Mineralogy and petrology of some lunar samples

Chemical analyses and norms of four samples are presented which confirm original estimates of low silica, unusual abundance of titania, and low oxidation state of the rocks. Accounts are given of mineralogy and petrology of fine-and coarse-grained igneous rocks and microbreccias with emphasis on chemical composition of individual minerals and glasses. The glasses are either spheres that scatter widely around the composition of lunar basalts or coating glasses that approximate basalts and microbreccias in composition.     

Mineralogy and petrology of coarse particulate material from lunar surface at tranquillity base

Five grams of coarse fines (10085,11) contains 1227 grains, mostly mafic holocrystalline rock fragments, microbreccia, and glass spatter and agglomerates with less abundant anorthosite fragments and regularly shaped glass. The crystalline lithic fragments in the coarse fines and microbreccias represent a closely related suite of gabbroid igneous rocks that have a wider range of modal analyses and textures than seen in the larger crystalline rock samples returned by Apollo 11. Petrographic evidence of shock metamorphism is common, and the abundant glass is almost all shock-produced. None of the glass observed is similar to tektite glass.     

Mineralogy and petrography of lunar samples

The lunar samples consist largely of augite, calcic plagioclase, and ilmenite. Olivine is a minor constituent of some rocks, as is cristobalite. Other minerals present in small amounts include tridymite, chromite, kamacite, taenite, and troilite. The principal rock types can be broadly grouped into ilmenite basalts and breccias. Except for their high ilmenite content, the lunar rocks resemble the calcium-rich achondritic meteorites (eucrites and howardites) in composition and structure. Evidence of a meteoritic increment in the lunar soil is provided by the presence of nickel-iron particles in glass and breccia, and the occurrence of metal-troilite spheroids; the breccias contain occasional silicate aggregates that resemble meteoritic chondrules. The lunar fines contain 325 parts of watersoluble calcium per million.     

Mineralogy and deformation in some lunar samples

Observations on the mineralogy and deformation in samples of crystalline rocks, breccias, and fines from Tranquillity Base provide evidence for magmatic and impact processes. Overall homogeneity, igneous textures, and absence of xenoliths in the crystalline rocks indicate derivation from a common titanium-rich magma by internal, anorogenic volcanism rather than by impact. Crystallization conditions allowed strong compositional variation in pyroxenes, olivine, and plagioclase and the growth of a new mineral, the iron analog of pyroxmangite. Subsequently, impact produced breccias containing shock-deformed crystals and glasses of varying compositions.     

Mineralogy and petrology of comet 81P/Wild 2 nucleus samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.     

Experimental petrology of lunar material: the nature of mascons, seas, and the lunar interior

One-atmosphere melting data show that Apollo 11 samples are near cotectic. Melting relations at pressures up to 35 kilobars show that clinopyroxenite or amphibole peridotite are possible lunar interiors. Mascons cannot be eclogite; they may be ilmenite accumulate. Hot lunar surface material will boil off alkalis.     

Thermoluminescence of lunar samples

Appreciable natural thermoluminescence with glow curve peaks at about 350 degrees centigrade for lunar fines and breccias and above 400 degrees centigrade for crystalline rocks has been recognized in lunar samples. Plagioclase has been identified as the principal carrier of thermoluminescence, and the diference in peak temperatures indicates compositional or structural differences between the feldspars of the different rock types. The present thermoluminescence in the lunar samples is probably the result of a dynamic equilibrium between acquisition from radiation and loss in the lunar thermal environment. A progressive change in the glow curves of core samples with depth below the surface suggests the use of thermoluminescence disequilibrium to detect surfaces buried by recent surface activity, and it also indicates that the lunar diurnal temperature variation penetrates to at least 10.5 centimeters.     

Gallium, germanium, indium, and iridium in lunar samples

Neutron activation analyses of gallium, germanium, indium, and iridium in eight lunar samples and in meteorites and rocks (including four calciulnrich achondrites and five terrestrial basalts) with similar bulk compositions are reported. Lunar gallium concentrations are remarkably constant at about 5 parts per million, three times higher and four times lower than those in eucritic (calcium-rich) achondrites and terrestrial basalts, respectively. Lunar germanium concentrations range from 相似文献   

Mineral chemistry of lunar samples

Glass spherules, glass fragments, augite, ferroaugite, titanaugite, pyroxmangite, pigeonite, hypersthene, plagioclase, potassium feldspar, maskelynite, olivine, silica, ilmenite, TiO(2), "ferropseudobrookite," spinel, ulv?spinel, native iron, nickel-iron, troilite, and chlorapatite were analyzed with the electron microprobe. There are no indications of large-scale chemical differentiation, chemical weathering, or hydrous minerals. Contributions of meteoritic material to lunar surface rocks are small. Rocks with igneous textures originated from a melt that crystallized at or near the surface, and oxygen fugacities have been low. Shock features indicate that at least some surface material is impact-produced.     

Spectral reflectivity of lunar samples

Twelve rock chips and two samples of fines all have electronic absorption bands in diffuse reflected light between 0.32 and 2.5 micrometers. Major bands occur between 0.94 and 1.00 micrometer and at 2.0 micrometers, and arise from Fe(2+) in clinopyroxene and to a lesser extent in olivine. A band at 0.95 micrometer and other details of curve slope and shape for the lunar surface fines match McCord's telescopic curve for an 18-kilometer area that includes the Apollo-il site. Results confirm mineralogical predictions based on telescopic data and support the feasibility of obtaining mineralogical information by remote and in glass content. reflectivity measurements.     

Magnetic properties of lunar samples

The magnetic properties of samples of rock, fines, and magnetic separate from the fines from Apollo 11 have been measured. Native iron, or possibly nickel-iron, of submicroscopic particle size is the most important constituent, with minor contributions from ilmenite, paramagnetic iron minerals, and other iron-titanium oxides. The remanent magnetization of a sample of the micro-breccia rapidly acquires a viscous magnetization and does not appear to have a significant stable remanence. The crystalline sample has a weak natural remanence showing some stability.     

Chemical analyses of lunar samples 10017, 10072, and 10084

A crystalline rock, a vesicular rock, and a dust sample returned by Apollo 11 were chemically analyzed by several methods. The compositions of these samples are unlike that of any known rock or meteorite.     

Mossbauer spectrometry of lunar samples

Nuclear gamma resonance measurements for the nuclide (57)Fe in lunar material were made in transmission on lunar fines and in scattering on intact lunar rock chips. No appreciable amnount of ferric iron was detected. Resonances were observed for ilmenite in all samples. Strong resonances attributed to ferrous iron in silicates, including pyroxenes and, in some samples, glasses and olivine, were also present. Metallic iron, alloyed with nickel, and troilite were also detected in the lunar fines. Differences in the spectra of various samples of lunar material and their significance are discussed.     

Magnetic studies of lunar samples

The remanent magnetismn of a lunar type C breccia sample includes a large viscous component with a time constant of several hours, and a high coercivity remanence, possibly acquired by impact processes on the lunar surface. Ilmenite(?) and metallic iron in breccias, and ferrous and metallic iron in glass beads separated from lunar fines (type D) were identified by high-field and low-temperature experiments. The iron appears to occur in a wide range of grain sizes including the single domain and multidomain states.     

Surface properties of lunar samples

Fine-grained samples disrupted after exposure to oxygen and oxygen with 3.5 percent water above 2 torr. Chemical etching revealed plastic deformation in some samples, adhesion due to impact melting in others, dislocations in crystalline phases and evidence that some glasses were partially devitrified. Specimens of rock that were fractured in ultrahigh vacuum exhibited a time-dependent adhesion and a network of localized electrostatically charged areas.     

Phase chemistry, structure, and radiation effects in lunar samples

Phase chemistry, structure, and radiation effects were studied in rock, breccia, and soil samples. The regolith apparently developed in the final stages of accretion and was modified by later impact processes and radiation weathering. Exposure ages indicate transfer of buried igneous rock fragments to the near surface late in lunar history. With a few exceptions igneous rock fragments, soil, and breccia share the same distinctive chemistry, probably acquired before accretion of the moon. The igneous rocks texturally resemble basaltic achondrites, and the soil and breccias contain glassy spheres analogous to chondrules.     

Shock metamorphism in lunar samples

Indications of shock metamorphism produced by pressures up to the megabar region have been observed in the fine material and the breccias, but very rarely in the coarser fragments of crystalline rocks. These indications are deformation structures in plagioclase and pyroxene, diaplectic plagioclase glasses, and glasses formed by shock-induced melting of lunar rocks. Two sources of shock waves have been distinguished: primary impact of meteorites and secondary impact of crater ejecta. There are two major chemical types of shock-induced melts. The differences in chemistry may be related to impact sites in mare and highland areas.     

Surface-related mercury in lunar samples

Lunar samples contain mercury, which may be volatilized at lunar daytime temperatures. Such mercury may constitute part of the tenuous lunar atmosphere. If mercury can escape from the atmosphere by a nonthermal mechanism, an interior reservoir or exterior sources (such as meteorite infall or solar wind, or both) are required to replenish it. Core samples exhibit an increase in surface-related mercury with depth, which suggests that a cold trap exists below the surface. The orientation of rocks on the lunar surface may be inferred by differences in the amounts of surface-related mercury found on exterior and interior samples.     

Mineralogical and petrological investigations of lunar samples

Fragments of igneous rocks and breccias, and one coarse-grained rock with thin sections, have been studied. Minerals found include pyroxene, plagioclase, olivine, ilmenite, troilite, ulv?spinel, native iron, cristobalite, tridymite, alkali feldspar, apatite, and quartz. Textures are described and interpreted. Among features revealed by optical, microprobe, x-ray diffraction, and electron microscope methods are extreme zoning and unmixing in pyroxene grains, compositional variations in ilmenites, and effects of shock metamorphism. Some trace elements were determined by x-ray fluorescence analysis.