The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for unders...The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching;thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 lm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications.展开更多
In this analysis, natural systems are posed to subsystemize in a manner facilitating both structured information/energy sharing and an entropy maximization process projecting a three-dimensional, spatial outcome. Nume...In this analysis, natural systems are posed to subsystemize in a manner facilitating both structured information/energy sharing and an entropy maximization process projecting a three-dimensional, spatial outcome. Numerical simulations were first carried out to determine whether n × n input-output matrices could, once entropy-maximized, project a three-dimensional Euclidean metric. Only 4 × 4 matrices could;a small proportion passed the test. Larger proportions passed when grouped random patterns on and within two- and three-dimensional forms were tested. The pattern of structural zonation within the earth was then tested in analogous fashion using spatial autocorrelation measures, and for three time periods: current, 95 million years b.p. and 200 million years b.p. All expected results were obtained;not only do the geometries of zonation project a three-dimensional structure as anticipated, but also do secondary statistical measures reveal levels of equilibrium among the zones in all three cases that are nearly total, distinguishing them from simulations that do not incorporate a varying-surface zone-width element.展开更多
The compressional sound velocity VP for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of VP (in km/s) ...The compressional sound velocity VP for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of VP (in km/s) on Hugoniot pressure (P, in GPa) can be described by lnVP= 3.079-0.691 ln(P) + 0.094(lnP)2. VP satisfies Birch’s law: VP= 4.068 + 1.677p, where p is corresponding density, which indicated that enstatite is stable throughout the conditions of the lower mantle. The wave velocity P is 0.5% lower and the wave velocity S is 2% higher than that of PREM respectively. We concluded that the lower mantle is mainly composed of perovskite-(Mg1-x, Fex) SiO3 and only a small amount of (Mg1-x, Fex) O is allowed in it.展开更多
Deployments of seismic stations in Antarctica are an ambitious project to improve the spatial resolution of the Antarctic Plate and surrounding regions. Several international programs had been conducted in wide area o...Deployments of seismic stations in Antarctica are an ambitious project to improve the spatial resolution of the Antarctic Plate and surrounding regions. Several international programs had been conducted in wide area of the Antarctic continent during the International Polar Year (IPY 2007-2008). The “Antarctica’s GAmburtsev Province (AGAP)”, the “GAmburtsev Mountain SEISmic experiment (GAMSEIS)” as a part of AGAP, and the “Polar Earth Observing Network (POLENET)” were major contributions to the IPY. The AGAP/GAMSEIS was an internationally coordinated deployments of more than few tens of broadband seismographs over the wide area of East Antarctica. Detailed information on crustal thickness and mantle structure provides key constraints on an origin of the Gamburtsev Mountains;and more broad structure and evolution of the East Antarctic craton and sub-glacial environment. From POLENET data obtained, local and regional signals associated with ice movements were recorded together with a significant number of teleseismic events. Moreover, seismic deployments have been carried out in the Lützow-Holm Bay (LHB), East Antarctica, by Japanese activities. The recorded teleseismic and local events are of sufficient quality to image the structure and dynamics of the crust and mantle, such as the studies by receiver functions suggesting a heterogeneous upper mantle. In addition to studies on the shallow part of the Earth, we place emphasis on these seismic deployments’ ability to image the Earth’s deep interior, as viewed from Antarctica, as a large aperture array in the southern high latitude.展开更多
Redox state is an important parameter in describing the thermodynamic state of the Earth’s interior.In contrast to the considerable efforts in early studies that have been expended on the redox state of Earth’s diff...Redox state is an important parameter in describing the thermodynamic state of the Earth’s interior.In contrast to the considerable efforts in early studies that have been expended on the redox state of Earth’s different spheres,much attention in the recent about 10 years has been paid to the effects of redox state on the various geodynamical aspects of Earth’s interior,or more commonly the redox geodynamics.Redox geodynamics plays a critical role in driving many processes that are involved in the accretion,differentiation,and re-shaping of the Earth from its early birth to modern periods and from its surface to the deep interior,including the structure,composition,nature,and evolution of the Earth and the significant effects on many important issues such as the climate change and habitability of the planet.This field has blossomed in these years around the chemical and physical properties of the Earth.In this review,a brief summary is provided for the basic concepts,general background and applications relevant to redox geodynamics.The redox state of the crust and mantle and its evolution have received particular attention in the past years,however,there are still fundamental issues remaining ambiguous,poorly quantified and/or even controversial.At the same time,significant progress has been made,mostly through experimental studies,on the redox geodynamics of the Earth’s interior,including(but are not limited to)the early oxidation of the shallow mantle,the rapid growth of the early continental crust,the redox freezing and melting associated with carbon or hydrogen,the transfer of metal elements and formation of ore deposits,the low seismic velocity and high attenuation of the asthenosphere,the aerobic processes around the core-mantle boundary,and the magma degassing and released gases.Redox geodynamics is becoming increasingly important in renewing the understanding of the chemical evolution,physical properties,and dynamical processes of the Earth.展开更多
Mean heat flows and heat losses of the Northern and Southern hemispheres are calculated using degree 12 spherical harmonic representation of the global heat flow field (Pollack et al., 1993). Mean heat flows and heat ...Mean heat flows and heat losses of the Northern and Southern hemispheres are calculated using degree 12 spherical harmonic representation of the global heat flow field (Pollack et al., 1993). Mean heat flows and heat losses of 0° hemisphere and 180° hemisphere, with median lines being 0° longitude and 180° longitude, are also calculated. The mean heat flow of the Southern Hemisphere is 99.3 mW·m -2, significantly higher than that of the Northern Hemisphere (74.0 mW·m -2). The mean heat flow of 0° hemisphere (94.1 mW·m -2) is also higher than the value of 180° hemisphere (79.3 mW·m -2). The mantle heat loss from the Southern Hemisphere is 22.1×10 12 W, as twice as that from the Northern Hemisphere ( 10.8×10 12 W). The 16.9×10 12 W mantle heat loss from 0° hemisphere is close to 16.0×10 12 W from 180° hemisphere. The hemispherical asymmetry of global heat loss is originated by the asymmetry of geographic distribution of continents and oceans. The asymmetric distribution of heat loss is a long-term phenomenon in the geological history.展开更多
The increment method is adopted to calculate oxygen isotope fractionation factors for mantle minerals, particularly for the polymorphic phases of MgSiO 3 and Mg 2SiO 4. The results predict the following sequence of 18...The increment method is adopted to calculate oxygen isotope fractionation factors for mantle minerals, particularly for the polymorphic phases of MgSiO 3 and Mg 2SiO 4. The results predict the following sequence of 18 O enrichment: pyroxene (Mg, Fe, Ca) 2Si 2O 6>olivine (Mg,Fe) 2SiO 4>spinel (Mg,Fe) 2SiO 4>ilmenite (Mg,Fe,Ca)SiO 3>perovskite (Mg,Fe,Ca)SiO 3. The calculated fractionations for the calcite perovskite (CaTiO 3) system are in excellent agreement with the experimental calibrations. If there would be complete isotopic equilibration in the mantle, the spinel structured silicates in the transition zone are predicted to be enriched in 18 O relative to the perovskite structured silicates in the lower mantle but depleted in 18 O relative to olivines and pyroxenes in the upper mantle. The oxygen isotope layering of the mantle might result from differences in the chemical composition and crystal structure of mineral phases at different mantle depths. Assuming isotopic equilibrium on a whole earth scale, the chemical structure of the Earth’s interior can be described by the following sequence of 18 O enrichment: upper crust>lower crust>upper mantle>transition zone>lower mantle>展开更多
基金the National Natural Science Foundation of China (41574080 and U1530402).
文摘The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching;thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 lm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications.
文摘In this analysis, natural systems are posed to subsystemize in a manner facilitating both structured information/energy sharing and an entropy maximization process projecting a three-dimensional, spatial outcome. Numerical simulations were first carried out to determine whether n × n input-output matrices could, once entropy-maximized, project a three-dimensional Euclidean metric. Only 4 × 4 matrices could;a small proportion passed the test. Larger proportions passed when grouped random patterns on and within two- and three-dimensional forms were tested. The pattern of structural zonation within the earth was then tested in analogous fashion using spatial autocorrelation measures, and for three time periods: current, 95 million years b.p. and 200 million years b.p. All expected results were obtained;not only do the geometries of zonation project a three-dimensional structure as anticipated, but also do secondary statistical measures reveal levels of equilibrium among the zones in all three cases that are nearly total, distinguishing them from simulations that do not incorporate a varying-surface zone-width element.
文摘The compressional sound velocity VP for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of VP (in km/s) on Hugoniot pressure (P, in GPa) can be described by lnVP= 3.079-0.691 ln(P) + 0.094(lnP)2. VP satisfies Birch’s law: VP= 4.068 + 1.677p, where p is corresponding density, which indicated that enstatite is stable throughout the conditions of the lower mantle. The wave velocity P is 0.5% lower and the wave velocity S is 2% higher than that of PREM respectively. We concluded that the lower mantle is mainly composed of perovskite-(Mg1-x, Fex) SiO3 and only a small amount of (Mg1-x, Fex) O is allowed in it.
文摘Deployments of seismic stations in Antarctica are an ambitious project to improve the spatial resolution of the Antarctic Plate and surrounding regions. Several international programs had been conducted in wide area of the Antarctic continent during the International Polar Year (IPY 2007-2008). The “Antarctica’s GAmburtsev Province (AGAP)”, the “GAmburtsev Mountain SEISmic experiment (GAMSEIS)” as a part of AGAP, and the “Polar Earth Observing Network (POLENET)” were major contributions to the IPY. The AGAP/GAMSEIS was an internationally coordinated deployments of more than few tens of broadband seismographs over the wide area of East Antarctica. Detailed information on crustal thickness and mantle structure provides key constraints on an origin of the Gamburtsev Mountains;and more broad structure and evolution of the East Antarctic craton and sub-glacial environment. From POLENET data obtained, local and regional signals associated with ice movements were recorded together with a significant number of teleseismic events. Moreover, seismic deployments have been carried out in the Lützow-Holm Bay (LHB), East Antarctica, by Japanese activities. The recorded teleseismic and local events are of sufficient quality to image the structure and dynamics of the crust and mantle, such as the studies by receiver functions suggesting a heterogeneous upper mantle. In addition to studies on the shallow part of the Earth, we place emphasis on these seismic deployments’ ability to image the Earth’s deep interior, as viewed from Antarctica, as a large aperture array in the southern high latitude.
基金supported by the National Natural Science Foundation of China(Grant No.41725008)the National Key R&D Program of China(Grant No.2018YFA0702704)。
文摘Redox state is an important parameter in describing the thermodynamic state of the Earth’s interior.In contrast to the considerable efforts in early studies that have been expended on the redox state of Earth’s different spheres,much attention in the recent about 10 years has been paid to the effects of redox state on the various geodynamical aspects of Earth’s interior,or more commonly the redox geodynamics.Redox geodynamics plays a critical role in driving many processes that are involved in the accretion,differentiation,and re-shaping of the Earth from its early birth to modern periods and from its surface to the deep interior,including the structure,composition,nature,and evolution of the Earth and the significant effects on many important issues such as the climate change and habitability of the planet.This field has blossomed in these years around the chemical and physical properties of the Earth.In this review,a brief summary is provided for the basic concepts,general background and applications relevant to redox geodynamics.The redox state of the crust and mantle and its evolution have received particular attention in the past years,however,there are still fundamental issues remaining ambiguous,poorly quantified and/or even controversial.At the same time,significant progress has been made,mostly through experimental studies,on the redox geodynamics of the Earth’s interior,including(but are not limited to)the early oxidation of the shallow mantle,the rapid growth of the early continental crust,the redox freezing and melting associated with carbon or hydrogen,the transfer of metal elements and formation of ore deposits,the low seismic velocity and high attenuation of the asthenosphere,the aerobic processes around the core-mantle boundary,and the magma degassing and released gases.Redox geodynamics is becoming increasingly important in renewing the understanding of the chemical evolution,physical properties,and dynamical processes of the Earth.
文摘Mean heat flows and heat losses of the Northern and Southern hemispheres are calculated using degree 12 spherical harmonic representation of the global heat flow field (Pollack et al., 1993). Mean heat flows and heat losses of 0° hemisphere and 180° hemisphere, with median lines being 0° longitude and 180° longitude, are also calculated. The mean heat flow of the Southern Hemisphere is 99.3 mW·m -2, significantly higher than that of the Northern Hemisphere (74.0 mW·m -2). The mean heat flow of 0° hemisphere (94.1 mW·m -2) is also higher than the value of 180° hemisphere (79.3 mW·m -2). The mantle heat loss from the Southern Hemisphere is 22.1×10 12 W, as twice as that from the Northern Hemisphere ( 10.8×10 12 W). The 16.9×10 12 W mantle heat loss from 0° hemisphere is close to 16.0×10 12 W from 180° hemisphere. The hemispherical asymmetry of global heat loss is originated by the asymmetry of geographic distribution of continents and oceans. The asymmetric distribution of heat loss is a long-term phenomenon in the geological history.
文摘The increment method is adopted to calculate oxygen isotope fractionation factors for mantle minerals, particularly for the polymorphic phases of MgSiO 3 and Mg 2SiO 4. The results predict the following sequence of 18 O enrichment: pyroxene (Mg, Fe, Ca) 2Si 2O 6>olivine (Mg,Fe) 2SiO 4>spinel (Mg,Fe) 2SiO 4>ilmenite (Mg,Fe,Ca)SiO 3>perovskite (Mg,Fe,Ca)SiO 3. The calculated fractionations for the calcite perovskite (CaTiO 3) system are in excellent agreement with the experimental calibrations. If there would be complete isotopic equilibration in the mantle, the spinel structured silicates in the transition zone are predicted to be enriched in 18 O relative to the perovskite structured silicates in the lower mantle but depleted in 18 O relative to olivines and pyroxenes in the upper mantle. The oxygen isotope layering of the mantle might result from differences in the chemical composition and crystal structure of mineral phases at different mantle depths. Assuming isotopic equilibrium on a whole earth scale, the chemical structure of the Earth’s interior can be described by the following sequence of 18 O enrichment: upper crust>lower crust>upper mantle>transition zone>lower mantle>
