An Iron Meteorite from Akyumak

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.     

Surviving Metal in Meteoritic Iron Oxide from The Wolf Creek,Western Australia,Meteorite Crater

Abstract. Some very small particles of metal, revealed by polishing a chunk of Wolf Creek meteoritic iron oxide, appear to consist entirely of moderately shocked kamacite. The apparent lack of surviving taenite tentatively suggests that the Wolf Creek crater was formed by a hexahedrite, although medium octahedrites have recently been found within 4000 meters of the crater. Macrosegregation of nickel within the Wolf Creek meteoroid could account for the discrepancy. Further research on surviving metal is indicated.     

乌希里克铁陨石的组织结构、冷却历史和定量预测模型

铁陨石记录了陨石母体所经历的熔融、分异和冷却的热历史, 研究铁陨石内部的组织结构对理解陨石母体的热历史和内部圈层结构有重要的指导意义. 分析阿勒泰铁陨石个体-乌希里克(Wuxilike)铁陨石中铁纹石和镍纹石所构造的维斯台登(Widmanstatten)纹、梳状合纹石以及云状区等组织结构来探究其各自的形成过程. 通过热动力学计算软件和数据库, 建立了Widmanstatten经过取向校正的冷却速率计算模型, 并据此计算了该陨石在695℃–400℃区间内的冷却速率; 通过研究梳状合纹石内部铁、镍纹石中Ni元素的成分分布及其位相关系, 推理得到梳状合纹石的低温马氏体分解形成机制; 通过研究云状区域中颗粒大小和局部Ni含量的关系, 得出形成云状区域所对应的铁陨石在350℃下的冷却速率. 据此模拟计算出该铁陨石在695℃–200℃范围内形成Widmanstatten纹、各类合纹石和云状区的整个热历史. 基于固态相变所建立的定量模型可望为分析铁陨石的冷却历史提供更为准确的分析手段.     

The Oshkosh Meteorite

Abstract In the fall of 1961, fragments of an olivine-bronzite chondrite were found about 2 miles NNW of Oshkosh, Wisconsin, the total weight being 144.8 g. This paper fixes the exact location and describes the circumstances of the find.     

Troilite Push-Out Pit on the Surface of a Freshly-Fallen Iron Meteorite

Abstract. The surface of the Withrow meteorite shows an unusual pit about two inches in diameter. This is explained as the result of pushing out of a plug of metal by expansion of an underlying troilite nodule.     

The Fremont Butte,Washington Co., Colorado,Meteorite

Abstract The Fremont Butte meteorite was found near Fremont Butte, Colorado, in 1963. A single individual was found weighing 6.6 kg. It is an olivine-hypersthene or L group chondrite showing brecciation and a small number of well formed chondrules and olivine phenocrysts.     

The Belle Plaine III Meteorite

Abstract The Belle Plaine III meteorite is one of three meteorites, all of about the same size, found within a 2 mile strip southeast of Belle Plaine, Kansas. The meteorite weighs 23.9 kg, and consists of about 28% metallic minerals and 72% silicates. Nickel-iron, magnetite, hypersthene and olivene are the major constituents. The meteorite is an olivene-hypersthene chondrite.     

The Tuxtuac,Mexico, Meteorite,an LL5 Chondrite Fall

Abstract— The Tuxtuac meteorite fell in Zacatecas state, Mexico, on 16 October 1975, at 1820 hours. Two partly crusted masses, weighing 1924 g and 2340 g, were recovered. The stone is an ordinary chondrite, LL5, with olivine Fa₃₀ and 19.22 weight % total iron. The silicates contain numerous voids and a froth-like mesostasis is present within some chondrules. Metal phases present are kamacite (5.7–6.4% Ni, 6–7% Co) and high nickel metal (taenite 37–41% Ni, 1.7 ± 0.3% Co; tetrataenite 47–52% Ni, 0.8–1.4% Co). The stone is unusual for an LL-group chondrite in that it exhibits neither large-scale brecciation features nor dark veins.     

Withrow — a New Iron Meteorite from the State of Washington

Abstract. About 1950 an iron meteorite weighing 19 1/4 pounds was found a mile west of Withrow in Douglas County, Washington. The discovery site happens to be a little less than 5 miles SSE from that of the Waterville meteorite. However, the two irons are definitely not from a single fall. Withrow is a medium octahedrite showing secondary recrystallization of the type ascribed to cosmic heating. It was apparently picked up not more than a few years after it fell. Weathering is minimal, and effects of passage through the atmosphere are well preserved.     

The Bur-Gheluai Meteorite (Mineralogy,Structure and Metamorphism)

Abstract The principal data about the fall and the distribution of the fragments of the Bur-Gheluai, Bur Acaba, Somalia (CN = EO436,024) meteorite are collected. A complete individual, weighing 744.2 g, preserved in the Geological Institute, Agricultural Dept., University of Perugia, Italy, is described in some detail. Crust morphology, mineralogical composition and structure are studied. Optical data are established by microscopical analysis of eight thin sections and two polished surfaces. Compared with electron-probe analysis, they are found in good agreement. Bur-Gheluai is an holocrystalline, olivine-bronzite chondrite, with evident features of recrystal-lization and metamorphism.     

The Infrared Transmission Spectrum of the Salzwedel Meteorite

Abstract— The paper presents the infrared transmission spectrum of the Salzwedel meteorite. Further, the spectrum is used to characterize the meteorite's mineralogical composition.     

Meteorite fusion crust variability

Abstract— Two assumptions commonly employed in meteorite interpretation are that fusion crust compositions represent the bulk‐rock chemistry of the interior meteorite and that the vesicles within the fusion crust result from the release of implanted solar wind volatiles. Electron microprobe analyses of thin sections from lunar meteorite Miller Range (MIL) 05035 and eucrite Bates Nunataks (BTN) 00300 were performed to determine if the chemical compositions of the fusion crust varied and/or represented the published bulk rock composition. It was determined that fusion crust compositions are significantly influenced by the incorporation of fragments from the substrate, and by the composition and grain size of those minerals. Because of compositional heterogeneities throughout the meteorite, one cannot assume that fusion crust composition represents the bulk rock composition. If the compositional variability within the fusion crust and mineralogical differences among thin sections goes unnoticed, then the perceived composition and petrogenetic models of formation will be incorrect. The formation of vesicles within these fusion crusts were also compared to current theories attributing vesicles to a solar wind origin. Previous work from the STONE‐5 experiment, where terrestrial rocks were exposed on the exterior of a spacecraft heatshield, produced a vesicular fusion crust without prolonged exposure to solar wind suggesting that the high temperatures experienced by a meteorite during passage through the Earth's atmosphere are sufficient to cause boiling of the melt. Therefore, the assumption that all vesicles found within a fusion crust are due to the release of implanted volatiles of solar wind may not be justified.     

Compositional Study of a Suite of Samples from the 28-t Armanty (Xinjiang) Iron Meteorite

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 Berduc L6 chondrite fall: Meteorite characterization,trajectory, and orbital elements

Abstract– The fall of the Berduc meteorite took place on April 7, 2008, at 01 h 02 min 28 s ± 1 s UTC. A daylight fireball was witnessed by hundreds of people from Argentina and Uruguay, and also recorded by an infrasound array in Paraguay. From the available data, the fireball trajectory and radiant have been reconstructed with moderate accuracy. The modeled trajectory was tested to fit the infrasound and strewn field data. From the computed apparent radiant α = 87 ± 2° and δ = ?11 ± 2° and taking into account a range of plausible initial velocities, we obtained a range of orbital solutions. All of them suggest that the progenitor meteoroid originated from the main asteroid belt and followed an orbit of low inclination. Based on petrography, mineral chemistry, magnetic susceptibility, and bulk chemistry, the Berduc meteorite is classified as an L6 ordinary chondrite.     

Meteorite transport—Revisited

Meteorites are delivered from the asteroid belt by way of chaotic zones (Wisdom 1985a). The dominant sources are believed to be the chaotic zones associated with the ν₆ secular resonance, the 3:1 mean motion resonance, and the 5:2 mean motion resonance. Though the meteorite transport process has been previously studied, those studies have limitations. Here I reassess the meteorite transport process with fewer limitations. Prior studies have not been able to reproduce the afternoon excess (the fact that approximately twice as many meteorites fall in the afternoon as in the morning) and suggested that the afternoon excess is an observational artifact; here it is shown that the afternoon excess is in fact consistent with the transport of meteorites by way of chaotic zones in the asteroid belt. By studying models with and without the inner planets it is found that the inner planets significantly speed up the transport of meteorites.     

Finding a New Meteorite

Following is an account of the incidents relevant to the discovery of several new meteorites, in particular a small stony specimen (an aerolite) weighing about 4 pounds, found recently on a farm in the northern part of Cowley County, Kansas.     

Meteorite finds from southern Tunisia

Abstract— We report on the meteorite search campaign of April 2008, conducted by a joint Tunisian‐Italian scientific expedition in southern Tunisia (Dahar region). Nine likely unpaired meteorites (seven H‐class and two L‐class chondrites) totalling ?1.3 kg were recovered by exploring an approximately 45 km²area, therefore demonstrating that southern Tunisia is a suitable terrain for systematic searches for meteorites.