Evidence for deep mantle convection and primordial heterogeneity from nitrogen and carbon stable isotopes in diamond

Palot, M.; Cartigny, Pierre; Harris, Jeff W.; Kaminsky, Felix V.; Stachel, Thomas

doi:10.1016/j.epsl.2012.09.015

Cited by 100 publications

(77 citation statements)

References 103 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thomassot et al 2007;Palot et al 2012). As mantle convection should be an efficient mixing mechanism (Kellogg 1992) and carbon residence time in the mantle is estimated to be significantly <4 Ga (Dasgupta and Hirschmann 2010), preservation of a primordial reservoir is hard to explain.…”

Section: Subducted Source Of Isotopically Light Carbonmentioning

confidence: 99%

“…Many studies of natural diamonds have used carbon and nitrogen isotopic compositions to determine the source of diamond-forming material and to model the type of the processes involved in diamond formation (Boyd et al 1987;Cartigny et al 1998;Mikhail et al 2013;Palot et al 2012;Thomassot et al 2007). It is widely believed that the mantle has a relatively uniform carbon isotopic composition of δ 13 C = −5 ‰, a composition reflected in the worldwide diamond population (Cartigny 2005).…”

Section: Subducted Source Of Isotopically Light Carbonmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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

show abstract

Section: Subducted Source Of Isotopically Light Carbonmentioning

confidence: 99%

Section: Subducted Source Of Isotopically Light Carbonmentioning

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

View full text Add to dashboard Cite

show abstract

“…15 N values down to −25 ‰ and −40 ‰ observed in a few mantle diamonds are interpreted to be relicts of primordial nitrogen and are used to argue for an enstatite chondrite origin of Earth's nitrogen (Javoy, 1997;Palot et al, 2012;Cartigny and Marty, 2013 A significant fraction of nitrogen may have been segregated into the core during core-mantle separation (Roskosz et al, 2013). However, so far the potential influence of core-mantle separation on Earth's mantle nitrogen isotope evolution has never been investigated.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen isotope fractionation during terrestrial core-mantle separation

Li¹,

Marty²,

Shcheka³

et al. 2016

Geochem. Persp. Let.

View full text Add to dashboard Cite

doi: 10.7185/geochemlet.1614The origin and evolution of the terrestrial nitrogen remains largely unresolved. In order to understand the potential influence of core-mantle separation on terrestrial nitrogen evolution, experiments were performed at 1.5 to 7.0 GPa and 1600 to 1800 °C to study nitrogen isotope fractionation between coexisting liquid Fe-rich metal and silicate melt. The results show that the metal/silicate partition coefficient of nitrogen D N metal/silicate ranges from 1 to 150 and the nitrogen isotope fractionation d15 N metal-silicate is −3.5 ± 1.7 ‰. Calculations show that the bulk Earth is more depleted in d 15 N than the present-day mantle, and that the presentday mantle d 15 N of −5 ‰ could be derived from an enstatite chondrite composition via terrestrial core-mantle separation, with or without the addition of carbonaceous chondrites. These results strongly support the notion that enstatite chondrites may be a main component from which the Earth formed and a main source of the terrestrial nitrogen. Moreover, in the deep reduced mantle, the Fe-rich metal phase may store most of the nitrogen, and partial melting of the coexisting silicates may generate oceanic island basalts (OIBs) with slightly positive d15 N values.

show abstract

“…The shift from average mantle δ 13 C values towards lighter compositions in our studied cuboid diamonds, seems typical for diamonds of eclogitic parageneses and their wide range of carbon isotope compositions suggests formation from distinct mantle and crustal carbon sources [7]. Diamonds with extremely light and heavy nitrogen isotope compositions may reflect sources from an isolated, 15 N-depleted primordial mantle reservoir and from a 15 N-enriched mantle reservoir that contains recycled crustal components, respectively [29][30][31]. Significant general variations in the nitrogen isotope composition of peridotitic diamonds (Figure 3) may be related to primordial mantle heterogeneity.…”

Section: Discussionmentioning

confidence: 99%

“…3). It is recognised that eclogitic diamonds with low δ 13 C values and positive δ 15 N signatures were formed from crustal material [30,31]. Alternatively, Cartigny et al, 2001 [17] suggested that the very negative δ 13 C values associated with positive δ 15 N values can result from an open-system fractionation of metasomatic fluids.…”

Section: Discussionmentioning

confidence: 99%

The Carbon and Nitrogen Isotope Characteristics of Type Ib-IaA Cuboid Diamonds from Alluvial Placers in the Northeastern Siberian Platform

Zedgenizov¹,

Reutsky²,

Wiedenbeck³

2017

Preprint

View full text Add to dashboard Cite

Cuboid diamonds are particularly common in the placers of the northeastern Siberian platform but their origin remains unclear. These crystals usually range in color from dark yellow to orange and more interestingly, are characterized by unusual low aggregated nitrogen impurities (non-aggregated C-center) suggesting a short residence time and/or low temperatures at which they have been stored in the mantle. In order to track possible isotopic signature that could help deciphering cuboid diamond's crystallization processes, δ 13 C values, δ 15 N values and nitrogen contents have been determined in-situ in three samples using secondary ion mass spectrometry (SIMS), whereas nitrogen aggregation state have been determined by FTIR spectroscopy. The samples fall out the δ 13 C vs. δ 15 N field of canonical mantle composition. Different scale of carbon and nitrogen fractionation may produce the observed variations. Alternatively, mixing of mantle and crustal material would obscure initial co-variations of δ 13 C values with δ 15 N or nitrogen content.

show abstract

Evidence for deep mantle convection and primordial heterogeneity from nitrogen and carbon stable isotopes in diamond

Cited by 100 publications

References 103 publications

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

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

Nitrogen isotope fractionation during terrestrial core-mantle separation

The Carbon and Nitrogen Isotope Characteristics of Type Ib-IaA Cuboid Diamonds from Alluvial Placers in the Northeastern Siberian Platform

Contact Info

Product

Resources

About