trace elements in ilmenite a way to discriminate provenance or age in coastal sands trace elements and ti percentage in ilmenite grains magnetically separated from modern and late pleistocene coastal sands of southeastern virginia and northwestern north carolina were used to distinguish different deposits multivariate analysis of ilmenite composition ti mn mg cr v ni and cu from coastal deposits and potential source rivers enabled the identification of dominant source rivers using the trace element content of one mineral instead of heavy mineral suites eliminated most of the hydraulic sorting selective weathering and intrastratal solution problems that often obscure heavy mineral provenance determinations most ilmenite grains lacked exsolution or twinning which are common to ilmenite however there were no significant optical differences between river and coastal deposits and thus weathering effects were considered to be negligible in provenance determinations based on ilmenite composition owing to the dynamic mixing of beach sands during deposition they contained more homogeneous ilmenite trace element values than did river or bay sands late pleistocene and modern beach deposits were compositionally similar but different from associated bay sands bay sands were more similar to different source river deposits than were beach sands despite a similar primary or distal provenance subtle differences in the mixture of proximal sources were revealed between the ilmenite composition of samples from a modern and a late pleistocene beach deposit besides aiding in provenance determination ilmenite trace element content thus might be used for distinguishing beach deposits of different ages and for subsurface correlation of discontinuous segments from a barrier island chain or other similarly well mixed sand deposit

global mantle heterogeneity and its influence on teleseismic regional tomography abstract a new global p wave tomography model is determined using a flexible grid parameterization this new model better reveals the mantle structure under the polar regions than the previous tomographic models the subducting slabs are generally imaged clearly as high velocity high v zones the young slabs are still subducting in the upper mantle and the mantle transition zone mtz whereas the old and ancient slabs are either stagnant in the mtz or have subducted down to the lower mantle even reaching the core mantle boundary low velocity low v anomalies are generally revealed in the mantle under the hotspot regions it seems that a variety of mantle upwelling plumes exist some strong plumes are visible in the whole mantle under the long living hotspots such as those in south central pacific africa hawaii and iceland whereas weak plumes are visible in only some depth range under the minor hotspots under the intraplate volcanoes in east eurasia bering sea and west alaska significant low v anomalies are revealed in the upper mantle which may reflect hot and wet upwelling associated with corner flows in the big mantle wedge bmw above the stagnant pacific slab in the mtz and perhaps deep slab dehydration as well the subduction triggered magmatism in the bmw may be a new class of mantle plumes we also used the new global model to investigate the influence of whole mantle heterogeneity on the determination of upper mantle tomography under japan with a teleseismic inversion method the results show that the mantle heterogeneities outside the target volume of regional tomography can cause significant changes 0 2 0 4 s to the observed relative travel time residuals of a distant earthquake the pattern of regional tomography remains the same even after correcting for the whole mantle heterogeneity but there are some changes in the amplitude of velocity anomalies in the regional tomography hence it is necessary to correct for the mantle heterogeneities outside the target volume so as to obtain a better regional tomography

the hercynian crust in northwestern spain a seismic survey abstract in summer 1982 a network of crustal seismic profiles was established in nw spain with shotpoints at sea and on land some profiles were designed to capture the general features of the crust whereas others were aimed at resolving the detailed structure of specific geological features the interpretation of three profiles aimed at the most important features of the earth s crust in northwest spain is discussed here the crust consists of three layers with compressional velocities of 6 0 6 1 km s 6 2 6 3 km s and 6 7 6 9 km s the thicknesses of these layers vary laterally the average values under the central part of galicia being 13 km 8 km and 10 km the fine structure of the lower crust has still to be determined so far lateral variations in the velocity structure of the lower crust from a constant velocity layer to a gradient layer have been detected along the main profile from ne to sw over a distance of 250 km the moho discontinuity is reached at 30 32 km in the central part of the surveyed area this decreases to 23 27 km to the north and to the west on the basis of pmp amplitudes the moho seems to be rather sharp the pn velocity is close to 8 3 km s which is slightly above the normal value elsewhere in hercynian europe the crustal structure is remarkably similar to other hercynian domains particularly brittany the massif central and the central iberian massif

estudio sismico de la corteza iberica norte 3 3 a seismic image of the variscan crust in the hinterland of the nw iberian massif an offshore vertical incidence reflection seismic study with simultaneous on land wide angle recording has been conducted as part of the estudio sismico de la corteza iberica norte escin project

a model for the thermal and chemical evolution of the moon s interior implications for the onset of mare volcanism crystallization of the lunar magma ocean creates a chemically stratified moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior within the magma ocean cumulates the last liquids to crystallize form dense ilmenite rich cumulates that contain high concentrations of incompatible radioactive elements the underlying olivine orthopyroxene cumulates are also stratified with later crystallized denser more fe rich compositions at the top this paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy rayleigh taylor instability causes the dense ilmenite rich cumulate layer and underlying fe rich cumulates to sink toward the center of the moon forming a dense lunar core after this overturn radioactive heating within the ilmenite rich cumulate core heats the overlying mantle causing it to melt in this model the source region for high tio2 mare basalts is a convectively mixed layer above the core mantle boundary which would contain small and variable amounts of admixed ilmenite and kreep this deep high pressure melting as required for the generation of mare basalts occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the moon regardless of details implied by particular model parameters gravitational overturn driven by the high density of magma ocean fe rich cumulates should concentrate high tio2 mare basalt sources and probably a significant fraction of radioactive heating toward the center of the moon this will have important implications for both the thermal evolution of the moon and for mare basalt genesis

internal structure of the moon inferred from apollo seismic data and selenodetic data from grail and llr the internal structure of the moon is important for discussions on its origin and evolution however the deep structure of the moon is still debated due to the absence of comprehensive seismic data this study explores lunar interior models by complementing apollo seismic travel time data with selenodetic data which have recently been improved by gravity recovery and interior laboratory grail and lunar laser ranging llr the observed data can be explained by models including a deep seated zone with a low velocity s wave velocity 2 9 0 5 km s and a low viscosity 3 1016 pa s the thickness of this zone above the core mantle boundary is larger than 170 km showing a negative correlation with the radius of the fluid outer core the inferred density of the lowermost mantle suggests a high tio2 content 11 wt which prefers a mantle overturn scenario

re examination of the lunar magma ocean cumulate overturn hypothesis melting or mixing is required abstract there is a long standing hypothesis that the last fraction of the lunar magma ocean crystallized into a layer of dense ti rich cumulate minerals at shallow depths 100 km early in the moon s history many questions remain about the stability of these high ti cumulates it has been suggested that the cumulates subsequently sank deep into the moon because of gravitational instability but high ti material is required at shallower depths by 3 5 ga to create the high ti mare basalts and picritic glasses the high ti material may have re erupted from depth or some or all of it may have remained at shallow depths throughout lunar history data on phase stabilities bulk compositions densities and temperatures of melting and crystallizing in addition to results from numerical modeling suggest that the high ti cumulates would sink only under highly specific conditions five scenarios for sinking high ti cumulate materials are examined and only two are found plausible in particular it is found that simple sinking of solidified high ti cumulates is unlikely because the temperature at which the cumulates solidify is low and viscosity under these conditions is very high it is however possible that high ti cumulates mixed with a substantial fraction of olivine would have viscosity low enough to allow them to sink as solids further because clinopyroxene and ilmenite melt in a ratio of 2 1 remelted high ti cumulates would be negatively buoyant and sink as liquids percolating downward through the underlying mantle and beginning to recrystallize ilmenite at 200 km depth making a hybrid heterogeneous mantle

new data on the rock magnetism in the ivrea verbano zone northern italy and its relationships to the magnetic anomalies abstract the ivrea verbano zone southern alps northern italy is regarded as a typical example of a section of the lower continental crust a considerable magnetic anomaly runs along its outcrop area a study has been made of 153 samples collected along three transverse sections the cannobina strona and sessera valleys and from the southernmost outcrops near ivrea to determine the relationships between this anomaly and the magnetic properties of the rocks and to gain an insight into the nature of magnetism of the lower crust most rocks displayed magnetic susceptibility values ranging from 100 to 10 000 10 6 si units serpentinized peridotites from the finero and baldissero massifs the main gabbro and kindred units and a few amphibolites and mafic granulites of the kinzigite series are the only rocks with values 29 000 200 000 10 6 si comparable with those required to produce the observed anomaly in addition the intensity of their remanent magnetization is of the same order of magnitude as the induced magnetization and the directions of remanence are mostly scattered around the direction of the present field their total magnetization is enough to explain the anomaly of the ivrea verbano zone the results of these measurements and the surface geology suggest that a set of distinct slab like bodies formed of serpentinized peridotite and main gabbro can be proposed as a model for interpretation of the ivrea verbano magnetic anomaly amphibolites and mafic granulites can be regarded as responsible for the short wavelength anomalies only the main magnetic minerals are pyrrhotite which is widely distributed but always in low concentrations and magnetite which is confined to a few lithotypes but can reach high concentrations magnetite must thus be held responsible for the anomaly as in other sections of the lower crust investigated so far the reason for its presence in individual lithotypes however is not always the same and no systematic regional correlation with mineralogical and metamorphic characteristics can be established in conclusion the phenomena observed in the ivrea verbano zone suggest that the magnetism of rocks regarded as typical of the lower crust is highly variable and that there is no ready explanation for the high magnetization values postulated in the light of the satellite data

density of dry peridotite magma at high pressure using an x ray absorption method the density of a peridotite magma was measured up to 2 5 gpa and 2300 k using an x ray absorption method the method allowed measurement of the density of a peridotite melt under seven different conditions and clarified the pressure and temperature dependence of the density a fit of the pressure density temperature data to the high temperature birch murnaghan equation of state yielded the isothermal bulk modulus k t 0 24 0 1 3 gpa its pressure derivative k 7 3 0 8 and the derivative of bulk modulus k t t p 0 0027 0 0017 gpa k at 2100 k the large bulk modulus and its pressure derivative of the peridotite melt compared with that of basaltic melt is consistent with previous results from sink float experiments

chemical fingerprinting a precise and efficient method to determine sediment sources abstract an accurate method of determining source locations for detrital sediment is presented using the chemical composition of fe oxide minerals like a fingerprint this method is an improvement in the use of fe oxide minerals for provenance determinations because it requires less time and fewer source samples a rigorous test of the method uses a database of more than 38 000 grains from known locations the average error of matching grains back to 45 source locations designated for this database is less than 2 the method allows for proportional matching of a grain to multiple sources if other grains in the source database meet the compositional match criteria which helps reduce the error of incorrect matches most provenance studies do not involve source basins as large as the entire arctic ocean where sediment can be ice rafted several thousand kilometers for most studies only a few samples 100 grain analyses sample would be required to characterize a source if strategically placed such as near a river mouth deposits more than 40 million years old can be traced to specific sources using this method because fe oxide grains are relatively stable in most deposits

pressure and temperature dependence of p and s wave velocities seismic anisotropy and density of sheared rocks from the sierra alpujata massif ronda peridotites southern spain seismic wave velocities and densities and their pressure and temperature dependence of rock samples recovered from surface exposures at the sierra alpujata were determined in order to better understand the petrological controls on velocity and density the rock samples studied are representative of the major lithologies of the ronda ultramafic body and its metamorphic aureole the suite of ultramafic rocks includes dunite harzburgite and lherzolite exhibiting different degrees of deformation and serpentinization the rocks representing the metamorphic aureole comprise coarse grained migmatites to ultramylonitic migmatites gneisses and eclogites the experimental data include measurements of elastic wave velocities vp vs and densities at confining pressures up to 600 mpa and temperatures up 600 c at 600 mpa the determination of the pressure and temperature derivatives of velocities and densities and the determination of velocity anisotropy average p and s wave velocities at 600 mpa for rocks of the ultramafic body vary from 6 47 to 8 22 km s 1 and 3 27 to 4 75 km s 1 respectively mainly due to different degrees of serpentinization maximum vp and vs anisotropy is about 8 0 and 9 5 respectively and is primarily related to the preferred orientation of olivine in rocks of the metamorphic aureole average p velocities are in the range 5 61 7 23 km s 1 and s velocities vary from 3 48 to 4 04 km s 1 p and s velocity anisotropy is highest about 6 4 and 4 6 in sheared rocks mylonites and is mainly due to the preferred orientation of biotite and sillimanite the geophysical significance of the experimental data is briefly discussed

density of magmas at depth knowing the density of silicate liquids at high pressure is essential to answer questions relevant to the presence of magmas at depth whether that be in the present earth or in its earliest times during differentiation of the planet melts have unique physical and chemical properties which vary as a function pressure and chemical composition the focus here will be on in situ measurements of the density of magmas with a presentation of the available methods and of the main results obtained so far including why some magmas may be trapped at depth understanding the macroscopical physical properties of magmas requires an accurate microscopic structural description structural descriptions of compressed magmas are becoming more widely available from experiments and from theoretical calculations these structural inputs are used to understand the compression mechanisms at stake in the densification of magmas e g the collapse of voids coordination increase for the major cations and bond compressibility these densification processes profoundly affect not only the physical properties of the melt but also its chemical properties i e the way elements partition between the magma and a metallic melt or between the magma and crystals

teleseismic imaging of alpine crustal underthrusting beneath niberia 1 the deep crustal structure of the northern part of iberia extensively explored by active seismic methods has been investigated here by the teleseismic receiver function rf technique two n s transects were implemented across the cantabrian mountains cmt and the western pyrenees wpt the resulting rfs were migrated to obtain depth sections of the lithosphere these images are fairly consistent with previous seismic sections and velocity depth modeling the wpt shows a clear northward dipping interface interpreted as the iberian lower crust underthrusting an european moho identified at the northern end of the transect in the cmt a similar pattern can be inferred although the deep crustal geometry is not well resolved in this transect intra crustal convertors are associated to high velocity materials of european lower crust imbricated at shallower levels the new results provide farther evidence on the lateral extent of the alpine underthrusting of iberia beneath europe

three dimensional gravity and magnetic modeling of crustal indentation and wedging in the western pyrenees cantabrian mountains 1 the complex crustal structure of the boundary zone between the iberian and european plates from the western pyrenees to the cantabrian mountains is probed by three dimensional 3 d gravity and magnetic modeling constrained by deep seismic profiles the 3 d modeling results support the presence of a continuous iberian crustal root and suggest that the geometry of the orogenic belt that formed in latest cretaceous tertiary times along the northern margin of iberia was conditioned by oblique structures separating areas characterized by different tectonic styles in the western pyrenees and the basque cantabrian basin a thick mesozoic basin presently incorporated to the pyrenean cantabrian belt the relatively narrow thinning of the crust inherited from the mesozoic rifting stage conditioned a structural style in which portions of the southward indenting european lower crust are interpreted to be back thrusted toward the north and uplifted to shallow depths promoting the appearance of significant potential field anomalies in the basque cantabrian basin the strongest aeromagnetic anomaly of the whole iberian mainland is superimposed on the eastern part of a well defined positive gravity anomaly similar in amplitude and wavelength to those located along the north pyrenean zone these observations suggest that the eastern part of the dense lower crustal causative body is strongly magnetized and may correspond to a gabbroic cumulate originated in the axis of the ancient mesozoic rift to the west tertiary compression affected the north iberian cantabrian passive continental margin whose geometry and inherited structures conditioned the formation of a double crustal delamination and the uplift of the cantabrian mountains

on application of three dimensional interactive modeling in gravity and magnetics by h j gotze and bernd lahmeyer geophysics 53 1096 1108 august 1988 gotze and lahmeyer present the main principles and results new automatic system for the interactive modeling of three dimensional 3 d gravity and magnetic fields the high efficiency of the system is demonstrated convincingly on a practical example of a geologic study in the northwest german basin the importance and timeliness of this work are beyond doubt nonetheless a few remarks on the analytical results seem to be appropriate

density of hydrous magma abstract magmas in the interior of the earth have been geophysically observed the generation of magmas is closely related to h2o because the water induced decrease in the melting temperature of mantle rocks is an essential process which forms hydrous magmas due to h2o incorporation into the molten rocks knowledge on physical properties of hydrous magmas such as density can give us better understanding of the magma behavior inside the earth the density of hydrous magma can be controlled by the partial molar volume of h2o v h 2 o and its pressure and temperature dependences the new compression behavior of v h 2 o using vinet equation of state is proposed based on compiled data since h2o is one of the most compressible oxides in the magma at lower pressure a rapid densification of hydrous magma can be observed at shallower mantle the dense hydrous magma can be gravitational stable above and below mantle transition zone

synthetic heavy mineral stratigraphy applications and limitations abstract a multi disciplinary study of the dominantly fluvial lower triassic otter sandstone formation east devon uk is presented the approach integrates a variety of methods including sedimentology conventional heavy mineral analysis single grain microprobe analysis and elemental whole rock geochemistry icp aes and icp ms a species level conventional heavy mineral study is compared to a whole rock geochemical analysis for the corresponding samples to investigate whether or not heavy mineral compositions can be discriminated from elemental whole rock data the comparison provides sufficient evidence that the absolute and relative abundance of some of the heavy minerals apatite iron titanium oxides monazite and zircon can be discriminated geochemically the established element mineral relationships are used to construct both synthetic heavy mineral assemblages and synthetic heavy mineral index values from the geochemical data which show considerable similarity to those of the conventional heavy mineral analysis the presented synthetic heavy mineral logs display intraformational packages that enable subdivision of this barren continental succession furthermore the observed subdivision is correlatable over a considerable distance when extended into the offshore wessex basin the chemical approach unquestionably lacks the sensitivity of conventional heavy mineral analysis however by comparison it is rapid this novel approach demonstrates that synthetic heavy mineral stratigraphy based as here on a well constrained stratotype has considerable potential for creating high resolution correlations in both outcrops and the subsurface and may be of significant value to people working with reservoir characterisation

magmatic evolution of the moon although incomplete because of the imperfect and somewhat random sampling of rock types by the apollo and luna missions 1969 1976 the history of lunar magmatism has been reconstructed by numerous researchers over the past three decades these reconstructions have illustrated the continuous nature of lunar magmatism from 4 6 to approximately 2 0 ga and the large influence of early differentiation and catastrophic bombardment on lunar mantle dynamics magmatism and eruptive style in this review we group magmatism into multiple stages of activity based on sampled rock types and evaluate the models for each stage stage 1 is early lunar differentiation and associated magmatism partial melting of the moon soon after accretion was responsible for producing an anorthositic crust and a differentiated lunar interior the extent of lunar melting and mantle processing depends strongly on the mechanisms that induced melting estimates for the time over which melting and crystallization occurred range from tens to hundreds of millions of years stage 2 is the disruption of lunar magma ocean cumulates soon after the crystallization of most of the lunar magma ocean the cumulate pile experienced gravitational overturn this resulted in transport of late forming cumulates into the deep lunar mantle and mixing of magma ocean cumulates on a variety of scales stage 3 is the post magma ocean highland magmatism whereas the ferroan anorthositic crust was probably produced during the crystallization of a magma ocean the slightly younger mg suite and alkali suite plutonic rocks may have been generated by decompressional melting of early magma ocean cumulates during cumulate pile overturn a kreep and crustal signature was incorporated into these primitive basaltic magmas through assimilation near the base of the lunar crust or through melting of a hybridized mantle the alkali suite could represent either the differentiation products of mg suite parental magmas or a separate but contemporaneous episode of basaltic magmatism stage 4 is pre basin volcanism sample analysis and remote sensing data indicate that early lunar volcanism kreep basalts and high alumina basalts was contemporaneous with periods of highlands plutonism and catastrophic bombardment of the lunar surface the relationship between early stages of lunar volcanism and the contemporaneous plutonism is not clear the kreep basalts may be volcanic equivalents to both the mg suite and alkali suite stage 5 is the late remelting of magma ocean cumulates and eruption of mare basalts basin associated eruption of mare basalts occurred during and following the late stages of catastrophic bombardment this volcanic activity was possibly an extension of the thermal event that initiated pre basin volcanism mare basalts exhibit a wide range of composition resulting from near surface fractionation of chemically distinct primary basaltic magmas most likely mare basalts were produced by small to moderate degrees of partial melting of hybrid cumulate sources in the deep lunar mantle alternatively the mixed chemical signatures observed in many mare basalts may be interpreted as indicating assimilation of late stage evolved cumulates by melts produced deep in the cumulate pile the wide range of compositions exhibited by the mare basalts compared with earlier episodes of basaltic magmatism may reflect the thermal regime in the lunar mantle that limited the extent of partial melting and melt source homogenization

the effects of serpentinization on density and magnetic susceptibility a petrophysical model abstract new measurements are presented of initial magnetic susceptibility and density for serpentinized harzburgites from the josephine peridotite oregon an inverse correlation between density and susceptibility which is typical of these rocks and similar rocks from other localities is not explained by simple serpentinization reactions calculations of density and susceptibility as a function of reaction progress for reactions that produce magnetite show susceptibilities that are larger than those observed at low degrees of serpentinization susceptibilities of fe bearing serpentine and brucite are calculated from a molecular field model initially developed for the olivine and orthopyroxene solid solutions at high degrees of serpentinization susceptibilities that are lower than those observed are predicted by reactions where iron is sequestered by serpentine and brucite observed density susceptibility trends of serpentinized harzburgites fall between the values predicted by these limiting reactions the observed properties may be modelled by multiple reactions involved in multi stage serpentinization processes such that the production of magnetite increases with the degree of serpentinization the empirical and calculated properties provide a complementary characterization of density and susceptibility values of serpentinites

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

gravity constraints on the deep structure of the pyrenean belt along the ecors profile abstract in order to furnish further constraints to modelling the ecors pyrenees deep seismic profile gravity data were collected along a stripe 20 km wide and 220 km long containing the seismic line a total of 4020 stations have been used to derive a bouguer anomaly map of the area a large and roughly symmetrical negative anomaly 100 mgal is centered on the axial zone a local positive anomaly over the north pyrenean zone disturbs the negative regional trend somewhat detailed densities were assigned to the sedimentary cover on the basis of borehole samples refraction data and a velocity density relationship were used to constrain the densities adopted for the deeper layers the results of the two dimensional gravity modelling confirm the asymmetrical shape of the crust mantle boundary beneath the pyrenean belt the downward deflection of the iberian moho from the ebro basin leads to a maximum depth of 65 km under the paleozoic axial zone whereas a depth of 35 km is found for the european moho under the north pyrenean zone two extreme models are proposed for the northern limit of the iberian crust a vertical contact in the downward continuity of the north pyrenean fault or a 70 northward sloping interface the positive anomalies beneath the north pyrenean zone may be explained by dense intracrustal mantle slices or lower crustal sheets the outcrop of granulitic basic gneiss within the labourd massif suggests that the anomaly results from lower crustal sheets

density of high ti basalt magma at high pressure and origin of heterogeneities in the lunar mantle abstract the density of the apollo 14 black glass melt which has the highest tio 2 content of pristine mare glasses was measured to 4 8 gpa and 2100 k using an x ray absorption method a fit of the pressure density temperature data to the high temperature birch murnaghan equation of state yielded the isothermal bulk modulus k t 0 9 0 1 2 gpa its pressure derivative k 0 16 0 3 4 and the temperature derivative of the bulk modulus k t t p 0 0030 0 0008 gpa k at 1700 k the high ti basalt magma is less dense than the lunar mantle below about 1 0 gpa therefore the high ti basalt magma produced in the hybridized source 100 200 km can ascend to the lunar surface the basalt formed at the higher pressure could not ascend but move downwards and solidify in the lunar mantle the solidified high ti basalt components can create chemical heterogeneities in the lunar mantle and can cause the low velocity anomalies observed seismologically

sediment dispersal patterns in a deep marine back arc basin evidence from heavy mineral provenance studies heavy mineral provenance studies can aid reservoir description in deep marine depositional systems by providing a clearer understanding of the lateral extent of discrete sediment bodies in this study the lower gustav group lagrelius point kotick point and whisky bay formations of james ross island antarctica which was deposited in a deep marine slope apron submarine fan complex has been investigated the kotick point and whisky bay formations crop out in two separate areas on the west coast of james ross island the provenance of the group has been studied by both standard sandstone petrography and electron microprobe analysis of the heavy minerals garnet pyroxene and fe ti oxides the sandstones are lithic to arkosic arenites derived from the adjacent antarctic peninsula magmatic arc although the general source area can be recognized individual stratigraphical or depositional units cannot be distinguished on the basis of sandstone petrography however electron microprobe analyses of the detrital heavy minerals allows a more detailed discrimination of sediment provenance in particular analyses of the detrital fe ti oxide minerals show that in the whisky bay formation the southern outcrop area contains ilmenite whilst the northern outcrop area contains titanomagnetite in conjunction with the available biostratigraphical and palaeocurrent evidence this can be interpreted in two ways firstly if the two outcrop areas are direct age equivalents then they were derived from separate point sources and deposited as discrete sediment lobes alternatively if they are not directly time equivalent the depositional system may have switched laterally with time with sediment derived from source rocks of varying composition either interpretation has implications for the understanding of the deep marine depositional system detrital opaque minerals are commonly source specific and should not be ignored during provenance studies

crustal structure of the external variscides in northwest spain from deep seismic reflection profiling abstract recent deep crustal seismic reflection profiling escicantabrica 1 provides a detailed image of the external parts of the variscan belt in northwest spain these seismic data together with surface geological information provide constraints on the crustal structure of the foreland thrust and fold belt cantabrian zone and the transition to the hinterland areas narcea antiform area the image in the cantabrian zone includes strong inclined reflections in the upper 5 s that correspond to mappable paleozoic rocks at the surface which have been deformed by thrusting and folding during the carboniferous some of the major thrust faults imaged show a ramp flat geometry at depth and merge into a highly reflective band between 5 and 6 s that corresponds to the cantabrian zone detachment the precambrian basement is almost transparent underneath the cantabrian zone detachment there are a few subhorizontal discontinuous reflections at 11 s that may correspond to the reflection moho at the transition to the hinterland the seismic profile includes short inclined reflections grouped in several reflective bands in the upper 6 s these correspond to the narcea antiform which comprises at the surface a stack of thrust sheets containing precambrian rocks the narcea antiform is placed above a crustal scale ramp imaged by strong w dipping reflections between 6 and 9 s these reflections merge upwards into the cantabrian zone detachment at 6 s and downwards into a reflective lower crustal zone located between 9 and 12 s these midcrustal reflectors are interpreted as a major variscan shear zone that marks the transition between the thin skinned tectonics of the external areas and the thick skinned tectonics of the hinterland areas the lower crust is highly reflective below the narcea antiform area and reflectivity fades out to the east beneath the foreland thrust and fold belt the different seismic responses at middle and lower crustal levels in the foreland and hinterland areas suggest that variscan tectonics strongly affected deep crustal levels in the hinterland areas whereas they remained undeformed beneath the foreland

seismic image of the cantabrian mountains in the western extension of the pyrenees from integrated escin reflection and refraction data abstract integrated analysis of normal incidence and large aperture seismic reflection data collected in 1992 and 1993 within the spanish escin and complementary projects provide a first complete n s crustal transect across the northern iberian peninsula and continental margin images of the crustal structure of the cantabrian mountains and their transition to the duero basin and to the cantabrian margin are obtained from a a 65 km long vertical reflection profile escin 2 on land b a 200 km long reversed refraction profile and c wide angle recordings of the marine escin 4 profile consistent results between reflectivity pattern and velocity depth distribution reveal important lateral variations in the deep structure the reflective crust imaged in the escin 2 profile changes its attitude from sub horizontal beneath the duero basin to north dipping beyond the mountain front basement thrusts are observed in the upper crust merging into a detachment at 6 s twt and may have triggered the alpine uplift of the range the moho is identified at the bottom of the reflective lower crust and deepens from 12 to 15 s at the northern end of the profile about 35 km inland modelling of the refraction data laterally extends the seismic image and provides evidence for variscan crustal features beneath the duero basin northwards the velocity in the lower crust decreases and the moho constrained by the wide angle data from profile escin 2 deepens to about 60 km ending abruptly at the shoreline the velocity depth model is constrained along the asturian platform up to the continental slope where the crust mantle boundary is located at 24 km depth this margin moho shows a progressive deepening southwards and extends to the coast where it is found at 30 km depth the present seismic data support an important alpine reworking and thickening of the crust under the cantabrian mountains the onshore offshore transition is marked by an imbrication of two crusts of very different thicknesses this signature offers a strong parallelism with the one previously observed further east across the pyrenees in the ecors seismic profile

new geophysical constraints on the deep structure of the pyrenees a 2d modeling of geoid quasigeoid data across the pyrenees is consistent with electromagnetic images of the pyrenean lithospheric structure showing a subducted iberian lower crust using new magnetotelluric data acquired through the orogen a 3d electrical conductivity model of the pyrenean lithospheric structure is obtained the most outstanding feature is the presence of a high conductivity zone at lower crustal depths along the orogen in the contact zone between the iberian and european plates the integration of various geophysical parameters suggests that the simplest and most reasonable mechanism to explain the observed data is partial melting of the subducted iberian lower crust

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

3d gravity modeling of the triassic salt diapirs of the cubeta alavesa northern spain abstract up to now subsurface information permitted the delineation of the top of the triassic salt all throughout the cantabro navarro domain although little was known on the location and geometry of its base and thus on the estimation of the total salt thickness a 3d gravity inversion scheme combined with a 3d analytic method has been conducted to map out the geometry of the main salt structures of the basin the gravity modeling results have been constrained by well log information and available geological and reflection seismic data the combined 3d scheme integrated with available geological and geophysical data has allowed us to obtain the geometry of the main diapirs that characterize the central and marginal regions of the basin from our interpretation the salinas de anana diapir has almost vertical flanks and can be divided into two different parts one of them forming a lateral overhang of the main body the salinas de oro diapir has near vertical flanks and a main axis in the n s direction also the anomaly is rather more extensive than the outcrop of the diapir which implies an important expansion of non outcropping salt in this area like the hoz sobron diapir the salinas de ollo diapir is long and narrow stretching in the nw se direction which includes three important highs plus an intense zone of salt migration the estella and alloz diapirs crop out individually in spite of being connected at depth also two non outcropping salt domes have been detected to the south of atauri that like the estella diapir are related to the thrust front we point out the gravity signature of the murguia diapir which shows an intense gravity high probably due to the presence of high density rocks in the cap rock or more probably due to the existence of triassic volcanites of ophitic texture pinched off into the diapir

diapirism and the origin of high tio2 mare glasses high tio2 mare picritic glasses are derived from cumulate source regions that are only modestly endowed with ilmenite enriched crystallization products these sources are mobilized by the heat derived from the primitive interior and evolve into diapirs which rise adiabatically from depths in excess of 700 km as these diapirs undergo pressure release melting they also stir in significant portions of the surrounding mantle

initiation of an active margin at the north iberian continent ocean transition 1 the north iberian or cantabrian margin located at the southern flank of the bay of biscay underwent successive tectonic regimes of rifting passive margin and compression from mesozoic to tertiary times a complete crustal cross section of the north iberian margin from the abyssal plain to the shoreline and a reconstruction of its undeformed upper cretaceous structure are presented here it is constrained after the compilation and interpretation of different geophysical data sets recently available in the area the reflective pattern is provided by deep seismic reflection profile escin 4 complemented by commercial profiles and well information from the north iberian platform and the velocity depth control comes from an onshore offshore wide angle seismic profile tested also with gravity modeling the detailed cross section of the meso tertiary basins that fill the platform and abyssal plain shows structures from the three main tectonic events 1 normal faults and asymmetric basins from the permian to lower cretaceous extensional stage 2 upper cretaceous sediments deposited under stable conditions during the passive margin period and 3 inverted faults thrusts and folds related to the tertiary compression the deep structure of the crust beneath the margin is poorly constrained from escin 4 profile that shows reflectivity in the lower crust only at a small area under the platform however the corresponding wide angle experiment provides a conspicuous image of the moho that shows a continued deepening toward the continent on the basis of the geophysical results we propose a new model for this margin where the lower crust is detached and underthrusted to the south as a result of the partial closure of the bay of biscay an interpreted mesozoic crustal scale extensional detachment could be the weakness zone that allowed the lower crust to slide southward under the upper crust resulting in the indentation of the cantabrian margin lower crust into the iberian crust plate convergence stopped at an early stage making this a unique area to study the initial stages of deformation of a passive margin

mesozoic extensional tectonics stratigraphy and crustal evolution during the alpine cycle of the eastern iberian basin abstract sequence stratigraphy subsidence analysis and the integration of the basin fill data allow to the identification of four successive evolutionary stages in the basins of the eastern iberian margin during mesozoic extension 1 triassic rift late permian hettangian 2 early and middle jurassic postrift sinemurian oxfordian 3 late jurassic and early cretaceous rift kimmeridgian middle albian and 4 late cretaceous postrift late albian maastrichtian the present day crustal structure of the eastern iberian range and evidence of its evolution are deduced from the analysis of a new gravity map and other geophysical data a regional gravity low along the iberian range is interpreted in terms of crustal thickening beneath the orogen as a result of the collision between the ebro block and the iberian plate during the paleogene the boundary between these blocks coincides with a magnetic lineament that is interpreted as an inherited signature of the thinning that occurred during mesozoic extension a geodynamic scenario for the crustal evolution of the eastern part of the iberian peninsula based on the evaluation of mesozoic extensional tectonics and an analysis of the available geophysical data includes three main successive evolutionary stages 1 1 mesozoic crustal thinning 2 2 paleogene crustal thickening 3 3 neogene crustal thinning based on new geological and geophysical arguments this study offers an alternative and a more complete geodynamic history of the eastern iberian basins related to the evolution of the iberian plate and the central north atlantic

east asia seismotectonics magmatism and mantle dynamics abstract in this article we review the significant recent results of geophysical studies and discuss their implications on seismotectonics magmatism and mantle dynamics in east asia high resolution geophysical imaging revealed structural heterogeneities in the source areas of large crustal earthquakes which may reflect magma and fluids that affected the rupture nucleation of large earthquakes in subduction zone regions the crustal fluids originate from the dehydration of the subducting slab magmatism in arc and back arc areas is caused by the corner flow in the mantle wedge and dehydration of the subducting slab the intraplate magmatism has different origins the continental volcanoes in northeast asia such as changbai and wudalianchi seem to be caused by the corner flow in the big mantle wedge bmw above the stagnant slab in the mantle transition zone and the deep dehydration of the stagnant slab as well the tengchong volcano in southwest china is possibly caused by a similar process in bmw above the subducting burma microplate or indian plate the hainan volcano in southernmost china seems to be a hotspot fed by a lower mantle plume associated with the pacific and philippine sea slabs deep subduction in the east and the indian slab s deep subduction in the west down to the lower mantle the occurrence of deep earthquakes under the japan sea and the east asia margin may be related to a metastable olivine wedge in the subducting pacific slab the stagnant slab finally collapses down to the bottom of the mantle which may trigger upwelling of hot mantle materials from the lower mantle to the shallow mantle beneath the subducting slabs and cause the slab plume interactions some of these issues such as the origin of intraplate magmatism are still controversial and so further detailed studies are needed from now

deep seismic reflection and refraction profiling along the aquitaine shelf bay of biscay summary the 300 km ecors bay of biscay profile was carried out along the aquitaine shelf and comprised a complete set of experiments including zero offset and 7 5 km constant offset vertical seismic reflection and six expanding spread profiles large offset recordings were fundamental for the definition of the layered lower crust and the moho while esps provided decisive complementary information for the geological interpretation these data show a strong variation in crustal thickness from about 20 km beneath the rifted parentis basin a failed arm of the oceanic bay of biscay up to 35 km to the north below the armorican shelf in the hercynian domain and to the south below the cantabria shelf in the vicinity of the pyrenean deformation front the results have important implications for the behaviour of the crust during the formation of rifted sedimentary basins and during continental collision

weathering of ilmenite from granite and chlorite schist in the georgia piedmont ilmenite grains from weathering profiles developed on granite and ultramafic chlorite schist in the georgia piedmont were studied for evidence of morphological and chemical alteration ilmenite rich concentrates from the fine sand 90 150 m component were studied to test the assumption that there is no difference between ilmenite in the parent rock and that in colluvium delivered to primary drainage systems ilmenite grains in the granite profile are rounded to subhedral and commonly contain hematite exsolution blebs dissolution pits are observed along the boundaries of the exsolution blebs with goethite occurring as an alteration product ilmenite grains in the schist profile occur as fractured anhedral grains with uncommon lamellae of rutile grain fractures are filled with goethite and hematite particularly in the b horizon ilmenite from the granite profile is mn rich 7 15 mol mntio3 whereas ilmenite from the schist profile contains only 1 2 mol mntio3 and up to 8 mol mgtio3 two populations of grains develop in both profiles grains with abundant exsolution blebs and fractures alter through a proposed two step reaction mechanism it is proposed that ilmenite first undergoes a solid state transformation to pseudorutile via an anodic oxidation mechanism oxidized fe and mn diffuse from the structure and precipitate as goethite and mno2 pseudorutile is ephemeral and undergoes incongruent dissolution to form anatase hematite and goethite the second population of grains experienced only slight oxidation and dissolution on grain surfaces and they persist through the weathering profile the fe2 content of competent ilmenite grains is somewhat lower in the c horizon compared with grains in the host rock in horizons above the c horizon the fe2 contents of the ilmenite are similar to those in the host rock this study shows that using ilmenite minor element chemistry as a tracer for sediment provenance is a valid technique however textural features of ilmenite in colluvium may be distinct from those in the parent rock also the production of secondary phases such as anatase goethite and hematite in soil profiles results in part from the alteration of ilmenite

hornblende content of georgia south carolina u s a nearshore sands support for shoreward sediment transport in the nearshore zone core top samples from 51 box cores taken about 1 km apart in several transects off hilton head island south carolina and tybee wassaw and ossabaw islands georgia have been analyzed for heavy mineral composition of acid insoluble 3 2 fractions to determine hornblende content and for acid soluble principally calcium carbonate plus carbonate fluorapatite content and grain size data for acid insoluble sand and gravel fractions 4 and for unacidified samples heavy mineral contents of acid insoluble 3 2 fractions range from 0 2 to 2 3 with hornblende and epidote the most abundant heavy minerals individual hornblende and epidote abundances range from 16 2 to 52 0 hornblende and epidote contents vary antithetically with maxima in hornblende content and minima in epidote content at nearshore and offshore ends of transects and with minima in hornblende content and maxima in epidote content over middle portions of transects ilmenite is the most abundant opaque mineral identified with abundances from 1 3 to 24 5 ilmenite maxima are associated with hornblende minima at several stations off hilton head and tybee islands apparently due to winnowing acid insoluble residues are very fine to fine 4 2 sands with very fine sand recent dominant within 5 km of shore and fine sand relict or palimpsest most abundant farther offshore acid soluble contents in our study area are 25 of total sample weight for nearly all samples analyzed and are often 15 high hornblende contents at seaward ends of transects indicate shoreward transport of hornblende rich sediments from the adjacent inner continental shelf low hornblende contents in middle portions of transects indicate dilution of hornblende rich sands by hornblende poor coastal plain sediments derived from coastal plain rivers and exposed by shoreface erosion 4 8 m deep and by tidal inlet erosion high hornblende contents at nearshore ends of transects reflect contribution of hornblende rich sediment from piedmont rivers to the nearshore zone

farside deep moonquakes and deep interior of the moon 1 an effort to find farside deep moonquakes among the recently discovered nests of deep moonquakes has identified about 30 nests that are likely to be on the farside although only a few of them are locatable with currently available data and those few provide little new information about the deep interior of the moon the inferred distribution of the rest of these nests indicates that either the region of the moon s deep interior within about 40 degrees from the antipode of the moon is nearly aseismic or alternatively the very deep interior of the moon severely attenuates or deflects seismic waves since this has important bearing on the origin and evolution of the moon future missions to the moon need to be oriented toward resolving this uncertainty some limited data favor the attenuation deflection hypotheses

cosmogenic 3he production rate in ilmenite and the redistribution of spallation 3he in fine grained minerals cosmogenic nuclide surface exposure dating and erosion rate measurements in basaltic landscapes rely primarily on measurement of 3he in olivine or pyroxene however geochemical investigations using 3he have been impossible in the substantial fraction of basalts that lack separable olivine or pyroxene crystals or where such crystals were present but have been chemically weathered fine textured basalts often contain small grains of ilmenite a weathering resistant mineral that is a target for cosmogenic 3he production with good he retention and straightforward mineral separation but with a poorly constrained production rate here we empirically calibrate the cosmogenic 3he production rate in ilmenite by measuring 3he concentrations in basalts with fine grained 20 m cross section ilmenite and co existing pyroxene or olivine from the columbia river and snake river plain basalt provinces in the western united states the concentration ratio of ilmenite to pyroxene and olivine is 0 78 0 02 yielding an apparent cosmogenic 3he production rate of 93 6 7 7 atom g 1 yr 1 that is 20 30 greater than expected from prior theoretical and empirical estimates for compositionally similar minerals the production rate discrepancy arises from the high energy with which cosmic ray spallation reactions emit tritium and 3he and the associated long stopping distances that cause them to redistribute within a rock fine grained phases with low cosmogenic 3he production rates like ilmenite will have anomalously high production rates owing to net implantation of 3he from the surrounding higher 3he production rate matrix semi quantitative modeling indicates implantation of spallation 3he increases with decreasing ilmenite grain size leading to production rates that exceed those in a large grain by 10 when grain radii are 150 m the modeling predicts that for the ilmenite grain size in our samples implantation causes production rates to be 20 greater than expected for a large grain and within uncertainty resolves the discrepancy between our calibrated production rate theory and rates from previous work the redistribution effect is maximized when the host rock and crystals differ substantially in mean atomic number as they do between whole rock basalt and ilmenite

diagenesis of titaniferous minerals in jurassic sandstones from the norwegian sea abstract ti oxides anatase and in some cases rutile that attain various textures and modes of occurrence are minor yet very common authigenic minerals in the jurassic sandstones of the haltenbanken oil field offshore central norway these ti oxides pyrite commonly occur as pseudomorphs after detrital fe ti oxides usually ilmenite titanomagnetite and titanohematite pseudomorphs comprised of ti oxides as well as quartz and or calcite are believed to result upon alteration of detrital sphene ti oxides have also resulted upon kaolinization of detrital biotite and less significantly muscovite authigenic sphene occurs in very small amounts in some of the jurassic sandstones at burial depths 2000 m it displays three major crystallization habits 1 as almond shaped crystals that have most commonly crystallized on authigenic calcite 2 as discrete rhombic crystals that have crystallized adjacent to altered fe ti oxides and biotite and 3 as aggregates of euhedral and subhedral crystals these crystallization habits suggest that sphene has been formed by reaction of si and ti ions with calcite crystallization from pore fluids and replacement of fe ti oxides respectively microprobe analyses of authigenic sphene revealed that al and fe 3 substitute ti in appreciable amounts average 0 08 and 0 04 moles per 5 oxygen atoms respectively whereas substitutions of ca by mn k and na and of ti by mg are negligible

compressibility of molten high ti mare glass evidence for crystal liquid density inversions in the lunar mantle static compression density measurements of molten apollo 14 black glass have been performed at liquidus conditions in the pressure range 1 0 11 5 gpa a range of values for the birch murnaghan isothermal bulk modulus k2173 k 13 23 gpa and the pressure derivative dkdp 7 3 respectively fit the data within the uncertainties k2173 k 15 5 gpa and dkdp 5 2 provides the best fit to the four measured pressure density pairs corrected to isothermal conditions the ultramafic high ti mare glass is significantly more compressible than other ultrabasic and basic silicate liquids previously studied the compressibility appears to be related to tio2 content the apollo 14 black glass sample has the highest tio2 content of the pristine mare glasses which are thought to be primary melts from a differentiated and strongly heterogeneous lunar mantle our density measurements confirm the prediction that molten black glass will be denser than equilibrium olivine and orthopyroxene at pressures greater than 2 0 and 0 5 gpa respectively these density inversions correspond to depths greater than approximately 410 and 100 km in the lunar mantle since orthopyroxene replaces olivine at 1 5 gpa 300 km on the liquidus our results constrain the maximum depth of buoyancy for high ti magmas at 400 km in the lunar mantle

rare earth mineral potential in the southeastern u s coastal plain from integrated geophysical geochemical and geological approaches we combined geophysical geochemical mineralogical and geological data to evaluate the regional presence of rare earth element ree bearing minerals in heavy mineral sand deposits of the southeastern u s coastal plain we also analyzed regional differences in these data to determine probable sedimentary provenance analyses of heavy mineral separates covering the region show strong correlations between thorium monazite and xenotime suggesting that radiometric equivalent thorium eth can be used as a geophysical proxy for those ree bearing minerals airborne radiometric data collected during the national uranium resource evaluation nure program cover the southeastern united states with line spacing varying from 2 to 10 km these data show eth highs over cretaceous and tertiary coastal plain sediments from the cape fear arch in north carolina to eastern alabama these highs decrease with distance from the piedmont quaternary sediments along the modern coasts show weaker eth anomalies except near coast parallel ridges from south carolina to northern florida prominent eth anomalies are also observed over large riverbeds and their floodplains even north of the cape fear arch where surrounding areas are relatively low these variations were verified using ground geophysical measurements and sample analyses indicating that radiometric methods are a useful exploration tool at varying scales further analyses of heavy mineral separates showed regional differences not only in concentrations of monazite but also of rutile and staurolite and in magnetic susceptibility the combined properties suggest the presence of subregions where heavy mineral sediments are primarily sourced from high grade metamorphic low grade metamorphic or igneous terrains or where they represent a mixing of these sources comparisons between interpreted sources of heavy mineral sands near the fall line and igneous and metamorphic piedmont and blue ridge units showed a strong correspondence with rocks closest to the fall line and poor correspondence with rocks farther inland this strongly suggests that the primary source of those heavy minerals especially monazite is the rocks that formed the rocky coast that was present during opening of the atlantic ocean which in turn indicates the importance of coastal processes in forming heavy mineral sand concentrations furthermore narrow radiometric eth and k anomalies are associated with major rivers indicating limited spatial influence of fluvial processes later coastal plain sediment deposition appears to have involved reworking of sediments providing an inheritance of the rocky coast composition that persists for some distance from the fall line however this inheritance is reduced with distance and sediments within 100 km of the coast in georgia and florida exhibit properties indicative of mixing from multiple sources

crustal density structure in the spanish central system derived from gravity data analysis central spain abstract shallow and deep sources generate a gravity low in the central iberian peninsula long wavelength shallow sources are two continental sedimentary basins the duero and the tajo basins separated by a narrow mountainous chain called the spanish central system to investigate the crustal density structure a multitaper spectral analysis of gravity data was applied to minimise biases due to misleading shallow and deep anomaly sources of similar wavelength first an estimation of gravity anomaly due to cenozoic sedimentary infill was made power spectral analysis indicates two crustal discontinuities at mean depths of 31 1 3 6 and 11 6 0 2 km respectively comparisons with seismic data reveal that the shallow density discontinuity is related to the upper crust lower limit and the deeper source corresponds to the moho discontinuity a 3d depth model for the moho was obtained by inverse modelling of regional gravity anomalies in the fourier domain the moho depth varies between a mean depth of 31 km and 34 km maximum depth is located in a nw se trough gravity modelling points to lateral density variations in the upper crust the central system structure is described as a crustal block uplifted by ne sw reverse faults the formation of the system involves displacement along an intracrustal detachment in the middle crust this detachment would split into several high angle reverse faults verging both nw and se the direction of transport is northwards the detachment probably being rooted at the moho

interior structure of the moon constraints from seismic tomography gravity and topography abstract seismic tomography can be combined with constraints from geoid topography and other surface observations to gain information about mantle structure and dynamics this approach has been taken with much success for the earth mantle and here it is for the first time applied to the moon lunar tomography has much lower resolution as for the earth and is mostly restricted to the near side nevertheless we can assess under what assumptions the fit between predicted geoid based on a tomography model and observed geoid is best among the models tested we find the most similar pattern correlation about 0 5 if we only consider tomography below 225 km depth if density anomalies cause little or no dynamic topography and if we compare to the geoid with the flattening l 2 m 0 term removed this could mean that a like for the earth seismic anomalies shallower than 225 km are caused by a combination of thermal and compositional effects and therefore cannot be simply converted to density anomalies b the lithosphere is sufficiently thick to prevent dynamic topography more than a small fraction of total topography and c flattening is a fossil bulge unrelated to present day mantle anomalies however we have to be cautious with interpreting our results because for models with a comparatively higher correlation and a conversion from seismic velocity to density anomalies similar to the earth s upper mantle the amplitude of the predicted geoid is much lower than observed this could either mean that the tomography model is strongly damped or that the geoid is mostly due to shallow causes such as crustal thickness variations with only a small part coming from the deeper mantle

basaltic magmatism on the moon a perspective from volcanic picritic glass beads abstract it is widely accepted that basaltic magmas are products of partial fusion of periodotite within planetary mantles as such they provide valuable insights into the composition structure and processes of planetary interiors those compositions which approach primary melt compositions provide the most direct information about planetary interiors and serve as a starting point to understand basaltic evolution within the collection of lunar samples returned by the apollo and luna missions are homogeneous picritic glass beads of volcanic origin these picritic glasses are our closest approximations to primary magmas as such these glass beads provide a unique perspective concerning the origin of mare basalts the characteristics of the lunar interior and processes in the early differentiation of the moon we have obtained trace element data for these picritic glasses using sims techniques these data and literature isotopic and experimental data on the picritic glasses are placed within the framework of mare basaltic magmatism the volcanic glasses are very diverse in their trace element characteristics for example they have a wide range of ree pattern shapes and concentrations like the crystalline mare basalts all picritic glasses have a negative eu anomaly unlike the crystalline mare basalts there is little correlation between the size of the eu anomaly and overall ree concentrations trace element differences among the various glasses suggests that a kreep component was incorporated into their mantle source this implies large scale mixing of the lunar magma ocean derived cumulate pile subtle differences among glasses suggest that local mixing of sources may also have been an important process preservation of subtle chemical differences in the picritic glasses and crystalline basalts may be interpreted as indicating that they were produced by small to moderate degrees of partial melting and that the lunar mantle did not experience extensive melting during episodes of mare volcanism several lines of evidence are consistent with the view that the picritic glasses were derived from mantle sources that were compositionally distinct from the sources for crystalline mare basalts these are parallel but no common liquid lines of descent chemical differences between picritic glasses and the more primitive crystalline mare basalts experimental studies indicating that the picritic glasses are multiply saturated at depths greater than that of the mare basalts differences in lead isotopic data and the mode of eruption i e fire fountaining for glass beads these data also provide circumstantial evidence that suggests that the picritic glasses were derived from a source somewhat more volatile rich than that of the mare basalts several petrogenetic models are suggested by the trace element characteristics of the picritic glasses 1 1 partial melting of heterogeneous lunar mantle at depths greater than 300 km to produce the parental magmas picritic for both the mare basalts and picritic glasses picritic magmas represented by glass beads were erupted to the surface with small degrees of fractional crystallization while mare basalts were produced by larger degrees of fractional crystallization 15 30 of similar but not identical picritic magmas 2 2 picritic magmas represented by the glass beads were generated at depths greater than 400 km in a volatile enriched relative to the mare basalt source heterogeneous mantle while mare basalts are fractional crystallization products of picritic magmas generated at depths of less than 400 km 3 3 the picritic magmas represented by the glass beads represent polybaric melting that initiated at depths of at least 1000 km a primitive mantle component or less processed cumulate mantle components may have been involved in the generation of the picritic glasses in any of these models

the provenance of triassic continental sandstones from the beryl field northern north sea mineralogical geochemical and sedimentological constraints a geochemical study of the heavy mineral suite in triassic strata from two wells in the beryl embayment was undertaken in order to identify changes in provenance through the lewis formation detailed provenance studies also allow the reconstruction of paleodrainage patterns and aid in predicting facies distributions the heavy mineral assemblage in the lewis formation is dominated by almandine pyrope garnets which are typically derived from pelitic metasediments together with zircon apatite tourmaline and rutile some of which are rich in niobium nb these latter phases could have been sourced either from metasediments or granitic protoliths although nb rich rutiles have a more restricted paragenesis being associated with alkaline plutonic rocks and granite pegmatites in the uppermost members of the lewis formation influxes of more exotic provenance specific heavy minerals such as cr spinel staurolite and chloritoid become more common the chemistry of the detrital cr spinel implies that it was derived from an ophiolitic source gross grain size and facies changes in the embayment suggest a nw to se dispersal of detritus although hydraulic sorting of the heavy mineral suite between relatively distal and proximal locations has resulted in subtle variations in whole rock trace element geochemical signatures the complete overlap in the geochemical data from distal and proximal wells requires that the sediments were essentially derived from a single source area the combination of mineralogical sedimentological and geochemical data implies that the dominant source for these sediments was the devonian old red sandstone ors the shetland ophiolite and the underlying dalradian metasedimentary rocks of the shetland isles and the east shetland platform provenance studies such as this are central to the reconstruction of paleo drainage patterns which in turn lead to improved prediction of potential reservoir quality distribution and connectivity

neutral buoyancy of titanium rich melts in the deep lunar interior the absence of very deep moonquakes implies that the lower mantle of the moon is partially molten an analysis of the density range of lunar melts at high pressures suggests that only titanium rich melt is neutrally buoyant deep within the moon

trace metal diagenesis in sulfidic sediments insights from chesapeake bay abstract sediments were recovered from the mid bay portion of the chesapeake bay when bottom water conditions were sulfidic metal concentrations fe mn ba v ni cu co cd mo u and re were determined in both pore waters and solid phase samples which were determined using total and nitric acid digestion epa 3051a methods v cr and ni were preferentially retained in pore waters even under sulfidic conditions that would normally result in authigenic accumulation likely due to complexation with dissolved organic matter dom mo was efficiently removed from pore waters in the zone in which fes phases and polysufides are available re was not delivered to the sediments through the mn fe shuttle so that its diffusive flux into sediments solely depends on the extent of reducing conditions a non steady state oxygenation event was recorded in the solid phase with coincident solid phase enrichments in fe mn ni cu and co deeper enrichments in u and mo likely reflect remobilization from the relict fe and mn peaks downward diffusion into more reducing conditions and subsequent immobilization the absence of peaks in solid phase re cr and cd was indicative of their lack of association with mn and fe oxides and or resistance of their respective authigenic phases to oxidation on these seasonal to yearly timescales relative changes within the solid phase profiles were captured using the acid digestion method for fe ni and co and acid digestion concentrations were within 90 of the total concentration for mn and cu the presence of excess pore water sulfide may have promoted the removal of trace metals from the detrital fraction resulting in the formation of authigenic sulfides that might become mobile during oxygenation events

measurement of hydrous peridotite magma density at high pressure using the x ray absorption method abstract the density of hydrous peridotite magma containing 5 wt h 2 o was measured at pressures and temperatures up to 4 3 gpa and 2073 k respectively using the x ray absorption method a fit of pressure density temperature data to the high temperature birch murnaghan equation of state yields isothermal bulk modulus k t 8 8 1 9 gpa its pressure derivative k 9 9 3 6 and the temperature derivative of the bulk modulus k t t p 0 0022 0 0015 gpa k at 1773 k the small bulk modulus of the hydrous peridotite magma compared with that of the dry peridotite magma reflects the effect of water which is more compressible than the silicate melt the partial molar volume of h 2 o in magma under high pressure conditions was calculated and fitted using the vinet equation of state the isothermal bulk modulus was k t 2 4 1 0 gpa and its pressure derivative was k 5 7 1 5 at 1973 k

2 d seismic modeling of the variscan foreland thrust and fold belt crust in nw spain from escin 1 deep seismic reflection data abstract the foreland thrust and fold belt cantabrian zone of the variscan belt in nw spain and the transition to the hinterland westasturian leonese zone was the location of a seismic experiment in 1991 the seismic reflection profile escin 1 is 140 km long and runs in an e w direction the interpretation and seismic modeling of the main reflective interfaces in the profile were made integrating available geological and geophysical data including surface geology deep seismic reflection data from escin 1 transmission velocities from a borehole refraction and laboratory data the geological and velocity model of the crust was tested obtaining synthetic seismograms and can be correlated with surface geology the velocity model images the main crustal structures interpreted from escin 1 the basal detachment of the foreland thrust and fold belt dips gently from 12 km in the easternmost part of the profile to 16 km in the transition to the hinterland to the west a new interpretation is proposed for the structure above the basal detachment in the eastern end of the profile where the basal detachment at a depth of 12 km is duplicated at 6 5 km by a n dipping alpine thrust that also duplicates part of the basement in the western part two deep reflective bands dip westward and the most conspicuous one can be followed from 16 27 km depth the two bands previously interpreted as crustal ramps join a reflective lower crust that is located between 25 and 29 km and fades westwards a reflective moho interpreted at the base of the reflective lower crust dips and fades in the same direction from 30 34 km

magnetic petrology of deep crustal rocks ivrea zone italy magnetic petrology is an extension of petrology integrating magnetic property studies with conventional petrology for the purpose of understanding the development and modification of the magnetization in rocks the magnetic properties of a suite of samples from the ivrea zone northern italy are described with the aim of developing a magnetic petrology for deep crustal rocks samples studied include a variety of metamorphosed mafic granulites granofelses plagioklasfelse amphibolite pyriclasite and pelitic quartzo feldspathic rocks acid granulites stronalite and kinzigite gneisses schists and representative ultramafic rocks phlogopite peridotite pyroxenite hornblendite ilmenite is the chief oxide mineral in a majority of the samples but in a few mafic rocks magnetite is the principal oxide constituent cr al spinel is common in ultramafic samples and rutile is present in some metapelites sulfides are generally subordinate in abundance to oxide minerals the mafic rocks in the ivrea section have the broadest range of magnetic properties and include the most strongly magnetic samples the ivrea ultramafic rocks are moderately magnetic the magnetite present appears to be secondary and is associated with crustal alterations while pelitic and quartzo feldspathic lithologies are dominantly paramagnetic or only weakly magnetic the main ferromagnetic mineral in all strongly magnetic samples is magnetite that is nearly pure fe3o4 in composition consequently curie temperatures are 565 580 c for these rocks pyrrhotite contributes to the magnetism in several ultramafic and mafic rocks and it is the sole ferromagnetic mineral in the pelitic and quartzo feldspathic samples the results of our study indicate that certain mafic rock types amphibolites mafic granulites pyriclasites are the most likely source of the ivrea zone s regional scale magnetic anomalies if the ivrea zone represents a tectonically exposed cross section of continental crust the geographic distribution of these rock types suggests the presence of multiple and variably thick strongly magnetic layers with magnetite curie temperatures in the deep crust petrographic evidence suggests however that the magnetic mineralogy of the sampled ivrea rocks might have been changed subsequent to peak metamorphic conditions therefore considerable care must be taken in evaluating the magnetic record in these crustal cross sections particularly if they are to be used to model the magnetic characteristics of the lower crust

gravity anomaly map of the pyrenean region and a comparison of the deep geological structure of the western and eastern pyrenees abstract a gravity anomaly map based on over 13 000 observations accurately delineates the major features of the pyrenean region an extensive gravity anomaly low in the south of the region appears to result from crustal thickening associated with the pyrenean mountain building episode several large positive gravity anomalies are apparent in the north pyrenean zone in the centre and west of the mountain chain but are absent in the east the interpretation of a series of gravity anomaly profiles along the pyrenees has been controlled by existing geophysical data the interpretations confirm the cause of the southern gravity anomaly low as thickened iberian crust and demonstrate as shown by previous seismic investigations that the transition to much thinner european crust is quite abrupt the sources of the positive anomalies in the north pyrenean zone are bodies in the upper crust with densities too high to be explained in terms of crustal materials these are interpreted as segments of upper mantle that originated in transtensional n s separation across the north pyrenean fault and were emplaced at shallow levels by thrusting during pyrenean orogenesis this is the first time that evidence has been presented for the presence of such mantle bodies in the pyrenees it is suggested that their absence in the east is caused by less extension between iberia and europe in this region during the transform motion between them prior to orogenesis allowing only limited ascent of deep material the greater extension in the west would have allowed the ascent of upper mantle into the space between iberia and europe which would have been further elevated during the thrusting associated with pyrenean orogenesis

heavy mineral based provenance analysis of mesozoic continental marine sediments at the western edge of the bohemian massif se germany with special reference to fe ti minerals and the crystal morphology of heavy minerals during the mesozoic the epicontinental germanic basin and the regensburg strait the latter being an embayment of the tethys ocean that had subsided into the moldanubian zone of the central european variscides were filled with terrigenous continental marine sediments both sediments heavy mineral hm grains and aggregates have been studied in a drill section in the wackersdorf area se germany the majority of them belong to the semi opaque group of fe ti minerals in wackersdorf the entire stratigraphy of the basin fill which occurred between the triassic and the late cretaceous is well exposed in addition to the chemical composition of hm the morphology and texture of zircon apatite and fe ti compounds have been studied in a provenance related mineral classification provenance analysis has yielded five discrete source rock lithologies 1 moldanubian h t metamorphics 2 late paleozoic sub volcanic rocks 3 gneisses of the tepla barrandian unit 4 ophiolites of the tepla barrandian unit 5 silicified shear zones and quartz cores of pegmatites the detrital minerals include zircon tourmaline dravite schoerl apatite monazite ce th la nd xenotime biotite rutile ilmenite nigrine ilmenite rutile intergrowth sphene amphibole staurolite garnet and spinel cr mg al based on the allogenic ti and fe minerals a magnetite type source area eh 0 near surface felsic to intermediate sub volcanic rocks was distinguished from an ilmenite type source area eh 0 deeply eroded crystalline basement rocks gneiss granite shear zones the latter may be subdivided into nigrine i deep and nigrine ii intermediate subtypes according to the level of erosion in the source area at the jurassic cretaceous transition extrabasinal erosion provoked a noticeable variation of allogenic heavy minerals with the incisions of rivers into source rock lithologies 4 and 5 uplift and erosion along the western edge of the bohemian massif took place contemporaneously with spreading and closure in the central parts of the adjacent tethys ocean

crustal transition between continental and oceanic domains along the north iberian margin from wide angle seismic and gravity data deep crustal features of the transition between the north iberian mainland and the bay of biscay are constrained from new wide angle seismic and gravity data velocity depth models are derived from far offset recordings onshore of two n s marine profiles complemented with new refraction data inland and tested against models that fit the gravity anomalies important lateral variations are inferred along the north iberian margin in the western transect a variscan crust is documented from the mainland across the continental shelf and a rapid crustal thinning beneath the slope marks the transition to the oceanic domain the eastern transect shows an outstanding crustal thickening beneath the coastline moho depths around 50 km and a gradual thinning across the shelf differences are related to the v shape of the bay of biscay that causes a w e transition along the margin from a short lived oceanic subduction to continental collision during the tertiary oblique convergence between europe and iberia

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

seismic signature of variscan and alpine tectonics in nw iberia crustal structure of the cantabrian mountains and duero basin the seismic structure of the crust of the nw iberian peninsula along the cantabrian mountains and their southern foreland the duero basin is investigated from the first data set available from refraction and wide angle reflection profiles the velocity depth distributions obtained along e w and n s transects evidence lateral variations in crustal structure that can be associated to variscan and alpine tectonic episodes the western part of the range toward the variscan hinterland zones as well as the duero basin below the sediments show a crustal structure similar to that of the variscan belt elsewere in europe the total crustal thickness is 30 32 km and three main layers upper middle and lower crust with average velocities 6 0 6 25 and 6 8 km s are resolved some paleozoic structures such as the basal detachment of the cantabrian zone are expressed in the seismic models the crust appears to vary eastward in the external zones the most outstanding feature is a crustal root beneath the highest cantabrian summits where the moho is found at 47 km depth a prominent alpine reworking of the crust in the eastern part of the cantabrian zone is thus revealed and the n s seismic transects delineate a geometry similar to the one found across the central pyrenees in the etude continentale et oceanique par reflexion et refraction sismique ecors profile revealing the importance of the alpine deformations in the northern part of the iberian plate

unconventional rutile deposits in the quebec appalachians product of hypogene enrichment during low grade metamorphism unconventional rutile deposits occur in heavy mineral paleoplacers of the pinnacle formation in the humber zone of the quebec appalachians detrital hemo ilmenite represents 65 percent of the heavy mineral assemblage and is the main titanium mineral detrital rutile is also present in trace amounts postdepositional and metamorphic alteration processes increased the titanium content of the hemo ilmenite grains by leaching elements particularly fe new minerals created by these processes include pseudorutile anatase a tio 2 polymorph and neorutile early metamorphic magnetite enclosed detrital grains and preserved evidence of premetamorphic weathering or diagenetic processes by isolating the grains from metamorphic fluids thus preventing further leaching detrital grains that were not protected by this magnetite were metamorphically leached to the purer tio 2 mineral phase of anatase grains of anatase locally recrystallized to neorutile during a late orogenic back thrusting event in the silurian this is supported by 18 o water in equilibrium with metamorphic magnetite and by the fact that neorutile is limited to the eastern part of a synformal keel near the back thrust fault and is rarely observed farther west where anatase is predominant rutile formed under greenschist metamorphic conditions from primary hemo ilmenite detrital grains via intermediate pseudorutile and anatase phases this is the first known report of titanium mineral enrichment occurring under low pressure and low temperature metamorphic conditions our results could have significant implications for titanium exploration because they demonstrate that paleoplacer source regions are not restricted to eclogite and granulite facies terrains

magnetic properties of variably serpentinized abyssal peridotites we have compiled new and published data on the magnetic properties of 245 serpentinized abyssal peridotites from seven deep sea drilling project and ocean drilling program sites the magnetic susceptibility k of these samples does not increase linearly with the degree of serpentinization s instead k remains modest in partially serpentinized samples s 75 peridotites in the oceanic crust moderately serpentinized peridotites s 75 have nrm values 5 a m and k 0 05 si low temperature oxidation of magnetite is found to lower the nrm and k values of seafloor samples and of cataclastically deformed drilled samples

a 2 5 d interpretation of the basque country magnetic anomaly northern spain geodynamical implications the basque country magnetic anomaly follows a nw se trend over the basque country northern spain with intensities up to 250 nt measured at 3000 m above sea level the paired negative part of the anomaly is located to the north and presents intensities down to 60 nt a model of the magnetic properties of the crust in the area taking into account previous geological and geophysical data indicates a wedge of material with a magnetic susceptibility of 0 07 si emplaced along a ne directed basal thrust the anomalous wedge is composed of basic and or ultrabasic cretaceous intrusives and lower crustal rocks and reaches a minimum depth which increases towards the northwest from 5 7 to 12 km according to previous works geological features of the rocks on top of the anomalous wedge indicate that during the cretaceous this zone constituted a deep marine environment which underwent important crustal thinning related to rifting the transition towards the southwest was to a normal continental platform alpine deformation gave rise to displacement on a basal thrust which can be correlated with the lower contact of the magnetic wedge and emplacement of this wedge towards the northeast the southeastern termination of the anomaly can be related to the lateral termination of the basic rocks which constitute the anomalous wedge in a transform fault related to the rifting event

the density of andesitic melts and the compressibility of dissolved water in silicate melts at crustal and upper mantle conditions abstract many magmatic processes including the extraction of partial melts fractional crystallization and buoyancy overpressure depend on the density of the silicate melt phase because of its low molecular weight water has a disproportionately large effect on melt density and accurate data on the effect of water on melt density is required to model density dependent processes however the volumetric properties of the hydrous component at crustal and mantle conditions remain debated in this study we determined the density of dry and hydrous 0 9 wt h2o haplo andesitic melts from 0 7 to 4 0 gpa and 1600 to 1930 k using the x ray absorption method in a paris edinburgh press to determine the partial molar volume of water at high pressure our in situ data were combined with atmospheric pressure data to derive the first experimental equation of state for andesitic melts valid for crustal and subduction zone conditions with k t 17 2 gpa and k 6 3 2 5 3 3 at 1273 k in addition the partial molar volume and compressibility of dissolved water in andesitic melts were derived from the in situ data with v 0 19 2 1 9 2 4 cm 3 mol k t 2 7 2 2 7 6 gpa and k 3 6 2 7 13 5 at 1273 k combined with available literature data for other melt compositions our results support a compositionally independent partial molar volume of water in silicate melts at least within the currently attainable precision of the in situ measurements this observation greatly simplifies the construction of future models for magma density

seismic velocity structure of the lunar mantle i have inverted the recently completed set of seismic arrival times from the apollo lunar seismic network to estimate the average seismic velocities in three sections of the lunar mantle two for the upper mantle and one for the middle mantle the method used is a variation of the linearized least squares inversion where the inversion is accomplished in steps the estimated average velocities in the upper mantle decrease from vp 7 74 km s and vs 4 49 km s in the section above 270 km depth to vp 7 46 km s and vs 4 25 km s in the section between 270 and 500 km depth confirming the earlier finding of negative gradients based on seismic amplitude variations the average velocities in the middle mantle between the depths of 500 km and 1000 km of vp 8 26 km s and vs 4 65 km s are significantly higher than those in the upper mantle contradicting earlier estimates based on more limited data the higher velocities may suggest initial melting of the moon down to at least 1000 km depth

evidence for the hudson river as the dominant source of sand on the us atlantic shelf previous attempts to determine the origin of sand on the us atlantic shelf by standard heavy mineral analysis have concluded that local rivers and coastal erosion were probable sources1 here a new approach to determine the history of surficial sand dispersal is developed using the elemental composition of detrital fe ti oxide grains primarily ilmenite instead of heavy mineral abundances sands from the entire middle atlantic shelf latitude 35 n to 41 n have been interpreted as coming from specific drainage basins1 2 more than half of the sand samples collected as far south as north carolina can be traced to the hudson river and other new england sources the dominance of the hudson river is cause for rethinking sources of shelf sediment south of new jersey these findings suggest that the hudson river may have rivalled the sediment discharge of much larger rivers like the mississippi or amazon rivers at least during brief glacial melting events

crustal structure and orogenic material budget in the west central pyrenees surface and subsurface data are combined to construct a crustal scale cross section of the western central pyrenees france and spain at the boundary between the european and iberian plates the position of moho reflections in the ecors arzacq reflection profile suggests a tectonic wedge of european crust and upper mantle had indented the iberian plate at lower crustal levels the european wedge is overlain by an upper iberian wedge thus constituting a double stacked wedge geometry the upper wedge was delaminated and deformed giving rise to the pyrenean orogenic prism manifested as a bivergent fan in upper crustal levels the underthrust lower iberian plate has been imaged to depths of 55 60 km but crustal budget considerations based on a palinspastic reconstruction require that this continental root subducted to depths up to 90 km total orogenic contraction calculated from surface structures is about 75 80 km which was accomplished between the latest cretaceous and the early miocene at an averaged rate of 1 2 mm yr consistent with these moderate values exhumation of the orogen is much less than in the more shortened eastern parts of the range paleozoic basement and preorogenic mesozoic rocks are little eroded and much of the exhumation involved cannibalization of early foreland basins which once covered the entire poorly emergent orogen at this transect this resulted in a continuous process of sediment recycling and coupled with a considerable lateral arrival of material a bulk negative erosion sedimentation budget