Isotopic fractionation of tungsten for meteoritical materials

Irisawa, Keita  ; Hirata, Takafumi*; Tanimizu, Masaharu*

Currently, the best chronometer for metal-silicate separation is 182Hf-182W systematics. In the previous studies, the Earth's core could have separated from the silicate mantle within the first 30 million years of accretion, if Earth's accretion was terminated by a giant impact and accompanied by complete metal-silicate equilibration. In order to constrain the age of the core-mantle differentiation and of the Moon-forming giant impact in the Earth, we should estimate W behavior between metal and a silicate phases through the planetary formation. To determine W isotopic fractionation for chondrites, achondrites, and iron meteorites have potential interpretation of planetary core-mantle differentiation. In this study, an external correction technique using 185Re/187Re ratio was applied in order to detect W isotopic fractionation for various meteoritic materials, and therefore, we will discuss about a new interpretation of the age of Moon-forming giant impact.