Geochemistry of coexisting hornblende and biotite from the Ambalavayal granite, Kerala

  • M Santosh


Major and trace element geochemistry of coexisting hornblendes and biotites from the Ambalavayal granite, northern Kerala, are presented. The hornblendes correspond to edenitic composition, whereas the biotites correspond to annite. The hornblendes typically show high Al2O3 contents (9·69–11·89%) comparable with those from anorogenic granites. The biotites are characteristically low Mg-type, similar to those reported from alkaline rocks. The distribution coefficients calculated for all the major and trace elements are presented and an evaluation of the nature of variation indicate near-chemical equilibrium conditions during the crystallization of the two minerals. The hornblende-biotite tie lines in the Fe3+−Fe2+−Mg compositional triangle, lie parallel to those of buffered biotites, indicating crystallization in an environment closed to oxygen and well above the Ni−NiO buffer. It is inferred that thefH2O increased towards the residual stage andfO2 values were high, in the range of 10−15 bars.


Granite hornblende biotite geochemistry distribution coefficients fH2fO2 Ambalavayal 


  1. Anderson J L 1980Am. J. Sci. 280 289Google Scholar
  2. Brown W L and Parsons I 1981Contrib. Mineral. Petrol. 54 43Google Scholar
  3. Czamanske G K, Wones D R and Richelberger J C 1977Am. J. Sci. 277 1073Google Scholar
  4. Day H W, Brown V M and Abraham K 1980Bull. Geol. Soc. Am. 91 1669Google Scholar
  5. Dodge F C W, Smith V C and Mays R E 1969J. Petrol. 10 250Google Scholar
  6. Dodge F C W and Ross D C 1971J. Geol. 79 158Google Scholar
  7. Foster M D 1960 Interpretation of the composition of the trioctahedral micas, us Geol. Surv. Professional Paper, 354-B, pp. 48Google Scholar
  8. Gorbatschev R 1970Bull. Geol. Surv. Finland 42 23Google Scholar
  9. Ishihara S 1977Min. Geol. J. 27 293Google Scholar
  10. Kretz R 1959J. Geol. 67 371CrossRefGoogle Scholar
  11. Kretz R 1960Geochim. Cosmochim. Acta 20 161CrossRefGoogle Scholar
  12. Leake B E 1978Can. Mineral. 16 501Google Scholar
  13. Leelanandam C 1970J. Petrol. 11 475Google Scholar
  14. Maaloe S and Wyllie P J 1975Contrib. Mineral. Petrol. 52 175CrossRefGoogle Scholar
  15. Nair N G K, Santosh M, Thampi P K and Balasubramonian G 1982Q. J. Geol., Min. Metall. Soc. India 54 28Google Scholar
  16. Santosh M 1986J. Geol. Soc. India 27 185Google Scholar
  17. Santosh M and Nair N G K 1983Proc. Indian Acad. Sci. (Earth Planet. Sci.) 92 297Google Scholar
  18. Santosh M, Nair N G K, Gopalan K and Pande K 1985J. Geol. Soc. India (in press)Google Scholar
  19. Saxena S K 1966Neues Jahrb. Mineral Monatsh 1 67Google Scholar
  20. Stephenson N C N 1977Lithos 10 9CrossRefGoogle Scholar
  21. Wones D R and Eugster H P 1965Am. Mineral. 50 1228Google Scholar

Copyright information

© Indian Academy of Sciences 1986

Authors and Affiliations

  • M Santosh
    • 1
  1. 1.Centre for Earth Science StudiesTrivandrumIndia

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