Complete agreement of the post-spinel transition with the 660-km seismic discontinuity

Ishii, Takayuki; Rong, Hong; Fei, Hongzhan; Koemets, Iuliia; Liu, Zhaodong; Maeda, Fumihiko; Yuan, Liang; Wang, Lin; Druzhbin, Dmitry; Yamamoto, Takafumi; Bhat, Shrikant; Farla, Robert; Kawazoe, Takaaki; Tsujino, Noriyoshi; Kulik, Eleonora; Higo, Yuji; Tange, Yoshinori; Katsura, Tomoo

doi:10.1038/s41598-018-24832-y

Cited by 28 publications

(39 citation statements)

References 33 publications

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“…Although a problem of pressure scale for high‐pressure experiment is still in debate (e.g., Fei, Li, et al, ), our results also suggest that the pSp transition in harzburgite with lower Al 2 O 3 content than pyrolite may reconcile this discrepancy. The recent study with respect to the pSp transition pressure in Mg 2 SiO 4 , which completely agreed with the 660‐km discontinuity depth (Ishii, Huang, et al, ), also supports this hypothesis of harzburgite‐rich transition zone of less aluminous composition than pyrolite.…”

Section: Resultssupporting

confidence: 78%

Phase Relations of Harzburgite and MORB up to the Uppermost Lower Mantle Conditions: Precise Comparison With Pyrolite by Multisample Cell High‐Pressure Experiments With Implication to Dynamics of Subducted Slabs

2019

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We determined phase relations of harzburgite and basalt (mid-ocean ridge basalt, MORB) at 12-28 GPa and 1600-2200°C with a large number of experiments using a multianvil high-pressure apparatus. These phase relations were precisely compared with those of pyrolite simultaneously determined by multisample cell technique. The post-spinel (pSp) transition of harzburgite occurs at 23 GPa and 1600°C with the boundary slope of −3 ± 1 MPa/°C. The post-garnet (pGt) transition boundary of MORB, defined as the beginning of the majorite garnet-bridgmanite transition, is located at 25 GPa and 1600°C, with a slope of 1.5 ± 1 MPa/°C. The pSp transition of harzburgite occurs at higher pressure by 0.5 GPa at 1600°C and has the more negative slope than that of pyrolite (−1 ± 1 MPa/°C). The pGt transition of MORB occurs at higher pressure by 3 GPa than the pSp transition of harzburgite. At 1600°C, the density of pyrolite is smaller than those of harzburgite and MORB before the pSp transition of pyrolite (pyrolite-harzburgite/MORB = −0.17 g/cm 3 ). After the pSp transition of pyrolite, harzburgite has lower densities than that of pyrolite at 22-27 GPa (pyrolite-harzburgite = 0.31 and 0.08 g/cm 3 before/after the pSp transition in harzburgite, respectively). On the other hand, the density of MORB becomes the highest among the three rocks above 25 GPa after the pGt transition of MORB (pyrolite-MORB = −0.18 g/cm 3 ). The present density contrasts suggest that harzburgite and MORB may stagnate and accumulate in the transition zone by slab subduction, resulting in that the pyrolitic part of slabs is subducted into the lower mantle.

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Section: Resultssupporting

confidence: 78%

Phase Relations of Harzburgite and MORB up to the Uppermost Lower Mantle Conditions: Precise Comparison With Pyrolite by Multisample Cell High‐Pressure Experiments With Implication to Dynamics of Subducted Slabs

2019

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“…If we were to use the same Ak-Bm transition pressure point (at 1873 K and 22.3 GPa) that is used in Ishii et al [37] as an internal calibration point, our multi-anvil BAM triple point would lie at almost the same P and T as that in Ishii et al [37]. Although it would depend on experimental setup, including the sample geometry and anvil materials, possible pressure change during heating is an important factor to consider for improving pressure estimation in LVP experiments [46]. In order to further gain insight into the differences between the DAC and LVP pressures and to possibly close the gap, it would be worthwhile to make detailed measurements on the BAM triple point in situ using the same sample and Pt pressure standard that was used in the LHDAC.…”

Section: Discussionmentioning

confidence: 88%

The Bridgmanite–Akimotoite–Majorite Triple Point Determined in Large Volume Press and Laser-Heated Diamond Anvil Cell

et al. 2020

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The bridgmanite–akimotoite–majorite (Bm–Ak–Mj or BAM) triple point in MgSiO3 has been measured in large-volume press (LVP; COMPRES 8/3 assembly) and laser-heated diamond anvil cell (LHDAC). For the LVP data, we calculated pressures from the calibration provided for the assembly. For the LHDAC data, we conducted in situ determination of pressure at high temperature using the Pt scale at synchrotron. The measured temperatures of the triple point are in good agreement between LVP and LHDAC at 1990–2000 K. However, the pressure for the triple point determined from the LVP is 3.9 ± 0.6 GPa lower than that from the LHDAC dataset. The BAM triple point determined through these experiments will provide an important reference point in the pressure–temperature space for future high-pressure experiments and will allow mineral physicists to compare the pressure–temperature conditions measured in these two different experimental methods.

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“… 34 ) can dissociate and produce oxygen in this pressure range, offering an abundant source of O 2 for these proposed reactions inside Earth’s mantle. The resulting compound CaO 3 , which was not previously considered, provides an alternative mechanism to explain seismic anomalies near 660 km depth in Earth’s mantle where pressure is ~20 GPa 35 , 36 .…”

Section: Resultsmentioning

confidence: 96%

Pressure-stabilized divalent ozonide CaO3 and its impact on Earth’s oxygen cycles

Wang

Yang

et al. 2020

Nat Commun

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High pressure can drastically alter chemical bonding and produce exotic compounds that defy conventional wisdom. Especially significant are compounds pertaining to oxygen cycles inside Earth, which hold key to understanding major geological events that impact the environment essential to life on Earth. Here we report the discovery of pressure-stabilized divalent ozonide CaO3 crystal that exhibits intriguing bonding and oxidation states with profound geological implications. Our computational study identifies a crystalline phase of CaO3 by reaction of CaO and O2 at high pressure and high temperature conditions; ensuing experiments synthesize this rare compound under compression in a diamond anvil cell with laser heating. High-pressure x-ray diffraction data show that CaO3 crystal forms at 35 GPa and persists down to 20 GPa on decompression. Analysis of charge states reveals a formal oxidation state of −2 for ozone anions in CaO3. These findings unravel the ozonide chemistry at high pressure and offer insights for elucidating prominent seismic anomalies and oxygen cycles in Earth’s interior. We further predict multiple reactions producing CaO3 by geologically abundant mineral precursors at various depths in Earth’s mantle.

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Complete agreement of the post-spinel transition with the 660-km seismic discontinuity

Cited by 28 publications

References 33 publications

Phase Relations of Harzburgite and MORB up to the Uppermost Lower Mantle Conditions: Precise Comparison With Pyrolite by Multisample Cell High‐Pressure Experiments With Implication to Dynamics of Subducted Slabs

Phase Relations of Harzburgite and MORB up to the Uppermost Lower Mantle Conditions: Precise Comparison With Pyrolite by Multisample Cell High‐Pressure Experiments With Implication to Dynamics of Subducted Slabs

The Bridgmanite–Akimotoite–Majorite Triple Point Determined in Large Volume Press and Laser-Heated Diamond Anvil Cell

Pressure-stabilized divalent ozonide CaO3 and its impact on Earth’s oxygen cycles

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