Skip to main content Accessibility help

Mg-Fe-Mn distribution in amphiboles, pyroxenes, and garnets and implications for conditions of metamorphism of high-grade early Archaean iron-formation, southern West Greenland

  • R. P. Hall (a1)


Remnants of early Archaean (Akilia) iron-formation occur as enclaves within the c. 3700 Ma Amitsoq gneisses in the eastern Godthåb-Sukkertoppen region of southern West Greenland. Amphibole- and pyroxene-bearing assemblages are preserved respectively in these two areas. The amphibole-facies rocks comprise one, two, and three-amphibole-bearing assemblages, coexisting with magnetite and quartz (and locally garnet). Experimentally determined phase equilibria suggest that the amphibole-bearing types have not exceeded c. 700 °C, while distribution coefficients in the two-pyroxene ironformation indicate a maximum temperature of around 625 °C.

Mg-Fe distribution relationships between the phases are:


where the numbers are generalized distribution coefficients and in phase a). Mn distribution is:


The distribution coefficients are variable both from one rock to another and internally from one set of grain pairs to another. The development of the observed variable silicate phase assemblages is dependent upon a complex interaction of not only metamorphic grade (P and T) and element availability, but more importantly a H2o and f o2 . In particular, the possibility of reactions between observed assemblages containing cummingtonite + actinolite, magnesian actinotite + magnetite and ferrohypersthene+ferrosalite suggest lesser or greater degrees of dehydration under oxidizing or reducing conditions. For example:




Hide All
Allaart, J. H. (1982) (compiler) 1:500000 scale geological map Frederikshåb lsblink-Sondre Strømfjord. Geol. Surv. Greenland.
Appel, P. W. U. (1980) Precambrian Res. 11, 73-87.
Bayley, R. W., and James, H. L. (1973) Econ. Geol. 68, 934-59.
Beukes, N. J. (1973) Ibid. 68, 960-1004.
Bridgwater, D., Keto, L., McGregor, V. R., and Myers, J. S. (1976) In Geology of Greenland (Escher, A. and Watt, S., eds.). GGU, Copenhaben, 1875.
Brown, G. C., Hughes, D. J., and Esson, J. (1973) Chem. Geol. 11, 223-9.
Cameron, K. L. (1975) Am. Mineral. 60, 375-91.
Coe, R. S., and Kirby, S. H. (1975) Contrib. Mineral. Petrol. 52, 2955.
Coe, R. S., and Muller, W. F. (1973) Science 180, 64-6.
Dorr, J. V. N. II (1973) Econ. Geol. 68, 1005-22.
Ellis, D. J., and Green, D. H. (1979) Contrib. Mineral. Petrol. 71, 13-22.
Floran, R. J., and Papike, J. J. (1978) J. Petrol. 19, 215-88.
Fonarev, V. I., and Korolkov, G. Y. (1980) Contrib. Mineral. Petrol. 73, 413-20.
Fonarev, V. I. and Dokina, T. N. (1977) Contrib. Physiochem. Petrol. VI, 224-35.
French, B. M. (1973) Econ. Geol. 68, 1063-74.
Fryer, B. J. (1977) Can. J. Earth Sci. 14, 1598-610.
Gilbert, M. C., Helz, R. T., Popp, R. K., and Spear, F. S. (1982) In Amphiboles: petrology and experimental phase relations (Veblen, D. R. and Ribbe, P. H., eds.). Mineral. Soc. Am., Washington, 229353.
Graham, C. M., and Powell, R. (1984) J. Metamorphic Geol. 2, 13-31.
Hall, R. P. (1978) Rapp. Gronlands geol. Unders. 90, 57-60.
Hall, R. P. (1980) Ibid. 97, 20 pp.
Hall, R. P. (1981) Unpubl. Ph.D. thesis, CNAA (Portsmouth Polytech.).
Hall, R. P. and Friend, C. R. L. (1983) Geol. J. 18, 7791.
Hall, W. D. M., and Goode, A. D. T. (1978) Precarnbrian Res. 7, 129-84.
Hamilton, P. J., O'Nions, R. K., Bridgwater, D., and Nutman, A. (1983) Earth Planet. Sci. Lett. 62, 263-72.
Harley, S. L., and Green, D. H. (1982) Nature, 300, 697-701.
Herrman, A. G. (1970) In Handbook of geochernistry II/3 (Wedepohl, K. H., ed.). Springer, New York, 5771.
Immega, I., and Klein, C. (1976) Am. Mineral. 61, 1117-44.
Klein, C. (1966) J. Petrol. 7, 240-305.
Klein, C. (1968) Ibid. 9, 281-330.
Kranck, S. H. (1961) Ibid. 2, 13784.
Kretz, R. (1978) J. Geol. 86, 599619.
Laajoki, K., and Lavikainen, S. (1977) Bull. Geol. Soc. Finland, 49, 105-23.
La Berge, G. L. (1964) Econ. Geol. 59, 1313-42.
Leake, B. E. (1978) Mineral. Mag. 42, 533-63.
Lindsley, D. H. (1983) Am. Mineral. 68, 477-93.
McGregor, V. R., and Mason, B. (1977) Am. Mineral. 62, 887904.
Mason, B. (1966) Principles of geochemistry. Wiley, New York, 310 pp.
Miyano, T., and Klein, C. (1983) Ibid. 68, 699-716.
Moorbath, S., Allaart, J. H., Bridgwater, D., and McGregor, V. R. (1977) Nature, 270, 43-5.
Moorbath, S., Taylor, P. N., and Goodwin, R. (1981) Geochirn. Cosmochim. Acta, 45, 1051-60.
Nutman, A. P., Bridgwater, D., Dimroth, E., Gill, R. C. O., and Rosing, M. (1983) Rapp. Gronlands geol. Unders. 112, 5-22.
Popp, R. K., Gilbert, M. C., and Craig, J. R. (1977a) Am. Mineral. 62, 112.
Popp, R. K., Gilbert, M. C., and Craig, J. R. (1977b) Ibid. 62, 1320.
Robinson, P., Ross, M., and Jaffe, H. F. (1971) Ibid. 56, 1005-41.
Simmons, E. C., Lindsley, D. H., and Papike, J. J. (1974) J. Petrol. 15, 539-65.
Taylor, P. N., Moorbath, S., Goodwin, R., and Petry-kowski, A. C. (1980) Geochirn. Cosrnoehirn. Acta, 44, 1437-53.
Taylor, S. R., and McClennan, S. M. (1981) Spec. Publ. Geol. Soc. Austral. 7, 255-61.
Trommsdorff, V., and Wenk, H. R. (1968) Contrib. Mineral. Petrol. 19, 158-68.
Turekian, K. K., and Wedepohl, K. H. (1961) Bull. Geol. Soc. Am. 72, 175-92.
Vaniman, D. T., Papike, J. J., and Labotka, T. (1980) Am. Mineral. 65, 1087-102.
Wildeman, T. R., and Haskin, L. A. (1973) Geochim. Cosmochim. Acta, 37, 419-38.


Mg-Fe-Mn distribution in amphiboles, pyroxenes, and garnets and implications for conditions of metamorphism of high-grade early Archaean iron-formation, southern West Greenland

  • R. P. Hall (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.