Journal of the Mineralogical Society of Korea (한국광물학회지)

The Mineralogical Society of Korea (한국광물학회)
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formation Mechanisms of 1:1 Clay Minerals by Biotite Weathering In a Granitic Gneiss

흑운모의 풍화작용에 의한 1:1 점토광물의 형성 메커니즘

  • 이석훈 (한국기초과학지원연구원 중앙분석기기부) ;
  • 김수진 (서울대학교 지구환경과학부)
  • Published : 2002.09.01
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Abstract

Weathering of biotite shows a biotite-vermiculite-kaolinite sequence at the early stage, but presents biotite-kaolinite sequence without a significant intermediate phase (vermiculite) at the late stage from the weathering profile of the granitic gneiss. Secondary 1:1 phyllosilicates are kaolinite and halloysite which show different weathering textures originated by a different formation mechanism. Kaolinitization began from the edges of biotite and propagated toward the interior of grain along a multilayered front. $10 \AA$ layers of biotite are interleaving with $7\AA$ layers of kaolinite and c-axis of two phases is consistent. Kaolinite pseudomorph of biotite is isovolumetric, compared to the biotite boundary and includes many band-like porosities parallel to the cleavage. Platy kaolinite formed by 1:1 layer fur layer replacement of biotite. Halloysitization proceeded outward from the grain edges which were foliated as fine flakes and bent at the right angle for cleavage Halloysites were extensively fanning out and greatly increased the volume of grain. This indicated that halloysite tubes were formed by epitaxial overgrowth on the surface of biotite with import of Si and Al from the external solution by dissolution of plagioclase. These halloysites have abnormally high Fe content ( ~11%).

화강암질 편마암의 풍화단면에서 풍화초기에 흑운모-질석-캐올리나이트로의 변질과정을 보여 주었으나, 지표층으로 가면서 질석 중간 상이 거의 인지되지 않고 흑운모-캐올리나이트 변질과정을 나타낸다. 흑운모의 풍화작용에 의해 생성된 1:1 규산염 층상광물은 캐올리나이트와 할로이사이트이며, 다른 메커니즘에 의해 형성되어 각기 다른 풍화조직을 보여준다. 캐올리나이트화작용은 입자의 가장자리로부터 내부로 진행되었다. 변질과정에서 $10\AA$의 흑운모 다층과 $7\AA$의 캐올리나이트 다층이 교호하고 있고, 두 상의 c-축이 일치한다. 변질된 캐올리나이트의 가상은 흑운모 입자의 외곽선에 기준하여 부피의 변화 없이 일정하고, 많은 공극이 벽개면을 따라 발달해 있어 판상의 캐올리나이트는 흑운모와의 1:1의 엽층 대 엽층 교대작용에 의해 형성된 것으로 보인다. 할로이사이트화작용은 흑운모의 엽편들은 보다 얇게 분리되어 벽개면에 수직방향으로 휘어져 렌즈상의 공극을 형성하고, 할로이사이트는 그 가장자리에서 외곽 방향으로 부채모양으로 발달하여 할로이사이트의 가상은 흑운모 입자의 현저한 부피 증가를 초래했다. 관상의 할로이사이트는 사장석의 용해작용에 의한 외부용액으로부터 Si와 Al을 공급받아 흑운모의 표면에 침전되어 성장되었다 이렇게 형성된 할로이사이트는 비정상적으로 높은 Fe(~11%)를 함유하고 있다.

Keywords

References

  1. 이석훈, 김수진 (2000) 유구지역 화강암질 편마암의 풍롸작용에 의한 광물 조성의 변화, 한국광물학회지, 13, 121-137.
  2. Banfield, J.F. and Eggleton, R. (1988) Transmission electron microscope study of biotite weathering, Clay and Clay Minerals, 36, 47-60.
  3. Churchman, G.J., Whitton, .I.S., and Claridge, F.G.C.,(1984) Intercalation method using formamide for differentiating halloysite from kaolinite. Clays and Clay Minerals, 32, 241- 248.
  4. Churchman, C.J. and Gilks, R.J. (1989) Recognition of intermediates in the possible transformation of halloysitc to kaolinite in weathering profiles, Clay Minerals, 24, 579-590.
  5. Dong, H., Peacor, D.R., and Murphy, s.r. (1998) TEM srudy of progressive alteration of igneous biotite to kaolinite throughout a weathered soil profile. Gcochim, Cosmochim., 62, 1881-1888.
  6. Eswaran, II. and Bin, W.C. (1978) A study of a deep weathering profile on granite in penisular Malaysia. II: Mineralogy of the clay, silt and sand fractions, Soil Sci. Soc. Am. L 4, 149-153.
  7. Eswaran, II. and l lcng, Y.Y. (1976) The weathering of biotite in a profile on gneiss in Malysia, Gcodcrrna, 16. 9-20.
  8. Gilkes, R.J. and Suddhiprakarn, A. (1979a) Biotite alteration in deeply weathered granite. I. Morphological, mineralogical, and chemical porperties, Clay and Clay Minerals. 27, 349-360.
  9. Gilkes, R.J. and Suddhiprakarn, A. (1979b) Biotite alteration in deeply weathered granite. II. The oriented growth of secondary minerals. Clay and Clay Minerals. 27, 349-360.
  10. Harris, W.G., Zelazny, L.W., Baker, .I.C.. and Martens, D.C. (1985a) Biotite Kaolinization in Virgina Piedmont Soils: I. Extent. profile Trends, and Grain Morphological Effects, Soil Sci. Soc.Am. .J. 49, 1290-1297.
  11. Harris. W.G., Zelazny, L.W., Baker, .I.C., and Martens, D. C. (1985b) Biotite Kaolinization in Virgina Piedmont Soils: II. Zonation in Single Grains, Soil Sci. Soc. Am. .J. 49, 1297-1302.
  12. Jeong, G.Y. (1998) Vermicular kaolinite cpitactic on primary phyllosilicatcs in the weathering profiles of anorthosite. Clays Clay Miner., 46, 509-520.
  13. Lee, S.H. (1999) Electron microscopic study on the weathering of the granitic gneiss in the Yoogoo area, Korea. PhD thesis in Seoul National Univcristy,200p.
  14. Kittrick, .J.A. (1973) Mica-derived vermiculites as unstable intermediate. Clays Clay Miner., 21, 479488.
  15. Novikoff, A., Tsawlossou, G., Gac, .J.Y., Bourgeat, F., and Tardy, Y. (1972) Weathering of biotitcs in temperate, tropical and equatorial countries, Sci. Geol. Bnll., 25, 287-306.
  16. Rebertus, R.A., Weed, S.B., and Buol, S.W. (1986) Transformation of biotite to kaolinite during saprolite-soil weathering, Soil Sci. Soc. Am. .I. 50.810-819.
  17. Samotoin, N.D., Norikov, V.M., and Magazina, L,,O.(1987) Paragenesis of secondary clavs in a bauxitebearing granite weathering zone. Inter, Geol. Rev. V. H. Winston & Sons, 1215-1227.
  18. Stoch, L. and Sikora, W. (1976) Transformation of micas in the process of kaolinization of granite and gneisses. Clays Clay Mincr., 24, 156-162.
  19. Velbel M.A. (1989) Weathering of hornblende to ferruguinous products by a dissolution-precipitation mechanism: Petrography and stoichiometry. Clay and Clay Minerals, 37, 515-524.
  20. Wilson, M.J. (1966) The weathering of biotite in some Abcrdccnshirc soils, Mineral Mag., 35, 1080-1093.
  21. Wilson, M..J. (1970) A study of weathering in soil derived from a biotite- hornblende rock. Clay Mineral 8. 291-303.