Helium isotope investigation on magnetic reversal boundaries of loess-paleosol sequence at Luochuan, central Chinese Loess Plateau
2007
Du, XueQing | Wang, Yonghong | Ren, JianGuo | Ye, XianRen | Lu, Huayu
Extraterrestrial particles have higher ³He/⁴He ratios than those of terrestrial sediments (> 100 Ra versus < 0.03 Ra, where Ra is the ³He/⁴He ratio normalized to the atmospheric value of 1.4×10⁻⁶). The interplanetary dust particles (IDPs), which are very rich in ³He, continuously bombard the Earth and can accumulate in deposits. IDPs sedimentation rate changes can significantly influence ³He concentration in the Earth surface sediments. Since IDPs are not easy to detect in terrestrial deposits, measuring helium isotopes is a helpful approach to examine changes in IDPs. Helium concentration and helium isotopic composition magnetic substances and the quartz particles were examined for helium concentration and helium isotopic ratio. Results show that the ³He/⁴He ratio and the ³He concentrations of the magnetic substances are clearly higher than those of the bulk samples and the quartz particles, and, the ³He/⁴He ratio of the extracted magnetic substances is also higher than that of the average level of the Earth’s crust. The higher helium content in the magnetic fractions can be explained by an influx of IDPs.
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