surface wave tomography of the western united states from ambient seismic noise rayleigh and love wave phase velocity maps summary we present the results of rayleigh wave and love wave phase velocity tomography in the western united states using ambient seismic noise observed at over 250 broad band stations from the earthscope usarray transportable array and regional networks all available threecomponent time series for the 12 month span between 2005 november 1 and 2006 october 31 have been cross correlated to yield estimated empirical rayleigh and love wave green s functions the love wave signals were observed with higher average signal to noise ratio snr than rayleigh wave signals and hence cannot be fully explained by the scattering of rayleigh waves phase velocity dispersion curves for both rayleigh and love waves between 5 and 40 speriod were measured for each interstation path by applying frequency time analysis the average uncertainty and systematic bias of the measurements are estimated using a method based on analysing thousands of nearly linearly aligned station triplets we find that empirical green s functions can be estimated accurately from the negative time derivative of the symmetric component ambient noise cross correlation without explicit knowledge of the source distribution the average traveltime uncertainty is less than 1 s at periods shorter than 24 s we present rayleigh and love wave phase speed maps at periods of 8 12 16 and 20 s the maps show clear correlations with major geological structures and qualitative agreement with previous results based on rayleigh wave group speeds

fractal density modeling of crustal heterogeneity from the ktb deep hole fractal or multifractal concepts have significantly enlightened our understanding of crustal heterogeneity much attention has focused on 1 f scaling natures of physico chemical heterogeneity of earth crust from fractal increment perspective in this study fractal density model from fractal clustering point of view is used to characterize the scaling behaviors of heterogeneous sources recorded at german ktb main hole and of special contribution is the local and global multifractal analysis revisited by using haar wavelet transform hwt fractal density modeling of mass accumulation generalizes the unit of rock density from integer e g g cm3 to real numbers e g g cm so that crustal heterogeneities with respect to source accumulation are quantified by singularity strength of fractal density in dimensional space from that perspective we found that the bulk densities of metamorphic rocks exhibit fractal properties but have a weak multifractality decreasing with the depth the multiscaling natures of chemical logs also have been evidenced and the observed distinct fractal laws for mineral contents are related to their different geochemical behaviors within complex lithological context accordingly scaling distributions of mineral contents have been recognized as a main contributor to the multifractal natures of heterogeneous density for low porosity crystalline rocks this finally allows us to use de wijs cascade process to explain the mechanism of fractal density in practice the proposed local singularity analysis based on hwt is suggested as an attractive high pass filtering to amplify weak signatures of well logs as well as to delineate micro lithological changes

heterogeneity spectrum and scale anisotropy in the upper crust revealed by the german continental deep drilling ktb holes crustal heterogeneities and their statistical characteristics bear important information about the dynamic processes and evolution of the crust the velocity well log data from the german continental deep drilling project ktb offer a rare opportunity to measure directly the properties of crustal heterogeneities in this study we first estimated the power spectrum of crustal heterogeneities from the p velocity well logs of the two holes for the first time a power law spectrum of crustal heterogeneities was directly observed in the spatial wavelength range from a few meters to a few kilometers the slope of the vertical 1d power spectrum of the random velocity perturbations is about 1 1 corresponding to a flicker noise random medium the scale anisotropy ratio aspect ratio and the horizontal spectral slope of crustal heterogeneities were also estimated by cross correlation analysis between these two holes to be about 1 8 and 2 0 respectively

unpairing metamorphic belts p t paths and a tectonic model for the ryoke belt southwest japan southwest japan is divided into outer and inner zones by the median tectonic line mtl a major transcurrent fault the outer zone is composed of the sambagawa high pressure intermediate or high p t type metamorphism chichibu and shimanto belts in the inner zone the ryoke belt andalusite sillimanite or low p t type metamorphism was developed mainly within a jurassic accretionary complex this spatial relationship between high p t type and low p t type metamorphic belts led miyashiro to the idea that metamorphic belts were developed as paired systems textural relationships and petrogenetically significant mineral assemblages in pelites from the ryoke belt imply peak p t conditions of 5 kbar and up to 850 c in migmatitic garnet cordierite rocks from the highest grade metamorphic zone it is likely that the thermal anomaly responsible for metamorphism of the ryoke belt was related to a segment of the farallon izanagi ridge as it subducted under the eastern margin of the asian continent during the cretaceous the sequence of mineral assemblages developed in pelites implies a metamorphic field gradient with shallow dp dt slope inferred to have been generated by a nested set of hairpin like clockwise p t paths these p t paths are characterized by limited prograde thickening minor decompression at peak t and near isobaric cooling features that may be typical of p t paths in low p t type metamorphic belts caused by ridge subduction a ridge subduction model for the ryoke belt implies that juxtaposition of the high p t metamorphic rocks of the sambagawa belt against it was a result of terrane amalgamation belt parallel ductile stretching recorded as syn metamorphic predominantly constrictional strain in both ryoke and sambagawa belt rocks and substantial sinistral displacement on the mtl are consistent with left lateral oblique convergence diachroneity in fast cooling of the ryoke belt is implied by extant thermochronological data and is inferred to relate to progressive sw to ne docking of the sambagawa belt thus an alternative interpretation of paired metamorphic belts in japan is that they represent laterally contemporaneous terranes rather than outboard and inboard components of a trench arc paired system amalgamation of laterally contemporaneous terranes during large translations of forearcs along continental margins may explain other examples of paired metamorphic belts in the geological record

multiscaling nature of sonic velocities and lithology in the upper crystalline crust evidence from the ktb main borehole the observed scaling of sonic logs is generally described using a monofractal model fractional brownian motion with hurst exponent typically between 0 1 and 0 2 or fractional levy motion even though such a description recognizes the existence of the self similarity of the logs it offers only a limited account of the actual symmetry as it misses the displayed heterogeneous fractality intermittency of the velocity increments is here observed and calls for the use of a multifractal description we quantify such a multifractality in the case of the p wave sonic log recorded at the ktb main borehole we also show that the associated lithology inferred from the gamma log has a multifractal distribution as well though characterized by a stronger intermittency it can be expected that the multifractality of the sonic log is partially induced by the lithology though the observed discrepancy in the degree of intermittency between the two logs indicates that the scaling symmetry of the seismic velocity is probably due to many different contributions such statistics for both sonic and gamma logs have important implications on our understanding of wave propagation and rock strength and permeability in the crystalline crust as they show the crust to be more heterogeneous than is usually modeled

deep structure of the crust along the fennoscandia sarmatia junction zone central belarus results of a geophysical geological integration abstract the eurobridge 96 seismic refraction and wide angle reflection profile in belarus crosses the 2 0 1 9 ga palaeoproterozoic central belarus belt cb subdivided by ne trending minsk fault into the northwestern nwcb and southeastern secb sub terranes differing in their styles of tectonothermal evolution the first interpretation of the eurobridge 96 profile however did not indicate any difference between the nwcb and secb and revealed a high velocity zone beneath the secb with a p wave velocity of 6 6 km s at a depth of 6 km which does not correlate with any pronounced positive bouguer anomaly we present a detailed analysis of the seismic and gravity data obtained along the eurobridge 96 profile complemented with petrological and petrophysical observations on the main rock types of the cb our integrated interpretation shows that the dip orientation of the main reflectors and the p wave velocity and density are different in the nwcb and secb the minsk fault zone is distinguished as an area of relatively high velocities 6 2 km s in the upper crust increased reflectivity in the middle crust se of the minsk fault may be explained by a laminated structure composed of alternating tectonically deformed amphibolite facies and granulite facies rocks that produce a certain seismic anisotropy this seismic anisotropy is proposed as an alternative explanation for the high p wave velocity in the middle crust beneath the secb that does not result in any corresponding positive gravity anomaly the laminated structure beneath the secb might be formed during the uplift of the nwcb and juxtaposition of the nwcb and secb

electron microprobe and la icp ms study of monazite hydrothermal alteration implications for u th pb geochronology and nuclear ceramics this paper presents new data that quantify the response of magmatic monazite to three main types of hydrothermal alteration namely sericitization chloritization and greisenization the samples were taken from three paleozoic granites the st nectaire granite massif central france the carnmenellis granite cornwall england and the skiddaw granite lake district england fluid inclusion thermometry and hydrothermal parageneses indicate that alteration took place at temperatures ranging from 260 to 340 c and salinities from 3 to 18 wt nacl equivalent possible monazite alteration mechanisms found in the course of this study using backscattered scanning electron microscopy bse sem electron microprobe laser raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry la icp ms include cationic substitutions monoclinic to hexagonal structure transition accompanied by chemical exchanges selective th removal dissolution reprecipitation and dissolution with replacement by a different mineral these results show that despite the compositional and crystallographic simplicity of monazite it exhibits varied chemical responses to different mineral fluid interactions elemental and isotopic measurements by la icp ms for the unaltered monazites yield statistically significant 232th 208pb and 238u 206pb magmatic crystallization ages in some cases it was possible to give a reasonable estimate of the age of mineral fluid interaction using the altered parts of the monazites or newly precipitated crystals for other minerals 232th 208pb and 238u 206pb systematics were strongly disturbed by variable inputs and or depletions of u th and pb the data suggest that monazite like nuclear waste forms would be good hosts for tetravalent actinides but may release the lanthanides and actinides with lower and higher valencies especially if the fluids are oxidizing or tend to dissolve monazite

physics and seismic modeling for monitoring co2 storage we present a new petro elastical and numerical simulation methodology to compute synthetic seismograms for reservoirs subject to co2 sequestration the petro elastical equations model the seismic properties of reservoir rocks saturated with co2 methane oil and brine the gas properties are obtained from the van der waals equation and we take into account the absorption of gas by oil and brine as a function of the in situ pore pressure and temperature the dry rock bulk and shear moduli can be obtained either by calibration from real data or by using rock physics models based on the hertz mindlin and hashin shtrikman theories mesoscopic attenuation due to fluids effects is quantified by using white s model of patchy saturation and the wet rock velocities are calculated with gassmann equations by using an effective fluid modulus to describe the velocities predicted by white s model the simulations are performed with a poro viscoelastic modeling code based on biot s theory where viscoelasticity is described by generalizing the solid fluid coupling modulus to a relaxation function using the pseudo spectral method which allows general material variability a complete and accurate characterization of the reservoir can be obtained a simulation that considers the utsira sand of the north sea illustrates the methodology

disturbance versus preservation of u th pb ages in monazite during fluid rock interaction textural chemical and isotopic in situ study in microgranites velay dome france monazite is extensively used to date crustal processes and is usually considered to be resistant to diffusive pb loss nevertheless fluid assisted recrystallisation is known to be capable of resetting the monazite chronometer this study focuses on chemical and isotopic disturbances in monazite grains from two microgranite intrusions in the french central massif charron and montasset petrologic data and oxygen isotopes suggest that both intrusions have interacted with alkali bearing hydrothermal magmatic fluids in the charron intrusion regardless of their textural location monazite grains are sub euhedral and cover a large domain of compositions u pb chronometers yield a lower intercept age of 297 4 ma an inherited component at 320 ma is responsible for the scattering of the u th pb ages the montasset intrusion was later affected by an additional f rich crustal fluid with crystallisation of ca ree fluorocarbonates fluorite calcite and chloritisation pristine monazite is chemically homogeneous and displays 208pb 232th and 206pb 238u concordant ages at 307 2 ma by contrast groundmass monazite shows dissolution recrystallisation features associated with apatite and thorite precipitation th silicate and strong chemical reequilibration 208pb 232th ages are disturbed and range between 270 and 690 ma showing that the th pb ratio is highly fractionated during the interaction with fluids apparent u pb ages are older due to common pb incorporation yielding a lower intercept age at 312 10 ma the age of the pristine monazite these results show that f rich fluids are responsible for th mobility and incorporation of excess pb which thus strongly disturbed the u th pb chronometers in the monazite

compositional and metamorphic controls on velocity and reflectivity in the continental crust an example from the grenville province of eastern quebec we present velocity and density data for a suite of gabbros and metagabbros over a range of metamorphic grades from subgreenschist to the eclogite facies most of these rocks have a mesocratic protolith with overlapping bulk chemistry ranges providing an opportunity to investigate the systematics of mineralogy and physical properties across a wide range of metamorphic grades with minimal compositional variation in addition more mafic gabbros in the eclogite facies were also investigated in order to take into account variations in the extent of transformation of gabbro to eclogite controlled by bulk chemistry the physical properties data are used as the basis for a first order crustal model composed of granitic anorthositic and gabbroic components the objective of constructing the crustal model is to evaluate the relative contribution of compositional variation and metamorphism to the velocity density and reflectivity structure of the continental crust the model suggests that in the upper crust if fracture porosity is neglected composition dominates the velocity and density structure while in the middle and lower crust composition and metamorphism play equally important roles simulations designed to predict potential reflection coefficient size distributions for the various bulk chemistries and mineralogies in the crustal model indicate step increases in the potential for large reflection coefficients that are dominantly controlled by metamorphic grade step increases in reflectivity are predicted between the lower and upper amphibolite facies and between incompletely and completely eclogitized metagabbros in the eclogite facies we also consider several alternative mixing models which account for the effects of one of the three lithologic components occurring as isolated bodies rather than perfectly mixed with the other two components these models indicate a reduction of the potential for large reflection coefficients by as much as 50 emphasizing the importance of the degree of mixing for crustal reflectivity

parsimonious surface wave interferometry we thank the sponsors for supporting the consortium of subsurface imaging and fluid modeling csim we also thank kaust for providing funding by the crg grant ocrf 2014 crg3 2300 for computer time this research used the resources of the it research computing group and the supercomputing laboratory at kaust

multifractal characteristics of natural fracture apertures using information acquired from microscanner logs in horizontal boreholes fracture apertures are shown to be characterized by multifractal scaling a representative f spectrum can be modeled using a multiplicative cascade based on a two scale cantor set the resulting cascade can be used to simulate fracture aperture distributions at any scale when compared to well data the simulations show good agreement with aperture sizes and reproduce the clustering commonly recognized in fracture networks

discrimination between pressure and fluid saturation changes from time lapse seismic data explicit expressions for computing saturation and pressure related changes from time lapse seismic data have been derived and tested on a real time lapse seismic data set necessary input is near and far offset stacks for the baseline seismic survey and the repeat survey the method has been tested successfully in a segment where pressure measurements in two wells verify a pore pressure increase of 5 to 6 mpa between the baseline survey and the monitor survey estimated pressure changes using the proposed relationships fit very well with observations between the baseline and monitor seismic surveys 27 of the estimated recoverable hydrocarbon reserves were produced from this segment the estimated saturation changes also agree well with observed changes apart from some areas in the water zone that are mapped as being exposed to saturation changes which is unlikely saturation changes in other segments close to the original oil water contact and the top reservoir interface are also estimated and conf

triggering of seismicity at short timescales following californian earthquakes 1 a method for measuring seismicity rate changes caused by the occurrence of major earthquakes in the surrounding crust is proposed it is based on a nonstationary poisson modeling of earthquake activity an estimate of the seismicity rate change and a probability measure of seismicity triggering following a large shock are derived and the removal of the influence of independent aftershock sequences of other nearby previous earthquakes is attempted without using more traditional declustering techniques the seismicity rate change estimator is corrected for its natural bias in favor of positive changes at short timescales that has so far strongly hindered measures of seismicity quiescences three californian earthquakes are examined using this method the 1989 m7 1 loma prieta the 1992 m7 3 landers and the 1994 m6 7 northridge earthquakes positive triggering is very commonly observed as expected but quiescence is however more seldomly obtained for timescales up to 100 days after the main shock this relative absence of quiescence as compared to typical predictions of coulomb modeling for example is also independently observed through direct correlation analyses of californian seismicity the possibility that the stresses caused by the main shock are spatially highly variable may explain these observations

nature and origin of upper crustal seismic velocity fluctuations and associated scaling properties combined stochastic analyses of ktb velocity and lithology logs the main borehole of the german continental deep drilling program ktb extends over 9000 m into a crystalline upper crust consisting primarily of interlayered gneiss and metabasite we present a joint analysis of the velocity and lithology logs in an effort to extract the lithology component of the velocity log covariance analysis of lithology log approximated as a binary series indicates that it may originate from the superposition of two brownian stochastic processes fractal dimension 1 5 with characteristic scales of 2800 m and 150 m respectively covariance analysis of the velocity fluctuations provides evidence for the superposition of four stochastic process with distinct characteristic scales the largest two scales are identical to those derived from the lithology confirming that these scales of velocity heterogeneity are caused by lithology variations the third characteristic scale 20 m also a brownian process is probably related to fracturing based on correlation with the resistivity log the superposition of these three brownian processes closely mimics the commonly observed 1 k decay fractal dimension 2 0 of the velocity power spectrum the smallest scale process characteristic scale 1 7 m requires a low fractal dimension 1 0 and accounts for 60 of the total rms velocity variation a comparison of successive logs from 6900 7140 m depth indicates that such variations are not repeatable and thus probably do not represent true velocity variations in the crust the results of this study resolve disparity between the differing published estimates of seismic heterogeneity based on the ktb sonic logs and bridge the gap between estimates of crustal heterogeneity from geologic maps and borehole logs

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

time lapse monitoring of fluid induced geophysical property variations within an unstable earthwork using p wave refraction abstracta significant portion of the uk s transportation system relies on a network of geotechnical earthworks cuttings and embankments that were constructed more than 100 years ago whose stability is affected by the change in precipitation patterns experienced over the past few decades the vulnerability of these structures requires a reliable cost and time effective monitoring of their geomechanical condition we have assessed the potential application of p wave refraction for tracking the seasonal variations of seismic properties within an aged clay filled railway embankment located in southwest england seismic data were acquired repeatedly along the crest of the earthwork at regular time intervals for a total period of 16 months p wave first break times were picked from all available recorded traces to obtain a set of hodocrones referenced to the same spatial locations for various dates along the surveyed period of time traveltimes extracted from each acquisition were then compared to trac

progressive sequence of reactions of the ryoke metamorphism in the yanai district southwest japan the formation of cordierite the compositions of biotite and muscovite were examined in terms of the paragenesis and the metamorphic grade in low to medium grade pelitic rocks of the ryoke metamorphism in the yanai district southwest japan the biotite and muscovite that coexist with k feldspar have a higher k component in an a kf diagram than those in rocks lacking k feldspar this fact reflects an increase in the k2o content in muscovite but in biotite it reflects an increase of not only the k2o content but also of the octahedral vacancy at higher metamorphic grade beyond the cordierite isograd where cordierite coexists with neither chlorite nor k feldspar the biotite shows an increase in illite k aliv xii 1 si 1 and tschermak components alvi aliv r 1 si 1 where xii and r denote the interlayer vacancy and fe mg mn respectively a reaction to define the cordierite isograd is proposed by treating this chemical change as being responsible for the first appearance of cordierite i e k al poor biotite phengitic muscovite k al rich biotite cordierite quartz water by treating this as a key reaction in medium grade metamorphism a set of reaction in a progressive metamorphism is established for the ryoke metamorphism a typical low pressure type metamorphism some textures in one of the high grade areas the k feldspar cordierite zone suggest that a further two prograde reactions have taken place i e andalusite biotite quartz cordierite k feldspar water and andalusite sillimanite quartz cordierite k feldspar water this implies that this zone probably has a p t path involving isobaric heating

fractional levy motion as a model for spatial variability in sedimentary rock a new approach to the modeling of spatial variability in sedimentary formations is introduced this approach avoids the assumption of gaussian behavior specifically borehole measurements of physical properties of sedimentary rock from contrasting geological settings are shown to have a statistical character consistent with fractional levy motion successive increments in the measurement sequences are accurately modeled as having levy stable distributions the levy parameters are similar for boreholes in the same sedimentary basin but vary from basin to basin thinly bedded formations have smaller values for the levy index suggesting that the levy index may be a useful measure of heterogeneity the measurement sequences are also statistically self similar and have long range negative dependence among the increments antipersistence in addition to reproducing the statistical properties of well logs the new model also mimics the most striking visual features of sedimentary formations

monazite xenotime miscibility gap thermometry i an empirical calibration rare earth element ree and yttrium concentrations of coexisting monazite and xenotime were determined from a suite of seven metapelites from the variscan fold belt in ne bavaria germany the metapelites include a continuous prograde mainly low p 3 5 kbar metamorphic profile from greenschist c 400 c to lower granulite facies conditions c 700 c the lree la sm are incorporated preferentially in monoclinic monazite reo9 polyhedron whereas the hree plus y are concentrated in tetragonal xenotime reo8 polyhedron the major element concentrations of both phases in all rocks are very similar and do not depend on metamorphic grade monazite consists mainly of la ce and nd la0 20 0 23 ce0 41 0 45 nd0 15 0 18 po4 all other elements are below 6 mol likewise xenotime consists mainly of ypo4 with some dy and gd solid solutions y0 76 0 80 dy0 05 0 07 gd0 04 0 06 in contrast the minor hree concentrations in monazite increase strongly with increasing metamorphic grade y dy and gd increase by a factor of 3 5 from greenschist to granulite facies rocks monazite crystals often show zonation with cores low in hree and rims high in hree that is interpreted as growth zonation attained during prograde metamorphism similarly sm and nd in xenotimes increase by a factor of 3 4 with increasing metamorphic grade prograde zonation in single crystals of xenotime was not observed the xhree y in monazite and xlree in xenotime of the seven rocks define two limbs along the strongly asymmetric miscibility gap from c 400 c to 700 c the empirical calibration of the monazite miscibility gap limb coexisting with xenotime is appropriate for geothermometry due to its contents of u and th monazite has often been used for u pb age determination the combination of our empirical thermometer on prograde zoned monazite along with possible age determination of zoned single crystals may provide information about prograde branches of temperature time paths

lithologic characterization of a reservoir using continuous wavelet transforms we consider the problem of characterizing the lithology of a reservoir using gamma ray logs as well as seismic traces around the well we first calculate the continuous wavelet transform of the the data and then use the fact that the energy of such transformation is proportional to a power of its scale the technique consists in estimating the power transformation obtaining a set of values of the same size as the original data and then modeling the distribution of these values using a double exponential we find that wells that are predominantly sand correspond to distributions that are significantly different from those that correspond to wells that are predominantly gravel this happens in both cases gamma rays and seismic traces we use this characterization to classify other points in the reservoir

coda wave interferometry for estimating nonlinear behavior in seismic velocity in coda wave interferometry one records multiply scattered waves at a limited number of receivers to infer changes in the medium over time with this technique we have determined the nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions this technique can be used in warning mode to detect the presence of temporal changes in the medium or in diagnostic mode where the temporal change in the medium is quantified

two stage breakdown of monazite by post magmatic and metamorphic fluids an example from the veporic orthogneiss western carpathians slovakia abstract the initial to advanced stage of monazite breakdown was identified in a granitic orthogneiss from the pre alpine basement in the ve k zelen potok valley the veporic unit western carpathians central slovakia monazite ce formed during variscan metamorphism of the original cambrian to ordovician granitic rock two younger permian post magmatic hydrothermal and cretaceous metamorphic hydrothermal events caused a breakdown of the monazite to secondary egg shaped coronal structures 100 to 500 m in diameter with concentric newly formed mineral phases two principal breakdown stages and newly formed mineral assemblages are recognizable 1 partial to complete replacement of primary monazite with an internal apatite thsio 4 huttonite or thorite zone and an external allanite ce to clinozoisite zone 2 hydroxylbastnasite ce partly replacing apatite thsio 4 and allanite to clinozoisite aggregates the monazite breakdown was initiated by fluid sources differing in composition stage 1 originated due to post magmatic hydrothermal fluids whereas stage 2 indicates an input of younger co 2 bearing metamorphic hydrothermal fluids

seismic facies characterization by monoscale analysis relating sedimentary records to seismic data is a major challenge by shifting focus to a scale invariant sharpness characterization for the reflectors we develop an attribute that can capture and categorize the main reflector features without being sensitive to amplitudes sharpness is defined by a scale exponent which expresses singularity order and determines the reflection signature waveform local scale exponent estimates are obtained with a new monoscale method compared to multiscale wavelet analysis our method has the advantage of measuring transition exponents at a single fixed scale using a simple on off criterion the exponents contain amplitude variation information and describe lithological onsets we create an image of the earth s local singularity structure by applying our method to seismic traces and well log data the singularity map facilitates interpretation facies characterization and integration of well and seismic data

deep borehole log evidence for fractal distribution of fractures in crystalline rock summary sonic velocity and electrical resistivity logs run to a depth of 3 5 km in crystalline rock near the san andreas fault at cajon pass in southern california correlate over scale lengths both small sub metre and large tens to hundreds of metres no such correlations are seen with the more lithologically sensitive natural gamma intensity log the correlation between the sonic velocity and electrical resistivity logs suggests that a non lithologic property of the crystalline rock controls fluctuations in situ fracture intensity is a logical candidate for the controlling rock property the fluctuations of the individual sonic velocity and electrical resistivity logs are examined with the hurst rescaled range parameter over borehole log intervals 1 5 m l 1500 m for log fluctuations arising from a scale invariant physical process the hurst rescaled range scales with data interval as lh 0 h 1 a purely random sequence of in situ fractures produces a scaling exponent h 0 50 fluctuations in the cajon pass sonic velocity and electrical resistivity logs yield h 0 70 evidence that in situ fracture sets tend to occur in clusters rather than at purely random intervals the tendency for fracture clustering over log intervals 1 5 m l 1500 m suggests that fracture formation is a fractal process independent of length scale in which larger fracture intervals form from clustering of numerous smaller fracture intervals seismic reflectivity derived from the borehole sonic velocity log is also scale independent over the range of data intervals 1 5m l 1500 m with a hurst exponent h 0 21 if we associate fracture clustering with crustal fault formation the cajon pass borehole sonic velocity and electrical resistivity logs predict that crustal faults scale fractally with fractal dimension d 2 30 the equivalent b value for earthquake size distribution is b d 2 1 15 on this hypothesis observed b values 1 15 indicate a tendency for earthquakes to cluster on existing weak faults a scale independent mechanics for crystalline rock fracture formation in which larger scale fractures form as clusters of smaller scale fractures provides a mechanical link between the small pervasive stress aligned flaws cracks and microfractures which can impart anisotropy to crystalline rock and the larger scale fractures associated with finite strain and faulting thus in crustal regions of active but low strain fracture anisotropy is observed to be aligned with the inferred maximum principal stress while in actively faulted crust fracture anisotropy is observed to be more nearly fault parallel as if the fractures are aligned by the finite strain faulting process

fracture network characterization using 1d and 2d data of the moragy granite body southern hungary abstract a disposal system for low and medium level nuclear waste in hungary is being constructed inside the fractured rock body of the lower carboniferous moragy granite previous studies proved that the granitoid massif is rather heterogeneous in terms of lithological composition brittle structure and hydrodynamic behaviour a significant part of the body consists of monzogranite while other portions are more mafic in composition and are monzonites as a result of at least three significant brittle deformation events the area is at present crosscut by wide shear zones that separate intensively fractured zones and poorly deformed domains among them due to late mineralization processes some of these fractured zones are totally sealed and cannot conduct fluids while others are excellent migration pathways the spatial distribution of these two types nevertheless does not show any systematics hydrodynamic behaviour clearly reflects this heterogeneous picture in some places hydraulic jumps as great as 25 m at compartment boundaries can be detected in this study the fracture network of the moragy granite body is evaluated from a geometric aspect using datasets measured at a wide range of scales 2d digitized images of a hand specimen one large 20 60 m and 12 smaller subvertical wall rocks outcrops and 120 images from tunnel faces representing the ground level of the underground repository site were analysed moreover 1d data from 13 wells that all penetrate the granitoid massif were studied based on measured geometric data spatial position length orientation and aperture fracture networks are simulated to study connectivity relations and for computing the fractured porosity and permeability at different scales the results prove the scale invariant geometry of the fracture system geostatistical calculations indicate that measurable fracture geometry parameters behave as regionalized variables and so can be extended spatially estimated localities of connected subsystems fit very well with fault zones mapped previously moreover the spatial position of regimes of different hydrodynamic behaviours can be explained by connectivity relations both regionally and within wells

boron in metapelites controlled by the breakdown of tourmaline and retrograde formation of borosilicates in the yanai area ryoke metamorphic belt sw japan tourmaline out isograd formed by the breakdown of tourmaline is defined in the upper amphibolite facies metapelites in the yanai area ryoke metamorphic belt sw japan the rim composition of tourmaline progressively becomes aluminous with ascending metamorphic grade and the chemical zoning of tourmaline is controlled by x alna 1mg 1 and mgtiyal 2 vectors in low to medium grade zones where muscovite is stable whereas it is controlled by mg oh yal 1o 1 camgox 1 yal 1 oh 1 and mgtiyal 2 vectors in further higher grade muscovite unstable zones the size of tourmaline increases drastically where breakdown of muscovite quartz takes place probably due to the growth of tourmaline during breakdown of muscovite on the high temperature side of the tourmaline out isograd depletion of whole rock boron is observed escape of boron bearing melt or the fluid evolved from the melt during its crystallization probably caused this depletion although locally trapped boron bearing melt or fluid formed irregularly shaped tourmaline and dumortierite during retrograde metamorphism

some remarks on the estimation of fractal scaling parameters from borehole wire line logs well logging provides a direct means of assessing fluctuations in petrophysical properties with depth and thus allows for the statistical characterisation of crustal heterogeneity using records from three super deep boreholes ktb and cajon pass and synthetic data we assess three different techniques for estimating fractal dimension and correlation length inaccurate correlation lengths may result from the way in which the autocorrelation is calculated for well logs leading to an incorrect application of the von karman function analysis of the rescaled range power spectra and autocorrelation allow us to model the data as k where k wavenumber and exponent 5 2d for fractal dimension d process with values of fractal dimension displaying anti persistence

fault scaling and 1 f noise scaling of seismic velocity fluctuations in the upper crystalline crust sonic logs are detailed measurements of the in situ seismic velocity along borehole walls power spectra of sonic logs typically decay approximately as the reciprocal of spatial frequency f regardless of the chemical composition geologic age and tectonic history of the probed lithologies data sequences of this type are fractal or scale invariant the origins of this uniform 1 f scaling of seismic structure are not clear particularly in low porosity crystalline rocks but faults fractures and cracks are considered to be important fault structures also follow fractal scaling laws and have significant effects on seismic velocity this paper presents a quantitative model that evaluates the role played by faults in determining the scaling laws of seismic velocity fluctuations the model is based on current knowledge of the structure and scaling properties of brittle faults and of associated regions of microcracking by approximating the relationship between crack density and velocity variation as linear this model yields a brownian power spectrum 1 f 2 for velocity perturbations across a single fault zone in a medium of otherwise constant velocity the power spectrum of velocity fluctuations induced by a population of faults is then obtained by superposing the corresponding brownian power spectra weighted according to the observed frequency size scaling relationship of brittle faults the results of this study indicate that the uniform 1 f scaling of velocity fluctuations in crystalline rocks seems to be linked to the correspondingly uniform scaling properties of fault structures

spectral analyses of the ktb sonic and density logs using robust nonparametric methods we use robust techniques to estimate power spectra coherences and transfer functions of the german continental deep drilling program ktb sonic and density logs and lithologically defined subsets thereof our results confirm the overall 1 wavelength decay of the power spectra inferred by parametric analyses but provide superior resolution and nonparametric estimates of errors and statistical significance we demonstrate the absence of any statistically meaningful coherence between the velocity logs from the main and pilot holes suggesting a spatially quasi isotropic upper crustal velocity structure also there is little coherence between the physical and caliper logs indicating that disturbances introduced by breakouts and uneven relief of the borehole wall mostly contribute to the uncorrelated portions of the velocity logs coherence between the gamma and physical logs is weak to absent indicating that the observed velocity and density fluctuations are dominated by the physical state of the rocks rather than by their petrological composition attempts to derive poisson s ratio and its variation with wavelength from the relationship between the shear and compressional velocity logs met with limited success but imply that caution should be exercised when comparing poisson s ratio derived from laboratory studies on samples representative of a region to crustal scale seismic determinations our preferred interpretation is that fluctuations in the physical logs in the intermediate wavelength range 10 150 m are dominated by cracks and their level of fluid saturation at larger wavelengths 50 150 m the effects of the petrology becomes more significant as shown by changes in slope of the power spectra and the emerging coherence between the vp and the gamma logs

pb diffusion in monazite a combined rbs sims study abstract we report measurements of pb diffusion in both synthetic cepo4 and natural monazites run under dry 1 atm conditions powdered mixtures of prereacted cepo4 and pbzro3 were used as the source of pb diffusant for in diffusion experiments conducted in sealed pt capsules for durations ranging from a few hours to several weeks following the diffusion anneals pb concentration profiles were measured with rutherford backscattering spectroscopy rbs and supplemented by measurements with secondary ion mass spectrometry sims in order to evaluate potential compositional effects upon pb diffusivity and simulate diffusional pb loss that might occur in natural systems we also conducted out diffusion experiments on pb bearing natural monazites in these experiments monazite grains were surrounded by a synthetic zircon powder to act as a sink monazites from these experiments were analyzed with sims over the temperature range 1100 to 1350 c the arrhenius relation determined for in diffusion experiments on synthetic monazite is given by d 0 94 exp 592 39 kj mol 1 rt m 2 s 1 diffusivities for synthetic and natural monazites are similar as are results of measurements made on the same samples using both rbs and sims the activation energy for pb diffusion we determined is more than three times that for natural monazite reported previously with pb diffusivities at

the ryoke plutonometamorphic belt crustal section of the cretaceous eurasian continental margin abstract the ryoke belt comprising low pressure regional metamorphic rocks and low level granitoids expresses a deep in the crust of the cretaceous eurasian continental margin before the opening of japan sea the petrological p t estimation of the metamorphic rocks indicates the condition of upper to middle crust level the zonally arranged areal distribution of the san yo shallow facies to ryoke deep facies granitic provinces from back arc side to fore arc side is concordant with the occurrence of the associated low grade to high grade regional metamorphic rocks they are regarded as an upper to middle crustal section of the cretaceous eurasian continental margin these metamorphic rocks are derived mainly from the jurassic accretionary complex in the migmatitic high grade part the metasedimentary rocks were just being transformed into continental crust isotopic ages of these metamorphic and granitic rocks show an along arc variation of the systematic eastward younging from 100 ma to 70 ma for 800 km it cannot be interpreted with the steady state subduction model and indicates that the orogeny was caused by an episodic event presumably the subduction of kula pacific ridge beneath the eurasian continent during cretaceous the present juxtaposition of the ryoke and the sanbagawa paired metamorphic belts inevitably needs a secondary displacement from their birthplace two possibilities should be examined along arc transcurrent movement or across arc overthrusting

low temperature alteration of monazite fluid mediated coupled dissolution precipitation irradiation damage and disturbance of the u pb and th pb chronometers abstract low temperature alteration of monazite is documented in three centimeter sized monazite crystals from norway arendal madagascar ambato and sri lanka the three crystals have different chemical compositions especially in their u th y and pb contents and have 208 pb 232 th ages ranging from 491 to 900 ma optical microscope om scanning electron microscope sem and transmission electron microscope tem images and electron microprobe analyses epma show that all three preserve a similar patchy texture this texture is interpreted as resulting from an alteration reaction in which unaltered monazite mnz1 reacts to form a secondary th u y depleted high th u monazite mnz2 accompanied by thorite huttonite thsio 4 thorianite tho 2 and xenotime ypo 4 the proportions of which are dependent upon the initial composition of the monazite mnz1 images reveal variably intense internal fracturing with cracks filled with th rich fe rich phases monazite xenotime thermometry demonstrates that the pristine monazites mnz1 interacted with a low temperature fluid the alteration process is interpreted to follow a mechanism of fluid mediated coupled dissolution precipitation chemical dating with the electron microprobe shows no th u pb age differences between primary and secondary monazites except in the case of the ambato monazite in which altered domains yield older 750 ma apparent ages than the pristine mnz1 domains u pb and th pb isotope dating using la icp ms yields ages consistent with electron probe dates for pristine mnz1 zones however disturbance of these systems in the altered monazite domains leads to variable age results for these depending on sample in the case of sri lanka and arendal only 208 pb 232 th dates provide a reasonable estimate of the age of alteration which are constrained to be 450 and 864 ma respectively u pb systems are disturbed due to common pb contamination up to 40 and u fractionation relative to th during alteration responsible for depletion of u in altered monazites and increase of th u in contrast for the ambato monazite both the u pb and th pb systems were affected and yield inconsistent older dates for altered zones this is attributed to significant common pb contamination up to 80 which affects all pb isotopes and explains why electron probe ages are erroneous th u silicate contamination during measurement resulting from the presence of a numerous nano phases and nano fractures filled with th u silicates that are visible only under tem also contributes to the anomalously old ages for these disturbed mnz2 domains these results demonstrate the important role of radiation damage effects in particular swelling induced fracturing and the essential role of porosity and cracks which allow fluid charged with elements migration through monazite during low temperature alteration

modelling curved surface wave paths membrane surface wave synthetics summary earth s heterogeneity near the surface is so severe that surface waves with period 20 s exhibit complicated propagation effects such as curved paths and multiple rays in order to take account of these effects a new method to analyse surface waves is developed the method which we call the membrane surface wave method is an approximation to the green s function method in a 3 d medium and is valid for a laterally smoothly varying media we also present the formulae to invert the seismograms as an example we apply the method to a preliminary california model use of the method for the forward calculation shows that heterogeneity in the model is so severe that the wavefront due to the whittier narrows earthquake is split in two by the time it reaches the san francisco bay area the kernels in the inverse formula to the six berkeley stations show curved paths multipathings and finite wavelength effects and visually demonstrate how waves sample the medium the method is attractive in that these complications cause no problems in its application

surface and guided wave inversion for near surface modeling in land and shallow marine seismic data in several domains of applied geophysics surface and guided waves are considered as a source of information for characterizing the near surface which in a marine environment includes the seabed by contrast in exploration seismic surveys these waves have traditionally been regarded as coherent noise that should be filtered out as soon as possible the authors consider that surface and guided waves are not noise but a signal that can be lifted from the seismic record and exploited for a variety of well established geophysical solutions surface and guided waves constitute a large part of the recorded energy and with proper acquisition analysis and inversion they can be used to characterize the near surface with surprisingly high resolution in this role they can provide valuable information for tasks such as perturbation correction adjustment for near surface traveltime distortions they can also be used for velocity and geological modeling in this article the authors discuss a workflow for the a

crystal chemistry of the monazite and xenotime structures monazite and xenotime the re p04 dimorphs are the most ubiquitous rare earth re minerals yet accurate structure studies of the natural phases have not been reported here we report the results of high precision structure studies of both the natural phases and the synthetic re p04 phases for all individual stable rare earth elements monazite is monoclinic p2 n and xenotime is isostructural with zircon space group 14 amd both atomic arrangements are based on 001 chains of intervening phosphate tetrahedra and re polyhedra with a reogpolyhedron in xenotime that accommodates the heavy lanthanides tb lu in the synthetic phases and a re09 polyhedron in monazite that preferentially incorporates the larger light rare earth elements la gd as the structure transforms from xenotime to monazite the crystallographic properties are comparable along the 00i chains with structural adjustments to the different sizes of re atoms occurring principally in 00i there are distinct similarities between the structures that are evident when their atomic arrangements are projected down 001 in that projection the chains exist in 100 planes with two planes per unit cell in monazite the planes are offset by 2 2 a along 010 relative to those in xenotime in order to accommodate the larger light re atoms the shift of the planes in monazite allows the re atom in that phase to bond to an additional 02 atom to complete the re09 polyhedron

chime dating of monazite xenotime zircon and polycrase protocol pitfalls and chemical criterion of possibly discordant age data abstract this paper outlines the chime chemical th u total pb isochron method dating method which is based on precise electron microprobe analyses of th u and pb in th and u bearing accessory minerals such as monazite xenotime zircon and polycrase the age mapping technique that is applicable to young monazite and zircon is also described chime dating consists of analyzing multiple spots within homogeneous age domains that show sufficient compositional variation and then these data are used to construct a pseudo isochron from which an age can be obtained via regression this method when coupled with discrimination of possibly concordant age data by chemical criteria such as the ca si th u pb s ratio for monazite and ca and s contents for zircon has the potential advantage of significant precision and the ability to work with minerals that have a significant initial common pb component this technique can identify two or more homogeneous domains that are separated by age gaps smaller than the error on individual spot age analysis many features that are insignificant in major element analysis can have major impact in the acquisition of trace element data critical factors include the roles of collimator slit detector gas background estimation accelerating voltage probe current x ray interferences and count rate in affecting the accuracy and a way to apply the th and u interference correction without pure th and u oxides or synthesized pure thsio4 the age mapping procedure for young monazite and zircon includes acquiring pbm or pbm intensity of individual pixels with multiple spectrometers correcting background with background maps computed from a measured background intensity by the intensity relationships determined in advance of the measurement calibrating of intensity with standards and calculating of ages from the th u and pb concentrations this technique provides age maps that show differences in age domains on the order of 20 ma with in monazite as young as 100 ma the effect of sample damage by irradiation of intense and prolonged probe measurement is also described

on the cause of 1 f power spectral scaling in borehole sonic logs borehole logs provide in situ information about the scaling of fluctuations in the elastic properties of rock a surprising finding has been the widespread 1 f type 0 5 1 5 scaling of borehole sonic log power spectra yielding no clear correlation with geological age type or history raising questions about the reliability and origin of these findings ubiquitous fractures for example have been evoked as the most likely explanation of these results firstly we show that the smoothing effects of the logging tool must be taken into account in order to obtain reliable values of we then investigate the scaling properties of lithology only in perfectly exposed metamorphic rock by explicitly excluding fractures we find clear 1 f scaling for reconstructed velocity data based solely on lithological variations although fractures are certainly important in contributing to 1 f fluctuations in borehole logs intrinsic geology may also play a significant role

electron microprobe monazite geochronology of magmatic events examples from variscan migmatites and granitoids massif central france u th pb dating of monazite with the electron probe microanalyser epma is increasingly documented as a reliable geochronological method offering high spatial resolution this method has been applied on monazite from the cevennes migmatites and granitoids from the southeast of the french massif central measurements were performed on separated grains after systematic back scattered electron bse imaging monazites from migmatites record two main ages i a protolith age of about 550 543 ma obtained on inherited cores and ii a migmatization event between 329 5 and 323 3 ma recorded by monazite rims and all other monogenetic grains monazite from the peraluminous rocles pluton yields a 318 3 ma age finally three granite dykes are dated at 333 6 318 5 and 311 5 ma the older dyke is the most deformed of them and is interpreted as linked to the migmatization event the two other dykes are geochronologically petrologically and structurally coeval with the rocles pluton the data constrain the timing of crustal melting following variscan thickening in the northern cevennes area migmatization of ordovician protoliths took place at 329 323 ma and was shortly followed by intrusion of leucogranite at 318 311 ma the study shows that epma dating of monazite can be successfully used to resolve a close succession of regional melting events

u pb systematics of monazite and xenotime case studies from the paleoproterozoic of the grand canyon arizona monazite is accepted widely as an important u pb geochronometer in metamorphic terranes because it potentially preserves prograde crystallization ages however recent studies have shown that the u pb isotopic system in monazite can be influenced by a variety of processes that partially obscure the early growth history in this paper we attempt to interpret complex monazite and xenotime u pb data from three paleoproterozoic granite dikes exposed in the grand canyon single crystal monazite analyses from an unfoliated granite dike spread out along concordia from the crystallization age of the dike defined by u pb zircon data to be 1685 1 ma to 1659 2 ma a span of 26 million years back scattered electron bse imaging reveals that magmatic domains within most crystals from this sample are truncated by secondary domains associated with prominent embayments at the grain margin fragments of a single crystal yield contrasting concordant dates and fragments from the edges and tips of crystals yield the youngest dates based on these observations we suggest that the secondary domains formed at least 26 million years after the crystal formed monazite and xenotime dates from the second sample a sheared dike that cross cuts the previous dike spread out along concordia over 16 million years and range up to 2 4 normally discordant again bse imaging reveals secondary domains that truncate both magmatic zoning and xenocrystic cores fragments sliced from specific domains of a previously imaged monazite crystal demonstrate that the secondary domain is 13 million years younger than the core domain textures revealed in bse images suggest that the secondary domains formed by fluid mineral interaction normal discordance appears to result from both radiation damage accumulated at temperatures below 300 c and water mineral interaction monazite data from the third sample exhibit dispersion in both the 207pb 206pb dates 1677 1690 ma and discordance 1 6 to 3 1 reverse discordance in these monazites cannot be explained by incomplete dissolution or excess thorogenic 206pb sliced fragments from several crystals reveal dramatic intragrain u pb disequilibrium that does not correlate with either th or u concentration or position within the crystal we suggest that reverse discordance resulted from mechanisms that involve exchange or fractionation of elemental u or elemental pb and that neither the u pb dates nor the 207pb 206pb dates are reliable indicators of the rock s crystallization age given the large number of processes proposed in the recent literature to explain monazite u pb systematics from rocks of all ages our results can be viewed as another cautionary note for single crystal and multi crystal monazite geochronometry however we suggest that because individual crystals can preserve a temporal record of primary and secondary monazite growth micro sampling of individual monazite crystals may provide precise absolute ages on a variety of processes that operate during the prograde peak and or retrograde history of metamorphic terranes