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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Electron Microprobe Analyses of Lithic Fragments and Their Minerals from Luna 20 Fines

The bulk analyses (determined with the broad beam electron microprobe technique) of lithic fragments are given in weight percentages and are arranged according to the rock classification. Within each rock group the analyses are arranged in order of increasing FeO content. Thin section and lithic fragment numbers are given at the top of each column of analysis and correspond to the numbers recorded on photo mosaics on file in the Institute of Meteoritics. CIPW molecular norms are given for each analysis. Electron microprobe mineral analyses (given in oxide weight percentages), structural formulae and molecular end member values are presented for plagioclase, olivine, pyroxene and K-feldspar. The minerals are selected mostly from lithic fragments that were also analyzed for bulk composition. Within each mineral group the analyses are presented according to the section number and lithic fragment number. Within each lithic fragment the mineral analyses are arranged as follows: Plagioclase in order of increasing CaO; olivine and pyroexene in order of increasing FeO; and K-feldspar in order of increasing K2O. The mineral grains are identified at the top of each column of analysis by grain number and lithic fragment number.

Conrad, G. H.↗
NASA NTRS1975

Fault tectonics and earthquake hazards in the Peninsular Ranges, Southern California

The author has identified the following significant results. Thin sections of rock exposed along the San Diego River linear were prepared and determined to be fault breccia. Single band and ratio images of the western Mojave Desert were prepared from the multispectral scanner digital tapes. Subtle differences in color of soil and rock are enhanced on the ratio images. Two north-northeast trending linears (Horsethief Canyon and Pine Valley Creek) and an east-west linear (Pine Creek) were concluded to have resulted from erosion along well-developed foliation in crystalline basement rocks.

Merifield, P. M.↗
NASA NTRS1975

Mineralogy of lunar norite 78235 - Second lunar occurrence of P2 sub 1 ca pyroxene from Apollo 17 soils

A thin section of lunar rock 78235 is examined optically as well as with an electron microprobe and is shown to be a highly-shocked coarse norite. The rock is found to consist of approximately 30% low-Ca pyroxene, 55% Ca-rich plagioclase, and 15% glass veins. The composition of the glass veins is analyzed, and it is suggested that they resulted from shock melting of the norite. Comparisons with other noritic rocks indicate that the pyroxene in rock 78235 has P2 sub 1 ca symmetry. Based on this symmetry plus the coarse grain size, it is concluded that rock 78235 was formed under plutonic conditions. The origin of the minor phases in this rock is briefly considered.

Steele, I. M.↗
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 NTRS1977

Mineralogic and petrologic study of the low-temperature minerals in carbonaceous chondrites

Samples and petrographic thin sections of the Orgueil, Ivuna, and Alais chondrites were examined by optical, X-ray, and SEM techniques. Mineral species identified as primary vein constituents were epsomite, gypsum, and a calcium-magnesium carbonate. Relative abundances and textural relationships have suggested that fracture mineralization was a multi stage process, with individual mineralizations closely associated with impact brecciation events. Mass balance considerations of carbonaceous chondrite matrix support the prevailing view that the source of the fracture filling minerals was local. By inference they also suggest that the phyllosilicate matrix has been chemically altered and that there are probably very few primitive mineral phases in the primitive Cl chondrites.

Wood, J. A.↗
NASA NTRS1976

The Apollo 16 drill core - Modal petrology and characterization of the mineral and lithic component

A string of 59 polished thin sections covering the length of the Apollo 16 deep drill core has been examined. A modal analysis, involving the optical classification of 116,000 points was made, and over 500 mineral and lithic fragments from the core were chemically analyzed using an electron microprobe. These data were used to identify and characterize the source areas of the core material and to reconstruct the accumulation history of the core.

Vaniman, D. T.↗
NASA NTRS1976

Agglutinates and carbon accumulation in Apollo 17 lunar soils

A critical review of maturity with respect to the abundance of implanted solar wind elements (SWE) in lunar soils indicates: (1) that the Rosiwal Principle has limited applicability in determining implantation of SWE in lunar soils, and (2) that despite a depletion of SWE in agglutinitic glass, agglutinates are enriched in SWE due to the presence of buried surfaces of numerous clasts within agglutinates. A statistical analysis of published data of several Apollo 17 soils indicates that the abundance of carbon and, by analogy, the abundance of other SWE are correlatable with the agglutinate content and the mean grain size of lunar soils. Microscopic examination of more than 5000 grains of agglutinates in polished thin sections reveals a wide range of variability in the mineralogy, grain size distribution, degree of recycling, etc., of the clast population in agglutinates. This indicates that the volume-correlated SWE content of agglutinates may vary and need not be constant.

Basu, A.↗
NASA NTRS1976

Sample size and sampling errors as the source of dispersion in chemical analyses

The paper describes a Monte Carlo model for simulation of two-dimensional representations of thin sections of some of the more common igneous rock textures. These representations are extrapolated to three dimensions to develop a volume of 'rock'. The model (here applied to a medium-grained high-Ti basalt) can be used to determine a statistically significant sample for a lunar rock or to predict the probable errors in the oxide contents that can occur during the analysis of a sample that is not representative of the parent rock.

Clanton, U. S.↗
NASA NTRS1976

Compositional interrelationships of mare basalts from bulk chemical and melt inclusion studies

Petrographic and electron microprobe data (355 new analyses) are presented on melt inclusions and their host phases found in a reexamination of the Apollo thin section collection. In addition, occurrences of early armalcolite and ilmenite are described and new data are presented on quench-pyroxene compositions and melt inclusions in chromian ulvospinel. Compositional differences between mare basalt types and their melt inclusions are illustrated with plots of compositions normalized to a terrestrial lava composition, that of the 1965 Makaopuhi lava lake. The plots emphasize the fact that mare basalts are not significantly differentiated relative to the compositions that are possible as defined by the melt inclusion data. Distribution coefficients for Fe and Mg partitioning between trapped melt and host olivine and ilmenite are calculated and show a range about probable equilibrium values. It is suggested that the crystallization sequence olivine-ilmenite-plagioclase-pyroxene defined by the melt inclusion data may be the actual sequence which obtained generally for Apollo 11 and 17 mare basalts just prior to eruption.

Weiblen, P. W.↗
NASA NTRS1976

Mineralogy and petrology of complex breccia 14063,14

Breccia 14063,14 is a complex, probably pre-Imbrian, unmetamorphosed breccia dominated almost entirely by mineral clasts. Electron-probe and microscope examination showed at least four distinct lithologies in a centimeter-sized thin-section. Examination of each lithology showed or suggested the following contributing rock types or mineralogies: (1) dunite with minor chromite, very high-Mg ilmenite and bronzite; (2) spinel troctolite with olivine and Mg-Al spinel; (3) high-Ti mare-like basalt with high-Mg ilmenite and coarse pyroxene; (4) low-KREEP noritic breccia; (5) anorthosite; (6) very Ni-rich Fe metal.

Steele, I. M.↗
NASA NTRS1977

Rare accessory uraninite in a Sierran granite

One grain of uraninite was found in a single thin-section of Sierran granite. Electron and ion microprobe analysis were used to determine the composition. Since the U-Pb age calculated for the uraninite does not differ greatly from the K-Ar age of the unit in which it occurs, it is suggested that the mineral is primary and not reworked from a preexisting rock. No uraninite has been detected in heavy mineral concentrates from other rocks of the local area.

Snetsinger, K. G.↗
NASA NTRS1979

Mounting procedure for geological samples

Mounting procedure originally developed for lunar samples preserves geological specimens. Sequence of potting and grinding operations produces thin sections through grains that are easy to handle and are well protected for storage. Method results in more representative sections of mixture of grains of different sizes and more effective distribution of grains uniformly over slide.

Jezek, D. I.↗
NASA NTRS1977

Provenance of Apollo 15 deep drill core sediments

Modal analysis and electron probe microanalysis were performed on polished thin sections prepared from Apollo 15 deep drill core soils in an effort to characterize their provenance. The particles were in the 0.25-1.00 mm size range. The particles were classified into mineral fragments, agglutinates, glasses, rock fragments, and breccias. The results show that highland and mare material occur in the core in an approximately 60:40 ratio, with mare component generally increasing from bottom to top in the core. Quartz-normative basalts are nearly twice as abundant as olivine basalts. Nonmare sources include KREEP basalt flow units from some depth in the crust, excavated by cratering events and supplied to the site as 'rays'.

Basu, A.↗
NASA NTRS1975

Origin of 78235, a lunar norite cumulate

A chemical and petrographic study is reported of the phases from the rock 78235 which was returned on the Apollo 17 mission. Petrographic analysis of the thin sections from the bounder confirm its cumulate origin. In order to develop further the crystallization history for 78235, its subsequent shock history, and its relationship to other lunar crustal rocks, orthopyroxene, plagioclase, glass, and whole-rock samples were prepared and analyzed for major, minor, and trace elements. It is speculated that an early fractional crystallization event producing a layer of orthopyroxene-plagioclase cumulate with varying amounts of trapped liquid took place within 20 km of the surface of the moon.

Winzer, S. R.↗
NASA NTRS1978

Petrographic and petrological studies of lunar rocks

Thin sections and polished electron probe mounts of Apollo 15 glasscoated breccias 15255, 15286, 15466, and 15505 were examined optically and analyzed by sem/microprobe. Sections from breccias 15465 and 15466 were examined in detail, and chemical and mineralogical analyses of several larger lithic clasts, green glass, and partly crystallized green glass spheres are presented. Area analyses of 33 clasts from the above breccias were also done using the SEM/EDS system. Mineralogical and bulk chemical analyses of clasts from the Apollo 15 glass-coated breccias reveal a diverse set of potential rock types, including plutonic and extrusive igneous rocks and impact melts. Examination of the chemistry of the clasts suggests that many of these clasts, like those found in 61175, are impact melts. Their variability suggests formation by several small local impacts rather than by a large basin-forming event.

Winzer, S. R.↗
NASA NTRS1978

Soils from Mare Crisium - Agglutinitic glass chemistry and soil development

Agglutinates were studied in 29 polished thin sections of grain mounts from various size fractions of six Luna 24 soil horizons. Three populations of agglutinitic glass compositions were found: a high-MgO, high-FeO group identified as a coarse-grained basaltic component; a low-MgO, low-FeO group from a highland source; and a low-MgO, high-FeO group probably from the subophitic basalt component. The presence of a significant amount of admixed highland component probably accounts for an enrichment in plagioclase and a depletion in ferromagnesian elements displayed by the agglutinitic glass compositions relative to the bulk soil.

Hu, H.-N.↗
NASA NTRS1979

Pyroxenes in Serra de Mage - Cooling history in comparison with Moama and Moore County

Thin sections and single grains of pyroxenes from the Serra de Mage feldspar cumulate eucrites were studied by X-ray crystallography, electron microprobe and optical techniques. It was concluded that the pyroxene crystallized as pigeonite. On cooling augite was exsolved along (001) and inverted to hypersthene, with exsolution of (100) augite from hypersthene during continued slow cooling. The estimated original bulk composition of the pigeonite pyroxene is Wo10En51Fs39. The compositional data, textural relations, and existence of P2 sub 1 ca hypersthene suggest very low cooling (about 0.0004 deg C/year) below 800 deg. The Serra de Mage augite lamellae were found to be as thick or thicker than those of Moore County and Moama meteorites.

Harlow, G. E.↗
NASA NTRS1978

Green glass vitrophyre 78526 - An impact of very low-Ti mare basalt composition

Rake sample 78526 is an 8.77 g rock consisting primarily of vitrophyric pale green glass with subordinate mineral and lithic relics. Petrographic and compositional evidence leads to the following conclusions: (1) the bulk composition represents that of a mixture formed by impact melting of at least two different textural and compositional varieties of VLT mare basalt that are now present in the rock as lithic relics and a poorly defined low-Ti mare basalt component observed in thin section only in the form of isolated mineral relics; (2) the admixed VLT mare basalts had REE abundances lower than those found in other mare basalts (but probably higher than emerald green glass) and REE patterns showing significant enrichment of the heavy relative to light REE's, suggesting that they were derived by comparatively high degrees of partial melting of a clinopyroxene-rich source region; and (3) the impact melt supercooled to produce the vitrophyre, with rather sharply contrasting textural domains present in the vitrophyre resulting from differences in nucleation kinetics and degrees of supercooling in various portions of the sample.

Warner, R. D.↗