철원분지의 백악기 화산암류에 대한 암석학적 연구 = Petrology of the Cretaceous Volcanic Rocks in Cheolwon Basin.

다국어 초록 (Multilingual Abstract)

This article deal with the petrographical and petrochemical characteristics on the cretaceous volcanic rocks in the Cheolwon basin.
The volcanic rocks areas are composed of basalt in Gungpyeong Formation Basalt, Geumhaksan Andesite, Dongmakgol Tuff, rhyolite, Sinseo Breccia, Jijangbong Tuff, intrusive Bojangsan Andesite, acidic intrusive rocks, in ascending order. According to chemical analyses for major elements, the volcanic rocks show the calc-alkaline rock series ranged medium-K to high-K. The compositional variations of major elements show that contents of Al2O3, Fe2O3, TiO2, MnO, CaO, MgO, and P2O5 decrease with increasing SiO2, but Na2O contents are dispersed and almost constant, K2O are increased slightly. The trace element compositions and REE patterns of the volcanic rocks, which are characterized by a high LILE/HFSE ratio and enrichments in LREE, suggest that they are typical of calc-alkaline rock series of continental margin arc that produced under the subduction environment. On the discrimination diagram, the volcanic rocks discriminate as the continental margin arc. From these results, the rhyolitic magma seems to have been evolved from the basaltic andesitic magma with fractional crystallization of plagioclase, pyroxene, hornblende, biotite.

목차 (Table of Contents)

• 목 차
• 1. 서언 1
• 2. 연구방법 4
• 3. 지질개요 6
• 4. 암석기재 12
• 4.1. 궁평층 현무암 12
• 4.2. 금학산안산암 13
• 4.2.1. 안산암질 회류응회암 13
• 4.2.2. 안산암 용암 14
• 4.3. 동막골응회암 14
• 4.4. 지장봉응회암 18
• 4.4.1. 강하응회암 18
• 4.4.2. 회류응회암 18
• 4.5. 백악기 관입암류 20
• 4.5.1. 보장산안산암 20
• 4.5.2. 산성 관입암류 20
• 5. 암석화학 22
• 5.1. 화학조성과 암석분류 22
• 5.2. 화학적 성질과 조성변화 26
• 5.2.1. 주원소 26
• 5.2.2. 미량원소 37
• 5.2.3. 희토류원소 47
• 5.3. 암석 조구조적 위치 50
• 6. 토의 57
• 7. 결론 59
• 참고문헌 60
• Abstract 65
• List of figures
• Fig. 1. Index map of the study area. 10
• Fig. 2. Geological map of the study area. 11
• Fig. 3. Basalt lavas, intercalated in the Gungpyeong Formation 13
• Fig. 4. Photomicrograph of the Geumhaksan Andesite. 16
• Fig. 5. Photomicrograph of the Dongmakgol Tuff. 17
• Fig. 6. Photomicrograph of the Jijangbong Tuff. 19
• Fig. 7. Photomicrograph of ash-flow tuff in Jijangbong Tuff. 19
• Fig. 8. photomicrograph of later dike. 21
• Fig. 9. Location of representative samples in the study area. 25
• Fig. 10. Na2O+K2O vs. 100xK2O/(Na2O+K2O) (wt.%) diagram for the volcanic rocks in the study area(after Hughes, 1973). 27
• Fig. 11. Total alkalis vs. SiO2 (wt.%) plotting for the volcanic rocks in the study area(Le Maiter et al., 1989). 28
• Fig. 12. Classification diagram for volcanic rocks in the study area(after Cox et al., 1979). 29
• Fig. 13. K2O vs. SiO2 variation diagram for the volcanic rocks in the study area(Gill, 1981). 30
• Fig. 14. SiO2(wt.%) vs. Zr/TiO2x0.0001 diagram for the volcanic rocks (Winchester and Floyd, 1977). 31
• Fig. 15. Alkalis versus SiO2 diagram(after Irvine and Baragar, 1971). 32
• Fig. 16. (Na2O+K2O)-FeO*-MgO(AFM) diagram for the volcanic rocks in the study area (Kuno, 1968; Irvine and Baragar, 1971). 35
• Fig. 17. Haker variation diagrams for the volcanic rock in the study area. 36
• Fig. 18. Haker variation diagrams for the volcanic rock in the study area. 44
• Fig. 19. Primitive mantle-normalized spider diagrams for the volcanic rocks. 46
• Fig. 20. Chondrite-normalized REE patterns for the volcanic rocks. 48
• Fig. 21. Variation diagrams of Eu/Eu* vs Sr, and Eu/Eu* vs SiO2 for the volcanic rocks. 49
• Fig. 22. Tectonomagmatic discimination diagram of Hf/3-Th-Nb/16 for the volcanic rocks in the study area. 52
• Fig. 23. Tectonomagmatic discimination diagram of Zr/117=th-Nb/16 for the volcanic rocks in the study area (after Wood, 1980). 53
• Fig. 24. Schematic diagrams of incompatible trace element ratio of La vs. Ba, and La vs. Th. 54
• Fig. 25. Discriminant diagram of Rb versus Y+Nb showing the aparrent affinity of volcanic arc for the volcanic rocks. 55
• Fig. 26. Rb/Zr vs. Nb diagram showing arc maturity(Brown et al., 1984). 56
• List of table
• Table 1. Stratigraphic sequence of the study area. 9
• Table 2. Major element compositions(wt.%) for the volcanic rocks in the Cheolwon basin. 23
• Table 3. Trace element abundances(ppm) for the volcanic rocks. 39
• Table 4. Rare earth element abundances(ppm) for the volcanic rocks. 42