DOI QR코드

DOI QR Code

청송 부남암주의 동심원상 누대와 포유체로부터 마그마 혼합작용의 야외증거

Field Evidence of Magma Mixing from Concentric Zoning and Mafic Microgranular Enclaves in Bunam Stock, Korea

  • 황상구 (안동대학교 지구환경과학과) ;
  • 서승환 (안동대학교 지구환경과학과)
  • Hwang, Sang Koo (Department of Earth and Environmental Science, Andong National University) ;
  • Seo, Seung Hwan (Department of Earth and Environmental Science, Andong National University)
  • 투고 : 2016.10.31
  • 심사 : 2016.11.20
  • 발행 : 2016.12.31

초록

부남암주(면적 $29.5km^2$)는 조립질 화강암, 석영몬조섬록암, 화강섬록암과 세립질 화강암 등의 4개 암상으로 분류되는 심성암 복합체이다. 세립질 화강암을 제외한 3개 암상은 석영몬조섬록암을 중심으로 화강섬록암과 조립질 화강암 순으로 동심원상 누대분포를 나타내며, 암상 간에는 매우 불규칙한 경계를 가지고 점이적 조성변화를 나타낸다. 또한 화강섬록암에서는 둥근 모양의 고철질 미립상 포유체(MME)를 흔하게 산출한다. 얼마의 MME는 경계가 들쭉날쭉하고 모양이 수평면에서 원상이지만 수직벽에서 상하로 긴 타원상이며 입도가 대개 세립질이지만 극세립질 냉각연변대를 가진다. 이러한 모양과 입도는 부분적으로 결정질인 규장질-고철질 마그마의 동시성 흐름과 혼화작용을 지시한다. 즉 MME는 규장질 마그마 속으로 주입하는 고철질 마그마가 방울로서 과냉각됨으로 타원체 모양을 이루며 어두운 극세립질 연변대를 나타내는 것이다. 부남암주에서 관찰되는 동심원상 누대분포, 불규칙한 경계 및 점이적 조성변화, 화강섬록암에서 MME의 산출과 타원체 배열 및 냉각연변대 등의 야외관계들에 의하면 두 개의 단구성원은 규장질 마그마에 의한 조립질 화강암과 고철질 마그마에 의한 석영몬조섬록암이고, 혼성암은 포유체를 함유하는 화강섬록암이라는 것이 증명된다. 그리므로 이들은 규장질 마그마 속으로 고철질 마그마가 주입할 때 중간에 혼합작용이 일어남으로써 고철질 단구성원을 중심으로 동심원상 누대를 나타내는 것이다. 여기서 석영몬조섬록암은 화강암질 마그마챔버 속으로 운반되는 고철질 마그마의 고기 화도를 나타내는 것으로 볼 수 있다. 고철질 마그마는 마그마 혼합작용에 효과적인 환경으로서 화도를 통해 상승하였던 것이다. 이러한 모든 특징은 부남암주에서 칼크알칼리 마그마의 혼합과정에 의해 만들어졌음을 암시해준다.

The Bunam Stock ($29.5km^2$ area) is an outcrop of plutonic complex classified four facies: coarse-grained granite, quartz monzodiorite, granodiorite and fine-grained granite. Three facies except the last one exhibit very irregular boundaries with gradational compositional variations between both facies and show concentric zoning from the central quartz monzodiorite through granodiorite to outer coarse-grained granite. Mafic microgranular enclaves (MME) commonly occur in granodiorite. Some MMEs, have very fine-grained chilled margins and indentedly crenulate contacts, and display horizontally circular and vertically elongate shapes. Their shape and granularity indicate coeval flow and mingling of partly crystalline felsic and mafic magmas. MMEs exhibit dark fine-grained margins giving them a ellipsoidal form that has been attributed to undercooling of a mafic magma as blobs intruded into a felsic magma. The observed relations in the Bunam Stock identify that two endmembers are coarse-grained granite from a felsic magma and quartz monzodiorite from a mafic magma, and hybrid is granodiorite including MMEs. So they exhibit concentric zoning that lays the center on the mafic endmember due to magma mixing at the contacts of two magmas, when mafic magma injected into felsic magma. Thus the quartz monzodiorite may probably represent an ancient conduit of mafic magma transport through a granitic magma chamber. Mafic magma would rise through the conduit in which favorable conditions for magma mixing occurred. All these features suggest that they formed from mixing processes of calc-alkaline magma in the Bunam Stock.

키워드

참고문헌

  1. Ahn, U.S. and Hwang, S.K., 2007, Determination of flow direction from indicators in the Muposan Tuff, southern and eastern Cheongsong, Korea. Journal of Economic and Environmental Geology of Korea, 42, 253-271 (in Korean with English abstract).
  2. Barbarin, B., 1991, Enclave of the Mesozoic calc-alkalline granitoids of the Sierra Nevada batholith, California. In: Didier, J. and Barbarin, B. (Eds.), Enclaves and Granite Petrology. Development in Petrology, 13, Elsevier, Amsterdam, 135-154.
  3. Blake, S. and Campell, I.H., 1986, The dynamics of magma-mixing during flow in volcanic conduits. Contributions to Mineralogy and Petrology, 94, 72-81. https://doi.org/10.1007/BF00371228
  4. Blundy, J.D. and Sparks, R.S.J., 1992, Petrogenesis of mafic inclusion in granitoids of the Admello Massif, Italy. Journal of Petrology, 33, 1039-1104. https://doi.org/10.1093/petrology/33.5.1039
  5. Campbell, I.H. and Turner, J.S., 1985, Turbulent mixing between fluids with different viscosities. Nature, 313, 39-42. https://doi.org/10.1038/313039a0
  6. Castro, A., Moreno-Ventas, I. and De la Rosa, J.D., 1991, H-type (hybrid) granitoids: a proposed revision of the granite type classification and nomenclature. Earth Science Review, 31, 237-253. https://doi.org/10.1016/0012-8252(91)90020-G
  7. Castro, A., Rosa, J.D. and Stephens, W.E., 1990, Magma mixing in the subvolcanic environment: petrology of the Gerena interaction zone near Seville, Spain. Contributions to Mineralogy and Petrology, 105, 9-26.
  8. Clemens, J.D. and Mawer, C.K., 1992, Granitic magma transport by fracture propagation. Tectonophysics, 204, 339-360. https://doi.org/10.1016/0040-1951(92)90316-X
  9. Didier, J. and Barbarin, B., 1991, Enclaves and Granite Petrology. Development in Petrology, 13. Elsevier, Amsterdam, 625p.
  10. Dodge, F.C.W. and Kistler, R.W., 1990, Some additional observations on inclusions in the granitic rocks of the Sierra Nevada. Journal of Geophysical Research, 95, 17841-17848. https://doi.org/10.1029/JB095iB11p17841
  11. Dorais, M.J., Whitney, J.A. and Stormer, (Jr.) J.C., 1991, Mineralogical constraints on the petrogenesis of trachytic inclusions, Carpenter ridge tuff, Central San Juan Volcanic Field, Colorado. Contributions to Mineralogy and Petrology, 107, 219-230. https://doi.org/10.1007/BF00310708
  12. Fernandez, A.N. and Barbarin, B., 1991, Relative rheology of coeval mafic and felsic magma; Nature of resulting interaction processes and shape and mineral fabrics of mafic microgranular enclaves. In: Didier, J. and Barbarin, B., (eds.), Enclaves and Granite Petrology. Amsterdam, Elsevier, 263-275.
  13. Hibbard, M.J., 1995, Petrography and petrogenesis. Prentis Hall, New jersey, 587p.
  14. Hibbard, M.J. and Watters, R.J., 1985, Fracturing and diking of incompletely crystallized granitic plutons. Lithos, 18, 1-12. https://doi.org/10.1016/0024-4937(85)90002-7
  15. Holden, P., Halliday, A.N. and Stephems, W.E., Henney, P.J., 1991, Chemical and isotopic evidence for major mass transfer between mafic enclaves and felsic magma. Chemical Geology, 92, 135-152. https://doi.org/10.1016/0009-2541(91)90053-T
  16. Hort, M., 1998, Abrupt change in magma liquidus temperature because of volatile loss or magma mixing: effects on nucleation, crystal growth and thermal history of the magma. Journal of Petrology, 39, 1063-1076. https://doi.org/10.1093/petroj/39.5.1063
  17. Huppert, H.E., Sparks, R.S.J. and Turner, J.S., 1984, Some effects of viscosity on the dynamics of replenished magma chamber. Journal of Geophysical Research, 89, 6875-6877.
  18. Hwang, S.K. and Jo, I.H., 2016, Chemical Evidence of Magma Mingling and Mixing in Plutonic Rocks of the Bunam Stock, Cheongsong. Journal of Geological Society of Korea, 52, 863-883 (in Korean with English abstract). https://doi.org/10.14770/jgsk.2016.52.6.863
  19. Hwang, S.K., Jo, I.H. and Yi, K., 2016, SHRIMP Zircon UPb Dating and Stratigraphical Relationship of the Bunam Stock and Muposan Tuff, Cheongsong. Journal of Geological Society of Korea, 52, 405-419 (in Korean with English abstract). https://doi.org/10.14770/jgsk.2016.52.4.405
  20. Hwang, S.K and Kim, S.H., 2006, Magmatic processes of the Muposan Tuff, southern and eastern Cheongsong, Korea. Journal of Geological Society of Korea, 42, 253-271 (in Korean with English abstract).
  21. Hwang, S.K. and Lee, B.H., 2002, Reversely Zoned Compositional Variations and their Origins of the Andong Pluton, Andong Batholith, Korea. Economic and Environmental Geology, 35, 75-95 (in Korean with English abstract).
  22. Johnston, A.D. and Wyllie, P.J., 1988, Interaction of granitic and basic magmas: experimental observations on contamination processes at 10 Kbar with H,O. Contributions to Mineralogy and Petrology, 98, 352-362. https://doi.org/10.1007/BF00375185
  23. Jwa, Y.-J. and Kim, K.-K., 2000, Petrology of host granites and enclaves from the Bohyeonsan area, Euiseong basin. Korea. Journal of Petrological Society of Korea, 9, 187-203 (in Korean with English abstract).
  24. Kim, J.S., Kim, K.-K., Jwa, Y.-J. and Lee, J.-D., 2004, Petrographical study for the enclaves of the granitic rocks, in the Gyeongsang Basin, Korea. Journal of Petrological Society of Korea, 13, 1-15 (in Korean with English abstract).
  25. Kim, J.S., Kim, K.-K., Jwa, Y.-J. and Son, M., 2012, Cretaceous to early Tertiary granites and magma mixing in South Korea: Their spatio-temporal variations and tectonic implications (multiple slab window model) Journal of Petrological Society of Korea, 21, 203-216 (in Korean with English abstract). https://doi.org/10.7854/JPSK.2012.21.2.203
  26. Kim, K.-K., Kim, J.S. and Jwa, Y.-J., 2005, Petrological study of Cretaceous granitic rocks in the Waryongsan area, southwestern Gyeongsang Basin: Compositional change of granitic rocks by magma mingling. Journal of Petrological Society of Korea, 14, 12-23 (in Korean with English abstract).
  27. Kouchi, A. and Sunagawa, I., 1983, Mixing basaltic and dacitic magmas by forced convection. Nature, 304, 527-528. https://doi.org/10.1038/304527a0
  28. Kouchi, A. and Sunagawa, I., 1985, A model for mixing basaltic and dacitic magmas as deduced from experimental data. Contributions to Mineralogy and Petrology, 89, 17-23. https://doi.org/10.1007/BF01177586
  29. Reid, J.B., Evans, O.C. and Fate, D.G., 1983, Magma mixing in granitic rocks of the central Sierra neveda, California. Earth Planetary Science Letters, 66, 243-261. https://doi.org/10.1016/0012-821X(83)90139-5
  30. Sparks, R.S.J., Sigurdsson, H. and Wilson, L., 1977, Magma mixing: a mechanism for triggering acid explosive eruptions. Nature, 267, 6337-6344.
  31. Spera, F.J., 1980, Aspects of magma transport. In: Hargraves, R (ed) Physics of Magmatic Processes. Princeton University Press, New York, 263-323.
  32. Troll, V.R., Donaldson, C.H. and Emelus, C.H., 2004, Preeruptive magma mixing in ash-flow deposits of the Tertiary Rum Igneous Center, Scotland, Contributions to Mineralogy and Petrology, 147, 722-739. https://doi.org/10.1007/s00410-004-0584-0
  33. Vernon, R.H., 1984, Microgranitoid enclave in granites-globules of hybrid magma quenched in plutonic environment. Nature, 309, 438-439. https://doi.org/10.1038/309438a0
  34. Vernon, R.H., Etheridge, M.A. and Wall, V.J., 1988, Shape and microstructures of microgranitoids enclaves: indicators of magma mimgling and flow. Lithos, 22, 1-11. https://doi.org/10.1016/0024-4937(88)90024-2
  35. Wager, L.R. and Bailey, E.B., 1953, Basic magma chilled against acid magma. Nature, 172, 68-70. https://doi.org/10.1038/172068a0
  36. Wall, V.J., Clemens, J.D. and Clarke, D.B. 1987, Models for granitoid evolution and source compositions. Journal of Geology, 95, 73-79.
  37. Wiebe, R.A., 1994, Silicic magma chambers as traps for basaltic magmas: the Cadillac mountain intrusive complex, Mount Desert island, Maine. Journal of Geology, 102, 423-427. https://doi.org/10.1086/629684
  38. Wiebe, R.A. and Collins, W.J., 1998, Depositional features and stratigraphic sections in granitic plutons: implications for the emplacement and cryatallization of granitic magma. Journal of Structural Geology, 20, 1273-1289. https://doi.org/10.1016/S0191-8141(98)00059-5
  39. Wiebe, R.A., Smith, D., Sturn M., King, E.M. and Seckler, 1997, Enclaves in the Cadillac Mountain granite (Coastal Maine): samples of hybrid magma from the base of the chamber. Journal of Petrology, 38, 393-426. https://doi.org/10.1093/petroj/38.3.393
  40. Zorpi, M.J., Coulon, C., Orsini, J.B., and Cocirta, C., 1989, Magma mingling zoning and emplacement in calc-alkaline granitoid plutons. Tectonophysics, 157, 315-329. https://doi.org/10.1016/0040-1951(89)90147-9

피인용 문헌

  1. Chemical evidence of magma mingling and mixing in plutonic rocks of the Bunam Stock, Cheongsong vol.52, pp.6, 2016, https://doi.org/10.14770/jgsk.2016.52.6.863