alternative waveform inversion for surface wave analysis in 2 d media in the context of near surface seismic imaging a few hundreds of metres we propose an alternative approach for inversion of surface waves in 2 d media with laterally varying velocities it is based on full waveform inversion fwi but using an alternative objective function formulated in the frequency wavenumber f k domain the classical fwi objective function suffers from severe local minima problems in the presence of surface waves it thus requires a very accurate initial model the proposed objective function is similar to the one used in classical surface wave analysis in this approach the data are first split using sliding windows in the time space t x domain for each window the amplitude of the f k spectrum is computed the objective function measures the least squares misfit between the amplitude of observed and modelled 2 d fourier transformed data sets we call this formulation the windowed amplitude waveform inversion w awi the w awi objective function reduces some local minima problems as shown here through numerical examples the global minimum basin is wider in the w awi approach than in fwi synthetic examples show that w awi may achieve convergence if the lowest data frequency content is twice higher than the one needed by fwi for elastic inversion w awi can be used to reconstruct a velocity model explaining surface waves this surface wave inversion procedure can be used to retrieve near surface model parameters in lateral varying media

estimation of rock physics properties from seismic attributes part 2 applications abstractthe estimation of quantitative rock physics properties is of great importance for reservoir characterization and monitoring in co2 storage or enhanced oil recovery as an example we have combined the high resolution results of full waveform inversion fwi methods with rock physics inversion because we consider a generic and dynamic rock physics model our method is applicable to most kinds of rocks for a wide range of frequencies the first step allows determination of viscoelastic effective properties i e quantitative seismic attributes whereas the rock physics inversion estimates rock physics properties porosity solid frame moduli fluid phase properties or saturation this two step workflow is applied to time lapse synthetic and field cases the sensitivity tests that we had previously carried out showed that it can be crucial to use multiparameter inputs to accurately recover fluid saturations and fluid properties however due to the limited data availability and difficulties in get

regional geologic and petrologic framework for iron oxide apatite rare earth element and iron oxide copper gold deposits of the mesoproterozoic st francois mountains terrane southeast missouri usa this paper provides an overview on the genesis of mesoproterozoic igneous rocks and associated iron oxide apatite ioa rare earth element iron oxide copper gold iocg and iron rich sedimentary deposits in the st francois mountains terrane of southeast missouri usa the st francois mountains terrane lies along the southeastern margin of laurentia as part of the eastern granite rhyolite province the province formed during two major pulses of igneous activity 1 an older early mesoproterozoic ca 1 50 1 44 ga episode of volcanism and granite plutonism and 2 a younger middle mesoproterozoic ca 1 33 1 30 ga episode of bimodal gabbro and granite plutonism the volcanic rocks are predominantly high silica rhyolite pyroclastic flows volcanogenic breccias and associated volcanogenic sediments with lesser amounts of basaltic to andesitic volcanic and associated subvolcanic intrusive rocks the iron oxide deposits are all hosted in the early mesoproterozoic volcanic and volcaniclastic sequences previous studies have characterized the st francois mountains terrane as a classic a type within plate granitic terrane however our new whole rock geochemical data indicate that the felsic volcanic rocks are effusive derivatives from multicomponent source types having compositional similarities to a type within plate granites as well as to s and i type granites generated in an arc setting in addition the volcanic hosted ioa and iocg deposits occur within bimodal volcanic sequences some of which have volcanic arc geochemical affinities suggesting an extensional tectonic setting during volcanism prior to emplacement of the ore forming systems the missouri iron orebodies are magmatic related hydrothermal deposits that when considered in aggregate display a vertical zonation from high temperature magmatic hydrothermal ioa deposits emplaced at moderate depths 1 2 km to magnetite dominant ioa veins and iocg deposits emplaced at shallow subvolcanic depths the shallowest parts of these systems include near surface iron oxide only replacement deposits surficial epithermal sediment hosted replacement deposits synsedimentary ironstone deposits and mn rich exhalite deposits alteration associated with the ioa and iocg mineralizing systems of the host volcanic rocks dominantly produced potassic with lesser amounts of calcic and sodic rich mineral assemblages no deposits are known to be hosted in granite implying that the mineralizing systems were operative during a relatively short postvolcanic period yet prior to intrusion of the granitoids companion studies in this special issue on mineral chemistry stable isotopes and iron isotopes suggest that the magnetite within the ioa deposits formed from high temperature fluids of magmatic or magmatic hydrothermal origin however the data do not discriminate between a magmatic hydrothermal source fluid exsolved from an fe rich immiscible liquid or an fe rich silicate magma mineral chemical fluid inclusion and stable isotope data from these new studies record the effects of metasomatic fluids that interacted with crustal reservoirs such as volcanic rocks or seawater

the role of attenuation in 2d full waveform inversion of shallow seismic body and rayleigh waves abstractfull waveform inversion fwi of rayleigh waves is attractive for shallow geotechnical investigations due to the high sensitivity of rayleigh waves to the s wave velocity structure of the subsurface in shallow seismic field data the effects of anelastic damping are significant dissipation results in a low pass effect as well as frequency dependent decay with offset we found this by comparing recorded waveforms with elastic and viscoelastic wave simulation the effects of anelastic damping must be considered in fwi of shallow seismic rayleigh waves fwi using elastic simulation of wave propagation failed in synthetic inversion tests in which we tried to reconstruct the s wave velocity in a viscoelastic model to overcome this q values can be estimated from the recordings to quantify viscoelasticity waveform simulation in the fwi then uses these a priori values when inferring seismic velocities and density a source wavelet correction which is inevitable in fwi of field data can compensate a

linearized inversion of seismic reflection data this is the first of a series of papers giving the solution of the inverse problem in seismic exploration the acoustic approximation is used together with the assumption that the velocity field has the form the forward problem is then linearized thus neglecting multiple reflected waves and the inverse problem of estimating is set up its rigorous solution can be obtained using an iterative algorithm each step consisting of a classical kirchhoff migration hyperbola summation plus a classical forward modeling step circle summation

evidence of multiple halogen sources in scapolites from iron oxide copper gold iocg deposits and regional nacl metasomatic alteration norrbotten county sweden abstract scapolites from barren regional na cl metasomatic assemblages rm iron oxide copper gold deposits iocg scapolite altered metabasic rocks iocg m and from iocg proximal alteration na skarns iocg ps from norrbotten county in northern sweden have been analysed for halogen content and cl stable isotope composition the aim of the study was to constrain the source of halogens within alteration assemblages and to investigate the possible fractionation of cl isotopes between scapolite and the hydrothermal fluid scapolite separates were analysed for cl br and major oxide concentrations using electron probe micro analysis epma and micro x ray fluorescence xrfm spectrometry chlorine was extracted from the scapolite separates via pyrohydrolysis and then analysed for their stable cl isotope compositions by isotope ratio mass spectrometry irms all samples of scapolite investigated in this study are marialitic in composition one of the scapolites from the gruvberget deposit iocg ps had a cl br molar ratio of 2363 which is the highest amongst all scapolites reported in the literature to date cl br molar ratios lower than seawater 650 were identified in two iocg ps scapolite samples cl br 554 and 271 as well as in two iocg m scapolites cl br 393 and 565 three rm scapolites had cl br molar ratios very close to or slightly higher than seawater values 639 to 770 samples with cl br molar ratios less than seawater are inferred to have halogens derived from evaporative residual brines whereas samples with molar ratios higher than seawater may have halogens derived from fluids that have dissolved halite and or are from magmatic systems considering the wide variation of the cl br molar ratios in the iocg ps and iocg m scapolites compared to the restricted composition of the regional alteration rm it is proposed that the hydrothermal fluids interacted with several different protoliths to generate the iocg alteration rm alteration scapolites had 37 cl values from 0 1 to 0 3 two iocg m scapolites had values of 0 2 and iocg ps scapolites had 37 cl values from 0 1 to 1 0 using a previously published 37 cl value from fluid inclusion leachates 1 7 from the iocg m mineralisation at pahtohavare and the 37 cl value of co existing scapolite measured in this study 0 2 an empirical fluid scapolite fractionation factor was calculated to be 1 9 this large fractionation factor is not supported by previous predictions for monovalent chlorides and assuming equilibrium indicates that 37 cl was preferentially accommodated in the a site of the scapolite structure this indicates that either the stable cl isotope partitioning between the cacl 2 rich brine and the scapolite may differ from currently available estimates for nacl brines in equilibrium with silicate minerals or that the scapolite and brine are not in isotopic equilibrium overall the data in this study suggest that halogens in early scapolites were derived from residual brines and halite during metamorphism of evaporites linked to the rm alteration later in the history of the norrbotten district components of the rm alteration were recycled and mixed during magmatic and local metasomatic events to varying extents resulting in the brines associated with iocg alteration

in situ la icp ms u pb dating of metavolcanics of norrbotten sweden records of extended geological histories in complex titanite grains in situ u pb dating of a variety of mineral phases is an important goal in petrology this study reports data chiefly from titanite but also from rutile and apatite obtained using the laser ablation la icp ms methodology on polished thick sections in order to retain as much petrologic information as possible and allowing trace element analyses from adjacent areas to the u pb analyses the samples analysed come from svecofennian intermediate to acid volcanic rocks of the porphyry group within the major iron ore province of norrbotten northern sweden where titanite is a common phase associated with the mineralisation using a laser beam of 30 45 m in diameter accurate and relatively precise 2 3 2 on 206pb 238u ratios data can be obtained on titanite similar precision on pb u ratios can be obtained in rutile but accuracy cannot be assessed because of the lack of well characterised standards however the data are a priori accurate as they are geologically reasonable apatite shows reverse discordance which could be explained by a number of scenarios however the 207pb 206pb ages are fairly precise 1 3 2 and the calculated age is geologically reasonable suggesting that the data may be accurate the titanite grains studied show complex internal structures rare earth element ree analysis by la icp ms demonstrates that the core and rim zones are distinct and supports a model for two stage evolution in two out of three samples with the rims in these samples being enriched in total ree and particularly in lree in one sample and displaying a positive y anomaly in contrast to the cores in situ u pb analysis reveals that core zones from all samples retain distinct older ages of c 2050 ma whereas the reworked rims have either distinct younger or strongly reset ages the older cores are interpreted as representing the first alteration metamorphism of the volcanic pile titanite rims record a u pb age of 1870 24 ma 2 at luossavaara and 1826 15 ma 2 at the smaller fe oxide apatite body at gruvberget in both cases the ages are consistent with previous age determinations from the fe oxide apatite deposits a sample from malmberget records a slightly different scenario where u pb ages spread along concordia from c 1920 to 1708 ma we attribute this pattern to metamorphic reworking of primary metasomatic titanite rutile ages from inclusions within the core of gruvberget titanite essentially mimic the ages obtained from the surrounding titanite and suggest that they have undergone the same history apatite inclusions within titanite at malmberget record a younger age of 1584 12 ma 2 which we attribute to later events known to have affected the area these data indicate that the porphyry group volcanics must be at least c 2050 ma in age in contrast to previous age determinations from zircon which suggested a deposition age of c 1960 to 1880 ma the large grain size of the titanites studied coupled with the ability for the first time to obtain in situ u pb ages from small areas has allowed probing of this hitherto unrecognised event smaller zircon grain size coupled with extremely saline hot pressurised high p t metasomatic fluids relating to regional magnetite apatite mineralisation in the period 1900 to 1800 ma may have resulted in resetting of zircon u pb systematics 2007 elsevier b v all rights reserved

seismic imaging of complex onshore structures by 2d elastic frequency domain full waveform inversion quantitative imaging of the elastic properties of the subsurface at depth is essential for civil engineering applications and oil and gas reservoir characterization a realistic synthetic example provides for an assessment of the potential and limits of 2d elastic full waveform inversionfwiof wide aperture seismic data for recovering high resolution p and s wave velocity models of complex onshore structures fwi of land data is challengingbecauseoftheincreasednonlinearityintroducedbyfreesurface effects such as the propagation of surface waves in the heterogeneous near surface moreover the short wavelengths of the shear wavefield require an accurate s wave velocity starting modeliflowfrequenciesareunavailableinthedata weevaluated different multiscale strategies with the aim of mitigating the nonlinearities massively parallel full waveform inversion was implemented in the frequency domain the numerical optimization relies on a limited memory quasi newton algorithm that outperforms the more classic preconditioned conjugate gradient algorithm the forward problem is based upon a discontinuous galerkin dg method on triangular mesh which allows accuratemodelingoffree surfaceeffects sequentialinversionsofincreasingfrequenciesdefinethemostnaturallevelofhierarchyin multiscale imaging in the case of land data involving surface waves the regularization introduced by hierarchical frequency inversions is not enough for adequate convergence of the inversion a second level of hierarchy implemented with complexvalued frequencies is necessary and provides convergence of the inversion toward acceptable p and s wave velocity models amongthepossiblestrategiesforsamplingfrequenciesintheinversion successive inversions of slightly overlapping frequency groups is the most reliable when compared to the more standard sequential inversion of single frequencies this suggests that simultaneous inversion of multiple frequencies is critical when consideringcomplexwavephenomena

shallow structure characterization by 2d elastic full waveform inversion assessing the effectiveness of elastic full waveform inversion fwi algorithms when applied to shallow 2d structures in the presence of a complex topography is critically important by using fwi we overcome inherent limitations of conventional seismic methods used for near surface prospecting acoustic tomography and multichannel spectral analysis of surface waves the elastic forward problem formulated in the frequency domain is based on a mixed finite element p0p1 discontinuous galerkin method to ensure accurate modeling of complex topography effects at a reasonable computing cost the inversion problem uses an fwi algorithm to minimize the misfit between observed and calculated data based on results from a numerical experiment performed on a realistic landslide model inspired from the morphostructure of the super sauze earthflow we analyzed the effect of using a hierarchical preconditioning strategy based on a simultaneous multifrequency inversion of damped data to mitigate the strong nonlinearities coming from the surface waves this strategy is a key point in alleviating the strong near surface effects and avoiding convergence toward a local minimum using a limited memory quasi newton method improved the convergence level these findings are analogous to recent applications on large scale domains although limited sourcereceiver offset ranges low frequency content of the source and domination of surface waves on the signal led to some difficulties regarding the impact of data decimation on the inversion results we have learned that an inversion restricted to the vertical data component can be successful without significant loss in terms of parameter imagery resolution in our investigations of the effect of increased source spacing we found that a sampling of 4 m less than three times the theoretical maximum of one half wavelength led to severe aliasing

8 precambrian geodynamics and ore formation the fennoscandian shield abstract compared with present day global plate tectonics archaean and palaeoproterozoic plate tectonics may have involved faster moving hotter plates that accumulated less sediment and contained a thinner section of lithospheric mantle this scenario also fits with the complex geodynamic evolution of the fennoscandian shield from 2 06 to 1 78 ga when rapid accretion of island arcs and several microcontinent continent collisions in a complex array of orogens was manifested in short lived but intense orogenies involving voluminous magmatism with a few exceptions all major ore deposits formed in specific tectonic settings between 2 06 and 1 78 ga and thus a strong geodynamic control on ore deposit formation is suggested all orogenic gold deposits formed syn to post peak metamorphism and their timing reflects the orogenic younging of the shield towards the sw and west most orogenic gold deposits formed during periods of crustal shortening with peaks at 2 72 to 2 67 1 90 to 1 86 and 1 85 to 1 79 ga the ca 2 5 to 2 4 ga ni cu pge deposits formed both as part of layered igneous complexes and associated with mafic volcanism in basins formed during rifting of the archaean craton at ca 2 5 to 2 4 ga svecokarelian ca 1 89 to 1 88 ga ni cu deposits are related to mafic ultramafic rocks intruded along linear belts at the accretionary margins of microcratons all major vms deposits in the fennoscandian shield formed between 1 97 and 1 88 ga in extensional settings prior to basin inversion and accretion the oldest cyprus type deposits were obducted onto the archaean continent during the onset of convergence the pyhasalmi vms deposits formed at 1 93 to 1 91 ga in primitive bimodal arc complexes during extension of the arc in contrast the skellefte vms deposits are 20 to 30 million years younger and formed in a strongly extensional intra arc region that developed on continental or mature arc crust deposits in the bergslagen uusimaa belt are similar in age to the skellefte deposits and formed in a microcraton that collided with the karelian craton at ca 1 88 to 1 87 ga the bergslagen uusimaa belt is interpreted as an intra continental or continental margin back arc extensional region developed on older continental crust iron oxide copper gold iocg deposits are diverse in style at least the oldest mineralizing stages at ca 1 88 ga are coeval with calc alkaline to monzonitic magmatism and coeval and possibly cogenetic subaerial volcanism more akin to continental arcs or to magmatic arcs inboard of the active subduction zone younger mineralization of similar style took place when s type magmatism occurred at ca 1 80 to 1 77 ga during cratonization distal to the active n s trending subduction zone in the west possibly interaction of magmatic fluids with evaporitic sequences in older rift sequences was important for ore formation finally the large volumes of anorthositic magmas that characterize the sveconorwegian orogeny formed a major concentration of ti in the sw part of the sveconorwegian orogenic belt under granulite facies conditions about 40 million years after the last regional deformation of the sveconorwegian orogeny between ca 930 and 920 ma

crustal seismic imaging from multifold ocean bottom seismometer data by frequency domain full waveform tomography application to the eastern nankai trough 1 in offshore surveys the deep crust is generally investigated by traveltime tomography applied to sparse ocean bottom seismometer data the inferred velocity models are of limited resolution precluding a quantitative analysis of deep tectonic discontinuities if dense arrays of ocean bottom seismometers can be deployed the resulting data sets become amenable to full waveform processing which should lead to a significant improvement in the resolution of structures such acquisition and processing were achieved on the eastern nankai subduction zone full waveform inversion is entirely implemented in the frequency domain enabling efficient finite difference wave modeling and allowing to limit the inversion to a few discrete frequencies of increasing value such a hierarchical procedure defines a multiresolution approach to seismic imaging the data set was recorded by 93 instruments deployed along a 105 km long profile thirteen frequencies ranging from 3 to 15 hz were inverted sequentially wavelengths imaged by the full waveform inversion typically range between 0 5 and 8 km full waveform tomography reveals an intense compression in the upper prism and underlying backstop as evidenced by several thrusts the frontal ones still active corresponding to negative velocity anomalies the subducting paleo zenisu ridge is also reconstructed above which stands the decollement velocities in the upper mantle beneath the ridge are rather low 7 5 km s 1 suggesting partially serpentinized mantle beneath the ridge this paper demonstrates the feasibility of full waveform tomography based on dense ocean bottom seismometer data sets and its ability to quantitatively image the entire crust with a significantly improved resolution compared to what is usually achieved through traveltime tomography

effects of surface scattering in full waveform inversion in full waveform inversion of seismic body waves often the free surface is ignored on grounds of computational efficiency asyntheticstudywasperformedtoinvestigatetheeffectsofthissimplification intermsofsizeandfrequency the testmodelanddataconformtoareallong offsetsurveyofthe upper crust across the san andreas fault random fractal variations are superimposed on a background model with strong lateral and vertical velocity variations ranging from 1200to6800m s syntheticdatawerecomputedandinverted forthismodelanddifferenttopographies afullyviscoelastic time domain code was used to synthesize the seismograms and a viscoacoustic frequency domain code was utilized to invert them the inversion was focused on early arrivals which are dominated by p waves but also contain strong p rayleigh wave conversions from the near field of the receiver resulting waveform models show artifacts and a loss of resolution from neglecting the free surface in the inversion but the inversions are stable and they still improve the resolution of kinematic models the extent of deterioration dependsmoreonthesubsurfacethanonthesurfacestructure inversion results were improved at no additional expense by introducing a weak contrast along a staircase function above shotsandreceivers

the geology of the rakkurijarvi cu au prospect norrbotten a new iron oxide copper gold deposit in northern sweden the rakkurijarvi prospect consists of a group of mineralized magnetite and lithic breccias within the ca 2 05 to 1 90 ga proterozoic supracrustal sequence of the kiruna district northern sweden potentially economic grades of cu and au largely in the form of chalcopyrite and other sulfide assemblages are hosted in brecciated magnetite and metavolcanic rocks the extent of the mineralization is currently open both downdip and along strike the deposit was discovered through an integrated geophysical and geochemical program focused on iron oxide copper gold iocg style mineralization it is hosted by brecciated greenschist facies metavolcanic rocks within and adjacent to an east northeast trending shear zone the dominant characteristics of the deposit are consistent with the iocg class and include magnetite and lithic breccias hosted in a metavolcanic sequence with matrices of albite actinolite and calcite surrounded by halos of sodic albitescapolite and potassic scapolite k feldspar biotite alteration a distinctive accessory mineral assemblage includes apatite titanite and allanite the paragenesis and textural evolution of the deposit includes early narich alteration accompanying massive magnetite alteration the na rich alteration is overprinted by potassic alteration also associated with magnetite although the paragenesis is complex and multiple generations of both sodic and potassic alteration are recognized alteration of lithic clasts to magnetite confirms a metasomatic origin as opposed to an orthomagmatic origin for the magnetite mineralization re os analyses of two separates of molybdenite intergrown with magnetite interpreted as cogenetic with the sulfide assemblage yield mineralization ages of 1853 6 and 1862 6 ma reconnaissance bulk rock chemistry of the host volcanic rocks is consistent with an intermediate volcanic protolith but much of the original character of the rocks is masked by albitization and incipient iron sodic and potassic alteration the data also indicate significant element mobility during metasomatism and in particular the addition of ti to the rock mass in biotite and as titanite the compositions of secondary minerals are consistent with alteration and mineralization caused by highly saline fluids of relatively low f activity the stable isotope characteristics of calcite with 18osmow ranging from 9 43 to 19 89 per mil and 13cpdb ranging from 11 69 to 4 88 per mil suggest that the fluids of the calcite and sulfide stage were derived from a magmatic source but had interacted extensively with local sedimentary and volcanic rocks

a parametric analysis of two dimensional elastic full waveform inversion of teleseismic data for lithospheric imaging the development of dense networks of broad band seismographs makes teleseismic data amenable to full waveform inversion fwi methods for high resolution lithospheric imaging compared to scattered field migration fwi seeks to involve the full seismic wavefield in the inversion we present a parametric analysis of 2 d frequency domain fwi in the framework of lithospheric imaging from teleseismic data to identify the main factors that impact on the quality of the reconstructed compressional p wave and shear s wave speed models compared to controlled source seismology the main adaptation of fwi to teleseismic configuration consists of the implementation with a scattered filed formulation of plane wave sources that impinge on the base of the lithospheric target located below the receiver network at an arbitrary incidence angle seismic modelling is performed with a hp adaptive discontinuous galerkin method on unstructured triangular mesh a quasi newton inversion algorithm provides an approximate accounting for the hessian operator which contributes to reduce the footprint of the coarse acquisition geometry in the imaging a versatile algorithm to compute the gradient of the misfit function with the adjoint state method allows for abstraction between the forward problem operators and the meshes that are during seismic modelling and inversion respectively an approximate correction for obliquity is derived for future application to real teleseismic data under the two dimension approximation comparisons between the characteristic scales involved in exploration geophysics and in teleseismic seismology suggest that the resolution gain provided by full waveform technologies should be of the same order of magnitude for both applications we first show the importance of the surface reflected wavefield to dramatically improve the resolving power of fwi by combining tomography like and migration like imaging through the incorporation of the forward scattered and the backscattered wavefields in the inversion the resolution of fwi is assessed through checkerboard tests and confirms a resolution of the order of the wavelength for both the p and s speeds when the full wavefield is incorporated in the inversion secondly we show that computationally efficient strategies which consist of decimating the number of frequency components involved in the inversion do not apply to teleseismic acquisitions because the scattering angle bandwidth sampled by plane wave sources can be narrow and coarsely sampled compared to that provided by dense profiles of point sources in exploration seismology the waveform inversion is less sensitive to the band of incidence angles spanned by the plane wave sources and to the sampling of this band however the deficit of vertically propagating plane waves hampers the vertical resolution of planar layers aliasing artefacts created by coarse arrays of receivers are illustrated we show how taking into account the hessian in the inversion and the suitable management of frequencies in the inversion help to mitigate these artefacts acceptable reconstructions are shown for both the p and s wave speeds for a receiver spacing of up to 20 km in the 0 1 0 4 hz frequency range building a reliable initial model for fwi is a highly non linear problem in exploration seismology we show how the low frequency content of the teleseismic sources allow us to build accurate p and s wave speed models starting from simple vertical gradient velocity models all of these results are derived using a 2 d realistic synthetic experiment that was performed with noise free data most of conclusions of this parametric study should apply in three dimensions the impact of noise and the footprint of other experimental parameters such as the estimation of the temporal plane wave signature and the estimation of the incidence angle of the impinging plane waves need however to be assessed in the future

line source simulation for shallow seismic data part 2 full waveform inversion a synthetic 2 d case study full waveform inversion fwi of shallow seismic surface waves is able to reconstruct lateral variations of subsurface elastic properties line source simulation for point source data is required when applying algorithms of 2 d adjoint fwi to recorded shallow seismic field data the equivalent line source response for point source data can be obtained by convolving the waveforms with sqrt 1 t t traveltime which produces a phase shift of 4 subsequently an amplitude correction must be applied in this work we recommend to scale the seismograms with sqrt 2 r v ph at small receiver offsets r where v ph is the phase velocity and gradually shift to applying a sqrt 1 t time domain taper and scaling the waveforms with r sqrt 2 for larger receiver offsets r we call this the hybrid transformation which is adapted for direct body and rayleigh waves and demonstrate its outstanding performance on a 2 d heterogeneous structure the fit of the phases as well as the amplitudes for all shot locations and components vertical and radial is excellent with respect to the reference line source data an approach for 1 d media based on fourier bessel integral transformation generates strong artefacts for waves produced by 2 d structures the theoretical background for both approaches is presented in a companion contribution in the current contribution we study their performance when applied to waves propagating in a significantly 2 d heterogeneous structure we calculate synthetic seismograms for 2 d structure for line sources as well as point sources line source simulations obtained from the point source seismograms through different approaches are then compared to the corresponding line source reference waveforms although being derived by approximation the hybrid transformation performs excellently except for explicitly back scattered waves in reconstruction tests we further invert point source synthetic seismograms by a 2 d fwi to subsurface structure and evaluate its ability to reproduce the original structural model in comparison to the inversion of line source synthetic data even when applying no explicit correction to the point source waveforms prior to inversion only moderate artefacts appear in the results however the overall performance is best in terms of model reproduction and ability to reproduce the original data in a 3 d simulation if inverted waveforms are obtained by the hybrid transformation

finite difference calculation of travel times the travel times of the first arriving seismic waves through any velocity structure can be rapidly computed on a two or three dimensional numerical grid by finite difference extrapolation from point to point wavefronts rather than the traditional rays are tracked head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 03 per cent are found between the results of this technique and raytracing for a complex two dimensional model this scheme is useful for the windowing of finite difference calculations to increase computing speed and promises to aid in earthquake location tomographic inversion and kirchhoff migration in structures that have strong lateral velocity gradients

tracing the fluid evolution of the kiruna iron oxide apatite deposits using zircon monazite and whole rock trace elements and isotopic studies the ore genesis of the paleoproterozoic iron oxide apatite deposits in the vicinity of kiruna in northern sweden is poorly understood despite a century long mining history and 2500 mt of iron ore with grades of 30 to 70 wt fe produced in the region to date zircon grains from the ore recently dated at ca 1874 ma show very different appearances compared to zircon from surrounding host rocks ca 1880 ma and related intrusions ca 1880 and ca 1874 ma particularly an inclusion rich rim in contrast zircon from the host rocks and a proximal granite intrusion exhibit typical igneous growth zoning electron microprobe results show near stoichiometric composition for zr si and hf in the host rock zircon grains the ore zircon crystals have low analytical totals with significant concentrations of ca fe y and p and infrared spectroscopy showed several weight percent of water these ore zircon grains further show fe rich inclusions zones and or veins in elemental x ray maps and light rare earth elements lree enrichment transmission electron microscopy tem shows that the lree are not due to micro or nano inclusions in the zircon but are likely hosted as lree oxides in amorphous regions of the grains based on these characteristics the rims on ore zircon grains are interpreted to be of hydrothermal origin uranium pb in monazite from the ore measured by sims suggests a secondary event influencing the area at ca 1624 ma a period of known geologic activity in fennoscandia electron microprobe x ray mapping of these monazite grains shows no zoning and relatively low u and th concentrations stark contrasts are visible between the ore depleted mantle influence and host rocks crustal influence in the whole rock lu hf and sm nd data the depleted mantle signature of the ore could be related to the kiruna greenstone group as a potential source region for the iron the sm nd isotopic composition of monazite from the ore shows a crustal influence and indicates that the younger event has not disturbed the whole rock sm nd signature of the ore the hydrothermal nature of the ore zircon grains and the isotopic signatures point to a hydrothermal influence on the ore formation with a high temperature magmatic fluid related to the intrusions as most likely heat and fluid source

a comparison of phase inversion and traveltime tomography for processing near surface refraction traveltimes with phase inversion one can estimate subsurface velocities using the phases of first arriving waves which are the frequency domain equivalents of the traveltimes phase inversion is modified to make it suitable for processing traveltimes from near surface refraction surveys the modifications include parameterizing the model correcting the observed phases and selecting the complex frequency this modified phase inversion is compared to traveltime tomography for two comparisons using computer simulated traveltimes the difference between the estimated and correct models the residual mean and the residual standard deviation are smaller for the phase inversion than they are for the traveltime tomography for a comparison using field data from an s wave refraction survey both methods estimate models that are consistent with the known geology nonetheless the phase inversion model includes small scale features in the bedrock that are geologically plausible the residual mean and the residual standard deviation are smaller for the phase inversion than they are for the traveltime tomography

effects of topography on seismic wave propagation an example from northern taiwan topography influences ground motion and in general increases the amplitude of shaking at mountain tops and ridges whereas valleys have reduced ground motions as is observed from data recorded during and after real earthquakes and from numerical simulations however recent publications have focused mainly on the implications for ground motion in the mountainous regions themselves whereas the impact on surrounding low lying areas has received less attention here we develop a new spectral element mesh implementation to accommodate realistic topography as well as the complex shape of the taipei sedimentary basin which is located close to the central mountain range in northern taiwan spectral element numerical simulations indicate that high resolution topography can change peak ground velocity pgv values in mountainous areas by 50 compared to a half space response we further demonstrate that large scale topography can affect the propagation of seismic waves in nearby areas for example if a shallow earthquake occurs in the i lan region of taiwan the central mountain range will significantly scatter the surface waves and will in turn reduce the amplitude of ground motion in the taipei basin however as the hypocenter moves deeper topography scatters body waves which subsequently propagate as surface waves into the basin these waves continue to interact with the basin and the surrounding mountains finally resulting in complex amplification patterns in taipei city with an overall pgv increase of more than 50 for realistic subduction zone earthquake scenarios off the northeast coast of taiwan the effects of topography on ground motion in both the mountains and the taipei basin vary and depend on the rupture process the complex interactions that can occur between mountains and surrounding areas especially sedimentary basins illustrate the fact that topography should be taken into account when assessing seismic hazard

application of waveform tomography to a crooked line 2d land seismic data set abstractonshore hydrocarbon exploration in the back arc region of japan suffers from seismic imaging challenges seismic data are typically acquired in a difficult environment along a crooked line over a rough surface topography underlain by severe near surface weathering layers the area is geologically complex and prestack depth processing is desirable however the data quality is suboptimal at near offsets and it hinders the migration velocity analysis required for depth processing thus a geologic interpretation needs to rely on time processing results nevertheless some data sets are rich in low frequency components and contain clear refracted and wide angle reflected waves both of which are favorable conditions for the application of waveform tomography we have used one such data set and we determined the applicability of waveform tomography to estimate the p wave velocity distribution to mitigate difficulties in the data we carefully optimized waveform tomography strategies and diligentl

2 d multiparameter viscoelastic shallow seismic full waveform inversion reconstruction tests and first field data application 2d full waveform inversion fwi of shallow seismic wavefields has recently become a novel way to reconstruct s wave velocity models of the shallow subsurface with high vertical and lateral resolution in most applications seismic wave attenuation is ignored or considered as a passive modelling parameter only in this study we explore the feasibility and performance of multi parameter viscoelastic 2d fwi in which seismic velocities and attenuation of p and s waves respectively and mass density are inverted simultaneously synthetic reconstruction experiments reveal that multiple crosstalks between all viscoelastic material parameters may occur the reconstruction of s wave velocity is always robust and of high quality the parameters p wave velocity and density exhibit weaker sensitivity and can be reconstructed more reliably by multi parameter viscoelastic fwi anomalies in s wave attenuation can be recovered but with limited resolution in a field data application a small scale refilled trench is nicely delineated as a low p and s wave velocity anomaly the reconstruction of p wave velocity is improved by the simultaneous inversion of attenuation the reconstructed s wave attenuation reveals higher attenuation in the shallow weathering zone and weaker attenuation below the variations in the reconstructed p and s wave velocity models are consistent with the reflectivity observed in a gpr profile

multiscale imaging of complex structures from multifold wide aperture seismic data by frequency domain full waveform tomography application to a thrust belt summary an application of full waveform tomography to dense onshore wide aperture seismic data recorded in a complex geological setting thrust belt is presented the waveform modelling and tomography are implemented in the frequency domain the modelling part is solved with a finite difference method applied to the visco acoustic wave equation the inversion is based on a local gradient method only the p wave velocity is involved in the inversion the inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies this defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images the linearized waveform tomography requires an accurate starting velocity model that has been developed by first arrival traveltime tomography after specific pre processing of the data 16 frequency components ranging between 5 4 and 20 hz were inverted ten iterations were computed per frequency component leading to 160 tomographic models the waveform tomography has successfully imaged southwest dipping structures previously identified from other geophysical data as being associated with high resistivity bodies the relevance of the tomographic images is locally demonstrated by comparison of a velocity depth function extracted from the waveform tomography models with a coincident vertical seismic profiling vsp log available on the profile moreover comparison between observed and synthetic seismograms computed in the starting traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide angle reflections from southwest dipping geological structures this study demonstrates that the combination of first arrival traveltime and frequency domain full waveform tomographies applied to dense wide aperture seismic data is a promising approach to quantitative imaging of complex geological structures indeed wide aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography this is critical because the building of the macromodel remains an open question when only near vertical reflection data are considered

160 ma of magmatic hydrothermal and metamorphic activity in the gallivare area re os dating of molybdenite and u pb dating of titanite from the aitik cu au ag deposit northern sweden host rocks to the aitik cu au ag deposit in northern sweden are strongly altered and deformed early proterozoic mica amphibole schists and gneisses the deposit is characterised by numerous mineralisation styles vein and alteration types four samples were selected for re os molybdenite dating and 12 samples for u pb titanite dating in order to elucidate the magmatic hydrothermal and metamorphic history following primary ore deposition in the aitik cu au ag deposit samples represent dyke vein and alteration assemblages from the ore zone hanging wall and footwall to the deposit re os dating of molybdenite from deformed barite and quartz veins yielded ages of 1 876 10 ma and 1 848 8 ma respectively a deformed pegmatite dyke yielded a re os age of 1 848 6 ma and an undeformed pegmatite dyke an age of 1 728 7 ma u pb dating of titanite from a diversity of alteration mineral associations defines a range in ages between 1 750 and 1 805 ma with a peak at ca 1 780 ma the ages obtained together with previous data bracket a 160 ma 1 890 1 730 ma time span encompassing several generations of magmatism prograde to peak metamorphism and post peak cooling events resulting in the redistribution and addition of metals to the deposit this multi stage evolution of the aitik ore body suggests that the deposit was affected by several thermal events that ultimately produced a complex ore body the re os and u pb ages correlate well with published regional re os and u pb age clusters which have been tied to major magmatic hydrothermal and metamorphic events primary ore deposition at ca 1 890 ma in connection with intrusion of haparanda granitoids was followed by at least four subsequent episodes of metamorphism and magmatism early metamorphism at 1 888 1 872 ma overlapping with haparanda 1 890 1 880 ma and perthite monzonite 1 880 1 870 ma magmatism clearly affected the aitik area as well as late metamorphism and lina magmatism at 1 810 1 774 ma and tib1 magmatism at 1 800 ma the 1 848 ma re os ages obtained from molybdenite in a quartz vein and pegmatite dyke suggests that the 1 850 ma magmatism recorded in parts of northern norrbotten also affected the aitik area

two dimensional shallow soil profiling using time domain waveform inversion near surface characterization has now gained significance among exploration geophysicists and many methods are being proposed to retrieve the 2d structures of shallow soils because most of these methods are based on the modal inversion of the surface waves they can only be applied to laterally homogeneous or smoothly heterogeneous soil models we have developed a time domain waveform inversion method for 2d near surface exploration that offers an alternative approach to existing surfacewave techniques for layered soils with a flat surface our method directly fits the input rayleigh waveforms to retrieve the 2d soil structure without need of any modal identification allowing the inversion of soil models that can be challenging with modal inversion based approaches in our method the forward problem formulated in the time domain is based on a 2 5d staggered grid finite difference scheme to simulate the p sv wavefield soil modeling was achieved by dividing soil layers into specific number of blocks with discontinuous interfaces the inversion strategy depends on attributing suitable values for the interface depth and s wavevelocity for each block to reconstruct a numerical soil model that fit the input waveforms because we cannot know the source signature during data acquisition source deconvolution by a reference station is applied to observed and calculated waveforms to make a waveform inversion free of the source signature numerical experiments revealed that our method was able to sufficiently reconstruct soil structures with strong lateral velocity gradient or soils with a blind layer in noisy environments using a single source and reasonable number of receivers we also applied this method to real waveform data and we succeeded in obtaining good correlation between the inverted 2d soil model and the existing borehole data

oldest volcanic hosted submarine iron ores in south china evidence from zircon u pb geochronology and geochemistry of the paleoproterozoic dahongshan iron deposit abstract the dahongshan iron deposit is hosted in the paleoproterozoic submarine metavolcanic rocks of the dahongshan group in the yangtze block south china la icp ms dating of hydrothermal zircon grains from the genetically associated albitite and dolomite albitite show ca 2008 ma ages that are consistent with the zircon ages from the host metavolcanic rocks ca 2012 ma and postdated the post ore diabase dike ca 1724 ma marking the dahongshan iron deposit as the oldest submarine volcanic hosted deposit so far as known the ore hosting metavolcanic rocks in the dahongshan deposit have low ni 9 1 77 4 ppm cr 1 0 63 0 ppm and co contents 5 6 62 9 ppm suggesting the fractionation of olivine clinopyroxene and plagioclase within the magma chamber the major and trace element features of the alkaline to tholeiitic metavolcanic rocks are consistent with high degree partial melting of the mantle wedge metasomatized by melts enriched in high field strength elements hfses which were derived from the subducted slab in volcanic arc setting based on an evaluation of the morphology of orebody ore fabrics petrology and melt fluid inclusions as well as the geochemical characteristics of the major ore mineral magnetite we correlate the iron mineralization in the dahongshan deposit with hydrothermal process induced by the high temperature high salinity and fe rich brines derived through magmatic exsolution the similar characteristic of ce and eu anomalies of the dahongshan iron deposit and banded iron formations bifs suggest that the dahongshan deposit was formed in reducing environment although the two types of iron ores were generated through distinct processes with hydrothermal processes dominating for the submarine volcanic hosted iron deposits whereas the bifs were formed through chemical precipitation

waveform tomography at a groundwater contamination site vsp surface data set application of 2d frequency domain waveform tomography to a data set from a high resolution vertical seismic profiling vsp experiment at a groundwater contamination site in hill air force base hafb utah reveals a surprisingly complicated shallow substructure with a resolution of approximately 1 5 m variance in the waveform misfit function is reduced 69 4 by using an initial velocity model from first arrival traveltime tomography the waveform tomography model suggests 1 a low velocity layer at 1 to 4 m depth 2 a high vertical velocity gradient of 80 m s m on average and 3 severe lateral variations velocity contrasts as large as about 200 m s occur in a distance as short as 1 5 m the model is well correlated with lithologic logs and is interpreted geologically a q value of 20 is estimated for the target area the extreme lateral and vertical variations of the subsurface compromise many standard seismic processing methods

new constraints on the timing of host rock emplacement hydrothermal alteration and iron oxide apatite mineralization in the kiruna district norrbotten sweden high spatial resolution zircon u pb geochronological data obtained directly on the kiirunavaara iron oxide apatite ioa deposit related orebodies and host rocks provide new constraints on the timing of mineralization in these deposits these data raise new arguments in the debate of a magmatic versus hydrothermal metasomatic genesis of these major 2 500 mt 30 70 wt fe paleoproterozoic deposits the main orebody at kiirunavaara contains ti poor magnetite and minor 0 05 5 wt p apatite located between a trachyandesite footwall and a rhyodacite hanging wall which also hosts smaller orebodies nukutus rektorn and tuolluvaara the pervasive na and k metasomatism in the host rock is documented by whole rock geochemical data and cathodoluminescence cl microscopy zircon u pb data for the metavolcanic rocks in the footwall and hanging wall cluster between 1884 4 and 1880 3 ma in the footwall a syenite aplite system yields ages of 1880 7 and 1881 4 ma a granite pluton exposed underground has an age of 1874 4 ma zircons in two ore samples never directly dated before this study yield ages of 1877 4 and 1874 7 ma brecciation at the contacts between the ore and host rocks the tight age at ca 1880 ma for most volcanic and plutonic rocks in the footwall and hanging wall and the marginally younger age for ore at ca 1877 to 74 ma matching the age of the spatially related granite pluton suggest a magmatic hydrothermal emplacement model for the kiruna area ioa ores

low rhenium molybdenite by metamorphism in northern sweden recognition genesis and global implications abstract re os dating of molybdenite is an accurate means to date intrusions and intrusion related ore deposits using the model age or isochron approach but molybdenite has a new niche in the greenschist to granulite facies metamorphic environment re os ages for metamorphic molybdenite may be used to construct regional metamorphic histories age significance and accuracy are established by analyzing multiple molybdenite separates extracted from single petrographically characterized molybdenite occurrences in this study twelve geologically distinct molybdenite bearing samples from two small mo districts in northern sweden trace a 150 m y paleoproterozoic svecofennian metamorphic history from 1900 to 1750 ma these data reveal a little known widespread and protracted late svecofennian anatexis in northern sweden the kataberget mo cu f deposit is located in the moskosel granite batholith north of the economically renown skellefte district four different molybdenite samples from outcrop at kataberget indicate an intrusion age of 1895 6 ma with the formation of later pegmatite aplite at 1875 6 ma the allebuoda bjorntjarn and munka mo w deposits in the rappen district are represented by three outcrop and five drill core samples of molybdenite bearing aplite pegmatite granite these two deposits were previously described as intrusion related climax type mo mineralization re os ages for molybdenites from these deposits range from 1865 to 1750 ma and significantly re concentrations are markedly low extending to the sub ppm level age agreement within the deposits is conspicuously lacking whereas with one exception age agreement within any single sample geologic occurrence as established by analysis of additional molybdenite separates is very good these data together with fundamental geologic observations discussed in this paper suggest that mo w mineralization in northern sweden is not intrusion related but the local product of episodic melting of archean paleoproterozoic supracrustal gneisses related to the svecofennian orogeny petrographic traverses across the boundary between widespread foliation parallel units of aplitic to pegmatitic pink granite and hosting biotite gneiss directly capture the process of ore formation dehydration breakdown of zircon rich biotite aligned with the foliation in the gneiss is accompanied by formation of new pristine post deformational biotite plus sulfides oxides hydrothermal zircon and fluorite all associated with microcline dominant leucosomes this process has profound implication for the traditional leucogranite intrusion related genesis attributed to the broad classification of mo w sn base and precious metal mineralization e g south mountain batholith nova scotia okiep namaqualand south africa mactung yukon pogo liese tintina alaska carajas and goias rio tocantins brazil new england batholith nsw australia bergslagen sweden nevoria western australia alpeinerscharte austria erzgebirge germany sardinia corsica batholith in addition to biotite metallogenic contributions e g mo w sn u bi cu pb zn fe ni co au ag te as sb ree in various combinations may also be controlled by breakdown of amphibole in effect the trace element composition of dehydrating or recrystallizing components in a gneissic rock essentially defines the local and district metallogenic suite in the absence of focusing structures e g shear zones sheeted vein development this process will generally form small and disconnected subeconomic deposits with erratic and unpredictable grades low re content in associated molybdenite is a key indicator for a subeconomic origin by local melting of biotite gneiss mo w or muscovite schist sn w

timing of plutonism in the gallivare area implications for proterozoic crustal development in the northern norrbotten ore district sweden zircon ion probe secondary ion mass spectrometry or sims data from a set of intrusive rocks emplaced in the vicinity of major ore bodies as well as from large igneous intrusions in the gallivare

comparing mineral magnetic properties of sediments in two reservoirs in strongly and mildly eroded regions on the guizhou plateau southwest china a tool for inferring differences in sediment sources and soil erosion shibanqiao reservoir 0 24 km 2 and xiaohe reservoir 0 28 km 2 have catchments of 6 00 km 2 and 22 69 km 2 respectively they essentially represent strongly eroded shibanqiao and mildly eroded xiaohe regions in guizhou plateau southwestern china sediment cores were retrieved from the two reservoirs and soils were also sampled from their catchments mineral magnetic measurements were performed on the sediments and soils and the particle size analysis of selected sediment cores and soil profiles were also made sirm versus chi if was used to compare sediment and soil samples in addition correlations between percentages of different particle size fractions and magnetic parameters ratios of sediment samples were also checked these results revealed differences in sediment sources and soil erosion in these two representative catchments the sediments in shibanqiao reservoir are derived from both the topsoil and subsoil when erosion is relatively weak it is limited to the topsoil and preferentially transports the relatively finer magnetic grains into the reservoir which may imply rain splash and or sheet erosion in this relatively steep catchment stronger erosional forces are capable of not only moving relatively coarser ferrimagnetic grains from the topsoil but also incising the subsoil and moving anti ferromagnetic minerals into the reservoir which seems to hint at not only sheet wash but also rill and gully erosion as there are no stable streams nor channel networks developed in this mountainous catchment contributions from river bank erosion to sediment yield are almost negligible the sediments in xiaohe reservoir which has a lower relief are predominately derived from topsoil erosion here erosion is concentrated to the topsoil and preferentially transports the relatively fine magnetic grains into the reservoir when erosional forces are weak however even when erosional forces increase in this relatively flat catchment erosion is still restricted to the topsoil thus relatively coarser ferrimagnetic grains from the topsoil are transported to the reservoir but the subsoil remains undisturbed and there are no significant changes in the proportion of anti ferromagnetic minerals in the sediments consequently only sheet washing occurs even when erosion is intensifying in this hilly plain catchment in general the more effective erosion in the shibanqiao catchment is probably due to its steeper topography than xiaohe catchment although higher and more seasonal rainfalls and lower percentages of woodlands may also contribute to the differences in susceptibility to erosional forces c 2011 elsevier b v all rights reserved less

application of a complete workflow for 2d elastic full waveform inversion to recorded shallow seismic rayleigh waves abstractthe s wave velocity of the shallow subsurface can be inferred from shallow seismic rayleigh waves traditionally the dispersion curves of the rayleigh waves are inverted to obtain the local s wave velocity as a function of depth two dimensional elastic full waveform inversion fwi has the potential to also infer lateral variations we have developed a novel workflow for the application of 2d elastic fwi to recorded surface waves during the preprocessing we apply a line source simulation spreading correction and perform an a priori estimation of the attenuation of waves the iterative multiscale 2d elastic fwi workflow consists of the preconditioning of the gradients in the vicinity of the sources and a source wavelet correction the misfit is defined by the least squares norm of normalized wavefields we apply our workflow to a field data set that has been acquired on a predominantly depth dependent velocity structure and we compare the reconstructed s wave velocity model with the result

early arrival waveform tomography on near surface refraction data we develop a waveform tomography method for estimating the velocity distribution that minimizes the waveform misfit between the predicted and observed early arrivals in space time seismograms by fitting the waveforms of early arrivals early arrival waveform tomographyewt naturally takes into account more general wave propagation effects compared to the high frequency method of traveltime tomography meaning that ewt can estimate a wider range of slowness wavenumbers another benefit of ewt is more reliable convergence compared to full waveform tomography because an early arrival misfit function contains fewer local minima synthetic test results verify that the waveform tomogram is much more accurate than the traveltime tomogram and that this algorithm has good convergence properties for marine data from the gulf of mexico the statics problem caused by shallow gassy muds was attacked by using ewt to obtain a more accurate velocity model using the waveform tomogram to correct for statics the stacked section was significantly improved compared to using the normal moveout nmo velocity and moderately improved compared to using the traveltime tomogram inverting high resolution land data from mapleton utah showed an ewt velocity tomogram that was more consistent with the ground truth trench log than the traveltime tomogram our results suggest that ewt can provide supplemental shorter wavelength information compared to the traveltime tomogram for both shallow and moderately deep seismic data

detecting near surface objects with seismic waveform tomography three shallow high velocity rubble filled targets are imaged using waveform tomography in an engineering scale clay embankment at seven sisters falls manitoba canada to locate targets buried at approximately 7 m as a blind test of geophysical imaging methods previous studies use near offset reflection methods to image the targets however this test uses waveform tomography of the long offset refracted arrivals to image p velocity and seismic attenuation the targets are invisible to standard traveltime tomography using weight drop data with frequencies of 20 150 hz the subwavelength targets are resolved in the velocity images and complementary images of seismic q are produced the interpreted target locations are consistent with limited survey information from the embankment construction multiple quality control efforts paired with a very good fit between model and observed data indicate the reliability of the results

alteration paragenesis and mineral chemistry of the tjarrojakka apatite iron and cu au occurrences kiruna area northern sweden the northern norrbotten area in northern sweden is an important mining district and hosts several deposits of fe oxide cu au type one of the best examples of spatially and possibly genetically related apatite iron and copper gold deposits in the region is at tjarrojakka 50 km wsw of kiruna the deposits are hosted by strongly sheared and metamorphosed intermediate volcanic rocks and dolerites and show a structural control the tjarrojakka iron deposit is a typical apatite iron ore of kiruna type and the tjarrojakka copper occurrence shows the same characteristics as most other epigenetic deposits in norrbotten the host rock has been affected by strong albite and k feldspar alteration related to mineralisation resulting in an enrichment of na k and ba fe and v were depleted in the altered zones and added in mineralised samples ree were enriched in the system with the greatest addition related to mineralisation y was also mobile associated with albite alteration and copper mineralisation the tjarrojakka iron and copper deposits show comparable hydrothermal alteration minerals and paragenesis which might be a product of common host rock and similarities in ore fluid composition or overprinting by successive alteration stages mineralogy and mineral chemistry of the alteration minerals apatite scapolite feldspars amphiboles and biotite indicate a higher salinity and ba k ratio in the fluid related to the alterations in the apatite iron occurrence than in the copper deposit where the minerals are enriched in f and s the presence of hematite barite and in so4 in scapolite suggests more oxidising rich conditions during the emplacement of the tjarrojakka cu deposit from existing data it might be suggested that one evolving system created the two occurrences with the copper mineralisation representing a slightly later product

seismic waveform inversion in the frequency domain part 2 fault delineation in sediments using crosshole data a crosshole experiment was carried out in a layered sedimentary environment in which a normal fault is known to cut through the section initial traveltime inversions produced stable but low resolution images from which the fault could be only vaguely inferred to image the fault wavefield inversion was used to produce a velocity model consistent with the detailed phase and amplitude of the data at a number of frequencies our wavefield inversion scheme uses a classical descent type algorithm for decreasing the data misfit by iteratively computing the gradient of this misfit by repeated forward and backward propagations our propagator is a full wave equation frequency domain acoustic finite difference method the use of the frequency space domain yields computational advantages for multisource data and allows an easy incorporation of viscous effects by running wavefield inversion on the field data a quantitative velocity image was produced that yielded a significantly improved image of the fault when compared with the original traveltime inversions because the original field data were noisy and contained a high degree of multiple scattering from the layering of the sediments the transmitted arrivals were selectively windowed to enhance the image the sediments at the site were strongly attenuating we therefore used a viscoacoustic model during the modeling and the inversion that correctly simulated the observed decrease in amplitude with increasing frequency and source receiver offset furthermore since the traveltime inversion indicated a high degree of anisotropy at the site a fixed homogeneous level of anisotropy was used during the inversion tests at varying levels of anisotropy confirmed the improvement in image quality and in data fit when anisotropy was incorporated the final image was verified by examining the distribution of the residuals in the frequency domain by comparing time domain modeled wavefields with the observed data and by direct comparison with borehole logs

waveform tomography at a groundwater contamination site surface reflection data wehaveappliedacoustic waveformtomographyto452d seismic profiles to image the 3d geometry of a buried paleochannel at a groundwater contamination site at hill air force base in utah the paleochannel which is incised into an alluvium covered clay aquitard acts as a trap for dense nonaqueous phase liquids dnapls that contaminate the shallowest groundwater system in the study area the 2d profiles were extracted from a 3d surface reflection data set first arrival traveltime tomography provided initial velocity models for the waveform tomography we inverted for six frequency components in the band 30 90 hz of the direct and refracted waves to produce 45 2d velocity models the flanks and bottom of a channel with a maximum depth of about 15 m were well modeled in most of the 45 parallel 2d slices whichallowedustoconstructa3dimageofthechannel by combining and interpolating between the 45 image slices the 3d model of the channel will be useful for siting extraction wells within the site remediation program the alluvium that fills the channel showed marked vertical and lateral velocity heterogeneity traveltime tomography and waveform tomography can be complementary approaches used together they can provide high resolution images of complicatedshallowstructures

comparison of seismic attenuation models using zero offset vertical seismic profiling vsp data for seismic frequencies it is common to use an empirical equation to model attenuation usually the attenuation coefficient is modeled with linear frequency dependence a model referred to as the kolsky futterman model other models have been suggested in the geophysical literature we compare eight of these models on a zero offset vertical seismic profiling vsp data set the kolsky futterman the power law the kjartansson the muller the azimi second the azimi third the cole cole and the standard linear solid sls models for three separate depth zones we estimate velocities and q values for all eight models a least squares model fitting algorithm gives almost the same normalized misfit for all models thus none of the models can be preferred or rejected based on the given data set slightly better overall results are obtained for the kolsky futterman model for one depth zone the sls model gave the best result

individual and joint 2 d elastic full waveform inversion of rayleigh and love waves we investigate the performance of the individual 2 d elastic full waveform inversion fwi of rayleigh and love waves as well as the feasibility of a simultaneous joint fwi of both wave types the fwi of surface waves can provide a valuable contribution to near surface investigations since they are mainly sensitive to the s wave velocity and hold a high signal to noise ratio in synthetic reconstruction tests we compare the performance of the individual wave type inversions and explore the benefits of a simultaneous joint inversion in these tests both individual wave type inversions perform similarly well given that the initial p wave velocity model is accurate enough in this case the joint fwi further improves the result for an inaccurate initial p wave velocity model we observe artifacts in the results of the rayleigh wave fwi and the joint fwi subsequently we recorded a near surface field dataset to verify the results by a realistic example in the field data application the love wave fwi is superior to the rayleigh wave fwi possibly due to the initial p wave velocity model also in this case the joint fwi further improves the inversion result

laser ablation icp ms titanite u th pb dating of hydrothermal ore deposits a case study of the tonglushan cu fe au skarn deposit se hubei province china abstract titanite from the tonglushan cu fe au skarn deposit daye district eastern china has been successfully dated by laser ablation inductively coupled plasma mass spectrometry la icp ms hydrothermal titanite from both skarn ores and calcite veins cutting the ore bodies are characterized by having much lower ree and th u and lu hf ratios compared to their magmatic equivalents from the ore related yangxin quartz diorite intrusion and a late stage albitite dike titanite from the yangxin quartz diorite and an albitite dike which intrudes both the quartz diorite intrusion and ore bodies yield weighted mean 206pb 238u ages of 136 0 1 5 ma and 120 6 2 3 ma 2 respectively in agreement within analytical uncertainty to their 208pb 232th ages in situ analysis of epidote enclosed hydrothermal titanite in thin sections of a skarn ore sample yields a mean 206pb 238u age of 135 9 1 3 ma and 208pb 232th age of 138 2 4 5 ma whereas titanite in calcite from a calcite dominated vein cross cutting the skarn ore body has consistent 206pb 238u and 208pb 232th ages of ca 121 ma the data thus reveal two independent hydrothermal events the earlier event was responsible for the known cu fe au skarn mineralization at tonglushan and throughout the daye district and was caused by coeval magmatism that has resulted in the emplacement of the yangxin quartz diorite the later event previously unrecognized was associated with a second magmatic pulse as represented by the albitite dikes and provides potential for discovering new mineral deposits at tonglushan and possibly over the daye district this study represents the first direct dating of skarn deposits using titanite u th pb geochronometer and signifies the utilization of titanite for precise dating of hydrothermal ore formation

sinkhole detection using 2d full seismic waveform tomography we have developed an application of 2d time domain waveform tomography for detection of embedded sinkholes and anomalies the measured seismic surface wavefields were inverted using a full waveform inversion fwi technique based on a finite difference solution of 2d elastic wave equations and the gauss newton inversion method the key advantage of this approach is the ability to generate all possible wave propagation modes of seismic wavefields body waves and rayleigh waves that are then compared with measured data to infer complex subsurface properties the pressure wave p wave and shear wave s wave velocities are inverted independently and simultaneously the fwi was applied to one synthetic and two real experimental data sets the inversion results of synthetic data showed the useful capability of the waveform analysis in identifying an embedded void the inversion results of real data sets showed that the waveform analysis was able to delineate 1 an embedded concrete culvert and 2 a complex profile with an embedded void and highly variable bedrock laterally and vertically an independent invasive test standard penetration test was also conducted to verify the seismic test results

direct dating of fe oxide cu au mineralization by u pb zircon geochronology we present results for direct dating of fe oxide cu au iron oxide copper gold iocg mineralization by u pb zircon geochronology constraining the timing of mineralization has important geodynamic implications for the processes involved in the genesis of these types of deposits and the tectonic evolution of rocks associated with these deposits hydrothermal zircon crystals were separated from four iocg type ore deposits associated with the lyon mountain granite in the adirondack mountains united states zircon grains from these low ti magnetite deposits reveal at least two periods of mineralization one episode ca 1039 ma and a second between ca 1015 and 1000 ma previous age determinations of these deposits were constrained by the age of the altered host granitoids and the assumption that fe mineralization was directly related to pluton emplacement zircon crystals extracted from the ore yield ages that show that ore mineralization was episodic and younger than pluton emplacement

geochronology of the kiruna iron ores and hydrothermal alterations the magnetite apatite iron ores at kiruna are hosted in a suite of alkaline volcanic and subvolcanic rocks that was formed in a short time interval of about 20 m y between 1900 and 1880 ma u pb dating of titanite from magnetite titanite dikes in the footwall of the luossavaara orebody indicates that the age of the magnetite apatite ores is 1888 or 6 ma titanite actinolite calcite assemblages in amygdules are related to the hydrothermal and metasomatic alteration of the wall rocks and the ore the u pb titanite age of the amygdule fill is 1876 or 9 ma the geographic distribution of the alteration suggests that it is not related to the formation of the iron ores the youngest major magmatic units in the kiruna area are 1792 or 4 ma syenites that intruded the supracrustal rocks the kiruna area underwent a weak metamorphic overprint during the caledonian orogeny our data are inconsistent with a hydrothermal event at ca 1 5 ga as has been suggested earlier

full waveform tomography for lithospheric imaging results from a blind test in a realistic crustal model summary a comprehensive validation of 2 d frequency domain acoustic wave equation tomography was undertaken in a blind test using third party realistic elastic wave equation data the synthetic 2 d wide angle seismic data were provided prior to a recent workshop on the methods of controlled source seismology the true model was not revealed to the authors until after the presentation of our waveform tomography results the original model was specified on a detailed grid with variable p wave velocity s wave velocity density and viscoelastic q factor structure designed to simulate a section of continental crust 250 km long and 40 km deep synthetic vertical and horizontal component data were available for 51 shot locations spaced every 5 km recorded at 2779 receivers spaced every 90 m evenly spread along the surface of the model the data contained energy from 0 2 to 15 hz waveform tomography a combination of traveltime tomography and 2 d waveform inversion of the early arrivals of the seismic waveforms was used to recover crustal p velocity structure from the vertical component data using data from 51 sources 1390 receivers and frequencies between 0 8 and 7 0 hz the waveform tomography result contained apparent structure at wavelength scale resolution that was not evident on the traveltime tomography result the predicted acoustic waveforms in the final result matched the original elastic data to a high degree of accuracy during the workshop the exact model was revealed over much of the model the waveform tomography results provided a good correspondence with the true model from large to intermediate wavelength scales with a resolution limit on the order of 1 km a significant near surface low velocity zone invisible to traveltime methods was correctly recovered the results also provided a high resolution image of the complex structure of the entire crust and the depth and nature of the crust mantle transition some inaccuracies were observed near the edges of the images due to the limited ray coverage inherent to the footprint of the survey geometry several aspects of the waveform tomography strategy were critical to the success of the acoustic method with realistic synthetic viscoelastic data i the accuracy of the starting model from traveltime tomography ii implementation in the frequency domain iii the use of complex valued frequencies to effect time damping of the data residuals iv the selection of a suitable subset of data and data frequencies v progressive inversion of low to high frequency components of the data vi initial pre inversion matching of the amplitudes between observed and modelled data and vii sufficient preconditioning of both the data and the update images combined these strategies were effectively equivalent to a multiscale approach that mitigated the non linearity of the seismic inverse problem during the inversion we carried out repeated forward modelling to ensure our modelled waveforms matched the observed data as closely as possible in both frequency and time domains the synthetic data set used in this paper provides a benchmark for future testing of modelling inversion and imaging algorithms for wide angle lithospheric imaging

estimation of multivalued arrivals in 3d models using wavefront construction part i1 a new 3d wavefield modelling approach based on dynamic ray tracing is presented this approach is called wavefront construction and it can be used in 3d models with constant or smoothly varying material properties s and p velocity and density separated by smooth interfaces wavefronts consisting of rays arranged in a triangular network are propagated stepwise through the model at each time step the differences in a number of parameters are checked between each pair of rays on the wavefront new rays are interpolated whenever this difference between pairs of rays exceeds some predefined maximum value a controlled sampling of the wavefront at all time steps is thus obtained receivers are given multiple event values by interpolation when the wavefronts pass them the strength of the wavefront construction method is that it is robust and efficient

upb systematics of stilbite bearing low temperature mineral assemblages from the malmberget iron ore northern sweden minerals with a low thermal stability strongly constrain the history of cooling and later tectonic reworking of an area provided these minerals can be dated the possible use of stilbite a ca al silicate of the zeolite group for geochronologic studies was investigated open fractures in the palaeoproterozoic malmberget iron ore northern sweden contain low temperature mineral assemblages with various combinations of apatite stilbite calcite biotite and less commonly titanite and monazite two generations of fractures that are characterized by calcite and stilbite with distinctly radiogenic initial 87sr 86sr at ca 0 720 and ca 0 708 are dated at ca 1740 ma monazite and 1620 1613 ma titanite respectively apatite samples even those intimately intergrown with ca 1740 ma old monazite yield u pb ages at 1620 1600 ma which indicates that apatite apparently recrystallized and reset its u pb system older stilbite yields a secondary lead isochron at 1730 6 4 ma 2 which unequivocally demonstrates that the ambient temperature in the malmberget area from then on remained below the thermal stability of stilbite ca 150 c stilbite is a natural ion exchanger and its u pb systematics indicates recent mobility of uranium and lead however the 1730 6 4 ma 2 age demonstrates that some of the older stilbite was not disturbed during younger fracturing hydrothermally altered and secondary stilbite samples yield scattered lead arrays that correspond to secondary isochrons at ca 1650 1600 d4a which agrees with the u pb titanite and apatite ages thus in combination with other geochronometers the generally imprecise stilbite ages provide information on the cooling history of an area

metal source and tectonic setting of iron oxide copper gold iocg deposits evidence from an in situ nd isotope study of titanite from norrbotten sweden titanite occurs as a widespread accessory phase in mineralized zones and alteration associated with iron oxide copper gold iocg and iron oxide apatite ioa deposits of norrbotten county sweden and is a major host of the ree in these deposits in situ analyses of sm nd isotope ratios in titanites previously analysed for u pb geochronology and trace element composition confirms previous interpretations of grain scale isotopic heterogeneity initial nd isotope ratios expressed relative to chur range from 3 to 8 in ioa deposits from 1 to 9 in iocg deposits and from 2 to 4 in the most cu rich deformed iocg deposits of the nautanen deformation zone within individual ioa deposits at valkommen malmberget from 1 4 to 5 7 in grain cores and 7 2 to 8 2 in grain rims rim at gruvberget and from 3 0 to 6 0 in grain cores and from 5 8 to 7 1 in grain rims at luossavaara in iocg deposits at rakkurijarvi iocg dpeosits at nautanen from 1 3 to 2 3 these values are consistent with the derivation of the ree and potentially economically enriched metals from the local volcanic sequence either via granitic melts or directly by leaching by metasomatic fluids the most cu rich deposits reflect the involvement of more basic protoliths the age distribution of these deposits suggest ioa deposit formation during the collisional phase of the svecofennian orogeny 1 9 1 8 ga and iocg mineralization during this phase and during post orogenic collapse 1 8 1 7 ga whilst model ages indicate the ultimate enrichment of the continental crust in these metals during pre collisional extensional and subduction related basic magmatism these processes underscore the importance of continental cycles both in producing the preserved geological record of orogenic ore deposition and in the generation of fertile continental crust from which metals can be mobilised by subsequent events nd varies relative to chur from 3 1 to 4 0 nd varies from 6 1 to 7 1 and in deformed iocg dpeosits at nautanen from 1 3 to 2 3 these values are consistent with the derivation of the ree and potentially economically enriched metals from the local volcanic sequence either via granitic melts or directly by leaching by metasomatic fluids the most cu rich deposits reflect the involvement of more basic protoliths the age distribution of these deposits suggest ioa deposit formation during the collisional phase of the svecofennian orogeny 1 9 1 8 ga and iocg mineralization during this phase and during post orogenic collapse 1 8 1 7 ga whilst model ages indicate the ultimate enrichment of the continental crust in these metals during pre collisional extensional and subduction related basic magmatism these processes underscore the importance of continental cycles both in producing the preserved geological record of orogenic ore deposition and in the generation of fertile continental crust from which metals can be mobilised by subsequent events

seismic study of the low permeability volume in southern france karst systems locating groundwater in deep seated karst aquifers is inherently difficult with seismic methods we studied the upper epikarst and the underneath low permeability volume lpv of several karst systems located in the southern quercy and larzac regions of france and found that refraction tomography was effective only in the epikarst and not in the lpv we evaluated a 3d case study using a combination of surface records and downhole receivers to overcome this limitation this 3d approach unveiled a set of elongated furrows at the base of the epikarst and identified heterogeneities deep inside the lpv that may represent high permeability preferred pathways for water inside the karst to achieve the same result when no borehole was available we studied seismic amplitudes of the wavefield recognizing that wave induced fluid flow in low permeability carbonates is a driving mechanism of seismic attenuation we developed a workflow describing the heterogeneity of the lpv with spectral attributes derived from surface consistent decomposition principles and we validated its effectiveness at benchmark locations we applied this workflow to the 3d study and found a low amplitude signal area at depth we interpreted this anomaly as a water saturated body perched above the aquifer

improved amplitude preservation for prestack depth migration by inverse scattering theory a prestack reverse time migration image is not properly scaled with increasing depth the main reason for the image being unscaled is the geometric spreading of the wavefield arising during the back propagation of the measured data and the generation of the forward modelled wavefields this unscaled image can be enhanced by multiplying the inverse of the approximate hessian appearing in the gauss newton optimization technique however since the approximate hessian is usually too expensive to compute for the general geological model it can be used only for the simple background velocity model we show that the pseudo hessian matrix can be used as a substitute for the approximate hessian to enhance the faint images appearing at a later time in the 2d prestack reverse time migration sections we can construct the pseudo hessian matrix using the forward modelled wavefields which are used as virtual sources in the reverse time migration by exploiting the uncorrelated structure of the forward modelled wavefields and the impulse response function for the estimated diagonal of the approximate hessian although it is also impossible to calculate directly the inverse of the pseudo hessian when using the reciprocal of the pseudo hessian we can easily obtain the inverse of the pseudo hessian as examples supporting our assertion we present the results obtained by applying our method to 2d synthetic and real data collected on the korean continental shelf

mineral equilibria and zircon garnet and titanite u pb ages constraining the ptt path of granite related hydrothermal systems at the big bell gold deposit western australia the big bell deposit 75 t gold is located in a narrow spur of the meekatharra greenstone belt yilgarn craton western australia two ore bodies are located in a calcic potassic contact alteration zone overprinting lineated granodiorite dykes and amphibolite almandine cummingtonite hornblende skarn 1 3 g t au 1700 g t as 330 g t w and the muscovite microcline gneiss 3 5 g t au 580 g t sb 620 g t w of the main lode genetic models vary from pre to post metamorphic replacement hornblende plagioclase pairs in amphibolite constrain peak metamorphic temperature to 670 50 c in contrast garnet biotite thermometry provides estimates of 578 50 and 608 50 c for garnet cordierite biotite schist bordering the skarn and enveloping the main lode garnet cordierite and garnet hornblende pairs extend the range of fluid temperature to 540 65 c well below peak metamorphic temperature at 540 600 c the alteration assemblage andalusite sillimanite constrains pressure to 300 400 mpa corresponding to 11 14 km crustal depth published u pb ages indicate that metamorphism took place in the aureole of the southeast granodiorite tonalite batholith 2740 2700 ma followed by gold mineralization at 2662 5 ma and by the emplacement of biotite granite and sn ta nb granite pegmatite dykes at 2625 2610 ma amphibolite xenoliths in granite northwest of the deposit record the lowest temperature 628 50 c suggesting it lacks a metamorphic aureole the rare metal dykes are spatially associated with epidote albite and andradite diopside skarns 1 5 g t au mined where enriched in the weathered zone we analysed hydrothermal zircon intergrown with andradite concordant u pb ages of 2612 7 and 2609 10 ma confirm the presence of a second granite related system the zircons display oscillatory zoning and have low th u ratios 0 05 0 08 low th titanite from an albite granite dyke has a concordant but reset u pb age of 2577 7 ma

apatite monazite relations in the kiirunavaara magnetite apatite ore northern sweden the magnetite apatite ores in the kiruna area northern sweden are generally considered to be of magmatic origin formed in a subvolcanic volcanic environment during the early proterozoic they are thought to have crystallised from volatile rich iron oxide magmas derived by immiscibility in calc alkaline to slightly alkaline parental magmas three major morphological types of the magnetite apatite ore primary brecciated and banded have been investigated for textural relations and mineral chemistry using transmitted light back scattered electron imaging bse electron microprobe analysis empa and laser ablation inductively coupled plasma mass spectrometry la icpms in all three types th and u poor monazite is present as small inclusions in the apatite larger up to 150 m recrystallised monazite grains both along apatite grain boundaries and intergrown with magnetite and silicate minerals are present in the brecciated and banded samples primary apatite grains without monazite inclusions are generally enriched in light rare earth elements lrees together with na and si petrological and mineralogical evidence suggest that the kiruna magnetite apatite ore experienced successive stages of fluid rock interaction the first stage occurred under high temperature conditions 700 800 c shortly after emplacement and crystallisation of the ore magmas and involved concentrated probably cl dominated brines expelled from the magma this fluid is held to be responsible for the nucleation of the numerous small monazite inclusions within the apatite due to high temperature leaching of na and si while the lrees were concentrated in the monazite the large monazite grains in the brecciated and banded samples are proposed to be the product of recrystallisation from the much smaller monazite inclusions during greenschist facies metamorphism t 300 400 c fluids from the surrounding country rock caused strong lree na si depletion along apatite grain boundaries and cracks in the apatite lrees were either redeposited as monazite grains along apatite grain boundaries or were flushed out of the ore this fluid interaction also introduced the silicate components responsible for the interstitial formation of allanite talc tremolite chlorite serpentine muscovite quartz and carbonates along apatite grain boundaries

the sources and evolution of mineralising fluids in iron oxide copper gold systems norrbotten sweden constraints from br cl ratios and stable cl isotopes of fluid inclusion leachates we have analysed the halogen concentrations and chlorine stable isotope composition of fluid inclusion leachates from three spatially associated fe oxide cu au mineralising systems in norrbotten sweden fluid inclusions in late stage veins in fe oxide apatite deposits contain saline brines and have a wide range of br cl molar ratios from 0 2 to 1 1 10 3 and 37cl values from 3 1 to 1 0 leachates from saline fluid inclusions from the greenstone and porphyry hosted cu au prospects have br cl ratios that range from 0 2 to 0 5 10 3 and 37cl values from 5 6 to 1 3 finally the cu au deposits hosted by the nautanen deformation zone ndz have br cl molar ratios from 0 4 to 1 1 10 3 and 37cl values that range from 2 4 to 0 5 although the bulk of the data fall within 0 0 5 the br cl ratios of leachates are consistent with the derivation of salinity from magmatic sources or from the dissolution of halite most of the isotopic data from the fe oxide apatite and greenstone deposits are consistent with a mantle derived source of the chlorine with the exception of the four samples with the most negative values the origin of the low 37cl values in these samples is unknown but we suggest that there may have been some modification of the cl isotope signature due to fractionation between the mineralising fluids and cl rich silicate assemblages found in the alteration haloes around the deposits if such a process has occurred then a modified crustal source of the chlorine for all the samples cannot be ruled out although the amount of fractionation necessary to generate the low 37cl values would be significantly larger the source of cl in the ndz deposits has a crustal signature which suggests the cl in this system may be derived from meta evaporites or from input from crustal melts such as granitic pegmatites of the lina suite