The miscibility of calcium silicate perovskite and bridgmanite: A single perovskite solid solution in hot, iron-rich regions

Muir, Joshua M.R.; Thomson, A. P. J.; Zhang, Feiwu

doi:10.1016/j.epsl.2021.116973

Cited by 7 publications

(2 citation statements)

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“…The latter is readily accommodated in Brg as FeSiO 3 (heroseite), with the interesting property of Fe dissociation (3Fe 3+ = 2Fe 2+ + Fe 0 ) making it a prominent sink for ferric Fe in the lower mantle ( 61 , 62 ). For Ca, there is a limited solid solubility of davemaoite (CaSiO 3 ) in Brg ( 33 ), but increased miscibility to a single phase can be achieved in the presence of high iron (Fe 2+ Fe 3+ ) concentrations ( 63 , 64 ) and extreme P (>90 GPa) as determined experimentally by ( 33 ) and thermodynamically by ( 62 , 64 ). A similar effect is demonstrated for Ti in which Ilm-Cpx intergrowths are stable experimentally at ~55 GPa and Opx-Ilm at 35 GPa ( 33 ), and thermodynamically for the binary Pvr-Brg with the corresponding values of 80 and 45 GPa, respectively ( 34 ).…”

Section: Discussionmentioning

confidence: 99%

“…As outlined above, P > 80 GPa is required, but as important: Is this in any way related to kimberlite magmatism? Single-phase Ca-Fe 2+ Fe 3+ Ti Brg-Dvm (davemaoite CaSiO 3 ) is predicted at high P-T conditions and is modeled around CMB rising plumes ( 62 ) or in LLSVP seismic anomalies at the CMB ( 63 , 64 ). Although the origin and composition of the large (thousands of kilometer wide × tens of kilometer thick) thermochemical bodies remain uncertain ( 78 ), Dvm is considered a possible candidate ( 79 ), and in combination with Ca, Fe, and Ti, the inferred composition of the Brg progenitor is achieved.…”

Section: Discussionmentioning

confidence: 99%

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Perovskite-bearing crystal-controlled oxide-silicate mantle xenoliths: Resolution to controversial origins?

Haggerty

2023

Sci. Adv.

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Classic lamellar clinopyroxene-ilmenite intergrowths (type 1) are extended to include discovery of olivine-ilmenite-perovskite-wüstite (type 2) and olivine-spinel-perovskite (type 3) xenoliths in kimberlites from Liberia. Low titanium solubilities in olivine, garnet, and pyroxene cannot account for exsolution-like relations. Because the oxides coexist with high-pressure perovskite-structured silicate minerals in diamond, a permissive conclusion is that type 1 to type 3 xenoliths are of super-deep origin. Phase equilibria and thermodynamic studies show that type 1 xenoliths are stable at P > 80 GPa, with type 2 and type 3 at 35 to 50 GPa consistent with an origin in anomalous large low shear velocity province bodies anchored at the core-mantle boundary. Dissociated precursor perovskite-structured Ca-Fe-Ti bridgmanite is proposed and is indirectly supported by the copresence of type II diamonds with a sublithospheric lower mantle origin.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Perovskite-bearing crystal-controlled oxide-silicate mantle xenoliths: Resolution to controversial origins?

Haggerty

2023

Sci. Adv.

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The effect of Ti on Ca-pv and Mg-pv phase stability

Muir

Zhang

2022

Physics of the Earth and Planetary Interiors

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Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

Hernandez

Mohn

Guren

et al. 2022

Geophysical Research Letters

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The lower mantle is dominated by the two silicate perovskites, bridgmanite and Ca-perovskite, constituting about 77 and 5 mol%, respectively, of peridotites and about 34 and 24 mol%, respectively, of recycled oceanic crust of basaltic composition (e.g., Stixrude & Lithgow-Bertelloni, 2012). The melting curves of the end member components MgSiO 3 , CaSiO 3 and MgO in the system CaO-MgO-SiO 2 system (CMS) may inform about the crystallization history of the magma ocean and the nature of the ultra-low velocity zones (e.g., Trønnes et al., 2021). Although the melting curves for MgO-periclase and MgSiO 3 -bridgmanite are reasonably well established through the lower mantle pressure range, the Ca-perovskite melting curve remains poorly constrained, in particular at the lowermost mantle pressures (Figure 1). The melting of Ca-perovskite at 14-15 and 16-60 GPa, respectively, has been investigated by multi-anvil (Gasparik et al., 1994) and laser-heated diamond anvil cell (LH-DAC) experiments (Shen & Lazor, 1995;Zerr et al., 1997). Multi-anvil experiments with resistive heating and W-Re thermocouples might provide more accurate and reproducible melting temperatures than the LH-DAC experiments, which are in poor agreement with each other with a difference in melting temperature of about 880 K at 45 GPa. Nomura et al. (2017) performed multi-anvil experiments along the MgSiO 3 -CaSiO 3 join at 24 GPa and developed a thermodynamic model, anchored to the Zerr et al. (1997) melting curve. Although the experimentally based melting curves converge in the 2500-2800 K range at 14-16 GPa, the large variation in their dT/dp slopes yields increasing discrepancies with increasing pressure. The melting curve of Gasparik et al. (1994) is steeper (212 K/ GPa in the 13-15 GPa range) than those determined by the LH-DAC experiments of Shen and Lazor (1995) and Zerr et al. (1997). The latter slopes, measured in the 17-20 GPa range are 32 and 61 K/GPa, respectively. The Ca-perovskite melting curve has also been investigated by classical molecular dynamics (MD) based on empirical atomic potentials (Liu et al., 2010) and density functional theory (DFT) MD calculations (BraithwaiteAbstract Melting curves of Ca-perovskite (pure CaSiO 3 ) were determined by ab initio density functional theory, using two solid-liquid coexistence methods and two free energy approaches, in the form of thermodynamic integration and two-phase thermodynamics. The melting curves based on the solid-liquid coexistence methods and thermodynamic integration rise steeply from 2000 K at 14 GPa to 7000 K at 136 GPa. The melting temperature at 136 GPa is 1400 K higher than previous ab initio predictions. The high thermal stability of Ca-perovskite is linked to its high-symmetry isometric structure and consistent with experiments, demonstrating that Ca-perovskite is the most refractory phase in basaltic compositions in the lower mantle pressure range. The steep dT/dp slope of the melting curve also shows that the Ca-perovskite liquidus field expands relative to those of bridgmanite...

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The miscibility of calcium silicate perovskite and bridgmanite: A single perovskite solid solution in hot, iron-rich regions

Cited by 7 publications

References 58 publications

Perovskite-bearing crystal-controlled oxide-silicate mantle xenoliths: Resolution to controversial origins?

Perovskite-bearing crystal-controlled oxide-silicate mantle xenoliths: Resolution to controversial origins?

The effect of Ti on Ca-pv and Mg-pv phase stability

Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

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