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Smith, J. V.

Publications and source records attributed to Smith, J. V..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Reduced chromium in olivine grains from lunar basalt 15555 - X-ray Absorption Near Edge Structure (XANES)

The oxidation state of Cr in 200-micron regions within individual lunar olivine and pyroxene grains from lunar basalt 15555 was inferred using X-ray Absorption Near Edge Structure (XANES). Reference materials had previously been studied by optical absorption spectroscopy and included Cr-bearing borosilicate glasses synthesized under controlled oxygen fugacity and Cr-doped olivines. The energy dependence of XANES spectral features defined by these reference materials indicated that Cr is predominantly divalent in the lunar olivine and trivalent in the pyroxene. These results, coupled with the apparent f(02)-independence of partitioning coefficients for Cr into olivine, imply that the source magma was dominated by divalent Cr at the time of olivine crystallization.

Sutton, S. R.↗
NASA NTRS1993

The x ray microprobe determination of chromium oxidation state in olivine from lunar basalt and kimberlitic diamonds

The synchrotron x-ray microprobe is being used to obtain oxidation state information on planetary materials with high spatial resolution. Initial results on chromium in olivine from various sources including laboratory experiments, lunar basalt, and kimberlitic diamonds are reported. The lunar olivine was dominated by Cr(2+) whereas the diamond inclusions had Cr(2+/Cr(3+) ratios up to about 0.3. The simpliest interpretation is that the terrestrial olivine crystallized in a more oxidizing environment than the lunar olivine.

Sutton, S. R.↗
NASA NTRS1993

Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

Sutton, S. R.↗
NASA NTRS1987

Copper and nickel partitioning in iron meteorites

Trace element analyses using proton induced X-ray emission and synchrotron X-ray fluorescence have been made on metal and troilite from nine iron meteorites representing five geochemical groups. Nickel and copper distribution coefficients D (troilite/metal) vary by factors of 600 and 20, respectively, correlate positively with kamacite bandwidth and correlate negatively with bulk nickel content. Meteorites with bulk Ni of less than 10 percent have Cu-enriched troilite while those with Ni greater than 10 percent have Cu-depleted troilite. Since magmatic evolution and partial melting will produce Cu-enriched troilite only, the observation of Cu-depleted troilite in Ni-rich meteorites is evidence for subsolidus reequilibration, a process which reduces D(Cu) by transfer of Cu to exsolving metal. Elemental redistribution may have played an important role in establishing the present chemical trends in iron meteorites.

Sutton, S. R.↗
NASA NTRS1985

Cathodoluminescence zoning and minor elements in forsterites from the Murchison (C2) and Allende (C3V) carbonaceous chondrites

Cathodoluminescence has been applied to look for textural features of olivine in carbonaceous meteorites relevant to the unresolved dispute over the origin of the olivine, whether from a vapor or a liquid. Cathodoluminescence photographs of forsterite grains in Murchison (C2) and Allende (C3) meteorites presented here reveal a blue core with planar boundaries to a red or dark rim. High-precision electron microprobe analyses have been performed which reveal unusually large amounts of the 'minor' elements Al, Ti, and Ca in the blue cores of these forsterites, suggesting formation by crystallization at high temperatures from a source rich in these metals. Following conclusions drawn from previous analyses of olivine in meteorites, it is argued that the minor element signature should be able to characterize olivines in micrometeorites and in deep-sea particles.

Steele, I. M.↗
NASA NTRS1985

Minor-element signature of relic olivine grains in deep-sea particles - A match with forsterites from C2 meteorites

The results of high-precision electron microprobe analyses on relic forsterites in 13 different deep sea particles (DSP) are described, comparing their 'minor' element (Mn, Cr, Ca, Ti, Al) signatures with those of olivines found in several types of meteorites. The results show that the DSP olivines do not match those from terrestrial and lunar rocks and achondritic meteoroties, match poorly those of the carbonaceous Allende (CV3) and Orgeuil (CI) meteorites, but are well matched with olivines from C2 meteorites, including the unusual Belgica 7904 meteorite.

Steele, I. M.↗
NASA NTRS1984

Achondrite ALHA77005 - Alteration of chromite and olivine

The olivine crystals of the 77005 achondrite are brown except for colorless shock lamellae, mottled patches, and grains adjacent to pools of impact melt. Sporadic dark alteration patches in brown olivine and Cr-rich spinel gave the following average electron-microprobe analyses: (olivine) P2O5 0.9, SiO2 57.9, TiO2 0, Al2O3 0.7, Cr2O3 0.4, V2O3 0, Fe2O3 (assumed oxidation state) 17.0, MgO 1.6, CaO 0.2, Na2O 0, K2O 1.8, SO3 (assumed oxidation state) 9.2, Cl 0.1, sum 89.8 wt pct; (spinel) P2O5 3.5, SiO2 2.1, TiO2 2.2, Al2O3 2.1, Cr2O3 13.4, V2O3 0.8, Fe2O3 40.7, MgO 0.9, CaO 0.1, Na2O 0, K2O 2.0, SO3 11.1, Cl 0.1, sum 79.0 wt pct. Ion-microprobe analyses revealed H in both. Rare orange patches in brown olivine from another area gave SiO2 33-35, FeO 30-28, MgO 28-32, sum 93 wt pct. Thermal metamorphism under dry oxidizing conditions is discussed as a possible alternative to shock-induced oxidation for generation of the brown olivine (McSween and Stoeffler, 1980). Because alteration patches transgress shock lamellae, and because sulfatic alteration occurs in fusion crusts of Antarctic meteorites (Gibson et al., 1983), alteration of the 77005 achondrite at the Antarctic surface is preferred to a complex series of processes needed for preterrestrial alteration.

Smith, J. V.↗
NASA NTRS1984

Chemical substitution in silica polymorph

Ion and electron probe analyses are presented for trace elements (Al, Na, K, Li, Ti) in quartz, tridymite, cristobalite and melanophlogite. Quartz and melanophlogite show low levels of trace elements relative to tridymite and cristobalite. The previously determined alpha-beta inversion temperature decreases as the Al content of quartz increases. For all silica polymorphs, Al is greater than or equal to Na + K + Li on an atom basis, with the excess Al probably balanced by H.

Smith, J. V.↗
NASA NTRS1984

Minor elements in relict olivine grains of deep-sea spheres: Match with Mg-rich olivines from C2 meteorites

The bulk composition and relict minerals of meteoroid ablation spheres from deep sea sediments can be related to the parental material, and bulk compositions and elemental ratios favor a CI/CM affinity for most spheres. Although largely melted, some deep sea spheres (DSS) have retained rare grains apparently unmodified chemically by ablation heating or seawater alteration. Minor elements in relict olivines for comparison with compositions of olivines in known meteorites were analyzed. All relict olivines are very Mg rich. No terrestrial olivines match the chemical features which reinforces other evidence for an extraterrestrial origin. There is no match with achondritic olivines. Mg rich olivines occur in all types of carbonaceous meteorites, but the minor elements of most DSS olivines do not match with those for Allende (C3) olivines, and fit poorly with those of Murchison (C2) olivines. There is a good fit for Fe and Cr with those of the olivines in the unusual Belgica 7904 (C2) meteorite (3). It seems likely that the relict olivines of at least many deep sea spheres are chemically related to olivines in at least one C2 meteorite.

Smith, J. V.↗
NASA NTRS1984

Minor elements and cathodoluminescence of Mg-rich olivines from Murchison and Allende carbonaceous meteorites

The morphology and inclusions of individual Mg rich olivine grains from C2 chondrites provide disputed evidence for origin either from a liquid or a vapor. Olivine grains from Murchison (C2) and Allende (C3) meteorites were examined to extend data on Belgica 7904 (C2. Cathodoluminescence revealed the relation of chemical zoning to external shape and inclusions. High precision electron probe analyses of selected spots for Na, Al, P, Ca, Ti, Cr and Mn provided chemical constraints on the source material. From several possible explanations tentative suggestions are for at least two stages: (1) growth of the blue core from a vapor enriched in refractory elements (hence lack of inclusions); and (2) growth of red/dark rim from an unenriched liquid which entrapped the blue core. Mechanical transfer may be involved. The channels and networks are puzzling at this time. Whatever the true explanation, a complex history is needed for a simple mineral, and further study should provide additional restraints on formation of carbonaceous meteorites.

Steele, I. M.↗
NASA NTRS1983

Mineral chemistry of the shergottites, nakhlites, Chassigny, Brachina, pallasites and urelites

The mineral chemistry is compared for selected achondrites. Olivine in the ALHA 77005 and EETA 79001 shergottites, olivine-rich Chassigny and Brachina, and the nakhlites, contains Ni indicative of oxidizing conditions, whereas pallasitic and ureilitic olivines contain much lower Ni due to reducing conditions. The Brachina olivine and pyroxene have distinctively higher Fe/Mn than the shergottites and Chassigny, further indicating that Brachina is unique. The Chassigny and 77005 olivines contain lower Cr2O3 (0.03 wt. pct) than the Brachina and 79001 olivines. Values of Fe/Mn for cumulus augites in nakhlites are higher than for the shergottites, whereas those for ferropigeonites are not. The 77005 shergottite contains troilite FeS in contrast to 79001, Shergotty, Zagami, and Chassigny, which contain pyrrhotite. Further analyses are needed, but the present survey indicates that at least Brachina is not chemically cogenetic with the other 'oxidized achondrites', and that the Fe/Mn ratio of the cumulus augites in nakhlites is a problem for the assignment of the nakhlites, shergottites, and Chassigny to a single genetic group.

Smith, J. V.↗
NASA NTRS1982

Petrography, mineral chemistry and origin of Type I enstatite chondrites

The petrography and mineralogy of four Type I enstatite chondrites were examined by optical and cathololuminescent and electron microprobe means to discern particular chemical and mechanical processes present during solar system condensation. The specimens examined included sections of the Indarch, Abee, Kota-Kota, and Adhi-Kot chondrites. Textural interpretations were performed, as well as chemical analyses of the degree of similarity of the clinoenstatite, olivine, accessory silicates, metal, schreibersite, troilite, oldhamite, and niningerite grains in each sample. Simple models of progressive condensation either at equilibrium or with mechanical removal of early condensates were ruled out due to the occurrence of both blue and red enstatite crystals in metal clasts. A need for sequential processes of mixing, melting, crystallization, condensation, fracturing, and mechanical aggregation are suggested as necessary to model the formation mechanisms of the mineral aggregates.

Leitch, C. A.↗
NASA NTRS1982

Ion probe analysis of plagioclase in three howardites and three eucrites

Ion microprobe data for plagioclase from a small group of achondrites are presented, and lunar data reported by Steele et al. (1980) are used as a basis for comparison. The elements are discussed in sequence, using observations on lunar plagioclase as a guide. Attention is given to lithium, potassium, strontium, barium, and titanium. The presented data provide encouragement regarding the significance of studies of the trace element content of plagioclase in the achondrites. It is pointed out that the trace-element signature should prove important in classifying and comparing the individual components of the polymict eucrites and howardites. Thus, the simple patterns in Jodzie contrast with the more complex patterns in Frankfort and particularly Brient.

Steele, I. M.↗
NASA NTRS1982

Heterogeneous growth of meteorites and planets, especially the earth and moon

It is pointed out that enough information remains in meteorites to show that the solar nebula was chemically inhomogeneous, and that it did not develop under physical and chemical equilibrium. It is found that the earth is not in chemical equilibrium, and that it still retains vestiges of its heterogeneous growth in spite of prolonged convection and volcanism. The present investigation has the aim to unify simple ideas into a comprehensive, complex scheme for heterogeneous growth of the planets and parent bodies of meteorites. A scheme is considered for the conversion of dust and gas in the solar nebula into the present population of bodies. Attention is given to possible processes for the growth and development of planetesimals from dust via clouds, the major episodes in the development of the solar system, the relation of meteorites to a solar nebula with monotonic variation of temperature and oxidation state, the significance of meteorite properties, the composition of the inner planets, and the development of the earth.

Smith, J. V.↗
NASA NTRS1981

The first 800 million years of earth's history

It is pointed out that there is no direct geological information on the first 750 Ma of earth history. Consequently the reported study is based on controversial inferences drawn from the moon, other planets and meteorites, coupled with backward extrapolation from surviving terrestrial rocks, especially those of Archaean age. Aspects of accretion are considered, taking into account cosmochemical and cosmophysical evidence, a new earth model, and convection systems. Attention is given to phase-equilibrium constraints, estimates of heat production, the bombardment history of the moon and implications for the earth, and the nature of the early crust. From a combination of physical, chemical, and petrological arguments, it is concluded that the earth's surface underwent intense volcanism in the pre-Archaean era, and that the rock types were chemically similar to those found in the early Archaean era.

Smith, J. V.↗
NASA NTRS1981

Mechanical aggregation of enstatite chondrites from an inhomogeneous debris cloud

Enstatite chondrites have oxygen isotope ratios closer to those of the earth and moon than other meteorites. Their minerals are chemically reduced; metal contains Si, and some Ca, Ti, Mg and Mn are incorporated in sulphides rather than silicates. Clinoenstatite and olivine are virtually Fe-free. Two types of clinoenstatite in the Indarch enstatite chondrite have been reported, one luminescing blue and one red. Similar clinoenstatites in the Kota-Kota enstatite chondrite are associated with two distinct types of forsteritic olivine, one luminescing orange and the other blue. The textural relations and differences in chemical composition cannot be explained by progressive condensation from the solar nebula and require the mechanical mixing of material from at least two sources. It is suggested here that enstatite chondrites result from mechanical and chemical processes during aerodynamic sorting and gravitational settling of debris from a hot cloud of dust, liquid and gas produced during collision of planetesimals.

Leitch, C. A.↗