The depth of sub-lithospheric diamond formation and the redistribution of carbon in the deep mantle

Beyer, Christopher; Frost, Daniel J.

doi:10.1016/j.epsl.2016.12.017

Cited by 34 publications

(53 citation statements)

References 64 publications

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“…GPa coexisting pyroxene dissolves progressively into garnet as the majoritic components (Mg,Fe)4Si4O12 and Na2MgSi5O12 . The concentrations of these components in majoritic garnet give an equilibrium pressure provided pyroxene is present in the source 11 . In the absence of pyroxene in the source, the derived pressure is a minimum estimate.…”

Section: Introductionmentioning

confidence: 99%

“…2). Assuming the presence of pyroxene in the pyroxenitic diamond substrates, garnet compositions yield pressures of formation of 7.7-17.9 GPa using the Beyer and Frost majorite geobarometer 11 . These are minimum pressures, however, because the majoritic garnet equilibrium with pyroxene has not been demonstrated.…”

Section: Introductionmentioning

confidence: 99%

“…Although we recognise that this is a crude assumption, we show below that it yields (correctly) oxygen fugacities consistent with the stability of metallic Fe in experiments performed in iron capsules on similar compositions by Rohrbach et al 24 . We took thermodynamic data for equilibrium (1) from the database of Holland and Powell and Holland et al 25,26 and calculated oxygen fugacities for pressures given by the Beyer-Frost geobarometer 11 at temperatures corresponding to a mantle adiabat with a potential temperature of 1350°C 27 (Methods).…”

Section: Introductionmentioning

confidence: 99%

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Oxidized iron in garnets from the mantle transition zone

et al. 2018

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The oxidation state of iron in Earth's mantle is well known to depths of ~200km, but has not been measured in samples from the lowermost upper mantle (200-410 km depth) or the transition zone (410-660 km). Here we use Synchrotron Mössbauer Source spectroscopy complemented by single crystal X-ray diffraction to make the first measurements of the oxidation state of Fe in inclusions of ultrahigh pressure majoritic garnet in diamond. The garnets show a pronounced increase in oxidation state with depth, with Fe 3+ /(Fe 3+ + Fe 2+) increasing from 0.08 at ~240 km depth to 0.30 at ~500 km depth. The latter majorites, which come from pyroxenitic bulk compositions, are twice as rich in Fe 3+ as the most oxidised garnets from the shallow mantle. Corresponding oxygen fugacities are above the upper stability limit of Fe metal. This observation implies that the increase in oxidation state is not linked to the putative disproportionation of Fe 2+ to Fe 3+ plus Fe metal. Instead, the Fe 3+ increases with depth are consistent with the hypothesis that carbonated fluids or melts are the oxidising agents responsible for the high Fe 3+ contents of the inclusions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxidized iron in garnets from the mantle transition zone

et al. 2018

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“…Application of these methods has yielded the whole range of depths from 110 to 150 km, corresponding to the graphite-diamond boundary in the lithosphere, to over 660 km, lying within the lower mantle. 14,[22][23][24][25] Thus, these studies have provided direct evidence for the recycling of surficial carbon to lower-mantle depths. Traditional geobarometric methods, however, have several limitations: they can only be applied to rare types of mineral inclusions; touching inclusions may re-equilibrate after diamond growth; non-touching inclusions may be incorporated under different conditions and may not be in equilibrium; and protogenetic inclusions 26,27 may not re-equilibrate completely during diamond growth.…”

Section: Measuring the Depth Of Diamond Formationmentioning

confidence: 86%

Deep Carbon

Werner¹,

Fischer²,

Aiuppa³

et al. 2019

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“…Geobarometers are an essential tool for understanding geochemical and geodynamic processes of the Earth's interior. Their uses are manifold, ranging from the modelling of Simakov, 2008;Ashchepkov et al, 2010;Beyer et al, 2015) and have also been used to infer inclusion formation depths in diamonds (Collerson et al, 2010;Wijbrans et al, 2016;Beyer and Frost, 2017). The majority of barometers used on mantle rocks have been calibrated using experiments where sample pressures have been previously calibrated using known high pressure mineral transformations or equilibria.…”

Section: Introductionmentioning

confidence: 99%

An internally consistent pressure calibration of geobarometers applicable to the Earth’s upper mantle using in situ XRD

Beyer

Rosenthal

Myhill

et al. 2018

Geochimica et Cosmochimica Acta

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We have performed an experimental cross calibration of a suite of mineral equilibria within mantle rock bulk compositions that are commonly used in geobarometry to determine the equilibration depths of upper mantle assemblages. Multiple barometers were compared simultaneously in experimental runs, where the pressure was determined using in-situ measurements of the unit cell volumes of MgO, NaCl, Re and h-BN between 3.6 and 10.4 GPa, and 1250 and 1500 �C. The experiments were performed in a large volume press (LVPs) in combination with synchrotron x ray diffraction. Noble metal capsules drilled with multiple sample chambers were loaded with a range of bulk compositions representative of peridotite, eclogite and pyroxenite lithologies. By this approach, we simultaneously calibrated the geobarometers applicable to different mantle lithologies under identical and well determined pressure and temperature conditions. We identified discrepancies between the calculated and experimental pressures for which we propose simple linear or constant correction factors to some of the previously published barometric equations. As a result, we establish internally-consistent cross-calibrations for a number of garnet-orthopyroxene, garnet-clinopyroxene, Ca-Tschermaks-in-clinopyroxene and majorite geobarometers.

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The depth of sub-lithospheric diamond formation and the redistribution of carbon in the deep mantle

Cited by 34 publications

References 64 publications

Oxidized iron in garnets from the mantle transition zone

Oxidized iron in garnets from the mantle transition zone

Deep Carbon

An internally consistent pressure calibration of geobarometers applicable to the Earth’s upper mantle using in situ XRD

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