摘要:

The fall of a meteorite shower in Parambú, Ceará State, Brazil, is described. Parambú is an L‐group chondrite (Urey and Craig, 1953). The mineralogical composition is olivine Fa28. ortho‐ and clinopyroxenes, plagioclase, maskelynite, whitlockite, nickel‐iron, troilite, chromite, and ilmenite. The structure of Parambú is characteristically polymict and shows an advanced brecciation. Interesting features of metamorphism are notable, with good evidence

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00057.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Grossular garnet has been observed in several white inclusions in the Allende meteorite. Compositions range from Gro9sPy5toGro88Py12in five inclusions. Its mottled appearance indicates that it crystallized from a glass of near‐grossular composition and not by a solid state reaction between wollastonite, anorthite and melilite. These grossular‐bearing inclusions either condensed directly as metastable liquids from the solar nebula or if initial solid condensates were liquefied by some subsequent heating process. In either case, a prolonged residence time in a thermal blanket appears necessary to effect crystallization of the grossu

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00058.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Toulon is an olivine‐bronzite chondrite found near Toulon, Illinois in 1962. It contains abundant, well preserved chondrules, as well as glasses that are not well devitrified. Most of the metal has been weathered out. Olivine and pyroxene are well equilibrated. We have classified it as an H5 chondrit

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00059.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

One hundred metallic particles from Apollo 16 soils (61181, 65701) and rocks (60018, 60315, 66055) have been investigated microscopically and by electron microprobe analysis. Their cobalt content indicates a meteoritic origin for all but one particle. However, most contain more phosphorus than typical meteoritic metal, possibly due to the reduction of phosphates in the lunar rocks. Compositions of coexisting kamacite and schreibersite indicate temperatures of about 550–650°C which are thought to have occurred during metamorphism. The bulk nickel content of the lunar metal is somewhat low by comparison with most iron meteorites or the metallic component of common stony meteorites. However, this may be due to compositional changes that occurred after emplacement in the lunar surface lay

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00060.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Vigarano, a type 3 carbonaceous chondrite, contains a chondrule composed of highly refractory Ca and Al rich glass with minor spinel. The chondrule formed from material similar to the Ca, Al, Ti‐rich aggregates that are common in Vigarano and other type 3 chondrites and formation of these refractory aggregates must predate formation of some Vigarano chondrules. Experiments with synthetic analogues and a comparison with studies in the system CaO‐MgO‐Al2O3‐SiO2indicate a temperature for formation of the chondrule at or above 1700 °C followed by very rapid

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00061.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The use of thermoluminescence (TL) to determine the terrestrial age of meteorites is investigated. It is found that meteorites can be divided into two groups. One group, in which members lose their low temperature TL rather rapidly (the “low retentivity” group), may be dated up to about 100 years after fall, although with little accuracy. The other (the “high” group) is more retentive, and may still be dated several hundred years after fall. A meteorite of unknown date of fall may be assigned to the high or low group by laboratory determination of the rate of decay of the low temperature TL.Weathering coats the grains with limonite and lowers the intensity of the TL. The percentage reduction is constant for various intensities, but the peak height ratio is changed. Therefore, for weathered specimens, a method which examines the decrease in the intensity of a single peak is preferred to one which depends upon peak height ratios: this is made possible by artificially irradiating the meteorites. The following terrestrial ages for finds were obtained: Plainview 225–300 years; Dimmitt 280–330 years; Calliham 350–400 years. Bluff, Etter, Potter, Shields and Wellman (c) proved to be too old to be dated by our methods (≥ 500 years). None of the low group finds available to us proved to be young enough to be dated precisely. Terrestrial ages indicate an extremely low efficiency of recovery (≤ 1%) for meteorites that are not seen to fall.Artificially irradiating the meteorites also revealed the fact that 9 of our 19 meteorites were saturated with respect to thermoluminescence when they entered the atmosphere, and therefore that a technique based on this phenomenon would not be applicable to such specimens to obtain their cosmic

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00062.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Observed differences in the abundance ratios of moderately volatile elements found in ordinary chondrites relative to CI chondrites may have resulted from a continuous loss of nebular gas from the ordinary‐chondrite formation region during condensation. If this occurred, the nebular volatility of these elements should be inversely correlated with their abundance ratios. Such a nebular gas loss can occur as a result of momentum exchange between solids and gases, as a result of interactions between the nebular gas and solar photons or particles at the surface of the nebula, or as a result of the settling of previously condensed solids to the median plane of the nebul

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00063.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00064.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00065.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0026-1114    

DOI:10.1111/j.1945-5100.1974.tb00066.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY