摘要:

The saturation magnetization of some carbonaceous chondrites was studied using a Faraday balance. The Faraday balance was shown to be an accurate (± 3%), reliable technique for measuring saturation magnetization by comparison with vibrating‐sample magnetometer measurements on the same samples. Hyman and Rowe (1983) previously used these saturation magnetization measurements to measure the magnetite content of the five CI chondrites. Here, we present measurements on the magnetite contents of some CM2, CV3 and a CV5 chondrites. The method was also used to measure the content of metallic nickel‐iron in Ornans, 3.4 ± 0.3%. Of the CM2 chondrites examined, only Bells, Essebi and Haripura had magnetite contents over about 1% by weight. A number of CV chondrites have magnetite between 2.3 and 13%, with little or no metallic iron. Leoville and Vigarano contain both magnetite and metallic iron, complicating the saturation magnetization results. Arch and Allende have very little metallic iron or magnetite, probably<1% of either. This technique measures only ferrimagnetic magnetite; superparamagnetic magnetite with particle size<300Å is i

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01222.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The Qingzhen (EH3) chondrite contains a population of spheroidal metal‐sulfide nodules, which display textural evidence of reheating and melting. Evidence of metal sulfuration is also present, suggesting replacement of metal by sulfide during melting. This process has led to the nucleation of perryite along metal‐sulfide interfaces.Gallium‐bearing sphalerite and a Cu‐sulfide of composition intermediate between chalcopyrite and cubanite occur as inclusions within the metal of some nodules. Other phases present are: kamacite, troilite, Ga‐free sphalerite, niningerite, perryite, schreibersite, oldhamite, Cr‐sulfide (minerals A and B), djerfisherite, SiO2, albite and enstatite. The Ga‐bearing sphalerite may have formed by injection of molten sulfide droplets into the metal followed by subsolidus diffusion of Ga from the metal into the sulfide. The latter may occur because of Ga supersaturation in the metal during progressive sulfuration and its decreased affinity for the metal phase during cooling below the taenite‐kamacite t

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01223.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The Maryville chondrite fell on January 28, 1983 in eastern Tennessee. Compositions of olivine (Fa 24.5), orthopyroxene (Fs 20.8), plagioclase (An 10.6), along with the bulk composition and siderophile concentrations, indicate L‐group classification. The presence of highly equilibrated minerals, strongly recrystallized matrix, and the development of large, clear plagioclase grains suggest petrologic type 6 classification. Subsequent to metamorphism the meteorite was subjected to high transient pressures that converted some feldspar to glass, deformed the silicates, and caused small amounts of melting to occur. The effects of this shock event correspond to shock facies “d” o

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01224.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

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 chlori

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01225.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

In the summer of 1984, two meteorites fell in the northern part of Honshu, Japan; Aomori, at 1:50 p.m. on June 30, and Tomiya, at 1:35 p.m. on August 22.Coordinates of the falls of the Aomori and the Tomiya are at 140°47.1'E., 40°48.6'N., and 140°51.9'E., 38°22.0'N., respectively.Results of chemical analyses of major elements, ratios of Fetotal/SiO2(0.546 and 0.803) and Femetal/Fetotal(0.332 and 0.581), and molar compositions of olivines (Fa25and Fa19) indicate that the Aomori and the Tomiya are typical L‐ and H‐group ordinary chondrites, respectively.In the Aomori, chondrules are present as relicts in the well‐recrystallized matrix. Olivine and pyroxene are homogeneous in composition, and coarse clear feldspar, up to 100 micrometers in size, is well developed in the chondrules and matrix. Though the Aomori is a petrologic type 6 based on its texture and mineralogy, it includes a few grains of multiple twinned clinobronzite which is rarely observed in highly equilibrated ordinary chondrites.In the Tomiya, chondrules possess a fine‐grained mesostasis, and both orthopyroxene and clinobronzite are noticeable in thin sections. Plagioclase is mostly microcrystalline, but is also sparsely present as tiny, visible grains. Thus, the Tomiya was classified to be petrologic type between 4 and 5.The deformation texture of olivine, pyroxene and plagioclase indicates that both meteorites were shocked by 0.2‐0.25 Mb.In conjunction with the discussion of the frequency of meteorite‐falls, all observed falls of meteorites in Japan are tabulate

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01226.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The bulk composition of metal (kamacite plus perryite) was determined in eleven E‐chondrites and eight aubrites. The data are compatible with the subdivision of the E‐chondrites into two groups (Yavnel, 1963; Anders, 1964), St Mark's and St Sauveur belonging to type I (Easton, 1985).The Ni content of kamacite plus perryite in Kota Kota (5.49%) is within the range covered by the remaining E‐chondrites. Normative perryite, (Fe, Ni)x(Si,P)yconstitutes 2.1% of Kota Kota and 2.7% of South Oman. The Ni content in the bulk metal of Aubres, Bishopville, Norton County and Peña Blanca Spring is about half the average Ni content in the metal of E‐chondrites or the remaining aubrites (Bustee, Khor Temiki, Mayo Belwa and Shallowater). High Ga/Ni and Ge/Ni ratios distinguish the metal in E‐chondrites and aubrites from that in ordinary chondrites.In a large metal grain from Aubres perryite formed on reheating, whereas in one from Khor Temiki there is evidence of shock and displacement of fragmented schreibersite (rhabdite). Thirty‐eight metal grains (<1.5 mm diameter) from Khor Temiki have a wide compositional range like that in Mayo Belwa (Graham, 1978). In Shallowater the distribution of Ni in the metal is bimodal (5.2 and 11.6%) and there is evidence of rapid cooling.The composition of both bulk metal and individual grains in aubrites makes it unlikely that they represent residual metal trapped during magmatic differentiation and/or fractional crystallization of E6 material. Compositional differences between metal grains strongly indicate that the aubrites are polym

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The yields of stable isotopes of Bi, Pb, Tl and Hg as well as yields of205Pb are calculated with a parameterized model for “minir‐processing” in the Ne, O, C‐rich zones of explosive burning in massive stars. The Pb isotopic compositions stand out by their comparatively low207Pb yields and by the fact that thisr‐process variant yields204Pb quite abundantly. The average205Pb/204Pb yield ratio of 6.1 is the same order of magnitude as yield ratios deduced fors‐processing. The Hg from this minir‐process looks like normal solar‐system mercury, but with196Hg missing and the lights‐isotopes A = 198, 199, 200 and 201 depleted (especially t

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01228.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The gas permeability of 11 ordinary chondrites was measured at various gas pressures (0.5‐2.5 bars) under confining pressures up to 120 bars. The gas permeability ranges from less than a nanodarcy to a few millidarcies. There is a positive correlation between the permeability and the porosity. The permeability decreased by as much as 50% when the confining pressure was increased from 10 to 100 bars, suggesting that the permeability of some chondrites is partly due to cracks. A linear relation between gas flow pressure dependence and confining pressure dependence of the gas permeability is observed, suggesting that on average, crack apertures are larger than pore spaces. The permeability of heavily‐shocked chondrites is less than that of mildly shocked chondrites. Using the measured permeability data we estimated the size of a possible shocked‐chondrite precursor

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01229.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

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/sti

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01230.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Microscopic and electron microprobe studies indicate that the Garraf meteorite is a highly‐recrystallized chondrite of petrologic type 6. Olivine (Fa24.7; PMD 1.1) and low‐Ca pyroxene (Fs20.9; PMD 1.1) compositions indicate that it belongs to the L‐group. Based on contents of noble gases, pervasive fracturing of silicates, common undulose extinction of olivine and plagioclase, and the lack of melt pockets and maskelynite, we place Garraf into shock facies b. We conclude that Garraf is a highly recrystallized L6b chondrite that, after recrystallization, was cataclased and comminuted by

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1986.tb01231.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY