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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Microstructural Changes and Pb Mobility During the Zircon to Reidite Transformation: Implications for Planetary Impact Chronology

Impact events modify and leave behind a complex history of rock metamorphism on terrestrial planets. Evidence for an impact event may be recorded in physical changes to minerals, such as mineral deformation and formation of high P-T polymorphs, but also in the form of chemical fingerprints, such as enhanced elemental diffusion and isotopic mixing. Here we explore laboratory shock-induced physical and chemical changes to zircon and feldspar, the former of which is of interest because its trace elements abundances and isotope ratios are used extensively in geochemistry and geochronology. To this end, a granular mixture of Bishop Tuff sanidine and Kuehl Lake zircon, both with well characterized Pb isotope compositions, was prepared and then shocked via a flat plate accelerator. The peak pressure of the experiment, as calculated by the impedance matching method, was ~24 GPa although a broader range of P-T conditions is anticipated due to starting sample porosity. Unshocked and shocked materials were characterized via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and Raman spectroscopy. These methods show that the starting zircon material had abundant metamict regions, and the conversion of the feldspar to glass in the post-shock material. Analyses of the shocked product also yielded multiple occurrences of the high-pressure ZrSiO 4 polymorph reidite, with some domains up to 300 μm across. The possibility of U-Pb system disturbance was evaluated via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ion mass spectrometry (SIMS). The isotopic data reveal that disturbance of the U-Pb geochronometer in the reidite was minimal (<2% for the main U-Pb geochronometers). To better constrain the P-T conditions during the shock experiment, we complement impedance matching pressure calculations with iSALE2D impact simulations. The simulated results yield a range of P-T conditions experienced during the experiment and show that much of the sample may have reached >30 GPa, which is consistent with formation of reidite. In the recovered shocked material, we identified lamellae of reidite, some of which interlock with zircon lamellae. Reidite {112} twins were identified, which we interpret to have formed to reduce stress between the crystal structure of the host zircon and reidite. These two findings support the interpretation that shear transformation enabled the transition of zircon to reidite. The size and presence of reidite found here indicate that this phase is probably common in impact-shocked crustal rocks that experienced ~25 to ~35 GPa, especially when the target material has porosity. Additionally, shock loading of the zircon and transformation to reidite at these pressures in porous materials is unlikely to significantly disturb the U-Pb system in zircon and that the reidite inherits the primary U and Pb elemental and isotopic ratios from the zircon.

Bishop Tuff↗
NASA NTRS1983

Mare glasses from Apollo 17 - Constraints on the moon's bulk composition

Two previously unreported varieties of mare volcanic glass have been discovered in Apollo 17 samples. Twenty-three chemical types of volcanic glass have now been analyzed from the six Apollo landing sites. These volcanic glasses, which may be samples of primary magmas derived from the differentiated lunar mantle, define two linear arrays that seem to reflect regional, if not global, regularities among the source regions of these melts. Additional systematics among these glasses have been used to estimate the bulk composition of the moon. The results suggest that the refractory lithophile elements are present at abundances of 1.7 x chondrites. The silicate portion of the moon appears to have a major-element composition similar to a volatile (Si, Na, K)-depleted, earth's upper mantle. The theory involving an earth-fission origin of the moon can be tested further through trace element analyses on the volcanic glasses, and through determination of the N/Ar-36 ratio and noble gas isotopes from primordial lunar gas trapped within vesicles associated with mare volcanic glass.

Delano, J. W.↗
NASA NTRS1983

Laboratory actinide partitioning - Whitlockite/liquid and influence of actinide concentration levels

The partition coefficients between synthetic whitlockite (beta Ca-phosphate) and coexisting silicate melts are determined for the actinide elements Th, U and Pu. Experiments were performed at 1 bar pressure and 1250 C at oxygen fugacities from 10 to the -8.5 to 10 to the -0.7 bars, and partitioning was determined from trace element radiography combined with conventional electron microprobe analysis. Results show Pu to be more readily incorporated into crystalline phases than U or Th under reducing conditions, which is attributed to the observation that Pu exists primarily in the trivalent state, while U and Th are tetravalent. Corrected partition coefficients for whitlockite of 3.6, less than or equal to 0.6, 1.2, 0.5 and less than or equal to 0.002 are estimated for Pu(+3), Pu(+4), Th(+4), U(+4) and U(+6), respectively. Experiments performed at trace levels and percent levels of UO2 indicate that Si is involved in U substitution in whitlockite, and show a reduced partition coefficient at higher concentrations of U that can be explained by effects on melt structure or the fraction of tetravalent U.

Benjamin, T. M.↗
NASA NTRS1993

New low-Ni (igneous?) particles among the C and C? types of cosmic dust

Low-Ni particles with major element abundances, optical properties, and morphologies sufficiently similar to chondritic interplanetery dust particles (IDP's) to receive JSC Cosmic Dust Catalog classifications of C or C?-types were shown to have trace element contents and mineralogies similar to igneous material. Examination of the JSC Catalog EDX spectra by Cooke et al. has shown that 13 percent of the C-type and 38 percent of the C?-type particles are potentially low-Ni particles. Two new low-Ni particles were identified, and it was shown that an additional fragment from the L2002*C cluster has an igneous composition. A newly analyzed fragment of the W7066*A cluster has a chondritic composition. The W7066*A cluster is important because it has yielded a fragment of igneous composition and another fragment having high concentrations of He and Ne suggesting an extraterrestrial origin.

Flynn, G. J.↗
DOE OSTI2025

The Elements of Life, Photosynthesis and Genomics

I am a Professor of Biochemistry, Biophysics and Structural Biology and Plant and Microbial Biology at the University of California in Berkeley. I was born and raised in India, emigrated to the United States to attend university, earning a B.S. in Molecular Biology and a Ph.D. in Biochemistry at the University of Wisconsin in Madison. Following post-doctoral studies with Lawrence Bogorad at Harvard University where I became interested in genetic control of trace element quotas, I joined the department of Chemistry and Biochemistry at UCLA. One of the first to appreciate essential trace metals as potential regulators of gene expression, I articulated the details of the nutritional Cu regulon in Chlamydomonas. In parallel, I used genetic approaches to discover the genes governing missing steps in tetrapyrrole metabolism, including the attachment of heme to apocytochromes in the thylakoid lumen and the factors catalyzing the formation of ring V in chlorophyll. After biochemistry and classical genetics, I embraced genomics, taking a leadership role on the Joint Genome Institute’s efforts on the Chlamydomonas genome and more recently, contributing to high quality assemblies of several genomes in the green algal radiation, and large transcriptomic and proteomic datasets — focusing on the diel metabolic cycle in synchronized cultures and acclimation to key environmental and nutritional stressors — that are well-used and appreciated by the community. Finally, a new venture in Berkeley is the promotion of Auxenochlorella protothecoides as the true “green yeast” and as a platform for engineering algae to produce useful bioproducts.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1976

Mare basalts - Crystal chemistry, mineralogy, and petrology

The paper attempts a synthesis of the major-element chemistry, petrography, mineral chemistry, and crystal chemistry of the mare basalts returned by Apollo and Luna missions. A classification of the mare basalts based on major-element chemistry is given, and textural sequences within each major-element group are identified. The mineral chemistry and crystal chemistry of each mineral group are considered within the framework of the major-element groups and the textural sequences. The various classes of models for the origin of the mare basalts and the nature of their source regions are discussed in the context of the major- and trace-element chemistries and experimental investigations.

Papike, J. J.↗
NASA NTRS1994

The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene

FeO-rich (Fs(sub 6)-34) pyroxene lacking cathodoluminescence (CL), hereafter black pyroxene, is a major constituent of some of the chondrules and fragments in unequilibrated (type 3) enstatite chondrites (UECs). It contains structurally oriented zones of Cr-, Mn-, V-rich, FeO-poor enstatite with red CL, associated with mm-sized blebs of low-Ni, Fe-metal and, in some cases, silica. These occurrences represent clear evidence of pyroxene reduction. The black pyroxene is nearly always rimmed by minor element (Cr, Mn, V)-poor enstatite having a blue CL. More commonly, red and blue enstatites, unassociated with black pyroxene, occur as larger grains in chondrules and fragments, and these constitute the major silicate phases in UECs. The rare earth element (REE) abundance patterns of the black pyroxene are LREE-depleted. The blue enstatite rims, however, have a near-flat to LREE-enriched pattern, approx. 0.5-4x chondritic. The petrologic and trace element data indicate that the black pyroxene is from an earlier generation of chondrules that formed in a nebular region that was more oxidizing than that of the enstatite chondrites. Following solidification, these chondrules experienced a more reducing nebular environment and underwent reduction. Some, perhaps most, of the red enstatite that is common throughout the UECs may be the product of solid-state reduction of black pyroxene. The blue enstatite rims grew onto the surfaces of the black pyroxene and red enstatite as a result of condensation from a nebular gas. The evolutionary history of some of the enstatite and chondrules in enstatite chondrites can be expressed in a four-stage model that includes: Stage 1. Formation of chondrules in an oxidizing nebular environment. Stage 2. Solid-state reduction of the more oxidized chondrules and fragments to red enstatite in a more reducing nebular environment. Stage 3. Formation of blue enstatite rims on the black pyroxene as well as on the red enstatite. Stage 4. Reprocessing, by various degrees of melting, of many of the earlier-formed materials.

Weisberg, Michael K.↗
NASA NTRS2000

Los Angeles: The Most Differentiated Basaltic Martian Meteorite

Los Angeles is a new martian meteorite that expands the compositional range of basaltic shergottites. Compared to Shergotty, Zagami, QUE94201, and EET79001-B, Los Angeles is more differentiated, with higher concentrations of incompatible elements (e.g., La) and a higher abundance of late-stage phases such as phosphates and K-rich feldspathic glass. The pyroxene crystallization trend starts at compositions more ferroan than in other martian basaits. Trace elements indicate a greater similarity to Shergotty and Zagami than to QUE94201 or EET79001-B, but the Mg/Fe ratio is low even compared to postulated parent melts of Shergotty and Zagami. Pyroxene in Los Angeles has 0.7-4-microns-thick exsolution lamellae, approx. 10 times thicker than those in Shergotty and Zaganii. Opaque oxide compositions suggest a low equilibration temperature at an oxygen fugacity near the fayafite-magnetitequartz buffer. Los Angeles cooled more slowly than Shergotty and Zagami. Slow cooling, coupled with the ferroan bulk composition, produced abundant fine-grained intergrowths of fayalite, hedenbergite, and silica, by the breakdown of pyroxferroite. Shock effects in Los Angeles include maskelynitized plagioclase, pyroxene with mosaic extinction, and rare fault zones. One such fault ruptured a previously decomposed zone of pyroxferroite. Although highly differentiated, the bulk composition of Los Angeles is not close to the low-Ca/Si composition or the globally wind-stirred soil of Mars.

Rubin, Alan E.↗
NASA NTRS1981

Isotopic and REE studies of lunar basalt 12038 - Implications for petrogenesis of aluminous mare basalts

Sr, Nd, and Sm isotopic studies of lunar basalt 12038, one of the so-called aluminous mare basalts, are reported. The evolution of the Sr and Nd isotopic compositions and the rare earth element (REE) abundances is successfully modeled within the framework of the model developed by Nyquist et al. (1977, 1979) for Apollo 12 olivine-pigeonite and ilmenite basalts. It is pointed out that the isotopic and trace element features of 12038 can by modeled as produced by partial melting of a cumulate mantle source which crystallized from a lunar magma ocean with a chondrite-normalized REE pattern of constant negative slope. Chondrite-normalized La/Yb is equal to 2.2 for this hypothetical magma ocean pattern.

Nyquist, L. E.↗
DOE OSTI2020

Spatially-Resolved Characterization Techniques and Their Implications for Nuclear Debris Formation.

Debris from nuclear tests has a complex formation process and can inform multiple fields of study such as geology, atmospheric science, shock physics, and chemistry under extreme conditions. Macroscopic nuclear debris forms as the result of fireball interaction with surrounding materials (e.g., structural and environmental component), which rapidly undergo melting and vaporization followed by condensation, convective/diffusive mixing, and solidification over the course of seconds. In atmospheric events, some of this material may disperse over long distances, but much of the material is deposited close-in to ground zero, often in multicomponent, partially (or entirely) amorphous debris formations. During the U.S. nuclear testing program, this material was collected and analyzed, particularly for radionuclide composition. Fallout formation models were developed from nuclear test data based on such radionuclide compositional analyses. These models were not just used to understand fallout dispersion (i.e. the spread of radioactivity over geographical regions) but also guide radiochemical interpretations of historical nuclear tests.6 Developments in analytical techniques over the past several decades have made it possible to make new analyses on historical debris, some of which may be more than a half-century old. For example, inductively-coupled plasma mass spectrometry (ICP-MS) has been used to look at the trace elements in glassy fallout material from aboveground nuclear tests (including the Trinity test). Advanced analyses using X-ray absorption allowed for the measurement of oxidation state of fallout constituents, including actinides. The ability to measure trace actinides and their subsequent oxidation state is important to understanding how the surrounding environment may have influenced the resultant fallout composition and may have implications for why certain fractionation trends have been observed. Here we present data from historic nuclear test debris illustrating the power of spatially resolved methods to connect interaction of the near-field environment with the explosion and provide new insights into nuclear debris formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

Platinum group elements in a 3.5 Ga nickel-iron occurrence - Possible evidence of a deep mantle origin

This paper reports the results of new field observations and the geochemical analyses for the area of the Bon Accord (BA) (the Kaapvaal craton, South Africa) Ni-Fe deposit, with particular consideration given to the trace element, platinum-group element, and isotopic (Pb, Nd, and Os) compositions. On the basis of these data, an interpretation of BA is suggested, according to which the BA deposit is a siderophile-rich heterogeneity remaining in the deep mantle after a process of incomplete core formation. The implications of such a model for the study of core-mantle segregation and the geochemistry of the lowermost mantle are discussed.

Tredoux, Marian↗
NASA NTRS2006

Highly Siderophile Elements in Pallasites and Diogenites, Including the New Pallasite, CMS 04071

Pallasites are long thought to represent a metallic core-silicate mantle boundary, where the IIIAB irons are linked to the crystallization history of the metallic fraction, and the HED meteorites may be linked to the silicate fraction. However, measurement of trace elements in individual metallic and silicate phases is necessary in order to fully under-stand the petrogenetic history of pallasites, as well as any magmatic processes which may link pallasites to both IIIAB irons and HED meteorites. In order to achieve this objective, abundances of a suite of elements were measured, including the highly siderophile elements (HSEs), in kamacite, taenite, troilite, schreibersite, chromite and olivine for the pallasites Admire, Imilac, Springwater, CMS 04071. In the diogenites GRO 95555, LAP 91900, and MET 00436, metal, sulfide, spinel, pyroxene, and silica were individually measured.

Danielson, L. R.↗
DOE OSTI2025

The CO2 mineralization potential of New Mexico basalts and associated critical element behavior and mobility.

This presentation reports on laboratory experiments assessing the carbon dioxide (CO₂) mineralization potential of New Mexico basalts, including trachybasalt and basalt lithologies. Using simulated groundwater and controlled conditions, the study evaluates the kinetics of CO₂ sequestration, mineral saturation indices, and secondary mineral formation. It also investigates the mobility of critical and trace elements such as Ni, Zn, Cu, and Li during basalt dissolution. Results indicate that New Mexico basalts can effectively sequester CO₂ through carbonate formation, with grain size and mineral composition influencing reaction rates and elemental behavior. These findings support the viability of geologic carbon storage in mafic volcanic terrains and inform strategies for critical element recovery.

36 MATERIALS SCIENCE↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Chondrules: The Never-Ending Story

The session "Chondrules: The Never-Ending Story" included the following reports:Dust Size Distribution in Solar Nebula Inferred from Shock-Wave Heating Model for Chondrule Formation; Collisional Destruction of Chondrules in Shock Waves and Inferred Dust to Gas Mass Ratio; Evaporation and Accompanying Isotopic Fractionation of Sulfur from Fe-S Melt During Shock Wave Heating ; Evaporation During Chondrule Formation, Recondensation as Fine Particles, and the Condensation of S and Other Volatile Elements; Fe Isotopes and the Formation of Chondrules; Pristine and Processed Metal in CR Chondrites: Condensation in the Solar Nebula and Partial Reequilibration During Chondrule Formation; Variation of the Condensation Path of Supercooled Silicate Melt; Volatile and Moderately Volatile Trace Element Composition of Chondrules and Matrix from CM Chondrites: Implications for Chondrule Formation; Opaque Mineral Assemblages at Chondrule Boundaries in the Vigarano CV Chondrite: Evidence for Gas-Solid Reactions Following Chondrule Formation; Forsterite and Olivine in Sahara-97210 (LL3.2) and Chainpur (LL3.4) Chondrules: Compositional Evolution and the Influence of Melting; The Vaguries of Pyroxene Nucleation and the Resulting Chondrule Textures; Contemporaneous Formation of Chondrules in the Al-26-Mg-26 System for Ordinary and CO Chondrites; and Al-Mg Isotopic Systematics in Ferromagnesian Chondrules from the Unequilibrated Ordinary Chondrite.

Source record↗
NASA NTRS2017

Diffusivities of Redox-Sensitive Elements in Basalt vs. Oxygen Fugacity Determined by LA-ICP-MS

Several diffusion experiments were conducted in a piston cylinder device across a range of oxygen fugacities (FMQ-3 FMQ-1.2, FMQ+6) at 1 GPa and 1300 C. This was done to explore the effects of oxygen fugacity (fO2) on diffusivity of redox sensitive trace elements. This allows investigation of how these elements diffuse across the fO2 range encountered in different reservoirs on planets and moons in our solar system. The University of Rochester LA-ICP-MS system was used for analysis of samples. Analyses were conducted using an Agilent 7900 quadrupole mass spectrometer connected to a Photon Machines 193 nm G2 laser ablation (LA) system equipped with a HelEx 2-volume sample chamber. Spots used were 35 micrometers circles spaced at 65 micrometers intervals. Laser fluence was 7.81 J/cm^2 with a rep rate of 10 Hz. The iolite software package was used to reduce data collected from laser ablation analysis of experiments with Si-29 used as the internal standard isotope. Iolite's global fit module was used to simultaneously fit elements' diffusivities in each experiment while keeping the Matano interface constant. Elements analysed include V, Nb, W, Mo, La, Ce, Pr, Sm, Eu, Gd, Ta, and W. Figures

Szumila, Ian↗
NASA NTRS1973

Elemental abundances of Apollo 16 samples

Results are presented for the multielement analysis of samples of lunar soil (60501 and 64501), igneous rock (60315), and the light portion of breccia 60017. A mixing model for soil compositions has been proposed consisting of linear combinations of the KREEP basalt 60315 and the anorthositic gabbroic sample 60017. A comparison of trace elements in lunar soils from different missions indicates the marked depletion of the LIL elements in the Apollo 16 samples.

Morrison, G. H.↗
DOE OSTI2022

Sulphur variations in annually layered stalagmites using benchtop micro-XRF

Variation of sulphur in annually laminated stalagmites can be used to infer the impact of past volcanic activities, anthropogenic pollution, and climate change due to increased bushfire activity. The synchrotron radiation micro-X-Ray fluorescence (SR-XRF) microprobe is a powerful tool to analyse and image sulphur recorded in stalagmites with micrometre resolution. However, access to SR-XRF beamlines can be limited, so researchers must select the most promising stalagmites for imaging. Benchtop micro-XRF is an effective tool for trace elemental analysis of speleothem samples and is a candidate for routine laboratory measurement of sulphur along stalagmite laminae and screening for SR-XRF. Here, this study describes a protocol using matrix-matched standards to measure annual variations of sulphur at trace to percent level along the laminae of two Western Australian stalagmites, one of which already having been analysed using SR-XRF. Parameters that affected quantitation include X-ray tube voltage and current, spot size of the X-ray beam and stalagmite surface roughness and porosity. The use of a 20 μm X-ray spot size provides sub-annual spatial resolution that can be completed in an overnight scan. The features in a 1000 point micro-XRF analysis of sulphur along a 20 mm transect show good consistency with SR-XRF microprobe data. Micro-XRF mapping was also performed to produce chemical images on the stalagmite and compared with Raman and X-ray diffraction (XRD) to confirm that the stalagmite is exclusively calcite, with no aragonite, and that the source of sulphur in the samples was gypsum and anhydrite. Regions of very high sulphur in the micro-XRF maps were found to be artefacts due to diffraction of the incident beam but these could be efficiently removed by using a multiple point statistics approach to produce a clean image suitable for analysis of the laminae. This work shows the potential of micro-XRF for routine analysis of sulphur in stalagmites, and to streamline sample characterisation before SR-XRF imaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗