scholarly journals Erratum: Thickness and Clapeyron slope of the post-perovskite boundary

Nature ◽  
2010 ◽  
Vol 463 (7279) ◽  
pp. 384-384 ◽  
Author(s):  
Krystle Catalli ◽  
Sang-Heon Shim ◽  
Vitali Prakapenka
Keyword(s):  
Clapeyron Slope

scholarly journals Influence of the Ringwoodite-Perovskite transition on mantle convection in spherical geometry as a function of Clapeyron slope and Rayleigh number

2011 ◽  
Vol 3 (2) ◽  
pp. 713-741 ◽  
Author(s):  
M. Wolstencroft ◽  
J. H. Davies
Keyword(s):  
Phase Transition ◽  
Rayleigh Number ◽  
Phase Change ◽  
Mantle Convection ◽  
Spherical Geometry ◽  
Earth History ◽  
Buoyancy Parameter ◽  
Seismic Discontinuity ◽  
Clapeyron Slope

Abstract. We investigate the influence on mantle convection of the negative Clapeyron slope ringwoodite to perovskite and ferro-periclase mantle phase transition, which is correlated with the seismic discontinuity at 660 km depth. In particular, we focus on understanding the influence of the magnitude of the Clapeyron slope (as measured by the Phase Buoyancy parameter, P) and the vigour of convection (as measured by the Rayleigh number, Ra) on mantle convection. We have undertaken 76 simulations of isoviscous mantle convection in spherical geometry varying Ra and P. Three domains of behaviour were found: layered convection for high Ra and more negative P, whole mantle convection for low Ra and less negative P and transitional behaviour in an intervening domain. The boundary between the layered and transitional domain was fit by a curve P = αRaβ where α = −1.05, and β = −0.1, and the fit for the boundary between the transitional and whole mantle convection domain was α = −4.8, and β = −0.25. These two curves converge at Ra≈2.5×104 and P≈−0.38. Extrapolating to high Ra, which is likely earlier in Earth history, this work suggests a large transitional domain. It is therefore likely that convection in the Archean would have been influenced by this phase change, with Earth being at least in the transitional domain, if not the layered domain.

scholarly journals Subduction-transition zone interaction: A review

Geosphere ◽  
2017 ◽  
Vol 13 (3) ◽  
pp. 644-664 ◽  
Author(s):  
Saskia Goes ◽  
Roberto Agrusta ◽  
Jeroen van Hunen ◽  
Fanny Garel
Keyword(s):  
Transition Zone ◽  
Lower Mantle ◽  
Dynamic Models ◽  
Flat Slabs ◽  
Mantle Silicates ◽  
Effective Yield ◽  
Current Transition ◽  
Clapeyron Slope ◽  
Plate Subduction

Abstract As subducting plates reach the base of the upper mantle, some appear to flatten and stagnate, while others seemingly go through unimpeded. This variable resistance to slab sinking has been proposed to affect long-term thermal and chemical mantle circulation. A review of observational constraints and dynamic models highlights that neither the increase in viscosity between upper and lower mantle (likely by a factor 20–50) nor the coincident endothermic phase transition in the main mantle silicates (with a likely Clapeyron slope of –1 to –2 MPa/K) suffice to stagnate slabs. However, together the two provide enough resistance to temporarily stagnate subducting plates, if they subduct accompanied by significant trench retreat. Older, stronger plates are more capable of inducing trench retreat, explaining why backarc spreading and flat slabs tend to be associated with old-plate subduction. Slab viscosities that are ∼2 orders of magnitude higher than background mantle (effective yield stresses of 100–300 MPa) lead to similar styles of deformation as those revealed by seismic tomography and slab earthquakes. None of the current transition-zone slabs seem to have stagnated there more than 60 m.y. Since modeled slab destabilization takes more than 100 m.y., lower-mantle entry is apparently usually triggered (e.g., by changes in plate buoyancy). Many of the complex morphologies of lower-mantle slabs can be the result of sinking and subsequent deformation of originally stagnated slabs, which can retain flat morphologies in the top of the lower mantle, fold as they sink deeper, and eventually form bulky shapes in the deep mantle.

Thickness and Clapeyron slope of the post-perovskite boundary

Nature ◽  
2009 ◽  
Vol 462 (7274) ◽  
pp. 782-785 ◽  
Author(s):  
Krystle Catalli ◽  
Sang-Heon Shim ◽  
Vitali Prakapenka
Keyword(s):  
Clapeyron Slope

Phase relationships in the Ti–Si–C system at high pressures

1992 ◽  
Vol 7 (6) ◽  
pp. 1473-1479 ◽  
Author(s):  
S. Sambasivan ◽  
W.T. Petuskey
Keyword(s):  
Silicon Carbide ◽  
Electron Probe ◽  
High Pressures ◽  
Kinetic Characteristics ◽  
Experimental Conditions ◽  
Backscattered Electron Imaging ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
Clapeyron Slope ◽  
Phase Relationships

The compatibility of phases in the Ti–Si–C system was studied for pressures from 10 to 20 kbars (1 to 2 GPa) and temperatures from 1200 °C to 1500 °C via an interfacial reaction between titanium and silicon carbide. The interface was characterized by backscattered electron imaging and electron probe microanalysis. Ti3Si was stabilized at high pressures exhibiting an appreciable solubility for carbon (up to 9 at. %). At higher temperatures and lower pressures, it decomposed to Ti5Si3, Ti(Si, C), and TiCx according to the relation Ti3Si (Cz) = (0.70588)TiCx + (0.32437)Ti5Si3 + (0.67227)Ti (Si, C), where the mathematical coefficients were calculated using z = 0.4 and x = 0.5. No detectable quantities of carbon dissolved in Ti5Si3 under these conditions. A clapeyron slope of 0.08 (±0.01) kbar/K was measured for this reaction. The microstructure of the reaction zone and other general thermodynamic and kinetic characteristics are discussed for different experimental conditions.

A reappraisal of peridotite solidus phase equilibria from 6 to 14 GPa in the system CaO-MgO-Al2O3-SiO2

2021 ◽  
Author(s):  
Shantanu Keshav ◽  
Gudmundur H Gudfinnsson
Keyword(s):  
Crystalline Phase ◽  
Fusion Reaction ◽  
Lanthanum Chromite ◽  
Phase Assemblage ◽  
Composition Space ◽  
Single Temperature ◽  
Partial Fusion ◽  
Invariant Points ◽  
Future Work ◽  
Clapeyron Slope

Abstract Experimentally determined isobaric invariant melting phase relations from 6 to 14 GPa in the system CaO-MgO-Al2O3-SiO2 (CMAS), involving the crystalline phases, forsterite + orthopyroxene + clinopyroxene + garnet, and liquid, are reported. Experiments were conducted using a multianvil device with stepped lanthanum chromite heaters in the pressure cells. At a fixed pressure, the five-phase assemblage identified above can exist only at a single temperature. As such, these isobaric invariant points correspond to the solidus of model garnet peridotite in this part of the composition space in the studied system, as is the case at lower pressures in some previous studies. The solidus of model peridotite is univariant in pressure-temperature space, has a positive Clapeyron slope, and the isobaric invariant solidus temperatures, at, 6, 8, 10, 12, and 14 GPa, are, 1965oC, 2090oC, 2200oC, 2280oC, and 2320oC, respectively. Over the investigated pressure range, orthopyroxene is in reaction relation with the liquid, with the fusion reaction taking the form, forsterite + clinopyroxene + garnet = orthopyroxene + liquid. The compositions of liquids in the experiments reported here do not seem to depend on orthopyroxene being present in the experiments. Compositionally, liquids here are quite magnesian and siliceous, and have lower alumina and lime concentrations than at lower pressures with the identical crystalline phase assemblage in the system CMAS. In contrast to some previous studies, in this work, there is evidence neither of maximum and minimum normative forsterite concentration of the isobaric invariant liquid at around 8 GPa and 12 GPa, respectively, nor of a substantial curvature in the track of liquid compositions, when such liquids coexist with the mentioned four-phase crystalline phase assemblage. Instead, here, with increasing pressure from 6 to 14 GPa, liquids at the isobaric invariant points (defining the univariant solidus) become progressively (quasi-linearly) enstatite-normative. This experimental observation on liquid compositions from the present study might be important for future work directed at attempting to investigate chemistry of liquids derived from partial fusion of anhydrous peridotite at pressures, and corresponding depths in Earth, greater than investigated here.

scholarly journals Influence of the Ringwoodite-Perovskite transition on mantle convection in spherical geometry as a function of Clapeyron slope and Rayleigh number

Solid Earth ◽  
2011 ◽  
Vol 2 (2) ◽  
pp. 315-326 ◽  
Author(s):  
M. Wolstencroft ◽  
J. H. Davies
Keyword(s):  
Phase Transition ◽  
Rayleigh Number ◽  
Phase Change ◽  
Mantle Convection ◽  
Spherical Geometry ◽  
Earth History ◽  
Buoyancy Parameter ◽  
Seismic Discontinuity ◽  
Clapeyron Slope

Abstract. We investigate the influence on mantle convection of the negative Clapeyron slope ringwoodite to perovskite and ferro-periclase mantle phase transition, which is correlated with the seismic discontinuity at 660 km depth. In particular, we focus on understanding the influence of the magnitude of the Clapeyron slope (as measured by the Phase Buoyancy parameter, P) and the vigour of convection (as measured by the Rayleigh number, Ra) on mantle convection. We have undertaken 76 simulations of isoviscous mantle convection in spherical geometry, varying Ra and P. Three domains of behaviour were found: layered convection for high Ra and more negative P, whole mantle convection for low Ra and less negative P, and transitional behaviour in an intervening domain. The boundary between the layered and transitional domain was fit by a curve P = α Raβ where α = −1.05, and β = −0.1, and the fit for the boundary between the transitional and whole mantle convection domain was α = −4.8, and β = −0.25. These two curves converge at Ra ≈ 2.5 × 104 (well below Earth mantle vigour) and P ≈ −0.38. Extrapolating to high Ra, which is likely earlier in Earth history, this work suggests a large transitional domain. It is therefore likely that convection in the Archean would have been influenced by this phase change, with Earth being at least in the transitional domain, if not the layered domain.

scholarly journals Pressure–Temperature Phase Diagram of Ta-H System up to 9 GPa and 600 °C

2021 ◽  
Vol 11 (15) ◽  
pp. 6719
Author(s):  
Hiroyuki Saitoh ◽  
Shigeyuki Takagi ◽  
Toyoto Sato ◽  
Shin-ichi Orimo
Keyword(s):  
Phase Diagram ◽  
High Pressure ◽  
Entropy Change ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Hydrogenation Reactions ◽  
Pressure Synthesis ◽  
Temperature Phase Diagram ◽  
Clapeyron Slope

High-pressure hydrogenation behaviors of pure metals have not been investigated extensively, although intense research of hydrogenation reactions under high pressure has been conducted to find novel functional hydrides. The former provides us with valuable information for the high-pressure synthesis of novel functional hydrides. A pressure–temperature phase diagram of the Ta–H system has been determined using the in situ synchrotron radiation X-ray diffraction technique below 9 GPa and 600 °C in this study. At room temperature, the phase boundary obtained between distorted bcc TaH~1 and hcp TaH~2 was consistent with the previously reported transition pressure. The experimentally obtained Clapeyron slope can be explained via the entropy change caused by hydrogen evolution from TaH~2.

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