No abstract

No abstract

Elemental abundances of noble gases in siliceous microfossils from deep‐sea sediments were determined employing the stepwise heating technique. Almost all the Ar and about 80% of the total Kr were released in the lowest temperature fraction of 800°C. Only Xe was released in higher temperature fractions, suggesting that Xe was tightly trapped inside silica. The Xe concentrations of siliceous microfossils seem to lie on the correlation line of Xe content vs. the temperature of geothermal water obtained for amorphous silica of geothermal origin. The selective trapping of Xe at high temperatures in amorphous silica indicated the possibility that amorphous silica is the reservoir of the terrestrial "missing" Xe. However, quantitative calculation showed that the total amount of Xe in amorphous silica could be at most only 5‐20 % of the total "missing" Xe.

No abstract

Abstract-High-resolution transmission electron microscopy micrographs of acid-resistant residues of the Allende, Leoville, and Vigarano meteorites show a great variety of carbon structures: curved and frequently twisted and intertwined graphene sheets, abundant carbon black-like particles, and hollow "sacs". It is suggested that perhaps all of these are carriers for the planetary Q-noble gases in these meteorites. Most of these materials are pyrocarbons that probably formed by the pyrolysis of hydrocarbons either in a gas phase, or on hot surfaces of minerals. An attempt was made to analyze for argon with particle-induced x-ray emission in 143 spots of grains of floating and suspended matter from freeze-dry cycles of an Allende bulk sample in water, and floating "black balls" fiom sonication in water of samples fiom the Allende meteorite. The chemical compositions of these particles were obtained, but x-ray signals at the wavelength of argon were obtained on only a few spots.-