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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The origin of type C inclusions from carbonaceous chondrites

The origin of type C inclusions found in carbonaceous chondrites and the relationship of the type C inclusions to other Ca- and Al-rich chondrules are discussed on the basis of major-element composition of these objects. The results on bulk composition analysis of primary phase assemblages in eight Allende-type inclusions and an Allende glass-spinel inclusion were found to be consistent with the following scenario: (1) the condensation of melilite + spinel + perovskite +/- hibonite +/- CaAl4O7; (2) the reaction of melilite + spinel with SiO2(g); (3) the removal of inclusions from further interaction with the reacting gas; (4) melting with little or no volatilization; (5) crystallization; (6) alteration; and (7) incorporation of inclusions into host meteorite. Type C inclusions are considered to be precursors to Al-rich chondrules in ordinary and enstatite chondrites, i.e., they are considered to be a spinel-rich class of type A that reacted with silica from a coexisting gas to produce anorthite plus diopside.

Beckett, John R.↗
NASA NTRS1992

Refractory inclusions with unusual chemical compositions from the Vigarano carbonaceous chondrite

Neutron activation was used to test ten inclusions, nine Vigarano and one from Leoville, for major and trace elements. Six Vigarano refractory inclusions have refractory element fractionations that are rare or absent in Allende inclusions. Vig 1623-11 has Th/La and Ir/Mo ratios that are lower than those of any Allende Group I or modified Group I inclusions, and Os/La, Ir/La, and Zr/Hf ratios that are among the lowest in those inclusions. The low Os/La, Ir/La, and Ir/Mo ratios seem to require nonrepresentative sampling of condensate phase in the nebula to a degree that is usual for Allende Group I and modified group I inclusions. The nature and origins of the different inclusions are discussed.

Sylvester, Paul J.↗
NASA NTRS1982

Silicon and oxygen isotopes in selected Allende inclusions

Silicon and oxygen data are presented for a number of Allende samples. It is found that based on oxygen and silicon isotopes, Allende samples EGG-1, EGG-6, BG1a, and 3529Yc are typical, unfractionated Allende inclusions. Where magnesium data are available, they indicate the same thing. EGG-3 is fractionated in both oxygen and silicon, as it is in magnesium. Sample D7 melilite is fractionated in oxygen by several per mil along the C2-matrix line, away from typical Allende melilites. Inclusion BG10a is a FUN inclusion with an inferred original oxygen isotopic fractionation of 8-9 per mille/amu relative to the Allende line. Silicon data for two density fractions of inclusion 3A with different mineralogies show a difference of about 2 per mille, which indicates that silicon, like oxygen, has been added to at least some mineral phases in Allende inclusions from a reservoir other than the one in which the inclusion first began to form.

Becker, R. H.↗
NASA NTRS1983

Refractory inclusions in the Murchison meteorite

Although melilite-rich and feldspathoid-bearing inclusions have been revealed in the Murchison C2 chondrite by mineralogical and petrographic studies, none of these is identical to the inclusions found to date in Allende. Each type of inclusion is characterized by a different suite of alteration products and/or rim layers from all the other types, indicating modification of the inclusions in a wide range of different physicochemical environments after their primary crystallization. All of these inclusions contain some iron-free rim phases which could not have formed by reaction of the inclusions with fluids in the Murchison parent body, because the latter would presumably have been rich in oxidized iron.

Macpherson, G. J.↗
NASA NTRS1984

Two forsterite-bearing FUN inclusions in the Allende meteorite

Two forsterite-, fassaite-, spinel-rich inclusions in Allende which share common mineralogy and texture with three previously described inclusions are described. These inclusions were at least partially molten at temperatures over 1400 C, and their crystallization sequence was spinel, olivine, fassaite, and Mg-rich melilite. At least some of them experienced partial volatilization of MgO and SiO2 from their outer margins. At least one of the inclusions is highly enriched in MgO relative to CaO and Al2O3 compared to Allende coarse-grained inclusions, although it is just as strongly enriched in refractory trace elements as the latter, relative to C1 chondrites. Two of the objects are FUN inclusions on the basis of their oxygen, magnesium, and silicon isotopic compositions.

Clayton, R. N.↗
NASA NTRS1985

Interaction between a crack and a soft inclusion

With the application to weld defects in mind, the interaction problem between a planar-crack and a flat inclusion in an elastic solid is considered. The elastic inclusion is assumed to be sufficiently thin so that the thickness distribution of the stresses in the inclusion may be neglected. The problem is reduced to a system of four integral equations having Cauchy-type dominant kernels. The stress intensity factors are calculated and tabulated for various crack-inclusion geometries and the inclusion to matrix modulus ratios, and for general homogeneous loadiong conditions away from the crack-inclusion region.

Xue-Hui, L.↗
NASA NTRS1983

Petrography and classification of refractory inclusions in the Allende and Mokoia CV3 chondrites

Results are reported for a comprehensive petrographic survey of the refractory inclusions in the Allende and Mokoia CV3 chondrites. More than 600 refractory inclusions in 22 thin sections of the meteorites were studied by optical and scanning-electron microscopy. Olivine-rich inclusions and Ca, Al-rich inclusions (CAIs) are aggregates of various combinations of three fundamental petrographic constituents: rimmed concentric objects, Ca, Si-rich chaotic material, and mafic inclusion matrix. A new classification system for refractory inclusions is developed that is based on the size and abundance of these three fundamental constituents. The new classification system avoids several problems that are inherent in other classification systems, which use the term 'coarse-grained' too restrictively for many simple CAIs and inaccurately for most mililite-rich complex CAIs.

Kornacki, A. S.↗
NASA NTRS1988

Fluid inclusions in Martian samples: Clues to early crustal development and the hydrosphere

Major questions about Mars that could be illuminated by examining fluid inclusions in Martian samples include: (1) the nature, extent and timing of development (and decline) of the hydrosphere that existed on the planet; and (2) the evolution of the crust. Fluid inclusion analyses of appropriate samples could provide critical data to use in comparison with data derived from analogous terrestrial studies. For this study, sample handling and return restrictions are unlikely to be as restrictive as the needs of other investigators. The main constraint is that the samples not be subjected to excessively high temperatures. An aqueous fluid inclusion trapped at elevated pressure and temperature will commonly consist of liquid water and water vapor at room temperature. Heating (such as is done in the laboratory to fix P-V-T data for the inclusion) results in moderate pressure increases up to the liquid-vapor homogenization temperature followed by a sharp increase in pressure with continued heating because the inclusion is effectively a fixed volume system. This increased pressure can rupture the inclusion; precise limits are dependent on size, shape, and composition as well as the host material.

Brown, Philip E.↗
NASA NTRS1989

Origin of zoned fine-grained inclusions in the Allende meteorite

The mineral and bulk compositions in the three zones of the fine-grained Ca-Al-rich inclusion in the Allende meteorite are studied. Mineral analyses for the inclusions are presented and the principle mineral composition for the three zones of the inclusions are described. The nature of the alteration and the physical and chemical environment which caused the three-fold zonation are examined. An alteration and origin of zonation for the Allende inclusions are proposed. It is noted that the fine-grained inclusions display alteration processes such as Ca-Fe-silicate condensation and characteristics of the primary inclusion such as different rim type.

Mcgurie, Anne V.↗
NASA NTRS1990

Comparative study of flux pinning flux creep and critical currents between YBaCuO crystals with and without Y2BaCuO5 inclusions

In the Y-Ba-Cu-O system YBa2Cu3Ox phase is produced by the following peritectic reaction: Y2BaCuO5 + liquid yields 2YBa2Cu3Ox. Through the control of processing conditions and starting compositions it becomes possible to fabricate large crystals containing fine Y2BaCuO5(211) inclusions. Such crystals exhibit Jc values exceeding 10000 A/sq cm at 77 K and 1T. Recently, researchers developed a novel process which can control the volume fraction of 211 inclusions. Elimination of 211 inclusions is also possible. In this study, researchers prepared YBaCuO crystals with and without 211 inclusions using the novel process and compared flux pinning, flux creep and critical currents. Magnetic field dependence of Jc for YBaCuO crystals with and without 211 inclusions is shown. It is clear that fine 211 inclusions can contribute to flux pinning. It was also found that flux creep rate could be reduced by increasing flux pinning force. Critical current density estimates based on the conventional flux pinning theory were in good agreement with experimental results.

Murakami, Masato↗
NASA NTRS1991

Comparative study of flux pinning, creep and critical currents between YBaCuO crystals with and without Y2BaCuO5 inclusions

In the Y-Ba-Cu-O system, YBa2Cu3O(x) phase is produced by the following peritectic reaction: Y2BaCuO5 + liquid yields 2YBa2Cu3O(x). Through the control of processing conditions and starting compositions, it becomes possible to fabricate large crystals containing fine Y2BaCuO5(211) inclusions. Such crystals exhibit Jc values exceeding 10000 A/sq cm at 77 K and 1T. Recently, researchers developed a novel process which can control the volume fraction of 211 inclusions. Elimination of 211 inclusions is also possible. In this study, researchers prepared YBaCuO crystals with and without 211 inclusions using the novel process, and compared flux pinning, flux creep and critical currents. Magnetic field dependence of Jc for YBaCuO crystals with and with 211 inclusions is shown. It is clear that fine 211 inclusions can contribute to flux pinning. It was also found that flux creep rate could be reduced by increasing flux pinning force. Critical current density estimates based on the conventional flux pinning theory were in good agreement with experimental results.

Murakami, Masato↗
NASA NTRS1992

Evidence for distillation in the formation of HAL and related hibonite inclusions

New Ca- and Ti-isotopic analyses of DH-H1, 7-404, and 7-971, and Mg-isotopic analyses on DH-H1 and 7-404 are reported. O-isotopic analyses of HAL, 7-404, 7-971, and a variety of other refractory inclusions from Murchison were made in order to establish the presence or absence of FUN O-isotopic systematics. A higonite-rich residue produced by the evaporation of kaersutite was analyzed for its trace-element and isotopic abundances to see if any of the characteristics of FUN hibonite inclusions can be produced by distillation in the laboratory. These data are then used to evaluate for all four inclusions the HAL-type formation models originally proposed by Allen et al. (1980) and Lee et al. (1980). The four inclusions were found to have very similar chemical and isotopic features. All are characterized by large Ce depletions and very low Mg, Ti, and V concentrations compared to other meteoritic hibonites. All four inclusions have delta(C-48) within error of -5 per mil. Ca-, Ti-, and O-isotopic compositions are fractionated with enrichments of the heavy isotopes, and the Ti-isotopic mass fractionation is inversely correlated with Ti concentration. It is concluded that the inclusions formed primarily as distillation residues in accord with the early conclusions.

Ireland, Trevor R.↗
NASA NTRS1993

The stability of hibonite and other aluminous phases in silicate melts: Implications for the origin of hibonite-bearing inclusions

Phase fields in which hibonite (Hib) and silicate melt coexist with spinel (Sp), CaAl4O7 (CA2), gehlenitic melilite (Mel), anorthite (An), or corundum (Cor) in the system CaO-MgO-Al203-SiO2-TiO2 (CMAST) were determined and activity models developed for Mel and Hib solid solutions. Experimentally determined partition coefficients for Ti between Hib and coexisting melt, D sub t, vary from 0.8 to 2.1 and generally decrease with increasing TiO2 content in the liquid (L). Based on Ti partioning between Hib and melt, bulk inclusion compositions and Hib-saturated liquid use phase diagrams, the Hib in Fluffy Type A inclusions (FTA's) from Allende and at least some of the Hib from Hib-rich inclusions is relict; much of the Hib from Hib-glass spherules probably crystallized from a melt under nonequilibrium conditions. Bulk compositions for all of these Ca-Al-rich inclusions (CAI's) are consistent with an origin as Mel + Hib + Sp + perovskite (Pv) proto-inclusions in which Mel was partially altered. In some cases, the proto-inclusion was partially or completely melted with vaporization occurring over a period of time sufficient to remove any Na introduced by the alteration process but frequently insufficient to dissolve all of the original hibonite. If equilibration temperatures based on Hib-bearing CAI's reflect condensation in a cooling gas of solar composition, then Hib + Cor condensed at approximately 1260 C (referenced to 10 exp -3 atm) and Hib + Sp + Mel at approximately 1215 +/- 10 C. Simple thermochemical models for the substitution of trace elements into the Ca-site of meteoritic Hib suggest that virtually all Eu is divalent in early condensate Hibs but that Eu(2+)/Eu(3+) decreases by a factor of 20 or more during the course of condensation, primarily because the ratio is proportional to the partial pressure of Al, which decreases dramatically as aluminous phases condense. The relative sizes of Eu and Yb anomalies in meteoritic Hibs and CAI's may be influenced by this effect.

Beckett, J. R.↗
NASA NTRS1993

An iridium-rich iron micrometeorite with silicate inclusions from the Moon

We have found a 0.1 mg iron micrometeorite containing meteoritic silicate inclusions in an agglutinate from 2-2.5 cm deep in regolith core 60014. The metal is 93 percent iron, 6.5 percent nickel, 0.5 percent cobalt, approximately 150 ppm iridium, and less than 2 ppm gold. Although the Ir concentration is higher than that reported previously for any iron meteorite group, it lies on the extrapolation to low Ni and high Ir concentrations of several meteorite groups on Ni,Ir plots (groups 2C,D,E, and 3AB,E,F). Tiny, subrounded silicate inclusions comprise low-Ca pyroxene (En83), olivine (FO80), and albitic and potassic feldspars, as mixtures of minerals or glasses. Minor phases include oldhamite (CaS) and, tentatively, hercynite (FeAl2O4). The inclusions have pyroxene FeO/MnO of approximately 25 and olivine FeO/MnO of 40-60. In comparison with known iron meteorites, the inclusions are most similar to those in type 2E, e.g., Weekeroo Station, Colomera, and Kodaikanal. As far as we know, this is the first observation of an iron meteorite with silicate inclusions from a lunar sample. No metal fragments with meteoritic, nonmetallic inclusions were reported in several previous, exhaustive studies of soil particles.

Jolliff, Bradley L.↗
NASA NTRS1993

On origin of the olivine inclusions from the Kainsaz CO carbonaceous chondrite

Olivine inclusions and chondrules of Kainsaz were formed in a unique process of dust matter melting. The elemental abundances of four fractions of olivine (01) inclusions from Kainsaz were analyzed by INAA. The inclusions of fraction A (160 less than d less than 260 microns) have Fe-Ni grains, the inclusions of fractions B (100 less than d less than 160 microns), C (160 less than d less than 260 microns), and D (260 less than d less than 360 microns) do not. The average elemental enrichment factors relative to CI chondrite for each fraction and chondrules of Kainsaz is shown. The enrichment factors of siderophile Co, Ni, Ir, Au, and non-refractory Na in all fractions are less than 1. The factors of refractory Ca, Sc, La, Sm, and Yb are comparative with the corresponding values of O1 aggregates of Allende CV (average 4.76). For chondrules of Kainsaz these values are lower. Fraction A is enriched in Co, Ir, Au, and relative Ni and CI chondrites: Ir greater than Au greater than Co. The values of (Me/Ni)inc/(Me/Ni)CI are equal to 3.25 for Ir, 2.1 for Au, and 1.2 for Co. The superabundances in Ir and Au relative to Ni witness to formation of Fe-Ni grains of O1 inclusions by agglomeration of grains enriched in refractory metal with grains enriched in non-refractory metal (Au). The enrichments of fraction A in Ca, Sc, La, Sm, and Yb witness about presence of high-temperature phases in O1 inclusions.

Lavrukhina, A. K.↗
NASA NTRS1993

Petrography and origin of refractory inclusions from the Murray and Murchison C2 chondrites

By freeze-thaw disaggregation, we have recovered a total of 47 refractory inclusions. New discoveries include the following: a hibonite-pyroxene spherule from Murray; a CaAl4O7-bearing spherule from Murchison; and a Sc-fassaite-bearing ultrarefractory inclusion from Murchison. Freeze-thaw disaggregation, combined with density separation and hand-picking as described is a proven method for recovering rare objects from carbonaceous chondrites. This method is especially effective on C2's due to their porosity and typically results in the discovery of new types of refractory inclusions. Because few refractory inclusions from Murray have been described, we studied this meteorite, although only a small amount of material (730 mg) was available for disaggregation. Many refractory inclusions from Murchison have been described, and we disaggregated a larger amount (approximately 18 g) of Murchison in an attempt to find new types of refractory inclusions, especially corundum-bearing ones.

Simon, S. B.↗
DOE OSTI2025

Revisiting single inclusive jet production: timelike factorization and reciprocity

Factorization theorems for single inclusive jet production play a crucial role in the study of jets and their substructure. In the case of small radius jets, the dynamics of the jet clustering can be factorized from both the hard production dynamics, and the dynamics of the low scale jet substructure measurement, and is described by a matching coefficient that can be computed in perturbative Quantum Chromodynamics (QCD). A proposed factorization formula describing this process has been previously presented in the literature, and is referred to as the semi-inclusive, or fragmenting jets formalism. By performing an explicit two-loop calculation, we show the inconsistency of this factorization formula, in agreement with another recent result in the literature. Building on recent progress in the factorization of single logarithmic observables, and the understanding of reciprocity, we then derive a new all-order factorization theorem for inclusive jet production. The use of a jet algorithm, being only a modification of the infrared structure of the measurement, modifies the structure of convolutions in the factorization theorem, as compared to inclusive fragmentation, but maintains the universality of the inclusive hard function and its associated Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution, which are ultraviolet properties. However, the non-trivial structure of convolutions in the factorization theorem implies that the jet functions exhibit a modified evolution. We perform an explicit two-loop calculation of the jet function in both N = 4 super Yang-Mills (SYM), and for all color channels in QCD, finding exact agreement with the structure derived from our renormalization group equations. In addition, we derive several new results, including an extension of our factorization formula to jet substructure observables, a jet algorithm definition of a generating function for the energy correlators, and new results for exclusive jet functions. Our results are a key ingredient for achieving precision jet substructure at colliders.

Effective Field Theories↗
NASA NTRS1976

Compositional interrelationships of mare basalts from bulk chemical and melt inclusion studies

Petrographic and electron microprobe data (355 new analyses) are presented on melt inclusions and their host phases found in a reexamination of the Apollo thin section collection. In addition, occurrences of early armalcolite and ilmenite are described and new data are presented on quench-pyroxene compositions and melt inclusions in chromian ulvospinel. Compositional differences between mare basalt types and their melt inclusions are illustrated with plots of compositions normalized to a terrestrial lava composition, that of the 1965 Makaopuhi lava lake. The plots emphasize the fact that mare basalts are not significantly differentiated relative to the compositions that are possible as defined by the melt inclusion data. Distribution coefficients for Fe and Mg partitioning between trapped melt and host olivine and ilmenite are calculated and show a range about probable equilibrium values. It is suggested that the crystallization sequence olivine-ilmenite-plagioclase-pyroxene defined by the melt inclusion data may be the actual sequence which obtained generally for Apollo 11 and 17 mare basalts just prior to eruption.

Weiblen, P. W.↗