Portal de Periódicos da CAPES

Angra dos Reis: Plutonium distribution and cooling history

1977; Elsevier BV; Volume: 35; Issue: 2 Linguagem: Inglês

10.1016/0012-821x(77)90132-7

1385-013X

D. Störzer, P. Pellas,

Isotope Analysis in Ecology

The preatmospheric mass of Angra dos Reis is estimated to be about 80 kg, based on cosmic ray track densities of 1−3 × 106 cm−2 in feldspars, olivines, and pyroxenes. The244Pu-fission track densities in pyroxenes and adjacent olivine-feldspar track detectors, as well as in whitlockites and adjacent pyroxene-olivine detectors are about 20 and 280 × 106 cm−2 respectively. These values correspond exactly to the244Pu-fission xenon contents in the two minerals. This suggests an almost instantaneous cooling (>70 K per m.y.) of the Angra dos Reis material 4.55 b.y. ago. This fast cooling is the reason for a quantitative4He retention since that time. If the4He excess found in Angra dos Reis is a real effect, the source of this excess remains unknown.