bluuebunny/crossref_metadata_2025 huggingface dataset:
RAGLAND, AN LL3.4 CHONDRITE FIND FROM NEW MEXICO
Authors: Recca S.I. , Scott E.R.D. , Keil K. , Clayton R.N. , Mayeda T.K. , Huss G.I , Jarosewich E. , Weeks K.S. , Hasan F.A. , Sears D.W.G. , Wieler R. , Signer P.
Published: June 2012

The Ragland, New Mexico chondrite was found in 1978, and consists of a single stone of 12.16 kg that broke into three pieces. The stone is moderately weathered and has a pronounced chondritic texture. Bulk composition favors an LL classification, and modal analysis and oxygen isotopic composition are consistent with this. The thermoluminescence sensitivity of 0.056 ± 0.020 normalized to Dhajala, compositional variability of olivine (mean Fa 18.3, σ = 10.1) and low‐Ca pyroxene (mean Fs 14.6, σ = 6.7), and Ca concentrations in olivine indicate metamorphic subtype 3.4 ± 0.1. The isotopically heavy oxygen composition, which is characteristic of subtypes 3.0–3.1, may be a primary characteristic and not a result of weathering. Low concentrations of radiogenic 40Ar and planetary 36Ar suggest noble gas loss.
A DETERMINATION OF THE ABSOLUTE AGES OF SEVEN FRONT FACE LUNAR BASINS†
Authors: BALDWIN RALPH B.
Published: June 2012

Careful examination of seven giant front face basins on the moon will show that the basins most densely covered by younger craters are the oldest. With increasing age they exhibit lower external rims, not scarp heights. The rims are progressively more subdued with age. This paper proposes that absolute ages for these basins can be obtained by calculating an effective viscosity of the moon's outer layers from 3.85 × 109 y, the date of Imbrium, to the present. Similarly viscosity measures can be determined for the oldest basin. To do this we need the present and the original rim heights. The present values are observed. The original heights are calculated by extrapolating the relationship between diameter and rim height for normal Class I craters. It turns out that as long as the larger basins have proportionately higher original heights than the smaller, the absolute values are of little importance and the ages are definitive. There are many similar families of viscosity changes with age and they yield similar absolute ages. In each case equations relating viscosity changes with age were derived and for each basin there is only one age that will yield the final rim height. Ages, × 109 y, of the basins are: Orientale 3.82, Imbrium 3.85, Crisium 4.00, Nectaris 4.07, Serenitatis 4.14, Humorum 4.23 and an Unnamed basin between Werner and the Altai ring 4.30.
LATE EOCENE IMPACT MICROSPHERULES: STRATIGRAPHY, AGE AND GEOCHEMISTRY
Authors: Keller G. , D'Hondt S.L. , Orth C.J. , Gilmore J.S. , Oliver P.Q. , Shoemaker E.M. , Molina E.
Published: June 2012

Recent discoveries of microtektite and related crystal bearing microspherule layers in deep‐sea sediments of the west equatorial Pacific DSDP Sites 292, 315A and 462, off‐shore New Jersey in Site 612 and in southern Spain have confirmed the presence of at least three microspherule layers in Late Eocene sediments. Moreover, these discoveries have extended the North American strewn field from the Caribbean and Gulf of Mexico region to the northwest Atlantic, and have established a third strewn field in western equatorial Pacific and Indian Ocean which may extend to the Mediterranean.

Stratigraphically the oldest microspherule layer occurs in the planktonic foraminifer Globigerapsis semiinvoluta Zone about 0.5 m.y. prior to the closely spaced crystal bearing microspherule layer and North American microtektite layer in the Globorotalia cerroazulensis Zone. Major element composition of the G. semiinvoluta Zone layer and the crystal bearing microspherule layer overlap, but there is a clear trend towards higher Al2O3 and FeO values in SiO2 equivalent microspherules of the latter layer. The G. semiinvoluta Zone microspherules also contain a higher percentage of non‐crystalline spherules (microtektites) than the crystal bearing microspherule layer, but lower than the North American microtektite layer. Excess iridium due to an abrupt increase in supply is associated with the middle crystal bearing microspherule layer and to a lesser extent with the other two layers. But, Ir excess due to concentration as a result of carbonate loss was also observed at two sites (462, 612).

The three late Eocene microspherule layers do not precisely coincide with planktonic foraminiferal species extinctions, but a major faunal assemblage change is associated with the G. semiinvoluta Zone layer. Abundant pyrite is present in the North American microtektite layer of DSDP Site 612 suggesting reducing conditions possibly due to a sudden influx of biologic matter (dead bodies) to the ocean floor, and the crystal bearing microspherule layer coincides with five radiolarian extinctions. All three microspherule layers are associated with decreased carbonate possibly due to sudden productivity changes, increased dissolution as a result of sea‐level and climate fluctuations, or the impact events.
MAJOR ELEMENT COMPOSITIONAL VARIATION WITHIN AND BETWEEN DIFFERENT LATE EOCENE MICROTEKTITE STREWNFIELDS
Authors: D'Hondt Steven L. , Keller Gerta , Stallard Robert F.
Published: June 2012

Major element compositional overlap exists between microspherules of different microtektite layers or strewnfields. For this reason, microspherules of similar composition cannot, a priori, be assumed to belong to the same microtektite event and those of different compositions cannot, a priori, be assumed to result from different events. Nevertheless, despite major element compositional overlap between microspherules of different strewnfields, multivariate factor analysis shows microtektites and related microspherules of three stratigraphically different late Eocene layers to follow recognizably different compositional trends.

The microtektite population of the North American strewnfield (Globorotalia cerroazulensis Zone) follows compositionally well defined trends and is characterized by high concentrations of SiO2, Al2O3, and TiO2. The microspherule population of the slightly older crystal‐bearing Globorotalia cerroazulensis Zone microspherule layer is more heterogeneous and characterized by microspherules which are relatively enriched in FeO and MgO and relatively impoverished in SiO2 and TiO2. The microspherule population of the oldest microspherule layer in the uppermost Globigerapsis semiinvoluta Zone is highly heterogeneous and characterized by microspherules which are relatively enriched in CaO and impoverished in Al2O3 and Na2O. Individual microspherules of this oldest late Eocene horizon often exhibit major element compositions similar to those of the lower Gl. cerroazulensis Zone layer and occasionally exhibit major element compositions similar to North American layer microtektites. Nevertheless, late Eocene microspherule occurrences can be assigned to appropriate late Eocene microtektite horizons on the basis of major element compositional trends.
MONTICELLO: A GLASS‐RICH HOWARDITE
Authors: Olsen Edward J. , Dod Bruce D. , Schmitt Roman A. , Sipiera Paul P.
Published: June 2012

Monticello is a new howardite similar to Malvern in that it contains abundant (15%) glass fragments. These fragments show a range of compositions from olivine‐normative to quartz‐normative. Like Kapoeta, it contains pyroxene grains that range up to highly magnesian compositions, Fs16. Because their pyroxenes are more magnesian than those occurring in diogenites, Monticello and Kapoeta are exceptions to the simple two‐component mixing model in which howardites are considered to be mechanical mixtures of fragmented eucrites and diogenites. Monticello also contains clasts of what appear to be a cumulate eucrite and a non‐cumulate eucrite, as well as a radiating pyroxene chondrule from a chondrite. Monticello is a regolith breccia containing more evolved components than are usually considered in eucrite‐diogenite genesis models. As such, it supports those models that involve reworking of a complex parent body crust rather than straightforward partial melting of primitive chondritic parent material.
The Binningup H5 Chondrite: A New Fall from Western Australia
Authors: Bevan A. W. R. , McNamara K. J. , Barton J. C.
Published: June 2012

Abstract— Following a brilliant daylight fireball at 10:10 a.m. (local time) on 30 September 1984, a single stone weighing 488.1 grams was recovered from Binningup beach (33°09′23″S, 115°40′35″E), Western Australia. Data from 23 reported sightings of the fireball indicate an angle of trajectory 20–40° from the horizontal, a flight‐path bearing N210°E and an end‐point (ca. 32°39′S, 115°54.5′E) at a height of ∼20–30 km.

A recrystallized chondritic texture and the presence of olivine and low‐Ca orthopyroxene with compositions of Fa18.4 (PMD 1.1)and Fs16.1 (PMD 1.1), respectively, show that Binningup is a typical member of the H‐group of ordinary chondrites. Uniform mineral compositions and the presence of generally microcrystalline plagioclase feldspar indicate that the meteorite belongs to petrologic type 5. Pervasive fracturing of silicates suggests mild pre‐terrestrial shock loading.

Measurements (dpm kg−1) of cosmogenic radionuclides including 22Na (61 ± 5), 26Al (49 ± 3) and 54Mn (66 ± 10) indicate a normal history of irradiation.
A New Component of the Mezö‐Madaras Breccia: A Microchondrule‐ and Carbon‐Bearing L‐Related Chondrite
Authors: Michel‐Lévy Miteille Christophe
Published: June 2012

Abstract— Microchondrules with apparent diameters of 2 to 150 μm are found in a black carbon—bearing inclusion in Mezö‐Madaras. Some are homogeneous (glassy or micro‐crystalline) others show two phases: mainly silica and a pyroxene‐rich glass. The bulk chemical composition of the inclusion is related to the host‐chondrite in which silica‐pyroxene chondrules are ubiquitous. Small black lumps of the same kind are dispersed in bulk Mezö‐Madaras. This L‐related carbon‐bearing material may represent a new specimen of C‐rich ordinary chondrite.
Trace Element Partitioning between Taenite and Kamacite; Relationship to the Cooling Rates of Iron Meteorites
Authors: Rasmussen Kaare L. , Malvin Daniel J. , Wasson John T.
Published: June 2012

Abstract— Instrumental neutron activation analysis (INAA) was used to determine Ni, Co, Cu, Ga, As, Au, W, Re and Ir in taenite lamellae isolated by acid dissolution from eight iron meteorites from groups IA, IIIAB and IVA. Taenite is enriched in Ni, Cu, Ga, As, Au, W, Re and Ir relative to kamacite, whereas taenite is depleted in Co. Taenite/kamacite partition ratios in slowly cooled IAB meteorites are farther from unity than those in rapidly cooled IVA meteorites. Taenite/kamacite partition ratios for Cu, Ir, Au and Co may be sensitive cooling rate indicators.
Petrology and Pairing of Mesosiderites from Victoria Land, Antarctica
Authors: Hewins Roger H.
Published: June 2012

Abstract— The Allan Hills mesosiderites A77219, A81059 and A81098 are classified as subgroup 1B (Hewins, 1984), on the basis of very fine‐grained silicate matrix, low plagioclase content and absence of highly ferroan pyroxenes. Since they are so similar petrologically, it is reasonable to pair them. ALHA 81208, a highly weathered orthopyroxenite, is probably a clast from one of the Allan Hills mesosiderites. Reckling Peak A80258, is a Floran 2B or Hewins 4B mesosiderite. It contains reversely zoned orthopyroxene clasts in a sparse matrix with interstitial/poikilitic plagioclase and highly magnesian (chadacryst) orthopyroxene (close to En80). All pyroxene is much lower in FeO/MnO than Allan Hills mesosiderite pyroxene of similar FeO content. The other Reckling Peak mesosiderites A79015, A80229, A80246 and A80263 contain orthopyroxene and recrystallized orthopyroxenite clasts in a metal‐troilite matrix. Orthopyroxenite clasts in ALH A81059 are very similar texturally and modally to RKPA 79015 orthopyroxenite, but differ in pyroxene composition. Orthopyroxene in RKPA 79015 (Prinz et al., 1982) is very similar in Fe/Mg and Fe/Mn to the cores of (reversely zoned) pyroxene clasts in RKPA 80258. On this basis, RKPA 80258 is related to the other Reckling Peak mesosiderites and they could all be paired, assuming that three components (metal, pyroxenite and silicate matrix) were very irregularly mixed in these breccias. Pairing is problematical, in that specimens of a polymict breccia can be so different that they would not be paired if they were not known to have fallen together. The silicate fraction of mesosiderites ranges from diogenitic (RKPA 79015) to analogous to polymict eucrite (Dyarrl Island) although the silicate fractions are not equivalent in detail. The mesosiderite subdivision scheme is amended recognizing this, permitting the classification of the formerly “anomalous” RKPA 79015.
The Cuban Tektite Revisited
Authors: Koeberl Christian
Published: June 2012

Abstract— A tektite, probably found in Cuba, was previously classified as belonging to the North American tektite strewn field on the basis of chemistry, age, isotopic, and petrographic characteristics. New major element analyses and trace element analyses show that the sample falls within the range of other North American tektites, and is close to the bediasite compositions. There are, however, some differences to normal georgiaites and bediasites. In a Na2O/K2O diagram the sample plots between the two distinct fields formed by georgiaites and bediasites. The rare earth elements and some lithophile trace elements are slightly enriched compared to bediasites, and much higher than in georgiaites. The discovery of tektite fragments from locations at Barbados and a DSDP site off the coast of New Jersey makes it likely that the North American strewn field is larger than previously thought, in agreement with microtektite distributions. Thus it is possible that the “Cuban” tektite really originated from Cuba.
Moldavites from Austria
Authors: Koeberl C. , Brandstätter F. , Niedermayr G. , Kurat G.
Published: June 2012

Abstract— Several moldavites have been discovered in the northern part of Lower Austria. Tektites from two new locations (Altenburg and Radessen) have been analyzed. These new finds lend credibility to old reports about tektites from Lower Austria, some of which are associated with artefacts of prehistoric cultures. The new locations are situated between the Bohemian and Moravian parts of the moldavite strewn field, which is thus shown to extend further south than previously known. Most of the samples show clear indications of surface alterations by water and/or humic substances, and one sample shows signs of fluviatile transport. The geological setting of the moldavite‐bearing sediments is similar to the Czechoslovakian occurrences but is probably less disturbed. Chemically the samples show considerable variations even within one location. No unambiguous association with either the Bohemian or the Moravian group is evident either for the major or trace element abundances.
Classification of Six Ordinary Chondrites from Texas
Authors: Ehlmann Arthur J. , Keil Klaus
Published: June 2012

Abstract— Based on optical microscopy, modal and electron microprobe analyses, six ordinary chondrites from Texas preserved in the Monnig Meteorite Collection at Texas Christian University, Fort Worth, Texas, were classified in compositional groups, petrologic types, and shock facies. These meteorites are Comanche (stone), L5c; Haskell, L5c; Deport (a), H4b; Naruna (a), H4b; Naruna (b), H4b; and Clarendon (b), H5d.
An Iron Meteorite from Akyumak
Authors: ÇOlakoglu K. , Ceylan M.
Published: June 2012

Abstract— The microstructure of an iron meteorite which fell near Akyumak, East Anatolia, Turkey on 2 August 1981 has been examined and its composition determined. The Ni content is 7.7% and kamacite bandwidth is 0.32 ± 0.06 mm. The kamacite contains Neumann bands and some daubreelite inclusions. Taenite and plessite account for about 45 to 50% of the metal; finger, cellular and net plessite are observed. Gallium (1.9 ppm), Ge (< 40 ppm) and Ir (1.81 ppm) were determined by neutron activation. The microstructural observations and chemical data show Akyumak to be a fine octahedrite and a member of group IVA.
The Kirbyville Eucrite
Authors: Jackson Hiram S. , Ehlmann Arthur J.
Published: June 2012

Abstract— The Kirbyville meteorite is an equilibrated monomict eucrite with a mode (calculated in wt.%): plagioclase 37, inverted pigeonite 58, silica 3, ilmenite 1.4 and troilite 0.3. The pyroxene compositional range is Wo 2–42, Fs 27–62, En 30–40 with an average of Wo 7. The plagioclase average mean is An 89. Kirbyville is one of the “main group” eucrites.
40Ar‐39Ar Dating of the Haughton Impact Structure
Authors: Jessberger Elmar K.
Published: June 2012

Abstract— 40Ar‐39Ar dating of a strongly shocked, vesiculated gneiss clast in a breccia from the Haughton impact structure yields an isochron age of 23.4 ± 1.0 Ma. The sample contains excess 40Ar.
Gravity and Magnetic Investigations in the Haughton Impact Structure, Devon Island, Canada
Authors: Pohl Jean , Eckstaller Alfons , Robertson P. Blyth
Published: June 2012

Abstract— The results of a new gravity survey show that the Haughton impact structure is associated with a 24 km diameter negative Bouguer gravity anomaly with a maximum amplitude of −12 mgal. A local minimum with a half‐width of 2 km and an amplitude of −4 mgal is located at the center of the structure. A positive magnetic total field anomaly with a half‐width of 0.6 km and an amplitude of 700 nT coincides with the local central gravity anomaly. The overall negative gravity anomaly is explained by lowered rock densities due to impact‐related fracturing in the crater area. The central gravity and magnetic anomalies are believed to be due to highly shocked and heated sedimentary and crystalline basement rocks forming the unexposed peak of the central uplift in the Haughton impact structure.
The Haughton Impact Structure: Summary and Synthesis of the Results of the HISS Project*
Authors: Grieve Richard A. F.
Published: June 2012

Abstract— Surface and subsurface structural studies undertaken under the Haughton impact structure study (HISS) project indicate that the 23 Ma‐old Haughton impact structure, (Devon Island, Canadian Arctic) consists of a central basin of uplifted strata, an inner zone of uplifted megablocks at 3.5–5.5 km radius, a complex, faulted annulus of megablocks at 5.5–7.0 km radius and an outer zone of downfaulted blocks. No evidence of a previously suggested structural multi‐ring form was found. The geophysical studies suggest an original diameter of 24 km, slightly larger than previous estimates and the seismic data indicate considerably more faulting in the western portion than has been mapped from surface exposures. Detailed studies of the allochthonous breccia deposits found no major radial variations in lithology and shock levels. The only anomaly is the concentration of highly shocked, cobble‐sized clasts in the central area coincident with the maximum gravity and magnetic anomalies. It is suggested that this local component is related to the highly shocked rocks of the central uplift and may have been shed from the uplift during late stage adjustments. There is no visible central topographic peak of uplifted bedrock at Haughton but studies of the post‐impact Haughton Formation suggest that the center of the structure subsided 300–350 m soon after formation. Breccia studies also indicate the occurrence of shock‐melted sediments, including shales, but no evidence of shock melted carbonates, the most common target lithology. This may be ascribed to the ease with which carbonates are volatilized by relatively moderate shock levels. The large amount of volatiles released on impact helped disperse the highly shocked products leading to the formation of a relatively cool clastic and polymict breccia deposit in the interior, as opposed to a coherent melt sheet. In this regard, the breccia deposit is somewhat analogous to the suevite deposits within the Ries crater. Sedimentological studies indicate that the Cretaceous‐age Eureka Sound Formation was present at the time of impact and that the Haughton area has undergone as much as 200 m of erosion since the time of impact.
North American tektite debris and impact ejecta from DSDP Site 612
Authors: Glass Billy P.
Published: June 2012

Abstract— A layer of tektite glass and shock‐metamorphosed grains found in an upper Eocene section of core 21 from DSDP Site 612 taken on the continental slope off New Jersey may belong to the North American tektite strewn field. However, the Site 612 glasses generally have higher K2O and lower Na2O contents for a given SiO2 content and different Sr and Nd isotopic compositions. In order to better define the layer, a series of samples was taken continuously through the layer at 1 cm intervals. Tektite fragments are in an 8 cm thick layer; microtektites are concentrated in the upper 4 cm, while spherules with “crystalline” textures (microkrystites) are concentrated in the lower half of the layer. Millimeter‐size splash forms are mostly in the lower part of the tektite‐bearing layer. Rock and mineral grains showing evidence of shock metamorphism are abundant in the upper half of the tektite‐bearing layer. Coesite is abundant, and stishovite was found in one rock fragment. The size and abundance of the tektite glass and the abundance of shocked debris indicate that Site 612 is relatively close to the source crater, which may be to the north of Site 612 on the coastal plain or adjacent continental shelf.
Meteorites from the Nullarbor Region, Western Australia: I. A review of past recoveries and a procedure for naming new finds
Authors: Bevan A. W. R. , Binns R. A.
Published: June 2012

Abstract— Currently, 44 distinct meteorites are recorded from the Nullarbor Region in Western Australia. Recovery data for the Billygoat Donga, Cardanumbi, Cocklebiddy, Forrest Lakes, Laundry East, Lookout Hill, North East Reid, North Reid, Reid, Webb, West Forrest, West Reid and Yayjinna meteorites are amended, and North Forrest is recognized as distinct from North West Forrest (H).

Since 1971, the recovery of more than 500 specimens (predominantly ordinary chondrites) from the desert has made the Nullarbor Region one of the most productive areas of the world for meteorite recoveries and has caused major problems for meteorite nomenclature. To overcome a lack of geographical names, we have delineated a grid of 47 named ‘areas’ in the Nullarbor Region. Henceforth, distinct meteorites will take the name of the ‘area’ in which they are found and a number (e.g., 001) in order of discovery. In general, the names of past recoveries remain unchanged. The absence of transportation processes in the region, and accurate documentation of the distribution of finds allows ‘pairing’ of specimens to at least 90% level of confidence.
Trace element study of high‐ and low‐refractive index Muong Nong‐type tektites from Indochina
Authors: Glass Billy P. , Koeberl Christian
Published: June 2012

Abstract— Previous work indicates that Muong Nong‐type tektites from Indochina with low refractive indices and high silica contents contain relict mineral grains while those with high refractive indices and low silica contents do not. Instrumental Neutron Activation Analysis (INAA) was used to determine selected trace element concentrations for four Muong Nong‐type tektites with high refractive indices and no relict mineral inclusions and one with low refractive index and relict inclusions, to determine if there are any systematic differences in trace element compositions between the two groups. The data also were compared with published trace element data for sixteen Muong Nong‐type tektites which have low refractive indices and, therefore, should contain relict inclusions. Except for Ta which had lower concentrations in the high refractive index group, there is no consistent difference in trace element compositions between the two groups. We interpret these results to indicate a single, slightly heterogeneous source for the Muong Nong‐type tektites, rather than different source regions.
A distinct variant of high‐titanium mare basalt from the Van Serg core, Apollo 17 landing site
Authors: Ryder Graham
Published: June 2012

Abstract— A fragment of basalt picked from the drive tube collected at Van Serg crater at the Apollo 17 landing site has a bulk chemistry more primitive than that of other high‐titanium mare basalt groups collected at the site. The sample has a fine‐grained olivine phyric, subophitic texture that is distinct from that of other high‐titanium basalt samples. The grain size and texture suggest that the sample has a composition close to that of a magma. The crystallization sequence, with appearance of oxide minerals later than in other groups, and other petrographic features such as more‐calcic plagioclase and early pigeonite rather than augite, are consistent with this sample representing a distinct variant of Apollo 17 high‐titanium basalts. It is not related through closed‐system igneous processes to any of the other mare basalt groups identified among Apollo 17 samples. Its characters emphasize the complexity of contemporaneous magma processes on the Moon and the heterogeneity of that part of the mantle that was melted.
The Bencubbin chondrite breccia and its relationship to CR chondrites and the ALH85085 chondrite
Authors: Weisberg Michael K. , Prinz Martin , Nehru Cherukupalli E.
Published: June 2012

Abstract— Bencubbin is an unclassified meteorite breccia which consists mainly of host silicate (∼40 vol.%) and host metal (∼60%) components. Rare (< 1%) ordinary chondrite clasts and a dark xenolith (formerly called a carbonaceous chondrite clast) are also found. A petrologic study of the host silicates shows that they have textures, modes, mineralogy and bulk compositions that are essentially the same as that of barred olivine (BO) chondrules, and they are considered to be BO chondritic material. Bulk compositions of individual host silicate clasts are identical and differ only in their textures which are a continuum from coarsely barred, to finely barred, to feathery microcrystalline; these result from differing cooling rates. The host silicates differ from average BO chondrules only in being angular clasts rather than fluid droplet‐shaped objects, and in being larger in size (up to 1 cm) than most chondrules; but large angular to droplet‐shaped chondrules occur in many chondrites. Bencubbin host metallic FeNi clasts have a positive Ni‐Co trend, which coincides with that of a calculated equilibrium nebular condensation path. This appears to indicate a chondritic, rather than impact, origin for this component as well. The rare ordinary chondrite clast and dark xenolith also contain FeNi metal with compositions similar to that of the host metal.

Two scenarios are offered for the origin of the Bencubbin breccia. One is that the Bencubbin components are chondritic and were produced in the solar nebula. Later brecciation, reaggregation and minor melting of the chondritic material resulted in it becoming a monomict chondritic breccia. The alternative scenario is that the Bencubbin components formed as a result of major impact melting on a chondritic parent body; the silicate fragments were formed from an impact‐induced lava flow and are analogous to the spinifex‐textured rocks characteristic of terrestrial komatiites. Both scenarios have difficulties, but the petrologic, chemical and isotopic data are more consistent with Bencubbin being a brecciated chondrite.

Bencubbin has a number of important chemical and isotopic characteristics in common with the major components in the CR (Renazzo‐type) chondrites and the unique ALH85085 chondrite, which suggests that their major components may be related. These include: (1) Mafic silicates that are similarly Mg‐rich and formed in similar reducing environments. (2) Similarly low volatiles; TiO2, Al2O3 and Cr2O3 contents are also similar. (3) Similar metallic FeNi compositions that sharply differ from those in other chondrites. (4) Remarkable enrichments in 15N. (5) Similar oxygen isotopic compositions that lie on the same mixing line. Thus, the major components of the Bencubbin breccia are highly similar to those of the ALH85085 and CR chondrites and they may have all formed in the same isotopic reservoir, under similar conditions, in the CR region of the solar nebula.
Temperature conditions for chondrule formation
Authors: Hewins Roger H. , Radomsky Patrick M.
Published: June 2012

Abstract— The liquidus temperatures of chondrules range from about 1200 °C to almost 1900 °C, based on the calculation of Herzberg (1979). Dynamic melting and crystallization experiments with no external seeding suggest that some chondrule textures formed with initial temperatures below the liquidus (e.g., porphyritic, granular) and some were completely melted (e.g., excentroradial, glassy). Type I and III chondrules in carbonaceous chondrites in this interpretation consist of incompletely melted magnesian chondrules, completely melted silica‐rich chondrules and intermediate composition chondrules with both porphyritic and nonporphyritic textures. A similar pattern for ordinary chondrites, with data also for Type II porphyritic and barred olivine chondrules, suggests that few chondrules with liquidus temperatures over 1750 °C were completely melted and few with under 1400 °C were incompletely melted. The range of liquidus temperatures for barred olivine chondrules, for which initial temperatures appear to have been essentially at the liquidus, is similar. Most chondrules may therefore have been heated to temperatures of 1400–1750 °C and, because of a peak in the distribution of barred olivine chondrule temperatures at 1500–1550 °C, the temperatures appear normally distributed within this range. Given a narrow range of temperatures, bulk composition is at least as important as initial temperature in controlling chondrule textures.

Truly granular (not microporphyritic) Type I and truly glassy Type II and III chondrules appear under‐represented in nature according to this model, based on internal nucleation experiments. External heterogeneous nucleation, or seeding due to droplet‐dust collisions, is likely to occur in a dusty nebula and has been shown to reproduce chondrule textures experimentally. Generally high initial temperatures (1600–1800 °C), coupled with dust‐seeding of superheated droplets of less refractory composition is an alternative explanation of chondrule textures. Cooling rates of 100–1000 °C/hr are required for chondrules, which must have been mass produced in clouds with sufficient particle density to buffer cooling rate and perhaps also initial temperature. Melting precursor particles in a thick clump and/or the nebular mid‐plane would provide evaporation and thus explain the high oxidation state and volatile content of chondrules, relative to the bulk hydrogen‐rich nebula, as well as the nature of the cooling.
The Trebbin chondrite
Authors: Andrehs G. , Adam K.
Published: June 2012

Abstract— The Trebbin chondrite (fall, 1988) is a shocked, cataclastic breccia of LL6 parentage.
The Murchison meteorite: Circumstances of its fall
Authors: Seargent David A. J.
Published: June 2012

Abstract— Visual reports of the fall of the Murchison meteorite constrain the time of arrival to within approximately one minute of 00:58 UT 28 September 1969 and indicate an azimuth close to south east. On the basis of recent orbital and radiant determinations, reference is made to the apparent similarities with the theoretical radiant for meteors associated with Comet P/Finlay and orbital similarities with Apollo asteroid 1979 VA.
Regolith evolution in the laboratory: Scaling dissimilar comminution experiments
Authors: Cintala Mark J. , Hörz Friedrich
Published: June 2012

Abstract— Repeated impacts into fragmental targets simulating unconsolidated debris on planetary surfaces have provided empirical insight into the evolution of planetary regoliths. Quantitative understanding and interpretation of these results, however, are often made difficult by the complex, multivariate nature of the impact process, even under controlled laboratory conditions. The techniques of dimensional analysis have been employed to quantify and examine the relationships between the more important variables in the evolution of these experimental regoliths. Application of this method to the results of ten experimental series shows that the quantity of comminuted target mass is directly proportional to (a) the number of impacts sustained by the target, (b) the diameter of the projectile, (c) the mean size of the crystals composing the target rock, (d) the mean grain‐size of the evolving “regolith,” (e) the total target mass, (f) the impactor density, and (g) the ratio of the impact velocity to the velocity of sound in the target rock. The comminuted mass is inversely proportional to the density of the target rock and the sorting of the “regolith.” Similar results hold for the creation of new surfaces by fracturing, except that the initial surface area possessed by the target takes the place of the total target mass. In addition, the ease with which new surfaces are created is independent of the mean crystal‐size. Although it appears that the ratio between impactor and target densities is an important parameter in both cases, more experiments will be necessary to establish the quantitative contribution of that parameter, as well as those of the total target mass and the effective strengths of the individual minerals composing the target rock.
An improved technique for preparing polished thin sections of stony‐iron meteorites
Authors: Künstler F. , Arndt N. T.
Published: June 2012

Abstract— Polished thin sections of stony‐iron meteorites can be prepared easily and quickly using a new technique in which the cooling water to the polishing machine is refrigerated. When using this technique, the silicate and sulfide phases do not heat up and expand differentially, as is often the case when normal procedures are used, and do not pluck out during the polishing process.
Discrediting the late Eocene microspherule layer at Cynthia, Mississippi
Authors: Byerly Gary R. , Hazel Joseph E. , McCabe Charles
Published: June 2012

Abstract— Glassy microspherules recently reported from the late Eocene of central Mississippi are physically and chemically similar to impact‐produced microspherules, especially those from Molino de Cobo, Spain, leading several investigators to conclude that these samples document another late Eocene impact event. A careful evaluation of the sample site and spherule compositions, however, suggests that these glasses are modern contaminants. Similar contaminants could be widespread throughout industrialized countries.
Evidence for the existence of groups of meteorite‐producing asteroidal fragments
Authors: Halliday Ian , Blackwell Alan T. , Griffin Arthur A.
Published: June 2012

Abstract— The MORP camera network in western Canada observed 56 events which we associate with meteorites larger than 0.1 kg. An additional 33 Prairie Network (central USA) fireballs with published orbits were previously identified as the sources of meteorites of at least 0.25 kg. A comparison of the MORP orbits with each other and with the PN orbits, using the D′ criterion of orbital similarity, exhibits a surprising number of small values. This suggests there are groups of related objects among the 89 events. We evaluate the probability of small values of D′ arising by chance from a group of random orbits that has the distribution of orbital elements expected for meteorites. There is an excess of small values of D′ among the 89 meteoritic objects over the expectation for random orbits and a marked excess of very small values. Four groups comprising a total of 16 objects account for this excess. These groups exhibit a preference for the larger masses of the population and a very strong concentration of perihelia just slightly inside the Earth's orbit.

Although it has been shown by others that gravitational perturbations will disperse Earth‐crossing streams in times that are much less than cosmic‐ray exposure ages, the properties of the four groups suggest they may be streams of fragments that crossed the Earth's orbit only recently. Such streams may include a considerable fraction of meteorites falling at a given time. Orbital evolution of these streams could alter the sample of meteorites arriving on Earth over time intervals that are less than the accumulation time of the Antarctic collections.
Electron microscopy study of the iron meteorite Santa Catharina
Authors: Zhang J. , Williams D. B. , Goldstein J. I. , Clarke R. S.
Published: June 2012

Abstract— Characterization of the microstructural features of the metal of the Santa Catharina meteorite was performed using a variety of electron optical techniques. Sample USNM#6293 is chemically homogeneous on the micron scale and has a Ni content of 28.2 wt.%. Its microstructure is similar to that of the Twin City ataxite and contains clear taenite II, i.e., fcc taenite with domains of tetrataenite, < 10 nm in size. Sample USNM#3043 is a more typical Santa Catharina specimen with dark and light regions as observed with the light optical microscope. The dark regions are inhomogeneous and contain 45–50 wt.% Ni and 7–12 wt.% O. The light regions are homogeneous and contain 35 wt.% Ni and no detectable oxygen. The microstructure is that of cloudy zone, i.e., islands of tetrataenite, ∼20 nm in size, in a honeycomb matrix. The honeycomb phase contains Ni rich oxide in the dark regions and contains metal, fcc taenite, in the light regions. The original metal structure of USNM#3043 is cloudy zone which formed during cooling into the low temperature miscibility gap of the Fe‐Ni phase diagram. The dark regions were developed from the metal by selective corrosion of the honeycomb structure, transforming it into Ni containing oxides, possibly non‐stoichiometric Fe2NiO4 while retaining the tetrataenite islands. Using the results of this study, many of the existing discrepancies concerning the microstructure of Santa Catharina can be explained.
Dissimilarities in Perseid meteoroids
Authors: Russell John A.
Published: June 2012

Abstract— A shutter‐chopped, direct photograph of a 1980 Perseid meteor is discussed in which no shutter breaks are apparent. Evidence is considered that it is indeed a Perseid and that the phenomenon is the result of an extraordinary fragmentation of the meteoroid. Tentative evidence is presented for the existence in 1980 of a second radiant from which the apparently unchopped meteor and a second meteor, also showing marked fragmentation, emanated. The fragmentation of these two meteors and the concentration of their radiant are consonant with the concept of their origin from recently released material from the nearby parent comet.
Lechatelierite inclusions in indochinites and the origin of tektites
Authors: Kinnunen Kari A.
Published: June 2012

Abstract— The grain size distribution and shapes of lechatelierite inclusions (silica glass inclusions) have been determined from 20 splash‐form tektites from the Khorat Plateau, northeastern Thailand. The chemical and petrographic properties are reviewed, and the absence of any type of inclusion other than bubbles is confirmed. These data suggest that the parent material for the lechatelierite inclusions is not the conventional detrital quartz. One possible precursor is silica of plant origin in the form of biogenic opal‐CT. According to this model, the lechatelierite inclusions are formed by shock melting of opal phytoliths in plants. These opal phytolith melts were included in the shock‐melted soil and bedrock, jetted from the impact site. The expansion of the vapor plume ejected the melt droplets in ballistic trajectories. This model is extended to all tektite groups, because of the similarity between lechatelierite inclusions in them.
Element mobility due to weathering in the L5 Bayard chondrite
Authors: Struempler Arthur W.
Published: June 2012

Abstract— In order to assess weathering effects, sixteen elements were determined by neutron activation in the surficial layer and the interior of the extensively weathered Bayard L5 chondrite. Na, As, Sb, La and Sm show enrichment in the surface; for these elements soil concentrations are greater than in the meteorite. Elements showing no significant differences between surface and interior are Sc, Cr, Fe, Co, Ni, Zn, Se, Eu, Yb, Ir and Au; with the exception of Eu and Yb, soil concentrations were lower than those in the chondrite. Concentrations of Fe, Ni and Co, and to some extent Na, are lower than the mean of the L‐chondrite values probably due to oxidation and leaching from the chondrite. The data support an L classification for the Bayard chondrite.
Classification of five new chondrite finds from Roosevelt County, New Mexico
Authors: Pun Aurora , McCoy T. J. , Keil Klaus , Wilson Ivan E.
Published: June 2012

Abstract— Five small, weathered meteorites recovered from Roosevelt County, New Mexico, USA, are called Roosevelt County 066–070. Based on optical microscopy and electron microprobe analysis of mafic minerals, RC 066–070 are classified as L5a chondrites. RC 068 and 069 are tentatively paired. RC 066 and RC 067 are not paired with RC 068 and RC 069. RC 066, 067 and 070 do not appear to be paired with each other or with RC 001–031.
Accretion in the inner nebula: The relationship between terrestrial planetary compositions and meteorites*
Authors: Taylor Stuart Ross
Published: June 2012

Abstract—The bulk compositions of the terrestrial planets are assessed. Venus and Earth probably have similar bulk compositions, but Mars is enriched in volatile elements. The inner planets are all depleted in volatile elements, as shown by K/U ratios, relative to most meteorites and the CI primordial values. Terrestrial upper mantle Mg/Si ratios are high compared with CI data. If they are representative of the bulk Earth, then the Earth accreted from a segregated suite of planetesimals that had non‐chondritic major element abundances. The CI meteorite abundances, despite aqueous alteration, match the solar data and provide the best estimate for the composition of the solar nebula, including the iron abundance. The widespread depletion of volatile elements in the inner solar nebula is most likely caused by heating related to early violent solar activity (e.g., T Tauri and FU Orionis stages) which, for example, drove water out to a “snow line” in the vicinity of Jupiter. The variation in composition among the meteorites and the apparent lack of mixing among the groups indicates accretion from narrow feeding zones. There appears to have been little mixing between meteorite and planetary formation zones, as shown by the oxygen isotope variations, lack of mixing of meteorite groups, and differences in K/U ratios. In summary, it appears that the final accretion of planets did not result in widespread homogenization, and that mixing zones were not more than about 0.3 A.U. wide. Although the composition of the Moon is unique, and its origin due to an essentially random event, its presence reinforces the planetesimal hypothesis and the importance of stochastic processes during planetary accretion in the inner solar system.
Mineralogy and possible origin of an unusual Cr‐rich inclusion in the Los Martinez (L6) chondrite
Authors: Brearley Adrian J. , Casanova Ignacio , Miller Mark L. , Keil Klaus
Published: June 2012

Abstract— During a petrological study of the previously unclassified ordinary chondrite Los Martínez, we discovered a highly unusual Cr‐rich inclusion which we believe is unique in both extraterrestrial and terrestrial mineralogy. The inclusion is highly zoned both compositionally and optically, with a Ca‐Al rich, cloudy core and an opaque, Cr‐Na‐rich rim (up to 24 wt.% Cr2O3). Detailed SEM and TEM studies show that the inclusion now consists of a highly zoned, single crystal of plagioclase intergrown with chromium‐rich spinel. The spinel has a well‐developed crystallographic orientation relationship with the host plagioclase, which indicates that it is the product of exsolution. Although superficially similar to a plagioclase feldspar in composition, in detail the inclusion is Si‐deficient and Al‐enriched relative to a stoichiometric feldspar. We have not been able to identify a viable precursor mineral phase to the plagioclase‐chromite intergrowth and suggest that it may be an unknown metastable phase. The Cr‐rich precursors of the inclusion probably have close affinities to the chromite‐plagioclase chondrules observed by Ramdohr (1967) in several ordinary chondrites. Based on the zoning in the inclusion, we suggest that it is the product of fractional crystallization from a melt, which may have formed as a liquid condensate, or by melting of solid condensates, in the solar nebula. Subsequent cooling of this melt condensate resulted in crystallization of the, as yet, unidentified phase. After crystallization, the inclusion was probably incorporated into a parent body where it underwent metamorphism and was probably shocked to some degree. During this period of parent body metamorphism, exsolution and decomposition of the unknown precursor occurred to produce the observed intergrowth of plagioclase and chromite. Finally, we have classified Los Martínez as an L6 ordinary chondrite breccia.
Spinel‐bearing, Al‐rich chondrules in two chondrite finds from Roosevelt County, New Mexico: Indicators of nebular and parent body processes
Authors: McCoy Timothy J. , Pun Aurora , Keil Klaus
Published: June 2012

Abstract— Two rare, spinel‐bearing, Al‐rich chondrules have been identified in new chondrite finds from Roosevelt County, New Mexico—RC 071 (L4) and RC 072 (L5). These chondrules have unusual mineralogies, dominated by highly and asymmetrically zoned, Al‐Cr‐rich spinels. Two alternatives exist to explain the origin of this zoning—fractional crystallization or metamorphism. It appears that fractional crystallization formed the zoning of the trivalent cations (Al, Cr) and caused a localized depletion in chromites around the large Al‐Cr‐rich spinels. The origin of the zoning of the divalent cations (Fe, Mg, Zn) is less certain. Diffusive exchange and partitioning of Fe and Mg between olivine and spinel during parent body metamorphism can explain the asymmetric zoning of these elements. Unfortunately, appropriate studies of natural and experimental systems to evaluate the formation of zoning of the divalent cations by fractional crystallization have not yet been conducted. The bulk compositions of the chondrules suggest affinities with the Na‐Al‐Cr‐rich chondrules, as would be expected from the abundance of Al‐Cr‐rich spinels. Melting of rare and unusual precursors produced the compositions of Na‐Al‐Cr‐rich chondrules, possibly including a spinel‐rich precursor enriched in Cr2O3 and ZnO. The two chondrules we studied have larger modal abundances of Al‐Cr‐rich spinels than reported in other Na‐Al‐Cr‐rich chondrules of similar composition, and Al‐rich chondrules even more enriched in spinel are reported in the literature. These differences indicate that factors other than bulk composition control the mineralogy of the chondrules. The most important of these factors are the temperature to which the molten chondrule was heated and the cooling rate during crystallization. These two chondrules cooled rapidly from near the liquidus, as indicated by the zoning, occurrence and sizes of spinels, radiating chondrule textures and localized chromite depletions. The range of mineralogies in other Al‐rich chondrules of similar composition reflect a range of peak temperatures and cooling rates. We see no reason to believe that this range is fundamentally different from the range of thermal histories experienced by “normal” Fe‐Mg‐rich chondrules.