| Abstract: | Helium isotope compositions of the mantle xenoliths and megacrysts in the Cenozoic basalts in the eastern China were measured.
The samples were collected from Ludao of Heilongjiang, Huinan and Jiaohe of Jilin, Kuandian of Liaoning, Hannuoba of Hebei,
Nüshan of Anhui, Dingan of Hainan. The3He/4He ratios of the mantle xenoliths and megacrysts from the most areas were about 1 × 10-5, and were similar to those of the MORB, thus reflecting the characteristics of the MORB-typed depleted mantle. The3He/4He ratios of the mantle xenoliths from Jiaohe were 4.8×10-6 and the3He/4He ratios of xenoliths from Hannuoba vary from 0.15× 10-6 to 7.4 ×10-6, obviously lower than those of the MORB, and even lower than the atmospheric helium isotope ratios, indicating that the continental
mantle was strongly replaced in Jiaohe and Hannuoba areas. The helium isotope compositions of the mantle xenoliths and megacrysts
in the same region vary in a very wide range. It is inferred that the mantle xenoliths and megacrysts were from different
parts of the continental mantle. There were not necessary origin relations between the mantle xenoliths, megacrysts and their
host basalts. An extremely high3He/4He ratio of garnet megacryst from Hannuoba, Hebei was found. |
