HR: 1340h
AN: MR43A-0882    [Abstracts]
TI: Reaction Between Liquid Iron and Mg-perovskite and Solubility of Silicon and Oxygen in Liquid Iron
AU: * Kawazoe, T
EM: kawazoe@ganko.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Faculty of Science, Tohoku University, Aoba-ku, Sendai, 980-8578 Japan
AU: Ohtani, E
EM: ohtani@mail.tains.tohoku.ac.jp
AF: Institute of Mineralogy, Petrology and Economic Geology, Faculty of Science, Tohoku University, Aoba-ku, Sendai, 980-8578 Japan
AB: A reaction between liquid iron and Mg-perovskite was investigated at 28 GPa and 2550-2940 K to discuss the core formation process and light elements in earth's core. The earth's core contains small amount of light elements. These light elements were dissolved into liquid iron to form the core during core formation process. Deep magma ocean is supposed to have extended to a depth of lower mantle in the core formation stage (Ohtani et al., 1997; Li and Agee, 2001). Because Mg-perovskite is the most dominant mineral in the lower mantle, reaction between the liquid iron and the Mg-perovskite must have occurred at base of the deep magma ocean and could have provided Si and O as the light elements into the liquid iron. Knittle and Jeanloz (1991) and Hillgren and Boehler (1999) have studied this reaction with a laser-heating diamond anvil cell. But their studies had a large temperature gradient in the sample room resulting in a possibility of disequilibrium. In this study, high pressure and temperature experiments were conducted with a Kawai-type multi-anvil apparatus and samples were reached to equilibrium with uniform heating by Re cylindrical heater. Pure iron rod was packed into MgSiO$_{3}$ or (Mg$_{0.9}$, Fe$_{0.1}$) SiO$_{3}$ powder capsule, which transformed to Mg-perovskite in experimental conditions. The sample was compressed to a desired load and then heated to a desired temperature and finally quenched. Run products were analyzed with an electron microprobe. Magnesiow\"{u}site was formed at the boundary between liquid iron and Mg-perovskite. Quenched liquid iron contained oxide blobs in all runs and stishovite grew in the quenched liquid in the run made at 2940 K and 1.72 log units below IW buffer. The liquid iron reacted with Mg-perovskie to form the magnesiow\"{u}stite and Si and O dissolved into the liquid iron at temperatures above 2550 K. Si and O solubility in the liquid iron decreased and increased with increasing oxygen fugacity, respectively, and both increased with increasing temperature. Si and O contents in liquid iron were 1.70 wt% and 2.33 wt%, respectively, in the run made at 2940 K and 1.72 log units below IW buffer. They were 0.18 wt% and 7.52 wt%, respectively, in the run made at 2830 K and 0.20 log units above IW buffer.
DE: 3630 Experimental mineralogy and petrology
DE: 3924 High-pressure behavior
DE: 1020 Composition of the crust
DE: 1010 Chemical evolution
DE: 1015 Composition of the core
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting