siderophile trace elements in alh84001 other snc meteorites and eucrites evidence of heterogeneity possibly time linked in the mantle of mars we report neutron activation analyses including radiochemical determination of trace siderophile elements au ge ir ni os and re for three snc martian meteorites and os and re results for numerous eucrites ratios such as ga al in the snc orthopyroxenite alh84001 confirm its martian affinity its many distinctive characteristics most notably its near primordial age notwithstanding to the list of alh84001 s idiosyncrasies can now be added extraordinarily low concentrations of au ni and especially re 17 pg g for a martian meteorite we consider several possible origins for the anomalously low re content in alh84001 including metasomatism or alteration the pyroxene cumulate nature of this rock probably does not account for its low re content other snc meteorites are also cumulates an examination of re nd variations among terrestrial basalts and komatiites suggests that re is compatible with mantle minerals in general and only incompatible with olivine however olivine dominates the mantle residuum especially during komatiite genesis our preferred model is that the alh84001 parent melt formed in a mantle source region that was far more re depleted and or at a substantially lower oxygen fugacity than the sources of the young snc meteorites such a contrast is consistent with models that replenish siderophile elements in planetary mantles by gradual admixture of late accreting matter and similarly derive most planetary water which serves as an oxidant very late in accretion according to this model alh84001 formed before the siderophile rich matter and water had been mixed well into the martian interior possibly the martian mantle never became generally as re rich and or oxidized as the source region s of the younger sncs

petrogenesis of the elephant moraine a79001 meteorite multiple magma pulses on the shergottite parent body abstract the eeta 79001 achondrite consists of two distinct igneous lithologies joined along a planar non brecciated contact both are basaltic rocks composed primarily of pigeonite augite and maskelynite but one contains zoned megacrysts of olivine orthopyroxene and chromite that represent disaggregated xenoliths of harzburzite both lithologies probably formed from successive volcanic flows or multiple injections of magma into a small shallow chamber many similarities between the two virtually synchronous magmas suggest that they are related possible mechanisms to explain their differences involve varying degrees of assimilation fractionation from similar parental magmas or partial melting of a similar source peridotite of these assimilation of the observed megacryst assemblage seems most plausible however some isotopic contamination may be required in any of these petrogenetic models the meteorite has suffered extensive shock metamorphism and localized melting during a large impact event that probably excavated and liberated it from its parent body both basaltic lithologies and the inferred ultramafic protolith of the megacryst assemblage are petrologically similar to other members of the shergottite group and all may have been derived from a volcanic plutonic complex on a planetary body

ce anomalies in the lew85300 eucrite evidence for ree mobilization during antarctic weathering abstract there is abundant evidence for widespread ree mobilization in antarctic eucrites resulting in ce and eu anomalies and lower whole rock ree abundances relative to typical eucrites using secondary ion mass spectrometry sims we investigated the microdistribution of ce anomalies in the antarctic polymict eucrite lew85300 ce anomalies positive and or negative are present in all three of the minerals plagioclase pyroxene and silica analysed the anomalies occur in grains from all four clasts as well as in mineral and lithic fragments from the surrounding matrix thus there appears to be no lithologic association silica which has been heavily shocked and altered exhibits a lree enriched pattern with negative ce and eu anomalies consistent with a derivation of the ree from ca phosphate dissolution trivalent ree are leached from the phosphates with preferential retention of tetravalent ce and redeposited on silica pyroxene is also widely affected by ree mobilization due to an extensive shock induced microcrack network along cleavage planes a tendency for the largest ce anomalies to occur at low lree concentrations suggests that pyroxene itself experienced ree leaching with concomitant ce retention ce anomalies are rare in plagioclase because this mineral lacks an extensive network along which ree can be mobilized the widespread ree mobilization and evidence for other forms of weathering requires that trace element data be used cautiously especially for antarctic eucrites

mineral chemistry and the origin of enstatite in unequilibrated enstatite chondrites abstract a comprehensive study of the petrography cathodoluminescence cl rare earth element ree abundances and magnesium and silicon isotopic compositions of enstatite the major mineral in unequilibrated enstatite chondrites uecs is reported for comparison observations were also made in equilibrated enstatite chondrites eecs and aubrites in uecs there are no ree patterns or abundances that uniquely characterize the cl color and intensity grain size or occurrence of enstatite red enstatite is dominant in uecs and blue enstatite in eecs three ree patterns represent the diversity observed in uec enstatite many grains are depleted in one or more of the three most volatile rees under reducing conditions i e yb eu and sm all ree patterns are compatible with the fractional crystallization during chondrule formation of melts whose precursors either had flat ree patterns or were depleted in the most volatile rees no evidence was found to suggest that enstatite grains require nebular condensation or multiple reservoirs as suggested by others magnesium and silicon isotopic ratios are normal therefore excluding the role of evaporation in separating the rees this fractionation was most likely accomplished during condensation of the chondrule precursors our data combined with synthetic experiments support the idea that coexisting red and blue cl enstatites formed by crystallization from a single melt most of the red enstatite was converted to blue by diffusion and recrystallization to form the more equilibrated e chondrites it is not clear why enstatite is depleted in the most volatile rees while oldhamite a highly refractory mineral which is the major carrier of ree in e chondrites commonly has enrichments of these elements

petrology and chemistry of the new shergottite dar al gani 476 in 1998 dar al gani dag 476 was found in the libyan desert the meteorite is classified as a basaltic shergottite and is only the 13th martian meteorite known to date it has a porphyritic texture consisting of a fine grained groundmass and larger olivines the groundmass consists of pyroxene and feldspathic glass minor phases are oxides and sulfides as well as phosphates the presence of olivine orthopyroxene and chromite is a feature that dag 476 has in common with lithology a of elephant moraine eet a79001 however in dag 476 these phases appear to be early phenocrysts rather than xenocrysts shock features such as twinning mosaicism and impact melt pockets are ubiquitous terrestrial weathering was severe and led to formation of carbonate veins following grain boundaries and cracks with a molar mgo mgo feo of 0 68 dag 476 is the most magnesian member among the basaltic shergottites compositions of augite and pigeonite and some of the bulk element concentrations are intermediate between those of lherzolitic and basaltic shergottites however major elements such as fe and ti as well as lree concentrations are considerably lower than in other shergottites noble gas concentrations are low and dominated by the mantle component previously found in chassigny a component similar to that representing martian atmosphere is virtually absent the ejection age of 1 35 0 10 ma is older than that of eeta79001 and could possibly mark a distinct ejection dar al gani 476 is classified as a basaltic shergottite based on its mineralogy it has a fine grained groundmass consisting of clinopyroxene pigeonite and augite feldspathic glass and chromite ti chromite ilmenite sulfides and whitlockite isolated olivine and single chromite grains occur in the groundmass orthopyroxene forms cores of some pigeonite grains shock features such as shock twinning mosaicism cracks and impact melt pockets are abundant severe weathering in the sahara led to significant formation of carbonate veins crosscutting the entire meteorite dar al gani 476 is distinct from other known shergottites chemically it is the most magnesian member among known basaltic shergottites and intermediate in composition for most trace and major elements between iherzolitic and basaltic shergottites unique are the very low bulk ree element abundances the ci normalized abundances of lrees are even lower than those of iherzolitic shergottites the overall abundance pattern however is similar to that of que 94201 textural evidence indicates that orthopyroxene as well as olivine and chromite crystallized as phenocrysts from a magma similar in composition to that of bulk dag 476 whether such a magma composition can be a shergottite parent melt or was formed by impact melting needs to be explored further at this time it cannot entirely be ruled out that these phases represent relics of disaggregated xenoliths that were incorporated and partially assimilated by a basaltic melt although the texture does not support this possibility trapped noble gas concentrations are low and dominated by a chassigny like mantle component virtually no martian atmosphere was trapped in dag 476 whole rock splits the exposure age of 1 26 0 09 ma is younger than that of most shergottites and closer to that of eeta79001 the ejection age of 1 35 0 1 ma could mark another distinct impact event

petrology of magmatic silicate inclusions in the allan hills 77005 lherzolitic shergottite magmatic inclusions occur in both chadacrystic olivine and oikocrystic pigeonite in alh 77005 but are different from each other magmatic inclusions in olivine consist mainly of aluminous pyroxenes intergrowths of plagioclase and silica silica predominant glass and rhyodacitic glass with minor amounts of chromite spinel pyrrhotite and whitlockite those in pigeonite consist mainly of aluminous pyroxenes nonaluminous ferroan pyroxenes kaersutite spinel and k rich trachytic glass with minor amounts of pyrrhotite and whitlockite the magmatic inclusions in chadacrystic olivine formed from trapped melts that were basaltic apparently dry and crystallized additional olivine metastably the basaltic magma with entrained olivine experienced magma mixing with k rich and wet magmas or assimilation of such crustal rocks in the early to middle stages of the crystallization sequence of alh 77005 during crystallization of chadacrystic olivine prior to precipitation of oikocrystic pigeonite however the amount of mixed magmas or assimilated rocks was minor in comparison to the basaltic magma crystallization of pigeonite augite and plagioclase in the host lithologies took place in a shallow magma reservoir under an open system condition and the pigeonite trapped basaltic andesite to trachyandesitic melts which resulted in magmatic inclusions in oikocrystic pigeonite the magmatic inclusions in both olivine and pigeonite were formed under a rapid cooling condition resulting in a variety of inclusions kaersutite in magmatic inclusions in oikocrystic pigeonite crystallized under a closed system wet condition during the late stage crystallization of the inclusions

the igneous crystallization history of an ancient martian meteorite from rare earth element microdistributions rare earth element ree and other selected trace and minor element concentrations were meas ured in individual grains of orthopyroxene feldspathic glass of plagioclase composition and merrillite of the alh 84001 martian meteorite unlike in other martian meteorites phosphate is not the main ree car rier in alh 84001 the ree pattern of alh 84001 bulk rock is dependent on the modal abundances of three ree bearing phases namely orthopyroxene which contains most of the heavy rare earth elements hrees feldspathic glass which dominates the eu abundances and merrillite which contains the majority of the light rare earth elements lrees variations in the ree abundances previously observed in different splits of alh 84001 can easily be explained in terms of small variations in the modal abundances of these three minerals without the need to invoke extensive redistribution of lrees at least some orthopyroxenes i e those away from contacts with feldspathic glass in alh 84001 appear to have preserved their original ree zonation from igneous fractionation an estimate of the alh 84001 parent magma composition from that of the unaltered orthopyroxene core i e zoned orthopyroxene with the lowest ree abundances indicates that it is lree depleted this implies that the martian mantle was already partly depleted within 100 ma of solar system formation which is consistent with rapid accretion and differentiation of mars although equilibration and exchange of rees between phases in particular transport of lrees into the interstitial phases feldspathic glass and merrillite cannot be ruled out our data suggest that the lree enrichment in melts in equilibrium with these interstitial phases is most likely the result of late stage infil tration of the cumulate pile by a lree enriched melt

shock induced melting recrystallization and exsolution in plagioclase from the martian lherzolitic shergottite grv 99027 plagioclase in the martian lherzolitic shergottite grove mountains grv 99027 was shocked melted and recrystallized the recrystallized plagioclase contains lamellae of pyroxene olivine and minor ilmenite 1 m wide both the pyroxene and the olivine inclusions enclosed in plagioclase and grains neighboring the plagioclase were partially melted into plagioclase melt pools the formation of these lamellar inclusions in plagioclase is attributed to exsolution from recrystallizing melt distinct from other martian meteorites grv 99027 contains no maskelynite but does contain recrystallized plagioclase this shows that the meteorite experienced a slower cooling than maskelynite bearing meteorites we suggest that the parent rock of grv 99027 could have been embedded in hot rocks which facilitated a more protracted cooling history

martian meteorite dhofar 019 a new shergottite dhofar 019 is a new martian meteorite found in the desert of oman in texture mineralogy and major and trace element chemistry this meteorite is classified as a basaltic shergottite olivine megacrysts are set within a groundmass composed of finer grained olivine pyroxene pigeonite and augite and maskelynite minor phases are chromite ulvospinel ilmenite silica k rich feldspar merrillite chlorapatite and pyrrhotite secondary phases of terrestrial origin include calcite gypsum celestite fe hydroxides and smectite dhofar 019 is most similar to the elephant moraine eeta 79001 lithology a and dar al gani dag 476 489 shergottites the main features that distinguish dhofar 019 from other shergottites are lack of orthopyroxene lower ni contents of olivine the heaviest oxygen isotopic bulk composition and larger compositional ranges for olivine maskelynite and spinel as well as a wide range for pyroxenes the large compositional ranges of the minerals are indicative of relatively rapid crystallization modeling of olivine chemical zonations yield minimum cooling rates of 0 5 0 8 c h spinel chemistry suggests that crystallization took place under one of the most reduced conditions for martian meteorites at an f o2 3 log units below the quartz fayalite magnetite qfm buffer the olivine megacrysts are heterogeneously distributed in the rock crystal size distribution analysis suggests that they constitute a population formed under steady state conditions of nucleation and growth although a few grains may be cumulates the parent melt is thought to have been derived from partial melting of a light rare earth element and platinum group element depleted mantle source shergottites eeta79001 lithology a dag 476 489 and dhofar 019 although of different ages comprise a particular type of martian rocks such rocks could have formed from chemically similar source s and parent melt s with their bulk compositions affected by olivine accumulation

the variations of stable carbon isotope ratio of land plant derived n alkanes in deep sea sediments from the bering sea and the north pacific ocean during the last 250 000 years two piston cores one located far from the continents the north pacific ocean es core and another located comparatively closer to the continents the bering sea bow 8a core were investigated to reconstruct environmental changes on source land areas the results show significant contribution of terrestrial organic matter to sediments in both cores the d 13 c values of n c27 n c29 and n c31 alkanes in sediments from the north pacific es core show significant glacial to interglacial variation whereas those from the bering sea core do not variations of d 13 c values of land plant n alkanes are related to the environmental or vegetational changes in the source land areas environmental changes especially aridity rainfall and pco2 during glacial interglacial transitional periods can affect vegetation and therefore c3 c4 plant ratios resulting in d 13 c changes in the preserved land plant biomarkers maximum values of d 13 c as well as maximum average chain length values of long chain n alkanes in the es core occur mostly at the interglacial to glacial transition zones reflecting a time lag related to incorporation of living organic matter into soil and transportation into ocean basins via wind and or ability of c4 plants to adapt for a longer period before being replaced by c3 plants when subjected to gradual climatic changes irregular variations with no clear glacial to interglacial trends in the bow 8a core may result from complex mixture of aerosols from westerly winds and riverine organic matter from the bering sea catchments in addition terrestrial organic matter entering the bering sea could originate from multiple pathways including eolian riverine and ice rafted debris and possibly be disturbed by turbidity and other local currents which can induce resuspension and re sedimentation causing an obliterated time relation in the bering sea biomarker records d 2005 elsevier b v all rights reserved

a petrogenetic model for the origin and compositional variation of the martian basaltic meteorites the major element trace element and isotopic compositional ranges of the martian basaltic meteorite source regions have been modeled assuming that planetary differentiation resulted from crystallization of a magma ocean the models are based on low to high pressure phase relationships estimated from experimental runs and estimates of the composition of silicate mars from the literature these models attempt to constrain the mechanisms by which the martian meteorites obtained their superchondritic cao al2o3 ratios and their source regions obtained their parent daughter 87 rb 86 sr 147 sm 144 nd and 176 lu 177 hf ratios calculated from the initial sr nd and hf isotopic compositions of the meteorites high pressure experiments suggest that majoritic garnet is the liquidus phase for mars relevant compositions at or above 12 gpa early crystallization of this phase from a martian magma ocean yields a liquid characterized by an elevated cao al2o3 ratio and a high mg olivine pyroxene garnet dominated cumulates that crystallize subsequently will also be characterized by superchondritic cao al2o3 ratios melting of these cumulates yields liquids with major element compositions that are similar to calculated parental melts of the martian meteorites furthermore crystallization models demonstrate that some of these cumulates have parent daughter ratios that are similar to those calculated for the most incompatible element depleted source region i e that of the meteorite queen alexandra que 94201 the incompatible element abundances of the most depleted que 94201 like source region have also been calculated and provide an estimate of the composition of depleted martian mantle the incompatible element pattern of depleted martian mantle calculated here is very similar to the pattern estimated for depleted earth s mantle melting the depleted martian mantle composition reproduces the abundances of many incompatible elements in the parental melt of que 94201 e g ba th k p hf zr and heavy rare earth elements fairly well but does not reproduce the abundances of rb u ta and light rare earth elements the source regions for meteorites such as shergotty are successfully modeled as mixtures of depleted martian mantle and a late stage liquid trapped in the magma ocean cumulate pile melting of this hybrid source yields liquids with major element abundances and incompatible element patterns that are very similar to the shergotty bulk rock

martian basalt shergottite queen alexandra range 94201 and lunar basalt 15555 a tale of two pyroxenes we present here ion microprobe analyses of rare earth and other selected trace and minor elements in pyroxenes of shergottite queen alexandra range 94201 and lunar basalt 15555 pyroxene zonation patterns record the crystallization histories of these two basaltic samples from mars and the moon respectively and allow a comparison of mafic melt evolution on these two planetary bodies elemental abundances and trends in pyroxenes of these two rocks indicate that their minerals formed by continuous closed system fractional crystallization of their respective parent melts this further supports the idea that que 94201 closely represents the composition of a true martian basaltic melt mcsween et al 1996 the main differences in pyroxene elemental zonation patterns in these two objects are attributed to earlier crystallization of whitlockite in que 94201 i e before the fe rich pyroxenes than in 15555 after the fe rich pyroxenes the size of eu anomalies in pyroxenes of que 94201 is intermediate between that in pyroxenes of 15555 and the other shergottites and may imply that fo2 conditions during crystallization of this martian basalt were significantly more reducing than for other shergottites although not quite as reducing as for lunar basalts cerium anomalies appear to be less prevalent in pyroxenes of que 94201 than other antarctic shergottites and could be indicative of lesser degree of weathering in the antarctic

chassigny petrogenesis melt compositions intensive parameters and water contents of martian magmas abstract the snc meteorites are a class of eight basaltic achondrites that have extremely young crystallization ages 1 3 ga chassigny a unique snc meteorite is a dunite containing fo68 olivines and rare poikilitic ca pyroxenes it is one of the most primitive snc meteorites and thus is most likely to reveal information about the snc basalt source region this study presents a detailed examination of partially crystallized melt inclusions in cumulus olivine grains in chassigny these trapped melts are argued to be representative samples of the melt that existed when chassigny crystallized this melt has been modified however by interaction with the host olivine and by closed system crystallization the phases inside the melt inclusions include hydrous ti rich amphibole kaersutite biotite two pyroxenes and rhyolitic and alkali feldspar glasses all phases have been extensively analyzed with an electron microprobe the new mineralogical information is combined with a complementary experimental study of kaersutite melt equilibria this combined data set can be used to formulate a system of linear equations which can then be solved to determine the composition of the originally trapped melt this calculation reveals that the trapped melt was an feo rich and al2o3 poor basalt the melt composition is shown to be consistent with the crystallization sequence both inside the melt inclusions and in the rock matrix the major element chemistry of this liquid closely resembles terrestrial boninite lavas the new data also allow the intensive conditions temperature total pressure and water fugacity of chassigny crystallization to be estimated two pyroxene geothermometry indicates that equilibration temperatures were 1000 50 c although amphibole does not coexist with melt until t 960 c the trapped liquid initially contained 1 5 wt dissolved water crystallization of anhydrous phases caused water to buildup in the trapped melt prior to kaersutite crystallization the melt must have contained at least 4 wt dissolved water suggesting that a minimum of 1 5 kbar total pressure is required a maximum total pressure cannot be inferred but all available data are consistent with low pressure 5 kbar crystallization finally x h2o in the fluid in the melt inclusion is estimated to have been at least 0 8 in order to stabilize amphibole without plagioclase implying that the water fugacity was 1480 bars the existence of hydrous melts and conditions appropriate for amphibole crystallization suggest that evolved sio2 rich lavas exist on the chassigny parent body mars

chronology and petrogenesis of young achondrites shergotty zagami and alha77005 late magmatism on a geologically active planet a study was undertaken to determine the chronology petrogenesis and relationships among the shergottites shergotty and zagami and the unique achondrite alha77005 these meteorites are the product of a variety of complex processes petrogenesis chondrite normalized abundance patterns of shergotty and zagami are very similar and show pronounced depletions of both the light ree la nd and heavy ree dy lu relative to sm gd these characteristic depletions are even more pronounced for alha77005 the light ree depletion is qualitatively consistent with the presence of cumulus pyroxene and or olivine in these meteorites but trace element models show that the parental magmas of all three meteorites were probably also light ree depleted both trace element model calculations and combined rb sr and sm nd isotopic systematics show that the meteorites could not have been co magmatic nor can alha77005 be representative of the source material of the shergottites light ree depletion of the parental magmas also implies light ree depletion of the source material the sm nd systematics of the shergottites require a time averaged sub chondritic light ree enriched sm nd ratio since 4 6 ae ago the sm nd systematics of alha77005 permit a time averaged super chondritic light ree depleted sm nd ratio if its crystallization age is less than tice 0 72 ae chronology rb sr internal isochrons for all three meteorites and a sm nd internal isochron for zagami are concordant at 180 myr 39ar 40ar plateau ages of shergotty and zagami maskelynite are 250 260 myr these ages apparently reflect resetting of these isotopic systems by shock metamorphism which converted the feldspar to maskelynite the concordance of these ages suggests a single shock event during which the meteorites were in close physical proximity the time of this event is most precisely given by the rb sr age of 180 4 myr for zagami the crystallization ages of the meteorites were not precisely determined extreme upper limits are determined by sm nd model ages relative to an eucrite initial 143nd144nd 0 505835 at 4 6 ae ago these model ages for shergotty zagami and alha77005 are 3600 3500 and 2850 myr respectively the sm nd whole rock age of 1340 60 myr for the three meteorites gives the crystallization age if the sm nd ratios of the precursor materials were always the same we consider this 1340 myr age as a best estimate upper limit best estimate lower limits for shergotty and zagami are taken from the average 39ar 40ar ages of 1200 and 900 myr of pyroxene separates the average 39ar 40ar age of a whole rock sample of alha77005 was 1600 myr and can be partitioned between a low temperature feldspar phase and a high temperature olivine pyroxene inclusions phase the average apparent 39ar 40ar age of the low temperature phase is 1050 myr which is chosen as the best estimate lower limit to the age the crystallization ages of shergotty zagami and alha77005 probably lie within the ranges of 1200 1300 900 1300 and 1000 1300 myr respectively the rb sr whole rock age of 4400 400 myr and single stage babi model ages of 4800 5100 myr are interpreted as reflecting differentiation of the parent body at 4600 myr ago the complex geochemical and isotopic evolution recorded by these meteorites suggests a geologically active parent body capable of sustaining melting at two or more epochs in its history

petrography and bulk chemistry of martian lherzolite lew88516 the meteorite lewis cliffs 88516 is a gabbroic lherzolite with geochemical and petrologic characteristics typical of the shergottites a distinct subgroup of basaltic achondrites belonging to the snc martian meteorite clan we report new inaa and microprobe data for lew88516 noting small but significant differences between our results and those previously published for this meteorite these discrepancies are mainly attributed to heterogeneities in the bulk rock powder which was distributed to several laboratories for geochemical studies other discrepancies are attributed to interlaboratory bias we emphasize that even minor variations between datasets may have the potential to significantly affect geochemical models for martian basalts small differences in bulk trace element chemistry between lew88516 and martian lherzolite alh77005 may indicate that they crystallized from different magmas copyright 1997 elsevier science ltd

composition of the first bulk melt sample from a volcanic region of mars queen alexandra range 94201 antarctic meteorite queen alexandra range que 94201 is a 12 g basaltic achondrite dominated by plagioclase now maskelynite and zoned low and high ca pyroxene petrologic geochemical and isotopic analyses indicate that it is related to previously described basaltic and lherzolitic shergottites which are a group of igneous meteorites that are believed to be from mars unlike previous shergottites however que 94201 represents a bulk melt rather than a cumulate fraction meaning it can be used to infer magmatic source regions and the compositions of other melts on mars this melt has much more fe and p than basaltic melts produced on earth and formed at a much lower oxygen fugacity this has altered the crystallization sequence of the melt removing olivine from the liquidus to produce a plagioclase and 2 pyroxene assemblage if the high phosphorus and low oxygen fugacity conditions represented by que 94201 are common in magmatic regions of mars then olivine may be rare in martian basalts no solar cosmic ray effects were seen in the concentrations of 10be 26al and 36cl with depth in the meteorite implying at least 3 cm of ablation during entry to earth significant excesses of neutron capture noble gas isotopes 80 82kr and 128 131xe suggest that the que 94201 sample came from a depth 22 cm in a meteoroid of at least that radius the meteorite also has very low 21ne 22ne which would often be interpreted to mean little ablation contradicting above evidence but in this case appears to reflect a very low abundance of mg the principal target element for ne in the meteorite consistent with our bulk chemical analyses the meteorite has a terrestrial 36cl age of 0 29 0 05 myr and a 10be exposure age of 2 6 0 5 myr in a 4 geometry implying an ejection age of 2 9 0 5 myr

aliphatic and diterpenoid hydrocarbons and their individual carbon isotope compositions in coals from the liaohe basin china abundant tricyclic diterpanes i e pimarane dehydroabietane and simonellite and tetracyclic diterpanes e g phyllocladane were detected in coal samples from the third member of the shahejie formation lower eogene liaohe basin china gas chromatography isotope ratio mass spectrometry gc irms analyses show that the carbon isotopic composition of terrigenous tricyclic and tetracyclic diterpenoid hydrocarbons are about 4 6 enriched in 13c compared to n alkanes in the same samples in addition the pimaranes and phyllocladane have comparatively narrow stable carbon isotopic compositions among the different samples with a slightly wider range in 13c compositions for the abietanes i e abietane dehydroabietane and simonellite the n alkanes and triterpenoids reflect the 13c compositions of higher plant wax

petrology and geochemistry of olivine phyric shergottites lar 12095 and lar 12240 implications for their petrogenetic history on mars larkman nunatak lar 12095 and lar 12240 are recent olivine phyric shergottite lnds we report the results of petrographic and chemical analyses of these two samples to understand their petrogenesis on mars based on our analyses we suggest that these samples are likely paired and are most similar to other depleted olivine phyric shergottites particularly dar al gani dag 476 and sayh al uhaymir sau 005 and samples paired with those the olivine megacryst cores in lar 12095 and lar 12240 are not in equilibrium with the groundmass olivines we infer that these megacrysts are phenocrysts and their major element compositions have been homogenized by diffusion the cores of the olivine megacrysts have mg 70 whereas megacryst rims and groundmass olivines typically have mg 58 60 the rare earth element ree microdistributions in the various phases olivine low and high ca pyroxene maskelynite and merrillite in both samples are similar and support the likelihood that these two shergottites are indeed paired the calculated parent melt i e in equilibrium with the low ca pyroxene which is one of the earliest formed ree bearing minerals has an ree pattern parallel to that of melt in equilibrium with merrillite i e one of the last formed minerals this suggests that the lar 12095 12240 paired shergottites represent the product of closed system fractional crystallization following magma emplacement and crystal accumulation utilizing the europium oxybarometer we estimate that the magmatic oxygen fugacity early in the crystallization sequence was iw finally petrographic evidence indicates that lar 12095 12240 experienced extensive shock prior to being ejected from mars

methyl halides in surface seawater and marine boundary layer of the northwest pacific 1 the partial pressures of methyl halides ch3x x cl br or i and of chclf2 hcfc 22 which are all volatile organic compounds vocs were measured in the air of the marine boundary layer pvocair and in surface seawater pvocwater during a cruise from the subarctic to subtropical regions of the northwest pacific in summer of 2008 in the northern transition water twn with high biological activity high levels of the three ch3xs in surface seawater were frequently observed probably owing to their enhanced production by phytoplankton supersaturation of ch3br was only present in twn water with a saturation anomaly sch3br of 0 95 sch3x pch3xwater pch3xair pch3xair the highest saturation anomalies for ch3cl sch3cl 1 6 and ch3i sch3i 91 were found in the southern subtropical water sts with low biological production south of the subtropical front we found that the molar concentrations of ch3cl cch3cl and ch3i cch3i sharply increased with increasing sea surface temperature sst in the subtropical waters the maximum cch3cl 144 pmol l 1 was present in sts water at sst 30 c and is 1 5 times the value extrapolated from the previously reported relationship between cch3cl and sst photochemical production might have contributed to the production of ch3cl and ch3i in sts water

bulk chemical composition of lherzolitic shergottite grove mountains 99027 constraints on the mantle of mars we report the concentration of 50 elements including rare earth elements rees and platinum group elements pges in bulk samples of the grove mountains grv 99027 lherzolitic shergottite the abundances of rees are distinctly lower than those of allan hills alh a77005 and other lherzolitic shergottites indicating that grv 99027 is not paired with them it may nevertheless sample the same igneous unit as the others lin et al 2005b wang and chen 2006 the ci normalized elemental pattern of grv 99027 reveals low 0 004 0 008 ci and unfractionated pges except for pd of 0 018 ci without depletion of w or ga relative to lithophile element trends fractionation between siderophile and lithophile elements become less pronounced with increase of volatility except for high abundances of ni and co these characteristics are probably representative of the mantle of mars which is consistent with previous work that the martian mantle formed in a deep magma ocean followed by a later accretion of chondritic materials

hydrocarbon geochemistry of the puget sound region ii sedimentary diterpenoid steroid and triterpenoid hydrocarbons cyclic components of the aliphatic hydrocarbon mixtures extracted from puget sound sediment cores include a suite of c19 and c20 diterpenoid hydrocarbons of which fichtelite sandaracopimaradiene and isopimaradiene have been identified although apparently also derived from vascular plants these diterpenoid hydrocarbons have relative abundances distinctly different from the co existing plant wax n alkane suite five c27 c28 and c29 diasteranes and four c29 c30 and c31 17 h 21 h hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage these chromatographically resolved cycloalkanes along with the strongly covarying unresolved complex mixture have been introduced to puget sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill naturally occurring triterpenoid hydrocarbons including hop 22 29 ene diploptene are also present a new group of c30 polyenes has been detected which contains compounds apparently structurally related to a co existing bicyclic c25 diene and to c20 and c25 acyclic multibranched hydrocarbons described in a previous paper barrick et al 1980

sayh al uhaymir 094 a new martian meteorite from the oman desert sayhal uhaymir sau 094 is a 223 3 g partially crusted strongly to very strongly shocked melanocratic olivine porphyric rock of the shergottite group showing a microgabbroic texture the rock consists of pyroxene 52 0 58 2 vol dominantly prismatic pigeonite en60 68fs20 27wo7 9 associated with minor augite en46 49fs15 16wo28 31 brown shock oxidized olivine fo65 69 22 1 31 completely isotropic interstitial plagioclase glass maskelynite an50 64or0 3 0 9 8 6 13 0 chromite and titanian magnesian chromite 0 9 1 0 traces of ilmenite ilm80 86 pyrrhotite fe92 100 0 1 0 2 merrillite 0 1 and pockets 4 8 6 7 consisting of green basaltic to basaltic andesitic shock glass that is partially devitrified into a brown to black product along boundaries with the primary minerals the average maximum dimensions of minerals are olivine 1 5 mm pyroxene 0 3 mm and maskelynite 0 3 mm primary melt inclusions in olivine and chromite are common and account for 0 1 0 6 of the rock x ray tomography revealed that the specimen contains 0 4 vol of shock melt associated vesicles up to 3 mm in size which show a preferred orientation fluidization of the maskelynite melting and recrystallization of pyroxene olivine and pyrrhotite indicate shock stage s6 minor terrestrial weathering resulted in calcite veining and minor oxidation of sulfides the meteorite is interpreted as paired with sau 005 008 051 the modal composition is similar to dar al gani 476 489 670 735 876 with the exception that neither mesostasis nor titanomagnetite nor apatite are present and that all phases show little zonation the restricted mineral composition predominance of chromite among the oxides and abundance of olivine indicate affinities to the lherzolitic shergottites

new insights into the origin of perylene in geological samples abstract the origin of the polycyclic aromatic hydrocarbon pah perylene in sediments and petroleum has been a matter of continued debate reported to occur in phanerozoic organic matter om fossil crinoids and tropical termite mounds its mechanism of formation remains unclear while a combustion source can be excluded structural similarities to perylene quinone like components present in e g fungi plants crinoids and insects potentially suggest a product precursor relationship here we report perylene concentrations 13c 12c and d h ratios from a holocene sediment profile from the qingpu trench yangtze delta region china perylene concentrations differ from those of pyrogenic pahs and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores in this zone perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol d h ratios between 284 and 317 similar to the methoxy groups in lignin as well as co variation with spores from wood degrading fungi 13c 12c of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin which is isotopically lighter than cellulose and whole wood during progressive lignin degradation the relative carbon isotopic ratio of the perylene decreases we therefore hypothesise a relationship of perylene to the activity of wood degrading fungi to support our hypothesis we analysed a wide range of phanerozoic sediments and oils and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants and to be generally absent from marine sourced oils few exceptions being attributed perhaps to a contribution of marine and or terrestrial derived fungi anoxia especially under marine conditions and or contamination of core material by fungi a series of low molecular weight aromatic quinones bearing the perylene backbone were detected in devonian and cretaceous sediments potentially representing precursor components to perylene

probable fungal origin of perylene in late cretaceous to paleogene terrestrial sedimentary rocks of northeastern japan as indicated from stable carbon isotopes abstract perylene is present in high concentration in paleogene sediments from the sanriku oki borehole of the ministry of international trade and industry miti northeastern japan the borehole penetrates a thick sequence of late cretaceous to neogene sediments deposited under a range of conditions including fluvial deltaic and shallow marine organic petrological and geochemical data show the sediments to be rich in organic matter om derived from higher plants biomarker analysis of aliphatic and aromatic hydrocarbons confirms a significant input from higher plants with extracts dominated by numerous gymnosperm and angiosperm derived biomarkers such as diterpanes oleanenes des a triterpanes and their aromatized counterparts the highest concentration of perylene occurs in middle eocene sediments deposited in a relatively reducing environment stable carbon isotope compositions show 13 c enrichment in perylene compared to gymnosperm and angiosperm biomarkers consistent with a fungal origin this elevated abundance of sedimentary perylene could relate to a paleogene continental climate where fungi probably flourished

physical properties of martian meteorites porosity and density measurements martian meteorites are fragments of the martian crust these samples represent igneous rocks much like basalt as such many laboratory techniques designed for the study of earth materials have been applied to these meteorites despite numerous studies of martian meteorites little data exists on their basic structural characteristics such as porosity or density information that is important in interpreting their origin shock modification and cosmic ray exposure history analysis of these meteorites provides both insight into the various lithologies present as well as the impact history of the planets surface we present new data relating to the physical characteristics of twelve martian meteorites porosity was determined via a combination of scanning electron microscope sem imagery image analysis and helium pycnometry coupled with a modified archimedean method for bulk density measurements our results show a range in porosity and density values and that porosity tends to increase toward the edge of the sample preliminary interpretation of the data demonstrates good agreement between porosity measured at 100 and 300 magnification for the shergottite group while others exhibit more variability in comparison with the limited existing data for martian meteorites we find fairly good agreement although our porosity values typically lie at the low end of published values surprisingly despite the increased data set there is little by way of correlation between either porosity or density with parameters such as shock effect or terrestrial residency further data collection on additional meteorite samples is required before more definitive statements can be made concerning the validity of these observations

petrography mineral chemistry and petrogenesis of antarctic shergottite lew88516 abstract lew88516 lew like its near twin alh77005 alh is a maskelynite bearing harzburgite and a member of the snc family of achondrites lew is texturally heterogenous exhibiting both poikilitic pyroxene oikocrysts enclosing subhedral olivine and euhedral chromite and non poikilitic cumulus framework of olivine and minor pyroxene with interstitial maskelynite and secondary minerals textures pyroxenes in lew appear to be slightly more iron rich and more varied in composition than those in alh lew olivines have distinctly higher fe contents most of the olivine grains in lew have compositions more iron rich than any alh olivine observed lew olivine in non poikilitic areas is substantially more iron rich than olivine armored by pyroxene trace element and minor element patterns of lew and alh minerals are essentially identical and are consistent with closed system large volume crystallization of the major phases followed by development of later phases after assembly of the crystal pile major element compositions show the effects of moderate near solidus re equilibration in both meteorites the compositions of possible lew parent magmas calculated from mass balance methods using the components of magmatic inclusions in large olivine grains are very similar to those proposed earlier for alh and the eeta79001 shergottite while the subtle differences between lew and alh suggest they are not part of the same fall it is likely that they are derived from the same igneous processes

a petrologic and trace element study of dar al gani 476 and dar al gani 489 twin meteorites with affinities to basaltic and lherzolitic shergottites we present the results of a combined mineralogic petrologic and ion microprobe study of two martian meteorites recently recovered in the lybian sahara dar al gani 476 dag 476 and dar al gani 489 dag 489 having resided in a hot desert environment for an extended time dag 476 and dag 489 were subjected to terrestrial weathering that significantly altered their chemical composition in particular analyses of some of the silicates show light rare earth element lree enrichment resulting from terrestrial alteration in situ measurement of trace element abundances in minerals allows us to identify areas unaffected by this contamination and thereby to infer the petrogenesis of these meteorites no significant compositional differences between dag 476 and dag 489 were found supporting the hypothesis that they belong to the same fall these meteorites have characteristics in common with both basaltic and lherzolitic shergottites possibly suggesting spatial and petrogenetic associations of these two types of lithologies on mars however the compositions of fe ti oxides and the size of eu anomalies in the earliest formed pyroxenes indicate that the two saharan meteorites probably experienced more reducing crystallization conditions than other shergottites with the exception of queen alexandra range que 94201 as is the case for other shergottites trace element microdistributions in minerals of the dag martian meteorites indicate that closed system crystal fractionation from a lree depleted parent magma dominated their crystallization history furthermore rare earth element abundances in the orthopyroxene megacrysts are consistent with their origin as xenocrysts rather than phenocrysts

crystal chemistry of lunar merrillite and comparison to other meteoritic and planetary suites of whitlockite and merrillite merrillite also known as whitlockite is one of the main phosphate minerals along with apatite that occur in lunar rocks martian meteorites and in many other groups of meteorites signi cant structural differences between terrestrial whitlockite and lunar and meteoritic varieties warrant the use of merrillite for the h free extraterrestrial material and the systematic enrichment of ree in lunar merrillite warrants the use of re merrillite laser raman spectroscopy of extraterrestrial merrillite and terrestrial whitlockite con rms the absence of h in the former and presence of h in the latter lunar merrillite ideally mg fe 2 mn 2 2 ca18 x y ree x na2 x p si 14o56 contains high concentrations of y ree reaching just over 3 atoms per 56 o atoms or up to 18 wt as y re 2o3 in the absence of extensive si p substitution the availability of the na site limits y ree substitution to 2 atoms per 56 o atoms higher concentrations of y ree with coupled substitution of si for p to balance charge are possible but rare in lunar material intrinsically low na concentrations in lunar rocks combined with the typical formation of merrillite in late stage basaltic mesostasis or residual intercumulus melt pockets produce these high ree concentrations lunar merrillite typically contains 0 1 0 4 na atoms per 56 o atoms for comparison martian merrillite contains signi cantly higher na concentrations up to 1 7 na atoms per 56 o atoms and much lower ree concentrations meteoritic merrillite has relatively low ree contents but exists in both ca rich and na rich varieties concentrations of fe and mg in all varieties sum to near 2 atoms per 56 o atoms merrillite in lunar crustal lithologies typically has mg fe however fe rich mare basalts contain up to 1 8 fe 2

petrogenesis of shergottite meteorites inferred from minor and trace element microdistributions abstract as an extension of our previous work on the lherzolitic shergottites alha77005 and lew88516 ion microprobe measurements of rees and other selected trace and minor elements were made in individual minerals of the basaltic shergottites shergotty zagami and eeta79001 whole rock ree abundances in these achondrites are dominated by whitlockite which is usually present only in trace amounts one of the most significant features is the extensive zoning of trace and minor elements in pyroxenes this zonation which provides information on the crystallization histories of these meteorites is of primary magmatic origin and not the result of secondary processes such as diffusive reequilibration and or metasomatic infiltration coherent trends in element element plots for low ca pyroxenes indicate that each shergottite formed essentially by progressive closed system fractional crystallization the calculated ree patterns of the parent melts of all shergottites are lree depleted and parallel to their whole rock ree patterns also indicative of closed system fractional crystallization on the basis of observations reported in this study as well as previously determined petrologic and geochemical including isotopic characteristics we present a model that suggests possible relationships among all five known shergottites

perylene an indicator of alteration processes or precursor materials abstract perylene is a polycyclic aromatic hydrocarbon pah that is found pervasively in both marine and freshwater sediments yet its origin remains obscure we have explored relationships between perylene and possible precursor materials in two 210 pb dated sediment cores from lake ontario in which contributions of aquatic and land plant organic matter and concentrations of anthropogenic pahs have been measured no significant correlations were identified between perylene occurrence and indicators of terrigenous or aquatic sources of organic matter distinct differences between perylene and anthropogenic pah sedimentary profiles rule out an industrial source for perylene at these locations the general pattern of low to absent perylene concentrations in upper oxic sediments and increasing concentrations with depth indicates that in situ diagenesis under anoxic conditions produces perylene and that its formation is kinetically controlled the results of our study suggest that perylene is formed from non specific precursor materials by biotic or abiotic transformation processes if this scenario accurately describes its formation then perylene is an indicator of depositional conditions rather than the source of organic matter

petrogenetic linkages among martian basalts implications based on trace element chemistry of olivine the shergottites exhibit a range of major and trace element compositions crystallization ages and initial sr nd hf and pb isotopic compositions to constrain the physical mechanisms by which shergottites obtain their compositional characteristics we examined the major and trace element record preserved in olivine in the more primitive shergottites based on such characteristics as the mg v zoning calculated dni co the olivine in y 980459 are most likely phenocrysts many of these same characteristics indicate that the olivines in other shergottites are not in equilibrium with the adjacent melt however in most cases they are not xenocrystic but additions of olivine from the same basaltic system elephant moraine eet a79001 may be an exception with the olivine data suggesting that it is xenocrystic in this case the olivine crystallized from a reduced and lreedepleted melt and was incorporated into an oxidized and enriched basalt vanadium and cao in olivine appear to record the appearance of spinel and pyroxene on the liquidus of most of the shergottites most of the olivine shergottites represent basalts produced by melting of reduced iw to iw 1 depleted mantle sources olivine data indicate that many of the primary melts derived from this source had similar ni co and mn shergottites such as northwest africa nwa 1110 1068 and perhaps roberts massif rbt 04261 that appear to be derived from more enriched sources have distinctly different olivine in the case of nwa 1110 1068 the olivine data suggests that the enriched component was added to system prior to olivine crystallization

two stage polybaric formation of the new enriched pyroxene oikocrystic lherzolitic shergottite nwa 7397 northwest africa nwa 7397 is a newly discovered enriched lherzolitic shergottite the third described example of this group this meteorite consists of two distinct textural lithologies 1 poikilitic comprised of zoned pyroxene oikocrysts with chadacrysts of chromite and olivine and 2 nonpoikilitic comprised of olivine low ca and high ca pyroxene maskelynite and minor abundances of merrillite spinel ilmenite and pyrrhotite the constant ti al ratios of pyroxene oikocrysts suggests initial crystallization of the poikilitic lithology at depth equivalent to pressures of approximately 10 kbar followed by crystallization of the nonpoikilitic lithology at shallower levels oxygen fugacity conditions become more oxidizing during crystallization ranging from fo2 conditions of approximately qfm 2 to qfm 0 7 magma calculated to be in equilibrium with the major rock forming minerals is lree enriched relative to depleted or intermediate shergottites and has flat overall profiles therefore we suggest that the parental magma for nwa 7397 had sampled an enriched oxidized martian geochemical source similar to that of other enriched basaltic and olivine phyric shergottites we present a polybaric formation model for the lherzolitic shergottite nwa 7397 to account for the petrologic constraints three successive stages in the development of nwa 7397 are discussed 1 formation of a ree enriched parental magma from a distinct martian mantle reservoir 2 magma ponding and development of a staging chamber concomitant with initial crystallization of the poikilitic lithology and 3 magma ascent to the near surface with entrainment of cumulates from the staging chamber and subsequent crystallization of the nonpoikilitic lithology en route to the surface

the behavior of co and ni in olivine in planetary basalts an experimental investigation cobalt and nickel in olivine from lunar martian and terrestrial basalts show systematic differences that appear to be related to planetary parentage we present results from a series of 1 atm experiments designed to examine the partitioning of co and ni in olivine over a range of conditions relevant to planetary basalts our results confirm the suggestions of previous workers that the partitioning of co is such that an increase in d cool with crystallization is balanced by a decrease in co concentration in the melt resulting in constant co in olivine either within olivine showing otherwise normal igneous zoning or within a suite of basalts related by fractionation it is evident that the partitioning of co and ni into planetary olivine is influenced by such intensive variables as temperature oxygen fugacity and composition although separating these effects is not possible our data demonstrate that over the range of oxygen fugacity of lunar martian and terrestrial basalts oxygen fugacity has no significant effect on co and ni partitioning into olivine we propose that an increase in melt polymerization with decreasing temperature coupled with the preference of co and ni for the octahedral sites in olivine is the mechanism by which d cool and d niol increase with crystallization with our experimental results as a baseline we interpret data from co and ni in olivine from lunar martian and terrestrial basalts and conclude that the cause of increases in co concentrations in olivine either core to rim or within a co genetic suite and observed primarily in martian and terrestrial basalts is enrichment of the melt as crystallization progresses we hypothesize that this enrichment is attributable either to crystallization of a phase in which co is incompatible such as plagioclase or replenishment of the igneous system with co enriched melt

que94201 shergottite crystallization of a martian basaltic magma abstract basaltic shergottites are commonly described as having crystallized from magmas that contained entrained or cumulus pyroxenes complexly zoned clinopyroxenes in que94201 a newly recovered antarctic shergottite are similar to those formed during continuous growth in some lunar basaltic melts pyroxene cores have nuclei of magnesian pigeonite mantled by augite in turn rimmed by strongly zoned ferroan pigeonite with outer rims of pyroxferroite fe ti oxide compositions indicate that this meteorite crystallized under relatively reducing conditions more like lunar basalts than other shergottites ree and other trace element abundances in zoned pyroxenes maskelynite and phosphates are consistent with continuous pyroxene crystallization from an evolving magma punctuated by the appearance of new phases on the liquidus the higher proportion of maskelynite in que94201 suggests that its composition may be closer to multiple saturation with pyroxenes plagioclase than other shergottites and all pyroxene zones show negative eu anomalies thus this meteorite may represent the first example of a martian magma unaffected by crystal accumulation the fe fe mg ratio and proportions of incompatible elements reflected in 4 modal whitlockite are high implying that this is a fractionated melt the calculated bulk ree pattern shows extreme lree depletion suggesting either less contamination with enriched crustal materials or a more lree depleted source than other basaltic shergottites

noble gases and nitrogen in martian meteorites dar al gani 476 sayh al uhaymir 005 and lewis cliff 88516 efa and extra neon meteorite finds from the terrestrial hot deserts have become a major contributor to the inventory of martian meteorites in order to understand their nitrogen and noble gas components we have carried out stepped heating experiments on samples from two martian meteorites collected from hot deserts we measured interior and surface bulk samples glassy and non glassy portions of dar al gani 476 and sayh al uhaymir 005 we have also analyzed noble gases released from the antarctic shergottite lewis cliff 88516 by crushing and stepped heating for the hot desert meteorites significant terrestrial ar kr xe contamination is observed with an elementally fractionated air efa component dominating the low temperature releases the extremely low ar kr xe ratios of efa may be the result of multiple episodes of trapping loss during terrestrial alteration involving aqueous fluids we suggest fractionation processes similar to those in hot deserts to have acted on mars with acidic weathering on the latter possibly even more effective in producing elementally fractionated components addition from fission xenon is apparent in dag 476 and sau 005 the ar kr xe patterns for lew 88516 show trends as typically observed in shergottites including evidence for a crush released component similar to that observed in eeta 79001 a trapped ne component most prominent in the surface sample of dag 476 may represent air contamination it is accompanied by little trapped ar 20ne 36ar 50 and literature data suggest its presence also in some antarctic finds data for lew 88516 and literature data on the other hand suggest the presence of two trapped ne components of martian origin characterized by different 20ne 22ne possibly related to the atmosphere and the interior caution is recommended in interpreting nitrogen and noble gas isotopic signatures of martian meteorites from hot deserts in terms of extraterrestrial sources and processes nevertheless our results provide hope that vice versa via noble gases and nitrogen in meteorites and other relevant samples from terrestrial deserts martian secondary processes can be studied

the parent magma of the nakhlite meteorites clues from melt inclusions abstract several forms of trapped liquid found within nakhlite meteorites have been examined including interstitial melt and magmatic inclusions within the cores of large olivine grains differences in the mineralogy and texture between two types of trapped melt inclusions and between these inclusions and the mesostasis indicate that vitrophyric inclusions are most appropriate for estimating the composition of a nakhlite parental magma in equilibrium with early forming olivine and augite parent liquids were calculated from the mineralogy of large inclusions in nakhla and governador valadares using a system of mass balance equations solved by linear regression methods the chosen parental liquids were cosaturated in olivine and augite and had mg fe values consistent with measured augite liquid kd s these parental magma compositions are similar to other published compositions for nakhla chassigny and shergotty parental melts and may correspond to a significant magma type on mars

sulfide isotopic compositions in shergottites and alh84001 and possible implications for life on mars abstract the shergottite and alh84001 meteorites hold keys for understanding geologic and possibly biologic processes on mars recently it has been proposed that carbonates in alh84001 and the fe sulfides they contain are products of extraterrestrial biogenic activity mckay et al 1996 here we report ion microprobe analyses of sulfides in shergottites and alh84001 the sulfur isotope ratios of igneous pyrrhotites in shergottites mean 34 s cdt shergotty 0 4 zagami 2 7 eeta79001a 1 9 eeta79001b 1 7 lew88516 1 9 que94201 0 8 are similar to those of terrestrial ocean floor basalts suggesting that the sulfur isotopic composition of the martian mantle may be similar to that of the mantle of the earth the sulfur isotopic systematics of alh84001 sulfides are distinct from the shergottites measured sulfur isotope ratios of eight pyrite grains 34 s cdt 2 0 to 7 3 in crushed zones confirm previously reported analyses of isotopically heavy sulfides shearer et al 1996 and are indistinguishable from an fe sulfide zone within a carbonate globule 34 s cdt 6 0 analyses of synthesized fine grained mixtures of sulfide carbonate and magnetite indicate that the measured sulfur isotope ratio is independent of the presence of carbonate and magnetite in the sputtered volume confirming the accuracy of the analysis of the fine grained sulfide in the carbonate globule terrestrial biogenic sulfate reduction typically results in light isotopic enrichments the similarity of 34 s values of the sulfides in alh84001 imply that the fe sulfide zones within alh84001 carbonates are probably not the result of bacterial reduction of sulfate

evolution of the martian mantle inferred from the 187re 187os isotope and highly siderophile element abundance systematics of shergottite meteorites abstract shergottite meteorites are a suite of mafic to ultramafic igneous rocks whose parental magmas probably derived from the martian mantle in this study a suite of 23 shergottites spanning their known range in bulk compositions rb sr sm nd and lu hf isotopes were measured for 187re 187os isotopic systematics and highly siderophile element abundances hse including os ir ru pt pd re the chief objective was to gain new insight on the chemical evolution of the martian mantle by unraveling the long term hse budget of its derivative melts possible effects upon hses related to crustal contamination as well as terrestrial and or martian surface alteration are also examined some of the shergottites are hot arid desert finds their respective acetic acid leachates and residues show that both re and os display open system behavior during sample residence at or near the martian and or terrestrial surfaces in some meteorites the alteration effects can be circumvented by analysis of the leached residues for those shergottites believed to record robust re os isotopic systematics calculated initial 187os 188os are well correlated with the initial 143nd 144nd shergottites from mantle sources with long term melt depleted characteristics initial e143nd of 36 to 40 have chondritic initial 187os ranging from 0 5 to 2 5 shergottites with intermediate initial e143nd of 8 to 17 have a range in initial 187os of 0 6 to 2 3 which overlaps the range for depleted shergottites shergottites from long term enriched sources with initial e143nd of 7 are characterized by suprachondritic 187os values of 5 to 15 the initial 187os variations for the shergottites do not show a correlation with indices of magmatic differentiation such as mgo or any systematic differences between hot arid desert finds antarctic finds or observed falls the strong correlation between the initial e143nd and 187os in shergottites from approximately 40 and 0 to 7 and 15 respectively is assessed in models for mixing depleted mantle derived melts with ancient crust modeled to be similar to evolved shergottite in composition and with assimilation fractional crystallization these models show that the correlation is unlikely to result from participation of martian crust more likely this correlation relates to contributions from depleted and enriched reservoirs formed in a martian magma ocean at ca 4 5 ga these models indicate that the shergottite endmember sources were generated by mixing between residual melts and cumulates that formed at variable stages during solidification of a magma ocean the expanded database for the hse abundances in shergottites suggests that their martian mantle sources have similar hse abundances to the terrestrial mantle consistent with prior studies the relatively high hse abundances in both planetary mantles likely cannot be accounted for by high pressure temperature metal silicate partitioning at the bases of magma oceans as has been suggested for earth if the hse were instead supplied by late accretion this event must have occurred prior to the crystallization of the last martian magma ocean

the parental magma of the nakhla achondrite ultrabasic volcanism on the shergottite parent body the nakhla meteorite is an augite rich igneous cumulate rock magma trapped among the cumulus grains is now represented by fine grained mesostasis and post cumulus overgrowths on cumulus grains the composition of the intercumulus magma calculated by mass balance is ultrabasic sio2 45 and enriched in incompatible elements lalu 6 ci the cumulus augite and intercumulus magma were in chemical equilibrium implying that the intercumulus magma is a sample of nakhla s parental magma complex processes like infiltration metasomatism were therefore unimportant nakhla contains olivine crystals which are as large or larger than the cumulus augite crystals the largest olivine crystals probably xenocrysts preserve core compositions too fe rich to have been in equilibrium with the intercumulus magma other smaller olivine grains may have been phenocrysts the closest terrestrial analogs to nakhla and the other nakhlites are pyroxene rich cumulate layers in differentiated picrite and komatiite flows and shallow sills spinel or garnet was fractionated from the parental magmas of the nakhlites or their parental mantle based on the superchondritic caoal2o3 ratio of nakhla s intercumulus magma and its lack of an eu anomaly the three nakhlites and chassigny are half of the known samples of the shergottite parent body spb one may tentatively infer that ultrabasic volcanism was much more important on the spb than on the moon eucrite parent body or present day earth

constraints on the petrogenesis of martian meteorites from the rb sr and sm nd isotopic systematics of the lherzolitic shergottites alh77005 and lew88516 abstract detailed rb sr and sm nd isotopic analyses have been completed on the lherzolitic shergottites alh77005 and lew88516 alh77005 yields a rb sr age of 185 11 ma and a sm nd age of 173 6 ma whereas the rb sr and sm nd ages of lew88516 are 183 10 and 166 16 ma respectively the initial sr isotopic composition of alh77005 is 0 71026 4 and the initial end value is 11 1 0 2 these values are distinct from those of lew88516 which has an initial sr isotopic composition of 0 71052 4 and an initial end value of 8 2 0 6 several of the mineral and whole rock leachates lie off the rb sr and sm nd isochrons indicating that the isotopic systematics of the meteorites have been disturbed the sm nd isotopic compositions of the leachates appear to be mixtures of primary igneous phosphates and an alteration component with a low 143nd 144nd ratio that was probably added to the meteorites on mars tie lines between leachate residue pairs from lew88516 mineral fractions and whole rocks have nearly identical slopes that correspond to rb sr ages of 90 1 ma this age may record a major shock event that fractionated rb sr from lattice sites located on mineral grain boundaries on the other hand the leachates could contain secondary alteration products and the parallel slopes of the tie lines could be coincidental nearly identical mineral modes compositions and ages suggest that these meteorites are very closely related nevertheless their initial sr and nd isotopic compositions differ outside analytical uncertainty requiring derivation from unique sources assimilation fractional crystallization models indicate that these two lherzolitic meteorites can only be related to a common parental magma if the assimilant has a sr nd ratio near 1 and a radiogenic sr isotopic composition further constraints placed on the evolved component by the geochemical and isotopic systematics of the shergottite meteorite suite suggest that it a formed at 4 5 ga b has a high la yb ratio c is an oxidant and d is basaltic in composition or is strongly enriched in incompatible elements the composition and isotopic systematics of the evolved component are unlike any evolved lunar or terrestrial igneous rocks its unusual geochemical and isotopic characteristics could reflect hydrous alteration of an evolved martian crustal component or hydrous metasomatism within the martian mantle

magmatic cristobalite and quartz in the nwa 856 martian meteorite silica rich late stage crystallization pockets in the martian meteorite northwest africa nwa 856 were investigated by transmission electron microscopy tem the pockets occur as wedges between maskelynite laths or between maskelynite and pyroxene they consist of elongated grains of cristobalite and quartz embedded in a silica rich glass interstitial to the amorphous phase and silica minerals a number of small accessory minerals have been identified typical for late stage crystallization products they are ilmenite tranquillityite fayalite troilite baddeleyite apatite and chloroapatite cristobalite and quartz are shocked as revealed by the occurrence of numerous amorphous lamellae this assemblage suggests metastable dendritic crystallization under hydrous conditions cristobalite crystallization was probably facilitated by the presence of impurities such as na or h2o our observations show that silica minerals can be formed under magmatic conditions on mars

magnetic properties of antarctic shergottite meteorites eeta 79001 and alha 77005 possible relevance to a martian magnetic field abstract the possibility that the parent body of the snc meteorites is mars implies that the magnetic properties of these meteorites may provide evidence concerning ancient martian magnetic fields eeta 79001 possesses a weak very stable primary magnetization the properties of which are consistent with its acquisition in an ambient magnetic field either during the meteorite s formation or during the severe shock event later in its history the samples of alha 77005 studied possessed no measurable primary magnetization the observed remanence appears to be a viscous magnetization acquired in local laboratory fields the magnetic carriers in the meteorites are fine grained magnetite and a lower curie point mineral probably titanomagnetite or pyrrhotite present to the extent of less than 0 1 by weight estimates of the strength of the magnetizing field for eeta 79001 are in the range 1 10 t

rare earth elements in minerals of the alha77005 shergottite and implications for its parent magma and crystallization history abstract rare earth element ree and selected trace element abundances were measured in individual grains of pyroxenes whitlockite maskelynite and olivine of the alha77005 shergottite minor 1 whitlockite which displays a negative eu anomaly indicative of co crystallization with plagioclase dominates the bulk rock ree pattern detectable ce anomalies in 20 of the pyroxene grains analyzed appear to be the result of weathering in the antarctic environment and indicate that pyroxene is particularly susceptible to element remobilization mineral compositions and textural observations suggest that alha77005 is a cumulate with 50 cumulus material olivine chromite olivine re equilibrated with intercumulus liquid on cooling the intercumulus liquid then crystallized as a closed system to form successively poikilitic low ca and high ca pyroxene followed by interstitial pyroxenes plagioclase whitlockite and other minor phases and reacted with cumulus crystals to form rims of different composition this crystallization sequence provides a constraint on the shergottite source region composition the alha77005 and shergotty intercumulus liquids had similar ree compositions however as opposed to shergotty if alha77005 was formed during the last 0 72 ga its parent melt was not contaminated by lree enriched material

chemical alteration and ree mobilization in meteorites from hot and cold deserts the effects of terrestrial weathering on ree mobilization are evaluated for a variety of uncommon meteorites found in antarctica and in hot deserts the meteorites analyzed include 7 non cumulate eucrites 10 shergottites 3 nakhlites 2 lunar meteorites 4 angrites 10 acapulcoites 1 winonaite and 1 brachinite in situ concentration measurements of lanthanides and selected other minor and trace elements were made on individual grains by secondary ion mass spectrometry sims in antarctic meteorites oxidation converts ce 3 to ce 4 which is less soluble than the trivalent ree resulting in ce anomalies the mineral most affected is low ca pyroxene however not all grains of a given mineral are and distinct analyses of a single grain can even yield ree patterns with and without ce anomalies the effect is most pronounced for antarctic eucrites in which ce anomalies are observed not only in individual minerals but also in whole rock samples although ce anomalies are observed in meteorites from hot deserts as well the most characteristic signs of chemical alteration in this environment are a lree enrichment with a typical crustal signature as well as sr ba and u contaminations these can modify the whole rock ree patterns and disturb the isotope systematics used to date these objects the lree contamination is highly heterogeneous affecting some grains and not others of a given mineral mainly olivine and low ca pyroxene the two minerals with the lowest ree concentrations the major conduit for ree movement is through shock induced cracks and defects and the highest levels of contamination are found in altered material filling such veins and cracks meteorites that experienced low shock levels and those that are highly recrystallized are the least altered copyright 2003 elsevier ltd

defining the mechanisms that disturb the sm nd isotopic systematics of the martian meteorites examples from dar al gani 476 and allan hills 77005 microbeam studies of martian meteorites dar al gani dag 476 and allan hills alh 77005 have been conducted to identify potential causes of disequilibrium exhibited in their sm nd isotopic systematics olivine and maskelynite mineral fractions on the dag 476 isochron are displaced relative to their positions as dictated by measured mineral compositions the olivine mineral fractions from alh 77005 not only have a relatively low sm nd ratio but appear to contain an unradiogenic component that shifts the olivine mineral fraction off the isochron defined by the pyroxene and maskelynite mineral fractions trace components such as melt inclusions impact melt high si mesostasis and altered olivine were analyzed using scanning electron microscopy quantitative electron microscopy and secondary ion mass spectrometry to determine their potential for disturbing the isotopic systematics of the mineral fractions assuming that the mineral fractions were not completely pure mixing models indicate that the presence of melt inclusions in the dag 476 olivine mineral fraction lowered its sm nd ratio the maskelynite mineral fraction contains a related but more evolved mesostasis component that raised the sm nd ratio of the fraction the position of two olivine mineral fractions below the alh 77005 isochron is interpreted to reflect small additions of impact melt with a light rare earth element enriched pattern and a non indigenous unradiogenic nd component furthermore the presence of rare earth elements in olivine and maskelynite from both igneous and non igneous components such as melt inclusions mesostasis and impact melt is observed on a fine 30 m scale despite the addition of this material the sm nd ages are not affected this study demonstrates that detailed mineral separation procedures as employed by modern geochronology laboratories permit reliable ages to be derived from shocked and altered samples

northwest africa 1950 mineralogy and comparison with antarctic lherzolitic shergottites nwa 1950 is a new lherzolitic shergottite recently recovered from morocco and is the first sample of this group found outside antarctica major constituent phases of nwa 1950 are olivine pyroxenes and plagioclase glass maskelynite and the rock shows a two distinct textures poikilitic and non poikilitic typical of lherzolitic shergottites in poikilitic areas several millimeter sized pyroxene oikocrysts enclose cumulus olivine and chromite in contrast pyroxenes are much smaller in non poikilitic areas and olivine and plagioclase glass are more abundant olivine in non poikilitic areas is more fe rich fa29 31 and shows a narrower distribution than that in poikilitic areas fa23 29 pyroxenes in non poikilitic areas are also more fe rich than those in poikilitic areas that show continuous chemical zoning suggesting fractional crystallization under a closed system these observations indicate that pyroxene in non poikilitic areas crystallized from evolved interstitial melts and olivine was re equilibrated with such melts nwa 1950 shows similar mineralogy and petrology to previously known lherzolitic shergottites alh 77005 lew 88516 y 793605 and grv 99027 that are considered to have originated from the same igneous body on mars olivine composition of nwa 1950 is intermediate between those of alh 77005 grv 99027 and those of lew 88516 y 793605 but is rather similar to alh 77005 and grv 99027 the subtle difference of mineral chemistry especially olivine composition can be explained by different degrees of re equilibration compared to other lherzolitic shergottites perhaps due to different location in the same igneous body thus nwa 1950 experienced a high degree of re equilibration similar to alh 77005 and grv 99027

localized shock melting in lherzolitic shergottite northwest africa 1950 comparison with allan hills 77005 the lherzolitic martian meteorite northwest africa nwa 1950 consists of two distinct zones 1 low ca pyroxene poikilically enclosing cumulate olivine fo70 75 and chromite and 2 areas interstitial to the oikocrysts comprised of maskelynite low and high ca pyroxene cumulate olivine fo68 71 and chromite shock metamorphic effects most likely associated with ejection from the martian subsurface by large scale impact include mechanical deformation of host rock olivine and pyroxene transformation of plagioclase to maskelynite and localized melting pockets and veins these shock effects indicate that nwa 1950 experienced an equilibration shock pressure of 35 45 gpa large millimeter size melt pockets have crystallized magnesian olivine fo78 87 and chromite embedded in an fe rich al poor basaltic to picro basaltic glass within the melt pockets strong thermal gradients minimum 1 c m existed at the onset of crystallization giving rise to a heterogeneous distribution of nucleation sites resulting in gradational textures of olivine and chromite dendritic and skeletal olivine crystallized in the melt pocket center has a nucleation density 1 0 x 10 3 crystals mm 2 that is two orders of magnitude lower than olivine euhedra near the melt margin 1 6 x 10 5 crystals mm 2 based on petrography and minor element abundances melt pocket formation occurred by in situ melting of host rock constituents by shock as opposed to melt injected into the lherzolitic target despite a common origin nwa 1950 is shocked to a lesser extent compared to allan hills alh 77005 45 55 gpa assuming ejection in a single shock event by spallation this places nwa 1950 near to alh 77005 but at a shallower depth within the martian subsurface extensive shock melt networks the interconnectivity between melt pockets and the ubiquitous presence of highly vesiculated plagioclase glass in alh 77005 suggests that this meteorite may be transitional between discreet shock melting and bulk rock melting

mineralogy and petrology of the dar al gani 476 martian meteorite implications for its cooling history and relationship to other shergottites dar al gani 476 the 13th martian meteorite was recovered from the sahara in 1998 it is a basaltic shergottitic rock composed of olivine megacrysts reaching 5 mm 24 vol set in a finegrained groundmass of pyroxene 59 vol and maskelynitized plagioclase 12 vol with minor amounts of accessory phases spinel merrillite ilmenite dar al gani 476 is similar to lithology a of elephant moraine a79001 eeta79001 in petrography and mineralogy but is distinct in several aspects low ca pyroxenes in the dar al gani 476 groundmass are more magnesian en76fs21 wo3 en58fs30wo12 than those in lithology a of eeta79001 en73fs22wo5 en45fs43wo12 rather similar to pyroxenes in lherzolitic martian meteorites en76fs21 wo3 en63fs22wo15 dar al gani 476 olivine is less magnesian and shows a narrower compositional range fo76 58 than eeta79001 olivine fo81 53 and is also similar to olivines in lherzolitic martian meteorites fo74 65 the orthopyroxene olivine chromite xenolith typical in the lithology a of eeta79001 is absent in dar al gani 476 it seems that dar al gani 476 crystallized from a slightly more primitive mafic magma than lithology a of eeta79001 and several phases olivine pyroxene chromite and ilmenite in dar al gani 476 may have petrogenetic similarities to those of lherzolitic martian meteorites olivine megacrysts in dar al gani 476 are in disequilibrium with the bulk composition the presence of fractured olivine grains in which the most mg rich parts are in contact with the groundmass suggests that little diffusive modification of original olivine compositions occurred during cooling this observation enabled us to estimate the cooling rates of dar al gani 476 and eeta79001 olivines giving similar cooling rates of 0 03 3 c h for dar al gani 476 and 0 05 5 c h for eeta79001 this suggests that they were cooled near the surface burial depth shallower than about 3 m at most probably in lava flows during crystallization of groundmass as is proposed for lithology a of eeta79001 it may be possible to consider that dar al gani 476 has an impact melt origin a mixture of martian lherzolite and other martian rock queen alexandra range 94201 nakhlites

anhydrous liquid line of descent of yamato 980459 and evolution of martian parental magmas we report the results of nominally anhydrous equilibrium and fractional crystallization experiments on a synthetic yamato 980459 y98 bulk composition at 0 5 gpa these experiments allow us to test a suggested fractional crystallization model calculated using melts by symes et al 2008 in which a y98 like initial liquid yielded a magma closely resembling the bulk composition of que 94201 although the two meteorites cannot be cogenetic owing to their age difference they are thought to represent bona fide magmatic liquids rather than products of crystal accumulation as are most martian basaltic meteorites hence understanding possible petrogenetic links between these types of liquids could be revealing about processes of melting and crystallization that formed the range of martian basalts we find that y98 can in fact generate a residual liquid closely resembling que but only after a very different crystallization process and different degree of crystallization than that modeled using melts in addition both the identity and sequence of crystallizing phases are very different between model and experiments our fractional crystallization experiments do not produce a que like liquid and the crystallizing phases are an even poorer match to the melts calculated compositions than in the equilibrium runs however residual liquids from our experiments define a liquid line of descent that encompasses bulk compositions of parental melts calculated for several martian basaltic meteorites suggesting that the known martian basaltic meteorites had their ultimate origin from the same or very similar source lithologies these are in turn similar to source rocks modeled by previous studies as products of extensive crystallization of an initial martian magma ocean

accretion and core formation on mars molybdenum contents of melt inclusion glasses in three snc meteorites abstract molybdenum cerium barium yttrium and rubidium contents of glasses in melt inclusions in three snc meteorites lew 88516 governador valadares and chassigny have been measured by ion microprobe ratios of mo ba and mo ce have been used to estimate the mo content of the primitive martian mantle 120 60 ppb abundances of five moderately siderophile elements ni co mo w and p and re in the martian mantle are consistent with metal silicate equilibrium between s bearing metallic liquid in a core 22 wt of the planet and peridotite melt at 75 kb 1620 c and oxygen fugacity 1 4 logfo2 units below the iw buffer this homogeneous accretion scenario is different than many heterogeneous accretion models for the earth but similar to recent studies suggesting homogeneous accretion in the presence of a deep terrestrial magma ocean

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

petrology and trace element geochemistry of tissint the newest shergottite fall the fall and recovery of the tissint meteorite in 2011 created a rare opportunity to examine a martian sample with a known short residence time on earth tissint is an olivine phyric shergottite that accumulated olivine antecrysts within a single magmatic system coarse olivine grains with nearly homogeneous cores of mg 80 suggest slow re equilibration many macroscopic features of this sample resemble those of lar 06319 including the olivine crystal size distribution and the presence of evolved oxide and olivine compositions unlike lar 06319 however no magmatic hydrous phases were found in the analyzed samples of tissint minor and trace element compositions indicate that the meteorite is the product of closed system crystallization from a parent melt derived from a depleted source with no obvious addition of a lree rich crustal component prior to or during crystallization the whole rock ree pattern is similar to that of intermediate olivine phyric shergottite eeta 79001 lithology a and could also be approximated by a more olivine rich version of depleted basaltic shergottite que 94201 magmatic oxygen fugacities are at the low end of the shergottite range with log fo2 of qfm 3 5 to 4 0 estimated based on early crystallized minerals and qfm 2 4 estimated based on the eu in pyroxene oxybarometer these values are similarly comparable to other depleted shergottites including sau 005 and que 94201 tissint occupies a previously unsampled niche in shergottite chemistry containing olivines with mg 80 resembling the enriched olivine phyric shergottite lar 06319 in its crystallization path and comparable to intermediate olivine phyric shergottite eeta 79001a depleted olivine phyric shergottite dag 476 and depleted basaltic shergottite que 94201 in its trace element abundances and oxygen fugacity the apparent absence of evidence for terrestrial alteration in tissint particularly in trace element abundances in the whole rock and individual minerals confirms that exposure to the arid desert environment results in only minimal weathering of samples provided the exposure times are brief

perylene occurrence alkylation and possible sources in deep ocean sediments abstract 81 deep ocean sediment samples obtained from the dsdp ipod program legs 63 66 and six gravity cores from dsdp ipod leg 64 guaymas basin gulf of california site survey cruise sio were analyzed for perylene s perylene was found to be most abundant in anoxic diatomaceous sediments containing moderate amounts of silts and or clays elevated perylene yields normalized to organic carbon contents coincided with enhanced preservation of autochthonous tetraterpenoid and tetrapyrrole pigments indicating a requirement of anoxia in the formation of perylene strongly euxinic conditions correlate with decreased perylene yields but not its total absence as found for strongly aerobic deposition and or redeposition perylene alkylation occurs in response to increasing in situ temperatures alt sub bottom depth this alkylation was found to begin with the generation of methyl c 1 perylene and to eventually yield a perylene alkyl perylene homologous series in decreasing abundance through the equivalent of c 3 trimethyl methyl ethyl propyl perylene the realm of most intense perylene alkylation for quaternary or pliocene miocene sediments corresponds with present in situ temperatures of 40 50 c or 30 35 c respectively thus the degree of perylene alkylation may represent an organic indicator for the thermal history of immature sediments geological phenomena such as reworking and igneous intrusions were found to complicate downhole perylene alkylation patterns a substituted c4h7o2 perylene was isolated from several anoxically deposited diatomaceous oozes and may represent one of the many possible perylene precursors the possible source compounds and biota for sedimentary perylene are discussed in light of the present study and review of past reports

fe3 in shocked olivine crystals of the alha 77005 meteorite abstract alha 77005 a shocked achondrite of the shergottite group is unique in containing cumulus olivine crystals which display a brownish color in thin section mossbauer epr and optical spectroscopic studies show the presence of fe 3 in the olivine approximately 4 5 wt of the total iron in the olivine 24 wt as feo is in the trivalent state the fe 3 ions preferentially occupy m2 lattice positions charge transfer between fe 3 and fe 2 as well as between fe 3 and oxygen ligands causes a broad absorption band in the optical spectrum at high energies which is the reason for the olivine color it is concluded that the color of the alha 77005 olivine is preterrestrial and may be the result of shock induced oxidation of the olivine crystals on the meteorite parent body

petrology geochemistry and cosmic ray exposure age of lherzolitic shergottite northwest africa 1950 northwest africa nwa 1950 is a new member of the lherzolitic shergottite clan of the martian meteorites recently found in the atlas mountains the petrological mineralogical and geochemical data are very close to those of the other known lherzolitic shergottites the meteorite has a cumulate gabbroic texture and its mineralogy consists of olivine fo66 to fo75 low and high ca pyroxenes en 78 fs 19 wo 2 en 60 fs 26 w 14 en 53 fs 16 wo 31 en 45 fs 14 wo 41 and plagioclase an 57 ab 41 or 1 to an 40 ab 57 or 3 entirely converted into maskelynite during intense shock metamorphism accessory minerals include phosphates merrillite chromite and spinels sulfides and a glass rich in potassium the oxygen isotopic values lie on the fractional line defined by the other snc meteorites delta 17 o 0 312 parts per thousand the composition of nwa 1950 is very similar to the other lherzolitic shergottites and suggests an origin from the same magmatic system or at least crystallization from a close parental melt cosmogenic ages indicate an ejection age similar to those of the other lherzolitic shergottites the intensity of the shock is similar to that observed in other shergottites as shown by the occurrence of small melt pockets containing glass interwoven with stishovite

mineral chemistry and the petrogenesis of eucrites ii cumulate eucrites abstract we carried out an ion microprobe study of rees and other selected trace and minor element concentrations in orthopyroxene augite lamellae and plagioclase of two cumulate eucrites moama and moore county in order to reevaluate the relationships between cumulate and noncumulate eucrites and among cumulate eucrites pyroxene and plagioclase in these two meteorites are more homogeneous in major minor and trace elements than in noncumulate eucrites and trace and minor element concentrations in moore county are higher than in moama although subsolidus equilibration erased and original igneous zoning it did not affect the ree patterns of these minerals both pigeonite and plagioclase of moama and moore county have higher lree hree ratios than those phases in noncumulate eucrites this indicates that cumulate eucrites derived from melts with fractionated ree patterns and thus are not related to noncumulate eucrites in addition the inconsistency between degrees of fractional crystallization deduced from major and trace elements and the differences of lree hree ratios recorded in pigeonite and plagioclase also suggest that moama and moore county did not form in the same fractional crystallization sequence this study confirms earlier observations and conclusions of ma and schmitt 1979 and poses problems for prevalent models

the lherzolitic shergottite grove mountains 99027 rare earth element geochemistry we report here on an ion probe study of rare earth element ree geochemistry in the lherzolitic shergottite grove mountains grv 99027 this meteorite shows almost identical mineralogy petrology and ree geochemistry to those of the lherzolitic shergottites allan hills alh a77005 lewis cliff lew 88516 and yamato y 793605 ree concentrations in olivine pyroxenes maskelynite merrillite and melt glass are basically comparable to previous data obtained from alh a77005 lew 88516 and y 793605 olivine is the dominant phase in this meteorite it is commonly enclosed by large up to several mm pigeonite oikocrysts non poikilitic areas consist of larger olivine grains mm pigeonite augite and maskelynite minor merrillite up to 150 m in size is widespread in non poikilitic regions occurring interstitially between olivine and pyroxene grains it is the main ree carrier in grv 99027 and has relatively higher rees 200 1000 x ci than that of other lherzolitic shergottites a ree budget calculation for grv 99027 yields a whole rock ree pattern very similar to that of other lherzolites it is characterized by the distinctive light ree depletion and a smooth increase from light rees to heavy rees ree microdistributions in grv 99027 strongly support the idea that all lherzolitic shergottites formed by identical igneous processes probably from the same magma chamber on mars despite many similarities in mineralogy petrography and trace element geochemistry subtle differences exist between grv 99027 and other lherzolitic shergottites grv 99027 has relatively uniform mineral compositions both major elements and rees implying that it suffered a higher degree of sub solidus equilibration than the other three lherzolites it is notable that grv 99027 has experienced terrestrial weathering in the antarctic environment as its olivine and pyroxenes commonly display a light ree enrichment and a negative ce anomaly caution needs to be taken in future chronological studies

rare earth element carriers in the shergotty meteorite and implications for its chronology ion probe measurements of the rare earth element ree concentrations of individual grains of the shergotty meteorite are reported phases analyzed include whitlockite apatite baddeleyite augite pigeonite maskelynite and k rich glass u concentrations of whitlockite and apatite crystals were also obtained the whole rock ree pattern is dominated by whitlockite which contains over 95 of the light rare earth elements lree ree concentrations in apatite are much lower than estimated by laulet al 1986 all the whitlockites whether intergrown with pyroxene equant or interstitial have the same relative abundances of lree i e patterns are almost flat from la to sm the observation by joneset al 1985 of a skeletal whitlockite with lree enrichment is not confirmed by analyses of the same grain pyroxene rims are not enriched in lree no leachable carrier enriched in lree and associated with pyroxene laulet al 1986 jagoutz and wanke 1986 has been found instead either a laboratory contamination or a petrographically cryptic phase such as a film on grain boundaries is suspected as the carrier of lree enrichments if a grain boundary film carries the enrichments it would not be resistant to the metamorphic resetting which has affected other isotopic reservoirs in this sample thus there is no compelling reason to consider the sm nd pyroxene leachates line jagoutz and wanke 1986 as a 360 m y isochron estimates of ree abundances in the shergotty intercumulus melt indicate that a complex petrogenesis is required in agreement with the conclusions of mckayet al 1986a pyroxene distribution coefficients measured experimentally mckayet al 1986a are compared with estimates from measured ree abundances in augite and pigeonite evolution of ree abundances in the shergotty late stage interstitial melt as inferred from analyses of whitlockite conforms with trends predicted from partitioning considerations and requires no special processes such as metasomatism the average u concentrations of whitlockite and apatite are respectively 540 and 1 550 ppb although the calcium phosphates are enriched in u they contain less than 20 of the u in shergotty

s nc multiple source areas for martian meteorites the shergottite nakhlite and chassigny snc meteorites are igneous rocks from mars inferred previously to have been propelled into space and to earth by a single impact event however the sum of petrologic chemical and chronological data suggests two distinct sites of origin s from one nc from another differences between the s and nc include distributions of terrestrial residence ages cosmic ray exposure ages impact shock effects preterrestrial aqueous alteration products bulk magma compositions trace element magma chemistries and mantle source compositions if the s and nc did not come from the same site on mars selection criteria for determining source craters are relaxed and a number of craters become candidate sources formation of two meteorite source craters on young martian surfaces 1300 ma within the last 20 m y spanning the cosmic ray exposure ages seems to require either smaller source craters or greater cratering rates than allowed in current theories both of these options suggest that meteorites from nonvolcanic and ancient martian surfaces ought to be more common than the known types of martian meteorites the absence of such meteorites may reflect the physical properties of nonvolcanic and ancient surfaces or a failure to recognize these rock types as meteorites the alh84001 meteorite long classified as a diogenite may be such a sample of the ancient martian crust

clinopyroxene ree distribution coefficients for shergottites the ree content of the shergotty melt abstract ree distribution coefficients were measured between synthetic pyroxenes and melts similar in composition to the inferred shergotty intercumulus liquid by in situ analysis with the electron microprobe using samples doped to per cent concentration levels these coefficients exhibit a strong positive correlation with pyroxene wollastonite content recommended values for augites similar in composition to the shergotty cumulus augite cores wo32en48 are d la 0 023 d ce 0 039 d nd 0 10 d sm 0 17 d eu 0 16 d gd 0 20 d yb 0 29 and d lu 0 30 recommended values for pigeonites similar in composition to the shergotty cumulus pigeonite cores wo12en58 are d la 0 002 d ce 0 004 d nd 0 019 d sm 0 031 d yb 0 13 and d lu 0 13 these values resemble distribution coefficients measured for terrestrial basalts of higher mg fe than the shergotty melt rather than those of more evolved siliceous rocks of similar mg fe to the shergotty melt thus it appears that mg fe is considerably less important than other factors in determining distribution coefficient values for pyroxenes ree abundances were computed for the shergotty intercumulus melt using distribution coefficients measured for the natural phase compositions these computed abundances display lree depletion such lree depleted abundance patterns cannot be generated by simple partial melting of a mafic mineral assemblage having the lree enriched patterns required for a two stage sm nd evolution history this result implies that either 1 the melting process was complex e g continuous melting 2 the source region had a more complex history than that of the simple 2 stage model or 3 shergotty does not satisfy the closed system assumption of the calculation and has suffered post magmatic lree enrichment

the composition and thickness of the crust of mars estimated from rare earth elements and neodymium isotopic compositions of martian meteorites isotopic and trace element compositions of martian meteorites show that early differentiation of mars produced complementary crustal and mantle reservoirs that were sampled by later magmatic events this paper describes a mass balance model that estimates the rare earth element ree content and thickness of the crust of mars from the compositions of shergottites the diverse ree and nd isotopic compositions of shergottites are most easily explained by variable addition of light rare earth element lree enriched crust to basaltic magmas derived from lree depleted mantle source regions antarctic shergottites eet 79001 alh 77005 lew 88516 and que 94201 all have strongly lree depleted patterns and positive initial 143nd isotopic compositions which is consistent with the generation of these magmas from depleted mantle sources and little or no interaction with enriched crust in contrast shergotty and zagami have negative initial 143nd isotopic compositions and less pronounced depletions of the lree which have been explained by incorporation of enriched crustal components into mantle derived magmas jones 1989 longhi 1991 borg et al 1997 the mass balance model presented here derives the ree composition of the crustal component in shergotty by assuming it represents a mixture between a mantle derived magma similar in composition to eet 79001a and a lree enriched crustal component the amount of crust in shergotty is constrained by mixing relations based on nd isotopic compositions which allows the ree pattern of the crustal component to be calculated by mass balance the effectiveness of this model is demonstrated by the successful recovery of important characteristics of the earth s continental crust from terrestrial columbia river basalts self consistent results for nd isotopic compositions and ree abundances are obtained if shergotty contains 10 30 of lree enriched crust with 10 ppm nd this crustal component would have moderately enriched lree sm nd 0 25 0 27 147sm 144nd 0 15 0 17 la yb 2 7 3 8 relatively unfractionated heavy rare earth elements hree and no eu anomaly crust with these characteristics can be produced from a primitive lherzolitic martian mantle by modest amounts 2 8 of partial melting and it would have a globally averaged thickness of 45 km which is consistent with geophysical estimates mars may serve as a laboratory to investigate planetary differentiation by extraction of a primary basaltic crust

snc meteorites clues to martian petrologic evolution the shergottites nakhlites and chassigny snc meteorites are apparently cumulate mafic and ultramafic rocks that crystallized at shallow levels in the crust of their parent body the mineralogy and chemistry of these meteorites are remarkably like equivalent terrestrial rocks although their ratios of fe fe mg and certain incompatible elements and their oxygen isotopic compositions are distinctive all have crystallization ages of 1 3 b y or younger and formed from magmas produced by partial melting of previously fractionated source regions isotope systematics suggest that the snc parent body had a complex and protracted thermal history spanning most of geologic time some meteorites have been severely shock metamorphosed and all were ejected from their parent body at relatively recent times possibly in several impact events late crystallization ages complex petrogenesis and possible evidence for a large gravitational field suggest that these meteorites are derived from a large planet trapped gases in shergottite shock melts have compositions similar to the composition measured in the martian atmosphere ejection of martian meteorites may have been accomplished by acceleration of near surface spalls or other mechanisms not fully understood if snc meteorites are of martian origin they provide important information on planetary composition and evolution the bulk composition and redox state of the martian mantle as constrained by shergottite phase equilibria must be more earthlike than most current models planetary thermal models should benefit from data on the abundances of radioactive heat sources the melting behavior of the mantle and the timing of planetary differentiation calculated depletion of chalcophile elements in source regions indicates a core dominated by sulfides and paleomagnetic measurements suggest the presence of a weak magnetic field within the last several hundred thousand years concentrations of volatile elements indicate that the snc parent body was not volatile depleted and trapped atmospheric components measured in shock melts may be useful in understanding planetary degassing by providing comparisons for spectral reflectance data and viking soil analyses these meteorites may also constrain surface mineralogy and weathering mechanisms

trace and minor elements in minerals of nakhlites and chassigny clues to their petrogenesis abstract ion microprobe measurements of ree rare earth element and other selected trace and minor element concentrations were made in clinopyroxene olivine feldspar and chlorapatite in chassigny and the three nakhlites nakhla governador valadares and lafayette in chassigny we have found pigeonite occurring in a poikilitic habit it is the first reported occurrence of this mineral in this meteorite the most significant implication of this finding is that estimates of the major element composition of the chassigny parent melt will have to accommodate pigeonite as a primary mineral crystallizing before plagioclase chlorapatite contains the highest ree abundances in all meteorites studied here the ree patterns of chlorapatite plagioclase and augite in nakhlites and chassigny are similar although the downward trends of ree patterns are somewhat steeper for these minerals in chassigny than in the nakhlites pyroxenes in nakhlites and chassigny are extensively zoned in rees and other trace and minor elements such as y zr ti and al which appear to be resistant to diffusive reequilibration thus primary igneous zoning of these elements has been preserved in the pyroxenes of these meteorites and can be used to infer their crystallization histories the calculated ree patterns of the parent melts of nakhlites and chassigny are lree enriched and parallel to their whole rock ree patterns indicating that once crystal accumulation occurred the intercumulus trapped melt fractionally crystallized in an essentially closed system and that infiltration i e metasomatism by lree enriched magmas need not be invoked to explain the lree enrichment in bulk samples of these meteorites fractional crystallization model calculations for nakhla also confirm these conclusions the distributions of trace and minor elements in augites in nakhlites and chassigny suggest that all three nakhlites could be samples from different horizons of the same lithologic unit but that chassigny was not comagmatic with the nakhlites

micro raman spectroscopy of amphiboles and pyroxenes in the martian meteorites zagami and lewis cliff 88516 we studied micro raman spectroscopy of amphiboles and pyroxenes in the martian meteorites zagami and lewis cliff lew 88516 the obtained raman spectra of the amphiboles are similar to those of kaersutite reconfirming the previous studies that they are kaersutitic amphiboles enriched in ca al and ti even though actinolite belongs to the same amphibole group calcic amphibole as kaersutite the raman spectra of terrestrial actinolite are distinct from those of kaersutite probably reflecting complex amphibole crystal structures the al ti rich pyroxene observed in the magmatic inclusions within lew 88516 olivine is compositionally similar to kaersutite but shows raman spectra nearly identical to the regular pyroxene rather than amphibole in contrast to amphibole this will be due to relatively simple crystal structures of pyroxene thus the raman spectra of al ti rich phases in the martian meteorites are distinct between kaersutite and al ti rich pyroxene and this study demonstrates that micro raman spectroscopy is one of the best tools to perform mineralogical characterization of mineral phases in martian meteorites