摘要:

The Ella Island, Greenland, meteorite was found in August of 1971. Electron microprobe study of the meteorite revealed it to contain olivine, low‐calcium pyroxene, high‐calcium pyroxene, plagioclase, kamacite, taenite, chromian‐hercynite and troilite. On the basis of fayalite and ferrosilite content, poorly‐defined chondrules, absence of glass in chondrules, presence of well‐developed feldspar in the matrix and chondrules, and degree of recrystallization of the matrix, the Ella Island meteorite is classified as an L‐

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Individual and splinter specimens of the iron meteorite shower of Sikhote‐Alin and rock samples from impact craters have been studied magnetically. The results indicate that: 1) Histograms for the distribution of natural remanent magnetization Jnof individual and splinter specimens are characterized by a high correlation coefficient (0.82 ± 0.06). For the splinter specimens, a trend to an increase in number of specimens with anomalously high Jnvalues is observed; 2) the Earth's magnetic field did not greatly affect the magnetic properties of this iron meteorite; and 3) for rock samples taken from different craters, there was found to be a relation between the natural remanent magnetization and the energy conditions of the crater formati

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The parent body of the Farmington meteorite experienced sufficient heating, probably from shock accompanying a major collision occurring at 520 × 106years ago, to erase the record of any magnetization acquired prior to that event. Therefore, the observed magnetization in the Farmington meteorite must have been acquired after the collision. Shock‐produced magnetization is unlikely because of the finite cooling time indicated by the burial depth of ≥ several meters. The possibility of shock or irradiation‐produced magnetizations should be studied experimentally, even though neither appears likely to have produced the magnetic field which produced the magnetization in the parent body of the Farmington met

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Gobabeb, an ordinary chondrite, was found near Gobabeb, South West Africa in 1969. Chemically and petrographically it belongs in the H4 group. But, in addition to almost homogeneous silicates and chromites, it contains rare, non‐opaque spinels that vary greatly in composition from grain to grain. A similar association in an “almost equilibrated” portion of the Mezö‐Madaras chondrite has been interpreted as evidence against the hypothesized metamorphic homogenization of ordinary chondrites. A comparison of the chromites and variable spinels from Mezö‐Madaras and Gobabeb suggests, instead, that cation exchange is simply slower in the variable spinels than in the chromites. Based on the evidence to date, the survival of these highly variable spinels is not incompatible with a metamorphic episode for both these

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The Ashmore olivine‐bronzite chondrite is a group H, type 5 stone which differs from other H5 chondrites mainly in its higher proportion of chromite (0.9 wt %) and in the relatively lower iron and higher magnesium content of the chromite. The modal proportions of opaque phases were obtained by point‐counting in reflected light, and the modal proportions of nonopaque silicate phases in the matrix were estimated from traverses of a selected small area by electron microprobe. The consistency between the bulk chemical analysis and the chemical composition calculated from the modal mineral proportions implies that the bulk silicate composition of the chondrules is very similar to that of the silicate matrix and suggests a common source for both chondrules and mat

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Microprobe analyses of the major silicates in Clovis (no. 1), New Mexico, establish it as an H3 chondrite. Inclusions identified in Clovis are: breccia fragments; angular and vesicular chondrule or rock fragments composed almost entirely of glass and olivine (Fa12–22);chondrules, composed principally of pyroxene (Fs2–33) and olivine (Fa1–28); and Ca, Al and Ti‐rich inclusions. These refractory enriched inclusions, similar in composition to those found in some carbonaceous chondrites, are rare in ordinary chondrites but in this study were observed in Sharps, Virginia (H3), Gobabeb, South Africa (H4), Dimmitt, Texas (H4), Weston, Connecticut (H4–6) and Clovis. Sodium, known to rim similar inclusions in carbonaceous chondrites, also occurs in the interiors of inclusions observed in this study, sometimes in moderate amounts. The Na distribution is regarded as primary and is not attributable, at least in total, to secondary Na extraction from the ho

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The San Juan Capistrano chondrite fell on 15 March 1973; the total recovered mass was 56 g. Electron microprobe, chemical and petrographic studies show it to be a member of the H group and of petrologic type 6. Rare gas studies show that only minor radiogenic gas loss has occurred and yield a K‐Ar age of 4.6 × 109years and a Kr‐Kr exposure age of 29 × 106

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

A meteorite, named for the location of its discovery near Lone Tree, Iowa, was found by Loren Westfall in May 1971. Electron microprobe and petrographic studies reveal its mineral composition to be olivine, low‐calcium clinopyroxene, high‐calcium clinopyroxene, troilite, kamacite, taenite and iron oxides.On the basis of texture, olivine composition (19% Fa), low‐calcium clinopyroxene composition (17% Fs, 2% Wo) and metal (determined by modal analysis), this meteorite is classified as an H group bronzite chondrite. While it has characteristics of classes 3 and 4 (Van Schmus and Wood, 1967, Table 2) it fits class 4 better since low‐calcium pyroxene has a MD of 5.6%, olivine has a MD of 3.2%, turbid glass is present in chondrules, feldspar is absent, and the matrix is opaque. The opacity of the matrix may be due to iron oxides in microfractures in a microcrystalline

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1975.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY