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Louis-Jean J, Inglis JD, Hanson S, Pollington A, Meininger D, Reilly S, Steiner R. New loading method for high precision Sm isotope analysis of nuclear materials using thermal ionization mass spectrometry. J Radioanal Nucl Chem 2021. [DOI: 10.1007/s10967-020-07513-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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2
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Ku Y, Jacobsen SB. Potassium isotope anomalies in meteorites inherited from the protosolar molecular cloud. SCIENCE ADVANCES 2020; 6:eabd0511. [PMID: 33036981 PMCID: PMC7546711 DOI: 10.1126/sciadv.abd0511] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 08/19/2020] [Indexed: 05/31/2023]
Abstract
Potassium (K) and other moderately volatile elements are depleted in many solar system bodies relative to CI chondrites, which closely match the composition of the Sun. These depletions and associated isotopic fractionations were initially believed to result from thermal processing in the protoplanetary disk, but so far, no correlation between the K depletion and its isotopic composition has been found. Our new high-precision K isotope data correlate with other neutron-rich nuclides (e.g., 64Ni and 54Cr) and suggest that the observed 41K variations have a nucleosynthetic origin. We propose that K isotope anomalies are inherited from an isotopically heterogeneous protosolar molecular cloud, and were preserved in bulk primitive meteorites. Thus, the heterogeneous distribution of both refractory and moderately volatile elements in chondritic meteorites points to a limited radial mixing in the protoplanetary disk.
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Affiliation(s)
- Y Ku
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA.
| | - S B Jacobsen
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA
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Marks NE, Borg LE, Shearer CK, Cassata WS. Geochronology of an Apollo 16 Clast Provides Evidence for a Basin-Forming Impact 4.3 Billion Years Ago. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2019; 124:2465-2481. [PMID: 31894195 PMCID: PMC6919926 DOI: 10.1029/2019je005966] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 07/23/2019] [Accepted: 08/15/2019] [Indexed: 06/10/2023]
Abstract
We examined lithic breccias from the Apollo sample collection in order to identify ferroan anorthosite samples suitable for geochronology, and better define the age relationships between rocks of the lunar highlands. Clast 3A is a previously unstudied noritic anorthosite from Apollo 16 lithic breccia 60016 with textural evidence of slow subsolidus recrystallization. We estimate a cooling rate of ~10 °C/Myr and calculate a pyroxene solvus temperature of 1,100-1,000 °C. Pyroxene exsolution lamellae (1-3 μm) indicate that the last stage of cooling was rapid at ~0.2 °C/year, typical of rates observed in thick ejecta blankets. We calculate concordant ages from the 147Sm-143Nd, 146Sm-142Nd, Rb-Sr, and Ar-Ar isotopic systems of 4,302 ± 28, 4,296 + 39/-53, 4,275 ± 38, and 4,311 ± 31 Ma, respectively, with a weighted average of 4,304 ± 12 Ma. The closure temperature of the Sm-Nd system is ~855 ± 14 °C, whereas the closure temperature of the Ar-Ar system is 275 ± 25 °C. Cooling from 855 to 275 °C at 10 °C/Myr should result in an age difference between the two isotopic systems of ~60 Myr. The concordant Sm-Nd, Rb-Sr, and Ar-Ar ages imply that they record the time the rock was excavated by a large impact from the midcrust. The ages clearly predate various late accretion scenarios in which an uptick in impacts at 3.8 Ga is preceded by a period of relative quiescence between 4.4 and ~4.1 Ga, and instead are consistent with decreasing accretion rates following the formation of the Moon.
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Affiliation(s)
- N. E. Marks
- Nuclear and Chemical Sciences DivisionLawrence Livermore National LaboratoryLivermoreCAUSA
| | - L. E. Borg
- Nuclear and Chemical Sciences DivisionLawrence Livermore National LaboratoryLivermoreCAUSA
| | - C. K. Shearer
- Institute of MeteoriticsUniversity of New MexicoAlbuquerqueNMUSA
| | - W. S. Cassata
- Nuclear and Chemical Sciences DivisionLawrence Livermore National LaboratoryLivermoreCAUSA
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Holden NE, Coplen TB, Böhlke JK, Tarbox LV, Benefield J, de Laeter JR, Mahaffy PG, O’Connor G, Roth E, Tepper DH, Walczyk T, Wieser ME, Yoneda S. IUPAC Periodic Table of the Elements and Isotopes (IPTEI) for the Education Community (IUPAC Technical Report). PURE APPL CHEM 2018. [DOI: 10.1515/pac-2015-0703] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Abstract
The IUPAC (International Union of Pure and Applied Chemistry) Periodic Table of the Elements and Isotopes (IPTEI) was created to familiarize students, teachers, and non-professionals with the existence and importance of isotopes of the chemical elements. The IPTEI is modeled on the familiar Periodic Table of the Chemical Elements. The IPTEI is intended to hang on the walls of chemistry laboratories and classrooms. Each cell of the IPTEI provides the chemical name, symbol, atomic number, and standard atomic weight of an element. Color-coded pie charts in each element cell display the stable isotopes and the relatively long-lived radioactive isotopes having characteristic terrestrial isotopic compositions that determine the standard atomic weight of each element. The background color scheme of cells categorizes the 118 elements into four groups: (1) white indicates the element has no standard atomic weight, (2) blue indicates the element has only one isotope that is used to determine its standard atomic weight, which is given as a single value with an uncertainty, (3) yellow indicates the element has two or more isotopes that are used to determine its standard atomic weight, which is given as a single value with an uncertainty, and (4) pink indicates the element has a well-documented variation in its atomic weight, and the standard atomic weight is expressed as an interval. An element-by-element review accompanies the IPTEI and includes a chart of all known stable and radioactive isotopes for each element. Practical applications of isotopic measurements and technologies are included for the following fields: forensic science, geochronology, Earth-system sciences, environmental science, and human health sciences, including medical diagnosis and treatment.
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Affiliation(s)
- Norman E. Holden
- National Nuclear Data Center, Brookhaven National Laboratory , Upton, NY , USA
| | | | | | | | | | | | | | | | - Etienne Roth
- Commissariat à l’énergie atomique (CEA) , Gif-sur-Yvette, France
| | | | - Thomas Walczyk
- Department of Chemistry , National University of Singapore , Singapore , Singapore
| | - Michael E. Wieser
- Department of Physics and Astronomy , University of Calgary , Calgary , Canada
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5
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Primitive Solar System materials and Earth share a common initial (142)Nd abundance. Nature 2016; 537:399-402. [PMID: 27629644 DOI: 10.1038/nature19351] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 08/04/2016] [Indexed: 11/08/2022]
Abstract
The early evolution of planetesimals and planets can be constrained using variations in the abundance of neodymium-142 ((142)Nd), which arise from the initial distribution of (142)Nd within the protoplanetary disk and the radioactive decay of the short-lived samarium-146 isotope ((146)Sm). The apparent offset in (142)Nd abundance found previously between chondritic meteorites and Earth has been interpreted either as a possible consequence of nucleosynthetic variations within the protoplanetary disk or as a function of the differentiation of Earth very early in its history. Here we report high-precision Sm and Nd stable and radiogenic isotopic compositions of four calcium-aluminium-rich refractory inclusions (CAIs) from three CV-type carbonaceous chondrites, and of three whole-rock samples of unequilibrated enstatite chondrites. The CAIs, which are the first solids formed by condensation from the nebular gas, provide the best constraints for the isotopic evolution of the early Solar System. Using the mineral isochron method for individual CAIs, we find that CAIs without isotopic anomalies in Nd compared to the terrestrial composition share a (146)Sm/(144)Sm-(142)Nd/(144)Nd isotopic evolution with Earth. The average (142)Nd/(144)Nd composition for pristine enstatite chondrites that we calculate coincides with that of the accessible silicate layers of Earth. This relationship between CAIs, enstatite chondrites and Earth can only be a result of Earth having inherited the same initial abundance of (142)Nd and chondritic proportions of Sm and Nd. Consequently, (142)Nd isotopic heterogeneities found in other CAIs and among chondrite groups may arise from extrasolar grains that were present in the disk and incorporated in different proportions into these planetary objects. Our finding supports a chondritic Sm/Nd ratio for the bulk silicate Earth and, as a consequence, chondritic abundances for other refractory elements. It also removes the need for a hidden reservoir or for collisional erosion scenarios to explain the (142)Nd/(144)Nd composition of Earth.
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Day JM, Walker RJ. Highly siderophile element depletion in the Moon. EARTH AND PLANETARY SCIENCE LETTERS 2015; 423:114-124. [PMID: 34465923 PMCID: PMC8404368 DOI: 10.1016/j.epsl.2015.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Coupled 187Os/188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance data are reported for Apollo 12 (12005, 12009, 12019, 12022, 12038, 12039, 12040), Apollo 15 (15555) and Apollo 17 (70135) mare basalts, along with mare basalt meteorites La Paz icefield (LAP) 04841 and Miller Range (MIL) 05035. The most magnesian samples have chondrite-relative HSE abundances and chondritic measured and calculated initial 187Os/188Os, with mare basalts having consistently low HSE abundances at ~2 ×10-5 to 2 ×10-7 the chondritic abundance. The lower and more fractionated HSE compositions of evolved mare basalts can be reproduced with bulk-partition coefficients of ~2 for Os, Ir, Ru, Pt and Pd and ~1.5 for Re. Lunar mare basalt bulk-partition coefficients are probably higher than for terrestrial melts as a result of more reducing conditions, leading to increased HSE compatibility. The chondritic-relative abundances and chondritic 187Os/188Os of the most primitive high-MgO mare basalts cannot be explained through regolith contamination during emplacement at the lunar surface. Instead, mare basalt compositions can be modelled as representing ~5-11% partial melting of metal-free sources with low Os, Ir, Ru, Pd (~0.1 ng g-1), Pt (~0.2 ng g-1) Re (~0.01 ng g-1) and S, with sulphide-melt partitioning between 1000 and 10000. Apollo 12 olivine-, pigeonite- and ilmenite normative mare basalts define an imprecise 187Re-187Os age of 3.0 ±0.6 Ga. This age is within uncertainty of 147Sm-143Nd ages for the same samples and the isochron yields an initial 187Os/188Os of 0.109 ±0.008. The Os isotopic composition of the Apollo 12 source indicates that the lunar mantle source of these rocks evolved with Re/Os within ~10% of chondrite meteorites from the time that the mantle source became a system closed to siderophile additions to the time that the basalts erupted. The similarity in absolute HSE abundances between mare basalts from the Apollo 12, 15 and 17 sites, and from unknown regions of the Moon (La Paz mare basalts, MIL 05035) indicates relatively homogeneous and low HSE abundances within the lunar interior. Low absolute HSE abundances and chondritic Re/Os of mare basalts are consistent with ~0.02% late accretion addition that was added prior to the formation of the lunar crust and significantly prior to cessation of lunar mantle differentiation (>4.4 Ga) to enable efficient mixing and homogenization. The HSE abundances are also consistent with the observed, small 182W excess (20 ppm) in the bulk silicate Moon relative to the bulk silicate Earth.
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Affiliation(s)
- James M.D. Day
- Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093-0244, USA
| | - Richard J. Walker
- Department of Geology, University of Maryland, College Park, MD 20742, USA
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7
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Carlson RW, Borg LE, Gaffney AM, Boyet M. Rb-Sr, Sm-Nd and Lu-Hf isotope systematics of the lunar Mg-suite: the age of the lunar crust and its relation to the time of Moon formation. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130246. [PMID: 25114305 PMCID: PMC4128267 DOI: 10.1098/rsta.2013.0246] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
New Rb-Sr, (146,147)Sm-(142,143)Nd and Lu-Hf isotopic analyses of Mg-suite lunar crustal rocks 67667, 76335, 77215 and 78238, including an internal isochron for norite 77215, were undertaken to better define the time and duration of lunar crust formation and the history of the source materials of the Mg-suite. Isochron ages determined in this study for 77215 are: Rb-Sr=4450±270 Ma, (147)Sm-(143)Nd=4283±23 Ma and Lu-Hf=4421±68 Ma. The data define an initial (146)Sm/(144)Sm ratio of 0.00193±0.00092 corresponding to ages between 4348 and 4413 Ma depending on the half-life and initial abundance used for (146)Sm. The initial Nd and Hf isotopic compositions of all samples indicate a source region with slight enrichment in the incompatible elements in accord with previous suggestions that the Mg-suite crustal rocks contain a component of KREEP. The Sm/Nd-(142)Nd/(144)Nd correlation shown by both ferroan anorthosite and Mg-suite rocks is coincident with the trend defined by mare and KREEP basalts, the slope of which corresponds to ages between 4.35 and 4.45 Ga. These data, along with similar ages for various early Earth differentiation events, are in accord with the model of lunar formation via giant impact into Earth at ca 4.4 Ga.
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Affiliation(s)
- Richard W Carlson
- Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington DC 20015, USA
| | - Lars E Borg
- Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA 94550, USA
| | - Amy M Gaffney
- Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA 94550, USA
| | - Maud Boyet
- Laboratoire Magmas et Volcans, Universite Blaise Pascal, CNRS UMR 6524, 5 Rue Kessler, Clermont-Ferrand 63038, France
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8
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Borg LE, Connelly JN, Boyet M, Carlson RW. Chronological evidence that the Moon is either young or did not have a global magma ocean. Nature 2011; 477:70-2. [DOI: 10.1038/nature10328] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 06/20/2011] [Indexed: 11/09/2022]
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146Sm-142Nd systematics measured in enstatite chondrites reveals a heterogeneous distribution of 142Nd in the solar nebula. Proc Natl Acad Sci U S A 2011; 108:7693-7. [PMID: 21515828 DOI: 10.1073/pnas.1017332108] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The short-lived (146)Sm-(142)Nd chronometer (T(1/2) = 103 Ma) is used to constrain the early silicate evolution of planetary bodies. The composition of bulk terrestrial planets is then considered to be similar to that of primitive chondrites that represent the building blocks of rocky planets. However for many elements chondrites preserve small isotope differences. In this case it is not always clear to what extent these variations reflect the isotope heterogeneity of the protosolar nebula rather than being produced by the decay of parent isotopes. Here we present Sm-Nd isotopes data measured in a comprehensive suite of enstatite chondrites (EC). The EC preserve (142)Nd/(144)Nd ratios that range from those of ordinary chondrites to values similar to terrestrial samples. The EC having terrestrial (142)Nd/(144)Nd ratios are also characterized by small (144)Sm excesses, which is a pure p-process nuclide. The correlation between (144)Sm and (142)Nd for chondrites may indicate a heterogeneous distribution in the solar nebula of p-process matter synthesized in supernovae. However to explain the difference in (142)Nd/(144)Nd ratios, 20% of the p-process contribution to (142)Nd is required, at odds with the value of 4% currently proposed in stellar models. This study highlights the necessity of obtaining high-precision (144)Sm measurements to interpret properly measured (142)Nd signatures. Another explanation could be that the chondrites sample material formed in different pulses of the lifetime of asymptotic giant branch stars. Then the isotope signature measured in SiC presolar would not represent the unique s-process signature of the material present in the solar nebula during accretion.
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10
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(142)Nd evidence for an enriched Hadean reservoir in cratonic roots. Nature 2009; 459:1118-21. [PMID: 19553997 DOI: 10.1038/nature08089] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 04/23/2009] [Indexed: 11/08/2022]
Abstract
The isotope (146)Sm undergoes alpha-decay to (142)Nd, with a half-life of 103 million years. Measurable variations in the (142)Nd/(144)Nd values of rocks resulting from Sm-Nd fractionation could therefore only have been produced within about 400 million years of the Solar System's formation (that is, when (146)Sm was extant). The (142)Nd/(144)Nd compositions of terrestrial rocks are accordingly a sensitive monitor of the main silicate differentiation events that took place in the early Earth. High (142)Nd/(144)Nd values measured in some Archaean rocks from Greenland hint at the existence of an early incompatible-element-depleted mantle. Here we present measurements of low (142)Nd/(144)Nd values in 1.48-gigayear-(Gyr)-old lithospheric mantle-derived alkaline rocks from the Khariar nepheline syenite complex in southeastern India. These data suggest that a reservoir that was relatively enriched in incompatible elements formed at least 4.2 Gyr ago and traces of its isotopic signature persisted within the lithospheric root of the Bastar craton until at least 1.48 Gyr ago. These low (142)Nd/(144)Nd compositions may represent a diluted signature of a Hadean (4 to 4.57 Gyr ago) enriched reservoir that is characterized by even lower values. That no evidence of the early depleted mantle has been observed in rocks younger than 3.6 Gyr (refs 3, 4, 7) implies that such domains had effectively mixed back into the convecting mantle by then. In contrast, some early enriched components apparently escaped this fate. Thus, the mantle sampled by magmatism since 3.6 Gyr ago may be biased towards a depleted composition that would be balanced by relatively more enriched reservoirs that are 'hidden' in Hadean crust, the D'' layer of the lowermost mantle or, as we propose here, also within the roots of old cratons.
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11
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Bourdon B, Touboul M, Caro G, Kleine T. Early differentiation of the Earth and the Moon. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:4105-4128. [PMID: 18826925 DOI: 10.1098/rsta.2008.0125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We examine the implications of new 182W and 142Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of 182W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60Ma after the formation of calcium-aluminium-rich inclusions (4.568Gyr). This is not inconsistent with the apparent U-Pb age of the Earth. The new 142Nd data for Martian meteorites show that Mars probably has a super-chondritic Sm/Nd that could coincide with that of the Earth and the Moon. If this is interpreted by an early mantle differentiation event, this requires a buried enriched reservoir for the three objects. This is highly unlikely. For the Earth, we show, based on new mass-balance calculations for Nd isotopes, that the presence of a hidden reservoir is difficult to reconcile with the combined 142Nd-143Nd systematics of the Earth's mantle. We argue that a likely possibility is that the missing component was lost during or prior to accretion. Furthermore, the 142Nd data for the Moon that were used to argue for the solidification of the magma ocean at ca 200Myr are reinterpreted. Cumulate overturn, magma mixing and melting following lunar magma ocean crystallization at 50-100Myr could have yielded the 200Myr model age.
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Affiliation(s)
- Bernard Bourdon
- Institute of Isotope Geochemistry and Mineral Resources, ETH Zurich, Clausiusstrasse 25, Zurich 8092, Switzerland.
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12
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Carlson RW, Boyet M. Composition of the Earth's interior: the importance of early events. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:4077-4103. [PMID: 18826922 DOI: 10.1098/rsta.2008.0166] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The detection of excess 142Nd caused by the decay of 103Ma half-life 146Sm in all terrestrial rocks compared with chondrites shows that the chondrite analogue compositional model cannot be strictly correct, at least for the accessible portion of the Earth. Both the continental crust (CC) and the mantle source of mid-ocean ridge basalts (MORB) originate from the material characterized by superchondritic 142Nd/144Nd. Thus, the mass balance of CC plus mantle depleted by crust extraction (the MORB-source mantle) does not sum back to chondritic compositions, but instead to a composition with Sm/Nd ratio sufficiently high to explain the superchondritic 142Nd/144Nd. This requires that the mass of mantle depleted by CC extraction expand to 75-100 per cent of the mantle depending on the composition assumed for average CC. If the bulk silicate Earth has chondritic relative abundances of the refractory lithophile elements, then there must exist within the Earth's interior an incompatible-element-enriched reservoir that contains roughly 40 per cent of the Earth's 40Ar and heat-producing radioactive elements. The existence of this enriched reservoir is demonstrated by time-varying 142Nd/144Nd in Archaean crustal rocks. Calculations of the mass of the enriched reservoir along with seismically determined properties of the D'' layer at the base of the mantle allow the speculation that this enriched reservoir formed by the sinking of dense melts deep in a terrestrial magma ocean. The enriched reservoir may now be confined to the base of the mantle owing to a combination of compositionally induced high density and low viscosity, both of which allow only minimal entrainment into the overlying convecting mantle.
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Affiliation(s)
- Richard W Carlson
- Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.
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13
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Caro G, Bourdon B, Halliday AN, Quitté G. Super-chondritic Sm/Nd ratios in Mars, the Earth and the Moon. Nature 2008; 452:336-9. [DOI: 10.1038/nature06760] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Accepted: 01/18/2008] [Indexed: 11/09/2022]
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14
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Late formation and prolonged differentiation of the Moon inferred from W isotopes in lunar metals. Nature 2008; 450:1206-9. [PMID: 18097403 DOI: 10.1038/nature06428] [Citation(s) in RCA: 352] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 10/24/2007] [Indexed: 11/08/2022]
Abstract
The Moon is thought to have formed from debris ejected by a giant impact with the early 'proto'-Earth and, as a result of the high energies involved, the Moon would have melted to form a magma ocean. The timescales for formation and solidification of the Moon can be quantified by using 182Hf-182W and 146Sm-142Nd chronometry, but these methods have yielded contradicting results. In earlier studies, 182W anomalies in lunar rocks were attributed to decay of 182Hf within the lunar mantle and were used to infer that the Moon solidified within the first approximately 60 million years of the Solar System. However, the dominant 182W component in most lunar rocks reflects cosmogenic production mainly by neutron capture of 181Ta during cosmic-ray exposure of the lunar surface, compromising a reliable interpretation in terms of 182Hf-182W chronometry. Here we present tungsten isotope data for lunar metals that do not contain any measurable Ta-derived 182W. All metals have identical 182W/184W ratios, indicating that the lunar magma ocean did not crystallize within the first approximately 60 Myr of the Solar System, which is no longer inconsistent with Sm-Nd chronometry. Our new data reveal that the lunar and terrestrial mantles have identical 182W/184W. This, in conjunction with 147Sm-143Nd ages for the oldest lunar rocks, constrains the age of the Moon and Earth to Myr after formation of the Solar System. The identical 182W/184W ratios of the lunar and terrestrial mantles require either that the Moon is derived mainly from terrestrial material or that tungsten isotopes in the Moon and Earth's mantle equilibrated in the aftermath of the giant impact, as has been proposed to account for identical oxygen isotope compositions of the Earth and Moon.
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15
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Bennett VC, Brandon AD, Nutman AP. Coupled 142Nd-143Nd isotopic evidence for Hadean mantle dynamics. Science 2008; 318:1907-10. [PMID: 18096803 DOI: 10.1126/science.1145928] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The oldest rocks-3.85 billion years old-from southwest Greenland have coupled neodymium-142 excesses (from decay of now-extinct samarium-146; half-life, 103 million years) and neodymium-143 excesses (from decay of samarium-147; half-life, 106 billion years), relative to chondritic meteorites, that directly date the formation of chemically distinct silicate reservoirs in the first 30 million to 75 million years of Earth history. The differences in 142Nd signatures of coeval rocks from the two most extensive crustal relicts more than 3.6 billion years old, in Western Australia and southwest Greenland, reveal early-formed large-scale chemical heterogeneities in Earth's mantle that persisted for at least the first billion years of Earth history. Temporal variations in 142Nd signatures track the subsequent incomplete remixing of very-early-formed mantle chemical domains.
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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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16
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17
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Carlson RW, Boyet M, Horan M. Chondrite barium, neodymium, and samarium isotopic heterogeneity and early Earth differentiation. Science 2007; 316:1175-8. [PMID: 17525335 DOI: 10.1126/science.1140189] [Citation(s) in RCA: 188] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Isotopic variability in barium, neodymium, and samarium in carbonaceous chondrites reflects the distinct stellar nucleosynthetic contributions to the early solar system. We used 148Nd/144Nd to correct for the observed s-process deficiency, which produced a chondrite 146Sm-142Nd isochron consistent with previous estimates of the initial solar system abundance of 146Sm and a 142Nd/144Nd at average chondrite Sm/Nd ratio that is lower than that measured in terrestrial rocks by 21 +/- 3 parts per million. This result strengthens the conclusion that the deficiency in 142Nd in chondrites relative to terrestrial rocks reflects 146Sm decayand earlyplanetary differentiation processes.
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Affiliation(s)
- Richard W Carlson
- Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015, USA.
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18
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Lipschutz ME, Wolf SF, Culp FB, Kent AJR. Geochemical and Cosmochemical Materials. Anal Chem 2007; 79:4249-74. [PMID: 17477509 DOI: 10.1021/ac070648v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Michael E Lipschutz
- Department of Chemistry, Wetherill Laboratory, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2038, USA.
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19
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Ranen MC, Jacobsen SB. Barium Isotopes in Chondritic Meteorites: Implications for Planetary Reservoir Models. Science 2006; 314:809-12. [PMID: 17023611 DOI: 10.1126/science.1132595] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
High-precision barium isotope measurements yielded differences of up to 25 parts per million in the 137Ba/136Ba ratio and 60 parts per million in the 138Ba/136Ba ratio between chondrites and Earth. These differences probably arose from incomplete mixing of nucleosynthetic material in the solar nebula. Chondritic meteorites have a slight excess of supernova-derived material as compared to Earth, demonstrating that the solar nebula was not perfectly homogenized upon formation.
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Affiliation(s)
- Michael C Ranen
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA.
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Andreasen R, Sharma M. Solar nebula heterogeneity in p-process samarium and neodymium isotopes. Science 2006; 314:806-9. [PMID: 17023612 DOI: 10.1126/science.1131708] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Bulk carbonaceous chondrites display a deficit of approximately 100 parts per million (ppm) in 144Sm with respect to other meteorites and terrestrial standards, leading to a decrease in their 142Nd/144Nd ratios by approximately 11 ppm. The data require that samarium and neodymium isotopes produced by the p process associated with photodisintegration reactions in supernovae were heterogeneously distributed in the solar nebula. Other samarium and neodymium isotopes produced by rapid neutron capture (r process) in supernovae and by slow neutron capture (s process) in red giants were homogeneously distributed. The supernovae sources supplying the p- and r-process nuclides to the solar nebula were thus disconnected or only weakly connected.
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Affiliation(s)
- Rasmus Andreasen
- Radiogenic Isotope Geochemistry Laboratory, Department of Earth Sciences, Dartmouth College, 6105 Sherman Fairchild Hall, Hanover, NH 03755, USA
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