Hostname: page-component-848d4c4894-m9kch Total loading time: 0 Render date: 2024-05-21T18:40:55.949Z Has data issue: false hasContentIssue false
  • English
  • Français

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

Published online by Cambridge University Press:  05 July 2018

R. P. Hall
R. P. Hall*
Affiliation:
Department of Geology, Portsmouth Polytechnic, Burnaby Road, Portsmouth PO1 3QL
Get access Rights & Permissions [Opens in a new window]

Abstract

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:

and

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

and

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 aH2o and fo2. 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:

and

Keywords

amphibolespyroxenesgarnetsmetamorphismiron-formationSW Greenland
Type
Research Article
Information
Mineralogical Magazine , Volume 49 , Issue 350 , March 1985 , pp. 117 - 128
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1985 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Allaart, J. H. (1982) (compiler) 1:500000 scale geological map Frederikshåb lsblink-Sondre Strømfjord. Geol. Surv. Greenland.Google Scholar
Appel, P. W. U. (1980) Precambrian Res. 11, 73-87.Google Scholar
Bayley, R. W., and James, H. L. (1973) Econ. Geol. 68, 934-59.Google Scholar
Beukes, N. J. (1973) Ibid. 68, 960-1004.Google Scholar
Bridgwater, D., Keto, L., McGregor, V. R., and Myers, J. S. (1976) In Geology of Greenland (Escher, A. and Watt, S., eds.). GGU, Copenhaben, 18–75.Google Scholar
Brown, G. C., Hughes, D. J., and Esson, J. (1973) Chem. Geol. 11, 223-9.Google Scholar
Cameron, K. L. (1975) Am. Mineral. 60, 375-91.Google Scholar
Coe, R. S., and Kirby, S. H. (1975) Contrib. Mineral. Petrol. 52, 29–55.Google Scholar
Coe, R. S., and Muller, W. F. (1973) Science 180, 64-6.Google Scholar
Dorr, J. V. N. II (1973) Econ. Geol. 68, 1005-22.Google Scholar
Ellis, D. J., and Green, D. H. (1979) Contrib. Mineral. Petrol. 71, 13-22.Google Scholar
Floran, R. J., and Papike, J. J. (1978) J. Petrol. 19, 215-88.Google Scholar
Fonarev, V. I., and Korolkov, G. Y. (1980) Contrib. Mineral. Petrol. 73, 413-20.Google Scholar
Fonarev, V. I. and Dokina, T. N. (1977) Contrib. Physiochem. Petrol. VI, 224-35.Google Scholar
French, B. M. (1973) Econ. Geol. 68, 1063-74.Google Scholar
Fryer, B. J. (1977) Can. J. Earth Sci. 14, 1598-610.Google Scholar
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, 229–353.Google Scholar
Graham, C. M., and Powell, R. (1984) J. Metamorphic Geol. 2, 13-31.Google Scholar
Hall, R. P. (1978) Rapp. Gronlands geol. Unders. 90, 57-60.Google Scholar
Hall, R. P. (1980) Ibid. 97, 20 pp.Google Scholar
Hall, R. P. (1981) Unpubl. Ph.D. thesis, CNAA (Portsmouth Polytech.).Google Scholar
Hall, R. P. and Friend, C. R. L. (1983) Geol. J. 18, 77–91.Google Scholar
Hall, W. D. M., and Goode, A. D. T. (1978) Precarnbrian Res. 7, 129-84.Google Scholar
Hamilton, P. J., O'Nions, R. K., Bridgwater, D., and Nutman, A. (1983) Earth Planet. Sci. Lett. 62, 263-72.Google Scholar
Harley, S. L., and Green, D. H. (1982) Nature, 300, 697-701.Google Scholar
Herrman, A. G. (1970) In Handbook of geochernistry II/3 (Wedepohl, K. H., ed.). Springer, New York, 57–71.Google Scholar
Immega, I., and Klein, C. (1976) Am. Mineral. 61, 1117-44.Google Scholar
Klein, C. (1966) J. Petrol. 7, 240-305.Google Scholar
Klein, C. (1968) Ibid. 9, 281-330.Google Scholar
Kranck, S. H. (1961) Ibid. 2, 13784.Google Scholar
Kretz, R. (1978) J. Geol. 86, 599–619.Google Scholar
Laajoki, K., and Lavikainen, S. (1977) Bull. Geol. Soc. Finland, 49, 105-23.Google Scholar
La Berge, G. L. (1964) Econ. Geol. 59, 1313-42.Google Scholar
Leake, B. E. (1978) Mineral. Mag. 42, 533-63.Google Scholar
Lindsley, D. H. (1983) Am. Mineral. 68, 477-93.Google Scholar
McGregor, V. R., and Mason, B. (1977) Am. Mineral. 62, 887–904.Google Scholar
Mason, B. (1966) Principles of geochemistry. Wiley, New York, 310 pp.Google Scholar
Miyano, T., and Klein, C. (1983) Ibid. 68, 699-716.Google Scholar
Moorbath, S., Allaart, J. H., Bridgwater, D., and McGregor, V. R. (1977) Nature, 270, 43-5.Google Scholar
Moorbath, S., Taylor, P. N., and Goodwin, R. (1981) Geochirn. Cosmochim. Acta, 45, 1051-60.Google Scholar
Nutman, A. P., Bridgwater, D., Dimroth, E., Gill, R. C. O., and Rosing, M. (1983) Rapp. Gronlands geol. Unders. 112, 5-22.Google Scholar
Popp, R. K., Gilbert, M. C., and Craig, J. R. (1977a) Am. Mineral. 62, 1–12.Google Scholar
Popp, R. K., Gilbert, M. C., and Craig, J. R. (1977b) Ibid. 62, 1320.Google Scholar
Robinson, P., Ross, M., and Jaffe, H. F. (1971) Ibid. 56, 1005-41.Google Scholar
Simmons, E. C., Lindsley, D. H., and Papike, J. J. (1974) J. Petrol. 15, 539-65.Google Scholar
Taylor, P. N., Moorbath, S., Goodwin, R., and Petry-kowski, A. C. (1980) Geochirn. Cosrnoehirn. Acta, 44, 1437-53.Google Scholar
Taylor, S. R., and McClennan, S. M. (1981) Spec. Publ. Geol. Soc. Austral. 7, 255-61.Google Scholar
Trommsdorff, V., and Wenk, H. R. (1968) Contrib. Mineral. Petrol. 19, 158-68.Google Scholar
Turekian, K. K., and Wedepohl, K. H. (1961) Bull. Geol. Soc. Am. 72, 175-92.Google Scholar
Vaniman, D. T., Papike, J. J., and Labotka, T. (1980) Am. Mineral. 65, 1087-102.Google Scholar
Wildeman, T. R., and Haskin, L. A. (1973) Geochim. Cosmochim. Acta, 37, 419-38.Google Scholar