Article

Systematics and Evaluation of Meteorite Classification

January 2006

Authors:

Kingsborough Community College

Classification of meteorites is largely based on their mineralogical and petrographic characteristics and their whole-rock chemical and O-isotopic compositions. According to the currently used classification scheme, meteorites are divided into chondrites, primitive achondrites, and achondrites. There are 15 chondrite groups, including 8 carbonaceous (CI, CM, CO, CV, CK,CR, CH, CB), 3 ordinary (H, L, LL), 2 enstatite (EH, EL), and R and K chondrites. Several chondrites cannot be assigned to the existing groups and may represent the first members of new groups. Some groups are subdivided into subgroups, which may have resulted from asteroidal processing of a single group of meteorites. Each chondrite group is considered to have sampled a separate parent body. Some chondrite groups and ungrouped chondrites show chemical and mineralogical similarities and are grouped together into clans. The significance of this higher order of classification remains poorly understood. The primitive achondrites include ureilites, acapulcoites, lodranites, winonaites, and silicate inclusions in IAB and IIICD irons and probably represent recrystallization or residues from a low-degree partial melting of chondritic materials. The genetic relationship between primitive achondrites and the existing groups of chondritic meteorites remains controversial. Achondrites resulted from a high degree of melting of chondrites and include asteroidal (angrites, aubrites, howardites-diogenites-eucrites, mesosiderites, 3 groups of pallasites, 15 groups of irons plus many ungrouped irons) and planetary (martian, lunar) meteorites.

Астробиология

Book

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Oct 2024

A history of violence: insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes, and water contents

Preprint

Oct 2017

Carbonaceous chondrites (CCs) may have been the carriers of water, volatile and moderately volatile elements to Earth. Investigating the abundances of these elements, their relative volatility, and isotopes of state-change tracer elements such as Zn, and linking these observations to water contents, provide vital information on the processes that govern the abundances and isotopic signatures of these species in CCs and other planetary bodies. Here we report Zn isotopic data for 28 CCs (20 CM, 6 CR, 1 C2-ung, and 1 CV3), as well as trace element data for Zn, In, Sn, Tl, Pb, and Bi in 16 samples (8 CM, 6 CR, 1 C2-ung, and 1 CV3), that display a range of elemental abundances from case-normative to intensely depleted. We use these data, water content data from literature and Zn isotopes to investigate volatile depletions and to discern between closed and open system heating. Trace element data have been used to construct relative volatility scales among the elements for the CM and CR chondrites. From least volatile to most, the scale in CM chondrites is Pb-Sn-Bi-In-Zn-Tl, and for CR chondrites it is Tl-Zn-Sn-Pb-Bi-In. These observations suggest that heated CM and CR chondrites underwent volatile loss under different conditions to one another and to that of the solar nebula, e.g. differing oxygen fugacities. Furthermore, the most water and volatile depleted samples are highly enriched in the heavy isotopes of Zn. Taken together, these lines of evidence strongly indicate that heated CM and CR chondrites incurred open system heating, stripping them of water and volatiles concomitantly, during post-accretionary shock impact(s).

Reactivity of chondritic meteorites under H2-rich atmospheres: Formation of H2S.

Article

Nov 2024
MON NOT R ASTRON SOC

Current models of chemical evolution during star and planetary formation rely on the presence of dust grains to act as a third body. However, they generally ignore the reactivity of the dust grains themselves. Dust grains present in the protoplanetary phase will evolve as the solar system forms and, after protoplanets have appeared, they will be constantly delivered to their surfaces in the form of large aggregates or meteorites. Chondritic meteorites are mostly unaltered samples of the dust present in the first stages of the Solar System formation, that still arrive nowadays to the surface of Earth and allow us to study the properties of the materials forming the early Solar System. These materials contain, amongst others, transition metals that can potentially act as catalysts, as well as other phases that can potentially react in different astrophysical conditions, such as FeS. In this work, we present the reactivity of chondritic meteorites under H2-rich atmospheres, particularly towards the reduction of FeS for the formation of H2S and metallic Fe during the early phases of the planetary formation. We present the obtained results on the reaction rates and the percentage of FeS available to react in the materials. Additionally, we include a computational study of the reaction mechanism and the energetics. Finally, we discuss the implications of an early formation of H2S in planetary surfaces.

Reactivity of chondritic meteorites under H2-rich atmospheres: Formation of H2S

Preprint

Full-text available

Oct 2024

Current models of chemical evolution during star and planetary formation rely on the presence of dust grains to act as a third body. However, they generally ignore the reactivity of the dust grains themselves. Dust grains present in the protoplanetary phase will evolve as the solar system forms and, after protoplanets have appeared, they will be constantly delivered to their surfaces in the form of large aggregates or meteorites. Chondritic meteorites are mostly unaltered samples of the dust present in the first stages of the Solar System formation, that still arrive nowadays to the surface of Earth and allow us to study the properties of the materials forming the early Solar System. These materials contain, amongst others, transition metals that can potentially act as catalysts, as well as other phases that can potentially react in different astrophysical conditions, such as FeS. In this work, we present the reactivity of chondritic meteorites under \hydrogen-rich atmospheres, particularly towards the reduction of FeS for the formation of H2S and metallic Fe during the early phases of the planetary formation. We present the obtained results on the reaction rates and the percentage of FeS available to react in the materials. Additionally, we include a computational study of the reaction mechanism and the energetics. Finally, we discuss the implications of an early formation of H2S in planetary surfaces.

Chondrule sizes within the CM carbonaceous chondrites and measurement methodologies

Article

Full-text available

Aug 2024
METEORIT PLANET SCI

The sizes of chondrules are a valuable tool for understanding relationships between meteorite groups and the affinity of ungrouped chondrites, documenting temporal/spatial variability in the solar nebula, and exploring the effects of parent body processing. Many of the recently reported sizes of chondrules within the CM carbonaceous chondrites differ significantly from the established literature average and are more closely comparable to those of chondrules within CO chondrites. Here, we report an updated analysis of chondrule dimensions within the CM group based on data from 1937 chondrules, obtained across a suite of CM lithologies ranging from petrologic subtypes CM2.2 to CM2.7. Our revised average CM chondrule size is 194 μm. Among the samples examined, a relationship was observed between petrologic subtype and chondrule size such that chondrule long-axis lengths are greater in the more highly aqueously altered lithologies. These findings suggest a greater similarity between the CM and CO chondrites than previously thought and support arguments for a genetic link between the two groups (i.e., the CM-CO clan). Using the 2-D and 3-D data gathered, we also apply numerous stereological corrections to examine their usefulness in correcting 2-D chondrule measurements within the CM chondrites. Alongside this analysis, we present the details of a standardized methodology for 2-D chondrule size measurement to facilitate more reliable inter-study comparisons.

The petrology of the Ozerki meteorite constrained by electron backscatter diffraction and X‐ray computed tomography

Article

Full-text available

Apr 2025
METEORIT PLANET SCI

Combining electron backscatter diffraction (EBSD) with X‐ray computed tomography (XCT) offers a comprehensive approach to investigate shock deformation and rock texture in meteorites, yet such integration remains uncommon. In this study, we demonstrate the synergistic potential of XCT and EBSD in revealing deformation metrics, thereby enhancing our understanding of petrofabric strength and shock‐induced deformation. Our analysis focuses on the Ozerki (L6, S4/5, W0) meteorite fall, which was instrumentally observed on June 21, 2018, and subsequently recovered by the Ural's branch of the Russian Fireball Network (UrFU) recovery expedition a few days later. The trajectory analysis conducted by the Finnish Fireball Network facilitated the prompt retrieval of the meteorite. We show that Ozerki is deformed, with a moderate strength foliation fabric defined by metal and sulfide grain shapes. Microstructural analysis using EBSD shows that the parent body was likely still thermally active during this impact event. Our data suggest that these microstructures were likely produced during an impact while the Ozerki's parent body was still warm.

Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu

Article

Sep 2024
METEORIT PLANET SCI

The surface morphology of regolith grains from the C‐type asteroid Ryugu was studied in search of evidence of impact events on the asteroid. Scanning electron microscopy revealed that ~8% of C0105‐042 Ryugu grains have a smooth surface on one side of the grains. One of these grains has striated linear grooves (striations) on its smooth surface. Transmission electron microscopy of the grain showed that a porous fine‐grained Mg‐Fe phyllosilicate assemblage, which is the main component of Ryugu grains, is compacted near the smooth surface. The smooth surface with striations closely resembles a slickenside, a characteristic texture found in terrestrial fault rocks formed by shear deformation. There is no evidence of melting/decomposition in the Mg‐Fe phyllosilicates near the smooth surface, indicating that the shear heating temperature is less than ~1100 K. Assuming that the average length of the striations corresponds to the minimum displacement of the micro‐fault, the shock pressure recorded in the C0105‐042 Ryugu grain is estimated to be <~4.5 GPa by a fault mechanics calculation. The shock pressures of C0105‐042, together with those of C0014 (~2 GPa) and C0055 (>~3.9 GPa) in previous studies suggest that the impact velocities recorded in these grains are < ~0.89–1.63 km s ⁻¹ . Based on the impact velocities, these grains may record an impact event that occurred when asteroid Ryugu was in the orbit in Main Belt.

Crystalline forsterite to 160 GPa: the striking metastability of one of Universe's most abundant minerals

Preprint

Full-text available

Jul 2024

Among Universe's most consequential events are large impacts generating rapidly-evolving extreme pressures and temperatures. Crystalline and amorphous forms of (Mg, Fe)2SiO4 are abundant and widespread, within planets and in space. The behavior of these minerals is expected to deviate form thermodynamic equilibrium in many of the processes that are critical to the formation and evolution of planets, particularly shock events. To further the understanding of the behavior of the silicate under extreme conditions, we statically compressed a crystal of forsterite up to 160.5 GPa, far beyond the compound's stability field, and probed its long-range ordering with synchrotron microdiffraction. We found that forsterite retains long-range ordering up to the highest pressure reached. Forsterite III, emerging at about 58 GPa, persists in compression to 160.5 GPa and in decompression down to about 13 GPa, for a rare combined occurrence of a metastable phase of nearly 150 GPa. These observations dispute earlier reports of pressure-induced amorphization and are a unique testimony of the resilience of the crystalline state in quasi hydrostatic compression. We confirm that highly disordered forsterite can be obtained from the decompression of forsterite III as suggested from the substantial loss of long-range ordering observed at 7 GPa after further decompression. Such kinetic pathway may explain how synthetic olivine glass have been obtained in shock experiments and could be a mechanism of generation of amorphous forsterite in cosmic dust. The 120 GPa Hugoniot discontinuity finds no correspondence in our data, marking a departure from the parallelism between static "cold compression" and dynamic compression.

Abundance, Sizes, and Major Element Compositions of Components in CR and LL Chondrites: Formation from Single Reservoirs

Preprint

Full-text available

Jul 2024

Abundances, apparent sizes, and individual chemical compositions of chondrules, refractory inclusions, other objects and surrounding matrix have been determined for Semarkona (LL3.00) and Renazzo (CR2) using consistent methods and criteria on x-ray element intensity maps. These represent the non-carbonaceous (NC, Semarkona) and carbonaceous chondrite (CC, Renazzo) superclans of chondrite types. We compare object and matrix abundances with similar data for CM, CO, K, and CV chondrites. We assess, pixel-by-pixel, the major element abundance in each object and in the entire matrix. We determine the abundance of "metallic chondrules" in LL chondrites. Chondrules with high Mg/Si and low Fe/Si and matrix carrying opposing ratios complement each other to make whole rocks with near-solar major element ratios in Renazzo. Similar Mg/Si and Fe/Si chondrule-matrix relationships are seen in Semarkona, which is within 11% of solar Mg/Si but significantly Fe-depleted. These results provide a robust constraint in support of single-reservoir models for chondrule formation and accretion, ruling out whole classes of astrophysical models and constraining processes of chondrite component formation and accretion into chondrite parent bodies.

THE Formation of chondrule-like particles in RF discharge plasma

Article

Dec 2023

Assan Abdirakhmanov

Chondrules are fundamental components of chondritic meteorites and play a vital role in understanding the formation of the early solar system. This study focuses on the synthesis of chondrule-like particles in a plasma environment using a radiofrequency (RF) discharge. The experimental setup involves a vacuum chamber where argon gas, hexamethyldisiloxane (HMDSO), and ferrocene vapors are introduced. The plasma burning duration is optimized to facilitate chondrule formation, followed by analysis of the synthesized particles using scanning electron microscopy (SEM) and energy dispersive analysis. The results demonstrate the successful synthesis of chondrule-like particles with diverse sizes and morphologies. SEM imaging reveals particles ranging from 80 to 378 nm in diameter, exhibiting rounded and non-uniform shapes. Energy dispersive analysis confirms the presence of iron, carbon, oxygen, and silicon in the synthesized particles. Iron and carbon originate from the ferrocene and HMDSO precursors, respectively, while oxygen may indicate oxidation or the presence of oxide groups. Silicon, the main component, contributes to the key characteristics of the chondrule-like structures. These findings contribute to the understanding of chondrule formation mechanisms and pave the way for further investigations using combined discharges to simulate shock waves or nebular lightning. Additionally, the study suggests the possibility of introducing additional chondrule building blocks, such as magnesium and phosphorus, to explore their effects on particle synthesis and composition.

Prebiotic Vitamin B3 Synthesis in Carbonaceous Planetesimals

Article

Full-text available

Nov 2023

Aqueous chemistry within carbonaceous planetesimals is promising for synthesizing prebiotic organic matter essential to all life. Meteorites derived from these planetesimals delivered these life building blocks to the early Earth, potentially facilitating the origins of life. Here, we studied the formation of vitamin B3 as it is an important precursor of the coenzyme NAD(P)(H), which is essential for the metabolism of all life as we know it. We propose a new reaction mechanism based on known experiments in the literature that explains the synthesis of vitamin B3. It combines the sugar precursors glyceraldehyde or dihydroxyacetone with the amino acids aspartic acid or asparagine in aqueous solution without oxygen or other oxidizing agents. We performed thermochemical equilibrium calculations to test the thermodynamic favorability. The predicted vitamin B3 abundances resulting from this new pathway were compared with measured values in asteroids and meteorites. We conclude that competition for reactants and decomposition by hydrolysis are necessary to explain the prebiotic content of meteorites. In sum, our model fits well into the complex network of chemical pathways active in this environment.

Meteoritic Abundances of Fatty Acids and Potential Reaction Pathways in Planetesimals

Preprint

Sep 2018

The origin of fatty acids on the prebiotic Earth is important as they likely formed the encapsulating membranes of the first protocells. Carbon-rich meteorites (i.e., carbonaceous chondrites) such as Murchison and Tagish Lake are well known to contain these molecules, and their delivery to the early planet by intense early meteorite bombardments constitutes a key prebiotic source. We collect the fatty acid abundances measured in various carbonaceous chondrites from the literature and analyze them for patterns and correlations. Fatty acids in meteorites include straight-chain and branched-chain monocarboxylic and dicarboxylic acids up to 12 carbons in length---fatty acids with at least 8 carbons are required to form vesicles, and modern cell membranes employ lipids with ~12--20 carbons. To understand the origin of meteoritic fatty acids, we search the literature for abiotic fatty acid reaction pathways and create a candidate list of 11 reactions that could potentially produce these fatty acids in meteorite parent bodies. Straight-chain monocarboxylic acids (SCMA) are the dominant fatty acids in meteorites, followed by branched-chain monocarboxylic acids (BCMA). SCMA are most abundant in CM2 and Tagish Lake (ungrouped) meteorites, ranging on average from 10

^2

ppb to 4x10

^5

ppb, and 10

^4

ppb to 5x10

^6

ppb, respectively. In CM, CV, and Tagish Lake meteorites, SCMA abundances generally decrease with increasing carbon chain length. Conversely, SCMA abundances in CR meteorites peak at 5 and 6 carbons in length, and decrease on either side of this peak. This unique CR fatty acid distribution may hint at terrestrial contamination, or that certain fatty acid reactions mechanisms are active in different meteorite parent bodies (planetesimals). We identify Fischer-Tropsch-type synthesis as the most promising pathway for further analysis in the production of fatty acids in planetesimals.

Meteorites and the RNA World: A Thermodynamic Model of Nucleobase Synthesis within Planetesimals

Preprint

Nov 2016

The possible meteorite parent body origin of Earth's pregenetic nucleobases is substantiated by the guanine (G), adenine (A) and uracil (U) measured in various meteorites. Cytosine (C) and thymine (T) however are absent in meteorites, making the emergence of a RNA and later RNA/DNA/protein world problematic. We investigate the meteorite parent body (planetesimal) origin of all nucleobases by computationally modeling 18 reactions that potentially contribute to nucleobase formation in such environments. Out of this list, we identify the two most important reactions for each nucleobase and find that these involve small molecules such as HCN, CO, NH3, and water that ultimately arise from the protoplanetary disks in which planetesimals are built. The primary result of this study is that cytosine is unlikely to persist within meteorite parent bodies due to aqueous deamination. Thymine has a thermodynamically favourable reaction pathway from uracil, formaldehyde and formic acid, but likely did not persist within planetesimals containing H2O2 due to an oxidation reaction with this molecule. Finally, while FT synthesis is found to be the dominant source of nucleobases within our model planetesimal, NC synthesis may still be significant under certain chemical conditions (e.g. within CR2 parent bodies). We discuss several major consequences of our results for the origin of the RNA world.

Spectral Evidence for Amorphous Silicates in Least-processed CO Meteorites and Their Parent Bodies

Preprint

Feb 2018

Least-processed carbonaceous chondrites (carbonaceous chondrites that have experienced minimal aqueous alteration and thermal metamorphism) are characterized by their predominately amorphous iron-rich silicate interchondrule matrices and chondrule rims. The presence of abundant amorphous material in a meteorite indicates that the parent body, or at least a region of the parent body, experienced minimal processing since the time of accretion. The CO chemical group of carbonaceous chondrites has a significant number of these least-processed samples. We present visible/near-infrared and mid-infrared spectra of eight least-processed CO meteorites (petrologic type 3.0-3.1). In the visible/near-infrared, these COs are characterized by a broad weak feature that was first observed by Cloutis et al. (2012) to be at 1.3-um and attributed to iron-rich amorphous silicate matrix materials. This feature is observed to be centered at 1.4-um for terrestrially unweathered, least-processed CO meteorites. At mid-infrared wavelengths, a 21-um feature, consistent with Si-O vibrations of amorphous materials and glasses, is also present. This spectral signature is absent in both the near- and mid-infrared spectra of higher metamorphic grade COs because this material has recrystallized as crystalline olivine. Furthermore, spectra of least-processed primitive meteorites from other chemical groups (CRs, MET 00426 and QUE 99177, and C2-ungrouped Acfer 094), also exhibit a 21-um feature. Thus, we conclude that the 1.4- and 21-umm features are characteristic of primitive least-processed meteorites from all chemical groups of carbonaceous chondrites. Finally, we present an IRTF+SPeX observation of asteroid (93) Minerva that has spectral similarities in the visible/near-infrared to the least-processed CO carbonaceous chondrites. Minerva is likely the least-processed CO-like asteroid observed to date.

Two-Dimensional Transport of Solids in Viscous Protoplanetary Disks

Preprint

Dec 2008

F. J. Ciesla

Large-scale radial transport of solids appears to be a fundamental consequence of protoplanetary disk evolution based on the presence of high temperature minerals in comets and the outer regions of protoplanetary disks around other stars. Further, inward transport of solids from the outer regions of the solar nebula has been postulated to be the manner in which short-lived radionuclides were introduced to the terrestrial planet region and the cause of the variations in oxygen isotope ratios seen in primitive materials. Here, both outward and inward transport of solids are investigated in the context of a two-dimensional, viscously evolving protoplanetary disk. The dynamics of solids are investigated to determine how they depend on particle size and the particular stage of protoplanetary disk evolution, corresponding to different rates of mass transport. It is found that the outward flows that arise around the disk midplane of a protoplanetary disk aid in the outward transport of solids up to the size of CAIs and can increase the crystallinity fraction of silicate dust at 10 AU around a solar mass star to as much as

\sim

40% in the case of rapidly evolving disks, decreasing as the accretion rate onto the star slows. High velocity, inward flows along the disk surface aid in the rapid transport of solids from the outer disk to the inner disk, particularly for small dust. Despite the diffusion that occurs throughout the disk, the large-scale, meridonal flows associated with mass transport prevent complete homogenization of the disk, allowing compositional gradients to develop that vary in intensity for a timescale of one million years.

Composition of the L5 Mars Trojans: Neighbors, not Siblings

Preprint

Sep 2007

Mars is the only terrestrial planet known to have Tro jan (co-orbiting) asteroids, with a confirmed population of at least 4 objects. The origin of these objects is not known; while several have orbits that are stable on solar-system timescales, work by Rivkin et al. (2003) showed they have compositions that suggest separate origins from one another. We have obtained infrared (0.8-2.5 micron) spectroscopy of the two largest L5 Mars Tro jans, and confirm and extend the results of Rivkin et al. (2003). We suggest that the differentiated angrite meteorites are good spectral analogs for 5261 Eureka, the largest Mars Trojan. Meteorite analogs for 101429 1998 VF31 are more varied and include primitive achondrites and mesosiderites.

An unusual lunar origin and chondritic refractory Antarctic micrometeorites

Article

Full-text available

Nov 2024

Copper and its isotopes: a brief overview of its implications in geology, environmental system, and human health

Article

Oct 2024
ISOT ENVIRON HEALT S

How we can mine asteroids for space food

Article

Full-text available

Oct 2024

To deeply explore the solar system, it will be necessary to become less reliant on the resupply tether to Earth. An approach explored in this study is to convert hydrocarbons in asteroids to human edible food. After comparing the experimental pyrolysis breakdown products, which were able to be converted to biomass using a consortia, it was hypothesized that equivalent chemicals found on asteroids could also be converted to biomass with the same nutritional content as the pyrolyzed products. This study is a mathematical exercise that explores the potential food yield that could be produced from these methodologies. This study uses the abundance of aliphatic hydrocarbons in the Murchison meteorite (>35 ppm) as a baseline for the calculations, representing the minimum amount of organic matter that could theoretically be attributed to biomass production. Calculations for the total carbon in solvent-insoluble organic matter (IOM) represent the maximum amount of organic matter that could theoretically be attributed to food production. These two values will provide a range of realistic yields to determine how much food could theoretically be extractable from an asteroid. The results of this study found that if only the aliphatic hydrocarbons can be converted into biomass (minimum scenario) the resulting mass of edible biomass extractable from asteroid Bennu ranges from 5.070 × 10 ⁷ g to 2.390 × 10 ⁸ g. If the biomass extraction process, however, is more efficient, and all IOM is converted into edible biomass (maximum scenario), then the mass of edible biomass extractable from asteroid Bennu ranges from 1.391 × 10 ⁹ g to 6.556 × 10 ⁹ g. This would provide between 5.762 × 10 ⁸ and 1.581 × 10 ¹⁰ calories that is enough to support between 600 and 17 000 astronaut life years. The asteroid mass needed to support one astronaut for one year is between 160 000 metric tons and 5000 metric tons. Based on these results, this approach of using carbon in asteroids to provide a distributed food source for humans appears promising, but there are substantial areas of future work.

Is there a genetic relationship between chondrules and matrix?

Preprint

Full-text available

Sep 2024

Chondritic components such as chondrules and matrix are the key time capsules that can help us understand the evolution and dynamics of the protoplanetary disk from which the Solar System originated. Knowledge of where and how these components formed and to what extent they were transported in the gaseous disk provides major constraints to astrophysical models that investigate planet formation. Here, we explore whether chondrules and matrix are genetically related to each other and formed from single reservoirs per chondrite group or if every chondrite represents a unique proportion of components transported from a small number of formation reservoirs in the disk. These static versus dynamic disk interpretations of cosmochemical data have profound implications for the accretion history of the planets in the Solar System. To fully understand the relationship between chondrules and matrix and their potential complementarity, we dive into the petrological nature and origin of matrix, the chemical and isotopic compositions of chondrules and matrix and evaluate these data considering the effect of secondary alteration observed in chondrites and the potential complexity of chondrule formation. Even though we, the authors, have used different datasets and arrived at differing interpretations of chondrule-matrix relationships in the past, this review provides clarity on the existing data and has given us new directions towards future research that can resolve the complementarity debate.

Identification of a primordial high D/H component in the matrix of unequilibrated ordinary chondrites

Article

Full-text available

Jun 2024
GEOCHIM COSMOCHIM AC

Are Clay Minerals Systematically the Products of Aqueous Alteration in Cosmic Bodies?

Article

Full-text available

May 2024

The formation of chondrite materials represents one of the earliest mineralogical processes in the solar system. Phyllosilicates are encountered at various stages of the chondrule formation, from the initial stages (IDP agglomerates) to the final steps (chondrule internal alteration). While typically linked to aqueous alteration, recent studies reveal that phyllosilicates could precipitate directly from residual fluids in post-magmatic or deuteric conditions and under a wide range of temperatures, pressures, water/rock ratios, and H2/H2O ratio conditions. This study re-examined the formation of hydrated phyllosilicates in chondrules and associated fine-grained rims (FGRs) using published petrographical, mineralogical, and chemical data on carbonaceous chondrites. Given that chondrules originate from the melting of interplanetary dust particles, the water liberated by the devolatilization of primary phyllosilicates, including clay minerals or ice melting, reduces the melting temperature and leads to water dissolution into the silicate melt. Anhydrous minerals (e.g., olivine and diopside) form first, while volatile and incompatible components are concentrated in the residual liquid, diffusing into the matrix and forming less porous FGRs. Serpentine and cronstedtite are the products of thermal metamorphic-like mineral reactions. The mesostasis in some lobated chondrules is composed of anhydrous and hydrous minerals, i.e., diopside and serpentine. The latter is probably not the alteration product of a glassy precursor but rather a symplectite component (concomitant crystallization of diopside and serpentine). If so, the symplectite has been formed at the end of the cooling process (eutectic-like petrographical features). Water trapped inside chondrule porosity can lead to the local replacement of olivine by serpentine without external water input (auto-alteration). In the absence of water, hydrated phyllosilicates do not crystallize, forming a different mineral assemblage.

Brecciation at the grain scale within the lithologies of the Winchcombe Mighei-like carbonaceous chondrite

Article

Full-text available

Mar 2024
METEORIT PLANET SCI

The Mighei-like carbonaceous (CM) chondrites have been altered to various extents by water-rock reactions on their parent asteroid(s). This aqueous processing has destroyed much of the primary mineralogy of these meteorites, and the degree of alteration is highly heterogeneous at both the macroscale and nanoscale. Many CM meteorites are also heavily brecciated juxtaposing clasts with different alteration histories. Here we present results from the fine-grained team consortium study of the Winchcombe meteorite, a recent CM chondrite fall that is a breccia and contains eight discrete lithologies that span a range of petrologic subtypes (CM2.0-2.6) that are suspended in a cataclastic matrix. Coordinated multitechnique, multiscale analyses of this breccia reveal substantial heterogeneity in the extent of alteration, even in highly aqueously processed lithologies. Some lithologies exhibit the full range and can comprise nearly unaltered coarse-grained primary components that are found directly alongside other coarse-grained components that have experienced complete pseudomorphic replacement by secondary minerals. The preservation of the complete alteration sequence and pseudomorph textures showing tochilinite-cronstedtite intergrowths are replacing carbonates suggest that CMs may be initially more carbonate rich than previously thought. This heterogeneity in aqueous alteration extent is likely due to a combination of microscale variability in permeability and water/rock ratio generating local microenvironments as has been established previously. Nevertheless, some of the disequilibrium mineral assemblages observed, such as hydrous minerals juxtaposed with surviving phases that are typically more fluid susceptible, can only be reconciled by multiple generations of alteration, disruption, and reaccretion of the CM parent body at the grain scale.

Mineralogical studies of differentiated bodies in the early Solar System初期太陽系における分化天体の進化に関する鉱物科学的研究

Article

Feb 2024

Akira Yamaguchi

Although achondrites represent only 5% of the global collection, they offer insights into the early igneous and metamorphic processes that occurred on differentiated planetesimals and protoplanets in the early Solar System. I have studied achondrites, particularly focusing on the petrogenesis of HED meteorites (howardites, eucrites, and diogenites). HED meteorites are the largest group of differentiated achondrites that probably originated from the asteroid 4 Vesta. Based on the thermal history and geochemical characteristics of eucrites and diogenites, the crust of the HED parent body developed through lava eruptions and shallow intrusions of eucrites over a short period. Later, diogenite plutons intruded into the eucritic crust. These processes caused global crustal metamorphism and partial melting of the early crust. The presence of a few meteorites petrologically similar to eucrites but with different oxygen isotopic compositions suggests the existence of multiple protoplanets undergoing similar geologic processes in the early Solar System. The discovery of the oldest andesitic achondrite unveils new perspectives on the volcanism of differentiated meteorite parent bodies. The partial melting of chondritic meteorites likely produced Si- and Na-rich (i.e., andesitic) melts, yet such meteorites are extremely rare in global collections. It is inferred that the parent bodies of these achondrites have disrupted and did not survive. As the curator, I have been managing the Japanese Antarctic meteorite collection, making these valuable samples available to the scientific community. These meteorites provide crucial insights into the processes that took place in the early Solar System.

Fe hyperfine parameters and phase compositions in Fe-Ni-Co alloys from iron, stony-iron and stony meteorites

Article

Full-text available

Feb 2024
Hyperfine Interact

Basing on Mössbauer studies of various iron, stony-iron and stony meteorites, we considered a possible relationship of the ranges of magnetic hyperfine field (Heff), Fe-Ni-Co phases and the ranges of Ni concentration in these phases. We suppose that possible relationship of the ranges of Heff with Fe-Ni-Co phases and with the ranges of Ni concentration can be taken as follows: ~345 kOe ≤ Heff ≤ ~365 kOe for the α2-phase (~ 8–25 at% of Ni), ~ 327 kOe < Heff ≤ ~345 kOe for the α-phase (up to 7 at% of Ni), ~ 283 kOe ≤ Heff ≤ ~327 kOe for the γ-phase (~ 26–48 at% of Ni) with the values of ~ 283 kOe ≤ Heff ≤ ~295 kOe which may also be associated with the ordered γ-FeNi(Co) phase (~ 48–52 at% of Ni). The paramagnetic γ-Fe(Ni, Co) phase with ~ 29–33 at% of Ni has the values of isomer shift (δ) in the range of ~ − 0.200 mm/s < δ < ~0.150 mm/s.

Moderately volatile elemental and isotopic variations in variably shocked equilibrated ordinary chondrites from Antarctica

Article

Full-text available

Feb 2024
ICARUS

Volatile elements, crucial players in planetary evolution, condense at low temperatures from solar nebula. Despite extensive past research, gaps remain in understanding the volatile budget establishment and depletion mechanisms during the early stages of Solar System formation. This study investigates the role of shock events on multiple isotope systems in H6 ordinary chondrites with varying shock and weathering degrees. In this study, we classified fifteen H6 ordinary chondrites from Antarctica for their shock and weathering stages. We report the bulk trace elemental abundances of the samples and focus on Zn, Ga, Cu, and Fe isotope compositions, each with distinct 50% condensation temperatures at 726 K, 968 K, 1037 K, and 1334 K, respectively. Three of those elements (Zn, Ga, and Cu) are moderately volatile and trace elements whereas Fe is a moderately refractory and major element. Zinc, with the lowest condensation temperature in this suite, exhibits the widest range in isotopic fractionation (difference between maximum and minimum delta (δ) values in per mil, expressed as Δ hereafter) in our data set with Δ66Zn = 2.60 ‰. Gallium presents a much narrower range of fractionation with Δ71Ga = 0.62 ‰ while copper is three times lower at Δ65Cu = 0.21 ‰. Iron, with the highest condensation temperature, displays the lowest range with Δ56Fe = 0.18 ‰. Interestingly, we found that these variations in isotopic fractionation do not appear to correlate with the shock stage nor weathering grade of the samples. Our findings suggest that impacts cannot explain the observed isotopic fractionation. Evaporative loss due to thermal metamorphism on the parent body may account for Zn and Ga isotope fractionation but likely represents a minor process. Future research should investigate variously metamorphosed samples using in-situ techniques (e.g., laser ablation MC-IPC-MS or SIMS) to highlight condensation and accretion processes from the early solar nebula.

A sample preparation guide for clay‐rich carbonaceous chondrites

Article

Full-text available

Jan 2024

The matrix of the C2‐ungrouped Tarda meteorite contains abundant smectite minerals that swell and crumble when exposed to polar liquids, causing the sample to rapidly slake. This phenomenon presents a serious challenge when polishing the meteorite, as common polishing liquids used on carbonaceous chondrites, such as water, ethanol, ethylene glycol, and isopropyl alcohol, are polar and will cause the sample to swell, making it unsuitable for some analyses. Hexane and mineral oil are nonpolar liquids that were found to not induce swelling on highly expansive montmorillonite‐clay analog material and were effectively integrated into a polishing procedure for Tarda. Here, we detail a procedure for mounting, cutting, and polishing the Tarda meteorite to prepare a surface that is suitable for a variety of sensitive techniques, such as electron microprobe analysis. This work offers a practical methodology for the preparation of other clay‐rich samples, which may include the recently returned Ryugu and Bennu materials.

Strewn field, mineralogy, and petrology of Al Haggounia 001: A unique enstatite chondrite

Article

Jan 2024

In this work, we investigate macroscopic characteristics, magnetic susceptibility, mineralogy, and mineral composition of Al Haggounia 001. The samples were collected during eight field missions in the period between 2015 and 2019. In the strewn field of about 65 km in length, the specimens are found either on the surface or shallowly buried in loose sediments, which rules out the previous suggestions that this meteorite is a fossil meteorite. Macroscopically, the samples exhibit three major lithologies with various colors, porosities, and distributions of oxidized veins. The data obtained using transmitted and reflected light microscopy, scanning electron microscopy, and electron microprobe analysis confirm the macroscopic observations and show a heterogenous distribution of silicates and metal sulfides. Al Haggounia 001 is composed of enstatite, plagioclase, kamacite, taenite, schreibersite, daubreelite, troilite, graphite, sinoite, and silica polymorphs. We identified a new type of chondrules that are flattened and composed of rods of albite and enstatite, as well as elongated nodules of metal and sulfides, in addition to compression fractures in the form of subparallel veinlets. These features presumably reflect the deformation caused by shock. The magnetic susceptibility of Al Haggounia 001 (4.39 ± 0.20) is much lower than that of usual EH (5.48 ± 0.16) and EL (5.46 ± 0.04) chondrites but is in the range of E finds (5.05 ± 0.43). The thermomagnetic and hysteresis measurements are controlled by type, size, distribution of metal‐sulfide nodules, arrangement of oxyhydroxide veins, and weathering. Al Haggounia 001 is an anomalous meteorite with a polymict nature. It records multiple events revealing its unique origin which expends the groups of enstatite chondrites and provides insights into the complex formation and evolution history of their parent body.

A Comparative Study on the Radiation Attenuation Properties of Iron and Stony Meteorites: A Case of Mundrabilla and NWA 7629 Meteorites

Article

Aug 2022

Canel Eke

The goal of this paper is to compare and investigate the radiation attenuation properties of Mundrabilla and NWA 7629 meteorites in terms of the photon, fast neutron and charged particles. The linear attenuation coefficients of Mundrabilla are higher than those of NWA 7629. The half value layers, tenth value layers and mean free paths of NWA 7629 are greater than those of Mundrabilla. The effective atomic number, effective electron density, equivalent atomic number and effective conductivity of the Mundrabilla are nearly constant between 0.015 MeV–15 MeV. Both the exposure build-up factors and energy absorption build-up factors are maximum at 0.8 MeV for Mundrabilla and NWA 7629. The projected/ continuous-slowing-down approximation (CSDA) ranges for charged particles for NWA 7629 are higher than those of Mundrabilla. The fast neutron attenuation of Mundrabilla is better than those of NWA 7629. Consequently, it can be concluded that photon, fast neutron and charged particles attenuation capability of Mundrabilla are better than NWA 7629 due to the nickel content, higher density and higher content of iron.

Meteorite temperature measurements during ground testing

Article

Nov 2023
ICARUS

Classification of The Geochemical Composition of Meteorite of Punggur (Astomulyo) By k-Nearest Neighbor Algorithm

Article

Full-text available

Oct 2023

Triyana Muliawati

The fall of a meteorite in Astomulyo Village, Punggur, Lampung Province in early 2021 is an interesting topic for further study. This rare object has been suggested to have a unique geochemical composition and a special connection with other meteorites. We aimed to trace its classification by comparing it with other well-known meteorites studied previously. We approach the classification process using the k-nearest neighbor algorithm. The database used 211 represents the geochemical data for each known meteorite group from chemical analyses of meteorites. As a result, we identified that with a k-value = 5 and the proportion of test data 5/95 (in %), the geochemical composition of this meteorite is relatively close to that of the H-type chondrite group with a value accuracy of 91.67%. These results are consistent with the fact that the meteorite of Punggur has a high total iron and metallic composition.

Tying Shock Features to Impact Conditions: The Significance of Shear Deformation During Impact Cratering

Article

Full-text available

Oct 2023

Sanna Alwmark

Impact cratering is associated with extreme physical conditions with temperatures and pressures far exceeding conditions otherwise prevailing at the surfaces of terrestrial planets. As a consequence, shock‐metamorphosed rocks contain unique deformation features such as planar deformation features in quartz, high‐pressure mineral polymorphs and melted rock. While the physical conditions of formation for impact‐induced melting following the highest pressure and temperature conditions is relatively well understood, aspects of the formation of melt‐veins in otherwise seemingly relatively low shock material has been the topic of discussion. In a new study, Hamann et al. (2023, https://doi.org/10.1029/2023JE007742) are able to largely reproduce the current classification of progressive shock metamorphism of felsic rocks using a modern experimental set up that eliminates multiple shock wave reflections at sample containers and excavation and ejection of target material. Importantly, however, they find that shear deformation results in the formation of melt veins at pressures as low as 6 GPa. The authors recover stishovite in melt veins formed at low‐moderate (<18 GPa) shock pressure, lower than most previous studies. These results have bearing on our understanding of the conditions of progressive shock metamorphism at terrestrial impact structures. However, since the results are similar to data obtained from experiments on basaltic rocks, the results also have broader implications for understanding the shock histories of meteorite parent bodies. Hamann et al. show the importance of experimental impact cratering for bridging the gap between observations in shocked rocks from terrestrial impact structures, in meteorites, and in returned samples, and their formational conditions.

Magnetism of the Acapulco Primitive Achondrite and Implications for the Evolution of Partially Differentiated Bodies

Preprint

Full-text available

Sep 2023

Primitive achondrites like the acapulcoites-lodranites (AL) clan are meteorites that formed on bodies in the process of forming a metallic core, providing a unique window into how early solar system processes transformed unmelted material into differentiated bodies. However, the size and structure of the parent body of ALs and other primitive achondrites are largely unknown. Paleomagnetism can establish the presence or absence of a metallic core by looking for evidence of a dynamo magnetic field. We conducted a magnetic study of the Acapulco acapulcoite to determine its ferromagnetic minerals and their recording properties. This is the first detailed rock magnetic and first paleomagnetic study of a primitive achondrite group. We determined that metal inclusions located inside silicate grains consist of two magnetic minerals, kamacite and tetrataenite, which have robust recording properties. However, the mechanisms and timing by which these minerals acquired any natural remanent magnetization are unknown. Despite this, Acapulco has not been substantially remagnetized since arriving on Earth and therefore should retain a record dating to 4.55 billion years ago. Future studies could characterize this record by using high resolution magnetometry measurements of individual grains and developing an understanding of how and when they became magnetized. Our discovery of tetrataenite in ALs provides the first mineralogical evidence for slow cooling (~5 x 103 °C Ma-1) of the AL parent body at low temperatures (~320°C). Its presence means that the AL parent body is unlikely to have been catastrophically disrupted at AL peak temperatures (~1200°C) without subsequent reaccretion.

The quest for presolar grains: A historical perspective

Chapter

Jan 2025

Sachiko Amari

World Impact Caters

Article

Full-text available

Jul 2021

Yi Ding

This paper is a review article. It summarizes the research history and latest research achievements on meteorite craters in the world, including basic classification, key points of crater identification, world-famous craters, magmatic activities caused by meteorite impact on the earth, meteorite impact and life evolution, etc. To determine a crater, we should start with landforms with a certain radian, identify whether meteorites created craters or by other reasons, and comprehensively determine the petrological characteristics in the rock, whether there are impact metamorphic minerals, residual meteorite and gravity anomaly in the strata. Meteorites hit all the planets in the solar system, including the earth. Because of the severe weathering and erosion of the earth's surface, it is difficult for geologists to find impact craters. As of March 15, 2021, there are 190 certified craters in the global crater database, but there is only one in China. Chinese geologists still have a long way to go in discovering impact craters. It may not be very mature for recognizing a crater, but it can often change a strategy of the understanding of oil and gas exploration in an area and the theory of geological genesis in an area, and it may require the continuous efforts of several generations of scientists to form a complete evidence on a crater.

Benford’s Law: applications to chondrules and refractory inclusions

Article

Full-text available

Jan 2025
Discov Sp

Benford's Law is a scale- and base-invariant probability distribution wherein smaller numerals occur more often than higher numerals as the first digits in many large, naturally occurring datasets. In the present study, the areas of individual meteoritic chondrules and refractory inclusions were tested for conformity to Benford's Law. Datasets of chondrule, CAI, and AOA sizes from CO and CV carbonaceous chondrites from the literature were analyzed. In each dataset, the set of areas of all inclusions (chondrules and refractory inclusions combined) was found to conform most closely to Benford's Law. The area distributions are approximately log normal; they are positively skewed with decreasing numerical values from mean to median to mode. The conformity of the set of all chondrules and refractory inclusions to Benford’s Law suggests that Benford's Law may apply to the process of aerodynamic sorting in the protoplanetary disk prior to the agglomeration of chondritic planetesimals.

Metasomatic Alteration of Type 3 Ordinary and Carbonaceous Chondrites

Article

Full-text available

Jan 2025
SPACE SCI REV

Metasomatism refers to the process during which a pre-existing rock undergoes compositional and mineralogical transformations associated with chemical reactions triggered by the reaction of fluids which invade the protolith. It changes chemical compositions of minerals, promotes their dissolution and precipitation of new minerals. In this paper, we review metasomatic alteration of type 3 ordinary (H, L, LL) and carbonaceous (CV, CO, CK) chondrites, including (i) secondary mineralization, (ii) physicochemical conditions, (iii) chronology (⁵³Mn-⁵³Cr, ²⁶Al-²⁶Mg, ¹²⁹I-¹²⁹Xe) of metasomatic alteration, (iv) records of metasomatic alteration in H, O, N, C, S, and Cl isotopic systematics, (v) effects of metasomatic alteration on O- and Al-Mg-isotope systematics of primary minerals in chondrules and refractory inclusions, and (vi) sources of water ices in metasomatically altered CV, CO, and ordinary chondrites, and outline future studies.

Phyllosilicate Emission from Protoplanetary Disks: Is the Indirect Detection of Extrasolar Water Possible?

Preprint

Apr 2013

Phyllosilicates are hydrous minerals formed by interaction between rock and liquid water and are commonly found in meteorites originating in the asteroid belt. Collisions between asteroids contribute to zodiacal dust, which therefore reasonably could include phyllosilicates. Collisions between planetesimals in protoplanetary disks may also produce dust containing phyllosilicates. These minerals possess characteristic emission features in the mid-infrared and could be detectable in extrasolar protoplanetary disks. Here we determine whether phyllosilicates in protoplanetary disks are detectable in the infrared using instruments such as those on board the Spitzer Space Telescope and SOFIA (Stratospheric Observatory for Infrared Astronomy). We calculate opacities for the phyllosilicates most common in meteorites and compute the emission of radiation from a protoplanetary disk using a 2-layer radiative transfer model. We find that phyllosilicates present at the 3% level lead to observationally significant differences in disk spectra, and should therefore be detectable using infrared observations and spectral modeling. Detection of phyllosilicates in a protoplanetary disk would be diagnostic of liquid water in planetesimals in that disk and would demonstrate similarity to our own Solar System. We also discuss use of phyllosilicate emission to test the "waterworlds" hypothesis, which proposes that liquid water in planetesimals should correlate with the inventory of short-lived radionuclides in planetary systems, especially 26Al.

Cerium Stable Isotopic Composition of Non-Carbonaceous Chondrites

Article

Full-text available

Nov 2024

The elemental and isotopic compositions of the rare earth elements (REE) reveal critical information about the physicochemical dynamics of the solar nebula. Cerium (Ce) is the most abundant REE in the Solar System. It has recently received renewed attention due to the decay of 138La to 138Ce, but its stable isotopic composition still requires a better comprehension. Here, we report the Ce stable isotopic compositions (142Ce/140Ce, expressed as δ142Ce) of 18 well-characterized non-carbonaceous chondrites including 11 enstatite chondrites (EH and EL) and 6 ordinary chondrites (H, L, and LL) collected from the Antarctic, and one rumuruti chondrite collected from the Sahara Desert. The analyzed chondrites show relatively homogeneous δ142Ce compositions within 0.01 ± 0.30‰ (n = 18; 2SD). This observation indicates lack of any resolvable effects of nebular physicochemical variables, such as differences in fO2 and chemistry of the accretion regions, in different chondrites. A homogeneous isotopic composition among our analyzed samples also indicates a lack of evidence for any effects of thermal metamorphism on the δ142Ce composition of chondrites. In addition, considering a wide range of weathering degrees in our samples, we do not observe any modifications resulting from weathering. Considering the refractory and lithophile behavior of Ce and the limited variation of δ142Ce between various non-carbonaceous chondrite groups, their average will not be significantly different from the Ce isotopic composition of the Bulk Silicate Earth (BSE). We discuss the cosmochemical implications of our data and suggest extending the database of the stable isotopic composition of Ce and other REE in different types of chondrites and chondritic components.

Building Earth with pebbles made of chondritic components

Article

Nov 2024
GEOCHIM COSMOCHIM AC

Petrography and classification of NWA 14801, 14802 and 14803, HED meteorites.

Preprint

Full-text available

Oct 2024

Jose Garcia

In this report I present the petrographic characteristics and official classification of meteorites NWA 14801, NWA 14802 and NWA 14803, all of the HED group of achondrites, whose samples arrived at the laboratory during 2021 for research in order to certify them. Since the samples of scientific interest are accumulating in the laboratory repository, the process of classifying them has begun, in order to give part of them to scientific research, and officially record them with their corresponding classifications. The three meteorites were presented for official classification to The Meteoritical Bulletin in 2022, during this phase of relevant samples classification.

How to search for meteorites, and what to do when we find it.

Preprint

Full-text available

Sep 2024

Jose Garcia

Since 1986, interest in recovering meteorites in the planet's great deserts has spread to such an extent that today many teams of searchers spend entire days there, chasing rocks that have fallen from space. Although important specimens have occasionally been recovered, most of the pieces collected in the field are simple terrestrial rocks. In this work we carry out a study and propose the appropriate system for knowing how to search for meteorites and what to do when we find them. Systematizing field work will make new discoveries increase their value considerably when they are properly treated and classified.

The secondary classification of unequilibrated chondrites

Preprint

Full-text available

Sep 2024

The multiplication of decimal petrologic schemes for different or the same chondrite groups evinces a lack of unified guiding principle in the secondary classification of type 1-3 chondrites. We show that the current OC, R and CO classifications can be a posteriori unified, with only minor reclassifications, if the decimal part of the subtype is defined as the ratio

m=Fa_I/Fa_{II}

of the mean fayalite contents of type I and type II chondrules rounded to the nearest tenth (with adaptations from Cr systematics for the lowest subtypes). This parameter is more efficiently evaluable than the oft-used relative standard deviations of fayalite contents and defines a general metamorphic scale from M0.0 to M1 (where the suffixed number is the rounded m). Type 3 chondrites thus span the range M0.0-M0.9 and M1 designates type 4. Corresponding applications are then proposed for other chondrite groups. Known type 1 and 2 chondrites are at M0.0 (i.e. the metamorphic grade of type 3.0 chondrites). Independently, we define an aqueous alteration scale from A0.0 to A1.0, where the suffixed number is the (rounded) phyllosilicate fraction (PSF). For CM and CR chondrites, the subtypes can be characterized in terms of the thin-section-based criteria of previous schemes which are thus incorporated in the present framework. The rounding of the PSF to the (in principle) nearest tenth makes the proposed taxonomy somewhat coarser than those schemes, but hereby more robust and more likely to be generalized in future meteorite declarations. We propose the corresponding petrologic subtype to be 3-PSF, rounded to the nearest tenth (so that type 1 would correspond to subtypes 2.0 and 2.1). At the level of precision chosen, nonzero alteration and metamorphic degrees remain mutually exclusive, so that a single petrologic subtype

\approx

3+m-PSF indeed remains a good descriptor of secondary processes.

Planetary materials: A record of early Solar System events to planetary processes

Chapter

Sep 2024

Planetary materials provide fundamental insights into the composition and formation of the Solar System. Meteorites and their components preserve a record of the physicochemical conditions in the protoplanetary disk as well as of the evolution of planetary surfaces and interiors. Beyond the Moon, spacecraft missions have returned samples of the Solar wind (Genesis) and an S-type silcaceous asteroid (Hayabusa), as well as two C-type carbonaceous asteroids (Hayabusa2 and OSIRIS-REx) and the coma of a comet (Stardust) which sampled the outer Solar System. This chapter describes the chemical diversity of meteorites and mission returned samples and how their compositions have led to major advancements in understanding Solar System formation, planet accretion, and the building blocks of the only known life-bearing planet, Earth.

How to search for meteorites, and what to do when we find it.

Technical Report

Full-text available

Aug 2024

José García

Thermobarometric Methods for Ureilite Meteorite

Research Proposal

Full-text available

May 2024

Siddhesh Jadhav

The understanding of phase equilibrium relationships serves as a fundamental framework for comprehending the characteristics of igneous and metamorphic rocks, which originate from either the solidification of molten magma or the recrystallization of existing mineral assemblages. The process of recrystallization in rocks is instigated by the imperative of the rock or the rock/fluid system to progress toward thermodynamic equilibrium or attempt to sustain its proximity to equilibrium amidst alterations in physical and chemical conditions. Ureilites, classified as ultramafic achondrite meteorites, are believed to originate from a substantial celestial body. These meteorites feature large grains of olivine and pyroxene, exhibiting significant textural equilibrium through "triple-junction" contacts at their grain boundaries. Despite such equilibrium, ureilites also showcase primitive characteristics, including elevated levels of siderophile elements and carbon, as well as notable concentrations of noble gases. Moreover, the compositions of olivine and pyroxene within ureilites are often unaltered. The debate surrounding the origin of ureilites and their parent body persists due to the challenge of reconciling the observed textural equilibrium with these primitive traits. The proposed research aims to employ phase equilibrium modeling in conjunction with compositional analysis and comparison with computed phase relations to determine the temperature and pressure conditions at which ureilite NWA 14072 reached its last equilibrium state. Within this analytical framework, the mineral assemblage and compositions serve as a glimpse of the rock's evolutionary trajectory, offering potential insights into its parent body. This parent body could encompass scenarios such as the cooling history of a cumulated accumulation or the burial and subsequent exhumation of the rock

A Non‐Magnetized Chondrite Parent Body Revealed by Paleomagnetic Investigation of LL6 Chondrite NWA 14180

Article

Full-text available

May 2024

Magnetic records from meteorites provide valuable information about the formation and evolution of the solar system and planets. The parent planetesimals of chondrites are typically considered to be undifferentiated based on their primary chemical composition and texture. However, recent paleomagnetic investigations of various chondrites indicate that they carry a primary remanence generated by a dynamo, suggesting partial differentiation of their parent planetesimals. The presence of a dynamo within the parent planetesimal of LL chondrites remains uncertain due to the ambiguous origin of the remanent magnetism. Here, we report petrographic, paleomagnetic, and rock magnetic properties for the novel LL6 chondrite NWA 14180. The high metamorphic temperature experienced by NWA 14180 could have removed the pre‐accretionary remanence. The fusion crust baked‐contact test suggests that NWA 14180 preserves primary magnetic information about its parent body. Alternating field demagnetization results from interior subsamples reveal distinct low‐ and medium‐coercivity components that may represent a viscous remanent magnetization acquired in the geomagnetic field. No natural remanent magnetization was unblocked in the high coercivity range, implying that NWA 14180 cooled in zero‐field conditions. Therefore, we suggest that the parent body of NWA 14180 did not have a dynamo. Furthermore, this result suggests that the LL chondrite parent planetesimal accreted later and was smaller in size than other chondrite classes.

The H-poor nature of incompletely melted planetesimals: The view from acapulcoites and lodranites

Article

Apr 2024
GEOCHIM COSMOCHIM AC

Mineralogical composition, surface inspection and analysis by Mössbauer spectroscopy to identify a meteorite

Article

Full-text available

Mar 2024
Hyperfine Interact

A piece of rock belonging to the geological-mineralogical collection of the University of Antioquia, with a metallic aspect and labelled as “meteorite originating from Devil’s Canyon (USA)” was subject to several spectroscopic analysis in order to confirm that it was a meteorite. X-ray fluorescence spectroscopy (XRF) shows that Fe and Ni are present in significant amount. The elemental composition showed the rock to contain 90.63% Fe and 7.35% Ni. The remaining 2% of elements were found to be: Si, Co, P, Al and W. The X-ray diffraction (XRD) shows that the major mineralogical phase corresponds to α-Fe. Mössbauer spectroscopy (MS) measurements at room temperature indicated three iron sites present: Fe³⁺, and the others two corresponding to sextets that could be assigned to either kamacite or taenite. The inner surface was analysed using AFM (Atomic Force Microscopy). The topography of selected areas shows roughness values range from 2.99 to 86.80 nm. Finally, the metallographic images of the microstructure of the material were compared with those obtained in 2001 and it was possible to verify and conclude that the rock effectively corresponds to a meteorite.

The mineralogy and alteration history of the Yamato-type (CY) carbonaceous chondrites

Article

Sep 2023
GEOCHIM COSMOCHIM AC

Primitive FeNi metal grains in CH carbonaceous chondrites formed by condensation from a gas of solar composition

Article

Full-text available

Sep 1999

Some FeNi metal grains, ~150 μm in apparent diameter, in CH carbonaceous chondries are concentrically zoned in Ni(~5-10 wt%), Co(0.2-0.4 wt%), and Cr(0.3-0.8 wt%). Silicons present at the ~0.1 wt% level. These observations are consistent with predicted gas-solid conlensation from a gas of solar composition at temperatures of ~1370-1270 K and total pressure of ~10-4bar. Estimates of FeNi metal grain growth and cooling rates in this temperature range are consistent with brief and localized thermal episodes in the solar nebula. Compositionally similar FeNi metal grains have also been reported in CR and Bencubbin-like chondrites. Because FeNi metal is highly susceptible to secondary alteration (i.e., metamorphism, melting, oxidation), the observed FeNi metal condensates in CH, Bencubbin-like, and CR chondrites indicate that these meteorites experienced no thermal processing after their lithification and thus are among the most primitive meteorites in our collections.

Timescales and settings for alteration of chondritic meteorites

Article

Full-text available

Jan 2006

Most groups of chondritic meteorites experienced diverse styles of secondary alteration to various degrees that resulted in formation of hydrous and anhydrous minerals (e.g., phyllosilicates, magnetite, carbonates, ferrous olivine, hedenbergite, wollastonite, grossular, andradite, nepheline, sodalite, Fe,Ni-carbides, pentlandite, pyrrhotite, Ni-rich metal). Mineralogical, petrographic, and isotopic observations suggest that the alteration occurred in the presence of aqueous solutions under variable conditions (temperature, water/rock ratio, redox conditions, and fluid compositions) in an asteroidal setting, and, in many cases, was multistage. Although some alteration predated agglomeration of the final chondrite asteroidal bodies (i.e. was pre-accretionary), it seems highly unlikely that the alteration occurred in the solar nebula, nor in planetesimals of earlier generations. Short-lived isotope chronologies (²Al-²Mg, ³Mn-³Cr, ¹²I-¹²Xe) of the secondary minerals indicate that the alteration started within 1-2 Ma after formation of the Ca,Al-rich inclusions and lasted up to 15 Ma. These observations suggest that chondrite parent bodies must have accreted within the first 1-2 Ma after collapse of the protosolar molecular cloud and provide strong evidence for an early onset of aqueous activity on these bodies.

Petrology and Origin of Ferromagnesian Silicate Chondrules

Article

Full-text available

Jan 2006

Ferromagnesian silicate chondrules are major components of most primitive meteorites. The shapes, textures, and mineral compositions of these chondrules are consistent with crystallization of a molten droplet that was floating freely in space in the presence of a gas. The texture and mineralogy of a chondrule reflects the nature and composition of its precursor material as well as its thermal history. There is an enduring debate about the degree to which chondrules interacted with the ambient gas during formation. In particular, it is uncertain whether or not chondrules experienced evaporation during heating and recondensation during cooling. The extent to which these processes took place in chondrule melts varied as a function of the duration of heating as well as the environmental conditions such as pressure, temperature, composition, and size. Thus, locked in chondrule bulk compositions, mineralogy, and textures are clues to the ambient conditions of the solar nebula and the nature of material processing in the inner solar system at the early stages of planet formation. Here we survey what is known about the properties of ferromagnesian chondrules in primitive meteorites and use this information to place constraints on these important parameters.

Mineralogy, Petrography and Oxygen-Isotopic Compositions of Ca, Al-rich Inclusions and Amoeboid Olivine Aggregates in the CR Carbonaceous Chondrites

Article

Full-text available

Jan 2002

CAIs and AOAs in CRs are mineralogically pristine (unaltered). In spite of the O-isotopic homogeneity of individual CAIs, the compositions of the CR CAIs and AOAs spread almost continuously over a wide range: Delta17O = -30/00 - -240/00. All 16O-poor CAIs have igneous textures.

Oxygen isotopes in separated components of CI and CM

Article

Full-text available

Jan 1989

Chemical and physical studies of type 3 chondrites XII: The metamorphic history of CV chondrites and their components

Article

Full-text available

Nov 1995
Meteoritics

The induced thermoluminescence (TL) properties of 16 CV and CV-related chondrites, four CK chondrites and Renazzo (CR2) have been measured in order to investigate their metamorphic history. The petrographic, mineralogical and bulk compositional differences among the CV chondrites indicate that the TL sensitivity of the ~130°C TL peak is reflecting the abundance of ordered feldspar, especially in chondrule mesostasis, which in turn reflects parent-body metamorphism. The CK chondrites are unique among metamorphosed chondrites in showing no detectable induced TL, which is consistent with literature data that suggest very unusual feldspar in these meteorites. Using TL sensitivity and several mineral systems and allowing for the differences in the oxidized and reduced subgroups, the CV and CV-related meteorites can be divided into petrologic types analogous to those of the ordinary and CO type three chondrites. -from Authors

Asteroid Differentiation

Article

Full-text available

Jan 2006

Differentiation of silicate bodies was widespread in the inner solar system, producing an array of igneous meteorites. While the precursor material was certainly chondritic, direct links between chondrites and achondrites are few and tenuous. Heating by short-lived radionuclides (26Al and 60Fe) initiated melting. Formation of a basaltic crust would occur soon after the onset of melting, as would migration of the cotectic Fe, Ni-FeS component, perhaps forming a S-rich core. While some asteroids appear to be arrested at this point, many continued to heat up, with efficient segregation of metal to form large cores. Extensive melting of the silicate mantle occurred, perhaps reaching 40-75%. In the largest asteroids, the original, basaltic crust may have been resorbed into the mantle, producing a magma ocean. The crystallization of that magma ocean, whether by equilibrium or fractional crystallization, could have produced the layered structure typical of large differentiated asteroids like 4 Vesta. Spacecraft exploration of 4 Vesta promises to further extend our knowledge of asteroid differentiation.

Thermal Metamorphism in Chondrites

Article

Full-text available

Jan 2006

Thermal metamorphism has affected most chondritic meteorites to some extent, and in most ordinary chondrites, some carbonaceous chondrites, and many enstatite chondrites it has significantly modified the primary characteristics of the meteorites. Metamorphic grade, as described by the petrologic type, is one axis of the current two-dimensional system for classifying chondrites. Many changes are produced during thermal metamorphism, including textural integration and recrystallization, mineral equilibration, destruction of primary minerals, and growth of secondary minerals. Understanding these changes is critical if one hopes to infer the conditions under which chondrites originally formed. In addition to summarizing metamorphic changes, we also discuss temperatures, oxidation states, and possible heat sources for metamorphism.

Evolution of Asteroidal Cores

Article

Full-text available

Jan 2006

Magmatic iron meteorites provide the opportunity to study the central metallic cores of asteroid-sized parent bodies. Samples from at least 11, and possibly as many as 60, different cores are currently believed to be present in our meteorite collections. The cores crystallized within 100 m.y. of each other, and the presence of signatures from short-lived isotopes indicates that the crystallization occurred early in the history of the solar system. Cooling rates are generally consistent with a core origin for many of the iron meteorite groups, and the most current cooling rates suggest that cores formed in asteroids with radii of 3-100 km. The physical process of core crystallization in an asteroid-sized body could be quite different than in Earth, with core crystallization probably initiated by dendrites growing deep into the core from the base of the mantle. Utilizing experimental partitioning values, fractional crystallization models have examined possible processes active during the solidification of asteroidal cores, such as dendritic crystallization, assimilation of new material during crystallization, incomplete mixing in the molten core, the onset of liquid immiscibility, and the trapping of melt during crystallization.

Oxygen isotopic compositions of Enstatite chondrites and Aubrites

Article

Jan 1984

The rocks of Mars, from far and near

Article

Jan 2002

Harry McSween

The age, structure, composition, and petrogenesis of the martian lithosphere have been constrained by spacecraft imagery and remote sensing. How well do martian meteorites conform to expectations derived from this geologic context? Both data sets indicate a thick, extensive igneous crust formed very early in the planet's history. The composition of the ancient crust is predominantly basaltic, possibly andesitic in part, with sediments derived from volcanic rocks. Later plume eruptions produced igneous centers like Tharsis, the composition of which cannot be determined because of spectral obscuration by dust. Martian meteorites (except Allan Hills 84001) are inferred to have come from volcanic flows in Tharsis or Elysium, and thus are not petrologically representative of most of the martian surface. Remote-sensing measurements cannot verify the fractional crystallization and assimilation that have been documented in meteorites, but subsurface magmatic processes are consistent with orbital imagery indicating thick crust and large, complex magma chambers beneath Tharsis volcanoes. Meteorite ejection ages are difficult to reconcile with plausible impact histories for Mars, and oversampling of young terrains suggests either that only coherent igneous rocks can survive the ejection process or that older surfaces cannot transmit the required shock waves. The mean density and moment of inertia calculated from spacecraft data are roughly consistent with the proportions and compositions of mantle and core estimated from martian meteorites. Thermal models predicting the absence of crustal recycling, and the chronology of the planetary magnetic field agree with conclusions from radiogenic isotopes and paleomagnetism in martian meteorites. However, lack of vigorous mantle convection, as inferred from meteorite geochemistry, seems inconsistent with their derivation from the Tharsis or Elysium plumes. Geological and meteoritic data provide conflicting information on the planet's volatile inventory and degassing history, but are apparently being reconciled in favor of a periodically wet Mars. Spacecraft measurements suggesting that rocks have been chemically weathered and have interacted with recycled saline groundwater are confirmed by weathering products and stable isotope fractionations in martian meteorites.

A petrographic, electron microprobe, and ion microprobe study of mini-angrite Lewis Cliff 87051

Article

Jan 1990

Martian meteorites

Article

Jan 1998

Carbonaceous chondrites of the Omans type: A metamorphic sequence

Article

Jan 1977

Harry McSween

Refractory calcium-aluminum-rich inclusions and aluminum-diopside-rich chondrules in the metal-rich chondrites Hammadah al Hamra 237 and Queen Alexandra Range 94411

Article

Sep 2001
Meteoritics

The metal-rich chondrites Hammadah al Hamra (HH) 237 and Queen Alexandra Range (QUE) 94411, paired with QUE 94627, contain relatively rare (

Lunar samples

Article

Jan 1998

Lewis Cliff 85332: A unique carbonaceous chondrite

Article

Jan 1990
Meteoritics

The classification of meteorites

Article

G. Prior

Are carbonaceous chondrites primitive or processed? A review

Article

Aug 1979
REV GEOPHYS

Harry McSween

Carbonaceous chondrites, generally considered to be the most primitive surviving materials from the early solar system, form a distinctive group in terms of bulk Mg/Si, Ca/Si, and Al/Si ratios. The carbonaceous chondrites can be subdivided into five groups (CI, CM, CR, CO, and CV) based on a number of petrologic and chemical criteria. Petrographic observations indicate that most carbonaceous chondrites have been processed, either by thermal metamorphism in the case of CO and CV chondrites or by low-temperature aqueous alteration in the case of CI, CM, and CR chondrites. Thermal metamorphism resulted in Fe/Mg exchange between chondrules, olivine and pyroxene grains, and matrix, changes in the compositions of metal grains, and textural integration. Aqueous alteration probably produced hydrated phyllosilicate matrix phases and resulted in alteration of chondrules and replacement and vein filling by secondary carbonates and sulfates. The changes incurred during these processes appear to have been largely isochemical. However, if certain constituents behaved as open-system components, volatile elements or compounds may have been depleted during metamorphism, and isotopic patterns may have been changed during aqueous alteration. The recognition of two different types of postaccretional processes resulting in petrological modifications necessitates a reinterpretation of the classification system for carbonaceous chondrites.

Article

Jan 1996
GEOCHIM COSMOCHIM AC

The K (Kakangari) chondrite grouplet

Article

Jan 1996
GEOCHIM COSMOCHIM AC

Oxygen isotope studies of achondrites

Article

Jun 1996
GEOCHIM COSMOCHIM AC

Oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites. Among the differentiated achondrites, three isotopic groups are recognized: (l ) SNC (Mars), (2) Earth and Moon, and (3) HED (howardites, eucrites, diogenites). The HED group also contains the mesosiderites, main-group pallasites, and silicates from IIIAB irons. The angrites may be marginally resolvable from the HED group. Within each of these groups, internal geologic processes give rise to isotopic variations along a slope- fractionation line, as is well known for terrestrial materials. Variations of Δ17O from one planet to another are inherited from the inhomogeneities in the solar nebula, as illustrated by the isotopic compositions of chondrites and their constituents. Among the undifferentiated achondrites, five isotopic groups are found: (1) aubrites, (2) winonaites and IAB-IIICD irons, (3) brachinites, (4) acapulcoites and lodranites, and (5) ureilites. The isotopic compositions of aubrites coincide with the Earth and Moon, and also with the enstatite chondrites. These bodies apparently were derived from a. common reservoir, the isotopic composition of which was established at the chondrule scale by nebular processes. Isotopic similarities between chondrites and achondrites are seen only for the following instances: (1) enstatite chondrites and aubrites, (2) H chondrites and HE irons, and (3) L or LL chondrites and IVA irons. The isotopic data also support the following genetic associations: (1) winonaites and IAB-IIICD irons, (2) acapulcoites and lodranites, and (3) ureilites and dark inclusions of C3 chondrites. An attempt to reconcile the whole-planet isotopic compositions of Earth, Mars, and the eucrite parent body with mixing models of their chemical compositions failed. It is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive Solar System components.

Tafassasset: A Metal-rich Primitive Achondrite with Affinities to Brachinites

Article

Mar 2003

Tafassaset is a new brachinite-like meteorite. Its texture and mineralogy are similar to Brachina but it has a high metal abundance. Its oxygen isotopes differ from Brachina and the main group bachinites and plot near the LEW 88763 brachinite.

Growth mechanism and additional constraints on FeNi metal condensation in the solar nebula

Article

Dec 2001
J GEOPHYS RES

Chemically zoned FeNi metal grains in the metal-rich chondrites QUE 94411 and Hammadah al Hamra 237 formed by gas-solid condensation in the temperature range from ∼1500 to 1400 K during highly energetic thermal events in the solar nebula. We observe a linear correlation between the apparent diameter of the zoned FeNi metal grains and their inferred condensation temperature interval, which indicates that the grain growth rate was essentially constant. This lends strong support for a kinetic “hit-and-stick” growth model that yields growth timescales of ∼20–85 hours and gas cooling rates of ∼1–2 K h−1 for six representative zoned metal grains studied in QUE 94411. In the core regions of the zoned metal grains the Ni concentration is systematically lower than the thermodynamically predicted values, suggesting that solid-state diffusion played an important role in shaping the zoning profiles. Combined with existing data, our observations provide a set of constraints on the physics and chemistry of large-scale, high-temperature processes in the earliest solar nebula, which present astrophysicists with profound challenges.

Yamato-8002: Partial melting residue on the "unique" chondrite parent body

Article

Mar 1992

Hiroko Nagahara

An overview of the research consortium, "Antarctic carbonaceous chondrites with CI affinities, Yamato-86720, Yamato-82162, and Belgica-7904"

Article

Mar 1992

Yukio Ikeda

Yamato-86720: A CM carbonaceous chondrite having experienced extensive aqueous alteration and thermal metamorphism

Article

Jan 1989

Comparative Planetary Mineralogy: Chemistry of Melt-derived Pyroxene, Feldspar, and Olivine

Article

Mar 1998

J. J. Papike

Dhofar 225 vs. the CM Clan: Metamorphosed or New Type of Carbonaceous Chondrite?

Article

Jan 2002

Dhofar 225 is an anomalous carbonaceous chondrite. It demonstrates some characteristics of CM chondrites and also has some similarities to metamorphosed carbonaceous chondrites. Dhofar 225 probably has been affected by moderate or low heating.

The Dar al Gani 319 Polymict Ureilite and Its Lithic and Mineral Clasts

Article

Jul 2000
Meteoritics

Modal abundances of minerals of primitive achondrites and the endmember mineral assemblage of the differentiation trend

Article

Jan 1997

Ningqiang and Its Relationship to Oxidized CV3 Chondrites

Article

Jan 1996

Volatile-poor Chondrules in CH Carbonaceous Chondrites: Formation at High Ambient Nebular Temperature

Article

Mar 2000

Meteorite Kaidun - Composition and History of Formation

Article

Jan 1989

A. V. Ivanov

The Kaidun meteorite is characterized by a unique heterogeneity and consists of four rare types of meteoritic matter: CR2, C1, EH5, and EL3. The EL3 indicates the presence of two discrete groups of enstatite chondrites, EH and EL. The very unusual composition of the meteorite indicates that an unusual complex of processes acted during the formation of the parent body, including hydrothermal alteration of the material and the transport of metals in the form of carbonyl compounds.

Heideite, (Fe,Cr)1+x(Ti,Fe)2S4, A new mineral in the Bustee enstatite achondrite

Article

Jan 1973
Meteoritics

Pyroxene Pallasites: A New Pallasite Grouplet

Article

Sep 1995
Meteoritics

A new pallasite grouplet, the pyroxene pallasites, consisting of the meteorites Vermillion and Y8451, has been identified by petrologic, trace element, and oxygen isotopic data. Vermillion is a new 27 kg find from central Kansas with a texture that differs from main group (MG) and Eagle Station (ES) pallasites and consists of about (vol. %) 86 FeNi metal and 14 silicates. The silicates are interspersed with metal along bands up to 1.5 cm wide within the metal host. These bands contain micron to cm-sized silicates, including rounded to subrounded olivine (up to 1.5 cm), as well as orthopyroxene, chromite, and merrillite. Y8451, previously described in [1], is texturally similar to MG pallasites and consists of FeNi metal, rounded to subangular olivine (up to 1 cm), pyroxene, chromite, and merrillite. Modally, Vermillion silicates consist of (vol. %) about 93 olivine, 5 opx, 1.5 chromite, 0.5 merrillite, while Y8451 silicates consist of about 94 olivine, 4.8 opx, 1.1 cpx, and 0.1 merrillite. Vermillion olivine (Fo(sub)(87.0-88.9)) is comparable to MG pallasite olivine [2], while that of Y8451 (Fo(sub)(88.8-89.8)) is slightly more magnesian than MG [1]. Vermillion pyroxene (En(sub)(86-88.5) Wo(sub)(0.5-2.5)) typically occurs along the rims of smaller olivine grains, although larger pyroxene inclusions (up to 1 mm) of the same composition are sometimes found within olivine grains. Y8451 has two types of opx, a lower-Ca opx (En(sub)(89.1) Wo(sub)(0.6)) with 0.3 wt% CaO, and a higher-Ca opx (En(sub)(87.6-88.1) Wo(sub)(1.9-2.3)) with 1 wt% CaO; the lower-Ca opx coexists with cpx (En(sub)(51.5-51.8) Wo(sub)(43.7-44.1)). The higher-Ca opx has a smoothly fractionated REE pattern increasing from 0.3 x CI for La to 2.5 x CI for Lu, with no Eu anomaly, and does not appear to be in equilibrium with cpx, which has a fairly flat REE pattern at about 5 x CI (Fig. 1). The lower-Ca opx, however, is in equilibrium with cpx. Merrillites in Y8451 and Vermillion have relatively flat LREE (2 x CI) patterns, with HREE increasing to near 100 x CI in Lu, and do not appear to be in equilibrium with the higher-Ca opx or cpx. FeNi metal in Vermillion has a fine octahedrite texture and contains 65 micrograms/g Cr, 4.9 mg/g Co, 75 mg/g Ni, 130 micrograms/g Cu, 44 micrograms/g Ga, 13 micrograms/g As, 0.7 micrograms/g W, 1.9 micrograms/g Ir, and 1.4 micrograms/g Au. The metal is ungrouped and differs from MG or ES pallasite metal. Y8451 metal has not yet been analyzed. Oxygen isotopic compositions of olivine are similar in Vermillion (delta^(18)O=2.24, delta^(17)O=0.40, Delta^(17)O=-0.76) and Y8451 (delta^(18)O=2.26, delta^(17)O=0.41, Delta^(17)O=-0.77) and plot (Fig. 2) below the MG pallasite mass fractionation line (Delta^(17)O=-0.32). Pyroxene pallasites are clearly resolved from MG pallasites, as well as the acapulcoite-lodranite, and IAB-IIICD-winonaite groups. Conclusions: (1) Pyroxene pallasites constitute a new pallasite subgroup. (2) Application of the two-pyroxene thermometer [2] to Y8451 indicates an equilibration temperature of about 1000 degrees C. (3) The disequilibrium between silicates and phosphates is consistent with formation of merrillite by subsolidus reaction between metal and silicate where merrillite inherits the REE patterns of the olivine and orthopyroxene that probably formed as cumulates from a chondritic melt [3]. (4) The higher-Ca opx may be a xenocryst because of its disequilibrium pattern with the coexisting silicates. (5) The presence of pyroxene coexisting with olivine in pyroxene pallasites, in contrast to olivine alone in MG pallasites, may indicate a lower temperature of crystal accumulation for the pyroxene pallasites, assuming they both started from a similar chondritic melt. (6) The presence of three pallasite groups or grouplets may be indicative of three parent bodies, with only the MG pallasites related to the HED group. (7) Whatever the cause of the unusual metal-silicate relations in pallasites, this situation must have occurred in three different settings. References: [1] Yanai K. and Kojima H. (1995) Proc. NIPR Symp. Antarc. Meteorites, 8, 1-10. [2] Lindsley D. H. and Andersen D. J. (1983) Proc. LPSC 13th, in JGR, 88, A887-A906. [3] Davis A. M. and Olsen E. J. (1991) Nature, 353, 637-640.

Tafassasset: An Equilibrated CR Chondrite

Article

Mar 2002

Based on textural, compositional and isotopic evidence, the newly discovered chondrite Tafassasset is the first metamorphosed CR known.

A Chemical-petrologic Classification for the Chondritic Meteorites

Article

Jan 1967
GEOCHIM COSMOCHIM AC

A two-dimensional classification grid based on chemical and petrologic subdivisions of the chondritic meteorites is proposed. This grid extends the current chemical subdivisions to account for varying petrologic (implied metamorphic) properties of chondrites within the primary chemical groups. Six petrologic types are recognized, which, together with the five major chemical groups, produce 30 possible chondritic types. Representatives of 20 of the types are known. An Appendix giving the extended classification for 460 chondrites is included.

Plagioclase-augite-rich gabbro in the Caddo County IAB Iron and the missing basalts associated with iron meteorites (abstract)

Article

Jan 1997

Absence of basalts related to the formation of iron meteorites in the meteorite collections has been a mystery in Meteoritics. We found gabbroic materials rich in plagioclase and augite in the Caddo County IAB iron meteorite in the polished thin sections (PTS) made from areas rich in Al and Ca detected by the microfocus X-ray fluorescence (XRF) mapping technique. Discovery of another type of basaltic materials associated with iron meteorites, which are the products of partial melting, suggests that they were not lost into space as the explosive volcanism model proposed.

Petrology and Geochemistry of Lodranite GRA 95209

Article

Jul 1998

Frontier Mountain 93001: An Igneous-Textured Member of the Acapulco-Lodran Clan

Article

Jul 2003

EH3 and EL3 Chondrites: A Petrologic-Oxygen Isotopic Study

Article

Jan 1995

Meteorites: A Petrologic, Chemical and Isotopic Synthesis

Article

Jan 2004

Robert Hutchison

Opaque Minerals in the GRA 95209 Lodranite: A Snapshot of Metal Segregation

Article

Jan 1998

QUE 94204 - an EH-chondritic melt rock

Article

Mar 1997

We present a petrologic study of QUE 94204 (Q94), a new E meteorite, tentatively described as an E7. Our purpose is to understand the petrogenesis of Q94 in relation to other E meteorites and their parent bodies, and explore the question of impact vs internal melting on E chondritic parent bodies.

A Survey of Calcium-Aluminum-rich Inclusions from R Chondrites: Implications for Relationships Between Meteorite Groups

Article

Jul 1998

S. S. Russell

Condensation of Rocky Material in Astrophysical Environments

Article

Jan 2006

D. S. Ebel

Volatility-dependent fractionation of the rock-forming elements at high temperatures is an early, widespread process during formation of the earliest solids in protoplanetary disks. Equilibrium condensation calculations allow prediction of the identities and compositions of mineral and liquid phases coexisting with gas under presumed bulk chemical, pressure, and temperature conditions. A graphical survey of such results is presented for systems of solar and nonsolar bulk composition. Chemical equilibrium was approached to varying degrees in the local regions where meteoritic chondrules, Ca-Al-rich inclusions, matrix, and other components formed. Early, repeated vapor-solid cycling and homogenization, followed by hierarchical accretion in dust-rich regions, is hypothesized for meteoritic inclusions. Disequilibrium chemical effects appear to have been common at all temperatures, but increasingly so in less-refractory meteoritic components. Work is needed to better model high-temperature solid solutions, indicators of these processes.

Adelaide and Bench Crater - Members of a new subgroup of the carbonaceous chondrites

Article

Dec 1977
Meteoritics

The composition and mineralogy of Bench Crater and a new carbonaceous chondrite (Adelaide) are compared. They, Kakangari and possibly certain carbonaceous xenoliths from other meteorites constitute a distinct chemical subgroup of the carbonaceous chondrites characterized primarily by a calcium-to-aluminum ratio (atomic) of about 0.5. It is proposed to call this group the Kakangari (CK) group.

LEW 87223: A Unique E Chondrite with Possible Links to H Chondrites

Article

Jan 1993
Meteoritics

LEW87223 (paired with LEW87057, 87220, and 87234) is an enstatite chondrite with unique textural and compositional properties. The Si content of metal (~0.5%), the presence of alabandite instead of niningerite, and the bulk WNi ratio in this chondrite are all consistent with an EL classification, but the high metal (23 wt%) and siderophile element abundances are closer to those in the EH group [1,2]. The moderately volatile elements, Mn, Na, K, As, Ga, and Se are all depleted relative to EH and EL chondrites [2]. The presence of olivine is consistent with an E3 classification. Oxygen isotopes in LEW87220 and 87234 are in the EH and EL chondrite field [R. Clayton, priv. comm., 1993]. Zhang et al. [2] suggested that this meteorite formed from an EL3 chondrite that experienced fractionation during impact and brecciation. Shock and thermal processing undoubtedly occurred, but our work suggests that LEW87223 was not derived from normal EL starting material. A precursor with properties intermediate between H and E chondrites seems to be indicated. LEW87223 has an opaque-mineral assemblage unlike that of other E chondrites. It has EH-like amounts of metal and troilite, schreibersite is common, but penyite, sphalerite, and djerfisherite (all found in EH3 and EL3 chondrites; [3]) were not observed. Oldhamite does occur as rare, transparent, pink crystals up to 100 micrometers in size, completely enclosed in kamacite. Metal grains are comparable in size to chondrules, and equant. Although it is a type 3, LEW87223 chondrules commonly appear to be welded together, and share long boundaries with other chondrules and metal grains. The olivines show features consistent with shock stage 2 of Stoffler et al. [4]. Alabandite is Fe-rich [2] and occurs as recrystallized aggregates along FeS grain boundaries [A. El Goresy, priv. comm., 1993]. Many chondrules appear dark or opaque in transmitted light due to abundant sub-micrometer, pure Fe metal intergrown with enstatite and silica, all of which partially replace ferroan pyroxene ^FS(sub)15-18). All of these features are consistent with a history involving strong reduction, shock, and heating. We analyzed four large, unweathered oldhamite grains in LEW87220 and 87234 by ion probe, and found trace element characteristics similar to those seen in MAC88136, the only known EL3 chondrite [3]: Mg, Sr, and Zr are lower, and Mn is higher than in EH oldhamite. One grain has a REE pattem that is flat at 60 x CI for LREE, and decreases from 46 x CI at Eu to 15 x CI at Lu, with a positive Yb anomaly (Yb/Yb*=3). The other grains have flat REE patterns near 75 x CI, with negative Eu anomalies (Eu/Eu*=0.4). The first pattern is most likely nebular in origin. The second, more common pattern, with the negative Eu anomaly is unlikely to be nebular, and may be metamorphic in origin, in which case the meteorite contains a mixture of nebular and metamorphic oldhamite. Zhang et al. [2] explained the low abundances of alkalis, Mn, Ga, and Se, and high abundance of siderophiles in LEW87223 as being due to the addition of EL metal, and removal of sulfides during shock and thermal processing of a normal EL3. This seems highly implausible to us because of the physical difficulty of completely separating minor sulfides from FeS and metal, and because perryite, which is intimately associated with metal in E chondrites, is missing. It is more likely that the chondrite represents an entirely new group of E chondrites. The high abundance (10s of %) of blackened (reduced) chondrules also indicates a population of chondrules that was initially quite oxidized; in fact, the measured compositions of surviving ferroan pyroxene are in the H-chondrite range. Also evident in the published trace element data [2] is a siderophile element abundance pattern identical to that in H chondrites but different from those in EH and EL chondrites. LEW87223 may be a link between the ordinary and enstatite chondrite groups. References: [1] Mason (1989,1992) Ant. Meteor. Newslett., 12(1) and 15(1,2). [2] Zhang et al. (1993) LPS XXIV, 1571. [3] Lin et al. (1991) LPS XXll, 811. [4] Stoffler et al. (1991) GCA, 55, 3845.

Geochemical Relationships Between Some Pallasites and Iron Meteorites

Article

Jun 1977

Edward R. D. Scott

Published analyses for 14 trace and minor siderophilic elements have been interpreted to indicate a close relationship between the IIIAB iron meteorites and the main group of pallasites. These two groups respectively account for about 32 and 75 % of all irons and pallasites. The composition of the metal in the main group pallasites is very close to that calculated for the liquid after 8o % of a IIIAB iron melt has fractionally crystallized. The pallasites probably formed by the intrusion of residual molten metal from the core into

Systematics and Evaluation of Meteorite Classification

Abstract

No full-text available

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