Evidence for phase transitions in mineral inclusions in superdeep diamonds of the São Luiz deposit (Brazil)

Zedgenizov, D. A.; Shatsky, V. S.; Панин, А. В.; Evtushenko, O. V.; Ragozin, A. L.; Kagi, Hiroyuki

doi:10.1016/j.rgg.2015.01.021

Cited by 33 publications

(12 citation statements)

References 53 publications

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“…been proposed that many of the diamonds interpreted to have originated in the transition zone and lower mantle formed from subducted carbon (Burnham et al, 2015;Pal'yanov et al, 2002;Walter et al, 2011;Zedgenizov et al, 2015). However, it is likely that a fraction of super deep diamonds, many of which may have never reached the surface, formed during the crystallization of the mantle after the moon-forming impact in the Hadean and subsequently during the Archaean and Proterozoic eons (Gurney et al, 2010;Helmstaedt et al, 2010).…”

Section: Diamond Formationmentioning

confidence: 99%

Carbon Speciation and Solubility in Silicate Melts

Solomatova

Caracas

Cohen

2020

Geophysical Monograph Series

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To improve our understanding of the Earth's global carbon cycle, it is critical to characterize the distribution and storage mechanisms of carbon in silicate melts. Presently, the carbon budget of the deep Earth is not well constrained and is highly model-dependent. In silicate melts of the uppermost mantle, carbon exists predomi nantly as molecular carbon dioxide and carbonate, whereas at greater depths, carbon forms complex polymer ized species. The concentration and speciation of carbon in silicate melts is intimately linked to the melt's composition and affects its physical and dynamic properties. Here we review the results of experiments and calculations on the solubility and speciation of carbon in silicate melts as a function of pressure, temperature, composition, polymerization, water concentration, and oxygen fugacity.

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Section: Diamond Formationmentioning

confidence: 99%

Carbon Speciation and Solubility in Silicate Melts

Solomatova

Caracas

Cohen

2020

Geophysical Monograph Series

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“…To accommodate such a volume change, diamond had to have experienced cracking or considerable plastic deformation, features not detected by Anzolini et al (2016). In contrast, plastic and brittle deformations were observed around breyite inclusions in diamond by Cayzer et al (2008), Zedgenizov et al (2015), Burnham et al (2015Burnham et al ( , 2016 and Anzolini et al (2018), which emphasizes the possibility of the dual origin of breyite inclusions in diamond.…”

Section: Introductionmentioning

confidence: 95%

Breyite inclusions in diamond: experimental evidence for possible dual origin

et al. 2020

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Inclusions of breyite (previously known as walstromite-structured CaSiO 3 ) in diamond are usually interpreted as retrogressed CaSiO 3 perovskite trapped in the transition zone or the lower mantle. However, the thermodynamic stability field of breyite does not preclude its crystallization together with diamond under uppermantle conditions (6-10 GPa). The possibility of breyite forming in subducted sedimentary material through the reaction CaCO 3 + SiO 2 = CaSiO 3 + C + O 2 was experimentally evaluated in the CaO-SiO 2 -C-O 2 ± H 2 O system at 6-10 GPa, 900-1500 • C and oxygen fugacity 0.5-1.0 log units below the Fe-FeO (IW) buffer. One experimental series was conducted in the anhydrous subsystem and aimed at determining the melting temperature of the aragonite-coesite (or stishovite) assemblage. It was found that melting occurs at a lower temperature (∼ 1500 • C) than the decarbonation reaction, which indicates that breyite cannot be formed from aragonite and silica under anhydrous conditions and an oxygen fugacity above IW -1. In the second experimental series, we investigated partial melting of an aragonite-coesite mixture under hydrous conditions at the same pressures and redox conditions. The melting temperature in the presence of water decreased strongly (to 900-1200 • C), and the melt had a hydrous silicate composition. The reduction of melt resulted in graphite crystallization in equilibrium with titanite-structured CaSi 2 O 5 and breyite at ∼ 1000 • C. The maximum pressure of possible breyite formation is limited by the reaction CaSiO 3 + SiO 2 = CaSi 2 O 5 at ∼ 8 GPa. Based on the experimental results, it is concluded that breyite inclusions found in natural diamond may be formed from an aragonite-coesite assemblage or carbonate melt at 6-8 GPa via reduction at high water activity. Published by CopernicusPublications on behalf of the European mineralogical societies DMG, SEM, SIMP & SFMC. A. B. Woodland et al.: Breyite inclusions in diamond

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“…In the Earth, stishovite is stable above ~9 GPa, ~275 km depth (Ono et al, ; Zhang et al, ), and is a significant component of basaltic oceanic crust deeper than ~400 km (Perrillat et al, ). The decomposition products of aluminous stishovite have been found as inclusions in ultradeep diamonds (Bulanova et al, ; Thomson et al, ; Zedgenizov et al, ).…”

Section: Introductionmentioning

confidence: 99%

An Experimental Investigation of the Relative Strength of the Silica Polymorphs Quartz, Coesite, and Stishovite

Hunt

Whitaker

Bailey

et al. 2019

Geochem Geophys Geosyst

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In this study, quartz, coesite, and stishovite were deformed concurrently with an olivine reference sample at high pressure and 850 ± 50 °C. Olivine deformed with an effective stress exponent (n) of 6.9−2.2+3.1, which we interpret to indicate that the Peierls creep deformation mechanism was active in the olivine. Quartz and coesite had very similar strengths and deformed by a mechanism with n = 2.8−0.9+1.2 and 2.9−0.9+1.3, respectively, which are consistent with previous measurements of power law creep in these phases. Stishovite deformed with n = 8.1−2.7+3.7 and was stronger than both olivine and the other silica polymorphs. The high stress exponent of stishovite is greater than that typically observed for power law creep, indicating it is probably (but not certainly) deforming by Peierls creep. The rheology of SiO2 minerals appears therefore to be strongly affected by the change in silicon coordination and density from fourfold in quartz and coesite to sixfold in stishovite. If the effect of Si coordination can be generalized, the increase in Si coordination (and density) associated with bridgmanite formation may explain the tenfold to 100‐fold viscosity increase around 660 km depth in the Earth.

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Evidence for phase transitions in mineral inclusions in superdeep diamonds of the São Luiz deposit (Brazil)

Cited by 33 publications

References 53 publications

Carbon Speciation and Solubility in Silicate Melts

Carbon Speciation and Solubility in Silicate Melts

Breyite inclusions in diamond: experimental evidence for possible dual origin

An Experimental Investigation of the Relative Strength of the Silica Polymorphs Quartz, Coesite, and Stishovite

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