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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Petrography of Apollo 17 soils

An analysis of soils collected on the valley floor at Taurus-Littrow (dark mantle) reveals that these soils are formed by comminution of mare basalt flows and a clastic deposit consisting of black and orange glass spheres. There is no evidence for the pyroclastic origin of the dark mantle. It is found that the North Massif soils contain a large amount of mare-derived fragments being transported horizontally from the basaltic valley floor. A light mantle deposit of uniform composition including comminuted noritic and anorthositic breccia is observed. It is suggested that the light mantle is an avalanche deposit from regolith developed high on the South Massif.

Heiken, G.↗
NASA NTRS1975

The Nakhlites. I - Petrography and mineral chemistry. II - Where, when, and how

The two Nakhlite meteorites (Nakhla and Lafayette) are described, and their possible origin is discussed. It is shown that both objects are cumulates of clinopyroxene with augite as the major mineral and with lesser abundances of olivine, plagioclase, K-feldspar, Fe-Ti oxides, FeS, pyrite, chalcopyrite, and possibly iddingsite. Also, both meteorites are unbrecciated, and their texture is dominated by elongate subhedral to euhedral prisms of clinopyroxene. The data are shown to be compatible with the Nakhlites' being cumulative rocks from a common basaltic parent liquid. It is established that these objects are not of lunar origin, and it is concluded that the position of the parent body relative to other planetary bodies remains to be determined.

Bunch, T. E.↗
NASA NTRS1976

Petrography of isotopically-dated clasts in the Kapoeta howardite and petrologic constraints on the evolution of its parent body

Results are presented for petrographic and electron microprobe studies of the isotopically dated A, B, C, and rho basaltic rock fragments separated from the howardite Kapoeta. Other lithic clasts and numerous mineral fragments in thin sections of Kapoeta are investigated in order to outline the range in lithology and chemistry of the source materials from which the Kapoeta meteorite is derived. The data obtained are compared to those from other meteorite and lunar samples, with particular reference to the observational consequences for the evolution of the Kapoeta parent body. A major conclusion is that there is no clearcut evidence for young magmatism on the Kapoeta parent body. The observations preclude the interpretation that the Kapoeta is a simple mixture of eucrites and diogenites. In contrast to the moon, a source of anorthositic rocks does not appear to have been present on the Kapoeta parent body which involved chiefly pyroxene. The FeO-MnO relationships suggest that the source of the materials in the Kapoeta parent planet are fundamentally related.

Dymek, R. F.↗
NASA NTRS1976

Lithification of vitric- and clastic-matrix breccias - SEM petrography

A scanning electron microscope was used in a petrographic investigation of the matrix textures of 41 lunar breccias ranging from very friable soil clods through coherent microbreccias and tough vitric breccias to tough, fine-grained crystalline breccias. It was found that as their coherence increases, the matrices display a gradual increase in the content of glass from 1 or 2% as filaments less than 1 micron across through 5-50% as irregularly shaped patches up to 200 microns across to over 50% as continuous networks.

Phinney, W. C.↗
NASA NTRS1975

Pyroxene-phyric basalt 15075 - Petrography and petrogenesis

Sample 15075 is a holocrystalline gabbroic rock that can be classified as a coarse-grained variant of the Apollo 15 pyroxene-phyric basalt group. The phenocrysts of pyroxene show spectacular compositional zoning, from hypersthene-pigeonite, through subcalcic augite, to 'ferropyroxenes.' The predominant trend of differentiation is one of Fe enrichment, which is also reflected in the progressive increase of FeO content in the normally zoned plagioclase. As in other samples of pyroxene-phyric basalts, the plagioclase in 15075 did not crystallize until the pyroxenes had reached a subcalcic augite composition; the onset of plagioclase and Fe-rich pyroxene coprecipitation is marked by sharp discontinuity in the Ca/(Fe + Mg) and Ti/Al trends of the pyroxene.

Taylor, L. A.↗
NASA NTRS1975

Petrography and petrology of basaltic achondrite polymict breccias /Howardites/

The reported investigation is based on the results from petrographic observations, electron microprobe analyses of constituent phases, and defocused beam analyses of clasts and glasses. Howardites consist of mostly angular-to-rounded mineral, rock, and breccia clasts compacted in variable grain-sized matrices of finely comminuted materials. Attention is given to ophitic and subophitic rocks, granular basalts and microgabbros, mafic rocks, Al-rich rocks, breccia clasts, impact melt rocks, glasses, meteorite clasts, bulk composition, particle size distribution, howardite component composition, questions of breccia formation, and parent body implications. It is found that the four main rock types found in howardites do have certain analogies to lunar rocks. It is tempting to speculate that both the moon and the basaltic achondrite parent body formed similar rock suites in their evolutionary processes.

Bunch, T. E.↗
NASA NTRS1978

Scanning Electron Microscopy and Petrography of Glassy Particles Produced by Lava Fountain Eruptions

A conceptual model of a lava fountain consists of a vent, spatter ramparts, fountain column, downwind plume and associated pumice deposits. Glassy particles produced by lava fountain eruptions consist primarily of sideromelane glass and minor to moderate amounts of vesicles and crystals. Particles are classified on the basis of morphology as: (1) spherical, (2) elongate, (3) glass-coated mineral grain, (4) shard, (5) reticulite, (6) composite particle, and (7) lithic fragment.

Ladle, G. H.↗
NASA NTRS1978

Origin and modal petrography of Luna 24 soils

Petrographic modal analyses of polished grain mounts of fractions in the 20 to 250 micron size range from Luna 24 soil samples are presented and used to infer the nature and relative contributions of source rocks. It is found that more than 90% of the identifiable rock fragments are mare basalts, with about 11% of the soil consisting of the crystalline form. Soil breccias, which make up nearly 10% of the soil, are found to be immature. Electron probe analysis of glass particles reveals principle clusters conforming to anorthosite, anorthositic gabbro and mare basalts. More than half of the soil is composed of monomineralic particles, with pyroxene as the most abundant mineral. It is concluded that 85% of the regolith is derived from local mare basalts and gabbros and about 10% is derived from early cumulates of local mare basalt magma. Highland sources are considered to contribute not more than 3% of the regolith.

Basu, A.↗
NASA NTRS1978

Silicate petrography, classification, and origin of the mesosiderites - Review and new observations

A classification of mesosiderites proposed by Powell (1971) is modified and expanded to include impact melts. A petrographic study of all 20 mesosiderites reveals that most contain a complex assemblage of mineral, lithic, and metal clasts. The occurrence of lithic fragments in most mesosiderites and the subsequent metamorphism of the group indicate that they are highly evolved meteorites. A comparison with inferred lunar analogs indicates that the bulk of the mesosiderites can be considered annealed crystalline matrix breccias and may be meteoritic equivalents of granulitic impactites described by Warner et al. (1977).

Floran, R. J.↗
NASA NTRS1979

Petrography and olivine mineral chemistry of chondrules and inclusions in the Allende meteorite

The examination of 19 polished-thin sections from a sample of the Allende meteorite reveals that anhedral olivine chondrules (OCs) are the most abundant chondrule type (19.7% of total chondrules + inclusions), followed by recrystallized OCs (7.5%), euhedral OCs (2.9%), glassy/skeletal OCs (2.7%), and barred OCs (2.3%). The most abundant inclusions are those comprised of many small olivine crystals with varying amounts of opaque minerals and glass (31.5%), followed by fine grained inclusions (16.1%) and single olivine crystals (15.7%). Microprobe analyses of olivines show that recrystallized and barred chondrules are the most forsteritic and exhibit relatively narrow compositional ranges, whereas single crystals have the widest range, from Fa sub 0.3 to Fa sub 49.

Simon, S. B.↗
NASA NTRS1979

Petrography and provenance of Apollo 15 soils

Preliminary petrographic and electron probe data from Apollo 15 soils, collected as a part of a comprehensive project, are presented and four principal soil petrographic provinces at the Apollo 15 site are examined. The ratio of non-mare/mare component decreases gradually from the Apennine Front in the south to the mare surface in the north. KREEP basalts appear to be an essential component of the Apennine Bench Formation. The ANT suite rocks contribute only slightly to the population of monomineralic pyroxene, but approximately 30% of the monomineralic olivine are derived from this suite, suggesting troctolitic and dunitic sources.

Basu, A.↗
NASA NTRS1980

Mineralogy and petrography of HAL, an isotopically-unusual Allende inclusion

Results of a detailed mineralogical and textural study of the HAL (Hibonite ALlende) inclusion of the Allende meteorite, which has been found to exhibit no Mg-26 excesses despite very high Al-27/Mg-24 ratios and large fractionation effects with small nuclear effects in its Ca, are reported. The inclusion is found to consist of three up to 1-mm diameter hibonite crystals partially surrounded by a black rim resembling a devitrified glass and containing an anisotropic Al-Fe oxide, which is in turn surrounded by a 2-mm thick friable rim sequence consisting of five layers distinguishable by mineral composition. From the available evidence, it is concluded that each of the layers of the friable rim formed by the accretion of an assemblage of condensate grains rather than by the complete reaction of a HAL precursor with a nebular gas, thus explaining its unusual isotopic characteristics and supporting the conclusion that the solar nebular contained isotopically-distinct reservoirs.

Allen, J. M.↗
NASA NTRS1980

Petrography of lunar soil 15601

Lunar soil 15601 has been studied petrographically using grain size analysis, modal analysis, and electron probe microanalysis of monomineralic fragments in the 90-150-micron size fraction. The soil is immature; the grain size distribution is unimodal and very symmetrical, indicating that the soil is a homogeneous product of a single set of processes. It is concluded that 15601 is mostly a simple Apollo 15 mare basalt soil, and its properties can be used to approximate an end product of the array of complex soils that the lunar sample missions have returned.

Basu, A.↗
NASA NTRS1983

Regolith breccia Allan Hills A81005 - Evidence of lunar origin, and petrography of pristine and nonpristine clasts

It is shown that the ratios of MnO/FeO in pyroxene, texture (abundant brown and swirly glass, which are typical of lunar regolith breccias) and overall composition (approximately 75 percent plagioclase) indicate a lunar origin for the regolith breccia Allan Hills A81005, presumably from an unsampled region of the moon. The rock is found to differ in detail from other regolith samples; for example, it has exceptionally low contents of Na and KREEP. In addition, a pristine clast is found to contain exceptionally coarse augite in comparison with similar Apollo samples. It is found that ALHA81005 is not perceptibly more shocked than typical Apollo regolith breccias. It is concluded that the discovery of this rock on earth strengthens the suggestion that SNC achondrites were derived by impact ejection from Mars.

Warren, P. H.↗