bluuebunny/crossref_metadata_2025 huggingface dataset:
X‐RADIOGRAPHY OF SLABS OF THE ALLENDE METEORITE
Authors: Heymann D. , Smith M.J. , Anderson J.B.
Published: June 2012

X‐radiographs of eight slabs of the Allende meteorite, each about 8 mm thick, reveal significant chemical and textural heterogeneities of our Allende fragment at the 100–1000 g level. They also reveal systematic arrangements of chondrules (“strings”). Our preliminary interpretation is that the observed features are probably all due to regolith processes on Allende's parent body, and that these processes included “mini” slope slides along dry, “sandy” slopes.
SEVEN NEW BULK CHEMICAL ANALYSES OF AUBRITES
Authors: Easton A.J.
Published: June 2012

New bulk chemical analyses are given of Aubres, Bishopville, Bustee, Khor Temiki, Norton County, Peña Blanca Spring and Shallowater, Selective attack by dry chlorine (350°C) on magnetic and non‐magnetic fractions was used to determine the distribution of some normally lithophile elements (Al, Ca, Cr, K, Mg, Mn, Na, P and Ti) between silicate and sulphide groups of minerals.
THE BLOOMINGTON (LL6) CHONDRITE AND ITS SHOCK MELT GLASSES
Authors: Dodd Robert T. , Olsen Edward J. , Clarke Roy S.
Published: June 2012

The Bloomington meteorite, a 67.8 gram veined, brecciated chondrite, fell during the summer of 1938 in Bloomington, Illinois. Its olivine, orthopyroxene and metal compositions (fo69, en74 and Fe52 Ni48 respectively) and its texture identify it as a brecciated LL6 chondrite of shock facies d. Shock melt glasses occur in Bloomington as sparse melt pockets and veins in clasts and as isolated masses in the black, clast‐rich matrix. The vein glasses chemically resemble bulk LL‐group chondrites and thus appear to reflect total melting of the host meteorite. The melt pocket and matrix glasses, like those described previously in L‐group chondrites, have more varied compositions and are typically enriched in normative plagioclase. All glasses that we analyzed in Bloomington have FeO/MgO and Na/Al ratios similar to those of LL‐group chondrites, indicating that melting of this meteorite involved neither a significant change in the oxidation state of iron nor loss of sodium to a vapor phase. Bloomington is a monomict breccia whose components formed in place as a result of a single episode of shock and attendant melting.
THE GUJARGAON METEORITE
Authors: Gupta P.R. Sen , Ram Kashi , Das A.K. , Paul S.R. , Guha B.K. , Nag D.K.
Published: June 2012

The Gujargaon meteorite was observed to fall on a cotton field at Gujargaon in Dewas district, Madhya Pradesh, India, on the afternoon of the 4th of September, 1982. It is an oriented stone with a saucer‐shaped front and regmaglypted rear with surfaces of more than one generation, and is entirely covered by fusion crust.

Gujargaon is an H5 chondrite with rare chondrules integrated with the matrix. Intense fracturing with fractures filled by glassy veins, and undulose extinction and deformation‐twin lamellae in troilite bear evidences of shock. Compared to average H‐group chondrites Gujargaon appears to have higher contents of SiO2and normative pyroxene.
THE PARENT STRATUM AND DISTRIBUTION OF THE GEORGIA TEKTITES
Authors: Povenmire Harold
Published: June 2012

Seventy‐six field expeditions for Georgia tektites have been made to the vicinity of Dodge County, Georgia in an effort to determine the parent formation and distribution pattern by locating new specimens. About 67 new specimens have been recovered; they represent about 9 percent of all known specimens. The primary area of distribution is a fan shaped area approximately 30 by 72 kilometers. It is likely that these tektites have been transported by water from the parent formation. No correlation could be found between size, shape, soil type, elevation and tektite location. Georgia tektites have previously been found only in strata much younger than their 34 m.y. radiometric age. Here, however, the parent formation is identified as the Tobacco Road Sand of this age.
A POORLY GRAPHITISED CARBON CONTAMINANT IN STUDIES OF EXTRATERRESTRIAL MATERIALS
Authors: Rietmeijer Frans J.M.
Published: June 2012

Poorly‐graphitised carbon particles are formed during manufacture of sample substrates (holey carbon films) for Analytical Electron Microscopy studies of small particles. The particles form during heat treatment of cellulose acetobutyrate at about 975 °C and 1050 °C. In AEM studies of fine‐grained carbonaceous extraterrestrial materials, these particles are easily recognised.
MINERALOGY OF THE BOCAIUVA IRON METEORITE: A PRELIMINARY STUDY
Authors: Desnoyers C. , Michel‐Levy M. Christophe , Azevedo I.S. , Scorzelli R.B. , Danon J. , da Silva E. Galvão
Published: June 2012

The Bocaiuva iron contains 10 to 15% by volume of silicate inclusions which are surrounded by kamacite (6.5 wt % Ni). The metal shows a Widmanstätten pattern in metal areas devoid of silicates; taenite evolved in plessite fields. The silicate inclusions occur as nodules, and as irregular or chain‐like aggregates in which olivine may be rounded or faceted. The magnesian silicates (forsterite, enstatite, diopside) are similar in composition to those of the group IAB irons, whereas the interstitial plagioclase is much more calcic (An 50) than that usually found. Iron sulfide occurs as pyrrhotite and contains 1–2 wt% Cu. Chromite and euhedral magnetite are accessory phases always associated with pyrrhotite. Some patches of pyrrhotite enclose rounded chromite and small plagioclase crystals displaying compositions different from those of the ground mass of the inclusions. Schreibersite shows a compositional variability.

This preliminary study underlines the unusual nature of Ms iron and raises several questions concerning the genetic relations between silicates, sulfide and metal, and the thermal history of the whole material.
RARE EARTH ELEMENT ABUNDANCES IN SEPARATED PHASES OF MAYO BELWA, AN ENSTATITE ACHONDRITE
Authors: Graham A.L. , Henderson P.
Published: June 2012

Separated fractions from the Mayo Belwa aubrite have been analysed for the rare earth elements (REE). The data show no ytterbium anomalies but the feldspar and magnetic fractions show complementary europium anomalies. The separated phases together account for the total REE abundances in the bulk meteorite which are about 0.5 times chondritic. The REE content of the feldspar is greater than that of the bulk meteorite. The partition coefficients for the REE between feldspar and orthopyroxene are about 10 times (in favour of the feldspar) those of the nearest equivalent terrestrial feldspar/orthopyroxene pairs, implying that the distribution of the REE which would result from equilibrium co‐crystallisation from a single liquid has been disturbed by a later event. This occurred more recently than 4.33 b.y. ago and resulted in a redistribution of the REE between the feldspar and a REE enriched residue. However, the REE patterns of the minerals are very like those of terrestrial equivalents and appear to be the result of igneous cumulus processes on a parent body rather than condensation of dust from a nebular gas.
THE COLONY METEORITE AND VARIATIONS IN CO3 CHONDRITE PROPERTIES
Authors: Rubin Alan E. , James Janet A. , Keck Bradley D. , Weeks Karen S. , Sears Derek W.G. , Jarosewich Eugene
Published: June 2012

The Colony meteorite is an accretionary breccia containing several millimeter‐to centimeter‐size chondritic clasts embedded in a chondritic host. Colony is one of the least equilibrated CO3 chondrites; it has an unrecrystallized texture and contains compositionally heterogeneous olivine and low‐Ca pyroxene, kamacite with low Ni and Co and high Cr, amoeboid inclusions with low FeO and MnO, a fine‐grained silicate matrix with very high FeO, and numerous small chondrules with clear pink glass. However, Colony differs from normal CO chondrites in several respects: Although Al, Sc, V, Cr, Ir, Fe, Au and Ga abundances are consistent with a CO chondrite classification, certain lithophiles (Mg and Mn), siderophiles (Ni and Co) and chalcophiles (Se and Zn) are depleted by factors of 10–40%. The shape of Colony's thermoluminescence (TL) glow curve is similar to that of Allan Hills A77307 (another unequilibrated chondrite with CO3 petrological characteristics) and different from those of normal CO chondrites. [ALHA77307 also resembles Colony in having low Mg, Mn, Ni and Co, compared to normal CO chondrites, but it possesses CO‐CV levels of Se and Zn and nearly CV levels of Cd.]

Colony is badly weathered; it contains 22.7 wt.% Fe2O3 and 5.7 wt.% H2O. Recalculating the analysis on an H2O‐free basis with all Fe2O3, NiO and CoO converted to metal, yields an inferred original metallic Fe, Ni abundance of ∼ 19 wt.%. This is similar to that of Kainsaz (an unweathered CO3 fall), but much higher than that of all other CO3 chondrites (< 6.3 wt.%). Although it is possible that Colony and either ALHA77307 or Kainsaz constitute distinct CO3 chemical subgroups, the weathered nature of Colony and ALHA77307 preclude the drawing of firm conclusions. Nevertheless, it is clear that CO3 chondrites vary more in compositional and petrological properties than was previously recognized.
AMPHIBOLE AND HERCYNITE SPINEL IN SHERGOTTY AND ZAGAMI: MAGMATIC WATER, DEPTH OF CRYSTALLIZATION, AND METASOMATISM
Authors: Treiman Allan H.
Published: June 2012

Amphibole and spinel occur in the Shergotty and Zagami meteorites only in magmatic inclusions in pigeonite. The trapped magma is essentially identical to the parental magmas for Shergotty and Zagami. The amphibole is a kaersutite with minimal halogen content; by inference, it must have been hydrous. If so, the Shergotty and Zagami melts contained at least 0.2 wt % H2O and were probably H2O‐undersaturated. Pressures in excess of 1 kilobar seem necessary for the formation of amphibole. Spinel replaces magnetite in the inclusions, and olivine replaces magnetite elsewhere in the meteorites. To stabilize spinel, the melt in the inclusions must have become enriched in Al during fractionation, possibly because the small volume of the inclusions made nucleation of plagioclase unlikely. Pervasive replacement of magnetite through reduction reactions suggests that Shergotty and Zagami interacted with hydrogen‐rich fluids during their cooling.
CAMEL DONGA METEORITE, A NEW EUCRITE FROM THE NULLARBOR PLAIN, WESTERN AUSTRALIA
Authors: Cleverly W.H. , Jarosewich Eugene , Mason Brian
Published: June 2012

Twelve stones, ranging up to 504 g (total weight 2.92 kg), of a very fresh eucrite have been collected from a 1 km2 area on the Nullarbor Plain in Western Australia. The location is approximately 75 km N6°E from Nurina Siding on the Trans‐Australian Railway; coordinates 30°19′S, 126°37′E. This eucrite consists almost entirely of pyroxene (mean composition Wo 16 Fs 49) and plagioclase (mean composition An 85) in approximate proportions 3: 2, with 2% almost pure Fe metal and accessory amounts of troilite, ilmenite, and an SiO2 phase. Gabbroic and doleritic clasts are present in a groundmass of comminuted pyroxene and plagioclase. The chemical composition (weight per cent) is: SiO2 49.53, TiO2 0.74, Al2O3 12.49, Cr2O3 0.33, FeO 16.07, MnO 0.56, MgO 6.31, CaO 10.41, Na2O 0.49, K2O 0.04, P2O5 < 0.01, H2O + < 0.1, H2O — 0.07, Fe metal 2.07, Ni < 0.01, Co < 0.01, FeS 0.19, C 0.03, sum 99.33.
RECOVERY AND CLASSIFICATION OF THIRTY NEW METEORITES FROM ROOSEVELT COUNTY, NEW MEXICO
Authors: Scott Edward R.D. , McKinley Susan G. , Keil Klaus , Wilson Ivan E.
Published: June 2012

We report the discovery and classification of 30 new meteorites found in or close to Roosevelt County, New Mexico, including two H3 chondrites and a ureilite; the others are equilibrated ordinary chondrites. Over 160 meteorites representing at least 100 different falls have been recovered from this region, mostly from wind blowout areas. As in Antarctica, small specimens predominate and irons, achondrites and C and E chondrites are rare. Paired specimens are also very difficult to identify.
JERSLEV, THE FIRST IRON METEORITE FROM DENMARK
Authors: Buchwald Vagn Fabritius
Published: June 2012

Jerslev is a new iron meteorite of 40 kg, found 1976 on the island of Sjaelland, Denmark. The coordinates are 55°36'N, 11°13'E, and the altitude 20 m. It was excavated from moraine deposits from a depth of about 0.5 m. Jerslev is a coarsest octahedrite of group IIB, related to Mount Joy and Sikhote‐Alin. It shows intergranular corrosion from a long exposure to terrestrial groundwater rich in chlorides.
DETECTION OF HIGH‐PRESSURE SILICA POLYMORPHS IN WHOLE‐ROCK SAMPLES FROM A METEOR CRATER, ARIZONA, IMPACT SAMPLE USING SOLID‐STATE SILICON‐29 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
Authors: Yang Wang‐Hong , Kirkpatrick R. James , Vergo Norma , McHone John , Emilsson Tryggvi I. , Oldfield Eric
Published: June 2012

High‐resolution solid‐state silicon‐29 nuclear magnetic resonance spectroscopy using “magic‐angle” sample‐spinning can readily detect the presence of the high pressure silica polymorphs coesite and stishovite in whole‐rock samples from a Meteor Crater, Arizona, impact sample, and yields accurate coesite/stishovite ratios. Such determinations are being carried out by partially suppressing (saturating) intense quartz signals (which have long spin‐lattice relaxation times) by means of short experimental recycle‐times. This method enhances the signal‐to‐noise ratios of coesite and stishovite (which have relatively short spin‐lattice relaxation times). For the sample examined, the coesite/stishovite ratio is about 27.
Statistical Estimation of the Production of Cosmic‐Ray‐Induced Nuclides in Meteorites*
Authors: Honda Masatake
Published: June 2012

Abstract— Among iron meteorites there is a simple relationship estimating, with two parameters, the production rates of spallation products of mass A, that range in ΔA from 2 to 36 (Cr to Ne), where ΔA is 56 — A. This paper describes further applications of this relation, extending it to chondrites, in terms of the effective ΔA. It is possible to systematize the production of common products in chondrites such as 3He, 26Al,22Ne, 21Ne and 38Ar. For this purpose, data on products determined in the metal phases of chondrites are useful in correlating stones to irons. For general application to stone meteorites, statistical treatments for multielement target systems are employed, except for the lowest energy reaction products. Statistical methods for spallation products are thus now applicable for all iron and stone meteorites.
Igneous History of the Aubrite Parent Asteroid: Evidence from the Norton County Enstatite Achondrite
Authors: Okada Akihiko , Keil Klaus , Taylor G. Jeffrey , Newsom Horton
Published: June 2012

Abstract— We studied numerous specimens of the Norton County enstatite achondrite (aubrite) by optical microscopy, electron microprobe, and neutron‐activation analysis. Our main conclusions are the following: 1. Norton County is a fragmental impact breccia, consisting of a clastic matrix made mostly of crushed enstatite, into which are embedded a variety of mineral and lithic clasts of both igneous and impact melt origin. 2. The Norton County precursor materials were igneous rocks, mostly plutonic orthopyroxenites, not grains formed by condensation from the solar nebula. 3. The Mg‐silicate‐rich aubrite parent body experienced extensive melting and igneous differentiation, causing formation of diverse lithologies, some of which have not been described previously. These lithologies include dunites (represented by forsterite crystals), plutonic orthopyroxenites (represented by most enstatite crystals in the matrix), plutonic pyroxenites (the pyroxenitic clasts), and plagioclase‐silica rocks (like the feldspathic clasts). Presence of impact melt breccias (the microporphyritic clasts and the diopside‐plagioclase‐silica clast) of still different compositions further attest to the lithologic diversity of the aubrite parent body.
The Infrared Transmission Spectrum of the Salzwedel Meteorite
Authors: Wagner C. , Arnold G. , Wäsch R.
Published: June 2012

Abstract— The paper presents the infrared transmission spectrum of the Salzwedel meteorite. Further, the spectrum is used to characterize the meteorite's mineralogical composition.
Microbeam Analysis of Four Chondritic Interplanetary Dust Particles for Major Elements, Carbon and Oxygen
Authors: Blanford G. E. , Thomas K. L. , McKay D. S.
Published: June 2012

Abstract— Chemical compositions determined using electron excited x‐rays are reported for four interplanetary dust particles collected in the stratosphere. These analyses include measurements of carbon and oxygen abundances which are important elements in these primitive materials. Spot analyses show very heterogeneous compositions on a micrometer scale although average composition approaches that of C1 carbonaceous chondrites. While the spot analyses show intermediate compositions between cometary dust and carbonaceous chondrites, the heterogeneity more closely resembles that of comet Halley dust particles.
The Distribution and Significance of Evaporitic Weathering Products on Antarctic Meteorites
Authors: Velbel Michael Anthony
Published: June 2012

Abstract— The distribution of white evaporitic deposits differs among different meteorite compositional groups and weathering categories of Antarctic meteorites. Evaporites occur with unusual frequency on carbonaceous chondrites, and are especially common in carbonaceous chondrites of weathering categories A and B. Among achondrites, weathering categories A and A/B show the most examples of evaporite weathering. Unlike carbonaceous chondrites and achondrites, most evaporite‐bearing ordinary (H and L) chondrites are from rustier meteorites of weathering categories B and, to a lesser degree, B/C and C. LL chondrites are conspicuous by their complete lack of any evaporitic weathering product.

Almost two‐thirds of all evaporite‐bearing meteorites belong to weathering categories A, A/B, and B. Where chemical data are available, surficial evaporite deposits are associated with elemental anomalies in meteorite interiors. Meteorites of weathering classes B, A/B, and even A may have experienced significant element redistribution and/or contamination as a result of terrestrial exposure. Evaporite formation during terrestrial weathering cannot be neglected in geochemical, cosmochemical, and mineralogical studies of Antarctic meteorites. A lower‐case “e” should be added to the weathering classification of evaporite‐bearing Antarctic meteorites, to inform meteorite scientists of the presence of evaporite deposits and their associated compositional effects.
Formation of Ureilites by Impact‐Melting of Carbonaceous Chondritic Material
Authors: Rubin Alan E.
Published: June 2012

Abstract— Ureilites are modeled as impact‐melt products of CV‐chondrite‐like material. This model is consistent with the brecciated nature and cumulate textures of ureilites, O‐isotopic constraints (which indicate ureilite derivation from an isotopically heterogeneous body like the CV‐chondrite parent), the high abundance of planetary‐type noble gases, and the relatively high concentrations of siderophile and chalcophile elements (indicating incomplete separation of metal‐sulfide from silicate). Each ureilite may have been derived from a separate cratering event.
Raman Spectra of Shocked Minerals 1: Olivine
Authors: Heymann D. , Cellucci T. A.
Published: June 2012

Abstract— The Raman spectrum of olivine contained in a chip of the Twin Sisters Peak dunite shocked to 22.2 GPa is essentially identical to the spectrum of unshocked olivine in this rock. The Raman spectra of a powder of the rock shocked to 20.1 GPa and of chips shocked to 59.5 GPa and 60.7 GPa show strong and broad low‐frequency features with crests at 475 cm−1, 556 cm−1, and 572 cm−1, and strong as well as broad high‐frequency features near 1100 cm−1. We conclude that these features are most likely due to the formation of “olivine glass” with a considerable degree of three‐dimensional Si‐O‐Si linkage, having scattered domains of greatly variable grain size, internal structure, and, possibly, chemical composition. We cannot conclude with our results at hand whether olivine shocked to the highest pressures has not decomposed to very fine‐grained MgO plus an SiO2‐rich glass.

We also conclude from our results that the structural changes are not likely to have formed in the laser beam of the measurement.
Compositional Study of a Suite of Samples from the 28‐t Armanty (Xinjiang) Iron Meteorite
Authors: Wasson John T. , Ouyang Xinwei , Wang Daode
Published: June 2012

Abstract— Neutron activation analysis of 15 samples from widely separated locations on the surface of the 28‐t Armanty (Xinjiang) group‐IIIE iron meteorite showed no compositional variations attributable to magmatic fractionation processes such as fractional crystallization. The homogeneity contrasts with that observed in the Cape York IIIAB iron, in keeping with the idea that the latter is an exceptional case. From the maximum compositional gradients we estimate that the radius of the HIE core was > 1 km. One sample taken from a surface formed by fracture associated with its fall to Earth is slightly anomalous in composition; we suspect that this region is near the border between two parental γ crystals and has a high content of minor phases.
The Eagle, Nebraska Enstatite Chondrite (EL6)
Authors: Olsen Edward J. , Huss Glenn I , Jarosewich Eugene
Published: June 2012

Abstract— The Eagle enstatite chondrite (presently 9.2 kg) was an observed fall in October 1946. It was not recovered until the spring of 1947 and was allowed to remain out‐of‐doors until 1984. The meteorite appears relatively unweathered, although the absence of oldhamite and the depletion of calcium indicates it has suffered chemical weathering during its 37 years of exposure. Its bulk composition classifies it as an EL6. Its lack of chondrules or remnants of chondrules place it among the most recrystallized of enstatite chondrites. It contains unusual rounded black inclusions, up to 1 cm, composed of the same minerals as the host, but of significantly finer grain size. We conclude Eagle is a post‐metamorphic breccia, the breccia inclusions having been rounded by abrasion during regolith processing.
Ingella Station, a New Chondrite Find from the Tenham Strewnfield, Queensland, Australia
Authors: McCoy T. J. , Keil Klaus
Published: June 2012

Abstract— Based on optical microscopy and electron microprobe analysis of mafic minerals, Ingella Station, a new meteorite find from the area of the Tenham strewnfield, Queensland, Australia, is classified as an H5a chondrite.
The Haughton Impact Structure, Devon Island, Canada: Setting and History of Investigations
Authors: Robertson P. Blyth
Published: June 2012

Abstract— Although mapped initially as a piercement dome, subsequent discovery of shock metamorphism in clasts of an impact breccia, shatter cones in outcrops of uplifted target rocks and morphological and geophysical characteristics consistent with a complex crater, confirmed a meteorite impact origin for the Haughton structure, Devon Island.

Results of three field investigations carried out prior to 1984 defined a complex crater, 20 km in diameter, formed in a lower Paleozoic sedimentary sequence overlying gneisses of the Precambrian basement. The distribution of allochthonous breccia overlying the disturbed target rocks and of the sediments deposited in the crater‐filling lake were mapped. A Miocene or possibly Holocene age for the crater was based on paleo‐flora and fauna assemblages from the lake sediments. Gravity and magnetic surveys revealed anomalies coincident with the crater, but not interpretable from surface lithologies.

Some of the early investigations were of a reconnaissance nature and results and interpretation can only be considered preliminary. Other studies that were carried out in some detail, petrographic investigations in particular, require complementary work for a fuller understanding of their significance. As a result, in 1984 the HISS (Haughton Impact Structure Studies) group carried out a program of detailed geological mapping and sampling, and seismic, gravity, and magnetic surveys in an attempt to improve the definition of the surface and subsurface nature of Haughton, and to formulate a more complete understanding of its formation and subsequent history. Results of these various studies are presented in the eight succeeding papers of this volume.
The Allochthonous Polymict Breccia Layer of the Haughton Impact Crater, Devon Island, Canada
Authors: Redeker H.‐J. , Stöffler D.
Published: June 2012

Abstract— The central allochthonous polymict breccia of the Haughton impact structure is up to about 90 m thick and as much as 7.3 km in radial extent. It has been analyzed with respect to modal composition, grain‐size characteristics, and degree of shock metamorphism for the grain‐size ranges 10–∼ 50, 1–10, 0.03–1, and <0.03 mm. The mineralogy of the breccia matrix is dominated by dolomite and calcite, with minor amounts of quartz, other silicate minerals, and rare melt particles. The following lithic clasts have been identified in the 1–10 mm size fraction (averages of vol.% given in parentheses): dolomitic rocks (51), limestones (29), crystalline rocks (10), sandstones and siltstones (3.7), chert (0.7), melt particles (1.9). The mineral clasts (1–0.03 mm) comprise (with decreasing frequency) dolomite, quartz, calcite, feldspar, biotite, amphibole, garnet, opaques, rounded quartz derived from sandstones and accessory minerals. Lithic and mineral clasts display various degrees of shock. Fragments of crystalline rocks are shocked in the 0–60 GPa range; whole rock melts from the crystalline basement are lacking and unshocked rocks are very rare. In contrast, shock‐melted sandstones, shales, and chert were found in most samples. Large clasts of these melt rocks are highly concentrated near the center of the crater. Otherwise, no distinct change of the modal composition with radial range has been observed except that the frequency of limestone clasts increases slightly with radial range. The breccia near the center is more fine‐grained than that beyond about 1 km radius and the sorting parameter increases somewhat with radial range. Except for the high concentration of shock‐melted sedimentary rocks and highly shocked crystalline rocks near the center of the crater, the distribution of shock stages within the lithic clast population is quite uniform throughout the breccia formation. We conclude that the breccia constituents are derived from the lower part of the target stratigraphy (deeper than about 800 m) and that the total depth of excavation at Haughton is in the order of 2000 m. The mixing of sedimentary rocks of the Eleanor River Formation, Lower Ordovician, and Cambrian (∼850 m thickness) with crystalline basement rocks is quite thorough and homogeneous throughout the breccia lens, at least for the analyzed part. This may require an air‐borne mode of emplacement for the upper section of the breccia in analogy to the fall‐back suevite in the Ries crater. A calculation of the excavation (Z‐model) and of the shock pressure attenuation based on reasonable estimates of the energy and crater geometry of the Haughton impact confirms the observed maximum depth of excavation of about 2 km. Shock‐melted crystalline basement rocks, if present at all, must be confined to the very center of the structure below the excavation cavity.
Seismic Signature of the Haughton Structure
Authors: Scott D. , Hajnal Z.
Published: June 2012

Abstract— The western flank of the Haughton impact structure was imaged with a reflection profile generating 9.8 km of subsurface information. Ten reflecting horizons were recognized and have been correlated via a sonic log with the Paleozoic limestone/dolomite rock sequences. The seismic section is dominated by a dense and complex compound fault system with variable attitudes. These steeply dipping faults penetrated the sedimentary rocks but showed no recognizable extension into the crystalline basement. According to the seismically recognized fracture zones of the western margin, the structure is significantly larger than previously estimated. Reconstruction of the crater on the basis of the seismic information and existing scaling relationships reveals a structure with an apparent diameter of 23.9 km, and an excavated cavity of 10.3 km width and 1.97 km depth. The estimated diameters of the transient crater and the central uplift are 12 km and 11 km respectively. The morphologically distinct ring zones do not have seismically recognizable subsurface signatures. The underlying crystalline basement rocks did not exhibit seismically mappable impact‐related zones of disturbance. In the central interior region, coherent reflection signals are virtually absent. Valuable information for this area was provided by a 10.26 km long refraction profile that indicated nearly uniform velocities (∼5000 m/s) to a considerable depth. Major lateral variations in the velocity field across the structure were not detected.
Enstatite meteorites and their parent bodies*
Authors: Keil Klaus
Published: June 2012

Abstract— Enstatite meteorites are highly reduced rocks that consist of major, nearly FeO‐free enstatite, variable amounts of metallic Fe, Ni and troilite, and a host of rare minerals formed under highly‐reducing conditions. They are comprised of the EH and EL chondrites and the aubrites. Here I discuss some of their properties and the nature and number of their parent bodies. Conclusions: 1. EH and EL chondrites show bulk compositional differences in non‐volatile major elements that were established by nebular, not planetary processes. Occurrence of abundant breccias among them but lack of clasts of EL in EH chondrites (and vice versa) suggests that EH and EL chondrites represent two separate parent bodies. 2. Aubrites were not derived from known enstatite chondrites on the same parent bodies. Aubrites represent samples from a third enstatite meteorite parent body. 3. The aubrite parent body may have experienced collisional break‐up and gravitational reassembly of the debris into a rubble‐pile object. 4. The aubrite source material (parent body) was probably enstatite chondrite‐like in composition, but had a higher troilite/metallic Fe, Ni ratio, higher contents of titanium and diopside, and possibly less plagioclase than known enstatite chondrites. 5. Shallowater, the only non‐brecciated aubrite, does not appear to have formed on the EH, EL, or aubrite parent bodies by either internal (igneous) or external (impact) melting processes. Instead, Shallowater may be a sample from yet a fourth enstatite meteorite parent body. 6. Shallowater experienced a complex three‐stage cooling history, requiring an equally complex mode of origin: collisional break‐up of a molten or partly molten body by impact with a solid body, followed by gravitational reassembly. 7. It is unknown why some enstatite meteorite parent bodies melted (the aubrite and Shallowater bodies), and others did not (the EH and EL bodies). If unipolar dynamo induction by a primordial T Tauri sun was the dominant heat source that heated asteroidal‐sized bodies in the early Solar System, then the aubrite and Shallowater parent bodies may have melted because they were of intermediate sizes, whereas the EH and EL bodies did not melt because they were either much smaller or much larger.
Lea County 001, an H5 chondrite, and Lea County 002, an ungrouped type 3 chondrite
Authors: Zolensky Michael E. , Score Roberta , Schutt John W. , Clayton Robert N. , Mayeda Toshiko K.
Published: June 2012

Abstract— A search of active deflation basins near Jal, Lea County, New Mexico resulted in the discovery of two meteorites, Lea County 001 and 002. Lea County 001 has mean olivine and low‐Ca pyroxene compositions of Fa19 and Fs17, respectively. These and all other mineralogical and petrological data collected indicate a classification of H5 for this stone. Lea County 002 has mean olivine and low‐Ca pyroxene compositions of Fa2 and Fs4, and is unequilibrated. Although it is mineralogically most similar to Kakangari and chondritic clasts within Cumberland Falls, the high modal amount of forsterite makes Lea County a unique type 3 chondrite. Oxygen isotope data for Lea County 002 fall on an 16O‐mixing line through those of the enstatite meteorites and IAB irons, a feature shared by Kakangari.
Geochemistry of polymict ureilite EET83309, and a partially‐disruptive impact model for ureilite origin
Authors: Warren Paul H. , Kallemeyn Gregory W.
Published: June 2012

Abstract— For most elements, polymict ureilite EET83309 shows no significant compositional difference from other ureilites, including ordinary (“monomict”) ureilites. Polymict ureilites appear to be mixtures of a wide variety of ordinary ureilites, with little dilution by “foreign” extra‐ureilitic materials. Thus, they apparently were mixed (i.e., the ureilites in general formed) on a very small number of parent bodies. In one respect, polymict ureilites do stand out. Along with the only other polymict ureilite that has been analyzed for REE (Nilpena), EET83309 has much higher concentrations of light‐middle REE than most ordinary ureilites. Despite these relative enrichments in LREE, polymict ureilites are nearly devoid of basaltic (Al‐rich) material. A basaltic component should have formed along with (and presumably above) the ultramafic ureilites, in any closed‐system differentiation of an originally chondritic asteroid. This scarcity of complementary basaltic materials may be an important clue to ureilite origins. We suggest that ureilites originated as paracumulates (mushy, cumulate‐like, partial melt residues) deep within a primordially‐heated asteroid or asteroids. While still largely molten, the asteroid was severely disrupted, and most of its external basaltic portion was permanently blown away, by impact of a large, C‐rich projectile. This partially‐disruptive impact tended to permeate the paracumulates with C‐rich, noble‐gas‐rich, and 16O‐rich magma derived mainly from shock‐melting of the projectile. After reaccumulation and cooling, the resultant mixtures of cumulus mafic silicates with essentially “foreign” C‐matrix became “monomict” ureilites. Further small impacts produced polymict ureilites as components of a newly‐developed, basalt‐poor megaregolith. The consistently moderate pyroxene/olivine ratios of the ureilites are as expected for partial melt residues, but not for cumulate (sensu stricto) rocks. The final projectile/target mixing ratio tended to be greatest among the more magnesian and pyroxene‐rich portions of the paracumulate, because these portions were lowest in density, and thus concentrated toward the upper surface of the paracumulate layer. As a result, ureilites show correlations among C, Δ17O, and silicate‐core mg. This model appears to reconcile many paradoxical aspects of ureilite composition (primitive, near‐chondritic, except depleted in basalt, diverse Δ17O) and petrography (igneous, cumulate‐like).
The formation of weathering products on the LEW 85320 ordinary chondrite: Evidence from carbon and oxygen stable isotope compositions and implications for carbonates in SNC meteorites
Authors: Grady Monica M. , Gibson E. K. , Wright I. P. , Pillinger C. T.
Published: June 2012

Abstract— Isotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the δ13C and δ18O values of the two generations of bicarbonate (Antarctic and Texas) are different: δ13C = +7.9‰ and +4.2‰; δ18O = +17.9‰ and + 12.1‰ respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at −2 ± 4 °C (Antarctic) and +16 ± 4 °C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapour or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar δ13C values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.
The Torino, H6, meteorite shower
Authors: Bhandari N. , Bonino G. , Callegari E. , Castagnoli G. Cini , Mathew K. J. , Padia J. T. , Queirazza G.
Published: June 2012

Abstract— A meteorite shower fell at Torino, Italy on 18 May 1988. Petrographic studies indicate that the stone is an H6 chondrite having features of moderate to severe shock. Chemical analyses of the meteorite are reported. Cosmic ray produced 3He, 21Ne and 126Xe yield an exposure age of about 48 Ma. The cosmic ray track densities in three fragments range between 1.8 to 5 × 105/cm2 suggesting about 99% mass ablation in the atmosphere.

Twelve radioisotopes with half lives ranging between 5.6 days to 7.3 × 105 years have been measured with high precision (2 to 10%). Marginal signals were observed for several short‐lived nuclides and upper limits were obtained for the activity levels of eight radionuclides (24Na, 48Cr, 57Ni, 47Sc, 47Ca, 59Fe, 42Ar and 44Ti) some of which have not been hitherto detected in fresh falls. The data are generally consistent with the nuclide production by galactic cosmic rays when modulation due to the solar cycle is taken into consideration.

The preatmospheric radius of the chondrite is estimated to be 20 cm, consistent with track densities and activity levels of 60Co, 26Al and other radionuclides.
Isolated olivines in the Yamato 82042 CM2 chondrite: The tracing of major condensation events in the solar nebula
Authors: Kurat G. , Mayr M. , Ntaflos Th. , Graham A. L.
Published: June 2012

Abstract— Yamato 82042 is an unusual CM2 chondrite consisting mainly of phyllosilicates, a few olivines and carbonates, very minor sulphides and trace metal. Olivine occurs: (1) as isolated grains dispersed in the phyllosilicate matrix, (2) as constituents of mineral aggregates or accretionary fragments associated with abundant phyllosilicates and minor sulphides, and (3) as objects which resemble barred olivine chondrules also associated with phyllosilicates. Olivine, from all occurrences, ranges in composition from 0.26 to 22.6 weight % FeO, but generally contains less than 1.25 wt.% FeO. Minor element contents, particularly Ca, Al, and Cr, are relatively high and are generally correlated, as reported for olivines in other carbonaceous chondrites. However, we report here uncorrected trends for the same minor elements which occur in distinct areas (volumes) within the same olivines. These compositional trends may be due to condensation of olivine from a vapor of non‐solar composition and partial mobilization of Ca during later annealing. If this is the case, the data may be used to trace changes in the Ca/Al ratio of the parent medium during the formation of these olivines, provided that it is possible to distinguish the effects of any post‐formation annealing which could have redistributed the minor elements. Some isolated olivines show distinctive minor element zoning which severely limits the possibility of any post‐formation redistribution of these elements. Accordingly, these isolated olivines indeed retain evidence of early condensation processes in the solar nebula, though non‐classic conditions are implied for their formation.
Tin in a chondritic interplanetary dust particle
Authors: Rietmeijer Frans J. M.
Published: June 2012

Abstract— Submicron platey Sn‐rich grains are present in chondritic porous interplanetary dust particle (IDP) W7029*A and it is the second occurrence of a tin mineral in a stratospheric micrometeorite. Selected Area Electron Diffraction data for the Snrich grains match with Sn2O3 and Sn3O4. The oxide(s) may have formed in the solar nebula when tin metal catalytically supported reduction of CO or during flash heating on atmospheric entry of the IDP. The presence of tin is consistent with enrichments for other volatile trace elements in chondritic IDPs and may signal an emerging trend towards non‐chondritic volatile element abundances in chondritic IDPs. The observation confirms small‐scale mineralogical heterogeneity in fine‐grained chondritic porous interplanetary dust.
The typical meteorite event, based on photographic records of 44 fireballs
Authors: Halliday Ian , Blackwell Alan T. , Griffin Arthur A.
Published: June 2012

Abstract— We study the observational data relating to 44 events recorded by the Canadian fireball camera network between 1971 and 1984. Each event is believed to have dropped meteorites, with main masses in the range from 0.1 to 11 kg. Median values are given for 20 parameters describing the atmospheric behavior and orbital elements. A typical duration for a meteoritic fireball is 4 seconds, reaching an end height of 31 km and a velocity of 8 km s−1 at the end of the luminous path. The peak brightness is typically −9 magnitude but varies from −7 to −15. Meteorites may survive from relatively unspectacular fireballs.

Numerous correlations among parameters are investigated. The strong correlations of brightness with initial mass and of duration with slope of the trajectory could be anticipated. Moderate correlations also exist between: (1) initial mass and end height; (2) initial mass and duration of luminosity; (3) initial velocity and beginning height; (4) initial velocity and the fraction of the mass that survives as the largest fragment; (5) initial velocity and the perihelion distance of the orbit. Ablation limits the survival of small masses while fragmentation is usually severe for masses larger than 10 kg. The fractional survival may peak for entry masses between 1 and 10 kg.
Mineralogy of augite‐bearing ureilites and the origin of their chemical trends
Authors: Takeda Hiroshi , Mori H. , Ogata H.
Published: June 2012

Abstract— Three augite‐bearing ureilites from Antarctica, Y74130, MET78008 and ALH82106, have been studied by electron microprobe, scanning electron microscope (SEM), and analytical transmission electron microscope (TEM). The first two belong to the low‐16O subgroup of Clayton and Mayeda (1988) and are closely related; ALH82106 belongs to the high‐16O subgroup. MET78008 is an augite‐olivine ureilite, similar to the augite‐bearing part of the Y74130. Augites poikilitically include ellipsoidal pigeonites, and low‐Ca pyroxene poikilitically encloses ellipsoidal olivine and augite. The temperature of last equilibration deduced from an orthopyroxene‐pigeonite‐augite assemblage is above 1200 °C. The ALH82106 pigeonite contains irregular augite inclusions produced by decomposition. Augites in Y74130, MET78008 and ALH82106 (decomposed one) all show similar spinodal decomposition textures on the TEM scale. Cooling rates estimated from an experimentally calibrated diagram for the wavelengths of spinodal decomposition versus cooling rates are about 20 °C/hr. The calcic trend for the low‐16O subgroup including Y74130 and MET78008 shows large Ca variations in pyroxene with similar Mg/Fe ratio; differentiation involving reduction was not an important process. Augite in ALH82106 is a minor phase and contains lower Na2O contents than Y74130 and MET78008, confirming that ALH82106 is not directly related to them.
Test of a geometric model for the modification stage of simple impact crater development
Authors: Grieve R. A. F. , Garvin J. B. , Coderre J. M. , Rupert J.
Published: June 2012

Abstract— Small terrestrial hypervelocity impact craters have a bowl‐shaped form and are partially filled by an interior breccia lens, roughly parabolic in cross‐section, of allochthonous material. This interior breccia volume is geometrically modelled as the volume of material slumped off the interior wall of the transient cavity during late stage crater modification. This model is tested by comparing the estimated volume of the breccia lens based on observational data with the calculated volume of slump material based on known dimensional parameters. The model fits well for Meteor Crater and Brent and is highly sensitive to changes in input parameters (e.g., a 10% increase in the input diameter for Meteor Crater produces an almost 200% increase in the model breccia lens volume). Further testing of the model with less constrained data from West Hawk Lake and Lonar leads to reasonable fits, given the sensitivity of the model to input parameters. Fits to other craters: Aouelloul, Tenoumer and Wolf Creek, where previous depth data are constrained only by gravity data, are unsatisfactory. However, revised depths can be obtained that fit both the gravity data and the model. While these tests do not provide unqualified support for the model, they do suggest that it may represent a good first order approximation. More and better quality dimensional data are required for more rigorous testing.
Nd and Sr isotopic evidence for the origin of tektite material from DSDP site 612 off the New Jersey coast
Authors: Stecher O. , Ngo H. H. , D. A. Papanastassiou  , Wasserburg G. J.
Published: June 2012

Abstract— Late Eocene tektite material from DSDP site 612 is composed of angular to spherical tektites and microtektites containing abundant vesicles and a few unmelted to partially melted mineral inclusions. The major element compositions of the 612‐tektites are generally comparable to those of North American tektites, but the physical features suggest that the DSDP‐612 tektites were formed by less severe shock melting. The 87Sr/86Sr and 143Nd/144Nd compositions of 612‐tektites: a) show much wider ranges than the tightly constrained group of North American tektites and microtektites, and b) are significantly different from those of other groups of tektites. The existence of large isotopic variations in tektites from DSDP site 612 requires that they were formed from a chemically and isotopically heterogeneous material in a regime that is distinctive from that of other groups of tektites. TNDCHUR and TSrUR model ages of the 612‐tektites indicate that they were formed from a crustal source of late Precambrian mean age (800–1000 Ma) which in middle Palaeozoic time (≅400 Ma) was further enriched in Rb/Sr during sedimentary processes. These source characteristics suggest that the impact which produced the 612‐tektites occurred in rocks of the Appalachian orogeny or sediments derived from this orogenic belt. Potential source materials for both 612‐tektites and North American tektites are present on the eastern and southeastern part of the North American continent and its adjacent shelf. The distinct isotopic differences between 612‐tektites and North American tektites indicate that the two groups of tektites were either formed by the impact of more than one bolide in the same general area, or by a single impact event that sampled different layers.