Origin of isotopic fractionation of terrestrial xenon

By taking account of a size distribution of planetesimals, we show that noble gases gravitationally trapped by planetesimals in the solar nebula can explain the isotopic fractionation of terrestrial Xe relative to Xe in primitive meteorites, leaving Kr and other lighter noble gases almost unfractionated. However, this model is not successful in explaining noble gas elemental abundances in the Earth

The 3He/4He ratio in a clay from the K-T boundary,Hokkaido, Japan

We measured the He content and the ^3He/^4He ratio of a K-T boundary clay from Hokkaido. If some meteoritic debris which escaped total melting or evaporation at the K-T event remains in the clay, it may be possible to observe some ^3He in it. However, we could determine only the upper limits of the ^3He/^4He ratois ( for a bulk sample) because of the small amount of ^3He. Three alternatives are considered to explain the result

Radiometric age of lava flows of the Enrei ｆormations in central Japan (1).

Two samples from lava flows of the upper member of the Lower Enrei formations exposed at the top of Utsukushi-ga-hara volcano are dated approximately at 1.3 × 10v K-A years. The dates of these lava flows which are magnetized reversely and eastward are placed in the middle part of the Matuyama reversed epoch. The Ina formations equivalent of the Lower member of the Lower Enrei formations suggest that during this period climatic deterioration had already taken place, so that most parts of the Enrei formations should be younger than the base of the Pleistocene.Article信州大学理学部紀要 1(2): 93-96(1967)departmental bulletin pape

Search for the extra-terrestrial materials in deep sea sediments

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)^) and the He content (^3He : 1.6-10.7×(10)^(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)^) 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 ^Mn in the magnetic fractions was measured by the RNAA method. However, the large amount of ^Mn allowed us only to estimate the upper limits of the amount of ^Mn

Noble gases in submarine pillow volcanic glasses

Fifteen submarine glasses from the East Pacific Rise (CYAMEX), the Kyushu-Palau Ridge (DSDP Leg 59) and the Nauru Basin (DSDP Leg 61) were analysed for noble gas contents and isotopic ratios. Both the East Pacific Rise and Kyushu-Palau Ridge samples showed Ne excess relative to Ar and a monotonic decrease from Xe to Ar when compared with air noble gas abundance. This characteristic noble gas abundance pattern (type 2, classified by Ozima and Alexander) is interpreted to be due to a two-stage degassing from a noble gas reservoir with originally atmospheric abundance. In the Kyushu-Palau Ridge sample, noble gases are nearly ten times more abundant than in the East Pacific Rise samples. This may be attributed to an oceanic crust contamination in the former mantle source. There is no correlation between the He content and that of the other noble gas in the CYAMEX samples. This suggests that He was derived from a larger region, independent from the other noble gases. Except where radiogenic isotopes are involved, all other noble gas isotopic ratios were indistinguishable from air noble gas isotopic ratios. The 3He/4He in the East Pacific Rise shows a remarkably uniform ratio of (1.21 +/- 0.07)*10**-5, while the40Ar/36Ar ranges from 700 to 5600

40Ar-39Ar dating of rocks drilled at sites 60-458 and 60-459

40Ar-39Ar dating of a high-MgO bronzite andesite from near the top of basement drilled at Site 458 shows the characteristic symptoms of artificially disturbed samples - i.e., an inverse staircase-type age spectrum, approximate linearity on an isochron plot, and concordance between total fusion age and isochron age. From conclusions based on other artificially disturbed samples (Ozima et al., 1979), we suggest that the reference isochron age (33.6 Ma) approximates the age of the sample. A basalt from deeper in Hole 458 gives an isochron age of 19.1 ± 0.2 Ma, which is slightly younger than the plateau age of 21.4 ± 1.0 Ma. Both ages are, however, considerably younger than the age of fossils in the overlying sediments (30 - 34 Ma). The age discrepancy may be explained if the 40Ar-39Ar age represents the age of secondary minerals, which formed later. No useful age data were obtained from a basalt sample recovered from Hole 459B