エンスタタイトコンドライトおよびユレイライトに関する年代学的研究  [in Japanese] Chronology of enstatite chondrites and ureilites  [in Japanese]

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Abstract

This paper summarizes the chronological studies on enstatite chondrites and ureilites, both of which are special groups of meteorites with unknown origins. Two unequilibrated enstatite chondrites, Qingzhen and Yamato 6901 (E3), showed the highly disturbed Rb-Sr system, while their silicate fractions yielded the 2.1 Ga isochron. The thermally metamorphosed enstatite chondrite Khairpur (E6) showed the older Rb-Sr age of 4.50 Ga. The parent body of E3 chondrites experienceda late thermal event at low temperature, which broke down alkali-bearing sulfides in E3. The observed Rb-Sr data are consistent with the mobilization of Rb from alkali-sulfide to silicate phases. Ureilites show highly depleted trace elements abundance which makes it difficult to determine the age of the formation. The U-Pb and Sm-Nd age determination of low-Ca ureilite Goalpara showed that the Pb and Nd isotopes are heavily contaminated with terrestrial components. The acid residues of high-Ca ureilite MET-78008 were free of contamination and defined the old U-Pb age of 4.563 ± 0.006 Ga. The early formation of ureilites supports their formation through the collisional destruction of the parent body. Including the ureilite date, many evolved meteorites formed within the first 10 million years of the solar system history. Future studies on meteorite chronology with the purpose of understanding the early history of the solar system should focus on the fine time resolution through the precise U-Pb age determination or the relative age determination using the extinct nuclides with half lives less than 10 million years.

Journal

  • Chikyukagaku

    Chikyukagaku 33(2), 103-114, 1999

    The Geochemical Society of Japan

References:  45

Cited by:  1

Codes

  • NII Article ID (NAID)
    110008679974
  • NII NACSIS-CAT ID (NCID)
    AN00141280
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0386-4073
  • NDL Article ID
    4755859
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-645
  • Data Source
    CJP  CJPref  NDL  NII-ELS  J-STAGE 
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