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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Apollo 14 mare basalts - Petrology and geochemistry of clasts from consortium breccia 14321

It is pointed out that polymict lunar breccia 14321 has long been renowned for the relative abundance of mare basalt clasts which it contains. However, few detailed studies of these clasts exist. The most comprehensive studies to date are those of the first 14321 consortium. Although the studies produced important results, a number of questions remain still unanswered. Thus, it is not certain if the clasts studied are representative of the entire clast population. In addition, there is a lack of correlation of petrography and mineral chemistry information with specific, analyzed clasts, and the major elements Mg and Ca were not analyzed. A second 14321 consortium effort has been organized with the objective to address the remaining questions. The present investigation is concerned with the results of a combined petrographic, mineral /chemical, and geochemical study of 11 mare basalt clasts chipped from five separate subsamples of breccia 14321. It is found that the mare basalt suite at the Apollo 14 site comprises a diverse assemblage of petrographic and compositional types which confirm the importance of ancient mare volcanism.

Shervais, J. W.↗
NASA NTRS1985

Petrology and geochemistry of highlands samples from the Apennine Front

Individual rocks from the Hadley Delta massif, part of the Apennine Front, are described beginning with the simplest samples to the most complex breccias. Relationship among the samples were evaluated. Geological interpretations of the samples were speculative because of the limited data set, but provided models to be tested when additional data are available.

Lindstrom, M. M.↗
NASA NTRS1986

Geochemistry of granitoid rocks from the western Superior Province: Evidence for 2- and 3-stage crustal evolution models

The Superior Province is divisible into subprovinces that can be classified as greenstone-tonalite, paragneiss, or batholitic terranes and are distinguished by differences in lithologic proportions, metamorphic grade, and structural style. The origin and significance of contrasting geochemical characteristics of plutonic rocks from the Winnipeg River subprovince (a batholithic terrane) and the Wabigoon subprovince (a greenstone-tonalite terrane) are discussed.

Beakhouse, G. P.↗
NASA NTRS1986

Chronology and isotopic geochemistry of apollo 14 basalts and Skaergard Gabbro, Eastern Greenland

Work completed on Apollo 14 basalts has been published. The two dates obtained from these rocks comprised the oldest and two of the three oldest ages (4.1 and 4.3 billion years) known for lunar maria basalts; thus their ages are important in understanding the moon's earliest history. Owing to the antiquity of these rocks, two more fragments have been dated as part of a second ASEE/NASA SFF program. The new ages are 3.95 and 4.12 billion years, thus further establishing and amplifying the earlier results. This work, although perhaps more interesting for its chronologic information, was begun as a test of chemical and petrographic models. Fragments of Apollo basalt were placed into five categories, based on petrologic and chemical, especially rare-earth element, composition. Isotopic studies were begun in an attempt to determine if the five groups of basalts were related by age or initial isotopic composition (isotopic composition of lava at time of extrusion). Although a few of the representatives of the five groups have the same age and/or initial strontium-isotopic composition, within the analtytical uncertainties, most apparently are unrelated. Petrologic implications of these data will be published in an appropriate journal.

Dasch, E. J.↗
NASA NTRS1986

Distribution and geochemistry of aerosols in the tropical North Atlantic troposphere - Relationship to Saharan dust

Estimates of global aerosol production suggest that mobilization of natural eolian material greatly exceeds anthropogenic-related emissions, and it appears that soil material transported from arid regions by wind might be mainly responsible for the distribution of certain clay materials in oceanic sediments. In connection with studies related to an investigation of these possibilities, the present paper provides a discussion of the aerosol spatial distribution and its water-soluble chemical composition in the tropical North Atlantic troposphere during the ABLE-Barbados mission. Particular attention is given to the composition of the water-soluble fraction, since its chemical reactivity is important with respect to various atmospheric and biogeochemical processes. On the basis of the obtained results, it is suggested that Saharan dust has also a significant impact on the aerosol chemistry over the tropical North Atlantic.

Talbot, R. W.↗
NASA NTRS1986

Open system magnetic evolution of the taos plateau volcanic field, Northern New Mexico. I - The petrology and geochemistry of the servilleta basalt

MULTIFIT, an embodiment of the conceptual structure needed in modeling multisource and multiprocess magmatic systems, is described. This program, which uses familiar materials balance methodology and the equilibrium form of the Rayleigh equations, links evolutionary arrays, which is turn collectively relate the starting and final compositions of a given magmatic system. Moreover, MULTIFIT incorporates variations within major element data arrays; the linkage between them can be tested using an extension of the least squares algorithm, which selects the best branch point according to the minimum-sum-of-squared-residuals criterion. Advantages and disadvantages of the materials balance approach used in this program are discussed, an example is provided, and equations utilized by MULTIFIT are summarized. While MULTIFIT may not be the best approach for poorly constrained models involving partial melting for complex mixing, it may ultimately prove useful for ascertaining trace element partition coefficients in magnetic systems.

Dungan, M. A.↗
NASA NTRS1987

Petrology and geochemistry of alkali gabbronorites from lunar breccia 67975

Detailed results of petrologic and compositional studies of three clasts found in thin sections of the Apollo 16 lunar breccia 67975 and of four clasts extracted from the breccia (for instrumental neutron activation analysis) prior to thin sectioning are reported. The alkali gabbronorites of the breccia form two distinct subgroups, magnesian and ferroan. The magnesian gabbronorites are composed of bytownitic plagioclase, hypersthene, augite, a silica mineral, and trace Ba-rich K-feldspar. The ferroan gabbronorites are composed of ternary plagioclase, pigeonite, augite, Ba-rich K-feldspar, and a silica mineral. Trace minerals in both subgroups are apatite, REE-rich whitlockite, and zircon. The magnesian and ferroan alkali gabbronorites appear to have formed by progressive differentiation of the same, or closely related, parent REE-rich magmas.

James, Odette B.↗
NASA NTRS1987

Experimental geochemistry of Pu and Sm and the thermodynamics of trace element partitioning

An experimental study of the partitioning of Pu and Sm between diopside/liquid and whitlockite/liquid supports the hypothesis that Pu behaves as a light rare earth element during igneous processes in reducing environments. D-Pu/D-Sm is found to be about 2 for both diopsidic pyroxene and whitlockite, and the amount of fractionation would be decreased further if Pu were compared to Ce or Nd. Data indicate that temperature, rather than melt composition, is the most important control on elemental partitioning, and that P2O5 in aluminosilicate melts serves as a complexing agent for the actinides and lanthanides.

Jones, John H.↗
NASA NTRS1987

Rb-Sr and Sm-Nd isotope geochemistry and chronology of cherts from the Onverwacht Group (3.5 AE), South Africa

An Rb-Sr and Sm-Nd isotopic analysis of Archean chert samples from the Onverwacht Group, South Africa is presented, showing the same characteristic Rb and Sr concentrations as Phanerozoic cherts, with a very large range of Rb-87/Sr-86 ratios. A good correlation line in the Rb-87 to Sr-87 evolution diagram, corresponding to an age of about 2119 My and an initial Sr-87/Sr-86 ratio of about 0.72246, is derived which may be interpreted as reflecting the age of rehomogenization of the Sr in the protolith and the recrystallization of these cherts due to circulating hydrothermal fluids during regional metamorphism about 1.4 AE after deposition of the Onverwacht Group. The Sm-Nd systematics reflect an ancient source age of about 3.5 AE.

Weis, D.↗
NASA NTRS1987

The relationship between geology and geochemistry in the Undarum/Spumans/Balmer region of the moon

Based on regional maps of orbital geochemical variables, major geochemical heterogeneities in the Undarum/Sumans/Balmer region of the moon are found which are usually associated with distinct geological features, and which reveal a north/south dichotomy. The mapped mare and plains units are often the site of heterogeneity, and the plains units in the Balmer basin are probably composed of volcanic material, possibly KREEP-enriched basalt. Data suggest that the northeastern part of the region may contain a minor spinel component. Major mare units of the region are found to have two distinct compositions, possibly indicating two different source regions for the basalts deposited there, but more likely indicating contamination with different amounts of highland debris.

Clark, P. E.↗
NASA NTRS1987

An electrochemical series of redox couples in silicate melts - A review and applications to geochemistry

An electrochemical series for redox couples in a glass-forming oxide melt is developed. This series is a quantitative numerical scale of reference reduction potentials of the redox couples in a silicate melt that is a model for basaltic magmas. The redox couples are ordered in terms of their reference reduction potentials; the order appears to be relatively independent of the exact melt composition and temperature. Thus, upon calibration to a desired composition, oxygen fugacity, and temperature, this electrochemical series can provide estimates of redox state proportions in basaltic magmas on different planetary bodies. The geochemical electrochemical series can also be used to understand the interrelationship of the redox state of the magma and the presence of volatile species such as oxygen, water, sulfur gases, and carbon gases.

Schreiber, Henry D.↗
NASA NTRS1987

A new Cretaceous-Tertiary boundary site at Flaxbourne River, New Zealand - Biostratigraphy and geochemistry

On the basis of biostratigraphy data, it is shown that the Flaxbourne River Cretaceous-Tertiary boundary is among the most complete and least disturbed marine sequences yet found; this is particularly true with respect to its post-Ir anomaly and prelowermost Paleocene sequence. INAA and ICP analyses reveal that the boundary clay is also enriched in Cr and Ni, mainly from meteoritic material, and As, Co, Cu, Sb, and Zn from terrestrial sources. It is found that Zn/Sb, As/Sb, and Zn/As ratios generally fall between crustal and oceanic values, suggesting contributions from both sources.

Strong, C. P.↗
NASA NTRS1988

Atmospheric geochemistry of formic and acetic acids at a mid-latitude temperate site

Tropospheric concentrations of formic and acetic acids in the gas, the aerosol, and the rainwater phases were determined in samples collected 1-2 m above ground level at an open field site in eastern Virginia. These acids were found to occur principally (98 percent or above) in the gas phase, with a marked annual seasonality, averaging 1890 ppt for formate and 1310 ppt for acetate during the growing season, as compared to 695 ppt and 700 ppt, respectively, over the nongrowing season. The data support the hypothesis that biogenic emissions from vegatation are important sources of atmospheric formic and acetic acid during the local growing season. The same time trends were observed for precipitation, although with less defined seasonality. The relative increase of the acetic acid/formic acid ratio during the nongrowing season points to the dominance of anthropogenic inputs of acetic acid from motor vehicles and biomass combustion in the wintertime.

Talbot, R. W.↗
NASA NTRS1988

Martian regolith geochemistry and sampling techniques

Laboratory study of samples of the intermediate and fine-grained regolith, including duricrust peds, is a fundamental prerequisite for understanding the types of physical and chemical weathering processes on Mars. The extraordinary importance of such samples is their relevance to understanding past changes in climate, availability (and possible physical state) of water, eolian forces, the thermal and chemical influences of volcanic and impact processes, and the inventory and fates of Martian volatiles. Fortunately, this regolith material appears to be ubiquitous over the Martian surface, and should be available at many different landing sites. Viking data has been interpreted to indicate a smectite-rich regolith material, implying extensive weathering involving aqueous activity and geochemical alteration. An all-igneous source of the Martian fines has also been proposed. The X-ray fluorescence measurement data set can now be fully explained in terms of a simple two-component model. The first component is silicate, having strong geochemical similarities with Shergottites, but not other SNC meteorites. The second component is salt. Variations in these components could produce silicate and salt-rich beds, the latter being of high potential importance for microenvironments in which liquid water (brines) could exist. It therefore would be desirable to scan the surface of the regolith for such prospects.

Clark, B. C.↗
NASA NTRS1988

Implications of asteroid composition for the geochemistry of the ancient terrestrial projectile flux

The discovery of enhanced siderophile abundances at the Cretaceous/Tertiary boundary has provoked many searches for geochemical signatures which could reveal other catastrophic impacts in Earth's history. These searches implicitly assume that most large impactors are of chondritic, iron, or stony-iron composition, with a greatly enhanced abundance of siderophile elements. Impactors composed of asteroidal crust or mantle rocks analogous to the achondritic meteorites would not leave a distinct geochemical trace since their siderophile abundances are grossly similar to those of the Earth's crust. In recent years studies of the mineralogical composition of the current asteroid belt have suggested that the composition of impacting projectiles may be highly variable with both projectile size and time. In particular it seems possible that in the distant past projectiles derived from asteroid mantle material may have caused a large fraction of the cratering events on Earth. Such impacts would be missed by any geochemical search relying on iridium or any other siderophile element. The questions of the effect of size and time variations on projectile composition and the significance of hidden impacts missing in current geochemical searches are examined.

Bell, Jeffrey F.↗