Journal of the Mineralogical Society of Korea (한국광물학회지)

The Mineralogical Society of Korea (한국광물학회)
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K-Ar Ages of Illite from Clay Veins Distributed in Granitic Rocks in the Korean Peninsula

국내 화강암 중의 점토세맥에 포함되는 일라이트의 K-Ar 연대

  • KITAGAWA Ryuji (Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University) ;
  • NISHIDO Hirotsugu (Hizene Research Institute, Okayama University of Science) ;
  • HWANG Jin-Yeon (Geological Environmental Science Major, Division of Earth Environmental System, Pusan National University) ;
  • JIGE Mayumi (Department of Environmental Security Systems, Faculty of Risk and Crisis Management, Chiba Institute of Science)
  • ;
  • ;
  • 황진연 (부산대학교 자연과학대학 지질환경과학) ;
  • Published : 2005.09.01
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Abstract

Numerous clay veins along fractures such as fault, joints, cracks and small fissures are found in granitic rocks in the Korean Peninsula. Granitic rocks of three geological stages (Jurassic, Cretaceous and Paleogene) occur in the Korean Peninsula, and are known as the Daebo, Bulguksa and Hoam granites, respectively. Specimens from clay veins composed or mainly mica clay mineral (illite) were dated using the K-Ar method with the hosted granitoids. The respective ages were as follows. Jurassic: granites 143.7 Ma and 160 Ma, clay mineral veins 104 Ma and 107 Ma: Cretaceous: granite 133.2 Ma, clay mineral veins 93.6 Ma, 84.2 Ma and 84.3 Ma: Paleogene: granite 39.7 Ma and 35.4Ma, clay mineral veins 27.1 Ma and 23.9 Ma. The ages of the clay veins in the Korean Peninsula are clearly much younger than those of their hosted granitoids. This contrasts with data for similar clay veins in Cretaceous and Paleogene granitoids in southwest Japan, where the K-Ar ages of mica clay minerals are slightly younger than their host rocks, or are almost the same.

국내 화강암에는 수많은 점토세맥들이 단층, 절리, 열극 등을 따라 형성되어 있다. 화강암은 지질시대로 보아 쥬라기의 대보화강암, 백악기의 불국사 화강암, 고제3기의 호암 화강암으로 나누어진다. 이들 중에 운모점토광물(일라이트)을 주성분으로 하는 점토세맥의 시료와 그 모암에 대하여 K-Ar 방법에 의해 연대측정을 행하였다 그 결과, 쥬라기 화강암은 143.7 Ma 및 160 Ma이고 그 점토세맥은 104 Ma 및 107 Ma이였고, 백악기 화강암은 133.2 Ma이고, 그 점토세맥은 93.6 Ma, 84.2 Ma, 84.3Ma를 보였고, 고제3기 화강암은 39.7 Ma와 35.4 Ma이고, 그 점토세맥은 27.1 Ma 및 23.9 Ma를 나타냈다. 이와 같이 점토세맥의 연대는 모암인 화강암의 연대와는 큰 차이로 젊게 나타났다. 이러한 결과는 일본 남서부에 분포하는 백악기 및 고제3기 화강암류 중 점토세맥의 연대가 모암의 연대와 약간 젊든지 혹은 거의 같은 것으로 알려진 것과는 큰 대조를 보인다.

Keywords

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