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Paleomagnetic study of Proterozoic basic intrusive rocks in Enderby Land, East Antarctica

Research Project

Project/Area Number 15540434
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Geology
Research InstitutionKyoto University

Principal Investigator

ISHIKAWA Naoto  Kyoto Univ., Grad.School of Human and Environmental Studies, Assistant Professor, 大学院・人間・環境学研究科, 助教授 (30202964)

Co-Investigator(Kenkyū-buntansha) FUNAKI Minoru  National Institute of Polar Research, Assistant Professor, 研究系, 助教授 (10132713)
Project Period (FY) 2003 – 2005
Project Status Completed (Fiscal Year 2005)
Budget Amount *help
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥2,300,000 (Direct Cost: ¥2,300,000)
KeywordsPaleomagnetism / East Antarctica / Proterozoic / intrusive rock / Supercontinent / Gondwana / 塩基性貫入岩類 / 段階消磁実験 / 帯磁率異方性
Research Abstract

Paleomagnetic and rock-magnetic analyses were performed on Proterozoic basic intrusive rocks at the Mt. Riiser-Larsen area in Enderby Land, East Antarctica in order to obtain paleomagnetic information for clarifing the formation process of supercontinents. Radiometric ages of 1.9 Ga and 1.2 Ga were reported from samples of NE and N-S trending intrusive rocks, respectively. Results of progressive demagnetization and thermo-magnetic experiments indicated the presence of high-stability magnetic components carried by Ti-poor titanomagnetite. Site-mean directions of the stable magnetic components were determined at 21 sites out of 57 sites. Measurements of anisotropy of magnetic susceptibility (AMS) and microscopic observations of thin sections were also performed on the samples. Samples with deformation structure generally showed higher anisotropy degree than 1.3 and oblate shape of AMS fabrics. Out of the 21 sites, samples of 15 sites showed lower degree of AMS than 1.3 and little directional relationship between magnetic foliation and the mean directions of the stable components. The possibility was thus implied that the stable components of the 15 sites may have been primary magnetic components acquired at the formation of the intrusive rocks. The following three mean directions were determined from the mean directions of the 15 sites:
N-S trending intrusive rocks : declination=-44.4°, inclination =66.0°, α_<95>=48.5°
NE trending intrusive rocks : declination=-119.5°, inclination=-36.4°, α_<95>=34.8°
declination=-119.8°, inclination =39.1°, α_<95> =17.0°
Positions of paleomagnetic poles corresponding to the mean directions are not consistent with 1.9 and 1.2 Ga segments of an apparent polar wander path of Australia in the East Gondwanaland reference frame. It is possibly inferred that East Gondwanaland including East Antarctica and Australia might not have existed at 1.2 and 1.9 Ga.

Report

(4 results)
  • 2005 Annual Research Report   Final Research Report Summary
  • 2004 Annual Research Report
  • 2003 Annual Research Report
  • Research Products

    (1 results)

All 2005

All Journal Article (1 results)

  • [Journal Article] Magnetic fabric analysis of deformed rocks in the Riiser-Larsen Main Shear Zone, East Antarctica2005

    • Author(s)
      Nishioka, I., N.Ishikawa, M.Funaki
    • Journal Title

      Polar Geoscience 18

      Pages: 15-25

    • NAID

      110001840518

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2005 Annual Research Report 2005 Final Research Report Summary

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Published: 2003-04-01   Modified: 2016-04-21  

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