Dr. Qingyang Hu awarded Excellent Youth Paper at 18th NCHPSA
July 29th, 2016, Dr. Qingyang Hu, from HPSTAR, awarded Excellent Youth Paper at the 18th NCHPSA (the 18th National Conference on High Pressure Science and Academics). Dr. Hu presented his latest research on the conference, which reviewed the hydrogen cycle in the Earth.
The abstract of Dr. Hu's research is as follows:
Unconventional decomposition of FeOOH and its role in the Earth hydrogen cycle
Qingyang Hu, Duckyoung Kim, Wenge Yang, Ho-Kwang Mao
The Earth’s geochemistry can be regarded as a ternary system of oxygen, its most abundant element by atomic fraction, iron, its major redox ingredient, and hydrogen, its most mobile element responsible for electron transfer. The mineral goethite (α-FeOOH), exists ubiquitously as “rust” in the nature, and also concentrates by large quantity in bog iron ore. It has been used as a copious, renewable resource of iron ever since the “iron age”.
Here we conduct x-ray diffraction experiment with laser heating and first-principles simulation up to deep lower mantle (DLM) conditions. Our work is attempting to anticipate the fate of FeOOH within the cold subduction slabs. We observed a previously unknown Fe-O phase that holds an excessive amount of oxygen and it involves reactions that have major impacts to our understandings of the Earth. The reaction involves the decomposition of FeOOH that releases hydrogen that would diffuse, infiltrate or react to form hydrocarbon or other volatiles. The new iron oxide phase is left in DLM and cumulates through plate tectonics. Such process provides an alternative interpretation to the origin of seismic and geochemical anomalies in the DLM.
氢元素与氧元素的分布、积累和循环对地球内部的化学变化过程有着重要的影响。通过第一性原理计算和高温高压实验，我们在75 GPa和1800 K条件下发现了一种高度稳定的黄铁矿结构的二氧化铁新相，这个新相的氧元素含量显著高于其它已知的铁氧化物。进一步研究表明，针铁矿的主要成分——FeOOH也可以在下地幔温度压力条件下分解生成二氧化铁并释放氢气。这个化学反应将有可能导致密度较高的富含二氧化铁的矿物在下地幔缓慢沉积，低密度的氢元素上升迁移，最终会使地球内部的氢循环和氧循环在局域内实现分离。二氧化铁对下地幔存在的某些地质异常提供了一种新的可能解释。同时由于二氧化铁富含氧元素，且会在低压下分解释放氧气，因而可能为20亿年前的地质大氧化事件提供了一种突发的、少量的氧气来源。