[S-IT22] [EE] Interaction and Coevolution of the Core and Mantle in the Earth and Planets

[SIT22-P13] High precision analysis of W isotopes for OIB and MORB samples

*Asako Takamasa¹, Katsuhiko Suzuki¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:Core-Mantle co-evolution, Tungsten isotope ratio, Hf-W system

¹⁸²W is a decay product of ¹⁸²Hf (t_1/2=890 million year) which is extinct at now. The amount of ¹⁸²W can give information on evolution of very early solar system at the timescale from several million years from the solar system initial. Hf and W is a highly refractory element and the ¹⁸²W isotope evolution process in the bulk Earth could be the same as in chondrites. However, W is a highly siderophile element and Hf is a lithophile element. These elements could be partitioned into metal (core) and silicate (mantle) phases, which leads to higher Hf/W ratio of mantle.

To elucidate the core-mantle evolution of the early Earth, we have developed the high precision W isotope analysis using MC-ICP-MS (Thermo co. Ltd. NEPTUNE Plus) and have applied it to some OIB and MORB samples, such as Hawaiian basalts, South Africa Kimberite, Ontong Java Plateau lavas and Indian MORB.

We will present the W isotopic composition obtained for these samples and will discuss the early core-mantle co-evolution and core-mantle interaction, based on the W isotope, Os isotopes.