composition of iron oxides in archean and paleoproterozoic mafic ultramafic hosted ni cu pge deposits in northern fennoscandia application to mineral exploration using electron probe microanalyzer epma and laser ablation inductively coupled plasma mass spectrometry la icp ms we analyzed major and trace element compositions of iron oxides from ni cu pge sulfide deposits hosted by mafic ultramafic rocks in northern fennoscandia mostly focusing on finland the main research targets were the archean ruossakero ni cu deposit tulppio dunite and related ni pge mineralization hietaharju vaara and tainiovaara ni cu pge deposits and paleoproterozoic lomalampi pge ni cu deposit in addition some reference samples from the pechenga russia jinchuan china and kevitsa finland ni cu pge sulfide deposits and a barren komatiite sequence in the kovero area finland were studied magnetite and cr magnetite show a wide range of trace element compositions as a result of the variation of silicate and sulfide melt compositions and their post magmatic modification history most importantly the ni content in oxide shows a positive correlation with the ni tenor of the sulfide phase in equilibrium with magnetite regardless of whether the sulfide assemblage is magmatic or post magmatic in origin the massive sulfide samples contain an oxide phase varying in composition from cr magnetite to magnetite indicating that cr magnetite can crystallize directly from sulfide liquid the mg concentration of magnetites in massive sulfide samples is lowest among the samples analyzed and this can be regarded as a diagnostic feature of an oxide phase crystallized together with primitive fe rich mss monosulfide solid solution our results show that magnetite geochemistry plotted in appropriate discrimination diagrams together with petrographical observations could be used as an indicator of potential ni cu pge mineralization

resolving three dimensional surface displacements from insar measurements a review abstract one dimensional measurement along the line of sight los direction has greatly limited the capability of insar technique in the investigation of surface displacements and their dynamics in recent years great efforts have been made to resolve complete three dimensional 3 d displacements from insar measurements this contribution is intended to provide a systematic review of the progress achieved in this field based on an analysis of the insar los measurements we first cover two commonly used techniques i e offset tracking and multi aperture insar mai with which the surface displacement in the azimuth direction can be measured together with the los displacement several methods for mapping 3 d displacements using insar measurements are subsequently presented and categorized into three groups i combination of multi pass los and azimuth measurements ii integration of insar and gps data and iii prior information assisted approaches the strengths and weaknesses of each method are analyzed to show the applicability of each method to specific 3 d displacement mapping cases in hope to provide a useful guidance in choosing a suitable approach accordingly finally suggestions for resolving the challenging issues and outlook of future research are given

anomalous sulfur poor platinum group element mineralization in komatiitic cumulates mount clifford western australia an unusual occurrence of sulfur poor platinum group element pge mineralization has been discovered at mount clifford in the agnew wiluna belt western australia within the lower part of a 1 000 m thick komatiitic dunite body the host body consists primarily of strongly serpentinized olivine adcumulates with accessory chromite high precision whole rock icp ms data show that the pge mineralization extends over tens of meters whereas the lateral extent is unknown palladium and pt abundances are closely associated with base metal sulfides but show offset distribution patterns with maximum concentrations associated with the relatively sulfide poor base of a disseminated sulfide bearing layer whole rock concentrations range up to 4 100 ppb pd and 920 ppb pt iridium rh and ru follow the trends in pd and pt but are strongly depleted ir 0 4 ppb ru 0 5 ppb rh 0 1 ppb platinum group minerals pgm were located in essentially sulfide free serpentine 2 m below the peak in sulfide abundance and can be categorized into three groups pd antimonides pt dominated pgm and pt bearing ni antimonides the pge mineralization zone is underlain by an interval of strong ni depletion within olivine mesocumulates that is characterized by an unusual negative correlation between ni and the mg number of the rock this relationship is interpreted to be the result of an equilibration of olivine of variable forsterite content with a relatively large mass of magmatic sulfide however there is no direct evidence of this sulfide mass anywhere in the entire mount clifford dunite body the ni depletion is accompanied by strong depletion in ipge ir ru and rh the association of the pge zone with a reversal in the mg fe ratio of the host cumulates and a distinctive offset relationship of multiple pt pd and cu s peaks is suggestive of a primary magmatic origin however this is inconsistent with current models for offset reef pge concentrations which involve the onset of sulfide liquid saturation from a previously sulfur undersaturated pge undepleted magma the association of enriched pt and pd with highly depleted ni and ipge in immediately underlying cumulates conflicts with this model we suggest a combination of processes early sulfide segregation at low r values producing ni and ipge depleted olivine partial redissolution and removal of most of this sulfide component during a major replenishment event and subsequent overprint by a migrating pt pd cu rich fluid

interferometric daylight seismic imaging summary claerbout s daylight imaging concept is generalized to a theory of interferometric seismic imaging ii interferometric seismic imaging is defined to be any algorithm that inverts correlated seismic data for the reflectivity or source distribution as examples we show that ii can image reflectivity distributions by migrating ghost reflections in passive seismic data and generalizes the receiver function imaging method used by seismologists interferometric seismic imaging can also migrate free surface multiples in common depth point cdp data and image source distributions from passive seismic data both synthetic and field data examples are used to illustrate the different possibilities of ii the key advantage of ii is that it can image source locations or reflectivity distributions from passive seismic data where the source position or wavelet is unknown in some cases it can mitigate defocusing errors as a result of statics or an incorrect migration velocity the main drawback with ii is that severe migration artefacts can be created by partial focusing of virtual multiples

crystallization of sulfide liquids and the interpretation of ore composition we have been exploring ways to quantitatively assess the extent to which fractionation of sulfide melt has effected variations in composition within magmatic sulfide ore bodies our approach has been to determine by experiment the crystallization paths of sulfide liquids in temperature and composition dimensions in this paper the results of new major element partitioning experiments below 1050 c in the nickel free system are presented and summarized along with new and previous work in the fe ni cu s quaternary the partition coefficients d for cu between monosulfid solid solution mss and sulfide liquid in the ni free system dcu wt cu in mss wt cu in liquid cluster near 0 3 but decrease to nearly 0 1 for cu rich s poor liquids near 1000 c dni also declines with decreasing sulfur content of the liquid but increases with decreasing temperature preliminary data indicate that dni exceeds 1 0 in low ni liquids with greater than 16 wt cu at 1050 c the quality of available data on the

partition coefficients for ni cu pd pt rh and ir between monosulfide solid solution and sulfide liquid and the formation of compositionally zoned ni cu sulfide bodies by fractional crystallization of sulfide liquid many nickel copper sulfide orebodies contain cu and fe rich portions the fe rich ore is generally richer in os ir ru and rh and poorer in pt pd and au than the cu rich ore in komatiite hosted ores ni tends to be concentrated in the cu rich ore whereas in tholeiitic ores it tends to be concentrated in the fe rich ore the origin of this zonation could be due to crystal fractionation of fe rich monosulfide solid solution from a sulfide liquid the crystal fractionation would produce an fe rich cumulate enriched in os ir ru and rh and a fractionated liquid enriched in cu pt pd and au this model can be tested for zoned orebodies by applying experimentally determined partition coefficients for the metals into monosulfide solid solution we have compared our experimental results with those of other workers to show that the partition coefficients are strongly influenced by the sulfur content of the system there is a positive correlation between the partition coefficients and sulfur content of th

non chondritic platinum group element ratios in the earth s mantle the earth s upper mantle has an overabundance of highly siderophile elements platinum group elements gold and rhenium relative to what would be expected from equilibrium with the metallic core1 3 this excess is now widely believed to have been introduced as a late veneer by meteorite bombardment during early earth history but after separation of the core4 here we report high precision analyses of platinum group elements pges from fertile upper mantle iherzolites which show variations in relative abundances that exceed those in the chondritic meteorites that are thought to have furnished the late veneer5 in particular the pd ir ratio at about 1 76 is significantly greater than that of known chondritic meteorites6 our results combined with previous indications of both non chondritic and nearly chondritic pge ratios in the few other fertile mantle iherzolites that have been analysed2 3 7 11 strongly suggest that the mantle is heterogeneous in its pge content on scales of 100 kilometres if the observed pge ratios can be reconciled with a plausible meteoritic source the observed heterogeneity may reflect an original spatial variation in the late veneer otherwise an additional fractionation mechanism seems to be required

mapping ground surface deformation using temporarily coherent point sar interferometry application to los angeles basin abstract multi temporal interferometric synthetic aperture radar insar is an effective tool to detect long term seismotectonic motions by reducing the atmospheric artifacts thereby providing more precise deformation signal the commonly used approaches such as persistent scatterer insar psinsar and small baseline subset sbas algorithms need to resolve the phase ambiguities in interferogram stacks either by searching a predefined solution space or by sparse phase unwrapping methods however the efficiency and the success of phase unwrapping cannot be guaranteed we present here an alternative approach temporarily coherent point tcp insar tcpinsar to estimate the long term deformation rate without the need of phase unwrapping the proposed approach has a series of innovations including tcp identification tcp network and tcp least squares estimator we apply the proposed method to the los angeles basin in southern california where structurally active faults are believed capable of generating damaging earthquakes the analysis is based on 55 interferograms from 32 ers 1 2 images acquired during oct 1995 and dec 2000 to evaluate the performance of tcpinsar on a small set of observations a test with half of interferometric pairs is also performed the retrieved tcpinsar measurements have been validated by a comparison with gps observations from southern california integrated gps network our result presents a similar deformation pattern as shown in past insar studies but with a smaller average standard deviation 4 6 mm compared with gps observations indicating that tcpinsar is a promising alternative for efficiently mapping ground deformation even from a relatively smaller set of interferograms

correcting atmospheric effects on insar with meris water vapour data and elevation dependent interpolation model summary the propagation delay when radar signals travel from the troposphere has been one of the major limitations for the applications of high precision repeat pass interferometric synthetic aperture radar insar in this paper we first present an elevation dependent atmospheric correction model for advanced synthetic aperture radar asar the instrument aboard the envisat satellite interferograms with medium resolution imaging spectrometer meris integrated water vapour iwv data then using four asar interferometric pairs over southern california as examples we conduct the atmospheric correction experiments with cloud free meris iwv data the results show that after the correction the rms differences between insar and gps have reduced by 69 6 per cent 29 per cent 31 8 per cent and 23 3 per cent respectively for the four selected interferograms with an average improvement of 38 4 per cent most importantly after the correction six distinct deformation areas have been identified that is long beach santa ana basin pomona ontario san bernardino and elsinore basin with the deformation velocities along the radar line of sight los direction ranging from 20 mm yr 1 to 30 mm yr 1 and on average around 25 mm yr 1 and santa fe springs and wilmington with a slightly low deformation rate of about 10 mm yr 1 along los finally through the method of stacking we generate a mean deformation velocity map of los angeles over a period of 5 yr the deformation is quite consistent with the historical deformation of the area thus using the cloud free meris iwv data correcting synchronized asar interferograms can significantly reduce the atmospheric effects in the interferograms and further better capture the ground deformation and other geophysical signals

integration of insar time series analysis and water vapor correction for mapping postseismic motion after the 2003 bam iran earthquake atmospheric water vapor effects represent a major limitation of interferometric synthetic aperture radar insar techniques including insar time series ts approaches e g persistent or permanent scatterers and small baseline subset for the first time this paper demonstrates the use of insar ts with precipitable water vapor insar ts pwv correction model for deformation mapping we use medium resolution imaging spectrometer meris near infrafred nir water vapor data for insar atmospheric correction when they are available for the dates when the nir data are blocked by clouds an atmospheric phase screen aps model has been developed to estimate atmospheric effects using partially water vapor corrected interferograms cross validation reveals that the estimated aps agreed with meris derived line of sight path delays with a small standard deviation 0 3 0 5 cm and a high correlation coefficient 0 84 0 98 this paper shows that a better ts of postseismic motion after the 2003 bam iran earthquake is achievable after reduction of water vapor effects using the insar ts pwv technique with coincident meris nir water vapor data

persistent scatterer selection incorporating polarimetric sar interferograms based on maximum likelihood theory persistent scatterer ps interferometry analysis has been performed using single polarimetric synthetic aperture radar sar interferograms but newer sar satellites enable the use of polarimetric data for such analyses in this paper to analyze polarimetric sar interferograms we proposed the maximum likelihood method at the ps selection stage with the proposed method interferograms in a certain polarimetric component exhibiting high coherence contribute to the estimation of surface displacements whereas noisy interferograms of another polarimetric component are less used the proposed method was examined by analyzing full and dual polarimetric interferograms using data obtained from alos palsar images in full polarimetric acquisition mode the results showed an increase in the number of coherent pixels used to map surface displacements and that number increased particularly in the analysis of full polarimetric data for example in the case of full polarimetric interferograms in linear hv basis the number increased by a factor of 1 8 3 8 compared with those of single polarimetric interferograms and by a factor of 1 14 compared with a simple integration of the results of single polarimetric data our method increases the accuracy of the detection of the detailed spatial displacement pattern of a displacement phenomenon

reconstruction of dems from ers 1 2 tandem data in mountainous area facilitated by srtm data a new approach is presented in this paper to produce digital elevation model dem in mountainous areas with steep slope using ers 1 2 tandem data in order to reduce the impact of phase errors on the interferometric synthetic aperture radar insar generated dem an external dem such as that from shuttle radar topography mission srtm is utilized in this approach the proposed algorithm includes two steps the first step is to model and remove phase trends with a linear regression analysis before converting phase to height the second step is to filter unreliable height points before interpolating the dem from the insar height map the critical points are the following 1 determining the one to one correspondence between the interferogram and the srtm dem before knowing the insar derived elevation values and 2 estimating the elevation range of every pixel from srtm dem to solve the first problem an iteratively geocoding algorithm is performed a dem interpolation error model solves the second one for insar data processing the srtm dem is not only usable for modeling systematic phase errors but also for filtering gross height errors the experiments in zhangbei and the three gorges areas in china show that our approach has improved the accuracy of the resulting dems significantly without any ground control points

interferometric synthetic aperture radar insar atmospheric correction gps moderate resolution imaging spectroradiometer modis and insar integration atmospheric effects represent one of the major limitations of repeat pass interferometric synthetic aperture radar insar in this paper gps and moderate resolution imaging spectroradiometer modis data were integrated to provide regional water vapor fields with a spatial resolution of 1 km 1 km and a water vapor correction model based on the resultant water vapor fields was successfully incorporated into the jet propulsion laboratory california institute of technology roi pac software the advantage of this integration approach is that only one continuous gps station is required within a 2030 km 1354 km modis scene application to ers 2 repeat pass data over the los angeles southern california integrated gps network scign area shows that this integration approach not only helps discriminate geophysical signals from atmospheric artifacts but also reduces water vapor effects significantly which is of great interest to a wide community of geophysicists

atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps interferogram images derived from repeat pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor other tropospheric variations such as pressure and temperature also induce distortions but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term spatial and temporal changes of 20 in relative humidity lead to 10 cm errors in deformation products and perhaps 100 m of error in derived topographic maps for those pass pairs with unfavorable baseline geometries in wet regions such as hawaii these are by far the dominant errors in the spaceborne imaging radar c and x band synthetic aperature radar sir c x sar interferometric products the unknown time delay from tropospheric distortion is independent of frequency and thus multiwavelength measurements such as those commonly used to correct radar altimeter and global positioning system gps ionospheric biases cannot be used to rectify the error in the topographic case the errors may be mitigated by choosing interferometric pairs with relatively long baselines as the error amplitude is inversely proportional to the perpendicular component of the interferometer baseline for the sir c x sar hawaii data we found that the best longest baseline pair produced a map supporting 100 m contouring whereas the poorest baseline choice yielded an extremely noisy topographic map even at this coarse contour interval in the case of deformation map errors the result is either independent of baseline parameters or else very nearly so here the only solution is averaging of independent interferograms so in order to create accurate deformation products in wet regions many multiple passes may be required rules for designing optimal data acquisition and processing sequences for interferometric analyses in nondesert parts of the world are 1 to use the longest radar wavelengths possible within ionospheric scintillation and faraday rotation limits 2 for topography maximize interferometer baseline within decorrelation limits and 3 for surface deformation use multiple observations and average the derived products following the above recipe yields accuracies of 10 m for digital elevation models and 1 cm for deformation maps even in very wet regions such as hawaii

phase gradient approach to stacking interferograms the phase gradient approach is used to construct averages and differences of interferograms without phase unwrapping our objectives for change detection are to increase fringe clarity and decrease errors due to tropospheric and ionospheric delay by averaging many interferograms the standard approach requires phase unwrapping scaling the phase according to the ratio of the perpendicular baseline and finally forming the average or difference however unique phase unwrapping is usually not possible since the phase gradient due to topography is proportional to the perpendicular baseline phase unwrapping is unnecessary prior to averaging or differencing phase unwrapping may be needed to interpret the results but it is delayed until all of the largest topographic signals are removed we demonstrate the method by averaging and differencing six interferograms having a suite of perpendicular baselines ranging from 18 to 406 m cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design prestack filters a wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage outside of mountainous areas the topography has a relative accuracy of better than 2 m residual interferograms single interferogram minus stack have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay smaller scale waves with amplitudes of 15 mm are interpreted as atmospheric lee waves a few global positioning system gps control points within a frame could increase the precision to 20 mm for a single interferogram further improvements may be achieved by stacking residual interferograms

imaging with deep water multiples acquisition of on bottom hydrophone data recording of a near surface source provides an opportunity to treat water column multiples as useful signal a ray equation based kirchhoff depth migration is used to image primary reflections and deep water multiples recorded on an ocean bottom hydrophone obh the image of the subbottom sediments is shown to be improved by inclusion of the deep water multiple in the imaging process field data jointly acquired by woods hole oceanographic institute and university of texas institute for geophysics at austin and consisting of an obh 2300 m depth recording a 10 800 cubic inch air gun array are used to illustrate the feasibility of the technique images are obtained from both the primary reflections and from energy that has undergone an additional passage through the water column comparison of these images reveals an excellent correlation of reflectors with the predicted polarity reversal observed in the multiple s image synthetic data are used to examine the d

critical factors for the formation of a nickel copper deposit in an evolved magma system lessons from a comparison of the pants lake and voisey s bay sulfide occurrences in labrador canada the voisey s bay nickel copper deposit and the pants lake sulfide occurrences are the most important mineral systems discovered to date within the nain plutonic suite in northern labrador there are many intriguing similarities at both locations both are hosted by relatively small troctolite gabbro bodies that intrude the sulfide bearing paragneiss of the churchill province and these intrusions contain inclusions of the paragneiss similar chemical reactions of the gneissic inclusions with the host magmas are observed at both locations the reactions resulted in the addition of sio2 k2o na2o and sulfur to the magmas and are responsible for sulfide saturation and resultant segregation of immiscible sulfide liquids from the magmas the initial sulfide liquids in both cases were relatively poor in metals containing 2 5 wt ni and 2 wt cu the sulfides at pants lake remained poor in metals because of a lack of subsequent interaction with new chalcophile undepleted magma at voisey s bay the initial sulfides segregated in a dynamic conduit and were subsequently upgraded in metals to 6 wt ni and 3 wt cu by a new surge of undepleted magma using the same conduit these sulfides were then concentrated to form large sulfide bodies in the wider parts of the conduit and its entry to an upper chamber in response to a sudden change of liquid velocity in these environments this study confirms three of the most important factors for the formation of magmatic sulfide deposits in an evolved magma system 1 contamination of magma with sulfide bearing country rock to achieve sulfide saturation 2 a dynamic magmatic system such as a magma conduit to transport large volume of sulfide liquid and to concentrate them in limited localities and 3 upgrading of metals in the sulfide by new chalcophile undepleted magma

recursive imaging with multiply scattered waves using partial image regularization a north sea case study as more resources are directed toward reverse time migration an accurate velocity model including strong reflectors is necessary to form a clear image of the subsurface this is of particular importance in the vicinity of salt where singly scattered waves are often not ideal for imaging the salt flanks this has led to interest in processing doubly scattered waves also called duplex or prismatic waves for imaging salt flanks and thus improving the location of salt boundaries in a velocity model we used doubly scattered waves in a two pass one way method to image salt flanks in a north sea data set by working in the one way framework we were able to separately construct images with singly doubly and triply scattered waves we used a multistep imaging process that includes multiply scattered waves by using an imaged reflector to fix one or more of the scattering points allowing for multiply scattered energy from several reflectors potentially with poor continuity to be included without picking each reflector individually with this method we were able to image the flank of a north sea salt body

topography correlated atmospheric delay correction in radar interferometry using wavelet transforms 1 atmospheric delay is one of the major sources of error in repeat pass interferometry we propose a new approach for correcting the topography correlated components of this artifact to this aim we use multiresolution wavelet analysis to identify the components of the unwrapped interferogram that correlate with topography by using a forward wavelet transform we break down the digital elevation model and the unwrapped interferogram into their building blocks based on their frequency properties we apply a cross correlation analysis to identify correlated coefficients that represent the effect of the atmospheric delay thus the correction to the unwrapped interferogram is obtained by down weighting the correlated coefficients during inverse wavelet transform we test this approach on real and synthetic data sets that are generated over the san francisco bay area we find that even in the presence of tectonic signals this method is able to reduce the correlated component of the atmospheric delay by up to 75 and improves the signal in areas of high relief the remaining part is most likely due to 3d heterogeneities of the atmosphere and can be reduced by integrating temporal information or using complementary observations or models of atmospheric delay

the formation of pt ir alloys and cu pd rich sulfide melts by partial desulfurization of fe ni cu sulfides results of experiments and implications for natural systems abstract we propose a model of high temperature formation of platinum group element pge alloys from base metal sulfides subjected to decreasing sulfur fugacity f s 2 for this purpose we experimentally investigated the effect of partial desulfurization of monosulfide solid solution mss with variable ni and cu contents on the distribution behaviour of pt ir and pd at 1000 c we partially removed sulfur from the pge bearing mss using the tube in tube technique and pyrrhotite as an f s 2 buffer we found that mss undergoing s loss can produce 1 pt and ir exsolution from the mss matrix in the form of pge bearing alloys 2 partial melting of the cu ni bearing mss to form fe rich mss cu ni pd rich sulfide liquid and fe ir pt alloy both of these processes are geologically important the partial melting of the s depleted sulfides could explain the presence of two types of sulfides found in the mantle mss dominated sulfides and s poor sulfides consisting mainly of pentlandite and chalcopyrite we also suggest that the cu ni pd rich liquid formed by partial melting of the sulfides could migrate away from the mss and fe ir pt alloys thus spatially decoupling ir pt and cu pd as observed in reefs and mantle nodules in addition the formation of pge alloys in response to the desulfurization processes potentially could occur 1 after pressure falls during transport of the basalt magma with entrained sulfide droplets 2 after sulfur removal by s undersaturated melts or fluids from pge enriched sulfide proto ore 3 after degassing of the sulfide droplets occurring in a sub volcanic chamber and 4 as a result of sulfide interaction with chromite

interferometric synthetic aperture radar atmospheric correction gps topography dependent turbulence model 1 over the last two decades repeat pass interferometric synthetic aperture radar insar has been widely used as a geodetic technique for measuring the earth s surface including topography and deformation like other astronomical and space geodetic techniques repeat pass insar is limited by the variable spatial and temporal distribution of atmospheric water vapor in this paper a topography dependent turbulence model gttm for short has been developed using gps data only to produce zenith path delay difference maps for insar atmospheric correction application of the gttm model to ers tandem data over the los angeles southern california integrated gps network area has shown that use of the gttm can reduce water vapor effects on interferograms from 10 mm down to 5 mm which is of great interest to a wide community of geophysicists the principal finding of this paper is that interpolation methods should be applied to zenith total delay ztd differences from different times instead of ztd values themselves for the purpose of insar atmospheric correction this is crucial to reduce if not completely remove topographic effects on ztd values

imaging salt with turning seismic waves turning seismic waves which first travel downward and then upward before and after reflection have been recorded in a 3 d seismic survey conducted over an overhanging salt dome careful processing of these turning waves enables the imaging of the underside of the salt dome and of intrusions of salt into vertical faults radiating from the dome when seismic wave velocity increases with depth waves that initially travel downward are reflected and may turn so as to travel upward before reflection a simple geometrical argument suggests that these turning waves are likely to exhibit abnormal moveout in com mon midpoint cmp gathers in that reflection time decreases with increasing source receiver offset this abnormal moveout and the attenuation of turning waves by most migration methods suggest that conventional seismic processing does not properly image turning waves the most important step in imaging turning waves assuming that they have been recorded is the migration process simple and inexpensive modifications to the conventional phase shift migration method enable turning waves to be imaged for little additional computational cost the examples provided in this paper suggest that these and other such modifications to conventional processing should be used routinely when imaging salt domes

monitoring surface deformation over permafrost with an improved sbas insar algorithm with emphasis on climatic factors modeling abstract changes of permafrost not only affect regional and global water circulation carbon deposit and climate warming but also influence ground ecological geophysical and biogeochemical processes in cold region monitoring surface deformation over permafrost will help to understand the dynamics of these processes assess climate changes and prevent potential damages to engineering structures underlain by permafrost this article employs an improved small baseline subset interferometric synthetic aperture radar sbas insar technique to monitor the surface deformation over the danxiong yangbajing area in the southern qinghai tibet plateau qtp with emphasis on climatic factors modeling a new deformation model considering both the external mainly climatic and internal factors such as tectonic activities and thermal character of frozen soil is constructed and introduced into the sbas insar to estimate the surface deformation over permafrost the results show that the peak to peak annual deformation over natural surface is 3 6 5 0 cm while that along the qinghai tibet highway qth and the qinghai tibet railway qtr is 2 8 3 7 cm we also find that the surface deformation over frozen soil is negatively correlated to air temperature and precipitation with the correlation being 0 80 to 0 45 and 0 95 to 0 75 respectively the root mean squares rmss of the residual un modeled deformation got by the proposed method are much smaller than that by the existing methods we also successfully examine a time lag of about 60 days between the retrieved maximal subsidence and the highest air temperature in warm seasons from may to september after compensating for this time lag the rmss of the residual deformation reduce significantly and the correlation between the deformation and the temperature rises considerably varying from 0 95 to 0 65 the method presented in this paper is more suitable to model and analyze the surface deformation in permafrost areas

ni cu au and platinum group element contents of sulphides associated with intraplate magmatism a synthesis the tectonic setting of intraplate magmas typically a plume intersecting a rift is ideal for the development of ni cu platinum group element bearing sulphides the plume transports metal rich magmas close to the mantle crust boundary the interaction of the rift and plume permits rapid transport of the magma into the crust thus ensuring that no sulphides are lost from the magma en route to the crust the rift may contain sediments which could provide the sulphur necessary to bring about sulphide saturation in the magmas the plume provides large volumes of mafic magma thus any sulphides that form can collect metals from a large volume of magma and consequently the sulphides will be metal rich the large volume of magma provides sufficient heat to release large quantities of s from the crust thus providing sufficient s to form a large sulphide deposit the composition of the sulphides varies on a number of scales i there is a variation between geographic areas in which sulphides from the noril

petrogenesis of pelitic xenoliths at the babbitt cuni deposit duluth complex minnesota u s a abstract the babbitt deposit consists of disseminated cu fe ni sulfides found within mafic rocks of the duluth complex generally near contacts with underlying metasedimentary rock types host rocks for the deposit include troctolites olivine gabbros gabbronorites norites and occasionally country rock hornfels xenoliths of country rocks are abundant in the deposit and suggest a relationship between sulfide mineralization and country rock contamination country rocks in the babbitt area include those of the middle precambrian biwabik iron formation and both calcareous and non calcareous pelites of the virginia formation xenoliths contain the assemblage cordierite plagioclase biotite orthopyroxene and are thought to have been derived from virginia formation protoliths comparison of protoliths and xenoliths using composition volume element ratio and mass balance techniques suggests that xenoliths have been strongly depleted in volatiles alkalis and si footwall rocks show only a depletion in volatiles neither fluid phase transport nor diffusion through an intergranular fluid can account for the mass of material transferred extensive partial melting of xenoliths with residual enrichment of feo mgo and al2o3 is the most viable transfer process the lack of sio2 concentration gradients around xenoliths and anomalous igneous rock compositions suggest that desilicification occurred at a time when physical mixing of extracted partial melt and host magma was possible and prior to final emplacement sulfide saturation may have been initiated due to si assimilation with an auxiliary magma chamber however the composition of ores in the babbitt deposit is consistent with saturation being achieved by addition of sediment derived volatile sulfur independent of major element assimilation

platinum group element chromitite associations in the bushveld complex new and recently published platinum group element data of chromite rich layers in the bushveld complex are evaluated chondrite normalized platinum group element plots of these data show that trends for chromitite layers differ from that of the merensky reef the data furthermore indicate remarkable consistencies in compositional trends for many kilometers along strike of individual layers suggesting that the conditions of formation of chromitite layers and their associated platinum group element mineralization were very uniform over large areas of the magma chamber significant differences in the proportions of platinum group elements within a particular layer are only evident on a regional scale the platinum group minerals of the middle group of chromitite layers in the marikana area of the western bushveld are mainly sulfides and arsenides laurite is the most common platinum group mineral and is mostly enclosed by chromite a variety of other platinum group minerals occur in close association with base metal sulfides extremely low bulk sulfur content in the chromitite layers is ascribed to a postcumulus loss of sulfur postcumulus loss of sulfur and the existence of laurite enclosed within chromite casts doubt on the validity of any petrogenetic models for platinum mineralization in chromitite rich layers based on partition coefficients and the r factor

the geologic setting of the platiniferous ug 2 chromitite layer on the farm maandagshoek eastern bushveld complex the platiniferous ug 2 chromitite layer forms part of the upper chromitite group of the critical zone on the farm maandagshoek 254kt in the eastern bushveld complex the upper chromitite group is made up of four cyclic units namely ug 1 ug 2 ug 3 and ug 3a each of which consists of a basal chromitite layer with or without olivine overlain successively by melanorite and norite and terminated with anorthosite the ug 2 chromitite layer and its associated basal pegmatoid is found close to the base of the ug 2 cyclic unit the cyclic units are separated by sharp contacts and have a remarkable persistence along strike and downdip whole rock cu total ni pt and pd show an upward enrichment from the base of the ug 2 unit reaching a maximum in the main chromitite layer they are depleted in the hanging wall sequence of melanorite bulk analyses of the ug 2 chromitite and its enclosing lithologies for pt pd ru rh ir au s sulfide ni cu and co show that the platinum group elements and base metals are concentrated 1 close to the top and base of the main chromitite layer 2 in the leader layer and 3 in minor chromitite lenses and layers both in the footwall pegmatoid and the hanging wall melanorite the pt pt pd and cu ni ratios are low in the footwall pegmatoid and base of the main chromitite layer values of these ratios however increase upward with pt pt pd decreasing at the upper contact of the ug 2 layer the calculated concentration of platinum group metals in the sulfide phase in the ug 2 chromitite layer ranges from 3 000 to just under 12 000 ppm the above determination is primarily controlled by the concentration of s in the layer with the average precious metal distribution remaining relatively constant the calculated d super sulfide liquid sub silicate liquid with the parental liquid values in parentheses are pt 52 575 40 ppb pd 132 940 16 ppb rh 22 080 8 ppb ir 730 000 0 4 ppb and au 2 190 21 ppb evidence of an influx of magma into the eastern lobe of the bushveld complex at a level between the upper and middle chromitite groups is indicated by discontinuous and disturbed layers in borehole drilling on maandagshoek it is suggested that this magma batch was slightly more enriched in the platinum group elements in order to produce the increased value of these elements in the ug 2 chromitite layer it is proposed that preexisting sulfides in the ug 2 chromitite layer collected platinum group elements from upward migrating highly fractionated intercumulus fluids under highly reducing conditions during the early stages of formation of the layer the relatively large volume of sulfide initially present in the layer was later reduced by volatiles enriched in o 2 passing through the layer resorbing the sulfides and blowing off so 2 the partial resorption of the sulfides accounts for the presence of minor pt fe alloys and the abnormally high partition coefficients of the platinum group elements in the sulfide liquid of the ug 2 chromitite layer

nickel copper occurrences in the belleterre angliers belt of the pontiac subprovince and the use of cu pd ratios in interpreting platinum group element distributions within the belleterre angliers greenstone belt of the pontiac subprovince there are a number of ni cu sulfide occurrences associated with synvolcanic gabbros the stratigraphy and geochemistry of the belt suggest that it is a rifted island arc and that the gabbros which contain the ni cu sulfides were derived from the mantle plume that rifted the island arc the conditions under which the sulfides formed may be modeled either by recalculating the sulfide compositions to 100 percent sulfide or by using the cu pd ratios both approaches suggest that most of the sulfide occurrences formed from an enriched morb magma with r factors of 200 to 1 000 one of the occurrences la force is depleted in platinum group elements pge relative to cu and this depletion may be the result of the removal of sulfides from the magma prior to emplacement at this stratigraphic level the advantage of using the cu pd ratio rather than recalculating to 100 percent sulfide is that it is not necessary to have s analyses to model the conditions of formation of the sulfides further the cu pd ratio may be used as a prospecting tool rocks with ratios greater than mantle values formed from magmas depleted in pd possibly due to removal of sulfide from the magma this implies the potential for a pge bearing sulfide deposit at stratigraphically lower levels such an approach has been applied to pge targets in the eastern abitibi subprovince samples from four ni cu occurrences with cu pd ratios close to mantle ratios have the potential to produce pge as a by product samples from seven ni cu sulfide occurrences and the layered intrusions lac dore bell river and cummings complex have cu pd ratios much greater than mantle ratios indicating that these intrusions and sulfides are not good targets for pge at this stratigraphic level although there may be pge rich sulfides present at depth

prestack depth migration of primary and surface related multiple reflections part i imaging surface related multiples i e all seismic waves reflected at the free surface at least once often severely contaminate seismic recordings because conventional imaging techniques require input data that consist of primary reflections only significant processing effort is commonly dedicated to attenuating multiples prior to migration on the other hand surface related multiples provide additional illumination of the subsurface and therefore should not be considered as noise we present a prestack depth migration method that allows primary and multiple reflections to be imaged simultaneously depth imaging using primary and multiple reflections dipmr involves decomposing the datainto upgoing and downgoing wave constituents followed by downward extrapolation artifacts generated by interference of upgoing and downgoing events not associated with the same subsurface reflection points crosstalk are attenuated by using a 2d deconvolution imaging condition in contrast to existing methods dipmr doe

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

radarsat 1 and ers insar analysis over southeastern coastal louisiana implications for mapping water level changes beneath swamp forests detailed analysis of c band european remote sensing 1 and 2 ers 1 ers 2 and radarsat 1 interferometric synthetic aperture radar insar imagery was conducted to study water level changes of coastal wetlands of southeastern louisiana radar backscattering and insar coherence suggest that the dominant radar backscattering mechanism for swamp forest and saline marsh is double bounce backscattering implying that insar images can be used to estimate water level changes with unprecedented spatial details on the one hand insar images suggest that water level changes over the study site can be dynamic and spatially heterogeneous and cannot be represented by readings from sparsely distributed gauge stations on the other hand insar phase measurements are disconnected by structures and other barriers and require absolute water level measurements from gauge stations or other sources to convert insar phase values to absolute water level changes

toward operational compensation of ionospheric effects in sar interferograms the split spectrum method the differential ionospheric path delay is a major error source in l band interferograms it is superimposed to topography and ground deformation signals hindering the measurement of geophysical processes in this paper we proceed toward the realization of an operational processor to compensate the ionospheric effects in interferograms the processor should be robust and accurate to meet the scientific requirements for the measurement of geophysical processes and it should be applicable on a global scale an implementation of the split spectrum method which will be one element of the processor is presented in detail and its performance is analyzed the method is based on the dispersive nature of the ionosphere and separates the ionospheric component of the interferometric phase from the nondispersive component related to topography ground motion and tropospheric path delay we tested the method using various advanced land observing satellite phased array type l band synthetic aperture radar interferometric pairs with different characteristics high to low coherence moving and nonmoving terrains with and without topography and different ionosphere states ionospheric errors of almost 1 m have been corrected to a centimeter or a millimeter level the results show how the method is able to systematically compensate the ionospheric phase in interferograms with the expected accuracy and can therefore be a valid element of the operational processor

increasing illumination and sensitivity of reverse time migration with internal multiples reverse time migration is a two way time domain finite frequency technique that accurately handles the propagation of complex scattered waves and produces a bandlimited representation of the subsurface structure that is conventionally assumed to be linear in the contrasts in model parameters because of this underlying linear singlescattering assumption most implementations of this method do not satisfy the energy conservation principle and do not optimally use illumination and model sensitivity of multiply scattered waves migrating multiply scattered waves requires preserving the non linear relation between the image and perturbation of model parameters i modify the extrapolation of source and receiver wavefields to more accurately handle multiply scattered waves i extend the concept of the imaging condition in order to map into the subsurface structurally coherent seismic events that correspond to the interaction of both singly and multiply scattered waves this results in an imaging process referred to here as non linear reverse time migration it includes a strategy that analyses separated contributions of singly and multiply scattered waves to a final non linear image the goal is to provide a tool suitable for seismic interpretation and potentially migration velocity analysis that benefits from increased illumination and sensitivity from multiply scattered seismic waves it is noteworthy that this method can migrate internal multiples a clear advantage for imaging challenging complex subsurface features e g in salt and basalt environments the results of synthetic seismic imaging experiments including a subsalt imaging example illustrate the technique

mineralogy of the hse in the subcontinental lithospheric mantle an interpretive review abstract the highly siderophile elements hse os ir ru rh pt pd re au exist in solid solution in accessory base metal sulfides bms as well as nano to micron scale minerals in rocks of the subcontinental lithospheric mantle sclm the latter include platinum group minerals pgm and gold minerals which may vary widely in morphology composition and distribution the pgm form isolated grains often associated with larger bms hosted in residual olivine located at interstices in between peridotite forming minerals or more commonly in association with metasomatic minerals pyroxenes carbonates phosphates and silicate glasses in some peridotite xenoliths the pgm found inside residual olivine are mainly os ir and ru rich sulfides and alloys in contrast those associated with metasomatic minerals or silicate glasses of peridotite xenoliths consist of pt pd and rh bonded with semimetals like as te bi and sn nanoscale observations on natural samples along with the results of recent experiments indicate that nucleation of pgm is mainly related with the uptake of hse by nanoparticles nanominerals or nanomelts at high temperature 900 c in both silicate and or sulfide melts regardless of the residual or metasomatic origin of their host minerals a similar interpretation can be assumed for gold minerals our observations highlight that nanoscale processes play an important role on the ore forming potential of primitive mantle derived magmas parental to magmatic hydrothermal deposits enriched in noble metals the metal inventory in these magmas could be related with the physical incorporation of hse bearing nanoparticles or nanomelts during processes of partial melting of mantle peridotite and melt migration from the mantle to overlying continental crust

platinum group minerals in the middle group of chromitite layers at marikana western bushveld complex indications for collection mechanisms and postmagmatic modification the platinum group minerals in a drill core taken through the middle group of chromitite layers in the critical zone at marikana in the western bushveld complex were found to consist mainly of laurite as inclusions in chromite grains the platinum group minerals containing pt pd and rh are concentrated in the intercumulus silicates and frequently associated with base metal sulphides up to about 20 of all platinum group minerals in the investigated chromitite layers contain sub stantial amounts of as the base metal sulphides are strongly modified in the postmagmatic stage which led to a significant loss of fe and s in this way concentrating cu ni and the platinum group elements by factors of up to 10 interaction between chromite and base metal sulphides cannot account for all the fe lost in chromite poor samples and the importance of additional processes is indicated inclusions in chromite and orthopyroxene indicate the formation of discrete platinum group minerals and as rich phases before the

the composition of mineralization at the voisey s bay ni cu sulfide deposit with special reference to platinum group elements the ni cu platinum group element pge and au contents of massive sulfide mineralization leopard textured mineralization sulfides in basal breccia sequence and sulfides in varied troctolite from four mineralized environments the reid brook zone the discovery hill zone the ovoid and mini ovoid and the eastern deeps at voisey s bay have been determined modeling of the compositional data indicates that the large zone of massive sulfide comprising the ovoid has crystallized from the base upward with a fractionated residual liquid becoming concentrated toward the top massive mineralization from the mini ovoid reid brook zone and eastern deeps has undergone postcrystalliztion modification possibly due to the influence of heat from new influxes of magma through the plumbing system this has resulted in a considerable redistribution of cu and to a lesser extent of ni and au leopard textured mineralization from the reid brook and discovery hill zones corresponds closely with the postulated sulfide liquid compositions responsible for the ovoid and mini ovoid but mineralization composition from the feeder to the eastern deeps is exceptional in having many of the characteristics of a monosulfide solid solution cumulate the composition of disseminated and blotchy sulfides in the varied troctolite of the eastern deeps requires a variable but generally higher r factor than that affecting most of the sulfides to have operated here the compositional variability of the voisey s bay mineralization is best explained in terms of a model calling for repeated influxes of magma through the plumbing system to the deposit

atmospheric effect correction for insar with wavelet decomposition based correlation analysis between multipolarization interferograms this paper presents a wavelet decomposition based correlation analysis wdca method to correct atmospheric effects for interferometric synthetic aperture radar interferometry the main idea is based on the a priori knowledge that the atmospheric effects are independent of the polarizations this provides the possibility to find the identical atmospheric phases atps from the two different polarimetric interferograms to achieve this goal differential interferometry is performed with different topographic data so that the obtained differential interferograms d infs have different topographic errors a polynomial incorporating topographic information is then used to remove the orbit error phase thus the atps are the only identical components in the obtained d infs a forward wavelet transform is then utilized to perform multiresolution analysis for the two obtained d infs after this we apply correlation analysis to identify the wavelet coefficients attributed to the atmospheric effects the corrected d infs are then obtained by down weighting the wavelet coefficients during inverse wavelet transform the performance of the wdca method was tested with l band alos 1 palsar dual polarization sar images acquired over southern california and qilian mountain test sites characterized by different topographic conditions for the southern california test site two interferometric pairs with long and short baselines 750 and 50 m were formulated the results show that the wdca method can work well for both of the interferometric pairs and the root mean square errors rmses of the obtained dems with respect to the shuttle radar topography mission digital elevation model dem are 7 86 and 13 78 m and show a decrease of 34 7 and 80 4 for the long and short baseline cases respectively for the qilian mountain test site the corrected interferogram can provide a dem with an rmse of 19 73 m which is an improvement of 22 3 with respect to the dem containing the atmospheric signals in addition the above two experiments show that compared with the existing topographic information based wavelet method this approach can remove not only the topography dependent atp but also the turbulent atp

topographic mapping from interferometric synthetic aperture radar observations interferometric synthetic aperture radar observations provide a means for obtaining high resolution topographic terrain maps from data acquired simultaneously at two slightly displaced antennas calculation of the three dimensional coordinates of all the points in a radar image can be made from the combination of along track slant range and interferometer fringe measurements thus the result compensates for the layover exhibited by conventional radar maps and removes the false targets generated by multiple signal paths to a given object in the scene we have derived a topographic map of a portion of the san francisco bay area utilizing data that were recorded by a radar system mounted on a nasa cv990 aircraft and processed by a general purpose digital computer this map displays the height above sea level of a region approximately 11 km by 10 km in size sampled on an 11 m pixel grid uncertainties in the estimated height result from imprecise knowledge of the observational geometry radar bandwidth limitations and finite signal to noise ratios for our system each factor contributed approximately 3 4 m to a relative rms error of about 6 m additional global errors of the order of 10 m can result from inaccurate monitoring of aircraft attitude the statistical variation of the height measurements from the ocean portion of the map which we can presume to be quite flat is 2 10 m rms which is consistent with the theoretical estimate comparison of our results with u s geological survey contour maps indicates a high degree of correlation between the two sets of altitude data

prism waves for imaging steep geologic features and sediment terminations against salt flanks examples from the gulf of mexico abstract subsalt imaging in the gulf of mexico often suffers from illumination problems where various steep geologic features are not captured with conventional imaging techniques due to the lack of a direct wave path from the source to the steep reflector and back to the receiver the exact geometry of these invisible salt flanks or salt welds is of great interest to interpreters during salt model building and prospect mapping this paper discusses a suite of technologies that uses prism waves for imaging geologic interfaces with reverse time migration rtm prism wave rtm imaging represents an example of imaging with multiples due to its specific geometric setup it is often complementary to traditional rtms specifically the prism wave reflections can illuminate steep features that are invisible otherwise furthermore by utilizing prism wave rtm in reverse one can specify the steep event as the input prism wave generator often a well constrained salt boundary and obtain an alternative and per

noble metal enrichment processes in the merensky reef bushveld complex we have analysed sulphides silicates and chromites of the merensky introduction reef for platinum group elements pges re and au using laser the enrichment of noble metals in layered gabbroic ablation inductively coupled plasma mass spectrometry and synthetic intrusions to form stratiform merensky type ore horizons pyrrhotite standards annealed with known quantities of noble metals is an extremely efficient yet poorly understood process os ir and ru reside in solid solution in pyrrhotite and pentlandite metal enrichment must be related to the formation of rh and part of the reef s pd in pentlandite whereas pt au re magmatic layering as the ore horizons form an integral and some pd form discrete phases olivine and chromite often part of the magmatic stratigraphies of their host insuspected to carry os ir and ru are pge free all phases analysed trusions metal concentration is also related to the prescontain noble metals as discrete micro inclusions with diameters ence of magmatic sulphides because the noble metals are either dissolved in base metal sulphides or occur as typically 100 nm inclusions in sulphides commonly have the discrete noble mineral phases intergrown with sulphides element combinations os ir pt and pt pd au inclusions in vermaak hendriks 1976 ballhaus ryan 1995 olivine and chromite are dominated by pt au pd few inclusion ballhaus ulmer 1995 spectra can be related to discrete noble metal phases and few there is considerable controversy as to where the inclusions have formed by sub solidus exsolution rather some metals came from and how metal enrichment worked pge inclusions notably those in olivine and chromite are earlyfor a stratiform platinum group element pge deposit magmatic nuggets trapped when their host phases crystallized we inside the magmatic stratigraphy of a layered intrusion suggest that the silicate melt layer that preceded the merensky reef there are two possibilities either the metals were derived was pge oversaturated at early cumulus times experiments from the melt column above the ore horizon or they came combined with available sulphide silicate partition coefficients sugfrom the magma equivalent to the cumulate package gest that a silicate melt in equilibrium with a sulphide melt underlying the ore owing to the large density contrast containing the pge spectrum of the merensky ore would indeed be between silicate and sulphide melt a popular view is that oversaturated with respect to the least soluble noble metals sulphide the metals were enriched by gravitational settling of melt apparently played little role in enriching the noble metals in sulphide melt i e out of the magma column above the the merensky reef rather its role was to immobilize a pre existing ore campbell et al 1983 barnes naldrett 1985 in situ stratiform pge anomaly in the liquid stratified magma naldrett et al 1987 on the other hand it is well chamber established that gravitational crystal settling plays little role in producing magmatic layering and magmatic stratigraphies mcbirney noyes 1979 morse 1986 campbell 1987 and this cannot remain without consequence for stratiform noble metal deposits a third alternative is noble metal enrichment by late

metamorphic evolution of sulphide rich chromitites from the chernichevo ultramafic massif se bulgaria abstract the upper mantle rocks of the metamorphosed ophiolite of chernichevo rhodope metamorphic complex in southern bulgaria host small chromite ores with unusual mineralization of base metal sulphides rich in platinum group elements mineralogical and chemical data indicate that after their formation in the mantle the chernichevo s chromite ores were modified by the intrusion of an alkaline mafic melt which resulted in the precipitation of a suite of metasomatic minerals sulphides calcite apatite and ilmenite accompanied by an increase in feo tio2 ga zn vn mn and especially ti and fe2o3 contents in the chromite the degree of chemical modification and abundance of metasomatic minerals are positively correlated and mark the extent of reaction of the chromitite with the intruding melt sulphide segregation promoted the concentration of high amounts of pges up to 3661 ppb particularly pt and pd yielding chromite ores with a typical flat to positive sloped chondrite normalized pattern subsequently the chromite ores were deformed and metamorphosed together with their host rocks at ultra high pressure uhp 2 5 gpa 1200 c to be later retrograded under eclogite and finally hydrous amphibolite facies conditions giving rise to three microstructural types metamorphism of the most metasomatized i e sulphide rich chromitites at temperatures 700 c within the conditions of uhp and eclogite facies resulted in the formation of 1 non porous recrystallized chromite consisting of a granoblastic microstructure made up of coarse grained blasts and finer grained chromite neoblasts in contrast hydrous metamorphism on the less metasomatized i e sulphide poor chromitite under the conditions of amphibolite facies ca 482 483 c resulted in the formation of 2 partly altered chromite characterized by unaltered cores surrounded by fe2 rich and al depleted porous chromite containing abundant clinochlore and 3 porous chromite corresponding to a chromite that was entirely transformed by the metamorphic alteration to fe2 rich and al depleted porous chromite during metamorphism magmatic ni fe cu sulphides originally formed during the metasomatic event in the mantle were altered resulting in a major leaching of cu rich sulphides leading to significant remobilization of pt and pd

geology petrography geochemistry and genesis of sulfide rich pods in the lac des iles palladium deposits western ontario canada the lac des iles pd deposits are known for their pd rich sulfide poor mineralization however previously undocumented sulfide rich pods also occur within the intrusion that hosts the deposits given the complex magmatic and hydrothermal history of the mineralization at lac des iles the sulfide rich pods could have crystallized from magmatic sulfide liquids or precipitated from hydrothermal fluids sulfide rich pods occur throughout the stratigraphy in all rock types and along comagmatic shear zones and contain net textured to massive sulfides they can be divided into four main groups based on the variation in mineral assemblages 1 pyrrhotite pentlandite pyrite chalcopyrite magnetite ilmenite 2 chalcopyrite pyrrhotite pentlandite pyrite magnetite ilmenite 3 pyrite pentlandite chalcopyrite pyrrhotite magnetite ilmenite and 4 magnetite ilmenite pyrrhotite pentlandite pyrite chalcopyrite whole rock metal contents and s isotopic compositions do not change with the amount of pyrite present except for slight enrichments in as and bi the presence of an essentially magmatic sulfide mineral assemblage pyrrhotite pentlandite chalcopyrite with pentlandite exsolution flames in pyrrhotite in some pods suggests that the pods crystallized from magmatic sulfide liquids the very low cu contents of the pods suggests that they are mainly cumulates of monosulfide solid solution mss we propose a model whereby sulfide liquids were concentrated into dilation zones prior to crystallizing cumulus mss intermediate solid solution crystallized from the fractionated liquids at the edges of some pods leaving residual liquids enriched in pt pd au as bi sb and te these residual liquids are no longer associated with the pods during subsequent alteration pyrite replaced mss pyrrhotite but this did not affect the platinum group element contents of the pods

verification of the vertical error in c band srtm dem using icesat and landsat 7 otter tail county mn the shuttle radar topography mission srtm provided scientists with digital elevation data on a nearly global scale and with highly consistent accuracy this paper compares elevation values of the c band srtm 30 m digital elevation model dem with pointwise elevations from the ice cloud and land elevation satellite icesat laser altimetry for otter tail county minnesota the accuracy of srtm dem is measured as a function of land covers and geomorphologic characteristics the typical mean vertical difference between the srtm dem and icesat elevations in this paper was determined in each classified land use type and is approximately 1 5 m over bare ground with the srtm measuring lower elevations significant changes in the srtm dem uncertainties have been identified over different surface types classified from landsat 7 imagery e g bare ground urban and forested areas based on this result the difference of the srtm 30 m dem and icesat elevations has been removed from the dem and made available for improved hydrological applications

trace elements in sulfide inclusions from yakutian diamonds sulfide inclusions in diamonds may provide the only pristine samples of mantle sulfides and they carry important information on the distribution and abundances of chalcophile elements in the deep lithosphere trace element abundances were measured by proton microprobe in 50 sulfide inclusions sdi from yakutian diamonds about half of these were measured in situ in polished plates of diamonds providing information on the spatial distribution of compositional variations many of the diamonds were identified as peridotitic or eclogitic from the nature of coexisting silicate or oxide inclusions known peridotitic diamonds contain sdis with ni contents of 22 36 consistent with equilibration between olivine monosulfide solid solution mss and sulfide melt whereas sdis in eclogitic diamonds contain 0 12 ni a group of diamonds without silicate or oxide inclusions has sdis with 11 18 ni and may be derived from pyroxenitic parageneses eclogitic sdis have lower ni cu and te than peridotitic sdis the ranges of the two parageneses overlap for se as and mo the mo and se contents range up to 700 and 300 ppm respectively the highest levels are found in peridotitic diamonds among the in situ sdis significant zn and pb levels are found in those connected by cracks to diamond surfaces and these elements reflect interaction with kimberlitic melt significant levels of ru 30 1300 ppm and rh 10 170 ppm are found in many peridotitic sdis sdis in one diamond with wustite and olivine inclusions and complex internal structures have high levels of other platinum group elements pges as well and high chondrite normalized ir pd comparison with experimental data on element partitioning between crystals of monosulfide solid solution mss and sulfide melts suggests that most of the inclusions in both parageneses were trapped as mss while some high cu sdis with high pd rh may represent fractionated sulfide melts spatial variations of sdi composition within single diamonds are consistent with growth histories shown by cathodoluminescence images in which several stages of growth and resorption have occurred within magmatic environments that evolved during diamond formation

volcano wide fringes in ers synthetic aperture radar interferograms of etna 1992 1998 deformation or tropospheric effect mount etna 3300 m is the volcano that has been first and most studied by differential synthetic aperture radar previous papers gave evidence for a large scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models also atmospheric effects on mountainous areas are known to be very significant accordingly interferograms may reflect both deformation and tropospheric effects we investigate here the possibility of evaluating and correcting tropospheric effects directly from the interferograms from 38 ers synthetic aperture radar ascending scenes taken from 1992 to 1999 we have computed 238 interferograms the amount of data allows us to analyze how the coherence is maintained over long periods of time and thus how it reveals the location of permanent scatters from a simple analysis of phase elevation relation we give evidence for the clear difference in pattern between stratified tropospheric effects and large scale deformation produced by a source in a three dimensional elastic body with topography using combination of inversion processes we analyze both deformation source and tropospheric effects for the complete set of 238 interferograms finally time evolution of the parameters and modeling probability estimation are retrieved for each sar image estimated relative change in tropospheric delay varies in time from 2 7 to 3 0 1 2 fringes they are consistent with other tropospheric estimations at etna based on ground met and global positioning system observations on the same period of time magmatic volume variations remain below error bars and thus cannot be estimated properly finally some of the interferograms may be entirely explained by the difference in tropospheric conditions between the two acquisition periods without the need to invoking a deformation of the volcano

migration methods for imaging different order multiples multiples contain valuable information about the subsurface and if properly migrated can provide a wider illumination of the subsurface compared to imaging with vsp primary reflections in this paper we review three different methods for migrating multiples the first method is model based and it is more sensitive to velocity errors than primary migration the second method uses a semi natural green s function for migrating multiples where part of the traveltimes are computed from the velocity model and part of the traveltimes i e natural traveltimes are picked from the data to construct the imaging condition for multiples the third method uses cross correlation of traces the last two methods are preferred in the sense that they are significantly less sensitive to velocity errors and statics because they use natural data to construct part of the migration imaging conditions compared with the interferometric i e crosscorrelation imaging method the semi natural green s function method is more computationally efficient and is sometimes less prone to migration artifacts numerical tests with 2 d and 3 d vsp data show that a wider subsurface coverage higher fold and more balanced illumination of the subsurface can be achieved with multiple migration compared with migration of primary reflections only however there can be strong interference from multiples with different orders or primaries when multiples of high order are migrated one possible solution is to filter primaries and different orders of multiples before migration and another possible solution is least squares migration of all events a limitation of multiple migration is encountered for subsalt imaging here the multiples must pass through the salt body more than twice which amplifies the distortion of the image