Analysis of P-V-T data: constraints on the thermoelastic properties of high-pressure minerals

Jackson, Ian; Rigden, Sally M.

doi:10.1016/0031-9201(96)03143-3

Cited by 201 publications

(139 citation statements)

References 43 publications

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“…The values of the coefficient of thermal expansion obtained in large volume press experiments [ Funamori and Yagi, 1993;Wang et al, 1994;Utsumi et al, 1995) agree reasonably well with each other and the results of Raman spectroscopy measurements [ Chopelas, 1996). Secondly, such choice is supported by a statistical analysis of existing P-V-T data [Jackson and Rigden, 1996) and theoretical thermodynamic considerations [Anderson et al, 1995;Stacey, 1996). Besides, it has been suggested [Wang et al, 1994) that the early measurements of expansivity of (Mg,Fe)Si0 3 may have been made outside the stability field and so may not be correct.…”

Section: Adiabatic Model For Chemically Homogeneous Lower Mantlesupporting

confidence: 71%

Geodynamically consistent seismic velocity predictions at the base of the mantle

Sidorin¹,

Gurnis²

1998

The Core‐Mantle Boundary Region

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A model of thermoelastic properties for a chemically homogeneous adiabatic lower mantle is calculated. Constraints provided by this model are used in convection models to study dynamics of a chemically distinct layer at the bottom of the mantle. We find that the layer must be at least 2% denser than the overlying mantle to survive for a geologically significant period of time. Realistic decrease with depth of the thermal expansivity increases layer stability but is unable to prevent it from entrainment. Seismic velocities are computed for an assumed composition by applying the thermal and compositional perturbations obtained in convection simulations to the adiabatic values. The predicted velocity jump at the top of the chemical layer is closer to the CMB in the cold regions than in the hot. The elevation of the discontinuity above CMB in the cold regions decreases with increasing thermal expansivity and increases with increasing density contrast, while in the hot regions we find that the opposite is true. If the density contrast is small, the layer may vanish under downwellings. However, whenever the layer is present in the downwelling regions, it also exists under the upwellings. For a 4% density contrast and realistic values of expansivity, we find that the layer must be more than 400 km thick on average to be consistent with the seismically observed depth of the discontinuity. A simple chemical layer cannot be used to interpret the D" discontinuity: the required change in composition is large and must be complex, since enrichment in any single mineral probably cannot provide the required impedance contrast. A simple chemical layer cannot explain the spatial intermittance of the discontinuity.

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Section: Adiabatic Model For Chemically Homogeneous Lower Mantlesupporting

confidence: 71%

Geodynamically consistent seismic velocity predictions at the base of the mantle

Sidorin¹,

Gurnis²

1998

The Core‐Mantle Boundary Region

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“…The measured ␥ of PPv at 135 GPa and 2,300-2,700 K is 0.79 Ϯ 0.12, which is smaller than that of Pv (0.94-1.07) at the same P-T conditions (18,24,25), suggesting a 21 Ϯ 15% decrease in ␥ across the PPv transition (Fig. 3b).…”

Section: Resultsmentioning

confidence: 82%

Crystal structure and thermoelastic properties of (Mg _0.91 Fe _0.09 )SiO ₃ postperovskite up to 135 GPa and 2,700 K

Shim

Catalli

Hustoft

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Intriguing seismic observations have been made for the bottom 400 km of Earth's mantle (the D؆ region) over the past few decades, yet the origin of these seismic structures has not been well understood. Recent theoretical calculations have predicted many unusual changes in physical properties across the postperovskite transition, perovskite (Pv) 3 postperovskite (PPv), that may provide explanations for the seismic observations. Here, we report measurements of the crystal structure of (Mg 0.91Fe0.09)SiO3-PPv under quasi-hydrostatic conditions up to the pressure (P)-temperature (T) conditions expected for the core-mantle boundary (CMB). The measured crystal structure is in excellent agreement with the first-principles calculations. We found that bulk sound speed (V ⌽) decreases by 2.4 ؎ 1.4% across the PPv transition. Combined with the predicted shear-wave velocity (V S) increase, our measurements indicate that lateral variations in mineralogy between Pv and PPv may result in the anticorrelation between the V ⌽ and VS anomalies at the D؆ region. Also, density increases by 1.6 ؎ 0.4% and Grü neisen parameter decreases by 21 ؎ 15% across the PPv transition, which will dynamically stabilize the PPv lenses observed in recent seismic studies.equation of state ͉ mantle ͉ phase transition ͉ bulk sound speed ͉ Grü neisen parameter T he DЉ region is believed to play an important role for the dynamics of the mantle and the core. The recent discovery of the postperovskite (PPv) transition (1-3) at the P-T conditions relevant to the DЉ region has provided new opportunities to understand the seismic observations and dynamic processes in the region. First-principles calculations (1, 4, 5) have predicted drastic changes in some geophysically important properties across the PPv transition (6, 7). The unusual changes have been attributed to the fundamental differences in crystal structure between perovskite (Pv), a 3D network structure with cornersharing SiO 6 octahedra, and PPv, a 2D layered structure with both corner and edge sharing SiO 6 octahedra (1,4,8,9). Therefore, measurements of the crystal structure provide a fundamental test for the predicted properties of PPv. However, synthesis of an appropriate single crystal for PPv in its stability field is extremely challenging for current techniques, making Rietveld refinement the only plausible method for studying the crystal structure. Currently only a single Rietveld refinement (10) exists for MgSiO 3 -PPv at 116 GPa and 300 K (Table 1).Some theoretical studies (1, 4) have predicted that bulk sound speed (V ⌽ ) decreases across the PPv transition whereas shearwave velocity (V S ) increases. Shieh et al. (Table 2), suggesting a large increase in V ⌽ across the PPv transition. However, no pressure medium was used in this study. The larger amount of Fe in Mao et al. (12) may cause the difference, yet a first-principles calculation showed that Fe has little effect on the bulk modulus of PPv (13).We have measured x-ray diffraction patterns of (Mg 0.91 Fe 0.09 )SiO 3 -PPv under q...

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“…In order to compute the core density profile, we use the EoS for pure iron derived by Belonoshko (2010), which is similar to the Mie-Grüneisen-Debye EoS (Jackson & Rigden 1996), except for a different thermal pressure term. This EoS for iron is preferred, as it allows us to closely reproduce high-precision volumetric experiments of iron under high-pressure and high-temperature conditions.…”

Section: Eos For Iron Corementioning

confidence: 99%

Can we constrain the interior structure of rocky exoplanets from mass and radius measurements?

Dorn

Khan

Heng

et al. 2015

A&A

262

355

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Aims. We present an inversion method based on Bayesian analysis to constrain the interior structure of terrestrial exoplanets, in the form of chemical composition of the mantle and core size. Specifically, we identify what parts of the interior structure of terrestrial exoplanets can be determined from observations of mass, radius, and stellar elemental abundances. Methods. We perform a full probabilistic inverse analysis to formally account for observational and model uncertainties and obtain confidence regions of interior structure models. This enables us to characterize how model variability depends on data and associated uncertainties. Results. We test our method on terrestrial solar system planets and find that our model predictions are consistent with independent estimates. Furthermore, we apply our method to synthetic exoplanets up to 10 Earth masses and up to 1.7 Earth radii, and to exoplanet Kepler-36b. Importantly, the inversion strategy proposed here provides a framework for understanding the level of precision required to characterize the interior of exoplanets. Conclusions. Our main conclusions are (1) observations of mass and radius are sufficient to constrain core size; (2) stellar elemental abundances (Fe, Si, Mg) are principal constraints to reduce degeneracy in interior structure models and to constrain mantle composition; (3) the inherent degeneracy in determining interior structure from mass and radius observations does not only depend on measurement accuracies, but also on the actual size and density of the exoplanet. We argue that precise observations of stellar elemental abundances are central in order to place constraints on planetary bulk composition and to reduce model degeneracy. We provide a general methodology of analyzing interior structures of exoplanets that may help to understand how interior models are distributed among star systems. The methodology we propose is sufficiently general to allow its future extension to more complex internal structures including hydrogen-and water-rich exoplanets.

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Analysis of P-V-T data: constraints on the thermoelastic properties of high-pressure minerals

Cited by 201 publications

References 43 publications

Geodynamically consistent seismic velocity predictions at the base of the mantle

Geodynamically consistent seismic velocity predictions at the base of the mantle

Crystal structure and thermoelastic properties of (Mg _0.91 Fe _0.09 )SiO ₃ postperovskite up to 135 GPa and 2,700 K

Can we constrain the interior structure of rocky exoplanets from mass and radius measurements?

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Analysis of P-V-T data: constraints on the thermoelastic properties of high-pressure minerals

Cited by 201 publications

References 43 publications

Geodynamically consistent seismic velocity predictions at the base of the mantle

Geodynamically consistent seismic velocity predictions at the base of the mantle

Crystal structure and thermoelastic properties of (Mg 0.91 Fe 0.09 )SiO 3 postperovskite up to 135 GPa and 2,700 K

Can we constrain the interior structure of rocky exoplanets from mass and radius measurements?

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Crystal structure and thermoelastic properties of (Mg _0.91 Fe _0.09 )SiO ₃ postperovskite up to 135 GPa and 2,700 K