Thermal expansivity in the lower mantle

Chopelas, A.; Boehler, R.

doi:10.1029/92gl02144

Cited by 272 publications

(132 citation statements)

References 16 publications

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“…Here, its radial profile is constructed in a consistent way with the variation of other properties, with the assumption of a constant Gruëneisen parameter throughout the mantle. A decrease by a factor of four of the thermal expansivity is calculated from the surface to the CMB, a value in agreement with experimental measurements for olivine (17). A description of these various profiles can be found in ref.…”

Section: Model Descriptionsupporting

confidence: 63%

Topology of the postperovskite phase transition and mantle dynamics

Monnereau

Yuen

2007

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

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The postperovskite (ppv) phase transition occurs in the deep mantle close to the core-mantle boundary (CMB). For this reason, we must include in the dynamical considerations both the Clapeyron slope and the temperature intercept, T int, which is the temperature of the phase transition at the CMB pressure. For a CMB temperature greater than T int, there is a double crossing of the phase boundary by the geotherms associated with the descending flow. We have found a great sensitivity of the shape of the ppv surface due to the CMB from variations of various parameters such as the amount of internal heating, the Clapeyron slope, and the temperature intercept. Three-dimensional spherical models of mantle convection that can satisfy the seismological constraints depend on the Clapeyron slope. At moderate value, 8 MPa/K, the best fit is found with a core heat flow amounting for 40% of the total heat budget (Ϸ15 TW), whereas for 10 MPa/K the agreement is for a lower core heat flow (20%, Ϸ7.5 TW). In all cases, these solutions correspond to a temperature intercept 200 K lower than the CMB temperature. These models have holes of perovskite adjacent to ppv in regions of hot upwellings. has provoked an immense interest in the earth sciences because of the close proximity of the phase change to the core-mantle boundary (CMB), unveiling a large part of the enigmatic DЉ layer. The DЉ is a seismic structure whose complexity has remained puzzling for a long time. Interpreted in terms of phase boundary undulations, it would offer the chance to provide an absolute constraint on the temperature within the thermal boundary layer of the mantle. This would have great impact on our understanding of the dynamical state and thermal history of the earth. Concerted efforts recently have been devoted to sharpening the seismic imaging of DЉ (4-6), but results remain interpreted in the framework of 1D thermal models. On the other hand, previous work (7-11) investigating mantle convection with a ppv transition has focused more on dynamical effects and the magnitude of the Clapeyron slope than on the topology of the ppv surface itself. Thus, these investigators have neglected to consider the temperature intercept of the phase transition, which matters a lot in the case of a ppv transition because it is situated so near to the lower boundary of mantle convection.This delicate location makes it necessary for one to take into account the relative magnitude between the temperature at the CMB, T CMB , and the temperature of the ppv transition at the CMB pressure of 135 GPa. This latter temperature is called the temperature intercept, T int (see Fig. 1). In Fig. 1, we show the relationship between various geotherms (cold, warm, and hot) and the phase boundary, commonly known as the Clapeyron curve (red color), which is given by the equation cast in red. We note that in the case when T CMB is greater than T int , the geotherm may cross the phase boundary at two places (known as ''double-crossing'') (4). This feature is necessarily related to the existe...

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Section: Model Descriptionsupporting

confidence: 63%

Topology of the postperovskite phase transition and mantle dynamics

Monnereau

Yuen

2007

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

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“…The dependence is the same as the one in our previous studies Miyagoshi et al 2014;; α decreases by a factor of 10 from the surface to the bottom boundary. This profile is estimated for MgO in a former ab initio calculation (Tsuchiya and Tsuchiya 2011) and is consistent with the previous laboratory measurements under high pressure (Chopelas and Boehler 1992).…”

Section: Model Descriptionsupporting

confidence: 70%

Extremely long transition phase of thermal convection in the mantle of massive super-Earths

Miyagoshi

Kameyama

Ogawa

2017

Earth Planets Space

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Adiabatic compression is a key factor that exerts control over thermal convection in the compressible solid mantle of super-Earths. To discuss the effects of adiabatic compression, we present a numerical model of transient convection in the cooling mantle of a super-Earth that is ten times larger in size than the Earth. The calculations started with the shallow mantle that was hotter than expected by the extrapolation from the deep mantle conditions. This type of initial thermal state of the mantle is expected to naturally occur in real super-Earths due to heating by giant impacts at the time of their formation. With our initial setup conditions, the convection temporarily occurs as a layered convection for the first several to ten billion years of the calculation and then changes its style into a whole layer convection. The long duration of the transient stage suggests that mantle convection currently occurs as a temporal layered convection in many of the super-Earths. A temporal layered convection, if it occurs, can exert control over the tectonic activities of super-Earths. Future studies should clarify how internal heating and complicated rheological properties of mantle materials including their pressure dependence affect the duration of the temporal layered convection.

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“…The effects of phase transitions are incorporated by an effective thermal expansivity Þ [7,11]. It consists of a depthdependent background portion, which decreases by a factor of seven across the mantle [12] and an additional 'phase-transition' part, which peaks in the phase-transition regions and is negative for the endothermic spinel ! perovskite transformation.…”

Section: Model Descriptionmentioning

confidence: 99%

The influences of surface temperature on upwellings in planetary convection with phase transitions

Steinbach

Yuen

1998

Earth and Planetary Science Letters

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The importance of surface temperature for mantle convection appears with the presence of adiabatic heating and cooling and the release and consumption of latent heat in the presence of phase transitions. For some planetary bodies these effects cannot be neglected. The dimensionless surface temperature T 0 , which is the ratio between the temperature at the top of the convective region and the temperature drop across the mantle, is close to one for Mars and Venus. For the Earth, T 0 lies between 0.2 and 0.5. The dynamical influence of T 0 is especially poignant for internally heated convection with temperature-dependent viscosity. There is a tight coupling between the magnitude of the temperature field and the viscosity itself. We have studied temperature-dependent viscosity convection for both low-T 0 (0.2) and high-T 0 (1.2) situations and with internal heating in mantle convection with two upper-mantle phase transitions. Our results show that within this range of T 0 there exist two regimes for the evolution of upwellings in the mantle. In transient situations plume-plume collisions lead to the formation of megaplumes for high-T 0 regimes but are less likely to do so for low T 0 . In the long-term regime, plumes with low T 0 are prone to develop from the transition zone with a supply of hot material coming from the shallow lower mantle. In systems with high T 0 , however, long-lived plumes tend to have deeper mantle origins. In quasi-layered situations high T 0 may act as a positive feed-back mechanism in inducing powerful hot upwellings into the upper mantle.

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Thermal expansivity in the lower mantle

Cited by 272 publications

References 16 publications

Topology of the postperovskite phase transition and mantle dynamics

Topology of the postperovskite phase transition and mantle dynamics

Extremely long transition phase of thermal convection in the mantle of massive super-Earths

The influences of surface temperature on upwellings in planetary convection with phase transitions

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