geology and petrology of enormous volumes of impact melt on the moon a case study of the orientale basin impact melt sea abstract lunar basin forming impacts produce enormous volumes 10 5 km 3 of impact melt all known basin forming impacts combined may produce 10 8 km 3 of impact melt 1 20th the volume of the lunar crust despite their volumetric importance the geology and petrology of massive deposits of impact melt on the moon have been little studied in part because most basin impact melt deposits are old and have been obscured or buried by subsequent impact cratering and mare infill we investigate the geology and model the petrology of fresh massive impact melt deposits in the relatively young 930 km diameter orientale basin models of impact melt production combined with geologic analyses based on new lola topographic data suggest that most of the impact melt 2 3 produced by the orientale forming impact occurs in a 15 km thick impact melt sheet better described as an impact melt sea 350 km in diameter with a volume of 10 6 km 3 we anticipate that the orientale melt sea has undergone large scale igneous differentiation since terrestrial impact melt sheets such as manicouagan sudbury and morokweng less than a tenth of the thickness and a hundredth of the volume of the orientale melt sea have differentiated we develop a model for the cumulate stratigraphy of the solidified orientale impact melt sea a modeled cumulate stratigraphy occurring below a quench crust and anorthositic fallback breccia with an 8 km thick layer of norite overlying a 4 km layer of pyroxenite and a basal 2 km thick layer of dunite produced by equilibrium crystallization of a homogenized melt sea consistent with vigorous convection in that melt sea is supported by remotely sensed norite excavated by the central peak of maunder crater from 4 km depth generally we predict that very large basin forming impacts including the south pole aitken spa basin forming impact produce melt seas with a cumulate stratigraphy similar to that of the orientale melt sea impact melt differentiation may explain apparently anomalous lithologies excavated in the spa basin interior we note that impact melt differentiates are slow cooled the orientale melt sea took on the order of 10 5 years to solidify and if meteoritic siderophiles fractionate into metal or sulfide layers may not be siderophile enriched therefore impact melt differentiates may pass for pristine highland plutonic rocks in the lunar sample suite these predictions can be tested with current and future mission data

geochemistry and nd isotope systematics of archaean granites of the eastern goldfields yilgarn craton australia implications for crustal growth processes abstract the archaean granites and granitic gneisses of the eastern goldfields in the yilgarn craton western australia can be divided into two major groups high ca and low ca and three minor groups high hfse high field strength elements mafic and syenitic the high ca group 68 77 sio 2 with high al 2 o 3 na 2 o and sr and low y shares many features with typical archaean tonalite trondhjemite suites but has higher k 2 o rb and th contents the low ca group 70 76 sio 2 differs from the high ca group in having lower al 2 o 3 cao and na 2 o but higher k 2 o rb th zr y la and ce contents granites of the high hfse mafic and syenitic groups form a minor component 10 20 of the eastern goldfields granites the siliceous 74 77 sio 2 high hfse granites are restricted to a narrow nnw trending zone and are characterised by high tio 2 total feo mgo y zr and ce but only moderate rb th and pb contents the a type syenites 50 68 sio 2 are distinguished by their high total alkalies and mainly occur along tectonic lineaments the mafic group 55 70 sio 2 is lithologically diverse and exhibits a wide range of k 2 o rb th la and ce contents granite emplacement occurred between 2 69 and 2 60 ga contemporaneous with or post dating greenstone formation nd values for the high ca mafic and syenitic groups are similar mostly 0 0 to 2 5 whereas those for the low ca group show a pronounced polarity from 4 5 in the west to 2 0 in the east nd depleted mantle model ages for the low ca granites range from 3 2 ga in the west to 2 75 ga in the east model ages for the high ca group 2 75 2 9 ga overlap with ages for inherited zircons from these granites the high ca granites appear to have been derived at high pressures by partial melting of a mafic to intermediate source subducted oceanic crust crustal underplate or thickened crust or remelting of an older tonalitic source derived by such a process if the high ca granites were largely crust derived then their extensive source rocks must have formed less than 250 ma prior to granite formation the low ca granites appear to be the products of crustal reworking probably from a tonalitic to granodioritic protolith that was progressively younger towards the east perhaps in the order of several hundred million years younger or involved an additional younger component the localisation of the crustally derived high hfse granites suggests either geochemical zonation of the crust or specific tectonic processes such as rifting the mafic granites and possibly the syenites imply a significant mantle contribution and new crustal growth although the extent is equivocal the crust of the eastern goldfields appears to have been generated by both lateral and vertical accretion over a significant period from or before 3 0 ga until the time of granite emplacement

apollo 16 impact melt splashes petrography and major element composition we made petrographic and major element chemical analyses of 50 impact melt splash ims samples from the apollo 16 landing site to assess their origin and the nature of their subregolith source these melts possess volumes that are significantly larger than those of agglutinates but smaller than those represented by fragments of generally holocrystalline melt sheets most of these melts occur as splashes that drape various host rocks the majority appear to have been deposited onto their hosts inside growing crater cavities or during ballistic flight and subsequently piggy backed to their collection site s macroscopically ims s exhibit a glassy appearance but display varied crystallinity under the microscope schlieren rich glasses dominate the holohyaline areas most ims s contain generally feldspathic monomineralic and lithic clasts while purely regolithic materials i e agglutinates are absent crystalline portions are predominately spherulitic but definitive criteria to distinguish between crystallization from a melt or solid state devitrification are lacking more than half of the ims s possess a distinct crystallization front that we attribute to devitrification chemically most ims s are fairly homogeneous on the scale of a thin section variation among samples is much greater e g al2o3 varied from 24 to 32 wt feo from 2 to 6 wt such a wide range of melt compositions suggests that more than one impact generated these 50 ims s the chemistry of most ims s is unlike the local regolith and appears to represent varied mixtures of vha impact melt breccias and anorthosite i e are dimict like the host rocks are predominantly dimict breccias 70 or one of their component lithologies vha impact melt breccias and anorthosite because of the short surface residence times for these samples determined from microcrater populations on all samples and absolute exposure ages of 10 specimens many ims s might be associated with south ray and baby ray craters in the absence of absolute chronological ages for melt formation we cannot distinguish between a young scenario in which the melts were formed during excavation of south ray and or baby ray craters and an old scenario in which previously formed melts were exposed as part of the discontinuous ejecta of either or both of these craters we prefer the former in part because of the tight compositional cluster of most ims s in either case we conclude that most of these samples or their progenitors resided at depth within the south ray and or baby ray targets furthermore the cayley formation in the southern part of the apollo 16 landing site is a polymict deposit predominantly composed of vha impact melt breccias and anorthosites both lithologies must be intimately mixed as they are in dimict breccias and large coherent units of individual lithologies appear to be limited to 50 m in dimensions

forty years of ttg research abstract ttgs tonalite trondhjemite granodiorite are one of the archetypical lithologies of archaean cratons since their original description in the 1970s they have been the subject of many studies and discussions relating to archaean geology in this paper we review the ideas concepts and arguments brought forward in these 40 years and try to address some open questions both old and new the late 1960s and the 1970s mark the appearance of grey gneisses ttg in the scientific literature during this period most work was focused on the identification and description of this suite and the recognition that it is a typical archaean lithology ttgs were already recognised as generated by melting of mafic rocks this was corroborated during the next decade when detailed geochemical ttg studies allowed us to constrain their petrogenesis melting of garnet bearing metamafic rocks and to conclude that they must have been generated by archaean geodynamic processes distinct from their modern counterparts however the geodynamic debate raged for the following 30 years as many distinct tectonic scenarios can be imagined all resulting in the melting of mafic rocks in the garnet stability field the 1990s were dominated by experimental petrology work a wealth of independent studies demonstrated that melting of amphibolites as well as of mafic eclogites can give rise to ttg liquids whether amphibolitic or eclogitic conditions are more likely is still an ongoing debate from 1990s onwards one of the key questions became the comparison with modern adakites as originally defined these arc lavas are reasonably close equivalents to archaean ttgs pending issues largely revolve around definitions as the name ttg has now been applied to most archaean plutonic rocks whether sodic or potassic irrespective of their hree contents this leads to a large range of petrogenetic and tectonic scenarios a fair number of which may well have operated concurrently but are applicable only to some of the rocks lumped together in the ever broadening ttg bin

the petrology geochemistry and age of lunar regolith breccias miller range 090036 and 090070 insights into the crustal history of the moon meteorites ejected from the surface of the moon as a result of impact events are an important source of lunar material in addition to apollo and luna samples here we report bulk element composition mineral chemistry age and petrography of miller range mil 090036 and 090070 lunar meteorites mil 090036 and 090070 are both anorthositic regolith breccias consisting of mineral fragments and lithic clasts in a glassy matrix they are not paired and represent sampling of two distinct regions of the lunar crust that have protoliths similar to ferroan anorthosites 40ar 39ar chronology performed on two subsplits of mil 090070 33 a pale clast impact melt and a dark glassy melt component shows that the sample underwent two main degassing events one at 3 88 ga and another at 3 65 ga the cosmic ray exposure data obtained from mil 090070 are consistent with a short 8 9 ma exposure close to the lunar surface bulk rock feo tio2 and th concentrations in both samples were compared with 2 degree lunar prospector gamma ray spectrometer lp grs data sets to determine areas of the lunar surface where the regolith matches the abundances observed on the sample we find that mil 090036 bulk rock is compositionally most similar to regolith surrounding the procellarum kreep terrane whereas mil 090070 best matches regolith in the feldspathic highlands terrane on the lunar farside our results suggest that some areas of the lunar farside crust are composed of ferroan anorthosite and that the samples shed light on the evolution and impact bombardment history of the ancient lunar highlands

an integrated approach to understanding apollo 16 impact glasses chemistry isotopes and shape the major and minor element abundances were determined by electron microprobe in 1039 glasses from regoliths and regolith breccias to define the compositional topology of lunar glasses at the apollo 16 landing site in the central highlands of the moon while impact glasses with chemical compositions similar to local materials i e apollo 16 rocks and regoliths are abundant glasses with exotic compositions i e transported from other areas of the moon account for up to 30 of the population a higher proportion of compositionally exotic angular glass fragments exists when compared to compositionally exotic glass spherules ratios of non volatile lithophile elements i e al ti mg have been used to constrain the original source materials of the impact glasses this approach is immune to the effects of open system losses of volatile elements e g si na k four impact glasses from one compositionally exotic group low mg high k fra mauro lmhkfm were selected for 40ar 39ar dating the individual fragments of lmhkfm glass all yielded ages of 3750 50 ma for the time of the impact event based on the petrography of these individual glasses we conclude that the likely age of the impact event that formed these 4 glasses as well as the possible time of their ballistic arrival at the apollo 16 site from a large and distant cratering event perhaps in the procellarum kreep terrain zeigler et al 2004 is 3730 40 ma close to the accepted age for imbrium

neoarchean orogenic magmatic and hydrothermal events in the kalgoorlie kambalda area western australia constraints on gold mineralization in the boulder lefroy golden mile fault system the boulder lefroy golden mile blf gmf fault system is the most intensely mineralized structure 2150 t au to 2015 in the archean yilgarn craton western australia the fault system links the kalgoorlie and kambalda mining districts in the eastern goldfields province a continental margin orogen subdivided into the western kalgoorlie ensialic rift and the eastern kurnalpi volcanic arc after rifting the 2 73 2 66 ga greenstone greywacke succession in the kalgoorlie kambalda area underwent five phases of orogenic deformation predominantly during ene wsw shortening d1 upright folding at ca 2680 ma d2 sinistral strike slip faulting at 2678 2663 ma d3 folding of late conglomerate turbidite successions at 2665 2655 ma d4 dextral strike slip faulting at 2655 2640 ma and d5 east northeast striking normal faulting regional prehnite pumpellyite to greenschist facies burial metamorphism took place during d1 and d3 crustal thickening and amphibolite facies aureoles formed around granite batholiths during and after d3 at 400 100 mpa pressure the d2 blf offsets d1 folds by 12 km sw side south and contains a porphyry dyke 2676 7 ma boudinaged by transtensional oblique slip along a line pitching 21 southeast the blf is linked by transverse d2 thrusts to other sinistral faults recording strike slip until 2663 7 ma late d2 strike slip movement alternated with early d3 shortening d3 thrusts accommodated strain in fault blocks of rigid mafic ultramafic volcanic rocks consolidated during d1 while the sedimentary rocks in d3 synclines were foliated at high strain biotite sericite alteration and gold pyrite mineralization in the blf gmf system took place at 11 4 km burial depth in faults active during d2 and d3 the golden mile 1708 t au and other deposits are associated with stocks and dykes of high mg monzodiorite tonalite porphyry part of a late orogenic 2665 2645 ma mantle derived suite of adakitic affinity hornblende and apatite compositions indicate that these intrusions are characterized by high water contents 5 6 wt h2o in melt by high oxidation states nno 1 0 to 2 4 log units and by igneous anhydrite some stocks contain pervasive anhydrite pyrite mineralization of low gold grade 0 4 g t biotite sericite pyrite ore bodies such as those at kanowna belle 140 t au also replace faulted metamorphic rocks above batholith domes cored by plutons of the monzodiorite suite the d4 strike slip faults are barren at kambalda but control gold quartz vein ore at kalgoorlie 2651 9 ma and au ag breccia ore at black flag 2648 6 ma

chondritic late accretion to mars and the nature of shergottite reservoirs abstract mars is considered to have formed as a planetary embryo that experienced extensive differentiation early in its history shergottite meteorites preserve evidence for this history and for late accretion events that affected their mantle sources within mars here we report the first coupled 187re 187os 87sr 86sr highly siderophile element hse os ir ru pt pd re and major element abundance dataset for martian shergottites that span a range of mgo contents from 6 4 to 30 3 wt the shergottites range from picro basalt to basaltic andesite compositions have enriched to depleted incompatible trace element compositions and define fractional crystallization trends enabling the determination of hse compatibility for martian magmatism in the order os ir ru pt pd re this order of compatibility is like that defined previously for earth and the moon but the fractionation of strongly compatible os ir and ru appears to take place at higher mgo contents in martian magmas due to early onset of sulfide fractionation in general enriched shergottites have lower mgo contents than intermediate or depleted shergottites and have fractionated hse patterns re pd pt ru ir os and more radiogenic measured 87sr 86sr 0 7127 0 7235 and 187os 188os 0 140 0 247 than intermediate or depleted shergottite meteorites 87sr 86sr 0 7010 0 7132 187os 188os 0 127 0 141 osmium isotope compositions corrected for crystallization age define compositions that are implausibly unradiogenic in some enriched shergottites implying recent mobilization of re in some samples filtering for the effects of alteration and high re os through crystal liquid fractionation leads to a positive correlation between age corrected sr and os isotope compositions mixing between hypothetical martian crustal and mantle reservoirs are unable to generate the observed sr os isotope compositions of shergottites which require either distinct and discrete long term incompatible element depleted and enriched mantle sources or originate from hybridized melting of deep melts with metasomatized martian lithosphere using mgo regression methods we obtain a modified estimate of the bulk silicate mars hse composition of in ng g 1 0 4 re 7 4 pd 9 6 pt 6 2 ru 3 7 ir 4 os and a long term chondritic 187os 188os ratio 0 1312 this result does not permit existing models invoking high pressure and temperature partitioning of the hse instead our estimate implies 0 6 0 7 by mass of late accretion of broadly chondritic material to mars our results indicate that mars could have accreted earlier than earth but that disproportional accretion of large bodies and a relative constant flux of accretion of available materials in the first 50 100 ma of solar system led to the broad similarity in hse abundances between earth and mars

40ar 39ar ages of lunar impact glasses relationships among ar diffusivity chemical composition shape and size abstract lunar impact glasses which are quenched melts produced during cratering events on the moon have the potential to provide not only compositional information about both the local and regional geology of the moon but also information about the impact flux over time we present in this paper the results of 73 new 40ar 39ar analyses of well characterized inclusion free lunar impact glasses and demonstrate that size shape chemical composition fraction of radiogenic 40ar retained and cosmic ray exposure cre ages are important for 40ar 39ar investigations of these samples specifically analyses of lunar impact glasses from the apollo 14 16 and 17 landing sites indicate that retention of radiogenic 40ar is a strong function of post formation thermal history in the lunar regolith size and chemical composition this is because the ar diffusion coefficient at a constant temperature is estimated to decrease by 3 4 orders of magnitude with an increasing fraction of non bridging oxygens x nbo over the compositional range of most lunar impact glasses with compositions from feldspathic to basaltic based on these relationships lunar impact glasses with compositions and sizes sufficient to have retained 90 of their radiogenic ar during 750 ma of cosmic ray exposure at time integrated temperatures of up to 290 k have been identified and are likely to have yielded reliable 40ar 39ar ages of formation additionally 50 of the identified impact glass spheres have formation ages of 500 ma while 75 of the identified lunar impact glass shards and spheres have ages of formation 2000 ma higher thermal stresses in lunar impact glasses quenched from hyperliquidus temperatures are considered the likely cause of poor survival of impact glass spheres as well as the decreasing frequency of lunar impact glasses in general with increasing age the observed age frequency distribution of lunar impact glasses may reflect two processes i diminished preservation due to spontaneous shattering with age and ii preservation of a remnant population of impact glasses from the tail end of the terminal lunar bombardment having 40ar 39ar ages up to 3800 ma a protocol is described for selecting and analyzing lunar impact glasses

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

self induced fracture generation in zircon the mineral zircon has particular geological significance because of its use in the age determination of rocks and as a structural analogue phase for radioactive waste forms despite its widespread utility however radiation damage of the crystal structure metamictization causes a volume expansion of the crystal lattice and the generation of internal stresses which can induce fractures in the crystal a model has been developed which describes the state of stress in n concentric spherical shells each of which may have different material properties the case of a three shelled composite sphere has been examined explicitly in combination with fracture mechanics theory the model predicts that spatially distinct radial and or concentric fracture sets can be produced and such fracture patterns accurately describe the distribution and types of self induced fractures observed in natural zircons in general the formation of such microfractures in zircon is a function of the degree of metamictization shell thickness and the confining pressure the model predicts that the maximum depths in the earth s crust at which radial versus concentric fractures can form in a crystal are different suggesting that the types of fractures found in a suite of zircons from a particular rock might be potential indicators of the depth of burial because metamictization induced fractures may serve as potential pathways for the rapid leaching of various elements from the zircon crystal this may also have important implications in interpreting the u pb ages of fractured zircons or in evaluating the suitability of related crystalline phases as hosts for nuclear waste

array analysis of electromagnetic radiation from radio transmitters for submarine communication the array analyses used for seismic and infrasound research are adapted and applied here to the electromagnetic radiation from radio transmitters for submarine communication it is found that the array analysis enables a determination of the slowness and the arrival azimuth of the wave number vectors associated with the electromagnetic radiation the array analysis is applied to measurements of 20 24 khz radio waves from transmitters for submarine communication with an array of 10 radio receivers distributed over an area of 1 km 1 km the observed slowness of the observed wave number vectors range from 2 7 ns m to 4 1 ns m and the deviations between the expected arrival azimuths and the observed arrival azimuths range from 9 7 to 14 5 the experimental results suggest that it is possible to determine the locations of radio sources from transient luminous events above thunderclouds with an array of radio receivers toward detailed investigations of the electromagnetic radiation from sprites

40ar 39ar dating of apollo 12 regolith implications for the age of copernicus and the source of nonmare materials abstract twenty one 2 4 mm rock samples from the apollo 12 regolith were analyzed by the 40 ar 39 ar geochronological technique in order to further constrain the age and source of nonmare materials at the apollo 12 site among the samples analyzed are 2 felsites 11 kreep breccias 4 mare basalt bearing kreep breccias 2 alkali anorthosites 1 olivine bearing impact melt breccia and 1 high th mare basalt most samples show some degree of degassing at 700 800 ma with minimum formation ages that range from 1 0 to 3 1 ga we estimate that this degassing event occurred at 782 21 ma and may have been caused by the copernicus impact event either by providing degassed material or by causing heating at the apollo 12 site 40 ar 39 ar dating of two alkali anorthosite clasts yielded ages of 3 256 0 022 ga and 3 107 0 058 ga we interpret these ages as the crystallization age of the rock and they represent the youngest age so far determined for a lunar anorthosite the origin of these alkali anorthosite fragments is probably related to differentiation of shallow intrusives later impacts could have dispersed this material by lateral mixing or vertical mixing

physical volcanology and geochemistry of a late archaean volcanic arc kurnalpi and gindalbie terranes eastern goldfields superterrane western australia abstract late archaean 2715 2704 ma calc alkaline volcanic complexes in the kurnalpi terrane are identical in facies and geochemistry to modern intra arc volcanic complexes preserved volcanic rocks and associated feldspathic sedimentary rocks represent proximal to medial submarine facies of submarine to locally emergent intra oceanic arc related volcanoes the least altered volcanic rocks are dominantly andesite but range from basalt and basaltic andesite to rare rhyolite and are the product of magmas similar in composition to those of modern arcs intermediate magmas were most likely derived from large ion lithophile element lile enriched mafic magmas by fractional crystallisation with or without assimilation processes the kurnalpi terrane thus provides an example of a late archaean volcanic arc in which hydrated mantle wedge melting was the main mechanism for magma genesis ttd suite volcanism derived from slab melting was either absent or played a subordinate role the adjacent gindalbie terrane contains younger 2692 2680 ma bimodal basalt rhyolite volcanic complexes with associated quartz rich sedimentary rocks and calc alkaline intermediate silicic volcanic complexes volcanosedimentary basement to the gindalbie volcanic sequences is deeply eroded equivalents of the calc alkaline volcanic complexes their associated sedimentary rocks and younger basaltic sequences found in the kurnalpi terrane gindalbie basalt rhyolite successions locally contain volcanic hosted massive cu zn mineral deposits rhyolites derived by low pressure fractional crystallisation or melting of andesites are more abundant than in the kurnalpi volcanic complexes facies associations and the local occurrence of distinctive incompatible element enriched mildly peralkaline a type rhyolites are consistent with rifting of a mature arc system the two terranes most likely represent volcanic evolution of the same late archaean volcanic arc but are different tectonic fragments that were welded together by 2660 ma

a ferroan region of the lunar highlands as recorded in meteorites mac88104 and mac88105 macalpine hills 88104 and 88105 mac88104 5 are paired meteorites of noritic anorthosite composition from the lunar highlands mac88105 is a breccia composed mainly of melt breccia clasts in a fine grained fragmental and partly glassy matrix the most abundant melt lithologies are feldspathic and are similar in composition to the bulk meteorite other melt lithologies include feldspathic melt rocks mafic melt breccias and a rare melt breccia relatively enriched in incompatible trace elements subordinate lithic clasts are granulitic breccias and ferroan relatively low mg mg fe igneous lithologies including troctolitic anorthosite anorthositic norite gabbronorite and anorthosite igneous clasts having mafic mineral compositions more magnesian than fo55 and en60 were not observed rare fragments of glass spheres and shards as well as glass clasts indicate that the meteorite was derived from an immature regolith the bulk composition of mac88105 is characterized by a molar mg mg fe ratio of 0 62 at the extreme low end of the range for meteorites from the lunar highlands its low concentrations of incompatible trace elements and feldspathic bulk composition 29 al2o3 suggest that it like the other lunar meteorites formed at a site far removed from the areas sampled by the apollo missions similarities in mineral compositions among the different lithologies of the breccia melt breccia clasts granulitic breccias igneous fragments and the distribution of mineral fragments suggest that most components of the meteorite were derived from a crustal section dominated by material with a noritic anorthosite composition and an affinity to the ferroan suite of plutonic rocks the mafic melt breccias have roughly peritectic melt compositions similar to many low k fra mauro melt breccias in the apollo collection but much more ferroan and represent a source material distinct from the noritic anorthosite moderate ce anomalies both positive and negative occur in some separated clasts and to a lesser extent in some small chips dominated by matrix but not in powder prepared from 20 g of bulk meteorite these anomalies are almost certainly terrestrial weathering effects one granulitic breccia clast is rich in siderophile elements as a result of a large amount of fe ni metal the auir ratio of the clast 0 64 ci normalized is distinctly different from that of metal rich impact melts from apollo 16 3 ci normalized the compositional range observed among the nonmare lunar meteorites alha81005 y791197 y82192 3 y86032 and mac88104 5 is equivalent to that observed among representative samples of 1 mm fines from apollo 16 thus compositional data provide little constraint on the number of impacts required to eject these meteorites from the moon

an unusual clast in lunar meteorite macalpine hills 88105 a unique lunar sample or projectile debris lunar meteorite macalpine hills mac 88105 is a well studied feldspathic regolith breccia dominated by rock and mineral fragments from the lunar highlands thin section mac 88105 159 contains a small rock fragment 400 350 m in size which is compositionally anomalous compared with other mac 88105 lithic components the clast is composed of olivine and plagioclase with minor pyroxene and interstitial devitrified glass component it is magnesian akin to samples in the lunar high mg suite and also alkali rich akin to samples in the lunar high alkali suite it could represent a small fragment of late stage interstitial melt from an mg suite parent lithology however olivine and pyroxene in the clast have fe mn ratios and minor element concentrations that are different from known types of lunar lithologies as fe mn ratios are notably indicative of planetary origin the clast could either 1 have a unique lunar magmatic source or 2 have a nonlunar origin i e consist of achondritic meteorite debris that survived delivery to the lunar surface both hypotheses are considered and discussed the meteoritical society 2014

u pb dating constraints on the felsic and intermediate volcanic sequence of the nickel sulphide bearing cosmos succession agnew wiluna greenstone belt yilgarn craton western australia abstract the cosmos succession within the agnew wiluna greenstone belt of the yilgarn craton consists of ultramafic intermediate and felsic volcanic lithologies and contains several komatiite hosted nickel sulphide ore bodies the volcanic succession that forms the stratigraphic footwall to the mineralised komatiite lavas consists of an intercalated sequence of fragmental and coherent extrusive lithologies ranging from basaltic andesites through to rhyolites it also contains cross cutting felsic intrusions the stratigraphic hangingwall consists largely of reworked volcanic derived sedimentary rocks that include polymictic conglomerates containing granitic clasts sims u pb dating was undertaken on zircons from nine felsic lithologies spanning the established stratigraphy the footwall succession gives emplacement ages ranging from 2736 4 to 2724 3 ma the overlying cosmos ultramafic sequence consists of two units the basal ultramafic umu1 package and the upper ultramafic umu2 package which are separated by a discontinuous felsic volcanic horizon that sits approximately 30 60 m above the basal contact of the cosmos ultramafic sequence this discontinuous felsic horizon is dated at 2685 8 ma and represents a break in accumulation of komatiite lavas and may be associated with a major hiatus the succession also features two felsic intrusions emplaced at 2653 7 ma and 2670 6 ma where the latter cross cuts the upper contact of the umu2 package these results bracket the age of umu1 package between 2724 3 ma and 2685 8 ma and that of umu2 package between 2685 8 ma and 2670 6 ma this stratigraphic division of the cosmos ultramafic is further strengthened by the contrasting styles of mineralisation above and below the discontinuous felsic horizon and associated unconformity umu1 hosts several massive nickel sulphide deposits situated at the contact with the footwall volcanic succession while umu2 is typified by high tenor disseminated nickel sulphide deposits situated just above the discontinuous felsic horizon our data indicates that the cosmos volcanic succession was accumulated via punctuated volcanism spanning 50 ma that was followed by intrusive activity lasting for at least a further 32 ma the results also imply that construction of this relatively small mineralised greenstone succession lasted longer than anticipated on stratigraphic considerations alone an outcome that may have implications for the timing of emplacement of other bi modal volcanic successions in similar greenstone terranes

highly siderophile element depletion in the moon abstract coupled 187 os 188 os and highly siderophile element hse os ir ru pt pd re abundance data are reported for apollo 12 12005 12009 12019 12022 12038 12039 12040 apollo 15 15555 and apollo 17 70135 mare basalts along with mare basalt meteorites la paz icefield lap 04841 and miller range mil 05035 these mare basalts have consistently low hse abundances at 2 10 5 to 2 10 7 the chondritic abundance the most magnesian samples have broadly chondrite relative hse abundances and chondritic measured and calculated initial 187 os 188 os the lower abundances and fractionated hse compositions of more evolved mare basalts can be reproduced by modeling crystal liquid fractionation using rock melt bulk partition coefficients of 2 for os ir ru pt and pd and 1 5 for re lunar mare basalt bulk partition coefficients are probably higher than for terrestrial melts as a result of more reducing conditions leading to increased hse compatibility the chondritic relative abundances and chondritic 187 os 188 os of the most primitive high mgo mare basalts cannot readily be explained through regolith contamination during emplacement at the lunar surface mare basalt compositions are best modeled as representing 5 11 partial melting of metal free sources with low os ir ru pd 0 1 ng g 1 pt 0 2 ng g 1 re 0 01 ng g 1 and s 75 g g 1 with sulphide melt partitioning between 1000 and 10 000 apollo 12 olivine pigeonite and ilmenite normative mare basalts define an imprecise 187 re 187 os age of 3 0 0 9 ga with an initial 187 os 188 os of 0 107 0 010 this age is within uncertainty of 147 sm 143 nd ages for the samples the initial os isotopic composition of apollo 12 samples indicates that the source of these rocks evolved with re os within 10 of chondrite meteorites from the time that the mantle source became a system closed to siderophile additions to the time that the basalts erupted similarity in absolute hse abundances between mare basalts from the apollo 12 15 and 17 sites and from unknown regions of the moon la paz mare basalts mil 05035 indicates relatively homogeneous and low hse abundances within the lunar interior low absolute hse abundances and chondritic re os of mare basalts are consistent with a late accretion addition of 0 02 wt of the moon s mass to the mantle prior to the formation of the lunar crust late accretion must also have occurred significantly prior to cessation of lunar mantle differentiation 4 4 ga to enable efficient mixing and homogenization within the mantle low lunar hse abundances are consistent with proportionally 40 times more late accretion to earth than the moon disproportional late accretion to the two bodies is consistent with the small 182 w excess 21 28 ppm measured in lunar rocks compared to the silicate earth

district to camp controls on the genesis of komatiite hosted nickel sulfide deposits agnew wiluna greenstone belt western australia insights from the multiple sulfur isotopes the agnew wiluna greenstone belt of western australia is the largest komatiite hosted nickel sulfide belt in the world and contains two world class ni cu pge deposits and a host of smaller deposits this study focuses on the broader scale geology of this greenstone belt in order to understand the key controls on the genesis of the komatiite hosted ni cu pge deposits with specific focus on camp to district controls we apply multiple sulfur isotopes to this geologic framework and conclude not only that the addition of crustal sulfur is a prerequisite for ore genesis in komatiite systems but above all that the sulfur required to generate world class deposits is most likely derived from barren volcanic massive sulfide lenses which are spatially and genetically associated with felsic volcanic and volcaniclastic sequences that were emplaced coevally with large komatiitic sills and channelized lava flows multiple sulfur isotope data can be utilized in exploration at the deposit to district scales at the deposit scale the spatial pattern of mass independent s isotope values 33 s provides crucial insight into the identification of proximal high grade and high tenor ores in mineralized systems in fact sulfur data reflect the assimilation process that occurred upon komatiite emplacement whereby hot turbulent magma thermomechanically eroded and assimilated exhalative sulfides spatially located close to vent with negative to near zero 33 s values whereas less turbulent flows interacted with distal sulfidic shales having 33 s values above 0 per mil accordingly the spatial variation of multiple sulfur isotope values in magmatic sulfides and associated host rocks may be utilized as a vector towards high grade ores of poorly known systems at the district scale rather than ascertaining what controls the distribution of komatiite hosted ni cu pge deposits the appropriate question to ask is what controls the distribution of country rock sulfides considering that exhalative sulfides may be crucial to ore genesis in komatiite systems we propose that felsic lava domes unambiguously mark their vents and can be directly mapped or inferred from gravity data this work provides the first step in identifying district scale control on komatiite hosted ni cu pge deposits this is the scale that has high impact on exploration for new komatiite hosted nickel sulfide belts globally

isotope analysis of crystalline impact melt rocks from apollo 16 stations 11 and 13 north ray crater rubidium strontium and sm nd isotopic data were obtained for lunar impact melt rocks from apollo 16 stations 11 and 13 as part of the north ray crater target rock consortium study rubidium strontium whole rock data define an isochron age t 3 69 0 16 b y 0 0142 b y 1 and initial 87sr 86sr isr 0 69918 5 for feldspathic microporphyritic fm samples internal rb sr isochrons of t 3 86 0 05 b y isr 0 69952 10 and t 3 76 0 04 b y isr 0 69916 4 were determined for very high alumina vha melt rock 67747 and anorthositic noritic melt rock anmr 67559 respectively t isr for these and other lunar melt rocks were examined to infer the nature of the protolith for the rocks isr values for the an mr and fm rocks are consistent with an anorthositic protolith probably a mixture of nonpristine anorthositic gabbros and pristine anorthosites anorthositic norites norites troctolites and possibly dunites the source protolith of the vha rocks apparently had a significant kreep component and the protolith for apollo 16 kreep must have had nearly the same rb sr ratio as that of apollo 14 kreep two stage model calculations using the t isr parameters suggest that some of the melt rocks were open rb sr systems during impact melting rubidium strontium model ages for the fm and vha rocks show a smoothly monotonic decrease with increasing rb content model ages of the anmr are uniformly low relative to 4 56 b y it is suggested that these effects are due to formation of these rocks by impact partial melting rubidium strontium model ages of the kreep rocks do not vary with rb content suggesting that they were closed rb sr systems during impact melting samarium neodymium data for mineral separates of 67747 showed only a small variation in sm nd ratio and yield an imprecisely defined isochron of 3 6 0 4 b y plagioclase separates of 67559 appear not to have reached nd isotopic equilibrium during impact melting consequently the internal isochron age is also imprecisely defined at 4 0 0 4 b y nd values for the melt rocks are about 1 to 2 at their rb sr or 40ar 39ar ages are consistent with the protolith compositions inferred from the rb sr data and show that lunar crustal sm nd evolution departed from chondritic evolution early in lunar history the average chondritic uniform reservoir chur model age of those anmr and fm rocks that apparently remained closed rb sr and sm nd systems during impact melting is 4 37 0 10 b y consistent with earlier suggestions that the lunar crust formed at about that time the average chur model age of two vha rocks is 4 10 0 15 b y suggesting that these rocks were open sm nd systems as well as open rb sr systems during impact partial melting current hypotheses for the site geology stratigraphy and radiometric age data lead us to suggest that the nectaris basin and the descartes formation were formed about 4 1 b y ago and the imbrium basin and the cayley formation were formed about 3 81 3 86 b y ago the ages of some individual melt rocks probably date local cratering events however

paired lunar meteorites mac88104 and mac88105 a new fan of lunar petrology abstract new lunar meteorite mac88104 5 represents an exciting new opportunity to study a potentially unsampled region of the moon we have analyzed six thin sections by electron microprobe and three bulk samples by instrumental neutron activation ina in order to determine the chemical characteristics of this new lunar sample lunar meteorite macs 8104 5 is dominated by lithologies of the ferroan anorthosite fan suite and contains abundant granulitized highland clasts devitrified glass beads of impact origin and two small clasts which appear to be of basaltic origin one of these asaltic clasts clast e in mac88105 84 is probably mesostasis material whereas the second larger clast clast g may be similar to the very low ti vlt or low ti high alumina mare basalts impact melt clasts mac88105 69 and 72 have major and trace element compositions similar to the bulk meteorite there is little evidence of any lkfm low k fra mauro or low k kreep contribution to this meteorite as mac88104 5 and other brecciated lunar meteorites are fe rich and poor in the incompatible elements relative to apollo 16 regolith and feldspathic breccias while the exact site of origin for the lunar meteorites cannot be pinpointed it is evident that they were derived from a relatively kreep free ferroan anorthosite terrain

targeting the impactors siderophile element signatures of lunar impact melts from serenitatis abstract highly siderophile element compositions of lunar impact melt breccias provide a unique record of the asteroid population responsible for large cratering events in the inner solar system melt breccias associated with the 3 89 ga serenitatis impact basin resolve at least two separate impact events kreep rich melt breccias representing the apollo 17 poikilitic suite are enriched in highly siderophile elements 3 6 15 8 ppb ir with ci normalized patterns that are elevated in re ru and pd relative to ir and pt the restricted range of lithophile element compositions combined with the coherent siderophile element signatures indicate formation of these breccias in a single impact event involving an eh chondrite asteroid probably as melt sheet deposits from the serenitatis basin one exceptional sample a split from melt breccia 77035 has a distinctive lithophile element composition and a siderophile element signature more like that of ordinary chondrites indicating a discrete impact event the recognition of multiple impact events and the clear signatures of specific types of meteoritic impactors in the apollo 17 melt breccias shows that the lunar crust was not comprehensively reworked by prior impacts from 3 9 to 4 5 ga an observation more consistent with a late cataclysm than a smoothly declining accretionary flux late accretion of enstatite chondrites during a 3 8 4 0 ga cataclysm may have contributed to siderophile element heterogeneity on the earth but would not have made a significant contribution to the volatile budget of the earth or oxidation of the terrestrial mantle siderophile element patterns of apollo 17 poikilitic breccias become more fractionated with decreasing concentrations trending away from known meteorite compositions to higher re ir and pd pt ratios the compositions of these breccias may be explained by a two stage impact melting process involving 1 deep penetration of the serenitatis impactor into meteorite free lower crust followed by 2 incorporation of upper crustal lithologies moderately contaminated by prior meteoritic infall into the melt sheet trends to higher re ir with decreasing siderophile element concentrations may indicate an endogenous lunar crustal component or a non chondritic late accretionary veneer in the pre serenitatis upper crust

internal stratigraphic architecture of the komatiitic dunite hosted mkd5 disseminated nickel sulfide deposit mount keith domain agnew wiluna greenstone belt western australia the mkd5 nickel deposit is hosted by the mount keith ultramafic complex mkuc a dunite body of komatiitic affinity located in the agnew wiluna greenstone belt western australia the internal architecture of the mkuc comprises seven distinct internal units that range from extreme adcumulate dunite to relatively fractionated pyroxenitic and gabbroic horizons the mkuc is divided into three packages of units the main adcumulate domain mad which is situated in the lower portion of the complex contains the bulk of disseminated nickel sulfide and is dominated by coarse adcumulate olivine textures overlying the mad is an upper fractionated zone which is dominated by mesocumulate to orthocumulate peridotite with domains containing oikocrystic pyroxenite and gabbroic lenses an aerially restricted unit comprising texturally and chemically distinct olivine cumulate rocks is known as the western mineralized zone wmz the fractionation trend between the mad and upz indicates a westerly facing for the mkuc conformable with the bounding stratigraphy in the mkuc truncation of some of the uppermost internal stratigraphic units by the hangingwall contact indicates that the unit has undergone structural modification since its emplacement and suggests that a proportion of the upper section has been removed by faulting furthermore vertical and lateral textural transitions within the internal stratigraphy suggest that the mkuc excluding the wmz was emplaced from an essentially continuous magma flow with the mad representing the period of highest magma flux and the major constructional period of emplacement conversely the wmz is interpreted to represent a later pulse of ultramafic magma emplaced stratigraphically above the main mkuc comparison of the mkuc with other komatiitic dunites from both within the agnew wiluna greenstone belt and worldwide indicates that despite apparent geometrical differences between lens and sheet komatiitic dunites a broad facies architecture can be defined we suggest that the differences in geometry are related to differing degrees of flow localization within dunitic units and are a function of both differences in the thermal characteristics and the degree of litho facies heterogeneity of the enclosing lithologies

highly siderophile element constraints on accretion and differentiation of the earth moon system a new combined rhenium osmium and platinum group element data set for basalts from the moon establishes that the basalts have uniformly low abundances of highly siderophile elements the data set indicates a lunar mantle with long term chondritic highly siderophile element ratios but with absolute abundances that are over 20 times lower than those in earth s mantle the results are consistent with silicate metal equilibrium during a giant impact and core formation in both bodies followed by post core formation late accretion that replenished their mantles with highly siderophile elements the lunar mantle experienced late accretion that was similar in composition to that of earth but volumetrically less than approximately 0 02 lunar mass and terminated earlier than for earth

geochemistry and petrography of the macalpine hills lunar meteorites abstract macalpine hills 88104 and 88105 are anorthositic lunar meteorites recovered from the same area in antarctica which are demonstrated to be paired samples of the same fall petrographic studies of matrix and clasts show that mac88104 5 is a polymict breccia dominated by impact melt clasts it contains a small amount of highland impact glass and very few regolith glass spherules it is better classified as a fragmental breccia than a regolith breccia the bulk composition is ferroan mg 63 and highly aluminous al 2 o 3 28 ree and other incompatible element concentrations are very low compositions of anorthositic granulitic and impact melt breccia clasts are very similar to but distinct from matrix composition mac88104 5 is very similar in composition to the other anorthositic lunar meteorites but each of the meteorites is distinct the anorthositic lunar meteorites especially mac88104 5 and y82192 3 86032 are very similar to north ray crater feldspathic fragmental breccias in compositon and petrography these fragmental lunar meteorites may have been ancient deeply buried breccias from the megaregolith comparisons of chemical petrographic features and exposure histories suggest that the twelve lunar meteorites were derived from two to nine but probably four to seven impacts onto the lunar surface discrepancies between the proportions of lunar meteorites and results of apollo missions may be due to unrepresentative sampling lunar meteorites provide valuable new information on the nature of the lunar crust

phosphate ages in apollo 14 breccias resolving multiple impact events with high precision u pb sims analyses abstract the u pb systems of apatite and merrillite grains within four separate apollo 14 impact melt breccia samples were analysed by secondary ion mass spectrometry no systematic difference was identified between the 207 pb 206 pb ages of the apatites and merrillites a combined 207 pb 206 pb age of 3927 2 ma 95 conf is determined for three of these samples 14305 103 3926 4 ma 14306 150 3926 6 ma 14314 13 3929 4 ma by combining these data with the ages previously obtained for zircons in apollo 12 impact melt breccia fragments and the lunar meteorite sau 169 a weighted average age of 3926 2 ma 95 conf is obtained which is attributed to the formation of the imbrium basin an age of 3943 5 ma is determined for the fourth breccia 14321 134 which is similar to ages of 3946 15 ma and 3958 19 ma obtained from several older phosphates in 14305 103 and 14314 13 the weighted average of these three older ages is 3944 4 ma 95 conf this is indistinguishable to the age 3938 4 ma 2 obtained for a different apollo 14 impact melt breccia in a previous study after investigating likely sources for this older 3940 ma age we conclude that the humorum or serenitatis basin forming events are likely candidates the potential identification of two large impact events within 15 myrs has important implications for the rate of lunar bombardment around 3 95 3 92 ga this study demonstrates the importance of high precision age determinations for interpreting the impact record of the moon as documented in lunar samples

composition of the cayley formation at apollo 16 as inferred from impact melt splashes chemical data for impact melt splashes ims collected at the apollo 16 landing site show that ni concentrations and feo ni cr ni and co ni correlations are consistent with a chondritic meteoritic component present at levels between approximately 1 5 and 11 wt like apollo 16 soils the ims are intermediate in composition to apollo 16 rocks the chemical data for the ims are consistent with two main compositional groups the group a ims 28 samples are chemically distinct from local apollo 16 soils and are very similar to mixtures of anorthosite and low sc vha lscvha impact melt rocks calculated to a meteorite free basis their average sc concentration la sc mgo sc and tio2 mgo ratios and mg value are 6 1 ug g 1 94 9800 0 066 and 0 74 respectively the group b ims seven samples have chemical equivalents among the soils five samples are chemically very similar to mature apollo 16 soils from the central and southern parts of the landing site two are more similar to soils 67601 and 67941 from north ray crater generally the group b ims and soils are enriched in a composition similar to anorthositic norite 67215 or mixtures thereof with anorthosite as compared to the group a ims the average sc concentration la sc mgo and tio2 mgo ratios and mg value for the subgroup of five are 9 3 ug g 1 41 5780 0 124 and 0 66 respectively the corresponding values for the subgroup of two are 7 5 ug g 1 04 7400 0 090 and 0 71 respectively the group b ims and most soils have a minor high ti component not present in the group a ims if this component is high ti mare basalt its average concentration is approximately 1 6 wt the seven group a ims that have been dated by rare gas methods all have approximately 2 m y exposure ages an age generally associated with south ray crater these seven and potentially most group a ims are likely quenched samples of the melt volume produced by the south ray impact the chemical signature of the impacting projectile is chondritic and its average concentration for the group a ims is 7 3 wt like large coherent melt sheets from terrestrial impacts the impact melt volume of the south ray impact as represented by the group a ims is homogeneous with respect to target lithologies target lithologies at south ray crater which are represented by the host rocks for the ims include anorthosite lscvha impact melt rocks hscvha impact melt rocks and dimict breccias with the exception of 61016 the melt portion of analyzed dimict breccias has the hscvha composition implying that the dimensional scales of lscvha type of rocks and anorthosite in the south ray target do not extend to the 1 10 cm scale observed for the hscvha dimict breccias the compositional difference between group a ims and surface soils from the southern part of the landing site implies stratigraphic variation in the dominant type of vha impact melt rock within the cayley formation chemical data and mixing model results are consistent with a model in which hscvha rocks dominate lscvha rocks in the surface layer the lscvha rocks dominate hscvha rocks in the layer beneath the south ray impact penetrated both layers as both types of vha impact melt rocks are traceable as ejecta material its impact melt volume was formed primarily from the lower layer to give the observed composition of the group a ims that the north ray impact also sampled the lower layer is indicated by the chemical affinities of soils 67601 and 67941 with the lscvha composition away from north ray crater most soils have chemical affinities with the hscvha composition reflecting soil development primarily from the surface layer estimated average compositions give tio2 mgo sc and la concentrations of 0 69 and 7 1 wt and 10 5 and 21 2 ug g respectively for the surface cayley layer and 0 38 and 5 9 wt and 6 1 and 11 8 ug g respectively for the subsurface cayley layer an average composition estimated for the descartes formation from soil compositions has tio2 mgo sc and la concentrations of 0 25 and 3 5 wt and 7 7 and 2 2 ug g respectively the cayley formation is more kreepy more magnesian and less aluminous than the descartes formation

rhodium gold and other highly siderophile element abundances in chondritic meteorites abstract the abundances of the highly siderophile elements hse re os ir ru pt rh pd and au and 187os 188os isotope ratios have been determined for a set of carbonaceous ordinary enstatite and rumuruti chondrites using an analytical technique that permits the precise and accurate measurement of all hse from the same digestion aliquot concentrations of re os ir ru pt and pd were determined by isotope dilution icp ms and n tims analysis the monoisotopic elements rh and au were quantified relative to the abundance of ir differences in hse abundances and ratios such as re os 187os 188os pd ir and au ir between different chondrite classes are further substantiated with new data and additional rh and au data including new data for ci chondrites systematically different relative abundances of rh between different chondrite classes are reminiscent of the behaviour of re carbonaceous chondrites are characterized by low average rh ir of 0 27 0 03 1s which is about 20 lower than the ratio for ordinary 0 34 0 02 and enstatite chondrites eh 0 33 0 01 el 0 32 0 01 r chondrites show higher and somewhat variable rh ir of 0 37 0 07 well defined linear correlations of hse in particular for bulk samples of ordinary and el chondrites are explained by binary mixing and or dilution by silicates the hse carriers responsible for these correlations have a uniform chemical composition indicating efficient homogenization of local nebular heterogeneities during or prior to the formation of the host minerals in chondrite components excepting rumuruti chondrites and au in carbonaceous chondrites these correlations also suggest that metamorphism alteration and igneous processes had negligible influence on the hse distribution on the bulk sample scale depletion patterns for rh pd and au in carbonaceous chondrites other than ci are smoothly related to condensation temperatures and therefore consistent with the general depletion of moderately volatile elements in carbonaceous chondrites fractionated hse abundance patterns of ordinary enstatite and rumuruti chondrites however are more difficult to explain fractional condensation combined with the removal of metal phases at various times and later mixing of early and late formed metal phases may provide a viable explanation planetary fractionation processes that may have affected precursor material of chondrite components cannot explain the hse abundance patterns of chondrite groups hse abundances of some but not all rumuruti chondrites may be consistent with solid sulphide liquid sulphide fractionation processes during impact induced melting

lunar meteorites siderophile element contents and implications for the composition and origin of the moon abstract six lunar meteorites have thus far been discovered in antarctica although these meteorites are of undocumented lunar geographic provenance all other available lunar samples obtained from the apollo and luna programs came from a relatively minuscule region of the central nearside around which a polygon could be drawn covering just 4 7 of the lunar surface the five lunar meteorites that are now well studied represent at least two but probably three separate lunar source craters alha81005 and y791197 are probably from separate craters and compound meteorite y82192 6032 is certainly from a crater of its own at least alha81005 and y791197 and probably also at least in a loose sense y82192 6032 are highlands regolith breccias thus their compositions may be appropriately compared with compositions of apollo and luna highlands regolith samples compared with average highlands regolith samples from the central nearside apollo sites lunar meteorites have lower concentrations of siderophile elements in general and especially au ge and ni among anorthositic apollo samples i e mainly those from apollo 16 au ir and to a lesser extent ge ir ratios tend to be hyperchondritic most previous models for lunar regolith siderophile geochemistry assumed that the apollo 16 samples are representative of the overall lunar highlands such models tended to conclude that the hyperchondritic au ir and ge ir ratios were consequences of variations in the compositions of moon striking projectiles as a function of time it was even speculated that these temporal variations were consequences of the heterogeneous accretion of a moon with a general enrichment in refractory elements the lunar meteorites suggest that hyperchondritic au ir and ge ir are not general features of the highlands but peculiarities of the apollo 16 region or more generally the central nearside the high ni contents of the apollo 16 megaregolith substantially in excess of the ni implied by a model in which all meteoritic debris has an h chondritic ni ir ratio have been interpreted to imply that the mg rich fraction of the lunar crust is extremely ni rich and thus similar in siderophile geochemistry to terrestrial komatiites this coincidence has been interpreted as confirmation that the moon formed by modified fission from the earth s mantle after core formation plus late accretion effects had established the final siderophile pattern of the earth s mantle however the lunar meteorites and a survey of data for the luna 20 highlands regolith sample suggest that the high ni content of the apollo 16 regolith is strictly a peculiarity of the apollo 16 region and not a general feature of the moon s crust the anomalous siderophile composition of the central nearside regolith probably stems from a combination of regional heterogeneity in cratering projectile compositions plus regional enrichments in relatively labile siderophile elements most notably au ge and perhaps to a certain extent ni which might be loosely correlated with the anomalously high concentration of kreep over the central nearside

a 3 d geological and structural synthesis of the leinster area of the agnew wiluna belt yilgarn craton western australia with special reference to the volcanological setting of komatiite associated nickel sulfide deposits the leinster area is situated toward the southern end of the agnew wiluna belt in the yilgarn craton of western australia and hosts the giant perseverance komatiite associated nickel sulfide deposit at in excess of 1 2 mt contained ni this is the biggest type 1 basal sulfide rich accumulation deposit in the world and it is associated with a number of smaller deposits that extend over a strike length of 20 km adjacent to the perseverance fault on the eastern margin of the belt in broad terms the greenstone sequence comprises an eastern rift proximal komatiite dacite sequence and a western and more marginal basalt dominated sequence with minor komatiite the komatiites display a wide range of compositions and textures from highly magnesian olivine meso to adcumulate rocks composed of olivine with forsterite contents of up to 94 5 to sequences of thin spinifex textured komatiite flow units this compositional range indicates considerable variation in volcanic facies from rift proximal to distal loci of focused flow termed pathways indicated by thickened cord like bodies of more olivine rich rock occur at all scales and are intimately associated with the ni sulfide mineralization the pathways are linked by thinner sequences of lower mgo rocks either layered olivine orthocumulate rocks or sequences of thin spinifex textured flow units some of the lower mgo komatiite sequences appear to emanate from the tops of pathways in the manner of breakout flows in tube fed basaltic terrains variably sulfidic black shales and cherts and barren exhalative iron sulfide horizons are intimately interlayered with the komatiitic rocks the overprinting effects of regional deformation and metamorphism spanning at least 80 m y are considerable at least eight local deformation events have been recognized by previous workers these have been used to constrain the 3 d model and can be linked to craton wide structural schemes some of the major faults are clearly accretionary and reflect reactivation of underlying basin forming structures early north over south thrusting was followed by e w directed basin closure and the development of nnw trending open regional folds extension accompanied batholithic granitoid intrusion and reactivated rift parallel nnw trending faults producing the major strike slip fault systems that divide the greenstone succession into a series of structural and stratigraphic domains the ensuing orogenic collapse resulted in overturning of the stratigraphy to the east subsequent brittle deformation events have produced fault sets in a variety of orientations that can be related to ongoing shortening with a variable principal stress orientation there is a complex interplay of structural and volcanological controls on the formation and subsequent deformation of the ni sulfide deposits in this ancient terrane three dimensional modeling has furthered a detailed understanding of the geologic and structural evolution of the belt allowed the identification of komatiite pathway positions and their plunges and provided quantitative data on the magnitude and direction of fault offsets of different generations the modeling exercise has shown that it is possible to strip away the effects of overprinting metamorphism and deformation to reveal some of the primary controls on komatiite volcanism and the location of ni sulfide deposits even in those portions of greenstone belts that are highly deformed and have undergone amphibolite facies metamorphism this is illustrated with case studies of the perseverance venus rocky s reward harmony and sir lancelot deposits three dimensional modeling has the capacity to integrate geologic geochemical and geophysical datasets in a way that fully utilizes the results of past exploration programs and produces a premium geologic product that can be used to guide further exploration the recent discovery of the venus deposit is in part a tribute to the power of this approach

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

characterization of the dominant impactor signature for apollo 17 impact melt rocks abstract concentrations of the highly siderophile elements hse re os ir ru pt and pd and 187 os 188 os isotopic compositions are reported for seven apollo 17 impact melt rocks these data are used to examine the dominant chemical signature of the impactor that formed the melts six of the samples 72355 72435 72535 76035 76055 and 76135 have poikilitic textures one sample 73235 has an aphanitic texture data for the samples define linear correlations when ir is plotted versus other hse concentrations with y intercepts indistinguishable from zero for most hse in most rocks scatter about some of the trends and occasional trends with positive y intercepts indicate either mixing of additional components that are heterogeneously distributed within several rocks or modest fractionation of some hse by volatilization crystal fractionation or other processes during formation and evolution of the melt sheet there is no statistical difference between the aphanitic and poikilitic samples in terms of hse ratios after visible granulitic clasts were removed from aphanite 73235 hence earlier speculations that the two types of impact melt rocks at this site may have been generated by different impactors are not supported by our data most apollo 17 samples examined here and in prior studies are characterized by very similar hse signatures consistent with a common impactor these samples are characterized by elevated ru ir pd ir and re os relative to most chondrites collectively the data indicate that the impactor was characterized by the following hse ratios 2 re ir 0 093 0 020 os ir 1 03 0 28 ru ir 1 87 0 30 pt ir 2 36 0 31 pd ir 1 85 0 41 and present day 187 os 188 os of 0 1322 0 0013 the results most likely mean that the impactor was a body with a bulk composition that was just outside the range of meteoritic compositions currently sampled on earth

television image of a large upward electrical discharge above a thunderstorm system an image of an unusual luminous electrical discharge over a thunderstorm 250 kilometers from the observing site has been obtained with a low light level television camera the discharge began at the cloud tops at 14 kilometers and extended into the clear air 20 kilometers higher the image which had a duration of less than 30 milliseconds resembled two jets or fountains and was probably caused by two localizd electric charge concentrations at the cloud tops large upward discharges may create a hazard for aircraft and rocket launches and by penetrating into the ionosphere may initiate whistler waves and other effects on a magnetospheric scale such upward electrical discharges may account for unexplained photometric observations of distant lightning events that showed a low rise rate of the luminous pulse and no electromagnetic sferic pulse of the type that accompanies cloud to earth lightning strokes an unusually high rate of such photometric events was recorded during the night of 22 to 23 september 1989 during a storm associated with hurricane hugo

geochemistry and 40ar 39ar geochronology of impact melt clasts in feldspathic lunar meteorites implications for lunar bombardment history we studied 42 impact melt clasts from lunar feldspathic regolith breccias macalpine hills mac 88105 queen alexandra range que 93069 dar al gani dag 262 and dag 400 for texture chemical composition and or chronology although the textures are similar to the impactmelt clasts identified in mafic apollo and luna samples the meteorite clasts are chemically distinct from them having lower fe ti k and p thus representing previously unsampled impacts the 40ar 39ar ages on 31 of the impact melts the first ages on impact melt samples from outside the region of the apollo and luna sampling sites range from 4 to 2 5 ga we interpret these samples to have been created in at least six and possibly nine or more different impact events one inferred impact event may be consistent with the apollo impact melt rock age cluster at 3 9 ga but the meteorite impact melt clasts with this age are different in chemistry from the apollo samples suggesting that the mechanism responsible for the 3 9 ga peak in lunar impact melt clast ages is a lunar wide phenomenon no meteorite impact melts have ages more than 1 older than 4 0 ga this observation is consistent with but does not require a lunar cataclysm

timing of deformation in the norseman wiluna belt yilgarn craton western australia establishing relative and absolute time frameworks for the sedimentary magmatic tectonic and gold mineralisation events in the norseman wiluna belt of the archean yilgarn craton of western australia has long been the main aim of research efforts recently published constraints on the timing of sedimentation and absolute granite ages have emphasized the shortcomings of the established rationale used for interpreting the timing of deformation events in this paper the assumptions underlying this rationale are scrutinized and it is shown that they are the source of significant misinterpretations a revised time chart for the deformation events of the belt is established the first shortening phase to affect the belt d1 was preceded by an extensional event d1e and accompanied by a change from volcanic dominated to plutonic dominated magmatism at approximately 2685 2675 ma later extension d2e controlled deposition of the ca 2655 ma kurrawang sequence and was followed by d2 a major shortening event which folded this sequence d2 must therefore have started after 2655 ma at least 20 ma later than previously thought and after the voluminous 2670 2655 ma high ca granite intrusion younger transcurrent deformation d3 d4 waned at around 2630 ma suggesting that the crustal shortening deformation cycle d2 d4 lasted approximately 20 30 ma contemporaneous with low volume 2650 2630 ma low ca granites and alkaline intrusions time constraints on gold deposits suggest a late mineralisation event between 2640 2630 ma thus d2 d4 deformation cycle and late felsic magmatism define a 20 30 ma long tectonothermal event which culminated with gold mineralisation the finding that d2 folding took place after voluminous high ca granite intrusion led to research into the role of competent bodies during folding by means of numerical models results suggest that buoyancy driven doming of pre tectonic competent bodies trigger growth of antiforms whereas non buoyant competent granite bodies trigger growth of synforms the conspicuous presence of pre folding granites in the cores of anticlines may be a result from active buoyancy doming during folding 2002 elsevier science b v all rights reserved

osmium isotope and highly siderophile element constraints on ages and nature of meteoritic components in ancient lunar impact rocks abstract the concentrations of highly siderophile elements hse re os ir ru pt rh pd au and 187os 188os isotope compositions have been determined for 67 subsamples of six lunar impact rocks from the apollo 14 16 and 17 landing sites and the lunar meteorite dar al gani dag 400 using inductively coupled plasma mass spectrometry icp ms and negative thermal ionization mass spectrometry n tims we report the first re os isochron age on a lunar impact melt rock 187re 187os isotope systematics for apollo 16 sample 67935 define an isochron age of 4 21 0 13 ga mswd 1 5 which is interpreted to reflect localized partitioning processes between solid metal liquid metal as this rock melted the new age adds further constraints on the significance of pre 4 0 ga basin forming impacts on the moon and possible mixing of ancient impactor compositions in lunar impact rocks linear correlations displayed by subsamples of a given impact rock in plots of hse versus ir concentrations are explained by dilution processes through essentially hse free anorthositic lunar crustal target rocks or binary mixing between a high hse meteoritic end member and a low hse end member composition slope derived hse ratios and 187os 188os of the meteoritic component in granulitic impactites 67915 67955 and 79215 are similar to slightly volatile element depleted carbonaceous chondrites suprachondritic ratios of ru ir pt ir rh ir and pd ir for apollo 14 impact melt rock 14310 are similar to ratios observed for other apollo 14 samples and apollo 17 poikilitic impact melt rocks apollo 16 poikilitic and subophitic impact melt rocks 60315 and 67935 show slightly subchondritic os ir and suprachondritic ratios of 187os 188os ru ir pt ir rh ir pd ir and au ir their strongly fractionated hse compositions are similar to some members of the iva iron meteorite group and provide further evidence for an iron meteorite impactor component in apollo 16 impact melt rocks the range of chondritic to suprachondritic ratios of 187os 188os ru ir pt ir pd ir and chondritic to slightly subchondritic os ir of apollo 17 and 14 impact melt rocks may be explained by variable mixing of a carbonaceous chondrite like hse composition as in granulitic impactites with a suprachondritic iron meteorite like impactor composition as inferred from 67935 and 60315 and subsequent homogenization by younger impact events the inferred dispersal of these two components across the lunar nearside and their antiquity 4 2 ga suggest at least two basin forming impacts that predate the 3 9 3 8 ga basin forming era the hse composition of the silicate earth can be matched by a late veneer comprised of 80 volatile depleted carbonaceous chondrite like material and 20 differentiated meteoritic metal similar to what has been identified in ancient lunar impact rocks

mapping the radio sky with an interferometric network of low frequency radio receivers 1 the structure of the 100 khz radio sky is determined with two interferometric networks of 10 radio receivers which are distributed over local areas of 1 1 km2 and 10 10 km2 the radio waves arrive at individual receiver pairs with small time differences which are used to determine the arrival direction of the electromagnetic waves including both the bearing and the elevation angle the results show that the major part of the 100 khz radio wave energy comes from the horizon at bearings which are consistent with known locations of long range navigation loran transmitters some part of the radio wave energy arrives from the sky at elevation angles which are consistent with the first and second sky hop waves of loran transmissions a minor part of the 100 khz radio wave energy comes from lightning discharges at distances up to 1000 km with bearings which are consistent with lightning locations reported by the arrival time difference atd lightning detection network of the uk met office the angular resolution for mapping the radio sky depends on the network geometry the instrumental timing accuracy and on the signal to noise ratio of the radio waves the resulting angular resolution of the interferometric networks used in this study is 1 in bearing at zero elevation and several degrees in elevation

examining the compositions of impactors striking the moon using apollo impact melt coats and anorthositic regolith breccia meteorites abstract impactors striking the moon since the formation of its crust have left an indelible imprint on the lunar surface in the guise of craters and associated impact rocks the lunar crust has low intrinsic abundances of the highly siderophile elements hse re os ir ru pt rh pd au at greater than 3000 times lower than in chondrite meteorites consequently during impact bolides with chondritic or differentiated iron rich compositions should impart elevated hse signatures to the lunar crust here we examine glassy lunar impact melt coats imc from the outside rims of apollo 16 cataclastic anorthosites 60015 65325 and breccias 65035 as well as both fragments and powders of antarctic anorthositic regolith breccia arb meteorites miller range 090034 36 70 75 and macalpine hills 88105 for their petrography mineral chemistry and bulk rock compositions the hse concentrations for imc range from 0 001 to 0 1 ci chondrite with measured 187os 188os between 0 1189 and 0 1366 anorthositic regolith breccia meteorites which have components with 2 6 4 1 ga ages have similar hse concentrations to imc but typically have lower 187os 188os 0 1164 0 1284 these latter os ratios are generally less radiogenic than those measured in 3 8 3 9 ga apollo impact melt breccias the apollo 16 imc are not well dated but their kreepy trace element signatures and associated ages of 3 7 to 3 8 ga for apollo 16 glasses might imply at least in part an origin from the imbrium or serenitatis basin forming impacts within the imc metal schreibersite troilite assemblages record significant inter element hse fractionation which is also reflected in bulk hse patterns for both imc and arb meteorites variations in relative and absolute hse compositions directly reflect the control of metal and sulfide segregation within and between impact melt and breccia lithologies collectively imc and arb meteorites exhibit approximately 50 of the variation in ru ir and 187os 188os observed in lunar impact melt breccias these results imply that significant variations in inter element compositions can occur during impact brecciation and melting and so some impact melt rock hse compositions may not record the compositions of impactors that struck the moon with fidelity nonetheless the generally low 187re 188os of lunar impact melt rocks means that osmium isotope ratios provide evidence for impact composition and a change from ordinary to carbonaceous like impactors either with time or location striking the moon

an automatic seismic event processing for detection and location the p m c c method we present a new method for automatic detection and location of seismic events recorded on a network it is based on a progressive study of the interstation correlation functions which leads to a consistent set of time delays when a seismic phase is present three different examples are processed on networks of different sizes

evolution of the archaean granite greenstone terranes of the eastern goldfields western australia shrimp upb zircon constraints abstract thirty five high precision shrimp u pb zircon dates with an average 95 confidence error of 6 ma have been obtained from the granite greenstone terranes in the southern part of the eastern goldfields of western australia these dates establish the timing of major deformation metamorphism and granite intrusion events and test inferred stratigraphic relationships within the greenstones these new data reveal that felsic volcanic rocks were erupted throughout the southern part of the eastern goldfields between c 2713 and c 2672 ma analytically indistinguishable dates of c 2705 ma were obtained for felsic volcanic rocks interbedded with komatiitic lavas at three sites dates on felsic volcanic rocks within tectonostratigraphic packages that include komatiites are also consistent with an inferred eruption age for these komatiites of c 2705 ma komatiitic lavas in the southern part of the eastern goldfields were probably emplaced during a single voluminous eruption that resulted in the flooding of a vast area of the late archaean landscape filling the topographic lows around older felsic volcanic vents the stratigraphic complexity within tectonostratigraphic domains is attributed to the existence of an undulating topography during the eruption of the mafic and ultramafic lavas and to the rapid and localized deposition of felsic volcanic rocks close to a number of isolated volcanic centres prior to and after the komatiite lava eruption event between c 2685 and c 2675 ma early pre d2 intrusive equivalents of the felsic volcanic rocks were emplaced as thick granite sheets into the base of the greenstone sequences regional east west compression between c 2675 and c 2657 ma reactivated early extensional structures and resulted in the stacking of the greenstones this was accompanied by further intrusion of granite within developing antiforms burial of greenstone slices by stacking and the effect of hydrothermal fluids emanating from both the granites and buried greenstones resulted in regional metamorphism to greenschist facies prior to c 2640 ma monzogranite and granodiorite emplaced near the western southern and eastern margins of the greenstones were deformed and metamorphosed to upper amphibolite facies and converted into gneisses during d2 and d3 compression events movement along large scale transcurrent d3 shear zones had ceased by c 2635 ma remnants of a c 2958 to c 2930 ma greenstone sequence preserved near norseman and ravensthorpe in the southeastern yilgarn craton and xenocryst zircons ranging in age from c 2910 2730 ma in the c 2713 2672 ma felsic volcanic rocks indicate that the exposed greenstone sequences were deposited on continental basement the eastern goldfields granite greenstone terranes were formed by the closure of a series of narrow back arc rift basins that developed along a continental margin and above an active subduction zone located to the east of the rift basins

map of low frequency electromagnetic noise in the sky the earth s natural electromagnetic environment is disturbed by anthropogenic electromagnetic noise here we report the first results from an electromagnetic noise survey of the sky the locations of electromagnetic noise sources are mapped on the hemisphere above a distributed array of wideband receivers that operate in a small aperture configuration it is found that the noise sources can be localized at elevation angles up to 60 in the sky well above the horizon the sky also exhibits zones with little or no noise that are found toward the local zenith and the southwest of the array these results are obtained by a rigorous analysis of the residuals from the classic dispersion relation for electromagnetic waves using an array analysis of electric field measurements in the frequency range from 20 to 250 khz the observed locations of the noise sources enable detailed observations of ionospheric modification for example caused by particle precipitation and lightning discharges while the observed exclusion zones enable the detection of weak natural electromagnetic emissions for example from streamers in transient luminous events above thunderclouds

komatiites and nickel sulfide ores of the black swan area yilgarn craton western australia 2 geology and genesis of the orebodies the black swan ultramafic succession hosts a number of magmatic fe ni cu pge sulfide ore shoots ranging from high grade massive ore to low grade disseminated sulfides of these the most economically significant is the silver swan massive sulfide orebody associated with the basal contact of the succession the deposit varies in thickness between 5 and 20 m reaches a n s strike length of 75 m extends for at least 1 2 km of vertical plunge and is open at depth overlying matrix net textured ore is rare inclusions of dacite are abundant within the lower 5 m of the massive sulfide they range from angular fragments through smooth sinuous and plumose morphologies to fine lace like intergrowths with the sulfide matrix and comprise variable proportions of cores of porphyritic dacite and carapaces with skeletal plagioclase phenocrysts dynamic crystallisation and kinetic melting textures in the carapaces indicate that the inclusions have been heated to various temperatures some well above their liquidus temperature the composition of the inclusions ranges from a perfect match with the immediate footwall dacites to mixtures of dacite with up to 30 komatiite the consistent thickness of the inclusion bearing basal layer within the massive sulphide is interpreted as the extent of 3 d physical connectivity between the inclusions and a partially molten underlying hybrid layer primary contacts between the silver swan massive sulfide orebody and overlying ultramafic rocks are marked by thin rinds containing coarse grained chevron textured chromites with skeletal textures compositions of these chromites match those from kambalda perseverance and other localities and are inconsistent with a metamorphic origin they are interpreted as markers of primary magmatic contacts the combination of this feature with the general paucity of matrix ore implies that the massive ore accumulated and solidified before the accumulation of the overlying thick sequence of olivine cumulates taken together with observations on the internal fractionation of platinum group elements within the massive ores these observations are consistent with a model where the massive ore were emplaced at the floor of a small partially drained lava tube the floor of the tube had been previously heated by passage of large volumes of lava such that it had reached its melting range the felsic inclusions within the ore are the result of buoyant ascent of partially molten substrate into the ore magma this constitutes strong evidence for the operation of thermo mechanical erosion during ore emplacement the disseminated cygnet and black swan orebodies show a number of distinctive features cygnet contains a assemblage of clasts and inclusions which are interpreted as the result of rip up transport and redeposition of sulfides from a pre existing massive sulfide orebody of which black duck may be a remnant the black swan orebody by contrast does not show xenolithic features but is characterised by an association of sulfide blebs with segregation vesicles and by unusually coarse grained olivine the black swan orebody is interpreted as the result of transport of sulfide droplets within a lava charged with a suspended load of coarse olivine crystals

osmium isotope and highly siderophile element systematics of the lunar crust abstract coupled 187os 188os and highly siderophile element hse os ir ru pt pd and re abundance data are reported for pristine lunar crustal rocks 60025 62255 65315 ferroan anorthosites fan and 76535 78235 77215 and a norite clast in 15455 magnesian suite rocks mgs osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks previously identified as pristine contain meteorite derived hse low hse abundances in fan and mgs rocks are consistent with derivation from a strongly hse depleted lunar mantle at the time of formation the lunar floatation crust represented by fan had 1 4 0 3 pg g 1 os 1 5 0 6 pg g 1 ir 6 8 2 7 pg g 1 ru 16 15 pg g 1 pt 33 30 pg g 1 pd and 0 29 0 10 pg g 1 re 0 00002 ci and re os ratios that were modestly elevated 187re 188os 0 6 to 1 7 relative to ci chondrites mgs samples are on average characterised by more elevated hse abundances 0 00007 ci compared with fan this either reflects contrasting mantle source hse characteristics of fan and mgs rocks or different mantle crust hse fractionation behaviour during production of these lithologies previous studies of lunar impact melt rocks have identified possible elevated ru and pd in lunar crustal target rocks the new results provide no supporting evidence for such enrichments if maximum estimates for hse in the lunar mantle are compared with fan and mgs averages crust mantle concentration ratios d values must be 0 3 such d values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle with the notable exception of re given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust the potential similarities in crust mantle hse partitioning for the earth and moon are somewhat surprising low hse abundances in the lunar crust coupled with estimates of hse concentrations in the lunar mantle implies there may be a missing component of late accreted materials as much as 95 to the moon if the earth moon mass flux estimates are correct and terrestrial mantle hse abundances were established by late accretion

evolved mare basalt magmatism high mg fe feldspathic crust chondritic impactors and the petrogenesis of antarctic lunar breccia meteorites meteorite hills 01210 and pecora escarpment 02007 antarctic lunar meteorites meteorite hills 01210 and pecora escarpment 02007 are breccias that come from different regolith lithologies on the moon met 01210 is composed predominantly of fractionated low ti basaltic material and is classified as an immature predominantly basaltic glassy matrix regolith breccia pca 02007 is a predominantly feldspathic regolith breccia consisting of metamorphosed feldspathic noritic troctolitic and noritic anorthosite clasts agglutinate and impact glasses as well as a number of basaltic clasts with mare and possible non mare affinities the basalt clasts in met 01210 have undergone fenner trend enrichments in iron and may also have witnessed late stage crystallization of zircon or a zirconium rich mineral some of the features of met 01210 are similar to other basaltic lunar breccia meteorites e g northwest africa 773 elephant moraine 87521 96008 yamato 793274 981031 but it is not paired with them the presence of metamorphic anorthositic clasts as well as agglutinates indicates a small regolith component similarities with previously discovered evolved e g lapaz icefield 02205 northwest africa 032 and ferroan e g asuka 881757 yamato 793169 basaltic lunar meteorites suggest a similar mare source region for met 01210 despite lack of evidence for pairing pca 02007 shares many features with other feldspathic regolith breccias e g yamato 791197 queen alexandra range 94281 including a high mg fe whole rock composition glass spherules agglutinate fragments and a diverse clast inventory spanning the range of ferroan anorthosite and high magnesium suite rocks some of the basalt fragments in this sample are fractionated and have an igneous origin however the majority of the basalt fragments are impact melt clasts pca 02007 supports previous studies of feldspathic lunar meteorites that have suggested an aluminous crust for the moon with compositions more similar to magnesium granulite breccias than ferroan anorthosites a chondrule like fragment found in pca 02007 and unlike any previously described lunar material is described and tentatively identified as the remnants of a chondritic lunar impactor this clast is porphyritic with equant olivines that have forsterite rich cores fo 98 extreme normal zonation to more fayalitic rims fo 44 and a mineral assemblage with rare earth element abundances distinct from described lunar material and more similar to chondrules found in ordinary or carbonaceous chondrites its discovery and description is significant for understanding the composition of lunar impactors previously the main evidence for chondritic lunar impactors was from chondritic relative abundances and near chondritic ratios of highly siderophile elements in lunar impact melt breccias however the presence of this clast along with two other chondritic clasts from apollo soils 12037 and 15602 provides clues to the identity of ancient meteorite impactors on the moon

new sims u pb zircon ages from the langavat belt south harris nw scotland implications for the lewisian terrane model secondary ionization mass spectrometry sims u pb dating of zircon has been applied to rocks of the lewisian complex of south harris outer hebrides nw scotland yielding insights into the complex geological evolution of this region and enhancing our understanding of terranes in the lewisian gneiss complex results show that tonalite trondhjemite granodiorite magmatism occurred in the tarbert terrane between c 2850 and 2830 ma equivalent to similar rocks in other parts of the outer hebrides magmatism was accompanied or closely followed by high grade metamorphism at c 2830 ma the first reported occurrence of such an event at this time these rocks were affected by a subsequent high grade metamorphic event at c 2730 ma which has correlatives both in the outer hebrides and in the mainland lewisian gruinard terrane these data suggest that the terranes forming the outer hebrides and parts of the mainland lewisian were once contiguous and were fragmented by post 2730 ma events the c 1700 1660 ma ages from felsic sheets and pegmatites within the langavat shear zone may record the reassembly of these crustal fragments

geodynamics of the eastern yilgarn craton abstract over the last decade there have been significant advances in our understanding of the stratigraphy magmatism deformation metamorphism and timing of mineralisation in the eastern yilgarn craton eyc of western australia the integration of these disciplines has enabled a holistic review of the tectonic history of the eyc which favours a paraautochthonous tectonic model a significant advance has been the recognition of a 2810 ma rifting event off the eastern margin of the youanmi terrane which set up the north northwest trending architecture of the eyc rifting was followed by a 100 myr long phase of tectonic activity initiated by the establishment of a convergent margin at 2715 ma characterised by a west dipping subduction zone to the east of the eyc subduction was associated with the deposition of 2715 2670 ma volcanic stratigraphy and the emplacement of voluminous tonalite trondhjemite granodiorite magmatism which resulted in magmatic thickening of the crust volcanism was terminated by a 5 myr pulse of east northeast contraction followed by mid orogenic extension possibly linked to lithospheric and lower crustal delamination the lack of ultra high pressure metamorphism and the presence of high geothermal gradients preclude this contractional event from recording continent continent collision mid orogenic extension at 2665 ma resulted in the introduction of metasomatised mantle melts mafic granites and syenites deposition of siliciclastic basins which record metamorphic anticlockwise ptt paths and the start of significant economic gold mineralisation in the eyc high stretching factors and or delamination associated with this extension event resulted in significant heat input into the base of the crust which eventually led to the emplacement of low ca crustal melt granites and cratonisation of the eyc major gold mineralisation postdates mid orogenic extension and was associated with renewed compression transpression 2650 ma and the development of steep predominantly north northwest striking sinistral and later north to north northeast striking dextral strike slip faults during low ca granite emplacement

the cosmos greenstone succession agnew wiluna greenstone belt yilgarn craton western australia geochemistry of an enriched neoarchaean volcanic arc succession abstract the geodynamic setting of the neoarchaean eastern goldfields superterrane egs of the yilgarn craton is the subject of debate some authors propose plume models while others advocate variants on a subduction accretion model for the origin of mineralised greenstone belt sequences felsic volcanism in the kalgoorlie terrane the westernmost terrane of the egs is considered to have a tonalite trondhjemite granodiorite dacite ttg d geochemical affinity the cosmos greenstone succession which lies in the agnew wiluna greenstone belt awb of the kalgoorlie terrane contains several komatiite hosted nickel sulphide deposits the volcanic footwall to which consists of an intercalated succession of fragmental and coherent rocks ranging in composition from basaltic andesite to rhyolite light rare earth elements lrees and large ion lithophile elements liles are strongly enriched relative to high field strength elements hfses across all volcanic units and the rocks display strong positive pb and negative nb anomalies these geochemical characteristics resemble closely those of modern high k calc alkaline to shoshonite continental arc successions contrasting ree lile and hfse concentrations coupled with assimilation fractional crystallisation afc modelling shows that the intercalated dacitic and andesitic volcanic rocks within the footwall succession are not co genetic xenocrystic zircons within the felsic volcanic lithologies indicate that some assimilation of older continental crust contributed to the generation of the footwall volcanic sequence the geochemical characteristics of the cosmos volcanic succession indicate that parental melts were derived via partial melting of enriched peridotite that had been contaminated by subducted crustal material within the mantle wedge of a subduction zone in contrast two younger felsic porphyry intrusions which cross cut the volcanic succession have a distinct ttg d affinity therefore these intrusions are considered to be generated via partial melting of a subducting slab and are related to local high ca granitoid intrusions the cosmos volcanic succession represents the first extrusive high k calc alkaline to shoshonitic volcanic arc sequence described in the kalgoorlie terrane and coupled with age dating of the stratigraphy is indicative of formation in a long lived volcanic arc setting active from 2736 ma to later than 2724 ma the composition and geochemical affinity of the volcanic footwall succession to the cosmos komatiite hosted nickel sulphide deposits contrasts with the majority of felsic volcanic rocks within the awb and also the wider kalgoorlie terrane suggesting that the overall architecture of this region is more complex than is currently thought our conclusions not only have consequences for recent models of the tectonic evolution of the egs but also contribute to the debate on the operation of plate tectonics during the late archaean in general the arc affinity of the cosmos volcanic succession containing abundant high k calc alkaline andesite lavas provides further support for the operation of plate tectonics in the neoarchaean

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

geochemical comparison of impact glasses from lunar meteorites alha81005 and mac88105 and apollo 16 regolith 64001 abstract most glasses that occur in lunar highland regolith are quenched droplets of impact melt the chemical compositions of these glasses are equivalent in the absence of volatile losses to the original target materials the compositional range of impact glasses in a regolith reflects the chemical diversity that existed throughout the region up to the time of system closure e g breccia formation since these glasses are a product of widespread and random sampling both in terms of space and time they can be used for geochemical exploration of the moon the major element compositions of impact glasses occurring in three samples of lunar feldspathic regolith alha81005 mac88105 apollo 16 64001 have been determined by electron microprobe the glass populations among these three unrelated samples are compositionally distinct while most of the impact glasses within each of these three samples are compositionally similar to the regolith in which they are found up to 40 of the impact glasses are different some of the compositionally exotic glasses were ballistically transported from other areas of the moon and thereby provide information about the compositional range of regoliths that exist elsewhere since the geological setting of the apollo 16 region is well known compared to the source areas of the lunar meteorites the apollo 16 glasses provide a ground truth for interpretations the thirty four impact glasses in meteorite alha81005 overlap the compositional range of feldspathic regoliths represented by all of the lunar highland meteorites i e y86031 y82192 y791197 mac88105 alha81005 and are compositionally distinct from highland regoliths sampled by apollo 14 apollo 16 apollo 17 and luna 20 a small proportion of alha81005 glasses contain a mare component no kreep glasses were observed due to their scarcity only ten impact glasses in lunar meteorite mac88105 were analyzed the spherules occur in two broadly defined compositional groups one group of glasses is similar to the bulk composition of mac88105 whereas the other group is more mafic all of these glasses are distinct from highland regoliths sampled by apollo 14 apollo 16 and apollo 17 and luna 20 a low ti mare glass was also analyzed in mac88105 no kreep glasses were observed the two hundred and fifty three aluminous impact glasses analyzed in apollo 16 regolith 64001 display a prominent grouping of compositions equivalent to the local regolith in addition about 10 of the glasses in 64001 are distinct from the local regolith and chemically resemble the lunar highland meteorites alha81005 mac88105 these glasses may record the chemical composition of an ancient regolith that occurred in the apollo 16 region prior to the arrival of kreep and mare components twentythree percent of the glasses in 64001 have high ti mare affinities these mare glasses are clearly exotic to the apollo 16 site and have been transported from distances of at least 300 km

osmium isotope and highly siderophile element systematics of lunar impact melt breccias implications for the late accretion history of the moon and earth abstract to characterize the compositions of materials accreted to the earth moon system between about 4 5 and 3 8 ga we have determined os isotopic compositions and some highly siderophile element hse re os ir ru pt and pd abundances in 48 subsamples of six lunar breccias these are apollo 17 poikilitic melt breccias 72395 and 76215 apollo 17 aphanitic melt breccias 73215 and 73255 apollo 14 polymict breccia 14321 and lunar meteorite nwa482 a crystallized impact melt plots of ir versus other hse define excellent linear correlations indicating that all data sets likely represent dominantly two component mixtures of a low hse target presumably endogenous component and a high hse presumably exogenous component linear regressions of these trends yield intercepts that are statistically indistinguishable from zero for all hse except for ru and pd in two samples the slopes of the linear regressions are insensitive to target rock contributions of ru and pd of the magnitude observed thus the trendline slopes approximate the elemental ratios present in the impactor components contributed to these rocks the 187 os 188 os and regression derived elemental ratios for the apollo 17 aphanitic melt breccias and the lunar meteorite indicate that the impactor components in these samples have close affinities to chondritic meteorites the hse in the apollo 17 aphanitic melt breccias however might partially or entirely reflect the hse characteristics of hse rich granulitic breccia clasts that were incorporated in the impact melt at the time of its creation in this case the hse characteristics of these rocks may reflect those of an impactor that predated the impact event that led to the creation of the melt breccias the impactor components in the apollo 17 poikilitic melt breccias and in the apollo 14 breccia have higher 187 os 188 os pt ir and ru ir and lower os ir than most chondrites these compositions suggest that the impactors they represent were chemically distinct from known chondrite types and possibly represent a type of primitive material not currently delivered to earth as meteorites

experimental investigations of trace element fractionation in iron meteorites ii the influence of sulfur abstract we have investigated the partitioning of ir ge ga w cr au p and ni between solid metal and metallic liquid as a function of temperature and s concentration of the metallic liquid partition coefficients for siderophile elements such as ir w ga and ge increase by factors of 10 100 as the sconcentration of the metallic liquid increases from 0 30 wt partition coefficients for other siderophile elements such as ni au and p increase by only factors of 2 3 in contrast partition coefficients for the more chalcophile element cr decrease these experimentally determined partition coefficients have been used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of ni p au and ir during the magmatic evolution of groups iiab iiiab iva and ivb iron meteorites the mean s concentration for each group increases in the order ivb iva iiiab iiab in accord with cosmochemical prediction however we are unable to reproduce the geochemical behavior of ge ga w and cr in an internally consistent way we conclude that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed

compositional and lithological diversity among brecciated lunar meteorites of intermediate iron concentration we present new compositional data for 30 lunar stones representing about 19 meteorites most have iron concentrations intermediate to those of the numerous feldspathic lunar meteorites 3 7 feo and the basaltic lunar meteorites 17 23 feo all but one are polymict breccias some as implied by their intermediate composition are mainly mixtures of brecciated anorthosite and mare basalt with low concentrations of incompatible elements such as sm 1 3 g g these breccias likely originate from points on the moon where mare basalt has mixed with material of the fht feldspathic highlands terrane others however are not anorthosite basalt mixtures three 17 75 g g sm consist mainly of nonmare mafic material from the nearside pkt procellarum kreep terrane and a few are ternary mixtures of material from the fht pkt and maria some contain mafic nonmare lithologies like anorthositic norites norites gabbronorites and troctolite these breccias are largely unlike breccias of the apollo collection in that they are poor in sm as well as highly feldspathic anorthosite such as that common at the apollo 16 site several have high th sm compared to apollo breccias dhofar 961 which is olivine gabbronoritic and moderately rich in sm has lower eu sm than apollo samples of similar sm concentration this difference indicates that the carrier of rare earth elements is not kreep as known from the apollo missions on the basis of our present knowledge from remote sensing among lunar meteorites dhofar 961 is the one most likely to have originated from south pole aitken basin on the lunar far side

platinum group elements in the morokweng impact structure south africa evidence for the impact of a large ordinary chondrite projectile at the jurassic cretaceous boundary radiometric dating of melt rocks at impact craters has revealed that some giant impacts appear to overlap in time with major boundaries in earth history e g the cretaceous tertiary k t and jurassic cretaceous j k boundaries the morokweng impact crater in south africa is coincident in age with the j k boundary however the types of objects that generate large craters are poorly known because it is difficult to unambiguously identify the projectile from the signature it imparts into the impact rocks meteorites are highly enriched in the platinum group elements pge which have been widely used as a tool for identifying the presence of a meteorite signature here we present new pge analyses from the morokweng impact melt sheet our data reveal high pge concentrations and high degree of pge correlation through the melt sheet regression analysis was used to determine the projectile pge signature and constrain input from the terrestrial target rocks the closest match to morokweng is the pge signature of ordinary l or ll chondrite meteorites which is broadly in agreement with the results of an earlier cr isotope study the results of these independent studies provide strong evidence that a large ordinary chondrite projectile struck the area of morokweng in the late jurassic

komatiites and nickel sulphide orebodies of the black swan area yilgarn craton western australia 1 petrology and volcanology of host rocks the black swan succession is a bimodal association of dacitic and komatiitic volcanic rocks located about 50 km nne of kalgoorlie within the 2 7 ga eastern goldfields greenstone province of the yilgarn craton the komatiite stratigraphy comprises a steep dipping east facing package about 700 m in maximum thickness and about 2 5 km in strike length fig 1 which hosts a number of economically exploitable ni sulphide orebodies including the silver swan massive ore shoot approximately half a million tonnes at about 10 5 ni the sequence can be subdivided into a lower felsic unit comprising coherent and autobrecciated facies of multiple dacite lava flows an upper eastern and lower western ultramafic unit each showing marked lateral facies variation and an upper felsic unit coeval with the eastern ultramafic unit the komatiite sequence has been metamorphosed at sub greenschist facies in the presence of high proportions of co2 rich fluid giving rise to pervasive talc carbonate and talc carbonate quartz assemblages with extensive preservation of pseudomorphed igneous textures cores of lizardite serpentinite are present in the thickest parts of the ultramafic succession the degree of penetrative deformation is generally very low and original stratigraphic relationships are largely intact in much of the sequence the eastern ultramafic unit and western ultramafic unit are interpreted as components of a single large komatiite flow field representing overlapping stages in the emplacement of a series of distributory lava pathways and flanking sheet flows the western ultramafic unit which hosts the bulk of the high grade massive and disseminated ores is a sequence dominated by coarse grained olivine cumulates 2 km wide and up to 500 m thick with major magma pathways represented by thick homogenous olivine mesocumulate piles at its northern and southern ends respectively 400 and 200 m thick the sequence between the two major pathways consists of olivine orthocumulates ooc with minor spinifex textured intervals the unit is capped by a persistent spinifex textured crust less than 1 m thick and is locally vesicular the eastern ultramafic unit contains the black swan cumulate zone a 500 m thick sequence of very coarse grained hopper textured locally vesicular ooc containing disseminated sulphides in its lower 200 m the zone is flanked to the north and south by complexly interdigitated sequence of highly irregular spinifex capped olivine cumulate rich flow lobes between 1 and 100 m thick and dacitic lavas and tuffs the complexity of the 3 d spatial relationship of these units suggests a combination of simultaneous eruption of dacite and komatiite combined with thermal or thermomechanical erosion the eastern and western units are interpreted as the result of more or less continuous prolonged eruption of olivine charged komatiite lava which developed localised thermo mechanical erosion channels in the dacitic substrate komatiite and dacite eruption was synchronous giving rise to complex interdigitation and extensive contamination and hybridisation

abundance and distribution of iron on the moon the abundance and distribution of iron on the moon is derived from a near global data set from clementine the determined iron content of the lunar highlands crust 3 percent iron by weight supports the hypothesis that much of the lunar crust was derived from a magma ocean the iron content of lower crustal material exposed by the south pole aitken impact basin on the lunar farside is higher 7 to 8 percent by weight and consistent with a basaltic composition this composition supports earlier evidence that the lunar crust becomes more mafic with depth the data also suggest that the bulk composition of the moon differs from that of the earth9s mantle this difference excludes models for lunar origin that require the earth and moon to have the same compositions such as fission and coaccretion and favors giant impact and capture

the age of the kambalda greenstones resolved by ion microprobe implications for archaean dating methods abstract a chert horizon within the archaean basalt pile at kambalda western australia contains zircons from air fall tuffs erupted as the sediment was laid down ion microprobe analyses of these magmatic zircons constrain the long sought age of the kambalda lavas to 2692 4ma 2 and show that regional metamorphism and deformation of the greenstone pile occurred within 30 ma of deposition rare zircon xenocrysts are evidence of pre greenstone crust as old as 3450 ma exposed remnants of which are yet to be identified subsets of both the magmatic and xenocryst zircons show evidence of hitherto unsuspected low temperature u and or pb mobility in the proterozoic long after stabilisation of the craton the ion microprobe data unravel complexities of isotopic inheritance and alteration illustrating the hazards of using bulk or whole rock samples in archaean isotopic investigations identification of interflow cherts as a precisely dateable rock type opens the way to direct ion probe dating of mafic ultramafic piles and close numerical age control of the complex but ill exposed stratigraphic and structural relations in this richly mineralised greenstone belt

compositional variation in apollo 16 impact melt breccias and inferences for the geology and bombardment history of the central highlands of the moon abstract high precision data for the concentrations of a number of lithophile and siderophile elements were obtained on multiple subsamples from 109 impact melt rocks and breccias mostly crystalline from the apollo 16 site compositions of nearly all apollo 16 melt rocks fall on one of two trends of increasing sm concentration with increasing sc concentration the eastern trend lower sm sc mg fe and sm yb ratios consists of compositional groups 3 and 4 of previous classification schemes these melt rocks are feldspathic poor in incompatible and siderophile elements and appear to have provenance in the descartes formation to the east of the site the western trend higher sm sc mg fe and sm yb ratios consists of compositional groups 1 and 2 these relatively mafic kreep bearing breccias are a major component 35 of the cayley plains west of the site and are unusual compared to otherwise similar melt breccias from other sites in having high concentrations of fe ni metal 1 2 the metal is the carrier of the low ir au 0 3 chondritic siderophile element signature that is characteristic of the apollo 16 site four compositionally distinct groups 1m 1f 2db and 2nr of western trend melt breccias occur that are each represented by at least six samples compositional group 1 of previous classification schemes the poikilitic or lkfm melt breccias can be subdivided into two groups group 1m represented by six samples including 60315 is characterized by lower al2o3 concentrations higher mgo and alkali concentrations and higher mg fe and cr sc ratios than group 1f represented by fifteen samples including 65015 group 1m also has siderophile element concentrations averaging about twice those of group 1f and ir au and ir ni ratios that are even lower than those of other western trend melt rocks ir au 0 24 0 03 ci normalized at the mafic extreme of group 2 vha melt breccias the melt lithology occurring as clasts in feldspathic fragmental breccias from north ray crater group 2nr is compositionally distinct from the melt lithology of dimict breccias from the cayley plains group 2db in having higher concentrations of sc cr and heavy rare earth elements and lower concentrations of siderophile elements the distinct siderophile element signature high absolute abundances low ir au ratio suggest that the four groups of mafic melt breccia are all somehow related ratios of some lithophile elements also suggest that they are more closely related to each other than they are to melt breccias from other apollo sites however none of the breccia compositions can be related to any of the others by any simple process of igneous fractionation or mixing involving common lunar materials thus the origin of the four groups of mafic melt breccia is enigmatic if they were produced in only one or two impacts then a mechanism exists for generating regimes of impact melt breccia in a single impact that are substantially different from each other in composition for various reasons including the problem of delivering large volumes of four different types of melt to the apollo 16 site it is unlikely that any of these breccias were produced in basin forming impacts if they were produced in as many as four crater forming impacts then the unusual siderophile element signature is difficult to explain possible explanations are 1 1 the four groups of melt breccia all contain metal from a single earlier impact 2 2 they were each formed by related metal rich meteoroids or 3 3 some common postimpact process has resulted in metal of similar composition in each of four melt pools within a compositional group most intrasample and intersample variation in lithophile element concentrations is caused by differences among samples in the proportion of a component of normative anorthosite or noritic anorthosite in most cases this compositional variation probably reflects variation in clast abundance for group 2db and probably 2nr differences in abundance of a component of ferroan anorthosite estimated al2o3 32 accounts for the compositional variation for groups 1m and 1f the anorthositic component is more mafic estimated al2o3 26 some group 2 samples may be related by a troctolitic component of varying abundance

volcanological and structural controls on mineralization at the mount keith and cliffs komatiite associated nickel sulfide deposits agnew wiluna belt western australia implications for ore genesis and targeting the mount keith region of the agnew wiluna belt in western australia is perhaps best known for hosting the giant komatiite associated disseminated ni sulfide deposit known as mkd5 it also hosts the sizeable cliffs massive ni sulfide deposit which is the eighth largest in the archean yilgarn block a concerted program of regional scale three dimensional model construction has integrated a plethora of geological geochemical and geophysical data and led to a much better understanding of the tectonic and volcanic architecture of this ancient greenstone belt the disseminated mkd5 orebody occupies a curvilinear thickening in the olivine adcumulate core of the host mount keith ultramafic unit the orebody plunges shallowly to the south from surface over a distance of 3 5 km before bending sharply to plunge steeply to the north northwest at depth the thickest part of the orebody and the best ni grades are associated with the bend in the overall ore trend this also marks the approximate intersection point of two growth faults that appear to control the thickness variations in the adcumulate core and the plunge variations in the ore trend the olivine adcumulate core is mantled by olivine orthocumulate rocks which are best developed above and below the flanks of the orebody and a fractionated sequence of pyroxenitic and gabbroic rocks occurs at the top of the mount keith ultramafic unit above the inside of the bend in the ore trend these observations suggest a strong volcanological control on the position of the mkd5 orebody and the local curvilinear thickening in the adcumulate core is interpreted as a fluid pathway the locus of which was in turn controlled by the intersection of two broadly orthogonal growth faults the cliffs ultramafic unit consists of a lower olivine ortho to mesocumulate unit which varies in thickness along strike overlain by a sequence of thin spinifex textured komatiite flow units intercalated with variably sulfidic tuffaceous shales the cliffs massive ni sulfide deposit occurs at the base of a relative thickening to 100 m in the lower olivine ortho to mesocumulate unit the orebody is typically less than 6 m thick 500 m wide and plunges gently south from surface over a distance of 1 5 km terminating in a structurally complex zone across which there are marked differences in the internal stratigraphy and thickness of the cliffs ultramafic unit the orebody has relatively low tenor maximum 8 ni typically 5 ni and the tenor is strongly zoned with extremely low tenors 1 3 ni developed on the flanks a barren exhalative massive fe sulfide unit is typically present at the base of the cliffs ultramafic unit on the flanks of the orebody and probably acted as a source of sulfur the tenor zonation pattern suggests that the melting and entrainment of the underlying exhalative sulfide horizon occurred more vigorously in the center of the lava pathway the structurally complex zone at the southern end of the cliffs orebody is interpreted as a possible vent location this would explain the relatively low tenor of the orebody and the tenor zonation through limited mixing and entrainment of melted exhalative iron sulfide melt with the komatiite lava the poorly incised nature of the lava pathway and the abrupt change in internal komatiite stratigraphy across this zone there is good evidence that the southern terminations of both the mkd5 and the cliffs orebodies are marked by growth faults at a belt scale these points correspond roughly with the intersection of nne and nw trending lineaments these lineaments are on the order of 5 to 10 km in strike length and are visible in regional geophysical datasets both gravity and magnetics they are likely to mark the position of accretionary structures that were active at the time of volcanism and that probably controlled the volcanic architecture of the komatiite flow field and the location of ni sulfide accumulations within komatiite lava pathways repeated reactivation of these early crustal scale structures during subsequent orogenesis resulted in their upward propagation as sets of late brittle structures of broader significance to the understanding of the generation of komatiite associated nickel sulfide deposits is the conclusion that many such deposits may be developed proximal to vent rather than in a distal setting as has been proposed for the kambalda camp

the volcanology of komatiites as deduced from field relationships in the norseman wiluna greenstone belt western australia abstract komatiites in the western part of the norseman wiluna greenstone belt in the yilgarn block of western australia display a wide variety of volcanic facies ranging from very thin differentiated munro township type flow units through to very thick olivine rich cumulate flow units containing high proportions of adcumulate dunite cumulate flow units have been mapped in detail in the agnew wiluna segment of the norseman wiluna greenstone belt in the yakabindie and mt keith areas thick lenticular bodies of olivine adcumulate are flanked and overlain by thinner sheet like sequences of finer grained olivine orthocumulates they show fine scale internal layering broad scale cryptic layering and upper fractionated sequences containing harrisites pyroxene bearing cumulates and in some cases gabbroic derivatives low grade disseminated sulphide mineralisation occurs within the dunite lenses in the stratigraphically equivalent kathleen east area adcumulate dunite grades laterally into olivine orthocumulates and spinifex textured flows a similar relationship is also seen further south where the perseverance ultramafic complex consists of a thick central dunite lens flanked on one side by thin fine grained orthocumulate sequences and on the other by intercalated orthocumulates and spinifex textured flows these field relationships indicate an extrusive origin for the adcumulate dunite bodies the walter williams formation in the west central part of the norseman wiluna belt is a very large cumulate flow unit 150 km long and 30 km wide in presently exposed extent it consists of a central sheet like body of adcumulate dunite underlain and overlain by olivine orthocumulates the adcumulate sheet is everywhere capped by a distinctive thin layer of olivine harrisite at its northernmost extent the flow unit consists of cyclically layered olivine and pyroxene bearing cumulates capped by gabbros dolerites and pyroxene spinifex textured material interpreted as a periodically replenished lava lake sequence both the lenticular dunite bodies of the agnew wiluna belt and the sheet like dunite body of the walter williams formation are interpreted as crystallisation products of very large submarine komatiite lava flows which erupted and flowed at very high rates the adcumulate dunites are interpreted as the products of in situ crystallisation at low degrees of supercooling at the top of upward and inward accreting crystal piles at the bases of the flows flanking and overlying olivine orthocumulates reflect higher rates of heat loss at the site of crystallisation due to lower lava flow rates field evidence from perseverance and the general geometry of the dunite lenses suggest that the lenses formed within large thermal erosion channels developed by turbulent lava rivers flowing over low melting felsic volcanic substrates the textural range exhibited by komatiites can be integrated into a comprehensive model for the geometry of large komatiite flow fields formed by rapid extrusion dunite sheets form close to the eruption sites and dunite lenses as a result of channellisation further away from the vent or close to the vent in the situation where the substrate is non refractory and thermal erosion can take place readily kambalda type volcanic facies develop in more distal environments where lava emplacement is channellised and episodic and munro type flow units represent small scale lava tubes formed at low flow rates on the distal flanks of major eruptions or close to the vent of very small ones waning eruption rates leads to proximal facies being overridden by distal ones a common observation in komatiite sequences the size of thermal erosion channels requires very rapid eruption rates comparable to those in phanerozoic flood basalt terrains

a concise compilation of petrologic information on possibly pristine nonmare moon rocks ansrn q cr to facilitate systematic study of the surviving compositionally pristine endogenously igneous rocks of the ancient lunar crust a compilation has been generated of all likely samples along with key information on the petrologic characteristics and chemistry of each sample the compilation includes 260 samples besides information related to the likelihood of each sample being truly pristine i e mainly its texture and siderophile element abundances information is compiled on mineral content listing major phases present as well as basic information on mineral compositions on size expressed as mass and on whether a reasonably comprehensive chemical analysis has been published the compilation also classifies the samples into seven categories of confidence in the pristine composition of the samples reflecting an estimation of the relative likelihood that each arguably pristine sample is in fact pristine for many purposes it is crucial to avoid inclusion of polymict rocks in a data base on petrologic diagrams such as a plot of average mg mg 100 x molar mg mg fe in a low ca mafic silicate vs average an content in plagioclase rocks in the top three categories of the confidence in pristine character appear distinctly bimodal in composition with roughly half belonging to a ferroan suite characterized by high an despite relatively low mg when samples of low to moderate pristine character are included the bimodality appears less distinct sample mass can also be important with a data base restricted to samples more massive than i g there is a clear distinction in feldspar content and bulk density between ferroan and nonferroan mgsuite rocks such that only the ferroan suite rocks are likely to have formed as flotation cumulates with a data base including smaller samples the same basic pattern is seen but only in a blurred form as the two rock types show considerable overlap in their modal feldspar contents

late stage magmatic outgassing from a volatile depleted moon abstract the abundance of volatile elements and compounds such as zinc potassium chlorine and water provide key evidence for how earth and the moon formed and evolved currently evidence exists for a moon depleted in volatile elements as well as reservoirs within the moon with volatile abundances like earth s depleted upper mantle volatile depletion is consistent with catastrophic formation such as a giant impact whereas a moon with earth like volatile abundances suggests preservation of these volatiles or addition through late accretion we show using the rusty rock impact melt breccia 66095 that volatile enrichment on the lunar surface occurred through vapor condensation isotopically light zn 66zn 13 7 heavy cl 37cl 15 and high u pb supports the origin of condensates from a volatile poor internal source formed during thermomagmatic evolution of the moon with long term depletion in incompatible cl and pb and lesser depletion of more compatible zn leaching experiments on mare basalt 14053 demonstrate that isotopically light zn condensates also occur on some mare basalts after their crystallization confirming a volatile depleted lunar interior source with homogeneous 66zn 1 4 our results show that much of the lunar interior must be significantly depleted in volatile elements and compounds and that volatile rich rocks on the lunar surface formed through vapor condensation volatiles detected by remote sensing on the surface of the moon likely have a partially condensate origin from its interior

yakabindie revisited volcanological and structural controls on the komatiite hosted six mile well and goliath north deposits and implications for the architecture of the 2 7 ga rift event in the agnew wiluna belt yilgarn craton western australia the yakabindie area hosts significant deposits of disseminated fe ni cu sulfide in the six mile well 2 0 mt contained ni and goliath north 0 6 mt contained ni dunite lenses these dunite lenses form part of the same komatiitic ultramafic unit that hosts the giant mount keith mkd5 deposit 2 6 mt contained ni to the north but the morphology and internal stratigraphy of the host unit differs significantly three dimensional modeling of the yakabindie region reveals that each dunite lens is located at the intersection between steeply dipping nnw and nne trending synvolcanic faults which appear to have acted as conduits from which komatiitic lava vented onto the seafloor the igneous contacts dip more shallowly to the west and describe a w facing wedge of olivine cumulate rock probably less than 1 km in plunge extent and cored by adcumulate rock the mineralization at both six mile well and goliath north consists of multiple stacked lenses of disseminated fe ni cu sulfide associated with the olivine adcumulate core this core is interpreted as the pathway position that focused the flow of komatiite lava away from the vent rather than being linked by sheeted bodies of orthocumulate rocks as is typically the case along strike to the north the dunite lenses at yakabindie appear to be capped by a strike continuous sequence of thin komatiite flow units there is no evidence of the fractionated sequences of pyroxenite and dolerite which occur in pathway positions within the mount keith ultramafic unit to the north and which reflect late stage ponding and in situ fractionation of komatiite lava three sets of synvolcanic structures are recognized in the broader agnew wiluna belt and a model of oblique extension at ca 2 7 ga is proposed a nnw trending set of structures marks the overall rift orientation at ca 2 7 ga but is probably inherited from an earlier ca 2 81 ga phase of rifting a nw trending set is thought to represent ca 2 7 ga transfer faults but may also have much older roots these structures produce marked sinistral offsets in both the greenstone stratigraphy and the gravity response and can be used to divide the agnew wiluna belt into rift segments the third set of early structures trends nne subparallel with the volcanic grain of the greenstones as inferred from the orientation of komatiite lava pathways these are thought to have originated as extension orthogonal normal faults at ca 2 7 ga at the regional scale there is a strong spatial association between the larger fe ni cu sulfide deposits of the agnew wiluna belt and the locus of postulated nw trending transfer zones whereas at the deposit scale intersecting nw and nne trending synvolcanic faults exert a control on the location and best development in terms of thickness and or grade of fe ni cu sulfide mineralization in some deposits these spatial associations have major implications for exploration targeting at both regional and deposit scale

diverse impactors in apollo 15 and 16 impact melt rocks evidence from osmium isotopes and highly siderophile elements abstract concentrations of highly siderophile elements hse and 187 os 188 os isotopic compositions for eleven impact related rocks from the apollo 15 and 16 landing sites are reported and combined with existing geochronological data to investigate the chemical nature and temporal changes in the large impactors implicated in the formation of the lunar basins data for the samples all define linear trends on plots of hse versus ir concentrations whose slopes likely reflect the relative hse compositions of the dominant impactors that formed the rocks the inferred imbrium basin impactor that generated apollo 15 impact melt rocks 15445 and 15455 was characterized by modestly suprachondritic 187 os 188 os ru ir pt ir and pd ir ratios diverse impactor components are revealed in the apollo 16 impact melt rocks the 187 os 188 os and hse ir ratios of the impactor components in melt rocks 60635 63595 and 68416 with reported ages 4 0 ga by contrast the impactor components in melt rocks 60235 62295 and 67095 with reported ages of 3 9 ga are characterized by suprachondritic 187 os 188 os and hse ir ratios similar to the apollo 15 impact melt rocks and may also sample the imbrium impactor three lithic clasts from regolith breccias 60016 and 65095 also with 3 9 ga ages contain multiple impactor components of which the dominant composition is considerably more suprachondritic than those implicated for imbrium and serenitatis apollo 17 impactors the dominant composition recorded in these rocks was most likely inherited from a pre imbrium impactor consideration of composition versus age relations among lunar impact melt rocks reveals no discernable trend virtually all lunar impact melt rocks sampled by the apollo missions as well as meteorites are characterized by 187 os 188 os and hse ir ratios that when collectively plotted define linear trends ranging from chondritic to fractionated compositions the impact melt rocks with hse signatures within the range of chondritic meteorites are interpreted to have been derived from impactors that had hse compositions similar to known chondrite groups by contrast the impact melt rocks with non chondritic relative hse concentrations could not have been made by mixing of known chondritic impactors these signatures may instead reflect contributions from early solar system bodies with bulk chemical compositions that have not yet been sampled by primitive meteorites present in our collections alternately they may reflect the preferential incorporation of evolved metal separated from a fractionated planetesimal core pre 4 0 ga ages for at least some impactor components with both chondritic and fractionated hse raise the possibility that the bulk of the hse were added to the lunar crust prior to the later stage basin forming impacts such as imbrium and serenitatis as proposed by fischer godde and becker 2012 for this scenario the later stage basin forming impacts were more important with respect to mixing prior impactor components into melt rocks rather than contributing much to the hse budgets of the rocks themselves

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

reconstruction of an extensive archaean dacitic submarine volcanic complex associated with the komatiite hosted mt keith nickel deposit agnew wiluna greenstone belt yilgarn craton western australia abstract felsic volcanic rock units characterise a large portion of the 2 7 ga agnew wiluna greenstone belt western australia stratigraphy and form the hangingwall and footwall sequences to several komatiite hosted nickel sulphide deposits in the region the mt keith region of the agnew wiluna greenstone belt awb comprises a sequence of felsic mafic and ultramafic extrusive and intrusive units the felsic volcanic dominated footwall and hangingwall sequences to the mt keith nickel deposit comprise cyclical packages of coherent dacite lavas with associated monomictic in situ to resedimented breccias clasts in the monomictic breccia facies are identical to the coherent dacite and the two facies are often in gradational contact the dacites are interpreted as submarine lavas and the breccias as associated autoclastic facies hyaloclastite autobreccia these dacite lavas are inferred to have been emplaced into a deep water environment which retarded volatile exsolution suppressing explosive fragmentation and increasing lava mobility resulting in large tabular flow units the awb sequence has undergone multiple periods of deformation and metamorphism subsequent to emplacement resulting in strain and alteration in large sections of the coherent lava facies a notable textural variant within the lavas is a set of pseudo textures structures resembling tuffaceous and brecciated dacitic units the process of pseudo clastic texture structure generation is related to a combination of polyphase alteration brecciation and development of a secondary structural metamorphic layering understanding the origin of these pseudo clastic textures structures has allowed recognition of the lateral and vertical facies variation of the felsic sequence and reconstruction of the original volcanic architecture

the contribution of anisotropic conductivity in the ionosphere to lightning flash bearing deviations in the elf ulf range lightning flash bearing deviations in the elf ulf range are monitored at two independently operating measurement instruments in hollister california and silberborn germany the lightning flash bearing deviation at hollister exhibits a rotational dependence 12 associated with the conductivity contrast between the earth s crust and the nearby pacific ocean the bearing deviations at both stations exhibit a pronounced diurnal local time variation 11 this diurnal variation is attributed to the anisotropic conductivity in the ionosphere during day and nighttime conditions no bearing deviation dependency from the source receiver distance can be distinguished correction for the mean rotational dependence at hollister and the mean diurnal variation at both locations results in residual bearing deviations 10 which are related to the variability of anisotropic conductivity in the ionosphere on a subdiurnal time scale

depositional gaps in abitibi greenstone belt stratigraphy a key to exploration for syngenetic mineralization models of greenstone belt development are crucial for exploration allochthonous models predict belts to be a collage of unrelated fragments whereas autochthonous models allow for prediction of syngenetic mineral deposits within specific stratigraphic intervals superior province greenstone belts consist of mainly volcanic units unconformably overlain by largely sedimentary timiskaming style assemblages and field and geochronological data indicate that the abitibi greenstone belt developed autochthonously we describe major revisions to stratigraphy of the abitibi greenstone belt and the implications of an autochthonous development of the volcanic stratigraphy for exploration for syngenetic mineralization the abitibi greenstone belt is subdivided into seven discrete volcanic stratigraphic episodes on the basis of groupings of numerous u pb zircon ages of pre 2750 2750 to 2735 2734 to 2724 2723 to 2720 2719 to 2711 2710 to 2704 and 2704 to 2695 ma we present revised lithotectonic and or stratigraphic nomenclature using these time intervals including 1 isotopic inheritance in younger episodes which indicates that the older episodes 2750 2735 and 2734 2724 ma had greater extent than is presently seen 2 dikes feeding younger volcanic episodes 2706 ma cutting older volcanic units 2734 2724 ma and 3 2710 to 2704 ma mafic to ultramafic sills intruding the 2719 to 2711 ma episode changes to the nomenclature include the identification of pre 2750 ma volcanic episode supracrustal fragments in the northern and southern abitibi greenstone belt and subdivision of the 2719 to 2711 ma 2710 to 2704 ma and 2704 to 2695 ma episodes into lower and upper parts we present the results of this lithostratigraphic subdivision as the first geochronologically constrained stratigraphic and or lithotectonic map of the abitibi greenstone belt many of the volcanic episodes are intercalated with and capped by a relatively thin sedimentary interface zone dominated by chemical sedimentary rocks stratigraphic and geochronological analysis of these zones indicates discontinuous deposition with localized gaps of 2 to 27 m y between volcanic episodes the zones consist of up to 200 m of iron formation chert breccia heterolithic debris flows of volcanic provenance sandstone and or argillite and conglomerate modeling of the time required for deposition of the volcanic units based on rates of magma production in modern arc and plume environments is on the order of 103 to 104 years whereas the time interval between basalt rhyolite cycles is 106 years the sedimentary interface zones are therefore interpreted as condensed sections zones with very low rates of sedimentation in a basinal setting or zones with negligible rates of sedimentation marked by silicification of existing rock types the sedimentary interface zones are therefore considered submarine correlative conformities disconformities or unconformities separating the equivalent of group level stratigraphic and lithotectonic units the unconformity bounded stratigraphic model provides a new regional to deposit scale interpretive model for use in exploration for syngenetic mineralization

investigating the shock histories of lunar meteorites miller range 090034 090070 and 090075 using petrography geochemistry and micro ftir spectroscopy fourier transform infrared ftir spectroscopy and cathodoluminescence cl imaging techniques combined with electron microprobe analyses have been used to determine the physical state of feldspathic phases that have been subject to varying levels of shock in the grouped lunar meteorites miller range 090034 090070 and 090075 six feldspathic phases have been identified based on spectral textural and chemical properties a specific infrared wavelength band ratio 1064 932 cm 1 equivalent to 9 40 10 73 m chosen because it can distinguish between some of the feldspathic phases can be used to estimate the pressure regimes experienced by these phases in addition ftir spatial mapping capabilities allow for visual comparison of variably shocked phases within the samples by comparing spectral and compositional data the origin and shock history of this lunar meteorite group has been determined with each of the shocked feldspathic phases being related to events in its geological evolution as such we highlight that ftir spectroscopy can be easily employed to identify shocked feldspathic phases in lunar samples estimate peak shock pressures and when compared with chemical data can be used to investigate their shock histories

the macalpine hills lunar meteorite and implications of the lunar meteorites collectively for the composition and origin of the moon the mac88104 mac88105 meteorite is a lunar highlands regolith breccia even more anorthositic than previously available samples of highlands regolith clasts studied include two unusual pristine rocks one a 2 5 mm slightly granulitic clast rated as probably pristine contains extraordinarily fe rich fo40 olivine the other a 5 mm clast with clear vestiges of a poikilitic cumulate texture has silicate compositions that extend the range of the mg suite in the direction of the high mg end of the ferroan anorthositic suite the pyroxene of the latter clast is relatively ca rich and poorly equilibrated by lunar cumulate standards suggesting that it may have formed in an uncommonly shallow intrusion the four lunar highlands meteorites are all regolith breccias or in one case a marginal type between regolith breccia and ordinary polymict breccia and they probably represent three to four separate lunar source craters the proportion of regolith breccias is higher among lunar highlands meteorites than among rock samples from the classic highlands site apollo 16 9 regolith breccias for the majorelement composition of the crust the highlands meteorites confirm that the two low th central nearside sites luna 20 and especially apollo 16 are approximately representative the consistently high al2o3 composition indicated for the upper crust supports the magmasphere hypothesis for the trace element composition of the crust the highlands meteorites indicate that the central nearside apollo and luna sites are in several respects grossly unrepresentative concentrations of siderophile elements are far lower in highlands meteoritic regolith breccias than in their central nearside counterparts the high overall siderophile levels and hyperchondritic niir and auir ratios characteristic of highlands materials from apollo 16 and apollo 14 are evidently idiosyncracies of the central nearside concentrations of incompatible elements including k th and u are far lower in the highlands meteorites than in regolith samples from the central nearside this trend implies that certain lower limits on the bulk moon content of u and associated refractory lithophile elements should be relaxed models of lunar origin implying large enrichments of refractory lithophile elements are not favored by the new constraints from these meteorites

current bombardment of the earth moon system emphasis on cratering asymmetries abstract we calculate the current spatial distribution of projectile delivery to the earth and moon using numerical orbital dynamics simulations of candidate impactors drawn from a debiased near earth object neo model we examine the latitude distribution of impactor sites and find that for both the earth and moon there is a small deficiency of time averaged impact rates at the poles the ratio between deliveries within 30 of the pole to that of a 30 band centered on the equator is small for earth 0 958 0 001 and somewhat greater for the moon 10 0 903 0 005 the terrestrial arrival results are examined to determine the degree of am pm asymmetry to compare with the pm excess shown in meteorite fall times we find that the average lunar impact velocity is 20 km s which has ramifications in converting observed crater densities to impactor size distributions we determine that current crater production on the leading hemisphere of the moon is 1 28 0 01 that of the trailing when considering the ratio of craters within 30 of the apex to those within 30 of the antapex and that there is virtually no nearside farside asymmetry in agreement with observations of rayed craters as expected the degree of leading trailing asymmetry increases when the moon s orbital distance is decreased

crystal accumulation in a 4 2 ga lunar impact melt abstract the ages of lunar impact basins and the role of fractional crystallization in producing compositional heterogeneity of lunar melt sheets are long standing problems with significant implications for solar system dynamics and the petrologic evolution of the lunar crust here we document the formation of a basin scale impact on the moon at 4 20 0 07 ga based on the 147 sm 143 nd isochron age of a magnesian noritic anorthosite melt rock from lunar breccia 67955 major element compositions of plagioclase and mafic silicates in the melt rock imply a substantial component of primary mg suite cumulates or related lithologies in the pre impact crustal stratigraphy trace element compositions of the plagioclase including diagnostic ratios such as sr ba are also mostly similar to those in plagioclase from mg suite cumulates with a small number of grains trending toward compositions observed in ferroan anorthosites mineral melt distribution coefficients applied to trace element compositions of the 67955 plagioclase and pyroxene predict parental melt compositions that contrast strongly with the bulk rock compared to the whole rock parental melts calculated from the plagioclase are enriched in ree ree la yb 131 885 average 619 ppm vs 39 8 ppm and they have more fractionated ree patterns la yb n 1 2 9 8 average 4 9 vs 1 5 with deep negative eu anomalies eu eu 0 09 0 40 vs 1 36 trace element data for the pyroxenes also imply incompatible element enriched parental melts subsolidus equilibration between the plagioclase and the pyroxene apparently rotated the ree patterns but the conclusion that the parental melt was highly enriched in ree relative to the whole rock appears robust quantitative modeling shows that fractional crystallization of the 67955 whole rock composition cannot reproduce the range of ba sr ti and la concentrations measured in the 67955 plagioclase rather the models require an initial melt composition that was strongly enriched in these elements and they suggest that fractional crystallization became less efficient as crystallization proceeded the contrast between the inferred parental melt composition and the bulk rock implies formation of the 67955 noritic anorthosite as a crystal cumulate and that the cogenetic residual melt was strongly enriched in incompatible elements if so this would be the first documented example of fractional crystallization in a lunar impact melt sheet the petrological and geochemical characteristics of the 67955 noritic anorthosite suggest that it formed by an impact in the procellarum kreep terrane and was transported to the apollo 16 site as imbrium ejecta inheritance of ejecta related to this pre imbrium basin may contribute to the common occurrence of 4 2 ga 40 ar 39 ar plateau ages in breccia clasts and regolith fragments from the rim of north ray crater in that case those data may provide no constraints on the age of the nectaris basin despite its proximity to the apollo 16 site

formation of apollo 16 impactites and the composition of late accreted material constraints from os isotopes highly siderophile elements and sulfur abundances fe ni metal schreibersite troilite intergrowths in apollo 16 impact melt rocks and new highly siderophile element hse and s abundance data indicate that millimeter scale closed system fractional crystallization processes during cooling of impactor derived metal melt droplets in impact melts are the main reason for compositional variations and strong differences in abundances and ratios of hse in multiple aliquots from apollo 16 impact melt rocks element ratios obtained from linear regression of such data are therefore prone to error but weighted averages take into account full element budgets in the samples and thus represent a more accurate estimate of their impactor contributions modeling of solid metal liquid metal partitioning in the fe ni s p system and hse patterns in impactites from different landing sites suggest that bulk compositions of ancient lunar impactites should be representative of impact melt compositions and that large scale fractionation of the hse by in situ segregation of solid metal or sulfide liquid in impact melt sheets most likely did not occur the compositional record of lunar impactites indicates accretion of variable amounts of chondritic and non chondritic impactor material and the mixing of these components during remelting of earlier ejecta deposits the non chondritic composition appears most prominently in some apollo 16 impactites and is characterized by suprachondritic hse ir ratios which increase from refractory to moderately volatile hse and exhibit a characteristic enrichment of ru relative to pt large scale fractional crystallization of solid metal from sulfur and phosphorous rich metallic melt with high p s in planetesimal or embryo cores is currently the most likely process that may have produced these compositions similar materials or processes may have contributed to the hse signature of the bulk silicate earth bse

granite greenstone crust formation on the archaean earth a consequence of two superimposed processes abstract new u pb zircon age data reveal that volcanism in the greenstones of the eastern part of the yilgarn craton of western australia was coeval with that in the abitibi subprovince of the superior craton of canada and that komatiites in the eastern goldfields and abitibi terranes were erupted synchronously at 2705 ma however major granitoid intrusion and compression episodes in the eastern yilgarn craton post date those in the southern superior craton by at least 15 ma intrusion of late tectonic syenites movement on major shear zones metamorphism and deposition of post tectonic clastic sequences also occurred 25 40 ma later in the eastern yilgarn craton than in the southern superior craton indicating that these cratons occupied different tectonic settings between 2720 and 2620 ma these comparisons and the synchronous eruption of ultramafic magmas in the southern superior pilbara and kaapvaal cratons at 2715 ma provide evidence of global scale magmatic eruption events during the late archaean these considerations indicate that two superimposed processes global scale catastrophic convective overturn of the earth s mantle and plate tectonic processes were in operation during formation of granite greenstone crust in the late archaean