Validate global mapping of internal lunar magnetic field

In this work, we report a global mapping of vector lunar magnetic field based on new method of separation of internal and external fields. The magnetic measurements collected during the lifetime of lunar prospector (LP) extended mission during 1999 were strongly disturbed by the solar wind, a period which coincided with a maximum of the 23 cycle activity. The multiscale wavelength external fields were analyzed using spherical harmonic transform. The external field determined by inversion was then removed from each magnetic field component for each half orbit. To map the vector magnetic crustal anomalies, all LP magnetometer data collected at low altitudes in the three different lunar environments: (1) geomagnetic tail, (2) solar wind, and (3) geomagnetic sheath were processed using this new approach. The results obtained using these selection criteria allow us to get a global coverage of the lunar surface by the vector magnetic field at variable spacecraft low altitudes. To validate our mapping, we have developed and applied a method based on properties of potential fields functions. This method can be used to determine both horizontal north and east components using only vertical component. The validated lunar internal magnetic measurements obtained at variable spacecraft altitudes were then continued to a common altitude of 30 km using an inverse method. This mapping confirms firstly the nature of the crustal sources of lunar magnetic field and clearly shows that the strongest concentrations of anomalies are associated with high albedo and/or located antipodal to large young basins (Orientale, Serenitatis, Imbrium, and Crisium) of age about 3.9 Ga.     

A lunar core of Fe-Ni-S

Several workers have proposed that lunar samples were magnetized by a field created by a lunar core of molten Fe. Low abundances of siderophile elements in lunar rocks are compatible with formation of a metallic lunar core. A molten Fe core requires that the bulk of the Moon was above, or close to, the melting point, a requirement which disagrees with most models of the lunar thermal regime.A core (or perhaps a layer or pockets) of molten Fe-Ni-S, at or close to the eutectic composition would act as a lunar dynamo, and be at a temperature (approx. 1000°C) consistent with some reasonable models of lunar thermal history. The existence of a Fe-Ni-S core would also partly explain the depletion in volatile elements in lunar basalts. Such a core, occupying up to 20 per cent of the Moon's radius requires a bulk S content for the moon of only 0.3 wt per cent.     

The compositional classification of chondrites: II The enstatite chondrite groups

We present new data from a neutron activation analysis of four enstatite chondrites including the taxonomically important St. Sauveur, and discuss the classification of enstatite chondrites. The enstatite chondrites can be divided into two compositionally distinct sets; in one set abundances of nonrefractory siderophiles and moderately volatile chalcophiles and alkalis are 1.5–2.0× higher than in the other. A well-resolved compositional hiatus separates these two sets. The differences in composition are as great as those between the groups of ordinary chondrites, and therefore it appears best to treat these sets as separate groups. By analogy with the symbols used for ordinary chondrites we propose to designate the high-Fe, high siderophile group EH and the low-Fe, low-siderophile group EL. Known members of the EH group belong to petrologic types 4 and 5, whereas all EL members are petrologic type 6. Within the EH group no correlation is observed between petrologic type and abundance of nonrefractory siderophiles or moderately volatiles or alkalis.Two physical properties show only modest overlap between the EH and EL groups. Cosmic-ray ages for EH chondrites are 0.5–7 Ma, while those for EL chondrites are 4–18 Ma. Relative to Bjurböle, I-Xe formation intervals are $\text{?1.3 ± 0.6}$ Ma for EH chondrites and $\text{2.9 ± 0.5}$ Ma for EL chondrites. The weight of the chemical and physical evidence indicates that the EH and EL groups formed separate bodies at similar distances from the Sun.The available evidence for Shallowater and Happy Canyon, two strongly recrystallized silicate-rich meteorites containing > 40 mg/g Fe-Ni, indicates that the former is an enstatite-clan chondrite altered by loss of sulfide- and plagioclase-rich melts, whereas the latter is intermediate in composition between EL chondrites and the chondritic silicates in the Pine River IAB-anomalous meteorite.     

Trace element chemistry of Apollo 14 lunar soil from Fra Mauro

Analytical data are presented for Apollo 14 fines ( < 1 mm) sample 14163,136 for 31 trace elements. The heavy REE are enriched monotonically by factors of 105 ± 10 over chondrites. Eu shows a large depletion (30 × chondrites) and the light REE show a smooth progressive enrichment with a slight fall at La. Ba, Cs, Th, U, Nb, Zr and Hf are strongly enriched, relative to chondritic abundances. Thus the outer portions of the moon sampled by the Imbrium event, and now represented by the Fra Mauro Formation, possessed high concentrations (100–200 × chondrites) for many elements, prior to the excavation of the mare basins. A correlation may exist between Gd/Eu and Zr/Hf ratios in lunar materials.     

Light element geochemistry and spallogenesis in lunar rocks

The abundances and isotopic compositions of carbon, nitrogen and sulfur were measured in eleven lunar rocks. Samples were combusted sequentially at three temperatures to resolve terrestrial contamination from indigenous volatiles.Sulfur abundances in Apollo 16 highland rocks range from 73 to 1165 μg/g-whereas sulfur contents in Apollo 15 and 17 basalts range from 719 to 1455 μg/g and correlate with TiO₂ content. Lunar rocks as a group have a remarkably uniform sulfur isotopic composition, which may reflect the low oxygen fugacity of the basaltic magmas. Much of the range of reported δ³⁴S_cd values (?2 to + 2.5 permil) is caused by systematic analytical discrepancies between laboratories.Lunar rocks very likely contain less than 0.1 μg/g of nitrogen. The measured spallogenic production rate, 4.1 × 10^?6 μg ¹⁵N/g sample/m.y., agrees remarkably closely with previous estimates. An estimate which includes all available data is 3.7 × 10^?6 μg¹⁵N/g sample/m.y.Lunar basalts may contain no indigenous lunar carbon in excess of procedural blank levels (~0.7 μg/g). Highlands rocks consistently release about 1 to 5 μg/g of carbon in excess of blank levels, but this carbon might either derive from ancient meteoritic debris or be a mineralogie product of terrestrial weathering. The average measured spallogenic ¹³C production rate is 4.1 × 10^?6 μg¹³C/g sample/m.y. The ¹³C spallation exposure ages of rocks 15058 and 15499 are 184 and 135 m.y., respectively.     

The compositional classification of chondrites—I. The carbonaceous chondrite groups

Twenty carbonaceous chondrites were analyzed by instrumental and radiochemical neutron activation analysis for Na, Mg, Al, K, Ca, Sc, V. Cr, Mn. Fe, Co, Ni, Zn, Ga, Ge, As, Se. Br. Ru, Cd, In, Sb, La, Sm, Eu, Yb, Lu, Os, Ir, and Au. Analysis of 2 or more samples of all but 2 chondrites has helped yield a high precision that allowed the resolution of numerous previously unrecognized trends. Refractory lithophile abundances decrease through the sequence CV (1.33 × CI), CM-CO (1.11 × CI) and CI. The abundances of the common siderophiles Fe, Ni and Co follow the order CI >CM >CO >CV, with CV chondrites depleted about 15% relative to CI. Volatile lithophile (Mn to K) and volatile siderophile (As to Ge) abundances decrease in the order CI >CM >CO >CV. The volatile trends in CO and CV chondrites reverse for the more volatile elements (Br to Cd) producing the sequence CI >CM >CV >CO. These three different sequences in the ordering of group elemental abundances can be used to resolve compositionally the four carbonaceous chondrite groups.We define clans to consist of one or more groups formed at a narrow range of heliocentric distances. Quantization of refractory lithophile abundances indicates the existence of three carbonaceous chondrite clans: CI, CM-CO, and CV. Despite similarities in parameters such as volatile abundances and O-isotope compositions differences in chondrule size and refractory abundances suggest that CO and CV chondrites are indeed best placed in separate clans. The relative heliocentric distance at which CI chondrites formed cannot be inferred, thus it seems safer to assign them to a separate clan.     

Rhodium, gold and other highly siderophile element abundances in chondritic meteorites

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.     

Bismuth in stony meteorites and standard rocks

Bismuth has been determined by alpha counting of the ²¹⁰Po daughter activity of the ²¹⁰Bi formed by thermal neutron activation. Results are presented for thirty chondrites, six achondrites, eight separated meteoritic phases, and six U.S. Geological Survey standard rocks. There is no resolvable difference in Bi abundances among the different groups of ordinary chondrites. Bismuth concentration decreases with increasing petrologic grade among the ordinary chondrites. The enstatite chondrites are separable into two groups on the basis of Bi data.     

Coupled Ce-Nd isotope systematics and rare earth elements differentiation of the moon

¹³⁸Ce/¹⁴²Ce and ¹⁴³Nd/¹⁴⁴Nd isotope ratios of lunar samples are determined to constrain the petrogenetic differentiation and evolution of the moon. High-precision Ce-Nd isotope data, well-defined Rb-Sr isochrons, and rare earth elements (REE) abundances of lunar samples show that unexpectedly low La/Ce ratios of evolved lunar highland samples are preserved from at least 3.9 Ga. Precise analysis of REE abundances indicates that the low La/Ce ratio results from a depletion of La relative to other REE. This depletion can be seen in pristine KREEP basalts and Mg-suite rocks from 3.85 to 4.46 Ga. As REE abundances of all these samples are controlled by the presence of a KREEP component, the depletion was probably inherited from a late crystallization sequence of the lunar magma ocean related to the production of the original KREEP component.     

Genetic relations between meteorites and terrestrial and lunar rocks

According to their genesis, meteorites are classified into heliocentric (which originate from the asteroid belt) and planetocentric (which are fragments of the satellites of giant planets, including the Proto-Earth). Heliocentric meteorites (chondrites and primitive meteorites genetically related to them) used in this study as a characteristic of initial phases of the origin of the terrestrial planets. Synthesis of information on planetocentric meteorites (achondrites and iron meteorites) provides the basis for a model for the genesis of the satellites of giant planets and the Moon. The origin and primary layering of the Earth was initially analogously to that of planets of the HH chondritic type, as follows from similarities between the Earth’s primary crust and mantle and the chondrules of Fe-richest chondrites. The development of the Earth’s mantle and crust precluded its explosive breakup during the transition from its protoplanetary to planetary evolutionary stage, whereas chondritic planets underwent explosive breakup into asteroids. Lunar silicate rocks are poorer in Fe than achondrites, and this is explained in the model for the genesis of the Moon by the separation of a small metallic core, which sometime (at 3–4 Ga) induced the planet’s magnetic field. Iron from this core was involved into the generation of lunar depressions (lunar maria) filled with Fe- and Ti-rich rocks. In contrast to the parent planets of achondrites, the Moon has a olivine mantle, and this fact predetermined the isotopically heavier oxygen isotopic composition of lunar rocks. This effect also predetermined the specifics of the Earth’s rocks, whose oxygen became systematically isotopically heavier from the Precambrian to Paleozoic and Mesozoic in the course of olivinization of the peridotite mantle, a processes that formed the so-called roots of continents.     

Advances in the study of lunar opposition effect

1Introduction Thelightscatteredfromthesurfacesofsolarsys temobjectsbearsinformationonthenatureoftheirsur faces,whichcanimproveourknowledgeontheorigin andevolutionofthewholesolarsystem.Theopposition effectreferstothenarrowpeakintheintensityoflight scatteredfromaparticulatemediumdirectlybackin thedirectiontowardthesource,whichalsomeansthe brightnessincreaseswithdecreasingsolarphaseangle (Hapkeetal.,1998).Itisoneofthemajorchallen gesinopticsofplanetarysurfaces.Seeliger(1887) discoveredfirstly…     

月球物质的Re-Os同位素组成研究：对月球后期增生历史的指示

Re-Os同位素体系是理解月球强亲铁元素的分布规律和示踪月球的后期增生历史的重要手段。目前人们对月球物质Re-Os同位素成分的了解还是十分有限的,已有的Re-Os同位素数据显示一些能代表月幔成分特征的月海玄武岩具有很低的Re和Os的浓度,以及类似于球粒陨石的187Os／188Os成分特征,而月球火山玻璃和月壤等表现出相对高的Re-Os丰度和相对富放射成因Re-Os同位素成分。一般认为月球月幔的Re、0s和其他强亲铁元素相对球粒陨石是非常亏损的,而地球地幔则具有相对较高的强亲铁元素丰度（0．008倍CI球粒陨石的丰度）。新的Re-Os同位素结果证明月幔确实是亏损的,但是月球和地球在太阳系演化的较晚时期都有外来的球粒陨石物质的大量加入,即后期增生（late accretion）过程,导致了月球和地球上部物质（如月球火山玻璃、月壤等）相对地富集Os同位素和强亲铁元素,这些外来物质的后期增生可能是长期和持续的,增生过程主要发生在3．9～4．4Ga。但目前仍不清楚后期增生的陨石物质是被逐渐加入的,还是在一个相对较短的时期大量加入的,因此尚需对更多的月球物质做进一步的Re-Os同位素和强亲铁元素成分的研究。     

Records of ancient cosmic radiation in extraterrestrial rocks

Recent results on cosmic ray interactions in lunar samples and meteorites resulting in production of stable and radionuclides, particle tracks and thermoluminescence are reviewed. A critical examination of²⁶A1 depth profiles in lunar rocks and soil cores, together with particle track data, enables us to determine the long term average fluxes of energetic solar protons (>10 MeV) which can be represented by (J _s,R _o)=(125, 125). The lunar rock data indicate that this flux has remained constant for 5×10⁵ to 2×10⁶ years. Production rates of stable and radionuclides produced by galactic cosmic rays is given as a function of size and depth of the meteoroid. Radionuclide (⁵³Mn,²⁸Al) depth profiles in meteorite cores, whose preatmospheric depths are deduced from track density profiles are used to develop a general procedure for calculating isotope production rates as a function of meteoroid size. Based on the track density and²²Ne/²¹Ne production rates, a criterion is developed to identify meteorites with multiple exposure history.²²Ne/²¹Ne ratio <1·06 is usually indicative of deep shielded exposure. An examination of the available data suggests that the frequency of meteorites with multiple exposure history is high, at least 15% for LL, 27% for L and 31% for H chondrites. The epi-thermal and the thermal neutron density profiles in different meteorites are deduced from⁶⁰Co and track density data in Dhajala, Kirin and Allende chondrites. The data show that the production profile depends sensitively on the size and the chemical composition of the meteoroid. Cosmic ray-induced thermoluminescence in meteorites of known preatmospheric sizes has been measured which indicates that its production profile is nearly flat and insensitive to the size of the meteoroid. Some new possibilities in studying cosmic ray implanted radionuclides in meteorites and lunar samples using resonance ionisation spectroscopy are discussed.     

Volatile and siderophile trace elements in anorthositic rocks from Fiskenaesset. West Greenland: comparison with lunar and meteoritic analogues

Seventeen trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, Ir, Ni, Rb, Re, Sb, Se, Te, Tl, U, Zn) were analyzed by radiochemical neutron activation and 13 other elements (Ce, Co, Cr, Eu, Fe, Hf, La, Lu, Na, Sc, Sm, Tb, Yb) by instrumental neutron activation in a total of 12 rocks from the layered anorthositic complex at Fiskenaesset, West Greenland and in the plagioclase-rich unbrecciated eucrite, Serra de Magé.Garnet anorthosite 84428, which has an unusually sodic plagioclase, is spectacularly enriched in Cs, K, Rb. Tl and, to a lesser degree, Te. This appears to be the result of later metasomatism and not a reflection of fractionation trends within the anorthositic complex. For the remaining Fiskenaesset rocks, a factor analysis yields 5 principal factors for linear data for 22 elements and 6 factors for data transformed (log, ³√, √) to give approximately normal distributions. Linear correlations are controlled by high values, whereas the logarithmic transform increases the influence of the lowest values. Enrichment of several elements in chromitite 132022 underlies linear Factor 1. Six of these elements Co, Cr, Fe, Ir, Ni, Zn and possibly Re are probably hosted by chromite. In other zones of the intrusion, different fractionation trends may be more important, since in the transformed analysis these elements divide between Factor 1 (Co, Zn, Ni, Fe) and Factor 4 (Ir, Cr and also Au). Linear Factor 2 reflects the strong mutual correlation between Tl, Rb and An, the anorthite content of plagioclase. Transformed Factor 3 emphasizes the anticorrelation of Na and Sm with An. The positive correlations of Cs, U and Ge (linear Factor 3; transformed Factor 2) are largely due to their concentration in later crystallizates, but enrichment in lower zone gabbros of high An content perhaps indicates concentration in minor or accessory cumulate minerals. Flat chondrite-normalized rare earth element patterns in several anorthosites (except for a small positive Eu anomaly) suggests that the Fiskenaesset magma was relatively unfractionated.Factor 4 (linear) and Factor 5 (transformed) reflects the geochemical coherence of Se and Te. The sympathetic enrichment of Sb and Cd in 3 rocks, resulting in Factor 5 (linear) and Factor 6 (transformed) may be due to the lack of a suitable Zn sulfide host for Cd.In 3 rocks of true anorthosite composition, 8 volatile elements show rather constant abundance when normalized to Cl chondrites (mean 4.2 ± 0.4% Cl), possibly suggesting that volatile-rich material was accreted late in the Earth's formation, perhaps after core segregation. These anorthosites are higher than lunar anorthosite 15415 by a factor of 58 ± 9 in volatile elements. Siderophile and chalcophile elements are much more variable in Cl-normalized abundances in both lunar and terrestrial anorthosites, but surprisingly give somewhat similar Earth/Moon abundance ratios.Volatile elements in terrestrial oceanic basalts and lunar mare basalts are not as uniformly abundant as in anorthosites. but nevertheless yield a similar Earth/Moon ratio of 44 ± 8.Volatile elements in Serra de Magé are more abundant than in lunar anorthosites, but lower than in terrestrial equivalents, averaging (3.6 ± 0.8) × 10^?3C1.     

Mass spectrometric isotope dilution analyses of tellurium in meteorites and standard rocks

A stable isotope dilution technique using solid source mass spectrometry has been used to determine the elemental abundance of Te in 25 chondrites, 3 achondrites, 1 tektite, and 12 standard rocks. Mean values for the C1, C2, and CV3 meteorites are 2.34, 1.48, and 1.03 ppm, respectively; or atomic abundances for Te (normalized to Si = 10⁶ atoms) of 4.84, 2.49, and 1.46. The atomic abundance obtained for the C1 chondrite Orgueil is significantly lower than the accepted value of 6.42. As a consequence we recommend that the ‘cosmic’ abundance of Te and Xe should be re-examined. The depletion ratio for Te in ordinary chondrites of 0.10, is about the same as that for Zn. Elemental abundances of Te in 12 standard rocks are in the ppb range.     

Chemical and physical studies of type 3 chondrites—V: The enstatite chondrites

We report instrumental neutron activation analysis determinations of 19 major, minor and trace elements in three enstatite chondrites. Based on these, and literature data on the bulk and mineral composition of enstatite chondrites, we discuss the history of the type 3 or unequilibrated enstatite chondrites, and their relationship with the other enstatite chondrites. The type 3 enstatite chondrites have E chondrite lithophile element abundances and their siderophile element abundances place them with the EH chondrites, well resolved from the EL chondrites. Moderately volatile chalcophile elements are at the low end of the EH range and Cr appears to be intermediate between EH and EL. We suggest that the type 3 enstatite chondrites are EH chondrites which have suffered small depletions of certain chalcophile elements through the loss of shock-produced sulfurous liquids. The oxygen isotope differences between type 3 and other enstatite chondrites is consistent with equilibration with the nebula gas ~30° higher than the others, or with the loss of a plagioclase-rich liquid. The mineral chemistry of the type 3 chondrites is consistent with either low temperature equilibration, or, in some instances, with shock effects.     

Hydrogen isotope evidence for the origin and evolution of the carbonaceous chondrites

We present new hydrogen isotope data for separated matrix, hydrated chondrules, and other hydrated coarse silicate fragments from nine carbonaceous chondrites. These data were generated using a micro-analytical method involving stepped combustion of tens to hundreds of micrograms of hydrous solids. We also re-evaluate hydrogen isotope data from previous conventional stepped combustion experiments on these and other carbonaceous chondrites.Hydrogen isotope compositions of matrix and whole-rock samples of CM chondrites are correlated with oxygen isotope indices, major and minor-element abundances, and abundance and isotope ratios of other highly volatile elements. These correlations include a monotonic decrease in δD with increasing extent of aqueous alteration and decreasing abundances of highly volatile elements (including C, N and Ar), between extremes of ∼0‰ (least altered, most volatile rich) and −200‰ (most altered, least volatile rich). In plots involving only abundances and/or isotope ratios of highly volatile elements, CI chondrites fall on the high-δD, volatile rich end of the trends defined by CM chondrites; i.e., CI chondrites resemble the least altered CM chondrites in these respects. These trends suggest the protoliths of the CM chondrites (i.e., before aqueous alteration) contained an assemblage of volatiles having many things in common with those in the CI chondrites. If so, then the volatile-element inventory of the CI chondrites was a more widespread component of early solar system objects than suggested by the scarcity of recognized CI meteorites. Differences in volatile-element chemistry between the CI and average CM chondrites can be attributed to aqueous alteration of the latter.Previous models of carbonaceous chondrite aqueous alteration have suggested: (1) the protoliths of the CM chondrites are volatile poor objects like the CO or CV chondrites; and (2) the CI chondrites are more altered products of the same process producing the CM chondrites. Both suggestions appear to be inconsistent with hydrogen isotope data and other aspects of the volatile-element geochemistry of these rocks. We present a model for aqueous alteration of the CM chondrites that reconciles these inconsistencies and suggests revised relationships among the major subtypes of carbonaceous chondrites. Our model requires, among other things, that the water infiltrating CM chondrites had a δD value of ∼−158‰, consistent with initial accretion of CM parent bodies at ∼4 AU.     

陨石学及天体化学研究某些新进展

陨石是来自含气体-尘粒的太阳早期星云盘凝聚和吸积的原始物质,大多数原始物质因吸积后的作用过程而改变（如月球、地球及火星样品）,但有一些却完整的保存下来（如球粒陨石或球粒陨石中的难熔包体）。这些原始的物质通常依据同位素丰度特征来识别,依据其矿物-岩石学特征和成因可将已知的陨石划分许多更小的类型。陨石学及天体化学的新近进展包括：新近识别的陨石群;发现新类型球粒陨石及行星际尘粒中发现前太阳和星云组分;利用短寿命放射性核素完善了早期太阳系年代学;洞察宇宙化学丰度、分馏作用及星云源区及通过次生母体的作用过程阐释星云和前星云的记录。本文概述了早期太阳系内从星云到陨石的演化过程。依据这些资料,对早期太阳系所经历的多种核合成的输入、瞬时加热事件与星云动力学有一些新的认识,以及认识到小星子和行星体系的演化比以前预期的更快速。     

The compositional classification of chondrites: III. Ungrouped carbonaceous chondrites

Seven carbonaceous chondrites (Allan Hills A77307, Adelaide, Al Rais, Coolidge, Grosnaja, Karoonda and Renazzo) with uncertain classifications were analyzed by instrumental and radiochemical neutron activation analysis for 29 elements: Na, Mg, Al, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, As, Se, Br, Ru, Cd, Sb, La, Sm, Eu, Yb, Lu, Os, Ir and Au. Five of these chondrites (A77307, Adelaide, Al Rais, Karoonda and Renazzo) are unique ‘grouplets’, not closely related to other groups or to each other. Only Coolidge (CV4) and Grosnaja (CV3-an) are members of previously established groups. A77307 and Adelaide have refractory lithophile abundances similar to those in the CM-CO clan; A77307 probably is a member of that clan, but Adelaide, which shows CV-like petrographic characteristics, cannot as yet be assigned to a clan. Al Rais and Renazzo have similar refractory lithophile abundances (essentially at CI levels) and probably belong to the same clan, i.e., formed in the same region of the nebula. There are insufficient data to determine whether they formed at the same general region as the CI chondrites, but separates having O-isotope compositions near the terrestrial fractionation line indicate that this is plausible. Karoonda has refractory lithophile abundances ~ 1.21 × CI and appears to belong to a new clan distinct from CM-CO (1.11 × CI) and CV (1.34×).     

Lunar impact breccias: petrology,crater setting,and bombardment history of the Moon

Two general classes of lunar impact breccias have been recognised: fragmental breccias and melt breccias. Fragmental breccias are composed of clastic-rock debris in a finely comminuted grain-supported matrix of mineral and lithic fragments. Impact melt breccias have crystalline to glassy matrices that formed by cooling of a silicate melt. Most lunar impact breccias in our collection probably sample ejecta from large complex craters or multi-ring basins, although linking individual breccias to specific impact events has proven surprisingly difficult. A long-standing problem in lunar science has been distinguishing clast-poor impact melt breccias from igneous rocks produced by melting of the lunar interior. Concentrations and relative abundances of highly siderophile elements derived from the meteoritic impactor provide a useful discriminant, especially when combined with petrologic and geochemical evidence for mechanical mixing. Most lunar impact melt breccias have crystallisation ages of 4.0?–?3.8 Ga, corresponding to an episode of intensive crustal metamorphism recorded by whole-rock U?–?Pb isotopic compositions of lunar anorthosites. This may reflect a short-lived spike in the cratering rate, although other explanations are possible. The question of whether or not a cataclysmic bombardment struck the Earth and Moon at ca 3.9 Ga remains open and the subject of continuing investigations.