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NASA NTRS1988

Chemical and physical studies of type 3 chondrites. IX - Thermoluminescence and hydrothermal annealing experiments and their relationship to metamorphism and aqueous alteration in type below 3.3 ordinary chondrites

Thermoluminescence (TL) properties were measured in samples of four type-3.0 chondrites annealed at 400-850 C and 0.77-1 kbar in the presence of various amounts of water and sodium disilicate. Several changes recorded in TL characteristics, such as the lowering of TL sensitivity in certain samples, its increase in other samples, and changes in the peak position and peak width of TL suggested the occurrence of metamorphic processes in these samples. It is suggested that, for the chondrite types above 3.2, the observed changes in TL are consistent with the TL-metamorphism trends, being due to the formation of feldspar by the devitrification of chondrule glass during metamorphism. For types below 3.2, the TL data are consistent with the hypothesis that these chondrules experienced lower levels of metamorphism than the higher types or, alternatively, with the hypothesis that the type 3.0 chondrules are being produced from higher types by aqueous alteration.

Guimon, R. Kyle↗

NASA NTRS1988

Nature and origin of fluids in granulite facies metamorphism

The various models for the nature and origin of fluids in granulite facies metamorphism were summarized. Field and petrologic evidence exists for both fluid-absent and fluid-present deep crustal metamorphism. The South Indian granulite province is often cited as a fluid-rich example. The fluids must have been low in H2O and thus high in CO2. Deep crustal and subcrustal sources of CO2 are as yet unproven possibilities. There is much recent discussion of the possible ways in which deep crustal melts and fluids could have interacted in granulite metamorphism. Possible explanations for the characteristically low activity of H2O associated with granulite terranes were discussed. Granulites of the Adirondacks, New York, show evidence for vapor-absent conditions, and thus appear different from those of South India, for which CO2 streaming was proposed. Several features, such as the presence of high-density CO2 fluid inclusions, that may be misleading as evidence for CO2-saturated conditions during metamorphism, were discussed.

Newton, R. C.↗

NASA NTRS1991

Thermal histories of CO3 chondrites - Application of olivine diffusion modelling to parent body metamorphism

The petrologic sequence observed in the CO3 chondrite group has been suggested to be the result of thermal metamorphism on a parent body. A model developed to examine the possibility that chondrule and matrix olivines equilibrated in situ, during parent body metamorphism is presented. The model considers Fe-Mg interdiffusion between chondrule and matrix olivines. Zoning profiles comparable to those observed in chondrule olivines from partially equilibrated members of the series are reproduced successfully. Metamorphism of CO3 chondrites on a parent body is therefore a viable model for the observed equilibration. Results indicate that peak metamorphic temperatures experienced by the CO3 chondrites were around 500 C, and that the range of peak temperatures between unequilibrated and equilibrated subtypes was relatively narrow, around 100 C.

Jones, Rhian H.↗

NASA NTRS1991

Thermoluminescence constraints on the metamorphic, shock, and brecciation history of basaltic meteorites

The metamorphic, shock, and brecciation history of 18 eucrites, 13 howardites, 6 diogenites, and 15 mesosiderites is investigated via induced thermoluminescence measurements performed on them. The eucrites show a 15-fold range of TL sensitivities, which correlate with petrographic indicators of metamorphic intensity. The temperature of the dominant TL peak observed for basaltic meteorites, and experiments in which four eucrites with diverse petrographic properties were annealed at various temperatures in the laboratory, suggests that the metamorphic equilibration temperatures for most basaltic meteorites were not more than 800 C. Assuming this temperature was typical of conditions during metamorphism, then burial depths for type-above-5 eucrites were greater than 350 m and less than 50 m for type-2 eucrites. Since TL peak temperatures are related to the degree of disorder in the Al, Si chain in feldspar, the present data provide independent evidence for very slow cooling rates for mesosiderites and for the slower cooling rates for some cumulate eucrites relative to equilibrated noncumulate eucrites.

Batchelor, J. D.↗

NASA NTRS1990

Meteorite impact, cryptoexplosion, and shock metamorphism - A perspective on the evidence at the K/T boundary

A perspective on the evidence of a major impact event at the K/T boundary is proposed using field and laboratory studies of terrestrial impact craters. Recent assertions that diagnostic indications of shock metamorphism are also produced in volcanic environments are challenged. A general geological framework of impact structures is developed and the issue of volcanically induced shock metamorphism is examined. Cryptoexplosion is addressed by assessing the geology of two structures: the Slate Islands and Manson, which are often cited by advocates of an internal origin for shock metamorphism as volcanic structures. It is concluded that the link between shock metamorphism and meteorite impact is now established beyond reasonable doubt. The occurrence and worldwide distribution of shocked minerals at the K/T boundary is considered to be the conclusive evidence for a major impact event.

Sharpton, V. L.↗

NASA NTRS1995

Metamorphism and aqueous alteration in low petrographic type ordinary chondrites

In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondruies, chondruies were hand-picked from the Semarkona (petrographic type 3.0), Bishunpur (3. 1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron-microprobe and radiochemical neutron activation and the water and H-isotopic composition determined. The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to approx. 8000% SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work. With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondruies, indicating metamorphism-related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence for aqueous alteration, but the matrix contains H with approximately terrestrial D/H values, even though it contains much water. Secondary processes (probably aqueous alteration) presumably lowered the D/H of the matrix and certain chondrules. While chondrule properties appear to be governed primarily by formation processes and subsequent metamorphism, the matrix of Semarkona has a more complex history involving aqueous alteration as a meteorite-wide process.

Xie, T.↗

DOE OSTI2021

Inverted metamorphic GaInAs solar cell grown by dynamic hydride vapor phase epitaxy

We present an inverted metamorphic rear heterojunction ~1.0 eV GaInAs solar cell deposited by dynamic hydride vapor phase epitaxy (D-HVPE) with high growth rate. This device uses a Ga 1-x In x P compositionally graded buffer (CGB) to bridge the lattice constant gap between the GaAs substrate and the Ga0.71In0.29As emitter layer. High-resolution x-ray diffraction and transmission electron microscopy confirm that the Ga 0.71 In 0.29 As emitter is grown lattice-matched to the in-plane lattice constant of the CGB with minimal generation of defects at the GaInAs/GaInP interface. The device contains a threading dislocation density of 2.3 × 10 6 cm -2 , a level that enables high-performance minority carrier devices and is comparable to previously demonstrated GaInP CGBs grown by D-HVPE. The device exhibits an open-circuit voltage of 0.589 V under a one-sun AM1.5G illumination condition and a bandgap-voltage offset of 0.407 V, indicating metamorphic epitaxial performance nearly equal to state-of-the-art devices. We analyze the dark current of the device and determine that reducing recombination in the depletion region, which can be achieved by reducing the threading dislocation density and optimizing the device doping density, will improve the device performance. Furthermore, the CGB and device layers, comprising ~8 µm of thickness, are grown in under 10 min, highlighting the ability of D-HVPE to produce high-quality metamorphic devices of all types with the potential for dramatically higher throughput compared to present technology.

14 SOLAR ENERGY↗

DOE OSTI2025

A Tale from the Trenches: Applying Metamorphic and Differential Testing to Bioinformatics Software

Metamorphic and differential testing have been proposed as best practices for testing software that is difficult to test, such as for programs in scientific domains. An assumption is that these approaches can be easily customized and applied to almost any domain. However, scientific software is often data-driven, and metamorphic relations may require significant domain knowledge to develop. In addition, tools are often written for ad-hoc experimentation by the scientists and often embed many assumptions about the importance and representation of different natural phenomena. In this paper, we present our experience applying both metamorphic and differential testing to a set of four computational biology tools that predict the growth of an organism. While our original goal was to evaluate these techniques to improve our system-level testing, we encountered multiple roadblocks along the way. Although we did find faults (some confirmed by developers), we also uncovered a set of challenges, including the considerable manual effort required for (a) defining domain-specific tests, (b) validating correctness, and (c) distinguishing between issues stemming from poor data and those arising from incorrect software.

Marsh, Alexis L [Iowa State University/Ames Labora↗

NASA NTRS1972

Shock metamorphic effects in the Luna 16 soil sample from Mare Fecunditatis.

Diverse lunar soil fragments returned from the Luna 16 mission were examined for evidence in shock metamorphism in order to evaluate the role of meteorite impact in forming the lunar regolith at a new site relatively distant from the Apollo landing sites. It was found that shock metamorphic effects, characteristic of meteorite impact and virtually identical to those observed in Apollo samples, are common in the Luna 16 fragments. Two types of shock effects are present - i.e., a deformation and partial melting features in rock and mineral fragments, and heterogeneous glasses and glassy breccias produced by shock melting. It is concluded that these shock metamorphic effects indicate that regolith formation by meteorite impact has occurred in Mare Fecunditatis and is a general process over the entire moon.

French, B. M.↗

NASA NTRS1977

Carbonaceous chondrites of the Ornans type - A metamorphic sequence

The six identified carbonaceous chondrites classified as C3(O) (also known as the Ornans subtype or ornansites) are studied as a group. The Karoonda meteorite is also examined to determine whether it may be classified as a highly metamorphosed equivalent of the Ornans subtype. Petrographic and chemical similarities among these meteorites are discussed along with such systematic variations as textural, mineralogical, metallurgical, and chemical differences. Three metamorphic grades are delineated, chemical variations are correlated with the grades, and an attempt is made to determine why the Ornans meteorite belongs in a higher metamorphic grade on the basis of its chemical properties than on the basis of its petrographic characteristics. It is concluded that subtle differences among the meteorites may be related to small variations in the thermal metamorphism they have experienced.

Mcsween, H. Y., Jr.↗

NASA NTRS1985

Ubiquitous brecciation after metamorphism in equilibrated ordinary chondrites

Ten objects with aberrant Fe/(Fe + Mg) ratios have been found in apparently unbrecciated types 4-6 H and L chondrites. Since the Fe/(Fe + Mg) ratios of these objects are incompatible with the metamorphic history of the host chondrites, it is concluded that a high proportion of ordinary chondrites are breccias that were lithified after peak metamorphism. This is consistent with the results of Scott (1984), who concluded that most type three ordinary chondrites are breccias of materials with diverse thermal histories, even though they do not show prominent brecciation. It is found that the classification scheme of Van Schmus and Wood (1967) does not identify chondrites with similar thermal histories; the petrologic type of a chondrite is only a measure of the average thermal history of its ingredients. Chondrite and achondrite breccias are also compared in order to understand how brecciation of chondrites after metamorphism is so well camouflaged.

Scott, E. R. D.↗

NASA NTRS1987

Chemical and physical studies of type 3 chondrites. VIII - Thermoluminescence and metamorphism in the CO chondrites

A possible relationship between the thermoluminescence (TL) properties of CO chondrites and their metamorphic history was investigated by measuring the TL properties of seven normal CO chondrites and of the Colony and the Allan Hills A77307 (ALHA 77307) CO-related chondrites. With the exception of Colony and ALHA 77307, whose maximum induced TL emission is at approximately 350 C, the CO chondrites were found to exhibit two TL peaks: a 130 C and a 250 C peaks. Among the CO chondrites, the 130 C peak showed a 100-fold range in TL sensitivity and was found to correlate with various metamorphism-related phenomena, such as silicate heterogeneity, metal composition, and McSween's metamorphic subtypes. The peak at 250 did not show these correlations and, with exception of Colony, showed little variation.

Keck, Bradly D.↗

NASA NTRS1988

Planet Alsioff - A problem set for students of phase equilibria or metamorphic petrology

This paper presents a problem set that contains questions for students of phase equilibria or metamorphic petrology concerning a hypothetical planet Alsioff, for which incomplete data are given. On this panet, the SiF4 is the major volatile and Al, Si, O, and F are the only elements present. Progressive metamorphism on Alsioff mainly involves devolatilization of fluid SiF4. The problem set includes ten questions. Some of these are concerned with possible chemical reactions that should affect water, wollastonite, or Ca-SiO3 exposed to the atmosphere of Alsioff; the mechanism of controls of the O2 and F2 contents of the Alsioffian atmosphere; and the devolatilization reactions involving SiF4 with progressive thermal metamorphism.

Burt, Donald M.↗

NASA NTRS1988

Thermal metamorphism

Most chondrites have experienced thermal metamorphism, resulting in changes in texture, mineralogy and possibly chemical composition. The physical conditions for metamorphism range from approximately 400 to 1000 C at low lithostatic pressure. Metamorphism may have resulted from decay of short-lived radionuclides, electromagnetic induction or accretion of hot materials. Several thermal models for chondrite parent bodies have been proposed. The least metamorphosed type-3 chondrites probably carry the most information about the early solar system, but even these have been affected to some degree by thermal processing.

Mcsween, Harry Y., Jr.↗

NASA NTRS1993

Oxidation during metamorphism of the ordinary chondrites

It is suggested that some current concepts about the conditions of metamorphism in ordinary chondrites may be flawed. These meteorites display small systematic variations in the oxidation state of Fe. Evidence is presented that oxidation of Fe is linked to metamorphic grade in types 4-6 ordinary chondrites. This conclusion is at variance with a commonly accepted model for chondrite metamorphism that assumes Fe reduction by graphite.

Mcsween, Harry Y., Jr.↗

NASA NTRS1998

Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures

This handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures emphasizes terrestrial impact structures, field geology, and particularly the recognition and petrographic study of shock-metamorphic effects in terrestrial rocks. Individual chapters include: 1) Landscapes with Craters: Meteorite Impacts, Earth, and the Solar System; 2) Target Earth: Present, Past and Future; 3) Formation of Impact Craters; 4) Shock-Metamorphic Effects in Rocks and Minerals; 5) Shock-Metamorphosed Rocks (Impactities) in Impact Structures; 6) Impact Melts; 7) How to Find Impact Structures; and 8) What Next? Current Problems and Future Investigations.

French, Bevan M.↗

DOE OSTI2020

Inverted Metamorphic AlGaInAs/GaInAs Tandem Thermophotovoltaic Cell Designed for Thermal Energy Grid Storage Application

We demonstrate an inverted metamorphic multijunction (IMM) photovoltaic cell comprising lattice-mismatched 1.2 eV AlGaInAs and 1.0 eV GaInAs junctions optimized for high-temperature thermophotovoltaic (TPV) applications. This device differs from traditional IMM solar cells because the mismatched junctions are grown at a single lattice constant. This architecture enables removal of the compositionally graded buffer that otherwise filters light from the junctions below and absorbs sub-bandgap light via free-carrier absorption. Sub-bandgap absorption dramatically reduces the efficiency of TPV systems using high reflectivity cells to enable band edge spectrum filtering. Three components required development to enable this device: (1) a lattice-mismatched 1.2 eV AlGaInAs junction, (2) a metamorphic contact layer grown after the graded buffer, and (3) a transparent tunnel junction that sits in front of the 1.0 eV GaInAs junction. Growth conditions that minimize oxygen defect incorporation maximize AlGaInAs cell quality, enabling a 0.41 V bandgap open circuit voltage offset at 22 mA/cm2 under AM1.5D. A mismatched GaInAs:Se layer is developed as a low resistance contact. Lastly, we develop a GaAsSb:C/GaInP:Se tunnel junction suitable for high-power densities with more transparency than the GaAsSb:C/GaInAs:Se structure used in past IMM cells. We characterize the tandem device under a high-intensity spectrum that approximates the emission from a 2150°C blackbody radiator and deduce a projected ideal TPV efficiency of 39.9% at ~30% of the blackbody irradiance and 36% ideal TPV efficiency under the full 118 W/cm2 irradiance. Improvements to the back-surface reflectivity and series resistance are expected to increase the ideal TPV efficiency well above 40%.

25 ENERGY STORAGE↗

DOE OSTI2022

Metamorphism-facilitated faulting in deforming orthopyroxene: Implications for global intermediate-depth seismicity

Significance The exothermic metamorphic reaction in orthopyroxene (Opx), a major component of oceanic lithospheric mantle, is shown to trigger brittle failure in laboratory deformation experiments under conditions where garnet exsolution takes place. The reaction product is an extremely fine-grained material, forming narrow reaction zones that are mechanically weak, thereby facilitating macroscopic faulting. Oceanic subduction zones are characterized by two separate bands of seismicity, known as the double seismic zone. The upper band of seismicity, located in the oceanic crust, is well explained by dehydration-induced mechanical instability. Our newly discovered metamorphism-induced mechanical instability provides an alternative physical mechanism for earthquakes in the lower band of seismicity (located in the oceanic lithospheric mantle), with no requirement of hydration/dehydration processes.

58 GEOSCIENCES↗