Noble gases and nitrogen in Raghunathpura (IIAB) and Nyaung (IIIAB) iron meteorites

Noble gases and nitrogen were measured in two adjacent samples each from the Raghunathpura (IIAB) and the Nyaung (IIIAB) iron meteorite falls. Light noble gases in both the meteorites were of pure cosmogenic origin. Using (³He/⁴He)_c ratios and the production systematic of Ammon et al. ( 2009 ), we estimated the sample depth and meteoroid size for Nyaung (~8 cm depth in a ~15 cm radius object) and Raghunathpura (~12–14 cm depth in a ~25 cm object). We derived cosmic ray exposure ages of 1710 ± 256 Ma (for Nyaung, the highest reported so far for the IIIAB group) and 224 ± 34 Ma (for Raghunathpura). Variable amounts of trapped Kr and Xe were found in both meteorites. The phase Q‐like elemental ratio (⁸⁴Kr/¹³²Xe) suggests that the trapped component is of indigenous origin, and most likely hosted in the heterogeneously distributed micro‐inclusions of troilite/schreibersite. Trapped phase Q component is being reported for the first time, for a IIAB iron meteorite. Both meteorites showed light isotopic composition for nitrogen, and need at least two N components to explain the observed N isotopic systematic. Variable amounts of trapped noble gases and the presence of more than one N component suggest that the magmatic process that formed the parent body of these meteorites either could not completely homogenize or completely degas all the phases.     

Mineral and chemical composition of the new iron meteorite Javorje from Slovenia

Abstract– The single‐piece iron meteorite Javorje, with a mass of 4920 g, is the heaviest and largest meteorite found in the territory of Slovenia. The meteorite Javorje is a medium octahedrite with kamacite bandwidth of 0.85 ± 0.26 mm. The bulk composition of Ni (7.83 wt%), Co (0.48 wt%) and trace elements Ga (25 μg/g), Ge (47 μg/g), Ir (7.6 μg/g), As (5.8 μg/g), Au (0.47 μg/g), and Pt (13.4 μg/g) indicates that the meteorite Javorje belongs to the chemical group IIIAB. Mineral and bulk chemical compositions are consistent with other reported group IIIAB meteorites. The presence of numerous rhabdites, carlsbergite, sparse troilite, and chromite and abundance of daubréelites are in accordance with low‐Ni and low‐P IIIAB iron meteorites. The severely weathered surface and secondary weathering products in the interior of the meteorite suggest its high terrestrial age.     

Near-infrared spectroscopy of 3:1 Kirkwood Gap asteroids: Mineralogical diversity and plausible meteorite parent bodies

The 3:1 Kirkwood gap asteroids are a mineralogically diverse set of asteroids located in a region that delivers meteoroids into Earth-crossing orbits. Mineralogical characterizations of asteroids in/near the 3:1 Kirkwood Gap can be used as a tool to “map” conditions and processes in the early Solar System. The chronological studies of the meteorite types provide a “clock” for the relative timing of those events and processes. By identifying the source asteroids of particular meteorite types, the “map” and “clock” can be combined to provide a much more sophisticated understanding of the history and evolution of the late solar nebula and the early Solar System.A mineralogical assessment of seven 3:1 Kirkwood Gap asteroids has been carried out using near-infrared spectral data obtained over the years 2006–2009 combined with visible spectral data (when available) to cover the spectral interval of 0.4–2.5 μm. We explore the diversity, uniqueness, and possible links between the asteroids (198) Ampella, (329) Svea, (495) Eulalia, (556) Phyllis, (623) Chimaera, (908) Buda, and (1772) Gagarin, which are located adjacent to the 3:1 resonance, and the meteorite types in the terrestrial collections.     

Calcium–aluminum-rich inclusions in non-carbonaceous chondrites: Abundances,sizes, and mineralogy

As the Sun was forming, calcium–aluminum-rich inclusions (CAIs) were the first rocks to have condensed in the hottest regions of the solar nebula disk. Carbonaceous chondrites (CCs) contain abundant CAIs but are thought to have accreted in the outer Solar System, requiring that CAIs must have been transported outward. Curiously, CAIs are rare in ordinary, enstatite, rumuruti, and kakangari chondrites, non-carbonaceous chondrites (NCs), that likely formed in the inner Solar System. Thus, CAI abundances and characteristics can provide constraints on the early dynamical evolution of the disk. In this work, we address whether the hypothesis of an early-formed proto-Jupiter “opening a gap” in the disk can explain the dichotomy in the relative abundance of CAIs in CC and NC chondrites. We searched 76 NC meteorite sections to find 232 CAIs which have an average apparent diameter of 46 μm and comprise 0.01 area%, about half the size of and ~200 times less abundant than CC CAIs on average. Unlike CC CAIs, only 4% of the NC CAIs contain melilite and most contain alteration features suggesting that NC CAIs underwent pervasive fluid-assisted thermal metamorphism on asteroidal parent bodies. However, based on NC CAI populations correlating with meteorite metamorphic grade, we argue that disk dynamics is likely the primary reason behind the existence of small (<100 μm) and rare NC CAIs. Our data support astrophysical models which suggest that, after outward transport of CAIs, formation of a gap in the disk trapped CAIs in the outer Solar System.     

Buddha from space—An ancient object of art made of a Chinga iron meteorite fragment*

Abstract– The fall of meteorites has been interpreted as divine messages by multitudinous cultures since prehistoric times, and meteorites are still adored as heavenly bodies. Stony meteorites were used to carve birds and other works of art; jewelry and knifes were produced of meteoritic iron for instance by the Inuit society. We here present an approximately 10.6 kg Buddhist sculpture (the “iron man”) made of an iron meteorite, which represents a particularity in religious art and meteorite science. The specific contents of the crucial main (Fe, Ni, Co) and trace (Cr, Ga, Ge) elements indicate an ataxitic iron meteorite with high Ni contents (approximately 16 wt%) and Co (approximately 0.6 wt%) that was used to produce the artifact. In addition, the platinum group elements (PGEs), as well as the internal PGE ratios, exhibit a meteoritic signature. The geochemical data of the meteorite generally match the element values known from fragments of the Chinga ataxite (ungrouped iron) meteorite strewn field discovered in 1913. The provenance of the meteorite as well as of the piece of art strongly points to the border region of eastern Siberia and Mongolia, accordingly. The sculpture possibly portrays the Buddhist god Vai?ravana and might originate in the Bon culture of the eleventh century. However, the ethnological and art historical details of the “iron man” sculpture, as well as the timing of the sculpturing, currently remain speculative.     

The Gove relict iron meteorite from Arnhem Land,Northern Territory,Australia

On February 24, 1979, a deeply oxidized mass of iron meteorite was excavated from bauxite at an open cut mine on the Gove Peninsula, Northern Territory, Australia. The meteorite, measuring 0.75–1 m in diameter and of unknown total weight, was found at coordinates 12°15.8′S, 136°50.3′E. On removal from the ground, the meteorite is reported to have disintegrated rapidly. A preliminary analysis at the mine laboratory reportedly gave 8.5 wt% Ni. A modern analysis of oxidized material gave Ni = 32.9, Co = 3.67 (both mg g^?1), Cr = 168, Cu = 195, Ga = 22.5, Ge = <70, As = 4.16, W = 1.35, Ir = 10.5, Pt = 21.2, Au = 0.672 (all μg g^?1), Sb = <150, and Re = 844 (both ng g^?1). Competent fragments of oxidized material retain a fine to medium Widmanstätten pattern with an apparent average bandwidth of 0.5 mm (range 0.2–0.9 mm in plane section). Primary mineralogy includes rare γ–taenite and daubréelite, and secondary minerals produced by weathering include awaruite (with up to 78.5 wt% Ni) and an, as yet, unnamed Cu‐Cr‐bearing sulfide with the ideal formula CuCrS₂ that is hitherto unknown in nature. Deep weathering has masked many of the features of the meteorite; however, the analysis normalized to the analyses of fresh iron meteorites favors chemical group IIIAB. The terrestrial age of the meteorite is unknown, although it is likely to be in the Neogene (2.5–23 Ma), which is widely accepted as the major period of bauxite formation in the Northern Territory of Australia. Gove is the second authenticated relict meteorite found in Australia.     

Ejby—A new H5/6 ordinary chondrite fall in Copenhagen,Denmark

On February 6, 2016 at 21:07:19 UT, a very bright fireball was seen over the eastern part of Denmark. The weather was cloudy over eastern Denmark, but many people saw the sky light up—even in the heavily illuminated Copenhagen. Two hundred and thirty three reports of the associated sound and light phenomena were received by the Danish fireball network. We have formed a consortium to describe the meteorite and the circumstances of the fall and the results are presented in this paper. The first fragment of the meteorite was found the day after the fall, and in the following weeks, a total of 11 fragments with a total weight of 8982 g were found. The meteorite is an unbrecciated, weakly shocked (S2), ordinary H chondrite of petrologic type 5/6 (Bouvier et al. 2017). The concentration of the cosmogenic radionuclides suggests that the preatmospheric radius was rather small ~20 cm. The cosmic ray exposure age of Ejby (83 ± 11 Ma) is the highest of an H chondrite and the second highest age for an ordinary chondrite. Using the preatmospheric orbit of the Ejby meteoroid (Spurny et al. 2017) locations of the recovered fragments, and wind data from the date of the fall, we have modeled the dark flight (below 18 km) of the fragments. The recovery location of the largest fragment can only be explained if aerodynamic effects during the dark flight phase are included. The recovery location of all other fragments are consistent with the dark flight modeling.     

Petrology,mineralogy, porosity,and cosmic‐ray exposure history of Huaxi ordinary chondrite

A meteorite fall was heard and collected on July 13, 2010 at about 18:00 (local time) in the Shibanjing village of the Huaxi district of Guiyang, Guizhou province, China. The total mass of the fall is estimated to be at least 1.6 kg; some fragments are missing. The meteorite consists mainly of olivine, low‐Ca pyroxene, high‐Ca pyroxene, plagioclase, kamacite, taenite, and troilite. Minor phases include chromite and apatite. Various textural types of chondrules exist in this meteorite: most chondrule textures can be easily defined. The grain sizes of secondary plagioclase in this meteorite range from 2 to 50 μm. The chemical composition of olivine and low‐Ca pyroxene are uniform; Fa in olivine and Fs in low‐Ca pyroxene are, respectively, 19.6 ± 0.2 and 17.0 ± 0.3 (mole%). Huaxi has been classified as an H5 ordinary chondrite, with a shock grade S2, and weathering W0. The weak shock features, rare fractures, and the high porosity (17.6%) indicates that Huaxi is a less compacted meteorite. The preatmospheric radius of Huaxi is ~11 cm, corresponding to ~21 kg. The meteorite experienced a relatively short cosmic‐ray exposure of about 1.6 ± 0.1 Ma. The ⁴He and ⁴⁰Ar retention ages are older than 4.6 Ga implying that Huaxi did not degas after thermal metamorphism on its parent body.     

Analysis of a prehistoric Egyptian iron bead with implications for the use and perception of meteorite iron in ancient Egypt

Tube‐shaped beads excavated from grave pits at the prehistoric Gerzeh cemetery, approximately 3300 BCE, represent the earliest known use of iron in Egypt. Using a combination of scanning electron microscopy and micro X‐ray microcomputer tomography, we show that microstructural and chemical analysis of a Gerzeh iron bead is consistent with a cold‐worked iron meteorite. Thin fragments of parallel bands of taenite within a meteoritic Widmanstätten pattern are present, with structural distortion caused by cold‐working. The metal fragments retain their original chemistry of approximately 30 wt% nickel. The bulk of the bead is highly oxidized, with only approximately 2.4% of the total bead volume remaining as metal. Our results show that the first known example of the use of iron in Egypt was produced from a meteorite, its celestial origin having implications for both the perception of meteorite iron by ancient Egyptians and the development of metallurgical knowledge in the Nile Valley.     

Mineralogy,petrology, and distribution of meteorites at the Whitecourt crater,Alberta, Canada

The Whitecourt meteorite impact crater, Alberta, Canada is a rare example of a well‐preserved small impact structure, with which thousands of meteorite fragments are associated. As such, this crater represents a unique opportunity to investigate the effect of a low‐energy impact event on an impacting iron bolide. Excellent documentation of meteorite fragment locations and characteristics has generated a detailed distribution map of both shrapnel and regmaglypted meteorite types. The meteorites' distribution, and internal and external characteristics support a low‐altitude breakup of the impactor which caused atmospherically ablated (regmaglypted) meteorites to fall close to the crater and avoid impact‐related deformation. In contrast, shrapnel fragments sustained deformation at macro‐ and microscales resulting from the catastrophic disruption of the impactor. The impactor was significantly fragmented along pre‐existing planes of weakness, including kamacite lamellae and inclusions, resulting in a bias toward low‐mass (<100 g) fragments. Meteorite mineralogy was investigated and the accessory minerals were found to be dominated by sulfides and phosphides with rare carlsbergite, consistent with other low‐Ni IIIAB iron meteorites. Considerations of the total mass of meteoritic material recovered at the site relative to the probable fraction of the impactor that was preserved based on modeling suggests that the crater was formed by a higher velocity, lower mass impactor than previously inferred.     

Cosmic ray exposure and pre‐atmospheric size of the Gebel Kamil iron meteorite

Cosmogenic He, Ne, and Ar as well as the radionuclides ¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁵³Mn, and ⁶⁰Fe have been determined on samples from the Gebel Kamil ungrouped Ni‐rich iron meteorite by noble gas mass spectrometry and accelerator mass spectrometry (AMS), respectively. The meteorite is associated with the Kamil crater in southern Egypt, which is about 45 m in diameter. Samples originate from an individual large fragment (“Individual”) as well as from shrapnel. Concentrations of all cosmogenic nuclides—stable and radioactive—are lower by a factor 3–4 in the shrapnel samples than in the Individual. Assuming negligible ³⁶Cl decay during terrestrial residence (indicated by the young crater age <5000 years; Folco et al. 2011 ), data are consistent with a simple exposure history and a ³⁶Cl‐³⁶Ar cosmic ray exposure age (CRE) of approximately (366 ± 18) Ma (systematic errors not included). Both noble gases and radionuclides point to a pre‐atmospheric radius >85 cm, i.e., a pre‐atmospheric mass >20 tons, with a preferred radius of 115–120 cm (50–60 tons). The analyzed samples came from a depth of approximately 20 cm (Individual) and approximately 50–80 cm (shrapnel). The size of the Gebel Kamil meteoroid determined in this work is close to estimates based on impact cratering models combined with expectations for ablation during passage through the atmosphere (Folco et al. 2010 , 2011 ).     

TWO NEW IRON METEORITES FROM WESTERN AUSTRALIA

Two new iron meteorites from Western Australia are described: Cosmo Newberry — a 2.156 kg meteorite of unusual spiky shape, and Gnowangerup — a 33.6 kg pear-shaped meteorite. X-ray fluorescence spectrometry shows that Cosmo Newberry can be classified in Group IIA, whilst Gnowangerup is a member of Group IIIAB. Neither iron can be associated with any other Western Australian meteorite.     

NEW LIGHT ON THE ORIGIN OF THE HOLY BLACK STONE OF THE KA'BA

At various times the Black Stone of the Ka'ba has been considered to be lava, basalt, a meteorite and lately an agate. This paper discusses the possibility that it may consist of impactite glass, derived from the meteoritic craters of Al-Hadidah, called Wabar.     

Crystallization of magmatic iron meteorites: The role of mixing in the molten core

Abstract— The IIIAB group is the largest of the magmatic iron meteorite groups and consequently is commonly used to test models of asteroid core crystallization. Simple fractional crystallization calculations appear to reproduce the general shape of the elemental trends observed in the IIIAB group when these trends are plotted vs. Ni, as is traditionally done. However, when the elemental trends are examined vs. another element (such as Ge vs. Ir), simple fractional crystallization fails to match a significant portion of the trend, specifically meteorites formed during the final stages of crystallization. Our simple mixing model, which attempts to account for the possibility of inhomogeneities in the molten metallic core, is able to reproduce the entire IIIAB trend observed. This model is a variant of simple fractional crystallization and involves mixing between a zone of liquid involved in the crystallization process and a second zone too far from the crystallizing solid to be actively involved in crystallization. This model does not suggest one unique solution for the method by which an asteroidal core crystallizes; rather it demonstrates that including the effects of mixing in the molten core can account for the observed IIIAB elemental trends, particularly the late-stage crystallizing members, which other models have difficulty explaining.     

Compositional variation and mixing of impact melts on microscopic scales

Abstract— We investigated the compositional characteristics of schlieren-rich, holohyaline impact glasses from Ries, Wabar, and Meteor Crater using a Cameca SX 100 scanning electron microprobe. This instrument is capable of producing detailed maps of major elements at spatial resolutions of <10 μm. The objective was to characterize the composition of an unusually large number of individual schlieren and to evaluate details of the process that causes melts of lithologically diverse target rocks to mix on scales of micrometers. The Ries and Meteor Crater impacts involved lithologically heterogeneous targets; whereas, Wabar Crater formed in relatively uniform dune sand. Texturally heterogeneous, schlieren-rich glasses from the Ries Crater illustrate that schlieren of highly variable color can be surprisingly similar in composition, as first detailed by Stähle (1972). Consistent with these earlier findings, most schlieren represent mixtures of diverse rock melts; their compositions deviate only subtly from the average melt and do not resemble monomineralic melts nor binary mixtures of major rock-forming minerals. A specific population of schlieren is enriched in mafic elements (Mg, Fe, and Ca), which suggests incomplete homogenization of an amphibolite progenitor. In the case of Wabar Crater, a compositionally simple melt of dune sand mixed with projectile (IIIA iron meteorite) materials, and specific schlieren are variable mixtures of these two progenitors. The optically homogeneous glass from Meteor Crater is compositionally homogeneous as well, which suggests ideal mixing of such diverse lithologies as platform carbonates, sandstone, and a class IIIA iron meteorite. The mixing of projectile and target melts at Wabar and Meteor Crater unambiguously demonstrates that melts initially produced in distinctly different stratigraphic/structural locations will undergo wholesale mixing, if not homogenization. Also, the projectile melts unquestionably formed relatively early in the cratering process, and their dissemination throughout the prospective melt volume, albeit at variable concentration levels, suggests that the entire mixing process may be an early cratering feature. This also follows from the fact that we investigated ballistic melt ejecta, which thereby eliminates all of those mixing processes that may additionally operate during the pooling and generation of massive melt-ponds following gravitational collapse of large, structurally complex craters. Substantial turbulence ranging from field dimensions to microscopic scales seems inescapable to accomplish the observed degree of mixing, yet this is not readily inferred from current models of macroscopic material motions during hypervelocity impact.     

Mn‐Cr chronology of five IIIAB iron meteorites

Abstract— Mn‐Cr systematics in phosphates (sarcopside, graftonite, beusite, galileiite, and johnsomervilleite) in IIIAB iron meteorites were investigated by secondary ion mass spectrometry (SIMS). In most cases, excesses in ⁵³Cr are found and δ⁵³Cr is well correlated with Mn/Cr ratios, suggesting that ⁵³Mn was alive at the time of IIIAB iron formation. The inferred Mn‐Cr “ages” are different for different phosphate minerals. This is presumably due to a combined effect of the slow cooling rates of IIIAB iron meteorites and the difference in the diffusion properties of Cr and Mn in the phosphates. The ages of sarcopside are the same for the IIIAB iron meteorites. Johnsomervilleite shows apparent old ages, probably because of a gain of Cr enriched in ⁵³Cr during the closure process. Apparently, old Mn‐Cr ages reported in previous studies can also be explained in a similar way. Therefore, the IIIAB iron meteorites probably experienced identical thermal histories and thus derived from the core of a parent body. Thermal histories of the parent body of IIIAB iron meteorites that satisfy the Mn‐Cr chronology and metallographic cooling rates were constructed by computer simulation. The thermal history at an early stage (<10 Ma after CAI formation) is well determined, though later history may be more model‐dependent. It is suggested that relative timing of various events in the IIIAB parent body may be estimated with the aid of the thermal history. There is a systematic difference in Mn and Cr concentrations in various minerals (phosphates, sulfide, etc.) among the IIIAB iron meteorites, which seems to be mainly controlled by redox conditions.     

Dissemination and fractionation of projectile materials in the impact melts from Wabar Crater,Saudi Arabia

Abstract— We have analyzed small, ballistically dispersed melt samples in the form of aerodynamically shaped spheres, dumbbells, teardrops, etc., from Wabar Crater, Saudi Arabia, and have compared these to our previous study of the more massive, black and white melt specimens. The smaller melt samples differ from the more massive melts in that they are petrographically and chemically more homogeneous, possess fewer, more diffuse schlieren and contain much less clastic detritus. These observations suggest higher peak temperatures for the smaller melt samples than for the massive black and white melts which represent Wabar's major melt-zone. Analyses of the Wabar and Nejed (paired with Wabar) meteorites permit detailed comparison of the unaltered projectile with impactor residues in the melts. Siderophile element concentrations indicate that the small glass beads commonly contain > 10% meteoritic component, compared to < 5% for the massive black and white melts. One glass bead was found to contain ～ 17% meteoritic component. Based on models for melt production during cratering, we deduce that more meteoritic material was mixed with the upper stratigraphic horizons of Wabar's melt zone than with the lower parts. Siderophile elements in all Wabar melt specimens are fractionated relative to the Wabar-Nejed meteorite and have Fe/Ni ratios up to ～ 1.8 times that of Wabar-Nejed for the most siderophile element-rich glasses. The abundance sequence of siderophiles in the melts relative to the projectile is Fe ? Co > Ni ? Ir ? As » Au. Although this sequence seems incompatible with simple vapor fractionation of either elements or oxides, we believe that a complex vapor fractionation process most likely produced the observed siderophile element abundances. Our sample suite should be representative of all materials found in and around the Wabar structure, and we conclude that substantial quantities of the projectile were lost to the atmosphere, most likely as vapor. No fractionation of lithophile elements is observed in the glasses relative to the target rocks. Although fractionation of the impactor must have occurred prior to intimate mixing of projectile and target, details of the actual fractionation mechanism(s) remain poorly understood. The results of this study indicate that caution is necessary when attempting to define impactor types and masses from compositional data for impact melts from other craters.     

Meteorite and meteoroid: New comprehensive definitions

Abstract– Meteorites have traditionally been defined as solid objects that have fallen to Earth from space. This definition, however, is no longer adequate. In recent decades, man‐made objects have fallen to Earth from space, meteorites have been identified on the Moon and Mars, and small interplanetary objects have impacted orbiting spacecraft. Taking these facts and other potential complications into consideration, we offer new comprehensive definitions of the terms “meteorite,”“meteoroid,” and their smaller counterparts: A meteoroid is a 10‐μm to 1‐m‐size natural solid object moving in interplanetary space. A micrometeoroid is a meteoroid 10 μm to 2 mm in size. A meteorite is a natural, solid object larger than 10 μm in size, derived from a celestial body, that was transported by natural means from the body on which it formed to a region outside the dominant gravitational influence of that body and that later collided with a natural or artificial body larger than itself (even if it is the same body from which it was launched). Weathering and other secondary processes do not affect an object’s status as a meteorite as long as something recognizable remains of its original minerals or structure. An object loses its status as a meteorite if it is incorporated into a larger rock that becomes a meteorite itself. A micrometeorite is a meteorite between 10 μm and 2 mm in size. Meteorite– “a solid substance or body falling from the high regions of the atmosphere” ( Craig 1849 ); “[a] mass of stone and iron that ha[s] been directly observed to have fallen down to the Earth’s surface” (translated from Cohen 1894 ); “[a] solid bod[y] which came to the earth from space” ( Farrington 1915 ); “A mass of solid matter, too small to be considered an asteroid; either traveling through space as an unattached unit, or having landed on the earth and still retaining its identity” ( Nininger 1933 ); “[a meteoroid] which has reached the surface of the Earth without being vaporized” (1958 International Astronomical Union (IAU) definition, quoted by Millman 1961 ); “a solid body which has arrived on the Earth from outer space” ( Mason 1962 ); “[a] solid bod[y] which reach[es] the Earth (or the Moon, Mars, etc.) from interplanetary space and [is] large enough to survive passage through the Earth’s (or Mars’, etc.) atmosphere” ( Gomes and Keil 1980 ); “[a meteoroid] that survive[s] passage through the atmosphere and fall[s] to earth” ( Burke 1986 ); “a recovered fragment of a meteoroid that has survived transit through the earth’s atmosphere” ( McSween 1987 ); “[a] solid bod[y] of extraterrestrial material that penetrate[s] the atmosphere and reach[es] the Earth’s surface” ( Krot et al. 2003 ).     

The early geological history of the Moon inferred from ancient lunar meteorite Miller Range 13317

Miller Range (MIL) 13317 is a heterogeneous basalt‐bearing lunar regolith breccia that provides insights into the early magmatic history of the Moon. MIL 13317 is formed from a mixture of material with clasts having an affinity to Apollo ferroan anorthosites and basaltic volcanic rocks. Noble gas data indicate that MIL 13317 was consolidated into a breccia between 2610 ± 780 Ma and 1570 ± 470 Ma where it experienced a complex near‐surface irradiation history for ~835 ± 84 Myr, at an average depth of ~30 cm. The fusion crust has an intermediate composition (Al₂O₃ 15.9 wt%; FeO 12.3 wt%) with an added incompatible trace element (Th 5.4 ppm) chemical component. Taking the fusion crust to be indicative of the bulk sample composition, this implies that MIL 13317 originated from a regolith that is associated with a mare‐highland boundary that is KREEP‐rich (i.e., K, rare earth elements, and P). A comparison of bulk chemical data from MIL 13317 with remote sensing data from the Lunar Prospector orbiter suggests that MIL 13317 likely originated from the northwest region of Oceanus Procellarum, east of Mare Nubium, or at the eastern edge of Mare Frigoris. All these potential source areas are on the near side of the Moon, indicating a close association with the Procellarum KREEP Terrane. Basalt clasts in MIL 13317 are from a very low‐Ti to low‐Ti (between 0.14 and 0.32 wt%) source region. The similar mineral fractionation trends of the different basalt clasts in the sample suggest they are comagmatic in origin. Zircon‐bearing phases and Ca‐phosphate grains in basalt clasts and matrix grains yield ²⁰⁷Pb/²⁰⁶Pb ages between 4344 ± 4 and 4333 ± 5 Ma. These ancient ²⁰⁷Pb/²⁰⁶Pb ages indicate that the meteorite has sampled a range of Pre‐Nectarian volcanic rocks that are poorly represented in the Apollo, Luna, and lunar meteorite collections. As such, MIL 13317 adds to the growing evidence that basaltic volcanic activity on the Moon started as early as ~4340 Ma, before the main period of lunar mare basalt volcanism at ~3850 Ma.     

Impact melting of the largest known enstatite meteorite: Al Haggounia 001, a fossil EL chondrite

Al Haggounia 001 and paired specimens (including Northwest Africa [NWA] 2828 and 7401) are part of a vesicular, incompletely melted, EL chondrite impact melt rock with a mass of ~3 metric tons. The meteorite exhibits numerous shock effects including (1) development of undulose to weak mosaic extinction in low‐Ca pyroxene; (2) dispersion of metal‐sulfide blebs within silicates causing “darkening”; (3) incomplete impact melting wherein some relict chondrules survived; (4) vaporization of troilite, resulting in S₂ bubbles that infused the melt; (5) formation of immiscible silicate and metal‐sulfide melts; (6) shock‐induced transportation of the metal‐sulfide melt to distances >10 cm; (7) partial resorption of relict chondrules and coarse silicate grains by the surrounding silicate melt; (8) crystallization of enstatite in the matrix and as overgrowths on relict silicate grains and relict chondrules; (9) crystallization of plagioclase from the melt; and (10) quenching of the vesicular silicate melt. The vesicular samples lost almost all of their metal during the shock event and were less susceptible to terrestrial weathering; in contrast, the samples in which the metal melt accumulated became severely weathered. Literature data indicate the meteorite fell ~23,000 yr ago; numerous secondary phases formed during weathering. Both impact melting and weathering altered the meteorite's bulk chemical composition: e.g., impact melting and loss of a metal‐sulfide melt from NWA 2828 is responsible for bulk depletions in common siderophile elements and in Mn (from alabandite); weathering of oldhamite caused depletions in many rare earth elements; the growth of secondary phases caused enrichments in alkalis, Ga, As, Se, and Au.