Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “magma”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Crustal influence in the generation of continental flood basalts

The suggestion that primordial undifferentiated material may exist in the earth's mantle has recently been revived on the strength of Nd isotope data for two types of young continental rocks - flood basalts and kimberlites. The limited published data show a clustering of Nd isotopic compositions close to those for meteorites with chondritic relative rare-earth (REE) abundance. In contrast, data are presented for samples from the Columbia flood basalt province of the northwestern United States which show large isotopic variability suggestive of mixing processes acting after the separation of the primary magmas from their mantle source.

Carlson, R. W.↗
NASA NTRS1981

Trace element composition of the Mount St. Helens plume - Stratospheric samples from the 18 May eruption

Atmospheric particulate material collected from the stratosphere in the plume of the 18 May 1980 eruption of the Mount St. Helens volcano was quite similar in composition to that of ash that fell to the ground in western Washington. However, there were small but significant differences in concentrations of some elements with altitude, indicating that the stratospheric material was primarily produced from fresh magma, not fragments of the mountain.

Vossler, T.↗
NASA NTRS1981

Lead isotopic studies of the Samail ophiolite, Oman

The isotopic composition of Pb and the concentrations of U, Th, and Pb are determined for samples from massive sulfides and lithologic units of the Samail ophiolite. It is shown that the magma that formed the ophiolite was probably derived from a depleted mantle, similar in Pb isotopic composition to the source area of mid-ocean ridge basalt. The gross geochemical characteristics of the mantle sources have remained almost unchanged for the last 100 million years. It is also shown that the U-Th-Pb systematics of the Samail formation indicate that local vertical heterogeneity in the oceanic crust can result from crystal fractionation and metasomatism at, and near, an oceanic spreading center.

Chen, J. H.↗
NASA NTRS1980

Io - Energy constraints and plume volcanism

Observational and theoretical considerations, including near-surface energy constraints, suggest a model of Io that features a surface layer of sulfur overlying an active silicate crust. Such a model would imply frequent contact between silicate magma intrusions and the sulfur layer. This contact could produce volcanic plumes driven by high-temperature sulfur vapor. Plumes driven by sulfur vapor meet observational constraints for a wide range of possible conditions, in contrast to the special conditions required for plume generation by SO2. Characteristics of the two models are compared, and it is suggested that high-spatial-resolution infrared radiometry could identify the driving volatile.

Reynolds, R. T.↗
NASA NTRS1980

Surface evolution of two-component stone/ice bodies in the Jupiter region

Observational and theoretical data converge on the conclusion that planetesimals in Jupiter's region of the solar nebula were initially composed predominantly of a mixture of roughly 39-70% H2O ice by volume, and 30-61% dark stony material resembling carbonaceous chondrites. Recent observations emphasize a division of most asteroid and satellite surfaces in this region into two distinct groups: bright icy material and dark stony material. The present model accounts for these by two main processes: an impact-induced buildup of a dark stony regolith in the absence of surface thermal disturbance, and thermal-disturbance-induced eruption of 'water magmas' that create icy surfaces. 'Thermal disturbances' include tidal and radiative effects caused by nearness of a planet. A correlation of crater density and albedo, Ganymede's dark-ray craters, and other observed phenomena (listed in the summary) appear consistent with the model discussed here.

Hartmann, W. K.↗
NASA NTRS1981

Plate tectonics on Venus

The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.

Anderson, D. L.↗
NASA NTRS1980

Contribution of the mantle to the lunar asymmetry

Evidence of three kinds indicates a lunar compositional asymmetry: mare basalts are much more abundant on the near side; the incompatible rich KREEP component is mainly observed in near-side soils; and materials on the far side are less dense than those of the near side, as indicated by the 2-km offset between the center of mass and center of figure. Recent models to explain the 2-km offset are based on near side-far side differences in the thickness of crustal units. The most widely discussed model calls for a thickness of anorthosite of about 24 km greater on the far side than on the near side, but no satisfactory method of generating such a large difference has been proposed. It is suggested that much of the offset reflects longitudinal differences in mantle composition, primarily resulting from earlier (or more rapid) crystallization of the magma ocean on what is not the far-side hemisphere. As a result, the far-side mantle would be more magnesian and thus less dense than the near-side mantle.

Wasson, J. T.↗
NASA NTRS1981

The mineralogy and the isotopic composition of sulfur in hydrothermal sulfide/sulfate deposits on the East Pacific Rise, 21 deg N latitude

The mineralogy and isotopic composition of sulfur found in hydrothermal deposits associated with five groups of vents along the ridge axis of the East Pacific Rise near 21 deg N latitude are investigated. Solid samples of mixed sulfides and sulfates from mounds, chimneys and the surrounding sediment as well as fresh basaltic glass were examined with a portable X-ray fluorescence spectrometer and by scanning electron microscopy, X-ray diffractometry, and electron microprobe analysis. For the three vents of exit temperature close to 350 C, the chimneys are found to be rich in copper sulfides, while for those of temperatures around 300 C, zinc sulfide is found to predominate. The major sulfides found in the chimneys include wurtzite, chalcopyrite, pyrite and cubanite, with anhydrite the dominant sulfate. Significant mineralogical differences are found between active and inactive vents. The isotopic composition of sulfur in anhydrites from active vents is observed to be close to that of sea water and consistent with a derivation from sea water sulfate. The isotopic composition of sulfur in the sulfide minerals is explained in terms of precipitation from solutions with reduced sulfur derived from basalts or basaltic magmas, and sea water sulfate. Finally, the deposits are interpreted as the results of the mixing of H2S-dominated hydrothermal fluids with cold sea water near the sea floor.

Styrt, M. M.↗
NASA NTRS1981

Melt segregation from partially molten source regions - The importance of melt density and source region size

An investigation is conducted regarding the changes expected in the density contrast between basic melts and peridotites with increasing pressure using the limited data available on the compressibilities of silicate melts and data on the densities of mantle minerals. It is concluded that since compressibilities of silicate melts are about an order of magnitude greater than those of mantle minerals, the density contrast between basic melts and mantle minerals must diminish significantly with increasing pressure. An earlier analysis regarding the migration of liquid in partially molten source regions conducted by Walker et al. (1978) is extended, giving particular attention to the influence of the diminished density contrast between melt and residual crystals with increasing source region depth and to the influence of source region size. This analysis leads to several generalizations concerning the factors influencing the depths at which magmas will segregate from their source regions and the degrees of partial melting that can be achieved in these source regions before melt segregation occurs.

Stolper, E.↗
NASA NTRS1981

Hotspots, basalts, and the evolution of the mantle

It is noted that the trace element concentration patterns of continental and ocean island basalts and of mid-ocean ridge basalts are complementary. Estimates of the relative sizes of the source regions for these fundamentally different basalt types can be arrived at from the trace element enrichment-depletion patterns. Their combined volume occupies the greater part of the mantle above the 670 km discontinuity. It is pointed out that the source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt. The mid-ocean ridge basalts source evolved from an eclogite cumulate that gave up its late-stage enriched fluids at various times to the shallower mantle and continental crust. The mid-ocean ridge basalts source is rich in garnet and clinopyroxene, while the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment. These relationships are found to be consistent with the evolution of a terrestrial magma ocean.

Anderson, D. L.↗
NASA NTRS1981

Genesis of recent silicic magmatism in the Medicine Lake Highland, California - Evidence from cognate inclusions found at Little Glass Mountain

Sparse, granular inclusions of early-formed minerals found within the Little Glass Mountain rhyolite flows in northern California are shown to provide a means of characterizing the physical conditions, at depth, beneath the Medicine Lake Highland during the latest phase of volcanic activity. Mineral compositions, in combination with thermodynamic calculations and experiments, suggest crystalization at a pressure of 5,200 bars within a 966-836 C temperature range; implying that mineral segregation and equilibration occurred at a depth of 15-18 km beneath the surface. In addition, mass balance calculations indicate that the Medicine Lake flow is a close approximation to the parental magma for the latest silicic lavas.

Mertzman, S. A.↗
NASA NTRS1980

Electromagnetic inductive heating of the asteroids and moon as evidence bearing on the primordial solar wind

Thermal evolutionary models of the asteroids and the moon based on the hypothesis of electrical inductive heating by a dense primordial solar wind are compared with observation. Inferences (derived from spectroscopy) of asteroidal mineralogy when compared with electrical heating models, the variation of cooling rates recorded in iron meteorites, and the occurrence of the lunar magma ocean event lend support to the hypothesis of inductive heating. A high primordial solar rotation rate and magnetic field together with the loss due to plasma outflow of a substantial fraction of the initial solar mass would follow.

Herbert, F.↗
NASA NTRS1982

Extraterrestrial materials processing

The first year results of a multi-year study of processing extraterrestrial materials for use in space are summarized. Theoretically, there are potential major advantages to be derived from the use of such materials for future space endeavors. The types of known or postulated starting raw materials are described including silicate-rich mixed oxides on the Moon, some asteroids and Mars; free metals in some asteroids and in small quantities in the lunar soil; and probably volatiles like water and CO2 on Mars and some asteroids. Candidate processes for space materials are likely to be significantly different from their terrestrial counterparts largely because of: absence of atmosphere; lack of of readily available working fluids; low- or micro-gravity; no carbon-based fuels; readily available solar energy; and severe constraints on manned intervention. The extraction of metals and oxygen from lunar material by magma electrolysis or by vapor/ion phase separation appears practical.

Steurer, W. H.↗
NASA NTRS1981

Lunar volcanic glasses and their constraints on mare petrogenesis

The compositional properties of volcanic glasses from the Apollo 11, 14, 15 and 16 landing sites are examined and implications of the results for mare basalt petrogenesis and deep lunar structures are discussed. Major-element and nickel analyses were performed on the glasses using electron probe techniques, and R-mode principal component analysis was performed on the 19 different compositions of glass distinguished. The glasses are found to form two distinct chemical arrays based on the major elements and Ni. The presence of two chemically isolated cumulate systems in the mantle at different depths is thus inferred, and a model is developed for mare petrogenesis in which each system was itself composed of two lithologic components that underwent hybridization, assimilation or mixing to generate the large compositional range of magmas represented by the lunar volcanic glasses. The surface-correlated elements associated with the volcanic glasses are attributed to another reservoir in the deep interior which may be responsible for gas emissions causing lunar transient phenomena. The model developed allows predictions to be made concerning the liquidus phase relations, trace and radiogenic element distributions, nonradiogenic isotope compositions and sample ages.

Delano, J. W.↗
NASA NTRS1981

The 1883 eruption of Krakatau

The 1883 eruption of Krakatau was a modest ignimbrite-forming event. The deposits are primarily coarse-grained dacitic, non-welded ignimbrite. Large explosions produced pyroclastic flows that entered the sea, generating destructive tsunami. Grain-size studies of the ignimbrite suggest that these explosions were not driven by magma-seawater interaction. The total bulk volume of pyroclastic deposits, including co-ignimbrite ash, is estimated to be 18-21 cu km.

Self, S.↗
NASA NTRS1981

Columbia River volcanism - The question of mantle heterogeneity or crustal contamination

It is found that, although crystal fractionation played an important role in producing the chemical characteristics of Columbia River Province basalts displaying a wide range of chemical and isotopic compositions, the isotopic variability calls for the involvement of at least two isotopically distinct components. The major and trace element characteristics of the main volume of the basalts are not consistent with a metasomatized mantle source region, and the presence of a primordial mantel component is not supported by the chemical data. Models of simple binary mixing between a primary magma and Precambrian sialic crustal materials, while satisfying the observed Nd and Sr isotopic variations, fail to account for major trace element abundances. The combination of crustal assimilation and fractional crystalization is found to give a superior fit to the compositional data.

Carlson, R. W.↗
NASA NTRS1980

Predictions of mineral assemblages in planetary interiors

It is shown that mineral compatibilities in the model system CaO-MgO-Al2O3-SiO2 can be applied to deduce the mineral assemblages expected in planetary interiors and their variation with depth. In general, the available estimates of bulk composition of the terrestrial planets suggest that the terrestrial planets can be divided into two groups based on their predicted mineral assemblages. The terrestrial, Venusian, and lunar bulk compositions are expected to display the following sequence of mineral assemblages with increasing pressure: plagioclase lherzolite, spinel lherzolite, and garnet lherzolite. The sequences expected in Martian and Mercurian are different: spinel-plagioclase wehrlite, spinel lherzolite, and spinel-garnet wehrlite. These assemblages have a major influence on the compositions of liquids produced by melting of these planetary interiors, on the solidus temperatures, and thus on the nature of planetary differentiation and the types of magmas extruded at planetary surfaces.

Stolper, E.↗
NASA NTRS1980

Ion microprobe analysis and petrogenetic interpretations of Li, Mg, Ti, K, Sr, Ba in lunar plagioclase

The ion microprobe employed in the considered investigation utilizes a focused primary ion beam to sputter a tiny volume of a sample. A small fraction of the sputtered atoms is ionized and extracted from the sample region for subsequent analysis with a mass spectrometer. A systematic study was conducted to determine which elements can be detected and analyzed in lunar Ca-rich plagioclase. Attention is given to the method of quantitative determination, the selected samples, and aspects of data presentation. A number of general conclusions are discussed. All minor elements in plagioclases from anorthosites from several lunar sites show a restricted range consistent with a common origin. The simplest interpretation is that the anorthosites developed from a moon-wide event, or at least from closely-related events. A moon-wide magma ocean would satisfy this condition.

Steele, I. M.↗