Remnants of early Earth differentiation in the deepest mantle-derived lavas

Giuliani, Andrea; Jackson, Matthew G.; Dalton, Hayden

doi:10.7185/gold2021.3981

Cited by 5 publications

(24 citation statements)

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“…To compare the carbon-isotope composition of kimberlites with other geochemical tracers of kimberlite source evolution through time, we calculated average Sr, Nd, and Hf isotope compositions for kimberlites from the same pipe, cluster, or field using the recent compilation of Giuliani et al ( 24 ). For Nd and Hf isotope ratios, we used bulk-kimberlite analyses because these magmas are so enriched in incompatible trace elements ( 18 ) that crustal contamination generally has minimal effect on Nd and Hf isotope ratios of fresh samples.…”

Section: Methodsmentioning

confidence: 99%

“…While this process cannot be completely ruled out, it is not favored here because surface-derived, high-δ 13 C oxidized carbon can be efficiently recycled into the upper mantle as shown by some diamonds ( 83 ) and mantle xenoliths ( 84 ). Conversely, the transition zone provides an effective thermal barrier to the subduction of oxidized carbon into the lower mantle ( 43 ), from where most kimberlites are probably sourced ( 20 , 23 , 24 ).…”

Section: Methodsmentioning

confidence: 99%

“…The genetic link between kimberlites and deep mantle plumes is reinforced by the distribution of some kimberlite fields along age-progressive corridors corresponding to the continental portions of hot spot tracks ( 21 ). Furthermore, the relatively homogeneous Nd and Hf isotope composition and the occurrence of negative 182 W anomalies in kimberlites older than ~200 Ma requires tapping of a deep source largely isolated from mantle convection and associated recycled crustal components ( 22 , 23 ), and hence probably located in the lowermost mantle ( 24 ). This is supported by the entrainment of superdeep diamonds, which contain inclusions of minerals stable in the mantle transition zone and lower mantle [e.g., ringwoodite ( 25 ) and CaSi-perovskite ( 26 )], and the He and Ne isotope systematics of olivine in some kimberlites, which require deep-mantle plume contributions ( 27 ).…”

Section: Introductionmentioning

confidence: 99%

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Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

et al. 2022

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Earth’s carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth’s history, but the impact of these changes on the mantle carbon cycle is unclear. Here, we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The 13 C/ 12 C of kimberlites before ~250 Ma preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios—a switch coincident with a recognized surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low 13 C/ 12 C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth’s surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

et al. 2022

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“…While this process cannot be completely ruled out, it is not favored here because surface-derived, high- 13 C oxidized carbon can be efficiently recycled into the upper mantle as shown by some diamonds (83) and mantle xenoliths (84). Conversely, the transition zone provides an effective thermal barrier to the subduction of oxidized carbon into the lower mantle (43), from where most kimberlites are probably sourced (20,23,24).…”

Section: Carbon Isotopes Versus Sr-nd-hf Isotopesmentioning

confidence: 99%

“…The genetic link between kimberlites and deep mantle plumes is reinforced by the distribution of some kimberlite fields along ageprogressive corridors corresponding to the continental portions of hot spot tracks (21). Furthermore, the relatively homogeneous Nd and Hf isotope composition and the occurrence of negative 182 W anomalies in kimberlites older than ~200 Ma requires tapping of a deep source largely isolated from mantle convection and associated recycled crustal components (22,23), and hence probably located in the lowermost mantle (24). This is supported by the entrainment of superdeep diamonds, which contain inclusions of minerals stable in the mantle transition zone and lower mantle [e.g., ringwoodite (25) and CaSi-perovskite (26)], and the He and Ne isotope systematics of olivine in some kimberlites, which require deep-mantle plume contributions (27).…”

Section: Introductionmentioning

confidence: 99%

Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

Giuliani¹,

Drysdale

Woodhead

et al. 2022

Preprint

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Earth&#8217;s carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth&#8217;s history, but the impact of these changes on the mantle carbon cycle is unclear. Here we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The 13C/12C of kimberlites prior to ~250 Myr preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios &#8211; a switch coincident with a recognised surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low 13C/12C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth&#8217;s surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.

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Geodynamic and Isotopic Constraints on the Genesis of Kimberlites, Lamproites and Related Magmas From the Finnish Segment of the Karelian Craton

Dalton

Giuliani

Hergt

et al. 2022

Geochem Geophys Geosyst

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Despite the scientific and economic significance of kimberlites and related magmas, their origin is unclear. Here, we address this issue using whole‐rock and perovskite‐derived Sr‐Nd‐Hf isotopes for the three occurrences of kimberlite, lamproites and ultramafic lamprophyres (UMLs) in Finland. Mesoproterozoic olivine lamproites at Lentiira‐Kuhmo and UMLs at Kuusamo have different isotopic signatures yet were emplaced contemporaneously at 1,200 Ma in response to an extensional regime linked to the Baltica‐Laurentia breakup. The low εNd(i) and εHf(i) values of the olivine lamproites are consistent with an enriched subcontinental lithospheric mantle (SCLM) source while UML compositions are intermediate between those of typical kimberlites and lamproites and are interpreted to reflect mixing of asthenospheric melts and ∼10%–15% of melts sourced from metasomatized SCLM. The ∼750 Ma Kuusamo kimberlites, are probably linked to the mantle plume activity that initiated Rodinia's break‐up, exhibiting homogenous isotopic compositions which mirror the prominent Geodynamic and Source Constraints for ∼1,200 Ma Olivine Lamproite and Ultramafic Lamprophyre Magmatism in Eastern Finland (PREMA)‐like signature of kimberlites globally. By contrast, ∼620–585 Ma Kaavi‐Kuopio kimberlites show limited range in εNd(i) and 87Sr/86Sr(i) but have remarkably heterogeneous εHf(i) (+6.5 to −6.3) with a temporal trend toward lower εHf(i) values. While the Kuusamo kimberlites erupted during the early stage of continental break‐up, the Kaavi‐Kuopio kimberlites were emplaced when Rodinia break‐up was completed, coeval with formation of the Central Iapetus large igneous province. Magmas forming the Kaavi‐Kupio kimberlites may have formed from an upwelling mantle source similar to PREMA modified by increasing incorporation (up to 10%) of recycled crustal material through time accounting for the trend toward lower εHf(i) in these kimberlites.

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Remnants of early Earth differentiation in the deepest mantle-derived lavas

Cited by 5 publications

References 0 publications

Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

Perturbation of the deep-Earth carbon cycle in response to the Cambrian Explosion

Geodynamic and Isotopic Constraints on the Genesis of Kimberlites, Lamproites and Related Magmas From the Finnish Segment of the Karelian Craton

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