implanted 3he 4he and xe in further studies of diamonds from western australia in measurements of the noble gases in additional samples of diamonds from the argyle and ellendale lamproites in western australia we have failed to encounter any neon rich stones such as showed solar like isotopic compositions in earlier work no neon was detected above the relatively high blank levels in our glass apparatus white and brown diamonds showed no differences in noble gas content nor did samples segregated by the color of long wave uf fluorescence the rare gas patterns in the 1 2 ga argyle pipe are largely consistent with implanted 3he 4he and fissiogenic xe from u th in the matrix rock in which the diamonds have been stored for so long these implanted species are absent in diamonds from the much younger approximately 20 ma ellendale pipe we give implantation formulae for several models of inhomogeneously distributed u th differences in 3he content between pipe and alluvial argyle samples are consistent with expected cosmogenic production in the latter an expanded data base for helium and carbon isotopic data on the same samples supports a negative 4he 13 c correlation seen earlier in work from our group but if the argyle samples which contain light carbon are corrected for implanted 4he 13 c the correlation is considerably weakened we no longer see an earlier 3he 4he 13 c correlation

nitrogen components in primitive ordinary chondrites abstract nitrogen and ar in more than 20 primitive ordinary chondrites were studied by a stepped com bustion method several n carriers that are characterized by n isotopic composition n release pattern and trapped ar release pattern are recognized in the primitive ordinary chondrites large fractions of anomalous n and associated ar are removed by acid treatment in most cases the n isotopic anomalies cannot be explained by known presolar grains with a possible exception of graphite and some of the n isotopic anomalies may be due to unknown presolar grains there is no specific relationship between the type of n carriers contained in an ordinary chondrite and the chemical type h l or ll of the chondrite it is likely that as a result of impacts the carriers of isotopically anomalous n were mixed in various parent bodies as rock fragments rather than as individual fine particles the presence of distinctive n isotopic anomalies in primitive meteorites indicates that the primitive solar nebula may have been heterogeneous either spatially or temporally

artemis observations of terrestrial ionospheric molecular ion outflow at the moon the acceleration reconnection turbulence and electrodynamics of the moon s interaction with the sun artemis spacecraft observes outflowing molecular ionospheric ions at lunar distances in the terrestrial magnetotail the heavy ion fluxes are observed during geomagnetically disturbed times and consist of mainly molecular species n2 no and o2 approximately masses 28 32 amu on the order of 105 106 cm 2 s 1 at nearly identical velocities as concurrently present protons by performing backward particle tracing in time dependent electromagnetic fields from the magnetohydrodynamic open global geospace circulation model of the terrestrial magnetosphere we show that the ions escape the inner magnetosphere through magnetopause shadowing near noon and are subsequently accelerated to common velocities down the low latitude boundary layer to lunar distances at the moon the observed molecular ion outflow can sputter significant fluxes of neutral species into the lunar exosphere while also delivering nitrogen and oxygen to the lunar volatile inventory

the antiquity indicator argon 40 argon 36 for lunar surface samples calibrated by uranium 235 xenon 136 dating several solar gas rich lunar soils and breccias have trapped 40ar 36ar ratios 10 although solar ar is expected to yield a ratio of 0 01 radiogenic 40ar produced in the lunar crust from 40k decay was outgassed into the lunar atmosphere ionized accelerated in the electromagnetic field of the solar wind and reimplanted into lunar surface material the 40ar loss rate depends on the decreasing abundance of 40k in order to calibrate the time dependence of the 40ar 36ar ratio in lunar surface material the period of reimplantation of lunar atmospheric ions and of solar wind ar was determined using the 235u 136xe dating method that relies on secondary cosmic ray neutron induced fission of 235u we identified the trapped fissiogenic and cosmogenic noble gases in lunar breccia 14307 and lunar soils 70001 8 70181 74261 and 75081 uranium and th concentrations were determined in the 74261 soil for which we obtain the 235u 136xe time of implantation of 3 25 0 38 0 60 ga ago on the basis of several cosmogenic noble gas signatures we calculate the duration of this near surface exposure of 393 45 ma and an average shielding depth below the lunar surface of 73 7 g cm2 a second recent exposure to solar and cosmic ray particles occurred after this soil was excavated from shorty crater 17 2 1 4 ma ago using a compilation of all lunar data with reliable trapped ar isotopic ratios and pre exposure times we infer a calibration curve of implantation times based on the trapped40 ar 36ar ratio a possible trend for the increase with time of the solar 3he 4he and 20ne 22ne ratios of about 12 ga and about 2 ga respectively is also discussed

implanted solar helium neon and argon in individual lunar ilmenite grains surface effects and a temporal variation in the solar wind composition abstract solar implanted helium neon and argon were extracted from individual ilmenite grains from lunar soil 71501 and soil breccia 79035 using laser vaporization and analyzed by static mass spectrometry clear differences were observed for these two grain populations one from a contemporary soil and the other from an ancient soil exposed on the lunar surface approximately 1 ga ago the different trends between the 20 ne 22 ne ratios and the he ne ratios do not simply reflect differences either in regolith gardening or in diffusive losses but rather suggest a greater relative helium abundance in the ancient solar wind by a factor of about 1 8 the majority of the grains are enriched in solar energetic particle sep ne relative to solar wind sw ne in a manner that increases with surface exposure the progressive enrichment in retained sep ne relative to sw ne is explained by a combination of diffusion and nonfractionating losses of the less deeply implanted sw component the neon isotopic differences observed in various analyses of ilmenite separates from these two soils and previously attributed to a secular variation of either the sw sep flux ratio or the sw ne isotopic composition may alternatively be a natural consequence of greater sw losses which accompany an enhanced helium flux in the ancient solar wind

terrestrial carbon and nitrogen isotopic ratios from cretaceous tertiary boundary nanodiamonds one hypothesis for the origin of the nanometer size diamonds found at the cretaceous tertiary k t boundary is that they are relict interstellar diamond grains carried by a postulated asteroid the 13 c 12 c and 15 n 14 n ratios of the diamonds from two sites in north america however show that the diamonds are two component mixtures differing in carbon and nitrogen isotopic composition and nitrogen abundance samples from a site from italy show no evidence for either diamond component all the isotopic signatures obtained from the k t boundary are material well distinguished from known meteoritic diamonds particularly the fine grain interstellar diamonds that are abundant in primitive chondrites the k t diamonds were most likely produced during the impact of the asteroid with earth or in a plasma resulting from the associated fireball

the hydrochemical evolution of alkaline volcanic lakes a model to understand the south atlantic pre salt mineral assemblages abstract understand the origin of the exotic strontium rich calcite magnesium rich clay silica deposits formed during the early cretaceous in the south atlantic pre salt lakes is challenging our ability to comprehend the chemical evolution of alkaline volcanic lakes here we present a new hydrochemical model based on an open basin concept thermodynamic equilibrium and chemical data from lake baringo east african rift to shed light on the mechanisms facilitating carbonate clay silica precipitation this model explores the effects that the leakage to adjacent waterbodies the combination of lake evaporation and lake recharge with river hydrothermal and marine waters and the bathymetric effects of the partial co2 pressure have in the stationary precipitation of pre salt lacustrine mineral assemblages sediment thickness calculations suggest that the facies cyclicity in the pre salt and elsewhere are likely reflecting temporal fluctuations in the type of waters sourcing the lake and in the degree of leakage to aquifers over multiple evaporative freshening cycles a plausible link between enhanced strontium uptake into pre salt calcite allochems and ca2 co32 lake water stoichiometries allows to infer different scenarios for strontium rich calcite formation with or without magnesium clays our conceptual model allows to quantify the role that hydrology groundwater charge discharge to aquifers evaporation exert on carbonate clay silica precipitation providing with a refined framework to understand the basin scale chemical sedimentation in alkaline lakes furthermore this model represents a robust template upon which critically test the superimposed kinetic factors likely attached to the genesis of specific mineral factories such as those encountered in the south atlantic pre salt alkaline lakes

constraints on the flux of meteoritic and cometary water on the moon from volatile element n ar analyses of single lunar soil grains luna 24 core abstract we report new nitrogen and argon isotope and abundance results for single breccia clasts and agglutinates from four different sections of the luna 24 drill core in order to re evaluate the provenance of n trapped in lunar regolith and to place limits on the flux of planetary material to the moon s surface single luna 24 grains with 40ar 36ar ratios 10 1126 science 188 4184 162 is no longer apparent when the luna and apollo data are combined instead the n isotope signatures corrected for cosmogenic 15n are consistent with binary mixing between isotopically light solar wind sw n and a planetary n component with a 15n value of 100 to 160 the lower 15n values of luna 24 grains compared to apollo samples reflect a higher relative proportion of solar n resulting from the higher sw fluence in the region of mare crisium compared to the central near side of the moon carbonaceous chondrite like micro impactors match well the required isotope characteristics of the non solar n component trapped in low antiquity lunar regolith in contrast a possible cometary contribution to the non solar n flux is constrained to be 3 13 based on the mixing ratio of sw to planetary n obtained for recently exposed lunar soils we estimate the flux of micro impactors to be 2 2 5 7 103 tons yr 1 at the surface of the moon our estimate for luna 24 agrees well with that for young apollo regolith indicating that the supply of planetary material does not depend on lunar location thus the continuous influx of water bearing cosmic dust may have represented an important source of water for the lunar surface over the past 1 ga provided that water removal rates i e by meteorite impacts photodissociation and sputtering do not exceed accumulation rates

structural characterization of natural diamond shocked to 60 gpa implications for earth and planetary systems the possible presence of the high density carbon polymorph with hexagonal symmetry known as lonsdaleite provides an important marker for shock impact events it is typically considered to form as a metastable phase produced from graphite or other carbonaceous precursors however its existence has recently been called into question here we collected high resolution synchrotron x ray diffraction data for laboratory shocked and natural impact diamonds that both show evidence for deviations from cubic symmetry that would be consistent with the appearance of hexagonal stacking sequences these results show that hexagonality can be achieved by shocking diamond as well as from graphite precursors the diffraction results are analyzed in terms of a general model that describes intermediate stacking sequences between pure diamond fully cubic and lonsdaleite fully hexagonal phases with provision made for ordered vs disordered stacking arrangements this approach provides a hexagonality index that can be used to characterize and distinguish among samples that have experienced different degrees of shock or static high pressure high temperature treatments we have also examined the relative energetics of diamond and lonsdaleite structures using density functional theoretical dft methods the results set limits on the conditions under which a transformation between diamond and lonsdaleite structures can be achieved calculated raman spectra provide an indicator for the presence of extended hexagonal stacking sequences within natural and laboratory prepared samples our results show that comparable crystallographic structures may be developed by impact generated shockwaves starting from ambient conditions using either of the two different allotropes of carbon diamond graphite this broadens the scope for its occurrence in terrestrial and planetary systems

carbon nitrogen argon and helium study of impact diamonds from ebeliakh alluvial deposits and popigai crater nineteen diamond aggregate specimens 1 2 mm in size from impactites of popigai crater and five diamond samples 5 7 mm in size from ebeliakh river placers were studied our investigations indicate that samples from ebeliakh were formed in an impact event with the exception of one specimen y7 the carbon isotopic composition of diamonds from popigai varies within the previously reported limits 13c 8 to 22 whereas diamonds from ebeliakh placers show heavier values of 13c 7 to 10 all the specimens studied contain very low amounts of n mostly 20 ppm but a few contained up to 60 ppm for specimens where the quantity of n allowed reliable analysis 15n values were found to be in the range of 3 9 to 11 9 on the basis of combined ar and n study it was concluded that impact diamonds studied here can be a mixture of at least two types of gas carriers e g different diamond components a possible explanation would be involvement of a carbon vapour deposition cvd process or diamond growth in the impact melt in addition to the direct graphite diamond shock transformation the 13c distributions and different n 36ar correlations have indicated a difference between impact diamonds from ebeliakh and diamonds extracted from popigai crater this could be explained by the existence of different diamond populations formed during the popigai impact event on the other hand ebeliakh diamonds could have resulted from a separate impact event to popigai and an alternative crater is yet to be found

high enrichment of carbon and volatile elements in the surface layers of luna 16 soil sample 1635 result of comet or meteorite impact abstract surface analysis by x ray photoelectron spectroscopy xps in combination with ar etching was performed on a lunar regolith sample from the luna 16 drill core the sample contains only 10 of glass spherules these are of highly variable composition which distinguishes them from the pristine volcanic lunar glasses with their restricted compositional range the xps analyses revealed that practically all grains in this sample are coated by layers of different chemical composition the outer 1200 a have a normal fe mg silicate composition the middle zone between 1200 and 4400 a is strongly enriched in carbon up to 60 at and in zn 4 at from the electron binding energy of the carbon atoms it can be concluded that most of the carbon is present in the form of nanodiamonds and graphite other volatile elements cd pb ga p and cl were detected at the 0 1 0 2 at level in this zone the inner zone below 4400 a has again a silicate composition but is more refractory than the outer zone i e higher in ca and al we propose that this layering was formed by condensation from a carbon rich cloud originating from the impact of a comet or a carbonaceous chondrite like body xps analysis of the surface layers showed variations in the chemical state of the main elements mg si al ca fe in these layers corresponding to different molecular structures similar variations were found in condensate films produced in laser pulse impact simulation experiments

origins of carbonate spherulites implications for brazilian aptian pre salt reservoir abstract spherulites spherical to elliptical allochems composed of crystals radiating from a common core investigated from a variety of depositional settings e g hot springs ambient water temperature geyser tufa and caliche are all composed of a fine grained nucleus made up of carbonate encrusted bacterial bodies biofilms and or eps and surrounded by a cortex of radiating crystals of either aragonite or calcite the microbes and their by products in the nucleus induced the precipitation of carbonate overcoming the inhibition to initiate crystal formation the enveloping radiating crystals comprising aragonitic cortices tended to grow abiotically producing well formed euhedral crystals with a paucity of included bacterial fossils whereas those cortical crystals made up of calcite commonly contained bacterial fossils indicating that the bacterial colonies contributed to the calcitic cortical crystal precipitation similar spherulites form a thick widespread accumulation in the aptian pre salt lacustrine deposits in the campos basin offshore brazil as with the travertine tufa and caliche spherulites the pre salt spherulites most likely initiated carbonate precipitation around bacterial colonies and or their bioproducts probably while afloat in a lacustrine water column before settling to the water sediment interface absence of inter spherulite sediment and the spherulite to spherulite compaction indicate that cortical crystal growth continued while the spherulites were at the sediment water interface rather than displacively within a sediment

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

nanodiamond rich layer across three continents consistent with major cosmic impact at 12 800 cal bp abstracta major cosmic impact event has been proposed at the onset of the younger dryas yd cooling episode at 12 800 150 years before present forming the yd boundary ydb layer distributed over 50 million km2 on four continents in 24 dated stratigraphic sections in 10 countries of the northern hemisphere the ydb layer contains a clearly defined abundance peak in nanodiamonds nds a major cosmic impact proxy observed nd polytypes include cubic diamonds lonsdaleite like crystals and diamond like carbon nanoparticles called n diamond and i carbon the nd abundances in bulk ydb sediments ranged up to 500 ppb mean 200 ppb and that in carbon spherules up to 3700 ppb mean 750 ppb 138 of 205 sediment samples 67 contained no detectable nds isotopic evidence indicates that ydb nds were produced from terrestrial carbon as with other impact diamonds and were not derived from the impactor itself the ydb layer is also marked by abundance peaks in other impact related proxies including

nitrogen and argon release profiles in luna 16 and luna 24 regolith samples the effects of regolith reworking fines microbreccias and agglutinates from the luna 16 mature regolith 1635 and fines from the immature submature luna 24 regolith have been analysed for n and argon isotopes in order to understand the origin of isotopically distinct n released at different temperatures all high resolution runs reveal a similarity in the release of 36ar 40ar and n over a wide temperature interval the similarity in the 40ar and 36ar releases and the near coincidence in the 1635 agglutinates implies that the implanted species were redistributed and homogenised during regolith processing such that regardless of the huge difference in ion implantation energy between solar 36ar and non solar 40ar their present distribution and their release temperatures are now essentially equal a small amount of 40ar released in the lower temperature steps with elevated 40ar 36ar is considered to be trapped after reworking while such mixing and homogenisation may also be expected for n components of different origins to date all known stepped runs regularly demonstrate a reproducible variation in 15n suggesting no homogenisation we consider regolith n to be a mixture of several components trapped at different times and some nitrogen that was not involved in the reworking relatively heavy n released around 500 c appears to be the most pure form of the component trapped after reworking probably from accreted meteoritic matter middle temperature isotopically lighter n appears to be a mixture of solar and non solar n largely homogenised and therefore solar n can not be seen in its pure form bulk 15n as well as formally deconvoluted 15n thermal profiles imply that the non solar n has a variable 15n value several non solar n sources are considered with their input resulting in increasing regolith 15n with time because n from meteorites and idps appear to be dominant a mechanism is required to reduce the c n ratio typical of meteoritic matter to that approaching the low value observed in the lunar regolith preferential loss of methane appears to be a viable explanation following generation either by proton sputtering or in reducing vapour plumes

long term changes in solar wind elemental and isotopic ratios a comparison of two lunar ilmenites of different antiquities abstract an ilmenite separate from lunar regolith breccia 79035 a sample presumed to have been exposed to solar wind more than 2 ga ago was analyzed for noble gas and nitrogen elemental and isotopic abundances by stepwise oxidation and pyrolysis the gases appear to be distributed between two distinct reservoirs in the ilmenite defined by release patterns and isotopic considerations one of the reservoirs near grain surfaces yields elemental ratios that for the most part are solar while the other sited at greater depths within grains has severely fractionated elemental abundances and generally heavier isotopic ratios as well xenon provides an exception to the solar abundance pattern in the near surface reservoir being enhanced by about a factor of 2 relative to the expected value a comparison of the 79035 separate with a previously analyzed ilmenite from soil 71501 which received its solar wind exposure much more recently indicates that the two fold xenon enhancement occurs in the fractionated reservoir as well as the solar one and that it may therefore be attributable to a change in the solar wind elemental abundances other differences between the two ilmenites occur in helium and neon isotopic ratios and in he ar elemental ratios since mineralogical influences on retentivities of the gases in the two samples should be the same and possible contributions of non solar wind components to one ilmenite in preference to the other can generally be eliminated or accounted for all of these differences may reflect changes in the solar wind over time

composition and maturity of apollo 16 regolith core 60013 14 abstract samples from every half centimeter dissection interval of double drive tube 60013 14 sections 60013 and 60014 were analyzed by magnetic techniques for fe concentration and surface maturity parameter i s feo and by neutron activation for concentrations of 25 lithophile and siderophile elements core 60013 14 is one of three regolith cores taken in a triangular array 40 50 m apart on the cayley plains during apollo 16 mission to the moon the core can be divided into three zones based both on i s feo and composition unit a 0 44 cm depth is compositionally similar to other soils from the surface of the central region of the site and is mature throughout although maturity decreases with depth unit b 44 59 cm is submature and compositionally more feldspathic than unit a regions of lowest maturity in unit b are characterized by lower sm sc ratios than any soil obtained from the cayley plains as a result of some unidentified lithologic component with low surface maturity the component is probably some type of mafic anorthosite that does not occur in such high abundance in any of the other returned soils unit c 59 62 cm is more mature than unit b and compositionally equivalent to an 87 13 mixture of soil such as that from unit a and plagioclase such as found in ferroan anorthosite similar soils but containing greater abundances of anorthosite plagioclase are found at depth in the other two cores of the array these units of immature to submature soil enriched to varying degrees compared to the mature surface soil in ferroan anorthosite consisting of 99 plagioclase are the only compositionally distinct subsurface similarities among the three cores each of the cores contains other units that are compositionally dissimilar to any soil unit in the other two cores these compositionally distinct units probably derive from local subsurface blocks deposited by the event s that formed the cayley plains the ferroan anorthosite with 99 plagioclase however must represent some subsurface lithology that is significant on the scale of tens of meters the compositional uniformity of the surface soil 0 10 cm depth over distances of kilometers reflects the large scale uniformity of the plains deposits the fine structure reflects small scale nonuniformity and the inefficiency of the impact mixing process at depths as shallow as even one meter

lunar nitrogen indigenous signature and cosmic ray production rate abstract indigenous lunar nitrogen composition and abundances have been determined in old ferroan anorthosite 60025 and in anorthositic breccia 67915 from north ray crater as well as in 55 cm deep volcanic glasses of 74001 double drive core from shorty crater also included in the set is the well documented lunar basalt 75075 collected near the camelot crater indigenous lunar n abundances are low at ppm level but there is some variation between glass rich cores mare basalts and anorthosites the uniform indigenous n isotopic signature of 15 n 13 0 1 2 is consistent with data reported previously for shorty crater samples the indigenous 15 n cannot account for the light nitrogen component observed in the lunar regolith samples we have determined cosmic ray production rates p 15 n for the above rocks and the drill core samples the average production rate estimate for low shielding of p 15 n 5 8 0 6 pg 15 n g ma is 60 higher than published lunar 15 n production rates but consistent with the meteoritic production rate derived from silicates in the enon meteorite when normalized to 2 irradiation geometry from the observed cosmogenic 15 n excesses and the reported cosmogenic 21 ne abundances in core 74001 we derive a 15 n c 21 ne c production rate ratio of 4 0 0 3 for silicates

textural transition in an aragonite travertine formed under various flow conditions at pancuran pitu central java indonesia abstract a large travertine mound at pancuran pitu central java indonesia displays various types of lamination reflecting different hydrological conditions to understand the geomicrobiological processes of the laminated travertines we investigated the mound s hydrology water chemistry texture microbial composition and volume percentage of carbonate mineral vpc we identified four types of travertines dense travertine 80 vpc flow rate 200 cm s lithified microbial travertine 60 vpc flow rate 70 cm s fragile microbial travertine 30 vpc flow rate 10 cm s and poorly lithified microbial mat

diagenetic pathways linked to labile mg clays in lacustrine carbonate reservoirs a model for the origin of secondary porosity in the cretaceous pre salt barra velha formation offshore brazil

analyses of nitrogen and argon in single lunar grains towards a quantification of the asteroidal contribution to planetary surfaces abstract we performed nitrogen and argon isotopic analyses in single 200 m sized ilmenite grains of lunar regolith samples 71501 79035 and 79135 cosmogenic and trapped components were discriminated using stepwise heating with a power controlled co 2 laser cosmogenic 15 n and 38 ar correlate among different ilmenite grains yielding a mean 15 n c 38 ar c production ratio of 14 4 1 0 atoms atom this yields a 15 n production rate in bulk lunar samples of 3 8 5 6 pg g rock 1 ma 1 which agrees well with previous estimates the trapped 15 n values show large variations up to 300 among different grains of a given soil reflecting complex histories of mixing between different end members the 36 ar 14 n ratio which is expected to increase with increasing contribution of solar ions varies from 0 007 to 0 44 times the solar abundance ratio the trapped 15 n values correlate roughly with the 36 ar 14 n ratios from a non solar end member characterized by a 36 ar 14 n ratio close to 0 and variable but generally positive 15 n values to lower 15 n values accompanied by increasing 36 ar 14 n ratios supporting the claim of hashizume et al 2000 that solar nitrogen is largely depleted in 15 n relative to meteoritic or terrestrial nitrogen nevertheless the 36 ar 14 n ratio of the 15 n depleted solar end member is lower than the solar abundance ratio by a factor of 2 5 5 we explain this by a reprocessing of implanted solar wind atoms during which part of the chemically inert rare gases were lost we estimate that the flux of non solar n necessary to account for the observed 15 n values is comparable to the flux of micrometeorites and interplanetary dust particles estimated for the earth hence we propose that the variations in 15 n values observed in lunar regolith can be simply explained by mixing between solar wind contributions and micrometeoritic ones infalling on the moon temporal variations of 15 n values among samples of different antiquities could be due to changes in the micrometeoritic flux through time in which case such flux has increased by up to an order of magnitude during the last 0 5 ga

nitrogen isotopic compositions of iron meteorites abstract iron meteorites analyzed in this study have nitrogen concentrations 70 g g and 15n from 90 to 150 although the iron meteorites have a large range of 15n most have values more negative than 50 the nitrogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemical processes within the parent bodies the data do not suggest the existence of a well mixed solar nebular reservoir for nitrogen as was already inferred from data from stony meteorites the range of 1100 observed for 15n in bulk meteorites is probably too large to be accounted for by physical and chemical mass dependent fractionation processes in the solar nebula and thus reflects nebular inhomogeneities of nucleosynthetic origin nitrogen isotopes may serve as fingerprints for different reservoirs preserved in various parent bodies in a manner similar to that observed for oxygen isotopes in stony meteorites and oxygen bearing phases of stony irons

the microstructure of semarkona and bishunpur abstract the ordinary chondrites semarkona and bishunpur appear to have experienced in situ hydrous alteration here we report the results of the first detailed tem examination of them which supports this conclusion in semarkona all but the most magnesian mafic minerals have been destroyed and primary sulphides most likely troilite have been partially altered to phyllosilicates and ni rich pyrrhotite in bishunpur alteration is confined to the production of smectite from an amorphous feldspathic material in the chondrule rims and interchondrule matrix during hydrous alteration of both meteorites the temperature probably did not exceed 260 c the equilibrium composition of the gas present during the alteration of semarkona was not solar but was dominated by h2o the formation of smectite does not require the presence of liquid water however evidence for the redistribution of elements such as ca zn and si over tens of microns or more implies that there was at least some transient grain boundary fluid present the alteration in semarkona and bishunpur is far from complete thermodynamic modelling suggests that more altered ordinary chondrites would be mineralogically similar to the cm and ci carbonaceous chondrites superficially the mineralogy mineral chemistry and bulk chemistry of semarkona matrix rims resemble those of some chondritic interplanetary dust particles cidps the ordinary chondrite parent bodies may therefore be a source of some cidps

using magnetic susceptibility to find precambrian impact ejecta a proposal abstract layers with high magnetic susceptibility contain heavy minerals that are the most likely to preserve signatures of impact in metamorphosed precambrian rocks the following impact indicators are resistant to alteration and metamorphism and are likely to be found in heavy mineral layers impact diamond sic shocked zircon high pressure tio2 phases reidite and high pressure chromite coesite and stishovite could also be present but are not likely to be preserved in rocks metamorphosed above the greenschist facies looking for layers with high magnetic susceptibility will also identify layers that might contain concentrations of zircon for dating

the nature and origin of rims on lunar soil grains abstract space weathering processes that operate in the lunar regolith modify the surfaces of lunar soil grains transmission electron microscope analysis of the lunar soil grains from the fine size fraction of several lunar soils show that most grains are surrounded by thin 60 200 nm thick rims the microstructure and chemical compositions of the rims can be used to classify rims into four broad categories amorphous inclusion rich multiple and vesicular amorphous rims are noncrystalline generally lack crystalline inclusions show evidence for preferential sputtering of cations and are produced largely by solar wind irradiation damage inclusion rich rims contain abundant nanometer sized grains of fe metal as randomly dispersed inclusions or as distinct layers embedded in an amorphous silica rich matrix inclusion rich rims are compositionally distinct from their host grains and typically contain accumulations of elements that are not indigenous to the host inclusion rich rims are formed largely by the deposition of impact generated vapors with a contribution from the deposition of sputtered ions a continuum in the chemical and microstructural properties exists between typical amorphous rims and typical inclusion rich rims multiple rims consist of a distinct radiation damaged layer up to 50 nm thick that is overlain by vapor deposited material of comparable thickness vesicular rims are compositionally similar to their hosts and are characterized by an abundance of small the formation of rims on lunar soils is complex and involves several processes whose effects may be superimposed from this study it is shown that one process does not dominate and that the relative importance of vapor deposition is comparable to radiation damage in the formation of rims on lunar silicate grains the presence of rims on lunar soil grains particularly those with nanometer sized fe metal inclusions may have a major influence on the optical and magnetic properties of lunar soils

comprehensive analysis of nanodiamond evidence relating to the younger dryas impact hypothesis during the end of the last glacial period in the northern hemisphere near 12 9k cal a bp deglacial warming of the bolling allerod interstadial ceased abruptly and the climate returned to glacial conditions for an interval of about 1300 years known as the younger dryas stadial the younger dryas impact hypothesis proposes that the onset of the younger dryas climate reversal pleistocene megafaunal extinctions and disappearance of the clovis paleoindian lithic technology were coeval and caused by continent wide catastrophic effects of impact bolide events in north america while there are no known impact structures dated to the younger dryas onset physical evidence of the impact bolide events is argued to be present in sediments spanning several continents at stratigraphic levels inferred to date to the bolling allerod younger dryas boundary ydb reports of nanometer to submicron sized diamonds in ydb sediments in particular the rare 2h hexagonal polytype of diamond lonsdaleite have been presented as strong evidence for shock processing of crustal materials we review the available data on diamonds in sediments and provide new data we find no evidence for lonsdaleite in ydb sediments and find no evidence of a spike in nanodiamond concentration at the ydb layer to support the impact hypothesis

chassigny and the nakhlites carbon bearing components and their relationship to martian environmental conditions abstract the carbon and nitrogen inventories of chassigny and the nakhlites have been investigated by low resolution 100 c temperature increment stepped combustion in addition the contents and isotopic compositions of carbonate minerals have been assessed by the use of an acid dissolution technique low temperature carbon i e that which combusts below 500 c appears to be from two different sources one component is present in variable quantities 300 700 ppm and has 13 c 26 consistent with identification as terrestrial organic contamination the other is isotopically light with 13 c ca 36 which is unusual for normal sources of terrestrial contamination curiously the latter material is present in each sample in similar concentrations 45 15 ppm since this level of carbon is too high to be ascribed to a system blank it is considered that this component is probably indigenous to the meteorites the low temperature of release of the isotopically light carbonaceous material is testimony to its highly labile nature it is evidently organic material of some description the accompanying low temperature nitrogen also appears to be distributed between two components one with 15 n of ca 6 5 to 2 4 the other with 15 n 4 but it is not yet possible to establish relationships between the nitrogen and carbon components released below 500 c the meteorites investigated were found to contain 2 5 30 ppm carbon as carbonate with 13 c between 5 and 11 and 18 o between 23 and 29 variation in 13 c and 18 o of the carbonates indicates either a change in conditions during formation of the carbonate minerals or that there may be two distinct carbon sources magmatic species which are released on combustion at temperatures above 700 c apparently have an isotopically light carbon isotopic composition between 30 and 20 and are associated with light nitrogen 15 n superimposed on the magmatic species is a release of spallogenically produced isotopically heavy nitrogen seen most clearly in chassigny there is no evidence in any of the samples analysed for trapped martian atmospheric gases

formation and evolution of the masirah ophiolite constrained by paleomagnetic study of volcanic rocks abstract the extrusive rocks of the lower ophiolitic nappe of masirah island oman were paleomagnetically studied four mean directions of magnetization were isolated one at low temperature the others at high temperature the low temperature component found in most samples corresponds to a recent viscous and or chemical remagnetization the high temperature component found at three sites in the centre area is interpreted as a possible primary magnetization acquired during extrusion or more probably as an early remagnetization related to subsequent hydrothermal alteration and indicates formation of the masirah ophiolite around a paleolatitude of 40 s close to the present position of the west somali basin a second high temperature component found in three other sample sites in the hakl and in the thumi areas is probably a chemical remagnetization related to the emplacement of the upper ophiolite nappe in late maastrichtian to paleocene times finally a last high temperature component found only in the two sites from naft area could be a post tectonic remagnetization acquired in oligocene or miocene times or represents differential tilting of pillows and sedimentary blocks the high temperature components are usually fairly scattered due to the very complex tectonic history of the area nevertheless the relation between the defined paleopoles and the indian polar wander is unambiguous and the evolution of the masirah ophiolite from formation up to the emplacement of the second ophiolitic nappe is clearly related to the northward movement of the indian plate this new paleomagnetic study rules out the possibility of a common or related origin for the masirah and the semail ophiolites

first investigation of quartz and calcite shape fabrics in strained shales by means of x ray tomography abstract we document the evolution of the 3d fabric of shale along a km long strain gradient in the jaca basin southern pyrenees spain with respect to the distance from a thrust samples were collected in the cleavage free domain at the onset of the pencil cleavage domain within the pencil cleavage domain and within the slaty cleavage domain by combining high resolution x ray computed tomography xct and energy dispersive x ray spectroscopy eds the morphology and the shape preferred orientation spo of thousands of quartz grains calcite grains and pores was studied in the least deformed samples quartz and calcite display mean foliation parallel to bedding with comparable dispersion in the pencil cleavage domain quartz foliation still follows the bedding while calcite foliation is mostly governed by cleavage in the slaty cleavage domain calcite shows a much better organization with foliation parallel to cleavage mimicking closely the pore fabric by contrast the quartz shape fabric is much less defined scattered between bedding and cleavage planes this suggests that quartz grain act as rigid marker in the ductile matrix while calcite grain orientation is governed by dissolution precipitation processes

abiotic versus biotic controls on the development of the fairmont hot springs carbonate deposit british columbia canada the relict fairmont hot springs deposit formed largely of carbonates covers an area of 0ae 5k m 2 and is up to 16 m thick the triangle shaped discharge apron which broadens down valley is divided into a proximal part with beds dipping at 10 and a distal part with beds dipping at 10 to 15 the deposit is formed of the 1 basal macrophyte 2 lower carbonate 3 middle clastic 4 upper carbonate and 5 upper clastic sequences two charcoal samples embedded in the lower carbonate sequence yielded dates of 8690 90 and 8270 70 cal yr bp indicating that much of the deposit formed post glacially during the early to mid holocene deposit aggradation ceased in the mid to late holocene when the fairmont creek valley was incised the lower and upper carbonate sequences which are the thickest sequences are composed of nearly equal parts of travertine abiotic and tufa biotic with feather dendrite travertine radiating dendrite travertine and stromatolite tufa dominating competition between calcite precipitation rates and biotic growth rates controlled the distribution of tufa and travertine across the discharge apron calcite and biotic growth rates were controlled largely by flow velocity across the apron which in turn was controlled by topography and regular fluctuations in spring water discharge volume during times of high spring discharge slow sheet flow over the proximal part of the apron promoted stromatolite growth whereas fast turbulent flow on the distal part of the apron induced rapid feather dendrite formation during times of low spring discharge quiescent shallow evaporative pools conducive to radiating dendrite formation formed on the proximal part of the apron whereas slow flow on the distal part promoted stromatolite growth facies with high calcite supersaturation experienced rapid abiotic dendrite growth that precluded most biotic growth

shrub morpho types as indicator for the water flow energy tivoli travertine case central italy abstract travertines from tivoli area central italy possess abundant shrub like fabrics that are laterally continuous over hundreds of square meters they occur dominantly in horizontal layers with aggradational and progradational stacking patterns their fabrics and morphologies are remarkably similar to the shrubs lithotypes reported in literature for the pre salt reservoirs offshore brazil and angola with huge oil accumulations petrographic and micro computer tomography analyses allowed the identification of six shrub morpho types i e narrow dendriform wide dendriform fili dendriform arborescent arbustiform and pustular dendriform shrubs are the most common lithotype in tivoli area and three different subtypes could be distinguished according to the arrangement of their branches the shrubs consist largely of peloidal micritic aggregates engulfed in spar calcite ranging in average from 1 to 3 cm in height the shrubs are interpreted to have developed in very shallow extensive waterlogged slightly inclined flat areas changing laterally into a slope system with crusts as the main lithotype changes in the hydrodynamic conditions with episodes of stagnancy influenced the shrub morpho types making them very variegated shrub morphologies likely reflect specific micro environments that are controlled by water flow rates evaporation and microbial activity the latter processes influenced shrub fabric and morphology under high flow conditions co 2 degassing is the main process leading to carbonate precipitation consequently denser and tightly packed morphologies will precipitate composing mainly the crust lithotype in this scenario microbes are less dominant dendriform shrubs with narrow wide and fili morphologies are interpreted to occur in moderate to low energy water flows narrow dendriform shrubs reflect faster flowing conditions with decreasing impact of flow on the morphological aspects from wide dendriform shrubs to fili dendriform shrubs slow to very slow flowing waters are more characteristic for the arborescent arbustiform and pustular shrubs that possibly are highly influenced by evaporation a decrease of water flow likely allows higher microbial activity and consequently shrub morphologies become more fragile and enriched in peloidal micritic aggregate fabrics

shrub and pore type classification petrography of travertine shrubs from the ballik belevi area denizli sw turkey petrographical and petrophysical properties of the turkish ballik belevi travertine shrubs demonstrate the necessity of reservoir oriented classifications for shrub related lithotypes and associated pore types the presented shrub related lithotype classification incorporates morphology size and fabric which are linked to specific pore types and sizes the travertines show highly complex pore networks as observed from computed tomography reconstructions making them of interest for the development and optimization of pore characterization methodologies and techniques following an upscaling approach porosity 3 15 and permeability 0 505 md strongly vary for the ballik belevi travertines the highest porosities and permeabilities are measured for horizontal samples dominated by slightly dissolution enlarged intershrub and interdigit growth framework porosity mostly found for dendritic shrubs the presented shrub and pore type classification can be applied to shrubs worldwide studying outcrop analogues of continental carbonates helps to better understand heterogeneities lateral variability and properties of pre salt cretaceous continental carbonate reservoirs offshore brazil and angola

nitrogen and noble gases in micrometeorites micrometeorites mms currently represent the largest steady state mass flux of extraterrestrial matter to earth and may have delivered a significant fraction of volatile elements and organics to the earth s surface nitrogen and noble gases contents and isotopic ratios have been measured in a suite of 17 micrometeorites recovered in antarctica sampled in blue ice at cap prudhomme and greenland separated from cryoconite that have experienced variable thermal metamorphism during atmospheric entry mms were pyrolized using a co2 laser and the released gases were analyzed for nitrogen and noble gas abundances and isotopic ratios by static mass spectrometry after specific purification noble gases are a mixture of cosmogenic solar atmospheric and possibly chondritic components with atmospheric being predominant in severely heated mms 15 n values vary between 240 62 and 206 12 with most values being within the range of terrestrial and chondritic signatures given the uncertainties crystalline mms present very high noble gas contents up to two orders of magnitude higher than carbonaceous chondrite concentrations in contrast nitrogen contents between 4 ppm and 165 ppm are much lower than those of carbonaceous chondrites evidencing either initially low n content in mms and or degradation of phases hosting nitrogen during atmospheric entry heating and terrestrial weathering assuming that the original n content of mms was comparable to that of carbonaceous chondrites the contribution of nitrogen delivery by these objects to the terrestrial environment would have been probably marginal from 3 8 gyr ago to present but could have been significant 10 in the hadean and even predominant during the latest stages of terrestrial accretion

carbonado physical and chemical properties a critical evaluation of proposed origins and a revised genetic model abstract carbonado diamond is the most controversial of all diamond types and is found only in brazil and the central african republic bangui neither an affinity to earth s mantle nor an origin in the crust can be unequivocally established carbonado diamond is at least 3 8 ga old an age about 0 5 ga older than the oldest diamonds yet reported in kimberlites and lamproites on earth derived from neo to mid proterozoic meta conglomerates the primary magmatic host rock has not been identified discovered in 1841 the material is polycrystalline robust and coke like and is best described as a strongly bonded micro diamond ceramic it is characteristically porous which precludes an origin at high pressures and high temperatures in earth s deep interior yet it is also typically patinated with a glass like surface that resembles melting with exotic inclusions of highly reduced metals carbides and nitrides the origin of carbonado diamond is made even more challenging but the challenge is important because a new diamondiferous host rock may be involved and the development of a new physical process for generating diamond is possibly assured the combination of micro crystals and random crystal orientation leads to extreme mechanical toughness and a predicable super hardness the physical and chemical properties of carbonado are described with a view to the development of a mimetic strategy to synthesize carbonado and to duplicate its extreme toughness and super hardness textural variations are described with an emphasis on melt like surface features not previously discussed in the literature but having a very clear bearing on the history and genesis of carbonado selected physical properties are presented and the proposed origins diverse in character and imaginatively novel are critically reviewed from our present knowledge of the dynamic earth all indications are that carbonado is unlikely to be of terrestrial origin a revised model for the origin of carbonado is developed based on 1 new observations which show that white dwarf stars can have diamond cores 2 c rich exoplanets may have diamond bearing mantles and 3 new shock wave experiments on methane suggest that diamond may be present in large gaseous planets such as saturn uranus and neptune where diamond in the core is solid and in jupiter where liquid diamond may be present it is proposed that carbonado diamond was delivered to earth from extra solar sources during the episode of late heavy bombardment 4 1 3 8 ga if the currently held view that r process heavy elements were added as a late veneer to earth through the collision of white dwarfs in kilonova explosions then why not carbonado diamond during this epic event

a carbon and nitrogen isotope study of diamond from primitive chondrites diamonds isolated from primitive chondrites of the carbonaceous ordinary and enstatite groups have been analysed by high resolution stepped combustion followed by measurement of their c and n isotopes using a newly adapted technique that allows quantitative measurements of c n ratios the 13c of the diamond is shown to vary between meteorite groups from 32 to 38 0 and the measured c n ratios suggest that the n concentration of diamond ranges over a factor of 7 from 1800 ppm tieschitz to 13 000 ppm adrar 003 the 15n of n released from diamond is constrained to 348 7 the complexity of the c release pattern and c n ratio during combustion implies the presence of more than one component which suggests that either more than one type of diamond is present in the samples or unidentified additional phases are located in the acid resistant residue the components are present in varying proportions between meteorite groups the data are compatible with a model of a mix of different diamond populations some probably presolar and some possibly solar existing in the early solar nebula where each population originally contributed a roughly equal amount to chondrites of every class subsequent metamorphism has resulted in overall variations in 13c and c n ratios in diamond isolated from meteorites of differing petrologic grade without significantly altering the n isotopic composition possible ways for this to be achieved are explored

early proterozoic ultrahigh pressure metamorphism evidence from microdiamonds microdiamonds from the akluil k minette dykes nunavut canada are similar to diamonds formed in subducted metamorphic rocks high concentrations of unaggregated nitrogen and positive 15 n suggest that the microdiamonds formed within rocks subducted to ultrahigh pressures before being sampled by the minette magma 1 8 billion years ago this ultrahigh pressure metamorphism in north america probably related to the trans hudson orogen about 2 billion years ago extends the occurrence of ultrahigh pressure metamorphism from 0 6 billion years to before 1 8 billion years ago and suggests that phanerozoic type subductions were active by the early proterozoic

early cretaceous intra oceanic rifting in the proto indian ocean recorded in the masirah ophiolite sultanate of oman abstract the masirah ophiolite sultanate of oman was part of an oceanic basin proto indian ocean formed by the break up of gondwana in late jurassic times similar to the somali basin it was obducted onto the arabian continental margin in the early paleocene 100 ma after its formation hence it is possible to investigate the different tectonic and magmatic processes that have affected the oceanic lithosphere during these 100 ma tithonian ridge magmatism tectonism and hydrothermal alteration are responsible for the formation of the oceanic crust of the masirah ophiolite in the early cretaceous hauterivian barremian after 20 ma of normal drift and subsidence the oceanic lithosphere underwent extensional tectonics and renewed magmatism geometry kinematics intrusion mechanisms and related sedimentation during this intra oceanic rifting are widely described and illustrated by field observations exhumation of deep seated oceanic lithosphere alkaline volcanism intrusion of a hornblende gabbro dolerite granite suite and uplift of crustal blocks to sea level with the unconformable deposition of platform carbonates are the processes characterising this intra oceanic rifting the hauterivian barremian age of oceanic rifting coincides with an important reorganisation of the motion of the indian plate relative to africa antarctica and australia we interpret the rifting recorded in the masirah ophiolite as the local response to the motion of the indian plate due to the opening of the south atlantic and the spreading in the eastern indian ocean

a comparative and critical study of x ray ct and neutron ct as non destructive material evaluation techniques x ray computerized tomography ct has traditionally been used as a medical diagnostic tool this non destructive technique has developed as an important research tool for a wide variety of scientific subjects for material research medical ct microct and very recently nano or submicroct have been used as non destructive material evaluation techniques for engineering and geological purposes the fact that x ray ct visualizes the internal structure of natural building stones and yields information on porosity values and pore size distributions is a major advantage for the study of their conservation the penetration of fluids like water consolidants or water repellents inside porous materials is important when dealing with conservation and restoration research recently high speed neutron tomography has been introduced as a visualization technique for fluids inside porous materials high speed neutron tomography can be used as a complementary technique to x ray tomography as elements like hydrogen which have a weak attenuation for x rays are easy to detect using neutrons in this paper the basic principles of computerized tomography and more specifically x ray and neutron tomography are discussed in addition application possibilities advantages and limitations of medical ct x ray microct and high speed thermal neutron ct are outlined

masirah oman ophiolite sheeted dykes and pillow lavas geochemical evidence of the former ocean ridge environment abstract the island of masirah is composed of a fully developed late mesozoic ophiolite in which are exposed extensive tracts of regularly trending sheeted dyke complex and associated pillow lavas these upper ocean crust rocks have been subject to a hydrothermal constructive margin metamorphism which has had profound effects on their major and alkaline element geochemistry minor trace and rare earth element characteristics suggest 1 the involvement of extensive magma chamber fractional crystallisation in the development of their chemistry 2 their origin at a former spreading centre through whether mid ocean or marginal basin cannot be constrained by their geochemistry alone

evidence for a predominantly non solar origin of nitrogen in the lunar regolith revealed by single grain analyses we measured the amounts of 14n and 36ar in single mineral and glass grains from a lunar soil by laser extraction with the goal of studying the controversial origin of trapped nitrogen in the lunar regolith the average 14n 36ar ratio of 29 ilmenite grains is 379 similar to the value determined previously on a large ilmenite separate from the same soil and 10 times larger than the solar ratio of 37 however the 14n 36ar ratios in the individual grains vary between 1 and 440 times the solar ratio 36ar amounts in the ilmenite grains scatter by more than two orders of magnitude n amounts by less than a factor of 6 the variability of the 14n 36ar ratio forms a striking contrast to the very uniform relative abundances of ar kr and xe trapped from the solar corpuscular radiation observed earlier in ilmenite and other mineral grains from the same soil this strongly suggests that on average some 90 of the n in the grains has a non solar source contrary to the often expressed view that essentially all n in the lunar regolith has been trapped from the solar wind the conclusion that the lunar regolith testifies to a secular variation of the n isotopic composition in the solar wind of 30 becomes thus highly questionable the origin of the bulk of trapped lunar nitrogen remains unknown

volatile and siderophile element geochemistry of the moon a reappraisal abstract lunar volcanic glasses lvg contain high abundances of many volatile elements as compared to mare basalts whereas the latter were derived from devolatilized source regions in the outer few hundred kilometers of the moon lvg are believed to come from a globally extensive source region at greater depths which is relatively rich in volatile components abundances of volatile elements in lvg and their source regions are reviewed and in many cases found to resemble those in the earth s mantle likewise siderophile element abundances including the highly siderophile elements ir os au and re are similar in the earth s mantle and in the source regions of lvg the close geochemical similarity between the lvg source region i e the lunar lower mantle and the terrestrial mantle constitutes strong evidence that protolunar material was derived primarily from the earth s mantle since highly siderophile elements are believed to have been added to the earth as an oxidised veneer at the end of its accretion and then convectively mixed into the mantle the removal of protolunar material from the earth must have occurred after this late addition which may represent carbonaceous chondritic or cometary material from the outer solar system it is widely believed that the moon was formed by the impact of a giant planetesimal on the protoearth the planetesimal is presumed to have formed in the inner solar system and to have differentiated internally into a mantle and core numerical modelling of the giant impact shows that most of the material now in the moon would have been derived from the mantle of the impactor however this is contradicted by the geochemical evidence provided by lvg which implies that the moon is composed mainly of material derived from the terrestrial mantle a possible answer to this dilemma is provided by the observation that the lvg source region reflects the geochemistry of the late oxidised veneer which accreted on the earth this suggests that protolunar material may have been removed from the earth s mantle by impacts from one or more high velocity 30 km s planetesimals composed mainly of ices and derived from the outer solar system the volatiles from the impacting planetesimals were lost after these collisions the impacts probably ejected material from the earth s mantle as jets of molten matter which was rapidly quenched thereby retaining a large proportion of its terrestrial volatile inventory

bacterial shrubs crystal shrubs and ray crystal shrubs bacterial vs abiotic precipitation hot water travertine deposits commonly contain shrub like morphologies on the centimeter to meter scale that range from highly irregular forms bacterial shrubs to features that display regular geometric patterns crystal shrubs and ray crystal crusts the bacterial shrubs have been previously recognized as the product of bacterially induced precipitation whereas the ray crystal crusts have been described as due to dominantly abiotic precipitation the bacterial shrubs have a highly irregular morphology similar to woody plants in contrast end member crystal shrubs display distinct crystal habits and regular repeating morphologies i e they commonly have attributes of noncrystallographic as well as crystallographic dendrites there is a complete gradational relationship between the bacterial shrubs and crystal shrubs ray crystal crusts are large fan shaped features composed of subparallel extremely coarse bladed crystals of calcite all three types bacterial shrubs crystal shrubs and ray crystal crusts contain either a dense tangle of bacterial body fossils and or micron sized pores the micropores are bacterial molds the immediately enveloping spar crystals around all three morphologic types are devoid of bacterial body fossils and micropores the bacterial shrubs crystal shrubs and ray crystal crusts are to differing degrees the product of bacterially induced precipitation as well as abiotic mineral precipitation the differences in morphology are due to the relative contribution of bacterially induced precipitation as compared with that of abiotic mineral precipitation bacterially induced precipitates can form in environments too chemically harsh or otherwise inhospitable for other taxa to thrive epiphyton and renalcis commonly formed in occult environments under conditions inhospitable to other taxa consideration of the published descriptions and interpretations concerning epiphyton and renalcis and by analogy the origin of bacterial shrubs have led to the conclusion that epiphyton and renalcis also are bacterially induced precipitates

the role of photosynthesis and co2 evasion in travertine formation a quantitative investigation at an important travertine depositing hot spring le zitelle lazio italy le zitelle hot springs contain high concentrations of dissolved ca and co 2 and precipitate copious quantities of aragonite and calcite as travertine a study of precipitation rates in the upper section of the stream was undertaken using marble tablets this showed that 1 precipitation rate increased with distance from the spring over the section studied 2 the rate was positively correlated with flow agreeing with previous experimental and theoretical studies 3 precipitation rates during the day and night did not differ statistically the last finding demonstrated a negligible effect of photosynthesis on travertine formation and was supported by further precipitation rate studies undertaken in clear and blackened tubes this conflicts with previous work that suggested an important role for microbial photosynthesis in travertine deposition at le zitelle the microbial flora consisted mainly of cyanobacteria spirulina and photosynthetic bacteria with smaller quantities of diatoms the biomass in most of the travertine was extremely low and often endolithic carbon fixation rates were also low a mass balance calculation of carbon flow showed that of 100 units of dissolved carbon entering the stream section investigated 51 units were lost to the atmosphere as co 2 0 9 units were deposited as travertine 0 09 units were fixed by photosynthesis and 48 units remained in the stream water we conclude that most of the zitelle travertine is formed abiotically casting doubt on the supposed biotic origin of travertine at this and other italian sites

mantle related carbonados geochemical insights from diamonds from the dachine komatiite french guiana abstract carbonado is a unique type of polycrystalline diamond characterised among others by 13c depleted isotope compositions 13c 25 vs pdb little advanced nitrogen aggregation ib iaa and sintered ceramic like diamond grains its origin remains an enigma with models proposing a formation either in the earth s crust or even within an exploding super nova the possibility that carbonado formed in the earth s mantle is often rejected because diamond with carbonado like geochemical features has never been found in rocks such as kimberlites that carry diamonds from the mantle in this study it is shown that the c and n stable isotope compositions nitrogen contents and nitrogen speciation of diamonds from the dachine komatiite french guyana exhibit unambiguous similarities with carbonados these include c isotopes from 32 6 to 0 15 mode at 27 n aggregation only ib iaa diamonds from 2 to 76 of n pairs and n isotopes from 4 1 to 6 9 average 2 1 2 9 which all strikingly match the carbonado data this evidence illustrates that the main geochemical arguments usually called to reject a mantle origin of carbonado are no longer valid a model linking carbonado crystallisation from komatiite volatiles is developed in this model the sintering is produced by the high temperature of the komatiite magma thus accounting for their absence in colder kimberlites the low 13c compositions of carbonados would be inherited from the transition zone 300 km depths which is known to yield diamonds with distinct c isotope distributions compared to most lithospheric diamonds 150 300 km depths this model can account for most available observations of carbonados including their large size sintering photoluminescense cathodoluminescence features and geochemical characteristics

presalt stratigraphy and depositional systems in the kwanza basin offshore angola the lower cretaceous presalt section in the kwanza basin contains an excellent petroleum system that includes synrift strata barremian overlain by a sag interval aptian and capped by the loeme salt the upper synrift is generally limestone with widespread mollusk packstones and grainstones coquinas deposited in a fresh to moderately saline alkaline lake the sag interval is characterized by carbonate platforms and silica rich isolated buildups formed in highly evaporated highly alkaline lakes shrubby dendritic microbially influenced boundstones and intraclast spherulite grainstones accumulated in shallow water on platform tops microbial cherts were deposited as organic buildups on large isolated structural highs basinward west of platforms and they apparently formed at low temperatures in very alkaline lake water shrubby boundstones and microbial cherts have vuggy pores that are primary and result in high permeability wackestones and packstones with calcitic grains mainly spherulites in dolomite or argillaceous dolomite were deposited in slightly deeper low energy sag environments in addition clays especially stevensite precipitated out of the silica rich highly alkaline lake waters during sag deposition calcite precipitated on the shallow lake floor with morphologies that ranged from spherulites to shrubs and included a continuum of intermediate forms spherulites probably precipitated just below the sediment water interface spherulites and shrubby calcites are commonly recrystallized spherulites floating in stevensite probably formed in deeper lacustrine environments organic rich mudstones were deposited in even deeper lacustrine environments in synrift and sag intervals and they are likely the source of most hydrocarbons in this system these interpretations are supported by seismic core petrographic and stable isotope data

sedimentology and petrophysical analysis of pre salt lacustrine carbonate reservoir from the santos basin southeast brazil lacustrine carbonate deposits mark the rift sag sedimentation stage of the so called pre salt section of the campos and santos basins in the southeast brazilian continental shelf these salt sealed carbonate reservoirs form deep water giant and prolific oil fields that are currently responsible for approximately 70 of the brazilian oil and gas production in the santos basin the sag stage carbonates are represented by the aptian barra velha formation characterized by exotic textural and compositional features whose origin development and correlation with petrophysical properties have been broadly discussed in the last decade a geological and petrophysical study has been performed based on core samples plugs and thin sections of a well in the barra velha formation from the eastern santos basin the analyzed core interval was grouped into six depositional facies constituted by the association of five key textural components 1 crystal shrubs 2 calcite spherulites 3 hybrid forms 4 mud grade carbonates and dolomite and 5 intraclasts the relationship between the depositional framework and the poroperm system as evidenced by petrographic image analysis and ct scan data is highly complex the depositional control over porosity is erratic mainly due to the extensive diagenetic and possible hydrothermal overprint dolomite cementation dolomitization pervasive silicification and dissolution processes are the main primary porosity modifiers petrophysical analysis indicates that intraclastic and spherulitic grainstones rudstones affected by matrix dissolution may present the best reservoir properties in certain intervals even surpassing the shrubby framestones which are widely regarded as the best reservoir facies this study seeks to contribute to an emerging body of research about the brazilian pre salt lacustrine carbonates broadening the geological knowledge about these deposit while providing new data to improve hydrocarbon forecast and recovery

organic matter on the earth s moon abstract carbonaceous matter on the surfaces of black pyroclastic beads collected from shorty crater during the apollo 17 mission represents the first identification of complex organic material associated with any lunar sample we report the chemical physical and isotopic properties of this organic matter that together support a pre terrestrial origin we suggest the most probable source is through the accretion of exogenous meteoritic kerogen from micrometeorite impacts into the lunar regolith abiotic organic matter has been continuously delivered to the surfaces of the terrestrial planets and their moons by accretion of asteroidal and cometary material determining the nature distribution and evolution of such matter in the lunar regolith has important implications for understanding the prebiotic chemical inventory of the terrestrial planets

differences in isotopic composition of carbonaceous components in enstatite chondrites abstract carbon stable isotopic composition of the major carbonaceous component in enstatite chondrites varies with petrologic type investigation of a suite of hf hcl resistant residues has shown that this variation is due to an inherent difference in 13 c of the carbon and is not a result of the presence of small amounts of isotopically anomalous carbon bearing components these latter do occur in type eh3 and eh4 chondrites in concentrations similar to those found in c1 and c2 carbonaceous chondrites combustion of the major carbon component apparently elemental carbon not necessarily graphite occurs at relatively higher temperatures in enstatite chondrites of increasing petrologic type this is considered to reflect an increase in crystallinity or ordering of the carbonaceous component and is a measure of the degree of thermal processing to which the meteorites have been subjected during accretion and or metamorphism

intensive parameters of enstatite chondrite metamorphism abstract the enstatite oldhamite geothermometer eog developed by larimer and buseck 1974 makes use of the five phase assemblage kamacite quartz enstatite oldhamite troilite to determine metamorphic temperatures in enstatite chondrites a re evaluation of the thermodynamic foundation of the eog shows that several of the assumptions and approximations can be significantly improved with new thermodynamic data the geothermometer has been modified to reflect among other things the solution behavior of si in kamacite the solution behavior of a calcium silicate component in enstatite and metal sulfide fusion as a function of temperature and composition an analysis of the eog shows that the activity coefficient of si in kamacite and the ca rich component of enstatite are the model s most important parameters for si the activity coefficient data of sakao and elliot 1975 have been used the activity coefficient of a ca rich component of enstatite presents a unique problem since data on this parameter do not exist for one pyroxene systems and two pyroxene solution models do not provide unique activity coefficients in the absence of diopside the model therefore has been formulated using camgsi 2 o 6 as the ca rich component of enstatite and assumes that it behaves as a symmetric regular margules solution the margules interaction parameter w g is then used as an adjustable constant and is varied such that the resulting temperatures fall between minimum and maximum temperatures determined independently temperature minima were determined from the enstatite diopside solvus of carlson 1986 and indicate that the el6 chondrites have been metamorphosed to temperatures exceeding 900 1000 c the temperature of the enstatite plagioclase quartz eutectic 1090 c appropriate for el6 plagioclase compositions was used as the metamorphic maxima with these constraints a w g value of 52 kj mole was estimated as appropriate within the context of the model for el6 metamorphic conditions el6 temperatures determined via this method range from 981 c for yilmia to 1068 c for blithfield temperature estimates of greater than 1000 c for the highly equilibrated el6 chondrites require the formation of a metal sulfide liquid during metamorphism liquid fractionation of this predominantly fe fes liquid could explain the siderophile chalcophile and volatile element depletion in the el6 class relative to ci and eh chondrites liquid fractionation however is not required by the model and is consistent with a moderate cooling rate which is fast enough to lock in high cao contents in enstatite but slow enough to re equilibrate troilite and alabandite to low temperatures the oxygen fugacity determined in this study shows the enstatite chondrites to have equilibrated at extremely low f o 2 this as well as the activity of si that can be extracted from the eog indicates that the enstatite chondrites that contain sinoite si 2 n 2 o equilibrated under high nitrogen fugacities high f n 2 values imply that sinoite bearing e chondrites either formed in a nebula of high pressure f n 2 10 1 at 1050 c or more likely are products of planetary metamorphism

laboratory shock emplacement of noble gases nitrogen and carbon dioxide into basalt and implications for trapped gases in shergottite eeta 79001 abstract basalt samples have been analyzed mass spectrometrically for shock implanted noble gases n2 and co2 after exposure to 20 60 gpa 200 600 kbar shock in the presence of 0045 3 0 atm of ambient gas isotopically labelled gases were used in some samples to distinguish implanted atmospheric gases from contaminant or indigenous gases abundances of emplaced gases varied linearly with ambient gas pressure for constant shock pressure and gas emplacement was most efficient in the range of 35 50 gpa shock pressure uncrushed samples shocked in this range gave emplacement efficiencies number densities of gases in shocked samples number densities in ambient gas of 2 0 6 7 for heavy noble gases and nitrogen while powdered samples with higher effective porosity yielded 40 50 efficiencies indicating that 50 of noble gases and nitrogen available in porespaces was emplaced no elemental or isotopic fractionation was detected with ar kr xe or n2 helium and in some samples ne were lost by diffusion subsequent to shock emplacement efficiencies for co2 averaged a factor of 1 8 0 2 greater than those of n2 and noble gases in 4 samples with 20 50 gpa shock and yielded 3 2 times greater efficiency in a sample shocked to 60 gpa enhanced co2 emplacement is thought to be due to reaction with silicate materials data from shergottite eeta 79001 glass may be consistent with co2 efficiencies a factor of 2 3 greater than noble gas efficiencies trapped gases in eeta 79001 glass were probably emplaced by shock however apparent emplacement efficiencies are somewhat higher than even shocked powder samples possible explanations for the difference include atmospheric overpressure at the time of shock trapping of gas already in vugs by intruding melt material or collapse of gas filled vugs to form gas laden glass inclusions not enough is yet known about the behavior of vugs under shock to discount the latter possibility

the origin of chondritic macromolecular organic matter a carbon and nitrogen isotope study the n and c abundances and isotopic compositions of acid insoluble carbonaceous material in thirteen primitive chondrites five unequilibrated ordinary chondrites three cm chondrites three enstatite chondrites a ci chondrite and a cr chondrite have been measured by stepped combustion while the range of c isotopic compositions observed is only delta 13c 30 the n isotopes range from delta 15n approximately 40 to 260 after correction for metamorphism presolar nanodiamonds appear to have made up a fairly constant 3 4 wt of the insoluble c in all the chondrites studied the apparently similar initial presolar nanodiamond to organic c ratios and the correlations of elemental and isotopic compositions with metamorphic indicators in the ordinary and enstatite chondrites suggest that the chondrites all accreted similar organic material this original material probably most closely resembles that now found in renazzo and semarkona these two meteorites have almost m shaped n isotope release profiles that can be explained most simply by the super position of two components one with a composition between delta 15n 20 and 40 and a narrow combustion interval the other having a broader release profile and a composition of delta 15n approximately 260 although isotopically more subdued the ci and the three cm chondrites all appear to show vestiges of this m shaped profile how and where the components in the acid insoluble organics formed remains poorly constrained the small variation in nanodiamond to organic c ratio between the chondrite groups limits the local synthesis of organic matter in the various chondrite formation regions to at most 30 the most 15n rich material probably formed in the interstellar medium and the fraction of organic n in renazzo in this material ranges from 40 to 70 the isotopically light component may have formed in the solar system but the limited range in nanodiamond to total organic c ratios in the chondrite groups is consistent with most of the organic material being presolar