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NASA NTRS1980

Spectroscopic evidence for two achondrite parent bodies - Asteroids 349 Dembowska and 4 Vesta

A Fourier spectrometer was used to obtain IR spectra of asteroids 349 Dembowska and 4 Vesta. The spectrum of Dembowska shows olivine and pyroxene with an olivine/pyroxene abundance ratio greater than 2, and possibly as high as 10. This is probably an unsampled achondritic composition, similar to the unique achondrite ALHA 77005. Dembowska's mineralogy therefore appears related to the achondrites; pyroxene and plagioclase feldspar are seen, with a pyroxene/feldspar abundance ratio between 1.5 and 2.0. Time-resolved observations over one-half of the rotation period indicate compositional homogeneity; both 349 Dembowska and 4 Vesta can be considered as candidates for the parent bodies of igneous meteorites.

Feierberg, M. A.↗

NASA NTRS1980

Volatile element chemistry in the solar nebula - Na, K, F, Cl, Br, and P

The results of the most extensive set to date of thermodynamic calculations on the equilibrium chemistry of several hundred compounds of the elements Na, K, F, Cl, Br, and P in a solar composition system are reported. Two extreme models of accretion are investigated. In one extreme complete chemical equilibrium between condensates and gases is maintained because the time scale for accretion is long compared to the time scale for cooling or dissipation of the nebula. Condensates formed in this homogeneous accretion model include several phases such as whitlockite, alkali feldspars, and apatite minerals which are found in chondrites. In the other extreme complete isolation of newly formed condensates from prior condensates and gases occurs due to a time scale for accretion that is short relative to the time required for nebular cooling or dissipation. The condensates produced in this heterogeneous accretion model include alkali sulfides, ammonium halides, and ammonium phosphates. None of these phases are found in chondrites. Available observations of the Na, K, F, Cl, Br, and P elemental abundances in the terrestrial planets are found to be compatible with the predictions of the homogeneous accretion model.

Fegley, B., Jr.↗

NASA NTRS1980

A pristine eucrite-like gabbro from Descartes and its exotic kindred

A coarse-grained plagioclase-pyroxene gabbro (61224,6) with a cumulate texture suggestive of a slowly cooled plutonic rock was recovered from the 4-10 mm fraction of an Apollo 16 soil. The rock is uncommonly poor in feldspar and rich in Na for a lunar highlands lithology. Trace element analyses show extremely low siderophile element concentrations which confirm the pristine character indicated by the texture. The composition of 61224,6 is compared with those of 3 other pristine, exceptionally mafic, nonmare gabbros and of certain eucrites. 61224,6 and the three other gabbros have notable chemical differences but share relatively high ratios of Ti/Sm and Sc/Sm which suggest a possible genetic relationship. We conclude that 61224,6 represents a Na-rich cumulate from a layered intrusion within the highlands crust.

Marvin, U. B.↗

NASA NTRS1980

Modal studies of mesosiderites and related achondrites, including the new mesosiderite ALHA 77219

The Antarctic meteorite ALHA 77219 is found to be a new mesosiderite. It contains about 25% metal + troilite (+ rust) and the brecciated silicate portion is dominated by orthopyroxene (En 68-71). These features, together with the presence of olivine surrounded by coronas, and abundant tridymite + phosphate conform to the characteristics of mesosiderites. A comparison of the modal abundances of minerals in 77219 with modes of 20 mesosiderites, 14 howardites, six basaltic eucrites, three feldspar cumulate eucrites, and one orthopyroxene cumulate eucrite shows that there are major differences between mesosiderites and howardites. These differences are described in detail.

Prinz, M.↗

NASA NTRS1982

Petrology and petrogenesis of lunar breccia 12013

Sample 12013 is extremely rich in incompatible elements (K, P, U, Th, Pb, Ba, Rb, Zr, Nb, and rare earths) relative to other lunar samples, and it contains abundant granitic material composed of silica minerals and K-feldspar. The present investigation provides detailed petrologic and mineralogic descriptions of the rock and a discussion of its genesis and history. The sample is made up of two lithologies, including a mottled gray and white lithology, and a black lithology. A detailed petrology of the gray breccia is presented, taking into account lithic clasts, mineral clasts, deformation textures in clasts, the matrix, and felsite. A detailed petrology of the black breccia is also provided. Attention is given to a model for the formation of the breccia, an evaluation of the possible genetic relationships between the various components, and some constraints on the nature of the source area.

Quick, J. E.↗

NASA NTRS1982

The relationship of the lunar regolith less than 10 micrometer fraction and agglutinates. I - A model for agglutinate formation and some indirect supportive evidence

The first part of a study of the 'less than 10 micrometer' soil fraction and agglutinates is concerned with the chemical systematics of the considered fraction of lunar soils, taking into account a model for agglutinate formation based on the fusion of the finest fraction (FFF). Attention is given to some evidence which supports the FFF model. The evidence is based on some indirect approaches to an estimation of the composition of the fused soil component. It is found that the 'less than 10 micrometer' soil fraction from all Apollo sites except Apollo 16 (which can be explained) is more feldspathic and enriched in incompatible elements (e.g., K and Th) than the bulk soil. It is concluded that these systematics result from simple comminution in which feldspar breaks down to finer sizes than pyroxene and olivine and the fine-grained incompatible-element-enriched mesostasis concentrates in the 'less than 10 micrometer' soil fraction.

Papike, J. J.↗

NASA NTRS1982

Regolith maturation on the earth and the moon with an example from Apollo 15

Petrographic data on twelve Apollo 15 surface samples and on twelve samples from the double drive tube 15010/011 are presented in the form of triangular AML (agglutinate-monomineralic fragments-lithic fragments) plots. The triangular AML plots for different grain sizes show smoothly varying contour lines only for the solids derived mainly from mare basalts. These contour lines are interpreted as lines of isomaturity. The AML plots with isomature contours are somewhat similar to QFR (quartz-feldspar-rock fragments) triangular plots used for terrestrial clastic sediments. Both kinds of plots are sensitive to maturity and both may be used to predict evolution paths. Soils from predominantly highland areas and from other mixed terrains at Apollo 15 sites do not make smooth contours on AML diagrams. By analogy with QFR diagrams, the lack of smooth contours may be due to mixed source rock families, or to recent mixing, or both.

Basu, A.↗

NASA NTRS1982

Petrogenesis of light and dark portions of the Leighton gas-rich chondritic breccia

Individual dark fractions of the Leighton chondritic breccia are all enriched in volatile/mobile trace elements. Concentrations of the most highly volatile/mobile elements correlate with degree of equilibration, as expressed by compositional variability for silicates. Individual light clasts in the same meteorite are equilibrated and generally volatile-poor, except for enrichments in Rb and Cs. These alkali elements may have been redistributed by feldspar formation during metamorphism. Enrichments of other trace elements in dark portions may have been caused by mobilization during metamorphism in the parent body interior and deposition in the cooler surface layers. An alternative model involves accretional mixing of a diverse compositional population of primitive H group materials to form dark materials. Subsequent integration of light and dark materials was accomplished by impacts into a regolith.

Mcsween, H. Y., Jr.↗

NASA NTRS1982

Mars weathering analogs - Secondary mineralization in Antarctic basalts

Alkalic basalt samples from Ross Island, Antarctica, are evaluated as terrestrial analogs to weathered surface materials on Mars. Secondary alteration in the rocks is limited to pneumatolytic oxidation of igneous minerals and glass, rare groundmass clay and zeolite mineralization, and hydrothermal minerals coating fractures and vesicle surfaces. Hydrothermal mineral assemblages consist mainly of K-feldspar, zeolites (phillipsite and chabazite), calcite, and anhydrite. Low alteration rates are attributed to cold and dry environmental factors common to both Antarctica and Mars. It is noted that mechanical weathering (aeolian abrasion) of Martian equivalents to present Antarctic basalts would yield minor hydrothermal minerals and local surface fines composed of primary igneous minerals and glass but would produce few hydrous products, such as palagonite, clay or micas. It is thought that leaching of hydrothermal vein minerals by migrating fluids and redeposition in duricrust deposits may represent an alternate process for incorporating secondary minerals of volcanic origin into Martian surface fines.

Berkley, J. L.↗

NASA NTRS1981

Influence of CO2 on melting of model granulite facies assemblages - A model for the genesis of charnockites

A model is described for the melting of a simple granulite assemblage, in the presence of CO2-rich fluid phases, which can occur between 750 and 1000 C at crustal pressures and is therefore within the range estimated for such regional metamorphism as that of the Adirondacks. For melting which occurs at about 750 C in the presence of both H2O and CO2, pressures corresponding to the deep crust are required to generate a melt enriched in pyroxene and feldspar components, while melting the precense of pure CO2 at about 1000 C generates analogous melt compositions at lower pressures. These experimental reactions are in keeping with observations constraining charnockite occurrences: (1) pressure and temperature constraints; (2) mineralogical constraints; and (3) constraints on the compositions of volatiles associated with peak conditions of charnockite formation.

Wendlandt, R. F.↗

NASA NTRS1982

Visible and near-IR spectral reflectance of geologically important materials: A short review

Examples of reflectance spectra are presented and discussed for various mineral groups including pyroxenes, olivene, phylosilicates, amphiboles, feldspars, oxides and hydroxides, carbonates, and mixtures of minerals. The physical sources of some spectral features are also reviewed such as charge transfer and conduction bands, crystal field absorptions, and vibrational absorptions.

Singer, R. B.↗

NASA NTRS1982

Petrology of EETA79006 and implications for the formation of polymict eucrites

A newly found polymict eucrite, EETA79006, is described. Lithic clasts are similar to those found in howardites and fall into four groups: fine-grained (aphanitic), coarse-grained, basaltic, and cataclastic. All have eucritic compositions and differ mainly in cooling and deformation histories. Some basaltic clasts cooled faster than others and may be impact melts. Analysis of pyroxene and feldspar in the matrix and in 20 lithic clasts indicates that the matrix was not derived from the observed lithic clast population. This meteorite and similar polymict eucrites may have formed by addition of younger more fractionated lithic clasts to the regolith of the parent body.

Simon, S. B.↗

NASA NTRS1982

Hydrothermally altered impact melt rock and breccia - Contributions to the soil of Mars

An examination is made of samples of melt rock and breccia from 12 terrestrial impact craters to identify alteration minerals and their conditions of formation. It is found that in most cases the dominant assemblage is clay-silica-K feldspar-zeolite, suggesting hydrothermal alteration at low pressures and temperatures of 100-300 C. The clays are in the main Fe-chlorites and smectites, in most cases depleted in Al and enriched in Fe and Mg relative to their source rocks. The alteration of impact glass is found often to be complete, whereas the alteration of crystalline melt rock is limited to a few percent of the rock volume. Impact breccia is altered to only a slight extent compared with the alteration of glass. It is believed that impact-induced hydrothermal alteration is to be expected at Martian impact sites if significant quantities of ground ice and/or water are present.

Allen, C. C.↗

NASA NTRS1982

Lunar utilization

The resources, techniques, and purposes to which lunar materials could be put are discussed, with attention given to transporting lunar materials to cislunar space for the construction of space manufacturing and habitable facilities. A model molecule, demandite, which represents the mole fraction of all materials used in the U.S. in 1967, is used to assess the lunar resources defined during Apollo missions. It is shown that duplication of the same manufacturing, fuel, and life-support systems in space as those on earth would cost several orders of magnitude more if the materials originated on earth than on the moon. The demandite would be sent into cislunar orbit using linear electric motors. Lunar surface concentrations of pyroxenes, olivine, feldspars, ilmenite, basalts, anorthostatic rocks, and breccias are reviewed, noting that carbon in the regolith is solar-wind derived, while in lunar rocks the carbon is indigenous. Lunar mining techniques are envisioned, especially the capacity to move large masses at 1/6 the effort required on the earth.

Waldron, R. D.↗

NASA NTRS1983

Lead isotope systematics of some igneous rocks from the Egyptian Shield

Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

Gillespie, J. G.↗

NASA NTRS1983

An analytical and experimental study of zoning in plagioclase

A detailed electron microprobe study has been conducted on natural and experimentally grown zoned plagioclase feldspars. Discontinuous, sector, and oscillatory chemical zoning are observed superimposed on continuous normal or reverse zoning trends. The relative accuracy of 3 element (Na, Ca, K) microprobe traverses was found statistically to be 2 mole percent. Comparison of microprobe data on natural zoned plagioclase with zoned plagioclase grown in controlled experiments has shown that it may be possible to distinguish zonal development resulting from physio-chemical changes to the bulk magma from zoning related to local kinetic control on the growth of individual crystals.

Smith, R. K.↗

NASA NTRS1983

Possible lunar source areas of meteorite ALHA 81005 Geochemical remote sensing information

Antarctic meteorite ALHA 81005 is a regolith breccia apparently sent to earth by an impact event in the lunar highlands. Laboratory studies of this sample provide information that is used to understand the source region on the moon using remote sensing data. The meteorites low thorium content is inconsistent with thorium values measured for the central lunar nearside from orbit with Apollo gamma-ray spectrometers. Similarly, the mineral assemblages inferred from near-IR spectra of small impact craters on the lunar nearside do not exhibit the significant component of olivine and Fe-bearing feldspar that is observed in the meteorite spectra. The existing remote sensing data suggest the most probable source region for ALHA 81005 is the nearside limb or the lunar farside and that the composition of ALHA 81005 represents a surface unit that has not previously been extensively sampled.

Pieters, C. M.↗

NASA NTRS1984

Particle size distribution of typical ceramic raw materials by laser granulometry

The principles of the method are explained and the working of the CILAS 715 laser granulometer is described. The particle size distributions of milled glazes, quartz, feldspar and china clay were determined by this instrument and by Andreasen sedimentation. The agreement was good for isometric particles, but the china clay appears finer by sedimentation, because the platelets arrange themselves horizontally during sedimentation, while in the laser granulometer preferred orientation is prevented by circulation between the sample holder and the vibrated and stirred reservoir of the slip.

Wojnarovitsne, I. H.↗