The Journal of the Petrological Society of Korea (암석학회지)

The Petrological Society of Korea (한국암석학회)
권호 표지
DOI QR코드

DOI QR Code

Petrological Study on the Volcanic Rocks in Namoo and Namhyeongje Island, Off the Southern Coast of Busan City, Korea

부산광역시 남부 나무섬과 남형제섬 화산암의 암석학적 연구

  • Yun, Sung-Hyo (Department of Earth Science Education, Pusan National University)
  • 윤성효 (부산대학교 지구과학교육과)
  • Received : 2015.12.04
  • Accepted : 2015.12.28
  • Published : 2016.03.31
Download PDF
⟨ Previous Next ⟩

Abstract

This study reports the results about the petrography of volcanic rocks in Namoo island and Namhyeongje island, off the southern coast of Busan City. The rocks in the Namhyeongje island composed of dacitic crystal-vitric welded tuff, showing phenocrysts of plagioclase, rock fragment with flow structure of elongated and flattened pumice fragments. In thin section it shows pyroclastic texture. The volcanic rocks in Namoo island are mainly dark grey-bluish dacite with phenocrysts of plagioclase and gradually changed to pink-greyish rhyodacite with auto-brecciated. In the northeastern part of the island, the volcanic rocks occurred as aggromerate with a poorly sorted mixture of blocks, lappili and ash and felsic feeder dike intrude the aggromerate. Major element composition of the volcanic rocks in Namhyeongje island and Namoo island are $SiO_2$ 73.6~74.4 wt.% and 65.5~68.3 wt.%, respectively. The volcanic rocks in these island are felsic volcanic rocks.

부산광역시 남해안에 위치한 무인도서인 나무섬과 남형제섬은 규장질 화산암류로 구성된다. 남형제섬은 주로 데사이트질 응회암 즉 결정-유리질 용결응회암으로 구성되며, 사장석 반정과 소규모의 암편(岩片)을 함유하며, 압축 신장된 부석편이 나란하게 배열된 유상구조(流狀構造)를 볼 수 있다. 현미경하에서 사장석 결정, 부석편, 암편과 기질부에 부분적으로 압축 신장된 부석편을 보여주는 화성쇄설 조직을 나타낸다. 나무섬은 암청회색 기질부에 사장석 반정을 함유하는 데사이트로 구성되며, 섬의 상부로 감에 따라 암색이 자회색을 띠는 유문데사이트로 이화하고, 산정 부근에서는 대부분 용암으로 구성되나 부분적으로 자각력화작용으로 응회각력암~각력암으로 산출되기도 한다. 섬의 동북부 남서쪽 해식애를 따라 암괴와 화산력 그리고 화산재가 분급이 불량하게 쌓여 있는 집괴암상이 나타난다. 또한 이들 집괴암상을 절단하면서 관입하여 상단의 용암류로 연결되는 규장질 틈새화도암맥이 나타난다. 전암 주성분 분석 결과, 나무섬의 화산암류로서 데사이트($SiO_2$ 65.5~68.3 wt.%) 용암과 화성쇄설물, 남형제섬의 화산암류는 유문암질($SiO_2$ 73.6~74.4 wt.%) 결정-유리질 응회암으로 구성된다.

Keywords

References

  1. Chang, T.W., Kang, P.J., Park, B.H., Hwang, S.K., and Lee, D.W., 1983, Explanation text and geologic map(1:50,000) of Pusan and Gadeok sheet. KIGAM, 53p.
  2. Cho, H.S., Kim, J.S., Son, M., Sohn, Y.K., and Kim, I.S., 2011, Petrography and $^{40}Ar/^{39}Ar$ ages of the volcanic rocks in the Cretaceous Daedaepo basin, Busan: Accumulation time and correlation of the Dadaepo Formation. Journal of Geological Society of Korea, 47, 1-18.
  3. Hwang, S.K., 2012, Tectonic setting and arc volcanisms of the Gyeongsang arc in the southeastern Korean peninsula. Journal of Petrological Society of Korea, 21, 367-383. https://doi.org/10.7854/JPSK.2012.21.3.367
  4. KIGAM, 1996, Geological map of Busan sheet(1:250,000), Korea Institute of Geology, Mining and Materials, Korea
  5. Kim, S.W., Lee, J.Y., Kim, Y.K., and Koh, I.S., 1991, Petrology of Cretaceous volcanic rocks in southern Yuchon minor basin. Journal of Geological Society of Korea, 27, 24-39.
  6. Kim, H.M., Kim, J.S., and Son, J.D., 2006, Report of the volcanic geology of Yeongdo lighthouse and Mokdo island, activation of marine culture and uninhabited Islands tourism linkages research. Busan Regional Maritime Affairs and Fisheries Office, 271-274.
  7. Koh, J.S., Kim, E.H., and Yun, S.H., 2004, Petrology of the Cretaceous igneous rocks in Gadeog island, Busan, Korea. Journal of Petrological Society of Korea, 13, 47-63.
  8. Le Bas, M.J., Le Maitre, R.W., Streckeisenm A., Zanettin, B., and IUGS, 1986, A chemical classification of volcanic rocks based on the Total Alkali-Silica Diagram. Journal of Petrology, 27, 745-750. https://doi.org/10.1093/petrology/27.3.745
  9. Lee, S.M., Kim, S.W., and Jin, M.S., 1987, Igneous activities of the Cretaceous to the Early Tertiary and their tectonic implications in South Korea. Journal of Geological Society of Korea, 23, 338-359.
  10. Min, K.D., Kim, O.J., Yun, S.K., Lee, D.S., and Joo, S.W., 1982, Applicability of plate tectonics to the post-late Cretaceous igneous activities and mineralization in the southern part of South Korea(I). Mining Geology, 15, 123-154.
  11. Son, M., Kim, J.S., Hwang, B.H., Lee, I.H., Kim, J.M., Song, C.W., and Kim, I.S., 2007, Paleogene dyke swarms in the eastern Geoje Island, Korea: their absolute ages and tectonic implications. Journal of Petrological Society of Korea, 16, 82-99.
  12. Sun, S.S. and McDonough, W.F., 1989, Chemical and isotopic systematics of oceanic basalts; implications for mantle composition and processes. In: Magmatism in the ocean basins. Saunders, A.D. and Norry, M.J. (Editors), Geological Society of London, London, 42, 313-345.
  13. Winchester, J.A. and Floyd, P.A., 1977, Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20, 325-343. https://doi.org/10.1016/0009-2541(77)90057-2
  14. Wood, D.A., 1980, The application of a Th-Hf-Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas on the British Tertiary Volcanic Province. Earth and Planetary Science Letters, 50, 11-30. https://doi.org/10.1016/0012-821X(80)90116-8
  15. Yun, S.H., 1998, Volcanic activiy and petrology of the Cretaceous volcanic complex in Yuchon volcanic field of southeastern Korea. Journal of Korean Earth Science Society, 19, 408-424.
  16. Yun, S.H., Kim, J.S., and Kim, Y.L., 1994, Petrology of the Cretaceous volcanic rocks in Pusan area, Korea(II): - Petrogenesis and tectonic setting-. Journal of Korean Earth Science Society, 15, 356-365.
  17. Yun, S.H., Koh, J.S., and Kim, Y.L., 1996, Petrology of the Cretaceous andesiic volcanic rocks in southern Pusan area:- with special reference to Songdo-Tadaepo area-. Journal of Korean Earth Science Society, 17, 472-488.

Cited by

  1. Geochemical interpretation of magnesium and oxygen isotope systematics in granites with the REE tetrad effect vol.22, pp.5, 2018, https://doi.org/10.1007/s12303-018-0024-1