Calorimetric measurements of perovskites in the system CaTiO3–CaSiO3 and experimental and calculated phase equilibria for high-pressure dissociation of diopside

Koito, S; Akaogi, Masaki; Kubota, Osamu; Suzuki, Toshihiro

doi:10.1016/s0031-9201(99)00171-5

Cited by 14 publications

(4 citation statements)

References 24 publications

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“…In most regions only a single 520 km discontinuity may be detected, but the phase transition responsible for the discontinuity may vary spatially, as the bulk composition of the mantle varies from fertile to depleted. Unlike earlier experimental results, which found a negative or near-zero clapeyron slope for the Pyx→Ca-Pv+Gt transition (Canil 1994;Koito et al 2000;Akaogi et al 2004), current laboratory and theoretical constraints find that the clapeyron slope is positive for both phase transitions Saikia et al 2008), which will merge at around 540-560 km depth and 1600 K. In regions with only a single discontinuity, a strong shallow discontinuity at 500-520 km indicates a depleted region in which only the wadsleyite-ringwoodite transition is detected, whereas a single strong discontinuity at 540-560 km indicates a more fertile region in which only the Ca-perovskite transition is detected (Saikia et al 2008). Therefore, only regions with a sharp juxtaposition of fertile and depleted mantle, such as across a slab, are expected to exhibit a double discontinuity near 520 km depth.…”

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confidence: 95%

Mantle transition zone structure along a profile in the SW Pacific: thermal and compositional variations

Thomas¹,

Billen

2009

Geophysical Journal International

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S U M M A R YEvents from the South Pacific, recorded in the Tien Shan region are studied with a migration method, to measure discontinuity depth along a profile between the Mariana and Molucca Sea subduction zones. Deflections of the upper-mantle discontinuities within and between the subduction zones are investigated using PP precursors filtered to periods of 3 to 10 s. We find P-wave reflections near the 410, 520 and 660 km discontinuities. The 410 km discontinuity is elevated in the subduction region and near the predicted depth (410 km) in the average velocity region. In some cases, we find negative polarities of the reflection from the 410 km discontinuity, which may indicate water-induced melting above the olivine to wadsleyite transition. The 520 km discontinuity is shallow between the two subduction zones, and deepens towards the Mariana backarc region: this discontinuity topography may be due to detection of both the wadsleyite to ringwoodite transition in a depleted downwelling (elevated region) and the formation of calcium-perovskite in a more fertile upwelling (depressed region). The 660 km discontinuity is split in the Halmahera slab with one reflection each near 600 and 700 km depth, consistent with a cold sinking slab and detection of phase transitions for both garnet and olivine to perovskite, respectively. In the region between the subduction areas, we find a downward deflection of the 660 km discontinuity with short length-scale (100-300 km) undulations that may reflect compositional variation.

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confidence: 95%

Mantle transition zone structure along a profile in the SW Pacific: thermal and compositional variations

Thomas¹,

Billen

2009

Geophysical Journal International

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“…The ΔH T (CaTiO 3 ) and ΔS T (CaTiO 3 ) values determined in [48] correlate with the results from studies performed via solution calorimetry [37,41,42,44] and EMF [35,36] at lower temperatures and by Raman spectroscopy [46] and DTA [47] at similar temperatures (Table 1).…”

Section: Figuresupporting

confidence: 79%

“…Perovskite and its oxides are poorly soluble in oxide solvent Pb 2 B 2 O 5 ;Na 6 Mo 4 O 15 liquid alloy is quite volatile and cannot be used at temperatures above 1000 K; (Li,Na)BO 2 solution is hygroscopic, which creates difficulties in synthesizing [49]. The ΔH 1078 (CaTiO 3 ) value determined by Koito et al [44] by similar method (solution calorimetry in Pb 2 B 2 O 5 salt) is less accurate but close to the results obtained by Navrotsky et al [19,34,[37][38][39][40][41][42][43].…”

Section: The Thermodynamic Properties Of Perovskite Solid Phasementioning

confidence: 99%

Thermodynamics of Perovskite: Solid, Liquid, and Gas Phases

Shornikov¹

2021

Perovskite and Piezoelectric Materials

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“…[70] Phase transitions such as the transformation from wadsleyite (b phase) to-ringwoodite (g phase) and that from garnet to Ca-perovskite have been proposed to explain a midtransition zone discontinuity [e.g., Ita and Stixrude, 1992;Katsura and Ito, 1989;Koito et al, 2000]. The increase in V P and V S predicted from the transition of b to Figure B1.…”

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A petrologic anomaly accompanying outboard earthquakes beneath Fiji‐Tonga: Corresponding evidence from broadband P and S waveforms

Brudzinski

Chen

2003

J. Geophys. Res.

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[1] Using high-resolution, triplicate body waveforms, we investigate strong lateral variations in P and SH wave speeds (V P and V S ) beneath the Tonga subduction zone where cold lithosphere is subducting rapidly at 200 mm yr À1 . Under these conditions, the lack of prominent anomalies of high V P and V S in the lower mantle implies that a large amount of recently subducted material remains above the lower mantle. This inference is also evident from a subhorizontal swath of outboard earthquakes in the transition zone that is up to 1000 km away from the Wadati-Benioff zone. Beneath the back arc, we find a sharp, eastwest trending demarcation north of which outboard earthquakes occur and V P and V S abruptly drop by $3%. Thus the effect of cold temperature to raise V P and V S , as indicated by the presence of outboard earthquakes, must be counteracted by petrologic variations. We interpret that outboard earthquakes occur where impounding of subducted metastable olivine or volatiles reduces seismic wave speeds and triggers deep earthquakes. Considering the density of these candidates and the strong effect of partial melt on V S , volatiles in the form of hydrous phases or melt induced by dehydration are not consistent with observed reductions in V P and V S . Meanwhile, metastable olivine remains a viable candidate. As a cold slab passes below the 410-km discontinuity, olivine becomes metastable and makes the tip of the slab buoyant. Such a mechanism could explain why the leading end of a fast subducting slab may be successively sequestered in the transition zone.INDEX TERMS: 1025 Geochemistry: Composition of the mantle; 7203 Seismology: Body wave propagation; 8120 Tectonophysics: Dynamics of lithosphere and mantle-general; 7218 Seismology: Lithosphere and upper mantle; KEYWORDS: petrologic anomaly, mantle structure, seismic wave speeds, waveform modeling, outboard earthquakes, Fiji-Tonga Citation: Brudzinski, M. R., and W.-P. Chen, A petrologic anomaly accompanying outboard earthquakes beneath Fiji-Tonga: Corresponding evidence from broadband P and S waveforms,

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Calorimetric measurements of perovskites in the system CaTiO3–CaSiO3 and experimental and calculated phase equilibria for high-pressure dissociation of diopside

Cited by 14 publications

References 24 publications

Mantle transition zone structure along a profile in the SW Pacific: thermal and compositional variations

Mantle transition zone structure along a profile in the SW Pacific: thermal and compositional variations

Thermodynamics of Perovskite: Solid, Liquid, and Gas Phases

A petrologic anomaly accompanying outboard earthquakes beneath Fiji‐Tonga: Corresponding evidence from broadband P and S waveforms

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