Two Archean Sm-Nd ages of 3.2 and 2.5 Ga for the Marble Bar Chert, Warrawoona Group, Pilbara Block, Western Australia

この論文にアクセスする

この論文をさがす

著者

    • MINAMI Masayo
    • Department of Chemistry, The University of Electro-Communications
    • SHIMIZU Hiroshi
    • Department of Earth Sciences, Faculty of Science, Kumamoto University
    • MASUDA Akimasa
    • Department of Chemistry, The University of Electro-Communications
    • ADACHI Mamoru
    • Department of Earth and Planetary Sciences, School of Science, Nagoya University

抄録

Isotopic data of Sm-Nd, La-Ce and Rb-Sr systems, rare earth element (REE) abundances and major element compositions are reported for the Archean Marble Bar Chert from the Towers Formation of the Salgash Subgroup, Warrawoona Group, Pilbara Block, Western Australia. The Marble Bar Chert records two Sm-Nd ages; 3.2±0.3 Ga for red (or black) and white banded cherts and 2.5±0.2 Ga for yellowish gray cherts. These ages contain relatively large uncertainties and are younger than 3.45 Ga U-Pb zircon ages previously reported for the Salgash Subgroup. The results imply some later perturbation in Sm-Nd system of these cherts after their formation. However, the older age of 3.2±0.3 Ga is close to the U-Pb zircon ages for the Salgash Subgroup within analytical errors and therefore can be regarded as the formation time of the banded cherts. On the other hand, the younger age of 2.5±0.2 Ga for the yellowish gray cherts is thought to reflect the time of later thermal events and the cherts do not retain their original chemical features. The 3.2 Ga Sm-Nd age for the Marble Bar banded cherts is the first Archean record obtained for the Archean cherts; their initial ε<sub>Nd</sub> value of +1.0±3.0 holds the original nature at their formation without severe geochemical disturbance. The obtained mantle-like depleted or chondritic feature at 3.2 Ga for the banded cherts, together with their SiO<sub>2</sub> and Fe<sub>2</sub>O<sub>3</sub>∗ data and positive Eu anomalies in REE patterns, suggests substantially large contribution of hydrothermal solution derived from depleted- or chondritic-mantle to the cherts and inorganic origin of the cherts, which contrasts to Phanerozoic biogenic cherts.

収録刊行物

  • Geochemical journal : journal of the Geochemical Society of Japan

    Geochemical journal : journal of the Geochemical Society of Japan 29(6), 347-362, 1995-12-01

    GEOCHEMICAL SOCIETY OF JAPAN

参考文献:  43件中 1-43件 を表示

被引用文献:  1件中 1-1件 を表示

各種コード

  • NII論文ID(NAID)
    10008800274
  • NII書誌ID(NCID)
    AA00654975
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    00167002
  • データ提供元
    CJP書誌  CJP引用  J-STAGE 
ページトップへ