained from linear discriminant analysis of natural logarithm transformed ratios of major elements immobile major and trace elements and immobile trace elements in acid magmas the use of discordant outlier free samples prior to linear discriminant analysis had improved the success rates by about 3 on the average success rates of these new diagrams were acceptably high about 69 to 97 for the first set about 69 to 99 for the second set and about 60 to 96 for the third set testing of these diagrams for acid rock samples not used for constructing them from known tectonic settings confirmed their overall good performance application of these new diagrams to precambrian case studies provided the following generally consistent results a continental arc setting for the caribou greenstone belt canada at about 3000 ma sao francisco craton brazil at about 3085 2983 ma penakacherla greenstone terrane dharwar craton india at about 2700 ma and adola ethiopia at about 885 765 ma a transitional continental arc to collision setting for the rio maria terrane brazil at about 2870 ma and eastern felsic volcanic terrain india at about 2700 ma a collision setting for the kolar suture zone india at about 2610 ma and korpo area finland at about 1852 ma and a within plate likely a continental rift setting for malani igneous suite india at about 745 700 ma these applications suggest utility of the new discrimination diagrams for all four tectonic settings in fact all three sets of diagrams were shown to be robust against post emplacement compositional changes caused by analytical errors element mobility related to low or high temperature alteration or fe oxidation caused by weathering

the origin and pre cenozoic evolution of the tibetan plateau different hypotheses have been proposed for the origin and pre cenozoic evolution of the tibetan plateau as a result of several collision events between a series of gondwana derived terranes e g qiangtang lhasa and india and asian continent since the early paleozoic this paper reviews and reevaluates these hypotheses in light of new data from tibet including 1 the distribution of major tectonic boundaries and suture zones 2 basement rocks and their sedimentary covers 3 magmatic suites and 4 detrital zircon constraints from paleozoic metasedimentary rocks the western qiangtang amdo and tethyan himalaya terranes have the indian gondwana origin whereas the lhasa terrane shows an australian gondwana affinity the cambrian magmatic record in the lhasa terrane resulted from the subduction of the proto tethyan ocean lithosphere beneath the australian gondwana the newly identified late devonian granitoids in the southern margin of the lhasa terrane may represent an extensional magmatic event associated with its rifting which ultimately resulted in the opening of the songdo tethyan ocean the lhasa northern australia collision at similar to 263 ma was likely responsible for the initiation of a southward dipping subduction of the bangong nujiang tethyan oceanic lithosphere the yarlung zangbo tethyan ocean opened as a back arc basin in the late triassic leading to the separation of the lhasa terrane from northern australia the subsequent northward subduction of the yarlung zangbo tethyan ocean lithosphere beneath the lhasa terrane may have been triggered by the qiangtang lhasa collision in the earliest cretaceous the mafic dike swarms ca 284 ma in the western qiangtang originated from the panjal plume activity that resulted in continental rifting and its separation from the northern indian continent the subsequent collision of the western qiangtang with the eastern qiangtang in the middle triassic was followed by slab breakoff that led to the exhumation of the qiangtang metamorphic rocks this collision may have caused the northward subduction initiation of the bangong nujiang ocean lithosphere beneath the western qiangtang collision related coeval igneous rocks occurring on both sides of the suture zone and the within plate basalt affinity of associated mafic lithologies suggest slab breakoff induced magmatism in a continent continent collision zone this zone may be the site of net continental crust growth as exemplified by the tibetan plateau c 2012 international association for gondwana research published by elsevier b v all rights reserved

monitoring a building using deconvolution interferometry i earthquake data analysis abstract for health monitoring of a building we need to separate the response of the building to an earthquake from the imprint of soil structure coupling and from wave propagation below the base of the building seismic interferometry based on deconvolution where we deconvolve the wave fields recorded at different floors is a technique to extract this building response and thus estimate velocity of the wave that propagates inside the building deconvolution interferometry also allows us to estimate the damping factor of the building compared with other interferometry techniques such as cross correlation and cross coherence interferometry deconvolution interferometry is the most suitable technique to monitor a building using earthquake records for deconvolution interferometry we deconvolve the wave fields recorded at all levels with the waves recorded at a target receiver inside the building this receiver behaves as a virtual source and we retrieve the response of a cut off building a short building that is cut off at the virtual source because the cut off building is independent from the structure below the virtual source the technique might be useful for estimating local structure and local damage we apply deconvolution interferometry to 17 earthquakes recorded during two weeks at a building in fukushima japan and estimate time lapse changes in velocity and normal mode frequency as shown in a previous study the change in velocity correlates with the change in normal mode frequency we compute the velocities from both traveling waves and the fundamental mode using coda wave interferometry these velocities have a negative correlation with the maximum acceleration of the observed earthquake records

u pb dating of granites in the neoproterozoic sergipano belt ne brazil implications for the timing and duration of continental collision and extrusion tectonics in the borborema province abstract the sergipano belt is the outcome of collision between the pernambuco alagoas massif and the sao francisco craton during neoproterozoic assembly of west gondwana field relationships and u pb geochronology of granites intruded in garnet micaschists of the macurure domain are used to constrain the main collisional event d 2 in the belt the granites are divided into two groups the pre collisional granites pre to early d 2 and the syn collisional granites syn to tardi d 2 the latter were emplaced as sheets along the s 2 axial plane foliation or they were collected at the hinge zones of f 2 folds a u pb shrimp zircon age of 628 12 ma was obtained for the pre collisional camara tonalite two u pb tims titanite ages were obtained for the syn collisional granites 584 10 ma for the angico granite and 571 9 ma for the pedra furada granite and these ages are close to the garnet whole rock sm nd isochron of 570 ma found for the peak of metamorphism in the sergipano belt the ages of the camara tonalite 628 ma and the pedra furada granite 571 ma mark respectively the maximum age for beginning of the d 2 event and minimum age for the end in the macurure domain using these ages the main neoproterozoic d 2 collisional event has been in operation in the sergipano belt for at least 57 million years correlation with coeval granitoids farther north in the borborema province indicate that while in the sergipano belt the syn d 2 granites ca 590 570 ma were emplaced under compression in the borborema province they emplaced under extensional conditions related to regional strike slip shear zones these contrasting emplacement settings for contemporaneous neoproterozoic granitoids are explained by a combination of continent continent collision and extrusion tectonics

the applicability of microbially induced calcite precipitation micp for internal erosion control in gravel sand mixtures seepage induced internal erosion in earth filled embankment dams has been attracting the attention of civil engineering researchers and practitioners for decades microbially induced carbonate prec

structural sequence and geochronology of the qomo ri accretionary complex central qiangtang tibet implications for the late triassic subduction of the paleo tethys ocean abstract the late paleozoic qomo ri accretionary complex qrac in the central qiangtang region of tibet lies at the southern margin of the longmu co shuanghu suture qrac is tectonically linked with the nierong and jitang metamorphic complexes in eastern tibet and the yunling and lancang complexes in western yunnan province sw china this metamorphic complex is mainly composed of late paleozoic passive continental marginal strata of the south qiangtang basin which was underthrust beneath north qiangtang in the late triassic at least three stages of deformation d1 d2 and d3 with two corresponding metamorphic events m1 and m2 were identified within the qrac d1 is characterized by a penetrative foliation s1 bearing a dextral shear and a corresponding m1 mineral assemblage of phengite garnet and quartz this deformation was interpreted to be the result of the northwestward oblique subduction of the paleo tethys ocean and dated at 211 219 ma by phengite 40ar 39ar ages d2 a subsequent compression deformation followed d1 immediately and exhibits flexural folds and pervasive axial crenulation in foliation s2 deformations from d1 to d2 indicate that an oblique oceanic subduction was immediately followed by a collision between the north and south qiangtang blocks along the longmu co shuanghu suture the d3 recorded by minor folds and divisional axial cleavage s3 is related to a giant arc structure with an extension of 50 km

tectonic evolution of the early mesozoic blueschist bearing qiangtang metamorphic belt central tibet this is the published version copyright 2003 american geophysical union all rights reserved

crustal thickening and uplift of the tibetan plateau inferred from receiver function analysis the india eurasia collision crustal thickening and northward convergence leading to uplift of the tibetan plateau have been topics of multidisciplinary studies here we employ the h k stacking technique and depth domain receiver function to constrain the crustal thickness and p and s wave velocity ratio as well as the upper mantle discontinuity our results identify the signature of slab break off and lower crustal delamination in southern tibet which might have induced the mantle upwelling and crustal melting the convergence of the indian plate inducing northward crustal flow might be a major factor that contributes to the uplift and crustal thickening of tibet we also evaluate the e w trending cumulative compression as another dominant factor that contributes to the increase in crustal thickness in the northern tibet 2015 elsevier ltd all rights reserved

geophysical monitoring of moisture induced landslides a review author s whiteley js chambers je uhlemann s wilkinson pb kendall jm abstract 2018 the authors geophysical monitoring of landslides can provide insights into spatial and temporal variations of subsurface properties associated with slope failure recent improvements in equipment data analysis and field operations have led to a significant increase in the use of such techniques in monitoring geophysical methods complement intrusive approaches which sample only a very small proportion of the subsurface and walk over or remotely sensed data which principally provide information only at the ground surface in particular recent studies show that advances in geophysical instrumentation data processing modeling and interpretation in the context of landslide monitoring are significantly improving the characterization of hillslope hydrology and soil and rock hydrology and strength and their dynamics over time this review appraises the state of the art of geophysical monitoring as applied to moisture induced landslides here we focus on technical and practical uses of time lapse methods in geophysics applied to monitoring moisture induced landslide the case studies identified in this review show that several geophysical techniques are currently used in the monitoring of subsurface landslide processes these geophysical contributions to monitoring and predicting the evolution of landslide processes are currently underrealized hence the further integration of multiple parametric and geotechnically coupled geophysical monitoring systems has considerable potential the complementary nature of certain methods to map the distribution of subsurface moisture and elastic moduli will greatly increase the predictive and monitoring capacity of early warning systems in moisture induced landslide settings

imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise 1 forecasting the location of an eruption is of primary importance for risk management in volcanic regions locating the underground structural changes associated with a potential eruption is also a key issue to better understand the dynamics at work in a volcano using recent results in wave physics we develop an imaging procedure that is based on the sensitivity of multiply scattered waves to weak changes in heterogeneous media this procedure allows to locate changes in both mechanical and scattering properties of the studied medium we study ambient seismic noise from 19 broadband stations at the active volcano piton de la fournaise on reunion island recorded from june to december 2010 during this period two volcanic eruptions occurred at two different locations we calculate the noise cross correlations and study two types of changes in the coda apparent velocity variations related to changes in the elastic properties of the medium and waveform decoherence associated with variations in the scattering and thus the geological structures we observe that the temporal variations of both of these parameters provide potential precursors of volcanic eruptions at piton de la fournaise the locations determined from the preeruptive and coeruptive changes in both parameters are in good agreement with the actual eruptive activities these data demonstrate that the coda of ambient noise correlations contains deterministic information on the locations of the eruptive processes in an active volcano our analysis offers an original and significant constraint for the localization of forthcoming volcanic eruptions

time lapse monitoring of internal erosion in earthen dams and levees using ambient seismic noise earthen dams and levees are prone to progressive failure through internal erosion of their structure internal erosion is often invisible to current methods of inspection until it manifests itself

underestimation of body waves and feasibility of surface wave reconstruction by seismic interferometry interferometry is an approach to extract the green s function between two receivers as if the virtual source is at one of the receiver locations the green s function which is the response to an impulsive source accounts for the wave propagation in the medium between the two receivers it is commonly thought that green s function estimates obtained from interferometry accurately represent the full green s function but this is not always the case in fact the accuracy of the retrieved green s function which consists of the surface and body waves is in practice restricted by the limited distribution of the sources of field fluctuations we demonstrate the importance of adequate source distribution for the accuracy of the retrieved green s function using examples from interferometry applications in these examples sources are controlled as in exploration seismology or uncontrolled as in crustal seismology

geochemical and nd pb isotopic characteristics of the tethyan asthenosphere implications for the origin of the indian ocean mantle domain abstract it is unclear why the pb nd and sr isotopic composition of the modern mid ocean ridge basalts morb from the indian ocean is different from that of the north atlantic and pacific oceans a possible explanation for this is that the indian morb type isotopic signature is a long lived regional feature of the mantle as evidently shown by the isotopic composition of the 350 ma morb like mian lue northern ophiolite which was formed in the same region presently occupied by the indian ocean however this hypothesis is in conflict with the lack of indian morb type isotopic signature in a number of 150 ma tethyan and indian ocean crusts to further constrain the origin of the indian morb type isotopic signature we analyze the geochemical and pb nd and sr isotopic composition of representative mafic rocks from four tethyan ophiolites ranging in age from 90 to 360 ma the sr isotopic composition of the samples is unreliable due to alteration but the age corrected nd and pb isotopic ratios and geochemical data indicate that these tethyan rocks were derived from a geochemically depleted asthenospheric source that had a clear indian morb type isotopic signature we therefore conclude that the bulk of the indian suboceanic mantle was most probably inherited from the tethyan asthenosphere a few regions in both the tethyan and indian oceans however are most probably underlain by pacific and north atlantic morb type mantle and vice versa because of the flow of the asthenosphere in response to tectonic plate reorganizations that lead to openings and closures of ocean basins the indian morb type isotopic signature of the western pacific marginal basin crusts could be due to either flow of the indian ocean mantle into the western pacific or to endogenous production of such an isotopic signature from delaminated east asian sublithospheric materials during closure of the tethys ocean

monitoring the stability of tailings dam walls with ambient seismic noise tailings dams are massive structures designed to contain the waste slurry remaining after processing ore at open pit and underground mines these structures fail far more regularly than normal water storage dams in recent years catastrophic tailings dam failures have occurred causing significant damage to the environment and even loss of life to mitigate these catastrophic events in the future there is an urgent need to develop cost effective methods to monitor the structural stability of these constructions over time the lack of current cost effective monitoring methods prompted us to investigate whether ambient seismic noise can be used to detect internal changes in a tailings dam wall during a period of heavy rainfall we recorded three weeks of continuous seismic data with 10 short period geophones at a tailings dam in tasmania australia seismic interferometry was used on ambient noise to create virtual seismic sources with these virtual source signals small changes in seismic velocity were

apatite dissolution into peraluminous haplogranitic melts an experimental study of solubilities and mechanisms apatite ap dissolution and solubility in the peraluminous haplogranite system were investigated in three sets of experiments at 750 c and 200 mpa ph2o as functions of ap grain size abundance melt ap ratio and melt asi alumina saturation index mol al2o3 na2o k2o cao between an asi of 1 1 1 metaluminous to mildly peraluminous the solubility of ap as measured by p2o5 in the melt is low 0 1 wt p2o5 which agrees with previous work in equilibrium runs with more strongly peraluminous compositions however ap solubility increases linearly with asi to p2o5 0 63 wt in melt at asi 1 3 and can be denned by a simple equation p2o5 3 4 3 1 asi r 0 833 which agrees within error with previous calculations reported in the literature in experiments where ap grains are sparce and widely separated i e simulating ap distribution in an ap bearing peraluminous protolith undergoing anatexis the dissolution of ap involves transient disequilibrium that promotes higher solubility of p2o5 up to nearly six times the equilibrium values adjacent to ap at a given bulk asi of melt and this increases the al si of melt in the ap dissolution aureole the approach to equilibrium between ap and melt is hastened by increasing the ap melt ratio within the local melt pool e g the capsule or by decreasing ap grain size for a similar melt ap ratio diffusivity calculations using inverse error function methods for the normal diffusion of p and ca yield dp 10 11 cm2 s and dca 10 10 cm2 s confirming prior results that diffusion of p away from ap surfaces is the rate limiting factor in ap dissolution these results combined with previous work at higher temperatures but on similar hydrous melts yield an activation energy e for p diffusion of 16 5 kcal mol and a frequency factor d0 of 1 4 10 3 cm2 s phosphorus diffusion through the melt is accompanied by uphill diffusion of al resulting in an increase of up to 2 wt al2o3 in melt near the ap within the ap dissolution aureole melt contains one additional al cation for every p cation i e al p 1 1 which is suggestive of an associated alpo4 complex the exchange reaction in melt is represented by alpsi 1 in which 2 to4 clusters are created in the place of 1 this exchange should be accompanied by discernable changes in melt properties e g density molar volume viscosity the results have applications to equilibrium and local disequilibrium effects during anatexis of apbearing metapelites and to the saturation limits of ap during crystallization of peraluminous magmas the dissolution of flux bearing minerals such as ap e g those containing p b or f may influence the stability and solubility of other trace element bearing minerals during anatexis of metapelites texture e g grain size and distribution and spacial relationship to other minerals plays an important role in reaction kinetics and at least temporarily in mineral solubilities the disequilibrium behavior of accessory minerals has critical consequences for ree modelling of granites

zircon u pb geochronology and hf isotopic constraints on petrogenesis of the gangdese batholith southern tibet abstract during the mesozoic cenozoic northward neotethyan subduction and subsequent india asia collision gave rise to the extensive transhimalayan magmatism that stretches from burma and western yunnan through southern tibet to the ladakh and kohistan complexes to understand the age distribution and petrogenesis of the gangdese batholith the largest intrusive exposure along the transhimalayan magmatic belt fifty granitic samples were selected for in situ zircon u pb and hf isotopic analyses the u pb data suggest four discrete stages of magmatic activity i e 205 152 109 80 65 41 and 33 13 ma respectively with the 65 41 ma stage being the most prominent the hf isotopic data indicate that the gangdese batholith is overwhelmed by positive e hf t values which are comparable to those of the kohistan ladakh batholiths in the west but differ markedly from those of the chayu burma batholiths in the east most of the gangdese granites show similar and young hf model ages 1000 300 ma indicating their derivation from juvenile crust however those formed in the 65 41 ma stage exhibit more heterogeneous hf isotopic ratios with negative e hf t values being observed in some granites younger than 50 ma suggesting the involvement of old indian continental crust in their petrogenesis this age may thus mark the onset of the india asia collision the newly established zircon u pb age and hf isotope database of the gangdese batholith can be used as a powerful tracer or fingerprint when studying the source to sink relation of the sediments eroded from the southern tibetan plateau

syn and post collisional granitoids in the central tianshan orogen geochemistry geochronology and implications for tectonic evolution abstract the eastern part of the central tianshan belt in china is characterized by abundant granitoids which are not only indicators of the interaction between crust and mantle but also can be used for tracking the tectonic evolutionary history of the orogen four granitic plutons muscovite granites mg biotite monzonitic granites bmg biotite granites bg and alkali granites ag have been recognized to have intruded in the mishigou area central tianshan belt the mg has pronounced a s type affinity which is strongly peraluminous with a high aluminum saturation index and displays positive rb th u and lree anomalies with a strong negative ba nb sr p ti and eu anomalies therefore the magma of the mg is considered to have been derived from melting of thickened continental crust which is composed mainly of the sediments eroded from a pre silurian continental island arc the u pb zircon age of 424 5 2 6 ma constrains the age of mg and crust thickening the bg and bmg granitoids display i type geochemical features and have affinities to subduction arcs both of them are characterized by calc alkaline peraluminous granites with a significant lree enrichment and a negative eu anomaly as well as a depletion in ba nb ta sr p and ti and an enrichment in rb th u nd zr and sm these characteristics indicate that they were derived from a mixed magma source between lower continental crust and the input of components derived from the mantle wedge above the subduction zone the la icpms zircon u pb ages of 411 4 7 ma and 402 3 4 ma represent the formation ages of the bg and bmg granitoids respectively which also constrain that the subduction of the south tianshan oceanic crust also occurred during early devonian time the ag shows a typical a type granite affinity with depletion of nb ta sr p ti and y it is interpreted that ag was formed in a within plate tectonic setting and related to continental up doming and rifting zones as a consequence of the extensional collapse after the collision of the tianshan orogen the u pb zircon age of 290 5 1 ma represents the formation age of the ag and the time of the extensional collapse and rifting

sources and evolution of arc magmas inferred from coupled o and hf isotope systematics of plutonic zircons from the cretaceous separation point suite new zealand abstract coupled o and hf isotopic compositions of zircons from early cretaceous 113 124 ma granitoids of the separation point suite sps new zealand obtained by cathodoluminescence imaging guided micro beam methods sims la icpms are used as a record of evolving magma compositions in a prominent mesozoic arc system eight representative sps samples from individual plutons in the nelson and fiordland regions yield magmatic zircons with initial hf isotope ratios expressed in e hf ranging from 4 to 11 nelson and 5 to 12 fiordland respectively initial hf isotope ratios of zircons are extremely heterogeneous within individual samples with the vast majority of values distinctly less radiogenic than depleted mantle at 120 ma e hf 16 o isotope ratios are likewise variable with 18 o zircon smow values of 2 8 nelson and 0 7 fiordland the within rock variability in both zircon hf and o isotope ratios is testimony to open system processes that operated during magma evolution and zircon crystallisation average 18 o zircon for cores and rims allow constraints to be placed on the o isotopic composition of magmas from which zircon precipitated 18 o magma 4 8 elevated 18 o magma 6 5 require involvement of 18 o enriched supracrustal material weathered continental crust or low t seawater hydrothermally altered oceanic crust while 18 o magma 18 o depleted crustal component whole rock sr isotope nb ta and nd pb systematics are inconsistent with 18 o depleted slab melts 18 o 0 6 as a source component for sps magmas instead low 18 o values suggest incorporation of high t meteoric hydrothermally altered country rocks similar to those of the largs terrane presently exposed in northern fiordland in diagrams of sio 2 versus inferred 18 o magma the most primitive sps samples from the nelson and fiordland regions plot close to the expected composition for primitive arc magmas more evolved granitoids however show strongly divergent trends of o isotope composition as a function of sio 2 suggestive of assimilation coupled to fractional crystallisation afc in contrasting crustal environments emplacement level contamination by local crust is supported by age distributions of inherited zircons which indicate a predominance of palaeozoic and mesozoic zircons in nelson and fiordland granitoids respectively

petrogenesis and geodynamic setting of granitoids at machangqing cu mo au deposit western yangtze craton southwestern china constraints from zircon u pb and molybdenite re os geochronology lu hf isotopes and geochemistry the machangqing cu mo au deposit is located in the central part of the jinshajiang red river belt in the sanjiang orogen which lies across the qiangtang terrane and western yangtze craton sou

evidence for early 44 ma himalayan crustal thickening tethyan himalaya southeastern tibet abstract comprehensive understanding of himalayan orogenesis is limited in part by a poor knowledge of the eohimalayan episode a phase of tectonic activity predating the better understood neohimalayan crustal thickening associated with coaxial deformation along the main central thrust the cambo ordovician to tertiary metasedimentary sequences outcropping within the tethyan himalaya are the structurally highest units of the himalayan fold and thrust belt they and are inferred to have been the first to have accreted to asia a compilation of data from transects along the length of the main himalayan arc shows that the tethyan sequences have experienced at least five deformation events although the timing of these episodes is poorly constrained emplacement of a series of undeformed granitoid bodies following the second of these events which accounts for the majority of crustal thickening in the tethyan himalayan units is constrained by u pb zircon dating to be older than 44 1 1 2 ma thus significant crustal thickening had occurred along the length of the proto himalayan arc by the mid eocene or within 10 to 20 myr of the initiation of himalayan orogenesis

virtual source applications to imaging and reservoir monitoring the virtual source method is a breakthrough that allows us to image and monitor the subsurface in cases where surface seismic or vsp fail to deliver in settings where the overburden is complex or changing traditional time lapse signals are weak or nonrepeatable leading to ineffective seismic input to reservoir modeling and little of value generated by repeated seismic surveys on the other hand the virtual source method allows us to image under complex overburden yields repeatable data for reservoir monitoring enables shear seismic and may help us look ahead as we drill

zircon u pb and hf isotopic constraints from eastern transhimalayan batholiths on the precollisional magmatic and tectonic evolution in southern tibet abstract before the indian collision with asia northward subduction of the neo tethyan oceanic lithosphere produced an andean type convergent margin in south asia characterized by arc magmatism starting from the early jurassic and lasting until the eocene the magmatic arc is now represented by widespread intrusive bodies or the so called transhimalayan batholiths in the lhasa terrane of southern tibet that have been divided into two main magmatic suites i e the northern plutonic belt and the southern gangdese batholith their temporal distribution concerning how exactly the magmatic suites correlate eastwards and then southeastwards around the eastern himalayan syntaxis however remains poorly constrained here we report the first combined zircon u pb and hf isotopic study of the transhimalayan batholiths from the eastern part of the lhasa terrane 95 97 5 e and 28 5 30 n se tibet zircon u pb dating results of 24 granitoids indicate that the rocks were emplaced principally in the early cretaceous 133 110 ma and subordinately in the paleocene 66 57 ma long after an older granite intrusion in the earliest jurassic 198 ma the zircon ehf t values range from 5 to 20 yielding hf crustal model ages tdmc between 0 8 and 2 4 ga that peak at 1 7 ga suggesting a major episode of crustal growth in the proterozoic and a predominantly or even exclusively crustal source for the granitoid petrogenesis these zircon u pb and hf isotopic constraints together with whole rock geochemical characteristics allow us to correlate them to s type granitoids in the northern plutonic belt rather than to the i type gangdese batholith from the central part of the southern lhasa terrane in contrast to the gangdese magmatism that formed with a significant juvenile mantle input related to the neo tethyan subduction these s type granitoids show geochemical similarities to the north american cordilleran interior batholiths that did not form directly from a subduction setting thus we attribute the petrogenesis of the widespread early cretaceous granitoids in the northern belt and eastern himalayan batholiths to a postcollisional regime due to the late jurassic early cretaceous continental collision between the lhasa and qiangtang terranes under this framework the s type magmatism was generated in response to collision induced crustal thickening which may have capabilities of causing crustal anatexis by itself in the region however continued interplay with the neo tethyan subduction zone processes such as back arc extension could also have played a crucial and long lasting role in the magma generation

retrieval of local surface wave velocities from traffic noise an example from the la barge basin wyoming abstract in regions where active source seismic exploration is constrained by limitations of energy penetration and recovery cost and logistical concerns or regulatory restrictions analysis of natural source seismic data may provide an alternative in this study we investigate the feasibility of using locally generated seismic noise in the 2 6 hz band to obtain a subsurface model via interferometric analysis we apply this technique to three component data recorded during the la barge passive seismic experiment a local deployment in south western wyoming that recorded continuous seismic data between november 2008 and june 2009 we find traffic noise from a nearby state road to be the dominant source of surface waves recorded on the array and observe surface wave arrivals associated with this source up to distances of 5 kms the orientation of the road with respect to the deployment ensures a large number of stationary points leading to clear observations on both in line and cross line virtual source receiver pairs this results in a large number of usable interferograms which in turn enables the application of standard active source processing methods like signal processing common offset stacking and traveltime inversion we investigate the dependency of the interferograms on the amount of data on a range of processing parameters and on the choice of the interferometry algorithm the obtained interferograms exhibit a high signal to noise ratio on all three components rotation of the horizontal components to the radial transverse direction facilitates the separation of rayleigh and love waves though the narrow frequency spectrum of the surface waves prevents the inversion for depth dependent shear wave velocities we are able to map the arrival times of the surface waves to laterally varying group and phase velocities for both rayleigh and love waves our results correlate well with the known geological structure we outline a scheme for obtaining localized surface wave velocities from local noise sources and show how the processing of passive data benefits from a combination with well established exploration seismology methods we highlight the differences with interferometry applied to crustal scale data and conclude with recommendations for similar deployments

extracting earth s elastic wave response from noise measurements recent research has shown that noise can be turned from a nuisance into a useful seismic source in seismology and other fields in science and engineering the estimation of the system response from noise measurements has proven to be a powerful technique to convey the essence of the method we first treat the simplest case of a homogeneous medium to show how noise measurements can be used to estimate waves that propagate between sensors we provide an overview of physics research dating back more than 100 years showing that random field fluctuations contain information about the system response this principle has found extensive use in surface wave seismology but can also be applied to the estimation of body waves because noise provides continuous illumination of the subsurface the extracted response is ideally suited for time lapse monitoring we present examples of time lapse monitoring as applied to the softening of soil after the 2011 tohoku oki earthquake the detection of a precursor to a landslide and temporal changes in the lunar soil

mid eocene high sr y granites in the northern himalayan gneiss domes melting thickened lower continental crust abstract within the himalayan collisional belt granotoids occur along two sub parallel belts the northern himalayan gneiss domes nhgd and the high himalayan crystalline series hhcs in the yardoi area of nhgd two mica granite a new type granite occurs in the core of the yardoi gneiss dome ygd dala and quedang from north to south and extends at least 50 km long these granites have similar mineral composition elemental and radiogenic isotope geochemistry and age of formation shrimp zircon u pb dating indicates that the yardoi and the quedang two mica granites formed at 42 6 1 1 ma and 42 8 0 6 ma respectively similar to the dala pluton these two mica granites have 1 high sio2 68 wt al2o3 15 wt and a cnk 1 0 2 relatively high sr and lree but low y 40 and up to 250 and la yb 30 4 very weak or no eu anomalies and 5 as compared with those in the himalayan leucogranites low initial sr 87sr 86sr i

generalised receiver functions and seismic interferometry abstract classical seismological receiver functions are correlational or deconvolutional combinations of vertical and horizontal component seismometer recordings of earthquake waves that focus information on near receiver subsurface earth structure and properties we show that seismic interferometry can be thought of as a generalisation of receiver functions analysis to cases where recordings at pairs of receivers are considered simultaneously and where either the same or different component recordings are combined further seismic interferometry uses any of deconvolution convolution and cross correlation and energy from either impulsive or random noise sources we show both how receiver functions can logically be extended to a new convolutional form and that the now little used correlational form of receiver functions contains more intuitive information than previously realised seismic interferometry has provided other extraordinary extensions to seismologists arsenal passive noise recordings can be converted into seismograms from virtual imagined earthquakes that in turn can be used to image the real earth active sources e g earthquakes or man made sources can be redatumed into new virtual sources elsewhere or can be converted into virtual sensors seismometers that record seismograms from other real earthquakes man made sources or noise sources that occur either in the future or in the past and the ability to construct virtual sources and sensors at desired times and locations rather than having to wait for earthquake sources that occur at uncontrollable locations promises more repeatable monitoring of changes in earth subsurface properties over time indeed so called coda wave interferometry offers unprecedented accuracy in detecting such changes finally existing theoretical extensions to other regimes such as electromagnetic electrokinetic and diffusive energy propagation may lead to future revolutions in other domains of science

zircon u pb hf isotopes and whole rock geochemistry of gneissic granites from the jitang complex in leiwuqi area eastern tibet china record of the closure of the paleo tethys ocean abstract previous investigations have indicated that the changning menglian cmsz and longmu co shuanghu lssz suture zones represent the paleo tethys ocean of northern tibet and western yunnan of china respectively however our understanding of the paleo tethys suture zone in eastern tibet seems to be incomplete the north lancangjiang suture zone nlsz has been hypothesized to mark the paleo tethys ocean in eastern tibet the present study reports new zircon u pb ages and hf isotope data and whole rock major and trace element data from the gneissic granites from the jitang complex in the leiwuqi area of the nlsz in order to verify this hypothesis six samples of gneissic granites yielded weighted mean 206 pb 238 u ages of 249 237 ma the geochemical data show that the gneissic granites are characterized by high sio 2 70 79 77 75 wt k 2 o 2 00 6 13 wt low a cnk values hf t values from 2 7 to 2 5 and t c dm model ages 1447 1009 ma indicate that they were generated by the partial melting of the meso proterozoic juvenile crust these gneissic granites were interpreted to have formed in the post collisional tectonic setting related to the closure of the paleo tethys ocean by combining previously published and the new data we propose that the nlsz connects the lssz and cmsz in the tibetan plateau and marks a paleo tethys ocean basin in eastern tibet

seismic characterization of a rapidly rising jokulhlaup cycle at the a p olsen ice cap ne greenland rapidly rising jokulhlaups or glacial outburst floods are a phenomenon with a high potential for damage the initiation and propagation processes of a rapidly rising jokulhlaup are still not fully understood seismic monitoring can contribute to an improved process understanding but comprehensive long term seismic monitoring campaigns capturing the dynamics of a rapidly rising jokulhlaup have not been reported so far to fill this gap we installed a seismic network at the marginal ice dammed lake of the a p olsen ice cap apo in ne greenland episodic outbursts from the lake cause flood waves in the zackenberg river characterized by a rapid discharge increase within a few hours our 6 months long seismic dataset comprises the whole fill and drain cycle of the ice dammed lake in 2012 and includes one of the most destructive floods recorded so far for the zackenberg river seismic event detection and localization reveals abundant surface crevassing and correlates with changes of the river discharge seismic interferometry suggests the existence of a thin basal sedimentary layer we show that the ballistic part of the first surface waves can potentially be used to infer medium changes in both the ice body and the basal layer interpretation of time lapse interferograms is challenged by a varying ambient noise source distribution

u pb zircon geochemical and sr nd hf isotopic constraints on age and origin of jurassic i and a type granites from central guangdong se china a major igneous event in response to foundering of a subducted flat slab abstract the mesozoic geology of se china is characterized by widespread jurassic to cretaceous igneous rocks consisting predominantly of granites and rhyolites and subordinate mafic lithologies however the tectonic regime responsible for the inland jurassic granites remains controversial we report here u pb zircon ages geochemical and sr nd hf isotopic data for the nankunshan alkaline granite and the fogang granitic batholith in central guangdong mineralogical and geochemical features suggest that the fogang and nankunshan rocks are i and aluminous a type granites respectively shrimp u pb zircon analyses yield consistent ages ranging from 159 3 ma to 165 2 ma for four samples from the fogang batholith and an age of 158 5 ma for the nankunshan granite the fogang granites having i sr 0 7098 0 7136 e nd t 4 3 to 12 2 and e hf t 11 5 to 3 1 for the magmatic zircons were derived from paleoproterozoic mafic intermediate igneous protolith with minor addition of mantle derived magmas the nankunshan rocks have relatively lower i sr 0 706 0 708 higher e nd t 0 3 to 2 4 and e hf t 5 7 to 1 1 for the magmatic zircons and some oib like trace element ratios they were likely generated through extensive fractional crystallization of mantle derived alkaline parental magma associated with crustal assimilation these 160 ma i and a type granites in central guangdong were emplaced coeval with the widespread 165 155 ma i and a type granites and syenites following the initiation of intraplate basaltic and or bimodal igneous magmatism at 180 170 ma in the adjacent regions we interpret these jurassic igneous rocks as anorogenic magmatism formed during a major igneous event in response to foundering of an early mesozoic subducted flat slab beneath se china continent

geochemical investigation of early cretaceous igneous rocks along an east west traverse throughout the central lhasa terrane tibet article i nfo bulk rock major and trace element sr nd isotope zircon u pb and hf isotope data are reported for early cretaceous igneous rocks sampled along an east west traverse through the central lhasa subterrane e80 00 e89 in southern tibet these results offer new insights into the pre cenozoic geology and tectonomagmatic evolution of the lhasa terrane and provide boundary conditions for the origin and evolution of the tibetan plateau our new data together with data from the literature indicate that the early cretaceous magmatism in the central lhasa subterrane lasted for a long period 143 102 ma with a magmatic flare up at 110 ma the latter is accompanied by mafic magmatism in this terrane the silicic rocks are metaluminous to peraluminous and enrichedinrb th and u and depleted inba nb ta sr p and ti withvarying initial 87

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method