Title: FeO2 and FeOOH under deep lower mantle conditions and the Earth’s oxygen-hydrogen cycles

Time: 10:00 - 11:00 AM, Wednesday, May 11, 2016

Place: Auditorium Room 410, Building 6, HPSTAR (Shanghai)

Abstract:

The distribution, accumulation, and circulation of oxygen and hydrogen in the Earth’s interior dictate the geochemical evolutions of the hydrosphere, atmosphere, and biosphere1. Using first-principles calculations and direct experiments, here we show a highly stable, pyrite-structured FeO2 at 76 GPa and 1800 K that holds an excessive amount of oxygen. Further study shows that the mineral goethite, FeOOH, which exists ubiquitously as “rust” in the nature and concentrates by large quantity in bog iron ore, decomposes under the deep lower mantle (DLM) conditions to form FeO2 and release H2. The reaction causes accumulation of the heavy FeO2-bearing patches in the DLM, upward migration of hydrogen, and separation of the oxygen and hydrogen cycles. The process provides an alternative interpretation to the origin of seismic and geochemical anomalies in the DLM, as well as a sporadic oxygen source for the Great Oxidation Event over 2 billion years ago that created the present day oxygen atmosphere.

Biography of the Speaker:

Dr. Ho-Kwang Mao, the world eminent scientist in high pressure. He graduated from the Department of Geology, National Taiwan University, in 1963 and in 1968, he received his Ph.D. at the University of Rochester, New York. After that, he worked in Geophysical Laboratory, Carnegie Institution of Washington.  He was elected a follow of the National Academy of Sciences, USA, in 1993, a member of Chinese Academy of sciences in 1996, a member of the Royal Society, UK in 2008 and a member of Academia Sinica, Taiwan in 1994.  He is the director of the Center for High Pressure Science and Technology Advanced Research (HPSTAR) since 2012.