bluuebunny/crossref_metadata_2025_split huggingface dataset:
Authentication controversies and impactite petrography of the New Quebec Crater
Authors: Marvin Ursula B. , Kring David A. 
Published: June 2012

Abstract— A meteoritic origin was proposed for the New Quebec Crater in 1949 on the basis of an aerial photograph showing its unique circularity and raised rim amid Precambrian gneisses of the Canadian Shield. At that time, only those few craters associated with meteorites were generally accepted as of impact origin. When the earliest field expeditions failed to find meteorites or impact products, two leading meteoriticists, Frederick C. Leonard and Lincoln LaPaz, cited the “Chubb” Crater as a flagrant example for which claims of meteoritic origin were advanced without valid proof. They also listed the Lake Bosumtwi Crater in Ashanti (now Ghana) among crater‐like features, clearly of non‐meteoritic origin, misidentified as meteorite craters. Controversy over the origin these two craters continued for decades.In Part I of this paper, we trace the investigations that led to the current acceptance of New Quebec as an authentic impact crater. We note that, for reasons that are not entirely clear, a meteoritic origin for the New Quebec Crater achieved wider acceptance at an earlier date than for the Lake Bosumtwi Crater, where petrographic and chemical evidence is more abundant and compelling.In Part II, we describe the petrography of two impact melt samples from the New Quebec Crater and present new evidence on the degrees of shock metamorphism affecting the accessory minerals: apatite, sphene, magnetite and zircon. Zircon, in particular, shows a range from euhedral grains with no signs of alteration to those decomposed to baddeleyite plus silica.
The effect of Na vapor on the Na content of chondrules
Authors: Lewis R. Dean , Lofgren Gary E. , Franzen Hugo F. , Windom Kenneth E. 
Published: June 2012

Abstract— Chondrules contain higher concentrations of volatiles (Na) than expected for melt droplets in the solar nebula. Recent studies have proposed that chondrules may have formed under non‐canonical nebular conditions such as in particle/gas‐rich clumps. Such chondrule formation areas may have contained significant Na vapor. To test the hypothesis of whether a Na‐rich vapor would minimize Na volatilization reaction rates in a chondrule analog and maintain the Na value of the melt, experiments were designed where a Na‐rich vapor could be maintained around the sample. A starting material with a melting point lower that typical chondrules was required to keep the logistics of working with Na volatilization from NaCl within the realm of feasiblity. The Knippa basalt, a MgO‐rich alkali olivine basalt with a melting temperature of 1325°± 5 °C and a Na2O content of 3.05 wt%, was used as the chondrule analog. Experiments were conducted in a 1 atm, gas‐mixing furnace with the fO2 controlled by a CO/CO2 gas mixture and fixed at the I‐W buffer curve. To determine the extent of Na loss from the sample, initial experiments were conducted at high temperatures (1300 °C–1350 °C) for duration of up to 72 h without a Na‐rich vapor present. Almost all (up to 98%) Na was volatilized in runs of 72 h. Subsequent trials were conducted at 1330 °C for 16 h in the presence of a Na‐rich vapor, supplied by a NaCl‐filled crucible placed in the bottom of the furnace. Succeeding Knudsen cell weight‐loss mass‐spectrometry analysis of NaCl determined the PNa for these experimental conditions to be in the 10−6 atm range. This value is considered high for nebula conditions but is still plausible for non‐canonical environments. In these trials the Na2O content of the glass was maintained or in some cases increased; Na2O values ranged from 2.62% wt to 4.37% wt.The Na content of chondrules may be controlled by the Na vapor pressure in the chondrule formation region. Most heating events capable of producing chondrules are sufficient to volatilize Na. Sodium volatilization reaction rates will be reduced to varying degrees from melt droplets, depending on the magnitude of the PNa generated. A combination of Na vapor during, and Na diffusion back into chondrules after, formation could maintain and/or enrich Na concentrations in chondrules.
Basalt generation at the Apollo 12 site, Part 1: New data, classification, and re‐evaluation
Authors: Neal Clive R. , Hacker Matthew D. , Snyder Gregory A. , Taylor Lawrence A. , Liu Yun‐Gang , Schmitt Roman A. 
Published: June 2012

Abstract— New data are reported from five previously unanalyzed Apollo 12 mare basalts that are incorporated into an evaluation of previous petrogenetic models and classification schemes for these basalts. This paper proposes a classification for Apollo 12 mare basalts on the basis of whole‐rock Mg# [molar 100*(Mg/(Mg+Fe))] and Rb/Sr ratio (analyzed by isotope dilution), whereby the ilmenite, olivine, and pigeonite basalt groups are readily distinguished from each other. Scrutiny of the Apollo 12 feldspathic “suite” demonstrates that two of the three basalts previously assigned to this group (12031, 12038, 12072) can be reclassified: 12031 is a plagioclase‐rich pigeonite basalt (Nyquist et al, 1979); and 12072 is an olivine basalt Only basalt 12038 stands out as a unique sample (Nyquist et al., 1981) to the Apollo 12 she, but whether this represents a single sample from another flow at the Apollo 12 site or is exotic to this site is equivocal.The question of whether the olivine and pigeonite basalt suites are co‐magmatic is addressed by incompatible trace‐element chemistry: the trends defined by these two suites when Co/Sm and Sm/Eu ratios are plotted against Rb/Sr ratio demonstrate that these two basaltic types cannot be co‐magmatic. Crystal fractionation/accumulation paths have been calculated and show that neither the pigeonite, olivine, or ilmenite basalts are related by this process. Each suite requires a distinct and separate source region. This study also examines sample heterogeneity and the degree to which whole‐rock analyses are representative, which is critical when petrogenetic interpretation is undertaken. Sample heterogeneity has been investigated petrographically (inhomogeneous mineral distribution) with consideration of duplicate analyses, and whether a specific sample (using average data) plots consistently upon a fractionation trend when a number of different compositional parameters are considered. Using these criteria, four basalts have been identified where reported analyses are not representative of the whole‐rock composition: 12005, an ilmenite basalt; 12006 and 12036, olivine basalts; and 12031 previously classified as a feldspathic basalt, but reclassified as part of the pigeonite suite (Nyquist et al., 1979).
The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron‐rich pyroxene
Authors: Weisberg Michael K. , Prinz Martin , Fogel Robert A. 
Published: June 2012

Abstract— FeO‐rich (Fs6–34) pyroxene lacking cathodoluminescence (CL), hereafter black pyroxene, is a major constituent of some of the chondrules and fragments in unequilibrated (type 3) enstatite chondrites (UECs). It contains structurally oriented zones of Cr‐, Mn‐, V‐rich, FeO‐poor enstatite with red CL, associated with mm‐sized blebs of low‐Ni, Fe‐metal and, in some cases, silica. These occurrences represent clear evidence of pyroxene reduction. The black pyroxene is nearly always rimmed by minor element (Cr, Mn, V)‐poor enstatite having a blue CL. More commonly, red and blue enstatites, unassociated with black pyroxene, occur as larger grains in chondrules and fragments, and these constitute the major silicate phases in UECs. The REE abundance patterns of the black pyroxene are LREE‐depleted. The blue enstatite rims, however, have a near‐flat to LREE‐enriched pattern, ∼0.5–4x chondritic. The petrologic and trace element data indicate that the black pyroxene is from an earlier generation of chondrules that formed in a nebular region that was more oxidizing than that of the enstatite chondrites. Following solidification, these chondrules experienced a more reducing nebular environment and underwent reduction. Some, perhaps most, of the red enstatite that is common throughout the UECs may be the product of solid‐state reduction of black pyroxene. The blue enstatite rims grew onto the surfaces of the black pyroxene and red enstatite as a result of condensation from a nebular gas.The evolutionary history of some of the enstatite and chondrules in enstatite chondrites can be expressed in a four‐stage model that includes: Stage 1. Formation of chondrules in an oxidizing nebular environment Stage 2. Solid‐state reduction of the more oxidized chondrules and fragments to red enstatite in a more reducing nebular environment Stage 3. Formation of blue enstatite rims on the black pyroxene as well as on the red enstatite. Stage 4. Reprocessing, by various degrees of melting, of many of the earlier‐formed materials.
Acfer 217‐A new member of the Rumuruti chondrite group (R)
Authors: Bischoff A. , Geiger T. , Palme H. , Spettel B. , Schultz L. , Scherer P. , Loeken T. , Bland P. , Clayton R. N. , Mayeda T. K. , Herpers U. , Meltzow B. , Michel R. , Dittrich‐Hannen B. 
Published: June 2012

Abstract— Previously, three meteorites from Australia and Antarctica were described as a new chondritic “grouplet” (Carlisle Lakes, Allan Hills (ALH) 85151, Yamato (Y) −75302; Rubin and Kallemeyn, 1989). This grouplet was classified as the “Carlisle Lakes‐type” chondrites (Weisberg et al., 1991). Recently, one Saharan sample and four more Antarctic meteorites were identified to belong to this group (Acfer 217, Y‐793575, Y‐82002, PCA91002, PCA91241). The latter two are probably paired. With the meteorite Rumuruti, the first fall of this type of chondrite is known (Schulze et al., 1994). We report here on the Saharan meteorite Acfer 217 which has chemical and mineralogical properties very similar to Rumuruti and Carlisle Lakes. All eight members of this group, Rumuruti, Carlisle Lakes, ALH85151, Y‐75302, Y‐793575, Y‐82002, Acfer 217, and the paired samples PCA91002 and PCA91241 justify the introduction of a new group of chondritic meteorites, the Rumuruti meteorites (R).Acfer 217 is a regolith breccia consisting of up to cm‐sized clasts (∼33 vol%) embedded in a fine‐grained, well‐lithified clastic matrix. The most abundant mineral is olivine (∼72 vol%), which has a high Fa‐content of 37–39 mol%. The major minerals (olivine, low‐Ca pyroxene, Ca‐pyroxene, and plagioclase) show some compositional variability indicating a slightly unequilibrated nature of the meteorite. Considering the mean olivine composition of Fa37.8 ± 5.7, a classification of Acfer 217 as a R3.8 chondrite would result; however, Acfer 217 is a regolith breccia consisting of clasts of various petrologic types. Therefore, we suggest to classify Acfer 217 as a R3–5 chondrite regolith breccia. The bulk meteorite is very weakly shocked (S2).The bulk composition of Acfer 217 and other R‐meteorites show that the R‐meteorites are basically chondritic in composition. The pattern of moderately volatile elements is unique in R chondrites; Na and Mn are essentially undepleted, similar to ordinary chondrites, while Zn and Se contents are similar to concentrations in CM chondrites. The oxygen isotopic composition in Acfer 217 is similar to that of Rumuruti, Carlisle Lakes, ALH 85151, and Y‐75302. In a δ17O vs. δ18O‐diagram, the R‐meteorites form a group well resolved from other chondrite groups.Acfer 217 was a meteoroid of common size with a radius between 15–65 cm and with a single stage exposure history. Based on 21Ne, an exposure age of about 35 Ma was calculated.
A new titanium‐bearing calcium aluminosilicate phase: I. Meteoritic occurrences and formation in synthetic systems
Authors: Paque Julie M. , Beckett John R. , Barber David J. , Stolper Edward M. 
Published: June 2012

Abstract A new titanium‐bearing calcium aluminosilicate mineral has been identified in coarse‐grained calcium‐aluminum‐rich inclusions (CAIs) from carbonaceous chondrites. The formula for this phase, which we have temporarily termed “UNK,” is Ca3Ti(Al, Ti)2(Si, Al)3O14, and it is present in at least 8 of the 20 coarse‐grained CAIs from the Allende CV3 chondrite examined as part of this project. The phase occurs in Types A and B1 inclusions as small tabular crystals oriented along two mutually perpendicular planes in melilite.UNK crystallizes from melts in dynamic crystallization experiments conducted in air from four bulk compositions modeled after Types A, B1, B2 and C inclusions. Cooling rates resulting in crystallization of UNK ranged from 0.5 to 200 °C/h from maximum (initial) temperatures of 1375 to 1580 °C. Only below 1190 °C does UNK itself begin to crystallize. To first order, the presence or absence of UNK from individual experiments can be understood in terms of the compositions of residual melts and nucleation probabilities.Compositions of synthetic and meteoritic UNK are very similar in terms of major oxides, differing only in the small amounts of trivalent Ti (7–13% of total Ti) in meteoritic samples. UNK crystallized from the Type A analog is similar texturally to that found in CAIs, although glass, which is typically associated with synthetic UNK, is not observed in meteoritic occurrences. A low Ti end‐member of UNK (“Si‐UNK”) with a composition near that of Ca3Al2Si4O14 was produced in a few samples from the Type B1 analog. This phase has not been found in the meteoritic inclusions.
A new titanium‐bearing calcium aluminosilicate phase: II. Crystallography and crystal chemistry of grains formed in slowly cooled melts with bulk compositions of calcium‐ aluminum‐rich inclusions
Authors: Barber David J. , Beckett John R. , Paque Julie M. , Stolper Edward 
Published: June 2012

Abstract The crystallography and crystal chemistry of a new calcium‐titanium‐aluminosilicate mineral (UNK) observed in synthetic analogs to calcium‐aluminum‐rich inclusions (CAIs) from carbonaceous chondrites was studied by electron diffraction techniques. The unit cell is primitive hexagonal or trigonal, with a = 0.790 ± 0.002 nm and c = 0.492 ± 0.002 nm, similar to the lattice parameters of melilite and consistent with cell dimensions for crystals in a mixer furnace slag described by Barber and Agrell (1994). The phase frequently displays an epitactic relationship in which melilite acts as the host, with (0001)UNK | (001)mel and <10T0>UNK | <100>mel. If one of the two space groups determined by Barber and Agrell (1994) for their sample of UNK is applicable (P3ml or P31m), then the structure is probably characterized by puckered sheets of octahedra and tetrahedra perpendicular to the c‐axis with successive sheets coordinated by planar arrays of Ca. In this likely structure, each unit cell contains three Ca sites located in mirror planes, one octahedrally coordinated cation located along a three‐fold axis and five tetrahedrally coordinated cations, three in mirrors and two along triads. The octahedron contains Ti but, because there are 1.3–1.9 cations of Ti/formula unit, some of the Ti must also be in tetrahedral coordination, an unusual but not unprecedented situation for a silicate. Tetrahedral sites in mirror planes would contain mostly Si, with lesser amounts of Al while those along the triads correspondingly contain mostly Al with subordinate Ti. The structural formula, therefore, can be expressed aswith Si + Ti = 4. Compositions of meteoritic and synthetic Ti‐bearing samples of the phase can be described in terms of a binary solid solution between the end‐members Ca3TiAl2Si3O14 and Ca3Ti(AlTi)(AlSi2)O14. A Ti‐free analog with a formula of Ca3Al2Si4O14 synthesized by Paque et al. (1994) is thought to be related structurally but with the octahedral site being occupied by Al, that is
Metamorphism and aqueous alteration in low petrographic type ordinary chondrites
Authors: Sears Derek W. G. , Morse Andrew D. , Hutchison Robert , Guimon R. Kyle , Jie Lu , Alexander C. M. O'D. , Benoit Paul H. , Wright Ian , Pillinger Colin , Xie Tian , Lipschutz Michael E. 
Published: June 2012

Abstract— In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondrules, chondrules were hand‐picked from the Semarkona (petrographic type 3.0), Bishunpur (3.1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron‐microprobe and radiochemical neutron activation and the water and H‐isotopic composition determined.The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to ∼8000‰ SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work.With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondrules, indicating metamorphism‐related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence for aqueous alteration, but the matrix contains H with approximately terrestrial D/H values, even though it contains much water. Secondary processes (probably aqueous alteration) presumably lowered the D/H of the matrix and certain chondrules. While chondrule properties appear to be governed primarily by formation processes and subsequent metamorphism, the matrix of Semarkona has a more complex history involving aqueous alteration as a meteorite‐wide process.
Phase diagrams describing solid‐gas equilibria in the system Fe‐Mg‐Si‐O‐C‐H, and its bearing on redox states of chondrites
Authors: Tsuchiyama Akira , Kitamura Masao 
Published: June 2012

Abstract— Phase diagrams describing solid‐gas equilibria in the system Fe‐Mg‐Si‐O‐C‐H under H‐rich conditions (∼700–2000 K and 10−2–10−20 atm of Ph2), including solar nebula conditions, were constructed based on thermochemical calculations. Boundaries of vaporous phases, which are the first phases to condense from a gas, can be obtained without calculating condensation temperatures of individual gas compositions because the numbers of major gaseous species are the same as those of components in the concerned systems. Fractionations by condensation and/or evaporation can be discussed easily in such phase diagrams. A thermal divide, which is a barrier that vapors cannot cross by a single cooling process, was recognized in the phase diagrams. This is present on the Fe‐MgO‐SiO2‐CO‐H plane at high temperatures (≥500–700 K) and plays an important role in fractionations.Oxidizing states of ordinary chondrites and carbonaceous chondrites before aqueous alteration are located at the O‐rich side of the thermal divide. Such oxidizing states can be formed from the solar gas by fractionation in the primordial solar nebula because the solar composition is located on the O‐rich side. On the other hand, the reducing states of enstatite chondrites, located at the O‐poor side, cannot be formed as long as the thermal divide is present. The reducing states can be obtained by CO to CH4 molecular reaction at low temperatures (≤500–700 K), where the high‐temperature thermal divide is absent. Addition of H2O‐rich and CH4‐rich ice can explain establishment of the redox states of ordinary and enstatite chondrites, respectively.
Beryllium‐10 and aluminum‐26 in individual cosmic spherules from Antarctica
Authors: Nishiizumi K. , Arnold J. R. , Brownlee D. E. , Caffee M. W. , Finkel R. C. , Harvey R. P. 
Published: June 2012

Abstract— We present data for the cosmogenic nuclides 10Be and 26Al in a suite of 24 extraterrestrial spherules, collected from Antarctic moraines and deep sea sediments. All of the 10 large spherules collected in glacial till at Lewis Cliff are extraterrestrial. As in earlier work, the great majority of particles show prominent solar cosmic‐ray (SCR) production of 26Al, indicating bombardment ages on the order of 106 years or even longer. These long ages are in direct contradiction to model ages for small particles in the inner Solar System and may require reconsideration of models of small particle lifetimes. A small fraction of the particles so far measured (6/42) possess cosmogenic radionuclide patterns consistent with predictions for meteoroid spall droplets. We believe that most of the spherules were bombarded in space primarily as bodies not much larger than their present size.The content of in situ produced 10Be and 26Al in quartz pebbles in the same moraine suggests that these spherules may have on average a significant terrestrial age.
Aerobic neuromuscular electrical stimulation—an emerging technology to improve haemoglobin A1c in type 2 diabetes mellitus: results of a pilot study
Authors: Crowe Louis , Caulfield Brian 
Published: June 2012

ObjectivesA new generation of neuromuscular electrical stimulation (NMES) devices can exercise aerobically at equivalent rates to voluntary exercise. Many with type 2 diabetes cannot or will not exercise sufficiently. The objective of this pilot investigation was to see (1) if it was an acceptable training modality for men with type 2 diabetes mellitus and (2) to assess effects on haemoglobin A1c levels.Design, setting, participants and interventionA case series of eight men with type 2 diabetes mellitus (aged 53±8; body mass index 32±5 5 kg/m2) trained with the NMES system for 1 h 6 times weekly for 8 weeks, unsupervised, at home. There were no other medication or lifestyle interventions. The aerobic NMES exercise system delivers a repeating set of four complex staggered pulses at high intensities (typically 100 mA+) through an array of eight thigh electrodes.Outcome measuresThe primary outcome measures were changes in haemoglobin A1c and the responses in a questionnaire on participants' perceptions of the system. Body mass and composition were also measured before and after the NMES intervention period.ResultsAll participants could use the system at a level that left them breathless and sweaty and with a heart rate over 120 beats per minute. Haemoglobin A1c levels improved by 0.8±0.7% from 7.4±1.3% (mean ± SD) to 6.6±1.0% (p=0.01). All participants considered the system suitable for people with diabetes, would recommend it and would continue to use it twice a week ‘to maintain improvements’.ConclusionsThese results suggest that aerobic NMES may be acceptable and have a beneficial effect on haemoglobin A1c of some men with diabetes. The treatment may be of particular benefit in those who will not or cannot do adequate amounts of voluntary exercise. A randomised control trial is required for conclusive efficacy data.