Search for the extra-terrestrial materials in deep sea sediments

概要

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In order to characterize He carrier in deep sea sediments, we magnetically separated the deep sea sediments collected at three different sites, and measured the ^3He/^4He ratio and the He content in each fraction. The ^3He/^4He ratios (1.4-2.4×(10)^<-4>) and the He content (^3He : 1.6-10.7×(10)^<-9>(cm)^3 STP/g) in the magnetic fractions were high, which reveals that the He carrier was concentrated in the magnetic fractions. The ferromagnetic property of the He carrier may be due to magnetite which had been produced by decomposition of poorly crystallized silicates in the He carrier during their atmospheric entry. Stepwise heating experiment was applied to one of the magnetic fractions. The ^3He/^4He ratios were almost the same (2×(10)^<-4>) in each temperature fraction and the single activation energy, 17kcal/mol was obtained. The result strongly suggests that the observed He is of a single component. Thermomagnetic analyses gave us the information that the major part of the magnetic fractions is terrestrial titanomagnetite. The amount of ^<53>Mn in the magnetic fractions was measured by the RNAA method. However, the large amount of ^<55>Mn allowed us only to estimate the upper limits of the amount of ^<53>Mn.
国立極地研究所の論文