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Torrano ZA, Schrader DL, Davidson J, Greenwood RC, Dunlap DR, Wadhwa M. The relationship between CM and CO chondrites: Insights from combined analyses of titanium, chromium, and oxygen isotopes in CM, CO, and ungrouped chondrites. GEOCHIMICA ET COSMOCHIMICA ACTA 2021; 301:70-90. [PMID: 34316079 PMCID: PMC8312627 DOI: 10.1016/j.gca.2021.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A close relationship between CM and CO chondrites has been suggested by previous petrologic and isotopic studies, leading to the suggestion that they may originate from similar precursor materials or even a common parent body. In this study, we evaluate the genetic relationship between CM and CO chondrites using Ti, Cr, and O isotopes. We first provide additional constraints on the ranges of ε50Ti and ε54Cr values of bulk CM and CO chondrites by reporting the isotopic compositions of CM2 chondrites Murchison, Murray, and Aguas Zarcas and the CO3.8 chondrite Isna. We then report the ε50Ti and ε54Cr values for several ungrouped and anomalous carbonaceous chondrites that have been previously reported to exhibit similarities to the CM and/or CO chondrite groups, including Elephant Moraine (EET) 83226, EET 83355, Grosvenor Mountains (GRO) 95566, MacAlpine Hills (MAC) 87300, MAC 87301, MAC 88107, and Northwest Africa (NWA) 5958, and the O-isotope compositions of a subset of these samples. We additionally report the Ti, Cr, and O isotopic compositions of additional ungrouped chondrites LaPaz Ice Field (LAP) 04757, LAP 04773, Lewis Cliff (LEW) 85332, and Coolidge to assess their potential relationships with known carbonaceous and ordinary chondrite groups. LAP 04757 and LAP 04773 exhibit isotopic compositions indicating they are low-FeO ordinary chondrites. The isotopic compositions of Murchison, Murray, Aguas Zarcas, and Isna extend the compositional ranges defined by the CM and CO chondrites in ε50Ti versus ε54Cr space. The majority of the ungrouped carbonaceous chondrites with documented similarities to the CM and/or CO chondrites plot outside the CM and CO group fields in plots of ε50Ti versus ε54Cr, Δ17O versus ε50Ti, and Δ17O versus ε54Cr. Therefore, based on differences in their Ti, Cr, and O isotopic compositions, we conclude that the CM, CO, and ungrouped carbonaceous chondrites likely represent samples of multiple distinct parent bodies. We also infer that these parent bodies formed from precursor materials that shared similar isotopic compositions, which may indicate formation in regions of the protoplanetary disk that were in close proximity to each other.
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Affiliation(s)
- Zachary A. Torrano
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
| | - Devin L. Schrader
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
- Center for Meteorite Studies, Arizona State University, Tempe, AZ 85287, USA
| | - Jemma Davidson
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
- Center for Meteorite Studies, Arizona State University, Tempe, AZ 85287, USA
| | - Richard C. Greenwood
- Planetary and Space Sciences, School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom
| | - Daniel R. Dunlap
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
| | - Meenakshi Wadhwa
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
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Hazen RM, Morrison SM, Prabhu A. An evolutionary system of mineralogy. Part III: Primary chondrule mineralogy (4566 to 4561 Ma). THE AMERICAN MINERALOGIST 2021; 106:325-350. [PMID: 33867542 PMCID: PMC8051150 DOI: 10.2138/am-2020-7564] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Information-rich attributes of minerals reveal their physical, chemical, and biological modes of origin in the context of planetary evolution, and thus they provide the basis for an evolutionary system of mineralogy. Part III of this system considers the formation of 43 different primary crystalline and amorphous phases in chondrules, which are diverse igneous droplets that formed in environments with high dust/gas ratios during an interval of planetesimal accretion and differentiation between 4566 and 4561 Ma. Chondrule mineralogy is complex, with several generations of initial droplet formation via various proposed heating mechanisms, followed in many instances by multiple episodes of reheating and partial melting. Primary chondrule mineralogy thus reflects a dynamic stage of mineral evolution, when the diversity and distribution of natural condensed solids expanded significantly.
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Affiliation(s)
- Robert M. Hazen
- Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U.S.A
| | - Shaunna M. Morrison
- Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U.S.A
| | - Anirudh Prabhu
- Tetherless World Constellation, Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180, U.S.A
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Brennecka GA, Burkhardt C, Budde G, Kruijer TS, Nimmo F, Kleine T. Astronomical context of Solar System formation from molybdenum isotopes in meteorite inclusions. Science 2020; 370:837-840. [PMID: 33184211 DOI: 10.1126/science.aaz8482] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 09/16/2020] [Indexed: 11/02/2022]
Abstract
Calcium-aluminum-rich inclusions (CAIs) in meteorites are the first solids to have formed in the Solar System, defining the epoch of its birth on an absolute time scale. This provides a link between astronomical observations of star formation and cosmochemical studies of Solar System formation. We show that the distinct molybdenum isotopic compositions of CAIs cover almost the entire compositional range of material that formed in the protoplanetary disk. We propose that CAIs formed while the Sun was in transition from the protostellar to pre-main sequence (T Tauri) phase of star formation, placing Solar System formation within an astronomical context. Our results imply that the bulk of the material that formed the Sun and Solar System accreted within the CAI-forming epoch, which lasted less than 200,000 years.
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Affiliation(s)
- Gregory A Brennecka
- Lawrence Livermore National Laboratory, Livermore, CA, USA. .,Institut für Planetologie, University of Münster, Münster, Germany
| | | | - Gerrit Budde
- Institut für Planetologie, University of Münster, Münster, Germany.,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Thomas S Kruijer
- Lawrence Livermore National Laboratory, Livermore, CA, USA.,Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
| | - Francis Nimmo
- Department of Earth & Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Thorsten Kleine
- Institut für Planetologie, University of Münster, Münster, Germany
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Edwards GH, Blackburn T. Accretion of a large LL parent planetesimal from a recently formed chondrule population. SCIENCE ADVANCES 2020; 6:eaay8641. [PMID: 32494606 PMCID: PMC7159928 DOI: 10.1126/sciadv.aay8641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 01/22/2020] [Indexed: 06/11/2023]
Abstract
Chondritic meteorites, derived from asteroidal parent bodies and composed of millimeter-sized chondrules, record the early stages of planetary assembly. Yet, the initial planetesimal size distribution and the duration of delay, if any, between chondrule formation and chondrite parent body accretion remain disputed. We use Pb-phosphate thermochronology with planetesimal-scale thermal models to constrain the minimum size of the LL ordinary chondrite parent body and its initial allotment of heat-producing 26Al. Bulk phosphate 207Pb/206Pb dates of LL chondrites record a total duration of cooling ≥75 Ma, with an isothermal interior that cools over ≥30 Ma. Since the duration of conductive cooling scales with parent body size, these data require a ≥150-km radius parent body and a range of bulk initial 26Al/27Al consistent with the initial 26Al/27Al ratios of constituent LL chondrules. The concordance suggests that rapid accretion of a large LL parent asteroid occurred shortly after a major chondrule-forming episode.
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Abstract
An impasse exists between chemical and astrophysical models that explore the accretion of the Solar System’s building blocks, the chondrites. To resolve this issue means to gain an understanding of the dimensions of mass transport in the early Solar System and, hence, a crucial insight into the volatile inventory of the terrestrial planets. Here, we use element volatility patterns of chondrules and their dust rims to show that these main constituents of chondrites are not complementary to each other and did not form in the same chemical reservoirs. We propose a unifying chondrule and matrix accretion model that necessitates significant mass transport in the protoplanetary disk and an inward flux of volatile-rich CI-like (Ivuna-type carbonaceous chondrite) dust. The so far unique role of our Solar System in the universe regarding its capacity for life raises fundamental questions about its formation history relative to exoplanetary systems. Central in this research is the accretion of asteroids and planets from a gas-rich circumstellar disk and the final distribution of their mass around the Sun. The key building blocks of the planets may be represented by chondrules, the main constituents of chondritic meteorites, which in turn are primitive fragments of planetary bodies. Chondrule formation mechanisms, as well as their subsequent storage and transport in the disk, are still poorly understood, and their origin and evolution can be probed through their link (i.e., complementary or noncomplementary) to fine-grained dust (matrix) that accreted together with chondrules. Here, we investigate the apparent chondrule–matrix complementarity by analyzing major, minor, and trace element compositions of chondrules and matrix in altered and relatively unaltered CV, CM, and CR (Vigarano-type, Mighei-type, and Renazzo-type) chondrites. We show that matrices of the most unaltered CM and CV chondrites are overall CI-like (Ivuna-type) (similar to solar composition) and do not reflect any volatile enrichment or elemental patterns complementary to chondrules, the exception being their Fe/Mg ratios. We propose to unify these contradictory data by invoking a chondrule formation model in which CI-like dust accreted to so-called armored chondrules, which are ubiquitous in many chondrites. Metal rims expelled during chondrule formation, but still attached to their host chondrule, interacted with the accreted matrix, thereby enriching the matrix in siderophile elements and generating an apparent complementarity.
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Tenner TJ, Nakashima D, Ushikubo T, Tomioka N, Kimura M, Weisberg MK, Kita NT. Extended chondrule formation intervals in distinct physicochemical environments: Evidence from Al-Mg isotope systematics of CR chondrite chondrules with unaltered plagioclase. GEOCHIMICA ET COSMOCHIMICA ACTA 2019; 260:133-160. [PMID: 32255837 PMCID: PMC7121246 DOI: 10.1016/j.gca.2019.06.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Al-Mg isotope systematics of twelve FeO-poor (type I) chondrules from CR chondrites Queen Alexandra Range 99177 and Meteorite Hills 00426 were investigated by secondary ion mass spectrometry (SIMS). Five chondrules with Mg#'s of 99.0 to 99.2 and Δ17O of -4.2‰ to -5.3‰ have resolvable excess 26Mg. Their inferred (26Al/27Al)0 values range from (3.5 ± 1.3) × 10‒6 to (6.0 ± 3.9) × 10‒6. This corresponds to formation times of 2.2 (-0.5/+1.1) Myr to 2.8 (‒0.3/+0.5) Myr after CAIs, using a canonical (26Al/27Al)0 of 5.23 × 10-5, and assuming homogeneously distributed 26Al that yielded a uniform initial 26Al/27Al in the Solar System. Seven chondrules lack resolvable excess 26Mg. They have lower Mg#'s (94.2 to 98.7) and generally higher Δ17O (-0.9‰ to -4.9‰) than chondrules with resolvable excess 26Mg. Their inferred (26Al/27Al)0 upper limits range from 1.3 × 10‒6 to 3.2 × 10‒6, corresponding to formation >2.9 to >3.7 Myr after CAIs. Al-Mg isochrons depend critically on chondrule plagioclase, and several characteristics indicate the chondrule plagioclase is unaltered: (1) SIMS 27Al/24Mg depth profile patterns match those from anorthite standards, and SEM/EDS of chondrule SIMS pits show no foreign inclusions; (2) transmission electron microscopy (TEM) reveals no nanometer-scale micro-inclusions and no alteration due to thermal metamorphism; (3) oxygen isotopes of chondrule plagioclase match those of coexisting olivine and pyroxene, indicating a low extent of thermal metamorphism; and (4) electron microprobe data show chondrule plagioclase is anorthite-rich, with excess structural silica and high MgO, consistent with such plagioclase from other petrologic type 3.00-3.05 chondrites. We conclude that the resolvable (26Al/27Al)0 variabilities among chondrules studied are robust, corresponding to a formation interval of at least 1.1 Myr. Using relationships between chondrule (26Al/27Al)0, Mg#, and Δ17O, we interpret spatial and temporal features of dust, gas, and H2O ice in the FeO-poor chondrule-forming environment. Mg# ≥ 99, Δ17O ~-5‰ chondrules with resolvable excess 26Mg initially formed in an environment that was relatively anhydrous, with a dust-to-gas ratio of ~100×. After these chondrules formed, we interpret a later influx of 16O-poor H2O ice into the environment, and that dust-to-gas ratios expanded (100× to 300×). This led to the later formation of more oxidized Mg# 94-99 chondrules with higher Δ17O (-5‰ to -1‰), with low (26Al/27Al)0, and hence no resolvable excess 26Mg. We refine the mean CR chondrite chondrule formation age via mass balance, by considering that Mg# ≥ 99 chondrules generally have resolved positive (26Al/27Al)0 and that Mg# < 99 chondrules generally have no resolvable excess 26Mg, implying lower (26Al/27Al)0. We obtain a mean chondrule formation age of 3.8 ± 0.3 Myr after CAIs, which is consistent with Pb-Pb and Hf-W model ages of CR chondrite chondrule aggregates. Overall, this suggests most CR chondrite chondrules formed immediately before parent body accretion.
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Affiliation(s)
- Travis J Tenner
- WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
- Chemistry Division, Nuclear and Radiochemistry, Los Alamos National Laboratory, MSJ514, Los Alamos, NM 87545, USA
| | - Daisuke Nakashima
- WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Earth and Planetary Material Sciences, Faculty of Science, Tohoku University, Aoba, Sendai, Miyagi 980-8578, Japan
| | - Takayuki Ushikubo
- WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 200 Monobe Otsu, Nankoku, Kochi 783-8502, Japan
| | - Naotaka Tomioka
- Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 200 Monobe Otsu, Nankoku, Kochi 783-8502, Japan
| | - Makoto Kimura
- Faculty of Science, Ibaraki University, Mito 310-8512, Japan
- National Institute of Polar Research, Tokyo 190-8518, Japan
| | - Michael K Weisberg
- Kingsborough Community College and Graduate Center, The City University of New York, 2001 Oriental Boulevard, Brooklyn, NY 11235-2398, USA
- American Museum of Natural History, Central Park West at 79 Street, New York, NY, 10024-5192, USA
| | - Noriko T Kita
- WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
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Krot AN, Nagashima K, Fintor K, Pál-Molnár E. Evidence for oxygen isotopic exchange in chondrules from Kaba (CV3.1) carbonaceous chondrite during aqueous fluid-rock interaction on the CV parent asteroid. ACTA GEOGRAPHICA AC GEOLOGICA ET METEOROLOGICA DEBRECINA. GEOLOGIA, GEOMORFOLOGIA, TERMESZETFOLDRAJZ SOROZAT 2019; 246:419-435. [PMID: 30930966 PMCID: PMC6440695 DOI: 10.1016/j.gca.2018.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on the mineralogy, petrography, and oxygen isotopic compositions of primary olivine and plagioclase/feldspathic mesostases in chondrules and of secondary magnetite and fayalite in chondrules and matrix of an oxidized Bali-like CV3.1 carbonaceous chondrite, Kaba. In this meteorite, compositionally nearly pure fayalite (Fa98-100) associates with hedenbergite (Fs~50Wo~50), magnetite, and Fe,Ni-sulfides. There are several textural occurrences of this mineral paragenesis: (i) coarse-grained intergrowths in interchondrule matrix, (ii) veins starting at the opaque nodules in the peripheries of type I chondrules and crosscutting fine-grained rims around them, and (iii) rims overgrowing olivine of type I and type II chondrule fragments. Oxygen isotopic compositions of fayalite and magnetite are in disequilibrium with chondrule olivines. On a three-isotope oxygen diagram, δ17O vs. δ18O, compositions of olivine plot along primitive chondrule minerals (PCM) line having a slope of ~1.0; deviations from the terrestrial fractionation line, Δ17O = δ17O - 0.52 × δ18O, range from ~-8‰ to ~-5‰. In contrast, fayalite and magnetite plot along mass-dependent fractionation line with a slope of ~0.5; their δ18O values range from -1 to ~+9‰; Δ17O is nearly constant (average ± 2SE = -1.5±1‰). Oxygen isotopic compositions of chondrule plagioclase and feldspathic mesostases are in disequilibrium with chondrule olivines: they deviate to the right from the PCM line by ~12‰ and plot close to the mass-dependent fractionation line defined by fayalite and magnetite. Based on the mineralogy, petrography, oxygen isotopic compositions of fayalite and magnetite, and the previously published thermodynamic analysis of the fayalite-bearing assemblages in ordinary and carbonaceous chondrites, we conclude that Kaba fayalite and magnetite formed during aqueous fluid-rock interaction at low water/rock ratio (0.1-0.2) and elevated temperatures (~200-300°C) on the CV chondrite parent asteroid. The Δ17O values of Kaba fayalite and magnetite (-1.5±1‰) correspond to Δ17O of aqueous fluid that operated on the CV chondrite parent asteroid and resulted in its alteration. Plagioclase and feldspathic mesostases in Kaba chondrules experienced postcrystallization oxygen isotopic exchange with this 16O-depleted fluid; olivine grains retained their original compositions acquired during chondrule melts crystallization. The inferred oxygen isotopic exchange in Kaba chondrules appear to have not affected their Al-Mg isotope systematics.
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Affiliation(s)
- Alexander N. Krot
- School of Ocean, Earth Science and Technology, Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, HI 96822, USA
| | - Kazuhide Nagashima
- School of Ocean, Earth Science and Technology, Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, HI 96822, USA
| | - Krisztián Fintor
- ‘Vulcano’ Petrology and Geochemistry Research Group, Department of Mineralogy Geochemistry and Petrology, Faculty of Science and Informatics, University of Szeged, Hungary,
| | - Elemér Pál-Molnár
- ‘Vulcano’ Petrology and Geochemistry Research Group, Department of Mineralogy Geochemistry and Petrology, Faculty of Science and Informatics, University of Szeged, Hungary,
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Archer GJ, Walker RJ, Tino J, Blackburn T, Kruijer TS, Hellmann JL. Siderophile element constraints on the thermal history of the H chondrite parent body. GEOCHIMICA ET COSMOCHIMICA ACTA 2019; 245:556-576. [PMID: 30846885 PMCID: PMC6398954 DOI: 10.1016/j.gca.2018.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The abundances of highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Pd), as well as 187Re-187Os and 182Hf-182W isotopic systematics were determined for separated metal, slightly magnetic, and nonmagnetic fractions from seven H4 to H6 ordinary chondrites. The HSE are too abundant in nonmagnetic fractions to reflect metal-silicate equilibration. The disequilibrium was likely a primary feature, as 187Re-187Os data indicate only minor open-system behavior of the HSE in the slightly and non-magnetic fractions. 182Hf-182W data for slightly magnetic and nonmagnetic fractions define precise isochrons for most meteorites that range from 5.2 ± 1.6 Ma to 15.2 ± 1.0 Ma after calcium aluminum inclusion (CAI) formation. By contrast, 182W model ages for the metal fractions are typically 2-5 Ma older than the slope-derived isochron ages for their respective, slightly magnetic and nonmagnetic fractions, with model ages ranging from 1.4 ± 0.8 Ma to 12.6 ± 0.9 Ma after CAI formation. This indicates that the W present in the silicates and oxides was not fully equilibrated with the metal when diffusive transport among components ceased, consistent with the HSE data. Further, the W isotopic compositions of size-sorted metal fractions from some of the H chondrites also differ, indicating disequilibrium among some metal grains. The chemical/isotopic disequilibrium of siderophile elements among H chondrite components is likely the result of inefficient diffusion of siderophile elements from silicates and oxides to some metal and/or localized equilibration as H chondrites cooled towards their respective Hf-W closure temperatures. The tendency of 182Hf-182W isochron ages to young from H5 to H6 chondrites may indicate derivation of these meteorites from a slowly cooled, undisturbed, concentrically-zoned parent body, consistent with models that have been commonly invoked for H chondrites. Overlap of isochron ages for H4 and H5 chondrites, by contrast, appear to be more consistent with shallow impact disruption models. The W isotopic composition of metal from one CR chondrite was examined to compare with H chondrite metals. In contrast to the H chondrites, the CR chondrite metal is characterized by an enrichment in 183W that is consistent with nucleosynthetic s-process depletion. Once corrected for the correlative nucleosynthetic effect on 182W, the 182W model age for this meteorite of 7.0 ± 3.6 Ma is within the range of model ages of most metal fractions from H chondrites. The metal is therefore too young to be a direct nebular condensate, as proposed by some prior studies.
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Affiliation(s)
- Gregory J. Archer
- Department of Geology, University of Maryland, College Park, MD 20742, USA
- Institut für Planetologie, University of Münster, Münster 48149, Germany
| | - Richard J. Walker
- Department of Geology, University of Maryland, College Park, MD 20742, USA
| | - Jonathan Tino
- Department of Geology, University of Maryland, College Park, MD 20742, USA
| | - Terrence Blackburn
- Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Thomas S. Kruijer
- Institut für Planetologie, University of Münster, Münster 48149, Germany
- Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Jan L. Hellmann
- Institut für Planetologie, University of Münster, Münster 48149, Germany
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The Effect of Jupiter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites. ACTA ACUST UNITED AC 2018. [DOI: 10.3847/1538-4365/aad95f] [Citation(s) in RCA: 115] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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10
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Scott ERD, Krot AN, Sanders IS. Isotopic Dichotomy among Meteorites and Its Bearing on the Protoplanetary Disk. THE ASTROPHYSICAL JOURNAL 2018; 854:164. [PMID: 30842684 PMCID: PMC6398615 DOI: 10.3847/1538-4357/aaa5a5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Whole rock Δ17O and nucleosynthetic isotopic variations for chromium, titanium, nickel, and molybdenum in meteorites define two isotopically distinct populations: carbonaceous chondrites (CCs) and some achondrites, pallasites, and irons in one and all other chondrites and differentiated meteorites in the other. Since differentiated bodies accreted 1-3 Myr before the chondrites, the isotopic dichotomy cannot be attributed to temporal variations in the disk. Instead, the two populations were most likely separated in space, plausibly by proto-Jupiter. Formation of CCs outside Jupiter could account for their characteristic chemical and isotopic composition. The abundance of refractory inclusions in CCs can be explained if they were ejected by disk winds from near the Sun to the disk periphery where they spiraled inward due to gas drag. Once proto-Jupiter reached 10-20 M ⊕, its external pressure bump could have prevented millimeter- and centimeter-sized particles from reaching the inner disk. This scenario would account for the enrichment in CCs of refractory inclusions, refractory elements, and water. Chondrules in CCs show wide ranges in Δ17O as they formed in the presence of abundant 16O-rich refractory grains and 16O-poor ice particles. Chondrules in other chondrites (ordinary, E, R, and K groups) show relatively uniform, near-zero Δ17O values as refractory inclusions and ice were much less abundant in the inner solar system. The two populations were plausibly mixed together by the Grand Tack when Jupiter and Saturn migrated inward emptying and then repopulating the asteroid belt with roughly equal masses of planetesimals from inside and outside Jupiter's orbit (S- and C-type asteroids).
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Affiliation(s)
- Edward R D Scott
- Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, Honolulu, HI 96822, USA
| | - Alexander N Krot
- Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, Honolulu, HI 96822, USA
| | - Ian S Sanders
- Department of Geology, Trinity College, Dublin 2, Ireland
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11
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O'D Alexander CM, McKeegan KD, Altwegg K. Water Reservoirs in Small Planetary Bodies: Meteorites, Asteroids, and Comets. SPACE SCIENCE REVIEWS 2018; 214:36. [PMID: 30842688 PMCID: PMC6398961 DOI: 10.1007/s11214-018-0474-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 01/11/2018] [Indexed: 06/09/2023]
Abstract
Asteroids and comets are the remnants of the swarm of planetesimals from which the planets ultimately formed, and they retain records of processes that operated prior to and during planet formation. They are also likely the sources of most of the water and other volatiles accreted by Earth. In this review, we discuss the nature and probable origins of asteroids and comets based on data from remote observations, in situ measurements by spacecraft, and laboratory analyses of meteorites derived from asteroids. The asteroidal parent bodies of meteorites formed ≤4 Ma after Solar System formation while there was still a gas disk present. It seems increasingly likely that the parent bodies of meteorites spectroscopically linked with the E-, S-, M- and V-type asteroids formed sunward of Jupiter's orbit, while those associated with C- and, possibly, D-type asteroids formed further out, beyond Jupiter but probably not beyond Saturn's orbit. Comets formed further from the Sun than any of the meteorite parent bodies, and retain much higher abundances of interstellar material. CI and CM group meteorites are probably related to the most common C-type asteroids, and based on isotopic evidence they, rather than comets, are the most likely sources of the H and N accreted by the terrestrial planets. However, comets may have been major sources of the noble gases accreted by Earth and Venus. Possible constraints that these observations can place on models of giant planet formation and migration are explored.
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Affiliation(s)
- Conel M O'D Alexander
- Dept. Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington, DC 20015, USA. . Tel. (202) 478 8478
| | - Kevin D McKeegan
- Department of Earth, Planetary, and Space Sciences, University of California-Los Angeles, Los Angeles, CA 90095-1567, USA.
| | - Kathrin Altwegg
- Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland.
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Bollard J, Connelly JN, Whitehouse MJ, Pringle EA, Bonal L, Jørgensen JK, Nordlund Å, Moynier F, Bizzarro M. Early formation of planetary building blocks inferred from Pb isotopic ages of chondrules. SCIENCE ADVANCES 2017; 3:e1700407. [PMID: 28808680 PMCID: PMC5550225 DOI: 10.1126/sciadv.1700407] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 07/11/2017] [Indexed: 06/01/2023]
Abstract
The most abundant components of primitive meteorites (chondrites) are millimeter-sized glassy spherical chondrules formed by transient melting events in the solar protoplanetary disk. Using Pb-Pb dates of 22 individual chondrules, we show that primary production of chondrules in the early solar system was restricted to the first million years after the formation of the Sun and that these existing chondrules were recycled for the remaining lifetime of the protoplanetary disk. This finding is consistent with a primary chondrule formation episode during the early high-mass accretion phase of the protoplanetary disk that transitions into a longer period of chondrule reworking. An abundance of chondrules at early times provides the precursor material required to drive the efficient and rapid formation of planetary objects via chondrule accretion.
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Affiliation(s)
- Jean Bollard
- Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark
| | - James N. Connelly
- Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark
| | | | - Emily A. Pringle
- Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Lydie Bonal
- Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, France
| | - Jes K. Jørgensen
- Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark
| | - Åke Nordlund
- Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark
| | - Frédéric Moynier
- Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Martin Bizzarro
- Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark
- Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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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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14
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Age of Jupiter inferred from the distinct genetics and formation times of meteorites. Proc Natl Acad Sci U S A 2017; 114:6712-6716. [PMID: 28607079 DOI: 10.1073/pnas.1704461114] [Citation(s) in RCA: 244] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The age of Jupiter, the largest planet in our Solar System, is still unknown. Gas-giant planet formation likely involved the growth of large solid cores, followed by the accumulation of gas onto these cores. Thus, the gas-giant cores must have formed before dissipation of the solar nebula, which likely occurred within less than 10 My after Solar System formation. Although such rapid accretion of the gas-giant cores has successfully been modeled, until now it has not been possible to date their formation. Here, using molybdenum and tungsten isotope measurements on iron meteorites, we demonstrate that meteorites derive from two genetically distinct nebular reservoirs that coexisted and remained spatially separated between ∼1 My and ∼3-4 My after Solar System formation. The most plausible mechanism for this efficient separation is the formation of Jupiter, opening a gap in the disk and preventing the exchange of material between the two reservoirs. As such, our results indicate that Jupiter's core grew to ∼20 Earth masses within <1 My, followed by a more protracted growth to ∼50 Earth masses until at least ∼3-4 My after Solar System formation. Thus, Jupiter is the oldest planet of the Solar System, and its solid core formed well before the solar nebula gas dissipated, consistent with the core accretion model for giant planet formation.
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15
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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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