摘要:

In the Tysnes Island gas‐rich, H4 chondrite an inclusion was found which consists of two distinct portions: a tear‐drop shaped Fe‐FeS eutectic‐like intergrowth (0.5 cm greatest dimension) and a silicate consisting primarily of olivine in glass. The boundary between the two portions of the inclusion is smooth. Nickel is enriched in the metal at the metal‐sulfide boundaries and in nodules within the metal. The subhedral to skeletal olivine in the silicate portion is forsteritic, Fo75–90.The glass is very rich in SiO2,up to 70%. The glass is not homogeneous, but a fairly typical analysis is SiO2,66.9%; TiO2,0.4; Al2O3,0.4; Cr2O30.3; Na2O, 3.3; K2O, 0.9; CaO, 6.0; Fe, 10.9; Mg, 2.0. The Fe‐FeS and silicate portions appear to have separated from one another as immiscible liquids. The modal composition of each portion agrees well with compositions predicted for a total melt of an H‐group chondrite. This inclusion seems to be a “snapshot” of the process of metal‐silicate fractionation which Fodor and Keil (1976) have previously suggested must exist to explain the presence of metal‐ and sulfide‐free inclusions

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00795.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Inman (find, 1966) is a single, relatively unweathered stone of 7.25 kg that contains fresh metal and only few weathering products away from fractures. It has a pronounced chondritic texture, with 38 vol % of the meteorite being made up of chondrules of virtually all textural types. The recalculated bulk analysis, particularly the ratios of Fetotal/SiO2(0.46), Fe°/Fetotal(0.35), and Fe°/Ni° (6.67) and the contents of Fetotal(19.45%) and metallic nickel‐iron (7.94%), indicate that Inman is an L‐group chondrite. The pronounced chondritic texture; the compositional variabilities of olivine, pyroxene, chromite, and ilmenite; the presence of a fine‐grained, nearly opaque matrix, glass and twinned monoclinic low‐Ca pyroxene indicate that the chondrite belongs to petrolo

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00796.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The Yamato (j), (k), (l), and (m) meteorites collected from near the Yamato Mountains in December, 1973, are respectively an H‐4 and L‐5 chondrite, a howardite, and an L‐5 chondrite. Yamato (l), the howardite, is a polymict breccia of diogenite and eucrite clasts. Olivine in the chondrites ranges in composition from Fo75to Fo80,whereas in the howardite, where it is rare, the composition is about Fo60.Pyroxenes in the chondrites are mostly orthopyroxenes and (En83),while the pyroxenes in the howardite are more complex, comprising orthopyroxene, pigeonite, augite, and rare clinohypersthene (in the order of decreasing abundance), with the range from En80to En37.They form a definite trend, probably formed by the fractional crystallization of the parental magma of the achondrite, and later subjected to exsolution phenomena during the slow cooling. Plagioclase is high‐temperature oligoclase in the chondrites, and anorthite in the howardite. Maskelynitization is sometimes observed. Other shock effects are also observed.Opaque phases consist mostly of nickel‐iron, troilite, chromite, and rarely ilmenite. Intergrowth of these minerals are common. The accessory minerals comprise quartz, cristobalite, apatite, spinel, and rare uranium‐bearing minerals. The bulk composition and genetic significance ar

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00797.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Grain size frequency distributions of the ≥ 0.1 mm size fractions have been measured for 19 C2 and C3 carbonaceous chondrites (7 CM2, 5 CO3, 6 CV3 and 1 CV2). The grain size frequency distribution curves and summary statistics are remarkably similar for the CM2 and CO3 meteorites, with ranges of median grain size from 2.36φ to 2.67φ and graphic mean grain size from 2.20φ to 2.59φ. The CV3 specimens are distinctly coarser than the CM2 and CO3 meteorites and have a wider range of grain size summary statistics. The grain size frequency data for fluid drop chondrules and for lithic chondrules show approximately the same size frequency characteristics as the more abundant particles in each of the petrologic subgroups. If the chondrules and other particles were produced by different mechanisms or in different environments, an extremely effective size sorting process is required to produce the observed grain size frequency distributions. Alternatively, most of the particles and the observed grain size frequency distributions might have been produced by small impacts into an immature, accretionary regolith. The strong similarity between the grain sizes of the CM2 and CO3 meteorites, together with previously recognized chemical similarities, suggest a genetic relationship between the two petrologic subgroups. The grain size frequency distributions of chondrules and other particles in CM2 and CO3 meteorites are different from those found previously in ordinary chon

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00798.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The meteoritic occurrence of rhönite‐bearing calcium and aluminum rich inclusions (CAIs) appears to be restricted to the Allende meteorite. These inclusions, however, are very scarce as only four are known to the author. This report is primarily concerned with the descriptive mineralogy of one of these rare CAIs.The inclusion contains, in decreasing order of abundance, melilite (Ak15‐Ak55),spinel, fassaite, rhönite, perovskite, grossular, Ni‐Fe metal, hibonite, troilite, a vanadium‐iron oxide (20–27 wt % V2O3),molybdenite, geikielo‐ilmenite and magnetite. Although this mineral assemblage formed under nonequilibrium conditions from a molten drop, the coarse grained texture does not indicate rapid crystallization. Local chemistries evidently played a significant role in the formation of metastable phase relationships and symplectites, thereby confounding the construction of a plausible thermal history

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00799.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A chemical scheme is reported for the analysis of chondritic materials and results are presented for the Cocklebiddy meteorite. Analytical problems associated with chondrite inhomogeneity including phase leaching selectivity and the completeness of individual phase attack are considered. Data obtained by this method can be used to classify chondrites according to the accepted weight and molar ratio methods (Van Schmus and Wood, 1967: Wasson, 1974)The analytical scheme uses selective leaching techniques to determine, in each sample, the chemical composition of metallic, sulphide and silicate phases. Elemental concentrations are obtained by atomic absorption spectrometry, flame photometry, spectrophotometry or titration techniques, and the total sample average compositions are determined on fully oxidised specimens by XRF

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00800.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

We present JHK colors observed for ten asteroids and synthesized JHK colors for seven meteorite groups, samples of iron and nickel metal, pyroxene, olivine, feldspar, a lunar anorthite and some terrestrial mineral samples. Pronounced differences are apparent between the chondritic and achondritic meteorite classes; the chondritic classes show less subdued trends in J‐H color which reflect their metamorphic gradeWe find small but significant differences between the JHK colors of the predominant C and S classes of asteroids. All JHK colors of asteroids observed here fall within the limited domain defined by the various chondritic and iron‐rich meteorites but are strikingly different from those of most achondritic meteor

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00801.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A preliminary description and chemical analysis of the newly‐discovered Adelaide meteorite is given. This meteorite is a C2 chondrite with C3 affinities. However, the meteorite is unlike both C2 and C3 chondrites in having a Ca/Al ratio of 0.47. The subtype is ambiguous but is closer to the Vigarno than the Ornans subtype. The meteorite is unusual in that it contains primary magnetite. In many other respects this meteorite resembles the Allende meteori

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00802.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Veins in the C1 chondrites Orgueil, Alais, and Ivuna have been deposited during an extended period of impact brecciation and leaching. At least three generations of mineralization, dominated successively by carbonates, calcium sulfate, and magnesium sulfate, can be recognized. Vein minerals are derived locally by closed‐system reactions between matrix phyllosilicates and an aqueous fluid, with the result that few, if any, primitive mineral phases still exist in the C

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00803.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1978.tb00804.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY