The electrical conductivity of minerals under extreme conditions is governed by their variations in composition and structure.Constitution water,which is present in various polymorphic phases of olivine,can significan...The electrical conductivity of minerals under extreme conditions is governed by their variations in composition and structure.Constitution water,which is present in various polymorphic phases of olivine,can significantly enhance electrical conductivity under mantle pressure-temperature conditions,therefore playing a key role in proton transport.Despite this,the conductive mechanisms in hydrous olivine,particularly in hydrous ringwoodite,and the dynamic behavior of hydrogen at elevated temperatures,remain poorly understood.In this study,we investigated the proton conduction mechanisms in hydrous ringwoodite through first-principles calculations.Several hydrous models were considered,and ab initio molecular dynamics(AIMD)simulations were employed to simulate hydrous configurations at high temperatures.Calculations based on density functional perturbation theory(DFPT)and vibrational density of states(VDOS)analyses were conducted to probe the stability of hydrous structures,and investigate the dynamic behavior of internal hydrogen.Our results indicate that hydrogen trapped in Mg^(2+)and Fe^(3+)defects exhibits significantly higher mobility than hydrogen trapped in Si^(4+)defects.At elevated temperatures,we observed the ionization of hydrogen from cationic defects,leading to high and highly anisotropic proton conductivity along the[100]crystallographic direction.This thermal ionization-induced anisotropic conductivity is consistent with experimental observations of olivine single crystals.Finally,the conductivity of the 0.79 wt%hydrous ringwoodite structure was found to range from 10^(-0.3)to 10^(0.4)S/m,the 1.19 wt%structure ranged from 10^(0.4)to 10^(0.9)S/m in the transition region,and the 1.62 wt%structure exhibited conductivity ranging from 10^(0.7)to 10^(1.2)S/m.These results are in excellent agreement with prior experimental data,providing further insight into the proton conduction mechanisms of hydrous olivine under extreme mantle conditions.展开更多
A deformation experiment of ringwoodite with a strain of 9% was achieved at 20 GPa and 1 700 K and at a strain rate of 3×10^-5 s^-1 using a deformation-DIA （D-DIA） apparatus and a multi-anvil 6-6 （MA 6-6） ass...A deformation experiment of ringwoodite with a strain of 9% was achieved at 20 GPa and 1 700 K and at a strain rate of 3×10^-5 s^-1 using a deformation-DIA （D-DIA） apparatus and a multi-anvil 6-6 （MA 6-6） assembly. The crystallographic orientations of the deformed sample were successfully analyzed by the electron backscatter diffraction （EBSD） method, although any notable latticepreferred orientation （LPO） was not observed presumably due to the insufficient strain in the present experiment. In this study, the deformation experiment on ringwoodite succeeded at P-T conditions consistent with the lower part of the mantle transition zone and at a controlled strain rate for the first time. The present study extended the pressure range of deformation experiments in the D-DIA apparatus from 16 GPa in our earlier study to 20 GPa at 1 700 K. The successful extension of the pressure range demonstrates potential importance of the D-DIA apparatus in studying rheological properties of minerals under the P-T conditions of the whole mantle transition zone.展开更多
Ringwoodite is an important mineral in the mantle transition zone,and its cationic disorder can profoundly affect its physicochemical properties,but there is currently much controversy about this disorder.In this stud...Ringwoodite is an important mineral in the mantle transition zone,and its cationic disorder can profoundly affect its physicochemical properties,but there is currently much controversy about this disorder.In this study,we investigate the cation disorder states of pure Mg2SiO4-ringwoodite and defective ringwoodite under mantle transition zone conditions through DFT calculations and thermodynamic models.Two stable endmembers are seen,one with normal ringwoodite structure and the other with inverted structure(its Si atoms and half of its Mg atoms have swapped sites).Our results indicate that pure ringwoodite does not invert(swap Mg and Si cations)under normal mantle temperatures but the introduction of a Si-excess,Mg-deficient defect induces a swap at normal mantle temperatures and this swap is likely induced by a wide range of defects including water.Thus,in the presence of such a defect or similar defects the olivine phase transition sequence may then go from olivine to wadsleyite to inverse ringwoodite,and then normal ringwoodite.We calculate the seismic properties of normal and inverse ringwoodite and find significantly slower wave speeds in inverted ringwoodite.Due to this difference the presence of inverse ringwoodite may provide a potential explanation for the discontinuous interface of seismic waves at the depth of∼560 km.展开更多
Several of the known over 3000 minerals possess great typomorphic implication and experienced twists and turns of their discovery. Ringwoodite is the most outstanding of them. In 1931, Goldshmidt suggested that the cr...Several of the known over 3000 minerals possess great typomorphic implication and experienced twists and turns of their discovery. Ringwoodite is the most outstanding of them. In 1931, Goldshmidt suggested that the crystal structure of Mg<sub>2</sub>GeO<sub>4</sub> could show two polymorphs for olivine and spinel. Based on this, in 1936, J. D. Bernal put forward his bold assumption that the increase of seismic velocity in mantle is caused by展开更多
The images of the oceans often inspire us to take a poetic lift of the spirit for an escape from the daily boredom or troubles related to the social restriction based on the ideological hierarchy.On the other hand,how...The images of the oceans often inspire us to take a poetic lift of the spirit for an escape from the daily boredom or troubles related to the social restriction based on the ideological hierarchy.On the other hand,however,the collective human desires have no good ethics to discipline the insatiable enjoyment that has obviously damaged the environment and polluted the oceans.In this short paper,I focus on the concepts of the time event,Aion and Chronos,with the three poems related to the images of the oceans written by a Taiwan region of China poet,Hui Tong;I also try to understand how the origin of the water on our Earth comes from.In fact,our Earth has the“liquid”oceans on the surface and also the hidden“solid”oceans,the blue crystal rocks called ringwoodite,within Earth’s mantle.The oceans absorb heat and the tiny ocean plants called phytoplankton drifting with the oceanic currents produce oxygen through photosynthesis for the human health as well.But the contemporary environmental problem is that the chronic damages of the biodiversity by the human collective desires have affected the oceans to become seriously polluted.Therefore,we have the feelings of ambivalence toward the images of the oceans:tranquility,transience,creativity,oblivion or corruption and hostility for the human bad habits.展开更多
There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in ...There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in the mantle has attracted much attention from the societies of mineralogy and geophysics in recent years. In the subducting slab, serpentine breaks down at high temperature, generating a series of dense hydrous magnesium silicate(DHMS) phases, such as phase A, chondrodite, clinohumite, etc. These phases may serve as carriers of water as hydroxyl into the upper mantle and the mantle transition zone(MTZ). On the other hand, wadsleyite and ringwoodite, polymorphs of olivine, are most the abundant minerals in the MTZ, and able to absorb significant amount of water(up to about 3 wt.% H_2O). Hence, the MTZ becomes a very important layer for water storage in the mantle, and hydration plays important roles in physics and chemistry of the MTZ. In this paper, we will discuss two aspects of hydrous silicate minerals:(1) crystal structures and(2) equations of state(Eo Ss).展开更多
基金supported by the National Natural Science Foundation of China(41930112,91755215)the Sichuan Students'Innovation and entrepreneurship training program(s202310616086).
文摘The electrical conductivity of minerals under extreme conditions is governed by their variations in composition and structure.Constitution water,which is present in various polymorphic phases of olivine,can significantly enhance electrical conductivity under mantle pressure-temperature conditions,therefore playing a key role in proton transport.Despite this,the conductive mechanisms in hydrous olivine,particularly in hydrous ringwoodite,and the dynamic behavior of hydrogen at elevated temperatures,remain poorly understood.In this study,we investigated the proton conduction mechanisms in hydrous ringwoodite through first-principles calculations.Several hydrous models were considered,and ab initio molecular dynamics(AIMD)simulations were employed to simulate hydrous configurations at high temperatures.Calculations based on density functional perturbation theory(DFPT)and vibrational density of states(VDOS)analyses were conducted to probe the stability of hydrous structures,and investigate the dynamic behavior of internal hydrogen.Our results indicate that hydrogen trapped in Mg^(2+)and Fe^(3+)defects exhibits significantly higher mobility than hydrogen trapped in Si^(4+)defects.At elevated temperatures,we observed the ionization of hydrogen from cationic defects,leading to high and highly anisotropic proton conductivity along the[100]crystallographic direction.This thermal ionization-induced anisotropic conductivity is consistent with experimental observations of olivine single crystals.Finally,the conductivity of the 0.79 wt%hydrous ringwoodite structure was found to range from 10^(-0.3)to 10^(0.4)S/m,the 1.19 wt%structure ranged from 10^(0.4)to 10^(0.9)S/m in the transition region,and the 1.62 wt%structure exhibited conductivity ranging from 10^(0.7)to 10^(1.2)S/m.These results are in excellent agreement with prior experimental data,providing further insight into the proton conduction mechanisms of hydrous olivine under extreme mantle conditions.
基金supported by the Global Center of Excellence Program "Deep Earth Mineralogy" the Ministry of Education, Culture, Sports, Science, and Technology of the Japanese Government
文摘A deformation experiment of ringwoodite with a strain of 9% was achieved at 20 GPa and 1 700 K and at a strain rate of 3×10^-5 s^-1 using a deformation-DIA （D-DIA） apparatus and a multi-anvil 6-6 （MA 6-6） assembly. The crystallographic orientations of the deformed sample were successfully analyzed by the electron backscatter diffraction （EBSD） method, although any notable latticepreferred orientation （LPO） was not observed presumably due to the insufficient strain in the present experiment. In this study, the deformation experiment on ringwoodite succeeded at P-T conditions consistent with the lower part of the mantle transition zone and at a controlled strain rate for the first time. The present study extended the pressure range of deformation experiments in the D-DIA apparatus from 16 GPa in our earlier study to 20 GPa at 1 700 K. The successful extension of the pressure range demonstrates potential importance of the D-DIA apparatus in studying rheological properties of minerals under the P-T conditions of the whole mantle transition zone.
基金supported by the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB42000000)the Natural Science Foundation of China(Grant No.42373034).
文摘Ringwoodite is an important mineral in the mantle transition zone,and its cationic disorder can profoundly affect its physicochemical properties,but there is currently much controversy about this disorder.In this study,we investigate the cation disorder states of pure Mg2SiO4-ringwoodite and defective ringwoodite under mantle transition zone conditions through DFT calculations and thermodynamic models.Two stable endmembers are seen,one with normal ringwoodite structure and the other with inverted structure(its Si atoms and half of its Mg atoms have swapped sites).Our results indicate that pure ringwoodite does not invert(swap Mg and Si cations)under normal mantle temperatures but the introduction of a Si-excess,Mg-deficient defect induces a swap at normal mantle temperatures and this swap is likely induced by a wide range of defects including water.Thus,in the presence of such a defect or similar defects the olivine phase transition sequence may then go from olivine to wadsleyite to inverse ringwoodite,and then normal ringwoodite.We calculate the seismic properties of normal and inverse ringwoodite and find significantly slower wave speeds in inverted ringwoodite.Due to this difference the presence of inverse ringwoodite may provide a potential explanation for the discontinuous interface of seismic waves at the depth of∼560 km.
基金Project supported by the National Natural Science Foundation of China
文摘Several of the known over 3000 minerals possess great typomorphic implication and experienced twists and turns of their discovery. Ringwoodite is the most outstanding of them. In 1931, Goldshmidt suggested that the crystal structure of Mg<sub>2</sub>GeO<sub>4</sub> could show two polymorphs for olivine and spinel. Based on this, in 1936, J. D. Bernal put forward his bold assumption that the increase of seismic velocity in mantle is caused by
文摘The images of the oceans often inspire us to take a poetic lift of the spirit for an escape from the daily boredom or troubles related to the social restriction based on the ideological hierarchy.On the other hand,however,the collective human desires have no good ethics to discipline the insatiable enjoyment that has obviously damaged the environment and polluted the oceans.In this short paper,I focus on the concepts of the time event,Aion and Chronos,with the three poems related to the images of the oceans written by a Taiwan region of China poet,Hui Tong;I also try to understand how the origin of the water on our Earth comes from.In fact,our Earth has the“liquid”oceans on the surface and also the hidden“solid”oceans,the blue crystal rocks called ringwoodite,within Earth’s mantle.The oceans absorb heat and the tiny ocean plants called phytoplankton drifting with the oceanic currents produce oxygen through photosynthesis for the human health as well.But the contemporary environmental problem is that the chronic damages of the biodiversity by the human collective desires have affected the oceans to become seriously polluted.Therefore,we have the feelings of ambivalence toward the images of the oceans:tranquility,transience,creativity,oblivion or corruption and hostility for the human bad habits.
基金supported by the National Natural Science Foundation of China(Grant Nos.41590621&41473058)the Fundamental Research Funds for the Central University(Grant No.G1323531512)MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources(Grant No.MSFGPMR07),China University of Geosciences at Wuhan
文摘There are potentially huge amounts of water stored in Earth's mantle, and the water solubilities in the silicate minerals range from tens to thousands of part per minion(ppm, part per million). Exploring water in the mantle has attracted much attention from the societies of mineralogy and geophysics in recent years. In the subducting slab, serpentine breaks down at high temperature, generating a series of dense hydrous magnesium silicate(DHMS) phases, such as phase A, chondrodite, clinohumite, etc. These phases may serve as carriers of water as hydroxyl into the upper mantle and the mantle transition zone(MTZ). On the other hand, wadsleyite and ringwoodite, polymorphs of olivine, are most the abundant minerals in the MTZ, and able to absorb significant amount of water(up to about 3 wt.% H_2O). Hence, the MTZ becomes a very important layer for water storage in the mantle, and hydration plays important roles in physics and chemistry of the MTZ. In this paper, we will discuss two aspects of hydrous silicate minerals:(1) crystal structures and(2) equations of state(Eo Ss).
