Zhang Li, a researcher and associate researcher at the Shanghai High Voltage Advanced Science Research Center, told Xinhua that the iron-containing silicate perovskites had been stable under the temperature pressure in the deep mantle, but the researchers found it unstable. And it will decompose into iron-free perovskites and a new iron-rich, hexagonal structure.
The lower mantle is located above the core of the earth, spanning the bottom of the transition zone from a depth of 670 kilometers to the core boundary of 2900 kilometers. The earth's internal high temperature and high pressure, and temperature and pressure will increase with the increase of depth, so the lower mantle also has ultra-high temperature and pressure. For example, the pressure at 670 km is 240,000 atm and the temperature is 1600 Kelvin (Kelvin temperature = Celsius + 273.15). At the junction of the mantle and the core, the pressure and temperature rise to 1.35 million atm. And 2450 Kelvin.
Zhang Li and his team applied diamond anvil high-pressure technology combined with laser heating to simulate the high temperature and high pressure of the mantle under laboratory conditions. The compression was considered to constitute a mineral sample of the lower mantle, and then the X-ray was detected by synchrotron radiation. A change in properties that occurs as a function of temperature and pressure conditions.
Studies have shown that at temperatures between 950,000 and 1.01 million atmospheres and temperatures of 2,200 to 2,400 Kelvin, the iron in the perovskite is gradually lost, and new iron-rich minerals are formed. This new mineral has a hexagonal structure. Known as the H phase. "This result is beyond people's expectations," Zhang Li said.
The researchers say that new minerals and Other oxides carry most of the iron in the bottom third of the mantle, but the details of the new minerals and their relationship to other minerals on the surface remain to be confirmed.
Zhang Li said, "This discovery has changed our existing understanding of the composition of the deep mantle in the lower mantle and determined the existence of new major minerals." "For the lower mantle below 2000 km, all existing geodynamic models It is necessary to make corrections based on the newly established mineral model."
The Shanghai Advanced Research Center for High Voltage began to be established in September 2012. Under the framework of the â€œThousand Talents Planâ€ of China, the multi-disciplinary basic research institution led by Mao Heguang, an academician of the US Academy of Sciences, and his innovative team, Xiang Mo, to take the lead in compression science research.
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