암석학회지 (The Journal of the Petrological Society of Korea)

한국암석학회 (The Petrological Society of Korea)
권호 표지

옥천지역 쥬라기 옥천화강암의 변형구조와 호남전단운동

Deformation structures of the Jurassic Ogcheon granite and the Honam Shearing, Ogcheon Area, Korea

  • 강지훈 (안동대학교 지구환경과학과)
  • Kang, Ji-Hoon (Department of Earth and Environmental Sciences, Andong National University)
  • 투고 : 2010.01.12
  • 심사 : 2010.02.22
  • 발행 : 2010.03.31
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

옥천대의 중앙부에 위치하는 옥천지역에는 쥬라기 대보 옥천화강암이 분포한다. 본 논문은 옥천화강암에 발달하는 변형구조에 대한 구조암석학적 연구결과를 바탕으로 호남전단대의 운동시기를 새롭게 고찰해 보았다. 옥천화강암의 구조적 형태는 지질도상에서 동서 방향의 쐐기형 꼬리와 동북동 방향으로 약간 신장된 타원형 분포를 하고 있고, 주변암인 옥천누층군의 광역엽리 S1은 옥천화강암의 접촉부와 평행하게 발달한다. 이는 옥천화강암이 광역엽리 S1이 형성된 이후에 수동적으로 관입하였음을 지시한다. 옥천화강암의 주요 변형구조는 그 접촉부를 관통하는 고결후 형성된 남북 방향의 구조적 엽리와 동서 방향의 반화강암질 암맥 그 리고 그 동부 경계부에 북서 및 동서 방향의 좌수향 전단대 등이 있다. 남북 방향의 구조적 엽리와 동서 방향의 반화강암질 암맥은 옥천화강암이 관입후 냉각되는 약 $500{\sim}450^{\circ}C$ 부근의 변형온도에서 (북)북동 방향의 우수 주향-이동성 호남전단운동에 의해 형성되었으며, 북서 및 동서 방향의 좌수향 전단대는 옥천화강암의 원래의 관입위치에서 우수향 회전운동 동안에 옥천화강암과 주변암 사이에서 발생된 전단변형에 의해 형성되었다. 호남전단대의 활동시기 및 중생대 화성활동에 대한 기존 연구결과를 종합하여 옥천화강암의 관입 및 변 형작용사와 호남전단대의 운동시기를 고찰해 보면 다음과 같다. (1) 전기~중기 쥬라기 (187~170 Ma); 전기 호남전단운동과 관련된 동구조 엽리상 화강암의 관입. (2) 중기 쥬라기 (175~166 Ma); 쥬라기 화강암류의 주 관입기, 옥천화강암의 수동적 관입, (3) 중기~후기 쥬라기 (168~152 Ma); 쥬라기 화강암류의 주 냉각기, 후기 호남전단운동과 관련된 옥천화강암의 변형작용. 따라서 본 연구결과는 호남전단운동은 175~166 Ma 동안의 휴식기를 걸쳐 187~152 Ma 약 35 Ma 동안 적어도 2회 발생하였음을 제안한다.

The Jurassic Daebo Ogcheon granite is distributed in the Ogcheon area which is located in the central part of the Ogcheon Belt, Korea. This paper newly examines the timing of Honam shearing on the basis of the petrofabric researches on the deformation structures of the Ogcheon granite. The structural shape of Ogcheon granite is mainly characterized by a wedge shaped of E-W trend and an elongate shape of ENE trend in geological map and by contacts parallel to the regional S1 foliation in the host Ogcheon supergroup. It indicates that the pluton was permittedly emplaced after the S1 formation. The main deformation structures are marked by a solid-state tectonic foliation of N-S trend, which passes through the contact of the pluton, and by an aplitic dyke of E-W trend, and by sinistral, NW and E-W oriented shear zones on the eastern border of the pluton. The petrofabric study on the main deformation structures suggests that the tectonic foliation and the aplitic dyke were formed by the Honam dextral strike-slip shearing of (N)NE trend at ca. $500{\sim}450^{\circ}C$ deformation temperature, and that the sinistral shear zones could be induced by the dextral rotation of the pluton from its original site of intrusion, that is, by the shear strain which is due to sliding of the pluton past the host rocks. The history of emplacement and deformation of the Ogcheon granite and the previous results on the timing of Honam shearing would be newly established and reviewed as follows. (1) Early~Middle Jurassic(187~170 Ma); intrusion of syntectonic foliated granite related to Early Honam shearing, (2) Middle Jurassic(175~166 Ma); main magmatic period of Jurassic granitoids, the permitted emplacement of the Ogcheon granite, (3) Middle~Late Jurassic(168~152 Ma); main cooling period of Jurassic granitoids, the deformation of the Ogcheon granite related to Late Honam shearing. Thus, this study proposes that the Honam shear movement would occur two times at least during 187~152 Ma (ca. 35 Ma) through the intertectonic phase of 175~166 Ma.

키워드

참고문헌

  1. 권성택, 이진한, 1997, 호남전단대의 운동시기에 관한 소고. 지질학회지, 33, 183-188.
  2. 김동학, 장태우, 김원영, 황재하, 1978, 한국지질도(1: 50,000), 옥천 지질도폭 및 설명서. 자원개발연구소, 21p.
  3. 윤현수, 1999, 옥천화강암의 산상과 지구화학적 특성. 대한자원환경지질학회, 한국자원공학회, 한국지구물리탐사학회 1999년도 춘계공동학술발표회 논문집, 166.
  4. 이승렬, 이병주, 조등룡, 기원서, 고희재, 김복철, 송교영, 황재하, 최범영, 2003, 전주전단대 화강암류의 SHRIMP U-Pb 저어콘 연령측정: 호남전단대의 운동시기에 대한 고찰. 한국광물학회.한국암석학회 2003년 공동학술발표회 논문집, 55.
  5. 장태우, 이미경, 1996, 순창전단대내 화강분쇄암의 열구조 발달: 2. 열구조. 지질학회지, 32, 500-508.
  6. 최위찬, 김규봉, 홍승호, 이병주, 황재하, 박기화, 황상기, 최범영, 송교영, 진명식, 1995, 한국지질도(1: 1,000,000). 한국자원연구소.
  7. Bateman, R., 1984, On the role of diapirism in the segregation, ascent and final emplacement of granitoid magmas. Tectonophysics, 110, 211-231. https://doi.org/10.1016/0040-1951(84)90262-2
  8. Castro, A., 1986, Structural pattern and ascent model in the Central Extramadural batholith, Hercynian belt, Spain. Jour. Struct. Geol., 8, 633-645. https://doi.org/10.1016/0191-8141(86)90069-6
  9. Cho K,-H., Takagi, H. and Suzuki K., 1999, CHIME monazite age of granitic rocks in the Sunchang shear zone, Korea: timing of dextral ductile shear. Geosciences Journal, 3, 1-15. https://doi.org/10.1007/BF02910229
  10. Cluzel, D., Lee, B.J. and Cadet, J.P., 1991, Indosinian ductile dextral fault system and synkinematic plutonism in the southwest of Ogcheon belt (S. Korea). Tectonophysics, 194, 131-151. https://doi.org/10.1016/0040-1951(91)90277-Y
  11. Gapais, D. and Barbarin, B., 1986, Quartz fabric transition in a cooling syntectonic granite (Hermitage Massif, France). Tectonophysics, 125, 357-370. https://doi.org/10.1016/0040-1951(86)90171-X
  12. Gapais, D., 1989, Shear structures within deformed granites: mechanical and thermal indicators. Geology, 17, 1144-1147. https://doi.org/10.1130/0091-7613(1989)017<1144:SSWDGM>2.3.CO;2
  13. Guineberteau, B., Bouchez, J.-L. and Vigneresse, J.-L., 1987, The Montagne granite pluton (France) emplaced by pull-apart along a shear zone: structural and gravimetric arguments and regional implication. Bull. Geol. Soc. Amer., 99, 763-770. https://doi.org/10.1130/0016-7606(1987)99<763:TMGPFE>2.0.CO;2
  14. Hibbard, M.J., 1987, Deformation of incompletely crystallized magma systems: granitic gneisses and their tectonic implications. Jour. Geol., 93, 543-561.
  15. Hutton, D.H.W., 1988, Granite emplacement mechanisms and tectonic controls: inferences from deformational studies. Trans. Roy. Soc. Edinburgh. Earth Sci.,79, 245-255. https://doi.org/10.1017/S0263593300014255
  16. Kang, J.-H., 1995, Microstructural analysis on the Ogcheon granite in the Ogcheon area. Bull. Basic Sci. Andong Natl. Univ., 6, 133-142.
  17. Kang, J.-H., Hara, I., Hayasaka, Y., Sakurai, Y., Shiota, T. and Umemura, H., 1993, Time-relationship between deformation and metamorphism of the Ogcheon Zone in the Ogcheon district, South Korea. Mem. Geol. Soc. Japan, 42, 63-90.
  18. Kim, J.H. and Kee, W.S., 1994, Structural characteristics of the Soonchang shear zone, Korea. Journal of Southeast Asian Sciences, 9, 417-428. https://doi.org/10.1016/0743-9547(94)90053-1
  19. Kim, S.W., Oh, C.W, Choi, S.G., Ryu, I.-C. and Itaya, T., 2005, Ridge subduction-related Jurassic plutonism in and around the Okcheon Metamorphic Belt, South Korea, and implication for northeast Asian tectonics. International Geology Review, 47, 248-269. https://doi.org/10.2747/0020-6814.47.3.248
  20. Mainprice, D.H. and Bouchez, J.L., 1987, Characterization of slip systems in naturally deformed quartz by microstructural, X-ray texture goniometry and transmission electron microscopy studies: application to simple fabric types as a function of temperature. In Conference Report: Crystallographic fabrics and deformation histories (reported by R.D. Law), Jour. Geol. Soc. London, 144, 677(Abstract).
  21. Otoh S., Jwa Y.-J., Nomura R. and Sakai H., 1999, A preliminary AMS (anisotropy of magnetic susceptibility) study of the Namwon granite, southwest Korea. Geosciences Journal, 3, 31-41. https://doi.org/10.1007/BF02910232
  22. Paterson, S.R., Vernon, R.H. and Tobisch, O.T., 1989, A review of criteria for the identification of magmatic and tectonic foliations in granitoids. Jour. Struct. Geol., 11, 349-363. https://doi.org/10.1016/0191-8141(89)90074-6
  23. Ramsay, J.G. and Graham, R.H., 1970, Strain variation in shear belts, Can. Jour. Earth Sci., 7. 786-813. https://doi.org/10.1139/e70-078
  24. Sagong, H., Kwon, S.-T. and Ree, J.-H., 2005, Mesozoic episodic magmatism in South Korea and its tectonic implication. Tectonics, 24, TC5002, doi:10.1029/ 2004TC 001720
  25. Schmid, S.M. and Casey, M., 1986, Complete fabric analysis of some commonly observed quartz c-axis patterns. Geophys. Monogr., 36, 263-286.
  26. Simpson, C. and Schmid, S., 1983, An evaluation of criteria to deduce the sense of movement in sheared rocks, Bull. Geol. Soc. Amer., 94, 1281-1288. https://doi.org/10.1130/0016-7606(1983)94<1281:AEOCTD>2.0.CO;2
  27. Simpson, C., 1985, Deformation of granitic rocks across the brittle-ductile transition. Jour. Struct. Geol., 7, 503-511. https://doi.org/10.1016/0191-8141(85)90023-9
  28. Tullis, J. and Yund, R.A., 1977, Experimental deformation of dry Westerly granite. Jour. Geophys. Res., 82, 5705-5718. https://doi.org/10.1029/JB082i036p05705
  29. Tullis, J.A., 1983, Deformation of feldspars. In: Feldspar Mineralogy (ed. Ribbe, P.H.), Miner. Soc. Amer., short course notes, 2 (2nd Edn), 297-323.
  30. Turek, A. and Kim, J.B., 1995, U-Pb zircon age of Mesozoic plutons in the Damyang-Geochang area, Ryeongnam massif, Korea. Geochemical Journal, 29, 243-258. https://doi.org/10.2343/geochemj.29.243
  31. Yanai, S., Park, B.S. and Otoh, S., 1985, The Honam shear zone (S. Korea): deformation and tectonic implication in the Far East. Scientific Papers of the College of Arts and Sciences, University of Tokyo, 35, 181-210.