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Elasticity of Mantle Minerals 

Seismic studies image the internal structure of the Earth. To interpret the seismic observations, particular the observed velocity anomalies in various locations of the Earth's deep interior, requires detailed information on the elastic properties of the major minerals of the region. Combining diamond anvil cell techniques with Brillouin spectroscopy, we study the elasticity of minerals at relevant pressure and temperature conditions of the Earth's mantle.  With known elasticity and density, we construct the velocity profiles of mineral assemblage. Comparing the modeled velocity with seismic observations provides crucial constraints on the composition of the Earth's mantle.





Water in the Earth's Mantle

Subduction is the process to recycle the materials in the Earth's surface to the deep interior. With sinking subduction slabs, a number of hydrous minerals are going to dehydrate and release water to the overlying mantle wedge, causing partial melting and resulting in large scale island arc magmatisms. Decomposition of these hydrous minerals in the deep upper mantle and transition zone has also been proposed to be one of the three mechanisms for the deep earthquakes. Water from the breakdown of hydrous minerals in the subduction slab will be stored as hydroxyl in normal anhydrous minerals (NAMs) in the Earth’s mantle. We are interested in exploring the effect of water on the physical properties of the Earth's mantle, because the presence of small amount of water could significantly influence a number of physical properties of mantle minerals. Those studies are expected to provide new insights in the distribution of water in the Earth's mantle and help understanding the compositional heterogeneity and material circulation of the region.



Lower Mantle Minerals 

Based on the pyrolite model, Earth's lower mantle is composed by 75 vol.% bridgmanite, 17 vol.% ferropericlase, and 8 vol.% Ca-perovskite. Bridgmanite will undergo a phase transition from the perovskite structure to post-perovskite structure at relevant pressure and temperature conditions of the bottom transition zone. In addition, the sinking subduction slabs will bring various silicates, such as the high-pressure phase of SiO2, Al-Na rich phase (NAL and CF), to the lower mantle. Here, we work on the effect of compositional variations on the physical properties of lower mantle minerals, including density, thermal elastic parameters, phase transition, and spin transition. 

Carbon Circulation 

Studies on the high-pressure behavior of carbon-bearing minerals are of particular importance in understanding the global carbon cycle and carbon storage in the Earth’s interior. Due to its low solubility in mantle silicates, carbon is expected to be hosted in carbonates in the Earth’s mantle. Carbonates, such as magnesite (MgCO3), calcite (CaCO3), and dolomite [MgCa(CO3)]has been found as inclusions in natural diamonds, which are expected to be transported to the Earth’s mantle through the sinking subduction slabs. Our study focuses on the high-pressure behavior of those carbonates at mantle pressure-temperature conditions. We explore the phase stability and thermal elastic properties of carbonates at high pressure-temperature conditions. And we also work on the potential chemical reactions of carbonates with mantle minerals.


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Funding

National Science Foundation of China, 41522403, 2016-2018, 1,500,000, PI

National Science Foundation of China, 41590621, 2016-2020, 4,800,000, PI

National Science Foundation of China, 41374092, 2014-2017, 1,000,000

Fundamental Research Funds for the Central Universities in China, WK2080000052, 2014-2016, 1,000,000, PI

National Basic Research Program of China, 2014CB845904, 2016-2018, 450,000, co-PI

Strategic Priority Research Program of the Chinese Academy of Sciences, XDB18010404, 2016-2017, 350,000, co-PI

Thousand Young Talents Fellowship, Chinese Central Organization, KJ2080000016, 2013-2015, 3,000,000, PI

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