1998 年 32 巻 4 号 p. 233-241
Magnetic spherules were separated from the deep-sea sediments dredged off the Hawaii islands. Spherules were classified by size and magnetic property. The abundance of magnetic spherules in the sediments used in this study is 3.3 × 10-6g/g wet sediments. The trend seen in the size distribution of spherules with diameters ranging from several urn to 590μm is consistent with the reported one for magnetic spherules larger than 100μm. Twenty two magnetic spherules were individually analyzed by instrumental neutron activation analysis and Fe, Co, Ni and Ir were determined. Iridium contents, Ni/Fe ratios and Co/Fe ratios were suggested for effective criteria in discussing the origin of magnetic spherules. Judging from chemical compositions, at least 14 out of the 22 spherules analyzed in this study were inferred to be extraterrestrial in origin.
