Diamonds, dunites, and metasomatic rocks formed by melt/rock reaction in craton roots

Pintér, Zsanett; Foley, Stephen F.; Yaxley, Gregory M.

doi:10.1038/s43247-022-00630-3

Cited by 10 publications

(10 citation statements)

References 52 publications

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“…Kimberlites are generally found in, or marginal to, thick (150–250 km) cratons 1 , 3 , 7 , 8 , 11 , 13 , 30 (Extended Data Fig. 3a,b ).…”

Section: Kimberlites Rifting and Mantle Plumesmentioning

confidence: 99%

“…2 ). To investigate this, we can examine phase equilibria models of peridotite rocks 30 that dominate the cratonic keels 7 , 10 , 11 . In our model, migrating convective instabilities detach peridotite from the keel and kimberlite magmas result from partial melting of the convectively circulating peridotite.…”

Section: Hybridization Of Mantle Meltsmentioning

confidence: 99%

“…The shallowest keel is metasomatized, containing diamonds that probably formed through redox freezing 30 . Melting experiments show that hybridization of these reduced, depleted peridotites with oxidized, hydrous CO 2 -rich melts should drive strong melting reactions 30 . However, until now, a mechanism to decouple and hybridize these oxidized and reduced domains was lacking.…”

Section: Hybridization Of Mantle Meltsmentioning

confidence: 99%

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Rift-induced disruption of cratonic keels drives kimberlite volcanism

Gernon

Jones

Brune

et al. 2023

Nature

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Kimberlites are volatile-rich, occasionally diamond-bearing magmas that have erupted explosively at Earth’s surface in the geologic past1–3. These enigmatic magmas, originating from depths exceeding 150 km in Earth’s mantle1, occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity4. Whether their mobilization is driven by mantle plumes5 or by mechanical weakening of cratonic lithosphere4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted about 30 million years (Myr) after continental breakup, suggesting an association with rifting processes. Our dynamical and analytical models show that physically steep lithosphere–asthenosphere boundaries (LABs) formed during rifting generate convective instabilities in the asthenosphere that slowly migrate many hundreds to thousands of kilometres inboard of rift zones. These instabilities endure many tens of millions of years after continental breakup and destabilize the basal tens of kilometres of the cratonic lithosphere, or keel. Displaced keel is replaced by a hot, upwelling mixture of asthenosphere and recycled volatile-rich keel in the return flow, causing decompressional partial melting. Our calculations show that this process can generate small-volume, low-degree, volatile-rich melts, closely matching the characteristics expected of kimberlites1–3. Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles through progressive disruption of cratonic keels.

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“…Kimberlites are generally found in, or marginal to, thick (150–250 km) cratons 1 , 3 , 7 , 8 , 11 , 13 , 30 (Extended Data Fig. 3a,b ).…”

Section: Kimberlites Rifting and Mantle Plumesmentioning

confidence: 99%

Section: Hybridization Of Mantle Meltsmentioning

confidence: 99%

Section: Hybridization Of Mantle Meltsmentioning

confidence: 99%

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Rift-induced disruption of cratonic keels drives kimberlite volcanism

Gernon

Jones

Brune

et al. 2023

Nature

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“…At higher influxes of melt, carbonates will be deposited (dark vein system; the carbonation freezing front [ 66 ]). Reactions between carbonate-rich melts and peridotite produce a zone with minerals characteristic of hydrous mantle metasomatism [ 99 , 101 ]. (c) Reduced melts emanating from deeper in the asthenosphere (Fig.…”

Section: Entrapment Of Carbon In the Continental Lithospherementioning

confidence: 99%

The effects of local variations in conditions on carbon storage and release in the continental mantle

Foley,

Chen,

Jacob

2024

National Science Review

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Recent advances indicate that the amount of carbon released by gradual degassing from the mantle needs to be revised upwards, whereas the carbon supplied by plumes may have been overestimated in the past. Variations in rock types and oxidation state may be very local and exert strong influences on carbon storage and release mechanisms. Deep subduction may be prevented by diapirism in thick sedimentary packages, whereas carbonates in thinner sequences may be subducted. Carbonates stored in the mantle transition zone will melt when they heat up, recognised by coupled stable isotope systems (e.g. Mg, Zn, Ca). There is no single ‘mantle oxygen fugacity’, particularly in the thermal boundary layer (TBL) and lowermost lithosphere where very local mixtures of rock types coexist. Carbonate-rich melts from either subduction or melting of the uppermost asthenosphere trap carbon by redox freezing or as carbonate-rich dykes in this zone. Deeply-derived, reduced melts may form further diamond reservoirs, recognised as polycrystalline diamonds associated with websteritic silicate minerals. Carbon is released by either edge-driven convection, which tears sections of the TBL and lower lithosphere down so that they melt by a mixture of heating and oxidation, or by lateral advection of solids beneath rifts. Both mechanisms operate at steps in lithosphere thickness and result in carbonate-rich melts, explaining the spatial association of craton edges and carbonate-rich magmatism. High-pressure experiments on individual rock types, and increasingly on reactions between rocks and melts, are fine-tuning our understanding of processes and turning up unexpected results that are not seen in studies of single rocks. Future research should concentrate on elucidating local variations and integrating these with the interpretation of geophysical signals. Global concepts such as average sediment compositions and a uniform mantle oxidation state are not appropriate for small-scale processes; an increased focus on local variations will help to refine carbon budget models.

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“…Mantle metasomatism is one of the essential processes that exerts primary control on the evolution and modification of Earth (e.g., Green & Wallace, 1988; O’Reilly & Griffin, 2013). Specifically, fluid, silicate melt, and carbonate melt derived from the deep mantle and/or recycled materials that act as typical metasomatic agents are chemically distinct and reactive to the mantle, significantly affecting its geochemical and lithological properties (e.g., Herzberg, 2006; Hofmann, 2014; Jackson & Dasgupta, 2008; Pilet et al., 2008; Pintér et al., 2022). The geochemical variabilities in metasomatized mantle induced by incorporation of metasomatic agents and/or isotopic fractionation due to specific minerals thus contain a wealth of information about the evolution of the Earth.…”

Section: Introductionmentioning

confidence: 99%

Stable Zirconium Isotopic Compositions of the Metasomatized Mantle

Zou,

Xu,

Wang

et al. 2024

JGR Solid Earth

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Mantle metasomatism, which affects the geochemical and lithological properties of the Earth, is crucial to the evolution and modification of the Earth's interior. Variations in chemical proxy of metasomatism, including high‐field strength elements (HFSE, e.g., Zr‐Ti isotopes and isovalent Zr‐Hf), have been commonly utilized as a tool to unravel the processes associated with the evolution of the Earth. However, the impact of mantle metasomatism by diverse agents on the Zr isotopic compositions of metasomatized mantle remains poorly understood. Here we carried out high‐precision double‐spike δ94/90Zr measurements for a suite of basalts, which were derived from the mantle sources metasomatized by typical metasomatic agents of fluid, silicate melt and carbonate melt originating from the deep mantle or recycled crustal materials. Mantle metasomatism results in lithological diversities within the mantle, ranging from hybridized peridotites to pyroxenite/eclogite and carbonated eclogite, which can significantly fractionate the isovalent HFSEs. However, our data show that these basalts have primitive mantle‐like δ94ZrNIST values (−0.033–0.043 ‰), regardless of their superchondritic Zr/Hf. The primitive mantle‐like δ94ZrNIST, irrelevant to any proxy of metasomatism (e.g., Sr‐Nd isotopes, Zr/Hf and La/Sm), indicate that mantle metasomatism and subsequence melting produce no measurable Zr isotopic variations in metasomatized mantle‐derived basalts. The δ94ZrNIST of basalts thus can be representative of the mean metasomatized mantle compositions. Combined with previously reported komatiites and oceanic basalts, we show that the Earth's mantle displays consistent δ94ZrNIST (−0.013 ± 0.053 ‰), even if it has a secular dynamic evolution with the interaction between Earth's exterior and interior.

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Diamonds, dunites, and metasomatic rocks formed by melt/rock reaction in craton roots

Cited by 10 publications

References 52 publications

Rift-induced disruption of cratonic keels drives kimberlite volcanism

Rift-induced disruption of cratonic keels drives kimberlite volcanism

The effects of local variations in conditions on carbon storage and release in the continental mantle

Stable Zirconium Isotopic Compositions of the Metasomatized Mantle

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