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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Experimental partitioning of rare earth elements and scandium among armalcolite, ilmenite, olivine and mare basalt liquid

An experimental study was carried out to measure partition coefficients for two rare-earth elements (Sm and Tm) and Sc among armalcolite, ilmenite, olivine and liquid coexisting in a system modeled on high-Ti mare basalt 74275. This 'primitive' sample was chosen for study because its major and trace element chemistry as well as its equilibrium phase relations at atmospheric pressure are known from previous studies. Beta-track analytical techniques were used so that partition coefficients could be measured in an environment whose bulk trace element composition is similar to that of the natural basalt. Partition coefficients for Cr and Mn were determined in the same experiments by microprobe analysis. The only equilibrium partial melting model appears to be one in which ilmenite is initially present in the source region but is consumed by melting before segregation of the high-Ti mare basalt liquid from the residue.

Irving, A. J.↗
NASA NTRS1980

Infrared spectra of olivine polymorphs - Alpha, beta phase and spinel

The infrared absorption spectra of several olivines (alpha phase) and their corresponding beta phase (modified spinel) and spinel (gamma) high-pressure polymorphs are determined. Spectra were measured for ground and pressed samples of alpha and gamma A2SiO4, where A = Fe, Ni, Co; alpha and gamma Mg2GeO4; alpha Mg2SiO4; and beta Co2SiO4. The spectra are interpreted in terms of internal, tetrahedral and octagonal, and lattice vibration modes, and the spinel results are used to predict the spectrum of gamma Mg2SiO4. Analysis of spectra obtained from samples of gamma Mg2GeO4 heated to 730 and 1000 C provides evidence that partial inversion could occur in silicate spinels at elevated temperatures and pressures.

Jeanloz, R.↗
NASA NTRS1982

Evidence for the three-stage cooling history of olivine-porphyritic fluid droplet chondrules

A three-stage model for the cooling of olivine-porphyritic fluid droplet chondrules found in ordinary chondrites is proposed, in light of an experimental examination of three haplochondritic melts to determine thermal parameters in a pre-accretionary chondrule environment. The model encompasses: (1) initial continuous cooling from at least liquidus temperatures, at 300-4000 C/hour, to about 1300 C, over approximately 5-60 min; (2) interruption of the initial cooling by a short-duration isothermal event at about 1300 C; and (3) quenching. This thermal model, in which the entire history of fluid droplet chondrules is only a brief process in the early history of the solar system, suggests a specific and restricted physical origin for chondrules which is not likely to have been achieved by such repetitive, small-scale events as planetary surface impact splattering or volcanism. A single, large-scale event is postulated.

Planner, H. N.↗
NASA NTRS1982

Retention of ion-implanted-xenon in olivine: Dependence on implantation dose

The diffusion of Xe in olivine, a major mineral in both meteorites and lunar samples, was studied. Xe ions were implanted at 200 keV into single-crystal synthetic-forsterite targets and the depth profiles were measured by alpha particle backscattering before and after annealing for 1 hour at temperatures up to 1500 C. The fraction of implanted Xe retained following annealing was strongly dependent on the implantation dose. Maximum retention of 100% occurred for an implantion dose of 3 x 10 to the 15th power Xe ions/sq cm. Retention was less at lower doses, with (approximately more than or = 50% loss at one hundred trillion Xe ions/sq cm. Taking the diffusion coefficient at this dose as a lower limit, the minimum activation energy necessary for Xe retention in a 10 micrometer layer for ten million years was calculated as a function of metamorphic temperature.

Melcher, C. L.↗
NASA NTRS1984

A case for olivine on Mars

Results are reported which support earlier proposals that olivine may be an important phase on Mars. The analysis is based on the similarity of the laboratory reflectance spectrum of ALHA 77005, a meteorite proposed to be from Mars, and the telescopic spectrum of a dark area north of Hellas on Mars (15 S, 300 W). The Mars spectrum is shown as well as a continuum spectrum that, when divided into the Mars spectrum, reveals the absorption feature produced by the surface rocks and soil.

Huguenin, R.↗
NASA NTRS1983

Retention of ion-implemented-xenon in olivine - Dependence on implantation dose

The diffusion of Xe in olivine, a major mineral in both meteorites and linear samples, was studied. Xe ions were implanted at 200 keV into single-crystal synthetic-forsterite targets and the depth profiles were measured by alpha particle backscattering before and after annealing for 1 hour at temperatures up to 1500 C. The fraction of implanted XE retained following annealing was strongly dependent on the implantation dose. Maximum retention of 100 percent occurred for an implanting dose of 3 x 10 to the 15th power Xe ions/sq cm. Retention was less at lower doses, with approximately more than or = 50 percent loss at one hundred trillion Xe ions/sq cm. Taking the diffusion coefficient at this dose as a lower limit, the minimum activation energy necessary for Xe retention in a 10 micrometer layer for ten million years was calculated as a function of metamorphic temperature. Previously announced in STAR as N83-18528

Melcher, C. L.↗
NASA NTRS1985

The geologic history of quartz-normative and olivine-normative basalts in the vicinity of Hadley Rille (Apollo 15)

The geologic history of the quartz normative (QNB) and olivine normative (ONB) basalt types at Hadley Rille are discussed. A model for the geology of the mare basalts was constructed from a combination of field observations, sample chemistry, sample petrology and personal bias from terrestrial experience. The model proposes that the QNBs are the only mare lava type that is present as outcrop in the area traversed by the astronauts during the Apollo 15 mission. The returned QNB samples formed during a single eruptive phase of the Hadley Rille lava tube system. The ONB lavas are an exotic component transported to the site by a cratering event, or the ONBs are samples excavated from older are bedrock that was partly covered by the QNB lavas.

Grove, T. L.↗
NASA NTRS1986

Crystal/liquid partitioning of REE in basaltic systems Extreme fractionation of REE in olivine

The calculation of partial coefficients for Nd, Sm, Gd, and Yb between olivine and synthetic basaltic melts using the percent level doping technique and microprobe analytical techniques is examined. The experimental and analytical procedures are described. The relationship between rare earth elements (REEs) concentrations and crystal margins caused by Rees X-rays from surrounding glass is discussed. Average olivine/liquid distribution coefficients for Nd, Sm, Gd, and Yb for mare and highlands basaltic melts are presented. The data reveal that the distribution coefficients for light REEs are lower than those obtained in previous studies, and the slope of the olivine/liquid distribution coefficient pattern is steeper; potential sources of error in the previous and present studies which could explain the differences in distribution coefficients and slope are investigated.

Mckay, G. A.↗
NASA NTRS1987

Chemical frost weathering of olivine: Experimental study and implications

New experimental results are reported on the frost weathering of olivine. After first weathering, a decrease in Fe sup 2(+)M(2) absorption bands were noted. This decrease is related to the protonation of O(+) in the mineral. It is contented that this reaction may result in the regolith storage of 100 to 1000 m of H(sub 2) over the history of Mars.

Harris, S. L.↗
NASA NTRS1988

Partitioning of siderophile and chalcophile elements between sulfide, olivine, and glass in a naturally reduced basalt from Disko Island, Greenland

Major and trace elements in coexisting glass, olivines, and metal-sulfide spherules from a chilled margin sample of a strongly reduced basaltic dike from Disko Island, Greenland have been investigated. Three sets of partition coefficients are obtained, olivine/silicate liquid and metal-sulfide liquid/silicate liquid partition coefficients established at magmatic temperatures, and FeNi/FeS partition coefficients at lower temperatures. High metal-sulfide liquid/silicate liquid partition coefficients are found for Ni, Sb, As, Mo, Cu, Co, and W. The significance of the present results for planetary evolution and the formation of metal-rich or sulfide-rich metal cores is considered in terms of P, W, and Mo abundances in the mantles of the earth, moon, the Shergotty parent body, and the Eucrite parent body.

Klock, W.↗
NASA NTRS1989

An olivine-microchondrule-bearing clast in the Krymka meteorite

A small (150 x 200-micron-size) clast consisting of 20 vol pct olivine microchondrules (with barred and granular textures) and 80 vol pct recrystallized silicate matrix material occurs in Krymka (LL3.1). This is the fourth microchondrule-bearing clast to be described. The chondrules are zoned in FeO with concentrations increasing toward the surface. The clast most closely resembles a previously described radial-pyroxene-microchondrule-bearing clast in Piancaldoli (LL3.4).

Rubin, Alan E.↗
NASA NTRS1990

Cosmogenic Be-10, Al-26, and He-3 in olivine from Maui lavas

This paper reports the presence of cosmogenic Be-10 and Al-26 in olivines from the Maui Haleakala basalts in which cosmogenic He-3 and Ne-21 were discovered. Based on production-rate calibrations in quartz crystals from late Pleistocene granite exposures in the Sierra Nevada, the Haleakala crater erosion rates derived from Be-10 and Al-26 concentrations agree within 10 percent and give a mean rate of 12 m/Myr, about 40 percent greater than the rate of 8.5 m/Myr previously derived from He-3 measurements. These results establish the feasibility of the simultaneous use of radioactive and stable cosmogenic nuclides for studies of exposure-ages and erosion-rates in basaltic and andesitic terrains.

Nishiizumi, K.↗
NASA NTRS1991

Origin of plagioclase-olivine inclusions in carbonaceous chondrites

The origin of plagioclase-olivine inclusions (POIs) from three CV chondrites and one ungrouped chondrite was investigated by examining the chemical, mineralogical, and isotopic characteristics of a group of POIs from these chondrites. Results of these analyses demonstrate that the mixing and the partial melting processes in these inclusions were superimposed on more ancient isotopically heterogeneous material. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to the formation of POIs (such as condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting) are common to most CAIs and chondrules. A scenario for the origin of POIs is proposed, showing that the homogeneity of the final assemblage (whether a POI, a CAI, or a chondrite) is primarily a reflection of the thermal history rather than the nature of precursor materials.

Sheng, Y. J.↗
NASA NTRS1991

Chromite and olivine in type II chondrules in carbonaceous and ordinary chondrites - Implications for thermal histories and group differences

Unequilibrated chromite and olivine margin compositions in type II chondrules are noted to differ systematically among three of the chondrite groups, suggesting that type II liquids differed in composition among the groups. These differences may be interpreted as indicators of different chemical compositions of the precursor solids which underwent melting, or, perhaps, as differences in the extent to which immiscible metal sulfide droplets were lost during chondrule formation. Because zinc is detectable only in type II chromites which have undergone reequilibration, the high zinc contents reported for chondritic chromites in other studies probably reflect redistribution during thermal metamorphism.

Johnson, Craig A.↗
NASA NTRS1991

Olivines in angrite LEW 87051: Phenos or xenos

Nyquist et al. recently reported the presence of live Mn-53 in angrite LEW 86010 when it crystallized. Hence, melting must have occurred within approx. 10 Ma of the accretion of the angrite parent body, and LEW 86010 is the oldest known differentiated meteorite. This discovery has made it even more desirable to understand teh petrogenesis of angrites, which presumably were all formed at a similar time. As part of the continuing work on angrite petrogenesis, crystallization experiments were conducted on LEW 87051, the other Antarctic angrite, to clarify its petrogenesis. Several aspects of the experimental work is reported. Although the details are not understood, it is clear that the Cr abundance in the experimental olivines must be controlled by spinel crystallization.

Mckay, G.↗
NASA NTRS1991

The distribution of olivine in the crater Copernicus

Multispectral imaging in the visible and near-IR at four wavelengths (0.73, 0.96, 1.45, and 1.99 micron) of Copernicus crater has been used to map the distribution of olivine-rich, pyroxene-poor material known previously to occur in the central peak complex. Three additional portions of the crater exhibit spectral characteristics similar to those of the central peaks, strongly suggesting the presence of material similar to that exposed in the central peaks. These areas are a scarp forming a portion of the northern rim of Copernicus, and two slump blocks in the north wall which may have been derived from the same portion of the ejecta now exposed in the rim scarp. These occurrences decrease the minimum allowable depth for this unusual material in the Copernicus target site though still represent some of the deepest material exposed by Copernicus.

Lucey, Paul G.↗
NASA NTRS1992

The effect of oxygen fugacity on the partitioning of nickel and cobalt between olivine, silicate melt, and metal

The effect of oxygen fugacity, f(O2), on the partitioning behavior of Ni and Co between olivine, silicate melt, and metal was investigated in the CaO-MgO-Al2O3-SiO2-FeO-Na2O system, an analogue of a chondrule composition from an ordinary chondrite. The conditions were 1350 C and 1 atm, with values of f(O2) varying between 10 exp -5.5 and 10 exp -12.6 atm (i.e., the f(O2) range relevant for crystal/liquid processes in terrestrial planets and meteorite parent bodies). Results of chemical analysis showed that the values of the Ni and Co partitioning coefficients begin to decrease at values of f(O2) that are about 3.9 log units below the nickel-nickel oxide and cobalt-cobalt oxide buffers, respectively, near the metal saturation for the chondrule analogue composition.

Ehlers, Karin↗