on the spreading of the east pacific rise abstract we analyze through statistical methods the mechanics of the east pacific rise by considering the relative angular velocities of spreading of the pacific nazca pacifie cocos and pacific rivera margins we focus our attention on verifying the validity of some issues such as the constancy of the velocity of spreading the symmetry of the spreading and the rigid rotational behaviour of the plates our findings can be summarized in the following four points 1 a the relative velocities of all considered margins decreased in modulus around 1 5 m y ago 2 b the spreading is asymmetric and the pattern is in general agreement with the model of stein et al 1977 3 c the pacifie cocos and the pacific nazca margins are migrating respectively eastward and westward 4 d statistical evidence suggests that a rigid rotational behaviour is not always verified

nominally hydrous magmatism on the moon for the past 40 years the moon has been described as nearly devoid of indigenous water however evidence for water both on the lunar surface and within the lunar interior have recently emerged calling into question this long standing lunar dogma in the present study hydroxyl as well as fluoride and chloride was analyzed by secondary ion mass spectrometry in apatite ca5 po4 3 f cl oh from three different lunar samples in order to obtain quantitative constraints on the abundance of water in the lunar interior this work confirms that hundreds to thousands of ppm water of the structural form hydroxyl is present in apatite from the moon moreover two of the studied samples likely had water preserved from magmatic processes which would qualify the water as being indigenous to the moon the presence of hydroxyl in apatite from a number of different types of lunar rocks indicates that water may be ubiquitous within the lunar interior potentially as early as the time of lunar formation the water contents analyzed for the lunar apatite indicate minimum water contents of their lunar source region to range from 64 ppb to 5 ppm h2o this lower limit range of water contents is at least two orders of magnitude greater than the previously reported value for the bulk moon and the actual source region water contents could be significantly higher

assessment of shock effects on amphibole water contents and hydrogen isotope compositions 2 kaersutitic amphibole experiments to constrain the influence of impact shock on water and hydrogen isotope signatures of martian meteorite kaersutites we conducted shock recovery experiments on three terrestrial kaersutite crystals homogeneous impact shock to 32 gpa commensurate with shock levels experienced by martian meteorite kaersutites led to increases in kaersutite water contents h 2o 0 25 0 89 wt decreases in fe 3 fe 4 20 and enrichments in hydrogen isotope composition d 66 to 87 relative to pre shock values the latter values represent the largest shock induced hydrogen isotope fractionations measured to date these observations are explained most completely by a two step shock process first shock induced devolatilization led to hydrogen isotope enrichment through preferential loss of h relative to d second reaction of the kaersutite with the ambient atmosphere led to increased water contents and reduced fe fe reduction and water addition via the reaction fe 2 oh fe 3 o 2 h 2 explain the fe 3 fe data and some of the water data further water addition mechanisms irreversible adsorption shock implantation are necessary to fully explain the increased water contents addition of water from the terrestrial atmosphere which is isotopically light relative to the experimental kaersutite compositions means the measured hydrogen isotope enrichments are likely minima the measured minimum levels of hydrogen isotope enrichment are relevant to the hydrogen isotope variability within and among martian kaersutites but are minor relative to their absolute d values alternatively addition of water from the enriched martian atmosphere could explain both martian kaersutite hydrogen isotope variability and absolute d values however the low martian kaersutite water contents leave little room for significant water addition the importance of the ambient atmosphere to the outcome of the shock experiments makes it difficult to translate our results to mars given the unknown influence of its more tenuous atmosphere on the processes observed in the experiments our results suggest that shock is a feasible mechanism for influencing martian kaersutite water contents and hydrogen isotope compositions but that its complex signature precludes precise determination of that influence

hydrous melting of the martian mantle produced both depleted and enriched shergottites the search for water in our solar system is one of the primary driving forces for planetary science and exploration because water plays an important role in many geologic processes and is required for biologic processes as we currently understand them excluding earth mars is the most promising destination in the inner solar system to find water as it is undoubtedly responsible for shaping many geomorphologic features observed on the present day martian surface however the water content of the martian interior is currently unresolved much of our information about the martian interior comes from studies of the basaltic martian meteorites shergottites in this study we examined the water contents of magmatic apatites from a geochemically enriched shergottite the shergotty meteorite and a geochemically depleted shergottite the queen alexandria range 94201 meteorite from these data we determined that there was little difference in water contents between the geochemically depleted and enriched shergottite magmas the water contents of the apatite imply that shergottite parent magmas contained 730 2870 ppm h 2 o prior to degassing furthermore the martian mantle contains 73 290 ppm h 2 o and underwent hydrous melting as recently as 327 ma in the absence of plate tectonics the presence of water in the interior of mars requires planetary differentiation under hydrous conditions this is the first evidence of significant hydrogen storage in a planetary interior at the time of core formation and this process could support elevated h abundances in the interiors of other terrestrial bodies like the moon mercury venus large differentiated asteroids and earth

maskelynite hosted apatite in the chassigny meteorite insights into late stage magmatic volatile evolution in martian magmas apatite hosting maskelynite and alkali maskelynite within regions interstitial to cumulus olivine differ compositionally from that found within melt inclusions in the chassigny martian meteorite feldspar glass compositions within the interstitial regions evolve along a high temperature crystallization path within the melt inclusions feldspar glass shows evolution to low temperatures extending into the subsolidus regime coupled with these differences in maskelynite compositions are differences in volatile abundance in apatite included within the maskelynite apatite found within the large olivine hosted polyphase melt inclusions is uniformly fluorapatite whereas that interstitial to cumulus olivine is chlor fluorapatite we propose that the differences in maskelynite and apatite compositions within the melt inclusion and interstitial regions arose primarily from different crystallization conditions melt inclusion maskelynite and apatite are consistent with nearly closed system buildup of magmatic volatiles during crystallization within the melt inclusions exsolution of a cl bearing fluid phase and retention of this fluid phase within the melt inclusions into the hydrothermal regime for the interstitial regions however the higher solidus temperatures of the interstitial melts the early crystallization of feldspar with significant ternary component and the cl rich nature of the apatite all suggest open system fluid migration through the cumulus pile ingress of cl rich h2o poor brine from a hotter less evolved portion of the magma plumbing system and interaction of this cl rich fluid with melt prior to the crystallization of feldspar such processes of fluid migration through a cumulus pile have been suggested on earth in layered intrusions and apatite is the primary recorder of this process

hydrogen isotope evidence for loss of water from mars through time 1 the high d h of the martian atmosphere 5 6 terrestrial is considered strong evidence for the loss of martian water to space the timing and magnitude of the loss of water from mars can be constrained by measurements of d h in martian meteorites previous studies of martian meteorites have shown a large range in d h from terrestrial values to as high as the current martian atmosphere here we show that the ancient 4 ga mars meteorite alh84001 has a d h 4 terrestrial and that the young 0 17 ga shergotty meteorite has a d h 5 6 terrestrial we also find that the young los angeles shergottite has zoning in d h that can be correlated to igneous growth zoning strongly suggesting assimilation of d enriched water during igneous crystallization near the martian surface in contrast to previous studies we find higher and less variable d h ratios in these three meteorites our results suggest a two stage evolution for martian water a significant early loss of water to space prior to 3 9 ga followed by only modest loss to space in the last 4 billion years the current martian atmospheric d h has remained essentially unchanged for the last 165 ma

lunar apatite with terrestrial volatile abundances the moon is thought to be depleted relative to the earth in volatile elements such as h cl and the alkalis nevertheless evidence for lunar explosive volcanism has been used to infer that some lunar magmas exsolved a co rich and co 2 rich vapour phase before or during eruption although there is also evidence for other volatile species on glass spherules until recently there had been no unambiguous reports of indigenous h in lunar rocks here we report quantitative ion microprobe measurements of late stage apatite from lunar basalt 14053 that document concentrations of h cl and s that are indistinguishable from apatites in common terrestrial igneous rocks these volatile contents could reflect post magmatic metamorphic volatile addition or growth from a late stage interstitial sulphide saturated melt that contained 1 600 parts per million h 2o and 3 500 parts per million cl both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable terrestrial materials one possible implication is that portions of the lunar mantle or crust are more volatile rich than previously thought

hydrothermal jarosite and hematite in a pyroxene hosted melt inclusion in martian meteorite miller range mil 03346 implications for magmatic hydrothermal fluids on mars low temperature aqueous processes have been implicated in the generation of jarosite and hematite on the martian surface but little is known regarding the role that high temperature magmatic fluids may have played in producing similar assemblages on mars we have identified jarosite and hematite in a clinopyroxene hosted melt inclusion in martian meteorite mil 03346 that shows evidence of having been hydrothermally precipitated in addition to jarosite and hematite the melt inclusion contains titanomagnetite pyrrhotite potassic chlorohastingsite an iron rich silicate glass and possibly goethite these phases were identified and characterized using scanning electron microscopy sem con focal raman spectroscopy and electron probe microanalysis epma based on observed textural relationships and the compositions of the hosted phases we report that the jarosite bearing melt inclusion in mil 03346 has recorded a fluid rich history that began in the magmatic stage and continued to low temperatures this history begins at entrapment of a volatile rich silicate melt that likely reached fluid saturation after only minor crystallization within the melt inclusion this fluid rich in chlorine reacted with surrounding silicate material to produce the potassicchlorohastingsite as cooling proceeded the liquid phase eventually became more oxidized and reacted with the pyrrhotite sulfide oxidation resulted in so4 2 formation and concomitant acid production setting the stage for jarosite formation once the fluid cooled beyond the upper thermal stability of jarosite 200 c as the fluid cooled below 200 c jarosite continued to precipitate with hematite and or goethite until equilibrium was established or reactions became kinetically unfavorable this work suggests an additional jarosite hematite formation pathway on mars one that may be important wherever magmatic hydrothermal fluids come into contact with primary sulfide grains at the martian surface or subsurface moreover hydrothermal fluids rich in chlorine sulfur and iron are important for ore forming processes on earth and their indirect identification on mars may have important implications for ore formation on mars

silica as a shock index in shergottites a cathodoluminescence study silica in shergottites is a minor phase of great significance determining its structural state as either silica glass quartz cristobalite tridymite coesite stishovite or post stishovite could provide informations about their shock history the purpose of this work is to assess the shock intensity in shergottites using two spectroscopic methods on a conventional polished section a scanning electron microscope sem enables us to study the cathodoluminescence cl of silica at variable magnification the results were crosschecked by systematic raman spectroscopy of the selected areas cl spectra differ substantially from one another and enable separating stishovite high and low pressure silica glass quartz and cristobalite we studied a set of five shergottites northwest africa nwa 480 nwa 856 zagami shergotty and los angeles stishovite is common in shergotty zagami nwa 856 and nwa 480 and absent in the studied section of los angeles high pressure glass is very common particularly in close association with stishovite according to the textural relationship it may be a product of the retromorphosis amorphization during decompression of stishovite large stishovite areas result from the transformation of preexisting low pressure silica crystals while needles result from the high pressure transformation of pyroxene to glass melt and silica in the latter case they are found in melt pockets and represent a small fraction of areas of overall pyroxene composition needles exhibit square sections of about 1 m silica spots identical to those described previously as poststishovite are found in shergotty zagami nwa 480 and nwa 856 at present the spectroscopic distinction of post stishovite from stishovite is difficult post stishovite is destroyed under the raman beam and cl spectra are possible mixtures of several phases e g glass and post stishovite it is concluded that the shock intensity is highly heterogeneous and the pressure probably exceeded 60 gpa in all shergottites studied here

alpha particle x ray spectrometer apxs results from gusev crater and calibration report 1 the chemical composition of rocks and soils on mars analyzed during the mars exploration rover spirit mission was determined by x ray analyses with the alpha particle x ray spectrometer apxs details of the data analysis method and the instrument calibration are presented measurements performed on mars to address geometry effects and background contributions are shown cross calibration measurements among several instrument sensors and sources are discussed an unintentional swap of the two flight instruments is evaluated new concentration data acquired during the first 470 sols of rover spirit in gusev crater are presented there are two geological regions the gusev plains and the columbia hills the plains contain soils that are very similar to previous landing sites on mars a meteoritic component in the soil is identified rocks in the plains revealed thin weathering rinds the underlying abraded rock was classified as primitive basalt one of these rocks contained significant br that is probably associated with vein filling material of different composition one of the trenches showed large subsurface enrichments of mg s and br disturbed soils and rocks in the columbia hills revealed different elemental compositions these rocks are significantly weathered and enriched in mobile elements such as p s cl or br even abraded rock surfaces have high br concentrations thus in contrast to the rocks and soils in the gusev plains the columbia hills material shows more significant evidence of ancient aqueous alteration

insights into martian water reservoirs from analyses of martian meteorite que94201 the martian atmospheric d h value of 5 2 times terrestrial is significantly higher than any found on earth and has been ascribed to preferential loss of h relative to d from the atmosphere through jeans escape over time here based on ion microprobe analyses of apatite grains from martian meteorite que94201 it is shown that the pre jeans escape martian water reservoir has a d h value twice that of terrestrial water rather than the terrestrial value that has been assumed in prior work the data support a two stage history for martian volatiles in which early hydrodynamic escape enriched martian water to 2x terrestrial d h values subsequent jeans escape to produce the current atmospheric values has thus been responsible for less d enrichment than previously thought a martian crust containing 2 3 times more water than previously proposed is implied by the results

the sources of water in martian meteorites clues from hydrogen isotopes abstract h isotope measurements of carbonate phosphate feldspathic and mafic glasses and post stishovite silica phase in the shergottites zagami shergotty sau 005 dag 476 alha 77005 and eeta 79001 as well as in chassigny and alh 84001 show that all these phases contain deuterium enriched water of extraterrestrial origin the minerals and glasses analyzed may contain an initial primary hydrogen component but their isotopic composition was modified to varying degrees by three different processes interaction with a fractionated exchangeable water reservoir on mars hydrogen devolatilization by impact melting and terrestrial contamination positive correlations between d and water abundance in feldspathic glass and post stishovite silica in zagami shergotty and sau 005 is indicative of mixing of a high d component 3000 4000 and a less abundant low d component 0 the high d component is primarily derived from the martian exchangable reservoir but may also have been influenced by isotopic fractionation associated with shock induced hydrogen loss the low d component is either a terrestrial contaminant or a primary magmatic component the negative correlation between d and water abundances in mafic and feldspathic glasses in alh 84001 alha 77005 and eeta 79001 is consistent with the addition of a low d terrestrial contaminant to a less abundant high deuterium martian component the low d of magmatic glass in melt inclusions suggests that the d of martian parent magma was low and that the initial h isotope signature of mars may be similar to that of earth

compositional variability of terrestrial mantle apatites thermodynamic modeling of apatite volatile contents and the halogen and water budgets of planetary mantles abstract apatites in ultramafic xenoliths from hawaii kamchatka nunivak island lunar crater volcanic field and the navajo volcanic field have variable volatile f cl oh compositions that correlate with their petrogenesis apatites in metasomatized lherzolite harzburgite xenoliths are relatively cl rich whereas apatites in igneous pyroxenite and amphibolite xenoliths are relatively f rich our results support the generalization of o reilly and griffin 2000 that metasomatic apatites tend to be cl rich and magmatic apatites tend to be f rich mantle metasomatism may largely be the consequence of devolatilization of cl rich fluids from subducted lithosphere however the occurrence of metasomatic xenoliths far removed from subduction zones e g bullenmerri as well as the geochemistry of cl in some plume basalts and diamonds indicates that not all metasomatism is subduction triggered thermodynamic modeling of the influence on apatite compositions of variable f cl h2o and p abundances as well as temperature is consistent with the idea that terrestrial mantle fluids are h2o rich and that halogen enrichment in terrestrial apatites need not represent large absolute halogen abundances in the fluids the models indicate that the occurrence of volatile poor calcium phosphate merrillite whitlockite in the martian and terrestrial mantles is facilitated by halogen and phosphorus rich and water poor environments the rarity of this assemblage in the terrestrial mantle compared to mars is consistent with the relatively wet and halogen and phosphorus poor nature of the terrestrial mantle compared to that of mars

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

mineralogy of meteorite groups approximately 275 mineral species have been identified in meteorites reflecting diverse redox environments and in some cases unusual nebular formation conditions anhydrous ordinary carbonaceous and r chondrites contain major olivine pyroxene and plagioclase major opaque phases include metallic fe ni troilite and chromite primitive achondrites are mineralogically similar the highly reduced enstatite chondrites and achondrites contain major enstatite plagioclase free silica and kamacite as well as nitrides a silicide and ca mg mn na cr k and ti rich sulfides aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates complex organic compounds magnetite various sulfates and sulfides and carbonates in addition to kamacite and taenite iron meteorites contain carbides elemental c nitrides phosphates phosphides chromite and sulfides silicate inclusions in iab iiicd and iie iron meteorites consist of mafic silicates plagioclase and various sulfides oxides and phosphates eucrites howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides ureilites are made up mainly of calcic chromian olivine and low ca clinopyroxene embedded in a carbonaceous matrix accessory phases include the c polymorphs graphite diamond lonsdaleite and chaoite as well as metallic fe ni troilite and halides angrites are achondrites rich in fassaitic pyroxene i e al ti diopside minor olivine with included magnesian kirschsteinite is also present martian meteorites comprise basalts lherzolites a dunite and an orthopyroxenite major phases include various pyroxenes and olivine minor to accessory phases include various sulfides magnetite chromite and ca phosphates lunar meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase several meteoritic phases were formed by shock metamorphism martensite 2 fe ni has a distorted body centered cubic structure and formed by a shear transformation from taenite during shock reheating and rapid cooling the c polymorphs diamond lonsdaleite and chaoite formed by shock from graphite suessite formed in the north haig ureilite by reduction of fe and si possibly from olivine via reaction with carbonaceous matrix material ringwoodite the spinel form of mg fe 2sio4 and majorite a polymorph of mg fe sio3 with the garnet structure formed inside shock veins in highly shocked ordinary chondrites secondary minerals in meteorite finds that formed during terrestrial weathering include oxides and hydroxides formed directly from metallic fe ni by oxidation phosphates formed by the alteration of schreibersite and sulfates formed by alteration of troilite

partitioning in ree saturating minerals theory experiment and modelling of whitlockite apatite and evolution of lunar residual magmas we present compositions including rees determined by ion microprobe of apatite and whitlockite in lunar rock assemblages rich in incompatible trace elements total concentrations of ree oxides in whitlockites range from 9 13 wt and those in apatites range from 0 15 to 1 wt ratios of ree concentrations in whitlockite to those in coexisting apatite range from 10 to 60 the distribution of mg and fe between apatite and whitlockite is correlated to that of coexisting mafic silicates magnesium is strongly preferred by whitlockite and fe is preferred by apatite incorporation of rees in whitlockite is dominated by the coupled substitution of 2ree3 in ca b sites vacancy in ca iia for 2ca 2 in ca b sites and ca2 na in ca iia other substitutions account for only a small portion of the rees in whitlockite over the observed concentration range thus ree concentrations become partially saturated as the primary substitution approaches its stoichiometric limit of two rees per fifty six oxygens leading to reduced whitlockite melt distribution coefficients e g decreasing from twenty five to ten for nd the ree concentrations of lunar residual melts are not depleted by whitlockite crystallization in assemblages consisting mainly of other minerals in typical proportions distribution coefficients for the rees in lunar apatite appear to be low and variable e g 0 2 0 8 for nd variations in the modal ratio of whitlockite to apatite specifically the abundance of whitlockite lead to a range of ree concentrations in the phosphates and variations in the magnitude of ree concentration ratios between whitlockite and apatite if apatite crystallizes before whitlockite or in the absence of whitlockite as textures in several samples indicate then apatite zoned in rees and apatite crystals of different ree concentrations may occur in a given sample provided there is some amount of fractional crystallization and apatite does not later equilibrate this may occur because in the absence of whitlockite in the crystallizing assemblage the rees are highly incompatible relative to the crystalline assemblage so ree concentrations in lunar residual melts increase strongly during small increments of late stage crystallization once whitlockite begins to crystallize bulk distribution coefficients for the rees although still 1 are only mildly incompatible so the change in ree concentrations of residual melts with further crystallization is small consistent with the lack of ree zoning in whitlockite the ree concentrations in lunar whitlockites are modelled as resulting mainly from equilibrium crystallization of the assemblages in which they occur metasomatism or other secondary metamorphic processes are not indicated local melt pocket equilibrium at advanced stages of crystallization may lead to variable ree concentrations and variable whitlockite apatite concentration ratios within the same sample parent melts with extremely high ree concentrations are not required in order to crystallize ree rich lunar whitlockite if modal proportions of whitlockite are low

rare earth patterns in shergottite phosphates and residues leaching experiments with 1m hcl on alha 77005 power show that rare earth elements ree are concentrated in accessory phosphate phases whitlockite apatite that govern the ree patterns of bulk shergottites the ree patterns of whitlockite are typically light ree depleted with a negative eu anomaly and show a hump at the heavy ree side while the ree pattern of apatite in shergotty is light ree enriched parent magmas are calculated from the model compositions of residues of alha 77005 shergotty and eeta 79001 the parent magmas lack a eu anomaly indicating that plagioclase was a late stage crystallizing phase and it probably crystallized before the phosphates the parent magmas of alha 77005 and shergotty have similar ree patterns with a subchondritic nd sm ratio however the sm nd isotopics require a light ree depleted source for alha 77005 if the crystallization age is 600 m y and a light ree enriched source for shergotty distinct nd and sr isotopic signatures may suggest different source regions for shergottites copyright american geophysical union 1987

direct determination of europium valence state by xanes in extraterrestrial merrillite implications for ree crystal chemistry and martian magmatism the relative proportion of divalent and trivalent eu has proven to be a useful tool for estimating f sub o sub 2 in various magmatic systems however in most cases direct determination of the eu valence state has not been made in this study direct determination of eu valence by xanes and ree abundance in merrillite provide insights into the crystal chemistry of these phosphates and their ability to record conditions of magmatism merrillite strongly prefers eu sup 3 to eu sup 2 with the average valence state of eu ranging between 2 9 and 3 over approximately six orders of magnitude in f sub o sub 2 the dramatic shift in the ree patterns of merrillite in martian basaltic magmas from highly lree depleted to lree enriched parallels many other trace element and isotopic variations and reflects the sources for these magmas the behavior of ree in the merrillite directly reflects the relationship between the eightfold coordinated ca1 site and adjacent sixfold na and tetrahedral p sites that enables charge balancing through coupled substitutions

magmatic water in the martian meteorite nakhla abstract mars does not recycle crustal materials via plate tectonics for this reason the magmatic water reservoir of the martian mantle has not been affected by surface processes and the deuterium hydrogen d h ratio of this water should represent the original primordial martian value following this logic hydrous primary igneous minerals on the martian surface should also carry this primordial d h ratio assuming no assimilation of martian atmospheric water during crystallization and no major hydrogen fractionation during melt degassing hydrous primary igneous minerals such as apatite and amphibole are present in martian meteorites here on earth providing these minerals have not been affected by terrestrial weathering martian atmospheric water or shock processes after crystallization they should contain a good approximation of the primordial martian d h ratio as nakhla was seen to fall in the egyptian desert in 1911 terrestrial contamination is minimized in this meteorite the nakhlites are also among the least shocked of the martian meteorites therefore apatite within nakhla could contain primordial martian hydrogen isotope ratios we produced in situ measurements of the d h ratios in nakhla apatite grains using a cameca ims 1280 ion microprobe our measurements produced d h values in nakhla apatite similar to terrestrial values despite strong evidence that our samples were not significantly contaminated by terrestrial hydrogen these results suggest that water trapped in the martian mantle has a similar d h to that of the earth therefore the water of these two planets may have originated from the same source material the d h ratios of the carbonaceous chondrite meteorites and the jupiter family comet 103p hartley 2 are similar to the d h of the two planets making both these primitive inner solar system materials strong candidates for the source of the terrestrial planets water these results support recent dynamical models of the formation of the solar system which suggest material in the inner solar system was homogenized by the migration of jupiter

shock metamorphism and petrography of the shergotty achondrite the shergotty subsamples 1 and 12 consist of augite and pigeonite 67 5 maskelynite 24 ilmenite and titanomagnetite 2 pyrrhotite 0 4 whitlockite 1 8 apatite 0 1 quartz 0 5 baddeleyite trace fayalite 0 4 mesostasis 3 and shock induced local polymineralic melt products 0 6 the overall modal composition is similar to other shergotty samples except for the rather high whitlockite content the shock effects observed in the mineral constituents include mosaicism deformation bands planar fractures and mechanical twin lamellae in clinopyroxene isotropization of plagioclase with very rare remnants of birefringence planar deformation structures mosaicism and strongly reduced birefringence in quartz mechanical twinning of ilmenite localized in situ melting of neighbouring minerals at the contact of low and high density phases based on the refractive index of maskelynite average 1 5467 with average an content of 49 and the degree of isotropization of the plagioclase an equilibrium shock pressure of 29 1 gpa is derived the inferred post shock temperature is 200 20 c no heating event could have exceeded 400 c duke 1968 local stress and temperature concentrations reach 60 80 gpa and 1600 2000 c the observed shock effects can be explained by a single shock event a second weaker shock event as found by others appears to be highly improbable equilibrium shock pressures and post shock temperatures for the other known shergottites are 31 2 gpa and 220 50 c zagami 43 2 gpa and 400 800 c alha 77005 the pressure estimate for eeta 79001 by lambert 1985 is confirmed 34 1 gpa the post shock temperature is 250 50 c the abundance and textural setting of localized melt products in these meteorites confirm increasing shock pressures in the sequence shergotty zagami eeta 79001 alha 77005 undoubtedly the melts could have been formed by the same single shock which produced the equilibrium shock effects e g maskelynitization in these meteorites the shock induced particle velocities inferred from hugoniot data of basalts are in the 1 5 2 0 km s range for the parental rocks of the shergottites ejection velocities are therefore in the order of 3 4 km s special ejection mechanisms are required in order to exceed the escape velocity of a planet like mars without producing higher degrees of shock e g melting than those observed in the shergottites

volatile abundances of coexisting merrillite and apatite in the martian meteorite shergotty implications for merrillite in hydrous magmas whitlockite and merrillite are two ca phosphate minerals found in terrestrial and planetary igneous rocks sometimes coexisting with apatite whitlockite has essential structural hydrogen and merrillite is devoid of hydrogen whitlockite components have yet to be discovered in samples of extraterrestrial merrillite despite evidence for whitlockite merrillite solid solution in terrestrial systems the observation of merrillite in meteoritic and lunar samples has led many to conclude that the magmas from which the merrillite formed were very dry however the shergotty martian meteorite has been reported to contain both apatite and merrillite and recently the apatite has been shown to contain substantial oh abundances up to the equivalent of 8600 ppm h2o in the present study we determined the abundances of f cl h2o and s in merrillite from shergotty using secondary ion mass spectrometry sims we determined that the merrillite in shergotty was properly identified i e no discernible whitlockite component and it coexists with oh rich apatite the absence of a whitlockite component in shergotty merrillite and other planetary merrillites may be a consequence of the limited thermal stability of h in whitlockite stable only at t 1050 c which would prohibit merrillite whitlockite solid solution at high temperatures consequently the presence of merrillite should not be used as evidence of dry magmatism without a corresponding estimate of the t of crystallization in fact if a whitlockite component in extraterrestrial merrillite is discovered it may indicate formation by or equilibration with hydrothermal or aqueous fluids

chromite symplectites in mg suite troctolite 76535 as evidence for infiltration metasomatism of a lunar layered intrusion abstract despite the very low chromium concentrations in its cumulus olivine 140 ppm lunar troctolite 76535 contains large amounts of cr sporadically but highly concentrated in symplectite assemblages consisting of mg al chromite and two pyroxenes previously proposed symplectite formation mechanisms include crystallization of trapped interstitial melt diffusion of cr from cumulus olivine and or remobilization of cumulus chromite grains these mechanisms would imply that the highly cr depleted nature of mg suite parental magmas and their source materials inferred from cumulus olivine may be illusory we have conducted a detailed petrologic and textural study of symplectites as well as chromite veins intercumulus assemblages olivine hosted melt inclusions and clinopyroxene troilite veins in 76535 with the goals of constraining the origin of the symplectites and the degree of cr depletion in mg suite magmas relative to other lunar basalts orthopyroxene and clinopyroxene in melt inclusions are depleted in cr relative to their symplectite counterparts averaging 900 and 1200 ppm vs 7400 and 8100 ppm cr 2 o 3 respectively olivine in contact with symplectite assemblages may exhibit a diffusion profile of cr going into olivine whereas olivine boundaries away from symplectites show no diffusion profile there is also a distinct lack of primary chromite as inclusions in cumulus phases and melt inclusions multiple textural observations melt inclusion chemistry and modeling of chromite olivine equilibrium rule out previously proposed symplectite formation mechanisms and strongly suggest that chromite was not a primary crystallization product of the 76535 parental magma accordingly the post cumulus addition of cr and fe is required to produce the symplectites after considering multiple models the addition of cr and fe to 76535 via infiltration metasomatism by an exogenous chromite saturated melt is the model most consistent with multiple textural and geochemical observations failure of models that call upon cr diffusion out of olivine grains imply that the observed cr depleted nature of olivine observed in many mg suite lithologies is a primary feature of the cr depleted nature of the mg suite parental magmas and their source materials this substantial depletion of cr in the magma relative to mare basalt magmas still requires a satisfactory explanation in order to be consistent with mg suite petrogenetic models and currently accepted bulk moon compositions additionally if the intimate interaction of migrating melts with early lunar crustal lithologies was a widespread phenomenon after lmo solidification it provides another mechanism by which to reset or delay closure of radiogenic isotopic systems and explain the mg suite ferroan anorthosite age overlap

assessment of shock effects on amphibole water contents and hydrogen isotope compositions 1 amphibolite experiments abstract kaersutitic amphiboles found within a subset of the martian meteorites have low water contents and variably heavy hydrogen isotope compositions in order to assess if impact shock induced devolatilization and hydrogen isotope fractionation were determining factors in these water and isotopic characteristics of the martian kaersutites we conducted impact shock experiments on samples of gore mountain amphibolite in the ames vertical gun range avgr a parallel shock experiment conducted on an anorthosite sample indicated that contamination of shocked samples by the avgr hydrogen propellant was unlikely petrographic study of the experimental amphibolite shock products indicates that only 10 of the shock products experienced levels of damage equivalent to those found in the most highly shocked kaersutite bearing martian meteorites 30 35 gpa ion microprobe studies of highly shocked hornblende from the amphibolite exhibited elevated water contents h 2 o 0 1 wt and enriched hydrogen isotope compositions d 10 relative to unshocked hornblende water and hydrogen isotope analyses of tens of milligrams of unshocked moderately shocked and highly shocked hornblende samples by vacuum extraction uranium reduction and isotope ratio mass spectrometry irms respectively are largely consistent with analyses of single grains from the ion microprobe the mechanisms thought to have produced the excess water in most of the shocked hornblendes are shock induced reduction of hornblende fe and or irreversible adsorption of hydrogen addition of the isotopically enriched martian atmosphere to the martian meteorite kaersutites via these mechanisms could explain their enriched and variable isotopic compositions alternatively regrouping the water extraction and irms analyses on the basis of isotopic composition reveals a small but consistent degree of impact induced devolatilization 0 1 wt h 2 o and h isotope enrichment d 10 extrapolating the shock signature of the regrouped data to grains that experienced martian meteorite like shock pressures suggests that shock induced water losses and hydrogen isotope enrichments could approach 1 wt h 2 o and d 100 respectively if these values are valid then impact shock effects could explain a substantial fraction of the low water contents and variable hydrogen isotope compositions of the martian meteorite kaersutites

detection of structurally bound hydroxyl in fluorapatite from apollo mare basalt 15058 128 using tof sims fluorapatite grains from apollo 15 mare basalt 15058 128 were analyzed by raman spectroscopy raman spectral imaging time of flight secondary ion mass spectrometry tof sims field emission scanning electron microscopy fe sem and electron probe microanalysis epma in an attempt to detect structurally bound oh in the fluorapatite although oh could not be definitively detected by raman spectroscopy because of ree induced photoluminescence hydroxyl was detected in the fluorapatite by tof sims the tof sims technique is qualitative but capable of detecting the presence of hydroxyl even at trace levels electron microprobe data indicate that on average f and cl f cl fill the monovalent anion site in these fluorapatite grains within the uncertainties of the analyses about 0 07 0 01 atoms per formula unit however some individual spot analyses have f cl deficiencies greater than analytical uncertainties that could represent structural oh on the basis of epma data the fluorapatite grain with the largest f cl deficiency constrains the upper limit of the oh content to be no more than 4600 2000 ppm by weight the equivalent of 2400 1100 ppm water the tof sims detection of oh in fluorapatite from apollo sample 15058 128 represents the first direct confirmation of structurally bound hydroxyl in a lunar magmatic mineral this result provides justification for attributing at least some of the missing structural component in the monovalent anion site of other lunar fluorapatite grains to the presence of oh moreover this finding supports the presence of dissolved water in lunar magmas and the presence of at least some water within the lunar interior

unique meteorite from early amazonian mars water rich basaltic breccia northwest africa 7034 we report data on the martian meteorite northwest africa nwa 7034 which shares some petrologic and geochemical characteristics with known martian meteorites of the snc i e shergottite nakhlite and chassignite group but also has some unique characteristics that would exclude it from that group nwa 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent rover and orbiter missions it formed 2 089 0 081 billion years ago during the early amazonian epoch in mars9 geologic history nwa 7034 has an order of magnitude more indigenous water than most snc meteorites with up to 6000 parts per million extraterrestrial h2o released during stepped heating it also has bulk oxygen isotope values of 17o 0 58 0 05 per mil and a heat released water oxygen isotope average value of 17o 0 330 0 011 per mil suggesting the existence of multiple oxygen reservoirs on mars

partitioning of light lithophile elements during basalt eruptions on earth and application to martian shergottites an enigmatic record of light lithophile element lle zoning in pyroxenes in basaltic shergottite meteorites whereby lle concentrations decrease dramatically from the cores to the rims has been interpreted as being due to partitioning of lle into a hydrous vapor during magma ascent to the surface on mars these trends are used as evidence that martian basaltic melts are water rich mcsween et al 2001 lithium and boron are light lithophile elements lle that partition into volcanic minerals and into vapor from silicate melts making them potential tracers of degassing processes during magma ascent to the surface of earth and of other planets while lle degassing behavior is relatively well understood for silica rich melts where water and lle concentrations are relatively high very little data exists for lle abundance heterogeneity and degassing in basaltic melts the lack of data hampers interpretation of the trends in the shergottite meteorites through a geochemical study of lle volatile and trace elements in olivine hosted melt inclusions from kilauea volcano hawaii it can be demonstrated that lithium behaves similarly to the light to middle rare earth elements during melting magma mixing and fractionation considerable heterogeneity in lithium and boron is inherited from mantle derived primary melts which is dominant over the fractionation and degassing signal lithium and boron are only very weakly volatile in basaltic melt erupted from kilauea volcano with vapor melt partition coefficients 4 wt the observed terrestrial lle partitioning behavior is extrapolated to martian primitive melts through modeling the zoning observed in the shergottite pyroxenes is only consistent with degassing of lle from a martian melt near its liquidus temperature if the vapor melt partition coefficient was an order of magnitude larger than observed on earth the range in lle and trace elements observed in shergottite pyroxenes are instead consistent with concurrent mixing and fractionation of heterogeneous melts from the mantle

geochemical evidence for magmatic water within mars from pyroxenes in the shergotty meteorite observations of martian surface morphology have been used to argue that an ancient ocean once existed on mars1 it has been thought that significant quantities of such water could have been supplied to the martian surface through volcanic outgassing but this suggestion is contradicted by the low magmatic water content that is generally inferred from chemical analyses of igneous martian meteorites2 here however we report the distributions of trace elements within pyroxenes of the shergotty meteorite a basalt body ejected 175 million years ago from mars3 as well as hydrous and anhydrous crystallization experiments that together imply that water contents of pre eruptive magma on mars could have been up to 1 8 we found that in the shergotty meteorite the inner cores of pyroxene minerals which formed at depth in the martian crust are enriched in soluble trace elements when compared to the outer rims which crystallized on or near to the martian surface this implies that water was present in pyroxenes at depth but was largely lost as pyroxenes were carried to the surface during magma ascent we conclude that ascending magmas possibly delivered significant quantities of water to the martian surface in recent times reconciling geologic and petrologic constraints on the outgassing history of mars

water in the martian interior evidence for terrestrial morb mantle like volatile contents from hydroxyl rich apatite in olivine phyric shergottite nwa 6234 abstract understanding the distribution and behavior of volatiles in martian magmas and the corresponding mantle provides crucial constraints on planetary properties such as mantle melting temperatures and melt production as well as the availability of magmatic fluids for any potential occurrences of life current evaluations of the pre eruptive volatile concentrations of martian magmas are based on analyses of hydrous minerals in martian meteorites such as apatite because they record the volatile content oh f cl and the halogen and water fugacities of their parental magmas estimates for the pre eruptive volatile contents of martian basaltic magmas range from nearly anhydrous to 2 wt h2o however these magmas may have potentially degassed upon eruption and or emplacement losing their magmatic water while retaining some halogens here we report apatite compositional data from the martian meteorite nwa 6234 an intermediate olivine phyric shergottite and calculate f2 cl2 h2o fugacity ratios for its parental magma apatites in nwa 6234 contain the highest observed oh f content among martian meteorites and importantly have volatile fugacity ratios similar to terrestrial basalts this suggests that the actual content of fluorine chlorine and water of the martian mantle parental to snc meteorites are higher than previously thought and are similar to the volatile content of the terrestrial mid ocean ridge basalt source region

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

water in lunar anorthosites and evidence for a wet early moon water has been detected on the lunar surface and attributed to delivery by impacts and the solar wind to a dry early moon spectroscopic detections of water in lunar anorthosites from the apollo collection suggest that a significant amount of water is indigenous to the moon

mechanism for generating the anomalous uplift of oceanic core complexes atlantis bank southwest indian ridge atlantis bank is an anomalously uplifted oceanic core complex adjacent to the atlantis ii transform on the southwest indian ridge that rises 3 km above normal seafloor of the same age models of flexural uplift due to detachment faulting can account for 1 km of this uplift postdetachment normal faults have been observed during submersible dives and on swath bathymetry two transform parallel large offset hundreds of meters normal faults are identified on the eastern flank of atlantis bank with numerous smaller faults tens of meters on the western flank flexural uplift associated with this transform parallel normal faulting is consistent with gravity data and can account for the remaining anomalous uplift of atlantis bank extension normal to the atlantis ii transform may have occurred during a 12 m y period of transtension initiated by a 10 change in spreading direction ca 19 5 ma this extension may have produced the 120 km long transverse ridge of which atlantis bank is a part and is consistent with stress reorientation about a weak transform fault

petrogenesis of high phosphorous wishstone class rocks in gusev crater mars 1 the spirit rover has analyzed a wide variety of alkaline volcanic rocks in gusev crater among them are wishstone class tephrites with unusually high p2o5 5 wt abundances to obtain the chemical compositions of rock interiors we extrapolated a trend defined by brushed and abraded surface compositions the extrapolation analysis suggests the high p2o5 tephrite signature is not attributable to secondary aqueous alteration but represents an igneous rock composition assessment of the compositional trend also suggests that merrillite is the phosphate mineral in wishstone class modified cipw norm calculations using merrillite instead of apatite show that wishstone class rocks are silica saturated hypersthene olivine normative and alkaline the high p2o5 whole rock compositions plot above solubility curves of merrillite in a diagram of p2o5 versus aluminosity suggesting that mechanical admixture of merrillite is required a source supplying merrillite cannot be a common silicate magma instead it could be a carbonatitic melt or a highly fractionated residual melt jotunite after anorthosite crystallization comparison with earth analogs suggests that the wishstone class is akin to alkaline basalts in the eastern snake river plain with regard to its chemistry texture and geologic context these alkaline basalts are interpreted to originate from mantle metasomatized by co2 fluids and highly alkaline melts in the wake of the yellowstone hot spot thus we propose that the wishstone class represents a silica saturated alkaline suite that has mechanically mixed xenocrystic merrillites probably during explosive volcanic eruption the merrillites crystallized from carbonate rich magma produced by melting of a co2 bearing martian mantle

hydrogen isotope ratios in lunar rocks indicate delivery of cometary water to the moon water has been found in many lunar rock samples but its sources are unknown isotopic analyses of apollo samples of lunar mare basalts and highlands rocks suggest that a significant volume of water was delivered to the moon by comets shortly after its formation by giant impact

martian magmas contained abundant chlorine but little water the martian water cycle a key for the habitability of mars largely relies on the abundance of water in martian magmas and their mantle sources yet martian snc shergottite nakhlite and chassigny classes meteorites contain minimal water however some experimental studies have suggested that martian parental magmas contained as much as 2 h2o here we integrate mineral chemical experimental and cosmochemical constraints to show that martian magmas contained little water but abundant chlorine apatite and amphibole in martian meteorites are chlorine rich and water poor this constrains the chlorine contents in their parental magmas to 0 3 wt and water contents to 0 3 wt our experimental work has shown that large amounts of water are not needed to explain the mineralogy of the martian meteorites because chlorine has effects similar to those of water on crystallization such chlorine rich water poor martian magmas are consistent with mars being chlorine rich 2 5 compared with the earth furthermore the bulk cl composition of martian meteorites shows that they have not preferentially lost cl by degassing of an h2o rich vapor together these results show that chlorine not water was the dominant volatile species in martian basalts and that these basalts contributed little h2o to mars surface environment

apatite as a probe of halogen and water fugacities in the terrestrial planets abstract apatite preserves a record of the halogen and water fugacities that existed during the waning stages of crystallization of planetary magmas when they became saturated in phosphates we develop a thermodynamic formalism based on apatite merrillite equilibria that makes it possible to compare the relative values of halogen and water fugacities in martian lunar and terrestrial basalts accounting for possible differences in pressure temperature and oxygen fugacities among the planets we show that each of these planetary bodies has distinctive ratios among volatile fugacities at apatite saturation and that these fugacities are in some cases related in a consistent way to volatile fugacities in the mantle magma sources our analysis shows that the martian mantle parental to basaltic snc meteorites was dry and poor in both fluorine and chlorine compared to the terrestrial mantle the limited data available from mars show no secular variation in mantle halogen and water fugacities from 4 ga to 180 ma the water and halogens found in present day martian surface rocks have thus resided in the planet s surficial systems since at least 4 ga and may have been degassed from the planet s interior during a primordial crust forming event in comparison to the earth and mars the moon and possibly the eucrite parent body too appear to be strongly depleted not only in h 2 o but also in cl 2 relative to h 2 o chlorine depletion is strongest in mare basalts perhaps reflecting an eruptive process characteristic of large scale lunar magmatism