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1.
The distribution of minerals on the lunar surface is information which could contribute to studying lunar origin and evolution. In this paper, the distribution of clinopyroxene, orthopyroxene, olivine, ilmenite, and plagioclase on the lunar surface has been mapped based on Hapke radiative transfer model and linear unmixing of spectra with Clementine UVVIS/NIR data. The results have been validated on the basis of minerals modal abundance data of the Apollo samples, and problems in the minerals abundance mapping have been analyzed. The validation based on analysis data of Apollo samples indicates that plagioclase mapped in this paper represents the total abundance of plagioclase and agglutinitic glass. The minerals mapping results show that the lunar surface is mainly composed of pyroxene, plagioclase, agglutinitic glass, and ilmenite. Basalt in the lunar mare is mainly composed of clinopyroxene and ilmenite, and lunar highland is mainly composed of plagioclase and agglutinitic glass. Orthopyroxene is mainly distributed on the north of Mare Imbrium, on the south of Maria and Aitken Basin. According to our results, there is probably no large area of olivine distribution on the lunar surface which is different from earlier published results. Therefore, emphasis should be put on the olivine distribution in the minerals mapping using hyperspectral data such as M3 of Chandrayaan-1 and IIM of ChangE-1.  相似文献   

2.
Abstract— The lunar soil characterization consortium, a group of lunar‐sample and remote‐sensing scientists, has undertaken the extensive task of characterization of the finest fractions of lunar soils, with respect to their mineralogical and chemical makeup. These compositional data form the basis for integration and modeling with the reflectance spectra of these same soil fractions. This endeavor is aimed at deciphering the effects of space weathering of soils on airless bodies with quantification of the links between remotely sensed reflectance spectra and composition. A beneficial byproduct is an understanding of the complexities involved in the formation of lunar soil. Several significant findings have been documented in the study of the <45 μm size fractions of selected Apollo 17 mare soils. As grain size decreases, the abundance of agglutinitic glass increases, as does the plagioclase, whereas the other minerals decrease. The composition of the agglutinitic glass is relatively constant for all size fractions, being more feldspathic than any of the bulk compositions; notably, TiO2 is substantially depleted in the agglutinitic glass. However, as grain size decreases, the bulk composition of each size fraction continuously changes, becoming more Al‐rich and Fe‐poor, and approaches the composition of the agglutinitic glasses. Between the smallest grain sizes (10–20 and < 10 μm), the IS/FeO values (amount of total iron present as nanophase Fe0) increase by greater than 100% (>2x), whereas the abundance of agglutinitic glass increases by only 10–15%. This is evidence for a large contribution from surface‐correlated nanophase Fe0 to the IS/FeO values, particularly in the <10 μm size fraction. The surface nanophase Fe0 is present largely as vapor‐deposited patinas on the surfaces of almost every particle of the mature soils, and to a lesser degree for the immature soils (Keller et al., 1999a). It is reasoned that the vapor‐deposited patinas may have far greater effects upon reflectance spectra of mare soils than the agglutinitic Fe0.  相似文献   

3.
Abstract— Quantitative textural data for Northwest Africa (NWA) 032 and the LaPaz (LAP) mare basalt meteorites (LAP 02205, LAP 02224, LAP 02226, and LAP 02436) prvide constraints on their crystallization and mineral growth histories. In conjunction with whole‐rock and mineral chemistry, textural analysis provides powerful evidence for meteorite pairing. Petrographic observations and crystal size distribution (CSD) measurements of NWA 032 indicate a mixed population of slowly cooled phenocrysts and faster cooled matrix. LaPaz basalt crystal populations are consistent with a single phase of nucleation and growth. Spatial distribution patterns (SDP) of minerals in the meteorites highlight the importance of clumping and formation of clustered crystal frameworks in their melts, succeeded by continued nucleation and growth of crystals. This process resulted in increasingly poor sorting, during competition for growth, as the melt crystallized. Based on CSD and SDP data, we suggest a potential lava flow geometry model to explain the different crystal populations for NWA 032 and the LaPaz basalts. This model involves crystallization of early formed phenocrysts at hypabyssal depths in the lunar crust, followed by eruption and flow differentiation on the lunar surface. Lava flow differentiation would allow for formation of a cumulate base and facilitate variable cooling within the stratigraphy, explaining the varied textures and modal mineralogies of mare basalt meteorites. The model may also provide insight into the relative relationships of some Apollo mare basalt suites, shallow‐level crystal fractionation processes, and the nature of mare basalt volcanism over lunar history.  相似文献   

4.
We have classified 1858 lithic and vitreous fragments from the Luna 16 core-tube sample. They were taken from the soil fractions ranging in size from 150 to 425 μ, at levels A and G (γ). No important differences are observed between the proportions of particle types in levels A and G, nor between the soils of Luna 16 and those from the Apollo 11 landing site in the nearby Mare Tranquillitatis. Luna 16 basalts are texturally and mineralogically similar to Apollo 11 basalts, though the former are characterized by more Fe-rich olivines and pyroxenes and by lower ilmenite contents than are Apollo 11 basalts. The atomic ratio Al/Ti in Luna 16 basalt pyroxenes in about 1.5; Apollo 11 basalt pyroxenes have Al/Ti = 2.0, indicating the possibility of a lower mean valence for Ti in the Luna 16 material than in the Apollo 11 material. Most light-colored lithic fragments are anorthositic rather than noritic in character and are comparable to Apollo 11 anorthosites in mineral chemistry. We believe they are samples of terra regions to the north of the Luna 16 landing site. Triangular diagrams plotting normative plagioclase, normative mafics plus oxides, and normative orthoclase plus apatite neatly separate the three major types of lunar materials — mare basalts, anorthosites, and noritic rocks — and reveal that the Luna 16 regolith is composed of mare basalt and anorthosite, with very little norite component. Colorless-to-greenish glass occurs in the Luna 16 sample, which has high Fe and low Ti; it may represent gabbroic rock related to the anorthosites  相似文献   

5.
Abstract Remote sensing studies are the primary means of solar system exploration. In particular, spectral reflectance measurements involve determinations of the nature and compositions of other worlds through analysis of absorption features characteristic of the surface chemistry and mineralogy. These studies are particularly applicable to “airless” solar system bodies (e.g., the Moon), because atmospheres, such as on Earth, tend to interfere with the reflectance spectrum. The precision of the spectral measurements is greatly increased by calibration with actual lunar soils. In the past, these calibrations were done using particle-counting data collected for the study of soil formation processes, soil classification, and provenance determination. These particle counting data, while valuable in those areas of study, neither identify the true volume percentages of soil particles, nor give the true modal values for the various phases (i.e., minerals and glasses) which make up the soil grains. These data are paramount for accurate spectral reflectance calibrations. Therefore, in this paper, a new technique is presented that involves x-ray digital-imaging of lunar soils using an energy dispersive spectrometer (EDS) on an electron microprobe. In contrast to particle counting with an optical microscope, the digital-imaging method allows precise volume percentages of soil grains to be determined, including absolute modal abundances of the various phases locked within the particles as well as their chemistry. In order to validate this method for characterization of lunar soils, the technique was applied to four Apollo 17 soils that were previously described by Heiken and McKay (1974) via particle counts with an optical microscope, and similar results were obtained. In addition to verifying the x-ray digital-imaging technique, the obtained data were applied in order to better understand the lunar-soil formational process, specifically the variation of particle types with maturity.  相似文献   

6.
Abstract— Dhofar 287 (Dho 287) is a new lunar meteorite, found in Oman on January 14, 2001. The main portion of this meteorite (Dho 287A) consists of a mare basalt, while a smaller portion of breccia (Dho 287B) is attached on the side. Dho 287A is only the fourth crystalline mare basalt meteorite found on Earth to date and is the subject of the present study. The basalt consists mainly of phenocrysts of olivine and pyroxene set in a finer‐grained matrix, which is composed of elongated pyroxene and plagioclase crystals radiating from a common nucleii. The majority of olivine and pyroxene grains are zoned, from core to rim, in terms of Fe and Mg. Accessory minerals include ilmenite, chromite, ulvöspinel, troilite, and FeNi metal. Chromite is invariably mantled by ulvöspinel. This rock is unusually rich in late‐stage mesostasis, composed largely of fayalite, Si‐K‐Ba‐rich glass, fluorapatite, and whitlockite. In texture and mineralogy, Dho 287A is a low‐Ti mare basalt, with similarities to Apollo 12 (A‐12) and Apollo 15 (A‐15) basalts. However, all plagioclase is now present as maskelynite, and its composition is atypical for known low‐Ti mare basalts. The Fe to Mn ratios of olivine and pyroxene, the presence of FeNi metal, and the bulk‐rock oxygen isotopic ratios, along with several other petrological features, are evidence for the lunar origin for this meteorite. Whole‐rock composition further confirms the similarity of Dho 287A with A‐12 and A‐15 samples but requires possible KREEP assimilation to account for its rare‐earth‐element (REE) contents. Cooling‐rate estimates, based on Fo zonation in olivine, yield values of 0.2–0.8°C/hr for the lava, typical for the center of a 10–20 m thick flow. The recalculated major‐element concentrations, after removing 10–15% modal olivine, are comparable to typical A‐15 mare basalts. Crystallization modeling of the recalculated Dho 287A bulk‐composition yields a reasonable fit between predicted and observed mineral abundances and compositions.  相似文献   

7.
Approximately 180 glasses in each of three Apollo 15 soils have been analyzed for nine elements. Cluster analysis techniques allow the recognition of preferred glass compositions that are equated with parent rock compositions Green glass rich in Fe and Mg, poor in Al and Ti may be derived from deep seated pyroxenitic material now present at the Apennine Front. Fra Mauro basalt (KREEP) is most abundant in the LM soil and is tentatively identified as ray material from the Aristillus-Autolycus area. Highland basalt (anorthositic gabbro), believed to be derived from the lunar highlands, has the same composition as at other landing sites, but is less abundant. The Apennine Front is probably not true highland material but may contain a substantial amount of material with the composition of Fra Mauro basalt, but lacking the high-K content. Glasses with mare basalt compositions are present in the soils and four subgroups are recognized, one of which is compositionally equivalent to the large Apollo 15 basalt samples  相似文献   

8.
Z.C. Ling  Alian Wang 《Icarus》2011,211(1):101-113
Laser Raman spectroscopy is used to investigate four lunar soils, focusing on mineralogy of grains of <45 μm size. Apollo samples 14163, 15271, 67511, and 71501 were selected as endmembers to study, based on their soil chemistry, maturity, and sample locations. Typical Raman spectral features for major and minor lunar minerals are discussed on the basis of major vibrational modes. We used the Raman peak shift to calculate Mg/(Mg + Fe + Ca) and Ca/(Mg + Fe + Ca) for pyroxene and Mg/(Mg + Fe) for olivine, and thus obtained the compositional distributions of these two minerals in each of the four lunar soils. Classification of feldspar grains was made based on recognition of their Raman patterns. A Raman point-counting procedure was applied to derive mineral modes of the soils, and these are found to be consistent with published modal analysis of these soils. The compositional distributions of pyroxene and olivine grains in each soil sample, as well as the mineral modes, reflect characteristics of the main source materials for these soils. Raman patterns and peak positions also reflect shock effects on plagioclase and quartz, found in 14163.  相似文献   

9.
Abstract— Dhofar 287 (Dho 287), a recently found lunar meteorite, consists in large part (95%) of low‐Ti mare basalt (Dho 287A) and a minor, attached portion (?5%) of regolith breccia (Dho 287B). The present study is directed mainly at the breccia portion of this meteorite. This breccia consists of a variety of lithic clasts and mineral fragments set in a fine‐grained matrix and minor impact melt. The majority of clasts and minerals appear to have been mainly derived from the low‐Ti basalt suite, similar to that of Dho 287A. Very low‐Ti (VLT) basalts are a minor lithology of the breccia. These are significantly lower in Mg# and slightly higher in Ti compared to Luna 24 and Apollo 17 VLT basalts. Picritic glasses constitute another minor component of the breccia and are compositionally similar to Apollo 15 green glasses. Dho 287B also contains abundant fragments of Mg‐rich pyroxene and anorthite‐rich plagioclase grains that are absent in the lithic clasts. Such fragments appear to have been derived from a coarse‐grained, Mg#‐rich, Na‐poor lithology. A KREEP component is apparent in chemistry, but no highlands lithologies were identified. The Dho 287 basaltic lithologies cannot be explained by near‐surface fractionation of a single parental magma. Instead, magma compositions are represented by a picritic glass; a low‐Ti, Na‐poor glass; and a low‐Ti, Na‐enriched source (similar to the Dho 287A parental melt). Compositional differences among parent melts could reflect inhomogeneity of the lunar mantle. Alternatively, the low‐Ti, Na‐poor, and Dho 287A parent melts could be of hybrid compositions, resulting from assimilation of KREEP by picritic magma. Thus, the Dho 287B breccia contains lithologies from multiple magmatic eruptions, which differed in composition, formational conditions, and cooling histories. Based on this study, the Dho 287 is inferred to have been ejected from a region located distal to highlands terrains, possibly from the western limb of the lunar nearside, dominated by mare basalts and KREEP‐rich lithologies.  相似文献   

10.
Abstract— Soils of the 62-cm deep Apollo 16 double drive tube 60013/14 are mature at the top and submature at the bottom. Modal analyses of 5529 grains from the 90–150 μm and the 500–1000 μm. fractions from 12 levels of the core show that, in general, agglutinate abundance increases somewhat monotonically to the top and mimics the Is/FeO profile. There is a general decrease in the modal abundance of monomineralic fragments towards the top, suggesting that agglutinates were formed in part at the expense of monomineralic grains, especially feldspars, which are by far the most abundant mineral in these soils. In detail, the top 27 cm of the core differs from the bottom 21 cm, and the middle 14 cm is intermediate in its properties. In the upper segment, variations in the abundances of feldspars correspond with those of feldspathic fragmental breccias and cataclastic anorthosites; in the bottom segment, a similar but weak correspondence between feldspars and crystalline matrix breccias is observed. Mixing of the comminuted products of these three rock types likely produced the bulk of the core material. Many single feldspars in all size fractions are remarkably fresh, show no damage from shock, and are similar in appearance to the large feldspars in anorthosites and feldspathic fragmental breccias, which we consider to be the primary sources of single feldspars in this core. Major (Na, Al, Si, K, Ca) and minor (Fe, Ba) element analyses of 198 single feldspar grains indicate the presence of only one population of feldspars, which is consistent with our interpretation of feldspar provenance. Classification of 890 monomineralic feldspar, olivine, pyroxene, and glass spherules on the basis of the presence or absence of thin brownish coating—related to reworking at the surface—shows that coated grains are much more abundant in the top segment than in the bottom segment. A comparison with the mixing and maturation model (McKay et al., 1977) of soils in the core 60009/10, some 60 m away from 60013/14, shows that mixtures of an immature, nearly pure plagioclase soil (dominant in 60009/10) and another immature, crystalline breccia-rich soil (dominant in 60013/14) may have matured through in situ reworking to produce the soils under investigation. We conclude that the soils in this core are products of mixing along soil evolution Path 2 of McKay et al. (1974). Superimposed on that soil column is the reworking of the upper part, which has evolved more recently along Path 1. This core thus represents a consanguineous column of the lunar regolith with an upper reworked segment.  相似文献   

11.
Clast 100 in regolith breccia 15295 could be a key to resolving the relationship(s) between mare basalts and lunar picritic glasses. The clast is basaltic, with texture, mineralogy, mineral compositions, and calculated bulk composition suggesting that it crystallized in a thick lava flow or shallow intrusive body from a very‐low‐titanium (VLT) basaltic magma. The estimated bulk composition of clast 15295,100 is primitive (i.e., magnesian) compared to those of known VLT basalts, and is very close to those of VLT picritic green glasses, especially the Apollo 14 A green glass. From these similarities, we infer that clast 15295,100 is a crystalline product of a picritic magma similar to the Apollo 14 A glass. Clementine and M3 remotely sensed data of the lunar surface were used to find areas that have chemical compositions consistent with those of clast 15295,100, not only near the Apollo 15 site, but in a broad region surrounding the site. Two regions are consistent with clast's 15295,100 compositional data. The larger region is in southern Mare Imbrium, and a smaller region is in the eastern half of Sinus Aestuum. These locations should be considered as candidates for future missions focusing on sample science.  相似文献   

12.
Abstract— We present the petrography and geochemistry of five 2–4 mm basalt fragments from the Apollo 16 regolith. These fragments are 1) a high‐Ti vitrophyric basalt compositionally similar to Apollo 17 high‐Ti mare basalts, 2) a very high‐Ti vitrophyric basalt compositionally similar to Apollos 12 and 14 red‐black pyroclastic glass, 3) a coarsely crystalline high‐Al basalt compositionally similar to group 5 Apollo 14 high‐Al mare basalts, 4) a very low‐Ti (VLT) crystalline basalt compositionally similar to Luna 24 VLT basalts, and 5) a VLT basaltic glass fragment compositionally similar to Apollo 17 VLT basalts. High‐Ti basalt has been reported previously at the Apollo 16 site; the other basalt types have not been reported previously. As there are no known cryptomaria or pyroclastic deposits in the highlands near the Apollo 16 site (ruling out a local origin), and scant evidence for basaltic material in the Apollo 16 ancient regolith breccias or Apollo 16 soils collected near North Ray Crater (ruling out a basin ejecta origin), we infer that the basaltic material in the Apollo 16 regolith originated in maria near the Apollo 16 site and was transported laterally to the site by small‐ to medium‐sized post‐basin impacts. On the basis of TiO2 concentrations derived from the Clementine UVVIS data, Mare Tranquillitatis (?300 km north) is the most likely source for the high‐Ti basaltic material at the Apollo 16 site (craters Ross, Arago, Dionysius, Maskelyne, Moltke, Sosigenes, Schmidt), Mare Nectaris/Sinus Asperitatis (?220 km east) is the most likely source for the low‐Ti and VLT basaltic material (craters Theophilus, Madler, Torricelli), and a large regional pyroclastic deposit near Mare Vaporum (?600 km northwest) is the most likely source region for pyroclastic material (although no source craters are apparent in the region).  相似文献   

13.
We report measurements of the oxidation state of Fe nanoparticles within lunar soils that experienced varied degrees of space weathering. We measured >100 particles from immature, submature, and mature lunar samples using electron energy‐loss spectroscopy (EELS) coupled to an aberration‐corrected transmission electron microscope. The EELS measurements show that the nanoparticles are composed of a mixture of Fe0, Fe2+, and Fe3+ oxidation states, and exhibit a trend of increasing oxidation state with higher maturity. We hypothesize that the oxidation is driven by the diffusion of O atoms to the surface of the Fe nanoparticles from the oxygen‐rich matrix that surrounds them. The oxidation state of Fe in the nanoparticles has an effect on modeled reflectance properties of lunar soil. These results are relevant to remote sensing data for the Moon and to the remote determination of relative soil maturities for various regions of the lunar surface.  相似文献   

14.
The adsorption of molecular water onto lunar analog materials was investigated under ultra-high vacuum with the goal to better understand the thermal stability and evolution of water on the lunar surface. Temperature-programmed desorption (TPD) experiments show that lunar-analog basaltic-composition glass is hydrophobic, with water-water interactions dominating over surface chemisorption. This suggests that lunar agglutinates will tend not to adsorb water at temperatures above where water clusters and multilayer ice forms. The basalt JSC-1A lunar mare analog, which is a complex mixture of minerals and glass, adsorbs water above 180 K with an adsorption profile that extends to 400 K, showing evidence for a continuum of water adsorption sites. Bancroft albite adsorbs more water, more strongly, than JSC-1A, with a well-defined desorption peak near 225 K. This suggests that mineral surfaces will adsorb more water than mare or mature (glassy, agglutinate rich) surfaces and may explain the association of water with fresh feldspathic craters at high latitudes. The activation energies for the thermal desorption of water from these materials were determined, and along with values from the literature, used to model the grain-to-grain migration of water within the lunar regolith. These models suggest that a combination of recombinative desorption of hydroxyl along with molecular desorption of water and its subsequent migration within and out of the regolith may explain observed diurnal variations in the distribution of water and hydroxyl on the illuminated Moon.  相似文献   

15.
Siderophilic element/Ir ratios are higher in mature lunar soils from highlands sites than in those from mare sites. We infer that the population of materials responsible for the early intense bombardment of the Moon had high ratios, and that the population responsible for the essentially constant flux has low ratios. No group of chondrites has siderophile/Ir ratios identical to those in the mare or highlands soils; CM chondrites are the most similar, and CM-like materials may account for a major fraction of Earth-crossing materials during the past 3.7 b.y.Siderophile/Ir ratios may be used to determine the amount of highlands regolith in soils or breccias from the mare-highlands interface areas (Apollo 15 and 17), and to infer the time of formation of highlands breccias whose sideropbiles originated in mature soils. Arguments are summarized against the viewpoint that the siderophiles in most highlands breccias originated in basin-forming projectiles. Differences in mature soil siderophile concentrations at Apollo 14 and 16 indicate a substantially greater concentration at the latter site immediately following the Imbrium event.Siderophile concentrations are used to estimate mean regolith depths at the landing sites; as relative values these are more precise than estimates based on seismic or crater observations. The longlived flux is calculated to be 2.9 g cm–2 b.y.–1 averaged over the past 3.7 b.y. A consideration of the relationship between mass fluence and time indicates that the mass flux decreased with a half-life of about 40 m.y. immediately following the Imbrium event.  相似文献   

16.
Abstract— The meteorite Northwest Africa 773 (NWA 773) is a lunar sample with implications for the evolution of mafic magmas on the moon. A combination of key parameters including whole‐rock oxygen isotopic composition, Fe/Mn ratios in mafic silicates, noble gas concentrations, a KREEP‐like rare earth element pattern, and the presence of regolith agglutinate fragments indicate a lunar origin for NWA 773. Partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation. Terrestrial weathering has caused fracturing and precipitation of Carich carbonates and sulfates in the fractures, but lunar minerals appear fresh and unoxidized. The meteorite is composed of two distinct lithologies: a two‐pyroxene olivine gabbro with cumulate texture, and a polymict, fragmental regolith breccia. The olivine gabbro is dominated by cumulate olivine with pigeonite, augite, and interstitial plagioclase feldspar. The breccia consists of several types of clasts but is dominated by clasts from the gabbro and more FeO‐rich derivatives. Variations in clast mineral assemblage and pyroxene Mg/(Mg + Fe) and Ti/(Ti + Cr) record an igneous Fe‐enrichment trend that culminated in crystallization of fayalite + silica + hedenbergite‐bearing symplectites. The Fe‐enrichment trend and cumulate textures observed in NWA 773 are similar to features of terrestrial ponded lava flows and shallow‐level mafic intrusives, indicating that NWA 773 may be from a layered mafic intrusion or a thick, differentiated lava flow. NWA 773 and several other mafic lunar meteorites have LREE‐enriched patters distinct from Apollo and Luna mare basalts, which tend to be LREE‐depleted. This is somewhat surprising in light of remote sensing data that indicates that the Apollo and Luna missions sampled a portion of the moon that was enriched in incompatible heatproducing elements.  相似文献   

17.
Northwest Africa (NWA) 7611/10480 are lunar regolith breccia meteorites, composed of mineral fragments and various clasts including mare basalts, volcanic glasses, gabbroic lithologies, and a diverse variety of highland materials (ferroan anorthosite, Mg-suite, magnesian anorthosite, and alkali suite rocks) as well as different subvarieties of impact melt breccia. The Apollo two-component mixing model calculation reveals that the NWA 7611 source region contains 58 wt% mare materials and 42 wt% highland components, but the estimated mare components in NWA 10480 have a higher abundance (66 wt%). The predominantly very low-Ti (VLT) composition in both fine-grained basaltic and coarse-grained gabbroic lithologies indicates a provenance associated with a thick lava flow or a single magmatic system. The co-occurrence of zoning patterns and fine-scale exsolution lamellae in pyroxene debris supports a cryptomare deposit as the best candidate source. Phosphate Pb–Pb ages in matrix fragments, impact melt breccia, and basaltic clast indicate that the breccia NWA 7611 records geological events spanning approximately 4305–3769 Ma, which is consistent with the ages of ancient lunar VLT volcanism and the products of basin-forming impacts on the lunar nearside. The youngest reset age at ~3.2 Ga is potentially related to the strong shock lithification process of breccia NWA 7611. Moreover, the similar petrology, texture, geochemistry, cosmic-ray exposure data, and crystallization ages support that basaltic component in Yamato (Y)-793274, and Queen Alexandra Range (QUE) 94281, NWA 4884, and NWA 7611 clan came from the same basalt flow.  相似文献   

18.
Abstract— 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 μg/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 μ/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.  相似文献   

19.
Soils at the Apollo 16 site become progressively darker as the percentage of glassy agglutinates increases. Magnetic separates of the agglutinate fraction of a soil always are darker than the bulk soil, and darker than the non-agglutinate fraction that consists of rock and mineral fragments. Darkening of a soil with maturity is due mainly to the increasing proportion of agglutinates. Coating of rock and mineral fragments with thin deposits of glass aids darkening in a minor way, but most of these particles eventually are destroyed by melting as the soils mature.Present address: Dept. of Geological Sciences, University of Washington, Seattle, Wash., U.S.A.  相似文献   

20.
Apollo 12 ropy glasses revisited   总被引：1，自引：0，他引：1  
Abstract— We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and 39Ar-40Ar age dating. The ropy glasses have KREEP-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a 39Ar-40Ar degassing age of 800 ± 15 Ma (Bogard et al, 1992). Measurements of 39Ar-40Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus she, a part of the Moon that has not been sampled directly.  相似文献   

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