the terrestrial alteration of saharan shergottites dar al gani 476 and 489 a case study of weathering in a hot desert environment abstract rare earth element ree and other selected trace and minor element concentrations were determined in various phases of dar al gani 476 and 489 two basaltic shergottites recently found in the libyan sahara whereas merrillite and feldspathic glass compositions do not seem to have been altered since the fall of these meteorites olivine and pyroxenes commonly show light ree enrichments sometimes accompanied by ce anomalies that are attributed to terrestrial alteration sr and ba enrichments are also observed the calcium carbonate that resides in most cracks is essentially devoid of ree but a fine grained amorphous silicate material that fills some veins and pockets has striking light ree enrichments and elevated p sr and ba it is argued that this material likely to be impact melt as well as the notoriously light ree poor olivine and pyroxenes were preferentially affected by a crustal light ree rich contaminant caution is urged when using whole rock or even mineral separate compositional and isotopic data for hot desert meteorites

post depositional alteration of onshore tsunami deposits implications for the reconstruction of past events abstract sediments provide information on parameters governing their deposition however this information gets blurred by post depositional processes here we document post depositional alteration processes that affected an onshore tsunami deposit from its deposition in february 2010 until 2014 post depositional changes proceeded in three stages first the thickness was reduced by 20 within the first months because of erosion by runoff second vegetation returned and bioturbation destroyed the sedimentary structures and obliterated the basal contact the thickness was reduced further to 20 40 of its initial thickness the mean grain size decreased as silt and mud from the enclosing soil horizons were mixed into the deposit finally as post seismic subsidence together with damming by a coastal dune transformed the coastal plain into a wetland aqueous microbial magnetite reduction set in and dissolved up to 57 of the magnetite inverse models are used to reconstruct onshore tsunami flow parameters in order to quantify the intensity of ancient events thickness grain size and bulk density are input parameters to any model thus post depositional processes affect the reliability of the modeled flow parameters of the three documented processes the post depositional alteration of the grain size has the highest influence followed by the reduction of the thickness the change of the bulk density hardly had any effect our sensitivity analysis shows that the calculated flow velocity decreased by 60 from 4 2 m s for the pristine sediments to 2 5 m s for the altered deposits consequently inverse models will significantly underestimate tsunami intensity because of the alteration of the deposits

feldspathic clasts in yamato 86032 remnants of the lunar crust with implications for its formation and impact history abstract low concentrations of th and fe in the yamato y 86032 bulk meteorite support earlier suggestions that y 86032 comes from a region of the moon far distant from the procellarum kreep terrain pkt probably from the lunar farside 39 ar 40 ar rb sr sm nd and sm isotopic studies characterize the chronology of y 86032 and its precursors in the mega regolith one of the rock types present in a light gray breccia lithology is an anorthosite characterized by plagioclase with an 93 i e more sodic than lunar fans but with very low 87 rb 86 sr and 87 sr 86 sr similar to those of fans fan stands for ferroan anorthosite this an93 anorthosite has nd isotopic systematics similar to those of nearside norites a fan like an97 anorthosite is present in a second light colored feldspathic breccia clast and has a more negative e nd value consistent with residence in a lree enriched environment as would be provided by an early plagioclase flotation crust on the lunar magma ocean lmo this result contrasts with generally positive values of e nd for apollo 16 fans suggesting the possibility of assymetric development of the lmo other possible explanations for the dichotomy in e nd values are advanced in the text the y 86032 protolith formed at least 4 43 0 03 ga ago as determined from a sm nd isochron for mineral fragments from the breccia clast composed predominantly of an93 anorthosite and a second clast of more varied composition we interpret the mineral fragments as being predominatly from a cogenetic rock suite an 39 ar 40 ar age of 4 36 4 41 0 035 ga for a third clast composed predominantly of an97 anorthosite supports an old age for the protolith initial 143 nd 144 nd in that clast was 0 64 0 13 e units below 143 nd 144 nd in reservoirs having chondritic sm nd ratios consistent with prior fractionation of mafic cumulates from the lmo a maximum in the 39 ar 40 ar age spectrum of 4 23 0 03 ga for a second sample of the same feldspathic breccia clast probably reflects some diffusive 40 ar loss lack of solar wind and lunar atmosphere implanted ar in the light gray breccia clast allows determination of an 39 ar 40 ar age of 4 10 0 02 ga which is interpreted as the time of initial brecciation of this litholgy after correction for implanted lunar atmosphere 40 ar impact melt and dark regolith clasts give ar ages of 3 8 0 1 ga implying melt formation and final breccia assembly 3 8 ga ago some breccia lithologies were exposed to thermal neutron fluences of 2 10 15 n cm 2 only about 1 of the fluence experienced by some other lunar highlands meteorites other lithologies experienced neutron fluences of 1 10 15 n cm 2 thus y 86032 spent most of the time following final brecciation deeply buried in the megaregolith the neutron fluence data are consistent with cosmogenic 38 ar cos cosmic ray exposure ages of 10 ma variations among differing lithologies in the amount of several regolith exposure indicators including cosmogenic noble gas abundances neutron capture induced variations in sm isotopic abundances and ir contents are consistent with a period of early 3 8 ga ago lunar regolith exposure subsequent deep burial at 5 m depth and ejection from the moon 7 10 ma ago

palaeoenvironment of the upper cretaceous coniacian concretion bearing lagerstatten from poland abstract abundantly fossiliferous upper cretaceous sediments including decapod remains in the region of stary waliszow southern poland have been known for many years to date however no study has dealt specifically with detailed palaeoenvironmental and palaeoecological reconstruction the origin of these sediments is still uncertain and has been the source of considerable confusion and controversy mainly due to the strong bioturbation and decalcification of these sediments by using the fossil record comparative taphonomy and geochemical analyses of concretions we provide new insights into the paleoenvironment and the paleoecology of this unique coniacian ecosystem on the basis of ichno and body fossil assemblages composed almost exclusively of benthic organisms such as decapods molluscs and echinoderms which are commonly disarticulated but rarely abraded we suggest that the fossiliferous sediments in stary waliszow were formed in shallow normal saline and well oxygenated waters of the upper sublittoral zone with moderate sedimentation rate and low turbulence of waters the presence of angular terrigenous clasts well preserved delicate land flora and the near absence of planktonic and nektonic fossils strongly imply proximity to the land recorded taxa inhabited a soft bottom environment some organisms were fossilized inside siderite concretions these concretions were formed within the sediment below the zone of active bioturbation during the early stage of diagenesis remarkable preservation of decapod remains is due to phosphatization which replaced the cuticle

constraints on palaeoenvironments in the lower cretaceous wealden of southern england from the geochemistry of sphaerosiderites abstract sphaerosiderites are millimetre scale concretions of feco 3 that form predominantly in waterlogged environments and are of use in palaeoenvironmental and palaeohydrological studies we present petrographic elemental and stable isotopic 13 c 18 o data from sphaerosiderites collected from the lower cretaceous wealden sediments of southern england the sphaerosiderites are composed of very pure feco 3 with only small amounts of ca mg and mn present suggesting that they are well preserved and were precipitated from fresh groundwater 13 c values display a relatively large range from about 5 to 30 vpdb in contrast 18 o values are relatively invariant 1 0 83 with an average of 3 01 vpdb the relationship between carbon and oxygen suggests that the sphaerosiderites faithfully record palaeo groundwater 18 o likely 18 o values for groundwater were calculated using a published experimentally derived siderite water fractionation equation and plausible assumed values for palaeotemperature the average estimate was 4 9 smow the wealden sphaerosiderite oxygen isotope values are comparable with other early cretaceous data from similar palaeolatitudes but lower than estimated holocene values for equivalent latitudes this observation may indicate greater rainfall at 30 n during the cretaceous relative to the holocene and also suggests relative stability of palaeoclimatic conditions during the early cretaceous at this palaeolatitude

sm nd chronology and petrogenesis of mesosiderites we have obtained sm nd data from four mesosiderite silicate clasts including three clasts with a variety of textures from the vaca muerta type 1a mesosiderite and one gabbroic clast from the mt padbury mesosiderite the gabbroic vaca muerta pebble 12 and basaltic pebble 16 yield identical 147 sm 143 nd ages of 4 48 0 19 ae and 4 48 0 09 ae respectively while the highly recrystallized pebble 5 gives an age of 4 42 0 02 ae mt padbury yields an age of 4 52 0 04 ae all clasts show a correlation of 142 nd 144 nd with 147 sm 144 nd and provide unequivocal evidence for the presence of live 146 sm at the time of their formation calculated initial 146 sm 144 sm values range from 0 004 pebble 5 to 0 006 pebbles 12 16 and mt padbury and are generally consistent with the 147 sm 143 nd ages however discordance of whole rock leach and residue data and some disagreement between 146 sm 142 nd relative ages and 147 sm 143 nd absolute ages indicate small but significant disturbances to the sm nd systematics the ranges of ages and initial 146 sm 144 sm and 143 nd 144 nd values suggest that each of these silicate clasts underwent a separate protracted evolution on its parent body prior to mixing with metal textural and trace element criteria indicate that individual clasts from the same mesosiderite often had very different igneous sources and thermal histories prior to their incorporation in the meteorite pebble 12 is extremely lree depleted probably a result of several melt extraction events whereas pebbles 5 and 16 and mt padbury have nearly chondritic sm nd with bulk ree concentrations higher than chondrites by factors of 5 to 15 in general the sm nd systematics of mesosiderite silicates require formation of the silicates on a parent planet which underwent relatively early and extreme differentiation preservation of diverse old ages and the presence of 146 sm imply that metal silicate mixing did not seriously alter the sm nd isotopic memories of these clasts we present a model for metal silicate mixing which combines the cooling history with isotopic reequilibration for the case of thermal blanketing we show that the total amount of isotopic reequilibration in a sample can be related to the initial temperature depth of burial grain size and diffusion parameters application of this model to the silicate clasts measured in this study indicates that if the metal and silicate were thermally equilibrated above the metal solidus temperature during mixing then the clasts must have been buried no deeper than 1 10 m in regolith during the initial high temperature cooling phase in order to prevent the sm nd systems from being extensively reset in order to reconcile these results with the slow cooling rates at lower temperatures determined from studies of exsolution in the metal phase we infer that heat was transferred rapidly from hot metal to cold silicate material during initial metal silicate mixing and that the deeply buried portions of the mixture then cooled slowly after reaching thermal equilibrium at 600 700 c the data from this study point to the following history for the mesosiderite parent body 1 differentiation of a silicate parent body within the first 50 m y of solar system history to form diverse parent magmas 2 emplacement of primitive and differentiated mafic magmas near the planetary surface and extensive differentiation in the near surface environment 3 formation and reworking of regolith breccias through impact gardening at the near surface of the body 4 mixing of molten fe ni metal with the regolith followed by rapid cooling 100 150 m y after the origin of the solar system 5 slow cooling from temperatures of 700 c to produce the observed nickel diffusion profiles in the iron phase 6 mild impact metamorphism and brecciation to obtain the much younger k ar ages and 7 recent collisions or perturbations sending mesosiderite fragments into earth crossing trajectories

hf w chronometry of lunar metals and the age and early differentiation of the moon the use of hafnium tungsten chronometry to date the moon is hampered by cosmogenic tungsten 182 production mainly by neutron capture of tantalum 181 at the lunar surface we report tungsten isotope data for lunar metals which contain no 181 ta derived cosmogenic 182 w the data reveal differences in indigenous 182 w 184 w of lunar mantle reservoirs indicating crystallization of the lunar magma ocean 4 527 0 010 billion years ago this age is consistent with the giant impact hypothesis and defines the completion of the major stage of earth9s accretion

paleoenvironmental implications of early diagenetic siderites of the paraiba do sul deltaic complex eastern brazil abstract abundant early diagenetic siderites occur as spherulites and rhombohedral microcrystalline and macrocrystalline crystals in the cores of the 2 mu 1 rj well drilled in the paraiba do sul deltaic complex rio de janeiro brazil the host sediments of the siderites are siliciclastic hybrid and carbonate deposits intense pedogenetic processes affected the siliciclastic sediments immediately after deposition comprising clay illuviation plants bioturbation feldspar dissolution and iron oxide hydroxide precipitation siderite and pyrite are the main diagenetic constituents the other diagenetic products are kaolinite smectite argillaceous and carbonate pseudomatrix quartz overgrowths diagenetic titanium minerals jarosite and iron oxides hydroxides early diagenetic siderites were separated into four groups based on their elemental and stable isotopic composition as well as on their paragenetic relationships with the other constituents and with the host sediments spherulitic to macrocrystalline siderites from group 1 are almost pure average 94 7 mol feco3 1 2 mol mgco3 2 3 mol caco3 1 8 mol mnco3 and precipitated from meteoric porewaters in continental siliciclastic rocks under suboxic conditions 18ovpdb values range in 10 28 to 5 57 and the 13cvpdb values in 12 68 to 4 33 microcrystalline rhombohedral siderites from group 2 have zonation due to substantial ca and mg substitution core average 78 5 mol feco3 4 2 mol mgco3 15 7 mol caco3 1 6 mol mnco3 edge average 74 0 mol feco3 9 2 mol mgco3 15 6 mol caco3 1 1 mol mnco3 and 13cvpdb and 18ovpdb values of 0 17 and 1 96 precipitated from marine porewaters in packstones wackestones under methanogenic conditions the group 3 is represented by irregular spherulitic siderites with moderate ca and mg substitutions average 80 2 mol feco3 7 9 mol mgco3 11 3 mol caco3 0 6 mol mnco3 with 18ovpdb values ranging from 5 96 to 7 61 and 13cvpdb values ranging from 5 15 to 10 41 the group 4 microcrystalline siderites are magnesium rich average 57 3 mol feco3 31 4 mol mgco3 9 6 mol caco3 1 7 mol mnco3 13cvpdb 1 43 and 18ovpdb 14 09 the group 3 and 4 siderites were formed from brackish porewater under suboxic conditions in hybrid and siliciclastic rocks these variations in siderites are probably related to the paraiba do sul river dynamics to sea level changes and to climatic variations that took place during the quaternary

formation of diagenetic siderite in modern ferruginous sediments ferruginous conditions prevailed in the world s deep oceans during the archean and proterozoic eons sedimentary iron formations deposited at that time may provide an important record of environmental conditions yet linking the chemistry and mineralogy of these sedimentary rocks to depositional conditions remains a challenge due to a dearth of information about the processes by which minerals form in analogous modern environments we identified siderites in ferruginous lake towuti indonesia which we characterized using high resolution microscopic and spectroscopic imaging combined with microchemical and geochemical analyses we infer early diagenetic growth of siderite crystals as a response to sedimentary organic carbon degradation and the accumulation of dissolved inorganic carbon in pore waters we suggest that siderite formation proceeds through syntaxial growth on preexisting siderite crystals or possibly through aging of precursor carbonate green rust crystal growth ultimately leads to spar sized 50 m mosaic single siderite crystals that form twins bundles and spheroidal aggregates during burial early formed carbonate was detectable through microchemical zonation and the possible presence of residual phases trapped in siderite interstices this suggests that such microchemical zonation and mineral inclusions may be used to infer siderite growth histories in ancient sedimentary rocks including sedimentary iron formations

structural diagenesis of siderite layers in black shales albian black flysch northern spain abstractin this study we describe the structural diagenesis of diluted turbidite and abyssal lutite deposits of the late albian black flysch western pyrenees northern spain we analyze and interpret an association of brittle and ductile soft sediment deformation structures to our knowledge some of them are described for the first time although they are known in other tectonic settings we reconstruct a diagenetic history that commenced with a generalized siderite cement precipitation after siliciclastic turbidite deposition siderite replaced the finer grained diluted uppermost turbidite parts siderite precipitation was followed by calcite cementation in turbidites and by soft sediment brittle thrust planes shear veins and microveins and ductile fault bend folds and culminations developed in relation to thrust ramp strain deformation structures this occurred before hosting lutite lithification by dewatering and compaction

sideritic ironstones as indicators of depositional environments in the weald basin early cretaceous se england the lower cretaceous wealden sideritic ironstones have a wide occurrence and great potential to aid the reconstruction of the depositional environments of the weald basin in se england however mineralogical and geochemical datasets on the ironstones are scarce in the literature geochemical and mineralogical data on the sideritic ironstones are presented from the wadhurst clay formation within the weald basin the mineralogy of the ironstones was examined using a panalytical x pert pro x ray diffractometer and panalytical s highscore plus software elemental composition of the ironstones was measured using a panalytical minipal2 ed xrf benchtop x ray spectrometer the examination of the mineralogy of the wealden ironstones confirms the presence of early diagenetic siderites the trace element assemblage shows that the sideritic ironstones are chemically pure pointing to a freshwater origin the sideritic ironstones reveal anoxic conditions and palaeo salinity in the basin more generally it is suggested that the composition of the host rocks has significant controls on the composition of sideritic ironstones in sedimentary basins this work reinforces the importance of the composition of sideritic ironstones as useful non traditional data for understanding the depositional settings of sedimentary basins especially when traditional datasets are not readily available or insufficient

time and duration of lunar highlands crust formation abstract all radiometric systems indicate that crust mantle differentiation on the moon is dominated by events which occurred very early in lunar history however due to remaining uncertainties in model parameters and assumptions in the calculation of model ages it is not yet possible to resolve the precise times of occurrence of these events nor the duration of the formation of the highlands crust the strongest time constraints are offered by direct radiometric ages of samples formed during this earliest period two possible candidates for this material norites 78236 and 73255 27 45 were examined utilizing the sm nd radiometric system sm nd systematics of 78236 show post crystallization disturbance but indicate that this norite crystallized in the lunar crust about 4 34 ae ago data for 73255 27 45 define an isochron and yield a crystallization age of 4 23 0 05 ae the initial nd isotopic composition of both norites is within uncertainty of a chondritic reference reservoir at the time of their respective crystallizations the implications for lunar crustal formation persisting over a time span of close to 350 m y are discussed

the cristal zn prospect amazonas region northern peru part ii an example of supergene enrichments in tropical areas abstract the cristal zn prospect is located in the northernmost part of a wide mining district corresponding to the charlotte bongara zinc project which covers an area of approximately 110 km2 in the amazonas region in northern peru the mineralized area consists of many zn occurrences that contain mixed sulfide and nonsulfide mineralizations the nonsulfide ores are interpreted to be the product of weathering of primary mvt sulfide bodies the zn concentrations of the cristal prospect are hosted by platform carbonates of the condorsinga formation early jurassic which belongs to the pucara group the prospect extends over an area of approximately 2 1 km with nearly continuous zones of zn enrichment that has been detected in soil and rock samples the nonsulfide mineralization consists mainly of semi amorphous orange to brown zinc oxides that include hemimorphite smithsonite and fe hydr oxides the most important mineralized areas are the esperanza and yolanda occurrences which were also most intensively explored in both occurrences the supergene zn carbonates and silicates infill solution cavities or replace the carbonate host rocks and or the primary sulfides forming smithsonite and hemimorphite rich mineralizations the analyzed drill core samples have on average 20 wt zn and maximum ge concentrations of 200 ppm the bongara area experienced a prolonged phase of weathering from miocene to recent under tropical climatic conditions in these conditions the weathering processes affected many pre existing sulfide deposits e g cristal florida canyon mina grande where supergene profiles were developed under locally different settings that are defined primarily on the basis of mineralogical and geochemical data contrary to the mina grande deposit at cristal the development of a karst network was minor due to limited uplift and supergene alteration did not completely obliterate the roots of the original sulfide orebody the mineralogy and geochemistry of bongara nonsulfides is dependent on two main factors at the local scale 1 uplift rates and 2 host rock composition the latter may have favored the development of more e g mina grande or less e g cristal alkaline supergene environments uplift was controlled by the activity of local faults which allowed the exposure of sulfide protores at variable elevations in different periods of time and hydrological settings such different settings resulted in the precipitation of isotopically different supergene carbonates e g smithsonites and calcites at mina grande and cristal

analysis of lunar samples implications for planet formation and evolution the analysis of lunar samples returned to earth by the apollo and luna missions changed our view of the processes involved in planet formation the data obtained on lunar samples brought to light the importance during planet growth of highly energetic collisions that lead to global scale melting this violent birth determines the initial structure and long term evolution of planets once past its formative era the lunar surface has served as a recorder of more than 4 billion years of interaction with the space environment the chronologic record of lunar cratering determined from the returned samples underpins age estimates for planetary surfaces throughout the inner solar system and provides evidence of the dynamic nature of the solar system during the planet forming era

a young solidification age for the lunar magma ocean abstract the time at which the lunar magma ocean solidified can be determined from the lu hf isotope systematics of lunar rocks derived from magma sources that formed during crystallization of the lunar magma ocean the final magma ocean crystallization product termed urkreep is enriched in incompatible elements including k ree and p we have determined the initial hf isotopic compositions of four samples two kreep basalts and two mg suite norites the incompatible trace element compositions of these samples are controlled by an urkreep component and therefore the initial hf isotopic compositions of these samples represent the hf isotopic evolution of urkreep in order to correct the effects of neutron irradiation on the hf isotopic compositions of these samples we have developed a model that uses the stable hf and sm isotopic compositions measured on an irradiated sample to determine and correct for the thermal and epithermal neutron fluence that has modified the hf isotopic composition of the sample we use our corrected results to calculate a 176 lu 176 hf urkreep model age of 4353 37 ma and the 176 lu 177 hf of urkreep to be 0 0153 0 0033 the lu hf model age is concordant with the re calculated sm nd urkreep model age of 4389 45 ma and we take the average of these ages 4368 29 ma to represent the time at which urkreep formed this age is concordant with the age of the most reliably dated ferroan noritic anorthosite as well as 142 nd model ages for the formation or re equilibration of mare basalt sources taken together these ages indicate that the moon experienced a widespread large scale magmatic event around 4370 ma most plausibly attributed to solidification of the lunar magma ocean

the crystallographic fabric and texture of siderite in concretions implications for siderite nucleation and growth processes the crystallographic fabric of siderite in siderite concretions has been determined for upper carboniferous westphalian a non marine concretions and lower jurassic pliensbachian marine concretions compositional zoning indicates that individual siderite crystals grew over a period of changing pore water chemistry consistent with the concretions being initially a diffuse patch of cement which grew progressively the siderite crystallographic fabric was analysed using the anisotropy of magnetic susceptibility which is carried by paramagnetic siderite the siderite concretions from marine and non marine formations exhibit differences in fabric style although both display increases in the degree of preferred siderite c axis orientation towards the concretion margins the westphalian non marine siderites show a preferred orientation of siderite c axes in the bedding plane whereas the pliensbachian marine siderites have a preferred orientation of c axes perpendicular to the bedding in addition a single marine concretion shows evidence of earlier formed inclined girdle type fabrics which are intergrown with later formed vertical c axis siderite fabrics the marine and non marine fabrics are both apparently controlled by substrate processes at the site of nucleation which was probably clay mineral surfaces siderite nucleation processes on the substrate were most probably controlled by the bio chemistry of the pore waters which altered the morphology and crystallographic orientation of the forming carbonate the preferred crystallographic orientation of siderite results from the orientation of the nucleation substrate fabric changes across the concretions partially mimic the progressive compaction induced alignment of the clay substrates while the concretion grew during burial

age and isotopic relationships among the angrites lewis cliff 86010 and angra dos reis results of a wide ranging isotopic investigation of the unique antarctican angrite lew 86010 lew are presented together with a reassessment of the type angrite angra dos reis ador the principal objectives of this study are to obtain precise radiometric ages initial sr isotopic compositions and to search for the erstwhile presence of the short lived nuclei 146sm and 26al via their daughter products the isotopic compositions of sm u ca and ti were also measured this allows a detailed appraisal to be made of the relations between and the geneology of these two angrites lew proves to be severely contaminated with modern terrestrial pb which is shown to result from terrestrial weathering nevertheless concordant pb pb model ages of pyroxene separates were obtained 2 4 55784 52 ga for lew and 4 55780 42 ga for ador uranium isotopic compositions are normal within error the inferred initial pb isotopic composition is within error of primordial pb as defined by canon diablo troilite because of the extreme upb ratios of both angrites this places an upper limit of 2 ma on the time between volatile element loss of the angrite parent body or its precursor planetesimals and the final crystallization of the angrites as differentiates initial 87sr86sr ratios were found to be indistinguishable in lew ador and the cumulate eucrite moore county the derived initial 87sr86sr for all three meteorites is 0 698970 15 2 a 147sm 143nd isochron for lew was obtained yielding an age of 4 553 34 ga with an initial 143nd144nd of 0 506682 49 2 146sm142nd isotope systematics were also measured anomalies on 142nd arising from extinct 146sm were clearly resolved resulting in an initial 146sm144sm of 0 0071 17 with nd142 2 57 0 62 at the time of isotopic closure both of these sm nd methods imply derivation of lew from a reservoir with chondritic smnd ratio they are also quite consistent with the previously reported systematics for ador overall the age and isotopic similarities between lew and ador are striking it suggests almost simultaneous production on the same asteroid even though recent experimental studies imply that the two are not comagmatic calcium and titanium do not exhibit enrichments in the n rich isotopes in contrast to cais making it unlikely that the angrite parent body is inherently rich in early condensates from the solar nebula no evidence was found for live 26al in lew when combined with the pb pb age and initial 87sr86sr data this firmly excludes 26al being an important heat source in the early solar system heat supplied for for example 1 the differentiation of the angrite and eucrite parent bodies and 2 metamorphism of the chondrite parent bodies must come from some other source the debate over live vs extinct 26al in the earliest solar system remains unresolved by this new data from lew however both the angrite and eucrite parent bodies have extremely low rbsr and high upb ratios compared to the solar nebula therefore the common initial 87sr86sr of 0 698970 can be firmly associated with the u pb angrite age above and the formation of both bodies this enables an absolute chronology of the early solar system to be established based upon 87sr86sr differences the oldest cais are a minimum of 11 4 ma older than the angrites i e 4 569 5 ga the age and isotopic constraints are discussed with respect to current collapse condensation and accretion timescales calculated for the solar nebula

a new view of lunar ferroan anorthosites postmagma ocean petrogenesis 1 new melting experiments in the range of 0 1 mpa to 4 7 gpa provide the basis for calculations of polybaric crystallization which show that both a 300 km deep magma ocean mo enriched in refractory elements and a 600 km deep magma ocean with refractory element concentrations similar to the earth s upper mantle produce sufficient amounts of differentiated residual liquid capable of crystallizing the troctolitic noritic mineral assemblages that are prevalent in lunar ferroan anorthosites lfa however the both oceans become saturated with augite after 20 30 crystallization of the plagioclase saturated residuum and thereafter are no longer capable of producing noritic assemblages a second set of melting experiments reveals the existence of a previously unrecognized equilibrium augite liquid pigeonite plagioclase and a thermal minimum on the pigeonite plagioclase liquidus surface at 0 6 gpa these equilibria will produce melts of mafic cumulates with lower wo content than those from which the cumulates originally formed in a postmagma ocean environment of overturning mafic cumulates melt thus formed and entrained in a buoyant segregation of plagioclase would then form diapiric masses that would crystallize troctolitic noritic assemblages after intruding upward diapiric intrusions could also provide the local deformational environment needed to produce the apparently high 95 plagioclase modes of the lfa an unstable density profile in the cumulate pile following crystallization of most of the mo should provide the impetus for overturn and the heat for partially remelting mafic cumulates

middle and late jurassic roots of brachyuran crabs palaeoenvironmental distribution during their early evolution abstract knowledge of early mesozoic crabs is still rudimentary mainly due to the poor preservational potential of crustacean decapods fossil evidence suggests that the family prosopidae is ancestral to all other brachyurans including podotremata with a very close phylogenetic relationship to homolodromiidae dromiidae homolidae latreillidae dynomenidae xanthidae cyclodorippoidea and calappoidea prosopidae is an extinct family consisting mostly of mesozoic species almost exclusively known by their carapaces this family appeared in the late early jurassic late pliensbachian and disappeared at the end of the danian the early jurassic pliensbachian oldest crab species eocarcinus praecursor withers is transitional in many of its observable traits between the macruran glypheoidea middle triassic pseudopemphix and the early brachyuran prosopids especially the earliest known species eoprosopon klugi forster late pliensbachian middle jurassic prosopids lived in shallow sea soft bottom environments the oldest known prosopid species lived on a silty sea floor as did the first known crab late early pliensbachian and their presumed ancestors pemphicidae were probably also shallow water organisms middle jurassic prosopids lived both in shallow warm waters within organic buildups shelly accumulations and on silty sea floors during the bajocian bathonian as illustrated by a new example from central poland prosopids had an evolutionary climax during the late jurassic and were widely distributed in sponge microbial oxfordian buildups and coral reef kimmeridgian tithonian environments of europe pithonoton coelopus longodromites prosopon nodoprosopon lecythocaris glaessneropsis when biohermal and reef facies retreated at the end of the jurassic favourable conditions for prosopid crabs diminished and cretaceous prosopids are rare and spatially dispersed their closely related descendants the homolodromiids preferentially inhabited soft muddy bottoms in deeper colder waters as is well documented by cenozoic and recent occurrences

xas evidence for ni sequestration by siderite in a lateritic ni deposit from new caledonia mineralogical and spectroscopic analyses were conducted on a lateritic ni deposit from southern new caledonia results show that ni is incorporated in siderite feco3 found between 37 and 40 m depth in the laterite and saprolite units of the regolith sem edxs analyses of siderite rich samples indicate that a significant amount of nickel can be hosted by this crystalline phase 0 8 wt nio ni and fe k edge extended x ray absorption fine structure exafs spectroscopic analyses of the siderite rich samples from the regolith as well as comparison with synthetic ni bearing and ni free siderites demonstrate isomorphous substitution of ni2 for fe2 in the siderite structure linear combination fitting lcf of the ni k edge exafs data reveals that this ni bearing siderite species accounts for more than 90 of the total ni pool 1 wt nio in the siderite rich horizons of the regolith in addition lcf analysis of the exafs spectra indicates that goethite and serpentine are the major ni hosts in the upper horizons laterite and lower horizons saprolite of the regolith respectively formation of siderite an uncommon mineral species in such oxidized environments is attributed to the development of swampy conditions in organic rich lateritic materials that accumulated at the bottom of dolines these results thus show the importance of siderite as a host for nickel in lateritic ni deposits that have been affected by late hydromorphic and reducing conditions

origin of the lunar highlands mg suite an integrated petrology geochemistry chronology and remote sensing perspective the mg suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation this review examines the mineralogy geochemistry petrology chronology and the planetary scale distribution of this suite of highlands plutonic rocks presents models for their origin examines petrogenetic relationships to other highlands rocks and explores the link between this style of magmatism and early stages of lunar differentiation of the models considered for the origin of the parent magmas for the mg suite the data best fit a process in which hot solidus temperature at 2 gpa 1600 to 1800 c and less dense 3100 kg m3 early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn some decompressional melting would occur but placing a hot cumulate horizon adjacent to the plagioclase rich primordial crust and kreep rich lithologies at temperatures of 1300 c would result in the hybridization of these divergent primordial lithologies producing mg suite parent magmas as urkreep primeval kreep is not the petrologic driver of this style of magmatism outside of the procellarum kreep terrane pkt mg suite magmas are not required to have a kreep signature evaluation of the chronology of this episode of highlands evolution indicates that mg suite magmatism was initiated soon after primordial differentiation 10 m y alternatively the thermal event associated with the mantle overturn may have disrupted the chronometers utilized to date the primordial crust petrogenetic relationships between the mg suite and other highlands suites e g alkali suite and magnesian anorthositic granulites are consistent with both fractional crystallization processes and melting of distinctly different hybrid sources

the early differentiation history of mars from 182w 142nd isotope systematics in the snc meteorites we report here the results of an investigation of w and nd isotopes in the snc shergottite nakhlite chassignite martian meteorites we have determined that 182 w values in the nakhlites are uniform within analytical uncertainties and have an average value of 3 also while 182 w values in the shergottites have a limited range from 0 3 0 7 their 142 nd values vary considerably from 0 2 0 9 there appears to be no correlation between 182 w and 142 nd in the nakhlites and shergottites these results shed new light on early differentiation processes on mars particularly on the timing and nature of fraction ation in silicate reservoirs assuming a two stage model the metallic core is estimated to have formed at 12 myr after the beginning of the solar system major silicate differentiation established the nakhlite source reservoir before 4542 ma and the shergottite source reservoirs at 4525 19 ma these ages imply that within the uncertainties afforded by the 182 hf 182 w and 146 sm 142 nd chronometers the silicate differentiation events that established the source reservoirs of the nakhlites and shergottites may have occurred contempo raneously possibly during crystallization of a global magma ocean the distinct 182 w 142 nd isotope systematics in the nakhlites and the shergottites imply the presence of at least three isotopically distinct silicate reservoirs on mars two of which are depleted in incompatible lithophile elements relative to chondrites and the third is enriched the two depleted silicate reservoirs most likely reside in the martian mantle while the enriched reservoir could be either in the crust or the mantle therefore the 182 w 142 nd isotope systematics indicate that the nakhlites and the shergottites originated from distinct source reservoirs and cannot be petrogenetically related a further implication is that the source reservoirs of the nakhlites and shergottites on mars have been isolated since their establishment before 4 5 ga therefore there has been no giant impact or efficient global mantle convection to thoroughly homogenize the martian mantle following the establish ment of the snc source reservoirs copyright 2005 elsevier ltd

chronological evidence that the moon is either young or did not have a global magma ocean a new age determination for a moon rock collected close to the site of the apollo 16 lander has yielded a surprisingly young age of around 4 360 million years this age would require either that the moon solidified some 200 million years after the formation of the solar system significantly later than is assumed by most lunar formation models or that the long held theory that the moon once had a primordial global magma ocean is flawed in the latter case much of the lunar crust could have been produced by non magma ocean processes such as serial magmatism chemical evolution of planetary bodies ranging from asteroids to the large rocky planets is thought to begin with differentiation through solidification of magma oceans many hundreds of kilometres in depth1 2 3 the earth s moon is the archetypical example of this type of differentiation evidence for a lunar magma ocean is derived largely from the widespread distribution compositional and mineralogical characteristics and ancient ages inferred for the ferroan anorthosite fan suite of lunar crustal rocks the fans are considered to be primary lunar flotation cumulate crust that crystallized in the latter stages of magma ocean solidification according to this theory fans represent the oldest lunar crustal rock type2 3 4 attempts to date this rock suite have yielded ambiguous results however because individual isochron measurements are typically incompatible with the geochemical make up of the samples and have not been confirmed by additional isotopic systems5 6 7 8 9 by making improvements to the standard isotopic techniques we report here the age of crystallization of fan 60025 using the 207pb 206pb 147sm 143nd and 146sm 142nd isotopic systems to be 4 360 3 million years this extraordinarily young age requires that either the moon solidified significantly later than most previous estimates or the long held assumption that fans are flotation cumulates of a primordial magma ocean is incorrect if the latter is correct then much of the lunar crust may have been produced by non magma ocean processes such as serial magmatism10

chromium isotopic homogeneity between the moon the earth and enstatite chondrites abstract among the elements exhibiting non mass dependent isotopic variations in meteorites chromium cr has been central in arguing for an isotopic homogeneity between the earth and the moon thus questioning physical models of moon formation however the cr isotopic composition of the moon relies on two samples only which define an average value that is slightly different from the terrestrial standard here by determining the cr isotopic composition of 17 lunar 9 terrestrial and 5 enstatite chondrite samples we re assess the isotopic similarity between these different planetary bodies and provide the first robust estimate for the moon in average terrestrial and enstatite samples show similar e 54 cr on the other hand lunar samples show variables excesses of 53cr and 54cr compared to terrestrial and enstatite chondrites samples with correlated e 53 cr and e 54 cr per 10 000 deviation of the 53cr 52cr and 54cr 52cr ratios normalized to the 50cr 52cr ratio from the nist srm 3112a cr standard unlike previous suggestions we show for the first time that cosmic irradiation can affect significantly the cr isotopic composition of lunar materials moreover we also suggest that rather than spallation reactions neutron capture effects are the dominant process controlling the cr isotope composition of lunar igneous rocks this is supported by the correlation between e 53 cr and e 54 cr and 150sm 152sm ratios after correction of these effects the average e 54 cr of the moon is indistinguishable from the terrestrial and enstatite chondrite materials reinforcing the idea of an earth moon enstatite chondrite system homogeneity this is compatible with the most recent scenarios of moon formation suggesting an efficient physical homogenization after a high energy impact on a fast spinning earth and or with an impactor originating from the same reservoir in the inner proto planetary disk as the earth and enstatite chondrites and having similar composition

samarium neodymium evolution of meteorites we have obtained sm nd data on two differentiated meteorites ibitira a eucrite with distinct basaltic texture and with evidence of crystallization and morristown a group 3a mesosiderite as well as on acapulco an unclassified meteorite with chondritic chemical composition and a highly recrystallized texture we have demonstrated the presence of in situ decay of short lived 146 sm in these meteorites with initial abundance of 146 sm 144 sm from 0 009 to 0 007 for the different meteorites precisely defined 147 sm 143 nd internal isochrons were obtained yielding ages of 4 60 0 03 ae for acapulco 4 47 0 02 ae for morristown and 4 46 0 02 ae for ibitira the corresponding initial 143 nd 144 nd values obtained were 0 2 0 9 2 1 0 7 and 1 6 0 8 u epsilon units detailed consideration of the coupled 147 sm 143 nd and 146 sm 142 nd systematics and of the elevated initial 143 nd 144 nd values indicates the presence of inconsistencies in the data for the two sm nd parent daughter pairs in spite of the precise isochrons we present a model which provides an interpretation of the paired sm nd systematics in terms of an impulsive disturbance the abundance of phosphate with large concentrations of rees controls the ree economy plagioclase with low ree concentrations is assumed to be susceptible to exchange pyroxene is considered to be undisturbed because of the low diffusion coefficients of trace elements the experimental results can be reasonably explained by this model the results indicate that three meteorites studied some with very low ree concentrations including a mesosiderite are relatively ancient objects formed within the first 50 to 100 m y of the solar system by planetary differentiation and impact processes and were subjected to late metamorphism the time of late metamorphism is substantially younger than 4 4 ae and possibly as recent as 3 9 ae this metamorphism has resulted in partial very limited reequilibration between plagioclase and phosphate resulting in the observed shifts in initial 143 nd 144 nd sm nd model ages and the 142 nd 144 nd abundances but preserving the major temporal structures of early original formation and later disturbances these results show the need for care in the interpretation of the parent daughter systematics even when they appear well behaved and the mineral phases are viewed as highly resistant to mild metamorphism

groundwater table fluctuations recorded in zonation of microbial siderites from end triassic strata in a terrestrial triassic jurassic boundary succession of southern sweden perfectly zoned sphaerosiderites are restricted to a specific sandy interval deposited during the end triassic event underlying and overlying this sand interval there are several other types of siderite micromorphologies i e poorly zoned sphaerosiderite spheroidal ellipsoid siderite spherical siderite and rhombohedral siderite siderite overgrowths occur mainly as rhombohedral crystals on perfectly zoned sphaerosiderite and as radiating fibrous crystals on spheroidal siderite concretionary sparry microspar and or micritic siderite cement postdate all of these micromorphologies the carbon isotope composition of the siderite measured by conventional mass spectrometry shows the characteristic broad span of data probably as a result of multiple stages of microbial activity sims secondary ion mass spectrometry revealed generally higher 13c values for the concretionary cement than the perfectly zoned sphaerosiderite spheroidal siderite and their overgrowths which marks a change in the carbon source during burial all the various siderite morphologies have almost identical oxygen isotope values reflecting the palaeo groundwater composition a pedogenic freshwater origin is supported by the trace element compositions of varying fe mn ratios and low mg contents fluctuating groundwater is the most likely explanation for uniform repeated siderite zones of varying fe mn ratios reflecting alternating physiochemical conditions and hostility to microbial life activity bacterially mediated siderite precipitation likely incorporated mn and other metal ions during conditions that are not favourable for the bacteria and continued with fe rich siderite precipitation as the physico chemical conditions changed into optimal conditions again reflecting the response to groundwater fluctuations

a highly depleted moon or a non magma ocean origin for the lunar crust abstract coupled 146 147 sm 142 143 nd systematics were analyzed on lunar samples that span the range of source compositions created in the early lunar differentiation event ferroan anorthosites high mg suite norite kreep and low and high ti basalts if fit with a single isochron the data agree with previous suggestions of a 250 ma duration for closure of the sm nd system in the lunar interior the two crustal rocks 60025 and 78236 among oldest samples found on the lunar surface have high initial 142 nd 144 nd ratios e 142 nd 0 24 0 27 relative to o chondrites which indicates that they derive from a source strongly depleted in light rare earth elements lree 147 sm 144 nd 0 23 this result suggests either that the moon formed with a strongly superchondritic sm nd ratio or that the lunar crust formed as a product of a post magma ocean remelting of lree depleted cumulates in the lunar interior the basalt data measured here add support to the idea that the lunar interior evolved with a superchondritic sm nd similar to that of the early earth addition of differentiation steps adds complexity and inherit non uniqueness to the interpretation of the lunar nd isotope data but our preferred model has the first stage of lunar evolution 4 567 to 4 44 ga occurring on an already differentiated earth with the moon forming shortly before 4 45 ga and undergoing rapid magma ocean evolution to form the crust the high sm nd source reservoirs of many mare basalt types and kreep by 4 44 ga continued differentiation of the lunar interior through the increasing depletion of the source of high ti mare basalts then continued until 4320 ma

the lunar neutron energy spectrum inferred from the isotope compositions of rare earth elements and hafnium in apollo samples abstract the isotopic abundances of sm gd dy er yb and hf have been measured in nine lunar samples by mc icp ms the data were corrected for both instrumental mass bias and natural isotope fractionation we used the data to calculate the total flux and energy spectrum of the neutrons absorbed by the rocks we write the constitutive equations of the isotopic changes for these elements induced by neutrons and solve the inverse problem by computing local energy averages resonant absorption peaks can be used as convenient kernels to define the spectrum of epithermal neutrons we find that 149sm and 157gd anomalies correlate with neutron flux density for e 0 015 ev r 2 0 98 and e 0 13 ev r 2 0 85 while no significant correlation exists between the ratio of these anomalies and the epithermal thermal flux ratio at any value of energy neutron flux density variations can be used to trace the proportions of neutrons scattered out of the samples the spectrum in the thermal region follows the expected e 1 2 dependence but with notches corresponding to neutron absorption a major notch at the lowest end of the epithermal neutron spectrum 0 2 0 8 ev is possibly due to absorption of neutrons by 151eu 167er and 149sm in general we find a rather good correlation between the neutron flux density at specific energies and the exposure age which suggests a mean residence time of the samples at the surface of the regolith of 2 300 ma another correlation of epithermal neutrons with sample wt feo tio2 is consistent with orbital reflectance observations

146sm 142nd formation interval for the lunar mantle now extinct 146sm t1 2 103ma was present in the early solar system and lunar basalts might be expected to have inherited small anomalies in 142nd abundances from mantle sources with variable sm nd ratios established during the early global differentiation of the moon 142nd 144nd ratios were measured for several lunar basalts and values of nd142 deviations from terrestrial 142nd 144nd in parts in 104 calculated for them the nd142 values show very small variations attributable to 146sm decay neutron capture near the lunar surface also modified both the samarium and neodymium isotopic compositions of the basalt samples the calculated neutron fluences range from 0 to 7 8 1016 n cm2 both thermal and epithermal neutron fluences were calculated from the sm isotopic compositions of the basalts and used to correct the nd142 values for neutron capture by neodymium well resolved radiogenic enrichments nd142 and 0 17 0 08 2 respectively were measured for lunar meteorite asuka 881757 and apollo 17 basalt 74255 respectively for which the neutron fluences were nil basalts 70135 and 75075 which were exposed to small measureable neutron fluences of 2 5 1015 and 7 7 1015 n cm2 respectively have neutron corrected nd142 values of 0 25 0 15 and 0 29 0 11 respectively the average value of radiogenic nd142 for the three high ti basalts from apollo 17 is 0 22 0 06 neutron capture effects were greater for the other basalts but can be corrected using the measured neutron fluences derived from the samarium isotopic data the neutron corrected nd142 for apollo 12 ilmenite basalt 12056 consistent with its derivation from a highly depleted mantle source also three low ti basalts from apollo 12 and apollo 15 12038 15076 15555 have neutron corrected nd142 which are not resolved from zero and average 0 04 0 06 a fourth low ti basalt 12039 has neutron corrected nd142 but is subject to the largest neutron correction of 0 32 e units kreep basalt 14078 was exposed to only a small neutron fluence of 6 4 1015 n cm2 and has a small deficit of 142nd corresponding to nd142 the average neutron corrected nd142 of three kreep basalts is 0 05 0 04 the nd142 values of the basalts correlate with 147sm 144nd values for their source regions as calculated from their ages and initial nd142 values 147sm 143nd and 146sm 142nd systematics were combined in a three stage model yielding an isochron equation for the lunar mantle formation interval which was calculated to be 238 40 56 ma 2 sm nd ratios for the source regions also are derived from the model and compare favorably with values from conventional geochemical models of mare basalt petrogenesis if the moon were formed by impact of a large mars sized planetesimal with the earth the impact was early enough that the lunar mantle cooled to neodymium isotopic closure by 4 32 ga ago the bulk lunar moon142 evaluated from the mantle isochron at 147sm 144nd chur 0 1967 is 0 01 0 03 2 consistent with derivation of lunar and terrestrial neodymium from a common reservoir

accretion timescale and impact history of mars deduced from the isotopic systematics of martian meteorites abstract high precision sm nd isotopic analyses have been completed on a suite of 11 martian basaltic meteorites in order to better constrain the age of silicate differentiation on mars associated with the formation of their mantle sources these data are used to evaluate the merits and disadvantages of various mathematical approaches that have been employed in previous work on this topic ages determined from the sm nd isotopic systematics of individual samples are strongly dependent on the assumed nd isotopic composition of the bulk planet this assumption is problematic given differences observed between the nd isotopic composition of earth and chondritic meteorites and the fact that these materials are both commonly used to represent bulk planetary nd isotopic compositions ages determined from the slope of 146sm 142nd whole rock isochrons are not dependent on the assumed 142nd 144nd ratio of the planet but require the sample suite to be derived from complementary contemporaneously formed reservoirs in this work we present a mathematical expression that defines the age of formation of the source regions of such a suite of samples that is based solely on the slope of a 143nd 142nd whole rock isochron and is also independent of any a priori assumptions regarding the bulk isotopic composition of the planet this expression is also applicable to mineral isochrons and has been used to successfully calculate 143nd 142nd model crystallization ages of early refractory solids as well as lunar samples this permits ages to be obtained using only nd isotopic measurements without the need for 147sm 144nd isotope dilution determinations when used in conjunction with high precision nd isotopic measurements completed on martian meteorites this expression yields an age of formation of the martian basaltic meteorite source regions of 4504 6 ma because the sm nd model ages for the formation of martian source regions are commonly interpreted to record the age at which large scale mantle reservoirs formed during planetary differentiation associated with magma ocean solidification the age determined here implies that magma ocean solidification occurred several tens of millions of years after the beginning of the solar system recent thermal models however suggest that mars sized bodies cool rapidly in less than 5 ma after accretion ceases even in the presence of a thick atmosphere assuming these models are correct an extended period of accretion is necessary to provide a mechanism to keep portions of the martian mantle partially molten until 4504 ma late accretional heating of mars could either be associated with protracted accretion occurring at a quasi steady state or alternatively be associated with a late giant impact if this scenario is correct then accretion of mars sized bodies takes up to 60 ma and is likely to be contemporaneous with the core formation and possibly the onset of silicate differentiation this further challenges the concept that isotopic equilibrium is attained during primordial evolution of planets and may help to account for geochemical evidence implying addition of material into planetary interiors after core formation was completed

magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase a new bulk silicate moon model with sub chondritic ti ba sr ba and sr al ratios abstract the compositions of host magmas of ferroan anorthosites fan host magmas were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks the evolution of the magmas was investigated by considering phase relations based on the melts algorithm and by re examining partition coefficients for trace elements between plagioclase and melts data little affected by post magmatic processes were selected by using plagioclase with relatively primitive sc and co contents the fan host magma contained 90 174 ppm sr 40 119 ppm ba and 0 5 1 3 tio2 and had sub chondritic sr ba and ti ba ratios it is difficult to account for the formation of fan host magma on the basis of magma evolution processes of previously proposed bulk silicate moon models with chondritic ratios for refractory elements at global scale therefore the source of the fan host magma must have had primordial sub chondritic sr ba and ti ba ratios the fan host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites and some very low ti mare rocks from lunar meteorites here we propose an alternative bulk silicate moon model the cbsm model which is enriched in crustal components of proto bodies relative to the present whole earth moon system

old sm nd ages for cumulate eucrites and redetermination of the solar system initial 146sm 144sm ratio article i nfo sm 142 nd systematics short lived 146 sm 142 nd and long lived 147 sm 143 nd chronometers have been measured in three cumulate eucrites binda moore county and moama the two major mineral phases plagioclase and pyroxene present in these achondrites are characterized by a wide range of sm nd ratios that allows well resolved sm nd isochrons this group of meteorites thus is suitable to better constrain the initial 146 sm 144 sm ratio of the solar system binda and moore county give concordant ages of 4544 88 and 4542 85 ma respectively with initial 143 nd 144 nd ratios slightly higher to within error of chondritic these ages are in agreement with most of the radiometric ages determined on basaltic eucrites a best estimate for the solar system initial 146 sm 144 sm ratio is obtained using the five point regression line determined for binda the 146 sm 144

effect of bacteria on the elemental composition of early diagenetic siderite implications for palaeoenvironmental interpretations many ancient early diagenetic siderite concretions are thought to have been precipitated by microbially mediated reactions and their trace element chemistry has been used to infer palaeoenvironments of formation e g marine versus freshwater in this study pure cultures of the microorganism geobacter metallireducens were used to precipitate siderite in the laboratory at a range of temperatures 18 40 c magnesium and calcium in three different ratios 3 1 as in seawater 1 1 and 1 3 as in freshwater or manganese were added to some cultures at each incubation temperature to study trace element incorporation the siderite produced exhibited the rhombohedral crystal form typical of concretionary siderite however this microbial siderite did not simply retain the trace element chemistry of the water from which it precipitated as is assumed in palaeoenvironmental interpretations instead manganese and calcium incorporation were found to be inversely proportional to the rate of microbial activity which itself is dependent upon the nutritional status of the microorganisms magnesium incorporation was found to be rate independent and at high mg ca ratios it caused inhibition of calcium incorporation in short the influence of microorganisms on the trace element composition of early diagenetic siderite must be taken into account in order to produce valid palaeoenvironmental interpretations

a shorter 146sm half life measured and implications for 146sm 142nd chronology in the solar system radiometric dating relies on measuring the abundance of long lived radionuclides relative to the abundance of their radiogenic decay products a process determined by the original radionuclide s half life for primordial radionuclides that decay slowly such as 146sm decaying to 142nd this method provides the timing of some of the earliest processes in solar system history using accelerator mass spectrometry kinoshita et al p 1614 1 provide a revised estimate for the 146sm half life of 68 7 million years which is 30 shorter than the previously accepted value this shorter half life suggests that reductions need to be made in the estimated ages for differentiation of earth s mantle and the solidification of the moon s magma ocean and for other more recent processes 1 lookup doi 10 1126 science 1215510

an ancient sm nd age for a ferroan noritic anorthosite clast from lunar breccia 67016 strontium and neodymium systematics have been examined in a clast of ferroan noritic anorthosite from apollo 16 breccia 67016 two splits 328 and 326 of the same clast give different sm nd results split 328 gives a well defined internal isochron age of 4 562 0 068 ga and an initial 143nd 144nd ratio of 0 50673 10 corresponding to nd 0 1 0 2 2 optimized error relative to the murchinson carbonaceous chondrite the pyroxene separate from split 326 lies on the same isochron in contrast the plagioclase and whole rock from split 326 fall below this line indicating a small scale disturbance of the sm nd system this may reflect either an isotopic exchange between the plagioclase and a low sm nd mineral or a loss of radiogenic 143nd from the plagioclase possibly during the period of major impacts at 3 9 ga the preservation of an extremely old age for the noritic ferroan anorthosite 67016 328 suggests a rapid cooling of this rock at an early stage in the evolution of the lunar magma ocean this old age is also consistent with giant impact models for the formation of the moon but implies a relatively early event pre 4 50 ga and therefore rapid accretion and differentiation of the terrestrial planets

60fe in eucrites additional evidence for the existence in the early solar system of live60fe has been found in the basaltic achondrite juvinas the relative abundance of 60fe 56fe of x0223c 4 10 10 at the time of meteorite solidification is one order of magnitude lower than that previously observed for the eucrite chervony kut this difference corresponds to a 4 7 ma time interval between closure of the60fe 60ni isotopic system in the two meteorites the factor two higher initial 60ni 58ni ratio in juvinas is consistent with this time difference and a common bulk fe ni ratio in the two meteorites using the60fe 60ni isotope system as a chronometer various models for the evolution of the eucrite parent body of different degrees of complexity are discussed regardless of the detailed differences between these models a short time interval of only a few million years between planetary differentiation and basaltic crust formation is indicated

authigenic minerals in fossil bones from the mesozoic of england poor correlation with depositional environments abstract petrographic microscopy x ray diffractometry and scanning electron microscopy energy dispersion spectrometry studies of cavity infills of bone samples from english mesozoic vertebrate deposits isle of wight swanage lyme regis aust cliff westbury garden cliff tytherington allow a better understanding of the distribution of authigenic minerals in bone voids and shed light on the importance of diagenetic processes on bone preservation surprisingly few minerals were identified as void fillers in all depositional environments carbonates sulphides oxides and sulphates being most abundant calcite is present in almost all samples pyrite is very common in voids as well as incorporated into bone francolite in many samples several generations of infills are found often consisting of layered cements the co occurrence of the common minerals indicates anaerobic slightly alkaline and often sulphate reducing environments in the bone voids later oxidation is common in iron minerals calcite pyrite and barite lack unambiguous environmental control whereas sphalerite is possibly an indicator for marine deposits freshwater deposits show no particular mineral combination which would help in separating them from other environments in some instances sediment infills and pyrite show geopetal structures

carbonate precipitation under bulk acidic conditions as a potential biosignature for searching life on mars recent observations of carbonate minerals in ancient martian rocks have been interpreted as evidence for the former presence of circumneutral solutions optimal for carbonate precipitation sampling from surface and subsurface regions of the low ph system of rio tinto has shown unexpectedly that carbonates can form under diverse macroscopic physicochemical conditions ranging from very low to neutral ph 1 5 7 0 a multi technique approach demonstrates that carbonate minerals are closely associated with microbial activity carbonates occur in the form of micron size carbonate precipitates under bacterial biofilms mineralization of subsurface colonies and possible biogenic microstructures including globules platelets and dumbbell morphologies we propose that carbonate precipitation in the low ph environment of rio tinto is a process enabled by microbially mediated neutralization driven by the reduction of ferric iron coupled to the oxidation of biomolecules in microbially maintained circumneutral oases where the local ph at the scale of cells or cell colonies can be much different than in the macroscopic environment acidic conditions were likely predominant in vast regions of mars over the last four billion years of planetary evolution ancient martian microbial life inhabiting low ph environments could have precipitated carbonates similar to those observed at rio tinto preservation of carbonates at rio tinto over geologically significant timescales suggests that similarly formed carbonate minerals could also be preserved on mars such carbonates could soon be observed by the mars science laboratory and by future missions to the red planet

the formation and evolution of the moon s crust inferred from the sm nd isotopic systematics of highlands rocks abstract ages determined for magnesian and ferroan anorthosite crustal rock suites overlap suggesting they formed contemporaneously about 4 3 4 5 ga a notable exception is the sm nd age previously determined on mg suite gabbronorite 67667 which is at least 100 ma younger than the youngest ferroan anorthosite new chronologic measurements of 67667 presented here yield concordant sm nd and rb sr mineral isochron ages of 4349 31 ma and 4368 67 ma suggesting the sample is older than previous estimates furthermore a whole rock sm nd isochron of mg suite rocks from the apollo 14 15 16 and 17 landing sites yields an age of 4348 25 ma indicating that mg suite magmatism was widespread and roughly contemporaneous on the lunar nearside analysis of sm nd internal isochron ages confirms that mg suite magmatism was restricted to a period between about 4 33 and 4 35 ga at the apollo 14 15 16 and 17 landing sites and was synchronous with magmatism at the apollo 16 site associated with the ferroan anorthosite suite between 4 35 and 4 37 ga magnesian and ferroan anorthosite suite rocks with ages younger than 4 33 ga appear to have experienced slow cooling in the deep lunar interior so that the ages record when the samples cooled below the closure temperature of the sm nd isotopic system and not the time they crystallized the ages determined for mg suite and ferroan anorthosite suite rocks are concordant with the age determined for the formation of urkreep of 4350 34 ma using the sm nd isotopic systematics of 67667 and measurements completed on norite 78238 troctolite 76535 kreep basalt 15386 and gabbronorite nwa 773 crystallization ages of mg suite and fas are also concordant with the average of 146sm 142nd ages previously determined for the formation of the mare basalt source region of 4333 30 ma the similarity of ages for mg suite magmatism ferroan anorthosite suite magmatism urkreep formation and formation of the mare basalt source regions implies the processes that produced these rocks were petrogenetically linked it also implies that both early stage and late stage lunar magma ocean cumulates formed over a relatively short duration of

two stage models for lunar and terrestrial anorthosites petrogenesis without a magma ocean two stage diapiric models for lunar ferroan anorthosites and terrestrial massif anorthosites are examined the lunar model is developed to explain early lunar differentiation in the absence of a magma ocean if correct the terrestrial model serves as an analog for the development of lunar anorthositic diapirs there is field and textural evidence of transport of mostly crystalline anorthositic material within the terrestrial complexes this evidence combined with the absence of anorthositic lavas and phase equilibrium constraints inhibiting the production of hyperaluminous magmas is consistent with the detachment of plagioclase rich crystalline mushes from large uppermost mantle plutons and multiple diapiric intrusion of these mushes into the upper sialic crust with attendant anatexis rudimentary dynamical calculations suggest that a simple single layer source for the diapirs is improbable either there were several parental magma chambers or there was a single large chamber that was repeatedly replenished the lunar model is a development of wetherill s 1975 suggestion that following accretion the outer portion of the moon consisted of a stack of overlapping layered intrusions and that reheating of these intrusions mobilized their anorthositic layers which intruded upwards to produce the anorthositic lunar crust dynamical calculations show that gravitational instabilities in anorthositic layers 1 km thick could develop into diapirs on a reasonable time scale 50 100 m y only if the outer portion of the moon was partially remelted we suggest that partial melting of the interior due to the decay of long lived radionuclides with the subsequent onset of global convection heated the stack of intrusions from below thus causing melting and allowing the anorthositic diapirs to grow and ascend fairly rapidly as the convecting zone thickened a mass expulsion of anorthositic material out of the lunar interior may have occurred

isotopic evidence for a young lunar magma ocean abstract mare basalt sources and ferroan anorthosite suite cumulates define a linear array on a 146sm 144nd versus 142nd 144nd isochron plot demonstrating these materials were derived from a common reservoir at 4336 31 32 ma the minimum proportion of the moon that was in isotopic equilibrium at this time is estimated to be 1 3 of its entire volume based on the geographic extent from which the analyzed samples were collected and the calculated depths from which the samples were derived scenarios in which large portions of the moon were molten to depths of many hundreds of kilometers are required to produce the observed sm nd isotopic equilibrium between the mantle and crustal rocks at 4 34 ga this is a consequence of the fact that limited heating of a solid moon above the blocking temperature of the sm nd isotopic system is insufficient to diffusively homogenize radiogenic nd throughout the mantle and crust there are three scenarios that might account for global scale isotopic equilibrium on the moon relatively late in solar system history including 1 sm nd re equilibration of a solid moon resulting from widespread melting in response to mantle overturn or a very large impact 2 early accretion of the moon followed by delayed cooling due to the presence of an additional heat source that kept a large portion of the moon molten until 4 34 ga or 3 late accretion of the moon followed by rapid cooling of the magma ocean late in solar system history neither density driven overturn of the mantle nor a large impact are likely to homogenize the mantle and crust to the extent required by the sm nd isochron likewise secondary heating mechanisms such as tidal heating or radioactive decay are not efficient enough to keep the moon molten to the depth of the mare basalt source regions for many tens to hundreds of millions of years instead the age of equilibrium between such a compositionally diverse set of rocks produced on a global scale likely records the time of primordial solidification of the moon from a magma ocean this scenario accounts for both the petrogenetic characteristics of lunar rock suites as well as their sm nd isotopic systematics it is supported by the preponderance of 4 35 ga ages obtained for other hypothetical magma ocean crystallization products such as ferroan anorthosite suite rocks and k ree and p enriched cumulates that are thought to represent flotation cumulates of the magma ocean and the last vestiges of magma ocean solidification respectively

micromorphology and stable isotope geochemistry of historical pedogenic siderite formed in pah contaminated alluvial clay soils tennessee u s a abstract alluvial clay soil samples from six boreholes advanced to depths of 400 450 cm top of limestone bedrock from the chattanooga coke plant ccp site were examined micromorphologically and geochemically in order to determine if pedogenic siderite feco3 was present and whether siderite occurrence was related to organic contaminant distribution samples from shallow depths were generally more heavily contaminated with polycyclic aromatic hydrocarbons pahs than those at greater depth the upper 1 m in most boreholes consisted of mixtures of anthropogenically remolded clay soil fill containing coal clinker cinder grains and limestone gravel most layers of coarse fill were impregnated with creosote and coal tar most undisturbed soil below 1 m depth consisted of highly structured clays exhibiting fine subangular blocky ped structures as well as redox related features pedogenic siderite was abundant in the upper 2 m of most cores and in demonstrably historical 100 years old soil matrices two morphologies were identified 1 sphaerosiderite crystal spherulites ranging from 10 to 200 m in diameter and 2 coccoid siderite comprising grape like clusters of crystals 5 20 m in diameter the siderite formed in both macropores and within fine grained clay matrices indicates development of localized anaerobic low eh conditions possibly due to microbial degradation of organic contaminants stable isotope compositions of the siderite have 13c values spanning over 25 7 to 18 vpdb indicating fractionation of dic by multiple microbial metabolic pathways but with relatively constant 18o values 4 8 0 66 vpdb defining a meteoric sphaerosiderite line msl calculated isotope equilibrium water 18o values from pedogenic siderites at the ccp site are from 1 to 5 per mil lighter than the groundwater 18o values that we estimate for the site if confirmed by field studies in progress this observation might call for a reevaluation of low temperature siderite water 18o fractionations investigations at the ccp site thus provide valuable information on the geochemical conditions under which siderite can form in modern soils and thus insight on controls on siderite formation in ancient soils

re evaluating 142nd 144nd in lunar mare basalts with implications for the early evolution and bulk sm nd of the moon abstract the moon likely accreted from melt and vapor ejected during a cataclysmic collision between proto earth and a mars sized impactor very early in solar system history the identical w o k and cr isotope compositions between materials from the earth and moon require that the material from the two bodies were well homogenized during the collision process as such the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the earth two recent studies to obtain high precision 142nd 144nd ratios of lunar mare basalts yielded contrasting results in one study after correction of neutron fluence effects imparted to the nd isotope compositions of the samples the coupled 142nd 143nd systematics were interpreted to be consistent with a bulk moon having a chondritic sm nd ratio rankenburg k brandon a d and neal c r 2006 neodymium isotope evidence for a chondritic composition of the moon science 312 1369 1372 the other study found that their data on the same and similar lunar mare basalts were consistent with a bulk moon having a superchondritic sm nd ratio boyet m and carlson r w 2007 a highly depleted moon or a non magma origin for the lunar crust earth planet sci lett 262 505 516 delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the moon and for constraining the types of materials available for accretion into large terrestrial planets such as earth to further examine this issue the same six lunar mare basalt samples measured in rankenburg et al rankenburg k brandon a d and neal c r 2006 neodymium isotope evidence for a chondritic composition of the moon science 312 1369 1372 were re measured for high precision nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than 3 ppm 2 for 142nd 144nd ratios the measurements were repeated in a distinct second analytical campaign to further test their reproducibility evaluation of accuracy and neutron fluence corrections indicates that the multidynamic nd isotope measurements in this study and the 3 in boyet and carlson boyet m and carlson r w 2007 a highly depleted moon or a non magma origin for the lunar crust earth planet sci lett 262 505 516 are reproducible while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk moon with either chondritic or superchondritic sm nd ratios the multidynamic data are best explained by a bulk moon with a superchondritic sm nd ratio that is similar to the present day average for depleted morb hafnium isotope data were collected on the same aliquots measured for their 142nd 144nd isotope ratios in order to assess if the correlation line for 142nd 143nd systematics reflect mixing processes or times at which lunar mantle sources formed based on the combined 142nd 143nd 176hf obtained we conclude that the 142nd 143nd correlation line measured in this study is best interpreted as an isochron with an age of 229 24 20ma after the onset of nebular condensation the uncertainties in the data permit the sources of these samples to have formed over a 44 ma time interval these new results for lunar mare basalts are thus consistent with a later sm nd isotope closure time of their source regions than some recent studies have postulated and a superchondritic bulk sm nd ratio of the moon and earth the superchondritic sm nd signature was inherited from the materials that accreted to make up the earth moon system although collisional erosion of crust from planetesimals is favored here to remove subchondritic sm nd portions and drive the bulk of these bodies to superchondritic in composition removal of explosive basalt material via gravitational escape from such bodies or chondrule sorting in the inner solar system may also explain the compositional features that deviate from average chondrites that make up the earth moon system this inferred superchondritic nature for the earth similar to the modern convecting mantle means that there is no reason to invoke a missing subchondritic reservoir to mass balance the earth back to chondritic for sm nd ratios however to account for the subchondritic sm nd ratios of continental crust a second superchondritic sm nd mantle reservoir is required

spherulitic siderites in the holocene coastal deposits of korea eastern yellow sea elemental and isotopic composition and depositional environment abstract siderite concretions are recovered from both freshwater unit ii and tidal unit i deposits in the holocene macrotidal flat of kyunggi bay west coast of korea siderites from both units show a spherulitic and well rounded texture and well developed equant rhombs on the external surfaces the size of the concretions in unit ii 50 150 m in diameter is normally larger than that in unit i 10 20 m the siderites in unit ii are chemically pure and highly enriched in fe whereas those of unit i are relatively impure and distinctly zoned demarcating high mn up to 69 1 mol in the core and high fe up to 75 9 mol in the margin within siderites of unit i substitution for fe by ca and mg reaches up to 20 3 mol mean 15 1 mol and 16 1 mol mean 12 6 mol respectively bulk 18 o values 0 7 to 1 3 peedee belemnite pdb for siderites in unit i are relatively higher than those 7 1 to 0 5 pdb in unit ii regardless of units siderite 13 c values 21 3 to 11 2 pdb are persistently low indicating microbially mediated precipitation at shallow burial depth extensive mn ca and mg substitution coupled with enrichment of 18 o in the siderites of unit i seems to reflect marine influence during the holocene transgression the occurrence of early diagenetic siderites provides supporting evidence on the depositional environment marine vs non marine of the holocene muddy coastal deposits of korea eastern yellow sea

the age of ferroan anorthosite 60025 oldest crust on a young moon abstract sm nd isotopic data for mineral separates from the ferroan anorthosite 60025 define a precise isochron of 4 44 0 02ga age this age is roughly 110 m y younger than the formation of the first large solid objects in the solar nebula as recorded by the radiometric ages of the differentiated meteorites in the magma ocean model for early lunar differentiation ferroan anorthosites are the first crustal rocks to form on the moon if the moon is as old as the oldest meteorites the relatively young age determined for 60025 implies either that the magma ocean did not form synchronously with lunar formation or that the magma ocean required over 100 m y before reaching the stage of ferroan anorthosite crystallization alternatively we propose that the accumulated body of radiogenic isotope data for lunar rocks permit the moon to be as young as 4 44 4 51 ga if so isotopic evidence for chemical differentiation on the earth at about this same time suggests that the formation of the moon is reflected in the chemical evolution of the earth this in turn is consistent with the idea that the materials that now make up the moon were derived from the earth perhaps ejected by collision between the earth and another very large planetesimal during the final stages of accumulation of the terrestrial planets terrestrial origin models for the moon lessen the requirement that the earth and moon each have near chondritic relative abundances of the refractory elements and could require that certain chemical and isotopic characteristics of both bodies be considered in the framework of the chemical mass balance of the combined earth moon system

geochronology of an apollo 16 clast provides evidence for a basin forming impact 4 3 billion years ago we examined lithic breccias from the apollo sample collection in order to identify ferroan anorthosite samples suitable for geochronology and better define the age relationships between rocks of the lunar highlands clast 3a is a previously unstudied noritic anorthosite from apollo 16 lithic breccia 60016 with textural evidence of slow subsolidus recrystallization we estimate a cooling rate of 10 c myr and calculate a pyroxene solvus temperature of 1 100 1 000 c pyroxene exsolution lamellae 1 3 m indicate that the last stage of cooling was rapid at 0 2 c year typical of rates observed in thick ejecta blankets we calculate concordant ages from the 147sm 143nd 146sm 142nd rb sr and ar ar isotopic systems of 4 302 28 4 296 39 53 4 275 38 and 4 311 31 ma respectively with a weighted average of 4 304 12 ma the closure temperature of the sm nd system is 855 14 c whereas the closure temperature of the ar ar system is 275 25 c cooling from 855 to 275 c at 10 c myr should result in an age difference between the two isotopic systems of 60 myr the concordant sm nd rb sr and ar ar ages imply that they record the time the rock was excavated by a large impact from the midcrust the ages clearly predate various late accretion scenarios in which an uptick in impacts at 3 8 ga is preceded by a period of relative quiescence between 4 4 and 4 1 ga and instead are consistent with decreasing accretion rates following the formation of the moon

the timeline of the lunar bombardment revisited abstract the timeline of the lunar bombardment in the first gy of solar system history remains unclear basin forming impacts e g imbrium orientale occurred 3 9 3 7 gy ago i e 600 800 my after the formation of the moon itself many other basins formed before imbrium but their exact ages are not precisely known there is an intense debate between two possible interpretations of the data in the cataclysm scenario there was a surge in the impact rate approximately at the time of imbrium formation while in the accretion tail scenario the lunar bombardment declined since the era of planet formation and the latest basins formed in its tail end here we revisit the work of morbidelli et al 2012 that examined which scenario could be compatible with both the lunar crater record in the 3 4 gy period and the abundance of highly siderophile elements hse in the lunar mantle we use updated numerical simulations of the fluxes of asteroids comets and planetesimals leftover from the planet formation process under the traditional assumption that the hses track the total amount of material accreted by the moon since its formation we conclude that only the cataclysm scenario can explain the data the cataclysm should have started 3 95 gy ago however we also consider the possibility that hses are sequestered from the mantle of a planet during magma ocean crystallization due to iron sulfide exsolution o neil 1991 rubie et al 2016 we show that this is likely true also for the moon if mantle overturn is taken into account based on the hypothesis that the lunar magma ocean crystallized about 100 150 my after moon formation elkins tanton et al 2011 and therefore that hses accumulated in the lunar mantle only after this timespan we show that the bombardment in the 3 4 gy period can be explained in the accretion tail scenario this hypothesis would also explain why the moon appears so depleted in hses relative to the earth we also extend our analysis of the cataclysm and accretion tail scenarios to the case of mars the accretion tail scenario requires a global resurfacing event on mars 4 4 gy ago possibly associated with the formation of the borealis basin and it is consistent with the hse budget of the planet moreover it implies that the noachian and pre noachian terrains are 200 my older than usually considered

sequential growth of early diagenetic freshwater siderites in the holocene coastal deposits korea spherulitic siderite grains ranging from 100 to 250 am in diameter occur abundantly in a sediment layer which is almost 8600 years old in namyang bay on the west coast of korea these large siderite grains consist predominantly of feco3 average 65 and mnco3 average 22 and have low mg ca and mg fe ratios compositional scatter plots together with the high mn and low mg contents indicate that meteoric pore water was mainly involved in the siderite precipitation examination of the siderite grains with an electron microprobe reveals a systematic micron scale center to margin compositional variation within individual grains three zones are recognized on the basis of the compositional variations zone i center in which mn decreases and fe increases zone ii intermediate in which mn increases and fe decreases and zone iii outer in which both mn and fe decrease and mg increases this zoning is interpreted as a result of depth related early diagenetic reactions with different fe mn and mg concentrations in the sediment pore waters meanwhile compositional mapping of spherulitic grains implies that a siderite grain consists of numerous tiny siderite precipitates such dust like tiny siderite precipitates appear to be adhered to the large spherulitic siderite grain in some cases large siderite grains are adjoined together and occurred as a siderite aggregate we suggest that a spherulitic siderite grain is growing sequentially by adhering of numerous tiny siderite precipitates formed in each diagenetic zone onto the siderite grain like the formation of a snowball d 2004 elsevier b v all rights reserved

outcrop examples of soft sediment deformation associated with normal fault terminations in deepwater eocene turbidites a previously undescribed conjugate fault termination style abstract a set of small scale layer bound faults developed in a package of three eocene turbidite sandstone beds in a wave cut platform thandwe beach myanmar display unusual downward terminations between converging conjugate faults the faults were initially triggered by loading during deposition of the uppermost turbidite sandstone in the fault affected stratigraphic package the growth of a small gravity driven anticline and subsequent loading by a post deformation turbidite modified the initial fault geometry and re mobilized part of the layer bound sequence causing thinning of the sequence to zero in the vicinity of the fold crest typically conjugate faults display an x shaped pattern of intersection while the observed faults before reaching the point of intersection die out in a drastically thinned basal sandstone located in a keystone block which requires either an underlying detachment or that a volume of sand and fluid was lost from the basal layer probably a combination of gravity driven detachment primary movement and volume loss secondary permitted development of the faults the structures described represent yet another aspect of the wide variety of gravity driven features that form in the deepwater turbidite fan settings it is thought that such features have not been previously described in the literature and represent a new style variant within the general theme of conjugate fault development

the age of dar al gani 476 and the differentiation history of the martian meteorites inferred from their radiogenic isotopic systematics samarium neodymium isotopic analysis of the martian meteorite dar al gani 476 yields a crystallization age of 474 11 ma and an initial end143 value of 36 6 0 8 although the rb sr isotopic system has been disturbed by terrestrial weathering and therefore yields no age information an initial 87sr 86sr ratio of 0 701249 33 has been estimated using the rb sr isotopic composition of the maskelynite mineral fraction and the sm nd age the sr and nd isotopic systematics of dar al gani 476 like those of the basaltic shergottite que94201 are consistent with derivation from a source region that was strongly depleted in incompatible elements early in the history of the solar system nevertheless dar al gani 476 is derived from a source region that has a slightly greater incompatible enrichment than the que94201 source region this is not consistent with the fact that the parental magma of dar al gani 476 is significantly more mafic than the parental magma of que94201 and underscores a decoupling between the major element and trace element isotopic systematics observed in the martian meteorite suite combining the end142 end143 isotopic systematics of the martian meteorites yields a model age for planetary differentiation of 4 513 0 033 0 027 ga using this age the parent daughter ratios of martian mantle sources are calculated assuming a two stage evolutionary history the calculated sources have very large ranges of parent daughter ratios 87rb 86sr 0 037 0 374 147sm 144nd 0 182 0 285 176lu 177hf 0 028 0 048 these ranges exceed the ranges estimated for terrestrial basalt source regions but are very similar to those estimated for the sources of lunar mare basalts in fact the range of parent daughter ratios calculated for the martian meteorite sources can be produced by mixing between end members with compositions similar to lunar mare basalt sources two of the sources have compositions that are similar to olivine and pyroxene rich mafic cumulates with variable proportions of a rb enriched phase such as amphibole whereas the third source has the composition of liquid trapped in the cumulate pile i e similar to kreep after 99 crystallization correlation between the proportion of trapped liquid in the meteorite source regions and estimates of fo2 suggest that the kreep like component may be hydrous the success of these models in reproducing the martian meteorite source compositions suggests that the variations in trace element and isotopic compositions observed in the martian meteorites primarily reflect melting of the crystallization products of an ancient magma ocean and that assimilation of evolved crust by mantle derived magmas is not required furthermore the decoupling of major element and trace element isotopic systematics in the martian meteorite suite may reflect the fact that trace element and isotopic systematics are inherited from the magma source regions whereas the major element abundances are limited by eutectic melting processes at the time of magma formation differences in major element abundances of parental magma therefore result primarily from fractional crystallization after leaving their source regions

sediment pathway of the east china sea inferred from an r mode factor analysis of surface sediments in the okinawa trough major and trace elements loss on ignition loi and grain size distributions were determined on 190 surface sediment samples collected from the continental shelf slope and the north okinawa trough in the east china sea at water depths of 100 200 200 600 and more than 600 m respectively the sediments are composed mainly of sand and silt generally low clay contents average 10 5 increasing over the range of 0 12 53 6 from the shelf and slope to the trough sediments were sandier on the continental shelf particularly in the northern shelf sector spatial distributions in chemical compositions show that the contents of sio 2 cao sr and loi values were relatively high on the sandy continental shelf by contrast the contents of al 2 o 3 mgo na 2 o mno feo tio 2 cu zn co ni and cr were relatively high in the trough and along the central western shelf margin where the sediments were composed mainly of silt fe 2 o 3 p 2 o 5 and zr enrichment was highest in the slope sediments three factors were extracted by means of an r mode factor analysis of chemical composition factor 1 has two inversely correlated elemental assemblages 1 sio 2 k 2 o tio 2 al 2 o 3 and zr which can be associated with terrigenous debris input and show high positive factor scores in the southern sector of the shelf and 2 cao sr and loi which can be related with biogenic debris enrichment and show high negative factor scores in the northern shelf sector as well as in a more restricted area along the slope cao sio 2 k 2 o and sr represent the element assemblage of the shelf factor 2 comprises na 2 o feo al 2 o 3 tio 2 cu zn and ni and shows high scores in the trough sediments na 2 o cu zn and ni represent the elemental assemblage of the okinawa trough and can be associated with volcanic matter factor 3 comprises fe 2 o 3 mgo cr and co with high factor scores on the slope and along the central western shelf margin of the study area due to upwelling induced enrichments in nutrients and biogenic shells fe 2 o 3 and mgo are the slope elements based on the results of the distribution of the chemical compositions and the elemental assemblage of the surface sediment in the source to sink system the influence of the yellow river on the continental shelf is stronger than that of the yangtze river from the continental shelf and slope to the trough the influence of the yellow river decreased from north to south in the okinawa trough the sediment from the yellow river decreases and from the yangtze river increases and the chemical compositions changed c 2009 elsevier ltd and inqua all rights reserved

chronology geochemistry and petrology of a ferroan noritic anorthosite clast from descartes breccia 67215 clues to the age origin structure and impact history of the lunar crust the petrology major and trace element geochemistry and nd ar sr isotopic compositions of a ferroan noritic anorthosite clast from lunar breccia 67215 have been studied in order to improve our understanding of the composition age structure and impact history of the lunar crust the clast designated 67215c has an unusually well preserved igneous texture mineral compositions are consistent with classification of 67215c as a member of the ferroan anorthositic suite of lunar highlands rocks but the texture and mineralogy show that it cooled more rapidly and at shallower depths than did more typical ferroan anorthosites fans incompatible trace element concentrations are enriched in 67215c relative to typical fans but diagnostic signatures such as ti sm sc sm plagiophile element ratios and the lack of zr hf and nb ta fractionation show that this cannot be due to the addition of kreep alternatively 67215c may contain a greater fraction of trapped liquid than is commonly present in lunar fans 147sm 143nd isotopic compositions of mineral separates from 67215c define an isochron age of 4 40 0 11 gyr with a near chondritic initial 143nd of 0 85 0 53 the 40ar 39ar composition of plagioclase from this clast records a post crystallization thermal event at 3 93 0 08 gyr with the greatest contribution to the uncertainty in this age deriving from a poorly constrained correction for lunar atmosphere 40ar rb sr isotopic compositions are disturbed probably by the same event recorded by the ar isotopic compositions trace element compositions of fans are consistent with crystallization from a moderately evolved magma ocean and do not support a highly depleted source composition such as that implied by the positive initial 143nd of the ferroan noritic anorthosite 62236 alternatively the nd isotopic systematics of lunar fans may have been subject to variable degrees of modification by impact metamorphism with the plagioclase fraction being more strongly affected than the mafic phases 147sm 143nd isotopic compositions of mafic fractions from the 4 ferroan noritic anorthosites for which isotopic data exist 60025 62236 67016c 67215c define an age of 4 46 0 04 gyr which may provide a robust estimate for the crystallization age of lunar ferroan anorthosites

fe c and o isotope compositions of banded iron formation carbonates demonstrate a major role for dissimilatory iron reduction in 2 5 ga marine environments abstract combined fe c and o isotope measurements of 2 5 ga banded iron formation bif carbonates from the kuruman iron formation and underlying bif and platform ca mg carbonates of the gamohaan formation south africa constrain the biologic and abiologic formation pathways in these extensive bif deposits vertical intervals of up to 100 m were sampled in three cores that cover a lateral extent of 250 km bif fe carbonates have significant fe isotope variability 56fe 1 to 1 and relatively low 13c down to 12 and 18o values 18o 21 in contrast gamohaan and stratigraphically equivalent campbellrand ca mg carbonates have near zero 13c values and higher 18o values these findings argue against siderite precipitation from seawater as the origin of bif fe rich carbonates instead the c o and fe isotope compositions of bif fe carbonates reflect authigenic pathways of formation in the sedimentary pile prior to lithification where microbial dissimilatory iron reduction dir was the major process that controlled the c o and fe isotope compositions of siderite isotope mass balance reactions indicate that the low 13c and low 18o values of bif siderite relative to those expected for precipitation from seawater reflect inheritance of c and o isotope compositions of precursor organic carbon and ferric hydroxide that were generated in the photic zone and deposited on the seafloor carbon fe isotope relations suggest that bif fe carbonates formed through two end member pathways low 13c low 56fe fe carbonates formed from remobilized low 56fe aqueous fe2 produced by partial dir of iron oxide whereas low 13c high 56fe fe carbonates formed by near complete dir of high 56fe iron oxides that were residual from prior partial dir an important observation is the common occurrence of iron oxide inclusions in the high 56fe siderite supporting a model where such compositions reflect dir in place in the soft sediment in contrast the isotopic composition of low fe carbonates in limestone dolomite may constitute a record of seawater environments although our petrographic studies indicate that the presence of pyrite in most low fe carbonates may influence the fe isotope compositions the combined fe c and o isotope data from kuruman bif carbonates indicate that bif siderites that have negative near zero or positive 56fe values may all record biological fe cycling where the range in 56fe values records differential fe mobilization via dir in the sediment prior to lithification our results demonstrate that the inventory of low 56fe marine sedimentary rocks of neoarchean to paleoproterozoic age although impressive in volume may represent only a minimum of the total inventory of fe that was cycled by bacteria

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

isotopic studies of ferroan anorthosite 62236 a young lunar crustal rock from a light rare earth element depleted source isotopic analyses of mineral fractions and whole rocks from the ferroan anorthosite 62236 yield a sm nd isochron with an age of 4 29 0 06 ga and an initial end143 value of 3 1 0 9 we have also measured end142 anomalies of 0 25 on two fractions of 62236 these values are higher than the value of 0 1 predicted if 62236 was derived from a chondritic source at 4 29 ga but are consistent with the positive initial end143 value the sm nd isotopic composition of 62236 has been modified by the capture of thermal neutrons such that the 147sm 144nd 143nd 144nd and 142nd 144nd ratios measured on the mineral fractions and whole rocks must be corrected the corrections do not significantly alter the sm nd isotopic results determined on 62236 despite the fact that the ar ar and rb sr isotopic systematics of 62236 have been reset by impact metamorphism at 3 93 0 04 ga the sm nd systematics appear to have been unaffected the sm nd isotopic systematics of 62236 provide several constrains on models of lunar crustal differentiation provided they have not been reset since crystallization first the relatively young age of 62236 as well as the old ages determined on several crustal plutonic rocks of the mg suite require multiple sources of magmas on the moon very early in its history second positive end143 values determined on all analyzed ferroan anorthosites suggest that they were derived from sources depleted in light rare earth elements and third models based on initial end143 and present day end142 values suggest that the source of 62236 was depleted in light rare earth elements at 4 46 ga in order to reconcile these observations with the lunar magma ocean model 1 the magma ocean must have existed for a very short period of time and may have had a sub chondritic nd sm ratio and 2 the youngest ferroan anorthosites such as 62236 cannot be cumulates from the magma ocean but must form by other processes

microbial influence on the oxygen isotopic composition of diagenetic siderite abstract numerous early diagenetic siderite concretions previously described have been interpreted as the results of microbially mediated reactions interpretation of oxygen isotope data for such material requires an understanding of the effect of temperature on fractionation processes however whilst equilibrium fractionation of oxygen isotopes between siderite and water has been measured down to 33 c extrapolation to lower temperatures may be invalid furthermore inorganic measurements may not be applicable to microbial systems the specific iron reducing microorganism geobacter metallireducens has been cultured anaerobically in the laboratory using acetate as an organic substrate and amorphous feooh as an electron acceptor the acetate is oxidised to co2 with concurrent iron reduction and extracellular siderite precipitation rhombohedral siderite crystals up to 25 m in size have been precipitated over a range of temperatures 18 40 c stable isotopic analysis of these crystals and the solutions from which they precipitate shows that this microbial precipitation of siderite has an associated isotopic fractionation different from the published equilibrium and which is not simply a function of temperature in all cases 18o values of siderite are lower than predicted by inorganic equilibrium fractionation data this may explain the numerous anomalously low 18o values reported for early diagenetic marine siderites and previously attributed to mechanisms such as mixing with meteoric water sediment water interaction recrystallisation or variable isotopic fractionation despite a lack of supporting evidence