摘要:

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 Fa30and 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 featu

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00916.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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 abundan

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00917.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00918.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—A preliminary investigation into the carbon isotopic composition of deep‐sea spherules has been undertaken. A variety of particles have been analysed including both melted and unmelted samples of type S (stony) and type I (iron) spherules, emphasis being placed on surveying the carbon in different sorts of particles rather than analysing large numbers of samples. Some general observations can be made: there appear to be four different sorts of carbonaceous materials in the spherules. Melted and unmelted spherules of either type I or S, apparently contain two forms of low temperature combustible carbon distinguished, not by combustion temperature, but by isotopic composition. The low temperature of combustion is commensurate with these forms of carbon being organic in nature. The most likely explanation for this carbon is terrestrial biogenic contamination although there exists the possibility that there are some indigenous organic materials. Unmelted type S spherules contain a high temperature carbon component, characterised by a very minor13C‐enrichment, which is considered to be indigenous to the sample. All melted samples contain only small amounts of high temperature carbon with an isotopic composition suggestive of handling

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The Pine River IAB iron‐with‐silicate‐inclusions and the anomalous stony meteorite Mount Morris (Wisconsin) were recovered from closely neighbouring localities. Literature data on the petrography, mineralogy, and oxygen isotopic compositions of Mt. Morris (Wis.) and silicates in Pine River are virtually identical. Additionally, total carbon contents and carbon isotopic compositions (δ13C rel. to PDB) of both meteorites (this work) are within experimental error. These data combined with historical and geographical evidence suggest that Mt. Morris (Wis.) and Pine River are pieces of the same m

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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 la

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—A 664 gm stone fell into suburban Baton Rouge in November 1987. The stone has a nearly complete fusion crust and was undamaged upon impact. The ordinary chondrite contains equilibrated olivine, Fa28, and largely equilibrated bronzite, Fs23. Some bronzite is still compositionally zoned and polysynthetically twinned, thus requiring petrologic classification of the meteorite as a type 4. A major element analysis of the meteorite falls exclusively into the field for the LL compositional grou

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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), H5

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00923.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00924.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

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 I

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1988.tb00925.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY