The geochemistry and provenance of Apollo 16 mafic glasses

The regolith of the Apollo 16 lunar landing site is composed mainly of feldspathic lithologies but mafic lithologies are also present. A large proportion of the mafic material occurs as glass. We determined the major element composition of 280 mafic glasses (>10 wt% FeO) from six different Apollo 16 soil samples. A small proportion (5%) of the glasses are of volcanic origin with picritic compositions. Most, however, are of impact origin. Approximately half of the mafic impact glasses are of basaltic composition and half are of noritic composition with high concentrations of incompatible elements. A small fraction have compositions consistent with impact mixtures of mare material and material of the feldspathic highlands. On the basis of major-element chemistry, we identified six mafic glass groups: VLT picritic glass, low-Ti basaltic glass, high-Ti basaltic glass, high-Al basaltic glass, KREEPy glass, and basaltic-andesite glass. These glass groups encompass 60% of the total mafic glasses studied. Trace-element analyses by secondary ion mass spectroscopy for representative examples of each glass group (31 total analyses) support the major-element classifications and groupings. The lack of basaltic glass in Apollo 16 ancient regolith breccias, which provide snapshots of the Apollo 16 soil just after the infall of Imbrium ejecta, leads us to infer that most (if not all) of the basaltic glass was emplaced as ejecta from small- or moderate-sized impacts into the maria surrounding the Apollo 16 site after the Imbrium impact. The high-Ti basaltic glasses likely represent a new type of basalt from Mare Tranquillitatis, whereas the low-Ti and high-Al basaltic glasses possibly represent the composition of the basalts in Mare Nectaris. Both the low-Ti and high-Al basaltic glasses are enriched in light-REEs, which hints at the presence of a KREEP-bearing source region beneath Mare Nectaris. The basaltic andesite glasses have compositions that are siliceous, ferroan, alkali-rich, and moderately titaniferous; they are unlike any previously recognized lunar lithology or glass group. Their likely provenance is within the Procellarum KREEP Terrane, but they are not found within the Apollo 16 ancient regolith breccias and therefore were likely deposited at the Apollo 16 site post-Imbrium. The basaltic-andesite glasses are the most ferroan variety of KREEP yet discovered.     

Apollo 12 revisited

We present compositional data for 358 lithic fragments (2-4-mm size range) and 15 soils (<1-mm fines) from regolith samples collected at the Apollo 12 site. The regolith is dominated by mare basalt, KREEP impact-melt breccias (crystalline and glassy), and regolith breccias. Minor components include alkali anorthosite, alkali norite, granite, quartz monzogabbro, and anorthositic rocks from the feldspathic highlands. The typical KREEP impact-melt breccia of Apollo 12 (mean Th: 16 μg/g) is similar to that of the Apollo 14 site (16 μg/g), 180 km away. Both contain a minor component (0.3% at Apollo 12, 0.6% at Apollo 14) of FeNi metal that is dissimilar to metal in ordinary chondrites but is similar to metal found in Apollo 16 impact-melt breccias. The Apollo 12 regolith contains another variety of KREEP impact-melt breccia that differs from any type of breccia described from the Apollo sites in being substantially richer in Th (30 μg/g) but with only moderate concentrations of K. It is, however, similar in composition to the melt breccia lithology in lunar meteorite Sayh al Uhaymir 169. The average composition of typical mature soil corresponds to a mixture of 65% mare basalt, 20% typical KREEP impact-melt breccia, 7% high-Th impact-melt breccia, 6% feldspathic material, 2.6% alkali noritic anorthosite, and 0.9% CM chondrite. Thus, although the site was resurfaced by basaltic volcanism 3.1-3.3 Ga ago, a third of the material in the present regolith is of nonmare origin, mainly in the form of KREEP impact-melt breccias and glass. These materials occur in the Apollo 12 regolith mainly as a result of moderate-sized impacts into surrounding Fra Mauro and Alpes Formations that formed craters Copernicus (93 km diameter, 406 km distance), Reinhold (48 km diameter, 196 km distance), and possibly Lansberg (39 km diameter, 108 km distance), aided by excavation of basalt interlayers and mixing of regolith by small, local impacts. Anomalous immature soil samples 12024, 12032, and 12033 contain a lesser proportion of mare basalt and a correspondingly greater proportion of KREEP lithologies. These samples consist mainly of fossil or paleoregolith, likely ejecta from Copernicus, that was buried beneath the mixing zone of micrometeorite gardening, and then brought to the near surface by local craters such as Head, Bench, and Sharp Craters.     

Eskolaite in the regolith of the Taurus-Littrow Valley

Eskolaite crystals were discovered in the course of Scanning Electron Microscopy (SEM) studies of the regolith sample, which was delivered from the continental area between Serenitatis and Tranquilitatis Maria during the Apollo 17 mission. The finding was compared with an analogue sampled from Mare Crisium (Luna 24 mission). A condensate-impact origin of eskolaite is assumed for both findings. It was demonstrated that the eskolaite of the Apollo 17 probe is genetically and morphologically identical to the eskolaite from the Luna 24 probes.     

Composition and origin of lithic fragments and glasses in apollo 11 samples

Approximately 100 glasses and 52 lithic fragments from Apollo 11 lunar fines and microbreccias were analyzed with the electron microprobe. Ranges in bulk composition of lithic fragments are considerably outside the precision (<±1%) and accuracy (±2–5%) of the broad electron beam technique. Results of this study may be summarized as follows: i) A large variety of rock types different from the hand specimens (basalt) were found among the lithic fragments, namely anorthosites, troctolitic and noritic anorthosites, troctolites, and norites (different from Apollo 12 norites). ii) In analogy to the hand specimens, the basaltic lithic fragments may be subdivided into low-K and high-K groups, both of which extend considerably in composition beyond the hand specimens. iii) Glasses were divided into 6 groups: Group 1 are the compositional analogs of the anorthositic-troctolitic lithic fragments and were apparently formed in single-stage impact events directly from parent anorthosites and troctolites. iv) Group 2 glasses are identical in composition to Apollo 12 KREEP glass and noritic lithic fragments, but have no counterparts in our Apollo 11 lithic fragment suite. Occurrence of KREEP in Apollo 11,12, and 14 samples is indicative of its relatively high abundance and suggests that the lunar crust is less depleted in elements that are common in KREEP (e.g. K, rare earths, P) than was originally thought on the basis of Apollo 11 basalt studies. v) Group 3 glasses are the compositional analogs of the basaltic lithic fragments, but low-K and high-K glasses cannot be distinguished because of loss of K (and Na, P) by volatilization in the vitrification process. vi) Group 4 glasses have no compositional analogs among the lithic fragments and were probably derived from as yet unknown Fe-rich, moderately Ti-rich, Mg-poor basalts. vii) Group 5 (low Ti-high Mg peridotite equivalent) and 6 (ilmenite peridotite equivalent) glasses have no counterparts among the Apollo 11 lithic fragments, but rock equivalents to group 5 glasses were found in Apollo 12 samples. Group 6 glasses are abundant, have narrow compositional ranges, and are thought to be the products of impact melting of an as yet unrecognized ultramafic rock type. iix) The great variety of igneous rocks (e.g. anorthosites, troctolites, norites, basalts, peridotites) suggests that large scale melting or partial melting to considerable depth must have occurred on the moon.     

Flood Basalts, Basalt Floods or Topless Bushvelds? Lunar Petrogenesis Revisited

There is a conspicuous dichotomy in the conventional model oflunar petrogenesis between the total intra-crustal differentiationpostulated for the products of feldspathic volcanism in thelunar highlands and the near absence of differentiation postulatedfor the products of mare volcanism. Both the cumulate mantlemodel, and the selenotherm postulated to accompany genesis ofalleged ‘primary’ mare magmas by remelting of thosecumulates, imply supra-adiabatic thermal gradients in near-solidusmaterials throughout the lunar mantle 4·3–3·2Ga ago. This should have resulted in vigorous convective motion,which has not occurred. There is no positive europium anomalyin the average lunar highland crust. That crust cannot, therefore,have formed by plagioclase flotation from a lunar magma ocean,for which there is no other requirement. There is no negativeeuropium anomaly in the average mantle to be inherited by latermare basalts. Other rocky bodies of lunar size in the SolarSystem have accreted at rates that allowed incorporation ofplenty of volatiles and without forming global magma oceans.Partial melting in the presence of water, followed by near-surfacefractionation and volatile losses can explain the feldspathiccharacter, high incompatible element concentrations and lackof Eu anomaly in the lunar highlands. Volcanic eruption on theMoon must have been accompanied by selective volatilizationlosses of sodium, sulphur and other elements similar to theprocess seen on Io, which can account for the major differencesbetween terrestrial and lunar basalts. Siderophile element depletionin lunar lavas may reflect immiscible sulphide liquid and metalseparation, rather than global impoverishment in such elements,and large ore bodies may have formed close to the lunar surface.Mare basalt volcanism appears to have been a protracted, lowmagma productivity event with few similarities to terrestrialocean-floor, ocean-island, continental flood basalt or komatiitevolcanism. At low pressure the crystallization of plagioclasewell before pyroxene typifies those terrestrial mid-ocean ridgebasalt, ocean-island basalt and continental flood basalt magmas.A similar sequence is demanded of the postulated lunar primarymagmas. Mare basalt hand-specimen and pyroclastic glass beadcompositions do not, however, display the required crystallizationsequence and cannot represent the required primary melt compositions.The true erupted lava compositions which gave rise to the regolithcompositions across all the maria are much more feldspathicthan the majority of large hand specimens and, in common withbasalts on other planets, they are close to low-pressure plagioclase-saturatedcotectic residual liquids which have evolved by removal of gabbrosin crustal magma chambers, or perhaps in giant lava lakes akinto topless Bushveld complexes. Any further debate could be resolvedby a 100 m drill core in a few mare locations. Field provenanceof samples from Mars, a planet half covered by flood basaltsand products of central volcanoes, will be little better thanfor those from the Moon. It will be important to encourage multipleworking hypotheses, rather than to rush to a consensus. KEY WORDS: lunar; basalt; highland; magma ocean; europium     

On the origin of impact glass in the Apollo 16 regolith

This study addresses the issue of what fraction of the impact glass in the regolith of a lunar landing site derives from local impacts (those within a few kilometers of the site) as opposed to distant impacts (10 or more kilometers away). Among 10,323 fragments from the 64-210-μm grain-size fraction of three Apollo 16 regolith samples, 14% are impact glasses, that is, fragments consisting wholly or largely of glass produced in a crater-forming impact. Another 16% are agglutinates formed by impacts of micrometeorites into regolith. We analyzed the glass in 1559 fragments for major- and minor-element concentrations by electron probe microanalysis and a subset of 112 of the fragments that are homogeneous impact glasses for trace elements by secondary ion mass spectrometry. Of the impact glasses, 75% are substantially different in composition from either the Apollo 16 regolith or any mixture of rocks of which the regolith is mainly composed. About 40% of the impact glasses are richer in Fe, Mg, and Ti, as well as K, P, and Sm, than are common rocks of the feldspathic highlands. These glasses must originate from craters in maria or the Procellarum KREEP Terrane. Of the feldspathic impact glasses, some are substantially more magnesian (greater MgO/FeO) or have substantially lower concentrations of incompatible elements than the regolith of the Apollo 16 site. Many of these, however, are in the range of feldspathic lunar meteorites, most of which derive from points in the feldspathic highlands distant from the Procellarum KREEP Terrane. These observations indicate that a significant proportion of the impact glass in the Apollo 16 regolith is from craters occurring 100 km or more from the landing site. In contrast, the composition of glass in agglutinates, on average, is similar to the composition of the Apollo 16 regolith, consistent with local origin.     

Lunar materials: Their mineralogy,petrology and chemistry

The manned Apollo 11, 12, 14 and 15 and the automated Luna 16 lunar missions have provided us with lunar rock and regolith (soil) samples from a number of geologically distinct sites. The mare regions were sampled by Apollo 11, 12 and Luna 16, whereas Apollo 14 landed on a terrain with more relief, the Fra Mauro Formation which represents an ejecta blanket from the Imbrian Basin, and Apollo 15 touched down near the lunar highlands. The samples collected consist of a mixture, mainly of basalt, breccia and regolith (soil-particulate matter, generally < 1 cm in size). The basalts show considerable variation in texture, mineralogy and chemistry and probably represent fragments from various parts of relatively thin and extensive lava flows in the maria. The breccias represent regolith material which was indurated to varying degrees by impact events. The regolith is a product of the breakdown, again by impact, of coherent rock masses of basalt and breccia.     

The life and times of Big Bertha: lunar breccia 14321

The lithic units of polymict breccia 14321 (Big Bertha) have been grouped according to composition, texture, degree of metamorphism, and additional criteria based on a systematic study of the interrelationships of all clast-matrix pairs. From this information it has been possible to reconstruct the assembly and metamorphic history of this breccia. The earliest formed fragmental component of 14321 (microbreccia-1) is dominated by KREEP-rich norite, extruded and subsequently brecciated and lithified in an ejecta blanket at approximately 1000°C in the general region of Mare Imbrium after the Serenitatis impact but prior to the Imbrium impact. This early microbreccia component and lesser amounts of mare-type basalt, microgranite, rhyolite glass, anorthosite and olivine microbreccia were assembled at the Apollo 14 site as part of the Fra Mauro ejecta blanket from the Imbrium impact. The resulting microbreccia-3 incorporates all the lithic types above and accretionary lapilli structures (microbreccia-2) in a dark matrix annealed at approximately 700°C. A later impact on the Fra Mauro excavated and mutually abraded microbreccia-3 and a local, 14321-type, basalt which were assembled into polymict breccia 14321. Final placement of 14321 at its sampling location was accomplished during the minor Cone Crater impact event.     

Petrology of Luna 20 regolith from the lunar highlands

The Luna 20 regolith sample contains crystalline lithic fragments of mare basalt, the anorthosite-norite-troctolite group, and feldspathio basalt. Discrete mineral fragments and mineral fragments in regolith breccias can generally be assigned, based on chemical criteria, to one or the other of the first two rock types. A complex history is indicated for the regolith fragments involving repeated metamorphism and melting of the highlands due to impact events. The glass fragments and the feldspathic basalts probably are the result of this melting and their composition may be representative of a large portion of the regolith at this site.     

基于ArcGIS的月球虹湾地区数字地质图编制研究

虹湾幅月球数字地质图是中国首次编制的关于月球地质演化的地质图,应用的主要数据资料来源于"中国首次月球探测工程"嫦娥一号CCD影像数据、DEM数据,结合Clementine750nm影像数据,主要月坑的高分辨率图片,同时结合前人的研究成果,如主要矿物元素含量分布图、多波段反射率特征分布图等编制完成。所有的数据处理应用的是ArcMap平台,同时结合使用了MapGIS软件和Photoshop软件,数据模型采用Geodatabase地理数据模型。详细介绍了基于ArcGIS平台编制月球数字地质图的工作流程,编制方法及依据、编制规则及数据库的建立等,为今后开展月球数字地质图的编制积累了经验。     

The oxygen isotope composition, petrology and geochemistry of mare basalts: Evidence for large-scale compositional variation in the lunar mantle

To investigate the formation and early evolution of the lunar mantle and crust we have analysed the oxygen isotopic composition, titanium content and modal mineralogy of a suite of lunar basalts. Our sample set included eight low-Ti basalts from the Apollo 12 and 15 collections, and 12 high-Ti basalts from Apollo 11 and 17 collections. In addition, we have determined the oxygen isotopic composition of an Apollo 15 KREEP (K - potassium, REE - Rare Earth Element, and P - phosphorus) basalt (sample 15386) and an Apollo 14 feldspathic mare basalt (sample 14053). Our data display a continuum in bulk-rock δ¹⁸O values, from relatively low values in the most Ti-rich samples to higher values in the Ti-poor samples, with the Apollo 11 sample suite partially bridging the gap. Calculation of bulk-rock δ¹⁸O values, using a combination of previously published oxygen isotope data on mineral separates from lunar basalts, and modal mineralogy (determined in this study), match with the measured bulk-rock δ¹⁸O values. This demonstrates that differences in mineral modal assemblage produce differences in mare basalt δ¹⁸O bulk-rock values. Differences between the low- and high-Ti mare basalts appear to be largely a reflection of mantle-source heterogeneities, and in particular, the highly variable distribution of ilmenite within the lunar mantle. Bulk δ¹⁸O variation in mare basalts is also controlled by fractional crystallisation of a few key mineral phases. Thus, ilmenite fractionation is important in the case of high-Ti Apollo 17 samples, whereas olivine plays a more dominant role for the low-Ti Apollo 12 samples.Consistent with the results of previous studies, our data reveal no detectable difference between the Δ¹⁷O of the Earth and Moon. The fact that oxygen three-isotope studies have been unable to detect a measurable difference at such high precisions reinforces doubts about the giant impact hypothesis as presently formulated.     

月球冷海玄武岩矿物成分研究

月海玄武岩的矿物组成反映了岩浆源区的化学成分以及岩石形成时的物理和化学环境,对月球热演化研究以及月球资源的开发利用都具有重要意义。本文选择延展范围长的冷海为研究区,基于月球矿物成像光谱仪(Moon Mineralogy Mapper,简称M3)数据研究其矿物的空间变化特征。综合利用光谱、地形、元素等多源遥感数据将冷海划分为25个地质单元。提取169条新鲜坑光谱曲线,获取吸收中心波长、波段面积比等光谱参数。通过光谱吸收特征分析,获得冷海玄武岩铁镁质矿物变化特征。东部冷海地层较老,铁镁质矿物主要为单斜辉石,辉石钙含量较月球样品单斜辉石钙偏低,与澄海以及雨海老的地层矿物组成类似。西部冷海和露湾的地质单元较为年轻,富含橄榄石。风暴洋和雨海年轻玄武岩的矿物也富含橄榄石。这种富含橄榄石、大面积分布的玄武岩反映了月球晚期热演化的独特性。尽管地理上冷海为一个独立的月海,其东西部玄武岩矿物组成的差异以及与其同位置周围月海矿物组成的类似性反映了冷海玄武岩源区与周围月海具有联系。     

Feldspathic lunar meteorites Pecora Escarpment 02007 and Dhofar 489: Contamination of the surface of the lunar highlands by post-basin impacts

PCA (Pecora Escarpment) 02007 and Dhofar 489 are both meteorites from the feldspathic highlands of the Moon. PCA 02007 is a feldspathic breccia consisting of lithified regolith from the lunar surface. It has concentrations of both incompatible and siderophile elements that are at the high end of the ranges for feldspathic lunar meteorites. Dhofar 489 is a feldspathic breccia composed mainly of impact-melted material from an unknown depth beneath the regolith. Concentrations of incompatible and siderophile elements are the lowest among brecciated lunar meteorites. Among 19 known feldspathic lunar meteorites, all of which presumably originate from random locations in the highlands, concentrations of incompatible elements like Sm and Th tend to increase with those of siderophile elements like Ir. Feldspathic meteorites with high concentrations of both suites of elements are usually regolith breccias. Iridium derives mainly from micrometeorites that accumulate in the regolith with duration of surface exposure. Micrometeorites have low concentrations of incompatible elements, however, so the correlation must reflect a three-component system. We postulate that the correlation between Sm and Ir occurs because the surface of the Feldspathic Highlands Terrane has become increasingly contaminated with time in Sm-rich material from the Procellarum KREEP Terrane that has been redistributed across the lunar surface by impacts of moderate-sized, post-basin impacts. The most Sm-rich regolith breccias among feldspathic lunar meteorites are about 3× enriched compared to the most Sm-poor breccias, but this level of enrichment requires only a few percent Sm-rich material typical of the Procellarum KREEP Terrane. The meteorite data suggest that nowhere in the feldspathic highlands are the concentrations of K, rare earths, and Th measured by the Lunar Prospector mission at the surface representative of the underlying “bedrock;” all surfaces covered by old regolith (as opposed to fresh ejecta) are at least slightly contaminated. Dhofar 489 is one of 15 paired lunar-meteorite stones from Oman (total mass of meteorite: 1037 g). On the basis of its unusually high Mg/Fe ratio, the meteorite is likely to have originated from northern feldspathic highlands.     

Feldspathic lunar meteorites and their implications for compositional remote sensing of the lunar surface and the composition of the lunar crust

We present new compositional data for six feldspathic lunar meteorites, two from cold deserts (Yamato 791197 and 82192) and four from hot deserts (Dhofar 025, Northwest Africa 482, and Dar al Gani 262 and 400). The concentrations of FeO (or Al₂O₃) and Th (or any other incompatible element) together provide first-order compositional information about lunar polymict samples (breccias and regoliths) and regions of the lunar surface observed from orbit. Concentrations of both elements on the lunar surface have been determined from data acquired by orbiting spacecraft, although the derived concentrations have large uncertainties and some systematic errors compared to sample data. Within the uncertainties and errors in the concentrations derived from orbital data, the distribution of FeO and Th concentrations among lunar meteorites, which represent ∼18 source regions on the lunar surface, is consistent with that of 18 random samples from the surface. Approximately 11 of the lunar meteorites are low-FeO and low-Th breccias, consistent with large regions of the lunar surface, particularly the northern farside highlands. Almost all regoliths from Apollo sites, on the other hand, have larger concentrations of both elements because they contain Fe-rich volcanic lithologies from the nearside maria and Th-rich lithologies from the high-Th anomaly in the northwestern nearside. The feldspathic lunar meteorites thus offer our best estimate of the composition of the surface of the feldspathic highlands, and we provide such an estimate based on the eight most well-characterized feldspathic lunar meteorites. The variable but high (on average) Mg/Fe ratio of the feldspathic lunar meteorites compared to ferroan anorthosites confirms a hypothesis that much of the plagioclase at the surface of the feldspathic highlands is associated with high-Mg/Fe feldspathic rocks such as magnesian granulitic breccia, not ferroan anorthosite. Geochemically, the high-Mg/Fe breccias appear to be unrelated to the mafic magnesian-suite rocks of the Apollo collection. Models for the formation of the upper lunar crust as a simple flotation cumulate composed mainly of ferroan anorthosite do not account for the complexity of the crust as inferred from the feldspathic lunar meteorites.     

月壤的物理和机械性质

月壤是在O2、水、风和生命活动都不存在的情况下，由陨石和微陨石撞击、宇宙射线和太阳风轰击、月表温差导致岩石热胀冷缩破碎等因素的共同作用下形成的。月壤独特的形成过程，加上独特的月表环境，使月壤在粒度分布、颗粒形态、颗粒比重、孔隙比和孔隙率、电性和电磁性质、压缩性、抗剪性、承载力等方面均与地球土壤存在较大差异，这些参数的平均值和最佳估计值，可以作为月表机械设计和操作、宇航员装备设计、月球着陆场选址的主要依据，对月球资源开发和利用以及月球基地建设具有极其重要的意义。     

Lunar surface geochemistry: Global concentrations of Th, K, and FeO as derived from lunar prospector and Clementine data

Accurate estimates of global concentrations of Th, K, and FeO have an important bearing on understanding the bulk chemistry and geologic evolution of the Moon. We present empirical ground-truth calibrations (transformations) for Lunar Prospector gamma-ray spectrometer data (K and Th) and a modified algorithm for deriving FeO concentrations from Clementine spectral reflectance data that incorporates an adjustment for TiO₂ content. The average composition of soil samples for individual landing sites is used as ground-truth for remotely sensed data. Among the Apollo and Luna sites, Apollo 12 and 14 provide controls for the incompatible-element-rich compositions, Apollo 16 and Luna 20 provide controls for the feldspathic and incompatible-element-poor compositions, and Apollo 11, 15, and 17, and Luna 16 and 24 provide controls for Fe-rich compositions. In addition to these Apollo and Luna sample data we include the composition of the feldspathic lunar meteorites as a proxy for the northern farside highlands to extend the range of the calibration points, thus providing an additional anorthositic end-member composition. These empirical ground-truth calibrations for Lunar Prospector Th and K provide self consistency between the existing derived data and lunar-sample data. Clementine spectral-reflectance data are used to construct a TiO₂-sensitive FeO calibration that yields higher FeO concentrations in areas of high-Fe, low-Ti, mare-basalt-rich surfaces than previous FeO algorithms. The data set so derived is consistent with known sample compositions and regolith mixing relationships.     

Oxygen and bulk element abundances in Luna 20 fines

Abundances of O, Si, Al and Mn have been determined in Luna 20 fines sample 22001,9 by instrumental neutron activation analysis. The abundances of O, Si and Al are among the highest we have observed in lunar samples and reflect a highlands origin for much of this regolith sample. The Luna 20 abundances reported here most closely resemble those we have determined in four samples of two Apollo 16 fines, rock 14310, and a clast from breccia 15459. The Luna 20 $\text{O}\text{Si}$ ratio of 1.96 ± 0.05 is similar to that in most other lunar samples, but the $\text{Al}\text{Si}$ ratio of 0.532 ± 0.024 is exceeded only by our data on the Apollo 16 fines. This $\text{Al}\text{Si}$ ratio is in agreement with the value of 0.55 ± 0.06 determined by the remote X-ray fluorescence experiment for the highlands between Mare Crisium and Mare Smythii which lie near the Luna 20 site (Adleret al., 1972).     

基于撞击坑自动识别的月球雨海北部地区(LQ-4)月海玄武岩定年研究

月球表面定年研究对于理解和重建月球地质演化历史具有关键作用,撞击坑尺寸频率分布法(CSFD)是通过统计区域内不同尺寸撞击坑密度得到特定地质单元的绝对地质年龄。雨海北部地区(LQ 4)包括雨海北部、冷海西部地区以及风暴洋东北部等月海,位于雨海西北边缘的虹湾是中国嫦娥三号卫星预选软着落区,文中综合使用3种方法从影像和地形数据中自动提取了该区内的撞击坑。利用Clementine光谱数据对雨海北部和风暴洋东北部内玄武岩进行了分区,利用撞击坑尺寸频度法(CSFD)法得到每个玄武岩分区内的定年结果。对比该地区之前的定年数据后发现,使用自动识别结果得到的各分区定年结果新老整体趋势上与之前研究结果基本一致,但存在一定偏差。根据自动识别定年结果,认为该地区玄武岩新老顺序大致为：雨海东部(3.56 Ga)-虹湾(3.38 Ga)-风暴洋东北部(2.74 Ga)-雨海西部(2.63 Ga)-柏拉图坑(2.37 Ga)。结合撞击坑自动识别技术和CSFD法,形成了一条利用影像和地形遥感数据快速得到月球表面地质年龄的方法,为月球年代学研究提供一种新途径。     

我国低钛月海型模拟月壤初始物质选择的地球化学依据

以Apollo14月壤样品和美国JSC-1模拟月壤的地球化学特征为基础,结合我国低钛玄武岩火山的分布,对我国不同地区新生代玄武岩的化学成分、年龄、储量等方面进行对比分析结果表明,滇西北金沙江地区和吉林辉南红旗林场-四海地区的玄武质火山喷发物的化学成分与Apollo14月壤样品和美国JSC-1模拟月壤相似,比较适合用于我国低钛月海玄武岩模拟月壤研制的初始物质。野外地质调查发现,吉林省辉南县金川镇红旗林场—四海一带产出的玄武质火山渣为距今1600 a的该玄武质火山岩的喷发物,其储量大、质地纯、粒度均匀,而且比滇西北金沙江地区最近一期的玄武质火山渣新鲜,最适合作为我国低钛月海玄武岩模拟月壤研制的初始物质。