Geochemistry of Nd and Ce isotopes and REE abundances in Precambrian orthogneiss clasts from the Kamiaso conglomerate, central Japan

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Author(s)

    • SHIMIZU Hiroshi
    • Department of Earth Sciences, Faculty of Science, Kumamoto University
    • ADACHI Mamoru
    • Department of Earth and Planetary Sciences, School of Science, Nagoya University

Abstract

Neodymium and cerium isotopic ratios, rare earth clement abundances and major element compositions were determined for Precambrian orthogneiss and granite clasts in the Jurassic Kamiaso conglomerate from central Japan. Three types of REE patterns are observed for the Kamiaso samples: (1) reverse S-shaped patterns with high enrichment of LREE, (2) patterns consisting of upward convex La-Nd span and reverse S-shaped Nd-Lu span, and (3) patterns consisting of two or three rectilinear lines with an inflection at Ho (and Nd). Sm-Nd data on these rocks give an age of 2.07 ± 0.06 Ga (2σ) with ε<sub>Nd</sub> (2.07 Ga) = –1.9 ± 0.4. The Sm-Nd age is in accordance with the Rb-Sr whole-rock age of 2.05 Ga for quartzo-feldsparthic gneiss clasts by Shibata and Adachi (1974), confirming that the age of <i>ca.</i> 2.05 Ga indicates the time of formation of the original granitic rocks. The initial value of ε<sub>Nd</sub> (2.07 Ga) = –1.9 shows slightly enriched or chondritic feature for the source of original granitic rocks at 2.07 Ga. This study shows that Precambrian episodes and protolithic features can be understood from Precambrian orthogneiss and granite clasts in Mesozoic conglomerates, since the clasts have not undergone post-depositional thermo-tectonic influences.

Journal

  • GEOCHEMICAL JOURNAL

    GEOCHEMICAL JOURNAL 30(1), 57-69, 1996-02-01

    GEOCHEMICAL SOCIETY OF JAPAN

References:  50

Cited by:  6

Codes

  • NII Article ID (NAID)
    10008800561
  • NII NACSIS-CAT ID (NCID)
    AA00654975
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    00167002
  • Data Source
    CJP  CJPref  J-STAGE 
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