Geological Structures of Jucheon Area, Contact Area between Ogcheon Belt and Gyeonggi Massif

옥천대와 경기육괴의 경계부, 주천 지역의 지질구조

  • Kihm, You-Hong (Geological Research Division, Korea Institute of Geoscience and Mineral Resources) ;
  • Kee, Won-Seo (Geological Research Division, Korea Institute of Geoscience and Mineral Resources) ;
  • Jin, Gwang-Min (Mineral Resources Research Division, Korea Institute of Geosciences and Mineral Resources)
  • 김유홍 (한국지질자원연구원 국토지질연구본부) ;
  • 기원서 (한국지질자원연구원 국토지질연구본부) ;
  • 진광민 (한국지질자원연구원 광물자원연구본부)
  • Received : 2010.08.20
  • Accepted : 2010.11.26
  • Published : 2010.12.28

Abstract

The Songbong Formation (so-called Bangrim Group), correated to the lower part of Choseon Supergroup, unconformably overlies the Precambrian Gyeonggi massif at northeastem tip of the Ogcheon belt The contact relationship between the Choseon Supergroup and the Yeongnam massif is also known as an unconformity at northeastem part of the Ogcheon belt. lt implies that the Gyeonggi and Yeongnam massifs were probably connected each other before the Early Paleozoic. Three deformational phases are recognized in the study area, The first phase is the north-northeastward ductile thrusting, which places Precambrian granite of the Gyeonggi massif over the Paleozoic rocks of the Ogcheon belt. The second phase is characterized by the southeastward thrusting and deformation partitioning along the Nuruhaji compartment fault. The third phase is the reactivation of the Nuruhaji Fault into dextral strike-slip fault with over a few kilometers displacement.

옥천대의 북동변인 주천 지역에 분포하는 송봉층(소위 방림층군)은 선캠브리아 시대의 경기육괴 기반암위에 부정합 관계로 분포하며, 조선누층군의 하부 지층에 대비된다. 이것은 영남육괴와 조선누층군의 관계가 옥천대 남동변에서 역시 부정합이라는 사실과 함께 옥천대 양쪽 경계부의 기반암이 최소한 고생대 초에는 하나였을 것임을 의미한다. 주천 지역에서는 세 번의 변형작용이 인지된다. 첫 번째 변형작용에 의해서 선캠브리아 시대의 화강암이 연성전단대를 따라서 북북동 방향으로 옥천대의 고생대층 상위로 이동하였다. 두 번째 변형작용은 남동방향을 향한 충상단층운동과 이에 수반된 누루하지단층으로 특징 지워진다. 특히 누루하지단층을 경계로 하여 북동쪽 지괴와 남서쪽 지괴 사이에 변형작용 분리가 발생하였다. 세 번째 변형작용은 누루하지단층을 수 km의 변위를 갖는 우수향 주향이동단층으로 재활성시켰다.

Keywords

Acknowledgement

Grant : 국토 중서부 천부지각의 지구조 진화 연구

Supported by : 한국지질자원연구원

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