The elasticity of minerals at high temperature and pressure （PT） is critical for constraining the composition and temperature of the Earth＇s interior and understand better the deep water cycle and the dynamic Earth...The elasticity of minerals at high temperature and pressure （PT） is critical for constraining the composition and temperature of the Earth＇s interior and understand better the deep water cycle and the dynamic Earth. First-principles calcula- tions without introducing any adjustable parameters, whose results can be comparable to experimental data, play a more and more important role in investigating the elasticity of minerals at high PT mainly because of （1） the quick increasing of computational powers and （2） advances in method. For example, the new method reduces the computation loads to one-tenth of the traditional method with the comparable precise as the traditional method. This is extraordinarily helpful because first-principles calculations of the elasticity of minerals at high PT are extremely time-consuming. So far the elasticity of most of lower mantle minerals has been investigated in detail. We have good idea on the effect of temperature, pressure, and iron concentration on elasticity of main minerals of the lower mantle and the unusual softening in bulk modulus by the spin crosso- ver of iron in ferropericlase. With these elastic data the lower mantle has been constrained to have 10-15 wt% ferropericlase, which is sufficient to generate some visible effects of spin crossover in seismic tomography. For example, the spin crossover causes that the temperature sensitivity of P wave at the depth of -1700 km is only a fraction of that at the depth of -2300 kin. The disruptions of global P wave structure and of P wave image below hotspots such as Hawaii and Iceland at similar depth are in consistence with the spin crossover effect of iron in ferropericlase. The spin crossover, which causes anomalous ther- modynamic properties of ferropericlase, has also been found to play a control role for the two features of the large low shear velocity provinces （LLSVPs）： the sharp edge and high elevation up to 1000 km above core-mantle boundary. All these results clearly suggest the spin crossover of iron in the lower mantle. The theoretical investigations for the elasticity of minerals at the upper mantle and water effect on elasticity of minerals at the mantle transition zone and subducting slab have also been con- ducted extensively. These researches are critical for understanding better the composition of the upper mantle and water dis- tribution and transport in the Earth＇s mantle. Most of these were static calculations, which did not include the vibrational （temperature） effect on elasticity, although temperature effect on elasticity is basic because of high temperature at the Earth＇s interior and huge temperature difference between the ambient mantle and the subducting slab. Including temperature effect on elasticity of minerals should be important future work. New method developed is helpful for these directions. The elasticity of iron and iron-alloy with various light elements has also been calculated extensively. However, more work is necessary in order to meet the demand for constraining the types and amount of light elements at the Earth＇s core. Keywords Mantle temperature, Mantle composition, Composition of Earth＇s core, Ab initio method展开更多
The equations of state(EOSs)of MgO produced by two independent scale-free methods,(1)the simultaneous elastic wave velocity and in situ synchrotron X-ray measurements(Kono et al.,2010;Li et al.,2006)and(2)the first-pr...The equations of state(EOSs)of MgO produced by two independent scale-free methods,(1)the simultaneous elastic wave velocity and in situ synchrotron X-ray measurements(Kono et al.,2010;Li et al.,2006)and(2)the first-principles calculations(Wu et al.,2008),agree well with each other to at least 150 GPa and 2000 K.Furthermore,the EOS from first-principles calculations also agrees well with shock wave data,another pressure-scale-free data.These agreements strongly support that these EOSs provide reliable absolute pressure scales.Here we evaluate Au and Pt EOSs based on the EOS of Wu et al.(2008)using the simultaneously measured volume data of MgO,Au,and Pt from the literature.The primary pressure scales developed by Tange et al.(2009)and Yokoo et al.(2009)using only pressure-scale-free experimental data of MgO,Au,and Pt produce internal consistent pressure and agree with EOS of Wu et al.(2008).The Au EOS by Tsuchiya(2003)works well at room temperature but underestimates pressure at high temperature.The Au EOS by Fei et al.(2007)can well describe thermal pressure.The EOSs of Pt by Holmes et al.(1989)and Ono et al.(2011)work well at both room temperature and high temperature.The results also suggest that the discrepancy between bulk modulus of iron from experiments(Mao et al.,1990)and those from Earth's core(Dziewonski and Anderson,1981)is not originated from the overestimation of pressure by the EOS of Holmes et al.(1989).At high pressure and temperature,pressure uncertainty resulted from volume error becomes similarly important as the accuracy of the pressure scale.展开更多
基金supported by the State Key Development Program of Basic Research of China(Grant No.2014CB845905)the National Natural Science Foundation of China(Grant Nos.41590621,41274087,41473011)the Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams
文摘The elasticity of minerals at high temperature and pressure （PT） is critical for constraining the composition and temperature of the Earth＇s interior and understand better the deep water cycle and the dynamic Earth. First-principles calcula- tions without introducing any adjustable parameters, whose results can be comparable to experimental data, play a more and more important role in investigating the elasticity of minerals at high PT mainly because of （1） the quick increasing of computational powers and （2） advances in method. For example, the new method reduces the computation loads to one-tenth of the traditional method with the comparable precise as the traditional method. This is extraordinarily helpful because first-principles calculations of the elasticity of minerals at high PT are extremely time-consuming. So far the elasticity of most of lower mantle minerals has been investigated in detail. We have good idea on the effect of temperature, pressure, and iron concentration on elasticity of main minerals of the lower mantle and the unusual softening in bulk modulus by the spin crosso- ver of iron in ferropericlase. With these elastic data the lower mantle has been constrained to have 10-15 wt% ferropericlase, which is sufficient to generate some visible effects of spin crossover in seismic tomography. For example, the spin crossover causes that the temperature sensitivity of P wave at the depth of -1700 km is only a fraction of that at the depth of -2300 kin. The disruptions of global P wave structure and of P wave image below hotspots such as Hawaii and Iceland at similar depth are in consistence with the spin crossover effect of iron in ferropericlase. The spin crossover, which causes anomalous ther- modynamic properties of ferropericlase, has also been found to play a control role for the two features of the large low shear velocity provinces （LLSVPs）： the sharp edge and high elevation up to 1000 km above core-mantle boundary. All these results clearly suggest the spin crossover of iron in the lower mantle. The theoretical investigations for the elasticity of minerals at the upper mantle and water effect on elasticity of minerals at the mantle transition zone and subducting slab have also been con- ducted extensively. These researches are critical for understanding better the composition of the upper mantle and water dis- tribution and transport in the Earth＇s mantle. Most of these were static calculations, which did not include the vibrational （temperature） effect on elasticity, although temperature effect on elasticity is basic because of high temperature at the Earth＇s interior and huge temperature difference between the ambient mantle and the subducting slab. Including temperature effect on elasticity of minerals should be important future work. New method developed is helpful for these directions. The elasticity of iron and iron-alloy with various light elements has also been calculated extensively. However, more work is necessary in order to meet the demand for constraining the types and amount of light elements at the Earth＇s core. Keywords Mantle temperature, Mantle composition, Composition of Earth＇s core, Ab initio method
基金supported by the State Key Development Program of Basic Research of China(Grant No.2014CB845905)the National Natural Science Foundation of China(Grant Nos.41590621,41274087 & 41473011)the Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams
文摘The equations of state(EOSs)of MgO produced by two independent scale-free methods,(1)the simultaneous elastic wave velocity and in situ synchrotron X-ray measurements(Kono et al.,2010;Li et al.,2006)and(2)the first-principles calculations(Wu et al.,2008),agree well with each other to at least 150 GPa and 2000 K.Furthermore,the EOS from first-principles calculations also agrees well with shock wave data,another pressure-scale-free data.These agreements strongly support that these EOSs provide reliable absolute pressure scales.Here we evaluate Au and Pt EOSs based on the EOS of Wu et al.(2008)using the simultaneously measured volume data of MgO,Au,and Pt from the literature.The primary pressure scales developed by Tange et al.(2009)and Yokoo et al.(2009)using only pressure-scale-free experimental data of MgO,Au,and Pt produce internal consistent pressure and agree with EOS of Wu et al.(2008).The Au EOS by Tsuchiya(2003)works well at room temperature but underestimates pressure at high temperature.The Au EOS by Fei et al.(2007)can well describe thermal pressure.The EOSs of Pt by Holmes et al.(1989)and Ono et al.(2011)work well at both room temperature and high temperature.The results also suggest that the discrepancy between bulk modulus of iron from experiments(Mao et al.,1990)and those from Earth's core(Dziewonski and Anderson,1981)is not originated from the overestimation of pressure by the EOS of Holmes et al.(1989).At high pressure and temperature,pressure uncertainty resulted from volume error becomes similarly important as the accuracy of the pressure scale.
