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Formation processes of chondrule rims in the primitive meteorites : Verification of the solar nebula model and the parent body model

Research Project

Project/Area Number 12440149
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Petrology/Mineralogy/Science of ore deposit
Research InstitutionKobe University

Principal Investigator

TOMEOKA Kazushige  Kobe Univ., Science, Professor, 理学部, 教授 (00201658)

Co-Investigator(Kenkyū-buntansha) TOMIOKA Naotaka  Kobe Univ., Science, Assistant Professor, 理学部, 助手 (30335418)
小島 知子  神戸大学, 理学部, 助手 (80281137)
Project Period (FY) 2000 – 2003
Project Status Completed (Fiscal Year 2003)
Budget Amount *help
¥14,300,000 (Direct Cost: ¥14,300,000)
Fiscal Year 2003: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2002: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2001: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2000: ¥8,900,000 (Direct Cost: ¥8,900,000)
KeywordsCarbonaceous chondrite / Meteorite / Chondrule / Aqueous alteration / Thermal metamorphism / Shock metamorphism / Interplanetary dust / Planeary material / 含水鉱物 / 感星間塵 / 小惑星 / 衝撃変成 / 熱変成 / 暗色包有物 / ケイ酸塩暗色化 / カンラン石 / CKコンドライト / 層状ケイ酸塩 / コンドリュール・リム
Research Abstract

(1) Primitive chondrite meteorites consist mainly of chondrules and fine-grained matrix. Chondrules are commonly surrounded by fine-grained rims. The rims have widely been regarded to have formed by direct accretion of dust onto the surfaces of chondrules, while chondrules were in the solar nebula. We have performed detailed studies of chondrule rims in three CV3 chondrites and found that a certain proportion of chondrule rims in each chondrite consist of hydrous phyllosilicates. The phyllosilicate-rich rims and their host chondrules show much evidence of aqueous alteration. The evidence can not be reconciled with rim formation by direct accretion of dust in the solar nebula, but can be most plausibly explained by meteorite parent-body processes. We concluded that the chondrule/rim assemblages are clasts that formed by fragmentation, due to brecciation, of aqueously altered portions of the parent body. We proposed, for the first time, a model that explains the formation of rims on chon … More drules by parent-body processes.
(2) We discovered mineralogical evidence of aqueous alteration and subsequent dehydration in dark inclusions (DIs) in the Mokoia CV3 chondrite. We proposed, about 10 years ago, that DIs are lithic clasts that formed by aqueous alteration and subsequent dehydration on the meteorite parent body. Since then, there has been a controversy on whether DIs formed by accretion of dust in the solar nebula or physical and chemical processing in meteorite parent bodies. The results of our study provide strong support of the parent body origin.
(3) The study of four CO3 chondrites has revealed for the first time that dark inclusions (DIs) occur abundantly in CO3 chondrites. The DIs show evidence that they were formed by aqueous alteration and subsequent dehydration of a chondritic precursor. The major element compositions and mineralogy of the DIs suggest that their precursor is a CO chondrite. Thus they probably have a formation history similar to DIs in CV3 chondrites. The CO parent body has previously been regarded to have been dry, homogeneous and unprocessed. However, the present results suggest that the CO parent body was a heterogeneous conglomerate consisting of water-bearing regions and water-free regions, and as it acquired heat source, the water-bearing regions were aqueously altered and subsequently dehydrated.
(4) Silicate darkening is known from many metamorphosed chondrites but its true cause has been unknown. The Kobe CK4 chondrite exhibits pronounced silicate darkening of matrix and chondrules. Our study has revealed that the principal cause of the silicate darkening is vesicular olivine that contains high densities of small vesicles and grains of magnetite and pentlandite. The vesicular olivine has not been previously reported in any chondrites. It probably resulted from recrystallization of partially melted matrix olivine by shock.
Kobe exhibits light shock effects in olivine ; the degree of shock consistent with such shock effects is too low to explain the olivine melting. We suggest that the vesicular olivine in Kobe was produced by shock metamorphism at a relatively mild shock pressure (<20 GPa) and a high temperature (>600 ℃) Thus, the shock effects in olivine, manifest as fracturing and deformation, were relatively minor, but heating was strong enough to cause partial melting of matrix olivine. We proposed that vesicular olivine can be an indicator of shock events at high temperatures.
(5) Dust particles, 20-400 μm in size, accreted onto the Earth with an estimated flux of 〜30000 tons per year. Those collected on the Earth's surface, termed micrometeorites, are predominantly similar in chemistry and mineralogy to hydrated, porous meteorites. This contrasts with the meteorite falls, of which hydrated, porous type comprises only 2.8 %. This large difference in abundance has commonly been attributed to a "filtering" effect of the Earth's atmosphere, that is, porous meteorites are so friable that they would not survive the impact with the atmosphere. Here we report shock-recovery experiments on two porous meteorites, of which one is hydrated and the other is anhydrous. The hydrated meteorite responds to shock with extensive comminution and explosive expansion on pressure release in a much broader pressure range than the anhydrous meteorite. These results indicate that hydrated asteroids probably produce dust particles by mutual collisions at much higher rate than anhydrous asteroids. Thus they explain the different relative abundances of hydrated material in micrometeorites and meteorites, and imply that the abundances are established much before they enter the Earth's atmosphere. Less

Report

(5 results)
  • 2003 Annual Research Report   Final Research Report Summary
  • 2002 Annual Research Report
  • 2001 Annual Research Report
  • 2000 Annual Research Report
  • Research Products

    (32 results)

All Other

All Publications (32 results)

  • [Publications] K.Tomeoka: "Phyllosilicate-rich chondrule rims in the Vigarano CV3 chondrite : Evidence for parent-body processes"Geochimica et Cosmochimica Acta. 64. 1971-1988 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] T.Nakamura: "Impact-induced textural and compositional changes of CV carbonaceous chondrites : Expperimental reproduction"Icarus. 146. 289-300 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] T.Kojima: "A dark inclusion in the Manych LL(3.1) ordinary chondrite : A product of strong shock metamorphism"Antarctic Meteorite Research. 13. 39-54 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka: "Silicate darkening in the Kobe CK chondrite : Evidence for shock metamorphism at high temperature"Meteoritics & Planetary Science. 36. 1843-1856 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] I.Ohnishi: "Dark inclusions in the Mokoia CV3 chondrite : Evidence for aqueous alteration and subsequent thermal and shock metamorphism"Meteoritics & Planetary Science. 37. 1843-1856 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Nakamura: "Hollow organic globules in the Tagish Lake meteorite as possible products of primitive organic reactions"International Journal of Astrobiology. 1. 179-189 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka: "Interplanetary dust from the explosive dispersal of hydrated asteroids by impacts"Nature. 423. 60-62 (2003)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] D.Itoh: "Dark inclusions in the CO3 chondrites : New indicators of parent-body processes"Geochimica et Cosmochimica Acta. 67. 153-169 (2003)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka: "Sodium-metasomatism in chondrules in CO3 chondrites : Relationship to parent-body thermal metamorphism"Meteoritics & Planetary Science. 39(in press). (2004)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka, I.Tanimura: "Phyllosilicate-rich chondrule rims in the Vigarano CV3 chondrite : Evidence for parent-body processes."Geochimica et Cosmochimica Acta. 64. 1971-1988 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] T.Nakamura, K.Tomeoka, N.Takaoka, T.Sekine, H.Takeda: "Impact-induced textural and compositional changes of CV carbonaceous chondrites : Experimental reproduction."Icarus. 146. 289-300 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] T.Kojima, T.Yatagai, K.Tomeoka: "A dark inclusion in the Manych LL(3.1) ordinary chondrite : A product of strong shock metamorphism."Antarctic Meteorite Research. 13. 39-54 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka, I.Ohnishi, N.Nakamura: "Silicate darkening in the Kobe CK chondrite : Evidence for shock metamorphism at high temperature."Meteoritics & Planetary Science. 36. 1535-1545 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Nakamura, M.E.Zolensky, S.Tomita, S.Nakashima, K.Tomeoka: "Hollow organic globules in the Tagish Lake meteorite as possible products of primitive organic reactions."International Journal of Astrobiology. 1. 179-189 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] I.Ohnishi, K.Tomeoka: "Dark inclusions in the Mokoia CV3 chondrite : Evidence for aqueous alteration and subsequent thermal and shock metamorphism"Meteoritics & Planetary Science. 37. 1843-1856 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] D.Itoh, K.Tomeoka: "Dark inclusions in the CO3 chondrites : New indicators of parent-body processes"Geochimica et Cosmochimica Acta. 67. 153-169 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka, K.Kiriyama, K.Nakamura, Y.Yamahana, T.Sekine: "Interplanetary dust from the explosive dispersal of hydrated asteroids by impacts"Nature. 423. 60-62 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka, D.Itoh: "Sodium-metasomatism in chondrules in CO3 chondrites : Relationship to parent-body thermal metamorphism"Meteoritics & Planetary Science. 39(in press). (2004)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] K.Tomeoka: "Interplanetary dust from the explosive dispersal of hydrated asteroids by impacts"Nature. 423. 60-62 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] D.Itoh: "Dark inclusions in the CO3 chondrites : New indicators of parent-body processes"Geochimica et Cosmochimica Acta. 67. 153-169 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] N.Tomioka: "The breakdown of diopside to Ca-rich-majorite and -glass in a shocked H chondrite"Earth and Planetary Science Letters. 208. 271-278 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] D.Itoh: "Dark inclusions in the COIII chondrites : New indicators of parent-body processes"Geochimica et Cosmochimica Acta. 67. 153-169 (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] I.Ohnishi: "Dark inclusions in the Mokoia CVIII chondrite : Evidence for aqueous alteration and subsequent thermal and shock metamorphism"Meteoritics & Planetary Science. 37. 1843-1856 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] K.Nakamura: "Hollow organic globules in the Tagish Lake meteorite as possible products of primitive organic reactions"International Journal of Astrobiology. 1. 179-189 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] N.Tomioka: "The breakdown of diopside to Ca-rich-majorite and -glass in a shocked Hchondrite"Earth and Planetary Science Letters. 208. 271-278 (2003)

    • Related Report
      2002 Annual Research Report
  • [Publications] Z.Xie: "Natural occurrence of Fe_2SiO_4-spinel in the shocked Umbarger L6 chondrite"American Mineralogist. 87. 1257-1260 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] K.Tomeoka: "Silicate darkening in the Kobe CK chondrite : Evidence for shock Metamorphism at high temperature"Meteoritics & Planetary Science. 36. 1535-1545 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] K.Kiriyama: "Shock-recovery experiments on the Allende CV3 chondrite at 600 to 800℃"Proc. Interna. Conf. High Pressure Science and Technology. (in press). (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] J.Ando: "Striped iron zoning of olivine induced by dislocation creep in deformed peridoties"Nature. 414. 893-895 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] K.Tomeoka: "Phyllosilicate-rich chondrule rims in the Vigarano CV3 chondrite: Evidence for parent-body processes"Geochimica et Cosmochimica Acta. 64. 1971-1988 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] T.Nakamura: "Impact-induced textural and compositional changes of CV carbonaceous chondrites : Experimental reproduction"Icarus. 146. 289-300 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] T.Kojima: "A dark inclusion in the Maynch LL(3.1) ordinary chondrite: A product of strong shock metamorphism"Antarctic Meteorite Research. 13. 39-54 (2000)

    • Related Report
      2000 Annual Research Report

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Published: 2000-04-01   Modified: 2016-04-21  

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