lunar highland meteorites and the composition of the lunar crust abstract major minor and trace element data obtained by neutron activation techniques and by spark source mass spectrometry ssms on two lunar meteorites mac88104 and mac88105 are reported both mac samples were also analysed for their contents and isotopic compositions of rare gases additional ssms data were obtained on four lunar highland meteorites previously found in antarctica alha81005 y791197 y82192 and y86032 mac88104 and mac88105 are very similar in chemistry suggesting that they are pieces of a single fall event the bulk chemical composition of mac88104 5 is not very different from the other lunar highland meteorites highly aluminous with relatively low contents of ree and siderophile element concentrations slightly above 1 of a ci chondritic level however mafic element concentrations mg cr mn etc are slightly lower in mac88104 5 than in the other lunar highland meteorites the contents of solar rare gases in the two mac samples are low indicating only a small regolith contribution in agreement with rare petrographically identifiable regolith components the mac samples and also y82192 and y86032 are classified as fragmental breccias with negligible regolith components in contrast to alha81005 and y791197 which are regolith breccias with high solar wind derived rare gas contents there is no correlation among lunar meteorites between peak shock pressures and solar gas contents indicating that peak shock pressures of up to 25 gpa do not lead to gas loss a low 26al activity vogt et al 1990 and high contents of cosmogenic rare gases in mac88104 5 suggest a long exposure 400 000 years in the lunar sub surface k ar ages are in excess of 3 9 by lunar highland meteorites and compositionally similar granulitic rocks from the apollo 16 and 17 landing sites contain about 1 of a ci chondritic component according to siderophile and volatile element contents but independent of the amount of regolith components apparently the major fraction of meteoritic elements in these rocks was not provided by micrometeorites impacting the regolith the abundances of siderophile e g ir and volatile elements may therefore reflect the last spike of accretion of the moon after the formation of the anorthositic crust lunar meteorites of highland origin are chemically different from the bulk of the apollo 16 highland samples in having higher fe mg ratios and lower contents and less fractionated patterns of incompatible and siderophile elements since lunar highland meteorites are associated with at least three but probably four different fall events and since they are not derived from chemically exotic front side terranes they may represent a better sampling of the average chemical composition of the lunar crust than previous estimates based on returned lunar samples and remote sensing data a comparison between an average highland composition derived by taylor 1982 and an estimate based on lunar highland meteorites shows that the taylor composition contains higher concentrations and more fractionated incompatible elements mainly because of a substantial amount of kreep a trace element rich highly fractionated component from the front side of the moon not present at the sites from which the lunar meteorites come

regolith breccia allan hills a81005 evidence of lunar origin and petrography of pristine and nonpristine clasts mno feo ratios in pyroxene texture abundant brown swirly glass in general typical of lunar regolith breccias and overall composition 75 plagioclase all indicate that allan hills a81005 is of lunar origin it is presumably from a heretofore unsampled region of the moon it differs in detail from other regolith samples e g it has exceptionally low contents of na and kreep a pristine clast contains exceptionally coarse augite compared to similar apollo samples alha81005 is not perceptibly more shocked than typical apollo regolith breccias therefore its discovery on earth lends further credence to suggestions that snc achondrites were derived by impact ejection from mars

chromitite and ultramafic rock compositional zoning through a paleotransform fault poum new caledonia the major mylonitic shear zone of the northern part of the ophiolitic peridotite sheet of new caledonia has been described as a paleotransform fault secher 1981 located along this structure the poum ultramafic massif shows a wide spectrum of peridotite compositions ranging from plagioclase lherzolite to dunite across a 2 km thick transition zone the mylonitized plagioclase lherzolite contains abundant pyroxenite and mafic veins the poum ultramafic massif includes more than 30 chromitite orebodies their composition vanes according to the nature of the host peridotite al rich in the plagioclase lherzolite zone 31 43 al 2 o 3 and 25 36 cr 2 o 3 cr rich 39 60 cr 2 o 3 in the spinel lherzolite and clinopyroxene harzburgite zones and still richer in the harzburgite dunite zone 49 64 cr 2 o 3 in peridotites the accessory cr spinel also displays a cr enrichment from lherzolite to dunite segregations of cr rich chromite 50 60 cr 2 o 3 are present in orthopyroxenite veins displaying boninitic affinities the poum chromitites display low platinum group element pge contents and pd ir ratios as do the chromitite segregations of the orthopyroxenite veins suggesting a common parent magma or and common fractionation processes the compositional zoning of the poum massif can be explained by the contrasting behavior of ultramafic rocks and upwelling mafic melts away from the axis of the transform fault using the current ideas about the genesis of boninitic melts and the formation of dunite and harzburgite by magma rock interactions during melt percolation nicolas and prinzhofer 1983 kelemen 1990 kelemen et al 1992 takazawa et al 1992 in the lithospheric lherzolite zone that was cooled and mylonitized along the older wall of the transform fault melts were channeled along fractures leaving al rich chromitite pods by contrast pervasive percolation along the lithosphere asthenosphere boundary allowed important melt rock interactions resulting in the progressive formation of harzburgite and dunite and generating mg cr rich melts from which precipitated cr rich chromitites

three thousand years of flank and central vent eruptions of the san salvador volcanic complex el salvador and their effects on el cambio archeological site a review based on tephrostratigraphy the volcanic events of the last 3 000 years at san salvador volcanic complex are reviewed using detailed stratigraphic records exposed in new excavations between 2005 and 2007 at el cambio archeological site zapotitan valley el salvador and in other outcrops on the northern and northwestern sectors of the complex the sequences that overlie tierra blanca joven cal 429 107 ad from the ilopango caldera comprise the loma caldera cal 590 90 ad and el playon 1658 1671 deposits and the san andres tuff cal 1031 29 ad related to el boqueron volcano the surge deposits within the el playon san andres tuff and overlying talpetate ii sequences indicate the significance of phreatomagmatic phases in both central vent and flank eruptions during the last 1 600 years newly identified volcanic deposits underlying tierra blanca joven at el cambio extend the stratigraphic record of the area to 3 000 years bp paleosols interstratified with those deposits contain cultural artifacts which could be associated with the middle preclassic period 900 400 bc if correct human occupation of the site during the preclassic period was more intense than previously known and volcanic eruptions must have affected prehistoric settlements the archeological findings provide information on how prehistoric populations dealt with volcanic hazards thousands of years ago in the eastern zapotitan valley where several housing projects are currently being developed the new stratigraphic and volcanological data can be used as a basis for local and regional hazard assessment related to future secondary vent activity in the san salvador volcanic complex

northwest africa 482 a crystalline impact melt breccia from the lunar highlands northwest africa 482 nwa 482 is a crystalline impact melt breccia from the moon with highlands affinities the recrystallized matrix and the clast population are both highly anorthositic clasts are all related to the ferroan anorthosite suite and include isolated plagioclase crystals and lithic anorthosites troctolites and spinel troctolites potassium rare earth element and phosphorus bearing kreep and mare lithologies are both absent constraining the source area ofthis meteorite to a highland terrain with little to no kreep component most likely on the far side of the moon glass is present in shock veins cutting through the sample and in several large melt pockets indicating a second impact event there are two separate events recorded in the 40ar 39ar system one at 3750 ma which completely reset the k ar system and one at 2400 ma which caused onlypartial degassing these events could represent respectively crystallization ofthe impact melt breccia and later formation of the glass or the formation of the glass and a later thermal event the terrestrial age of the meteorite is 8 6 1 3 ka this age corresponds well with the modest amount ofweathering in the rock in the form ofsecondaryphyllosilicates and carbonates based on terrestrial age and location lithology and chemistry nwa 482 is unique among known lunar meteorites

lunar and martian meteorite delivery services launch mechanisms for lunar and martian meteorites have been investigated by integrating physical modeling constraints geochemical cosmic ray exposure cre constraints and petrologic constraints the potential source region for lunar meteorites is remarkably small compared to the final crater volume cre constraints indicate that most launches start at depths of 3 2 m and cratering theory implies derivation of suitably accelerated objects from a subvolume with diameter only about 0 3 the final crater diameter the shallow depth provenance is probably related to shock wave interference enhanced by the lunar regolith s extremely low compressional wave velocity cre constraints alone imply that four to five separate launch events are represented among the eight well studied lunar meteorites most of the lunar meteorites are regolith breccias which tend to show only limited compositional diversity within any kilometer scale region of the moon several others are polymict breccias which also show relatively subdued compositional diversity compared to igneous rocks the observed diversity among these samples in terms of abundances of mare basalt and kreep and in mg mg fe ratio implies that among eight well studied lunar meteorites only two potential source crater pairings are plausible between asuka 881757 y 793169 most probable and between y 793274 eet875721 altogether these eight lunar meteorites apparently represent at least six separate source craters including three in the past 105 years and five in the past 106 years cre constraints imply that snc meteorites are launched from systematically greater depths than lunar meteorites sncs are also systematically bigger and all nine well studied sncs are uncommonly young by martian standards mafic igneous rocks comparison between viking and apollo results reveals that rocks the size of common meteorites are remarkably scarce in the martian regolith probably due to pervasive weathering a plausible explanation for these trends is that most old small and shallow rocks on mars have been weakened by a two stage process of brecciation followed by pervasive weathering to the point where they seldom survive the stresses of spallation off the planet the scarcity of source crater pairing among the lunar meteorites implies that these objects can be launched from craters much smaller than previously estimated and tends to support the suggestion of rabinowitz 1993 astrophys j 407 412 427 that present day cratering rates for the earth moon region may be higher than previously estimated

some things we can infer about the moon from the composition of the apollo 16 regolith randy l korotev department of earth and planetary sciences and mcdonnell center for the space sciences washington university st louis missouri 63130 usa author s e mail address rlk levee wustl edu received 1996 september 16 accepted in revised form 1997 may 12 abstract characteristics of the regolith of cayley plains as sampled at the apollo 16 lunar landing site arereviewed and new compositional data are presented for samples of 1 mm fines soils and 1 2 mm rego lith particles as a means of determining which of the many primary igneous and secondary crystalline brec cias lithoiogic components that have been identified in the soil are volumetrically important and providing anestimate of their relative abundances more than 3 x 106 combinations of components representing nearly everylithology that has been observed in the apollo 16 regolith were systematically tested to determine which com binations best account for the composition of the soils conclusions drawn from the modeling include the fol lowing at the site mature soil from the cayley plains consists of 64 5 2 7 components representing prebasin materials anorthosites feldspathic breccias and a small amount 2 6 1 5 of total soil ofnonmare mafic plutonic rocks mostly gabbronorites on average these components are highly feldspathic with average concentrations of 31 32 a1203 and 2 3 feo and a molar mg mg fe ratio of 0 68 theremaining 36 of the regolith is syn and postbasin material 28 8 2 4 mafic impact melt breccias mimbs i e lkfm and vha basalts created at the time of basin formation 6 0 1 4 mare derived material impact and volcanic glass crystalline basalt with an average tio2 concentration of 2 4 and 1 postbasin meteoritic material the mimbs are the principal 80 90 carrier of incompatible traceelements rare earths th etc and the carrier of about one half of the siderophile elements and elementsassociated with mafic mineral phases fe mg mn cr sc most 71 of the fe in the present regolithderives from syn and postbasin sources mimbs mare derived material and meteorites thus althoughthe bulk composition of the apollo 16 regolith is nominally that of noritic anorthosite the noritic part themimbs and the anorthositic part the prebasin components are largely unrelated there is compositionalevidence that 3 4 of the soil is th rich material such as that occurring at the apollo 14 site and one frag ment of this type was found among the small regolith particles studied here if regolith such as that repre sented by the apollo 16 ancient regolith breccias was a protolith of the present regolith such regolith cannotexceed 71 of the present regolith the rest must be material added or redistributed since closure of theancient regolith breccias the postclosure material includes the mare derived material and the apollo 14 like component compositions of all mature surface soils from apollo 16 even those collected 4 km apart on the cayleyplains are very similar which is in stark contrast to the wide compositional range of the lithologies of whichthe soil is composed this uniformity indicates that the ratio of mimbs to feldspathic prebasin componentsis not highly variable in the megaregolith over distances of a few kilometers that there are no large sub surface concentrations of pure mafic impact melt breccia and that the intimate mixing is inherent to thecayley plains at a gross scale thus the mixing ofmafic impact melt breccias and feldspathic prebasin com ponents must have occurred during formation and deposition of the cayley plains such uniformity could nothave been achieved by small postdeposition impacts into a stratified megaregolith using this conclusion asone constraint and the known distribution of th on the lunar surface as another and the assumption that the im brium impact is primarily responsible for formation of the cayley plains arguments are presented that theapollo 16 mimbs derive from the imbrium region and consequently that one fourth of the apollo 16 regolithis primary imbrium ejecta in the form of mafic impact melt breccias

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

northwest africa 773 lunar mare breccia with a shallow formed olivine cumulate component inferred very low ti vlt heritage and a kreep connection abstract lunar meteorite northwest africa 773 herein referred to as nwa773 is a breccia composed predominantly of mafic volcanic components including a prominent igneous clast lithology the clast lithology is an olivine gabbro cumulate which on the basis of mineral and bulk compositions is a hypabyssal igneous rock related compositionally to volcanic components in the meteorite the olivine gabbro lithology exhibits cumulus textures and in our largest section of it includes some 48 olivine fo 64 to fo 70 average fo 67 27 pigeonite en 60 fs 24 wo 16 to en 67 fs 27 wo 6 11 augite en 50 fs 17 wo 33 to en 47 fs 13 wo 40 2 orthopyroxene en 70 fs 26 wo 4 11 plagioclase an 80 to an 94 and trace barian k feldspar ilmenite cr spinel re merrillite troilite and fe ni metal the mg fe ratios of the mafic silicates indicate equilibration of fe and mg however the silicates retain compositional variations in minor and trace elements that are consistent with intercumulus crystallization accessory mineralogy reflects crystallization of late stage residual melt both lithologies breccia and olivine cumulate of the meteorite have very low ti vlt major element compositions but with an unusual trace element signature compared to most lunar vlt volcanic compositions i e relative enrichment in light ree and large ion lithophile elements and greater depletion in eu than almost all other known lunar volcanic rocks the calculated composition of the melt that was in equilibrium with pyroxene and plagioclase of the cumulate lithology exhibits a kreep like ree pattern but at lower concentrations melt of a composition calculated to have been in equilibrium with the cumulate assemblage plus excess olivine yields a major element composition that is similar to known green volcanic glasses one volcanic glass type from apollo 14 in particular green glass b type 1 has a very low ti concentration and ree characteristics including extremely low eu concentration that make it a candidate parent melt for the olivine gabbro cumulate we infer an origin for the parent melt of nwa773 volcanic components by assimilation of a trace element rich partial or residual melt by a magnesian vlt magma deep in the lunar crust or in the mantle prior to transportation to the near surface accumulation of olivine and pyroxene in a shallow chamber eruption onto a volcanic surface and incorporation of components into local predominantly volcanic regolith prior to impact mixing of the volcanic terrain and related hypabyssal setting and ejection from the surface of the moon volcanic components such as these probably occur in the oceanus procellarum region near the site of origin of the green volcanic glasses found in the apollo 14 regolith

paleomagnetic results from the newer volcanics of victoria contribution to the time averaged field initiative 1 the newer volcanics of victoria australia were sampled in 2001 and 2003 as part of the time averaged field initiative which is designed to provide a reliable data set for modeling the earth s magnetic field over the past 5 my the collection consisted of ten cores per site at 42 sites complete demagnetization was carried out on all samples using af or thermal demagnetization and line fitting techniques were employed to determine the resultant vector thirty two of these sites gave results that met the criterion that n 5 and 95 was less than 6 20 sites were reversely magnetized dec 173 4 inc 54 6 95 3 8 and 13 normally magnetized dec 2 1 inc 62 3 95 6 3 the data gave a global mean paleomagnetic pole lat 87 2 long 21 9 and a95 4 4 which is not significantly different from the pole of rotation for the present location of victoria and for its latitude 2 5 million years ago when most of the lavas were erupted

petrography and geochemistry of the lapaz icefield basaltic lunar meteorite and source crater pairing with northwest africa 032 we report on the bulk composition and petrography of four new basaltic meteorites found in antarcticalap lapaz icefield 02205 lap 02224 lap 02226 and lap 02436 and compare the lap meteorites to other lunar mare basalts the lap meteorites are coarse grained up to 1 5 mm subophitic low ti basalts composed predominantly of pyroxene and plagioclase with minor amounts of olivine ilmenite and a groundmass dominated by fayalite and cristobalite all of our observations and results support the hypothesis that the lap stones are mutually paired with each other in detail the geochemistry of lap is unlike those of any previously studied lunar basalt except lunar meteorite nwa northwest africa 032 the similarities between lap and nwa 032 are so strong that the two meteorites are almost certainly source crater paired and could be two different samples of a single basalt flow petrogenetic modeling suggests that the parent melt of lap and nwa 032 is generally similar to apollo 15 low ti yellow picritic glass beads and that the source region for lap comes from a similar region of the lunar mantle as previously analyzed lunar basalts

constraining the source regions of lunar meteorites using orbital geochemical data lunar meteorites provide important new samples of the moon remote from regions visited by the apollo and luna sample return missions petrologic and geochemical analysis of these meteorites combined with orbital remote sensing measurements have enabled additional discoveries about the composition and age of the lunar surface on a global scale however the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar meteorite here we investigate the link between meteorite and source region on the moon using the lunar prospector gamma ray spectrometer remote sensing data set for the elements fe ti and th the approach has been validated using apollo and luna bulk regolith samples and we have applied it to 48 meteorites excluding paired stones our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar meteorites basaltic and intermediate fe regolith breccia meteorites are found to have the best constrained potential launch sites with some impact breccias and pristine mare basalts also having reasonably well defined potential source regions launch areas for highland feldspathic meteorites are much less well constrained and the addition of another element such as mg will probably be required to identify potential source regions for these

geochemistry petrology and ages of the lunar meteorites kalahari 008 and 009 new constraints on early lunar evolution abstract kalahari 008 and 009 are two lunar meteorites that were found close to each other in botswana kalahari 008 is a typical lunar anorthositic breccia kalahari 009 a monomict breccia with basaltic composition and mineralogy based on minor and trace elements kalahari 009 is classified as vlt very low ti mare basalt with extremely low contents of incompatible elements including the ree the lu hf data define an age of 4286 95 ma indicating that kalahari 009 is one of the oldest known basalt samples from the moon it provides evidence for lunar basalt volcanism prior to 4 1 ga pre nectarian and may represent the first sample from a cryptomare the very radiogenic initial 176hf 177hf ehf 12 9 4 6 the low ree th and ti concentrations indicate that kalahari 009 formed from re melting of mantle material that had undergone strong incompatible trace element depletion early in lunar history this unusually depleted composition points toward a hitherto unsampled basalt source region for the lunar interior that may represent a new depleted endmember source for low ti mare basalt volcanism apparently the moon became chemically very heterogeneous at an early stage in its history and different cumulate sources are responsible for the diverse mare basalt types evidence that kalahari 008 and 009 may be paired includes the similar fayalite content of their olivine the identical initial hf isotope composition the exceptionally low exposure ages of both rocks and the fact that they were found close to each other since cryptomaria are covered by highland ejecta it is possible that these rocks are from the boundary area where basalt deposits are covered by highland ejecta the concentrations of cosmogenic radionuclides and trapped noble gases are unusually low in both rocks although kalahari 008 contains slightly higher concentrations a likely reason for this difference is that kalahari 008 is a polymict breccia containing a briefly exposed regolith while kalahari 009 is a monomict brecciated rock that may never have been at the surface of the moon altogether the compositions of kalahari 008 and 009 permit new insight into early lunar evolution as both meteorites sample lunar reservoirs hitherto unsampled by spacecraft missions the very low th and ree content of kalahari 009 as well as the depletion in sm and the lack of a kreep like signature in kalahari 008 point to a possible source far from the influence of the procellarum kreep terrane possibly the lunar farside

40ar 39ar age determinations of lunar basalt meteorites asuka 881757 yamato 793169 miller range 05035 la paz icefield 02205 northwest africa 479 and basaltic breccia elephant moraine 96008 40ar 39ar data are presented for the unbrecciated lunar basaltic meteorites asuka a 881757 yamato y 793169 miller range mil 05035 lapaz icefield lap 02205 northwest africa nwa 479 paired with nwa 032 and basaltic fragmental breccia elephant moraine eet 96008 stepped heating 40ar 39ar analyses of several bulk fragments of related meteorites a 881757 y 793169 and mil 05035 give crystallization ages of 3 763 0 046 ga 3 811 0 098 ga and 3 845 0 014 ga which are comparable with previous age determinations by sm nd u pb th pb pb pb and rb sr methods these three meteorites differ in the degree of secondary 40ar loss with y 793169 showing relatively high ar loss probably during an impact event 200 ma ago lower ar loss in mil 05035 and no loss in a 881757 bulk and impact melt glass bearing samples of lap 02205 gave similar ages 2 985 0 016 ga and 2 874 0 056 ga and are consistent with ages previously determined using other isotope pairs the basaltic portion of eet 96008 gives an age of 2 650 0 086 ga which is considered to be the crystallization age of the basalt in this meteorite the ar release for fragmental basaltic breccia eet 96008 shows evidence of an impact event at 631 20 ma the crystallization age of 2 721 0 040 ga determined for nwa 479 is indistinguishable from the weighted mean age obtained from three samples of nwa 032 supporting the proposal that these meteorites are paired the similarity of 40ar 39ar ages with ages determined by other isotopic systems for multiple meteorites suggests that the k ar isotopic system is robust for meteorites that have experienced a significant shock event and not a prolonged heating regime

40ar 39ar chronology of lunar meteorites northwest africa 032 and 773 the 40ar 39ar dating technique has been applied to the lunar meteorites northwest africa 032 nwa 032 an unbrecciated mare basalt and northwest africa 773 nwa 773 composed of cumulate and breccia lithologies to determine the crystallization age and timing of shock events these meteorites may have experienced stepped heating analyses of several different samples of nwa 032 gave complex age spectra but indistinguishable total ages with a mean of 2 779 0 014 gyr possible causes of the complex age spectra obtained from nwa 032 include recoil of 39ar or the presence of pre shock 40ar incorporated into shock melt veins the effects of shock veins were investigated by laser fusion of 20 small samples expected to contain varying proportions of the shock veins the laser ages show a narrow age distribution between 2 61 2 86 gyr and a mean of 2 73 0 03 gyr identical to the total age of 2 80 gyr obtained for the bulk sample diffusion calculations based on the stepped heating data indicate that ar release can be reconciled by release from feldspar and possibly shock veins at low temperatures followed by pyroxene at higher temperatures the exposure age of nwa 032 is 212 11 myr and it contains low trapped solar ar stepped heating of cumulate and breccia portions of nwa 773 also give a relatively young age of 2 91 gyr the presence of trapped ar in the breccia makes the age determination of this component less precise but release of ar appears to be from the same mineral phase assumed to be plagioclase in both lithologies a marked difference in exposure age between the 2 lithologies also exists with the breccia having spent 81 myr longer at the lunar surface this finding is consistent with the higher trapped ar content of this lithology assuming that 2 80 gyr and 2 91 gyr are the crystallization ages of nwa 032 and nwa 773 respectively these two meteorites are the youngest lunar mare basalts available for study

the 2005 eruption of ilamatepec santa ana volcano el salvador abstract we report the stratigraphic sequence of the 2005 eruption of ilamatepec volcano together with sedimentological and chemical analyses of its products structural and textural characteristics of the deposits indicate that the eruption was driven by a small volume rhyolitic intrusion at shallow levels which resulted first in the collapse of the existing hydrothermally altered fan of previous deposits inside the crater lake driving phreatic explosions with launching of blocks on ballistic trajectories later the magma interacted with lake waters producing several hydromagmatic pyroclastic density currents pdcs these flows were energetic enough to knock down pine trees up to distances of 1 8 km from the crater in the e ne sector of the volcano finally ejection of ballistic blocks that landed on previously emplaced wet pyroclastic density current deposits caused the generation of a lahar that flowed down the steep eastern flank toward the el jabillal gully subsequent lahars occurred as a result of intense rain caused by hurricane stan radiocarbon ages on paleosols and charcoal fragments separating previous volcanogenic sequences indicate that similar eruptions have occurred more frequently in the past centuries than previously thought the new data confirms that ilamatepec volcano is one of the most active volcanoes in el salvador nevertheless more detailed studies of the eruptive sequence of ilamatepec volcano are mandatory to establish future eruptive patterns

petrogenesis of lunar mare basalt meteorite miller range 05035 miller range mil 05035 is a low ti mare basalt that consists predominantly of pyroxene 62 3 vol and plagioclase 26 4 vol pyroxenes are strongly shocked and complexly zoned from augite wo33 and pigeonite wo17 cores with mg 50 54 to hedenbergite rims coexisting pyroxene core compositions reflect crystallization temperatures of 1000 to 1100 c plagioclase has been completely converted to maskelynite with signs of recrystallization maskelynite is relatively uniform in composition an94ab6 an91ab9 except at contacts with late stage mesostasis areas elevated k contents an82ab15or3 symplectites intergrowth of fe augite fayalite and silica of different textures and bulk compositions in mil 05035 suggest formation by decomposition of ferro pyroxene during shock induced heating which is supported by the total maskelynitization of plagioclase melt pockets and the presence of a relict pyroxferroite grain petrography and mineral chemistry imply that crystallization of mil 05035 occurred in the sequence of fe poor pyroxenes mg 50 54 followed by plagioclase and fe rich pyroxenes mg 20 50 and finally hedenbergite fe ti oxides and minor late stage phases petrography bulk chemistry mineral compositions and the age of mil 05035 suggest it is possibly source crater paired with asuka a 881757 and yamato y 793169 and may also be launch paired with meteorite hills met 01210 mil 05035 represents an old 3 8 3 9 ga incompatible element depleted low ti basalt that was not sampled during the apollo or luna missions the light ree depleted nature and lack of eu anomalies for this meteorite are consistent with an origin distant from the procellarum kreep terrane and genesis from an early cumulate mantle source region generated by extensive differentiation of the moon

petrography geochronology and source terrain characteristics of lunar meteorites dhofar 925 961 and sayh al uhaymir 449 abstract dhofar dho 925 961 and sayh al uhaymir sau 449 are brecciated lunar meteorites consisting of mineral fragments and clasts from a range of precursor lithologies including magnesian anorthositic gabbronorite granulites crystalline impact melt breccias clast bearing glassy impact melt breccias lithic fragmental breccias mare basalts and evolved silica rich rocks on the similarity of clast type and mineral chemistry the samples are likely grouped and were part of the same parent meteorite phosphate pb pb ages in impact melt breccias and matrix grains demonstrate that dho 961 records geological events spanning 500 ma between 4 35 and 3 89 ga these pb pb ages are similar to the ages of ancient intrusive magmatic samples and impact basin melt products collected on the lunar nearside by the apollo missions however the samples bulk rock composition is chemically distinct from these types of samples and it has been suggested that they may have originated from the farside south pole aitken impact basin i e jolliff et al 2008 we test this hypothesis and conclude that although it is possible that the samples may be from the south pole aitken basin there are other regions on the moon that may have also sourced these complex breccias

nanoscale constraints on the in situ transformation of ru os ir sulfides to alloys at low temperature abstract we report new results of a combined focused ion beam high resolution transmission electron microscopy fib hrtem investigation of two grains of platinum group minerals pgm corresponding to the laurite rus2 erlichmanite oss2 solid solution series the grains are included within unaltered chromite and the serpentine dominant matrix of the mantle hosted chromitite body of monte bueno in eastern cuba at the micron scale the grain hosted in unaltered chromite preserves magmatic features including a complex oscillatory zoning defined by a core of erlichmanite surrounded by alternating bands of os rich os poor laurite revealed by conventional field emission scanning electron microscopy fe sem and x ray mapping by electron microprobe analyzer epma combining high magnification hmem high angle annular dark field haadf images and the corresponding energy dispersive spectra eds the elemental mappings acquired using hrtem showed that the oscillatory zoning occurs at both the micron and nano scales a specific feature highlighted by hrtem observations is the rather complex structure of the erlichmanite core consisting of an aggregation of much smaller cores

magnesian anorthositic granulites in lunar meteorites allan hills a81005 and dhofar 309 geochemistry and global significance abstract fragments of magnesian anorthositic granulite are found in the lunar highlands meteorites allan hills alh a81005 and dhofar dho 309 five analyzed clasts of meteoritic magnesian anorthositic granulite have mg molar mg mg fe 81 87 feo 5 wt al2o3 22 wt rare earth elements abundances 0 5 2 ci except eu 10 ci and low ni and co in a non chondritic ratio the clasts have nearly identical chemical compositions even though their host meteorites formed at different places on the moon these magnesian anorthositic granulites are distinct from other highlands materials in their unique combination of mineral proportions mg ree abundances and patterns ti sm ratio and sc sm ratio their mg is too high for a close relationship to ferroan anorthosites or to have formed as flotation cumulates from the lunar magma ocean compositions of these magnesian anorthositic granulites cannot be modeled as mixtures of or fractionates from known lunar rocks however compositions of lunar highlands meteorites can be represented as mixtures of magnesian anorthositic granulite ferroan anorthosite mare basalt and kreep meteoritic magnesian anorthositic granulite is a good candidate for the magnesian highlands component inferred from apollo highland impactites magnesian feldspathic and ree poor bulk compositions of meteorite magnesian anorthositic granulites are comparable to those inferred for parts of the lunar farside the feldspathic highlands terrane 4 5 wt feo 28 wt al2o3 and th 1 ppm thus magnesian anorthositic granulite may be a widespread and abundant component of the lunar highlands

rock types of south pole aitken basin and extent of basaltic volcanism the enormous pre nectarian south pole aitken spa basin represents a geophysically and compositionally unique region on the moon we present and analyze the mineralogical diversity across this basin and discuss the implications for basin evolution rock types are derived from clementine multispectral data based on diagnostic characteristics of ferrous absorptions in fresh materials individual areas are characterized as noritic dominated by low ca pyroxene gabbroic basaltic dominated by high ca pyroxene feldspathic 3 6 feo and olivine gabbro dominated by high ca pyroxene and olivine the anorthositic crust has effectively been removed from the interior of the basin the style of volcanism within the basin extends over several 100 myr and includes mare basalt and pyroclastic deposits several areas of ancient pre orientale volcanism or cryptomaria have also been identified the nonmare mafic lithology that occurs across the basin is shown to be noritic in composition and is pervasive laterally and vertically we interpret this to represent impact melt breccia deposits derived from the lower crust a few localized areas are identified within the basin that contain more diverse lithologies gabbro olivine gabbro some of which may represent material from the deepest part of the lower crust and perhaps uppermost mantle involved in the spa event

cryptomare magmatism 4 35 gyr ago recorded in lunar meteorite kalahari 009 the origin and evolution of the moon remain controversial one notable point of controversy being the timing of the beginning and end of basaltic volcanism in the lunar mares or plains lunar research over the past three decades has suggested that mare volcanism occurred mainly after the late heavy bombardment that ended 3 9 billion years ago because most of known mare basalts lunar meteorites and returned apollo and luna samples and remote sensing data indicate crystallization ages younger than 3 9 billion years but a new u pb dating of minerals in the lunar meteorite kalahari 009 gives an age of roughly 4 35 billion years for a lunar basalt this suggests that the volcanism started as early as 4 35 billion years ago relatively soon after lunar formation and differentiation and that kalahari 009 is our first sample of a cryptomare from the moon the result of u pb dating of minerals in a lunar meteorite kalahari 009 is reported analyses of five grains associated with basaltic clasts give an age of 4 35 0 15 billion years these are thought to represent the crystallization ages of parental basalt magma making kalahari 009 one of the oldest known mare basalt this suggests that mare basalt volcanism on the moon started as early as 4 35 billion years ago the origin and evolution of the moon remain controversial1 2 with one of the most important questions for lunar evolution being the timing and duration of basaltic mare magmatism1 3 4 5 6 7 8 here we report the result of ion microprobe u pb dating of phosphates in a lunar meteorite kalahari 009 which is classified as a very low ti mare basalt breccia in situ analyses of five phosphate grains associated with basaltic clasts give an age of 4 35 0 15 billion years these ancient phosphate ages are thought to represent the crystallization ages of parental basalt magma making kalahari 009 one of the oldest known mare basalts we suggest that mare basalt volcanism on the moon started as early as 4 35 gyr ago relatively soon after its formation and differentiation and preceding the bulk of lunar volcanism which ensued after the late heavy bombardment around 3 8 3 9 gyr refs 7 and 8 considering the extremely low abundances of incompatible elements such as thorium and the rare earth elements in kalahari 009 ref 9 and recent remote sensing observations illustrating that the cryptomaria tend to be of very low ti basalt type10 11 12 we conclude that kalahari 009 is our first sample of a very low ti cryptomare from the moon

lunar meteorite regolith breccias an in situ study of impact melt composition using la icp ms with implications for the composition of the lunar crust dar al gani dag 400 meteorite hills met 01210 pecora escarpment pca 02007 and macalpine hills mac 88104 88105 are lunar regolith breccia meteorites that provide sampling of the lunar surface from regions of the moon that were not visited by the us apollo or soviet luna sample return missions they contain a heterogeneous clast population from a range of typical lunar lithologies dag 400 pca 02007 and mac 88104 88105 are primarily feldspathic in nature and met 01210 is composed of mare basalt material mixed with a lesser amount of feldspathic material here we present a compositional study of the impact melt and impact melt breccia clast population i e clasts that were generated in impact cratering melting processes within these meteorites using in situ electron microprobe and la icp ms techniques results show that all of the meteorites are dominated by impact lithologies that are relatively ferroan mg 10 and have low incompatible trace element ite concentrations i e typically 10 ppm sm high magnesium suite typically 70 mg or high alkali suite high ites sc sm ratios 2 target rocks instead the meteorite mafic melts are more ferroan kreep poor and sc rich and represent mixing between feldspathic lithologies and low ti or very low ti vlt basalts as pca 02007 and mac 88104 05 were likely sourced from the outer feldspathic highlands terrane our findings suggest that these predominantly feldspathic regions commonly contain a vlt to low ti basalt contribution

alha 81005 meteorite chemical evidence for lunar highland origin based on the well established characteristic lunar and meteoritic ratios of feo mno cr2o3 v and k la and ree patterns alha 81005 meteorite is undoubtedly of lunar highland origin the alha 81005 meteorite is an anorthositic gabbro 72 pl and matches closely in chemical composition to apollo 15 15418 and luna 16 21013 highland rocks the rock is a non kreepy and vlt type the siderophiles au ni and ir content is high 1 5 cl equivalent and similar to other lunar highland breccias the clast has a different ancient meteorite component than the bulk and matrix the meteorite has a young terrestrial age implying a recent lunar cratering event therefore during major lunar basins formation in early eons the earth must have received a significant amount of lunar material which is now mixed in the crust the finding of a lunar meteorite lends credibility to the suggestion that snc achondrites may come from mars

antarctic meteorite alha 81005 a piece from the ancient lunar crust a 128 mg sample of the antarctic meteorite alha 81005 was analysed for major and trace elements by instrumental neutron activation techniques the meteorite or at least its major components may be older than 4 billion years and represent a piece of the ancient lunar crust before the formation of the large basins on the front side of the moon the evidence is derived from the low absolute content of incompatible elements and their slightly different fractionation pattern from kreep the dominant source for these elements on the front side the basically chondritic pattern of siderophile elements ni co ir au is clearly distinguished from younger basin related meteoritic components

distinguishing high alumina mare basalts using clementine uvvis and lunar prospector grs data mare moscoviense and mare nectaris 1 high alumina ha mare basalts are a unique group of the lunar sample collection sample geochemistry indicates that these basalts are derived from sources composed of late stage cumulates from the lunar magma ocean lmo their aluminous nature suggests their sources contained significant plagioclase which has implications regarding the efficiency of plagioclase separation from earlier forming mafic cumulates in the lmo to form the anorthositic lunar crust and hence the heterogeneity of the lunar mantle the apollo and luna missions sampled ha basalts from four different locations that are separated by 80 equatorial degrees 2400 km radiometric age dating of these samples demonstrates aluminous basaltic volcanism spanned over 1 billion years suggesting ha basalts may be more prevalent on the moon than implied by the sample population knowing their global occurrence would ultimately enhance our understanding of lunar evolution aluminous mare basalts occupy a unique location in th feo compositional space that suggests they can be identified using global remote sensing data of the moon we present our approach for distinguishing exposures of ha basalts using clementine ultraviolet visible infrared uvvis and lunar prospector gamma ray spectrometer lp grs data with constraints based on the feo tio2 and th abundances of apollo and luna ha samples we identified 34 regions of interest rois where ha basalts could be a prominent component of the lunar surface by analyzing the rims and proximal ejecta from small impacts 0 4 4 km in diameter into the mare surface we characterized compositionally distinct basaltic units that make up the mare and thus determined which units represent ha basalt lavas the results were used to generate maps that depict discrete mare units and classify their general basalt type here we focus on two rois mare moscoviense and mare nectaris mare moscoviense is composed of four basaltic units two of which are ha candidates clementine uvvis data of mare nectaris show evidence of up to three mare basalt units one is the remnants of a mid ti unit that capped earlier low ti flows the majority of the basin is filled by a compositionally indistinguishable low fe low ti basalt however spectral profiles suggest there are two units regardless the units both fit the criteria for a ha basalt

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

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

evidence for an ancient osmium isotopic reservoir in earth iridosmine grains from placer deposits associated with peridotite bearing ophiolites in the klamath mountains have extremely radiogenic 186 os 188 os ratios and old re os minimum ages from 256 to 2644 million years this indicates the existence of an ancient platinum group element reservoir with a supra chondritic pt os ratio such a ratio may be produced in the outer core as a result of inner core crystallization that fractionates os from pt however if the iridosmine os isotopic compositions are a signature of the outer core then the inner core must have formed very early within several hundred million years after the accretion of earth

lunar meteorites from oman abstract sixty named lunar meteorite stones representing about 24 falls have been found in oman in an area of 10 7 103 km2 in southern oman lunar meteorite areal densities average 1 g km 2 all lunar meteorites from oman are breccias although two are dominated by large igneous clasts a mare basalt and a crystalline impact melt breccia among the meteorites the range of compositions is large 9 32 al2o3 2 5 21 1 feo 0 3 38 g g 1 sm and 1 to 22 5 ng g 1 ir the proportion of nonmare lunar meteorites is higher among those from oman than those from antarctica or africa omani lunar meteorites extend the compositional range of lunar rocks as known from the apollo collection and from lunar meteorites from other continents some of the feldspathic meteorites are highly magnesian high mgo mgo feo compared with most similarly feldspathic apollo rocks two have greater concentrations of incompatible trace elements than all but a few apollo samples a few have moderately high abundances of siderophile elements from impacts of iron meteorites on the moon all lunar meteorites from oman are contaminated to various degrees with terrestrial na k p zn as se br sr sb ba u carbonates or sulfates the contamination is not so great however that it seriously compromises the scientific usefulness of the meteorites as samples from randomly distributed locations on the moon

osmium isotopes in ophiolites re and os concentrations and os isotopic composition are reported for ultramafic samples from ophiolites these data may be divided into two groups on the one hand isotopic values higher than mean upper mantle 187os 186os 1 05 correspond to back arc type ophiolites and could reflect injection of crustal material sediments on the other hand ophiolites referred to as being typical n morb plot very close to previous estimates for mean upper mantle 1 05 together with refined osmiridium results from well dated ultramafic suites the data on ophiolites lead to the following constraints 1 present day 187os 186os for the upper mantle seems for the time being constrained around 1 05 1 06 2 the mantle evolution curve for osmium isotopes through time when associated to recent os isotopic determinations from the literature for archaean samples shows a chondritic 187re 186os ratio of 3 33 and a linear closed system evolution

thorium abundances of basalt ponds in south pole aitken basin insights into the composition and evolution of the far side lunar mantle 1 imbrian aged basalt ponds located on the floor of south pole aitken spa basin are used to provide constraints on the composition and evolution of the far side lunar mantle we use forward modeling of the lunar prospector gamma ray spectrometer thorium data to suggest that at least five different and distinct portions of the far side lunar mantle contain little or no thorium as of the imbrian period we also use spatial correlations between local thorium enhancements and nonmare material on top of the basalt ponds to support previous assertions that lower crustal materials exposed in spa basin have elevated thorium abundances consistent with noritic to gabbronoritic lithologies we suggest that the lower crust on the far side of the moon experienced multiple intrusions of thorium rich basaltic magmas prior to the formation of spa basin the fact that many of the ponds on the lunar far side have elevated titanium abundances indicates that the far side of the moon experienced extensive fractional crystallization that likely led to the formation of a kreep like component however because the imbrian aged basalts contain no signs of elevated thorium we propose that the spa impact event triggered the transport of a kreep like component from the lunar far side and concentrated it on the nearside of the moon because of the correlation between basaltic ponds and basins within spa we suggest that imbrian aged basaltic volcanism on the far side of the moon was driven by basin induced decompressional melting

unexpectedly high pge chromitite from the deeper mantle section of the northern oman ophiolite and its tectonic implications unusually high platinum group element pge enrichments are reported for the first time in a podiform chromitite of the northern oman ophiolite the chromitite contains 1 5 ppm of total pge being highly enriched in the ipge subgroup ir os and ru and strongly depleted in the ppge subgroup rh pt and pd its platinum group minerals pgms are classified into three types arranged in order of abundance 1 sulphides os rich laurite laurite erlishmanite solid solution and an unnamed ir sulphide 2 alloys os ir alloy and ir rh alloy and 3 sulpharsenides irarsite and hollingworthite the high pge concentrations are observed only in a discordant chromitite deep in the mantle section which has high cr 0 7 spinel with an olivine matrix all the other types of chromitite in the moho transition zone mtz and concordant pods in the deeper mantle section are poor in pges and tend to have spinels with lower cr up to 0 6 this diversity of chromitite types suggests two stages of magmatic activity were responsible for the chromitite genesis in response to a switch of tectonic setting the first is residual from lower degree partial melting of peridotite which produced low cr pge poor chromitites at the moho transition zone and to a lesser extent within the mantle possibly beneath a fast spreading mid ocean ridge the second chromitite forming event involves higher degree partial melting which produced high cr pge rich discordant chromitite in the upper mantle possibly in a supra subduction zone setting

metamorphism disturbs the re os signatures of platinum group minerals in ophiolite chromitites the os isotope compositions of platinum group minerals pgms in ophiolite chromitites are commonly regarded as resistant to fluid related processes and have been used to track the evolution of earth s convecting mantle however we have found significant differences in 187os 188os between primary and secondary pgms from metamorphosed ophiolite chromitites of the dobromirtsi ultramafic massif in the central rhodope metamorphic core complex of southeastern bulgaria primary magmatic pgms hosted in unaltered chromite cores have 187os 188os from 0 1231 to 0 1270 and 187re 188os 0 002 t ma and t rd model ages calculated relative to the enstatite chondrite reservoir cluster around three main peaks ca 0 3 0 4 and 0 6 ga secondary pgms produced by alteration of magmatic pgms have a wider range of variation 187os 188os 0 1124 0 1398 187re 188os 0 024 these grains yield t ma and t rd model ages from 1 7 ga up to 2 2 ga the larger range in 187os 188os in the secondary pgms is interpreted as due to reactions between the primary pgms and infiltrating metamorphic hydrothermal fluids with a range of os isotope compositions this redistribution of os in pgms during metamorphism has significant implications for the interpretation of both whole rock and in situ os isotope data in mantle derived rocks

a petrological mineralogical and chemical analysis of the lunar mare basalt meteorite lapaz icefield 02205 02224 and 02226 lapaz icefield lap 02205 02226 and 02224 are paired stones of a crystalline basaltic lunar meteorite with a low ti 3 21 3 43 tio2 low al 9 93 10 45 al2o3 and low k 0 11 0 12 k2o composition they consist mainly of zoned pyroxene and plagioclase grains with minor ilmenite spinel and mesostasis regions large possibly xenocrystic forsteritic olivine grains 3 by mode contain small trapped multiphase melt inclusions accessory mineral and mesostasis composition shows that the samples have with silica oversaturation and late stage liquid immiscibility our section of lap 02224 has a vesicular fusion crust implying that it was at one time located sufficiently close to the lunar surface environment to have accumulated solar wind implanted gases the stones have a comparable major element composition and petrography to low ti low al basalts collected at the apollos 12 and 15 landing sites however the lap stones also have an enriched ree bulk composition and are more ferroan mg numbers in the range of 31 to 35 than similar apollo samples suggesting that they represent members of a previouslyunsampled fractionated mare basalt suite that crystallized from a relatively evolved lunar melt

highly silicic compositions on the moon using data from the diviner lunar radiometer experiment we show that four regions of the moon previously described as red spots exhibit mid infrared spectra best explained by quartz silica rich glass or alkali feldspar these lithologies are consistent with evolved rocks similar to lunar granites in the apollo samples the spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar the variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the moon basaltic underplating is the preferred mechanism for silicic magma generation leading to the formation of extrusive landforms this mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies

composition of bulk samples and a possible pristine clast from allan hills a81005 abundances of thirty five elements were determined in two bulk samples and a white clast in the allan hills a81005 meteorite high siderophile element content indicates that the sample is a regolith breccia an fe mn ratio of 77 in this meteorite eliminates parent bodies of known differentiated meteorites as the source of alha 81005 the incompatible elements are very similar to those found in most lunar highlands rocks and provide very strong evidence that the sample is lunar in origin the clast sample has the trace element pattern of a lunar anorthosite and is very low in kreep and siderophile elements it may be a fragment of a pristine lunar rock

genesis of sulfide rich chromite ores by the interaction between chromitite and pegmatitic olivine norite dikes in the potosi mine moa baracoa ophiolitic massif eastern cuba the potosi mine is located in the moa baracoa massif in the easternmost part of the cuban ophiolitic belt chromite mineralization occurs within the mantle crust transition zone two events of magma intrusion overprint the chromitite bodies one gave rise to the crystallization of pegmatitic olivine norite dikes and the other produced pegmatitic gabbro dikes sulfide poor chromite ores brecciated chromite ores and sulfide rich chromite ores can be distinguished in the different chromitite bodies sulfide poor ores represent more than 80 vol of the chromitites this type occurs far from the zones intruded by pegmatitic gabbro dikes and shows petrographic and chemical features similar to other chromitite bodies described in the moa baracoa massif brecciated chromite ores occur within pegmatitic gabbro dikes in this type chromite crystals occur included within chromian diopside and plagioclase these silicates often contain droplet like sulfide aggregates sulfide rich ores are spatially associated to the contacts between sulfide poor chromite and pegmatitic olivine norite dikes these ores mainly consist of recrystallized coarse chromite with interstitial pyrrhotite pentlandite cubanite and chalcopyrite chromite from sulfide rich ores exhibits tio2 feo v2o3 mno and especially fe2o3 contents higher than those of chromite from brecciated ores and much higher than those of chromite from sulfide poor ores the sulfide rich ores are pge rich up to 1 113 ppb of total pge and show nearly flat chondrite normalized pge patterns slightly above 0 1 times chondritic values mineralogical and chemical data indicate that the chromite ores of the potosi mine were modified by the intrusions of olivine norite and gabbro dikes the interaction between pre existing sulfide poor chromite ores and the intruding volatile rich silicate melts produced strong brecciation partial dissolution and recrystallization coarsening of chromite the sulfide assemblage formed by fractionation of the immiscible sulfide melt segregated from the volatile rich silicate melt that generated the pegmatitic olivine norite the segregation of the sulfide melt can be interpreted as the consequence of chemical interaction between intruding melts and the host chromite the variable extent of this interaction produced chromite ores with variable sulfide ratios the magmatic nature of the sulfide mineralization is supported by sulfur isotope data which range from 0 4 to 0 9 sulfide melt collected incompatible pge rh pt pd to produce the typical flat chondrite normalized pattern of sulfide rich chromite ores

thorium abundances on the lunar surface measurements of absolute thorium abundances on the lunar surface are presented using both the high and low altitude data taken with the lunar prospector gamma ray spectrometer an analysis of the uncertainties shows that the measured uncertainties are 7 g g are likely small area regions 150 km 2 using lunar topographic data we have shown that the thorium abundances in the lunar high lands and portions of south pole aitken spa basin are larger for lower elevations we have also studied a number of regions with anomalously high thorium abundances such as the northwestern region of spa basin the crater arago in western tranquillitatis and the compton belkovich region in the northeastern highlands the compton belkovich region appears to be enriched with evolved rocks such as alkali anorthosite and currently represents the only such extended region on the moon that has been identified in contrast tycho crater has very low thorium abundances which suggests that kreep was not assimilated at depth in this portion of the moon

lunar regolith breccia dhofar 287b a record of lunar volcanism dhofar 287 dho 287 a recently found lunar meteorite consists in large part 95 of low ti mare basalt dho 287a and a minor attached portion 5 of regolith breccia dho 287b the present study is directed mainly at the breccia portion of this meteorite this breccia consists of a variety of lithic clasts and mineral fragments set in a fine grained matrix and minor impact melt the majority of clasts and minerals appear to have been mainly derived from the low ti basalt suite similar to that of dho 287a very low ti vlt basalts are a minor lithology of the breccia these are significantly lower in mg and slightly higher in ti compared to luna 24 and apollo 17 vlt basalts picritic glasses constitute another minor component of the breccia and are compositionally similar to apollo 15 green glasses dho 287b also contains abundant fragments of mg rich pyroxene and anorthite rich plagioclase grains that are absent in the lithic clasts such fragments appear to have been derived from a coarse grained mg rich na poor lithology a kreep component is apparent in chemistry but no highlands lithologies were identified the dho 287 basaltic lithologies cannot be explained by near surface fractionation of a single parental magma instead magma compositions are represented by a picritic glass a low ti na poor glass and a low ti na enriched source similar to the dho 287a parental melt compositional differences among parent melts could reflect inhomogeneity of the lunar mantle alternatively the low ti na poor and dho 287a parent melts could be of hybrid compositions resulting from assimilation of kreep by picritic magma thus the dho 287b breccia contains lithologies from multiple magmatic eruptions which differed in composition formational conditions and cooling histories based on this study the dho 287 is inferred to have been ejected from a region located distal to highlands terrains possibly from the western limb of the lunar nearside dominated by mare basalts and kreep rich lithologies

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

lunar feldspathic meteorites constraints on the geology of the lunar highlands and the origin of the lunar crust abstract the composition of the lunar crust provides clues about the processes that formed it and hence contains information on the origin and evolution of the moon current understanding of lunar evolution is built on the lunar magma ocean hypothesis that early in its history the moon was wholly or mostly molten this hypothesis is based on analyses of apollo samples of ferroan anorthosites 90 plagioclase molar mg mg fe mg 75 and the assumption that they are globally distributed however new results from lunar meteorites which are random samples of the moon s surface and remote sensing data show that ferroan anorthosites are not globally distributed and that the apollo highland samples used as a basis for the model are influenced by ejecta from the imbrium basin in this study we evaluate anorthosites from all currently available adequately described lunar highland meteorites representing a more widespread sampling of the lunar highlands than apollo samples alone and find that 80 of them are significantly more magnesian than apollo ferroan anorthosites interestingly luna mission anorthosites collected outside the continuous imbrium ejecta are also highly magnesian if the lunar highland crust consists dominantly of magnesian anorthosites as suggested by their abundance in samples sourced outside imbrium ejecta a reevaluation of the lunar magma ocean model is a sensible step forward in the endeavor to understand lunar evolution our results demonstrate that lunar anorthosites are more similar in their chemical trends and mineral abundance to terrestrial massif anorthosites than to anorthosites predicted in a lunar magma ocean this analysis does not invalidate the idea of a lunar magma ocean which seems a necessity under the giant impact hypothesis for the origin of the moon however it does indicate that most rocks now seen at the moon s surface are not primary products of a magma ocean alone but are products of more complex crustal processes

compositional implications regarding the lunar origin of the alha81005 meteorite geochemically alha81005 has all the attributes expected of a regolith sample from the lunar highlands most important is its fe mn ratio 77 within uncertainty the same as the mean lunar ratio there are significant differences however in comparison to previously sampled lunar regoliths the closest precedents are the apollo 16 and luna 20 regoliths particularly the latter but alha81005 has lower contents of na ti and incompatible elements feldspathic granulitic breccias such as 72559 which texturally resemble the most abundant type of clast in alha81005 are also similar compositionally from its low kreep and na contents we infer alha81005 originated well away from the k th and u rich region near the center of the nearside at least as far away as the eastern limb

high cr and high al chromitites from the sagua de tanamo district mayari cristal ophiolitic massif eastern cuba constraints on their origin from mineralogy and geochemistry of chromian spinel and platinum group elements article i nfo several chromitite bodies of variable sizes are hosted in dunite harzburgite of the small b3 km mining district of sagua de tanamo in the mayari cristal ophiolitic massif eastern of cuba the chromian spinel in these bodies displays a large range in cr cr cr al atomic ratio from 0 74 to 0 45 in high cr chromitites cr and ti contents increase from harzburgite to dunite to chromitite a roughly opposite trend of variation in cr is observed in high al chromitites although in this case ti distributes randomly the differences in the type of chromian spinel i e high cr or high al in the chromitite coincide with a different behavior of the platinum group elements pge whereas high cr chromitites are rich in pge and contain abundant grains of platinum group minerals pgm high al chromitites are systematically poor in pge and in pgm the calculated melts in equilibrium with chromian spinel of high cr chromitite are island arc thoeliites iat with boninitic affinity whereas those in equilibrium with chromian spinel of high al chromitites are back arc basin basalts babb the formation of high cr chromitites is interpreted as a result of the extensive reaction of harzburgite with migrating island arc tholeiite melts of boninitic affinity melt rock reaction produces boninitic melts with variable composition and porous dunitic channels in which the mixing mingling of melts promotes crystallization of mononomineralic high cr chromian spinel in contrast high al chromitites formed by the mixing mingling of babb melts within conduits not in equilibrium with dunite percolation of primitive babb melts through pre existing dunite dissolved olivine producing melt conduits in which babb melts mixed and formed high al chromian spinel the higher pge and pgm in high cr chromitites is not only a function of the degree of partial melting but is linked to interaction between the migrating melt and mantle harzburgite during the formation of the chromitite the coexistence of both types of chromitites in one small mining district reflects the temporal and or spatial variations of separate melt intrusions emplaced in different subarc mantle domains during the opening of a back arc basin in a supra subduction zone environment

mineralogy and petrology of the lapaz icefield lunar mare basaltic meteorites five basaltic meteorites from the lapaz ice field are paired on the basis of their mineralogy and texture and represent a unique basalt type distinct from those in the apollo or luna sample collections lapaz icefield lap 02205 lap 02224 lap 02226 lap 02436 and lap 03632 all contain plagioclase pyroxene ilmenite spinel olivine and minor troilite metal phosphate baddeleyite and silica cristobalite brown glassy melt veins are ubiquitous and cross the primary igneous texture plagioclase the major mineral and occurring as laths in a subophitic texture is of narrow compositional range from an85 89 pyroxene also a major mineral is strongly zoned from augite and pigeonite cores to very iron rich rims ilmenite laths comprise approximately 3 5 of the basalts spinels show a large compositional range comparable to that documented in apollo 15 basalts indicating an early chromite rich stage followed by an intermediate to late stage with cr rich ulvspinel relatively large subhedral to skeletal olivine crystals fo46 62 are sparse and are too forich to be in equilibrium with the bulk rock indicating that these are xenocrysts rather than phenocrysts the presence of melt veins with a similar composition to the bulk rock maskelynitized plagioclase feldspar and metastable cristobalite indicate that these rocks underwent significant shock between 30 and 50 gpa calculated oxygen fugacity using spinel ilmenite iron metal equilibria is within the range defined by previous studies of lunar materials the bulk composition low mgo and low calculated temperatures together with modelling calculations indicate an origin by fractional crystallization of a more primitive low tio2 parent liquid similar to apollo 12 olivine basalt

siderophile lithophile and mobile trace elements in the lunar meteorite allan hills 81005 contents of siderophilic as au co ga and sb volatile mobile ag bi cd in se te tl and zn and lithophilic cs rb and u determined by radiochemical neutron activation analysis in alh a81005 are similar to those of lunar highlands samples returned by apollo missions indicating this meteorite s lunar origin five elements co ga and lithophiles reflect lunar crustal processes while the remaining 11 siderophile and mobile elements including the most mobile ones indicate 1 4 0 5 micrometeorite cl equivalent admixture or enrichment by thermal redistribution on the moon thus in contrast to l chondrites where severe shock caused trace element loss impact launching of alh a81005 to earth was free of substantial 20 gpa shock loading in this light a martian origin for severely shocked snc meteorites is plausible

the petrology and geochemistry of miller range 05035 a new lunar gabbroic meteorite miller range mil 05035 is a lunar gabbroic meteorite the mineralogy fe mn ratios in olivine and pyroxene bulk rock chemical composition and the bulk oxygen isotope values 17o 2 86 2 97 and 18o 5 47 5 71 are similar to those of other mare basalts and are taken as supporting evidence for a lunar origin for this meteorite the sample is dominated by pyroxene grains 54 61 by area mode of thin section along with large plagioclase feldspar 25 36 by mode and accessory quartz ilmenite spinel apatite and troilite the bulk rock major element composition of mil 05035 indicates that the sample has a very low ti vlt to low ti lunar heritage we measure bulk tio2 to be 0 9 wt and has low bulk incompatible trace element ite concentrations akin to samples from the vlt mare basalt suite to account for these geochemical characteristics we hypothesize that mil 05035 s parental melt was derived from a mantle region dominated by early cumulates of the magma ocean comprised principally of olivine and orthopyroxene mil 05035 is likely launch paired with the asuka 881757 and yamato 793169 basaltic lunar meteorites and the basaltic regolith breccia met 01210 this group of meteorites y a m m therefore may be a part of a stratigraphic column consisting of an upper regolith environment underlain by a coarsening downwards basalt lava flow

the lunar regolith chemistry mineralogy and petrology the lunar regolith a several meter thick layer of unconsolidated debris forms the interface between the moon and its space environment the regolith forms from lithic sources by the destructional processes of comminution and the constructional processes of agglutinate formation in this manner a steady state soil can develop and will remain in a type of dynamic equilibrium until the system is disturbed by burial or mixing with new soil mixing takes place mainly on a local scale vertically through meters and horizontally over several kilometers lateral transport is a relatively inefficient process and therefore most of the lunar soil components were derived locally there is no evidence for preferential transport of the finer soil fractions relative to the coarser fractions the truly exotic derived at distances of tens of kilometers component is generally in low abundance 1 therefore remotely sensed data should provide a reasonably accurate picture of bedrock geology the chemical composition of the regolith varies with grain size the 10 m fraction is chemically fractionated from the bulk soil in most cases the 10 m fraction is enriched in al2o3 cao na2o k2o light rare earth elements and th and depleted in mgo feo mno and sc these systematics are largely a result of simple comminution with feldspar and friable mesostasis from local source rocks concentrating in the finest fraction there is evidence that agglutinate glass forms preferentially by fusion of the finest soil fractions therefore agglutinate glass like the 10 m soil fraction appears to be fractionated from bulk soil compositions highland soils are distinct from mare soils both chemically and petrologically soil samples collected near mare highland contacts are mixtures of the two lithologies mineral chemical systematics of monomineralic fragments in the lunar soil provide important clues to soil provenance they can in some cases sort out the highland mare contributions and in special cases can even further pinpoint a lithic source in theory lunar regolith cores can serve as solar probes recording the sun s activity over billions of years in practice this has generally not been the case the formation and evolution of most cores is still poorly understood for most we have not established how they formed for example how many depositional and erosional events were involved what the time span involved in the accretion of the sampled soil column was and how long that soil column has remained in situ without this information it is difficult if not impossible to read the sun s record more interdisciplinary studies on cores must be carried out before they can be used as solar probes

volcanism in mare fecunditatis and mare crisium ar ar age studies the laser 40ar 39ar dating technique has been applied to five luna 16 basalt fragments and one impact glass and nine luna 24 basalt fragments and one breccia the textures of these basalts are fine grained ophitic and coarse grained basalts the samples contain high levels of solar and lunar atmospheric argon acquired during their residence on the lunar surface these trapped argon components are predominantly released at low temperature steps and can be distinguished from radiogenic and cosmogenic released at intermediate and high temperature steps the apparent ages obtained for luna 16 samples span a narrow range of 3 29 to 3 38 ga a young age of 0 988 ga was obtained for a basaltic impact glass indicating the age of an impact event in the vicinity of luna 16 landing site the ages obtained for luna 24 samples suggest the existence of at least three periods of volcanism occurring over a protracted interval of between 3 45 and 2 52 ga the long period of volcanism suggested for the mare crisium was likely due to a combination of geophysical and geochemical features in the surrounding and underlying areas of the crisium basin attempts at dating three luna 20 samples were inconclusive due to their high trapped argon contents

lunar surface geochemistry global concentrations of th k and feo as derived from lunar prospector and clementine data abstract accurate estimates of global concentrations of th k and feo have an important bearing on understanding the bulk chemistry and geologic evolution of the moon we present empirical ground truth calibrations transformations for lunar prospector gamma ray spectrometer data k and th and a modified algorithm for deriving feo concentrations from clementine spectral reflectance data that incorporates an adjustment for tio 2 content the average composition of soil samples for individual landing sites is used as ground truth for remotely sensed data among the apollo and luna sites apollo 12 and 14 provide controls for the incompatible element rich compositions apollo 16 and luna 20 provide controls for the feldspathic and incompatible element poor compositions and apollo 11 15 and 17 and luna 16 and 24 provide controls for fe rich compositions in addition to these apollo and luna sample data we include the composition of the feldspathic lunar meteorites as a proxy for the northern farside highlands to extend the range of the calibration points thus providing an additional anorthositic end member composition these empirical ground truth calibrations for lunar prospector th and k provide self consistency between the existing derived data and lunar sample data clementine spectral reflectance data are used to construct a tio 2 sensitive feo calibration that yields higher feo concentrations in areas of high fe low ti mare basalt rich surfaces than previous feo algorithms the data set so derived is consistent with known sample compositions and regolith mixing relationships

re os sm nd isotope and ree systematics on ultramafic rocks and pillow basalts from the earth s oldest oceanic crustal fragments isua supracrustal belt and ujaragssuit nunât area w greenland abstract ultramafic rocks and associated pillow basalts from the western northwestern sector of the isua supracrustal belt isb west greenland reveal a complex pattern of trace elements mainly with respect to their rare earth elements ree the heterogeneity of lree patterns in combination with widely scattering end t 3 81 ga values between 3 7 and 12 4 indicate that the ree systematics of the samples were disturbed by one or more metamorphic events which took place some considerable time after the original crystallization of the isua belt furthermore lree rich metasomatic fluids associated with the emplacement of tonalites into the supracrustals may have significantly altered the primary trace element budget extreme variations in whole rock os t 3 81 ga values of these rocks ranging from 8500 to 9 are favorably interpreted to derive from re additions during fluid hydrothermal alterations accompanying the early and late archean metamorphic events in contrast the re os isotope system remained intact in ultramafic hosted chromites from isua and from the ujaragssuit nun t area about 20 km se of the isb an average os t 3 81 ga value of 1 3 2 5 2 for the chromite population covers the entire range defined by the chondritic average the convecting primitive upper mantle pum nature 383 1996 517 geochim cosmochim acta 65 2001 1311 and models involving outer core entrainment at this time given the uncertainty in the origin of the ultramafic rocks and thus the chromites and the very high degree of alteration of these rocks within the isb our data do not conclusively allow to further impinge on the petrogenesis of the isb mantle derived rocks our data are the first though to vaguely hint at an early archean mantle with a possible slightly suprachondritic initial 187os 188os isotopic composition similarities of unaltered pillow basalts with phanerozoic boninites chem geol 184 2002 231 may indicate a formation in an intra oceanic subduction zone like geodynamic process in which extreme early hadean depletion of a mantle source by melt extraction was followed by a second stage of melting induced by enriched subduction components alternatively core mantle interaction as a plausible mechanism for possible weak 187os enrichments in these rocks remains a valid hypothesis

on the structure of mare basalt lava flows from textural analysis of the lapaz icefield and northwest africa 032 lunar meteorites quantitative textural data for northwest africa nwa 032 and the lapaz lap mare basalt meteorites lap 02205 lap 02224 lap 02226 and lap 02436 provide constraints on their crystallization and mineral growth histories in conjunction with whole rock and mineral chemistry textural analysis provides powerful evidence for meteorite pairing petrographic observations and crystal size distribution csd measurements of nwa 032 indicate a mixed population of slowly cooled phenocrysts and faster cooled matrix lapaz basalt crystal populations are consistent with a single phase of nucleation and growth spatial distribution patterns sdp of minerals in the meteorites highlight the importance of clumping and formation of clustered crystal frameworks in their melts succeeded by continued nucleation and growth of crystals this process resulted in increasingly poor sorting during competition for growth as the melt crystallized based on csd and sdp data we suggest a potential lava flow geometry model to explain the different crystal populations for nwa 032 and the lapaz basalts this model involves crystallization of early formed phenocrysts at hypabyssal depths in the lunar crust followed by eruption and flow differentiation on the lunar surface lava flow differentiation would allow for formation of a cumulate base and facilitate variable cooling within the stratigraphy explaining the varied textures and modal mineralogies of mare basalt meteorites the model may also provide insight into the relative relationships of some apollo mare basalt suites shallow level crystal fractionation processes and the nature of mare basalt volcanism over lunar history

antarctic meteorite alha81005 not just another lunar anorthositic norite seven subsamples of meteorite alha81005 a regolith breccia from the lunar highlands were analyzed by inaa for 32 elements four of them were also studied petrographically in bulk composition the rock corresponds to anorthositic norite with a very small component of kreep and is very similar to estimates of average lunar highlands surface compositions of the white clasts and the dark matrix are similar but the clasts are more magnesian and 30 50 as rich in kreep related elements the white clasts have fine grained granulitic textures and are generally similar to apollo 16 and 17 granulitic anorthositic norites but are more magnesian and only 20 as rich in kreep related elements some granulitic clasts are dominated by a magnesian anorthositic norite component not represented among the pristine apollo samples

water and dissolved gas geochemistry at coatepeque ilopango and chanmico volcanic lakes el salvador central america abstract coatepeque on the e slope of santa ana volcano ilopango inside ilopango caldera and chanmico associated with san salvador volcano are volcanic lakes in el salvador showing a thermocline at a relatively shallow depth from 30 to 40 m from 20 to 40 m and from 5 to 15 m depth respectively and anoxic conditions below 33 24 and 4 m depth respectively the na cl composition of the coatepeque and ilopango lakes displaying tds values up to 1226 and 1216 mg l respectively is likely due to hydrothermal fluids that feed these two lakes as also confirmed by cl br molar ratios 650 high as b li and si contents and cl so42 ratio 1 the mg2 hco3 water composition of lake chanmico whose tds values were between 566 and 856 mg l suggests water rock interaction processes with mafic ultramafic rocks variably affected by serpentinization processes which produced high mg2 si and b concentrations waters at depth were characterized by the presence of co2 from an extra lacustrine source as suggested by 13c co2 values significantly less negative than those typically related to biogenic processes albeit this gas was found in smaller quantities when compared to those recorded in other meromictic lakes hosted in quiescent volcanic systems e g lake kivu in drc monticchio albano and averno lakes in italy hule and rio cuarto lakes in costa rica lake pavin in france the occurrence of ch4 whose concentrations in lake chanmico were up to two orders of magnitude higher than those recorded in coatepeque and ilopango lakes suggests bacterial methanogenesis

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

in quest of lunar regolith breccias of exotic provenance a uniquely anorthositic sample from the fra mauro apollo 14 highlands polymict samples can be used to establish mass balance constraints regarding the bulk composition of the lunar crust and to gauge the degree of regional heterogeneity in the composition of the lunar crust the most ideally polymict type of sample is finely mixed regolith lunar soil or its lithified equivalent regolith breccia fortunately lunar regolith breccias can occasionally be found at great distances from their points of origin most of the known lunar meteorites are regolith breccias we are searching for examples of exotic regolith samples among the apollo regolith breccia collection most of the 21 apollo regolith breccias analyzed for this study strongly resemble the local soils over which they were collected nine regolith breccias from apollo 16 are surprisingly mature compared to previously analyzed apollo 16 regolith breccias and six of the seven from apollo 16 station 5 have lower more local soil like mg ratios than previously analyzed regolith breccias from this station several of the apollo 14 regolith breccias investigated show significantly highermg and lower al than the local soils the most interesting sample we have investigated is 14076 1 from a lithology that constitutes roughly half of a 2 0 g pebble the presence of spherules indicates a regolith derivation for 14076 1 yet its highly aluminous 30 wt al2o3 composition is clearly exotic to the 1 6 km traverse surface over which the apollo 14 samples were collected this sample resembles soils from the descartes apollo 16 highlands far more than it does any other polymict sample from the fra mauro apollo 14 region the i sfeo maturity index is extremely low but this may be a result of thermal annealing a variety of siderophile elements occur in 14076 1 at typical regolith concentrations the chemistry of the second most aluminous regolith sample from apollo 14 14315 can only be roughly approximated as a mixture of local regolith and 14076 1 like material however the low a priori statistical probability for long distance horizontal transport by impact cratering along with the relatively high contents of incompatible elements in 14076 1 despite its high al content suggest that this regolith breccia probably originated within a few hundred kilometers of the appollo 14 site if so its compositional resemblance to ferroan anorthosite tends to suggest that the regional crust is or originally was far richer in ferroan anorthosite than implied by the meager statistics for pristine rocks from this site thus 14076 1 tends to strengthen the hypothesis that ferroan anorthosite originated as the flotation crust of a global magmasphere

mg spinel lithology a new rock type on the lunar farside 1 high resolution compositional data from moon mineralogy mapper m3 for the moscoviense region on the lunar farside reveal three unusual but distinctive rock types along the inner basin ring these are designated oos since they are dominated by high concentrations of orthopyroxene olivine and mg rich spinel respectively the oos occur as small areas each a few kilometers in size that are widely separated within the highly feldspathic setting of the basin rim although the abundance of plagioclase is not well constrained within the oos the mafic mineral content is exceptionally high and two of the rock types could approach pyroxenite and harzburgite in composition the third is a new rock type identified on the moon that is dominated by mg rich spinel with no other mafic minerals detectable 5 pyroxene olivine all oos surfaces are old and undisturbed since basin formation they are effectively invisible in image data and are only recognized by their distinctive composition identified spectroscopically the origin of these unusual lithologies appears to be linked to one or more magmatic intrusions into the lower crust perhaps near the crust mantle interface processes such as fractional crystallization and gravity settling within such intrusions may provide a mechanism for concentrating the mafic components within zones several kilometers in dimension the oos are embedded within highly anorthositic material from the lunar crust they may thus be near contemporaneous with crustal products from the cooling magma ocean

northwest africa 773 lunar origin and iron enrichment trend the meteorite northwest africa 773 nwa 773 is a lunar sample with implications for the evolution of mafic magmas on the moon a combination of key parameters including whole rock oxygen isotopic composition fe mn ratios in mafic silicates noble gas concentrations a kreep like rare earth element pattern and the presence of regolith agglutinate fragments indicate a lunar origin for nwa 773 partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation terrestrial weathering has caused fracturing and precipitation of carich carbonates and sulfates in the fractures but lunar minerals appear fresh and unoxidized the meteorite is composed of two distinct lithologies a two pyroxene olivine gabbro with cumulate texture and a polymict fragmental regolith breccia the olivine gabbro is dominated by cumulate olivine with pigeonite augite and interstitial plagioclase feldspar the breccia consists of several types of clasts but is dominated by clasts from the gabbro and more feo rich derivatives variations in clast mineral assemblage and pyroxene mg mg fe and ti ti cr record an igneous fe enrichment trend that culminated in crystallization of fayalite silica hedenbergitebearing symplectites the fe enrichment trend and cumulate textures observed in nwa 773 are similar to features of terrestrial ponded lava flows and shallow level mafic intrusives indicating that nwa 773 may be from a layered mafic intrusion or a thick differentiated lava flow nwa 773 and several other mafic lunar meteorites have lree enriched patters distinct from apollo and luna mare basalts which tend to be lree depleted this is somewhat surprising in light of remote sensing data that indicates that the apollo and luna missions sampled a portion of the moon that was enriched in incompatible heatproducing elements

global silicate mineralogy of the moon from the diviner lunar radiometer we obtained direct global measurements of the lunar surface using multispectral thermal emission mapping with the lunar reconnaissance orbiter diviner lunar radiometer experiment most lunar terrains have spectral signatures that are consistent with known lunar anorthosite and basalt compositions however the data have also revealed the presence of highly evolved silica rich lunar soils in kilometer scale and larger exposures expanded the compositional range of the anorthosites that dominate the lunar crust and shown that pristine lunar mantle is not exposed at the lunar surface at the kilometer scale together these observations provide compelling evidence that the moon is a complex body that has experienced a diverse set of igneous processes

a potpourri of regolith breccias new samples from the apollo 14 16 and 17 landing sites forty suspected regolith breccias from the apollo 14 16 and 17 landing sites were studied as part of a search for regolith samples exotic to the small traverse areas associated with these missions as well as a general effort to constrain the nature and origins of regolith breccias of these 40 samples 31 are indeed regolith breccias regolith breccias from apollo 14 exhibit much greater compositional diversity than their soil sensu stricto counterparts 14004 55 displays incompatible element concentrations about 1 4 those found in typical apollo 14 regolith while 14315 is radically different in many respects higher al lower mg and fe lower incompatible elements from all other apollo 14 regolith materials and hence probably exotic to the apollo 14 traverse area application of mixing models to apollo 14 regolith materials suggests that whereas normal apollo 14 regolith contains only slightly more ferroan anorthosite fa than alkali anorthosite aa and far more kreep than fa and aa combined 14315 contains more fa than kreep and roughly 10 times more fa than aa three new regolith breccias from apollo 16 bring to 20 the total number of regolith breccias that have been analyzed for mg and fe from the site the molar mg mg fe or mg ratios of lunar regolith breccias are of great interest because lunar meteorite alha81005 has a much higher mg than two other lunar meteoritic regolith breccias y791197 and y82192 3 even though these three samples are remarkably similar in all other compositional respects a bimodality in mg among apollo 16 regolith breccias may result from 1 statistical scattering among the small number of samples 2 a tendency for older regolith breccias from this site to be compositionally distinct from their younger counterparts or 3 differences between the cayley and descartes formations among 10 samples from apollo 17 all but one proved to be typical apollo 17 regolith breccias however 72504 10 is 99 pure pyroclastic glass compositionally identical to the apollo 17 orange glass 74220 even though 72504 10 was obtained at a location over 4 km from shorty crater where 74220 was obtained the nearly pure concentration of 74220 identical glass spherules in 72504 10 attests to the widespread distribution of these distinctive deposits

distribution of platinum group elements and os isotopes in chromite ores from mayari baracoa ophiolitic belt eastern cuba the mayari baracoa ophiolitic belt in eastern cuba hosts abundant chromite deposits of historical economic importance among these deposits the chemistry of chromite ore is very variable ranging from high al cr 0 43 0 55 to high cr cr 0 60 0 83 compositions platinum group element pge contents are also variable from 33 ppb to 1 88 ppm and corre late positively with the cr of the ore bulk pge abundances correlate negatively with the pd ir ratio showing that chromite concentrates mainly os ir and ru which gives rise to the characteristic negatively sloped chrondrite normalized pge patterns in many chromitites this is consistent with the mineralogy of pges which is dominated by members of the laurite erlichmanite solid solution series rus2 oss2 with minor amounts of irarsite irass os ir alloys ru os ir fe ni alloys ni rh as and sulfides of ir os rh cu ni and or pd measured 187 os 188 os ratios from 0 1304 to 0 1230 are among the lower values reported for podiform chromitites the 187 os 188 os ratios de crease with increasing whole rock pge contents and cr of chromite furthermore cos values of all but one of the chromitite samples are negative indicating a subchondiritc mantle source cos decrease with increasing bulk os content and decreasing 187 re 188 os ratios these mineralogical and geochemical features are interpreted in terms of chromite crystallization from melts varying in composition from back arc basalts al rich chromite to boninites cr rich chromite in a su prasubduction zone setting chromite crystallization occurs as a consequence of magma mixing and assimi lation of preexisting gabbro sills at the mantle crust transition zone cr pge abundances and bulk os isotopic composition of chromitites are determined by the combined effects of mantle source heterogeneity the degree of partial melting the extent of melt rock inter actions and the local sulfur fugacity small scale l mt o cm chemical and isotopic heterogeneities in the plati num group minerals are controlled by the mechanism s of chromite crystallization in a heterogeneous environ ment created by the turbulent regime generated by suc cessive inputs of different batches of melt

iron abundances on the lunar surface as measured by the lunar prospector gamma ray and neutron spectrometers i global measurements of iron abundances on the lunar surface are presented using data from the lunar prospector lp gamma ray spectrometer grs and neutron spectrometer ns in this study we derive relative iron abundances from the low altitude high spatial resolution 45 km 2 lp data using the 7 6 mev neutron capture gamma ray doublet as part of the lp grs analysis we demonstrate the importance of accounting for variations in neutron number density across the lunar surface by measuring neutron fluxes using lp ns data in a first step of comparing the lp grs data with previously published iron abundances inferred from clementine spectral reflectance csr data we show that the existing csr feo data are nonlinear with respect to the lp relative iron abundances we use the lp data to linearize the relationship between the csr and the relative iron values then recalibrate the csr data to iron abundance using returned soil abundances we then correlate the csr data except for major anomalies with the lp relative iron measurements to convert the lp data to absolute iron abundances when we compare the lp grs and revised csr data sets we find a very good correspondence there are two locations mare tranquillitatis and south pole aitken spa basin that show major discrepancies suggesting that the csr data are locally overestimating iron abundances in both these regions the discrepancies identified by the lp grs csr comparison are possibly explained by mineralogical differences that are not accounted for in the csr to feo calibration in regards to our understanding of the moon the lp data have found the following i there exist large expanses of mare basalt in the western mare regions that have very high iron abundances 22 23 wt feo that are underrepresented but not absent from the returned sample collection and are highly unusual for mare soils which typically contain a significant amount of highlands contamination 2 the low iron abundances in the lunar highlands 5 feo wt are consistent with a previous analysis using thermal and epithermal neutrons and with the idea that the lunar crust formed by a relatively simple magma ocean process 3 the comparison of lp and csr derived iron abundances suggests that the material within spa basin is similar to a norite type rock without an enriched mantle feo signature 4 a comparison of lp and csr data at tycho crater shows a large discrepancy such that the csr data show moderate iron abundances of 8 9 wt feo while the lp data show very low iron abundances of 3 4 wt feo this discrepancy cannot yet be easily explained by any known process

antarctic lunar meteorites yamato 793169 asuka 881757 mil 05035 and met 01210 yamm launch pairing and possible cryptomare origin abstract the antarctic lunar meteorite meteorite hills met 01210 is a polymict regolith breccia dominantly composed of mare basalt components one relatively large 2 7 4 7 mm basalt clast in met 01210 met basalt shows remarkable mineralogical similarities to the lunar meteorite crystalline mare basalts yamato y 793169 asuka a 881757 and miller range mil 05035 all four basalts have similar rock texture mineral assemblage mineral composition pyroxene crystallization trend and pyroxene exsolution lamellae the estimated tio 2 contents 2 0 wt of the met basalt and mil 05035 are close to the bulk rock tio 2 contents of y 793169 and a 881757 these similarities suggest that y 793169 a 881757 mil 05035 and the met basalt came from the same basalt flow which we designate the yamm basalt the source basalt pairing of the yamm is also supported by their similar ree abundances crystallization ages approx 3 8 3 9 ga and isotopic compositions low u pb low rb sr and high sm nd the pyroxene exsolution lamellae which are unusually coarse up to a few microns by mare standards imply a relatively slow cooling in an unusually thick lava and or subsequent annealing within a cryptomare reported noble gas and cre data with close launch ages 1 ma and ejection depths deeper than several meters among the four meteorites further indicate their simultaneous ejection from the moon despite the marginally close terrestrial ages pairing in the conventional earth entry sense seems unlikely because of the remote recovery sites among the yamm meteorites the high abundance 68 of mare components in met 01210 estimated from a two component mixing model calculation could have resulted from either lateral mixing at a mare highland boundary or vertical mixing in a cryptomare the proportion of mare materials in met 01210 is greater than in apollo core samples at the mare highland boundary the burial depth several meters deep inferred from the lack of surface irradiation of met 01210 exceeds the typical mare regolith thickness a few meters thus the source of the yamm meteorites is likely a terrain of locally high mare highland mixing within a cryptomare we searched for a possible source crater of the yamm meteorites within the well defined cryptomare based on the multiple constraints obtained from this study and published data an unnamed 1 4 km diameter crater 53 w 44 5 s on the floor of the schickard crater is the most suitable source for the yamm meteorites the 238 u 204 pb value of the yamm basalts is extremely low relative to those of the apollo mare basalts but comparable to those of the luna 24 very low ti basalts the low source indicates a derivation from a less differentiated mantle with a lack of kreep components although the chemical sources of materials and heat source of melting might be independent the heat source that generated the source magma of the yamm and luna 24 basalts may not be related to kreep unlike the case of the apollo basalts the distinct chemical and isotopic compositions of mantle sources between the apollo basalts and the yamm lunar 24 basalts imply differences in mantle composition and thermal evolution between the procellarum kreep terrane pkt and non pkt regions of the nearside

asymmetric crustal growth on the moon indicated by primitive farside highland materials the origin of the dichotomy between the lunar nearside and farside is unclear analysis of spectral reflectance data from the kaguya lunar orbiter indicates a systematic difference in the degree of differentiation in the oldest lunar crustal terrains linking the lunar dichotomy to crystallization of the magma ocean

multiple events in the neo tethyan oceanic upper mantle evidence from ru os ir alloys in the luobusa and dongqiao ophiolitic podiform chromitites tibet in situ analysis of major elements platinum group elements and os isotope composition data for 170 grains of ru os ir alloys from podiform chromitites in the luobusa and dongqiao ophiolites tibet provide new constraints on the sources of the alloy grains the os isotope composition of the neo tethyan oceanic upper mantle and the timing of melt rock reactions in the ultramafic peridotites of the host ophiolites most alloy grains are osmiridium and iridosmine based on elemental and isotopic compositions two populations can be identified group i found in both ophiolite bodies has fractionated pge patterns typical of alloys and homogeneous 187 os 188 os 0 12645 4 2s n 145 group ii alloys from the dongqiao ophiolites show smooth pge patterns and 187 os 188 os ranges from 0 12003 to 0 12194 yielding re depletion ages 1 1 ga both the pge patterns and the os isotopic compositions of group ii resemble those of sulfides residual after melting group i alloys represent an early cumulate phase during the crystallization of magmas and are interpreted as derived from an asthenospheric melt in contrast group ii alloys are inferred to derive from the breakdown of residual sulfides from the mantle section of the ophiolite which may represent relics of a sub continental lithospheric mantle the coexistence of the two groups of alloys in dongqiao samples reflects interaction between asthenosphere derived melts and old depleted lithospheric mantle and suggests that the chromitites originated through melt rock reactions the data on the group i alloys support the hypothesis that the re os evolution of the convective oceanic mantle resembles that of enstatite chondrites 2007 elsevier b v all rights reserved

development importance and effect of a ground truth correction for the moon mineralogy mapper reflectance data set 1 we evaluate the effect and importance of a ground truth correction for the moon mineralogy mapper m3 level 2 reflectance data set this correction is derived from extensive laboratory characterizations of mature feldspathic lunar soils and is designed to improve the accuracy of 1 m absorption features in m3 reflectance data to evaluate the correction the band strength across a subset of the feldspathic highlands terrane fht is analyzed with m3 imaging spectroscopy data using m3 reflectance data and derived products we find significant differences in band strength and shape between m3 observations collected over identical terrain but under different observational and operational conditions the ground truth correction minimizes these differences in 1 m band strengths and also brings the 1 m band strengths measured with m3 data into closer agreement with laboratory measurements of lunar soil samples although the fht region studied was found to have very low band strengths the m3 ground truth correction results in overall stronger absorption features for all mature soils relative to uncorrected level 2 reflectance data for the same region these differences between m3 data collected under different operational conditions and the effects of the ground truth correction while minor in appearance can have significant implications for interpretations of any regional soil analyses with m3 data that rely on absolute 1 m absorption feature strength the m3 ground truth correction corrects only wavelengths below 1500 nm and comparisons between corrected and uncorrected wavelengths must be done with caution

petrogenesis and chronology of lunar meteorite northwest africa 4472 a kreepy regolith breccia from the moon northwest africa nwa 4472 is a polymict lunar regolith meteorite the sample is kreep rich high concentrations of potassium rare earth elements and phosphorus and comprises a heterogeneous array of lithic and mineral fragments these clasts and mineral fragments were sourced from a range of lunar rock types including the lunar high magnesian suite the high alkali suite kreep basalts mare basalts and a variety of impact crater environments the kreep rich nature of nwa 4472 indicates that the sample was ejected from regolith on the nearside of the moon in the procellarum kreep terrane and we have used lunar prospector gamma ray remote sensing data to show that the meteorite is most similar to and most likely sourced from regoliths adjacent to the imbrium impact basin u pb and pb pb age dates of nwa 4472 phosphate phases reveal that the breccia has sampled pre nectarian 4 35 ga rocks related to early episodes of kreep driven magmatism some younger phosphate u pb and pb pb age dates are likely indicative of impact resetting events at 3 9 4 ga consistent with the suggested timing of basin formation on the moon our study also shows that nwa 4472 has sampled impact melts and glass with an alkali depleted incompatible trace element rich high sc low rb th ratios low k compositional signature not related to typical apollo high k kreep or that sampled by kreepy lunar meteorite sayh al uhaymir sau 169 this provides evidence that there are numerous sources of kreep rich protoliths on the moon

new lunar meteorites impact melt and regolith breccias and large scale heterogeneities of the upper lunar crust we have analyzed nine highland lunar meteorites lunaites using mainly inaa several of these rocks are difficult to classify dhofar 081 is basically a fragmental breccia but much of its groundmass features a glassy fluidized texture that is indicative of localized shock melting also much of the matrix glass is swirly brown suggesting a possible regolith derivation we interpret dar al gani dag 400 as an extremely immature regolith breccia consisting mainly of impact melt breccia clasts we interpret dhofar 026 as an unusually complex anorthositic impact melt breccia with scattered ovoid globules that formed as clasts of mafic subophitic impact melt the presence of mafic crystalline globules in a lunar material even one so clearly impact heated suggests that it may have originated as a regolith our new data and a synthesis of literature data suggest a contrast in al2o3 incompatible element systematics between impact melts from the central nearside highlands where apollo sampling occurred and those from the general highland surface of the moon impact melts from the general highland surface tend to have systematically lower incompatible element concentration at any given al2o3 concentration than those from apollo 16 in the case of dhofar 026 both the bulk rock and a comparatively al poor composition 14 wt al2o3 7 g g sm extrapolated for the globules manifest incompatible element contents well below the apollo 16 trend impact melts from luna 20 57e distribute more along the general highland trend than along the apollo 16 trend siderophile elements also show a distinctive composition for apollo 16 impact melts ni ir averaging 1 8x chondritic in contrast lunaite impact melt breccias have consistently chondritic ni ir impact melts from luna 20 and other apollo sites show average ni ir almost as high as those from apollo 16 the prevalence of this distinctive ni ir ratio at such widely separated nearside sites suggests that debris from one extraordinarily large impact may dominate the megaregolith siderophile component of a nearside region 2300 km or more across highland polymict breccia lunaites and other kreep poor highland regolith samples manifest a strong anticorrelation between al2o3 and mg the magnesian component probably represents the chemical signature of the mg suite of pristine nonmare rocks in its most pure form unaltered by the major kreep assimilation that is so common among apollo mg suite samples the average composition of the ferroan anorthositic component is now well constrained at al2o3 29 30 wt implying about 17 19 wt modal mafic silicates in good agreement with the composition predicted for flotation crust over a ferroan magma ocean warren 1990

an improved age framework for late quaternary silicic eruptions in northern central america five new stepwise heating 40 ar 39 ar ages and one new high sensitivity 14 c date of ash fall and ash flow deposits from late quaternary silicic volcanoes in northern central america document the eruption rates and frequencies of five major rhyodacite and rhyolite calderas atitlan amatitlan ayarza coatepe que and ilopango located north of the basalt ande site and dacite stratovolcanoes of the central ameri can volcanic front these deposits form extensive time stratigraphic horizons that intercalate regionally and knowledge of dates and stratigraphy provides a valua ble framework for age determinations of more local ized volcanic and nonvolcanic events the new data es pecially when integrated with previous stratigraphic and dating work show that all five calderas erupted several times in the past 200 ka and despite a lack of historic activity should be considered as active centers that could produce highly explosive eruptions again because of their locations near the highly vulnerable economic hearts of guatemala and el salvador the risks of eruptions from these calderas should be care fully considered along with risks of major earthquakes and volcanic front volcanoes which are much more fre quent but inflict less severe and extensive damage this

os isotope heterogeneity of the upper mantle evidence from the mayari baracoa ophiolite belt in eastern cuba in an attempt to quantify the extent of geochemical heterogeneity within a restricted and well dated portion of the upper mantle 27 chromite separates from the 90 my old chromite deposits in the mayari baracoa ophiolite belt in eastern cuba have been investigated for platinum group element pge concentrations and re os isotopic systematics the samples are characterized by systematically subchondritic initial 187 os 188 os ratios and substantial heterogeneity the initial 187 os 188 os ratios vary with chromite chemistry and with geographical distribution reflecting differences in the os isotopic evolution for the different upper mantle sections represented by the ophiolite accordingly the os isotope data might be divided into three groups in the moa baracoa district where the chromite bodies are located in the mantle crust transition zone the calculated initial gos values average 0 97f0 69 n 13 in the sagua de tanamo district where chromite chemistry is highly variable and their location in relation the mantle sequence is less clear the initial gos values are intermediate with an average of 1 77f0 80 n 7 in the mayari district where the chromite bodies are located in the lower part of the mantle sequence initial gos values average 2 66f0 29 n 7 these subchondritic i e negative initial gos values are most simply explained by re depletion during ancient partial melting and or melt percolation events the os isotope heterogeneity documented here indicates a high degree of geochemical complexity on small to intermediate length scales in the upper mantle our results in combination with data on chromites from the literature show that an baverage present day os isotopic compositionq for the hypothetical depleted morb mantle dmm reservoir cannot be precisely established beyond the statement that it is bbroadly chondriticq indeed the upper mantle cannot be considered a sufficiently homogeneous geochemical breservoirq to serve meaningfully as a baseline against which geochemical banomaliesq are evaluated on the other hand our findings are consistent with the bstatistical upper mantle assemblageq or bsumaq concept according to which a high level of geochemical heterogeneity is maintained in the upper mantle at all relevant length scales as a result of the plate tectonic cycle and intra mantle processes such as melt migration and metasomatism d 2005 elsevier b v all rights reserved

global elemental maps of the moon the lunar prospector gamma ray spectrometer lunar prospector gamma ray spectrometer spectra along with counting rate maps of thorium potassium and iron delineate large compositional variations over the lunar surface thorium and potassium are highly concentrated in and around the nearside western maria and less so in the south pole aitken basin counting rate maps of iron gamma rays show a surface iron distribution that is in general agreement with other measurements from clementine and the lunar prospector neutron detectors

lunar fe and ti abundances comparison of lunar prospector and clementine data the lunar prospector neutron spectrometer data correlate well with iron and titanium abundances obtained through analysis of clementine spectral reflectance data with the iron and titanium dependence removed the neutron spectrometer data also reveal regions with enhanced amounts of gadolinium and samarium incompatible rare earth elements that are enriched in the final phases of magma crystallization these regions are found mainly around the ramparts of the imbrium impact basin but not around the other basins including the much larger and deeper south pole aitken basin this result confirms the compositional uniqueness of the surface and interior of the imbrium region

chemistry of the calcalong creek lunar meteorite and its relationship to lunar terranes the calcalong creek lunar meteorite is a polymict breccia that contains clasts of both highlands and mare affinity reported here is a compilation of major minor and trace element data for bulk clast and matrix samples determined by instrumental neutron activation analysis inaa petrographic information and results of electron microprobe analyses are included the relationship of calcalong creek to lunar terranes especially the procellarum kreep terrane and feldspathic highlands terrane is established by the abundance of thorium incompatible elements and their kreep like ci chondrite normalized pattern feo and tio2 the highlands component is associated with apollo 15 kreep basalt but represents a variant of the kreep derived material widely found on the moon sources of calcalong creek s mare basalt components may be related to low titanium lt and very low titanium vlt basalts seen in other lunar meteorites but do not sample the same source the content of some components of calcalong creek are found to display similarities to the composition of the south pole aitken terrane what appear to be vlt relationships could represent new high aluminum low titanium basalt types

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

basaltic fragments in lunar feldspathic meteorites connecting sample analyses to orbital remote sensing abstract the feldspathic lunar meteorites contain rare fragments of crystalline basalts we analyzed 16 basalt fragments from four feldspathic lunar meteorites allan hills alha 81005 macalpine hills mac 88104 88105 queen alexandra range que 93069 miller range mil 07006 and utilized literature data for another dhofar dho 1180 we compositionally classify basalt fragments according to their magma s estimated tio2 contents which we derive for crystalline basalts from pyroxene tio2 and the mineral melt ti distribution coefficient overall most of the basalt fragments are low ti basalts 1 6 tio2 with a significant proportion of very low ti basalts 10 tio2 and 6 10 tio2 respectively this distribution of basalt tio2 abundances is nearly identical to that obtained from orbital remote sensing of the moon both uv vis from clementine and gamma ray from lunar prospector however the distribution of tio2 abundances is unlike those of the apollo and luna returned samples we observe a paucity of high ti basalts the compositional types of basalt differs from meteorite to meteorite which implies that all basalt subtypes are not randomly distributed on the moon i e the basalt fragments in each meteorite probably represent basalts in the neighborhood of the meteorite launch site these differences in basalt chemistry and classifications may be useful in identifying the source regions of some feldspathic meteorites some of the basalt fragments probably originate from ancient cryptomaria and so may hold clues to the petrogenesis of the moon s oldest volcanism

uranium lead systematics of low ti basaltic meteorite dhofar 287a affinity to apollo 15 green glasses article i nfo dhofar 287 is a lunar meteorite found in oman in 2001 which consists of a major portion 95 of low ti mare basalt dho 287a and a minor attached part 5 of regolith breccia dho 287b here we report the u pb systematics of dho 287a using data collected with a sensitive high resolution ion microprobe shrimp in situ analyses of five merrillite and three apatite grains which are resistant to secondary petrologic events resulted in a total pb u isochron age of 3 34 0 20 ga in 238 u 206 pb 207 pb 206 pb 204 pb 206 pb 3 d space 95 confidence level the observed pb pb isochron of these eight phosphates coupled with four plagioclase grains alsoyieldeda 207 pb 206 pbageof3 35 0 13ga thisformationage whenconsideredasthecrystallizationageof

lunar prospector overview lunar prospector is providing a global map of the composition of the moon and analyzing the moon s gravity and magnetic fields it has been in a polar orbit around the moon since 16 january 1998 neutron flux data show that there is abundant h and hence probably abundant water ice in the lunar polar regions gamma ray and neutron data reveal the distribution of fe ti and other major and trace elements on the moon the data delineate the global distributions of a key trace element rich component of lunar materials called kreep and of the major rock types magnetic mapping shows that the lunar magnetic fields are strong antipodal to mare imbrium and mare serenitatis and has discovered the smallest known magnetosphere magnetosheath and bow shock complex in the solar system gravity mapping has delineated seven new gravity anomalies and shown that the moon has a small fe rich core of about 300 km radius

petrology and chemistry of apollo 12 regolith breccias petrographic mineral chemical and bulk chemical data are reported for the three large apollo 12 regolith breccias of the regolith breccia suite and for eight breccias handpicked from apollo 12 coarse fines two samples formed from non kreepy anorthositic regolith not presently found at the sampling site eight of the samples can be considered mixtures of local basalt and kreep components with minor anorthositic components mare kreep ratios indicated by chemical mixing models range from 86 7 to essentially endmember kreep one sample is unlike the others feo 23 7 mgo 21 7 and may be a new lithology or alternatively a nonrepresentative sample of the 11 samples studied 5 appear to be of local origin 3 are most likely exotic to the site and results for 3 others are inconclusive the anorthositic breccias formed from apollo 16 like regolith and may have been transported over several hundred kilometers from the non kreepy highlands to the east alternatively they may be of local origin formed from the material beneath the apollo 12 basalt flows

new insights into lunar petrology distribution and composition of prominent low ca pyroxene exposures as observed by the moon mineralogy mapper m3 1 lunar geochemical groups such as mg suite ferroan anorthosite and alkali suite rocks are difficult to distinguish from orbit because they are defined by both modal mineralogy and elemental composition of their constituent minerals while modal mineralogy can be modeled only specific minerals or elements can be directly detected at near infrared nir wavelengths pyroxenes are among the most spectrally distinctive minerals and their absorption bands are sensitive to structure and composition pyroxenes thus provide important clues to distinguish these geochemical groups and to understand lunar crustal evolution using moon mineralogy mapper data we search for lithologies dominated by strong low calcium pyroxene lcp signatures we compare the nir absorptions of 20 lcps to a suite of synthetic pyroxenes to determine which lunar pyroxenes appear magnesian enough to be candidate mg suite norites we detail three prominent regions of lcp 1 in south pole aitken basin spa 2 south of mare frigoris and 3 north of mare frigoris the absorption band positions suggest that the lcps north of mare frigoris and those in spa are compositionally similar to one another and of mg50 75 implying that the mafic material excavated by the spa impact was relatively iron rich modified gaussian modeling results suggest that the apollo basin may have tapped different composition material than is exposed in much of spa the lcps located in the highlands south of mare frigoris exhibit absorption bands at short wavelengths consistent with mg 80 the coincidence of these mg rich lcps with the thorium measured by lunar prospector make them good candidates for kreep related mg suite pyroxenes