Deep global cycling of carbon constrained by the solidus of anhydrous, carbonated eclogite under upper mantle conditions

Dasgupta, Rajdeep; Hirschmann, M. M.; Withers, A. C.

doi:10.1016/j.epsl.2004.08.004

Cited by 429 publications

(283 citation statements)

References 44 publications

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“…However, for this new phase to be actually present in the deep lower mantle, carbonates must be preserved during deep subduction. Although the lower mantle assemblage is speculated to induce reducing conditions (9), carbonates could remain stable at depths if isolated from the surrounding mantle, for instance, in a relatively cold subducted slab where oxygen fugacity, as controlled by the local mineral assemblage, is locally higher (10,26). This fraction of surviving carbonates may be transported beyond 1,800-km depth, where transformation into the newly observed Fe ðIIIÞ -bearing phase would occur.…”

Section: Resultsmentioning

confidence: 99%

New host for carbon in the deep Earth

Boulard

Gloter

Corgne

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

126

140

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The global geochemical carbon cycle involves exchanges between the Earth's interior and the surface. Carbon is recycled into the mantle via subduction mainly as carbonates and is released to the atmosphere via volcanism mostly as CO 2 . The stability of carbonates versus decarbonation and melting is therefore of great interest for understanding the global carbon cycle. For all these reasons, the thermodynamic properties and phase diagrams of these minerals are needed up to core mantle boundary conditions. However, the nature of C-bearing minerals at these conditions remains unclear. Here we show the existence of a new Mg-Fe carbon-bearing compound at depths greater than 1,800 km. Its structure, based on three-membered rings of corner-sharing ðCO 4 Þ 4− tetrahedra, is in close agreement with predictions by first principles quantum calculations [Oganov AR, et al. (2008)

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Section: Resultsmentioning

confidence: 99%

New host for carbon in the deep Earth

Boulard

Gloter

Corgne

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

126

140

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“…Small carbonated eclogite ''plums" in the upwelling mantle would cross their solidi first along a mantle adiabat at about 340 km. Carbonatite melts generated from carbonated eclogite at depths of $340 km (Dasgupta et al, 2004) will be enriched in FeO T and incompatible trace elements (Dasgupta et al, 2006), and will carry them the isotopic signatures of those eclogites. Carbonatite melts would migrate freely upward to shallower depths and would lead to shallower mantle sources becoming metasomatized (Fig.…”

Section: Contributions From the Subducted Pacific Slabmentioning

confidence: 99%

“…The solidus of a carbonated mantle source, either peridotitic, pyroxenitic, or ecologitic, will be crossed under lower P-T conditions than a corresponding carbonatepoor mantle source (e.g., Dasgupta et al, 2004Dasgupta et al, , 2007Dasgupta et al, , 2013. The solidi of carbonated eclogite ($340 km; Dasgupta et al, 2004), carbonated peridotite ($300 km; Fig.…”

Section: A Carbonated Peridotitic/garnet Pyroxenitic Source For the Lmentioning

confidence: 99%

Olivine and melt inclusion chemical constraints on the source of intracontinental basalts from the eastern North China Craton: Discrimination of contributions from the subducted Pacific slab

Ryan

et al. 2016

Geochimica et Cosmochimica Acta

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“…After this dehydration, the solidus of subducting lithologies is expected to rise, such that further melting may not be expected until the slab reaches the base of the upper mantle (e.g. Hammouda 2003;Dasgupta et al 2004Dasgupta et al , 2006Litasov and Ohtani 2010;Rohrbach and Schmidt, 2011). At pressures of the transition zone, and approaching the upper/lower mantle boundary, the experimentally determined melting curves of carbonated peridotite (Ghosh et al 2009;Rohrbach and Schmidt 2011) and eclogite (Kiseeva et al 2013) become flat or possibly have a negative slope (Thomson et al 2014), and slab melting is expected to occur somewhere in the deep mantle.…”

Section: Depth Of Individual Inclusion Formationmentioning

confidence: 99%

Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions

Thomson

Kohn²,

Bulanova

et al. 2014

Contrib Mineral Petrol

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interpreted as evidence of diamond growth from abiotic organic carbon added to the oceanic crust during hydrothermal alteration. The bulk isotopic composition of the oceanic crust, carbonates plus organics, is equal to the composition of mantle carbon (−5 ‰), and we suggest that recycling/mixing of subducted material will replenish this reservoir over geological time. Several exposed, syngenetic inclusions have bulk compositions consistent with former eclogitic magnesium silicate perovskite, calcium silicate perovskite and NAL or CF phases that have reequilibrated during their exhumation to the surface. There are multiple occurrences of majoritic garnet with pyroxene exsolution, coesite with and without kyanite exsolution, clinopyroxene, Fe or Fe-carbide and sulphide minerals alongside single occurrences of olivine and ferropericlase. As a group, the inclusions have eclogitic affinity and provide evidence for diamond formation at pressures extending to Earth's deep transition zone and possibly the lower mantle. It is observed that the major element composition of inclusions and isotopic compositions of host Juina-5 diamonds are not correlated. The diamond and inclusion compositions are intimately related to subducted material and record a polybaric growth history across a depth interval stretching from the lower mantle to the base of the lithosphere. It is suggested that the interaction of slabderived melts and mantle material combined with subsequent upward transport in channelised networks or a buoyant diapir explains the formation of Juina-5 diamonds. We conclude that these samples, despite originating at great mantle depths, do not provide direct information about the ambient mantle, instead, providing a snapshot of the Earth's deep carbon cycle. Keywords Diamonds · Sub-lithospheric mantle · Carbon cycle · SubductionAbstract Forty-one diamonds sourced from the Juina-5 kimberlite pipe in Southern Brazil, which contain optically identifiable inclusions, have been studied using an integrated approach. The diamonds contain <20 ppm nitrogen (N) that is fully aggregated as B centres. Internal structures in several diamonds revealed using cathodoluminescence (CL) are unlike those normally observed in lithospheric samples. The majority of the diamonds are composed of isotopically light carbon, and the collection has a unimodal distribution heavily skewed towards δ 13 C ~ −25 ‰. Individual diamonds can display large carbon isotope heterogeneity of up to ~15 ‰ and predominantly have isotopically lighter cores displaying blue CL, and heavier rims with green CL. The light carbon isotopic compositions are Communicated by O. Müntener. Electronic supplementary materialThe online version of this article

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Deep global cycling of carbon constrained by the solidus of anhydrous, carbonated eclogite under upper mantle conditions

Cited by 429 publications

References 44 publications

New host for carbon in the deep Earth

New host for carbon in the deep Earth

Olivine and melt inclusion chemical constraints on the source of intracontinental basalts from the eastern North China Craton: Discrimination of contributions from the subducted Pacific slab

Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions

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