1
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Bajgain SK, Ashley AW, Mookherjee M, Ghosh DB, Karki BB. Insights into magma ocean dynamics from the transport properties of basaltic melt. Nat Commun 2022; 13:7590. [PMID: 36481757 PMCID: PMC9731987 DOI: 10.1038/s41467-022-35171-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 11/17/2022] [Indexed: 12/13/2022] Open
Abstract
The viscosity of magma plays a crucial role in the dynamics of the Earth: from the crystallization of a magma ocean during its initial stages to modern-day volcanic processes. However, the pressure-dependence behavior of viscosity at high pressure remains controversial. In this study, we report the results of first-principles molecular dynamics simulations of basaltic melt to show that the melt viscosity increases upon compression along each isotherm for the entire lower mantle after showing minima at ~6 GPa. However, elevated temperatures of the magma ocean translate to a narrow range of viscosity, i.e., 0.01-0.03 Pa.s. This low viscosity implies that the crystallization of the magma ocean could be complete within a few million years. These results also suggest that the crystallization of the magma ocean is likely to be fractional, thus supporting the hypothesis that present-day mantle heterogeneities could have been generated during the early crystallization of the primitive mantle.
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Affiliation(s)
- Suraj K Bajgain
- Earth Materials Laboratory, Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL, USA.
- Department of Geology, School of Natural Resources & Environment, Lake Superior State University, Sault Ste Marie, MI, USA.
| | - Aaron Wolfgang Ashley
- Earth Materials Laboratory, Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL, USA
| | - Mainak Mookherjee
- Earth Materials Laboratory, Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL, USA.
| | - Dipta B Ghosh
- School of Electrical Engineering and Computer Science, Department of Geology and Geophysics, Center for Computation and Technology, Louisiana State University, Baton Rouge, LA, USA
| | - Bijaya B Karki
- School of Electrical Engineering and Computer Science, Department of Geology and Geophysics, Center for Computation and Technology, Louisiana State University, Baton Rouge, LA, USA.
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2
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A Review of the Lunar 182Hf-182W Isotope System Research. MINERALS 2022. [DOI: 10.3390/min12060759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In recent years, the extinct nuclide 182Hf-182W system has been developed as an essential tool to date and trace the lunar origin and evolution. Despite a series of achievements, controversies and problems exist. As a review, this paper details the application principles of the 182Hf-182W isotope system and summarizes the research development on W isotopes of the Moon. A significant radiogenic ε182W excess of 0.24 ± 0.01 was found in the lunar mantle, leading to heated debates. There are three main explanations for the origin of the excess, including (1) radioactive origin; (2) the mantle of the Moon-forming impactor; and (3) disproportional late accretion to the Earth and the Moon. Debates on these explanations have revealed different views on lunar age. The reported ages of the Moon are mainly divided into two views: an early Moon (30–70 Ma after the solar system formation); and a late Moon (>70 Ma after the solar system formation). This paper discusses the possible effects on lunar 182W composition, including the Moon-forming impactor, late veneer, and Oceanus Procellarum-forming projectile. Finally, the unexpected isotopic similarities between the Earth and Moon are discussed.
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3
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Earth’s geodynamic evolution constrained by 182W in Archean seawater. Nat Commun 2022; 13:2701. [PMID: 35577795 PMCID: PMC9110358 DOI: 10.1038/s41467-022-30423-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 04/28/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractRadiogenic 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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4
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Abstract
Due to active plate tectonics, there are no direct rock archives covering the first ca. 500 million y of Earth’s history. Therefore, insights into Hadean geodynamics rely on indirect observations from geochemistry. We present a high-precision 182W dataset for rocks from the Kaapvaal Craton, southern Africa, revealing the presence of Hadean protocrustal remnants in Earth’s mantle. This has broad implications for geochemists, geophysicists, and modelers, as it bridges contrasting 182W isotope patterns in Archean and modern mantle-derived rocks. The data reveal the origin of seismically and isotopically anomalous domains in the deep mantle and also provide firm evidence for the operation of silicate differentiation processes during the first 60 million y of Earth’s history. With plate tectonics operating on Earth, the preservation potential for mantle reservoirs from the Hadean Eon (>4.0 Ga) has been regarded as very small. The quest for such early remnants has been spurred by the observation that many Archean rocks exhibit excesses of 182W, the decay product of short-lived 182Hf. However, it remains speculative whether Archean 182W anomalies and also 182W deficits found in many young ocean island basalts (OIBs) mirror primordial Hadean mantle differentiation or merely variable contributions from older meteorite building blocks delivered to the growing Earth. Here, we present a high-precision 182W isotope dataset for 3.22- to 3.55-Ga-old rocks from the Kaapvaal Craton, southern Africa. In expanding previous work, our study reveals widespread 182W deficits in different rock units from the Kaapvaal Craton and also the discovery of a negative covariation between short-lived 182W and long-lived 176Hf–143Nd–138Ce patterns, a trend of global significance. Among different models, these distinct patterns can be best explained by the presence of recycled mafic restites from Hadean protocrust in the ancient mantle beneath the Kaapvaal Craton. Further, the data provide unambiguous evidence for the operation of silicate differentiation processes on Earth during the lifetime of 182Hf, that is, the first 60 million y after solar system formation. The striking isotopic similarity between recycled protocrust and the low-182W endmember of modern OIBs might also constitute the missing link bridging 182W isotope systematics in Archean and young mantle-derived rocks.
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5
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Nabiei F, Badro J, Boukaré C, Hébert C, Cantoni M, Borensztajn S, Wehr N, Gillet P. Investigating Magma Ocean Solidification on Earth Through Laser-Heated Diamond Anvil Cell Experiments. GEOPHYSICAL RESEARCH LETTERS 2021; 48:e2021GL092446. [PMID: 34219835 PMCID: PMC8244043 DOI: 10.1029/2021gl092446] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 05/18/2021] [Accepted: 05/22/2021] [Indexed: 05/09/2023]
Abstract
We carried out a series of silicate fractional crystallization experiments at lower mantle pressures using the laser-heated diamond anvil cell. Phase relations and the compositional evolution of the cotectic melt and equilibrium solids along the liquid line of descent were determined and used to assemble the melting phase diagram. In a pyrolitic magma ocean, the first mineral to crystallize in the deep mantle is iron-depleted calcium-bearing bridgmanite. From the phase diagram, we estimate that the initial 33%-36% of the magma ocean will crystallize to form such a buoyant bridgmanite. Substantial calcium solubility in bridgmanite is observed up to 129 GPa, and significantly delays the crystallization of the calcium silicate perovskite phase during magma ocean solidification. Residual melts are strongly iron-enriched as crystallization proceeds, making them denser than any of the coexisting solids at deep mantle conditions, thus supporting the terrestrial basal magma ocean hypothesis (Labrosse et al., 2007).
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Affiliation(s)
- Farhang Nabiei
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
- Electron Spectrometry and Microscopy LaboratoryEPFLLausanneSwitzerland
| | - James Badro
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Charles‐Édouard Boukaré
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Cécile Hébert
- Electron Spectrometry and Microscopy LaboratoryEPFLLausanneSwitzerland
| | - Marco Cantoni
- Interdisciplinary Centre for Electron MicroscopyEPFLLausanneSwitzerland
| | | | - Nicolas Wehr
- Université de ParisInstitut de Physique du Globe de ParisCNRSParisFrance
| | - Philippe Gillet
- Earth and Planetary Science LaboratoryEPFLLausanneSwitzerland
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6
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Suer TA, Siebert J, Remusat L, Day JMD, Borensztajn S, Doisneau B, Fiquet G. Reconciling metal-silicate partitioning and late accretion in the Earth. Nat Commun 2021; 12:2913. [PMID: 34006864 PMCID: PMC8131616 DOI: 10.1038/s41467-021-23137-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 03/30/2021] [Indexed: 11/09/2022] Open
Abstract
Highly siderophile elements (HSE), including platinum, provide powerful geochemical tools for studying planet formation. Late accretion of chondritic components to Earth after core formation has been invoked as the main source of mantle HSE. However, core formation could also have contributed to the mantle's HSE content. Here we present measurements of platinum metal-silicate partitioning coefficients, obtained from laser-heated diamond anvil cell experiments, which demonstrate that platinum partitioning into metal is lower at high pressures and temperatures. Consequently, the mantle was likely enriched in platinum immediately following core-mantle differentiation. Core formation models that incorporate these results and simultaneously account for collateral geochemical constraints, lead to excess platinum in the mantle. A subsequent process such as iron exsolution or sulfide segregation is therefore required to remove excess platinum and to explain the mantle's modern HSE signature. A vestige of this platinum-enriched mantle can potentially account for 186Os-enriched ocean island basalt lavas.
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Affiliation(s)
- Terry-Ann Suer
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Museum National d'Histoire Naturelle, Sorbonne Université, Paris, France. .,Department of Earth and Planetary Science, Harvard University, Cambridge, MA, USA.
| | - Julien Siebert
- Institut de Physique du Globe de Paris, UMR CNRS 7154, Paris, France.,Institut Universitaire de France, Paris, France
| | - Laurent Remusat
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Museum National d'Histoire Naturelle, Sorbonne Université, Paris, France
| | - James M D Day
- Department of Earth and Planetary Science, Harvard University, Cambridge, MA, USA.,Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | | | - Beatrice Doisneau
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Museum National d'Histoire Naturelle, Sorbonne Université, Paris, France
| | - Guillaume Fiquet
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Museum National d'Histoire Naturelle, Sorbonne Université, Paris, France
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7
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Williams HM, Matthews S, Rizo H, Shorttle O. Iron isotopes trace primordial magma ocean cumulates melting in Earth's upper mantle. SCIENCE ADVANCES 2021; 7:7/11/eabc7394. [PMID: 33712459 PMCID: PMC7954453 DOI: 10.1126/sciadv.abc7394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
The differentiation of Earth ~4.5 billion years (Ga) ago is believed to have culminated in magma ocean crystallization, crystal-liquid separation, and the formation of mineralogically distinct mantle reservoirs. However, the magma ocean model remains difficult to validate because of the scarcity of geochemical tracers of lower mantle mineralogy. The Fe isotope compositions (δ57Fe) of ancient mafic rocks can be used to reconstruct the mineralogy of their mantle source regions. We present Fe isotope data for 3.7-Ga metabasalts from the Isua Supracrustal Belt (Greenland). The δ57Fe signatures of these samples extend to values elevated relative to modern equivalents and define strong correlations with fluid-immobile trace elements and tungsten isotope anomalies (μ182W). Phase equilibria models demonstrate that these features can be explained by melting of a magma ocean cumulate component in the upper mantle. Similar processes may operate today, as evidenced by the δ57Fe and μ182W heterogeneity of modern oceanic basalts.
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Affiliation(s)
- Helen M Williams
- Department of Earth Sciences, The University of Cambridge, Cambridge, UK.
| | - Simon Matthews
- Department of Earth Sciences, The University of Cambridge, Cambridge, UK
| | - Hanika Rizo
- Department of Earth Sciences, Carleton University, Ottawa, ON, Canada
| | - Oliver Shorttle
- Department of Earth Sciences, The University of Cambridge, Cambridge, UK
- Institute of Astronomy, The University of Cambridge, Cambridge, UK
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8
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Convective isolation of Hadean mantle reservoirs through Archean time. Proc Natl Acad Sci U S A 2020; 118:2012626118. [PMID: 33443147 DOI: 10.1073/pnas.2012626118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although Earth has a convecting mantle, ancient mantle reservoirs that formed within the first 100 Ma of Earth's history (Hadean Eon) appear to have been preserved through geologic time. Evidence for this is based on small anomalies of isotopes such as 182W, 142Nd, and 129Xe that are decay products of short-lived nuclide systems. Studies of such short-lived isotopes have typically focused on geological units with a limited age range and therefore only provide snapshots of regional mantle heterogeneities. Here we present a dataset for short-lived 182Hf-182W (half-life 9 Ma) in a comprehensive rock suite from the Pilbara Craton, Western Australia. The samples analyzed preserve a unique geological archive covering 800 Ma of Archean history. Pristine 182W signatures that directly reflect the W isotopic composition of parental sources are only preserved in unaltered mafic samples with near canonical W/Th (0.07 to 0.26). Early Paleoarchean, mafic igneous rocks from the East Pilbara Terrane display a uniform pristine µ182W excess of 12.6 ± 1.4 ppm. From ca 3.3Ga onward, the pristine 182W signatures progressively vanish and are only preserved in younger rocks of the craton that tap stabilized ancient lithosphere. Given that the anomalous 182W signature must have formed by ca 4.5 Ga, the mantle domain that was tapped by magmatism in the Pilbara Craton must have been convectively isolated for nearly 1.2 Ga. This finding puts lower bounds on timescale estimates for localized convective homogenization in early Earth's interior and on the widespread emergence of plate tectonics that are both important input parameters in many physical models.
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9
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Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling. Proc Natl Acad Sci U S A 2020; 117:30993-31001. [PMID: 33229590 DOI: 10.1073/pnas.2009663117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rare high-3He/4He signatures in ocean island basalts (OIB) erupted at volcanic hotspots derive from deep-seated domains preserved in Earth's interior. Only high-3He/4He OIB exhibit anomalous 182W-an isotopic signature inherited during the earliest history of Earth-supporting an ancient origin of high 3He/4He. However, it is not understood why some OIB host anomalous 182W while others do not. We provide geochemical data for the highest-3He/4He lavas from Iceland (up to 42.9 times atmospheric) with anomalous 182W and examine how Sr-Nd-Hf-Pb isotopic variations-useful for tracing subducted, recycled crust-relate to high 3He/4He and anomalous 182W. These data, together with data on global OIB, show that the highest-3He/4He and the largest-magnitude 182W anomalies are found only in geochemically depleted mantle domains-with high 143Nd/144Nd and low 206Pb/204Pb-lacking strong signatures of recycled materials. In contrast, OIB with the strongest signatures associated with recycled materials have low 3He/4He and lack anomalous 182W. These observations provide important clues regarding the survival of the ancient He and W signatures in Earth's mantle. We show that high-3He/4He mantle domains with anomalous 182W have low W and 4He concentrations compared to recycled materials and are therefore highly susceptible to being overprinted with low 3He/4He and normal (not anomalous) 182W characteristic of subducted crust. Thus, high 3He/4He and anomalous 182W are preserved exclusively in mantle domains least modified by recycled crust. This model places the long-term preservation of ancient high 3He/4He and anomalous 182W in the geodynamic context of crustal subduction and recycling and informs on survival of other early-formed heterogeneities in Earth's interior.
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10
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Chu ZY, Xu JJ, Li CF, Yang YH, Guo JH. A Chromatographic Method for Separation of Tungsten (W) from Silicate Samples for High-Precision Isotope Analysis Using Negative Thermal Ionization Mass Spectrometry. Anal Chem 2020; 92:11987-11993. [PMID: 32786483 DOI: 10.1021/acs.analchem.0c02431] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new chromatographic method for isolation of W from large masses of silicate samples (>1 g) for ultrahigh precision isotopic analysis was developed. The purification of W was achieved through two stages of rapid chromatographic separations. In the first step, Ti, Zr, Hf, and W were separated collectively from the sample matrix through an AG1-X8 (100-200 mesh) column with a 10 mL resin volume. Subsequently, W was rapidly separated from Ti and Zr-Hf with high purity by a two-step extraction chromatographic method using 0.6 and 0.3 mL TODGA resin columns (50-100 μm particle size), respectively. The total yield of W, including the anion exchange and the TODGA chromatographic separation steps, is greater than 90%. The procedure was employed to isolate W from rock reference materials GSJ JB-3 and USGS BHVO-2; the separated W was analyzed by TRITON Plus TIMS, yielding a 182W/184W of 0.864898 ± 0.000005 (n = 8, 2 SD) for JB-3 and 182W/184W of 0.864896 ± 0.000006 (n = 5, 2 SD) for BHVO-2, which are in agreement with previously reported values within analytical errors.
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Affiliation(s)
- Zhu-Yin Chu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.,Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
| | - Jun-Jie Xu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.,School of Ocean Sciences, China University of Geosciences, Beijing 100083, China
| | - Chao-Feng Li
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.,Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
| | - Yue-Heng Yang
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.,Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
| | - Jing-Hui Guo
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.,Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
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11
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Ruthenium isotope vestige of Earth's pre-late-veneer mantle preserved in Archaean rocks. Nature 2020; 579:240-244. [PMID: 32161386 PMCID: PMC7212018 DOI: 10.1038/s41586-020-2069-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 01/15/2020] [Indexed: 12/03/2022]
Abstract
The accretion of volatile-rich material from the outer solar system represents a crucial prerequisite for Earth developing oceans and becoming a habitable planet1–4. However, the timing of this accretion remains controversial5–8. It was proposed that volatile elements were added to Earth by late accretion of a late veneer consisting of carbonaceous chondrite-like material after core formation had ceased6,9,10. This view, however, could not be reconciled with the distinct ruthenium (Ru) isotope composition of carbonaceous chondrites5,11 compared to the modern mantle12, and in fact also not with any known meteorite group5. As a possible solution, Earth’s pre-late veneer mantle could already have contained a significant amount of Ru that was not fully extracted by core formation13. The presence of such pre-late veneer Ru could only be proven if its isotope composition would be distinct from that of the modern mantle. Here we report the first high-precision mass-independent Ru isotope compositions for Eoarchean ultramafic rocks from SW Greenland, which display a relative 100Ru excess of +22 parts per million compared to the modern mantle value. This 100Ru excess indicates that the source of the Eoarchean rocks already contained a significant fraction of Ru prior to the late veneer. By 3.7 Gyr the mantle beneath the SW Greenland rocks had not yet fully equilibrated with late accreted material. Otherwise, no Ru isotopic difference relative to the modern mantle would be observed. By considering constraints from other highly siderophile elements beyond Ru14, the composition of the modern mantle can only be reconciled if the late veneer contained significant portions of carbonaceous chondrite-like materials with their characteristic 100Ru deficits. These data therefore relax previous constraints on the late veneer and now permit that volatile-rich material from the outer solar system was delivered to Earth during late accretion.
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12
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Xie L, Yoneda A, Yamazaki D, Manthilake G, Higo Y, Tange Y, Guignot N, King A, Scheel M, Andrault D. Formation of bridgmanite-enriched layer at the top lower-mantle during magma ocean solidification. Nat Commun 2020; 11:548. [PMID: 31992697 PMCID: PMC6987212 DOI: 10.1038/s41467-019-14071-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Accepted: 12/10/2019] [Indexed: 11/09/2022] Open
Abstract
Thermochemical heterogeneities detected today in the Earth’s mantle could arise from ongoing partial melting in different mantle regions. A major open question, however, is the level of chemical stratification inherited from an early magma-ocean (MO) solidification. Here we show that the MO crystallized homogeneously in the deep mantle, but with chemical fractionation at depths around 1000 km and in the upper mantle. Our arguments are based on accurate measurements of the viscosity of melts with forsterite, enstatite and diopside compositions up to ~30 GPa and more than 3000 K at synchrotron X-ray facilities. Fractional solidification would induce the formation of a bridgmanite-enriched layer at ~1000 km depth. This layer may have resisted to mantle mixing by convection and cause the reported viscosity peak and anomalous dynamic impedance. On the other hand, fractional solidification in the upper mantle would have favored the formation of the first crust. Following the impact of the protoplanet Theia, planet Earth likely transformed into a magma ocean. New high temperature and pressure experiments by Xie et al. suggest that a layer enriched in bridgmanite formed during the magma ocean phase of Earth–remnants of this ancient layer today may be responsible for the viscosity peak between 660 and 1500 km in present solid mantle.
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Affiliation(s)
- Longjian Xie
- Institute for Planetary Materials, Okayama University, Misasa, Tottori, 682-0193, Japan. .,Bayerisches Geoinstitut, University of Bayreuth, 95440, Bayreuth, Germany.
| | - Akira Yoneda
- Institute for Planetary Materials, Okayama University, Misasa, Tottori, 682-0193, Japan
| | - Daisuke Yamazaki
- Institute for Planetary Materials, Okayama University, Misasa, Tottori, 682-0193, Japan
| | - Geeth Manthilake
- Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, F‑63000, Clermont-Ferrand, France
| | - Yuji Higo
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo, 689-5198, Japan
| | - Yoshinori Tange
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo, 689-5198, Japan
| | | | | | | | - Denis Andrault
- Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, F‑63000, Clermont-Ferrand, France
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13
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García-Ruiz JM, van Zuilen MA, Bach W. Mineral self-organization on a lifeless planet. Phys Life Rev 2020; 34-35:62-82. [PMID: 32303465 DOI: 10.1016/j.plrev.2020.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 01/10/2020] [Indexed: 01/14/2023]
Abstract
It has been experimentally demonstrated that, under alkaline conditions, silica is able to induce the formation of mineral self-assembled inorganic-inorganic composite materials similar in morphology, texture and nanostructure to the hybrid biomineral structures that, millions of years later, life was able to self-organize. These mineral self-organized structures (MISOS) have been also shown to work as effective catalysts for prebiotic chemical reactions and to easily create compartmentalization within the solutions where they form. We reason that, during the very earliest history of this planet, there was a geochemical scenario that inevitably led to the existence of a large-scale factory of simple and complex organic compounds, many of which were relevant to prebiotic chemistry. The factory was built on a silica-rich high-pH ocean and powered by two main factors: a) a quasi-infinite source of simple carbon molecules synthesized abiotically from reactions associated with serpentinization, or transported from meteorites and produced from their impact on that alkaline ocean, and b) the formation of self-organized silica-metal mineral composites that catalyze the condensation of simple molecules in a methane-rich reduced atmosphere. We discuss the plausibility of this geochemical scenario, review the details of the formation of MISOS and its catalytic properties and the transition towards a slightly alkaline to neutral ocean.
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Affiliation(s)
- Juan Manuel García-Ruiz
- Laboratorio de Estudios Cristalográficos, Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. de las Palmeras 4, Armilla (Granada), Spain.
| | - Mark A van Zuilen
- Equipe Géomicrobiologie, Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France.
| | - Wolfgang Bach
- Geoscience Department and MARUM, University of Bremen, Klagenfurter Str. 2, 28359 Bremen, Germany.
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14
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Zhang R, Meija J, Huang Y, Pei X, Mester Z, Yang L. Determination of the isotopic composition of tungsten using MC-ICP-MS. Anal Chim Acta 2019; 1089:19-24. [PMID: 31627814 DOI: 10.1016/j.aca.2019.08.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 07/30/2019] [Accepted: 08/13/2019] [Indexed: 10/26/2022]
Abstract
The processes of planetary accretion or formation of the Earth and other celestial objects can be studied by using the 182Hf-182W chronometer which requires precise measurements of tungsten isotope ratios. Many comparative measurements for the isotopic composition of tungsten have been performed using either thermal ionization mass spectrometry (TIMS) or multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Yet, calibrated measurements of tungsten isotope ratios, and, in turn, isotopic abundances and atomic weight, are still lacking. In this study, we report the first independent measurements of all tungsten isotope ratios in five commercial tungsten reagents, including the new NRC candidate isotopic reference material WOLF-1 by MC-ICP-MS with use of the-state-of-the-art optimized regression mass bias correction model and NIST SRM 989 isotopic rhenium as calibrator.
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Affiliation(s)
- Rouxi Zhang
- National Research Council Canada, 1200 Montreal Rd, Ottawa, ON, K1A 0R6, Canada; Earth Science Department, Chengdu University of Technology, Chengdu, Sichuan, 610059, China
| | - Juris Meija
- National Research Council Canada, 1200 Montreal Rd, Ottawa, ON, K1A 0R6, Canada
| | - Yi Huang
- Earth Science Department, Chengdu University of Technology, Chengdu, Sichuan, 610059, China
| | - Xiangjun Pei
- Earth Science Department, Chengdu University of Technology, Chengdu, Sichuan, 610059, China
| | - Zoltán Mester
- National Research Council Canada, 1200 Montreal Rd, Ottawa, ON, K1A 0R6, Canada
| | - Lu Yang
- National Research Council Canada, 1200 Montreal Rd, Ottawa, ON, K1A 0R6, Canada.
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15
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Nebel O, Capitanio FA, Moyen JF, Weinberg RF, Clos F, Nebel-Jacobsen YJ, Cawood PA. When crust comes of age: on the chemical evolution of Archaean, felsic continental crust by crustal drip tectonics. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2018.0103. [PMID: 30275165 PMCID: PMC6189554 DOI: 10.1098/rsta.2018.0103] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/10/2018] [Indexed: 05/18/2023]
Abstract
The secular evolution of the Earth's crust is marked by a profound change in average crustal chemistry between 3.2 and 2.5 Ga. A key marker for this change is the transition from Archaean sodic granitoid intrusions of the tonalite-trondhjemite-granodiorite (TTG) series to potassic (K) granitic suites, akin (but not identical) to I-type granites that today are associated with subduction zones. It remains poorly constrained as to how and why this change was initiated and if it holds clues about the geodynamic transition from a pre-plate tectonic mode, often referred to as stagnant lid, to mobile plate tectonics. Here, we combine a series of proposed mechanisms for Archaean crustal geodynamics in a single model to explain the observed change in granitoid chemistry. Numeric modelling indicates that upper mantle convection drives crustal flow and subsidence, leading to profound diversity in lithospheric thickness with thin versus thick proto-plates. When convecting asthenospheric mantle interacts with lower lithosphere, scattered crustal drips are created. Under increasing P-T conditions, partial melting of hydrated meta-basalt within these drips produces felsic melts that intrude the overlying crust to form TTG. Dome structures, in which these melts can be preserved, are a positive diapiric expression of these negative drips. Transitional TTG with elevated K mark a second evolutionary stage, and are blends of subsided and remelted older TTG forming K-rich melts and new TTG melts. Ascending TTG-derived melts from asymmetric drips interact with the asthenospheric mantle to form hot, high-Mg sanukitoid. These melts are small in volume, predominantly underplated, and their heat triggered melting of lower crustal successions to form higher-K granites. Importantly, this evolution operates as a disseminated process in space and time over hundreds of millions of years (greater than 200 Ma) in all cratons. This focused ageing of the crust implies that compiled geochemical data can only broadly reflect geodynamic changes on a global or even craton-wide scale. The observed change in crustal chemistry does mark the lead up to but not the initiation of modern-style subduction.This article is part of a discussion meeting issue 'Earth dynamics and the development of plate tectonics'.
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Affiliation(s)
- O Nebel
- School of Earth, Atmosphere and Environment, Monash University, Clayton, 3800 Victoria, Australia
| | - F A Capitanio
- School of Earth, Atmosphere and Environment, Monash University, Clayton, 3800 Victoria, Australia
| | - J-F Moyen
- Laboratoire Magmas et Volcans, Université de Lyon, UJM-UCA-CNRS-IRD, 23 rue Dr. Paul Michelon, 42023 Saint Etienne, France
| | - R F Weinberg
- School of Earth, Atmosphere and Environment, Monash University, Clayton, 3800 Victoria, Australia
| | - F Clos
- School of Earth, Atmosphere and Environment, Monash University, Clayton, 3800 Victoria, Australia
| | | | - P A Cawood
- School of Earth, Atmosphere and Environment, Monash University, Clayton, 3800 Victoria, Australia
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Chaudhuri T, Wan Y, Mazumder R, Ma M, Liu D. Evidence of Enriched, Hadean Mantle Reservoir from 4.2-4.0 Ga zircon xenocrysts from Paleoarchean TTGs of the Singhbhum Craton, Eastern India. Sci Rep 2018; 8:7069. [PMID: 29728630 PMCID: PMC5935743 DOI: 10.1038/s41598-018-25494-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 04/19/2018] [Indexed: 11/25/2022] Open
Abstract
Sensitive High-Resolution Ion Microprobe (SHRIMP) U-Pb analyses of zircons from Paleoarchean (~3.4 Ga) tonalite-gneiss called the Older Metamorphic Tonalitic Gneiss (OMTG) from the Champua area of the Singhbhum Craton, India, reveal 4.24-4.03 Ga xenocrystic zircons, suggesting that the OMTG records the hitherto unknown oldest precursor of Hadean age reported in India. Hf isotopic analyses of the Hadean xenocrysts yield unradiogenic 176Hf/177Hfinitial compositions (0.27995 ± 0.0009 to 0.28001 ± 0.0007; ɛHf[t] = −2.5 to −5.2) indicating that an enriched reservoir existed during Hadean eon in the Singhbhum cratonic mantle. Time integrated ɛHf[t] compositional array of the Hadean xenocrysts indicates a mafic protolith with 176Lu/177Hf ratio of ∼0.019 that was reworked during ∼4.2-4.0 Ga. This also suggests that separation of such an enriched reservoir from chondritic mantle took place at 4.5 ± 0.19 Ga. However, more radiogenic yet subchondritic compositions of ∼3.67 Ga (average 176Hf/177Hfinitial 0.28024 ± 0.00007) and ~3.4 Ga zircons (average 176Hf/177Hfinitial = 0.28053 ± 0.00003) from the same OMTG samples and two other Paleoarchean TTGs dated at ~3.4 Ga and ~3.3 Ga (average 176Hf/177Hfinitial is 0.28057 ± 0.00008 and 0.28060 ± 0.00003), respectively, corroborate that the enriched Hadean reservoir subsequently underwent mixing with mantle-derived juvenile magma during the Eo-Paleoarchean.
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Affiliation(s)
- Trisrota Chaudhuri
- Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata, 700019, India
| | - Yusheng Wan
- Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China
| | - Rajat Mazumder
- Department of Applied Geology, Faculty of Engineering and Science, Curtin University Malaysia, CDT 250, Miri, 98009, Sarawak, Malaysia.
| | - Mingzhu Ma
- Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China
| | - Dunyi Liu
- Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China
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17
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Mundl A, Touboul M, Jackson MG, Day JMD, Kurz MD, Lekic V, Helz RT, Walker RJ. Tungsten-182 heterogeneity in modern ocean island basalts. Science 2017; 356:66-69. [PMID: 28386009 DOI: 10.1126/science.aal4179] [Citation(s) in RCA: 137] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 03/14/2017] [Indexed: 11/02/2022]
Abstract
New tungsten isotope data for modern ocean island basalts (OIB) from Hawaii, Samoa, and Iceland reveal variable 182W/184W, ranging from that of the ambient upper mantle to ratios as much as 18 parts per million lower. The tungsten isotopic data negatively correlate with 3He/4He. These data indicate that each OIB system accesses domains within Earth that formed within the first 60 million years of solar system history. Combined isotopic and chemical characteristics projected for these ancient domains indicate that they contain metal and are repositories of noble gases. We suggest that the most likely source candidates are mega-ultralow-velocity zones, which lie beneath Hawaii, Samoa, and Iceland but not beneath hot spots whose OIB yield normal 182W and homogeneously low 3He/4He.
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Affiliation(s)
- Andrea Mundl
- Department of Geology, University of Maryland, College Park, MD 20742, USA.
| | - Mathieu Touboul
- Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 7, France
| | - Matthew G Jackson
- Department of Earth Science, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - James M D Day
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA
| | - Mark D Kurz
- Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Vedran Lekic
- Department of Geology, University of Maryland, College Park, MD 20742, USA
| | | | - Richard J Walker
- Department of Geology, University of Maryland, College Park, MD 20742, USA
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18
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Marchi S, Canup RM, Walker RJ. Heterogeneous delivery of silicate and metal to the Earth by large planetesimals. NATURE GEOSCIENCE 2017; 11:77-81. [PMID: 30984285 PMCID: PMC6457465 DOI: 10.1038/s41561-017-0022-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
After the Moon's formation, Earth experienced a protracted bombardment by leftover planetesimals. The mass delivered during this stage of late accretion has been estimated to be approximately 0.5% of Earth's present mass, based on highly siderophile element concentrations in the Earth's mantle and the assumption that all highly siderophile elements delivered by impacts were retained in the mantle. However, late accretion may have involved mostly large (≥ 1,500 km in diameter)-and therefore differentiated-projectiles in which highly siderophile elements were sequestered primarily in metallic cores. Here we present smoothed-particle hydrodynamics impact simulations that show that substantial portions of a large planetesimal's core may descend to the Earth's core or escape accretion entirely. Both outcomes reduce the delivery of highly siderophile elements to the Earth's mantle and imply a late accretion mass that may be two to five times greater than previously thought. Further, we demonstrate that projectile material can be concentrated within localized domains of Earth's mantle, producing both positive and negative 182W isotopic anomalies of the order of 10 to 100 ppm. In this scenario, some isotopic anomalies observed in terrestrial rocks can be explained as products of collisions after Moon formation.
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Affiliation(s)
- S. Marchi
- Southwest Research Institute, Boulder, CO, USA
| | - R. M. Canup
- Southwest Research Institute, Boulder, CO, USA
| | - R. J. Walker
- Deptartment of Geology, University of MD, College Park, MD, USA
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19
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Bermingham K, Walker R. The ruthenium isotopic composition of the oceanic mantle. EARTH AND PLANETARY SCIENCE LETTERS 2017; 474:466-473. [PMID: 30956285 PMCID: PMC6448151 DOI: 10.1016/j.epsl.2017.06.052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The approximately chondritic relative, and comparatively high absolute m antle abundances of the highly siderophile elem ents (HSE), suggest that their concentrations in the bulk silicate Earth were primarily established during a final ~0.5 to 1% of "late accretion" to the mantle, following the cessation of core segregation. Consequently, the isotopic composition of the HSE Ru in the mantle reflects an amalgamation of the isotopic compositions of late accretionary contributions to the silicate portion of the Earth. Among cosm ochem ical materials, Ru is characterized by considerable mass-independent isotopic variability, making it a powerful genetic tracer of Earth's late accretionary building blocks. To define the Ru isotopic composition of the oceanic mantle, the largest portion of the accessible mantle, we report Ru isotopic data for materials from one Archean and seven Phanerozoic oceanic m antle domains. A sample from a continental lithospheric mantle domain is also examined. All samples have identical Ru isotopic compositions, within analytical uncertainties, indicating that Ru isotopes are well mixed in the oceanic mantle, defining a μ 100Ru value of 1.2 ± 7.2 (2SD). The only known meteorites with the same Ru isotopic composition are enstatite chondrites and, when corrected for the effects of cosmic ray exposure, mem bers of the Main Group and sLL subgroup of the lAB iron meteorite complex which have a collective CRE corrected μ 100Ru value of 0.9 ± 3.0. This suggests that materials from the region(s) of the solar nebula sampled by these m eteorites likely contributed the dominant portion of late accreted materials to Earth's mantle.
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Abstract
The short-lived Hf-W isotope system has a wide range of important applications in cosmochemistry and geochemistry. The siderophile behavior of W, combined with the lithophile nature of Hf, makes the system uniquely useful as a chronometer of planetary accretion and differentiation. Tungsten isotopic data for meteorites show that the parent bodies of some differentiated meteorites accreted within 1 million years after Solar System formation. Melting and differentiation on these bodies took ~1-3 million years and was fueled by decay of 26Al. The timescale for accretion and core formation increases with planetary mass and is ~10 million years for Mars and >34 million years for Earth. The nearly identical 182W compositions for the mantles of the Moon and Earth are difficult to explain in current models for the formation of the Moon. Terrestrial samples with ages spanning ~4 billion years reveal small 182W variations within the silicate Earth, demonstrating that traces of Earth's earliest formative period have been preserved throughout Earth's history.
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Affiliation(s)
- Thorsten Kleine
- Institut für Planetologie, University of Münster, 48149 Muenster, Germany
| | - Richard J Walker
- Department of Geology, University of Maryland, College Park, Maryland 20742
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21
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Archer GJ, Mundl A, Walker RJ, Worsham EA, Bermingham KR. High-precision analysis of 182W/ 184W and 183W/ 184W by negative thermal ionization mass spectrometry: Per-integration oxide corrections using measured 18O/ 16O. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2017; 414:80-86. [PMID: 30713466 PMCID: PMC6357970 DOI: 10.1016/j.ijms.2017.01.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Here we describe a new analytical technique for the high-precision measurement of 182W/184W and 183W/184W using negative thermal ionization mass spectrometry (N-TIMS). We improve on the recently reported method of Trinquier et al. (2016), which described using Faraday cup collectors coupled with amplifiers utilizing 1013 Ω resistors to continuously monitor the 18O/16O of WO3 - and make per-integration oxide corrections. In our study, we report and utilize a newly measured oxygen mass fractionation line, as well as average 17O/16O and 18O/16O, which allow for more accurate per-integration oxide interference corrections. We also report a Faraday cup and amplifier configuration that allows 18O/16O to be continuously monitored for WO3 - and ReO3 -, both of which are ionized during analyses of W using Re ribbon. The long-term external precision of 182W/184W is 5.7 ppm and 3.7 ppm (2SD) when mass bias corrected using 186W/184W and 186W/183W, respectively. For 183W/184W mass bias is corrected using 186W/184W, yielding a long-term external precision of 6.6 ppm. An observed, correlated variation in 182W/184W and 183W/184W, when mass bias corrected using 186W/184W, is most likely the result of Faraday cup degradation over months-long intervals.
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Affiliation(s)
| | - Andrea Mundl
- Department of Geology, University of Maryland, College Park, MD 20742, USA
| | - Richard J. Walker
- Department of Geology, University of Maryland, College Park, MD 20742, USA
| | - Emily A. Worsham
- Department of Geology, University of Maryland, College Park, MD 20742, USA
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22
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Dahl TW. Identifying remnants of early Earth. Science 2016; 352:768-9. [DOI: 10.1126/science.aaf2482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Isotope analysis reveals portions of Earth that have remained the same since accretion
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Affiliation(s)
- Tais W. Dahl
- Natural History Museum of Denmark, University of Copenhagen, DK-1350 Copenhagen K, Denmark
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23
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Rizo H, Walker RJ, Carlson RW, Horan MF, Mukhopadhyay S, Manthos V, Francis D, Jackson MG. Preservation of Earth-forming events in the tungsten isotopic composition of modern flood basalts. Science 2016; 352:809-12. [DOI: 10.1126/science.aad8563] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 04/05/2016] [Indexed: 11/02/2022]
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24
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Caracausi A, Avice G, Burnard PG, Füri E, Marty B. Chondritic xenon in the Earth’s mantle. Nature 2016; 533:82-5. [DOI: 10.1038/nature17434] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 02/08/2016] [Indexed: 11/09/2022]
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25
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26
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Bottke WF, Vokrouhlický D, Marchi S, Swindle T, Scott ERD, Weirich JR, Levison H. Dating the Moon-forming impact event with asteroidal meteorites. Science 2015; 348:321-3. [DOI: 10.1126/science.aaa0602] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- W. F. Bottke
- Southwest Research Institute and NASA Solar System Exploration Research Virtual Institute (SSERVI)–Institute for the Science of Exploration Targets (ISET), Boulder, CO, USA
| | - D. Vokrouhlický
- Institute of Astronomy, Charles University, V Holešovičkách 2, CZ-18000, Prague 8, Czech Republic
| | - S. Marchi
- Southwest Research Institute and NASA Solar System Exploration Research Virtual Institute (SSERVI)–Institute for the Science of Exploration Targets (ISET), Boulder, CO, USA
| | - T. Swindle
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- SSERVI Center for Lunar Science Exploration, Houston, TX, USA
| | - E. R. D. Scott
- Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Manoa, Honolulu, Hawai’i 96822, USA
| | - J. R. Weirich
- Department of Earth Sciences, Western University, London, ON, Canada
| | - H. Levison
- Southwest Research Institute and NASA Solar System Exploration Research Virtual Institute (SSERVI)–Institute for the Science of Exploration Targets (ISET), Boulder, CO, USA
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27
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Lunar tungsten isotopic evidence for the late veneer. Nature 2015; 520:534-7. [PMID: 25855296 DOI: 10.1038/nature14360] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 02/25/2015] [Indexed: 11/09/2022]
Abstract
According to the most widely accepted theory of lunar origin, a giant impact on the Earth led to the formation of the Moon, and also initiated the final stage of the formation of the Earth's core. Core formation should have removed the highly siderophile elements (HSE) from Earth's primitive mantle (that is, the bulk silicate Earth), yet HSE abundances are higher than expected. One explanation for this overabundance is that a 'late veneer' of primitive material was added to the bulk silicate Earth after the core formed. To test this hypothesis, tungsten isotopes are useful for two reasons: first, because the late veneer material had a different (182)W/(184)W ratio to that of the bulk silicate Earth, and second, proportionally more material was added to the Earth than to the Moon. Thus, if a late veneer did occur, the bulk silicate Earth and the Moon must have different (182)W/(184)W ratios. Moreover, the Moon-forming impact would also have created (182)W differences because the mantle and core material of the impactor with distinct (182)W/(184)W would have mixed with the proto-Earth during the giant impact. However the (182)W/(184)W of the Moon has not been determined precisely enough to identify signatures of a late veneer or the giant impact. Here, using more-precise measurement techniques, we show that the Moon exhibits a (182)W excess of 27 ± 4 parts per million over the present-day bulk silicate Earth. This excess is consistent with the expected (182)W difference resulting from a late veneer with a total mass and composition inferred from HSE systematics. Thus, our data independently show that HSE abundances in the bulk silicate Earth were established after the giant impact and core formation, as predicted by the late veneer hypothesis. But, unexpectedly, we find that before the late veneer, no (182)W anomaly existed between the bulk silicate Earth and the Moon, even though one should have arisen through the giant impact. The origin of the homogeneous (182)W of the pre-late-veneer bulk silicate Earth and the Moon is enigmatic and constitutes a challenge to current models of lunar origin.
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28
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Walker RJ. Siderophile element constraints on the origin of the Moon. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130258. [PMID: 25114313 PMCID: PMC4128271 DOI: 10.1098/rsta.2013.0258] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Discovery of small enrichments in (182)W/(184)W in some Archaean rocks, relative to modern mantle, suggests both exogeneous and endogenous modifications to highly siderophile element (HSE) and moderately siderophile element abundances in the terrestrial mantle. Collectively, these isotopic enrichments suggest the formation of chemically fractionated reservoirs in the terrestrial mantle that survived the putative Moon-forming giant impact, and also provide support for the late accretion hypothesis. The lunar mantle sources of volcanic glasses and basalts were depleted in HSEs relative to the terrestrial mantle by at least a factor of 20. The most likely explanations for the disparity between the Earth and Moon are either that the Moon received a disproportionately lower share of late accreted materials than the Earth, such as may have resulted from stochastic late accretion, or the major phase of late accretion occurred prior to the Moon-forming event, and the putative giant impact led to little drawdown of HSEs to the Earth's core. High precision determination of the (182)W isotopic composition of the Moon can help to resolve this issue.
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Affiliation(s)
- Richard J Walker
- Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD 20742, USA
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29
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Melosh HJ. New approaches to the Moon's isotopic crisis. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130168. [PMID: 25114301 PMCID: PMC4128260 DOI: 10.1098/rsta.2013.0168] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Recent comparisons of the isotopic compositions of the Earth and the Moon show that, unlike nearly every other body known in the Solar System, our satellite's isotopic ratios are nearly identical to the Earth's for nearly every isotopic system. The Moon's chemical make-up, however, differs from the Earth's in its low volatile content and perhaps in the elevated abundance of oxidized iron. This surprising situation is not readily explained by current impact models of the Moon's origin and offers a major clue to the Moon's formation, if we only could understand it properly. Current ideas to explain this similarity range from assuming an impactor with the same isotopic composition as the Earth to postulating a pure ice impactor that completely vaporized upon impact. Several recent proposals follow from the suggestion that the Earth-Moon system may have lost a great deal of angular momentum during early resonant interactions. The isotopic constraint may be the most stringent test yet for theories of the Moon's origin.
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Affiliation(s)
- H J Melosh
- Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA Aeronautical and Astronautical Engineering Departments, Purdue University, West Lafayette, IN 47907, USA
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30
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Canup RM. Lunar-forming impacts: processes and alternatives. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130175. [PMID: 25114302 PMCID: PMC4128262 DOI: 10.1098/rsta.2013.0175] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The formation of a protolunar disc by a giant impact with the early Earth is discussed, focusing on two classes of impacts: (i) canonical impacts, in which a Mars-sized impactor produces a planet-disc system whose angular momentum is comparable to that in the current Earth and Moon, and (ii) high-angular-momentum impacts, which produce a system whose angular momentum is approximately a factor of 2 larger than that in the current Earth and Moon. In (i), the disc originates primarily from impactor-derived material and thus is expected to have an initial composition distinct from that of the Earth's mantle. In (ii), a hotter, more compact initial disc is produced with a silicate composition that can be nearly identical to that of the silicate Earth. Both scenarios require subsequent processes for consistency with the current Earth and Moon: disc-planet compositional equilibration in the case of (i), or large-scale angular momentum loss during capture of the newly formed Moon into the evection resonance with the Sun in the case of (ii).
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Affiliation(s)
- R M Canup
- Southwest Research Institute, Planetary Science Directorate, 1050 Walnut St., Suite 300, Boulder, CO 80302, USA
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31
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Nagai Y, Yokoyama T. Chemical separation of Mo and W from terrestrial and extraterrestrial samples via anion exchange chromatography. Anal Chem 2014; 86:4856-63. [PMID: 24801276 DOI: 10.1021/ac404223t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new two-stage chemical separation method was established using an anion exchange resin, Eichrom 1 × 8, to separate Mo and W from four natural rock samples. First, the distribution coefficients of nine elements (Ti, Fe, Zn, Zr, Nb, Mo, Hf, Ta, and W) under various chemical conditions were determined using HCl, HNO3, and HF. On the basis of the obtained distribution coefficients, a new technique for the two-stage chemical separation of Mo and W, along with the group separation of Ti-Zr-Hf, was developed as follows: 0.4 M HCl-0.5 M HF (major elements), 9 M HCl-0.05 M HF (Ti-Zr-Hf), 9 M HCl-1 M HF (W), and 6 M HNO3-3 M HF (Mo). After the chemical procedure, Nb remaining in the W fraction was separated using 9 M HCl-3 M HF. On the other hand, Nb and Zn remaining in the Mo fraction were removed using 2 M HF and 6 M HCl-0.1 M HF. The performance of this technique was evaluated by separating these elements from two terrestrial and two extraterrestrial samples. The recovery yields for Mo, W, Zr, and Hf were nearly 100% for all of the examined samples. The total contents of the Zr, Hf, W, and Mo in the blanks used for the chemical separation procedure were 582, 9, 29, and 396 pg, respectively. Therefore, our new separation technique can be widely used in various fields of geochemistry, cosmochemistry, and environmental sciences and particularly for multi-isotope analysis of these elements from a single sample with significant internal isotope heterogeneities.
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Affiliation(s)
- Yuichiro Nagai
- Department of Earth and Planetary Sciences, Tokyo Institute of Technology , Ookayama, Tokyo 152-8551, Japan
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32
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Jacobson SA, Morbidelli A, Raymond SN, O'Brien DP, Walsh KJ, Rubie DC. Highly siderophile elements in Earth’s mantle as a clock for the Moon-forming impact. Nature 2014; 508:84-7. [DOI: 10.1038/nature13172] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 02/17/2014] [Indexed: 11/09/2022]
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Rizo H, Boyet M, Blichert-Toft J, O'Neil J, Rosing MT, Paquette JL. The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archaean rocks. Nature 2012; 491:96-100. [PMID: 23128231 DOI: 10.1038/nature11565] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Accepted: 08/30/2012] [Indexed: 11/09/2022]
Abstract
The first indisputable evidence for very early differentiation of the silicate Earth came from the extinct (146)Sm-(142)Nd chronometer. (142)Nd excesses measured in 3.7-billion-year (Gyr)-old rocks from Isua (southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean eon (about 4,570-4,000 Gyr ago). As dictated by mass balance, the differentiation event responsible for the formation of the Isua early-depleted reservoir must also have formed a complementary enriched component. However, considerable efforts to find early-enriched mantle components in Isua have so far been unsuccessful. Here we show that the signature of the Hadean enriched reservoir, complementary to the depleted reservoir in Isua, is recorded in 3.4-Gyr-old mafic dykes intruding into the Early Archaean rocks. Five out of seven dykes carry (142)Nd deficits compared to the terrestrial Nd standard, with three samples yielding resolvable deficits down to -10.6 parts per million. The enriched component that we report here could have been a mantle reservoir that differentiated owing to the crystallization of a magma ocean, or could represent a mafic proto-crust that separated from the mantle more than 4.47 Gyr ago. Our results testify to the existence of an enriched component in the Hadean, and may suggest that the southwest Greenland mantle preserved early-formed heterogeneities until at least 3.4 Gyr ago.
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Affiliation(s)
- Hanika Rizo
- Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, CNRS UMR 6524, IRD R 163, BP 10448, 63000 Clermont-Ferrand, France.
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Ćuk M, Stewart ST. Making the Moon from a fast-spinning Earth: a giant impact followed by resonant despinning. Science 2012; 338:1047-52. [PMID: 23076099 DOI: 10.1126/science.1225542] [Citation(s) in RCA: 432] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A common origin for the Moon and Earth is required by their identical isotopic composition. However, simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopic signature. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to that of the present day; however, Earth-mass planets are expected to have higher spin rates at the end of accretion. Here, we show that typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth's mantle. Furthermore, we find that a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon.
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Affiliation(s)
- Matija Ćuk
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA.
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Bennett VC. Probing the Mantle Past. Science 2012; 335:1051-2. [DOI: 10.1126/science.1219126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Precision isotope analysis can reveal details of the dynamic processes involved in the formation of Earth's mantle.
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Affiliation(s)
- Vickie C. Bennett
- Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
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