Long-term preservation of Hadean protocrust in Earth’s mantle

Tusch, Jonas; Hoffmann, J. Elis; Hasenstab, Eric; Fischer-Gödde, M.; Marien, Chris S.; Wilson, A. H.; Münker, Carsten

doi:10.1073/pnas.2120241119

Cited by 23 publications

(28 citation statements)

References 104 publications

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“…In-house rock reference material LP 1 is a historical OIB from La Palma (erupted 1480), AGC 351 is a 3455 Ma old granitic gneiss from the Kaapvaal Craton, Southern Africa 45 and 160245 is a 3270 Ma old Komatiite from the Pilbara Craton, NW Australia 11 . The W isotope composition for Cologne in-house rock reference materials reported in this study overlaps with the long-term average that has previously been obtained to assess the intermediate precision for W isotope composition analysis at University of Cologne (Supplementary Data 2 ) 11 , 40 , 41 .…”

Section: Methodssupporting

confidence: 74%

“…All studied Temagami BIF samples show positive 182 W offsets up to ~8 ppm compared to the inferred modern BSE value, suggesting an average positive µ 182 W signature of the total global W flux into the ocean at 2.7 Ga. With the exception of samples from the southern African region 14 , 39 , 40 , previously studied Archean rocks, irrespective of rock type, are characterized by positive µ 182 W compositions 4 , 5 , 12 , 13 , 41 (Supplementary Fig. 1 ).…”

Section: Resultsmentioning

confidence: 86%

“…University of Cologne: The separation of W followed established protocols, which were previously described in more detail 11 , 40 . In short, up to ca.…”

Section: Methodsmentioning

confidence: 99%

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Earth’s geodynamic evolution constrained by 182W in Archean seawater

et al. 2022

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Radiogenic isotope systems are important geochemical tools to unravel geodynamic processes on Earth. Applied to ancient marine chemical sediments such as banded iron formations, the short-lived 182Hf-182W isotope system can serve as key instrument to decipher Earth’s geodynamic evolution. Here we show high-precision 182W isotope data of the 2.7 Ga old banded iron formation from the Temagami Greenstone Belt, NE Canada, that reveal distinct 182W differences in alternating Si-rich (7.9 ppm enrichment) and Fe-rich (5.3 ppm enrichment) bands reflecting variable flux of W from continental and hydrothermal mantle sources into ambient seawater, respectively. Greater 182W excesses in Si-rich layers relative to associated shales (5.9 ppm enrichment), representing regional upper continental crust composition, suggest that the Si-rich bands record the global rather than the local seawater 182W signature. The distinct intra-band differences highlight the potential of 182W isotope signatures in banded iron formations to simultaneously track the evolution of crust and upper mantle through deep time.

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Section: Methodssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 86%

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Earth’s geodynamic evolution constrained by 182W in Archean seawater

et al. 2022

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“…Conversely, only samples with MORB-like W/Th may preserve the W isotope composition of their original magmatic source. Within the μ 182 W data set from the Kaapvaal Craton, only four samples exhibit MORB-like W/Th ratios (Tusch et al, 2022;this study). None of these samples show clearly resolvable W isotope anomalies (average μ 182 W = −2.2 ± 2.4), indicating that negative μ 182 W values are not intrinsic to the magmatic sources of analyzed volcanic rocks of the Craton.…”

Section: The Tungsten Budget Of Volcanic Rocks From the Kaapvaal And ...mentioning

confidence: 74%

Mobilization of Tungsten in Greenstone Belts of the Archean Kaapvaal and Singhbhum Cratons

Messling,

Jodder,

Hegner

et al. 2023

Geochem Geophys Geosyst

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Due to the inherently fluid‐mobile nature of W, the 182W record of the early Earth may have been obscured by fluid‐induced mobilization of W. To investigate W mobilization in Archean greenstone sequences, we analyzed 182W isotope systematics and major and trace element concentrations in samples from the 3.53 Ga old Onverwacht Group of the Kaapvaal Craton (South Africa) and the >3.51 Ga old Badampahar Group of the Singhbhum Craton (India). Our results for mafic and ultramafic metavolcanic rocks show W/Th ratios significantly higher than primary magmatic values, which suggests fluid‐induced W enrichment. Samples least affected by secondary W enrichment (W/Th < 0.26) show no resolvable W isotope anomalies from modern mantle values in both cratons. Samples from the Kaapvaal Craton with elevated W/Th exhibit deficits in 182W as low as −8.1 ± 4.3 ppm compared to the modern mantle. Covariations of μ182W with W/Th, and Ce/Pb suggest that negative isotope signatures were introduced during secondary fluid‐mediated processes. The enrichment of W is most evident in altered ultramafic rocks comprising serpentine, resulting in additional covariations between MgO, LOI, and W/Th. The W isotope composition of serpentinized komatiites reflects the composition of younger intruding granitoids. We therefore infer the latter as a possible source of W‐rich fluids. The Badampahar Group samples exhibit little W isotope variability. A well‐resolved 182W deficit of −6.2 ± 2.9 ppm was determined in a single komatiite sample, which indicates an unknown fluid source, currently not represented in any other unit of the Singhbhum Craton.

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“…Mundl et al 2017;Willbold et al 2011) has been suggested to imply inefficient mixing between Earth and the moon-forming impactor and, hence, speak against a planetary-mass impactor. However, the small 182 W deficits identified in modern deep-seated mantle plumes are thought to reflect interaction with Earth's core whereas the 182 W excesses measured in Archean rocks (Mundl-Petermeier et al 2020;Rizo et al 2019) are interpreted to reflect the composition of Earth's mantle prior to the addition of the late veneer (Willbold et al 2011;Tusch et al 2021). As such, the preservation of 182 W heterogeneities in Earth's deep mantle does not provide evidence for limited mixing during the moon-forming impact.…”

Section: Discussionmentioning

confidence: 99%

Anatomy of rocky planets formed by rapid pebble accretion

Johansen

Ronnet

Schiller

et al. 2023

A&A

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We explore the heating and differentiation of rocky planets that grow by rapid pebble accretion. Our terrestrial planets grow outside of the ice line and initially accrete 28% water ice by mass. The accretion of water stops after the protoplanet reaches a mass of 0.01 ME where the gas envelope becomes hot enough to sublimate the ice and transport the vapour back to the protoplanetary disc by recycling flows. The energy released by the decay of 26Al melts the accreted ice to form clay (phyllosilicates), oxidized iron (FeO), and a water surface layer with ten times the mass of Earth’s modern oceans. The ocean–atmosphere system undergoes a run-away greenhouse effect after the effective accretion temperature crosses a threshold of around 300 K. The run-away greenhouse process vaporizes the water layer, thereby trapping the accretion heat and heating the surface to more than 6000 K. This causes the upper part of the mantle to melt and form a global magma ocean. Metal melt separates from silicate melt and sediments towards the bottom of the magma ocean; the gravitational energy released by the sedimentation leads to positive feedback where the beginning differentiation of the planet causes the whole mantle to melt and differentiate. All rocky planets thus naturally experience a magma ocean stage. We demonstrate that Earth’s small excess of 182W (the decay product of 182Hf) relative to the chondrites is consistent with such rapid core formation within 5 Myr followed by equilibration of the W reservoir in Earth’s mantle with 182W-poor material from the core of a planetary-mass impactor, provided that the equilibration degree is at least 25–50%, depending on the initial Hf/W ratio. The planetary collision must have occurred at least 35 Myr after the main accretion phase of the terrestrial planets.

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Long-term preservation of Hadean protocrust in Earth’s mantle

Cited by 23 publications

References 104 publications

Earth’s geodynamic evolution constrained by 182W in Archean seawater

Earth’s geodynamic evolution constrained by 182W in Archean seawater

Mobilization of Tungsten in Greenstone Belts of the Archean Kaapvaal and Singhbhum Cratons

Anatomy of rocky planets formed by rapid pebble accretion

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