Hydrous peridotitic fragments of Earth’s mantle 660 km discontinuity sampled by a diamond

Gu, Tingting; Pamato, Martha G.; Novella, Davide; Alvaro, Matteo; Fournelle, John; Brenker, Frank E.; Wang, Wuyi; Nestola, Fabrizio

doi:10.1038/s41561-022-01024-y

Cited by 17 publications

(4 citation statements)

References 70 publications

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“…Ferropericlase, with which MgSiO 3 associates in sample #3.1.3, was high-Ni-low-Fe variety with mg# = 0.767-0.841. These Mg indices correspond precisely to the mg# values in coexisting ferropericlase and bridgmanite crystallized in experiments modelling the lower-mantle conditions beyond the 660 km discontinuity [12,13]. This gives the reason to consider the observed MgSiO 3 inclusions as former bridgmanite.…”

Section: Other Mineral Inclusionssupporting

confidence: 69%

“…(For simplicity, we use below the term "ferropericlase" (fPer) for all varieties of the (Fe,Mg)O compositions.) This contradicts experimental data in pyrolitic systems in the pressure range 25-60 GPa, according to which the magnesium index of ferropericlase, in lower-mantle material with mg# = 0.80-0.95, should be 0.73-0.88 [11,12]. In experiments at pressures up to 100 GPa, for the lower mantle with the most likely magnesium index of mg# = 0.89-0.92, the magnesium index of coexisting ferropericlase and bridgmanite should be, respectively, at 0.83 and 0.93 just beyond the 660 km discontinuity, and 0.85 and 0.92 at the core-mantle boundary [13].…”

Section: Introductionmentioning

confidence: 64%

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Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

Kaminsky,

Zedgenizov,

Sevastyanov

et al. 2023

Minerals

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Diamonds from the Rio Sorriso placer in the Juina area, Mato Grosso State, Brazil, contain mineral inclusions of ferropericlase associated with MgSiO3, CaSiO3, magnesite, merrillite, and other minerals. The ferropericlase inclusions in Rio Sorriso diamonds are resolved into two distinct genetic and compositional groups: (1) protogenetic, high-Ni and low-Fe (Ni = 8270–10,660 ppm; mg# = 0.756–0.842) ferropericlases, and (2) syngenetic, low-Ni and high-Fe (Ni = 600–3050 ppm; mg# = 0.477–0.718) ferropericlases. Based on the crystallographic orientation relationships between natural ferropericlase inclusions and host diamonds, high-Ni and low-Fe ferropericlases originate in the upper part of the lower mantle, while low-Ni and high-Fe ferropericlases, most likely, originate in the lithosphere. Mineral inclusions form the ultramafic lower-mantle (MgSiO3, which we suggest as bridgmanite, CaSiO3, which we suggest as CaSi-perovskite, and high-Ni and low-Fe ferropericlase) and lithospheric (CaSiO3, which we suggest as breyite, Ca(Si,Ti)O3, and low-Ni and high-Fe ferropericlase) associations. The presence of magnesite and merrillite inclusions in association with ferropericlase confirmed the existence of a deep-seated carbonatitic association. Diamonds hosting high-Ni and low-Ni ferropericlase have different carbon-isotopic compositions (δ13C = −5.52 ± 0.75‰ versus −7.07 ± 1.23‰ VPDB, respectively). It implies the carbon-isotopic stratification of the mantle: in the lower mantle, the carbon-isotopic composition tends to become isotopically heavier (less depleted in 13C) than in lithospheric diamonds. These regularities may characterize deep-seated diamonds and ferropericlases not only in the Juina area of Brazil but also in other parts of the world.

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Section: Other Mineral Inclusionssupporting

confidence: 69%

Section: Introductionmentioning

confidence: 64%

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

Kaminsky,

Zedgenizov,

Sevastyanov

et al. 2023

Minerals

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“…Previous studies have shown that significant amounts of water within the oceanic plates (sediments, altered oceanic crust, and lithospheric peridotite) can be transported to the deep upper mantle and mantle transition zone (MTZ) (Hacker, 2008; Hebert & Montési, 2013; van Keken et al., 2011). This has been confirmed by the discovery of hydrous ringwoodite (Gu et al., 2022; Pearson et al., 2014) that appear to indicate fluid transportation by plate subduction at least down to the uppermost lower mantle. Moreover, seismic observations show widespread seismic low‐velocity zones, seismic reflectors, and high electrical conductivity around subduction zones at 800–1,500 km, which are not readily explained by compositional heterogeneity (Kaneshima, 2016; Waszek et al., 2018).…”

Section: Introductionmentioning

confidence: 76%

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

Yang

Faccenda

2023

JGR Solid Earth

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The distribution of water within the Earth's mantle has significant implications for the Earth's dynamics and evolution. Recent mineral physics experiments indicate that dense hydrous magnesium silicates can contain large amounts of water stable up to 60 GPa or even beyond along slab geotherms. Here we perform petrological‐thermomechanical numerical simulations of water transportation by deep slab subduction and related magmatism in the mid‐mantle. Key parameters including those defining the slab thermal parameter and the water storage capacity in the oceanic lithosphere and surrounding mantle are explored. The results show two major dehydration events of ultramafic rocks at around 150 and 750 km by dehydration of serpentine at 600°C and superhydrous phase B in the entrained wet upper mantle, respectively. Large amounts of water, ∼1.5 wt% at least locally, are carried down to the mantle transition zone and lower mantle. We estimate an upper limit of slab water flux into the mid‐mantle of 0.1–0.28 × 1012 kg/yr, which is ∼13%–37% of the input water from the serpentinized mantle. Moreover, a substantial fraction of the water released by the slab is absorbed by the entrained mantle and overlying mid‐mantle portions, such that ∼30%–70% of the water injected at the trench could be delivered to the lower mantle. The deepest magmatism is observed at ∼1,500 km in case of phase H breakdown (MgO‐SiO2‐H2O system), coinciding with the depth of strong seismic attenuation. Overall, these simulations suggest that up to 0.2 ocean mass per billion years could be transported down to the mid‐mantle and beyond.

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“…Therefore, they may carry significant amounts of water down to the bottom of the mantle transition zone. This expectation has been supported by the discovery of hydrous ringwoodite and its decomposition products as diamond inclusions (Gu et al., 2022; Pearson et al., 2014). However, the main minerals in the lower mantle, i.e., bridgmanite and ferropericlase, can only incorporate less than 1000 and 100 wt.…”

Section: Introductionmentioning

confidence: 89%

Temperature Dependence of H₂O Solubility in Al‐Free Stishovite

Purevjav,

Fei,

Ishii

et al. 2024

Geophysical Research Letters

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The role of stishovite in transporting water in subducting slabs has been a subject of debate for several decades. Here we investigated stishovite's water solubility and its potential role in water transportation as a function of temperature from 1300 to 2100°C at 22 GPa. Under water‐saturated conditions, high‐quality, Al‐free stishovite single crystals were synthesized with multi‐anvil press, and their water contents were measured using infrared spectroscopy. The H2O solubility in stishovite increases from 128(20) to 521(47) wt. ppm with increasing temperature from 1300 to 1700°C and decreased to 145(26) wt. ppm at 2100°C. The maximum H2O content was about seven times larger than earlier high‐temperature multi‐anvil studies but significantly lower than recent laser‐heated diamond anvil cell and low‐temperature multi‐anvil studies. We suggest that Al‐free stishovite may not be a significant H2O carrier in subducting slabs, at least at the topmost lower mantle corresponding to our experimental conditions.

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Hydrous peridotitic fragments of Earth’s mantle 660 km discontinuity sampled by a diamond

Cited by 17 publications

References 70 publications

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

Temperature Dependence of H₂O Solubility in Al‐Free Stishovite

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Hydrous peridotitic fragments of Earth’s mantle 660 km discontinuity sampled by a diamond

Cited by 17 publications

References 70 publications

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

On the Dynamics of Water Transportation and Magmatism in the Mid‐Mantle

Temperature Dependence of H2O Solubility in Al‐Free Stishovite

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Product

Resources

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Temperature Dependence of H₂O Solubility in Al‐Free Stishovite