한반도 동남부 마이오세 포항분지 내 달전현무암의 층서적 의미

국문 초록 (Abstract)

달전현무암은 포항분지의 발달사 해석에 중요한 의미를 가지나 야외 산상, 층서적 위치, 동위원소 연대 등에서 연구자들 간에 많은 논란이 있다. 본 연구는 이러한 논란을 해결하기 위해 상세한 야외조사를 통해 이 암석의 분포와 연일층군과의 접촉관계를 밝히고 지화학 자료를 분석하였으며, <SUP>40</SUP>Ar/<SUP>39</SUP>Ar 동위연소 연대를 측정하였다. 달전저수지 주변에는 연일층군과 관입접촉 관계를 가지는 3매의 현무암체와 10여 개의 소규모 암맥과 암상이 분포하고 있음이 밝혀졌다. 경하관찰에서 이들은 감람석과 휘석을 반정으로 하는 반상조직을 보이며 기질은 사장석, 감람석, 휘석 등으로 구성된 알칼리 현무암의 특징을 보인다. 기존 지화학 분석결과를 재구성한 결과, 3 매의 암체와 소규모 관입암들은 TAS 도표, 미량원소와 희토류원소 패턴, Zr-Ti 도표상에서 모두 동일한 지화학적 특성을 보이고 있다. 이들은 모두 알칼리 계열로 도시되며, 부화된 해양성 현무암 또는 지판 내의 알칼리 현무암과 유사한 원소별 패턴을 보인다. 또한 <SUP>40</SUP>Ar/<SUP>39</SUP>Ar 동위연소 연대측정 결과, 13.82 Ma의 등시선 연대가 도출되었다. 이러한 결과들은 종합하면, 달전현무암은 알칼리 현무암으로써 층서적으로 연일층군을 관입한 포항분지 충전물에 속하는 것으로 결론지어진다.

다국어 초록 (Multilingual Abstract)

Although the Daljeon Basalt in the Pohang Basin is important for interpreting the basin evolution, its relative chronology, stratigraphic position, and isotopic age still remain controversial. In order to clear up the controversies, this study carried out detailed field investigation to determine its distribution and occurrence together with reanalysis of its previous geochemical data and <SUP>40</SUP>Ar/<SUP>39</SUP>Ar age dating. Based upon the field investigation, the basalt occurring in the central part of the Pohang basin is composed of three main bodies and a dozen of minor dikes and sills that intruded into the Yeonil Group. Their mineral assemblages consist of phenocrysts such as olivine and clinopyroxene and fine groundmasses of clinopyroxene, plagioclase, olivine, and opaque oxide, impling the porphyritic texture of alkaline basalt. All their geochemical data also show the similar geochemical characteristics in TAS, Zr-Ti, and REE/trace elements distribution diagrams. The samples are plotted on alkalic field in the total alkali-versus-silica diagram and show similar patterns to enrichment oceanic basalt or within plate basalt in trace elements. In addition, <SUP>40</SUP>Ar/<SUP>39</SUP>Ar isochron age of 13.82Ma is obtained. These results indicate that the Daljeon Basalt
is an alkaline intrusive rock belonging to the middle Miocene Yeonil Group.

목차 (Table of Contents)

• 요약
• Abstract
• 서론
• 지질학적 배경
• 달전현무암의 분포 및 야외 산상
• 암석·지화학적 특성 및 연대측정
• 달전현무암의 층서적 위치
• 결론
• Referneces

참고문헌 (Reference)

1 심성호, "한반도 동남부 제3기 연일, 어일분지에 나타나는현무암질암의 암석학적 연구" 한국암석학회 20 (20): 1-21, 2011

2 김종선, "한반도 남동부 제3기 암맥군과 화산암류의 40Ar/39Ar 연대" 한국암석학회 14 (14): 92-106, 2005

3 손문, "한반도 남동부 마이오세 지각변형, 분지발달 그리고 지구조적 의미" 대한지질학회 49 (49): 93-118, 2013

4 신성천, "한국 동남부 마이오세 분지 화산암과 기반암의 피션트랙 연대 재검토와 연대층서 고찰" 한국암석학회 22 (22): 83-115, 2013

5 최범영, "‘Singwang strike-slip duplex’ around the Pohang Basin, SE Korea: its structural evolution and role in opening and fill of the Miocene basin" 한국지질과학협의회 10 (10): 145-157, 2006

6 Ludwig, K. R., "Users manual for Isoplot/EX"

7 Kim, B. K., "The stratigraphic and paleontologic studies of the Tertiary (Miocene) of the Pohang area, Korea" 15 : 32-121, 1965

8 Cox, K. G., "The interpretation of igneous rocks" George Allen and Unwin 450-, 1979

9 Han, J. H., "Tectonic evolution and depositional environments of the Tertiary sedimentary basin, southeastern part of Korea" Korea Institute of Energy and Resources 109-, 1987

10 Sohn, Y.K., "Synrift stratigraphic geometry in a transfer zone coarse-grained delta complex, Miocene Pohang Basin, SE Korea" 51 : 1387-1408, 2004

11 Patton, F. D., "Summary of radiometric age dating of rock samples, Wolsung 2 Nuclear Power Plant" F.D. Patton Consultants Ltd., CANATOM-KIGAM 19-, 1981

12 Kim, W. H., "Significance of early to middle Miocene planktonic foraminiferal biostratigraphy of the E-core in the Pohang Basin, Korea" 6 : 144-164, 1990

13 Yoon, S.H., "Regional strike slip in the eastern continental margin of Korea and its tectonic implications for the evolution of Ulleung Basin, East Sea (Sea of Japan)" 107 : 83-97, 1995

14 Lee, D. Y., "Quaternary Deposits in the Coastal Fringe of the Korean Peninsula" Vrije University of Brussels 1985

15 Hong, S. W., "Provenance of coarse-grained detritus in fan-delta systems, Miocene Pohang Basin, SE Korea: implications for boundary fault movements" 2 : 46-58, 1998

16 Song, S., "Petrogenesis of the Tertiary volcanic rocks from the southeastern part of Korea" 93 : 441-461, 1998

17 Lee, H. K., "Paleomagnetism, stratigraphy and geologic structure of the Tertiary Pohang and Changgi basins; K-Ar ages for the volcanic rocks" 25 : 337-349, 1992

18 Son, M., "Paleomagnetism of Tertiary basins in southern Korea: 2. Basaltic rocks in the central part of Pohang Basin" 29 : 369-380, 1996

19 Kim, I.-S., "Palaeomagnetism of tertiary rocks in the Eoil Basin and its vicinities, southeast Korea" 25 : 273-293, 1989

20 Kim, I. -S., "Origin and tectonic evolution of the East Sea (Sea of Japan) and the Yangsan fault system: A new synthetic interpretation" 28 : 84-109, 1992

21 Middlemost, E. A. K., "Naming materials in the magma/igneous rock system" 37 : 215-224, 1994

22 Yi, S., "Miocene calcareous nannoplankton from the Pohang Basin, Korea" 237 : 113-158, 1995

23 Shimazu, M., "Major and minor element compositions and Sr, Nd isotope ratios of basaltic rocks from the Pohang-Yangnam area" 85 : 405-415, 1990

24 Sun, S.S., "Magmatism in ocean basins" Special Publication 313-345, 1989

25 Uto, K., "Laser-heating 40Ar/39Ar dating system of the Geological Survey of Japan: System outline and preliminary results" 48 : 23-46, 1997

26 Jin, M. -S., "K/Ar and fission-track datings for volcanic rocks in the Pohang-Kampo area" Korea Institute of Energy and Resources 65-105, 1988

27 Sawada, Y., "K-Ar age results of volcanic rocks in Southeast Korea (unpublished report)" 1988

28 Song, C. W., "Geometry and kinematics of the western marginal faults of the Miocene Pohang basin, SE Korea, and their tectonic implications" 241-, 2012

29 천영범, "Geometry and kinematics of the Ocheon Fault System along the boundary between the Miocene Pohang and Janggi basins, SE Korea, and its tectonic implications" 한국지질과학협의회 16 (16): 253-273, 2012

30 Yoon, S., "Geology and paleontology of the Tertiary Pohang district, Korea: Part 1, Geology" 11 : 187-214, 1975

31 Choi, H. -O., "Geochemical evolution of basaltic volcanism within the tertiary basins of southeastern Korea and the opening of the East Sea (Sea of Japan)" 249 : 109-122, 2013

32 Hwang, J. H., "Explanatory note of the Andong Sheet" Korea Institute of Geology 1996

33 Yoon, S.H., "Evolution of Neogene Sedimentary Basins in the Eastern Continental Margin of Korea" 1 : 15-27, 1993

34 Tateiwa, I., "Ennichi-Kyuryuho and Choyo Sheet (1:50,000)" 16-, 1924

35 Yun, H., "Emended Stratigraphy of the Miocene formations in the Pohang Basin, Part II: South of the Hyongsan Fault" 10 : 99-116, 1994

36 Kim, J. -M., "Early Neogene biochemostratigraphy of Pohang Basin: a paleoceanographic response to the early opening of the Sea of Japan (East Sea)" 36 : 269-290, 1999

37 Nakamura, N., "Determination of REE, Ba, Fe, Mg, Na and K in carbonaceous and ordinary chondrites" 38 : 757-775, 1974

38 Lee, Y. G., "Biostratigraphy and paleoenvironments of Yeonil Group in Pohang area" 7 : 32-62, 1991

39 Yun, H., "Biostratigraphic, chemostratigrapic, paleomagnetostratigraphic, and tephrochronological study for the correlation of Tertiary formations in southern part of Korea:Regional tectonics and its stratigraphical implication in the Pohang Basin, Korea" 7 : 1-12, 1991

40 Yun, H., "Basic volcanic rocks in the Pohang Basin, and its stratigraphic and petrogenetic implications" 11 : 125-145, 1995

41 Pearce, J. A., "Andesites: Orogenic Andesites and Related Rocks" John Wiley & Sons 525-548, 1982

42 You, H. S., "A study on the nannoplankton from the Neogene formation, Pohang, Korea" 2 : 137-154, 1986