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| Open AccessVariation in bridgmanite grain size accounts for the mid-mantle viscosity jump
Bridgmanite-enriched rocks in the deep lower mantle of Earth have a larger grain size and higher viscosity than those of the overlying pyrolitic rocks, which explain the mid-mantle viscosity jump.
- Hongzhan Fei
- , Maxim D. Ballmer
- & Tomoo Katsura
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Article |
Spin state and deep interior structure of Mars from InSight radio tracking
Analysis of radio science data from the NASA InSight Mars lander reveals details of the rotation of the planet, which have been used to determine fundamental information about its core, mantle and atmosphere.
- Sébastien Le Maistre
- , Attilio Rivoldini
- & W. Bruce Banerdt
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Article |
Core origin of seismic velocity anomalies at Earth’s core–mantle boundary
Investigations of the crystallization of FeSi in Fe–Si–H melt under high pressure−temperature conditions provide evidence of a new process that explains geochemical and geophysical observations at the core–mantle boundary.
- Suyu Fu
- , Stella Chariton
- & Sang-Heon Shim
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Article
| Open AccessPericlase deforms more slowly than bridgmanite under mantle conditions
The authors model the creep of MgO periclase at lower mantle pressures and temperatures, finding that it deforms more slowly than bridgmanite at mantle strain rate.
- Patrick Cordier
- , Karine Gouriet
- & Philippe Carrez
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Article |
Extreme redox variations in a superdeep diamond from a subducted slab
The authors investigate chemical anomalies in superdeep diamond inclusions, leading them to suggest that there is an extremely variable redox environment in the deep mantle.
- Fabrizio Nestola
- , Margo E. Regier
- & Jeffrey W. Harris
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Article |
Calcium dissolution in bridgmanite in the Earth’s deep mantle
Experiments show that calcium solubility in bridgmanite increases with depth in Earth’s lower mantle, resulting in the disappearance of CaSiO3 perovskite and indicating a transition from a two-perovskite to a single-perovskite domain.
- Byeongkwan Ko
- , Eran Greenberg
- & Sang-Heon Shim
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Article |
Nd isotope variation between the Earth–Moon system and enstatite chondrites
Isotopic analysis reveals that the samarium/neodymium ratio of the Earth–Moon system is higher than that of chondrites, and that the neodymium composition of Earth is similar to that of enstatite chondrites.
- Shelby Johnston
- , Alan Brandon
- & Peter Copeland
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Article |
Hadean isotopic fractionation of xenon retained in deep silicates
An explanation of the Earth’s ‘missing Xe’ problem that involves multiple magma ocean stages combined with atmospheric loss is proposed.
- Igor Rzeplinski
- , Chrystèle Sanloup
- & Denis Horlait
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Article |
Weak cubic CaSiO3 perovskite in the Earth’s mantle
At temperatures and pressures typical of the Earth’s lower mantle, cubic CaSiO3 perovskite is found to have lower strength and viscosity compared to bridgmanite and ferropericlase, providing clues to its role in subduction regions.
- J. Immoor
- , L. Miyagi
- & H. Marquardt
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Article |
Superionic iron alloys and their seismic velocities in Earth’s inner core
Molecular dynamics simulations show that the light elements hydrogen, oxygen and carbon become highly diffusive like liquid in solid iron under the inner-core conditions, leading to a reduction in the seismic velocities.
- Yu He
- , Shichuan Sun
- & Ho-kwang Mao
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Article
| Open AccessDepressed 660-km discontinuity caused by akimotoite–bridgmanite transition
X-ray diffraction experiments indicate that the depression of the Earth’s 660-kilometre seismic discontinuity beneath cold subduction zones is caused by a phase transition from akimotoite to bridgmanite, leading to slab stagnation.
- Artem Chanyshev
- , Takayuki Ishii
- & Tomoo Katsura
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Stress-induced amorphization triggers deformation in the lithospheric mantle
Amorphization at grain boundaries in olivine-rich rocks under stress and consequent grain-boundary sliding could explain the decrease in viscosity between the lithosphere and the asthenosphere.
- Vahid Samae
- , Patrick Cordier
- & Hosni Idrissi
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Article |
Seismic evidence for partial melt below tectonic plates
Analysis of global three-dimensional shear attenuation and velocity models implies that partial melting in the seismic low-velocity zone enables motion of oceanic plates by reducing the viscosity of the asthenosphere.
- Eric Debayle
- , Thomas Bodin
- & Yanick Ricard
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Letter |
Seismic velocities of CaSiO3 perovskite can explain LLSVPs in Earth’s lower mantle
Unexpectedly low seismic velocities of CaSiO3 perovskite in deeply subducted oceanic crust can explain the properties of anomalous continent-sized regions in Earth’s lower mantle.
- A. R. Thomson
- , W. A. Crichton
- & S. A. Hunt
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Matters Arising |
Reply to: Evidence for two blue (type IIb) diamond populations
- Evan M. Smith
- , Steven B. Shirey
- & Wuyi Wang
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Letter |
Magnetism in cold subducting slabs at mantle transition zone depths
Synchrotron Mössbauer source spectroscopy is used to reveal that haematite remains magnetic in cold subducting slabs at the depth of the transition zone in the Earth’s mantle, with implications for the locations of magnetic poles during inversions of the Earth’s magnetic field.
- I. Kupenko
- , G. Aprilis
- & C. Sanchez-Valle
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Letter |
Sound velocity of CaSiO3 perovskite suggests the presence of basaltic crust in the Earth’s lower mantle
In situ high-pressure and high-temperature measurements of the sound velocity of CaSiO3 perovskite suggest accumulation of basaltic crust in the Earth’s uppermost lower mantle.
- Steeve Gréaux
- , Tetsuo Irifune
- & Akihiro Yamada
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Brief Communications Arising |
Elasticity of lower-mantle bridgmanite
- Jung-Fu Lin
- , Zhu Mao
- & Suyu Fu
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Letter |
Blue boron-bearing diamonds from Earth’s lower mantle
Mineral inclusions in blue boron-bearing diamonds reveal that such diamonds are among the deepest diamonds ever found and indicate a viable pathway for the deep-mantle recycling of crustal elements.
- Evan M. Smith
- , Steven B. Shirey
- & Wuyi Wang
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Letter |
Low-temperature crystallization of granites and the implications for crustal magmatism
Thermobarometry and diffusion modelling in quartz crystals show that some granites may crystallize at much lower temperatures than we had thought, possibly explaining observations of cold magma storage.
- Michael R. Ackerson
- , B. O. Mysen
- & E. B. Watson
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Letter |
Redox-influenced seismic properties of upper-mantle olivine
Redox conditions and associated defect chemistry rather than water content, as previously thought, strongly influence the seismic properties of olivine, the main constituent mineral of Earth’s upper mantle.
- C. J. Cline II
- , U. H. Faul
- & I. Jackson
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Letter |
CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle
The composition of natural calcium silicate perovskite, the fourth most abundant mineral in the Earth, found within a diamond indicates an origin from oceanic crust subducted deeper than 700 kilometres into the Earth’s mantle.
- F. Nestola
- , N. Korolev
- & J. Davidson
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Letter |
Primordial clays on Mars formed beneath a steam or supercritical atmosphere
Many Martian clays formed when Mars’ primary crust reacted with a water/carbon dioxide steam or supercritical atmosphere and subsequent impacts and volcanism caused the distribution of clay exposures seen today.
- Kevin M. Cannon
- , Stephen W. Parman
- & John F. Mustard
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Letter |
Hydrogen-bearing iron peroxide and the origin of ultralow-velocity zones
A reaction between iron and water at the high pressure and temperature of the lowermost mantle is described that produces hydrogen-bearing iron peroxide, which has the properties expected of the ultralow-velocity zones at Earth’s core–mantle boundary.
- Jin Liu
- , Qingyang Hu
- & Wendy L. Mao
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Letter |
The pyrite-type high-pressure form of FeOOH
The pyrite-type high-pressure form of FeOOH is predicted from first principles, and found experimentally to be stable under the conditions at the base of the mantle, with implications for transport of water within Earth’s deep interior.
- Masayuki Nishi
- , Yasuhiro Kuwayama
- & Taku Tsuchiya
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Letter |
Evidence for a Fe3+-rich pyrolitic lower mantle from (Al,Fe)-bearing bridgmanite elasticity data
The authors report single-crystal elasticity data on (Al,Fe)-bearing bridgmanite and show that its elastic behaviour is markedly different from that of the MgSiO3 endmember.
- A. Kurnosov
- , H. Marquardt
- & L. Ziberna
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Letter |
Mantle dynamics inferred from the crystallographic preferred orientation of bridgmanite
Deformation experiments on bridgmanite indicate that it may be the main contributor to the shear wave anisotropy observed around several subducting plates.
- Noriyoshi Tsujino
- , Yu Nishihara
- & Eiichi Takahashi
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Letter |
An early geodynamo driven by exsolution of mantle components from Earth’s core
Experiments show that magnesium oxide can dissolve in core-forming metallic melts at very high temperatures; core formation models suggest that a giant impact during Earth’s accretion could have contributed large amounts of magnesium to the early core, the subsequent exsolution of which would have generated enough gravitational energy to power an early geodynamo and produce an ancient magnetic field.
- James Badro
- , Julien Siebert
- & Francis Nimmo
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Letter |
Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres
High-resolution near-infrared observations of the Occator bright areas on the dwarf planet Ceres suggest that the bright material is mostly made up of endogenous sodium carbonate.
- M. C. De Sanctis
- , A. Raponi
- & C. T. Russell
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Letter |
Experimental determination of the electrical resistivity of iron at Earth’s core conditions
Using a laser-heated diamond-anvil cell to measure the electrical resistivity of iron under the high temperature and pressure conditions of the Earth’s core yields a value that means Earth’s core has high thermal conductivity, suggesting that its inner core is less than 0.7 billion years old, much younger than thought.
- Kenji Ohta
- , Yasuhiro Kuwayama
- & Yasuo Ohishi
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Letter |
Dehydration of lawsonite could directly trigger earthquakes in subducting oceanic crust
Deformation experiments on lawsonite reveal that unstable fault slip occurs during dehydration reactions with continuous acoustic emission signals; this indicates the potential for unstable frictional sliding in natural lawsonite layers, which could possibly be the source of intermediate-depth earthquakes in cold subduction zones.
- Keishi Okazaki
- & Greg Hirth
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Letter |
Sublimation in bright spots on (1) Ceres
The dwarf planet (1) Ceres, the largest object in the main asteroid belt, is found to have localized bright areas on its surface; particularly interesting is a bright pit on the floor of the crater Occator that exhibits what is likely to be water ice sublimation, producing crater-bound haze clouds with a diurnal rhythm.
- A. Nathues
- , M. Hoffmann
- & J.-B. Vincent
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Letter |
Effects of electron correlations on transport properties of iron at Earth’s core conditions
Based on first-principles resistivity calculations, it was recently concluded that the thermal conductivity of iron in Earth’s core was too high to sustain thermal convection, thus invalidating such geodynamo models; new calculations including electron correlations find that electron–electron scattering is comparable to the electron–phonon scattering at high temperatures in iron, doubling the expected resistivity, and reviving conventional geodynamo models.
- Peng Zhang
- , R. E. Cohen
- & K. Haule
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Article |
Disclinations provide the missing mechanism for deforming olivine-rich rocks in the mantle
Using electron backscattering diffraction maps of deformed olivine to resolve the disclinations at grain boundaries, combined with a disclination-based model of a high-angle tilt boundary in olivine, reveals the missing mechanism for describing plastic flow in polycrystalline olivine: an applied shear induces grain-boundary migration through disclination motion.
- Patrick Cordier
- , Sylvie Demouchy
- & Claude Fressengeas
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Article |
Olivine crystals align during diffusion creep of Earth’s upper mantle
In Earth’s mantle, the shape change of olivine grains depending on temperature and the presence of melt can result in the development of olivine crystallographic preferred orientation during diffusion creep, meaning that the process may be the principal mechanism of mantle flow.
- Tomonori Miyazaki
- , Kenta Sueyoshi
- & Takehiko Hiraga
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Letter |
Small effect of water on upper-mantle rheology based on silicon self-diffusion coefficients
Measurements of the silicon self-diffusion coefficients in olivine at high temperature show that the effect of water content on rock deformation is actually very small, not large as was previously thought.
- Hongzhan Fei
- , Michael Wiedenbeck
- & Tomoo Katsura
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Letter |
Laboratory measurements of the viscous anisotropy of olivine aggregates
Measurements of the viscous anisotropy of highly deformed polycrystalline olivine find it to be approximately an order of magnitude larger than that predicted by grain-scale simulations; the maximum degree of anisotropy is reached at geologically low shear strain, such that deforming regions of the Earth’s upper mantle should exhibit significant viscous anisotropy.
- L. N. Hansen
- , M. E. Zimmerman
- & D. L. Kohlstedt
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News |
Stinky rocks hide Earth’s only haven for natural fluorine
Chemists settle centuries-old debate about what causes 'fetid fluorite' to smell.
- Katharine Sanderson
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Letter |
A perovskitic lower mantle inferred from high-pressure, high-temperature sound velocity data
Determination of the shear-wave velocities for silicate perovskite and ferropericlase under the pressure and temperature conditions of the deep lower mantle indicates that perovskite constitutes much more of the lower mantle than predicted by the conventional mantle model and is consistent with the chondritic Earth model.
- Motohiko Murakami
- , Yasuo Ohishi
- & Kei Hirose
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Brief Communications Arising |
Mineralogical constraints on Precambrian
- Christopher T. Reinhard
- & Noah J. Planavsky
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Brief Communications Arising |
Low
- N. Dauphas
- & J. F. Kasting
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Brief Communications Arising |
Rosing, Bird, Sleep & Bjerrum reply
- Minik T. Rosing
- , Dennis K. Bird
- & Christian J. Bjerrum
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Letter |
Low strength of deep San Andreas fault gouge from SAFOD core
This study reports on laboratory-strength measurements of fault core materials from a drill hole located northwest of Parkfield, California, near the southern end of a creeping zone of the San Andreas fault. It is found that the fault is profoundly weak at this location and depth, owing to the presence of the smectite clay mineral saponite—one of the weakest phyllosilicates known. These findings provide strong evidence that deformation of the mechanically unusual creeping portions of the San Andreas fault system is controlled by the presence of weak minerals rather than by high fluid pressure or other proposed mechanisms.
- David A. Lockner
- , Carolyn Morrow
- & Stephen Hickman
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News & Views |
Proposal with a ring of diamonds
Plate reconstructions show that ancient eruptions of diamond-bearing rocks occurred consistently above a ring-like region of plume-generation zones deep in Earth's mantle. Do such zones remain stationary?
- David A. D. Evans