Japan Geoscience Union Meeting 2015

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT06] Early Earth - from accumulation to formation -

Sun. May 24, 2015 10:00 AM - 10:45 AM 303 (3F)

Convener:*Tatsuya Sakamaki(Department of Earth Science, Tohoku University), Akio Suzuki(Department of Earth and Planetary Materials Science, Faculty of Science, Tohoku University), Seiji Kamada(Graduate school of Science, Tohoku University), Bjorn Mysen(Geophysical Laboratory, Carnegie Inst. Washington), Chair:Tatsuya Sakamaki(Department of Earth Science, Tohoku University)

10:15 AM - 10:30 AM

[SIT06-02] Contribution of volatile rich material to Earth's accretion

*Wei DU1, Tetsuo IRIFUNE1 (1.GRC, Ehime University; ELSI, Tokyo Institute of Technology)

Keywords:Carbonaceous chondrite, Tagish Lake meteorite, Earth accretion, High pressure and high temperature, partial melting, volatile

The planetary formation processes such as accretion and differentiation might have drastically modified the composition of Earth from the building blocks from the orginal so-called chondritic Earth model, especially on the elemental and isotopic compositions of the volatile elements. Recently, heterogeneous accretion model that describes that growth and evolution of Earth in two different stages from volatile-depleted and volatile-rich material was revised based on isotope geochemical studies (e.g. Nudds et al., 2010). However, the exact percentage and the time sequence of this volatile-rich material accretion need to be constrained. For example, models with ~2% carbonaceous chondrite (CI-CM) material added to a dry proto-Earth will result in estimation of carbon content of Earth to be over 500ppm, which could not be explained by the current silicate mantle composition of Earth. In addition, the modeling result needs to be consistent with the siderophile elements concentration in Earth mantle and the oxidation state of Earth mantle changes through the accretion process.

Therefore, we performed experimental studied on Tagish Lake chondrite (CI-CM), a new type of volatile rich carbonaceous chondrite at different pressure and temperature conditions. Our target is to explore the possible effect of the volatile component on Earth composition through the time sequence of Earth growth, the water budge of Earth at different accretion sequences, and other possible later impact.

Our melting experiment at 12GPa shows that the measured solidus temperature of Tagish Lake meteorite is much lower than CV3 meteorite because the existence of the large amount of volatile components; however, the measured liquid temperature is very close to that of CV3 meteorite, indicating the lost of volatile component through higher temperature (2000K) heating process. The experimental method we used works well to keep the volatile components (Carbon and Hydrogen) inside the meteorite sample during heating experiments with temperature lower than 2000K. Whether does the proto-core have carbon or other volatile element will rely on further experiments at higher pressure.